Probing New Physics with heavy hadron decays (original) (raw)

Heavy-flavor-conserving hadronic weak decays of heavy baryons

Journal of High Energy Physics, 2016

More than two decades ago, we studied heavy-flavor-conserving weak decays of heavy baryons within the framework that incorporates both heavy-quark and chiral symmetries. In view of the first observation of Ξ − b → Λ 0 b π − by LHCb recently, we have reexamined these decays and presented updated predictions. The predicted rates for Ξ − b → Λ 0 b π − in the MIT bag and diquark models are consistent with experiment. The major theoretical uncertainty stems from the evaluation of baryon matrix elements. The branching fraction of Ξ c → Λ c π is predicted to be of order 10 −4. It is suppressed relative to B(Ξ b → Λ b π) owing to the shorter lifetime of Ξ c relative to Ξ b and the destructive nonspectator W-exchange contribution. The kinematically accessible weak decays of the sextet heavy baryon Ω Q are Ω Q → Ξ Q π. Due to the absence of the B 6 − B3 transition in the heavy quark limit and the B 6 − B 6 transition in the model calculations, Ω Q → Ξ Q π vanish in the heavy quark limit.

Non-Leptonic Decays Op Beauty Hadrons – from Phenomenology to Theory

WORLD SCIENTIFIC eBooks, 1994

In the last few years considerable progress has been achieved in our understanding of the decays of heavy flavour hadrons. One can now calculate inclusive transition rates in QCD proper through an expansion in inverse powers of the heavy flavour quark mass without recourse to phenomenological assumptions. The non-perturbative contributions are treated systematically in this way; they are found to produce corrections of order a few percent in beauty decays, i.e. typically somewhat smaller than the perturbative corrections. One finds, among other things: (a) The lifetime of B − mesons is predicted to be longer than that of B 0 mesons by several percent. (b) The QCD prediction for the semileptonic branching ratio of B mesons appears to exceed present experimental values. We discuss the implications of this discrepancy. The phenomenological engineering that has been developed for the description of exclusive two-body modes of B mesons has reached a mature stage and awaits more precise and detailed experimental tests. First steps towards a genuine QCD treatment of these modes are being made.

Radiative decays of heavy baryons with heavy quark symmetry

Pramana, 1996

The decay widths for the radiative decays of heavy baryons are calculated in the heavy quark effective theory. Introducing the interpolating fields for heavy baryons we obtain the transition matrix elements and the corresponding decay widths. Considering the SU(6) flavor-spin wave functions for heavy baryons, the coupling constants are calculated in the nonrelativistic quark model. Since the masses of the heavy baryons are not available, we have taken the predicted bag model masses. We find our results are quite different from that of the heavy quark bag model calculations.

Electromagnetic and weak decays of baryons in the unquenched quark model

Journal of Physics: Conference Series, 2018

In this contribution, we discuss the electromagnetic and weak decays of baryons in the unquenched quark model and show that the observed discrepancies between the experimental data and the predictions of the constituent quark model can be accounted for in large part by the effects of sea quarks. Finally, the obtained results are discussed in terms of flavor-symmetry breaking.

Heavy-flavor-conserving nonleptonic weak decays of heavy baryons

Physical Review D, 1992

The heavy-flavor-conserving nonleptonic weak decays of heavy baryons are studied in a formalism that incorporates both heavy-quark symmetry and chiral symmetry. The phenomenological hS = 1 nonleptonic weak chiral Lagrangian for these transitions contains two independent coupling constants that describe the transitions between two flavor-SU(3) antitriplet heavy baryons, and the transitions between two flavor-SU(3) sextet heavy baryons. In the MIT bag model and the diquark model, only transitions between antitriplets are allowed. The coupling constants for these transitions are calculated in both models. The result is applied to specific nonleptonic decays such as =,~A,~, and the branching ratios are found to be of the order of 10. An example of a nonleptonic decay due to symmetry breaking is provided by 0,~:-, '~, which is estimated to have a smaller branching ratio, of the order of 10

