Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userPerturbative corrections to $B to D$ form factors in QCD
133
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We compute perturbative QCD corrections to $B to D$ form factors at leading power in $Lambda/m_b$, at large hadronic recoil, from the light-cone sum rules (LCSR) with $B$-meson distribution amplitudes in HQET. QCD factorization for the vacuum-to-$B$-meson correlation function with an interpolating current for the $D$-meson is demonstrated explicitly at one loop with the power counting scheme $m_c sim {cal O} left (sqrt{Lambda , m_b} right ) $. The jet functions encoding information of the hard-collinear dynamics in the above-mentioned correlation function are complicated by the appearance of an additional hard-collinear scale $m_c$, compared to the counterparts entering the factorization formula of the vacuum-to-$B$-meson correction function for the construction of $B to pi$ from factors. Inspecting the next-to-leading-logarithmic sum rules for the form factors of $B to D ell u$ indicates that perturbative corrections to the hard-collinear functions are more profound than that for the hard functions, with the default theory inputs, in the physical kinematic region. We further compute the subleading power correction induced by the three-particle quark-gluon distribution amplitudes of the $B$-meson at tree level employing the background gluon field approach. The LCSR predictions for the semileptonic $B to D ell u$ form factors are then extrapolated to the entire kinematic region with the $z$-series parametrization. Phenomenological implications of our determinations for the form factors $f_{BD}^{+, 0}(q^2)$ are explored by investigating the (differential) branching fractions and the $R(D)$ ratio of $B to D ell u$ and by determining the CKM matrix element $|V_{cb}|$ from the total decay rate of $B to D mu u_{mu}$.
rate research
Read More
We calculate the $Bto D^{(*)}$ form factors in the heavy-quark and large-recoil limits in the perturbative QCD framework based on $k_T$ factorization theorem, assuming the hierachy $M_Bgg M_{D^{(*)}}gg barLambda$, with the $B$ meson mass $M_B$, the $D^{(*)}$ meson mass $M_{D^{(*)}}$, and the heavy meson and heavy quark mass difference $barLambda$. The qualitative behavior of the light-cone $D^{(*)}$ meson wave function and the associated Sudakov resummation are derived. The leading-power contributions to the $Bto D^{(*)}$ form factors, characterized by the scale $barLambdasqrt{M_B/M_{D^{(*)}}}$, respect the heavy-quark symmetry. The next-to-leading-power corrections in $1/M_B$ and $1/M_{D^{(*)}}$, characterized by a scale larger than $sqrt{barLambda M_B}$, are estimated to be less than 20%. The $D^{(*)}$ meson wave function is determined from the fit to the observed $Bto D^{(*)} l u$ decay spectrum, which can be employed to make predictions for nonleptonic decays, such as $Bto D^{(*)}pi(rho)$.
We compute perturbative corrections to $B to pi$ form factors from QCD light-cone sum rules with $B$-meson distribution amplitudes. Applying the method of regions we demonstrate factorization of the vacuum-to-$B$-meson correlation function defined with an interpolating current for pion, at one-loop level, explicitly in the heavy quark limit. The short-distance functions in the factorization formulae of the correlation function involves both hard and hard-collinear scales; and these functions can be further factorized into hard coefficients by integrating out the hard fluctuations and jet functions encoding the hard-collinear information. Resummation of large logarithms in the short-distance functions is then achieved via the standard renormalization-group approach. We further show that structures of the factorization formulae for $f_{B pi}^{+}(q^2)$ and $f_{B pi}^{0}(q^2)$ at large hadronic recoil from QCD light-cone sum rules match that derived in QCD factorization. In particular, we perform an exploratory phenomenological analysis of $B to pi$ form factors, paying attention to various sources of perturbative and systematic uncertainties, and extract $|V_{ub}|= left(3.05^{+0.54}_{-0.38} |_{rm th.} pm 0.09 |_{rm exp.}right) times 10^{-3}$ with the inverse moment of the $B$-meson distribution amplitude $phi_B^{+}(omega)$ determined by reproducing $f_{B pi}^{+}(q^2=0)$ obtained from the light-cone sum rules with $pi$ distribution amplitudes. Furthermore, we present the invariant-mass distributions of the lepton pair for $B to pi ell u_{ell}$ ($ell= mu ,, tau$) in the whole kinematic region. Finally, we discuss non-valence Fock state contributions to the $B to pi$ form factors $f_{B pi}^{+}(q^2)$ and $f_{B pi}^{0}(q^2)$ in brief.
