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Title: Search for T-violating transverse muon polarization in the K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decay

Abstract

At the 12-GeV proton synchrotron of KEK, an experiment (KEK-PS-E246) was performed to measure the transverse muon polarization (P{sub T}) in K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decays as a direct search of violation of time reversal invariance (T-violation). P{sub T} is a very sensitive probe of CP violation beyond the standard model. A stopped positive kaon beam was used. An elaborate high-acceptance detector, in conjunction with a 12-sector superconducting toroidal spectrometer, was utilized. The stopped kaon method provided several advantages in performing a high-precision experiment. The decay was identified by detecting a {mu}{sup +} with the spectrometer and a {pi}{sup 0} with a CsI(Tl) calorimeter surrounding the target as two photons as well as one photon with high energy. For the P{sub T} measurement, {pi}{sup 0} events in the forward (fwd) and backward (bwd) regions in the calorimeter were relevant. Systematic errors were greatly suppressed by exploiting the rotational and fwd-bwd symmetry of the system. Polarization measurement was done in terms of asymmetry measurement of decay positrons of stopped muons in the polarimeter. A longitudinal field method was applied for the P{sub T} polarization component. In the data analysis a novel technique of the two-analysis method was employed. Two independent analysesmore » were performed following their own policy and criteria and good events were selected. Then, the two analyses were combined. A data quality check was carefully done by looking at the null asymmetry A{sub 0}, the sensitivity function A{sub N}, the kinematical attenuation coefficient, and the decay-plane distributions. The asymmetry measurement for finite-size muon stoppers was performed 'differentially' using the position information by the chamber in front of the polarimeter. From the measurements during 1996-2000, we accumulated 11.8x10{sup 6} good events after the two-analysis combination, and deduced P{sub T}=-0.0017{+-}0.0023(stat){+-}0.0011(syst), corresponding to the T-violating parameter Im{xi}=-0.0053{+-}0.0071(stat){+-}0.0036(syst). From these results the upper limits of |P{sub T}|<0.0050 (90% C.L.) and vertical bar Im{xi} vertical bar <0.016 (90% C.L.) were deduced. Systematic errors were carefully studied and estimated. Almost all of the errors were canceled by the 12-sector summation and/or fwd-bwd subtraction, and the total systematic error was concluded to be as a half of the statistical error. The present result set constraints on model parameters of several theoretical models. For the three-Higgs-doublet model, e.g., a limit |Im({alpha}{sub 1}{gamma}{sub 1}*)|<544(M{sub H{sub 1}}/GeV){sup 2} was obtained. Implications for several other models are discussed.« less

Authors:
 [1];  [2]; ; ; ; ; ; ; ; ; ;  [3]; ;  [4];  [5];  [1]; ;  [6];  [7];  [8] more »;  [9];  [10] « less
  1. Institute of Applied Physics, University of Tsukuba, Ibaraki 305-0006 (Japan)
  2. (KEK), Ibaraki 305-0801 (Japan)
  3. Institute for Nuclear Research, Russian Academy of Sciences, Moscow 117312 (Russian Federation)
  4. IPNS, High Energy Accelerator Research Organization (KEK), Ibaraki 305-0801 (Japan)
  5. (Japan)
  6. Department of Physics, University of Saskatchewan, Saskatoon, S7N 5E2 (Canada)
  7. Department of Physics, Virginia Polytechnic Institute and State University, Virginia 24061-0435 (United States)
  8. Laboratoire de Physique Nucleaire, Universite de Montreal, Montreal, Quebec, H3C 3J7 (Canada)
  9. Department of Physics and Astronomy, University of British Columbia, Vancouver, V6T 1Z1 (Canada)
  10. IPNS, High Energy Accelerator Research Organization (KEK), Ibaraki 305-0801 (Japan) (and others)
Publication Date:
OSTI Identifier:
20782784
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevD.73.072005; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; ATTENUATION; CP INVARIANCE; DATA ANALYSIS; ERRORS; GEV RANGE; HIGGS BOSONS; HIGGS MODEL; KAON BEAMS; KAONS PLUS; KEK SYNCHROTRON; MULTIPARTICLE SPECTROMETERS; MUONS PLUS; PHOTONS; PIONS NEUTRAL; POLARIMETERS; POLARIZATION; POSITRONS; SEMILEPTONIC DECAY; STANDARD MODEL; SYMMETRY; T INVARIANCE

