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1. Comparative analysis of machine learning methods by the example of the problem of determining muon decay

Author

Dmitry S. Kulyabov, Migran N. Gevorkyan, and Anastasia V. Demidova

Subjects
machine learning, Muon, Computer science, business.industry, muon decay, lcsh:Electronic computers. Computer science, Artificial intelligence, neural networks, Machine learning, computer.software_genre, business, computer, lcsh:QA75.5-76.95
Abstract

The history of using machine learning algorithms to analyze statistical models is quite long. The development of computer technology has given these algorithms a new breath. Nowadays deep learning is mainstream and most popular area in machine learning. However, the authors believe that many researchers are trying to use deep learning methods beyond their applicability. This happens because of the widespread availability of software systems that implement deep learning algorithms, and the apparent simplicity of research. All this motivate the authors to compare deep learning algorithms and classical machine learning algorithms. The Large Hadron Collider experiment is chosen for this task, because the authors are familiar with this scientific field, and also because the experiment data is open source. The article compares various machine learning algorithms in relation to the problem of recognizing the decay reaction + + + at the Large Hadron Collider. The authors use open source implementations of machine learning algorithms. We compare algorithms with each other based on calculated metrics. As a result of the research, we can conclude that all the considered machine learning methods are quite comparable with each other (taking into account the selected metrics), while different methods have different areas of applicability.

Published
2020

2. Search for lepton flavour violating muon decay mediated by a new light particle in the MEG experiment

Author

A. Stoykov, Valerio Pettinacci, Andrey Popov, S. Ogawa, Toshinori Mori, Stefan Ritt, K. Ieki, G. F. Tassielli, N. P. Kravchuk, Satoru Kobayashi, M. Panareo, M. De Gerone, P. Schwendimann, Malte Hildebrandt, Flavio Gatti, A. Papa, G. Pizzigoni, M. Francesconi, William Kyle, T. Libeiro, M. Usami, W. R. Molzon, Michele Biasotti, Yusuke Uchiyama, M. Chiappini, Satoshi Mihara, D. Nicolò, R. Onda, Dylan Palo, P.-R. Kettle, G. M. A. Lim, N. V. Khomutov, L. Galli, M. Nakao, Vladimir Malyshev, M. Nishimura, F. Ignatov, A. Kolesnikov, C. Chiri, Gianluigi Boca, F. Renga, Atsushi Oya, Ryu Sawada, G. Signorelli, A. de Bari, F. Grancagnolo, G. Cavoto, P. W. Cattaneo, H. Natori, Z. Hodge, R. Iwai, Yu.V. Yudin, Fabrizio Cei, F. Berg, Kazuki Toyoda, T. Iwamoto, M. Rossella, K. Yanai, Marco Grassi, Wataru Ootani, C. Voena, A. Corvaglia, A. M. Baldini, Nikolay Kuchinskiy, Aleksander Rozhdestvensky, Hajime Nishiguchi, Manuel Meucci, G. Chiarello, D. N. Grigoriev, A. Mtchedilishvili, Nobuo Matsuzawa, Baldini, A. M., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Chiri, C., Corvaglia, A., de Bari, A., De Gerone, M., Francesconi, M., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Grigoriev, D. N., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwai, R., Iwamoto, T., Kobayashi, S., Kettle, P. -R., Kyle, W., Khomutov, N., Kolesnikov, A., Kravchuk, N., Kuchinskiy, N., Libeiro, T., Lim, G. M. A., Malyshev, V., Matsuzawa, N., Meucci, M., Mihara, S., Molzon, W., Mori, Toshinori, Mtchedilishvili, A., Nakao, M., Natori, H., Nicolò, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Onda, R., Ootani, W., Oya, A., Palo, D., Panareo, M., Papa, A., Pettinacci, V., Pizzigoni, G., Popov, A., Renga, F., Ritt, S., Rozhdestvensky, A., Rossella, M., Sawada, R., Schwendimann, P., Signorelli, G., Stoykov, A., Tassielli, G. F., Toyoda, K., Uchiyama, Y., Usami, M., Voena, C., Yanai, K., and Yudin, Yu. V.

Subjects
Particle physics, Physics and Astronomy (miscellaneous), Flavour, Light particle, FOS: Physical sciences, lcsh:Astrophysics, MEG experiment, lepton flavour violation, muon decay, 01 natural sciences, High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), 0103 physical sciences, lcsh:QB460-466, Direct search, lcsh:Nuclear and particle physics. Atomic energy. Radioactivity, Lepton Flavour Violation, MEG experiment, 010306 general physics, Engineering (miscellaneous), Physics, Muon, 010308 nuclear & particles physics, Branching fraction, lcsh:QC770-798, High Energy Physics::Experiment, Lepton Flavour Violation, Lepton
Abstract

We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\upmu ^+ \rightarrow \mathrm {e}^+\mathrm {X}, \mathrm {X} \rightarrow \upgamma \upgamma \ $$ μ + → e + X , X → γ γ . This search uses a dataset resulting from $$7.5\times 10^{14}$$ 7.5 × 10 14 stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c$$^2$$ 2 for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c$$^2$$ 2 , down to $${\mathcal {O}}(10^{-11})$$ O ( 10 - 11 ) at 90% confidence level.

Published
2020

3. A photogrammetric method for target monitoring inside the MEG II detector

Author

S. Milana, G. Cavoto, F. Renga, M. Meucci, A. Hofer, M. Hildebrandt, K. Ieki, V. Pettinacci, C. Voena, and G. Chiarello

Subjects
Physics - Instrumentation and Detectors, FOS: Physical sciences, muon decay, Tracking (particle physics), 01 natural sciences, 010305 fluids & plasmas, photogrammety, High Energy Physics - Experiment, Momentum, High Energy Physics - Experiment (hep-ex), Optics, Position (vector), 0103 physical sciences, Instrumentation, 010302 applied physics, Physics, Muon, Spectrometer, business.industry, lepton flavour violation, Detector, Instrumentation and Detectors (physics.ins-det), Photogrammetry, Custom software, business
Abstract

An automatic target monitoring method based on photographs taken by a CMOS photo-camera has been developed for the MEG II detector. The technique could be adapted for other fixed-target experiments requiring good knowledge of their target position to avoid biases and systematic errors in measuring the trajectories of the outcoming particles. A CMOS-based, high resolution, high radiation tolerant and high magnetic field resistant photo-camera was mounted inside the MEG II detector at the Paul Scherrer Institute (Switzerland). MEG II is used to search for lepton flavour violation in muon decays. The photogrammetric method's challenges, affecting measurements of low momentum particles' tracks, are high magnetic field of the spectrometer, high radiation levels, tight space constraints, and the need to limit the material budget in the tracking volume. The camera is focused on dot pattern drawn on the thin MEG II target, about 1 m away from the detector endcaps where the photo-camera is placed. Target movements and deformations are monitored by comparing images of the dots taken at various times during the measurement. The images are acquired with a Raspberry board and analyzed using a custom software. Global alignment to the spectrometer is guaranteed by corner cubes placed on the target support. As a result, the target monitoring fulfils the needs of the experiment., Comment: 10 pages, 14 figures. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing

Published
2020
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4. The construction and commissioning of the ultra low mass MEG II drift chamber for the search of the mu^+ --> e^+ gamma decay at branching ratios below 10^(−13)

Author

Chiappini, Marco

Subjects
FIS/01 FISICA SPERIMENTALE, Drift chambers, Particle tracking, Lepton flavour violation, High energy physics, Particle physics, muon decay, MEG experiment, MEG II experiment, Paul Scherrer Institut, Physics detectors, Particle detectors, Gas detectors, Drift chambers, CDCH, Particle tracking, Particle physics, Paul Scherrer Institut, muon decay, Particle detectors, MEG experiment, Gas detectors, Physics detectors, Lepton flavour violation, FIS/04 FISICA NUCLEARE E SUBNUCLEARE, MEG II experiment, High energy physics, CDCH
Published
2019

5. Přesné měření oscilací elektronových antineutrin

Author

Pěč, Viktor, Vorobel, Vít, Trávníček, Petr, and Vénos, Drahoslav

Subjects
Physics::Instrumentation and Detectors, High Energy Physics::Experiment, experiment Daya Bay, oscilace neutrin, neutrino oscillations, muon decay, RPC, rozpad mionu, Daya Bay experiment
Abstract

The Daya Bay experiment is designed to precisely measure short-baseline disappearance of reactor antineutrinos from reactor cores at the Daya Bay nuclear power plant complex in the Guangdong Province of China. It pre- sented the most precise measurements of oscillation parameters sin2 2θ13 = 0.084 ± 0.005 and |∆m2 ee| = (2.42 ± 0.11) × 10−3 eV2 . Background to the antineutrino signals is mainly created by cosmic muons and is effectively suppressed by use of water Cherenkov and RPC muon detectors. This thesis describe testing of RPC detectors prior to their installation at the experi- mental site. Part of the cosmic muons stop in the experiment's antineutrino detectors, and they decay or are captured by 12 C producing 12 B. Isotope 12 B contribute to accidental background. Rates of muon decays in the detectors are estimated in the thesis. The experiment can register electron antineutri- nos from supernova with expected signals around 20 MeV. Energy scale of the detectors at 53 MeV is determined.

