We present a consistent renormalization of the top and bottom quark/squark sector of the MSSM with complex parameters (cMSSM). Various renormalization schemes are defined, analyzed analytically and tested numerically in the decays Stop_2 -> Sbot_i H+/W+ (i = 1,2). No scheme is found that produces numerically acceptable results over all the cMSSM parameter space, where problems occur mostly already for real parameters. Two schemes are identified that show the most robust behavior. A numerical analysis of the four partial stop decay widths is performed in our "preferred" scheme, "m_b, A_b DRbar". The full one-loop corrections to the corresponding partial decay widths are evaluated including hard QED and QCD radiation. We find mostly modest corrections at the one-loop level.
We present the next-to-leading strong interaction corrections to the Delta F=2 Hamiltonian in the MSSM with exact diagonalization of the squark mass matrices. These results allow phenomenological studies of neutral meson mixing in scenarios with non-degenerate squarks, with control over the renormalization scale and scheme dependence.
We present an extensive study of the MSSM parameter space allowing for general generation mixing in the squark sector. Employing an MCMC algorithm, we establish the parameter ranges which are allowed with respect to various experimental and theoretical constraints. Based on this analysis, we propose benchmark scenarios for future studies. Moreover, we discuss aspects of signatures at the LHC.
We present results on the full one-loop electroweak radiative corrections to the squark decay partial widths into charginos and neutralinos. We show the renormalization framework, and present numerical results for the third squark family. The corrections can reach values of ~ 10%, which are comparable to the radiative corrections from the strong sector of the model. Therefore they should be taken into account for the precise extraction of the SUSY parameters at future colliders.
In the contest of supersymmetric extensions of the Standard Model, we consider a spectrum in which the lightest Higgs boson has mass between 200 and 300 GeV and the first two generations of squarks have masses above 20 TeV, considering the Higgs boson mass and the Supersymmetric Flavour Problem as related naturalness problems. After the analysis of some models in which the previous spectrum can be naturally realised, we consider the phenomenological consequences for the LHC and for Dark Matter.
In this article I review some connections between flavor physics and collider physics. The first part discusses the effect of right-handed charged currents on the determination of the CKM elements V_ub. It is shown that such an effective right-handed W-coupling can be generated in the MSSM which would lead to a sizable enhancement of single-top production at the LHC. The second part of this article focuses on the constraints on the mass splitting between left-handed squarks from Kaon and D mixing. Such a mass splitting has interesting consequences for squark decay chains at colliders.
We study the complete one loop contribution to $H^\pm\to W^\pm V$, $V= Z, γ$, in the Minimal Supersymmetric Standard Model (MSSM). We evaluate the MSSM contributions taking into account $B\to X_sγ$ constraint as well as experimental constraints on the MSSM parameters. In the MSSM, we found that in the intermediate range of $\tanβ\la 10$ and for large $A_t$ and large $μ$, where lightest stop becomes very light and hence squarks contribution is not decoupling, the branching ratio of $H^\pm \to W^{\pm} Z$ can be of the order $10^{-3}$ while the branching ratio of $H^\pm \to W^{\pm} γ$ is of the o…
Restrictive upper bounds on the heavy bottom squark mass when the gluino and one bottom squark are both light are based on the predicted reduction of $R_b$ (the fraction of $Z$ hadronic decays to $b \bar b$ pairs) in such a scenario. These bounds are found to be relaxed by the process $Z \to b\bar{\tilde b}{\tilde g}/{\bar b}{\tilde b}{\tilde g}$, which may partially compensate for the reduction of $R_b$. The relaxation of bounds on the top squark and the scale-dependence of the strong coupling constant are also discussed.
