arXiv subjects

Margarita Gavrilova

Publications and source records attributed to Margarita Gavrilova.

7 recordsLinked to original sources

arXiv2026

One Sum To Rule Them All: A Second Order Master Rate Sum Rule for Charm Decays

We show that within the Standard Model any system of hadronic weak charm decays related by $U$-spin satisfies the following rate sum rule: (sum of CF and DCS CKM-free rates) divided by (sum of SCS CKM-free rates) = 1, which holds up to second order in $U$-spin breaking. We test this sum rule against available data and find that it is well satisfied in all cases. For systems in which some decay rates have not yet been measured, we use this sum rule to predict the missing rates.

hep-ph↗

arXiv2026

FlaSR: A Mathematica Package for the Automatic Generation of $U$-spin Sum Rules

We present FlaSR, a Mathematica package for the automatic generation of higher-order amplitude and amplitude-squared $SU(2)$ flavor sum rules, with a particular emphasis on $U$-spin. The package is based on recent insights into the mathematical structure of flavor sum rules. Given a system of symmetry-related processes defined by a list of particle multiplets in the initial and final states, together with the transformation properties of the symmetry-limit Hamiltonian, the package generates the full list of processes and outputs amplitude and amplitude-squared sum rules for the system. For amplitude sum rules, the package generates the complete set at all orders in symmetry breaking for which such relations exist. For amplitude-squared sum rules, which translate directly into sum rules among physical observables, the current version of the package is not guaranteed to generate the complete set. We illustrate the scope of the package with a range of representative examples.

hep-ph↗

arXiv2024

Systematics of U-Spin Sum Rules for Systems with Direct Sums

A rich mathematical structure underlying flavor sum rules has been discovered recently. In this work, we extend these findings to systems with a direct sum of representations. We prove several results for the general case. We derive an algorithm that enables the determination of all $U$-spin amplitude sum rules at arbitrary order of the symmetry breaking for any system containing a direct sum of the representations $0 \oplus 1$. Potential applications are numerous and include, for example, higher order sum rules for CP-violating charm decays with an arbitrary number of final states.

hep-ph↗

arXiv2024

Determination of the $D\rightarrow ππ$ ratio of penguin over tree diagrams

We study the penguin over tree ratio in $D\rightarrow ππ$ decays. This ratio can serve as a probe for rescattering effects. Assuming the Standard Model and in the isospin limit, we derive expressions that relate both the magnitude and the phase of this ratio to direct CP asymmetries and branching fractions. We find that the current data suggest that rescattering is large. A dedicated experimental analysis with current and future data will be able to significantly reduce the errors on these determinations, and enable us to check if indeed there is significant rescattering in $D \to ππ$ decays.

hep-ph↗

arXiv2023

Fermion pair radiation from accelerating classical systems

Accelerating classical systems that couple to a fermion-antifermion pair at the microscopic level can radiate pairs of fermions and lose energy in the process. In this work, we derive the generalization of the Larmor formula for fermion pair radiation. We focus on the case of a point-like classical source in an elliptical orbit that emits fermions through vector and scalar mediators. Ultra-light fermion emission from such systems becomes relevant when the mass of the mediator is larger than the frequency of the periodic motion. This enables us to probe regions of the parameter space that are inaccessible in on-shell bosonic radiation. We apply our results to pulsar binaries with mediators that couple to muons and neutrinos. Using current data on binary period decays, we extract bounds on the parameters of such models.

hep-ph↗

arXiv2022

The Mathematical Structure of $U$-Spin Amplitude Sum Rules

We perform a systematic study of $SU(2)$ flavor amplitude sum rules with particular emphasis on $U$-spin. This study reveals a rich mathematical structure underlying the sum rules that allows us to formulate an algorithm for deriving all $U$-spin amplitude sum rules to any order of the symmetry breaking. This novel approach to deriving the sum rules does not require one to explicitly compute the Clebsch-Gordan tables, and allows for simple diagrammatic interpretation. Several examples that demonstrate the application of our novel method to systems that can be probed experimentally are provided.

hep-ph↗

arXiv2019

Rotation-invariant observables as Density Matrix invariants

It is shown that general dilepton angular distribution (with parity violating terms taking into account) in vector particle decays can be described through a set of five SO(3) rotational-invariant observables. These observables are derived as invariants of the spacial part of the hadronic tensor (density matrix) expressed in terms of angular coefficients. The restrictions on the invariants following from the positivity of the hadronic tensor are obtained. Special cases of SO(2) rotations are considered. Calculation of invariants for available data on Z and J/ψ decays is performed.

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