Search

We study pair production of scalar top quarks (stop, \(\tilde t_1\)) in polarized photon-photon collisions with the subsequent decay of the top squarks into b quarks and charginos \(\tilde t_1 \to b\tilde \chi _1^ \pm\). We simulate this process by using PYTHIA6.4 for an electron beam energy \(2E_{beam}^e = \sqrt {s_{ee} } = 1000 GeV\). The energy spectrum of back-scattered photons is generated by CIRCE2 program. A set of criteria for physical variables is proposed which leads to a 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, provided that the neutralino mass is known.

We study the effect of squark generation mixing on squark production and decays at the LHC in the Minimal Supersymmetric Standard Model (MSSM). We show that the effect can be very large despite the very strong constraints on quark flavour violation (QFV) from experimental data on B mesons. We find that the two lightest up-type squarks can have large branching ratios for the decays into and at the same time, leading to QFV signals ‘ + missing-ET + X′ with a significant rate. The observation of this remarkable signature would provide a powerful test of supersymmetric QFV at LHC. This could have a significant impact on the search for squarks and the determination of the underlying MSSM parameters.

We calculate the decay width of $h^0 \to b \bar{b}$ in the Minimal Supersymmetric Standard Model (MSSM) with quark-flavour violation (QFV) at full one-loop level. The effect of $\tilde{c}-\tilde{t}$ mixing and $\tilde{s}-\tilde{b}$ mixing is studied taking into account the constraints from the B-meson data. We discuss and compare in detail the decays $h^0 \to c \bar{c}$ and $h^0 \to b \bar{b}$ within the framework of the perturbative mass insertion technique using the Flavour Expansion Theorem. The deviation of both decay widths from the Standard Model results can be quite large. While in $h^0 \to c \bar{c}$ it is almost entirely due to the flavour violating part of the MSSM, in $h^0 \to b \bar{b}$ it is mainly due to the flavour conserving part. Nevertheless, $\Gamma(h^0 \to b \bar{b})$ can fluctuate up to $\sim 7\%$ due to QFV chargino exchange with large $\tilde{c}-\tilde{t}$ mixing. due to QFV chargino exchange with large $\tilde{c}-\tilde{t}$ mixing., Comment: Talk given by E. Ginina at the Sixth Workshop on Theory, Phenomenology and Experiment on Flavour Physics, FPCapri2016, 11-13 June 2016 Villa Orlandi, Anacapri, Capri Island, Italy. Version to appear in Nuclear and Particle Physics Proceedings, HEPHY-PUB 979/16, UWThPh2016-16, supported by FWF, project No. P26338-N27

We study CP-sensitive observables in the neutralino production $e^ + e^-\to\tilde\chi^0_i \tilde\chi^0_j$ and the subsequent two-body decays of the neutralino $\tilde\chi^0_i \to \chi^0_n Z$ and of the Z boson $Z \to \ell \bar\ell (q\bar q)$ . 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 μ and 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 \to \ell \bar\ell $ and $18\%$ for $Z \to q\bar q$ and discuss the feasibility of measuring these asymmetries.

We have calculated the complete one-loop corrections to the sfermion pair production process e + e − → f i f j (f=t,b,τ,ν τ ) 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 ( s ∼1 TeV). At these energies an important part of the weak corrections stems from the box contribution. This is best seen in sneutrino production.

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 tan β , 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.

