اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSemileptonic charm decays $D to pi l u_{l}$ and $D to K l u_l$ from QCD Light-Cone Sum Rules
126
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present a new calculation of the $Dtopi$ and $D to K$ form factors from QCD light-cone sum rules. The $overline{MS}$ scheme for the $c$-quark mass is used and the input parameters are updated. The results are $f^+_{Dpi}(0)= 0.67^{+0.10}_{-0.07}$, $f^+_{DK}(0)=0.75^{+0.11}_{-0.08}$ and $f^+_{Dpi}(0)/f^+_{DK}(0)=0.88 pm 0.05$. Combining the calculated form factors with the latest CLEO data, we obtain $|V_{cd}|=0.225pm 0.005 pm 0.003 ^{+0.016}_{-0.012}$ and $|V_{cd}|/|V_{cs}|= 0.236pm 0.006pm 0.003pm 0.013$ where the first and second errors are of experimental origin and the third error is due to the estimated uncertainties of our calculation. We also evaluate the form factors $f^-_{Dpi}$ and $f^-_{DK}$ and predict the slope parameters at $q^2=0$. Furthermore, calculating the form factors from the sum rules at $q^2<0$, we fit them to various parameterizations. After analytic continuation, the shape of the $Dto pi,K $ form factors in the whole semileptonic region is reproduced, in a good agreement with experiment.
قيم البحث
اقرأ أيضاً
We analyse the semileptonic decay D+ -> K- pi+ l+ nu(l) using an effective Lagrangian developed previously to describe the decays D -> P l nu(l) and D -> V l nu(l). Light vector mesons are included in the model which combines the heavy quark effectiv
e Lagrangian and chiral perturbation theory approach. The nonresonant and resonant contributions are compared. With no new parameters the model correctly reproduces the measured ratio Gamma(nres)/Gamma(nres + res). We also present useful nonresonant decay distributions. Finally, a similar model, but with a modified current which satisfies the soft pion theorems at the expense of introducing another parameter, is analyzed and the results of the models are compared.
We employ the $Btopi$ form factors obtained from QCD light-cone sum rules and calculate the $Bto pi ell u_l$ width ($ell=e,mu$) in units of $1/|V_{ub}|^2$, integrated over the region of accessible momentum transfers, $0leq q^2leq 12.0 ~GeV^2$. Using
the most recent BABAR-collaboration measurements we extract $|V_{ub}|=(3.50^{+0.38}_{-0.33}big|_{th.}pm 0.11 big|_{exp.})times 10^{-3}$. The sum rule results for the form factors, taken as an input for a $z$-series parameterization, yield the $q^2$-shape in the whole semileptonic region of $Bto piell u_ell$. We also present the charged lepton energy spectrum in this decay. Furthermore, the current situation with $Bto tau u_tau$ is discussed from the QCD point of view. We suggest to use the ratio of the $Bto pi tau u_tau$ and $Bto piell u_l ~(ell =mu,e) $ widths as an additional test of Standard Model. The sensitivity of this observable to new physics is illustrated by including a charged Higgs-boson contribution in the semileptonic decay amplitude.
We revisit the calculation of the strong couplings $D^*Dpi$ and $B^*Bpi$ from the QCD light-cone sum rules using the pion light-cone distribution amplitudes. The accuracy of the correlation function, calculated from the operator product expansion nea
r the light-cone, is upgraded by taking into account the gluon radiative corrections to the twist-3 terms. The double spectral density of the correlation function, including the twist-2, 3 terms at ${cal O} (alpha_s)$ and the twist-4 LO terms, is presented in an analytical form for the first time. This form allows us to use vario
We derive new QCD sum rules for $Bto D$ and $Bto D^*$ form factors. The underlying correlation functions are expanded near the light-cone in terms of $B$-meson distribution amplitudes defined in HQET, whereas the $c$-quark mass is kept finite. The le
ading-order contributions of two- and three-particle distribution amplitudes are taken into account. From the resulting light-cone sum rules we calculate all $Bto Dst $ form factors in the region of small momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the sum rules reduce to a single expression for the Isgur-Wise function. We compare our predictions with the form factors extracted from experimental $Bto Dst l u_l$ decay rates fitted to dispersive parameterizations.
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 wi
th 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.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
