arXiv subjects

W. Majerotto

Publications and source records attributed to W. Majerotto.

At least 37 records · Page 2Linked to original sources

arXiv2009

On pair production of scalar top quarks in e+e- collisions at ILC and a possibility of their mass reconstruction

We study pair production of scalar top quarks in e+e- collisions with the subsequent decay of the top squarks into b-quarks and charginos. We simulate this process by using PYTHIA6.4 for the beam energy 2Ebeam = 350, 400, 500, 800, 1000 GeV. A set of criteria for physical variables is proposed, which provides good separation of stop signal events from top quark pair production being the main background. These criteria allow us to reconstruct the mass of the top squark with an integrared luminosity of 1000 1/fb provided that the neutralino mass is known.

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arXiv2008

Impact of slepton generation mixing on the search for sneutrinos

We perform a systematic study of sneutrino production and decays in the Minimal Supersymmetric Standard Model (MSSM) with slepton generation mixing. We study both fermionic decays like sneutrino \to l^- chargino^+, nu neutralino and bosonic decays such as sneutrino \to slepton^- H^+, slepton^- W^+. We show that the effect of slepton generation mixing on the sneutrino production cross sections and its decay branching ratios can be quite large in a significant part of the MSSM parameter space despite the very strong experimental limits on lepton flavour violating processes. This could have an important impact on the search for sneutrinos and the determination of the MSSM parameters at future colliders, such as LHC, ILC, CLIC and muon collider.

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arXiv2008

Collider aspects of flavour physics at high Q

This review presents flavour related issues in the production and decays of heavy states at LHC, both from the experimental side and from the theoretical side. We review top quark physics and discuss flavour aspects of several extensions of the Standard Model, such as supersymmetry, little Higgs model or models with extra dimensions. This includes discovery aspects as well as measurement of several properties of these heavy states. We also present public available computational tools related to this topic.

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arXiv2007

Complete one-loop corrections to decays of charged and CP-even neutral Higgs bosons into sfermions

We present the full one-loop corrections to charged and CP-even neutral Higgs boson decays into sfermions including also the crossed channels. The calculation was carried out in the minimal supersymmetric extension of the Standard Model and we use the on-shell renormalization scheme. For the down-type sfermions, we use DR-running fermion masses and the trilinear coupling A_f as input. Furthermore, we present the first numerical analysis for decays according to the Supersymmetric Parameter Analysis project. This requires the renormalization of the whole MSSM. The corrections are found to be numerically stable and not negligible.

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arXiv2006

CP violation in charged Higgs decays in the MSSM

In the MSSM with complex parameters loop corrections to the decays $H^+ \to t \bar{b}$ and $H^- \to \bar{t} b$ with $t \to b W$ and $W \to l ν$ lead to CP-violating asymmetries: a decay rate asymmetry, a forward-backward asymmetry and an energy asymmetry. We derive explicit formulas for them and perform a detailed numerical analysis. We study the dependence on the parameters and the phases involved. In particular, the influence of the running Yukawa coupling is taken into account. The decay rate asymmetry can go up to 25%, the forward-backward and the energy asymmetry up to 10%.

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arXiv2006

Test of lepton flavour violation at LHC

We study lepton flavour violating decays of neutralinos and sleptons within the Minimal Supersymmetric Standard Model, assuming two and three generation mixings in the slepton sector. We take into account the most recent bounds on flavour violating rare lepton decays. Taking the SPS1a' scenario as an example, we show that some of the lepton flavour violating branching ratios of neutralinos and sleptons can be sizable (~ 5-10%). We study the impact of the lepton flavour violating neutralino and slepton decays on the di-lepton mass distributions measured at LHC. We find that they can result in novel and characteristic edge structures in the distributions. In particular, double-edge structures can appear in the e tau and mu tau mass spectra if ~tau_1 is the lightest slepton. The appearance of these remarkable structures provides a powerful test of supersymmetric lepton flavour violation at LHC.

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arXiv2005

Supersymmetry Parameter Analysis: SPA Convention and Project

High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme, Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables at LHC and high energy e+e- linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles. In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision. We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference point.

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arXiv2005

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

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arXiv2005

CP-violating asymmetry in chargino decay into neutralino and W boson

In the MSSM with complex parameters, loop corrections to $\cha_i^\pm \to \neu_j^0 W^\pm$ lead to a CP violating asymmetry $\ACP = (Γ(\cha_i^+ \to \neu_j^0 W^+) - Γ(\cha_i^- \to \neu_j^0 W^-))/ (Γ(\cha_i^+ \to \neu_j^0 W^+) + Γ(\cha_i^- \to \neu_j^0 W^-))$. We calculate this asymmetry at full one-loop level. We perform a detailed numerical analysis for $\cha_1^\pm \to \neu_1^0 W^\pm$ and $\cha_2^\pm \to \neu_1^0 W^\pm$ analyzing the dependence on the parameters and phases involved. Asymmetries of several percent are obtained. We also discuss the feasability of measuring these asymmtries at LHC.

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arXiv2005

Full O(alpha) corrections to e+e- -> sf_i sf_j

We present a complete precision analysis of the sfermion pair production process e+e- -> sf_i sf_j (f = t, b, tau, nu_tau) in the Minimal Supersymmetric Standard Model. Our results extend the previously calculated weak corrections by including all one-loop corrections together with higher order QED corrections. We present the details of the analytical calculation and discuss the renormalization scheme. The numerical analysis shows the results for total cross-sections, forward-backward and left-right asymmetries. It is based on the SPS1a' point from the SPA project. The complete corrections are about 10% and have to be taken into account in a high precision analysis.

