arXiv subjects

Mikulas Gintner

Publications and source records attributed to Mikulas Gintner.

14 recordsLinked to original sources

arXiv2021

The mass exclusion limits for the BSM vector resonances with the direct couplings to the third quark generation

The upper bounds that the LHC measurements searching for heavy resonances beyond the Standard model set on the resonance production cross sections are not universal. They depend on various characteristics of the resonance under consideration, and their validity is also limited by the assumptions and approximations applied to their calculations. The bounds are typically used to derive the mass exclusion limits for the new resonances. We address some of the issues that emerge when deriving the mass exclusion limits for the strongly coupled composite $SU(2)_{L+R}$ vector resonance triplet which would interact directly to the third quark generation only. We show that the presence of such interactions in the model can lower the mass exclusion limits.

hep-ph↗

arXiv2017

The LHC mass limits for the $SU(2)_{L+R}$ vector resonance triplet of a strong extension of the Standard model

In this paper, we derive the mass exclusion limits for the hypothetical vector resonances of a strongly interacting extension of the Standard model using the most recent upper bounds on the cross sections for various resonance production processes. The $SU(2)_{L+R}$ triplet of the vector resonances under consideration is embedded into the effective Lagrangian based on the non-linear sigma model with the $125$-GeV $SU(2)_{L+R}$ scalar singlet. No direct interactions of the vector resonance to the SM fermions are assumed. We find that among eleven processes considered in this paper only those where the vector resonances decay to $WW$ and $WZ$ provide the mass exclusion limit. Depending on the values of other parameters of the model the mass limit can be as low as 1 TeV.

hep-ph↗

arXiv2016

The limits on the strong Higgs sector parameters in the presence of new vector resonances

In this paper, we investigate how the LHC data limit the Higgs-related couplings in the effective description of a strongly interacting extension of the Standard model. The Higgs boson is introduced as a scalar composite state and it is followed in the mass hierarchy by an $SU(2)$ triplet of vector composites. The limits are calculated from the constraints obtained in the recent ATLAS+CMS combined analysis of the data from 2011 and 2012. We find that the data prefer the scenario where the Higgs couplings to the electroweak gauge bosons differ from its couplings to the vector triplet. We also investigate the unitarity limits of the studied effective model for the experimentally preferred values of the Higgs couplings. We find from the $ππ\rightarrowππ$ scattering amplitudes that for the vector resonance masses between one and two TeV significant portions of the experimentally allowed regions are well below the unitarity limit. We also evaluate how the existing ATLAS and CMS Run-2 data restrict our model with the upper bounds on the resonance production cross section times its branching ratio for various decay channels. The masses in the range $1\;\mbox{TeV}\leq M_ρ\leq 2\;\mbox{TeV}$ are not excluded in parts or even full parameter space of our theory.

hep-ph↗

arXiv2013

A 125 GeV scalar improves the low-energy data support for the top-BESS model

We investigate how adding a scalar resonance of a mass 125 GeV affects the low-energy data support for the top-BESS model as well as its low-energy free parameter limits. The top-BESS model is an effective Lagrangian, a modification of the well-known BESS model, with an ambition to describe phenomenology of the lowest bound states of strongly-interacting theories beyond the Standard model. In particular, the SU(2)_{L+R} vector resonance triplet of hypothetical bound states is a centerpiece of BESS-like effective models. The top-BESS model assumes that the triplet couples directly to the third quark generation only. This assumption reflects a possible special standing of the third quark generation, and the top quark in particular, in physics of electroweak symmetry breaking. Our findings suggest that the 125 GeV scalar extension of the top-BESS model results in a higher statistical support for the model. The best-fit values of the model's free parameters are consistent with the top quark having a higher degree of compositeness than the bottom quark.

