PRECISION MEASUREMENT OF THE RATE OF MUON CAPTURE IN HYDROGEN GAS AND DETERMINATION IN THE PROTONS PSEUDOSCALAR COUPLING g P PNPI participants in MuCAP collaboration*) : V.A. Andreev, V.A. Ganzha, P. A.Kravtsov, A.G. Krivshich, M.P. Levchenko, E.M. Maev, O.E. Maev, G.E. Petrov, G.N. Schapkin, G.G. Semenchuk, M. A. Soroka, A.A. Vasilyev, A.A. Vorobyov, M.E. Vznuzdaev

Стандартная Модель и структура нуклонов G v = ± G a = ± G m = ± Gp(th) = 8.26 ± 0.23 Gp = 6 – 12 Gp (RMC) = 12.2 ± 0.9 ± 0.4

T = 12 s -1 pμ singlet (F=0) S = 691 s -1 n+ triplet (F=1) μ pμ ppμ para (J=0)ortho (J=1) λ op ortho =506 s -1 para =200 s -1 ppμ λpd ~ 1.4x10 10 s -1, λpp μ ~ x10 6 s -1 λμz ~ 5x10 10 s -1 pp P pp O p 100% LH 2 p pp P pp O 1 % LH 2 time ( s) λ pp

Стратегия MuCap эксперимента Измерение времени жизни с точностью 10ppm, регистрация e распадов S = 1/ - 1/ ~ 1% nОднозначность интерпретации захват из F=0 состояния p атома при плотности LH 2 1% Использование методики активной мишени (TPC) с точной регистрацией координат и времени остановок мюонов, реконструкция треков электронов к точке распада Использование ультрачистого водорода С z < Контроль примесей по реакциям: p + Z Z + p, ~10 ppb N 2 Обеспечение изотопической чистоты водорода p + d d + p eV, примесь D 2 ~1 ppm, диффузия d ~cm

IV. the new protium isotope separation facility: production of ultra-depleted protium 1) sample #74 from column after separation run: cd < 0.14 ppm (twice analyzed April-15 & May-18) 2) 3 stp-ltr protium sample from run-10 gas cd < 0.07 ppm 3) 0.5 stp-ltr sample with end-of-run-8 gas cd = 1.44±0.13 ppm

Ortho-Para Hydrogen Chromatogram (Natural hydrogen, Column pressure = 1.2 bar; Reboiler power = 10W) ParaOrtho

Muon-On-Demand concept Beamline Single muon requirement (to prevent systematics from pile-up) limits accepted rate to ~ 7 kHz, while PSI beam can provide ~ 70 kHz kV kV Kicker Plates 50 ns switching time detector TPC Fig will be improved ~3 times higher rate dc kicked 2-Dec-2005 Lan kicker TRIUMF rf design

Histogram shows dramatic accidental suppression in the lifetime spectrum due to m-e impact parameter cuts (cut radius given in the legend).

Общая набранная статистика Год μ + x 10 9 μ - x 10 9 D 2 (ppm)H 2 0 (ppm) ~ ~

Результаты анализа данных за 2004 год х λ μ+ = ± 4.4 s -1 (μLAN experiment, to be published) λ μ- = ± 12.5stat ± 8.5syst s -1 (MuCAP 2004) Λ S MuCap = ± 13.7stat ± 10.7syst s -1 Λ S Th = s -1 (averaged) s -1 (radiation correction) g P MuCap = g P Th + (dg P /dΛ S ) x (Λ S MuCap - Λ S Th ) = 7.3±1.1 (15%) g P Th = (2.8%)

Earlier, in 1998, we have studied the muon capture on 3 He. The muon capture rate in the channel μ He 3 H + ν μ was measured with high precision : Λ c = ± 4.0 s -1. This result have been used in some theoretical analyses (T.Gorringe and H.W.Fearing, 2004) for deriving the protons pseudoscalar coupling g P. They applied the microscopic theory based on impulse approximation supplemented by explicit calculations of the meson exchange corrections. Their result was g P = 8.77 ± 1.58.

Публикации в 2007 году по теме «Мюон» V.A. Andreev, T.I. Banks et al. Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling gP. Phys.Rev.Lett. 99, (2007) V.A. Ganzha, P.A. Kravtsov et al. A Circulating Hydrogen Ultra-High Purification System for the MuCap Experiment Nucl. Instr. Methods Phys. Res. A 578 (2007)

ФИНАНСЫ 2007 Тема РАН – 400 т.руб т.руб Грант CRDF ~49 K USD

ГРУППА МЕЗОЯДЕРНЫХ РЕАКЦИЙ Вед.н.с. к.н. - Семенчук Г.Г. Ст.н.с. к.н. - Маев Е.М. Ст.н.с. - Петров Г.Е. Cт.н.с. к.н. - Воропаев Н.И. Н.с. - Балин Д.В. Н.с. - Смиренин Ю.В. Н.с. - Маев О.Е. Инж. пр. - Фотиева Е.В. Инж.оп.пр. - Дубограй B.C. Монт. р/а - Еремеев А.Д.