arXiv subjects

W. Majerotto

Publications and source records attributed to W. Majerotto.

At least 55 records · Page 3Linked to original sources

arXiv2003

Impact of beam polarization on CP asymmetries in neutralino pair production

We analyze the dependence of CP-odd asymmetries on longitudinally polarized e+ and e- beams in neutralino production and subsequent leptonic two-body decays. We give numerical examples of the asymmetries and of the cross sections in the Minimal Supersymmetric Standard Model with complex parameters mu, M_1 and A_{tau} for a collider with sqrt{s}=500 GeV. We show that longitudinally polarized electron and positron beams can enhance considerably both the asymmetries and the cross sections.

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arXiv2003

CP asymmetries in neutralino production

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 decays \tildeχ^0_i \to \tilde{l} l of one of the neutralinos and of the slepton \tilde{l} \to \tildeχ^0_1 l at an e+e--linear collider with \sqrt{s} = 500 GeV. We calculate the asymmetries in the Minimal Supersymmetric Standard Model with complex parameters μand M_1. We show that the largest asymmetries are 10% or 25% and estimate the event rates which are necessary to measure 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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arXiv2003

Improved full one-loop corrections to A^0 -> \sf_1 \sf_2 and \sf_2 -> \sf_1 A^0

We calculate the full electroweak one-loop corrections to the decay of the CP-odd Higgs boson A^0 into scalar fermions in the minimal supersymmetric extension of the Standard Model. For this purpose many parameters of the MSSM have to be properly renormalized in the on-shell renormalization scheme. We have also included the SUSY-QCD corrections. For the decay into bottom squarks and tau sleptons, especially for large \tan\b, the corrections can be very large making the perturbation expansion unreliable. We solve this problem by an appropriate definition of the tree-level coupling in terms of running fermion masses and running trilinear couplings A_f. We also discuss the decay of heavy scalar fermions into light scalar fermions and A^0. We find that the corrections can be sizeable and therefore cannot be neglected.

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arXiv2003

Improved full one--loop corrections to A^0 -> \sq_1 \sq_2 and \sq_2 -> \sq_1 A^0

We calculate the full electroweak one-loop corrections to the decay of the CP-odd Higgs boson A^0 into scalar quarks in the minimal supersymmetric extension of the Standard Model (MSSM). Due to the complex structure of the electroweak sector a proper renormalization of many parameters in the on-shell renormalization scheme is necessary. For the decay into sbottom quarks, especially for large tanb, the corrections can be very large in the on-shell renormalization scheme, which makes the perturbation series unreliable. We solve this problem by an appropriate definition of the tree-level coupling in terms of running quark masses and running trilinear couplings A_q. We also discuss the decay of heavy scalar quarks into light scalar quarks and A^0. We find that the corrections are significant and therefore cannot be neglected.

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arXiv2003

Effect of supersymmetric phases on lepton dipole moments and rare lepton decays

We study the effect of SUSY phases on rare decays of leptons and on their magnetic and electric dipole moments. We consider the most general mass matrices for sleptons within the MSSM including left--right mixing, flavour mixing and complex phases. We show that the phases also affect CP even observables. Moreover, we demonstrate that contrary to common belief the phase of mu can be large even for slepton masses as small as 200 GeV provided the lepton flavour violating parameters are complex.

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arXiv2003

Analysis of the chargino and neutralino mass parameters at one-loop level

In the Minimal Supersymmetric Standard Model (MSSM) the masses of the neutralinos and charginos depend on the gaugino and higgsino mass parameters M, M' and $μ$. If supersymmetry is realized, the extraction of these parameters from future high energy experiments will be crucial to test the underlying theory. We present a consistent method how on-shell parameters can be properly defined at one-loop level and how they can be determined from precision measurements. In addition, we show how a GUT relation for the parameters M and M' can be tested at one-loop level. The numerical analysis is based on a complete one-loop calculation. The derived analytic formulae are given in the appendix.

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arXiv2003

Single Higgs boson production at future linear colliders including radiative corrections

The next generation of high energy e+ e- linear colliders is expected to operate at \sqrt{s} \gtsim 500 GeV. In this energy range the WW fusion channel dominates the Higgs boson production cross section e+ e- -> \barννh^0/H^0. We calculate the one-loop corrections to this process due to fermion and sfermion loops within the MSSM. We perform a detailed numerical analysis of the total cross section and the distributions of the rapidity, the transverse momentum and the production angle of the Higgs boson. The fermion-sfermion correction is substantial being of the order of -10% and is dominated by the fermion loops. In addition, we explore the possibility of polarized e+ / e- beams. In the so-called "intense coupling" scenario the production of the heavy Higgs boson H^0 is also discussed.

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arXiv2003

CP Phases, LFV, RpV & all that

Most phenomenological analyses of searches for supersymmetric particles have been performed within the MSSM with real SUSY parameters and conserved R-parity and lepton flavour. Here we summarize recent results obtained in the (s)lepton sector when one of the above assumptions is relaxed.

