arXiv subjects

Michal Iglicki

Publications and source records attributed to Michal Iglicki.

8 recordsLinked to original sources

arXiv2023

Thermal regularization of t-channel singularities in cosmology and particle physics: the general case

This paper presents a~way to regularize the $t$-channel singularity (which appears when a~massive, stable $t$-channel mediator of a~given process is allowed to be on-shell, making the cross section infinite) in a~general case of particles of any spin (0,~\nicefrac12,~1) interacting within a~thermal medium. Those interactions result in a~finite lifetime of the mediator and allow to introduce an~effective momentum- and temperature-dependent width. As a result, the would-be-singular cross section becomes finite. A~complete derivation and an analytical result for the width are provided. For an illustration, the method is used to calculate the thermal widths and cross sections within the~Vector-Fermion Dark Matter model.

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arXiv2021

Searches for invisible scalar decays at CLIC

The Compact Linear Collider (CLIC) is a proposed TeV-scale high-luminosity electron-positron collider at CERN. The first CLIC running stage, at 380\,GeV, will focus on precision Higgs boson and top quark studies while the main aim of the subsequent high-energy stages, at 1.5 TeV and 3 TeV, is to extend the sensitivity of CLIC to different Beyond the Standard Model (BSM) scenarios. We studied the prospects for measuring invisible Higgs boson and additional heavy scalar decays using CLIC data at 380 GeV and 1.5 TeV. The analysis is based on the WHIZARD event generator, with fast simulation of the CLIC detector response parametrised by the DELPHES package. We present the expected limits for the invisible decays of the 125 GeV Higgs boson, the cross section limits for production of an additional neutral Higgs scalar, assuming its invisible decays, and limits on the mixing angle between the SM-like Higgs boson and the new scalar of the "dark sector" in the framework of the vector-fermion dark matter model.

hep-ex↗

arXiv2020

Dark-matter-spin effects at future $e^{+} e^{-}$ colliders

We discuss possibility to detect spin 0, 1 and 1/2 dark matter (DM) at future $e^{+} e^{-}$ colliders. The models considered here are simple, consistent and renormalizable field theories, that provide correct DM abundance and satisfy direct detection, indirect detection and collider constraints. The intention of this paper was to verify to what extend it might be possible to disentangle models of different DM spins by measurement of the cross section for $e^{+} e^{-} \to Z + \ldots\,$ at future $e^{+} e^{-}$ colliders. We specialize to the case of the ILC operating at $\sqrt{s} = 250~\text{GeV}$, however our results apply as well for the FCC-ee and the CEPC colliders. For each model the cross section maximized with respect to parameters was calculated and compared to the expected 95% CL cross-section limits estimated for the ILC. It turned out that near $2 m_{\text{DM}}\simeq m_{1,2}$ resonances, where $m_{1}$ and $m_{2}$ are the SM Higgs boson and a non-standard Higgs boson masses, respectively, there exist substantial regions where the models are testable. A special attention has been payed to calculation of the cross section in the region where $m_{1}\simeq m_{2}$.

hep-ph↗

arXiv2020

Sensitivity to invisible Higgs boson decays at CLIC

We studied the possibility of measuring invisible Higgs boson decays at CLIC running at 380 GeV and 1.5 TeV. The analysis is based on the WHIZARD event generation and fast simulation of the CLIC detector response with DELPHES. We considered $e^+e^-$ background processes but also relevant $γγ$ and $γe^\pm$ interactions. The approach consisting of a two step analysis was used to optimize separation between signal and background processes. First, a set of preselection cuts was applied; then, multivariate analysis methods were employed to optimise the significance of observations. We estimated the expected limits on the invisible decays of the 125 GeV Higgs boson, as well as the cross section limits for production of an additional neutral Higgs-like scalar, assuming its invisible decays, as a function of its mass. Extracted model-independent branching ratio and cross section limits were then interpreted in the framework of the vector-fermion dark matter model to set limits on the mixing angle between the SM-like Higss boson and the new scalar of the "dark sector".

