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W. Majerotto

Publications and source records attributed to W. Majerotto.

At least 73 records · Page 4Linked to original sources
arXiv2001

One-loop corrections to neutral Higgs boson decays into neutralinos

We present the one-loop corrected decay widths for the decays of the neutral Higgs bosons h^0, H^0, and A^0 into a neutralino pair neu_m neu_n (m, n = 1, >..., 4) and to the decay neu_m -> (h^0, H^0, A^0) + neu_n. The corrections contain the one-loop contributions of all fermions and sfermions. All parameters are taken on-shell. This requires a proper treatment of the neutralino mass and mixing matrix. The dependence on the SUSY parameters is discussed. The corrections can be large in certain regions of the parameter space.

hep-ph↗
arXiv2001

One-loop corrections to the chargino and neutralino mass matrices in the on-shell scheme

We present a consistent procedure for the calculation of the one-loop corrections to the charginos and neutralinos by using their on-shell mass matrices. The on-shell gaugino mass parameters M and M', and the Higgsino mass parameter μare defined by the elements of these on-shell mass matrices. The on-shell mass matrices are different by finite one-loop corrections from the tree-level ones given in terms of the on-shell parameters. When the on-shell M and μare determined by the chargino sector, the neutralino masses receive corrections up to 4%. This must be taken into account in precision measurements at future e^+ e^- linear colliders.

hep-ph↗
arXiv2000

Improved SUSY QCD corrections to Higgs boson decays into quarks and squarks

The O(alpha_s) SUSY QCD corrections to the decays of the MSSM Higgs bosons into bottom quarks and squarks can be very large for large tan beta in the on--shell renormalization scheme. We improve the calculation by a careful choice of the tree-level Higgs boson couplings in terms of running parameters of quarks and squarks.

hep-ph↗
arXiv2000

Gaugino Mass Dependence of Electron and Neutron Electric Dipole Moments

Unless squarks and sleptons are in the multi-TeV region or above, CP violating induced electric dipole moments of elementary particles can pose significant puzzles for supersymmetric (SUSY) models. We study the dipole-moment-inducing one-loop amplitudes as a function of the fundamental SUSY parameters and show that these puzzles are removed if there is a sufficiently large hierarchy between the gaugino masses and the scalar mass. We comment on the experimental status of the low gaugino mass scenario.

hep-ph↗
arXiv2000

Impact of e^+ and e^- Beam Polarization on Chargino and Neutralino Production at a Linear Collider

We study the production processes e^+ e^- -> chi^+_i chi^-_j, i,j=1,2, and e^+ e^- -> chi^0_m chi^0_n, m,n=1,...,4, working out the advantages of polarizing both beams. For e^+ e^- -> chi^+_1 chi^-_1 with chi^-_1 -> chi^0_1 e^- nu and e^+ e^- -> chi^0_1 chi^0_2 with chi^0_2 -> chi^0_1 e^+ e^- we perform a detailed analysis, including the complete spin correlations between production and decay. We analyze the forward--backward asymmetry of the decay electron for various beam polarizations. We also study polarization asymmetries in e^+ e^- -> chi^0_1 chi^0_2. These asymmetries strongly constrain the gaugino parameter M_1 and the masses m_{\tilde{e}_L}, m_{\tilde{e}_R}, m_{\tilde{nu}} also if m_{\tilde{e}_{L,R}}, m_{\tilde{nu}} > sqrt{s}/2. We give numerical predictions for three scenarios for a linear collider with sqrt{s}=500-1000 GeV.

hep-ph↗
arXiv2000

Phenomenology of stops, sbottoms, tau-sneutrinos, and staus at an e+e- Linear Collider

We discuss production and decays of stops, sbottoms, tau-sneutrinos, and staus in e+e- annihilation in the energy range \sqrt{s} = 0.5-1 TeV. We present numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates, including one-loop radiative corrections as well as initial state radiation. We also study the importance of beam polarization for the determination of the underlying SUSY parameters. Moreover, we make a comparison of the potential to study squarks and sleptons of the 3rd generation between Tevatron, LHC, and Linear Collider.

