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19 results on '"Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany"'

1. Investigation of the Exclusive 3He(e, e’pn) 1H Reaction

Author

Kepler Centre for Astro and Particle Physics, Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany, Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany, Nikhef, P.O. Box 41882, 1009 DB Amsterdam, The Netherlands, Nikhef, P.O. Box 41882, 1009 DB Amsterdam, The Netherlands, Department of Physics, VU-university, Amsterdam, The Netherlands, Department of Physics, University of Zagreb, Zagreb, Croatia, M. Smoluchowski Institute of Physics, Jagiellonian University, PL-30059 Kraków, Poland, Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany, Department of Physics, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan, Institute for Advanced Simulation, Institut für Kernphysik, and Jülich Center for Hadron Physics, Forschungszentrum Jülich, D-52425 Jülich, Germany, Institute Jožef Stefan, University of Ljubljana, Ljubljana, Slovenia, Middleton, D. G., Annand, J. R. M., Antelo, M. Ases, Ayerbe, C., Barneo, P., Baumann, D., Bermuth, J., Bernauer, J., Blok, H. P., Böhm, R., Bosnar, D., Ding, M., Distler, M. O., Friedrich, J., García, Llongo J., Glazier, D. I., Golak, J., Glöckle, W., Grabmayr, P., Hehl, T., Heim, J., Hesselink, W. H. A., Jans, E., Kamada, H., Jover, Mañas G., Kohl, M., Lapikás, L., MacGregor, I. J. D., Martin, I., McGeorge, J. C., Merkel, H., Merle, P., Monstad, K., Moschini, F., Müller, U., Nogga, A., Pérez-Benito, R., Pospischil, Th., Potokar, M., Rosner, G., Seimetz, M., Skibiński, R., de, Vries H., Walcher, Th., Watts, D. P., Weinriefer, M., Weiss, M., Witała, H., Zihlmann, B., Kepler Centre for Astro and Particle Physics, Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany, Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany, Nikhef, P.O. Box 41882, 1009 DB Amsterdam, The Netherlands, Nikhef, P.O. Box 41882, 1009 DB Amsterdam, The Netherlands, Department of Physics, VU-university, Amsterdam, The Netherlands, Department of Physics, University of Zagreb, Zagreb, Croatia, M. Smoluchowski Institute of Physics, Jagiellonian University, PL-30059 Kraków, Poland, Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany, Department of Physics, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan, Institute for Advanced Simulation, Institut für Kernphysik, and Jülich Center for Hadron Physics, Forschungszentrum Jülich, D-52425 Jülich, Germany, Institute Jožef Stefan, University of Ljubljana, Ljubljana, Slovenia, Middleton, D. G., Annand, J. R. M., Antelo, M. Ases, Ayerbe, C., Barneo, P., Baumann, D., Bermuth, J., Bernauer, J., Blok, H. P., Böhm, R., Bosnar, D., Ding, M., Distler, M. O., Friedrich, J., García, Llongo J., Glazier, D. I., Golak, J., Glöckle, W., Grabmayr, P., Hehl, T., Heim, J., Hesselink, W. H. A., Jans, E., Kamada, H., Jover, Mañas G., Kohl, M., Lapikás, L., MacGregor, I. J. D., Martin, I., McGeorge, J. C., Merkel, H., Merle, P., Monstad, K., Moschini, F., Müller, U., Nogga, A., Pérez-Benito, R., Pospischil, Th., Potokar, M., Rosner, G., Seimetz, M., Skibiński, R., de, Vries H., Walcher, Th., Watts, D. P., Weinriefer, M., Weiss, M., Witała, H., and Zihlmann, B.

Abstract

type:Journal Article, Cross sections for the 3He(e,e' pn)1H reaction were measured for the first time at energy transfers of 220 and 270 MeV for several momentum transfers ranging from 300 to 450 MeV/c. Cross sections are presented as a function of the momentum of the recoil proton and the momentum transfer. Continuum Faddeev calculations using the Argonne V18 and Bonn-B nucleon-nucleon potentials overestimate the measured cross sections by a factor 5 at low recoil proton momentum with the discrepancy becoming smaller at higher recoil proton momentum.