Published
2016

6. Muon polarization in the MEG experiment: predictions and measurements

Author

Baldini, A. M., Bao, Y., Baracchini, E., Bemporad, C., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, Gianluca, Cei, F., Chiarello, G., Chiri, C., De Bari, A., De Gerone, M., D’Onofrio, A., Dussoni, S., Fujii, Y., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Graziosi, A., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwamoto, T., Kaneko, D., Kang, T. I., Kettle, P. R., Khazin, B. I., Khomutov, N., Korenchenko, A., Kravchuk, N., Lim, G. M. A., Mihara, S., Molzon, W., Mori, Toshinori, Mtchedlishvili, A., Nakaura, S., Nicolò, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Ootani, W., Panareo, M., Papa, A., Pepino, A., Piredda, G., Pizzigoni, G., Popov, A., Renga, F., Ripiccini, Emanuele, Ritt, S., Rossella, M., Rutar, G., Sawada, R., Sergiampietri, F., Signorelli, G., Tassielli, G. F., Tenchini, F., Uchiyama, Y., Venturini, M., Voena, C., Yamamoto, A., Yoshida, K., You, Z., Yudin, Y. u. V., Baldini, A. M., Bao, Y., Baracchini, E., Bemporad, C., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiarello, Gianluigi, Chiri, Claudio, Bari, A. De, Gerone, M. De, D’Onofrio, A., Dussoni, S., Fujii, Y., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Graziosi, A., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwamoto, T., Kaneko, D., Kang, T. I., Kettle, P. R., Khazin, B. I., Khomutov, N., Korenchenko, A., Kravchuk, N., Lim, G. M. A., Mihara, S., Molzon, W., Mori, Toshinori, Mtchedlishvili, A., Nakaura, S., Nicolò, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Ootani, W., Panareo, Marco, Papa, A., Pepino, Aurora, Piredda, G., Pizzigoni, G., Popov, A., Renga, F., Ripiccini, E., Ritt, S., Rossella, M., Rutar, G., Sawada, R., Sergiampietri, F., Signorelli, G., Tassielli, GIOVANNI FRANCESCO, Tenchini, F., Uchiyama, Y., Venturini, M., Voena, C., Yamamoto, A., Yoshida, K., You, Z., and Yudin, Y. u. V.

Subjects
Muon, Polarization, Lepton Flavor Violation, Michel decay, Physics - Instrumentation and Detectors, Physics and Astronomy (miscellaneous), High Energy Physics::Phenomenology, lepton flavour violation, FOS: Physical sciences, muon decay, Instrumentation and Detectors (physics.ins-det), High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), Physics::Accelerator Physics, High Energy Physics::Experiment, Engineering (miscellaneous)
Abstract

The MEG experiment makes use of one of the world's most intense low energy muon beams, in order to search for the lepton flavour violating process $\mu^{+} \rightarrow {\rm e}^{+} \gamma$. We determined the residual beam polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of energy. The initial muon beam polarization at the production is predicted to be $P_{\mu} = -1$ by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be $P_{\mu} = -0.85 \pm 0.03 ~ {\rm (stat)} ~ { }^{+ 0.04}_{-0.05} ~ {\rm (syst)}$ at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our ${\megsign}$ search induced by the muon radiative decay: $\mu^{+} \rightarrow {\rm e}^{+} \bar{\nu}_{\mu} \nu_{\rm e} \gamma$.

Published
2016

7. Single-hit resolution measurement with MEG II drift chamber prototypes

Author

Fabrizio Cei, M. Venturini, E. Ripiccini, C. Chiri, Marco Grassi, V. Martinelli, E. Baracchini, F. Renga, A. Pepino, F. Tenchini, G. Piredda, G. Chiarello, M. Chiappini, Michele Cascella, L. Galli, S. Dussoni, A. M. Baldini, C. Voena, G. F. Tassielli, D. Nicoló, F. Grancagnolo, G. Signorelli, G. Cavoto, M. Panareo, Baldini, A. M., Baracchini, E., Cavoto, G., Cascella, M., Cei, F., Chiappini, M., Chiarello, Gianluigi, Chiri, Claudio, Dussoni, S., Galli, L., Grancagnolo, F., Grassi, M., Martinelli, V., Nicolò, D., Panareo, Marco, Pepino, Aurora, Piredda, G., Renga, F., Ripiccini, E., Signorelli, G., Tassielli, GIOVANNI FRANCESCO, Tenchini, F., Venturini, M., and Voena, C.

Subjects
Materials science, Physics - Instrumentation and Detectors, Physics::Instrumentation and Detectors, chemistry.chemical_element, FOS: Physical sciences, Cosmic ray, muon decay, Tracking (particle physics), lepton flavour violation, 01 natural sciences, Particle detector, High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), Optics, Ionization, 0103 physical sciences, 010306 general physics, Instrumentation, Image resolution, Mathematical Physics, Helium, 010308 nuclear & particles physics, business.industry, Drift chambers, primary ionisation, MEG, tracker, hit resolution, Instrumentation and Detectors (physics.ins-det), Charged particle, chemistry, Measuring instrument, business
Abstract

Drift chambers operated with helium-based gas mixtures represent a common solution for tracking charged particles keeping the material budget in the sensitive volume to a minimum. The drawback of this solution is the worsening of the spatial resolution due to primary ionisation fluctuations, which is a limiting factor for high granularity drift chambers like the MEG II tracker. We report on the measurements performed on three different prototypes of the MEG II drift chamber aimed at determining the achievable single-hit resolution. The prototypes were operated with helium/isobutane gas mixtures and exposed to cosmic rays, electron beams and radioactive sources. Direct measurements of the single hit resolution performed with an external tracker returned a value of 110 $\mu$m, consistent with the values obtained with indirect measurements performed with the other prototypes., Comment: 18 pages, 18 figures

Published
2016
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8. Muon decay: an old, yet alive experiment in the university physics curriculum

Author

P. La Rocca, Simone Riggi, and Francesco Riggi

Subjects
Physics, Scintillation, Particle physics, Muon, 010308 nuclear & particles physics, Physics::Instrumentation and Detectors, Detector, muon lifetime, General Physics and Astronomy, Physics::Physics Education, Weak interaction, 01 natural sciences, Fundamental interaction, Particle detector, Nuclear physics, GEANT simulations, Particle decay, Muon decay, muon lifetime, GEANT simulations, educational measurements, 0103 physical sciences, educational measurements, High Energy Physics::Experiment, 010306 general physics, Muon decay, Lepton
Abstract

The classic experiment on muon decay is proposed in the undergraduate or master physics curriculum, making use of a single scintillation detector and observing in coincidence the delayed signal due to the electron following muon decay. Two experimental setups, with different geometries and scintillation materials, were considered, making use of standard equipment available in most undergraduate labs. The results obtained in the two cases were compared and discussed. For a better understanding of the results, and to also evaluate the possible effect of material surrounding the detector, detailed GEANT simulations were carried out for both experimental setups. Such simulations are also intended as an additional student activity to virtually exploit in a short time the effect of modifying detector and material configuration, which cannot be achieved during a single student session. The results of this experiment and its interpretation also proved to be a useful way to discuss with students many topics of interest in modern physics, such as—among others—the time dilation, the dependence of muon lifetime in matter, the Fermi weak interaction coupling constant and the parity violation in weak interactions....

Published
2016

9. A limit for the decay from the MEG experiment

Author

E. Baracchini, Stefan Ritt, J. Egger, N.P. Kravchuk, F. Xiao, M. Hildebrandt, H. Natori, R. Pazzi, C. Bemporad, Yusuke Uchiyama, A. M. Baldini, G. Piredda, S. Yamada, B. I. Khazin, P.-R. Kettle, Y. Nishimura, G. Gallucci, Y. Hisamatsu, A. Korenchenko, D.N. Grigoriev, A. de Bari, Tomiyoshi Haruyama, Flavio Gatti, M. Panareo, Roberto Di Nardo, F. Ignatov, C. Topchyan, S. Dussoni, V. Tumakov, Satoshi Mihara, M. De Gerone, J. Adam, Hajime Nishiguchi, G. Cecchet, Martin Schneebeli, O. Kiselev, S. Suzuki, C. Cerri, D. Kaneko, R. Valle, G. Cavoto, Ryu Sawada, B. Golden, D. Zanello, G. Boca, Fabrizio Cei, P. W. Cattaneo, W. R. Molzon, C. Voena, T. Iwamoto, L. Galli, T. Doke, A. Barchiesi, A.S. Popov, Angela Papa, D. Mzavia, F. Sergiampietri, Wataru Ootani, A. Maki, Giovanni Signorelli, X. Bai, S. Yamashita, Yu.V. Yudin, M. Grassi, Akira Yamamoto, Toshinori Mori, Donato Nicolo, F. Renga, and Massimo Rossella

Subjects
Superconductivity, Physics, Nuclear and High Energy Physics, Photon, Spectrometer, Branching fraction, Physics::Medical Physics, Analytical chemistry, chemistry.chemical_element, Calorimeter, Nuclear physics, Positron, Xenon, chemistry, High Energy Physics::Experiment, Limit (mathematics), Lepton flavour violation, Muon decay
Abstract

A search for the decay μ + → e + γ , performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of BR ( μ + → e + γ ) ⩽ 2.8 × 10 − 11 (90% C.L.). This corresponds to the measurement of positrons and photons from ∼ 10 14 stopped μ + -decays by means of a superconducting positron spectrometer and a 900 litre liquid xenon photon detector.

