scholarly journals Measurement of the Michel parameters (η‾, ξκ ) in the radiative leptonic decay of τ

2017 ◽  
Vol 287-288 ◽  
pp. 11-14 ◽  
Author(s):  
Nobuhiro Shimizu
Keyword(s):  
Leptonic Decay ◽  
Michel Parameters

scholarly journals Search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c.

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
◽  
M. Ablikim ◽  
M. N. Achasov ◽  
P. Adlarson ◽  
S. Ahmed ◽  
...  
Keyword(s):  
Confidence Level ◽  
Branching Fraction ◽  
Center Of Mass ◽  
Leptonic Decay ◽  
Mass Energy ◽  
Center Of Mass Energy ◽  
Upper Limit ◽  
Electron Positron

Abstract Using 10.1 × 109J/ψ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $$ \sqrt{s} $$ s = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction ℬ(J/ψ → D−e+νe + c. c.) < 7.1 × 10−8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.

scholarly journals Contribution of the Darwin operator to non-leptonic decays of heavy quarks

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Alexander Lenz ◽  
Maria Laura Piscopo ◽  
Aleksey V. Rusov
Keyword(s):  
Standard Technique ◽  
Quark Propagator ◽  
Leptonic Decay ◽  
Leptonic Decays ◽  
Interference Contribution ◽  
The Standard Model ◽  
Strength Tensor ◽  
Quark Flavour ◽  
Quark Decay ◽  
B Quark

Abstract We compute the Darwin operator contribution ($$ 1/{m}_b^3 $$ 1 / m b 3 correction) to the width of the inclusive non-leptonic decay of a B meson (B+, Bd or Bs), stemming from the quark flavour-changing transition b → $$ {q}_1{\overline{q}}_2{q}_3 $$ q 1 q ¯ 2 q 3 , where q1, q2 = u, c and q3 = d, s. The key ideas of the computation are the local expansion of the quark propagator in the external gluon field including terms with a covariant derivative of the gluon field strength tensor and the standard technique of the Heavy Quark Expansion (HQE). We confirm the previously known expressions of the $$ 1/{m}_b^3 $$ 1 / m b 3 contributions to the semi-leptonic decay b → $$ {q}_1\mathrm{\ell}{\overline{\nu}}_{\mathrm{\ell}} $$ q 1 ℓ ν ¯ ℓ , with ℓ = e, μ, τ and of the $$ 1/{m}_b^2 $$ 1 / m b 2 contributions to the non-leptonic modes. We find that this new term can give a sizeable correction of about −4 % to the non-leptonic decay width of a B meson. For Bd and Bs mesons this turns out to be the dominant correction to the free b-quark decay, while for the B+ meson the Darwin term gives the second most important correction — roughly 1/2 to 1/3 of the phase space enhanced Pauli interference contribution. Due to the tiny experimental uncertainties in lifetime measurements the incorporation of the Darwin term contribution is crucial for precision tests of the Standard Model.

scholarly journals Leptonic decay constants and in three flavor lattice QCD

2005 ◽  
Vol 140 ◽  
pp. 443-445 ◽  
Author(s):  
J.N. Simone ◽  
C. Aubin ◽  
C. Bernard ◽  
C. DeTar ◽  
M. di Pierro ◽  
...  
Keyword(s):  
Lattice Qcd ◽  
Leptonic Decay ◽  
Decay Constants

Aspects of the chirality of weak b→c transitions in the exclusive semi-leptonic decay

1989 ◽  
Vol 226 (1-2) ◽  
pp. 185-191 ◽  
Author(s):  
Jürgen G. Körner ◽  
Gerhard A. Schuler
Keyword(s):  
Leptonic Decay

scholarly journals B - and D -meson leptonic decay constants from four-flavor lattice QCD

2018 ◽  
Vol 98 (7) ◽  
Author(s):  
A. Bazavov ◽  
C. Bernard ◽  
N. Brown ◽  
C. DeTar ◽  
A. X. El-Khadra ◽  
...  
Keyword(s):  
Lattice Qcd ◽  
D Meson ◽  
Leptonic Decay ◽  
Decay Constants ◽  
Four Flavor

scholarly journals Measurement of the leptonic decay width of J/ψ using initial state radiation

2016 ◽  
Vol 761 ◽  
pp. 98-103 ◽  
Author(s):  
M. Ablikim ◽  
M.N. Achasov ◽  
X.C. Ai ◽  
O. Albayrak ◽  
M. Albrecht ◽  
...  
Keyword(s):  
Decay Width ◽  
Leptonic Decay ◽  
Initial State Radiation ◽  
Initial State ◽  
State Radiation

scholarly journals On spin asymmetry in muon and tau decays

2018 ◽  
Vol 33 (32) ◽  
pp. 1850191
Author(s):  
A. B. Arbuzov ◽  
T. V. Kopylova ◽  
I. K. Sklyarov
Keyword(s):  
Charged Lepton ◽  
Spin Asymmetry ◽  
Second Order ◽  
Tau Leptons ◽  
Mass Ratio ◽  
Fermi Model ◽  
Tau Decays ◽  
Standard Formula ◽  
Leading Logarithm ◽  
Michel Parameters

The angular asymmetry in decays of polarized muons and tau leptons is discussed. Both the standard [Formula: see text] Fermi model and the general parametrization via Michel parameters are considered. Numerical importance of contributions suppressed by charged lepton mass ratio is underlined. Contribution of the second order QED correction is estimated in the leading logarithm approximation.

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