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Register a new userThe transition form factors for semi-leptonic weak decays of $J/psi$ in QCD sum rules
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Within the Standard Model, we investigate the semi-leptonic weak decays of $J/psi$. The various form factors of $J/psi$ transiting to a single charmed meson ($D^{(*)}_{(d,s)}$) are studied in the framework of the QCD sum rules. These form factors fully determine the rates of the weak semi-leptonic decays of $J/psi$ and provide valuable information about the non-perturbative QCD effects. Our results indicate that the decay rate of the semi-leptonic weak decay mode $J/psi to D^{(*)-}_{s}+e^{+}+ u_{e}$ is at order of $10^{-10}$.
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We report on form factors for the B->K l^+ l^- semi-leptonic decay process. We use several lattice spacings from a=0.12 fm down to 0.06 fm and a variety of dynamical quark masses with 2+1 flavors of asqtad quarks provided by the MILC Collaboration. These ensembles allow good control of the chiral and continuum extrapolations. The b-quark is treated as a clover quark with the Fermilab interpretation. We update our results for f_parallel and f_perp, or, equivalently, f_+ and f_0. In addition, we present new results for the tensor form factor f_T. Model independent results are obtained based upon the z-expansion.
Semi-leptonic $B$ decays provide promising channels to test the Standard Model, search for signs of new physics, or determine fundamental parameters like CKM matrix elements. We present an update on our calculation of short distance contributions to GIM suppressed rare $B$ decays focusing in particular on $B_sto phi ell^+ ell^-$ decays. Furthermore we show first results for our calculation of $B_{(s)}to D_{(s)}^{(*)}ell u$ semi-leptonic decays involving $bto c$ transitions. Our calculations are based on RBC-UKQCDs 2+1 flavor domain-wall fermion and Iwasaki gauge field configurations featuring three lattice spacings in the range $1.73$ GeV $le a^{-1} le 2.77$ GeV and pion masses down to the physical value. We calculate the form factors by simulating $b$-quarks using the relativistic heavy quark action, create light $u/d$ and $s$ quarks with standard domain-wall kernel, and use optimised Mobius domain-wall fermions for charm quarks.
In this work, the full leading order results of the form factors for $Xi_{b}toXi_{c}$ and $Lambda_{b}toLambda_{c}$ are obtained in QCD sum rules. Contributions from up to dim-5 have been considered. For completeness, we also study the two-point correlation function to obtain the pole residues of $Xi_{Q}$ and $Lambda_{Q}$, and higher accuracy is achieved. For the three-point correlation function, since stable Borel regions can not be found, about $20%$ uncertainties are introduced for the form factors of $Xi_{b}toXi_{c}$ and $Lambda_{b}toLambda_{c}$. Our results for the form factors are consistent with those of the Lattice QCD within errors.
In our previous study, we calculated the transition from factors of $J/psito D^{(*)}_{(s)}$ using the QCD sum rules. Based on the factorization approximation, the obtained form factors can be applied to evaluate the weak non-leptonic decay rates of $J/psito D^{(*)}_{(s)}+M$, where $M$ stands for a light pseudoscalar or vector meson. We predict that the branching ratio for inclusive non-leptonic two-body weak decays of $J/psi$ which are realized via the spectator mechanism, can be as large as $1.3 times 10^{-8}$, in particular, the branching ratio of $J/psito D^{*pm}_s+rho^mp$ can reach $5.3 times 10^{-9}$. Such values will be marginally accessed by the ability of BESIII which will begin running very soon.
We review the calculations of form factors and coupling constants in vertices with charm mesons in the framework of QCD sum rules. We first discuss the motivation for this work, describing possible applications of these form factors to heavy ion collisions and to B decays. We then present an introduction to the method of QCD sum rules and describe how to work with the three-point function. We give special attention to the procedure employed to extrapolate results obtained in the deep euclidean region to the poles of the particles, located in the time-like region. We present a table of ready-to-use parametrizations of all the form factors, which are relevant for the processes mentioned in the introduction. We discuss the uncertainties in our results. We also give the coupling constants and compare them with estimates obtained with other methods. Finally we apply our results to the calculation of the cross section of the reaction $J/psi + pi rightarrow D + bar{D^*}$.
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