Published
2017

3. Nucleon Sigma Terms with N_{f}=2+1 Flavors of O(a)-Improved Wilson Fermions.

Author

Agadjanov A, Djukanovic D, von Hippel G, Meyer HB, Ottnad K, and Wittig H

Abstract

We present a lattice-QCD based analysis of the nucleon sigma terms using gauge ensembles with N_{f}=2+1 flavors of O(a)-improved Wilson fermions, with a complete error budget concerning excited-state contaminations, the chiral interpolation as well as finite-size and lattice spacing effects. We compute the sigma terms determined directly from the matrix elements of the scalar currents. The chiral interpolation is based on SU(3) baryon chiral perturbation theory using the extended on-mass shell renormalization scheme. For the pion nucleon sigma term, we obtain σ_{πN}=(43.7±3.6)  MeV, where the error includes our estimate of the aforementioned systematics. The tension with extractions based on dispersion theory persists at the 2.4-σ level. For the strange sigma term, we obtain a nonzero value, σ_{s}=(28.6±9.3)  MeV.

Published
2023
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4. Measurement of the α-Particle Monopole Transition Form Factor Challenges Theory: A Low-Energy Puzzle for Nuclear Forces?

Author

Kegel S, Achenbach P, Bacca S, Barnea N, Beričič J, Bosnar D, Correa L, Distler MO, Esser A, Fonvieille H, Friščić I, Heilig M, Herrmann P, Hoek M, Klag P, Kolar T, Leidemann W, Merkel H, Mihovilovič M, Müller J, Müller U, Orlandini G, Pochodzalla J, Schlimme BS, Schoth M, Schulz F, Sfienti C, Širca S, Spreckels R, Stöttinger Y, Thiel M, Tyukin A, Walcher T, and Weber A

Abstract

We perform a systematic study of the α-particle excitation from its ground state 0_{1}^{+} to the 0_{2}^{+} resonance. The so-called monopole transition form factor is investigated via an electron scattering experiment in a broad Q^{2} range (from 0.5 to 5.0  fm^{-2}). The precision of the new data dramatically supersedes that of older sets of data, each covering only a portion of the Q^{2} range. The new data allow the determination of two coefficients in a low-momentum expansion, leading to a new puzzle. By confronting experiment to state-of-the-art theoretical calculations, we observe that modern nuclear forces, including those derived within chiral effective field theory that are well tested on a variety of observables, fail to reproduce the excitation of the α particle.

Published
2023
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5. First Concurrent Extraction of the Leading-Order Scalar and Spin Proton Polarizabilities.

Author

Mornacchi E, Rodini S, Pasquini B, and Pedroni P

Abstract

We performed the first simultaneous extraction of the six leading-order proton polarizabilities. We reached this milestone thanks to both new high-quality experimental data and an innovative bootstrap-based fitting method. These new results provide a self-consistent and fundamental benchmark for all future theoretical and experimental polarizability estimates.

Published
2022
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6. Measurement of Compton Scattering at MAMI for the Extraction of the Electric and Magnetic Polarizabilities of the Proton.

Author

Mornacchi E, Martel PP, Abt S, Achenbach P, Adlarson P, Afzal F, Ahmed Z, Annand JRM, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dolzhikov AS, Downie EJ, Drexler P, Fegan S, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Kay SJD, Korolija M, Krusche B, Lazarev A, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Miskimen R, Mocanu M, Mullen C, Neganov A, Neiser A, Ostrick M, Paudyal D, Pedroni P, Powell A, Rostomyan T, Sokhoyan V, Spieker K, Steffen O, Strakovsky I, Strub T, Thiel M, Thomas A, Usov YA, Wagner S, Watts DP, Werthmüller D, Wettig J, Wolfes M, and Zachariou N

Abstract

A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4}  fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.

Published
2022
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7. Precise Measurement of the D^{0} and D^{+} Lifetimes at Belle II.

