Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · hep-ph/0007313

epsilon'/epsilon and Rare K and B Decays in the MSSM

A. J. Buras·P. Gambino·M. Gorbahn·S. Jager·L. Silvestrini
View original source ↗Read source document ↗Export metadata ↓

Abstract

We analyze the CP violating ratio epsilon'/epsilon and rare K and B decays in the MSSM with minimal flavour and CP violation, including NLO QCD corrections and imposing constraints on the supersymmetric parameters coming from epsilon, B_{d,s}^0-\bar B_{d,s}^0 mixings, B to X_s gamma, Delta rho in the electroweak precision studies and from the lower bound on the neutral Higgs mass. We provide a compendium of phenomenologically relevant formulae in the MSSM. Denoting by T(Q) the MSSM prediction for a given quantity normalized to the Standard Model result we find the ranges: 0.53 < T(epsilon'/epsilon) < 1.07, 0.65 < T(K^+ to pi^+ nu nubar) < 1.02, 0.41 < T(K_L to pi^0 nu nubar) < 1.03, 0.48 < T(K_L to pi^0 e^+ e^-) < 1.10, 0.73 < T(B to X_s nu nubar) < 1.34 and 0.68 < T(B_s to mu^+ mu^-) < 1.53. We point out that these ranges will be considerably reduced when the lower bounds on the neutral Higgs mass and tan beta improve. Some contour plots illustrate the dependences of the quantities above on the relevant supersymmetric parameters. As a byproduct of this work we update our previous analysis of epsilon'/epsilon in the SM and find in NDR epsilon'/epsilon = (9.2^{+6.8}_{-4.0}), a value 15 % higher than in our 1999 analysis.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. J. Buras, P. Gambino, M. Gorbahn, S. Jager, L. Silvestrini. 2000-07-27. epsilon'/epsilon and Rare K and B Decays in the MSSM. https://doi.org/10.1016/s0550-3213(00)00582-4

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

KEEP EXPLORING

Related papers

arXiv2026

Higgs-Portal Stueckelberg Dark Matter

We study dark photon dark matter X associated with a dark $U(1)_X$ gauge symmetry. To evade laboratory and cosmological constraints on kinetic mixing with the Standard Model $U(1)_Y$, we assign a $Z_2$-odd dark parity to X that forbids such mixing. The leading interactions then arise from gauge-invariant dimension-6 Higgs-portal operators, including both parity-even and parity-odd terms. We assume that the dark matter mass is generated via the Stueckelberg mechanism. In the interacting Stueckelberg EFT, a gauge-invariant dimension-6 parent reduces in unitary gauge to the nominal dimension-4 Higgs-portal interaction $(H^†H)X_μX^μ$, with its coefficient correlated with $m_X^2/Λ^2$, while additional derivative operators are organized by the same longitudinal-mode power counting. We investigate freeze-in production of X from Higgs-pair annihilations after reheating, incorporating both field-strength and Stueckelberg-allowed operators. First, we consider the case in which the Wilson coefficients of the gauge-invariant dimension-6 operators, C and $\tilde C$, are of order unity. Under a conservative single-cutoff power counting in which the strong-coupling scales of the longitudinal mode lie above the cutoff of the field-strength effective theory, we find that the Stueckelberg contributions remain subdominant in dark matter production. We emphasize that this ordering of scales is an explicit assumption rather than a universal consequence of perturbative unitarity. Next, we explore a more general situation in which C and $\tilde C$ are smaller than unity. In this second case, Stueckelberg-allowed operators can become comparable and generate contributions proportional to $T_{reh}^3$, $T_{reh}^5$, and $T_{reh}^7$, including sign-dependent interference effects. For both cases, we show that there exists a wide parameter space consistent with the observed dark matter relic density.

hep-ph↗
arXiv2026

Scaling laws for amplitude surrogates

Scaling laws describing the dependence of neural network performance on the amount of training data, the spent compute, and the network size have emerged across a huge variety of machine learning task and datasets. In this work, we systematically investigate these scaling laws in the context of amplitude surrogates for particle physics. We show that the scaling coefficients are connected to the number of external particles of the process. Our results demonstrate that scaling laws are a useful tool to achieve desired precision targets.

hep-ph↗
arXiv2026

Analysis of the $D_0^*(2300)$ resonance from lattice QCD under chiral symmetry

We reanalyze the lattice spectra for $I=1/2$ $Dπ$ scattering in the $A_1^+$ irreducible representation from [Phys. Rev. D 111, 014503 (2025)] to investigate the impact of chiral and SU(3) flavor symmetries in $S$-wave $Dπ$ scattering and the $D_0^*(2300)$ resonance. By fitting the phase shifts obtained via Lüscher's formula with both traditional and chirally modified effective-range expansion and $K$-matrix parameterizations, we find that the chiral factor shifts the extracted pole mass closer to the threshold (especially for resonances) and substantially reduces the resonance width. These findings are confirmed by unitarized chiral perturbation theory through a direct fit to the lattice spectra with both the single-channel and the $Dπ$-$Dη$-$D_s\bar{K}$ coupled-channel schemes. Once the coupled channels are incorporated, the two-pole structure of the $D_0^*(2300)$ emerges. The trajectories of the two poles are investigated by varying the pion mass.

hep-ph↗