P. Gosdzinsky

Theoretical update of the semileptonic branching ratio of B mesons

Abstract We reconsider the prediction of the semileptonic branching ratio of B mesons, using the recent calculation [E. Bagan et al., Nucl. Phys. B 432 (1994) 3] of the radiative corrections with account for finite quark masses in nonleptonic decays and taking into account 1 m b 2 corrections. For the semileptonic branching ratio we obtain B sl = (11.8 ± 1.6)% using pole quark masses and B sl = (11.0 ± 1.9) % using running MS quark masses. The uncertainty is dominated by unknown higher order perturbative corrections. We conclude that the present accuracy of the theoretical analysis does not allow to state a significant disagreement with the experimental results. However, our re-analysis of the decay b → ccs yields an increase of (35 ± 11) % due to next-to-leading order corrections including mass dependent terms, which further emphasizes the problem of the average charm quark content of the final states in B decays.

Charm quark mass dependence of QCD corrections to nonleptonic inclusive B decays

Abstract We calculate the radiative corrections to the nonleptonic inclusive B decay mode b → c u d taking into account the charm quark mass. Compared to the massless case, corrections resulting from a nonvanishing c quark mass increase the nonleptonic rate by (4–8)%, depending on the renormalization point. As a by-product of our calculation, we obtain an analytic expression for the radiative correction to the semileptonic decay b → uτ v taking into account the τ lepton mass, and estimate the c quark mass effects on the nonleptonic decay mode b → c c s .

Energy of the vacuum with a perfectly conducting and infinite cylindrical surface

Abstract Values for the vacuum energy of scalar fields under Dirichlet and Neumann boundary conditions on an infinite clylindrical surface are found, and they happen to be of opposite signs. In contrast with classical works, a complete zeta function regularization scheme is here applied. These fields are regarded as interesting both by themselves and as the key to describing the electromagnetic (e.m.) case. With their help, the figure for the e.m. Casimir effect in the presence of this surface, found by De Raad and Milton, is now confirmed.

Next-to-leading order radiative corrections to the decay b → ccs

Abstract We calculate the complete O ( α s ) corrections to the quark decay b → ccs taking full account of the quark masses, but neglecting penguin contributions. For a c to the b quark mass ratio m c m b = 0.3 and a strange quark mass of 0.2 GeV, we find that the next-to-leading order (NLO) corrections increase Γ ( b → ccs ) by (32 ± 15) % with respect to the leading order expression, where the uncertainty is mostly due to scale- and scheme-dependencies. Combining this result with the known NLO and non-perturbative corrections to other B meson decay channels we obtain an updated value for the semileptonic branching ratio of B mesons, B SL , of (12.0 ± 1.4) % using pole quark masses and (11.2 ± 1.7) % using running MS masses.

The Isgur-Wise function to O(αs) from sum rules in the heavy quark effective theory

Abstract Radiative corrections to both perturbative and non-perturbative contributions are added to existing calculations of the Isgur- Wise function ξ IW . To this end, we develop a method for calculating two-loop integrals in the heavy quark effective theory involving two different scales. The inclusion of O( α s ) terms causes ξ IW to decrease as compared to the lowest order result and shows the importance of quantum effects. The slope parameter ϱ 2 violates the bound given by de Rafael and Taron.

Vector meson masses in chiral perturbation theory

Abstract We discuss the vector meson masses within the context of chiral perturbation theory performing an expansion in terms of the momenta, quark masses and 1 / N c . We extend the previous analysis to include isospin breaking effects and also include up to order p 4 . We discuss vector meson chiral perturbation theory in some detail and present a derivation from a relativistic Lagrangian. The unknown coefficients are estimated in various ways. We also discuss the relevance of electromagnetic corrections and the implications of the present calculation for the determination of quark masses.

Chiral corrections to vector meson decay constants

Abstract We calculate the leading quark mass corrections of order m q log( m q ), m q and m q 3/2 to the vector meson decay constants within heavy vector meson chiral perturbation theory. We discuss the issue of electromagnetic gauge invariance and the heavy mass expansion. Reasonably good fits to the observed decay constants are obtained.

Full one-loop renormalization of the ratio of neutral and charged current Fermi constants in supersymmetric extensions of the standard model☆

Abstract We present an updated numerical analysis of the complete one-loop radiative corrections to the ϱ parameter, defined as the ratio of the neutral and charged current over-all strengths at zero momentum transfer, in the context of supersymmetric extensions of the standard model of strong and electroweak interactions. We choose a specific renormalization framework, in which neutrino-electron scattering is a fundamental ingredient, and we take into account all possible supersymmetric process-dependent contributions, apart from the universal ones. Contrary to usual claims, we find that the former contributions may well be as important as the latter and of either sign. To the extent that for a fairly broad range of sparticle masses the entire supersymmetric correction to ϱ is driven to negative values of order 10−3, thus reversing the sign of the maximal universal contributions. We also comment on the implications of this fact on the determination of the upper bound on the quark mass obtained from precise measurements of the ϱ parameter.

Renormalizability of the heavy quark effective theory

Abstract We show that the Heavy Quark Effective Theory is renormalizable perturbatively. We also show that there exist renormalization schemes in which the infinite quark mass limit of any QCD Green functions is exactly given by the corresponding Green function of the Heavy Quark Effective Theory. All this is accomplished while preserving BRS invariance.

Two-loop renormalization scale dependence of the Isgur-Wise function.

Abstract The two-loop anomalous dimension of a current consisting of two heavy quarks with velocities ν and ν ′ (relevant to the renormalization scale dependence of the Isgur-Wise function) is computed within the framework of the Heavy Quark Effective Theory. Our result agrees with Korchemsky and Radyushkins calculation of the cusp anomalous dimension of Wilson lines, thus resolving previous discrepancies in the literature.