Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSemileptonic width ratios among beauty hadrons
84
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present predictions based on the heavy quark expansion in QCD. We find SU(3) breaking in B mesons suppressed in the framework of the HQE. B_s is expected to have the semileptonic width about 1% lower and Lambda_b about 3% higher when compared to Gamma_{sl}(B_d). The largest partial-rate preasymptotic effect is Pauli interference in the b-->u ell nu channel in Lambda_b, about +10%. We point out that the Omega_b semileptonic width is expected not to exceed that of B_d and may turn out to be the smallest among stable b hadrons despite the large mass. The underlying differences with phase-space models are briefly addressed through the heavy mass expansion.
rate research
Read More
The motion of spectator quarks in decay of a beauty hadron is a nonperturbative effect which can usually be neglected. We find that the motion in some decay channels, which contribute total decay widths of beauty hadrons, can not be neglected.The contributions from these decay channels to decay widths are proportional to certain averages of the squared inverse of the momentum carried by a spectator quark. This fact results in that these contributions, suppressed by $1/m_b^3$ formally, are effectively suppressed by $1/m_b$. We find these contributions can be factorized into products of perturbative coefficients and nonperturbative parameters. We calculate these coefficients and define these nonperturbative parameters in terms of HQET matrix elements.Since these parameters are unknown, we are unable to give numerical predictions in detail. But with a simple model it can be shown that these contributions can be large.
In this work we study the predominantly orbital and radial excitations of hadrons containing a single heavy quark. We present meson and baryon mass splittings and ratios of meson decay constants (e.g., $f_{B_s}/f_B$ and $f_{B_s}/f_{B_s}$) resulting from quenched and dynamical two-flavor configurations. Light quarks are simulated using the chirally improved (CI) lattice Dirac operator at valence masses as light as $M_pi approx 350$ MeV. The heavy quark is approximated by a static propagator, appropriate for the $b$ quark on our lattices ($1/a sim 1-2$ GeV). We also include some preliminary calculations of the $O(1/m_Q^{})$ kinetic corrections to the states, showing, in the process, a viable way of applying the variational method to three-point functions involving excited states. We compare our results with recent experimental findings.
First observations of the decays $Lambda_b^0 to Lambda_c^+ D_{(s)}^-$ are reported using data corresponding to an integrated luminosity of $3,{rm fb}^{-1}$ collected at 7 and 8 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction ${mathcal{B}(B_s^0 to D^+D_s^-)}$ is made and a search is performed for the decays $B^0_{(s)} to Lambda_c^+ Lambda_c^-$. The results obtained are begin{eqnarray*} mathcal{B}(Lambda_b^0 to Lambda_c^+ D^-)/mathcal{B}(Lambda_b^0 to Lambda_c^+ D_{s}^-) &=& 0.042 pm 0.003({rm stat}) pm 0.003({rm syst}), left[frac{mathcal{B}(Lambda_b^0 to Lambda_c^+ D_{s}^-)}{mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+D_s^-)}right]big/left[frac{mathcal{B}(Lambda_b^0 to Lambda_c^+pi^-)}{mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+pi^-)}right] &=& 0.96 pm 0.02({rm stat}) pm 0.06({rm syst}), mathcal{B}(B_s^0 to D^+D_s^-)/mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+D_s^-) &=& 0.038pm0.004({rm stat})pm0.003({rm syst}), mathcal{B}({kern 0.2em}overline{kern -0.2em B}^0 to Lambda_c^+ Lambda_c^-)/mathcal{B}({kern 0.2em}overline{kern -0.2em B}_d^0 to D^+D_s^-) & < & 0.0022; [95% ; {rm C.L.}], mathcal{B}(B^0_{s} to Lambda_c^+ Lambda_c^-)/mathcal{B}(B_s^0 to D^+D_s^-) & < & 0.30; [95% ; {rm C.L.}]. end{eqnarray*} Measurement of the mass of the $Lambda_b^0$ baryon relative to the $B^0$ meson gives ${M(Lambda_b^0) -M(B^0) = 339.72pm 0.24({rm stat}) pm 0.18({rm syst})}$ MeV$/c^2$. This result provides the most precise measurement of the mass of the $Lambda_b^0$ baryon to date.
The Higgs boson branching ratio into vector bosons is sensitive to the decay widths of those vector bosons because they are produced with at least one boson significantly off-shell. Gamma(H to V V ) is approximately proportional to the product of the Higgs boson coupling and the vector boson width. Gamma Z is well known, but Gamma W gives an uncertainty on Gamma(H to W W ) which is not negligible. The ratio of branching ratios, BR(H to W W )/BR(H to ZZ) measured by a combination of ATLAS and CMS at LHC is used herein to extract a width for the W boson of Gamma W = 1.8+0.4-0.3 GeV by assuming Standard Model couplings of the Higgs bosons. This dependence of the branching ratio on Gamma W is not discussed in most Higgs boson coupling analyses.
It has been realized for a long time that knowing the eta and eta wave functions in terms of quark and gluon components probes our understanding of non-perturbative QCD dynamics. Great effort has been given to this challenge -- yet no clear picture has emerged even with the most recent KLOE data. We point out which measurements would be most helpful in arriving at a more definite conclusion. A better knowledge of these wave functions will significantly help to disentangle the weight of different decay subprocesses in semi-leptonic decays of D^+, D_s^+ and B^+ mesons. The resulting insights will be instrumental in treating even non-leptonic B transitions involving $eta$ and $eta^{prime}$ and their CP asymmetries; thus they can sharpen the case for or against New Physics intervening there.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