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arXiv2002

CP violation in charged Higgs boson decays into tau and neutrino

We calculate the CP-violating rate asymmetry of H^\pm decays into tau and neutrino at one loop in the MSSM with complex parameters. We find that the asymmetry is typically of the order of 10^-3, depending mainly on the phases of the trilinear coupling A_τand of the gaugino mass M_1.

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arXiv2002

Full electroweak one-loop corrections to A^0 -> \sf_1 \sf_2

We discuss the full electroweak one-loop corrections to the decay of the pseudoscalar Higgs boson A^0 into two sfermions within the Minimal Supersymmetric Standard Model. In particular, we consider the sfermions of the third generation, stops, sbottoms, and staus, including the left-right mixing. The electroweak corrections can go up to ~15% and can therefore not be neglected.

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arXiv2002

Large lepton flavour violating signals in supersymmetric particle decays

We study lepton flavour violating signals at a future e+ e- linear collider within the general MSSM, allowing for the most general flavour structure. We demonstrate that there is a large region in parameter space with large signals, while being consistent with present experimental bounds on rare lepton decays such as mu -> e gamma. In our analysis, we include all possible signals from charged slepton, sneutrino, neutralino, and chargino production and decay. We also consider the background from the Standard Model and the MSSM. We find that in general the signature e tau missing energy is the most pronounced one.

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arXiv2002

Radiative corrections to single Higgs boson production in e+e- annihilation

For energies relevant to future linear colliders, \sqrt{s} >~ 500 GeV, the WW fusion channel dominates the Higgs boson production cross section e+e- -> \barννh^0. We have calculated the one-loop corrections to this process due to fermion and sfermion loops in the context of the MSSM. As a special case, the contribution of the fermion loops in the SM has also been studied. In general, the correction is negative and sizeable of the order of 10%, the bulk of it being due to fermion loops.

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arXiv2002

CP violation in charged Higgs boson decays in the MSSM with complex parameters

Supersymmetric loop contributions can lead to different decay rates of H+\to t\bar b and H-\to b\bar t. We calculate the decay rate asymmetry δ^CP = \frac{Γ(H+\to t\bar b)-Γ(H-\to b\bar t)}{{Γ(H+\to t\bar b)+Γ(H-\to b\bar t)} at next-to-leading order in the MSSM with complex parameters. We analyse the parameter dependence of δ^CP with emphasis on the phases of A_t and A_b. It turns out that the most important contribution comes from the loop with stop, sbottom, and gluino. If this contribution is present, δ^CP can go up to 10-15% for tan(beta)~10, and to ~5% for large values of tan(beta).

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arXiv2002

CP violation in charged Higgs boson decays in the MSSM with complex parameters

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arXiv2002

Radiative Corrections to SUSY processes in the MSSM

We review the status of radiative corrections to SUSY processes. We present the method of the on-shell renormalization for the sfermion and the chargino/neutralino system and work out the appropriate renormalization conditions. In particular, we discuss slepton, squark, chargino and neutralino production in e+ e- collisions and the two-body decays of sfermions and of Higgs bosons into SUSY particles. It is necessary to take into account radiative corrections in the precision studies possible at a future linear e+ e- collider.

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arXiv2002

Radiative corrections to single Higgs boson production in $e^+ e^-$ annihilation

For energies relevant to future linear colliders, $\sqrt{s} \gsim 500$ GeV, the WW fusion channel dominates the Higgs boson production cross section $e^+ e^- \to \barν νh^0$. We have calculated the one-loop corrections to this process due to fermion and sfermion loops in the context of the MSSM. As a special case, the contribution of the fermion loops in the SM has also been studied. In general, the correction is negative and sizeable of the order of 10 percent, the bulk of it being due to fermion loops.

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arXiv2002

CP violating asymmetries in single top quark production at the Tevatron p pbar collider

Analytic expressions for the angular distributions of the $b$-quarks associated with single $t$-quark production in $p \bar p \to W^* \to t \bar b \to b \bar b W$ and of the leptons from the subsequent decay $W \to lν$ are obtained in the laboratory system. CP violation in the $t$-production vertex is assumed. Different angular and total cross section CP violating asymmetries are considered. Relations testing CP violation solely in the $t$-decay vertex are also obtained. A numerical analysis is performed in the MSSM with a CP violating phase of the trilinear coupling $A_{\tilde t}$. The asymmetries are typically of the order $10^{-3}$ - $10^{-4}$.

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arXiv2002

Large lepton flavor violating signals in supersymmetric particle decays at future e+ e- colliders

We study lepton flavor violating signals at a future e+ e- linear collider within the general MSSM, allowing for the most general flavor structure. We demonstrate that there is a large region in parameter space with large signals, while being consistent with present experimental bounds on rare lepton decays such as mu -> e gamma. In our analysis, we include all possible signals from charged slepton and sneutrino production and their decays as well as from the decays of neutralinos and charginos. We also consider the background from the Standard Model and the MSSM. We find that in general the signature e tau missing energy is the most pronounced one. We demonstrate that even for an integrated luminosity of 100 inverse fb the signal can be large. At a high luminosity linear collider, precision experiments will allow one to determine the lepton flavor structure of the MSSM.

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