Author

Abudinén F, Adachi I, Adamczyk K, Aggarwal L, Ahmed H, Aihara H, Akopov N, Aloisio A, Anh Ky N, Asner DM, Atmacan H, Aushev V, Babu V, Bacher S, Bae H, Baehr S, Bahinipati S, Bambade P, Banerjee S, Bansal S, Barrett M, Baudot J, Bauer M, Baur A, Becker J, Behera PK, Bennett JV, Bernieri E, Bernlochner FU, Bertemes M, Bertholet E, Bessner M, Bettarini S, Bhardwaj V, Bianchi F, Bilka T, Bilokin S, Biswas D, Bobrov A, Bodrov D, Bolz A, Bozek A, Bračko M, Branchini P, Braun N, Briere RA, Browder TE, Budano A, Bussino S, Campajola M, Cao L, Casarosa G, Cecchi C, Červenkov D, Chang MC, Chang P, Cheaib R, Chekelian V, Chen C, Chen YT, Cheon BG, Chilikin K, Chirapatpimol K, Cho HE, Cho K, Cho SJ, Choi SK, Choudhury S, Cinabro D, Corona L, Cremaldi LM, Cunliffe S, Czank T, Dattola F, De La Cruz-Burelo E, de Marino G, De Nardo G, De Pietro G, de Sangro R, Destefanis M, Dey S, De Yta-Hernandez A, Di Canto A, Di Capua F, Dingfelder J, Doležal Z, Domínguez Jiménez I, Dong TV, Dorigo M, Dort K, Dossett D, Dubey S, Duell S, Dujany G, Ecker P, Epifanov D, Ferber T, Ferlewicz D, Finocchiaro G, Flood K, Fodor A, Forti F, Fulsom BG, Gabrielli A, Gabyshev N, Gaz A, Gellrich A, Giakoustidis G, Giordano R, Giri A, Glazov A, Gobbo B, Godang R, Goldenzweig P, Golob B, Gradl W, Graziani E, Greenwald D, Gu T, Guan Y, Gudkova K, Guilliams J, Hadjivasiliou C, Halder S, Hara K, Hara T, Hartbrich O, Hayasaka K, Hayashii H, Hazra S, Hearty C, Heredia de la Cruz I, Hernández Villanueva M, Hershenhorn A, Higuchi T, Hill EC, Hirata H, Hoek M, Hohmann M, Hsu CL, Humair T, Iijima T, Inami K, Inguglia G, Ishikawa A, Itoh R, Iwasaki M, Iwasaki Y, Jacobs WW, Jaffe DE, Jang EJ, Jia S, Jin Y, Junkerkalefeld H, Kakuno H, Kaliyar AB, Kandra J, Kang KH, Karl R, Karyan G, Kato Y, Kawasaki T, Kiesling C, Kim CH, Kim DY, Kim YK, Kim Y, Kimmel TD, Kinoshita K, Kodyš P, Koga T, Kohani S, Konno T, Korpar S, Kovalenko E, Kowalewski R, Kraetzschmar TMG, Krinner F, Križan P, Krokovny P, Kuhr T, Kumar J, Kumar M, Kumar R, Kumara K, Kurz S, Kuzmin A, Kwon YJ, Lacaprara S, Lalwani K, Lam T, Lanceri L, Lange JS, Laurenza M, Lautenbach K, Le Diberder FR, Lee SC, Leitl P, Levit D, Li C, Li LK, Libby J, Lieret K, Liptak Z, Liu QY, Liventsev D, Longo S, Lueck T, Lyu C, Manfredi R, Manoni E, Marinas C, Martini A, Matsuda T, Matsuoka K, Matvienko D, McKenna JA, Meier F, Merola M, Metzner F, Miller C, Miyabayashi K, Mizuk R, Mohanty GB, Molina-Gonzalez N, Moon H, Moser HG, Mrvar M, Murphy C, Mussa R, Nakamura I, Nakamura KR, Nakao M, Nakazawa H, Natkaniec Z, Natochii A, Nazaryan G, Niebuhr C, Niiyama M, Nisar NK, Nishida S, Nishimura K, Ogawa S, Onishchuk Y, Ono H, Onuki Y, Oskin P, Oxford ER, Ozaki H, Pakhlov P, Paladino A, Pang T, Panta A, Paoloni E, Pardi S, Park H, Park SH, Paschen B, Passeri A, Pathak A, Patra S, Paul S, Pedlar TK, Peruzzi I, Peschke R, Pestotnik R, Pham F, Piccolo M, Piilonen LE, Pinna Angioni G, Podesta-Lerma PLM, Podobnik T, Pokharel S, Polat G, Popov V, Praz C, Prell S, Prencipe E, Prim MT, Purohit MV, Purwar H, Rad N, Rados P, Raiz S, Reiter S, Remnev M, Ripp-Baudot I, Rizzo G, Rizzuto LB, Robertson SH, Roney JM, Rostomyan A, Rout N, Rozanska M, Sahoo D, Sanders DA, Sandilya S, Sangal A, Santelj L, Sato Y, Savinov V, Scavino B, Schueler J, Schwanda C, Schwartz AJ, Seino Y, Selce A, Senyo K, Serrano J, Sfienti C, Shiu JG, Shwartz B, Sibidanov A, Simon F, Sobie RJ, Soffer A, Sokolov A, Solovieva E, Spataro S, Spruck B, Starič M, Stefkova S, Stottler ZS, Stroili R, Strube J, Sumihama M, Sutcliffe W, Suzuki SY, Svidras H, Tabata M, Takizawa M, Tamponi U, Tanaka S, Tanida K, Tanigawa H, Taniguchi N, Tenchini F, Tiwary R, Tonelli D, Torassa E, Toutounji N, Trabelsi K, Tsuboyama T, Ueda I, Uehara S, Uematsu Y, Uglov T, Unger K, Unno Y, Uno K, Uno S, Urquijo P, Ushiroda Y, Usov YV, Vahsen SE, van Tonder R, Varner GS, Vinokurova A, Vitale L, Vossen A, Waheed E, Wakeling HM, Wang E, Wang MZ, Wang XL, Warburton A, Watanabe M, Welsch M, Wessel C, Wiechczynski J, Won E, Xu XP, Yabsley BD, Yamada S, Yan W, Yang SB, Ye H, Yelton J, Yin JH, Yoshihara K, Yusa Y, Zani L, Zhilich V, Zhou QD, Zhou XY, Zhukova VI, and Žlebčík R

