Heavy quark symmetry at large recoil

Zeitschrift f�r Physik C Particles and Fields, 1993

We analyze the large recoil behaviour of heavy baryon transition form factors in semileptonic decays. We use a generalized Brodsky-Lepage hard scattering formalism where diquarks are considered as quasi-elementary constituents of baryons. In the limit of infinitely heavy quark masses the large recoil form factors exhibit a new model-independent heavy quark symmetry which is reminiscent but not identical to the Isgur-Wise symmetry at low recoil.

Physical Review D, 1995

The heavy quark effective theory is developed on the light-front. Based on this effective theory, a light-front heavy meson bound state with definite spin and parity is constructed. Within the effective theory, the Isgur-Wise function is derived in terms of the asymptotic light-front bound state amplitudes in the limit m Q → ∞; the result is a general expression for arbitrary recoil velocities. With the asymptotic form of the BSW amplitudes, the Isgur-Wise function is given by ξ(v • v ′) = 1/v • v ′. The slope at the zero-recoil point is ρ 2 = −ξ ′ (1) = 1, in excellent agreement with the recent CLEO result of ρ 2 = 1.01 ± 0.15 ± 0.09.

Physical Review D, 1998

In this paper we construct a covariant light-front model of heavy mesons within the framework of heavy quark effective theory (HQET). The covariant model consists of the light-front heavy meson bound states constructed in the heavy quark limit with heavy quark ...

Physical Review D, 1998

In this paper we present a detailed formulation for a recently proposed effective field theory to describe the nonperturbative QCD dynamics of heavy mesons. This effective theory incorporates with heavy quark symmetry (HQS) and the heavy quark effective theory (HQET). Heavy mesons in this theory are constructed as composite particles of a heavy quark bounded with the light degrees of freedom. The heavy meson properties in the heavy quark limit and the 1/m Q corrections can then be explicitly evaluated from this effective theory. All the basic parameters of the HQET, namely, the heavy quark mass m Q , the heavy meson residual mass Λ, and the HQS breaking mass parameters λ 1 and λ 2 , are consistently determined. λ 1 is found to be small due to a large cancellation between the heavy quark kinetic energy and the chromo-electric interaction between the heavy quark and light degrees of freedom. We also evaluate the Isgur-Wise function, the decay constant, and the axial-vector coupling constant of heavy mesons.

1992

The scaling behavior of semileptonic form-factors in Heavy to Light transitions is studied in the Heavy Quark Effective Theory. In the case of H → πeν it is shown that the same scaling violations affecting the heavy meson decay constant will be present in the semileptonic form-factors.

Physical Review

Various decay modes of 0+, 1+, and 2+ mesons are investigated in the impulse approximation with contribution from the recoil term. The formalism is then modi6ed to take into account the effect of scattering of the emitted meson by the other quark (or antiquark) before it finally emerges from the QQ composite. The results for the decay widths obtained in this formalism give better agreement with the experimental values than do the earlier results obtained using only the direct term and ignoring the rescattering sects.

Nuclear Physics B, 2010

We discuss a general framework for the inclusion of heavy quark mass contributions to deep-inelastic structure functions and their perturbative matching to structure functions computed in variable-mass schemes. Our approach is based on the so-called FONLL method, previously introduced and applied to heavy quark hadroproduction and photoproduction. We define our framework, provide expressions up to second order in the strong coupling, and use them to construct matched expressions for structure functions up to NNLO. After checking explicitly the consistency of our results, we perform a study of the phenomenological impact of heavy quark terms, and compare results obtained at various perturbative orders, and with various prescriptions for the treatment of subleading terms, specifically those related to threshold behaviour. We also consider the heavy quark structure function F 2 c and discuss issues related to the presence of mass singularities in their coefficient functions.

1998

We compute the effect of soft-gluon resummation, at the next-to-leading-logarithmic level, in the hadroproduction cross-section for heavy flavours. Applications to top, bottom and charm total cross-sections are discussed. We find in general that the corrections to the fixed next-to-leading-order results are larger for larger renormalization scales, and small, or even negative, for smaller scales. This leads to a significant reduction of the scale-dependence of the results, for most experimental configurations of interest.

Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields, 1996

Summary I discuss QCD sum rules determinations of the form factors governing the decay B→π(π)ℓν. For some of these form factors the computed dependence on the momentum transferred does not agree with the expectation from the nearest pole dominance hypothesis. Relations are observed among the form factors, that seem to be compatible with equations recently derived by Stech. The measurement of

Physical Review D, 2012

We present a general relativistic framework for the calculation of the electroweak structure of heavy-light mesons within constituent-quark models. To this aim the physical processes in which the structure is measured, i.e. electron-meson scattering and semileptonic weak decays, are treated in a Poincaré invariant way by making use of the point-form of relativistic quantum mechanics. The electromagnetic and weak meson currents are extracted from the 1-γ and 1-W-exchange amplitudes that result from a Bakamjian-Thomas type mass operator for the respective systems. The covariant decomposition of these currents provides the electromagnetic and weak (transition) form factors. Problems with cluster separability, which are inherent in the Bakamjian-Thomas construction, are discussed and it is shown how to keep them under control. It is proved that the heavy-quark limit of the electroweak form factors leads to one universal function, the Isgur-Wise function, confirming that the requirements of heavy-quark symmetry are satisfied. A simple analytical expression is given for the Isgur-Wise function and its agreement with a corresponding front-form calculation is verified numerically. Electromagnetic form factors for B − and D + and weak B → D (*)-decay form factors are calculated with a simple harmonic-oscilllator wave function and heavy-quark symmetry breaking due to finite masses of the heavy quarks is discussed.