Published
2010

10. One-loop corrections to radiative muon decay

Author

Andrej Arbuzov and E.S. Scherbakova

Subjects
Physics, Nuclear and High Energy Physics, Muon, Radiative decay, FOS: Physical sciences, Radiative corrections, Loop (topology), Nuclear physics, High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), Quantum electrodynamics, Radiative transfer, High Energy Physics::Experiment, Muon decay, Differential (mathematics)
Abstract

One-loop QED corrections to the differential width of radiative muon decay are considered. Results can be used to analyze high statistics data of modern and future experiments., 16 pp, 3 PostScript figures

Published
2004

11. First-order radiative corrections to polarized muon decay spectrum

Author

Andrej Arbuzov

Subjects
Physics, Particle physics, Nuclear and High Energy Physics, Muon, 010308 nuclear & particles physics, Physics::Instrumentation and Detectors, Spectrum (functional analysis), FOS: Physical sciences, Electron, First order, Radiative corrections, 01 natural sciences, High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), 0103 physical sciences, Radiative transfer, Physics::Accelerator Physics, High Energy Physics::Experiment, 010306 general physics, Muon decay
Abstract

The first order QED corrections to the polarized muon decay spectrum are considered. The exact dependence on electron and muon masses is kept. Numerical results are presented., 11 pages, elsart.cls, a typo in Eq.(12) is fixed

Published
2002
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12. Tests of fundamental symmetries with beta decay

Subjects
MUON DECAY, CP-VIOLATION, WEAK CURRENTS, MOTT ELECTRON POLARIMETRY, BIOMOLECULAR CHIRALITY, COLD DARK MATTER, MOLLER POLARIMETER, RIGHT-HANDED CURRENTS, SOLAR NEUTRINO PROBLEM, T-INVARIANCE
Abstract

Since the fall of parity in electroweak interactions the discrete transformations of parity, charge conjugation and time reversal are under close scrutiny for any sign of deviation from maximality where symmetry breaking seems to be complete (like P violation in beta decay) and for any sign of symmetry breaking when this has not yet been observed (like T violation in beta decay).The Standard Model (SM) of electroweak interactions remains robust in explaining the outcome of all experiments with beta rays. Bounds set by P- and T-reversal tests are tightening but remain stubbornly within the SM. However, the solar-neutrino issue enters the era beyond the SM by requiring upsilon oscillations and a non-zero upsilon mass. This review emphasizes experiments with beta rays, but includes solar-neutrino and beta beta-decay findings and devotes some attention to the broken symmetry in biochirality.Theoretical descriptions attempt to implement the symmetry breaking in a causal way, pointing to a possible earlier manifest left-right symmetry, and stimulating searches for deviations from the above maximality as a 'fossil' remnant of symmetry at a deeper level.

Published
1996

13. Tests of fundamental symmetries with beta decay

Subjects
MUON DECAY, CP-VIOLATION, WEAK CURRENTS, MOTT ELECTRON POLARIMETRY, High Energy Physics::Experiment, BIOMOLECULAR CHIRALITY, COLD DARK MATTER, MOLLER POLARIMETER, RIGHT-HANDED CURRENTS, SOLAR NEUTRINO PROBLEM, T-INVARIANCE
Abstract

Since the fall of parity in electroweak interactions the discrete transformations of parity, charge conjugation and time reversal are under close scrutiny for any sign of deviation from maximality where symmetry breaking seems to be complete (like P violation in beta decay) and for any sign of symmetry breaking when this has not yet been observed (like T violation in beta decay). The Standard Model (SM) of electroweak interactions remains robust in explaining the outcome of all experiments with beta rays. Bounds set by P- and T-reversal tests are tightening but remain stubbornly within the SM. However, the solar-neutrino issue enters the era beyond the SM by requiring upsilon oscillations and a non-zero upsilon mass. This review emphasizes experiments with beta rays, but includes solar-neutrino and beta beta-decay findings and devotes some attention to the broken symmetry in biochirality. Theoretical descriptions attempt to implement the symmetry breaking in a causal way, pointing to a possible earlier manifest left-right symmetry, and stimulating searches for deviations from the above maximality as a 'fossil' remnant of symmetry at a deeper level.

Published
1996

14. CPT-violating effects in muon decay

Author

Sebastian Hollenberg and Palash B. Pal

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Muon, Electron energy, CPT symmetry, High Energy Physics::Phenomenology, FOS: Physical sciences, Nuclear physics, High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), High Energy Physics::Experiment, CPT violation, Muon decay, Charged current, Lepton
Abstract

We consider low-energy CPT-violating modifications in charged current weak interactions and analyze possible ramifications in muon and antimuon decays. We calculate the lifetime of muon and antimuon with these modifications, and from the result, put bounds on the CPT-violating parameters. Moreover, we elaborate on the muon and antimuon decay rate differentials in electron energy and spatial angle, which entail interesting phenomenological consequences presenting new ways to constrain CPT violation in charged lepton decays., 6 pages

Published
2011

15. A limit for the μ → e γ decay from the MEG experiment

Author

J. Adam, X. Bai, A. Baldini, E. Baracchini, A. Barchiesi, C. Bemporad, G. Boca, P. W. Cattaneo, G. Cavoto, G. Cecchet, F. Cei, C. Cerri, A. De Bari, M. De Gerone, T. Doke, S. Dussoni, J. Egger, L. Galli, G. Gallucci, F. Gatti, B. Golden, M. Grassi, D. N. Grigoriev, T. Haruyama, M. Hildebrandt, Y. Hisamatsu, F. Ignatov, T. Iwamoto, D. Kaneko, P. R. Kettle, B. I. Khazin, O. Kiselev, A. Korenchenko, N. Kravchuk, A. Maki, S. Mihara, W. Molzon, T. Mori, D. Mzavia, H. Natori, R. Nardò, D. Nicolò, H. Nishiguchi, Y. Nishimura, W. Ootani, A. Papa, R. Pazzi, G. Piredda, A. Popov, F. Renga, S. Ritt, M. Rossella, R. Sawada, M. Schneebeli, F. Sergiampietri, G. Signorelli, S. Suzuki, C. Topchyan, V. Tumakov, Y. Uchiyama, R. Valle, C. Voena, F. Xiao, S. Yamada, A. Yamamoto, S. Yamashita, Y.u. V. Yudin, D. Zanello, PANAREO, Marco, J., Adam, X., Bai, A., Baldini, E., Baracchini, A., Barchiesi, C., Bemporad, G., Boca, P. W., Cattaneo, G., Cavoto, G., Cecchet, F., Cei, C., Cerri, A., De Bari, M., De Gerone, T., Doke, S., Dussoni, J., Egger, L., Galli, G., Gallucci, F., Gatti, B., Golden, M., Grassi, D. N., Grigoriev, T., Haruyama, M., Hildebrandt, Y., Hisamatsu, F., Ignatov, T., Iwamoto, D., Kaneko, P. R., Kettle, B. I., Khazin, O., Kiselev, A., Korenchenko, N., Kravchuk, A., Maki, S., Mihara, W., Molzon, T., Mori, D., Mzavia, H., Natori, R., Nardò, D., Nicolò, H., Nishiguchi, Y., Nishimura, W., Ootani, Panareo, Marco, A., Papa, R., Pazzi, G., Piredda, A., Popov, F., Renga, S., Ritt, M., Rossella, R., Sawada, M., Schneebeli, F., Sergiampietri, G., Signorelli, S., Suzuki, C., Topchyan, V., Tumakov, Y., Uchiyama, R., Valle, C., Voena, F., Xiao, S., Yamada, A., Yamamoto, S., Yamashita, Yudin, Y. u. V., and D., Zanello

Subjects
Lepton flavour violation, Muon decay
Abstract

A search for the decay μ+→e+γ, performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of BR(μ+→e+γ)2.8×10^−11 (90% C.L.). This corresponds to the measurement of positrons and photons from ~10^14 stopped μ+ decays by means of a superconducting positron spectrometer and a 900 litre liquid xenon photon detector.

Published
2010

16. Measuring CP-violating phases through studying the polarization of the final particles in $\mu \to eee$

Author

Yasaman Farzan

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, High Energy Physics::Phenomenology, Lepton flavor, CP-violation, Polarization (waves), Nuclear physics, High Energy Physics - Phenomenology, Angular distribution, Effective lagrangian, CP violation, High Energy Physics::Experiment, Muon decay, Positron annihilation, Lepton
Abstract

It is shown that the polarizations of the final particles in $\mu^+\to e^+e^-e^+$ provide us with information on the CP-violating phases of the effective Lagrangian leading to this Lepton Flavor Violating (LFV) decay., Comment: 10 pages, 1 figure; v2: Results generalized

Published
2009

17. Neutrina Mass Implications for Physics Beyond the Standard Model

Author

Wang, Peng

Subjects
Physics::Instrumentation and Detectors, Physics, High Energy Physics::Phenomenology, Neutrino, High Energy Physics::Experiment, muon decay, beta decay
Abstract