Abstract

We report a measurement of the D^{0} and D^{+} lifetimes using D^{0}→K^{-}π^{+} and D^{+}→K^{-}π^{+}π^{+} decays reconstructed in e^{+}e^{-}→cc[over ¯] data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy e^{+}e^{-} collider. The data, collected at center-of-mass energies at or near the ϒ(4S) resonance, correspond to an integrated luminosity of 72  fb^{-1}. The results, τ(D^{0})=410.5±1.1(stat)±0.8(syst)  fs and τ(D^{+})=1030.4±4.7(stat)±3.1(syst)  fs, are the most precise to date and are consistent with previous determinations.

Published
2021
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8. New Insight in the Q^{2} Dependence of Proton Generalized Polarizabilities.

Author

Beričič J, Correa L, Benali M, Achenbach P, Ayerbe Gayoso C, Bernauer JC, Blomberg A, Böhm R, Bosnar D, Debenjak L, Denig A, Distler MO, Downie EJ, Esser A, Fonvieille H, Friščić I, Kegel S, Kohl Y, Makek M, Merkel H, Middleton DG, Mihovilovič M, Müller U, Nungesser L, Paolone M, Pochodzalla J, Sánchez Majos S, Schlimme BS, Schoth M, Schulz F, Sfienti C, Širca S, Sparveris N, Štajner S, Thiel M, Tyukin A, Weber A, and Weinriefer M

Abstract

Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer Q^{2}: 0.10, 0.20, and 0.45  GeV^{2}, at the Mainz Microtron. Fits performed using either the low-energy theorem or dispersion relations allowed the extraction of the structure functions P_{LL}-P_{TT}/ε and P_{LT}, as well as the electric and magnetic generalized polarizabilities α_{E1}(Q^{2}) and β_{M1}(Q^{2}). These new results show a smooth and rapid falloff of α_{E1}(Q^{2}), in contrast to previous measurements at Q^{2}=0.33  GeV^{2}, and provide for the first time a precise mapping of β_{M1}(Q^{2}) in the low-Q^{2} region.

Published
2019
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9. First Measurement of the Q^{2} Dependence of the Beam-Normal Single Spin Asymmetry for Elastic Scattering off Carbon.

