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Register a new user$Sigma_{b}toSigma_c$ and $Omega_btoOmega_c$ weak decays in the light-front quark model
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The successful operation of LHC provides a great opportunity to study the processes where heavy baryons are involved. {In this work we mainly study} the weak transitions of $Sigma_bto Sigma_c$. Assuming the reasonable quark-diquark structure where the two light quarks constitute an axial vector, we calculate the widths of semi-leptonic decay $Sigma_{b}toSigma_c e u_e$ and non-leptonic decay modes $Sigma_{b}toSigma_c +M$ (light mesons) in terms of the light front quark model. We first construct the vertex function for the concerned baryons and then deduce the form factors which are related to two Isgur-Wise functions for the $Sigma_{b}toSigma_c$ transition under the heavy quark limit. Our numerical results indicate that $Gamma(Sigma_{b}toSigma_c e u_e)$ is about $1.38times10^{10}{rm s}^{-1}$ and $Gamma(Sigma_{b}toSigma_c +M)$ is slightly below $1times10^{10}{rm s}^{-1}$ which may be accessed at the LHCb detector. By the flavor SU(3) symmetry we estimate the rates of $Omega_btoOmega_c$. We suggest to measure weak decays of $Omega_btoOmega_c$, because $Omega_b$ does not decay via strong interaction, the advantage is obvious.
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In this work, we study $Lambda_{b}toLambda_{c}$ and $Sigma_{b}toSigma_{c}$ weak decays in the light-front quark model. As is well known, the key point for such calculations is properly evaluating the hadronic transition matrix elements which are dominated by the non-perturbative QCD effect. In our calculation, we employ the light-front quark model and rather than the traditional diquark picture, we account the two spectator light quarks as individual ones. Namely during the transition, they retain their color indices, momenta and spin polarizations unchanged. Definitely, the subsystem composed of the two light quarks is still in a color-anti-triplet and possesses a definite spin, but we do not priori assume the two light quarks to be in a bound system-diquark. Our purpose is probing the diquark picture, via comparing the results with the available data, we test the validity and applicability of the diquark structure which turns a three-body problem into a two-body one, so greatly simplifies the calculation. It is indicated that the two approaches (diquark and a subsystem within which the two light quarks are free) lead to similar numerical results even though the model parameters in the two schemes might deviate slightly. Thus, the diquark approach seems sufficiently reasonable.
Without contamination from the final state interactions, the calculation of the branching ratios of semileptonic decays $Xi^{()}_{c}toXi+e^+ u_e$ may provide us more information about the inner structure of charmed baryons. Moreover, by studying those processes, one can better determine the form factors of $Xi_ctoXi$ which can be further applied to relevant estimates. In this work, we use the light-front quark model to carry out the computations where the three-body vertex functions for $Xi_c$ and $Xi$ are employed. To fit the new data of the Belle II, we re-adjust the model parameters and obtain $beta_{s[sq]}=1.07$ GeV which is 2.9 times larger than $beta_{sbar s}=0.366$ GeV. This value may imply that the $ss$ pair in $Xi$ constitutes a more compact subsystem. Furthermore, we also investigate the non-leptonic decays of $Xi^{()}_cto Xi$ which will be experimentally measured soon, so our model would be tested by consistency with the new data.
We study the non-leptonic two-body weak decays of $Lambda_b^0 to p M$ with $ M=(pi^-,K^-)$ and $(rho^-,K^{*-})$ in the light-front quark model under the generalized factorization ansatz. By considering the Fermi statistic between quarks and determining spin-flavor structures in baryons, we calculate the branching ratios (${cal B}$s) and CP-violating rate asymmetries ($mathcal{A}_{CP}$s) in the decays. Explicitly, we find that ${cal B}( Lambda_b^0 to p pi^- ,pK^-)=(4.18pm0.15pm0.30, 5.76pm0.88pm0.23)times10^{-6}$ and ${mathcal{A}_{CP}}( Lambda_b^0 to p pi^- ,,pK^-)=(-3.60pm0.14pm0.14, 6.36pm0.21pm0.18)%$ in comparison with the data of ${cal B}( Lambda_b^0 to p pi^- ,pK^-)=(4.5pm0.8, 5.4pm1.0)times10^{-6}$ and ${mathcal{A}_{CP}}( Lambda_b^0 to p pi^- ,pK^-)=(-2.5pm 2.9, -2.5pm2.2)%$ given by the Particle Data Group, respectively. We also predict that ${cal B}( Lambda_b^0 to p rho^-,pK^{*-} )=(12.13pm3.27pm0.91, 2.58pm0.87pm0.13)times 10^{-6}$ and ${mathcal{A}_{CP}}( Lambda_b^0 to p rho^-,pK^{*-} )=(-3.32pm0.00pm0.14,19.25pm0.00pm0.80)%$, which could be observed by the experiments at LHCb.
In this work we study the weak decays of $Xi_{cc}toXi_c$ and $Xi_{cc}toXi_c$ in the light-front quark model. Generally, a naive, but reasonable conjecture suggests that the $cc$ subsystem in $Xi_{cc}$ ( $us$ pair in $Xi^{()}_c$) stands as a diquark with definite spin and color assignments. During the concerned processes, the diquark of the initial state is not a spectator, and must be broken. A Racah transformation would decompose the original $(cc)q$ into a combination of $c(cq)$ components. Thus we may deal with the decaying $c$ quark alone while keeping the $(cq)$ subsystem as a spectator. With the re-arrangement of the inner structure we calculate the form factors numerically and then obtain the rates of semi-leptonic decays and non-leptonic decays, which will be measured in the future.
We systematically study the semileptonic decays of ${bf B_c} to {bf B_n}ell^+ u_{ell}$ in the light-front constituent quark model, where ${bf B_c}$ represent the anti-triplet charmed baryons of $(Xi_c^0,Xi_c^+,Lambda_c^+)$ and ${bf B_n}$ correspond to the octet ones. We determine the spin-flavor structures of the constituents in the baryons with the Fermi statistics and calculate the decay branching ratios (${cal B}$s) and averaged asymmetry parameters ($alpha$s) with the helicity formalism. In particular, we find that ${cal B}( Lambda_c^+ to Lambda e^+ u_{e}, ne^+ u_{e})=(3.55pm1.04, 0.36pm0.15)%$, ${cal B}( Xi_c^+ to Xi^0 e^+ u_{e},Sigma^0 e^+ u_{e},Lambda e^+ u_{e})=(11.3pm3.35), 0.33pm0.09,0.12pm0.04%$ and ${cal B}( Xi_c^0 to Xi^- e^+ u_{e},Sigma^- e^+ u_{e})=(3.49pm0.95,0.22pm0.06)%$. Our results agree with the current experimental data. Our prediction for ${cal B}( Lambda_c^+ to n e^+ u_{e})$ is consistent with those in the literature, which can be measured by the charm-facilities, such as BESIII and BELLE. Some of our results for the $Xi_c^{+(0)}$ semileptonic channels can be tested by the experiments at BELLE as well as the ongoing ones at LHCb and BELLEII.
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