hep-ph↗
arXiv2000

Improved SUSY QCD corrections to Higgs boson decays into quarks and squarks

We improve the calculation of the supersymmetric $O(α_s)$ QCD corrections to the decays of Higgs bosons into quarks and squarks in the Minimal Supersymmetric Standard Model. In the on-shell renormalization scheme these corrections can be very large, which makes the perturbative expansion unreliable. This is especially serious for decays into bottom quarks and squarks for large $\tanβ$. Their corrected widths can even become negative. We show that this problem can be solved by a careful choice of the tree-level Higgs boson couplings to quarks and squarks, in terms of the QCD and SUSY QCD running quark masses, running trilinear couplings $A_q$, and on-shell left-right mixing angles of squarks. We also present numerical results for the corrected partial decay widths for the large $\tanβ$ case.

hep-ph↗
arXiv2000

Beam Polarization and Spin Correlation Effects in Chargino Production and Decay

We study chargino production e^+ e^- -> chi^+_1 chi^-_1 and the subsequent leptonic decay chi^-_1\to chi^0_1 e^- nu_e including the complete spin correlations between production and decay. We work out the advantages of polarizing the e^+ and e^- beams. We study in detail the polarized cross sections, the angular distribution and the forward--backward asymmetry of the decay electron. They can be used to determine the sneutrino mass m_{\tildeν_e}.

hep-ph↗
arXiv2000

Exploiting Spin Correlations in Neutralino Production and Decay with Polarized e^- and e^+ Beams

We study the production process e^+ e^- -> chi^0_1 chi^0_2 and the subsequent decay chi^0_2 -> chi^0_1 l^+ l^- with polarized e^+ and e^- beams, including the spin correlations between production and decay. We work out the advantages of polarizing both beams. We study in detail the angular distribution and the forward--backward asymmetry of the decay lepton as well as the opening angle distribution between the decay leptons. We investigate the dependence on the masses of tilde{e}_L and tilde{e}_R and on the mixing character of the neutralinos. In particular we study the dependence on the gaugino mass parameter M_1.

hep-ph↗
arXiv1999

Production and decays of stops, sbottoms, and staus

We present a phenomenological analysis of production and decays of stops, sbottoms, and staus in e+e- collisions with sqrt(s) = 500 - 800 GeV. We include SUSY-QCD and Yukawa coupling corrections as well as initial state radiation. We show that e- beam polarization is a powerful tool for a determination of the underlying SUSY parameters. Using in addition a polarized e+ beam improves the precision of the parameter determination by about 25%.

hep-ph↗
arXiv1999

Polarization and Spin Effects in Neutralino Production and Decay

We study the production of neutralinos e^+ e^- ->chi^0_i χ^0_j with polarized beams and the subsequent decays chi^0_i -> chi^0_k l^+ l^- and chi^0_j -> chi^0_l l^+ l^-, including the complete spin correlations between production and decay. We present analytical formulae for the differential cross section of the combined process of production and decay of neutralinos. We also allow for complex couplings. The spin correlations have a strong influence on the decay angular distributions and the corresponding forward-backward asymmetries. They are very sensitive to the SUSY parameters and depend strongly on the beam polarizations. We present numerical results for the cross section and the electron forward-backward asymmetry for e^+ e^- -> chi^0_1 chi^0_2, chi^0_2 -> chi^0_1 e^+ e^-. We study the dependence on the parameter M' for various mass splittings between tilde{e}_L and tilde{e}_R and different beam polarizations.

hep-ph↗
arXiv1999

Large Higgs Boson Exchange Contribution in Three-Body Neutralino Decays

We show that the Higgs boson exchange contribution can be large in three-body decays of neutralinos even in the case of small tan(beta). This enlarges the branching ratios for the decays neutralino_2 -> neutralino_1 b \bar{b} and neutralino_2 -> neutralino_1 tau- tau+. This is the case in the region of the parameter space where the two lightest neutralinos are gaugino-like, the sfermions are heavier than 300 GeV, and m_A0 = 200 GeV or smaller.

