Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · hep-ph/0104034

Quark mass effects in B -> Xs gamma

Paolo Gambino·Mikolaj Misiak
View original source ↗Read source document ↗Export metadata ↓

Abstract

The charm-loop contribution to B -> Xs gamma is found to be numerically dominant and very stable under logarithmic QCD corrections. The strong enhancement of the branching ratio by QCD logarithms is mainly due to the b-quark mass evolution in the top-quark sector. These observations allow us to achieve better control over residual scale dependence at the next-to-leading order. Furthermore, we observe that the sensitivity of the matrix element < Xs gamma | (sc)_(V-A)(cb)_(V-A) | b > to mc/mb is the source of a sizeable uncertainty that has not been properly taken into account in previous analyses. Replacing mc^pole/mb^pole in this matrix element by the more appropriate mc(mu)/mb^pole with mc < mu < mb causes an 11% enhancement of the SM prediction for BR[B -> Xs gamma]. For E_gamma > 1.6 GeV in the B-meson rest frame, we find BR[ B -> Xs gamma]_{E_gamma > 1.6 GeV} = (3.60 +_ 0.30) * 10^-4. The difference between our result and the current experimental world average is consistent with zero at the level of 1 sigma. We also discuss the implementation of new physics effects in our calculation. The lower bound on the charged Higgs boson mass in 2HDM(II) is found the be higher than 350 GeV.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Paolo Gambino, Mikolaj Misiak. 2001-09-11. Quark mass effects in B -> Xs gamma. https://doi.org/10.1016/s0550-3213(01)00347-9

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Covariant reggeization framework for diffraction. Part I: Hadronic tensors in Minkovsky space-time of any dimension

In this paper we consider the general structure of irreducible tensor representations of the Poincaré group of arbitrary space-time dimension $D$ with multiple sets of Lorentz indices and different ways to construct them from basic elements (Lorentz vectors and the metric tensor). Then we apply the same methods to obtain the expansion of general hadronic tensors in terms of these irreducible tensors. We propose to use an effective approach in hadronic diffraction, which was usually called covariant reggeization, and obtain basic functions and tensors to calculate all the diffractive cross-sections.

hep-ph↗
arXiv2026

Extraction of the pion-nucleon coupling constant using the effective-range expansion with the left-hand cut

We apply the generalized effective-range expansion of Phys. Rev. Lett. 135, 011903(2025), which incorporates the left-hand cut from one-pion exchange, to low-energy neutron-proton scattering in the $^1S_0$ and $^3S_1$ channels. The amplitude zero for the center-of-mass momentum near 0.35 GeV in the $^1S_0$ channel is naturally accommodated within this framework. We extract the pole position, scattering length, effective range, and the pseudoscalar pion-nucleon coupling constant $g_{πN}^2/(4π)$ at different expansion orders. The low-energy parameters are stable and consistent with established values, while $g_{πN}^2/(4π)$ exhibits larger uncertainties. The extraction of $g_{πN}^2/(4π)$ is data-driven, relying on the analytic constraints from the left-hand cut and phase-shift data within the one-pion-exchange approximation. Despite larger uncertainties compared to high-precision extractions, the consistency with established values demonstrates that this framework can probe the left-hand-cut singularity.

hep-ph↗
arXiv2026

Sexaquarks and $H$ dibaryons in the $uuddss$ system: a comparison within a constituent quark model

We study the $uuddss$ multiquark within a constituent quark model framework, solving the corresponding nonrelativistic Schrodinger equation by means of a diffusion Monte Carlo (DMC) method. The total wavefunction is written as the product of a radial component and an exact spin-color-flavor state, restricted to isospin $I$=0. For this isospin, all allowed flavor wave functions are included. We explore two distinct constructions of the six-quark system. In the first one, corresponding to a sexaquark, all six quarks are treated as indistinguishable and the wave function is fully antisymmetric with respect to the exchange of any two quarks. In the second one, corresponding to the $H$ dibaryon, the system is partitioned into two sets of three quarks, effectively mimicking a baryon-baryon-like configuration including hidden color terms in which antisymmetry is imposed only within each three-quark cluster. Only when the system is forced into a baryon-baryon-like configuration, and for certain values of the spin, color and flavor quantum numbers, do we obtain states with masses close to, but above, the two-baryon threshold. Those states are characterized by two loosely bound three-quark clusters separated from one another by a distance of $\sim$ 2.5 fm. The remaining structures are compact objects irrespectively of their internal wavefunction.

hep-ph↗