Muon decay: Measurement of the transverse polarization of the decay positrons and its implications for the fermi coupling constant and time reversal invariance

• Published in: Physical review letters Vol. 94; no. 2; pp. 021802.1 - 021802.4
• Main Authors: DANNEBERG, N, FETSCHER, W, STRZAŁKOWSKI, A, ZEJMA, J, KIRCH, K, KOZELA, A, STEPHAN, E, KÖHLER, K.-U, LANG, J, SCHWEIZER, T, VON ALLMEN, A, BODEK, K, JARCZYK, L, KISTRYN, S, SMYRSKI, J
• Format: Journal Article
• Language: English
• Published: Ridge, NY American Physical Society 21-01-2005
• Subjects: Charge conjugation, parity, time reversal, and other discrete symmetries; Decays of leptons; Decays of muons; Exact sciences and technology; General theory of fields and particles; Physics; Specific reactions and phenomenology; Symmetry and conservation laws; The physics of elementary particles and fields; Muon decay; Polarization; Coupling constants; T invariance; Positrons
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.94.021802

The two transverse polarization components P(T1) and P(T2) of the e(+) from the decay of polarized mu(+) have been measured as a function of the e(+) energy. Their energy averaged values are P(T1)=(6.3+/-7.7+/-3.4) x 10(-3) and P(T2)=(-3.7+/-7.7+/-3.4) x 10(-3). From the energy dependence of P(T1) and P(T2) the decay parameters eta,eta('') and alpha(')/A,beta(')/A are derived, respectively. Assuming only one additional coupling besides the dominant V-A interaction one gets improved limits on eta, beta(')/A, and the scalar coupling constant g(S)(RR): eta=(-2.1+/-7.0+/-1.0) x 10(-3), beta(')/A=(-1.3+/-3.5+/-0.6) x 10(-3), Re{g(S)(RR)}=(-4.2+/-14.0+/-2.0) x 10(-3), and Im{g(S)(RR)}=(5.2+/-14.0+/-2.4) x 10(-3).