Author

Esser A, Thiel M, Achenbach P, Aulenbacher K, Baunack S, Beričič J, Bosnar D, Correa L, Dehn M, Distler MO, Fonvieille H, Friščić I, Gorchtein M, Heidrich S, Herrmann P, Hoek M, Kegel S, Kohl Y, Kolar T, Kreidel HJ, Maas FE, Merkel H, Mihovilovič M, Müller J, Müller U, Nillius F, Palatchi C, Paschke KD, Pochodzalla J, Schlimme BS, Schoth M, Schulz F, Širca S, Spruck B, Štajner S, Tioukine V, Tyukin A, Weber A, and Sfienti C

Abstract

We report on the first Q^{2}-dependent measurement of the beam-normal single spin asymmetry A_{n} in the elastic scattering of 570 MeV vertically polarized electrons off ^{12}C. We cover the Q^{2} range between 0.02 and 0.05  GeV^{2}/c^{2} and determine A_{n} at four different Q^{2} values. The experimental results are compared to a theoretical calculation that relates A_{n} to the imaginary part of the two-photon exchange amplitude. The result emphasizes that the Q^{2} behavior of A_{n} given by the ratio of the Compton to charge form factors cannot be treated independently of the target nucleus.

Published
2018
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10. Study of η and η' Photoproduction at MAMI.

Author

Kashevarov VL, Ott P, Prakhov S, Adlarson P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Beck R, Braghieri A, Briscoe WJ, Cividini F, Codling R, Collicott C, Costanza S, Denig A, Downie EJ, Dieterle M, Ferretti Bondy MI, Fil'kov LV, Fix A, Gardner S, Garni S, Glazier DI, Glowa D, Gradl W, Gurevich G, Hamilton DJ, Hornidge D, Howdle D, Huber GM, Käser A, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Linturi J, Lisin V, Livingston K, MacGregor IJD, MacRae R, Mancell J, Manley DM, Martel PP, McGeorge JC, McNicol E, Middleton DG, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neiser A, Oberle M, Ostrick M, Otte PB, Oussena B, Paudyal D, Pedroni P, Polyanski VV, Rajabi A, Reicherz G, Robinson J, Rosner G, Rostomyan T, Sarty A, Schott DM, Schumann S, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strandberg B, Strakovsky II, Strub T, Supek I, Taragin MF, Thiel A, Thiel M, Tiator L, Thomas A, Unverzagt M, Wagner S, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, Workman RL, and Zana L

Abstract

The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96  GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η^{'} threshold, W=1896  MeV (E_{γ}=1447  MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η^{'} total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2^{-} state to both ηp and η^{'}p. Including the new high-accuracy results in the ηMAID fit to available η and η^{'} photoproduction data allows the determination of the N(1895)1/2^{-} properties.

Published
2017
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11. Observation of B→D(*) π^(+)π^(-)ℓ^(-)ν Decays in e^(+)e^(-) Collisions at the Υ(4S) Resonance.

