Semileptonic Decays of Heavy Baryons
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mileptonic Decays of Heavy Baryons V. O. Galkina and R. N. Faustova, * a
Institute of Cybernetics and Informatics in Education, Federal Research Center “Computer Science and Control”, Russian Academy of Sciences, Moscow, 119333 Russia *e-mail: [email protected] Received December 20, 2019; revised January 16, 2020; accepted January 29, 2020
Abstract—Semileptonic decays of heavy baryons are studied within the relativistic quark model based on the quasi-potential approach and quantum chromodynamics. Form factors parametrizing the matrix elements of weak transitions are calculated in the entire available kinematic interval with consistent consideration of relativistic effects. The results on the probabilities of semileptonic decays and other observable quantities are in good agreement with the available experimental data. DOI: 10.1134/S1063779620040280
1. INTRODUCTION In recent years, significant experimental progress has been made in the study of decays of heavy baryons. Numerous decay channels of these baryons have been observed. New, more accurate data are expected in the near future, since heavy baryons are produced in large quantities at the Large Hadron Collider (LHC). Weak decays of heavy baryons are an additional source for determining the elements of the Cabibbo–Kobayashi– Maskawa (CKM) matrix. Such decays can also be used to test lepton universality, indications of a possible violation of which were obtained in semileptonic decays of mesons. This report gives a review of the studies on the decays of bottom and charmed baryons within the relativistic quark model based on the quark–diquark picture of baryons and the quasi-potential approach [1‒4]. Such an approximation reduces the very complex relativistic three-body problem to a consistent solution of two significantly simpler two-body problems. First, the diquark is considered as a relativistic bound state of two light quarks, and then the baryon is considered as a bound state of the heavy quark and diquark. When carrying out such calculations, it should be taken into account that the diquark in the baryon is a composite system of two quarks. Therefore, it is not a point object and, thus, its interaction with gluons is smeared by a form factor that can be expressed via the overlap integral of the diquark wave functions. It is also necessary to consider the relativistic nature of light and heavy quarks and diquarks and, therefore, consider them fully relativistically. To find the decay rates of heavy baryons, it is necessary to calculate the form factors that parameterize the matrix elements of the weak current between the initial and final baryon states. Based on the relativistic quark model, explicit expressions were obtained for the form factors of weak transitions in the form of
overlap integrals of the baryon wave functions, which are known from the calculation of their mass spectra [5]. In this case, all relativistic effects were considered, including the contributions of intermediate states with negative energies, as well as the transformation of the wa
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