scholarly journals A comprehensive study on the semileptonic decay of heavy flavor mesons

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Lu Zhang ◽  
Xian-Wei Kang ◽  
Xin-Heng Guo ◽  
Ling-Yun Dai ◽  
Tao Luo ◽  
...  
Keyword(s):  
Vector Meson ◽  
Quark Model ◽  
Semileptonic Decay ◽  
Branching Fraction ◽  
Form Factors ◽  
Good Control ◽  
New Physics ◽  
Mean Value ◽  
Heavy Flavor ◽  
Final State

Abstract The semileptonic decay of heavy flavor mesons offers a clean environment for extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, which describes the CP-violating and flavor changing process in the Standard Model. The involved form factors where the dynamical information is encoded play an essential role in achieving any conclusive statement. That is, the knowledge of the form factors should be under good control, requiring one to examine more observables in addition to the branching fraction. In this paper, we provide the mean value and the q2-dependent shape for further observables [differential decay distribution (dΓ/dq2), forward-backward asymmetry $$ \left({\mathcal{A}}_{FB}^{ls}\right) $$ A FB ls , longitudinal $$ \left({P}_L^l\right) $$ P L l and transverse $$ \left({P}_T^l\right) $$ P T l polarization of a charged lepton, longitudinal polarization of a vector meson in the final state $$ \left({F}_L^l(V)\right) $$ F L l V , leptonic convexity parameter $$ \left({C}_F^l\right) $$ C F l , and trigonometric moments $$ \left({W}_i^l\right) $$ W i l in the decay of D(s) and B(s) to P/Vl+νl (l = e, μ or τ)], based on the predictions of the relevant form factors from the covariant light-front quark model. P and V denote the pseudoscalar and vector meson, respectively. As a comparison, we find a good agreement with the results from the covariant confining quark model and the relativistic quark model in the literature. As it has been observed that the $$ {P}_L^l $$ P L l and $$ {F}_L^l(V) $$ F L l V are crucial quantities to discriminate various New Physics models, the reexamination of these observables from a different method is also essential and necessary.

scholarly journals D → Klv semileptonic decay using lattice QCD with HISQ at physical pion masses

2018 ◽  
Vol 175 ◽  
pp. 13027 ◽  
Author(s):  
Bipasha Chakraborty ◽  
Christine Davies ◽  
Jonna Koponen ◽  
G Peter Lepage
Keyword(s):  
Standard Model ◽  
Lattice Qcd ◽  
Semileptonic Decay ◽  
Light Quark ◽  
Form Factors ◽  
New Physics ◽  
Ckm Matrix ◽  
Quark Masses ◽  
The Standard Model ◽  
Fertile Ground

he quark flavor sector of the Standard Model is a fertile ground to look for new physics effects through a unitarity test of the Cabbibo-Kobayashi-Maskawa (CKM) matrix. We present a lattice QCD calculation of the scalar and the vector form factors (over a large q2 region including q2 = 0) associated with the D→ Klv semi-leptonic decay. This calculation will then allow us to determine the central CKM matrix element, Vcs in the Standard Model, by comparing the lattice QCD results for the form factors and the experimental decay rate. This form factor calculation has been performed on the Nf = 2 + 1 + 1 MILC HISQ ensembles with the physical light quark masses.

scholarly journals Detailed study of the Λb → Λcτν̄τ decay

2018 ◽  
Vol 33 (29) ◽  
pp. 1850169 ◽  
Author(s):  
E. Di Salvo ◽  
F. Fontanelli ◽  
Z. J. Ajaltouni
Keyword(s):  
Standard Model ◽  
Semileptonic Decay ◽  
Form Factors ◽  
Higgs Doublet ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Left Handed ◽  
The Standard Model ◽  
Analogous Formula ◽  
Two Higgs Doublet Model

We examine in detail the semileptonic decay [Formula: see text], which may confirm previous hints, from the analogous [Formula: see text] decay, of a new physics beyond the Standard Model. First of all, starting from rather general assumptions, we predict the partial width of the decay. Then we analyze the effects of five possible new physics interactions, adopting in each case five different form factors. In particular, for each term beyond the Standard Model, we find some constraints on the strength and phase of the coupling, which we combine with those found by other authors in analyzing the analogous semileptonic decays of [Formula: see text]. Our analysis involves some dimensionless quantities, substantially independent of the form factor, but which, owing to the constraints, turn out to be strongly sensitive to the kind of nonstandard interaction. We also introduce a criterion thanks to which one can discriminate among the various new physics terms: the left-handed current and the two-Higgs-doublet model appear privileged, with a neat preference for the former interaction. Finally, we suggest a differential observable that could, in principle, help to distinguish between the two cases.