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arXiv2013

The vector resonance triplet with the direct coupling to the third quark generation

The effective Lagrangian with scalar and vector resonances that might result from new strong physics beyond the SM is formulated and studied. In particular, the scalar resonance representing the recently discovered 125-GeV boson is complemented with the SU(2)_{L+R} triplet of hypothetical vector resonances. Motivated by experimental and theoretical considerations, the vector resonance is allowed to couple directly to the third quark generation only. The coupling is chiral-dependent and the interaction of the right top quark can differ from that of the right bottom quark. To estimate the applicability range of the effective Lagrangian the unitarity of the gauge boson scattering amplitudes is analyzed. The experimental fits and limits on the free parameters of the vector resonance triplet are investigated.

hep-ph↗

arXiv2013

LHC and the strongly-interacting extensions of the Standard Model

This was a plenary talk at the 19th Conference of Slovak Physicists reviewing the status, consequences, and prospects of the 125-GeV boson discovery. To illustrate a possible impact of the discovery on the strongly-interacting extensions of the Standard Model the preliminary results of the analysis of the top-BESS effective model with the 125-GeV scalar boson added were shown. The complete analysis has appeared recently in arxiv:1301.2124.

hep-ph↗

arXiv2011

A brief outline of the top-BESS model

This is a brief outline of the top-BESS model and its properties. The top-BESS model is the higgsless effective description of the strong electroweak symmetry breaking with a single new SU(2)_L+R triplet vector resonance. In contrast with the universality of the fermion interactions of the BESS model, the top-BESS vector resonance couples directly to the third quark generation only. The complete formulation of the model along with its phenomenology can be found in arXiv:1107.0570.

hep-ph↗

arXiv2011

Top-BESS model and its phenomenology

We introduce the top-BESS model which is the effective description of the strong electroweak symmetry breaking with a single new SU(2)_L+R triplet vector resonance. The model is a modification of the BESS model in the fermion sector. The triplet couples to the third generation of quarks only. This approach reflects a possible extraordinary role of the top quark in the mechanism of electroweak symmetry breaking. The low-energy limits on the model parameters found provide hope for finding sizable signals in the LHC Drell-Yan processes as well as in the s-channel production processes at the ILC. However, there are regions of the model parameter space where the interplay of the direct and indirect fermion couplings can hide the resonance peak in a scattering process even though the resonance exists and couples directly to top and bottom quarks.

hep-ph↗

arXiv2009

The Kolmogorov-Smirnov test and its use for the identification of fireball fragmentation

We propose an application of the Kolmogorov-Smirnov test for rapidity distributions of individual events in ultrarelativistic heavy ion collisions. The test is particularly suitable to recognise non-statistical differences between the events. Thus when applied to a narrow centrality class it could indicate differences between events which would not be expected if all events evolve according to the same scenario. In particular, as an example we assume here a possible fragmentation of the fireball into smaller pieces at the quark/hadron phase transition. Quantitative studies are performed with a Monte Carlo model capable of simulating such a distribution of hadrons. We conclude that the Kolmogorov-Smirnov test is a very powerful tool for the identification of the fragmentation process.

nucl-th↗

arXiv2007

Fragmentation of the fireball and how to observe it

We argue that fragmentation at hadronisation is likely scenario in ultrarelativistic nuclear collisions. In case of crossover phase transition it is driven by a singularity of the bulk viscosity. We claim that such a scenario can explain the ``HBT puzzle'' and can be identified by non-statistical differences between event-wise rapidity distributions and by proton-proton rapidity correlations.

nucl-th↗

arXiv1996

t tbar Production via Vector Boson Fusion at High Energy e^+ e^- Colliders

We examine t tbar production via vector boson fusion at high energy e^+ e^- colliders using the effective vector-boson approximation. We show cross sections as functions of CM energy for various Higgs masses ranging from 100 GeV up to 1 TeV, and also for M_H = infinity which corresponds to the LET. We give expressions for sigma(V_i V_j -> t tbar) in the 2M_(W,Z)/sqrt(s) = 0 approximation and show how this approximation effects the results.

hep-ph↗

arXiv1996

Measurement of the W W gamma and W W Z Couplings in the Process $e^+e^- \to l νq\bar{q}'$

