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The ceiling and walls of the Low Background Facility at the Soudan Underground Laboratory are lined proportional tubes which form a 30 m × 17 m ×12 m muon tracker. The data acquisition records GPS-generated time stamps along with position information. The tracker is a refurbished version of the Soudan 2 proton-decay muon veto shield. It can now be used in conjunction with other experiments housed within its walls. Particularly interesting is the possible measurement of cavern muons coincident with high-energy neutron detections in the Neutron Multiplicity Meter (NMM), a 4-tonne gadolinium-loaded water Cherenkov neutron capture detector atop a 20-kilotonne lead target. Here we cover the ability of the shield and co-located detectors to achieve coincident timing resolutions of about 1 microsecond via GPS-synchronized absolute timing electronics. The usage of such technology for constraining muon-neutron correlations underground is discussed. [ABSTRACT FROM AUTHOR]

The MEG experiment is searching for the lepton-flavor violating muon decay, μ+→e+γ. We utilize the positive muon beam provided at Paul Scherrer Institute with an intensity of 3×107Hz as a muon source, a liquid-xenon detector to identify the signal gamma, and a positron spectrometer with gradient magnetic field to measure the signal positron. We set the 90% C.L. upper limit of the decay branching ratio of μ+→e+γ. using data taken in 2009 and 2010. This is the world's most stringent limit of the μ+→e+γ. branching ratio. [ABSTRACT FROM AUTHOR]

Advances in detector techniques, coupled to improved secondary beams at meson factories, have brought about major improvements in the experimental precision of pion and muon rare decay measurements over the last decade. We review recent results, focusing in particular on: π+→π0e+ν (pion beta, πe3, or πβ decay), and π+→e+νγ (radiative pion decay, πe2γ or RPD), as well as the radiative muon decay, μ+→e+ννγ (radiative muon decay, RMD), and their theoretical implications. The PIBETA experiment, with measurements completed at PSI, has brought about an order of magnitude improvement, or better, in the branching ratio precision for these processes. The successor PEN experiment, currently under way at PSI, aims to improve the precision of the π+→e+ν(πe2) decay branching ratio by about an order of magnitude. Each of these results contributes toward a better understanding of the limits on certain particles and interactions not included in the standard model, or toward improving the precision of chiral lagrangian and pion structure parameters. We finally review the near-term prospects for their further improvement. [ABSTRACT FROM AUTHOR]

Based on the 110M ψ(3686) data sample which has been collected by BESIII at year 2009, many χcJ decay modes have been measured, such as χcJ → π0π0, χcJ → ηη, χcJ → VV, χcJ → γV, and so on. Results presented in this document are preliminary. [ABSTRACT FROM AUTHOR]

After a decade of design, construction, improvement, data-taking, simulation, and analysis, the TRIUMF Weak Interaction Symmetry Test (TWIST) muon decay parameter measurements are nearly complete. While the final results are yet to be unblinded, a preliminary estimate of the final precision is available. The goal of an order-of-magnitude improvement on pre-TWIST precisions for the ρ, δ, and Pμξ decay parameters has essentially been achieved, making possible some tighter constraints on parameters of the left-right symmetric extension to the standard model as well as the fundamental coupling constants of the muon. [ABSTRACT FROM AUTHOR]

The TRIUMF Weak Interaction Symmetry Test (TWIST) has now completed its data collection period. These data represent the world’s most precise measurement of the muon decay spectrum. The experiment expects to meet its ambitious goals of an order of magnitude improvement over pre-TWIST results for the muon decay parameters ρ, δ and Pμπξ. Our most recent published results are presented. The measures that have been taken to reduce the systematic uncertainties for the upcoming final result are described. [ABSTRACT FROM AUTHOR]

The MEG experiment started a search for a lepton violating (LFV) muon decay, μ+→e+γ, at Paul Scherrer Institut(PSI) in Switzerland. The LFV muon decay does not occur in the standard model, while new theories, such as super symmetric grand unified theory and seesaw model of neutrinos, predict observable branching ratio just below the current upper limit (1.2×10-12). MEG is designed to improve the sensitivity by two orders of magnitude. In this article, the system of the MEG experiment and its data taking in 2008 are described. [ABSTRACT FROM AUTHOR]

Muon-Spin Rotation (μSR) is an experimental technique similar to Nuclear Magnetic Resonance (NMR). μSR data are recorded as a set of time-series histograms of muon-decay events. Both μSR and NMR regularly produce signals that are overlapping, weak and/or broadened in frequency space. These μSR histograms are usually analyzed by curve fitting and Fourier transformations. However, several NMR and μSR groups have developed Maximum Entropy (MaxEnt, ME) applications to improve the sensitivity of the time series analysis. We have focused on the application of the ME-Burg algorithm. The optimal number of autoregression coefficients is between N/3 and N/5 where N is the total number of data points. Selected results for simulated data and real data ME-μSR applications are reported. Most of our μSR work is for cuprate superconductor studies. The strength of the ME-Burg algorithm is fully used, as there is a clear relationship between the muon-spin signal S(i) at any time i and the signals S(i-k) at earlier times. ME-Burg has the major advantage of producing in the frequency transform only structure for which sufficient statistical evidence is present. [ABSTRACT FROM AUTHOR]

