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Register a new userProduction and Decay of Charmed Baryons: Spectra of Muons and Asymmetry between mu+ and mu-
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Authors
O. I. Piskounova
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The calculation of muon spectra from the decay of Lambda_c baryons was carried out on the basis of the description of recent data on charmed-baryon production in hadronic interactions. Data are described in the framework of Quark--Gluon String Model that allowes us to consider primary proton interactions of arbitrary high energy. MC code was built for charmed-baryon semileptonic decay in order to obtain the kinematical characteristics of resulting particles. It is predicted that the charge asymmetry between energy spectra of mu+ and mu- in laboratory system is clearly seen as the consequence of asymmetry between the spectra of charmed baryons and antibaryons.This extension of QGS Model can be useful to correct the calculations of muon and neutrino spectra in astrophysics.
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Up to now, the excited charmed and bottom baryon states are still not well studied both experimentally and theoretically. In the present paper, we predict the mass of $Omega_b^*$, the only $L = 0$ baryon state which has not been observed, to be 6069.2 MeV. The spectra of charmed and bottom baryons with the orbital angular momentum $L = 1$ are studied in two popular constituent quark models, the Goldstone boson exchange (GBE) and the one gluon exchange (OGE) hyperfine interaction models, respectively. Inserting the latest experimental data from the Review of Particle Physics, we find that in the GBE model, there exist some multiplets ($Sigma_{c(b)}$, $Xi_{c(b)}$ and $Omega_{c(b)}$) which total spins of three quarks in their lowest energy states are 3/2, but in the OGE model there is no such phenomenon. This is the most important difference between the GBE and OGE models. These results can be tested in the near future. We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for determining which hyperfine interaction model is realized in nature.
The very rare Bd0 --> mu+ mu- decay may be the last chance for New Physics in flavor sector at the LHC, before the 13 TeV run in 2015. Partially motivated by the known tension in sin(2beta/phi_1), enhancement beyond (3-4) x 10^-10 would likely imply the effect of a fourth generation of quarks. If observed at this level, the 126 GeV boson may not be the actual Higgs boson, while the b --> d quadrangle (modulo m_t) would jump out. The 2011-2012 data is likely not sensitive to values below 3 x 10^-10, and the mode should continue to be pursued with the 13 TeV run.
The process e^+e^- ->mu^+mu^- has been studied with SND detector at VEPP-2M e^+e^- collider in the vicinity of phi(1020) resonance. The product of branching ratios of phi meson into leptons sqrt{B(phi->mu^+mu^-) B(phi-> e^+e^-)}=(3.14+-0.22+-0.14)x10^{-4} was measured from the interference in the cross section of the process e^+e^- ->mu^+mu^-. The branching ratio B(phi->mu^+mu^-)=(3.30+-0.45+-0.32)x10^{-4} was obtained.
We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor.)) x 10^{-8}. We compare this result with predictions from chiral perturbation theory and estimates based on the decay K+ --> pi+ e+ e-.
We study constraints and implications of the recent LHCb measurement of ${cal B}(B_s to mu^+mu^-)$ for tree-level Higgs-mediated flavor-changing neutral current (FCNC) interactions. Combined with experimental data on $B_s$ mass difference $Delta m_s$, the $h to mu tau$, and the $h to tau^+tau^-$ decay branching ratios from the LHC, we find that the Higgs FCNC couplings are severely constrained. The allowed regions for $B_s to mu tau$, $tautau$ and $h to sb$ decays are obtained. Current data allow large CP violation in the $h to tau^+ tau^-$ decay. Consequences of the Cheng-Sher ansatz for the Higgs Yukawa couplings are discussed in some detail.
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