We compute the decay width of ${h}^{0}\ensuremath{\rightarrow}c\overline{c}$ in the minimal supersymmetric Standard Model with quark flavor violation (QFV) at full one-loop level adopting the $\overline{\mathrm{DR}}$ renormalization scheme. We study the effects of $\stackrel{\texttildelow{}}{c}\ensuremath{-}\stackrel{\texttildelow{}}{t}$ mixing, taking into account the constraints from the B meson data. We show that the full one-loop corrected decay width $\mathrm{\ensuremath{\Gamma}}({h}^{0}\ensuremath{\rightarrow}c\overline{c})$ is very sensitive to the minimal supersymmetric Standard Model QFV parameters. In a scenario with large ${\stackrel{\texttildelow{}}{c}}_{L,R}\ensuremath{-}{\stackrel{\texttildelow{}}{t}}_{L,R}$ mixing $\mathrm{\ensuremath{\Gamma}}({h}^{0}\ensuremath{\rightarrow}c\overline{c})$ can differ up to $\ensuremath{\sim}\ifmmode\pm\else\textpm\fi{}35%$ from its Standard Model value. After estimating the uncertainties of the width, we conclude that an observation of these supersymmetry QFV effects is possible at an ${e}^{+}{e}^{\ensuremath{-}}$ collider (International Linear Collider).

We calculate the decay width of $h^0(125GeV) \to c \bar{c}$ in the Minimal Supersymmetric Standard Model (MSSM) with non-minimal quark flavor violation (QFV) at full one-loop level. We adopt the $\overline{\rm DR}$ renormalization scheme. We study the effects of the mixing of the second and third squark generations (i.e. scharm-stop mixing) on the decay width, respecting the experimental constraints from B-meson data, the Higgs mass measurement and supersymmetric (SUSY) particle searches. We show that the decay width $\Gamma (h^0 \to c \bar{c})$ at the full one-loop level is very sensitive to the SUSY QFV parameters. In a scenario with large scharm-stop mixing, the decay width can differ up to $\sim \pm 35\%$ from its SM prediction. After taking into account the experimental and theoretical uncertainties of the decay width, we conclude that these QFV SUSY effects can be observed at a future $e^+ e^-$ collider such as ILC (International Linear Collider)., Comment: 7 pages, 3 figures, Proceedings of The European Physical Society Conference on High Energy Physics (EPS-HEP2015), Vienna, Austria, 22-29 July 2015. arXiv admin note: substantial text overlap with arXiv:1504.07792

For energies relevant to future linear colliders, $\sqrt{s} \gsim 500$ GeV, the WW fusion channel dominates the Higgs boson production cross section $e^+ e^- \to \bar{\nu} \nu h^0$. 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., Comment: Version to appear in Phys. Lett. B

This chapter of the 'Flavor in the era of LHC' workshop report discusses flavor-related issues in the production and decays of heavy states at the LHC at high momentum transfer Q, both from the experimental and the theoretical perspective. We review top quark physics, and discuss the flavor aspects of several extensions of the standard model, such as supersymmetry, little Higgs models or models with extra dimensions. This includes discovery aspects, as well as the measurement of several properties of these heavy states. We also present publicly available computational tools related to this topic. © Springer-Verlag / Società Italiana di Fisica 2008., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

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., 13 pages, 3 figures

We discuss production and decays of stops, sbottoms, τ-sneutrinos, and staus in e+e− annihilation in the energy range √s = 0.5-1TeV. 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.

We perform a detailed study of the decays of the heavier τ slepton ( τ 2 ) and τ-sneutrino ( ν τ ) in the Minimal Supersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons, i.e. τ − 2 → τ − 1 +(h 0 ,H 0 ,A 0 or Z 0 ) , τ − 2 → ν τ +(H − or W − ) , and ν τ → τ − 1 +(H + or W + ) , can be very important due to the sizable τ Yukawa coupling and large mixing parameters of τ . Compared to the decays into fermions, such as τ − 2 →τ − + χ 0 i and τ − 2 →ν τ + χ − j , these bosonic decay modes can have significantly different decay distributions. This could have an important influence on the search for τ 2 and ν τ and the determination of the MSSM parameters at future colliders.