We begin by working out an effective field theory valid below some new physics scale for Dirac neutrinos and Majorana neutrinos, respectively. For Dirac neutrinos, we obtain a complete basis of effective dimension four and dimension six operators that are invariant under the gauge symmetry of the Standard Model. As for Majorana neutrinos, we come up with a complete basis of effective dimension five and dimension seven operators that are invariant under the gauge symmetry of the Standard Model. Using the effective theory, we derive model-independent, "naturalness" upper bounds on the magnetic moments of Dirac neutrinos and Majorana neutrinos generated by physics above the scale of electroweak symmetry breaking. In the absence of fine-tuning of effective operator coefficients, for Dirac neutrinos, we find that current information on neutrino mass implies that the bound on neutrino magnetic moments is several orders of magnitude stronger than those obtained from analyses of solar and reactor neutrino data and astrophysical observations. As for Majorana neutrinos, the magnetic moment contribution to the mass is Yukawa suppressed. The bounds we derive for magnetic moments of Majorana neutrinos are weaker than present experimental limits if neutrino magnetic moments are generated by new physics at around 1 TeV, and surpass current experimental sensitivity only for new physics scales >10-100 TeV. The discovery of a neutrino magnetic moment near present limits would thus signify that neutrinos are Majorana particles. Then, we use the scale of neutrino mass to derive model-independent naturalness constraints on possible contributions to muon decay Michel parameters. We show that -- in the absence of fine-tuning -- the most stringent bounds on chirality-changing operators relevant to muon decay arise from one-loop contributions to neutrino mass. The bounds we obtain on their contributions to the Michel parameters are four or more orders of magnitude stronger than bounds previously obtained in the literature. We also show that, if neutrinos are Dirac fermions, there exist chirality-changing operators that contribute to muon decay but whose flavor structure allows them to evade neutrino mass naturalness bounds. We discuss the implications of our analysis for the interpretation of muon decay experiments. Finally, we use the upper limit on the neutrino mass to derive model-independent naturalness constraints on some non-Standard-Model interactions of beta decays. In the absence of fine-tuning of effective operator coefficients, our results yield constraints on scalar and tensor weak interactions one or more orders of magnitude stronger than a recent global fit after combined with the current experimental limits. We also show that, if neutrinos are Majorana fermions, there exist four-fermion operators that contribute to beta decay but whose flavor structure allows them to evade neutrino mass naturalness bounds. Constraints on the beta decay parameters by CKM Unitarity, ratio of positive pion decays, and pion beta decays are discussed as well.

Published
2007
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18. Neutrino Mass Constraints on Electroweak Parameters

Author

Erwin, Rebecca Joan

Subjects
domain-wall fermions, Physics, High Energy Physics::Phenomenology, High Energy Physics::Experiment, muon decay, neutrino mass
Abstract

We use the scale of neutrino mass and naturalness considerations to obtain model-independent expectations for the magnitude of possible contributions to muon decay Michel parameters from new physics above the electroweak symmetry-breaking scale. Focusing on Dirac neutrinos, we obtain a complete basis of effective dimension four and dimension six operators that are invariant under the gauge symmetry of the Standard Model and that contribute to both muon decay and neutrino mass. We show that - in the absence of fine tuning - the most stringent neutrino mass naturalness bounds on chirality-changing vector operators relevant to muon decay arise from one-loop operator mixing. The bounds we obtain on their contributions to the Michel parameters are two orders of magnitude stronger than bounds previously obtained in the literature. In addition, we analyze the implications of one-loop matching considerations and find that the expectations for the size of various scalar and tensor contributions to the Michel parameters are considerably smaller than those derived from previous estimates of two-loop operator mixing. We also show, however, that there exist gauge-invariant operators that generate scalar and tensor contributions to muon decay but whose flavor structure allows them to evade neutrino mass naturalness bounds. We discuss the implications of our analysis for the interpretation of muon decay experiments. We then repeat the analysis with Majorana neutrinos. Since the lowest dimension mass operator in this case is a five-dimensional operator, we start with a new basis of effective dimension five and dimension seven operators that contribute to muon decay and neutrino mass through radiative corrections. In contrast to similar studies of magnetic moments and masses using Dirac and Majorana neutrinos, which found substantially weaker bounds for Majorana magnetic moments, we find that the limits on muon decay Michel parameters from Majorana neutrinos are similar in magnitude to the limits from Dirac neutrinos. We also find, similar to the Dirac case, that there are operators in our basis whose coefficients are not bound by neutrino mass. Finally, we calculate one-loop renormalization factors of twist-two operators in massless QCD with domain-wall fermions. The Shamir type domain-wall fermion, with an infinitely large extra dimension to describe the massless fermion, is used.

Published
2007
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19. Constraints on Physics Beyond the Standard Model and its Observable Effects

Author

Kile, Jennifer E.

Subjects
Physics, High Energy Physics::Experiment, muon decay, linear collider, higgs production, extra dimensions, neutrino mass
Abstract

In this work, we describe three analyses, all of which involve physics beyond the Standard Model. The first two discussed here are closely related; they use effective operator analyses to constrain the contributions of physics beyond the SM to observable processes. The third project involves the investigations of a particular extra-dimensions model which addresses the cosmological constant problem. The first project which we will discuss uses the scale of neutrino mass to place model-independent constraints on the coefficients of the chirality-changing terms in the muon decay Lagrangian. We list all of the dimension-six effective operators which contribute to muon decay and Dirac mass for the neutrino. We then calculate the one-loop contributions that each of these operators makes to neutrino mass. Taking a generic element of the neutrino mass matrix to be of order ~ 1 eV, we derive limits on the contributions of these operators to the muon Michel parameters which are approximately four orders of magnitude more stringent than the current experimental results, and well below near-future experimental sensitivity. We also find two chirality-changing operators, which, due to their flavor structure, are unconstrained by neutrino mass yet contribute to muon decay. However, as these two operators differ from those constrained by neutrino mass only by their flavor indices, we naively expect their contributions to also be small; if their effects instead turn out to be observable, this may be an indication of beyond-the-Standard-Model physics with an interesting flavor structure. In the second analysis, we again perform an effective operator analysis, this time applied to Higgs production at a linear collider. Here we include all dimension-six operators containing fermions which contribute to Higgs production. We again include operators that contain right-handed Dirac neutrinos. We obtain limits on these operators from electroweak precision observables, the scale of neutrino mass, and limits on neutrino magnetic moments, and use these limits to constrain the contributions of these operators to the Higgs production cross-section. Although we find that all operators containing right-handed neutrinos contribute negligibly to Higgs production, we do find three operators containing only SM fields which could have observable contributions at an e⁺e⁻ linear collider. Lastly, we discuss the characteristics of a particular extra-dimensions model originally proposed by Carroll and Guica [54]. This model has two extra dimensions compactified into a sphere, a bulk magnetic field, and a bulk cosmological constant. In this model, the cosmological constant seen by a four-dimensional observer can be set to zero by fine-tuning the bulk magnetic field against the bulk cosmological constant. If branes with a tension are added at each of the poles of the two-sphere, solutions with zero four-dimensional cosmological constant are still possible, but the compactified dimensions must acquire a deficit angle which depends on the brane tension. However, the brane tension does not affect the fine-tuning relationship between the bulk cosmological constant and the bulk magnetic field. This feature led to the hope that, after this fine-tuning, the model might self-tune, keeping the four-dimensional cosmological constant zero regardless of what happens to the brane tension by adjusting the deficit angle. We speculated that this self-tuning property would imply a massless scalar mode in the perturbed Einstein's equations; as there exist very stringent limits on scalar-tensor theories of gravity, a massless scalar mode would make this model incompatible with observation. We conducted a search for such modes, and found none which satisfied the boundary conditions. This finding led us to speculate that this model does not, in fact, have a self-tuning property.

Published
2007
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20. Measurement of the Michel Parameter Rho Using the MEGA Positron Spectrometer

Author

Lee, Fei-sheng, Physics, Piilonen, Leo E., Simonetti, John H., Kinoshita, Kay, Abashian, Alexander, and Chang, Lay Nam

Subjects
Standard Model, V-A Theory, Physics::Accelerator Physics, High Energy Physics::Experiment, Muon Decay, Michel Parameter
Abstract

This experiment attempts to measure the Michel parameter Rho in normal muon decay Mu to e nu_{e} nu_{mu} with a precision of 0.001. The Standard Model with pure V-A interaction gives 0.75 for this parameter. The world average value is 0.7518 +/- 0.0026. A deviation of the value of Rho from 0.75 will indicate new physics. The experiment, RHO, was carried out at the Los Alamos Meson Physics Facility (LAMPF) of Los Alamos National Laboratory (LANL) in New Mexico, USA, in 1993. The existing experimental set-up that was built for the MEGA experiment was used for the RHO measurement. The experiment was a collaboration of about 50 physicists from Los Alamos National Laboratory, Stanford University, Fermi National Accelerator Laboratory, Virginia Tech, Texas A University, Indiana University, Valparaiso University, University of Houston, University of Chicago and University of Virginia. The result of the experiment is in agreement with Standard Model. The precision of this measurement was dominated by systematic uncertainties due to the fact that the positron spectrometer used in the measurement was designed for another experiment. Thus, the data analysis here focused mainly on the determination of systematic errors. Ph. D.

