Searcharxiv⌕ Search

arXiv subjects

Peter Maták

Publications and source records attributed to Peter Maták.

11 recordsLinked to original sources
arXiv2024

Asymmetric dark matter from semi-annihilation: unitarity constraints and long-lived final states

This work presents an asymmetric dark matter model with relic density determined by the freeze-out of asymmetric semi-annihilations into long-lived particles slowly decaying into the Standard Model states. We carefully consider the $CPT$ symmetry and unitarity constraints to the asymmetries entering the Boltzmann equation. The main idea of the paper is to point out a critical inconsistency in the previous literature, where these constraints are violated. We present a systematic approach to avoid the inconsistency.

hep-ph↗
arXiv2024

Dirac leptogenesis from asymmetry wash-in via scatterings

Leptogenesis typically requires the introduction of heavy particles whose out-of-equilibrium decays are essential for generating a matter-antimatter asymmetry, according to one of Sakharov's conditions. We demonstrate that in Dirac leptogenesis, scatterings between the light degrees of freedom -- Standard Model particles plus Dirac neutrinos - are sufficient to generate the asymmetry. The generation requires at least two effective charges conserved by the fast Standard Model interactions. Due to its vanishing source term in the Boltzmann equations, the asymmetry of right-handed neutrinos solely arises through wash-in processes. Sakharov's conditions are satisfied because the right-handed neutrino partners are out of equilibrium. Consequently, heavy degrees of freedom never needed to be produced in the early universe, allowing for a reheating temperature well below their mass scale. Considering a minimal leptoquark model, we discuss the viable parameter space along with the potential observational signature of an increased number of effective neutrinos in the early universe.

hep-ph↗
arXiv2023

Comment on "Dirac leptogenesis via scatterings"

In their recent letter, Heeck et al. [Phys. Rev. D 108, L031703] introduced a simple model of leptogenesis, in which the asymmetry originates from the scattering processes only. Here we argue that their calculation violates some of the basic principles of perturbative quantum field theory.

hep-ph↗
arXiv2023

Unitarity, real-intermediate states, and fixed-order approach to resonant dark matter annihilation

We study the role of perturbative unitarity in the resonant annihilation of two dark matter particles into the standard model bath. Systematically including all kinematically allowed holomorphic cuts of the corresponding forward-scattering diagram, cancelation of the singularities occurs, resulting in a fixed-order correction to the narrow-width approximation for the annihilation cross section. Unlike the standard approach based on including the finite width of the mediator, no double counting of intermediate states occurs.

hep-ph↗
arXiv2023

$CPT$ and unitarity constraints for higher-order $CP$ asymmetries at finite temperature

We use an unconventional diagrammatic approach to formulate $CPT$ and unitarity constraints for higher-order $CP$ asymmetries entering the source term in the Boltzmann equation. Usually, the reaction rate asymmetries in these constraints are computed within the classical kinetic theory, using zero-temperature quantum field theory to describe particles' interactions. We approximate the rates, otherwise obtained within the closed-time-path formalism, in terms of diagrams drawn on a cylindrical surface and their holomorphic cuts. The resulting equilibrium asymmetry constraints incorporate thermal-mass effects and allow tracking the cancellations of reaction rate asymmetries computed with quantum statistics. We use the top Yukawa corrections to the asymmetries in the seesaw type-I leptogenesis as an example.

hep-ph↗
arXiv2022

Cutting rules on a cylinder and simplified diagrammatic approach to $CP$ violation in quantum kinetic theory

We briefly explain a novel diagrammatic method for including thermal corrections in $CP$ asymmetric reaction rates entering the quantum Boltzmann equation. In thermal equilibrium, the asymmetries have to cancel precisely due to the $S$-matrix unitarity and $CPT$ invariance. Such cancelations are easy to track in zero-temperature leading-order calculations. However, accounting for medium effects requires modification of the on-shell part of propagators and, consequently, the $CP$ violating rates. In the literature, the correct form of the statistical factors in the asymmetry source term has been obtained employing the real-time-formalism of non-equilibrium field theory in a certain approximation. We demonstrate that the same results can be obtained by summing an infinite sequence of zero-temperature asymmetries. Those are derived from cuttings of forward diagrams drawn on a cylindrical surface, while thermal corrections come from windings of their propagators. The procedure is entirely diagrammatic, and the $CPT$ and unitarity cancelations are formulated for thermally corrected reaction rate asymmetries. The simplification achieved is the primary focus of our work. The aspect of infrared finiteness in higher-order corrections will also be discussed.

hep-ph↗
arXiv2021

Mass-derivative relations for leptogenesis

In this work, a diagrammatic representation of thermal mass effects is derived from the $S$-matrix unitarity both in the classical and quantum Boltzmann equations. Within the example of the seesaw type-I leptogenesis, we discuss the connection of the Higgs thermal mass and the cancelations of infrared divergences in zero- and finite-temperature calculations of the right-handed neutrino decay and scattering processes.

hep-ph↗
arXiv2021

Cutting rules on a cylinder: a bottom-up approach to quantum kinetic theory for the early universe

Nonequilibrium quantum field theory is often used to derive an approximation for the evolution of number densities and asymmetries in astroparticle models when a more precise treatment of quantum thermal effects is required. This work presents an alternative framework using the zero-temperature quantum field theory, $S$-matrix unitarity, and classical Boltzmann equation as starting points leading to a set of rules for calculations of thermal corrections to reaction rates. Statistical factors due to on-shell intermediate states are obtained from the cuts of forward diagrams with multiple spectator lines. It turns out that it is equivalent to cutting closed diagrams on a cylindrical surface.

hep-ph↗
arXiv2021

CP Asymmetries and Higher-Order Unitarity Relations

The main focus of this paper is to introduce a new method to control perturbative calculations of CP asymmetric reaction rates in the Boltzmann equation. CP asymmetries in particle reactions are traditionally calculated in terms of complex couplings, Feynman integrals, and Cutkosky rules. We use an expansion of the $S$-matrix unitarity condition instead, obtaining a general expression for the asymmetries without reference to the imaginary part of the loops. Asymmetry cancelations implied by CPT and unitarity are manifested in a diagrammatic way and easy to track at any order of perturbation theory. We demonstrate the power of this general framework within the right-handed neutrino and top-quark scattering asymmetries in seesaw type-I leptogenesis.

hep-ph↗
arXiv2014

Left-left squark mixing in $K^+\rightarrowπ^+ν\barν$ and minimal SUSY

We analyze the role of the left-left squark mixing in the rare $K^+ \rightarrow π^+ν\barν$ decay within the minimal supersymmetry with a large $\tanβ$. A Higgs boson mass of 125 GeV has been taken into account leading to correlation between stop masses and trilinear soft supersymmetry breaking coupling $A_{\tilde{t}}$. We find that measurable effects, similar to that of the well known $LR$ squark mixing terms, are possible for large $A_{\tilde{t}}$ combined with the off-diagonal $LL$-insertions. Precise measurements of the decay rate are expected from the ongoing NA62 experiment at CERN. We emphasize that the effect we present can put certain limits on the left-left flavor changing structure of the squark mass matrix.

hep-ph↗