We perform a detailed study of the decays of the heavier top and bottom squarks ( t 2 and b 2 ) in the Minimal Supersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons, i.e. t 2 → t 1 +(h 0 ,H 0 ,A 0 or Z 0 ) , t 2 → b 1,2 +(H + or W + ) , and the analogous b 2 decays, can be dominant in a wide range of the model parameters due to the large Yukawa couplings and mixings of t and b. Compared to the conventional decays into fermions, such as t 2 →t+( χ 0 i or g ) and t 2 →b+ χ + j , these bosonic decay modes can have significantly different decay structures and distributions. This could have an important impact on the search for t 2 and b 2 and the determination of the MSSM parameters at future colliders.

We calculate the supersymmetric ${\cal O}(\alpha_s)$ QCD corrections to stop and sbottom decays into vector bosons within the Minimal Supersymmetric Standard Model. We give analytic formulae and perform a numerical analysis of these decays. We find that SUSY-QCD corrections to the decay widths are typically -5% to -10% depending on the squark masses, squark mixing angles, and the gluino mass.

We present a comprehensive study of pair production and decay of stops, sbottoms, and staus in $e^+ e^-$ annihilation at LEP2. We give numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates, and discuss the important signatures. In the case of stau production we also study the polarization of the tau in the decays stau_1 -> tau + neutralino_{1,2}., 15 pages, LateX, 13 figures appended as uuencoded PS-file. LateX file and figures are also available via anonymous ftp at ftp://info.oeaw.ac.at/pub/hephy-pub/642

We study quark flavour violation (QFV) in the squark sector of the Minimal Supersymmetric Standard Model (MSSM). We assume mixing between the second and the third squark generations, i.e. sc_R-st_{L,R} mixing mixing. We focus on QFV effects in bosonic squark decays, in particular on the decay into the lightest Higgs boson h0, su_2 -> su_1 h0, where su_{1,2} are the lightest up-type squarks. We show that the branching ratio of this QFV decay can be quite large (up to 50 %) due to large QFV trilinear couplings, and large sc_R-st_{L, R} and st_L-st_R mixing, despite the strong constraints on QFV from B meson data. This can result in characteristic QFV final states with significant rates at LHC (14 TeV), such as pp -> gluino gluino X -> t + h0 + 3jets + Etmiss + X and pp -> gluino gluino X -> t t (or tbar tbar) + h0 + 2jets + Etmiss + X. The QFV bosonic squark decays can have an influence on the squark and gluino searches at LHC., Figure 3 replaced, Section 4 revised

We present a detailed study of the decays of the neutral Higgs bosons $H^0$ and $A^0$ within the Minimal Supersymmetric Standard Model. We find that the supersymmetric modes ${\tilde{t}}\bar{\tilde{t}}$ and ${\tilde{b}}\bar{\tilde{b}}$ can dominate the $H^0$ and $A^0$ decays in a wide range of the model parameters due to large Yukawa couplings and mixings of ${\tilde{t}}$ and ${\tilde{b}}$. Compared to the conventional modes $t\bar{t}$ and $b\bar{b}$, these modes have very distinctive signatures. This could have a decisive impact on the neutral Higgs boson searches at future colliders., Comment: 15 pages, LaTeX, also available at ftp://physics.ge.seikei.ac.jp/Pub/preprint/itpsu9603.uu (uuencoded postscript)

We calculate the supersymmetric QCD corrections in order $\alpha_s$ to the cross section $e^+ e^- \to \sq_i \bar\sq_j$ $(i,j = 1, 2)$ within the Minimal Supersymmetric Standard Model. We pay particular attention to the case of the left--right squark mixing and to the renormalization of the mixing angle. The corrections due to gluino exchange turn out to be smaller than those due to gluon exchange, but they can be significant at higher energies even for a gluino mass of a few hundred GeV., Comment: 18 pages including 5 figures

We present a complete calculation of the O ( α s ) QCD corrections to the width of the decay H + → t b within the Minimal Supersymmetric Standard Model. We find that the QCD corrections are quite important, and that the supersymmetric QCD corrections (due to gluino, t and b exchange) can be comparable to or even larger than the standard QCD corrections in a large region of the supersymmetric parameter space. This is mainly due to the effect of large left-right mixings of stop ( t ) and sbottom ( b ). This could significantly affect the phenomennology of the H + search.