The transverse polarization components of the e+ from the decay of polarized μ+ have been measured at the Paul Scherrer Institute by annihilating in flight the decay positrons with polarized electrons. The use of a stroboscopic method greatly reduces systematic errors. The energy dependence of the transverse polarization component PT1, which lies in the plane defined by muon spin and positron momentum, yields the low energy parameter η = (-2 ± 8) × 10-3 and thus an improved model-independent value of the Fermi coupling constant. For the transverse polarization PT2, averaged over the positron energy, we obtain = (-4 ± 8) × 10-3. This improves the previous limit on the violation of time invariance in muon decay by a factor of three. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

With the discovery of neutrino masses, it is clear that lepton-flavor is no longer a conserved quantity. This means that charged-lepton flavor violating processes (CLFV) including rare muon and tau decays (e.g. μ → eγ, τ → μe+e-) are, in principle, observable. I review some phenomenological aspects of CLFV (concentrating on rare muon processes) and briefly discuss a few Standard Model extensions that predict a “large” rate for CLFV. In several of these extensions there are deep relations between the physics that generates neutrino masses and mixing and CLFV. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The phsysics motivations for this experiment are presented. A general description of the experiment and of the R&D status of each sub-detector is given. The sensitivity of the experiment and its time schedule are finally presented. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The construction of the PRISM-FFAG ring has been started. It would be completed by the end of JFY 2005. Then phase-rotation, muon acceleration and muon ionization cooling could be studied using the ring. This paper describes the present designs of the RF system and the magnet system of PRISM-FFAG and its construction schedule. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

An analytical model is developed to describe the longitudinal phase space of a hybrid beam of pions and decay muons. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The exclusive photoproduction of J/ψ mesons, γp→J/ψp, has been studied in ep collisions with the ZEUS and H1 detectors at HERA using the e[sup +]e[sup -] and μ[sup +]μ[sup -] decay modes. The total cross section has been measured as a function of the photon-proton center-of-mass energy, W, in the kinematic range 20≤W≤290 GeV for ZEUS and 26≤W≤285 GeV for H1. The differential cross section dσ/dt, where t is the squared four-momentum at the proton vertex, has been measured. The Pomeron trajectory has been determined. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present here the latest result on the lepton flavor violating decay μ → eγ based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institute in 2009 and 2010. The likelihood analysis of the combined data sample, corresponding to a total of 1.8×1014 muon decays, provides a 90% C.L. upper limit of 2.4×10-12 on the μ → eγ branching ratio, constituting the most stringent limit on the existence of this decay to date. [ABSTRACT FROM AUTHOR]

Building on the rare pion and muon decay results of the PIBETA experiment, the PEN collaboration has undertaken a precise measurement of Bπe2≡Re/μπ, the π+ → e+ν(γ) decay branching ratio, at the Paul Scherrer Institute, to reduce the present 40× experimental precision lag behind theory to ∼6 - 7×. Because of large helicity suppression, Re/μπ is uniquely sensitive to contributions from non-(V - A) physics, making this decay a particularly suitable subject of study. Even at current precision, the experimental value of Bπe2 provides the most accurate test of lepton universality available. During runs in 2008-10, PEN has accumulated over 2 × 107 πe2 events; a comprehensive maximum-likelihood analysis is currently under way. The new data will also lead to improved precision of the earlier PIBETA results on radiative π and μ decays. [ABSTRACT FROM AUTHOR]

Design studies, for accelerator modules based on an injector cyclotron and a superconducting ring cyclotron able to accelerate H2+ molecules, are presented. H2+ molecules are stripped by a foil creating a proton beam, with a maximum energy of 800 MeV and a beam power of 8 MW (CW). This beam would be sent to a beam dump where neutrinos would be produced from pion and muon decays at rest for the Decay At rest Experiment for δCP At the Laboratory for Underground Science - DAEδALUS. We discuss the advantage of H2+ molecules for acceleration and present precise beam dynamics simulations w.r.t. extraction and beam losses. In general, beam losses are one of the most challenging aspects of such a high power cyclotron design and must be addressed very early on in the design. We also address H2+ dissociation and the stripping process, two other characteristic challenges of the DAEδALUS design. [ABSTRACT FROM AUTHOR]

