Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · hep-ph/0209250

The Radiative Leptonic Decays D^0 -> e^+ e^- gamma, mu^+ mu^- gamma in the Standard Model and Beyond

S. Fajfer·P. Singer·J. Zupan
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present a calculation of the rare decay modes D^0 -> e^+ e^- gamma and D^0 -> mu^+ mu^- gamma in the framework of Standard Model. For the short distance part, we have derived QCD corrections to the Wilson coefficients involved, including C_9. The latter is found to be strongly suppressed by the corrections, leading to diminished values for the c -> u l^+l^- branching ratios in the 10^(-10) range. Within SM the exclusive decays are dominated by long distance effects. Nonresonant contributions are estimated using heavy quark and chiral symmetries to be at the level of 10%, compared to the contributions arising from D^0-> V gamma->l^+ l^- gamma, with V=rho, omega, phi. The total SM branching ratio is predicted to be in the range (1-3) x 10^(-9). We also consider contributions coming from MSSM with and without R parity conservation. Effects from MSSM are significant only for the R-parity violating case. Such contributions enhance the branching ratio D^0-> mu^+ mu^- gamma to 0.5 x 10^(-7), based on appropriately allowed values for C_9 and C_{10}. This selects D^0->mu^+ mu^- gamma as a possible probe of new physics.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S. Fajfer, P. Singer, J. Zupan. 2002-09-22. The Radiative Leptonic Decays D^0 -> e^+ e^- gamma, mu^+ mu^- gamma in the Standard Model and Beyond. https://doi.org/10.1140/epjc%2Fs2002-01090-5

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↗