We calculate the supersymmetric O ( α s ) QCD corrections to the width of the decay within the Minimal Supersymmetric Standard Model. We find that the QCD corrections are significant, but that they do not invalidate our previous conclusion at tree-level on the dominance of the mode in a wide parameter region.

We study the effects of squark generation mixing on squark and gluino production and decays at LHC in the Minimal Supersymmetric Standard Model (MSSM) with focus on the mixing between second and third generation squarks. Taking into account the constraints from B-physics experiments we show that various regions in parameter space exist where decays of squarks and/or gluinos into quark flavour violating (QFV) final states can have large branching ratios. Here we consider both fermionic and bosonic decays of squarks. Rates of the corresponding QFV signals, e.g. pp -> t t bar{c} bar{c} missing-E_T X, can be significant at LHC(14 TeV). We find that the inclusion of flavour mixing effects can be important for the search of squarks and gluinos and the determination of the underlying model parameters of the MSSM at LHC., 7 pages, 4 figures, a reference updated, Proceedings of The 36th International Conference on High Energy Physics (ICHEP2012), Melbourne, Australia, July 4-11, 2012

We study the effect of squark generation mixing on gluino production and decays at LHC in the Minimal Supersymmetric Standard Model (MSSM) for the case that the gluino is lighter than all squarks and dominantly decays into three particles, $gl -> q qbar neut_k, gl -> q qbar' char_l$. We assume mixing between the second and the third squark generations in the up-type and down-type squark sectors. We show that this mixing can lead to very large branching ratios of the quark-flavour violating gluino three-body decays despite the strong constraints on quark-flavour violation (QFV) from the experimental data on B mesons. We also show that the QFV gluino decay branching ratios are very sensitive not only to the generation mixing in the squark sector, but also to the parameters of the neutralino and chargino sectors. We show that the branching ratio of the QFV gluino decay $gl -> c tbar (cbar t) neut_1$ can go up to ~ 40%. Analogously, that of the QFV decay $gl -> s bbar (sbar b) neut_1$ can reach ~35%. We find that the rates of the resulting QFV signatures, such as $pp -> t t cbar cbar E_T^mis$, can be significant at LHC. This could have an important influence on the gluino searches at LHC., 19 pages, 10 figures. References updated, typos corrected, wording improved

We study the effect of squark generation mixing on squark production and decays at LHC in the Minimal Supersymmetric Standard Model (MSSM). We show that the effect can be very large despite the very strong constraints on quark flavour violation (QFV) from experimental data on B mesons. We find that the two lightest up-type squarks su_{1,2} can have large branching ratios for the decays into 'c-quark + neutralino_1' and 't-quark + neutralino_1' at the same time due to squark generation mixing, leading to QFV signals 'pp -> c bar{t} (t bar{c}) + missing-E_T + X' with a significant rate. The observation of this remarkable signature would provide a powerful test of supersymmetric QFV at LHC. This could have a significant impact on the search for squarks and the determination of the underlying MSSM parameters., 23 pages, 9 figures, close to the published version

We present a detailed study of the decays of the charged Higgs boson H+ within the Minimal Supersymmetric Standard Model. We find that the supersymmtric mode t b can dominate the H+ decays in a wide range of the model parameters due to the large Yukawa couplings and mixings of t and b . Compared to the conventional modes τ+vτ and t b , this mode has very distinctive signatures. This could have a decisive impact on H+ searches at future colliders.

We study chargino production and decay in the energy region of LEP 200, exploring the relevant supersymmetry parameter space. We give numerical predictions for the cross sections and for the signaturesl++l−+p′, l+jet+p′, jet+jet+p′. New formulae are presented relating chargino masses and couplings to the supersymmetry parameters.

