Form factors of theB−Stransitions in the covariant quark model

Abstract

In the wake of exploring uncertainty in the full angular distribution of the B → Kπ + µ + µ − decay caused by the presence of the intermediate scalar K * 0 meson, we perform the straightforward calculation of the B(Bs) → S (S is a scalar meson) transition form factors in the full kinematical region within the covariant quark model. We restrict ourselves to the scalar mesons below 1 GeV: a0(980), f0(500), f0(980), and K * 0 (800). As an application of the obtained results we calculate the widths of the semileptonic and rare decays B(Bs) → Sℓν, B(Bs) → Sℓl and B(Bs) → Sνν. We compare our results with those obtained in other approaches.Recently, much attention has been paid to the rare flavor-changing neutral current decay B → K * (→ Kπ)µ + µ − . One of the reasons for this was the first measurement of form-factor-independent angular observables performed by the LHCb Collaboration [1,2]. It has been claimed that there is a 3.7σ deviation from the Standard Model (SM) prediction for one of the angular observables. Much effort has been spent to explain this deviation by invoking the effects of new physics (NP) (for example, see Refs. [3][4][5][6][7][8][9] and references therein). The main emphasis of the above-mentioned papers was on the search for the physical observables that have low sensitivity to the form factors.In addition to the NP effects, the uncertainties related to the presence of the intermediate scalar resonance K * 0 decaying into Kπ have been intensively discussed in the literature [10][11][12][13][14][15][16]. A detailed analysis of the B → K * J (→ Kπ)µ + µ − decay in the higher kaon resonance region was done in Ref. [10]. In many papers, the Breit-Wigner form for the Kπ mass spectra was used. However, this assumption cannot be justified for the broad scalar resonances like the K * 0 (800) meson. The improvement of the description was done in Ref.[11] by invoking the chiral perturbation theory for the Kπ interaction. This issue was also generalized to B s → Kπℓν in Ref. [12].As is well-known, short-distance physics is under control in the description of the rare B decays, whereas the effects of long-distance physics described by the hadronic form factors lead to large uncertainties since they involve nonperturbative QCD. The calculation of the B → K * transition form factors have been performed in many theoretical approaches and models. We must mention some of them: light-cone QCD sum rules [17], QCD sum rules [18], the lattice-constrained dispersion quark model [19], the simple dipole parametrization [20], perturbative QCD at large recoil region [21], the relativistic quark model [22], and the Dyson-Schwinger equations in QCD [23].The B s and D s to K * 0 (1430) transition form factors were calculated in Ref. [27] within an approach based on QCD sum rules. The form factors for the B → K * 0 (1430) transition have been evaluated in the light-front quark model [28]. The form factors of rare B → K * 0 (1430)ℓ + ℓ − decay were calculated in Ref. [29] within three-point QCD sum rules. The B → S transition...

Phenomenology of GeV-scale scalar portal

“…We assume that K * 0 (700) is a di-quark state and K * 0 (1430) is its excited state. There are no experimentally observed decays B → K * 0 (700)X, and therefore there is quite large theoretical uncertainty in determination of the form-factors (see a discussion in [87]). We will use [52], where there are results for B → K * 0 (700) and B → K * 0 (1430), and the results for the latter are in good agreement with the experimental data for B → K * 0 (1430)η decay.…”

Study of Bs→ℓ+ℓ−γ decays in covariant quark model

“…In this paper we use the results of the updated fit performed in Refs. [20,24,25]. The central values of the model parameters involved in this paper are given by (in GeV)…”

B → ρ decay form factors from covariant confined quark model

“…More details concerning the model can be found in our previous papers [10,11]. Below, we list the definitions of the dimensionless invariant transition form factors together with the covariant quark model expressions that allow one to calculate them.…”