Author

Lees JP, Poireau V, Tisserand V, Grauges E, Palano A, Eigen G, Stugu B, Brown DN, Kerth LT, Kolomensky YG, Lee MJ, Lynch G, Koch H, Schroeder T, Hearty C, Mattison TS, McKenna JA, So RY, Khan A, Blinov VE, Buzykaev AR, Druzhinin VP, Golubev VB, Kravchenko EA, Onuchin AP, Serednyakov SI, Skovpen YI, Solodov EP, Todyshev KY, Lankford AJ, Gary JW, Long O, Franco Sevilla M, Hong TM, Kovalskyi D, Richman JD, West CA, Eisner AM, Lockman WS, Panduro Vazquez W, Schumm BA, Seiden A, Chao DS, Cheng CH, Echenard B, Flood KT, Hitlin DG, Kim J, Miyashita TS, Ongmongkolkul P, Porter FC, Röhrken M, Andreassen R, Huard Z, Meadows BT, Pushpawela BG, Sokoloff MD, Sun L, Ford WT, Smith JG, Wagner SR, Ayad R, Toki WH, Spaan B, Bernard D, Verderi M, Playfer S, Bettoni D, Bozzi C, Calabrese R, Cibinetto G, Fioravanti E, Garzia I, Luppi E, Santoro V, Calcaterra A, de Sangro R, Finocchiaro G, Martellotti S, Patteri P, Peruzzi IM, Piccolo M, Zallo A, Contri R, Monge MR, Passaggio S, Patrignani C, Bhuyan B, Prasad V, Adametz A, Uwer U, Lacker HM, Mallik U, Chen C, Cochran J, Prell S, Ahmed H, Gritsan AV, Arnaud N, Davier M, Derkach D, Grosdidier G, Le Diberder F, Lutz AM, Malaescu B, Roudeau P, Stocchi A, Wormser G, Lange DJ, Wright DM, Coleman JP, Fry JR, Gabathuler E, Hutchcroft DE, Payne DJ, Touramanis C, Bevan AJ, Di Lodovico F, Sacco R, Cowan G, Brown DN, Davis CL, Denig AG, Fritsch M, Gradl W, Griessinger K, Hafner A, Schubert KR, Barlow RJ, Lafferty GD, Cenci R, Hamilton B, Jawahery A, Roberts DA, Cowan R, Cheaib R, Patel PM, Robertson SH, Dey B, Neri N, Palombo F, Cremaldi L, Godang R, Summers DJ, Simard M, Taras P, De Nardo G, Onorato G, Sciacca C, Raven G, Jessop CP, LoSecco JM, Honscheid K, Kass R, Margoni M, Morandin M, Posocco M, Rotondo M, Simi G, Simonetto F, Stroili R, Akar S, Ben-Haim E, Bomben M, Bonneaud GR, Briand H, Calderini G, Chauveau J, Leruste P, Marchiori G, Ocariz J, Biasini M, Manoni E, Rossi A, Angelini C, Batignani G, Bettarini S, Carpinelli M, Casarosa G, Chrzaszcz M, Forti F, Giorgi MA, Lusiani A, Oberhof B, Paoloni E, Rama M, Rizzo G, Walsh JJ, Lopes Pegna D, Olsen J, Smith AJ, Anulli F, Faccini R, Ferrarotto F, Ferroni F, Gaspero M, Pilloni A, Piredda G, Bünger C, Dittrich S, Grünberg O, Hess M, Leddig T, Voß C, Waldi R, Adye T, Olaiya EO, Wilson FF, Emery S, Vasseur G, Aston D, Bard DJ, Cartaro C, Convery MR, Dorfan J, Dubois-Felsmann GP, Dunwoodie W, Ebert M, Field RC, Fulsom BG, Graham MT, Hast C, Innes WR, Kim P, Leith DW, Luitz S, Luth V, MacFarlane DB, Muller DR, Neal H, Pulliam T, Ratcliff BN, Roodman A, Schindler RH, Snyder A, Su D, Sullivan MK, Va'vra J, Wisniewski WJ, Wulsin HW, Purohit MV, Wilson JR, Randle-Conde A, Sekula SJ, Bellis M, Burchat PR, Puccio EM, Alam MS, Ernst JA, Gorodeisky R, Guttman N, Peimer DR, Soffer A, Spanier SM, Ritchie JL, Schwitters RF, Izen JM, Lou XC, Bianchi F, De Mori F, Filippi A, Gamba D, Lanceri L, Vitale L, Martinez-Vidal F, Oyanguren A, Albert J, Banerjee S, Beaulieu A, Bernlochner FU, Choi HH, King GJ, Kowalewski R, Lewczuk MJ, Lueck T, Nugent IM, Roney JM, Sobie RJ, Tasneem N, Gershon TJ, Harrison PF, Latham TE, Band HR, Dasu S, Pan Y, Prepost R, and Wu SL

Abstract

We report on measurements of the decays of B¯ mesons into the semileptonic final states B¯→D^(*)π^(+)π^(-)ℓ^(-)ν¯, where D^(*) represents a D or D^(*) meson and ℓ^(-) is an electron or a muon. These measurements are based on 471×10^(6) BB ¯ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R_{π^{+}π^{-}}^{(*)}=B(B[over ¯]→D^{(*)}π^{+}π^{-}ℓ^{-}ν[over ¯])/B(B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]) using events in which the second B meson is fully reconstructed. We find R_{π^{+}π^{-}}=0.067±0.010±0.008 and R_{π^{+}π^{-}}^{*}=0.019±0.005±0.004, where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that B[over ¯]→D^{(*)}ππℓ^{-}ν[over ¯] decays, where π denotes either a π^{±} and π^{0} meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.