In the MSSM with complex parameters, loop corrections to the decay of a stop into a bottom quark and a chargino can lead to a CP violating decay rate asymmetry. We calculate this asymmetry at full one-loop level and perform a detailed numerical study, analyzing the dependence on the parameters and complex phases involved. If the stop can decay into a gluino, the self-energy and the vertex correction dominate due to the strong coupling. It is shown that the vertex contribution is always suppressed. We therefore give a simple approximate formula for the asymmetry. We account for the constraints on the parameters coming from several experimental limits. Asymmetries up to 25 percent are obtained. We also comment on the feasibility of measuring this asymmetry at the LHC., Version accepted for publication in Eur. Phys. J. C (8 pages, 8 figures)

We study gluino decays in the Minimal Supersymmetric Standard Model (MSSM) with squark generation mixing. We show that the effect of this mixing on the gluino decay branching ratios can be very large in a significant part of the MSSM parameter space despite the very strong experimental constraints on quark flavour violation (QFV) from B meson observables. Especially we find that under favourable conditions the branching ratio of the QFV gluino decay (g) over tilde -> c (t) over tilde)((c) over tildet)(chi) over tilde (0)(1) can be as large as similar to 50%. We also find that the squark generation mixing can result in a multiple-edge (3- or 4-edge) structure in the charm-top quark invariant mass distribution. The appearance of this remarkable structure provides an additional powerful test of supersymmetric QFV at LHC. These could have an important impact on the search for gluinos and the determination of the MSSM parameters at LHC. (C) 2009 Elsevier B.V. All rights reserved., This work is supported by the “Fonds zur Förderung der wissenschaftlichen Forschung (FWF) of Austria, project No. P18959-N16. The authors acknowledge support from EU under the MRTN-CT-2006-035505 and MRTN-CT-2006-503369 network programs. A.B. was supported by the Spanish grants SAB 2006-0072, FPA 2005-01269, FPA 2005-25348-E and FPA 2008-00319/FPA of the Ministero de Educacion y Ciencia. T.K. is supported by the Portuguese FCT through the projects POCI/FP/81919/2007 and CFTP-FCT UNIT 777, which are partially funded through POCTI (FEDER). W.P. is partially supported by the German Ministry of Education and Research (BMBF) project No. 05HT6WWA.

We study the effects of $CP$ violation in the associated production of a charged Higgs boson and a top quark at the LHC, $pp\ensuremath{\rightarrow}t{H}^{\ifmmode\pm\else\textpm\fi{}}+X$. We calculate the $CP$ violating asymmetry between the total cross section for ${H}^{+}$ and ${H}^{\ensuremath{-}}$ production at next-to-leading order in the minimal supersymmetric standard model (MSSM), and perform a detailed numerical analysis. In the production, the asymmetry is of the order of 20%. The asymmetry in the production and any subsequent decay of an on shell charged Higgs boson is to a good approximation the sum of the asymmetry in the production and the asymmetry in the decay. We consider subsequent decays of ${H}^{\ifmmode\pm\else\textpm\fi{}}$ to $tb$, ${\ensuremath{\nu}}_{\ensuremath{\tau}}{\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}}$ and $W{h}^{0}$. In the case with ${H}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}tb$ decay, mainly due to $CP$ violating box graphs with gluino, the asymmetry can go up to $\ensuremath{\sim}12%$.

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., Comment: 12 pages, 8 figures, Presented at XIX-th International Baldin Seminar on High Energy Physics Problems, XIX-th ISHEPP (JINR, Dubna, Russia, September 29 - October 4, 2008)

We present a detailed study of $$e + p \to \tilde e + \tilde q + X$$ and $$e + p \to \tilde v + \tilde q + X$$ and the subsequent decays of $$\tilde e$$ , $$\tilde v$$ , and $$\tilde q$$ at the LHC $$(\sqrt s = 1.4TeV)$$ . We explore the relevant supersymmetry parameter range. We calculate the cross sections as well as the rates for interesting signatures such as the production of one or two leptons on the lepton side.