Citation Formats

Abe, M., IPNS, High Energy Accelerator Research Organization, Aliev, M., Anisimovsky, V., Ivashkin, A.P., Khabibullin, M.M., Khotjantsev, A.N., Kudenko, Yu.G., Levchenko, A., Mineev, O.V., Okorokova, N., Yershov, N., Aoki, M., Horie, K., Department of Physics, Osaka University, Osaka 560-0043, Asano, Y., Baker, T., Rangacharyulu, C., Blecher, M., Depommier, P., Hasinoff, M., and Igarashi, Y. Search for T-violating transverse muon polarization in the K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decay. United States: N. p., 2006. Web. doi:10.1103/PHYSREVD.73.072005.
Abe, M., IPNS, High Energy Accelerator Research Organization, Aliev, M., Anisimovsky, V., Ivashkin, A.P., Khabibullin, M.M., Khotjantsev, A.N., Kudenko, Yu.G., Levchenko, A., Mineev, O.V., Okorokova, N., Yershov, N., Aoki, M., Horie, K., Department of Physics, Osaka University, Osaka 560-0043, Asano, Y., Baker, T., Rangacharyulu, C., Blecher, M., Depommier, P., Hasinoff, M., & Igarashi, Y. Search for T-violating transverse muon polarization in the K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decay. United States. doi:10.1103/PHYSREVD.73.072005.
Abe, M., IPNS, High Energy Accelerator Research Organization, Aliev, M., Anisimovsky, V., Ivashkin, A.P., Khabibullin, M.M., Khotjantsev, A.N., Kudenko, Yu.G., Levchenko, A., Mineev, O.V., Okorokova, N., Yershov, N., Aoki, M., Horie, K., Department of Physics, Osaka University, Osaka 560-0043, Asano, Y., Baker, T., Rangacharyulu, C., Blecher, M., Depommier, P., Hasinoff, M., and Igarashi, Y. Sat . "Search for T-violating transverse muon polarization in the K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decay". United States. doi:10.1103/PHYSREVD.73.072005.
@article{osti_20782784,
title = {Search for T-violating transverse muon polarization in the K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decay},
author = {Abe, M. and IPNS, High Energy Accelerator Research Organization and Aliev, M. and Anisimovsky, V. and Ivashkin, A.P. and Khabibullin, M.M. and Khotjantsev, A.N. and Kudenko, Yu.G. and Levchenko, A. and Mineev, O.V. and Okorokova, N. and Yershov, N. and Aoki, M. and Horie, K. and Department of Physics, Osaka University, Osaka 560-0043 and Asano, Y. and Baker, T. and Rangacharyulu, C. and Blecher, M. and Depommier, P. and Hasinoff, M. and Igarashi, Y.},
abstractNote = {At the 12-GeV proton synchrotron of KEK, an experiment (KEK-PS-E246) was performed to measure the transverse muon polarization (P{sub T}) in K{sup +}{yields}{pi}{sup 0}{mu}{sup +}{nu} decays as a direct search of violation of time reversal invariance (T-violation). P{sub T} is a very sensitive probe of CP violation beyond the standard model. A stopped positive kaon beam was used. An elaborate high-acceptance detector, in conjunction with a 12-sector superconducting toroidal spectrometer, was utilized. The stopped kaon method provided several advantages in performing a high-precision experiment. The decay was identified by detecting a {mu}{sup +} with the spectrometer and a {pi}{sup 0} with a CsI(Tl) calorimeter surrounding the target as two photons as well as one photon with high energy. For the P{sub T} measurement, {pi}{sup 0} events in the forward (fwd) and backward (bwd) regions in the calorimeter were relevant. Systematic errors were greatly suppressed by exploiting the rotational and fwd-bwd symmetry of the system. Polarization measurement was done in terms of asymmetry measurement of decay positrons of stopped muons in the polarimeter. A longitudinal field method was applied for the P{sub T} polarization component. In the data analysis a novel technique of the two-analysis method was employed. Two independent analyses were performed following their own policy and criteria and good events were selected. Then, the two analyses were combined. A data quality check was carefully done by looking at the null asymmetry A{sub 0}, the sensitivity function A{sub N}, the kinematical attenuation coefficient, and the decay-plane distributions. The asymmetry measurement for finite-size muon stoppers was performed 'differentially' using the position information by the chamber in front of the polarimeter. From the measurements during 1996-2000, we accumulated 11.8x10{sup 6} good events after the two-analysis combination, and deduced P{sub T}=-0.0017{+-}0.0023(stat){+-}0.0011(syst), corresponding to the T-violating parameter Im{xi}=-0.0053{+-}0.0071(stat){+-}0.0036(syst). From these results the upper limits of |P{sub T}|<0.0050 (90% C.L.) and vertical bar Im{xi} vertical bar <0.016 (90% C.L.) were deduced. Systematic errors were carefully studied and estimated. Almost all of the errors were canceled by the 12-sector summation and/or fwd-bwd subtraction, and the total systematic error was concluded to be as a half of the statistical error. The present result set constraints on model parameters of several theoretical models. For the three-Higgs-doublet model, e.g., a limit |Im({alpha}{sub 1}{gamma}{sub 1}*)|<544(M{sub H{sub 1}}/GeV){sup 2} was obtained. Implications for several other models are discussed.},
doi = {10.1103/PHYSREVD.73.072005},
journal = {Physical Review. D, Particles Fields},
number = 7,
volume = 73,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}