Published
2016
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12. Lattice QCD Calculation of Hadronic Light-by-Light Scattering.

Author

Green J, Gryniuk O, von Hippel G, Meyer HB, and Pascalutsa V

Abstract

We perform a lattice QCD calculation of the hadronic light-by-light scattering amplitude in a broad kinematical range. At forward kinematics, the results are compared to a phenomenological analysis based on dispersive sum rules for light-by-light scattering. The size of the pion pole contribution is investigated for momenta of typical hadronic size. The presented numerical methods can be used to compute the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. Our calculations are carried out in two-flavor QCD with the pion mass in the range of 270-450 MeV and contain so far only the diagrams with fully connected quark lines.

Published
2015
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13. Measurement of the transverse target and beam-target asymmetries in η meson photoproduction at MAMI.

Author

Akondi CS, Annand JR, Arends HJ, Beck R, Bernstein A, Borisov N, Braghieri A, Briscoe WJ, Cherepnya S, Collicott C, Costanza S, Downie EJ, Dieterle M, Fix A, Fil'kov LV, Garni S, Glazier DI, Gradl W, Gurevich G, Hall Barrientos P, Hamilton D, Hornidge D, Howdle D, Huber GM, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, MacGregor IJ, Mancel J, Manley DM, Martel P, McNicoll EF, Meyer W, Middleton D, Miskimen R, Mushkarenkov A, Nefkens BM, Neganov A, Nikolaev A, Oberle M, Ostrick M, Ortega H, Ott P, Otte PB, Oussena B, Pedroni P, Polonski A, Polyanski VV, Prakhov S, Reicherz G, Rostomyan T, Sarty A, Schumann S, Steffen O, Strakovsky II, Strub T, Supek I, Tiator L, Thomas A, Unverzagt M, Usov YA, Watts DP, Werthmüller D, Witthauer L, and Wolfes M

Abstract

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the γ[over →]p[over →]→ηp reaction up to a center-of-mass energy of W=1.9  GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of η meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

Published
2014
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14. Search at the Mainz Microtron for light massive gauge bosons relevant for the muon g-2 anomaly.

Author

Merkel H, Achenbach P, Ayerbe Gayoso C, Beranek T, Beričič J, Bernauer JC, Böhm R, Bosnar D, Correa L, Debenjak L, Denig A, Distler MO, Esser A, Fonvieille H, Friščić I, Gómez Rodríguez de la Paz M, Hoek M, Kegel S, Kohl Y, Middleton DG, Mihovilovič M, Müller U, Nungesser L, Pochodzalla J, Rohrbeck M, Ron G, Sánchez Majos S, Schlimme BS, Schoth M, Schulz F, Sfienti C, Sirca S, Thiel M, Tyukin A, Weber A, and Weinriefer M

Abstract

A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40  MeV/c^{2} to 300  MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge boson.

Published
2014
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15. Measurement of the neutron electric to magnetic form factor ratio at Q2=1.58  GeV2 using the reaction 3He[over →](e[over →],e'n)pp.

Author

Schlimme BS, Achenbach P, Ayerbe Gayoso CA, Bernauer JC, Böhm R, Bosnar D, Challand T, Distler MO, Doria L, Fellenberger F, Fonvieille H, Gómez Rodríguez M, Grabmayr P, Hehl T, Heil W, Kiselev D, Krimmer J, Makek M, Merkel H, Middleton DG, Müller U, Nungesser L, Ott BA, Pochodzalla J, Potokar M, Sánchez Majos S, Sargsian MM, Sick I, Sirca S, Weinriefer M, Wendel M, and Yoon CJ

Abstract

A measurement of beam helicity asymmetries in the reaction 3He[over →](e[over →],e'n)pp is performed at the Mainz Microtron in quasielastic kinematics to determine the electric to magnetic form factor ratio of the neutron GEn/GMn at a four-momentum transfer Q2=1.58  GeV2. Longitudinally polarized electrons are scattered on a highly polarized 3He gas target. The scattered electrons are detected with a high-resolution magnetic spectrometer, and the ejected neutrons are detected with a dedicated neutron detector composed of scintillator bars. To reduce systematic errors, data are taken for four different target polarization orientations allowing the determination of GEn/GMn from a double ratio. We find μnGEn/GMn=0.250±0.058(stat)±0.017(syst).

