Related papers: Muon decay spin asymmetry

In the framework of a recently proposed extension of the Standard Model, with N=1 SuperSymmetry in 5 dimensions, compactified on R^1/(Z_2 x Z'_2), we compute the muon anomalous magnetic moment at one loop to order (M_W R)^2, where R is the…

We compute O(alpha^3 ln alpha) relative corrections to the ground state hyperfine splitting of a QED two body bound state with different masses of constituents. The general result is then applied to muonium and positronium. In particular, a…

We study the explicit breaking of a $SU(2)$ symmetry to a $U(1)$ subgroup employing the entanglement asymmetry, a recently introduced observable that measures how much symmetries are broken in a part of extended quantum systems. We consider…

Higher-order QED radiative corrections to muon decay spectrum are evaluated within the QED structure function approach in the next-to-leading order logarithmic approximation. New analytical results are given in the…

We combine the constraint suggested by the recent BNL E821 measurement of the anomalous magnetic moment of the muon on the parameter space of the constrained MSSM (CMSSM) with those provided previously by LEP, the measured rate of b to s…

Top pair production at LHC is the ideal place to search for nonstandard Wtb couplings in t -> W b -> l nu b decays. The lb forward-backward asymmetry in the W rest frame is very sensitive to sigma_{mu nu} couplings, and can spot one-loop…

The QED contribution to the anomalous magnetic moments of electron and muon are known very precisely up to the order $\alpha^4$. However, the knowledge of $\alpha^5$ term will also be required when the precision of measurement improves…

We present results for the QED contributions to the anomalous magnetic moment of the muon containing closed electron loops. The main focus is on perturbative corrections at four-loop order where the external photon couples to the external…

We consider the O(alpha^2) hadronic corrections to the energy spectrum of the decay electron in muon decay. We find that the correction can be described, within good approximation, by a linear function in the electron energy. Explicit…

The Q weak experiment has made several interesting beam normal single spin asymmetry measurements. Preliminary result from a 3.2% measurement of the beam normal single spin asymmetry in elastic e+p scattering at E = 1.155 GeV and {\theta}…

We study the angular distribution of the charged lepton in the top-quark decay into a bottom quark and a W boson which subsequently decays into \ell\nu_{\ell}, when a hard gluon is radiated off. The absorptive part of the t \to bWg decay…

We report the result of our calculation of the complete tenth-order QED terms of the muon g-2. Our result is a_\mu^{(10)} = 753.29 (1.04) in units of (\alpha/\pi)^5, which is about 4.5 s.d. larger than the leading-logarithmic estimate 663…

Spin-averaged asymmetries in the azimuthal distributions of positive and negative hadrons produced in deep inelastic scattering were measured using the CERN SPS muon beam at $160$ GeV/c and a $^6$LiD target. The amplitudes of the three…

The Muon $g-2$ experiment at Fermilab aims to measure the muon anomalous magnetic moment with an unprecedented precision of 140 parts per billion (ppb). Data collection concluded in June 2023, and analysis of the largest dataset (2021-2023)…

The absence of "valence-gluon" degrees of freedom combined with an examination of radiative QCD diagrams leads to an implication that the gluon spin asymmetry in a proton, defined as A_G(x,Q^2) = (Delta G)/G, should be approximately Q^2…

We report results of a muon spin relaxation ($\mu$SR) study of YFe$_2$Al$_{10}$, a quasi-2D nearly-ferromagnetic metal in which unconventional quantum critical behavior is observed. No static Fe$^{2+}$ magnetism, with or without long-range…

Isospin is an almost exact symmetry of strong interactions and the corrections to the isosymmetric limit are, in general, at the percent level. For several hadronic quantities relevant for flavour physics phenomenology, such as pseudoscalar…

The recent measurement on the muon anomalous magnetic moment $a_\mu$ shows a $2.6\sigma$ deviation from the standard model value. We show that it puts strong constraints on the parameter space of the two-higgs doublet model (2HDM) II. The…

The TWIST Collaboration has measured the Michel parameter $\rho$ in normal muon decay, $\mu^+ \to e^+ \nu_e \bar{\nu}_{\mu}$. In the Standard Model, $\rho$ = 3/4. Deviations from this value require mixing of left- and right-handed muon and…

Positronium is an ideal system for the research of the bound state QED. New precise measurement of orthopositronium decay rate has been performed with an accuracy of 150 ppm. This result is consistent with the last three results and also…