Muon polarization in the MEG experiment: predictions and measurements

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Abstract

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 Pμ=−1 by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be Pμ=−0.86±0.02 (stat) +0.05−0.06 (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+ν¯μνeγ.

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Tutti gli autori

  • 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. , De Bari A. , 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 T. , 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 Y. u. V.

Titolo volume/Rivista

THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS

Anno di pubblicazione

2016

ISSN

1434-6044

ISBN

Non Disponibile

Numero di citazioni Wos

2

Ultimo Aggiornamento Citazioni

27/04/2018

Numero di citazioni Scopus

1

Ultimo Aggiornamento Citazioni

28/04/2018

Settori ERC

Non Disponibile

Codici ASJC

Non Disponibile