hep-ex↗

arXiv2018

Testing scalar versus vector dark matter

We investigate and compare two simple models of dark matter (DM): a vector and a scalar DM model. Both models require the presence of two physical Higgs bosons $h_1$ and $h_2$ which come from mixed components of the standard Higgs doublet $H$ and a complex singlet $S$. In the Vector model, the extra $U(1)$ symmetry is spontaneously broken by the vacuum of the complex field $S$. This leads to a massive gauge boson $X^μ$ that is a DM candidate stabilized by the dark charge conjugation symmetry $S \to S^*$, $X^μ\to -X^μ$. On the other hand, in the Scalar model the gauge group remains the standard one. The DM field $A$ is the imaginary component of $S$ and the stabilizing symmetry is also the dark charge conjugation $S \to S^*$ ($A \to - A$). In this case, in order to avoid spontaneous breaking, the $U(1)$ symmetry is broken explicitly, but softly, in the scalar potential. The possibility to disentangle the two models has been investigated. We have analyzed collider, cosmological, DM direct and indirect detection constraints and shown that there are regions in the space spanned by the mass of the non-standard Higgs boson and the mass of the DM particle where the experimental bounds exclude one of the models. We have also considered possibility to disentangle the models at $e^+e^-$ collider and concluded that the process $e^+e^-\to Z + \text{DM}$ provides a useful tool to distinguish the models.

hep-ph↗

arXiv2018

Multi-Component Dark Matter: the vector and fermion case

Multi-component dark matter scenarios constitute natural extensions of standard single-component setups and offer attractive new dynamics that could be adopted to solve various puzzles of dark matter. In this work we present and illustrate properties of a minimal UV-complete vector-fermion dark matter model where two or three dark sector particles are stable. The model we consider is an extension of the Standard Model (SM) by spontaneously broken extra $U(1)_X$ gauge symmetry and a Dirac fermion. All terms in the Lagrangian which are consistent with the assumed symmetry are present, so the model is renormalizable and consistent. To generate mass for the dark-vector $X_μ$ the Higgs mechanism with a complex singlet $S$ is employed in the dark sector. Dark matter candidates are the massive vector boson $X_μ$ and two Majorana fermions $ψ_\pm$. All the dark sector fields are singlets under the SM gauge group. The set of three coupled Boltzmann equations has been solved numerically and discussed. We have performed scans over the parameter space of the model implementing the total relic abundance and direct detection constraints. The dynamics of the vector-fermion dark matter model is very rich and various interesting phenomena appear, in particular, when the standard annihilations of a given dark matter are suppressed then the semi-annihilations, conversions and decays within the dark sector are crucial for the evolution of relic abundance and its present value. Possibility of enhanced self-interaction has been also discussed.

hep-ph↗

arXiv2018

One-loop contribution to dark matter-nucleon scattering in the pseudoscalar dark matter model

Recent dark matter (DM) direct searches place very stringent constraints on the possible DM candidates proposed in extensions of the Standard Model. There are however models where these constraints are avoided. One of the simplest and most striking examples comes from a straightforward Higgs portal pseudoscalar DM model featured with a softly broken $U(1)$ symmetry. In this model the tree-level DM-nucleon scattering cross section vanishes in the limit of zero momentum-transfer. It has also been argued that the leading-order DM-nucleon cross-section appears at the one-loop level. %, which is too small to be constrained experimentally. In this work we have calculated the exact cross-section in the zero momentum-transfer at the leading-order i.e., at the one-loop level of perturbative expansion. We have concluded that, in agreement with expectations, the amplitude for the scattering process is UV finite and approaches zero in the limit of vanishing DM masses. Moreover, we made clear that the finite DM velocity correction at tree-level is subdominant with respect to the one-loop contribution. Based on the analytic formulae, our numerical studies show that, for a typical choice of model parameters, the DM nuclear recoiling cross section is well below ${\cal O}(10^{-50}~{\rm cm}^2)$, which indicates that the DM direct detection signal in this model naturally avoids the present strong experimental limits on the cross-section.

hep-ph↗

arXiv2018

Vector-fermion dark matter

In this thesis a simple extension of the Standard Model has been investigated. The Standard Model gauge group has been extended by an additional $U(1)_X$ group. The model introduces a new Higgs particle as well as three particles (a gauge boson and two Majorana fermions) that can be candidates for dark matter. The thesis also contains a discussion of derivation of the Boltzmann equation, involving detailed analysis of the assumptions. The equation has been used to investigate behaviour of the dark matter density in time, with respect to values of the parameters of the model.

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