Muon polarization in the MEG experiment: predictions and measurements

Baldini, A. M.; Bao, Y.; Baracchini, E.; Bemporad, C.; Berg, F.; Biasotti, M.; Boca, G.; Cattaneo, P. W.; Cavoto, G.; Cei, F.; Chiarello, G.; Chiri, C.; 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, M.; Papa, A.; Pepino, A.; Piredda, G.; Pizzigoni, G.; Popov, A.; Renga, F.; Ripiccini, E.; 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, Yu. V.

doi:10.1140/epjc/s10052-016-4047-3

Title: Muon polarization in the MEG experiment: predictions and measurements

Journal Article · Fri Apr 22 00:00:00 EDT 2016 · European Physical Journal. C, Particles and Fields

DOI:https://doi.org/10.1140/epjc/s10052-016-4047-3· OSTI ID:1361495

Baldini, A. M.; Bao, Y.; Baracchini, E.; Bemporad, C.; Berg, F.; Biasotti, M.; Boca, G.; Cattaneo, P. W.; Cavoto, G.; Cei, F.; Chiarello, G.; Chiri, C.; Bari, A. De; Gerone, M. De; D’Onofrio, A.; Dussoni, S.; Fujii, Y.; Galli, L.; Gatti, F.; Grancagnolo, F. more »

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 μ⁺→e⁺γ. 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_μ=-1 by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be P_μ= -0.86 ± 0.02 (stat) $$+0.05\atop{-0.06}$$ (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 μ⁺→e⁺γ search induced by the muon radiative decay: μ⁺→e⁺$$\bar{v}$$_μν_eγ.

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Research Organization:: Univ. of California, Irvine, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Contributing Organization:: The MEG Collaboration

Grant/Contract Number:: FG02-91ER40679; 200021_137738; RBFR08XWGN; RFBR 14-22-03071

OSTI ID:: 1361495

Journal Information:: European Physical Journal. C, Particles and Fields, Vol. 76, Issue 4; ISSN 1434-6044

Publisher:: SpringerCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 11 works

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Cited By (3)

Search for the lepton flavour violating decay $$\mu ^+ \rightarrow \mathrm {e}^+ \gamma $$ μ + → e + γ with the full dataset of the MEG experiment: MEG Collaboration Baldini, A. M.; Bao, Y.; Baracchini, E. The European Physical Journal C, Vol. 76, Issue 8 https://doi.org/10.1140/epjc/s10052-016-4271-x	journal	August 2016
The design of the MEG II experiment: MEG II Collaboration Baldini, A. M.; Baracchini, E.; Bemporad, C. The European Physical Journal C, Vol. 78, Issue 5 https://doi.org/10.1140/epjc/s10052-018-5845-6	journal	May 2018
The design of the MEG II experiment Baldini, A. M.; Baracchini, E.; Bemporad, Carlo ETH Zurich https://doi.org/10.3929/ethz-b-000267051	text	January 2018

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