Semileptonic decays of heavy Λ baryons in a quark model

Physical Review C, 2005

The semileptonic decays of Λc and Λ b are treated in the framework of a constituent quark model. Both nonrelativistic and semirelativistic Hamiltonians are used to obtain the baryon wave functions from a fit to the spectra, and the wave functions are expanded in both the harmonic oscillator and Sturmian bases. The latter basis leads to form factors in which the kinematic dependence on q 2 is in the form of multipoles, and the resulting form factors fall faster as a function of q 2 in the available kinematic ranges. As a result, decay rates obtained in the two models using the Sturmian basis are significantly smaller than those obtained using the harmonic oscillator basis. In the case of the Λc, decay rates calculated using the Sturmian basis are closer to the experimentally reported rates. However, we find a semileptonic branching fraction for the Λc to decay to excited Λ * states of 11% to 19%, in contradiction with what is assumed in available experimental analyses. Our prediction for the Λ b semileptonic decays is that decays to the ground state Λc provide a little less than 70% of the total semileptonic decay rate. For the decays Λ b → Λc, the analytic form factors we obtain satisfy the relations expected from heavy-quark effective theory at the non-recoil point, at leading and next-to-leading orders in the heavy-quark expansion. In addition, some features of the heavyquark limit are shown to naturally persist as the mass of the heavy quark in the daughter baryon is decreased.

Constituent quark model analysis of weak mesonic decays of charm baryons

Physical Review D, 1994

In view of recent experimental trends we investigate the weak nonleptonic decays of charm baryons within the framework of the constituent quark model. Branching ratios and asymmetry parameters for all 2+~z'++0 charm-changing modes are calculated with appropriate QCD corrections. The effect of Savor dependence on the scale is found to be quite significant.

Radiative decays of single heavy flavour baryons

The European Physical Journal A, 2009

The electromagnetic transitions between (J P = 3 2 +) and (J P = 1 2 +) baryons are important decay modes to observe new hadronic states experimentally. For the estimation of these transitions widths, we employ a non-relativistic quark potential model description with color coulomb plus linear confinement potential. Such a description has been employed to compute the ground state masses and magnetic moments of the single heavy flavor baryons. The magnetic moments of the baryons are obtained using the spin-flavor structure of the constituting quark composition of the baryon. Here, we also define an effective constituent mass of the quarks (ecqm) by taking into account the binding effects of the quarks within the baryon. The radiative transition widths are computed in terms of the magnetic moments of the baryon and the photon energy. Our results are compared with other theoretical models.

Probing for new physics with rare charm baryon (Λc, Ξc, Ωc) decays

Journal of High Energy Physics

We analyze rare charm baryon decays within the standard model and beyond. We identify all null test observables in unpolarized Λc→ pℓ+ℓ−, ℓ = e, μ decays, and study the new physics sensitivities. We find that the longitudinal dilepton polarization fraction FL is sensitive to electromagnetic dipole couplings C7left(primeright){C}_7^{\left(\prime \right)}C7left(primeright) C 7 ′ , and to the right-handed 4-fermion vector coupling C9left(primeright){C}_9^{\left(\prime \right)}C9left(primeright) C 9 ′ . The forward-backward asymmetry, AFB, due to the GIM-suppression a standard model null test already, probes the left-handed axialvector 4-fermion coupling C10; its CP–asymmetry, AmathrmFBmathrmCP{A}_{\mathrm{FB}}^{\mathrm{CP}}AmathrmFBmathrmCP A FB CP probes CP-violating phases in C10. Physics beyond the standard model can induce branching ratios of dineutrino modes Λc→ pνoverlinenu\overline{\nu}overlinenu ν ¯ up to a few times 10−5, and one order of magnitude smaller if lepton flavor universality is assumed, while standard model rates are negligible. Charged lepton flavor violation allow...