We investigate the strong vertices among the Λ b , nucleon, and B meson as well as the Λ c , nucleon, and D meson in QCD. In particular, we calculate the strong coupling constants g Λ b NB and g Λ c ND for different Dirac structures entering the calculations. In the case of the Λ c ND vertex, we compare the result with the only existing prediction obtained at Q 2 ¼ 0.

The semileptonic decays of heavy spin-1/2, Ξ b(c) and Ξ ′ b(c) baryons to the light spin-1/2, Ξ and Σ baryons are investigated in the framework of light cone QCD sum rules. In particular, using the most general form of the interpolating currents for the heavy baryons as well as the distribution amplitudes of the Ξ and Σ baryons, we calculate all form factors entering the matrix elements of the corresponding effective Hamiltonians in full QCD. Having calculated the responsible form factors, we evaluate the decay rates and branching fractions of the related transitions. PACS number(s): 11.55. Hx, 13.30.Ce, 14.20.Mr, 14.20 Such an experimental progress stimulates the theoretical studies on properties of the heavy baryons as well as their electromagnetic, weak and strong transitions. The mass spectrum of the heavy baryons has been studied using various methods including heavy quark effective theory [2], QCD sum rules [3][4][5][6] and some other phenomenological models [7][8][9][10][11][12]. Some electromagnetic properties of the heavy baryons and their radiative decays have been investigated in different frameworks in [6,[13][14][15][16][17][18][19][20][21][22][23][24]. The strong decays of the heavy baryons have also been in the focus of much attention, theoretically (see for instance [25][26][27] and references therein).However, the weak and semileptonic decays of heavy baryons are very important frameworks not only in obtaining information about their internal structure, precise calculation of the main ingredients of standard model (SM) such as Kabbibbo-Kobayashi-Maskawa (CKM) matrix elements and answering to some fundamental questions like nature of the CP violation, but also in looking for new physics beyond the SM. The loop level semileptonic transitions of the heavy baryons containing single heavy quark to light baryons induced by the flavor changing neutral currents (FCNC) are useful tools, for instance, to look for the supersymmetric particles, light dark matter, fourth generation of the quarks and extra dimensions etc. [28,29]. Some semileptonic decay channels of the heavy baryons have been previously investigated in different frameworks (see for instance [30][31][32][33][34][35][36][37][38] and references therein).The present work deals with the semileptonic decays of heavy Ξ b(c) and Ξ ′ b(c) baryons to the light Ξ and Σ baryons. The considered channels are either at loop level described by twelve form factors in full QCD or at tree level analyzed by six form factors entering the transition matrix elements of the corresponding low energy Hamiltonian. Here, we should mention that by the "full QCD" we refer to the QCD theory without any approximation like heavy quark effective theory (HQET) so we take the mass of heavy quarks finite. In HQET approximation, the number of form factors describing the considered transitions reduce to only two form factors [39,40]. The considered processes take place in low energies far from the perturbative region, so to calculate the form factors as the main ingredie...

We explore the recently observed Ξ b (6227) − resonance to fix its quantum numbers. To this end, we consider various possible scenarios: It can be considered as either 1P /2S excitations of the Ξ − b and Ξ ′ b (5935) ground state baryons with spin-1 2 or 1P /2S excitations of the ground-state Ξ b (5955) with spin-3 2 . We calculate the masses of the possible angular-orbital 1P and 2S excited states corresponding to each channel employing the QCD sum rule technique. It is seen that all the obtained masses are in agreement with the experimentally observed value, implying that the mass calculations are not enough to determine the quantum numbers of the state under question. Therefore, we extend the analysis to investigate the possible decays of the excited states into Λ 0 b K − and Ξ − b π. Using the light cone QCD sum rule method, we calculate the corresponding strong coupling constants, which are used to extract the decay widths of the modes under consideration. Our results on decay widths indicate that the Ξ b (6227) − is 1P angular-orbital excited state of the Ξ b (5955) baryon with quantum numbers J P = 3 2 − . I. INTRODUCTIONThe theoretical studies of the heavy baryons involving their spectroscopic parameters and the interaction mechanisms improve our understanding on the nonperturbative regime of the strong interaction, as well as their nature and internal structure. As a result of the impressive developments in the experimental sector in the last decade, almost all of the ground state baryons with single heavy quark were observed [1][2][3][4][5][6][7][8][9].The spectroscopy of the heavy baryons containing b quark has been investigated within different models. These approaches include the quark model [10][11][12][13][14][15][16][17][18][19], the QCD sum rule approach [20-24], lattice QCD [25], 1/N c and 1/m b expansions [26] and Faddeev approach [27]. To gain deeper understanding on the single bottom baryons, their properties such as magnetic dipole moments and strong decays were investigated in Refs. [28][29][30][31][32][33]. In Ref.[34], their strong and radiative decays were studied using the constituent quark model.The quark model predicts existence of many new baryons with one, two, or three heavy quarks. The impressive developments in the experimental techniques indicate that more heavy baryons would be observed in near future. With this motivation and the motivation brought by the recent observation of the LHCb Collaboration [35], we investigate the masses and decay constants of the low-lying 2S and 1P excited Ξ b baryons having J = 1 2 and J = 3 2 . The LHCb collaboration recently reported the observation of Ξ b (6227) − with mass m Ξ b (6227) − = 6226.9 ± 2.0 ± 0.3 ± 0.2 MeV and width Γ Ξ b (6227) − = 18.1 ± 5.4 ± 1.8 MeV. From the observed mass and decay modes, it was stated that Ξ b (6227) − state may be 1P or 2S excited baryon (see also [35]). After this observation, this state is considered in Ref.[36] and its mass and strong decays were analyzed. The obtained results indicated the possibility of...

The tree level semileptonic Λ b → plν and Λc → nlν transitions are investigated using the light cone QCD sum rules approach in full theory. The spin-1/2, ΛQ baryon with Q = b or c, is considered by the most general form of its interpolating current. The time ordering product of the initial and transition currents is expanded in terms of the nucleon distribution amplitudes with different twists. Considering two sets of independent input parameters entering to the nucleon wave functions, namely, QCD sum rules and Lattice QCD parameters, the related form factors and their heavy quark effective theory limits are calculated and compared with the existing predictions of other approaches. It is shown that our results satisfy the heavy quark symmetry relations for lattice input parameters and b case exactly and the maximum violation is for charm case and QCD sum rules input parameters. The obtained form factors are used to compute the transition rates both in full theory and heavy quark effective theory. A comparison of the results on decay rate of Λ b → plν with those predicted by other phenomenological methods or the same method in heavy quark effective theory with different interpolating current and distribution amplitudes of the Λ b is also presented.

We study the strong vertices N * N π, N * N * π and N N π in QCD, where N * denotes the negative parity N (1535) state. We use the most general form of the interpolating currents to calculate the corresponding strong coupling constants. It is obtained that the coupling associated to N * N π vertex is strongly suppressed compared to those related to two other vertices. The strong coupling corresponding to N * N * π is obtained to be roughly half of that of N N π vertex. We compare the obtained results on N * N π and N N π vertices with the existing predictions of other theoretical studies as well as those extracted from the experimental data.