We update QCD calculations of $B to pi, K$ form factors at large hadronic recoil by including the subleading-power corrections from the higher-twist $B$-meson light-cone distribution amplitudes (LCDAs) up to the twist-six accuracy and the strange-quark mass effects at leading-power in $Lambda/m_b$ from the twist-two $B$-meson LCDA $phi_B^{+}(omega, mu)$. The higher-twist corrections from both the two-particle and three-particle $B$-meson LCDAs are computed from the light-cone QCD sum rules (LCSR) at tree level. In particular, we construct the local duality model for the twist-five and -six $B$-meson LCDAs, in agreement with the corresponding asymptotic behaviours at small quark and gluon momenta, employing the QCD sum rules in heavy quark effective theory at leading order in $alpha_s$. The strange quark mass effects in semileptonic $B to K$ form factors yield the leading-power contribution in the heavy quark expansion, consistent with the power-counting analysis in soft-collinear effective theory, and they are also computed from the LCSR approach due to the appearance of the rapidity singularities. We further explore the phenomenological aspects of the semileptonic $B to pi ell u$ decays and the rare exclusive processes $B to K u u$, including the determination of the CKM matrix element $|V_{ub}|$, the normalized differential $q^2$ distributions and precision observables defined by the ratios of branching fractions for the above-mentioned two channels in the same intervals of $q^2$.
Applying the vacuum-to-$B$-meson correlation functions with an interpolating current for the light vector meson we construct the light-cone sum rules (LCSR) for the effective form factors $xi_{parallel}(n cdot p)$, $xi_{perp}(n cdot p)$, $Xi_{parallel}(tau, n cdot p)$ and $Xi_{perp}(tau, n cdot p)$, defined by the corresponding hadronic matrix elements in soft-collinear effective theory (SCET), entering the leading-power factorization formulae for QCD form factors responsible for $B to V ell bar u_{ell}$ and $B to V ell bar ell$ decays at large hadronic recoil at next-to-leading-order in QCD. The light-quark mass effect for the local SCET form factors $xi_{parallel}(n cdot p)$ and $xi_{perp}(n cdot p)$ is also computed from the LCSR method with the $B$-meson light-cone distribution amplitude $phi_B^{+}(omega, mu)$ at ${cal O}(alpha_s)$. Furthermore, the subleading power corrections to $B to V$ form factors from the higher-twist $B$-meson light-cone distribution amplitudes are also computed with the same method at tree level up to the twist-six accuracy. Having at our disposal the LCSR predictions for $B to V$ form factors, we further perform new determinations of the CKM matrix element $|V_{ub}|$ from the semileptonic $B to rho , ell , bar u_{ell}$ and $B to omega , ell , bar u_{ell}$ decays, and predict the normalized differential branching fractions and the $q^2$-binned $K^{ast}$ longitudinal polarization fractions of the exclusive rare $B to K^{ast} , u_{ell} , bar u_{ell}$ decays.
We present an overview of state of the art lattice quantum chromodynamcis calculations for heavy-light quantities. Special focus is given to the calculation of form factors for semi-leptonic decays of $B_{(s)}$ and $D$ mesons, the extraction of the Cabibbo-Kobayashi-Maskawa matrix elements $|V_{ub}|$ and $|V_{cb}|$ as well as the determination of $R(D^{(*)})$ testing the universality of lepton flavors in $bto c$ transitions. In addition we report on the determination of $b$ and $c$ quark masses as well as on neutral $B_{(s)}$ meson mixing. Recent results are summarized and new developments highlighted.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