Published
2001

21. Measurement of the Michel Parameters and the Average $\tau$-Neutrino Helicity from $\tau$ Decays at LEP

Author

B. N. Jin, H. Nowak, W. Wallraff, S. Banerjee, Konrad Deiters, Alberto Aloisio, X. W. Tang, P. A. Piroué, B. Zhou, Tariq Aziz, Crisostomo Sciacca, G. Forconi, Jozsef Toth, Claudio Luci, S. Reucroft, Y. J. Pei, M. Campanelli, A. Barczyk, Adrian Biland, H. J. Lee, Marcella Diemoz, M. Vivargent, D. Piccolo, L. Cifarelli, Marco Pieri, Raffaello D'Alessandro, M. Schneegans, Pierluigi Paolucci, E. Valente, Bryan R. Smith, C. Lapoint, A. Arefiev, U. K. Chaturvedi, A. Engler, Francesca Cavallari, C. Leggett, A. Straessner, G. Carlino, Leonardo Merola, Luca Lista, Y. S. Lu, L. Tauscher, M. Capell, Samuel C.C. Ting, P. Duinker, M. von der Mey, A. Shvorob, H. S. Fesefeldt, E. Pistolesi, Giovanni Passaleva, I. Korolko, Simonetta Gentile, Juven Wang, T. Azemoon, G. Viertel, J. B. Ye, J. P. Martin, H. El Mamouni, K. Riles, Willis Lin, J. H. Field, F. Di Lodovico, Marcos Cerrada, Sabine Riemann, C. Y. Chien, A. Kirkby, G. Y. Zhu, E. Shumilov, A. Lebedev, Dong-Chul Son, J. J. Blaising, J. Hirschfelder, F. Marzano, G. Coignet, Y. Mi, W. Krenz, J. Schwenke, B. Stoyanov, S. Costantini, Dimitri Bourilkov, S. Schmidt-Kaerst, P. Spillantini, G. Cara Romeo, B. P. Roe, Axel König, B. Petersen, D. H. Kim, V. Shoutko, Stefano Giagu, A. Buijs, Egidio Longo, C. Cecchi, Yu. Galaktionov, R. Ostonen, A. Marin, E. Fiandrini, Gyorgy Vesztergombi, Luca Malgeri, P. Marchesini, B. De La Cruz, J. Alcaraz, P. Lebrun, G. Hu, S. X. Wu, P. L. de Guevara, Y. Uchida, V. Brigljevic, G. Sauvage, P. Bartalini, I. Vetlitsky, T. Angelescu, M. Acciarri, Guo-Ming Chen, D. Migani, A. Pevsner, M. Pohl, Harvey B Newman, Speranza Falciano, B. Borgia, J. Casaus, M. Steuer, Oleg Fedin, M. P. Sanders, B. L. Betev, Igor Vorobiev, A. Kasser, F. Ferroni, A. Mihul, R. Mount, G. Alemanni, P. Levtchenko, A. Chen, D. van Dierendonck, J. Salicio, M. Lebeau, Nicola Cavallo, Y. Zeng, P. Laurikainen, K. Banicz, Ren-Yuan Zhu, Panos A Razis, Pàl Hidas, S. Bhattacharya, D. Perret-Gallix, H. K. Park, Luciano Barone, G. Zilizi, R. Leiste, Christoph Paus, A. Kunin, J. G. Branson, S. Villa, W. W. Kinnison, S. C. Yeh, S. S. Gau, M. Pedace, Hafeez R Hoorani, T. van Rhee, A. M. Cartacci, G. Castellini, E. Drago, Francesca Nessi-Tedaldi, L. Z. Sun, C. G. Yang, A. Gurtu, J. Pothier, M. Gataullin, Yu. Zalite, H. Anderhub, Z. F. Gong, S. N. Ganguli, B. Monteleoni, A. Degré, Y. Karyotakis, M. W. Gruenewald, J. D. Burger, T. Siedenburg, W. J. Metzger, S. Goldfarb, G. M. Bilei, B. Hartmann, I. Josa-Mutuberria, A. Hasan, J. Berdugo, Joel Goldstein, M. Rattaggi, G. Rahal-Callot, N. Raja, D. Haas, S. Braccini, E. J. Sanchez, J. M. You, M. N. Kienzle-Focacci, J.V. Allaby, A. Favara, I. H. Park, F. L. Linde, S. Pensotti, Valery Schegelsky, Antonino Zichichi, S. P. Ahlen, A. Csilling, Z. Z. Xu, C. H. Lin, F. Muheim, S. Patricelli, P. Zemp, Howard A. Stone, V. Pojidaev, H. Rykaczewski, Giovanni Organtini, H. Suter, Ia Iashvili, R. de Asmundis, I. Fisk, Pablo Garcia-Abia, Alain Hervé, G. Schwering, D. Hatzifotiadou, Laszlo Boldizsar, Gobinda Majumder, Roberto Battiston, H. Milcent, D. Kim, A. Bay, V. Koutsenko, L. Fredj, C. Palomares, W. Kittel, G. Marian, Gerjan Bobbink, G. S. Muanza, J. Ulbricht, Jean Fay, Carlo Civinini, Y. Zhou, G. Raven, An.A. Vorobyov, T. Paul, S. C. Tonwar, D. Boutigny, T. Moulik, M. Aguilar-Benitez, G. F. Susinno, Nicolas Produit, C. Furetta, Herwig Schopper, S. Vlachos, O. Adriani, H. Postema, Lucas Taylor, I. Clare, Mingshui Chen, V. Soulimov, J. Rodin, D. P. Stickland, F. Ziegler, Y. H. Chang, J. Gerald, R. Faccini, X. L. Wang, G. G.G. Massaro, M. G. Alviggi, G. Gratta, J. S. Kapustinsky, T. Niessen, M. Pauluzzi, L. Romero, K. Sudhakar, M. Fabre, Mingming Yang, F. C. Erné, L. J. Gutay, D. Ren, Alexei Klimentov, A. Lavorato, U. Becker, J. Shukla, M. Bourquin, K. Freudenreich, I. Duran, A. P. Colijn, Joachim Mnich, F. J. Eppling, L. W. Jones, S. M. Ting, W. Lu, R. van Gulik, Federico Cindolo, C. Maña, P. Extermann, Salvatore Mele, Christoph Schäfer, B. Z. Yang, I. C. Brock, H. Hofer, A. Robohm, K. L. Tung, W. C. van Hoek, Frank Filthaut, Thomas Ferguson, P. Rosselet, D. Ruschmeier, Peter Denes, Paolo Bagnaia, S. C. Blyth, Marco Meschini, D. Kirkby, Christopher George Tully, Wolfgang Lohmann, H. Vogt, B. Bertucci, S. C. Kim, F. Anselmo, Nicanor Colino, Zheng Wang, Zhenyu Zhang, M. E. Sarakinos, A. Gougas, P. Payat, C-Q. Li, V. K. Gupta, D. Pandoulas, W. J. Burger, Michael Dittmar, F. DeNotaristefani, R. Barillère, J. D. Swain, D. Peach, D. O. Prokofiev, Manas Maity, P. Berges, Steve Nahn, Jasper Kirkby, M. A. Falagan, A. J.W. van Mil, A. Nippe, Anna Katharina Kopp, Alexander Malinin, S. Easo, Kati Lassila-Perini, V. Plyaskin, A. Böhm, S. Sakar, M. T. Dova, An. Zalite, Maurizio Biasini, Marta Felcini, Francesco Becattini, Lamberto Luminari, Y. D. Oh, H. J. Yang, S. Wynhoff, R. C. Ball, Pierre Lecomte, Werner Lustermann, Charles Timmermans, A. C. Weber, G. Mirabelli, K. Lübelsmeyer, A. Buffini, Alessandra Doria, N. Scholz, S. R. Hou, M. Wadhwa, D. J. Schotanus, P. Molnar, H. F. Chen, D. Kamrad, G. Chiefari, S. Shevchenko, F. Behner, Andrea Baschirotto, M. Rescigno, Peter H. Fisher, Aleandro Nisati, Joseph Quartieri, O. Rind, G. Ambrosi, Roger Moore, Georgi Sultanov, T. S. Dai, R. A. Khan, V. P. Andreev, M. Chemarin, G. M. Chen, Aaron Dominguez, Felicitas Pauss, S. Rosier-Lees, P. Le Coultre, M. Basile, D. Mangeol, J. K. Kim, D. Luckey, D. Kiss, Helmut Vogel, Kajari Mazumdar, X. D. Cai, F. Cesaroni, M. Chamizo, Emilio Leonardi, R. Bock, D. Sciarrino, L. Baksay, F. Cotorobai, Z. A. Liu, A. Vorvolakos, J. G. Xu, Stefan Roth, J. M. Le Goff, N. Gheordanescu, J. A. Rubio, D.W. Schmitz, G. Pascale, P. de Jong, N. Shivarov, Robert Clare, Thomas Hebbeker, Paul Lecoq, R. W. Kraemer, M. Napolitano, S. Petrak, D. Duchesneau, H. S. Chen, L. Servoli, G. Landi, Simone Paoletti, A. J.M. Muijs, Manjit Kaur, C. Dionisi, W. G. Ma, J. Busenitz, P. G. Rancoita, Laboratoire d'Annecy de Physique des Particules (LAPP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire de Lyon (IPNL), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), CMS, Institut de Physique des 2 Infinis de Lyon (IP2I Lyon), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), L3, IHEF (IoP, FNWI), L3 (IHEF, IoP, FNWI), Acciarri, M., Adriani, O., Aguilar Benitez, M., Ahlen, S., Alcaraz, J., Alemanni, G., Allaby, J., Aloisio, Alberto, Alviggi, Mariagrazia, Ambrosi, G., Anderhub, H., Andreev, V. P., Angelescu, T., Anselmo, F., Arefiev, A., Azemoon, T., Aziz, T., Bagnaia, P., Baksay, L., Ball, R. C., Banerjee, S., Banicz, K., Barczyk, A., Barillere, R., Barone, L., Bartalini, P., Baschirotto, A., Basile, M., Battiston, R., Bay, A., Becattini, F., Becker, U., Behner, F., Berdugo, J., Berges, P., Bertucci, B., Betev, B. L., Bhattacharya, S., Biasini, M., Biland, A., Bilei, G. M., Blaising, J. J., Blyth, S. C., Bobbink, G. J., Bock, R., Bohm, A., Boldizsar, L., Borgia, B., Bourilkov, D., Bourquin, M., Boutigny, D., Braccini, S., Branson, J. G., Brigljevic, V., Brock, I. C., Buffini, A., Buijs, A., Burger, J. D., Burger, W. J., Busenitz, J., Cai, X. D., Campanelli, M., Capell, M., Romeo, G. C., Carlino, G., Cartacci, A. M., Casaus, J., Castellini, G., Cavallari, F., Cavallo, N., Cecchi, C., Cerrada, M., Cesaroni, F., Chamizo, M., Chang, Y. H., Chaturvedi, U. K., Chemarin, M., Chen, A., Chen, G., Chen, G. M., Chen, H. F., Chen, H. S., Chen, M., Chiefari, Giovanni, Chien, C. Y., Cifarelli, L., Cindolo, F., Civinini, C., Clare, I., Clare, R., Coignet, G., Colijn, A. P., Colino, N., Costantini, S., Cotorobai, F., B. d., La, Csilling, A., Dai, T. S., Alessandro, R. D., Asmundis, R. d., Degre, A., Deiters, K., Denes, P., Denotaristefani, F., Diemoz, M., Dierendonck, D. v., Lodovico, F. D., Dionisi, C., Dittmar, M., Dominguez, A., Doria, A., Dova, M. T., Drago, E., Duchesneau, D., Duinker, P., Duran, I., Easo, S., Mamouni, H. E., Engler, A., Eppling, F. J., Erne, F. C., Extermann, P., Fabre, M., Faccini, R., Falagan, M. A., Falciano, S., Favara, A., Fay, J., Fedin, O., Felcini, M., Ferguson, T., Ferroni, F., Fesefeldt, H., Fiandrini, E., Field, J. H., Filthaut, F., Fisher, P. H., Fisk, I., Forconi, G., Fredj, L., Freudenreich, K., Furetta, C., Galaktionov, Y., Ganguli, S. N., Garcia Abia, P., Gataullin, M., Gau, S. S., Gentile, S., Gerald, J., Gheordanescu, N., Giagu, S., Goldfarb, S., Goldstein, J., Gong, Z. F., Gougas, A., Gratta, G., Gruenewald, M. W., Gulik, R. v., Gupta, V. K., Gurtu, A., Gutay, L. J., Haas, D., Hartmann, B., Hasan, A., Hatzifotiadou, D., Hebbeker, T., Herve, A., Hidas, P., Hirschfelder, J., Van, W. C., Hofer, H., Hoorani, H., Hou, S. R., Hu, G., Iashvili, I., Jin, B. N., Jones, L. W., Jong, P. d., Josa Mutuberria, I., Kasser, A., Khan, R. A., Kamrad, D., Kapustinsky, J. S., Karyotakis, Y., Kaur, M., Kienzle Focacci, M. N., Kim, D., Kim, D. H., Kim, J. K., Kim, S. C., Kinnison, W. W., Kirkby, A., Kirkby, D., Kirkby, J., Kiss, D., Kittel, W., Klimentov, A., Konig, A. C., Kopp, A., Korolko, I., Koutsenko, V., Kraemer, R. W., Krenz, W., Kunin, A., Lacentre, P., P. L., De, Landi, G., Lapoint, C., Lassila Perini, K., Laurikainen, P., Lavorato, A., Lebeau, M., Lebedev, A., Lebrun, P., Lecomte, P., Lecoq, P., Coultre, P. L., Lee, H. J., Leggett, C., J. M., Le, Leiste, R., Leonardi, E., Levtchenko, P., Li, C., Lin, C. H., Lin, W. T., Linde, F. L., Lista, L., Liu, Z. A., Lohmann, W., Longo, E., Lu, W., Y. S., Lu, Lubelsmeyer, K., Luci, C., Luckey, D., Luminari, L., Lustermann, W., W. G., Ma, Maity, M., Majumder, G., Malgeri, L., Malinin, A., Mana, C., Mangeol, D., Marchesini, P., Marian, G., Marin, A., Martin, J. P., Marzano, F., G. G. G., Mazumdar, K., Mele, S., Merola, Leonardo, Meschini, M., Metzger, W. J., Der, M. v., Mi, Y., Migani, D., Mihul, A., A. J. W., Milcent, H., Mirabelli, G., Mnich, J., Molnar, P., Monteleoni, B., Moore, R., Moulik, T., Mount, R., Muanza, G. S., Muheim, F., A. J. M., Nahn, S., Napolitano, Marco, Nessi Tedaldi, F., Newman, H., Niessen, T., Nippe, A., Nisati, A., Nowak, H., Y. D., Oh, Organtini, G., Ostonen, R., Palomares, C., Pandoulas, D., Paoletti, S., Paolucci, P., Park, H. K., Park, I. H., Pascale, G., Passaleva, G., Patricelli, Sergio, Paul, T., Pauluzzi, M., Paus, C., Pauss, F., Peach, D., Pedace, M., Pei, Y. J., Pensotti, S., Perret Gallix, D., Petersen, B., Petrak, S., Pevsner, A., Piccolo, D., Pieri, M., Piroue, P. A., Pistolesi, E., Plyaskin, V., Pohl, M., Pojidaev, V., Postema, H., Pothier, J., Produit, N., Prokofiev, D., Quartieri, J., Rahal Callot, G., Raja, N., Rancoita, P. G., Rattaggi, M., Raven, G., Razis, P., Ren, D., Rescigno, M., Reucroft, S., Rhee, T. v., Riemann, S., Riles, K., Rind, O., Robohm, A., Rodin, J., Roe, B. P., Romero, L., Rosier Lees, S., Rosselet, P., Roth, S., Rubio, J. A., Ruschmeier, D., Rykaczewski, H., Sakar, S., Salicio, J., Sanchez, E., Sanders, M. P., Sarakinos, M. E., Sauvage, G., Schafer, C., Schegelsky, V., Schmidt Kaerst, S., Schmitz, D., Schneegans, M., Scholz, N., Schopper, H., Schotanus, D. J., Schwenke, J., Schwering, G., Sciacca, Crisostomo, Sciarrino, D., Servoli, L., Shevchenko, S., Shivarov, N., Shoutko, V., Shukla, J., Shumilov, E., Shvorob, A., Siedenburg, T., Son, D., Soulimov, V., Smith, B., Spillantini, P., Steuer, M., Stickland, D. P., Stone, H., Stoyanov, B., Straessner, A., Sudhakar, K., Sultanov, G., Sun, L. Z., Susinno, F. G., Suter, H., Swain, J. D., Tang, X. W., Tauscher, L., Taylor, L., Timmermans, C., S. C. C., Ting, S. M., Tonwar, S. C., Toth, J., Tully, C., Tung, K. L., Uchida, Y., Ulbricht, J., Valente, E., Vesztergombi, G., Vetlitsky, I., Viertel, G., Villa, S., Vivargent, M., Vlachos, S., Vogel, H., Vogt, H., Vorobiev, I., Vorobyov, A. A., Vorvolakos, A., Wadhwa, M., Wallraff, W., Wang, J. C., Wang, X. L., Wang, Z. M., Weber, A., S. X., Wu, Wynhoff, S., Xu, J., Z. Z., Xu, Yang, B. Z., Yang, C. G., Yang, H. J., Yang, M., J. B., Ye, Yeh, S. C., You, J. M., Zalite, A., Zalite, Y., Zemp, P., Zeng, Y., Zhang, Z. P., Zhou, B., Zhou, Y., Zhu, G. Y., Zhu, R. Y., Zichichi, A., Ziegler, F., and Zilizi, G.