hep-ph↗
arXiv1999

Impact of bosonic decays on the search for stau_2 and tau-sneutrino

We perform a detailed study of the decays of the heavier tau slepton (stau_2) and tau-sneutrino (snu_tau) in the Minimal Supersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons, i.e. stau_2 -> stau_1 + (h^0, H^0, A^0 or Z^0), stau_2 -> snu_tau + (H^- or W^-), and snu_tau -> stau_1 + (H^+ or W^+), can be very important due to the sizable tau Yukawa coupling and large mixing parameters of stau. Compared to the decays into fermions, such as stau_2 -> tau + neutralino_i and stau_2 -> nu_tau + chargino_j^-, these bosonic decay modes can have significantly different decay distributions. This could have an important influence on the search for stau_2 and snu_tau and the determination of the MSSM parameters at future colliders.

hep-ph↗
arXiv1999

Yukawa coupling corrections to stop, sbottom, and stau production in e+ e- annihilation

We calculate within the MSSM the one-loop Yukawa coupling corrections to the processes e+ e- \to stops, sbottoms, and staus in order of Yukawa coupling squared. These corrections are due to the exchange of charginos, neutralinos, charged and neutral Higgs bosons, and charged and neutral Higgs ghosts. We give the complete analytical formulae. We also perform a detailed numerical analysis of the Yukawa coupling corrections, including also the SUSY-QCD corrections. It turns out that for stop and sbottom production the Yukawa coupling corrections are typically +/- 10% of the tree-level cross section. For stau production they are about +/- 5%.

hep-ph↗
arXiv1999

Constraining the minimal supergravity model parameter tan(beta) by measuring the dilepton mass distribution at LHC

We study the dependence on $\tanβ$ of the event kinematics of final states with $e^+e^- /μ^+μ^- /e^{\pm}μ^{\mp} + E_T^{\rm miss} + jets$, as expected in $pp$ collisions at CERN LHC, within the framework of the minimal supergravity model. With increase of $\tanβ$, the third generation sparticle masses $m_{\tildeτ_1}$ and $m_{\tilde{b}_1}$ decrease due to the increase of the tau and bottom Yukawa couplings. As a result, gluino, stop, sbottom, chargino and neutralino decays to third generation particles and sparticles are enhanced. With $\tanβ$ rising, we observe a characteristic change in the shape of the dilepton mass spectra in $e^+e^- /μ^+μ^- +E_T^{\rm miss} + jets$ versus $e^{\pm}μ^{\mp} + E_T^{\rm miss} + jets$ final states, reflecting the presence of the decays $\tildeχ_2^0\to \tilde{\ell}_{L,R}^{\pm}\ell^{\mp}\to \tildeχ_1^0 \ell^+\ell^-, \tildeχ_2^0\to \tildeχ_1^0 \ell^+\ell^-$ and $\tildeχ_2^0\to \tildeτ^{\pm}_1τ^{\mp}\to \tildeχ_1^0 τ^+ τ^-$, $\tildeχ_2^0\to τ^+ τ^- \tildeχ_1^0$, respectively. We exploit this effect for constraining the value of $\tanβ$.

hep-ph↗
arXiv1998

SUSY-QCD corrections to stop and sbottom decays into Higgs bosons

We calculate the order(α_s) SUSY-QCD corrections to the widths of stop and sbottom decays into Higgs bosons within the Minimal Supersymmetric Standard Model. We give the complete analytical formulae paying particular attention to the on-shell renormalization of the soft SUSY-breaking parameters. We also perform a detailed numerical analysis of both stop and sbottom decays into all Higgs bosons h^0, H^0, A^0, and H^\pm. We find that the SUSY-QCD corrections are significant, mostly negative and of the order of a few ten percent.

hep-ph↗
arXiv1998

Bosonic decays of stop_2 and sbottom_2

We perform a detailed study of the decays of the heavier top and bottom squarks (stop_2 and sbottom_2) in the Minimal Supersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons can be dominant in a wide range of the model parameters due to the large Yukawa couplings and mixings of stops and sbottoms. Compared to the conventional decays into fermions these bosonic decay modes can have significantly different decay structures and distributions. This could have an important impact on the search for stop_2 and sbottom_2 and the determination of the MSSM parameters at future colliders.

hep-ph↗