Results 1 - 10 of 1135392
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[en] The rate of the semileptonic decay b→clν is calculated with O(αs2) accuracy, as an expansion around the limit of equal masses of the b and c quarks. Recent results obtained around the limit of the c-quark much lighter than b are confirmed. Details of the new expansion method are described.
[en] We present technical aspects of next-to-next-to-leading order calculations for heavy-to-light decays such as top quark decay, semileptonic b quark decay into a u quark, muon decay, and radiative decays like b→sγ. Algebraic reduction of integrals to a set of master integrals is described, methods of determining the master integrals are presented, and a complete list of master integrals is given. As a sample application, the top quark decay width is calculated to O(αs2) accuracy
[en] We qualitatively corroborate the results of [W. Roberts, M. Pervin, Int. J. Mod. Phys. A 24 (2009) 2401] according to which hyperfine mixing greatly affects the decay widths of b→c semileptonic decays involving doubly heavy bc baryons. However, our predictions for the decay widths of the unmixed states differ from those reported in the work of Roberts and Pervin by a factor of 2, and this discrepancy translates to the mixed case. We further show that the predictions of heavy quark spin symmetry, might be used in the future to experimentally extract information on the admixtures in the actual physical bc baryons, in a model independent manner.
[en] Direct photon production in association with a heavy quark can serve as an excellent tool for the study of the heavy quark distributions. Currently it is believed that heavy quarks are produced radiatively inside the nucleus, and so there is no need to take into account heavy quark parameters inside global PDF analysis. Certain models taking into account the possibility of an intrinsic charm component exist. Here we present how these affect the γ+c cross section. While at pA collisions the potential of this process to constrain the gluon nuclear PDF which is currently largely unconstrained is presented.
[en] Recent experimental results on D-, F- and B-decays are interpreted on the basis of the valence quark model. Transition form factors of currents from heavy mesons to much lighter ones are calculated using relativistic wave functions. The semileptonic decay spectra are mainly determined by a few exclusive channels. The detection of the decay mode B- → ρ0e-antiν will be essential for obtaining |Vub/Vcb|. For nonleptonic decays generally good results are obtained using factorization with little direct annihilation. Small bare amplitudes can be fed by stronger amplitudes through channel mixing caused by strong interaction, an effect which possibly simulates in some instance a direct weak annihilation process. To some extent this proposition can be tested in F+-decays. 22 refs
[en] The implementation of heavy quarks and prompt photons in EPOS is presented. One of the interests of event generators is their capability to reproduce exclusive observables. Our results for charms and prompt photons, in p-p collisions at , are compared with experiments and FONLL calculations . (paper)
[en] In this introductory overview I will discuss recent developments in hadron spectroscopy that are of particular relevance to this meeting, including the spectroscopy of heavy quark hadrons, exotic and multiquark systems, and new theoretical results such as developments in LQCD. (author)
[en] In this paper, the electromagnetic mass differences of heavy hadrons are discussed, while the relevant hyperfine interactions are ignored. The effects of one-photon exchange interaction and up-down quark mass difference are parametrized. Two mass difference equations 2Σc+-(Σc+++Σc0)=2Σb0-(Σb++Σb-) and (Ξcc+-Ξcc++)+(Ξbb--Ξbb0)=2(Ξbc0-Ξbc+) for the heavy baryons are obtained. In addition, the masses of Σb0, Ξb0, and Ξcc++ are predicted based on the known experimental data.
[en] Using the helicity formalism, we compute the contribution of a quark-antiquark pair to the tree-level multigluon amplitudes in the high-energy limit. The bar qq-pair production is absent in the leading-log formalism, but contributes to the next-to-leading corrections to it, and is, therefore, relevant for the computation of parton-parton scattering in the high-energy limit and of the gluon anomalous dimension at small xBj, at next-to-leading accuracy. copyright 1996 The American Physical Society