Subjects
Physics, COLLISIONS, Nuclear and High Energy Physics, Particle physics, MUON DECAY, POLARIZATION, PAIR PRODUCTION, 010308 nuclear & particles physics, Electron–positron annihilation, 7. Clean energy, 01 natural sciences, Helicity, Spectral line, Nuclear physics, Pair production, Tau neutrino, 0103 physical sciences, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], Michel parameters, 010306 general physics, Particle Physics - Experiment, Charged current, Lepton
Abstract

Four of the Michel parameters and the average tau-neutrino helicity have been measured by analysing tan decay spectra in 147 pb(-1) of data collected by the L3 detector. The decays tau(-) --> e(-)nu(tau)(e), tau(-) --> mu(-)nu(tau)(mu), tau(-) --> pi(-)nu(tau), tau(-) --> rho(-)nu(tau) and their charge conjugates were considered. The results: rho = 0.762 +/- 0.035, eta = 0.27 +/- 0.14, xi = 0.70 +/- 0.16, xi delta = 0.70 +/- 0.11 and xi(h) = -1.032 +/- 0.031 are consistent with a V-A structure for the weak charged current and lepton universality, (C) 1998 Elsevier Science B.V. All rights reserved.

Published
1998

22. Measurement of the Michel parameters and the average tau neutrino helicity from tau decays in e(+)e(-)->tau(+)tau(-)

Author

Dai-Sik Kim, G. Landi, B. Monteleoni, S. X. Wu, F. Sticozzi, D. DiBitonto, M. Steuer, J. S. Lee, K. Banicz, T. Siedenburg, Y. G. Kim, Y. H. Chang, George Alverson, M. Schneegans, J. S. Kapustinsky, Bryan R. Smith, B. L. Betev, D. Perret-Gallix, Igor Vorobiev, K. Sudhakar, P. Levtchenko, Panos A Razis, M. von der Mey, Howard A. Stone, F. Tonisch, Simone Paoletti, Suchandra Dutta, C. Lapoint, J. B. Ye, A. C. Weber, Peter H. Fisher, O. Toker, Sc Yeh, L. Romero, Roberto Castello, Z. A. Liu, A. Vorvolakos, X. Y. Yao, J. G. Xu, M. W. Gruenewald, I. Josa-Mutuberria, J. Rodin, Manjit Kaur, A. Straessner, Luca Lista, D. Fernandez, Y. Karyotakis, J. Berdugo, Juven Wang, R. Barillère, E. J. Sanchez, Wt Lin, M. Bourquin, K. Strauch, M. Lenti, Stefan Roth, Francesca Cavallari, C. Leggett, Sabine Riemann, Zheng Wang, J. P. Martin, Tariq Aziz, Joachim Mnich, A. Robohm, J. M. Le Goff, N. Gheordanescu, O. Rind, G. Mirabelli, G. Y. Zhu, E. Shumilov, S. Pensotti, Valery Schegelsky, Antonino Zichichi, H. Anderhub, V. Shoutko, J. C. Sens, Jasper Kirkby, M. Sassowsky, A. J.W. van Mil, H. Rykaczewski, Giovanni Organtini, B. C. Riemers, A. Adam, Zhenyu Zhang, G. Forconi, L. J. Gutay, U. Becker, K. Lübelsmeyer, Crisostomo Sciacca, Jozsef Toth, R. Völkert, M. Tonutti, Mingshui Chen, S. Easo, Kati Lassila-Perini, V. Plyaskin, P. Extermann, Salvatore Mele, Christoph Schäfer, B. Z. Yang, H. Hofer, K. L. Tung, J. Gerald, R. Faccini, X. L. Wang, G. G.G. Massaro, Attilio Santocchia, Dimitri Bourilkov, I. Duran, M. Pauluzzi, P. Spillantini, S. P. Ahlen, P. Zemp, Jean Fay, F. J. Rodriguez, S. Reucroft, D. Boutigny, M. T. Choi, R. de Asmundis, Francesca Nessi-Tedaldi, M. T. Dova, A. Köngeter, Aaron Dominguez, E. Fiandrini, J. A. Rubio, F. Cesaroni, M. Chamizo, B. Alpat, C-Q. Li, Emilio Leonardi, D. Ren, Felicitas Pauss, F. J. Eppling, L. W. Jones, M. E. Sarakinos, J. D. Burger, S. S. Gau, H. O. Cohn, J. Shukla, G. Rahal-Callot, S. M. Ting, D. Pandoulas, V. K. Gupta, F. Muheim, Nicolas Produit, L. Ludovic, S. Rosier-Lees, P. Le Coultre, M. Basile, An.A. Vorobyov, A. P. Colijn, G. Sauvage, R. Bock, D. Sciarrino, S. Ro, F. DeNotaristefani, K. Hangarter, K. Schultze, J. K. Kim, Giovanni Ambrosi, A. Arefiev, P. Ladron de Guevara, O. Adriani, Yu. Efremenko, D. Luckey, H. Suter, R. Mount, Nicola Cavallo, S. C. Blyth, Marco Meschini, H. K. Park, Michael Dittmar, Lucas Taylor, V. Soulimov, L. Baksay, Reinhard W. Schulte, F. Cotorobai, P. G. Rancoita, Harvey B Newman, A. Macchiolo, M. G. Alviggi, E. Brambilla, Roger Moore, B. N. Jin, H. Nowak, D. Kirkby, Y. Zhou, G. Castellini, A. Gougas, Georgi Sultanov, T. S. Dai, R. A. Khan, K. Riles, T. Angelescu, E. Lieb, F. Marzano, Yu. Galaktionov, G. Coignet, W. Krenz, J. Casaus, Yu. Kamyshkov, Z. F. Gong, A. M. Cartacci, R. Raghavan, V. P. Andreev, M. Vivargent, J. Alcaraz, Manas Maity, P. Berges, Steve Nahn, Roberto Battiston, A. C. König, M. Chemarin, G. M. Chen, W. Wallraff, Gerjan Bobbink, B. Borgia, C. G. Yang, J. Ulbricht, Y. J. Pei, M. Rescigno, P. Bartalini, H. Kuijten, S. Banerjee, Zp Zhang, Christopher George Tully, D. P. Stickland, D. Antreasyan, M. N. Kienzle-Focacci, G. Gratta, A. Buijs, J. D. Swain, A. Chan, H. De Boeck, B. Schoeneich, I. Clare, P. Kapinos, Samuel C.C. Ting, P. Duinker, A. Tsaregorodtsev, Konrad Deiters, Alberto Aloisio, A. Ricker, J. P. Ernenwein, A. Mihul, G. Alemanni, B. Lindemann, I. Korolko, Simonetta Gentile, Marco Pieri, P. Rosselet, A. Klimentov, Egidio Longo, H. Tuchscherer, W. J. Burger, K. Y. Lee, Andre Sopczak, Joel Goldstein, C. Zaccardelli, Wolfgang Lohmann, H. Vogt, M. Möller, H. Janssen, Kenneth Francis Read, Y. F. Wang, Pierluigi Paolucci, Luisa Cifarelli, B. Bertucci, S. C. Kim, W. W. Kinnison, H. F. Chen, A. Buytenhuijs, M. M. Ilyas, X. W. Tang, P. A. Piroué, A. Pevsner, B. De La Cruz, P. de Jong, Nicanor Colino, A. Böhm, G. Hu, B. Zhou, A. Favara, G. Chiefari, S. Shevchenko, W. Lu, Federico Cindolo, F. Behner, Maurizio Biasini, Speranza Falciano, Z. Z. Xu, Andrea Baschirotto, Raffaello D'Alessandro, Alessandra Doria, H. El Mamouni, S. Mangla, S. Costantini, Marta Felcini, F. Di Lodovico, D.W. Schmitz, G. Pascale, A. Lebedev, Dong-Chul Son, G. Schwering, T. Kramer, G. F. Susinno, Leonardo Merola, Francesco Becattini, V. Pojidaev, A. Boucham, N. Scholz, J. J. Blaising, Stefano Giagu, L. Tauscher, J. C. Pinto, C. Dionisi, N. Shivarov, Claudio Luci, S. C. Tonwar, W. C. van Hoek, Frank Filthaut, Alain Hervé, S. R. Hou, M. Wadhwa, D. J. Schotanus, T. Azemoon, Gobinda Majumder, Robert Clare, Vincenzo Innocente, Thomas Ferguson, A. Bay, W. G. Ma, T. Paul, W. Kittel, Thomas Hebbeker, Paul Lecoq, R. W. Kraemer, Carlo Civinini, D. Peach, S. Wynhoff, Marcos Cerrada, Y. Mi, I. Vetlitsky, W. van Rossum, A. Nippe, Alexander Malinin, G. Raven, M. Napolitano, S. Petrak, Adrian Biland, E. Nagy, M. Aguilar-Benitez, D. Duchesneau, H. S. Chen, Kajari Mazumdar, Herwig Schopper, L. Servoli, S. Müller, H. Postema, Xd Cai, An. Zalite, M. Fabre, A. Engler, M. Capell, H. S. Fesefeldt, E. Pistolesi, L. Z. Sun, G. Passaleva, G. M. Bilei, J.V. Allaby, S. Patricelli, A. Kunin, Hafeez R Hoorani, Lamberto Luminari, L. Fredj, R. C. Ball, Pierre Lecomte, W. J. Metzger, Werner Lustermann, S. Goldfarb, EL Linde, Peter Denes, Paolo Bagnaia, S. Röhner, F. Wittgenstein, J. Busenitz, E. Drago, R. Ostonen, A. Marin, J. M. You, M. Caria, A. Koulbardis, V. Koutsenko, I. Dorne, U. K. Chaturvedi, Y. S. Lu, J. H. Field, C. Y. Chien, A. Kirkby, L. Malgeri, B. Stoyanov, S. Schmidt-Kaerst, G. Cara