We studied the sensitivity of the process $e^+e^-\to \ell νq\bar{q}'$ to anomalous trilinear gauge boson couplings of the $WWγ$ and WWZ vertices at the center of mass energies $\sqrt{s}=500$ GeV and 1 TeV. The bounds for the couplings we obtained result from an analysis of a five dimensional angular differential cross section. In our calculations we included all tree level Feynman diagrams contributing to the final state as well as the finite widths of the vector bosons. Both unpolarized and polarized beams were considered. We found that the 500 GeV measurements will be at the level of loop contributions to the couplings and may show hints of new physics while the 1 TeV should be sensitive to new physics at the loop level. We also explored $\ellνq\bar{q}$ final states off the W resonance and found that useful information could be extracted from this region of phase space.

hep-ph↗

arXiv1995

W-Pair Production in the Process $e^+e^- \to \ell νq\bar{q}'$ and Measurement of the $WWγ$ and $WWZ$ Couplings

We performed a detailed analysis of the process $e^+e^-\to \ell νq\bar{q}'$ where we included all tree level Feynman diagrams that contribute to this final state. We studied the sensitivity of this process to anomalous trilinear gauge boson couplings of the $WWγ$ and $WWZ$ vertices using two popular parametrizations. We used a maximum likelihood analysis of a five dimensional differential cross-section based on the $W$ and $W$ decay product angular distributions. We concentrated on LEP-200 energies, taking $\sqrt{s}=175$ GeV, and energies appropriate to the proposed Next Linear Collider (NLC), a high energy $e^+e^-$ collider with center of mass energies $\sqrt{s}=500$ and 1~TeV. At 175 GeV, $g_1^Z$ can be measured to about $\pm 0.2$, $κ_Z$ to $\pm 0.2$ and $κ_γ$ to $\pm 0.3$, $λ_Z$ to $\pm 0.2$ and $λ_γ$ to $\pm 0.3$. at 95\% C.L. assuming 500~pb$^{-1}$ integrated luminosity. Although these will be improvements of existing measurements they are not sufficiently precise to test the standard model at the loop level and are unlikely to see deviations from SM expectations. At 500~GeV with 50~fb$^{-1}$ integrated luminosity, $g_1^Z$ can be measured to about $\pm 0.01$, $κ_Z$ and $κ_γ$ to $\pm 0.005$ and $λ_Z$ and $λ_γ$ to $\pm 0.003$ at 95\% C.L. while at 1 TeV with 200~fb$^{-1}$ integrated luminosity, $κ_V$ and $λ_V$ can be measured to about $\pm 0.005$ and $\pm 10^{-3}$ respectively. The 500~GeV measurements will be at the level of loop contributions to the couplings and may show hints of new physics while the 1~TeV should be sensitive to new physics at the loop level.

hep-ph↗

arXiv1995

Measurement of the $WWγ$ and $WWZ$ Couplings at LEP200: The Benefits of Higher Energy?

We performed a detailed analysis of the process $e^+e^-\to \ell νq\bar{q}'$ to determine its sensitivity to anomalous trilinear gauge boson couplings of the $WWγ$ and $WWZ$ vertices and how the sensitivity varies with energy and integrated luminosity. We included all tree level Feynman diagrams that contribute to this final state and used a maximum likelihood analysis of a five dimensional differential cross-section based on the $W$ and $W$ decay product angular distributions. For constant luminosity, increasing $\sqrt{s}$ from 175~GeV to 192~GeV (220~GeV) improves the measurement sensitivity by a factor of 1.5 to 2 (2 to 3) depending on the parameter measured. However, the lower luminosity expected at higher $\sqrt{s}$ will reduce these improvements. In any case, the sensitivities for $\sqrt{s}$=175~GeV and L=500~pb$^{-1}$ of $δg_1^Z = \pm 0.22$, $δκ_Z = \pm 0.20$, $δκ_γ=\pm 0.27$, $δL_{9L}= \pm 55$, and $δL_{9R}= ^{+330}_{-230}$ are likely to be at least an order of magnitude too big to see the effects of new physics.

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