scholarly journals B → K(∗)μ+μ− in covariant quark model

2015 ◽  
Vol 39 ◽  
pp. 1560113
Author(s):  
A. Liptaj ◽  
S. Dubnička ◽  
A. Z. Dubničková ◽  
M. A. Ivanov
Keyword(s):  
Beyond Standard Model ◽  
Standard Model ◽  
Quark Model ◽  
Rare Decays ◽  
Form Factors ◽  
New Physics ◽  
Angular Distributions ◽  
Heavy Mesons ◽  
Theoretical Predictions ◽  
Covariant Quark Model

The covariant quark model with infrared confinement (CQM) is a well-suited theoretical framework to describe large variety of hadronic processes, including rare decays of heavy mesons. In this text we focus on the reactions [Formula: see text], which have been recently measured by Refs. 1–4. The measurements include also information about the angular distributions and their significance is given by possible New Physics (NP) effects which are predicted in numerous beyond Standard Model (SM) scenarios. Even with clever choice of experimental observables, a model dependence cannot be fully removed from the theoretical predictions. In this text we present the computation of the [Formula: see text] form factors within the CQM and give results for some of the most commonly used observables ([Formula: see text], [Formula: see text]).

scholarly journals Probing the Effects of New Physics in B¯⁎→Plν¯l Decays

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Qin Chang ◽  
Jie Zhu ◽  
Na Wang ◽  
Ru-Min Wang
Keyword(s):  
Spin Asymmetry ◽  
Branching Fraction ◽  
New Physics ◽  
Heavy Flavor ◽  
Independent Vector ◽  
Vector Type ◽  
Scalar Type ◽  
The Future ◽  
Significant Divergence ◽  
Model Independent

The significant divergence between the SM predictions and experimental measurements for the ratios, RD(⁎)≡B(B¯→D(⁎)τ-ν¯τ)/B(B¯→D(⁎)l′-ν¯l′) with (l′=e,μ), implies possible hint of new physics in the flavor sector. In this paper, motivated by the “RD(⁎) puzzle” and abundant B⁎ data samples at high-luminosity heavy-flavor experiments in the future, we try to probe possible effects of new physics in the semileptonic B¯u,d,s⁎→Pl-ν¯l  (P=D,Ds,π,K) decays induced by b→(u,c)l-ν¯l transitions in the model-independent vector and scalar scenarios. Using the spaces of NP parameters obtained by fitting to the data of RD and RD⁎, the NP effects on the observables including branching fraction, ratio RP⁎, lepton spin asymmetry, and lepton forward-backward asymmetry are studied in detail. We find that the vector type couplings have large effects on the branching fraction and ratio RP⁎. Meanwhile, the scalar type couplings provide significant contributions to all of the observables. The future measurements of these observables in the B¯⁎→Pl-ν¯l decays at the LHCb and Belle-II could provide a way to crosscheck the various NP solutions to the “RD(⁎) puzzle”.

WEAK DECAYS OF B−, $\bar{B}^0$ MESONS TO A PSEUDOSCALAR AND A SCALAR MESON IN THE FINAL STATE

1996 ◽  
Vol 11 (01) ◽  
pp. 129-139 ◽  
Author(s):  
A.C. KATOCH ◽  
R.C. VERMA
Keyword(s):  
Quark Model ◽  
Pseudoscalar Meson ◽  
Scalar Meson ◽  
Form Factors ◽  
Branching Ratios ◽  
Matrix Elements ◽  
Final State ◽  
Factorization Scheme ◽  
Weak Decays

Using the factorization scheme, we study two-body exclusive weak decays of B– and [Formula: see text] mesons to a pseudoscalar meson and a scalar meson in the final state. Employing the Isgur-Scora-Grinstein-Wise quark model to obtain the form factors involved in the decay matrix elements, we calculate the branching ratios for the decays involving b→c transition.

scholarly journals Relativistic calculations of R(D(∗)), R(Ds(∗)), R(ηc) and R(J/ψ)

2020 ◽  
Vol 35 (17) ◽  
pp. 2050076
Author(s):  
Tian Zhou ◽  
Tianhong Wang ◽  
Yue Jiang ◽  
Xiao-Ze Tan ◽  
Geng Li ◽  
...  
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Semileptonic Decay ◽  
Form Factors ◽  
Relativistic Correction ◽  
New Physics ◽  
Decay Rates ◽  
The Standard Model ◽  
Model Predictions