Published
2013
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16. Search for light gauge bosons of the dark sector at the Mainz Microtron.

Author

Merkel H, Achenbach P, Ayerbe Gayoso C, Bernauer JC, Böhm R, Bosnar D, Debenjak L, Denig A, Distler MO, Esser A, Fonvieille H, Friščić I, Middleton DG, Müller U, Nungesser L, Pochodzalla J, Rohrbeck M, Sánchez Majos S, Schlimme BS, Schoth M, Sirca S, and Weinriefer M

Abstract

A new exclusion limit for the electromagnetic production of a light U(1) gauge boson γ' decaying to e + e- was determined by the A1 Collaboration at the Mainz Microtron. Such light gauge bosons appear in several extensions of the standard model and are also discussed as candidates for the interaction of dark matter with standard model matter. In electron scattering from a heavy nucleus, the existing limits for a narrow state coupling to e + e- were reduced by nearly an order of magnitude in the range of the lepton pair mass of 210 MeV/c2}

Published
2011
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17. Measurement of strange quark contributions to the vector form factors of the proton at Q2 = 0.22 (GeV / c)2.

Author

Baunack S, Aulenbacher K, Balaguer Ríos D, Capozza L, Diefenbach J, Gläser B, von Harrach D, Imai Y, Kabuss EM, Kothe R, Lee JH, Merkel H, Mora Espí MC, Müller U, Schilling E, Stephan G, Weinrich C, Arvieux J, El-Yakoubi MA, Frascaria R, Kunne R, Maas FE, Morlet M, Ong S, van de Wiele J, Kowalski S, Prok Y, and Taylor S

Abstract

A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q;{2} = 0.22 (Ge V / c);{2} is reported here. The measured asymmetry is A_{LR} = (-17.23 +/- 0.82_{stat} +/- 0.89_{syst}) x 10;{-6}. The standard model prediction assuming no strangeness is A_{0} = (-15.87 +/- 1.22) x 10;{-6}. In combination with previous results from measurements at forward angles, it is possible to disentangle for the first time the strange form factors at this momentum transfer, G_{E};{s} = 0.050 +/- 0.038 +/- 0.019 and G_{M};{s} = -0.14 +/- 0.11 +/- 0.11.

Published
2009
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18. Recoil polarization and beam-recoil double polarization measurement of eta electroproduction on the proton in the region of the S11(1535) resonance.

Author

Merkel H, Achenbach P, Ayerbe Gayoso C, Bernauer JC, Böhm R, Bosnar D, Cheymol B, Distler MO, Doria L, Fonvieille H, Friedrich J, Janssens P, Makek M, Müller U, Nungesser L, Pochodzalla J, Potokar M, Sánchez Majos S, Schlimme BS, Sirca S, Tiator L, Walcher T, and Weinriefer M

Abstract

The beam-recoil double polarization P(x')(h) and P(z')(h) and the recoil polarization P(y') were measured for the first time for the p(e,e'p)eta reaction at a four-momentum transfer of Q(2) = 0.1 GeV(2)/c(2) and a center of mass production angle of theta = 120 degrees at the Mainz Microtron MAMI-C. With a center of mass energy range of 1500 MeV

Published
2007
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19. Neutral pion threshold production at Q(2) = 0.05 GeV(2)/c(2) and chiral perturbation theory.

Author

Merkel H, Bartsch P, Baumann D, Bermuth J, Bernstein AM, Bohinc K, Böhm R, Clawiter N, Derber S, Ding M, Distler MO, Ewald I, Friedrich JM, Friedrich J, Jennewein P, Kahrau M, Kohl M, Krygier KW, Kuss M, Liesenfeld A, Merle P, Miskimen RA, Müller U, Neuhausen R, Pavan MM, Pospischil T, Potokar M, Rosner G, Schmieden H, Seimetz M, Sirca S, Wagner A, Walcher T, and Weis M

Abstract

New data are presented on the p(e,e'p)pi(0) reaction at threshold at a four-momentum transfer of Q(2) = 0.05 GeV(2)/c(2). The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma(T), sigma(L), sigma(TT), and sigma(TL) are determined. The results are compared with calculations in heavy baryon chiral perturbation theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.

Published
2002
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