Romeo, B. P. Roe, C. Cecchi, Subir Sarkar, A. Bujak, M. Pohl, A. Kasser, J. G. Branson, Davide Piccolo, S. N. Ganguli, A. Degré, M. Rattaggi, M. Lebeau, Ren-Yuan Zhu, Luciano Barone, T. van Rhee, A. Gurtu, V. Commichau, B. Hartmann, C. Furetta, A. Hasan, P. Lebrun, M. Acciarri, Guo-Ming Chen, U. Uwer, A. Chen, D. van Dierendonck, J. Salicio, M. Campanelli, Marcella Diemoz, F. Ferroni, Y. Zeng, F. C. Erné, P. Schmitz, K. Freudenreich, C. Maña, I. C. Brock, P. Marchesini, V. Brigljevic, R. T. Van de Walle, E. Valente, D. McNally, G. Viertel, Hans J. Vogel, S. Morganti, J. Schwenke, Gianpaolo Carlino, R. Leiste, Christoph Paus, Acciarri, M., Adam, A., Adriani, O., Aguilarbenitez, M., Ahlen, S., Alpat, B., Alcaraz, J., Alemanni, G., Allaby, J., Aloisio, Alberto, Alverson, G., Alviggi, Mariagrazia, Ambrosi, G., Anderhub, H., Andreev, V. P., Angelescu, T., Antreasyan, D., Arefiev, A., Azemoon, T., Aziz, T., Bagnaia, P., Baksay, L., Ball, R. C., Banerjee, S., Banicz, K., Barillere, R., Barone, L., Bartalini, P., Baschirotto, A., Basile, M., Battiston, R., Bay, A., Becattini, F., Becker, U., Behner, F., Berdugo, J., Berges, P., Bertucci, B., Betev, B. L., Biasini, M., Biland, A., Bilei, G. M., Blaising, J. J., Blyth, S. C., Bobbink, G. J., Bock, R., Bohm, A., Borgia, B., Boucham, A., Bourilkov, D., Bourquin, M., Boutigny, D., Brambilla, E., Branson, J. G., Brigljevic, V., Brock, I. C., Buijs, A., Bujak, A., Burger, J. D., Burger, W. J., Busenitz, J., Buytenhuijs, A., Cai, X. D., Campanelli, M., Capell, M., Romeo, G. C., Caria, M., Carlino, G., Cartacci, A. M., Casaus, J., Castellini, G., Castello, R., Cavallari, F., Cavallo, N., Cecchi, C., Cerrada, M., Cesaroni, F., Chamizo, M., Chan, A., Chang, Y. H., Chaturvedi, U. K., Chemarin, M., Chen, A., Chen, G., Chen, G. M., Chen, H. F., Chen, H. S., Chen, M., Chiefari, Giovanni, Chien, C. Y., Choi, M. T., Cifarelli, L., Cindolo, F., Civinini, C., Clare, I., Clare, R., Cohn, H. O., Coignet, G., Colijn, A. P., Colino, N., Commichau, V., Costantini, S., Cotorobai, F., Delacruz, B., Dai, T. S., Dalessandro, R., Deasmundis, R., Deboeck, H., Degre, A., Deiters, K., Denes, P., Denotaristefani, F., Dibitonto, D., Diemoz, M., Vandierendonck, D., Dilodovico, F., Dionisi, C., Dittmar, M., Dominguez, A., Doria, A., Dorne, I., Dova, M. T., Drago, E., Duchesneau, D., Duinker, P., Duran, I., Dutta, S., Easo, S., Efremenko, Y., Elmamouni, H., Engler, A., Eppling, F. J., Erne, F. C., Ernenwein, J. P., Extermann, P., Fabre, M., Faccini, R., Falciano, S., Favara, A., Fay, J., Felcini, M., Furetta, C., Ferguson, T., Fernandez, D., Ferroni, F., Fesefeldt, H., Fiandrini, E., Field, J. H., Filthaut, F., Fisher, P. H., Forconi, G., Fredj, L., Freudenreich, K., Galaktionov, Y., Ganguli, S. N., Gau, S. S., Gentile, S., Gerald, J., Gheordanescu, N., Giagu, S., Goldfarb, S., Goldstein, J., Gong, Z. F., Gougas, A., Gratta, G., Gruenewald, M. W., Gupta, V. K., Gurtu, A., Gutay, L. J., Hangarter, K., Hartmann, B., Hasan, A., Hebbeker, T., Herve, A., Vanhoek, W. C., Hofer, H., Hoorani, H., Hou, S. R., Hu, G., Ilyas, M. M., Innocente, V., Janssen, H., Jin, B. N., Jones, L. W., Dejong, P., Josamutuberria, I., Kasser, A., Khan, R. A., Kamyshkov, Y., Kapinos, P., Kapustinsky, J. S., Karyotakis, Y., Kaur, M., Kienzlefocacci, M. N., Kim, D., Kim, J. K., Kim, S. C., Kim, Y. G., Kinnison, W. W., Kirkby, A., Kirkby, D., Kirkby, J., Kittel, W., Klimentov, A., Konig, A. C., Kongeter, A., Korolko, I., Koutsenko, V., Koulbardis, A., Kraemer, R. W., Kramer, T., Krenz, W., Kuijten, H., Kunin, A., Deguevara, P. L., Landi, G., Lapoint, C., Lassilaperini, K., Lebeau, M., Lebedev, A., Lebrun, P., Lecomte, P., Lecoultre, P., Lee, J. S., Lee, K. Y., Leggett, C., Legoff, J. M., Leiste, R., Lenti, M., Leonardi, E., Levtchenko, P., Li, C., Lieb, E., Lin, W. T., Linde, F. L., Lindemann, B., Lista, L., Ziu, Z. A., Lohmann, W., Longo, E., Lu, W., Y. S., Lu, Lubelsmeyer, K., Luci, C., Luckey, D., Ludovici, L., Luminari, L., Lustermann, W., W. G., Ma, Macchiolo, A., Maity, M., Majumder, G., Malgeri, L., Malinin, A., Mana, C., Mangla, S., Marchesini, P., Marin, A., Martin, J. P., Marzano, F., G. G. G., Mazumdar, K., Mcnally, D., Mele, S., Merola, Leonardo, Meschini, M., Metzger, W. J., Vondermey, M., Mi, Y., Mihul, A., A. J. W., Mirabelli, G., Mnich, J., Moller, M., Monteleoni, B., Moore, R., Morganti, S., Mount, R., Muller, S., Muheim, F., Nagy, E., Nahn, S., Napolitano, Marco, Nessitedaldi, F., Newman, H., Nippe, A., Nowak, H., Organtini, G., Ostonen, R., Pandoulas, D., Paoletti, S., Paolucci, P., Park, H. K., Pascale, G., Passaleva, G., Patricelli, Sergio, Paul, T., Pauluzzi, M., Paus, C., Pauss, F., Peach, D., Pei, Y. J., Pensotti, S., Perretgallix, D., Petrak, S., Pevsner, A., Piccolo, D., Pieri, M., Pinto, J. C., Piroue, P. A., Pistolesi, E., Plyaskin, V., Pohl, M., Pojidaev, V., Postema, H., Produit, N., Raghavan, R., Rahalcallot, G., Rancoita, P. G., Rattaggi, M., Raven, G., Razis, P., Read, K., Ren, D., Rescigno, M., Reucroft, S., Vanrhee, T., Ricker, A., Riemann, S., Riemers, B. C., Riles, K., Rind, O., Ro, S., Robohm, A., Rodin, J., Rodriguez, F. J., Roe, B. P., Rohner, S., Romero, L., Rosierlees, S., Rosselet, P., Vanrossum, V., Roth, S., Rubio, J. A., Rykaczewski, H., Salicio, J., Sanchez, E., Santocchia, A., Sarakinos, M. E., Sarkar, S., Sassowsky, M., Sauvage, G., Schafer, C., Schegelsky, V., Schmidtkaerst, S., Schmitz, D., Schmitz, P., Schneegans, M., Schoeneich, B., Scholz, N., Schopper, H., Schotanus, D. J., Schulte, R., Schultze, K., Schwenke, J., Schwering, G., Sciacca, Crisostomo, Sciarrino, D., Sens, J. C., Servoli, L., Shevchenko, S., Shivarov, N., Shoutko, V., Shukla, J., Shumilov, E., Siedenburg, T., Son, D., Sopczak, A., Soulimov, V., Smith, B., Spillantini, P., Steuer, M., Stickland, D. P., Sticozzi, F., Stone, H., Stoyanov, B., Straessner, A., Strauch, K., Sudhakar, K., Sultanov, G., Sun, L. Z., Susinno, G. F., Suter, H., Swain, J. D., Tang, X. W., Taucher, L., Taylor, L., S. C. C., Ting, S. M., Toker, O., Tonisch, F., Tonutti, M., Tonwar, S. C., Toth, J., Tsaregorodtsev, A., Tully, C., Tuchscherer, H., Tung, K. L., Ulbricht, J., Uwer, U., Valente, E., Vandewalle, R. T., Vetlitsky, I., Viertel, G., Vivargent, M., Volkert, R., Vogel, H., Vogt, H., Vorobiev, I., Vorobyov, A. A., Vorvolakos, A., Wadhwa, M., Wallraff, W., Wang, J. C., Wang, X. L., Wang, Y. F., Wang, Z. M., Weber, A., Wittgenstein, F., S. X., Wu, Wynhoff, S., Xu, J., Z. Z., Xu, Yang, B. Z., Yang, C. G., Yao, X. Y., J. B., Ye, Yeh, S. C., You, J. M., Zaccardelli, C., Zalite, A., Zemp, P., Zeng, Y., Zhang, Z., Zhang, Z. P., Zhou, B., Zhou, Y., Zhu, G. Y., Zhu, R. Y., and Zichichi, A.