We present a detailed study of gluino and squark decays for masses up to 1 TeV. We explore the whole supersymmetry parameter range relevant for LHC and SSC. We calculate the rates for interesting signatures such as the direct transition into the lightest supersymmetric particle, the production of two Z0s, and multimuons in the final state.

We give a complete presentation of all formulas for gluino and squark decays into charginos and neutralinos, taking into account the Yukawa coupling and all mass terms of the top quark. We calculate the branching ratios in the supersymmetry-parameter range relevant for the CERN Large Hadron Collider and the Superconducting Super Collider, and discuss the influence of the top-quark mass.

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.

We study systematically the interplay of the parameters of the minimalN=1 supergravity model in a large domain of the parameter space. We make use of the renormalization group equations and the requirement of a correct electroweak symmetry breaking. Particular attention is paid to the dependence on the top mass and the ratio of the two vacuum expectation values, tan β=v 2/v 1. We also investigate the mass spectrum of the supersymmetric particles within the allowed parameter range and discuss its relevance for LEP.

We discuss the production of the neutral Higgs bosons H10, H20, and H30 in the LEP energy range within the minimal supersymmetric model. It is shown that almost the whole possible mass range for H20 can be examined through the processes e+e− → μ+μ−H20 and e+e− → H30H20. At s =200 GeV even H10 with a mass smaller than 100 GeV can be produced at a sizeable rate. The Higgs bosons may also be found in the process of production and decay of a neutralino.

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., 34 pages, 17 figure

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., Comment: 18 pages, 8 figures; close to published version

18 páginas, 6 figuras, 12 tablas.-- et al., 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.

We present a complete precision analysis of the sfermion pair production process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\stackrel{\texttildelow{}}{f}}_{i}{\overline{\stackrel{\texttildelow{}}{f}}}_{j}(f=t,b,\ensuremath{\tau},{\ensuremath{\nu}}_{\ensuremath{\tau}})$ 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 $\mathrm{SPS}1{\mathrm{a}}^{\ensuremath{'}}$ point from the SPA project. The complete corrections are about 10% and have to be taken into account in a high precision analysis.

We present a high precision calculation of chargino and neutralino pair production at e{sup +}e{sup -} 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 (supersymmetry parameter analysis) project. The complete corrections are about 10% and in some cases even larger, in particular, for {chi}-tilde{sub i}{sup 0}{chi}-tilde{sub j}{sup 0} production with sizable Higgsino components. These corrections have to be taken into account in a high precision analysis.

In the MSSM with complex parameters, loop corrections to $\cha_i^\pm \to \neu_j^0 W^\pm$ lead to a CP violating asymmetry $\ACP = (\Gamma(\cha_i^+ \to \neu_j^0 W^+) - \Gamma(\cha_i^- \to \neu_j^0 W^-))/ (\Gamma(\cha_i^+ \to \neu_j^0 W^+) + \Gamma(\cha_i^- \to \neu_j^0 W^-))$. 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., Comment: 14 pages, 6 figures, version to be published in PLB

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., Comment: 15 pages

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 $\ensuremath{\mu}$ and ${M}_{1}$ for an ${e}^{+}{e}^{\ensuremath{-}}$ linear collider with $\sqrt{s}=800\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ and longitudinally polarized beams. The asymmetries can reach $7%$ and we discuss the feasibility of measuring these asymmetries.

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 \mu the 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., Comment: 10 pages, 3 figures

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 %., Comment: 15 pages, 9 figures

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.

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., Comment: 17 pages, latex, 10 figures (included); (v2) typos corrected and references added

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 $\mu$. 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., Comment: 16 pages, 8 figures