اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLimit on a Right-Handed Admixture to the Weak $b to c$ Current from Semileptonic Decays
77
0
0.0
(
0
)
تأليف
Robert Feger
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We determine an upper bound for a possible right-handed $b{to}c$ quark current admixture in semileptonic $bar{B} to X_{c} ell^{-} bar{ u}$ decays from a simulateous fit to moments of the lepton-enery and hadronic-mass distribution measured as a function of the lower limit on the lepton energy, using data measured by the babar detector. The right-handed admixture is parametrized by a new parameter $c_R$ as coefficient of computed moments with right-handed quark current. For the standard model part we use the prediction of the heavy-quark expansion (HQE) up to order $1/m_b^3$ and perturbative corrections and for the right-handed contribution only up to order $1/m_b^2$ and perturbative corrections. We find $cR=0.05asympm{+0.33}{-0.50}$ in agreement with the standard-model prediction of zero. Additionally, we give a contraint on a possible right-handed admixture from exclusive decays, which is with a value of $cR =0.01{pm}0.03$ more restrictive than our value from the inclusive fit. The difference in Vcb between the inclusive and exclusive extraction is only slightly reduced when allowing for a right-handed admixture in the range of $cR=0.01 {pm} 0.03$.
قيم البحث
اقرأ أيضاً
Motivated by the persistent anomalies reported in the $bto ctaubar{ u}$ data, we perform a general model-independent analysis of these transitions, in the presence of light right-handed neutrinos. We adopt an effective field theory approach and write
a low-energy effective Hamiltonian, including all possible dimension-six operators. The corresponding Wilson coefficients are determined through a numerical fit to all available experimental data. In order to work with a manageable set of free parameters, we define eleven well-motivated scenarios, characterized by the different types of new physics that could mediate these transitions, and analyse which options seem to be preferred by the current measurements. The data exhibit a clear preference for new-physics contributions, and good fits to the data are obtained in several cases. However, the current measurement of the longitudinal $D^*$ polarization in $Bto D^*tau bar u$ cannot be easily accommodated within its experimental $1sigma$ range. A general analysis of the three-body $Bto D tau bar u$ and four-body $Bto D^*(to Dpi)tau bar u$ angular distributions is also presented. The accessible angular observables are studied in order to assess their sensitivity to the different new physics scenarios. Experimental information on these distributions would help to disentangle the dynamical origin of the current anomalies.
We consider the recent LHCb result for $B_cto J/psi tau u$ in conjunction with the existing anomalies in $R(D)$ and $R(D^star)$ within the framework of a right-handed current with enhanced couplings to the third generation. The model predicts a line
ar relation between the observables and their SM values in terms of two combinations of parameters. The strong constraints from $bto s gamma$ on $W-W^prime$ mixing effectively remove one of the combinations of parameters resulting in an approximate proportionality between all three observables and their SM values. To accommodate the current averages for $R(D)$ and $R(D^star)$, the $W^prime$ mass should be near 1 TeV, and possibly accessible to direct searches at the LHC. In this scenario we find that $R(J/psi)$ is enhanced by about 20% with respect to its SM value and about 1.5$sigma$ below the central value of the LHCb measurement. The predicted $dGamma/dq^2$ distribution for $Bto D(D^star) tau u$ is in agreement with the measurement and the model satisfies the constraint from the $B_c$ lifetime.
In this paper, we study the extended Standard Model (SM) with an extra Higgs doublet and right-handed neutrinos. If the symmetry to distinguish the two Higgs doublets is not assigned, flavor changing neutral currents (FCNCs) involving the scalars are
predicted even at the tree level. We investigate the constraints on the FCNCs at the one-loop level, and especially study the semileptonic $B$ meson decays, e.g. $B to D^{(*)} tau u$ and $B to K^{(*)} ll$ processes, where the SM predictions are more than $2 sigma$ away from the experimental results. We also consider the flavor-violating couplings involving right-handed neutrinos and discuss if the parameters to explain the excesses of the semileptonic $B$ decays can resolve the discrepancy in the the anomalous muon magnetic moment. Based on the analysis, we propose the smoking-gun signals of our model at the LHC.
We give a summary of the discussions in Working Group V of the CKM2010 workshop dealing with determinations of the angle gamma of the unitarity triangle of the Cabibbo-Kobayashi-Maskawa matrix from B-meson decays into charmed final states.
We analyze the semileptonic rare decays of $B$ meson to $K_{1} (1270)$ and $K_{1} (1400)$ axial vector mesons. The $Bto K_{1} (1270,1400) ell^+ ell^-$ decays are significant flavor changing neutral current decays of the $B$ meson. These decays are se
nsitive to the new physics beyond SM, since these processes are forbidden at tree level at SM. These decays occurring at the quark level via $bto s ell^+ ell^- $ transition, also provide new opportunities for calculating the CKM matrix elements $V_{bt}$ and $V_{ts}$. In this study, the transition form factors of the $Bto K_{1} (1270,1400) ell^+ ell^-$ decays are calculated using three-point QCD sum rules approach. The resulting form factors are used to estimate the branching fractions of these decays.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