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, MUON DECAY, POLARIZATION, leptons, Electron–positron annihilation, Hadron, Física, Helicity, Spectral line, Nuclear physics, hadrons, ASYMMETRY, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Michel parameters, Neutrino, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Ciencias Exactas, Charged current, Lepton
Abstract

The Michel parameters ϱ, η, ξ, and ξδ, the chirality parameter ξh and the τ polarization Pτ are measured using 32012 τ pair decays. Their values are extracted from the energy spectra of leptons and hadrons in τ− → l−νlντ and τ− → π−ντ decays, the energy and decay angular distributions in τ− → ϱ−ντ decays, and the correlations in the energy spectra and angular distributions of the decay products. Assuming universality in leptonic and semileptonic τ decays, the results are ϱ = 0.794±0.039±0.031, η = 0.25±0.17±0.11, ξ = 0.94±0.21±0.07, ξδ = 0.81±0.14±0.06, ξh = −0.970±0.053±0.011, and Pτ = −0.154±0.018±0.012. The measurement is in agreement with the V-A hypothesis for the weak charged current., Facultad de Ciencias Exactas

Published
1996

23. A Novel Experiment to Search for the Decay μ→ eee

Author

Rohin Narayan, Andŕe Scḧoning, and Sebastian Bachmann

Subjects
Physics, Particle physics, Thin layers, Abstract design, Silicon, Physics::Instrumentation and Detectors, Detector, High Energy Physics::Phenomenology, chemistry.chemical_element, muon decay, lepton flavor, Physics and Astronomy(all), Nuclear physics, chemistry, pixel sensor, MAPS, LFV, High Energy Physics::Experiment, Sensitivity (control systems), Lepton
Abstract

Design studies for an experiment searching for the lepton flavor violating decay μ→ eee are presented. The detector concept is based on thin layers of silicon sensors with fast readout. The aim of this experiment is to reach a sensitivity of B(μ→ eee) ≈ 10 -16 corresponding to an improvement by a factor 10000 compared to previous experiments.

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