Recently, the deviation of the ratios [Formula: see text], [Formula: see text] and [Formula: see text] have been found between experimental data and the Standard Model predictions, which may be the hint of new physics. In this work, we calculate these ratios within the Standard Model by using the improved instantaneous Bethe–Salpeter method. The emphasis is pad to the relativistic correction of the form factors. The results are [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], which are consistent with predictions of other models and the experimental data. The semileptonic decay rates and corresponding form factors at zero recoil are also given.

scholarly journals QED factorization of non-leptonic B decays

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Martin Beneke ◽  
Philipp Böer ◽  
Jan-Niklas Toelstede ◽  
K. Keri Vos
Keyword(s):  
Weak Interactions ◽  
Branching Fractions ◽  
Form Factors ◽  
New Physics ◽  
Final States ◽  
Final State ◽  
Qcd Factorization ◽  
Factorization Formula ◽  
Qed Effects ◽  
Electrically Charged

Abstract We show that the QCD factorization approach for B-meson decays to charmless hadronic two-body final states can be extended to include electromagnetic corrections. The presence of electrically charged final-state particles complicates the framework. Nevertheless, the factorization formula takes the same form as in QCD alone, with appropriate generalizations of the definitions of light-cone distribution amplitudes and form factors to include QED effects. More precisely, we factorize QED effects above the strong interaction scale ΛQCD for the non-radiative matrix elements $$ \left\langle {M}_1{M}_2\left|{Q}_i\right|\overline{B}\right\rangle $$ M 1 M 2 Q i B ¯ of the current-current operators from the effective weak interactions. The rates of the branching fractions for the infrared-finite observables $$ \overline{B}\to {M}_1{M}_2\left(\gamma \right) $$ B ¯ → M 1 M 2 γ with photons of maximal energy ∆E ≪ ΛQCD is then obtained by multiplying with the soft-photon exponentiation factors. We provide first estimates for the various electromagnetic corrections, and in particular quantify their impact on the πK ratios and sum rules that are often used as diagnostics of New Physics.

scholarly journals THE ELECTRIC AND MAGNETIC FORM FACTORS OF THE NEUTRON

1993 ◽  
Vol 08 (22) ◽  
pp. 2135-2140 ◽  
Author(s):  
FELIX SCHLUMPF
Keyword(s):  
Wave Function ◽  
Vector Meson ◽  
Quark Model ◽  
Constituent Quark ◽  
Sum Rules ◽  
Form Factors ◽  
Constituent Quark Model ◽  
Specific Form ◽  
Vector Meson Dominance ◽  
Magnetic Form Factors

We derive the electric and magnetic form factors of the neutron in the framework of a relativistic constituent quark model. Our parameter free prediction agrees well with a recent, accurate measurement. The relativistic features of the model and the specific form of the wave function are essential for the result. Comparisons are made to other models based on vector meson dominance, perturbative QCD and QCD sum rules.

scholarly journals The role of right-handed neutrinos in b → cτ (πντ, ρντ, μ$$ \overline{\nu} $$μντ)$$ \overline{\nu} $$τ from visible final-state kinematics

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Neus Penalva ◽  
Eliecer Hernández ◽  
Juan Nieves
Keyword(s):  
Semileptonic Decay ◽  
Massive Particle ◽  
New Physics ◽  
Experimental Information ◽  
Final State ◽  
Spin Asymmetries ◽  
Decay Modes ◽  
Lepton Flavor ◽  
Rule Out

Abstract In the context of lepton flavor universality violation (LFUV) studies, we fully derive a general tensor formalism to investigate the role that left- and right-handed neutrino new-physics (NP) terms may have in b → cτ$$ \overline{\nu} $$ ν ¯ τ transitions. We present, for several extensions of the Standard Model (SM), numerical results for the Λb → Λcτ$$ \overline{\nu} $$ ν ¯ τ semileptonic decay, which is expected to be measured with precision at the LHCb. This reaction can be a new source of experimental information that can help to confirm, or maybe rule out, LFUV presently seen in $$ \overline{B} $$ B ¯ meson decays. The present study analyzes observables that can help in distinguishing between different NP scenarios that otherwise provide very similar results for the branching ratios, which are our currently best hints for LFUV. Since the τ lepton is very short-lived, we consider three subsequent τ-decay modes, two hadronic πντ and ρντ and one leptonic μ$$ \overline{\nu} $$ ν ¯ μντ, which have been previously studied for $$ \overline{B} $$ B ¯ → D(*) decays. Within the tensor formalism that we have developed in previous works, we re-obtain the expressions for the differential decay width written in terms of visible (experimentally accessible) variables of the massive particle created in the τ decay. There are seven different τ angular and spin asymmetries that are defined in this way and that can be extracted from experiment. Those asymmetries provide observables that can help in constraining possible SM extensions.

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