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arXiv2005

Precise predictions for chargino and neutralino pair production in $e^+e^-$ annihilation

We present a high precision calculation of chargino and neutralino pair production at $e^+e^-$ colliders. Within the Minimal Supersymmetric Standard Model, the full one-loop and higher order QED corrections are included. Special care has been taken in the definition of the Lagrangian input parameters. Furthermore, the proper inclusion of QED corrections and the separation of weak and QED corrections are discussed. We show numerical results for total cross sections, as well as forward-backward and left-right asymmetries for the SPS1a' scenario as proposed in the SPA project. The complete corrections are about 10% and in some cases even larger, in particular for $\neu_i \neu_j$ production with sizeable higgsino components. These corrections have to be taken into account in a high precision analysis.

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arXiv2004

CP sensitive observables in chargino production and decay into a W boson

We study CP sensitive observables in chargino production in electron-positron collisions with subsequent two-body decay of one chargino into a W boson. We identify the CP odd elements of the W boson density matrix and propose CP sensitive triple-product asymmetries of the chargino decay products. We calculate the density-matrix elements, the CP asymmetries and the cross sections in the Minimal Supersymmetric Standard Model with complex parameters μand M_1 for an e+ e- linear collider with \sqrt{s} = 800 GeV and longitudinally polarized beams. The asymmetries can reach 7% and we discuss the feasibility of measuring these asymmetries.

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arXiv2004

CP violation in chargino production and decay into sneutrino

We study CP odd asymmetries in chargino production E+ E- --> ~Chi(+-)(1) Chi(-+)(2) and the subsequent two-body decay of one chargino into a sneutrino. We show that in the Minimal Supersymmetric Standard Model with complex parameter μthe asymmetries can reach 30 %. We discuss the feasibility of measuring these asymmetries at a linear collider with \sqrt{s} = 800 GeV and longitudinally polarized beams.

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arXiv2004

CP sensitive observables in e+e- -> neutralino_i neutralino_j and neutralino decay into the Z boson

We study CP sensitive observables in neutralino production e+e- -> neutralino_i neutralino_j and the subsequent two-body decays of the neutralino neutralino_i -> neutralino_n Z and of the Z boson Z -> l \bar l (q \bar q). We identify the CP odd elements of the Z boson density matrix and propose CP sensitive triple-product asymmetries. We calculate these observables and the cross sections in the Minimal Supersymmetric Standard Model with complex parameters μand M_1 for an e+e- linear collider with \sqrt{s}=800 GeV and longitudinally polarized beams. We show that the asymmetries can reach 3% for Z -> l \bar l and 18% for Z -> q \bar q and discuss the feasibility of measuring these asymmetries.

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arXiv2004

Complete one--loop corrections to e+e- -> sf_i sf_j

We have calculated the complete one-loop corrections to the sfermion pair production process e+e- -> sf_i sf_j (f = t, b, tau, tau-neutrino) in the Minimal Supersymmetric Standard Model. Our results also include the previously calculated SUSY-QCD corrections. We present the details of the renormalization scheme used. It is found that the weak corrections are of the same magnitude as the SUSY-QCD corrections at higher energies (sqrt(s) ~ 1TeV). At these energies the main part of the weak corrections stems from the box contribution. This is best seen in sneutrino production.

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arXiv2004

Full one-loop corrections to SUSY Higgs boson decays into charginos

We present the decay widths of the heavier Higgs bosons $H^0$ and $A^0$ into chargino pairs in the minimal supersymmetric standard model, including full one-loop corrections. All parameters for charginos are renormalized in the on-shell scheme. The importance of the corrections to the chargino mass matrix and mixing matrices is pointed out. The full corrections are typically of the order of 10 %.

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arXiv2004

Full one-loop corrections to neutralino pair production in e+e- annihilation

We present the full one-loop radiative corrections to pair production of neutralinos in e+e- collisions within the Minimal Supersymmetric Standard Model. Particular attention is paid to the definition of weak and QED corrections. The non-universal QED corrections are extracted by subtracting the initial state radiation. We give numerical results for two different SUSY scenarios for e+e- -> neu_1 neu_2 and e+e- -> neu_2 neu_2. The weak and QED corrections are up to several percent or even higher and need to be taken into account at future linear collider experiments.

hep-ph↗

arXiv2003

CP asymmetries in neutralino production in e+e- collisions

We study two CP sensitive triple-product asymmetries for neutralino production e+e- \to\tildeχ^0_i \tildeχ^0_j and the subsequent leptonic two-body decay \tildeχ^0_i \to \tilde l l, \tilde l \to \tildeχ^0_1 l, for ł= e,μ,τ. We calculate the asymmetries, cross sections and branching ratios in the Minimal Supersymmetric Standard Model with complex parameters μand M_1. We present numerical results for the asymmetries to be expected at a linear electron-positron collider in the 500 GeV range. The asymmetries can go up to 25 %. We estimate the event rates which are necessary to observe the asymmetries. Polarized electron and positron beams can significantly enhance the asymmetries and cross sections. In addition, we show how the two decay leptons can be distinguished by making use of their energy distributions.

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