It is well established that a Near Detector positioned within 1 km of the muon decay pipe at a Neutrino Factory is essential for a true determination of the neutrino flux, necessary for the neutrino oscillation signal. Here we present a method for the the extraction of the oscillation probability parameters using the Near Detector, in combination with a long baseline Far Detector and demonstrate that by using this method, the sensitivity to oscillation parameters is maintained down values of θ13 one order of magnitude lower than the current world limit. [ABSTRACT FROM AUTHOR]

Cryogenic key technologies have been developed for the muon rare decay experiment (MEG) at the Paul Scherrer Institute, Switzerland. These technologies are the high power pulse tube cryocooler for precise temperature and pressure control of liquid xenon in the calorimeter, a purification system with a cryogenic liquid pump and a cryogenic dewar with 1000 L storage capacity. The paper describes the general concepts and the first test results of each technology. All the results imply a promising performance for the coming MEG experiment. [ABSTRACT FROM AUTHOR]

Muon Science laboratory at Material Life Science Facility is now under construction in J-PARC, where, four types of muon channels are planed to install. Present status of the superconducting and surface muon channel is briefly reported. [ABSTRACT FROM AUTHOR]

We derive model-independent constraints on chirality-changing terms in the muon decay Lagrangian using limits on neutrino mass. We consider all dimension-six operators invariant under the gauge symmetry of the Standard Model which contribute to either a Dirac neutrino mass or muon decay. Taking an upper limit on neutrino mass of 1eV, we derive limits on the contributions of chirality-changing operators to the Michel parameters four orders of magnitude tighter than the current experimental constraints. We also identify two operators which, due to their flavor structure, are not constrained by neutrino mass. If near-future experiments find contributions to muon decay from these operators, it could indicate interesting flavor structure in physics beyond the SM. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We performed a precision measurement of the positive muon lifetime at the RIKEN-RAL muon facility. A strong pulsed-muon beam was for the first time used to improve a data accumulation rate of the muon decay events. The most dominant systematic error in the present experiment was a count-loss effect caused by pile-up signals in a high rate data acquisition. To reduce this effect muon decay positrons were observed by using a multi-segmented detectors and residual count-loss events are corrected numerically in the off-line analysis. We obtain a preliminary result of the muon lifetime by this novel method. Further analysis is in progress. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The transverse polarization components of the positrons from the decay of polarized muons have been measured at the Paul Scherrer Institute by annihilating in flight the decay positrons with polarized electrons. The use of a stroboscopic method greatly reduces systematic errors. The energy dependence of the transverse polarization component PT1, which lies in the plane defined by muon spin and positron momentum, yields the low energy parameter η = (-2 ± 8) × 10 -3 and thus an improved model-independent value of the Fermi coupling constant. For the transverse polarization PT2, averaged over the positron energy, we obtain = (-4 ± 8) × 10-3. This improves the previous limit on the violation of time invariance in muon decay by a factor of three. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

As a test of the Standard Model in a purely leptonic decay interaction, the TWIST experiment is designed to precisely measure Michel parameters. TWIST has just published its first measurements of Michel parameters ρ and δ from the 2002 data, with a precision 2 to 3 times better than the previous results. The physics analyses of the 2004 data, taken under better conditions, are in progress. Some reductions in the systematic uncertainties have been achieved. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Muon decay allows for the most precise experiments in testing the Standard Model of electroweak interactions. An experiment aimed to measure one of the Michel parameters with an improvement of 70 is described. A production run is foreseen for summer 2000. [ABSTRACT FROM AUTHOR]

In the standard model (SM) of electroweak interactions the positron from the decay of polarized positive muons is mainly longitudinal polarized. However the model also predicts a small transverse polarization component P[sub T1], which lies in the plane spanned by muon-spin and positron momentum. Interference with additional scalar couplings, as they appear in supersymmetric extensions of the SM, would result in substantial values for P[sub T1] as well as in a non zero value of the transverse component P[sub T2] which is perpendicular to the above mentioned plane. A non zero component P[sub T2], proportional to the imaginary part ofa possible scalar coupling, would be the first observation of time reversal violation in a purely leptonic decay. Measuring P[sub T1], which is proportional to the real part, amounts to a model independent determination of the Fermi coupling constant. The μ[sub PT] experiment at the Paul Scherrer Institute will improve the current experimental limits P[sub T1] = (16 ± 22) · 10[sup -3], P[sub T2] - (7 ± 23) - 10[sup -3] by almost one order of magnitude. Besides a description of the experiment detailed results from the last run in August 1999 will be given. [ABSTRACT FROM AUTHOR]

Muon spin relaxation measurements in the III–V nitrides have provided data on the motion of each of the three charge-states of the muonium ‘isotope’ of hydrogen. Motional parameters are established for Mu+ in InN, Mu0 in AlN, and Mu- in GaN, with qualitative results in the other materials. Both Mu+ and Mu0 show tunneling below 300 K and thermal diffusion at higher temperatures leading to interactions with other impurities or extended defects. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]