Decays Of Bs Mesons Research Articles

Review of Flavor Anomalies

Lepton flavor universality exists in the Standard Model, and hence any observation of the violation of this universality will be a hint for new physics. Recent experimental searches for processes violating this symmetry have attracted much attention among theorists and experimentalists alike. In recent years, such hints have been observed in flavor changing neutral current weak processes such as b→sll and charged current weak processes such as b→clν processes by collider experiments like Belle, Belle II, BaBar, LHCb, ATLAS, and CMS collaborations, where b,s,c are the bottom, strange, and charm quarks, respectively, and l,ν stand for lepton and the corresponding lepton neutrino, respectively. This article is a review of some of the interesting anomalies observed in the B-sector and includes decays of Bs mesons.

Strange hadrocharmonium

It has been recently suggested that the charged charmoniumlike resonances Zc(4100) and Zc(4200) are two states of hadrocharmonium, related by the charm quark spin symmetry in the same way as the lowest charmonium states ηc and J/ψ. It is pointed out here that in this picture one might expect existence of their somewhat heavier strange counterparts, Zcs, decaying to ηcK and J/ψK. Some expected properties of such charmoniumlike strange resonances are discussed that set benchmarks for their search in the decays of the strange Bs mesons.

Quark-lepton mass relation and CKM mixing in anA4extension of the minimal supersymmetric standard model

An interesting mass relation between down type quarks and charged leptons has been recently predicted within a supersymmetric SU(3)_c \times SU(2)_L \times U(1)_Y model based on the A4 flavor symmetry. Here we propose a simple extension which provides an adequate full description of the quark sector. By adding a pair of vector-like up-quarks we show how the CKM entries Vub, Vcb, Vtd and Vts arise from deviations of the unitarity. We perform an analysis including the most relevant observables in the quark sector, such as oscillations and rare decays of Kaons, Bd and Bs mesons. In the lepton sector, model predicts an inverted hierarchy for the neutrino masses leading to a potentially observable rate of neutrinoless double beta decay.

Heavy-light mesons in lattice HQET and QCD

We present a study of a combination of HQET and relativistic QCD to extract the b-quark mass and the Bs-meson decay constant from lattice quenched simulations. We start from a small volume, where one can directly simulate the b-quark, and compute the connection to a large volume, where finite size effects are negligible, through a finite size technique. The latter consists of steps extrapolated to the continuum limit, where the b-region is reached through interpolations guided by the effective theory. With the lattice spacing given in terms of the Sommer's scale r0 and the experimental Bs and K masses, we get the final results for the renormalization group invariant mass Mb = 6.88(10) GeV, translating into mb(mb) = 4.42(6) GeV in the MSbar scheme, and fBs = 191(6) MeV for the decay constant. A renormalization condition for the chromo-magnetic operator, responsible, at leading order in the heavy quark mass expansion of HQET, for the mass splitting between the pseudoscalar and the vector channel in mesonic heavy-light bound states, is provided in terms of lattice correlations functions which well suits a non-perturbative computation involving a large range of renormalization scales and no valence quarks. The two-loop expression of the corresponding anomalous dimension in the Schroedinger functional (SF) scheme is computed starting from results in the literature; it requires a one-loop calculation in the SF scheme with a non-vanishing background field. The cutoff effects affecting the scale evolution of the renormalization factors are studied at one-loop order, and confirmed by non-perturbative quenched computations to be negligible for the numerical precision achievable at present.

Lattice HQET with exponentially improved statistical precision

We introduce an alternative discretization for static quarks on the lattice retaining the O(a)-improvement properties of the Eichten–Hill action. In this formulation, statistical fluctuations are reduced by a factor which grows exponentially with Euclidean time, x0. For the first time, B-meson correlation functions are computed with good statistical precision in the static approximation for x0>1 fm. At lattice spacings a≈0.1, 0.08, 0.07 fm, the Bs-meson decay constant is determined in the combined static and quenched approximation. A correction due to the finite mass of the b-quark is estimated by interpolating between the static result and a recent determination of FDs.

Weak radiative decays of Bs mesons.

We discuss the main rare radiative decays of the strange ${B}_{s}$ mesons, ${B}_{s}\ensuremath{\rightarrow}\ensuremath{\varphi}\ensuremath{\gamma}$ and ${B}_{s}\ensuremath{\rightarrow}{K}^{*}\ensuremath{\gamma}$. ${B}_{s}\ensuremath{\rightarrow}\ensuremath{\varphi}\ensuremath{\gamma}$ is the dominant mode, expected at a branching ratio of (0.3-0.5)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$. The calculation of these exclusive channels with two different approaches emphasizes an uncertainty in the prediction of about 2-3. Additional modes are ${B}_{s}\ensuremath{\rightarrow}\ensuremath{\varphi}{e}^{+}e$, ${B}_{s}\ensuremath{\rightarrow}\ensuremath{\varphi}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ at the ${10}^{\ensuremath{-}6}$ level and ${B}_{s}\ensuremath{\rightarrow}(\ensuremath{\eta},{\ensuremath{\eta}}^{\ensuremath{'}}){e}^{+}{e}^{\ensuremath{-}}$, ${B}_{s}\ensuremath{\rightarrow}(\ensuremath{\eta},{\ensuremath{\eta}}^{\ensuremath{'}}){\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ at the ${10}^{\ensuremath{-}7}$ level.