We present the numerical investigation of the fermionic two-body decays of squarks in the Minimal Supersymmetric Standard Model with complex parameters. In the analysis we particularly take into account the cosmological bounds imposed by WMAP data. We find that the phase dependences of the decay widths of the third family squarks, as well as those of the first and second families, are quite significant which can provide viable probes of additional CP sources. We plot the CP phase dependences for each fermionic two-body decay channel of squarks $\tilde q_i$ (i=1,2, q=u,d;c,s;t,b) and speculate …
We study neutral and charged Higgs boson production in association with stop and sbottom squarks at the Large Hadron Collider (LHC), within the so-called M-SUGRA scenario, i.e., the Supergravity (SUGRA) inspired Minimal Supersymmetric Standard Model (MSSM). For low values of \tanβonly the cases \tilde{t}_1\tilde{t}_1^* H, \tilde{t}_1\tilde{t}_1^* h and \tilde{t}_1\tilde{t}_2^* h give detectable rates while for \tanβgreater than 30 a variety of signals involving all Higgs bosons can be accessed, at high collider luminosity. The dependence of these reactions on the M-SUGRA parameters might furth…
Within the low-energy effective Minimal Supersymmetric extension of the Standard Model (effMSSM) we calculate the neutralino relic density taking into account slepton-neutralino, squark-neutralino and neutralino/chargino- neutralino coannihilation channels. By including squark (stop and sbottom) coannihilation channels we extend our comparative study to all allowed coannihilations and obtain the general result that all of them give sizable contributions to the reduction of the neutralino relic density. Due to these coannihilation processes some models (mostly with large neutralino masses) ente…
We present an extensive study of non-minimally flavour violating (NMFV) terms in the Lagrangian of the Minimal Supersymmetric Standard Model (MSSM). We impose a variety of theoretical and experimental constraints and perform a detailed scan of the parameter space by means of a Markov Chain Monte-Carlo (MCMC) setup. This represents the first study of several non-zero flavour-violating elements within the MSSM. We present the results of the MCMC scan with a special focus on the flavour-violating parameters. Based on these results, we define benchmark scenarios for future studies of NMFV effects …
We examine the case of neutralino dark matter in the focus point region of the MSSM, in which the scalar sparticles are too heavy to be produced at the LHC. Whilst it has been previously asserted that the LHC alone would fail to constrain the properties of the lightest neutralino for such a scenario, we find that one can obtain good predictions of astrophysical quantities such as the relic density, annihilation cross-section and direct search cross-sections by using the shape of the dilepton invariant mass spectrum to constrain neutralino mixing. We demonstrate our technique using a Bayesian a…
We study the decays of top squarks (~t_{1,2}) and bottom squarks (~b_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. We show that including the corresponding phases strongly affects the branching ratios of ~t_{1,2} and ~b_{1,2} decays in a large domain of the MSSM parameter space. This could have an important impact on the search for ~t_{1,2} and ~b_{1,2} and the determination of the underlying MSSM parameters at future colliders.
We present the complete computation of the tree-level and the next-to-leading order electroweak contributions to bottom-squark pair production at the LHC. The computation is performed within the minimal supersymmetric extension of the Standard Model. We discuss the numerical impact of these contributions in several supersymmetric scenarios.
In the Minimal Supersymmetric extension of the Standard Model (MSSM) squarks from the third generation, i.e., the bottom and the top squarks, have a common set of parameters that determine their masses and couplings. These are in the form of the common soft mass for the left handed squark from the third generation ($m_{\widetilde{Q}_{_{3L}}}$), the supersymmetry conserving Higgsino mass parameter $μ$ and $\tanβ$, the ratio of vacuum expectation values of the two Higgs doublets. This leads to an interesting possibility that the systems involving the bottom and the top squarks might get correlat…
We investigate the fermionic decays of top squarks tilde t_{1,2} and bottom squarks tilde b_{1,2}$ in the Minimal Supersymmetric Standard Model with complex parameters M_1, mu, A_t and A_b . In the analysis we particularly take into account the cosmological bounds imposed by WMAP data. We plot the CP phase dependences of stop and sbottom decay widths.
A detailed analysis of the top-quark/squark quantum corrections to the lightest CP-even Higgs boson (h^0) self-couplings is presented in the MSSM. By considering the leading one-loop Yukawa-coupling contributions of O(m_t^4), we discuss the decoupling behaviour of these corrections when the top-squarks are heavy compared to the electroweak scale. As shown analytically and numerically, the large corrections can almost completely be absorbed into the h^0-boson mass. Our conclusion is that the h^0 self-couplings remain similar to the coupling of the SM Higgs boson for a heavy top-squark sector.
We consider a scenario of Minimal Supersymmetric Standard Model (MSSM) with $R$-parity violation, where the lightest supersymmetric particle (LSP) is the lighter sbottom $(\tilde b_1)$. We study the production of a sbottom pair at the LHC and their subsequent decays through the baryon number violating $(U D D)$ operators leading to a top pair with two light quarks. Looking for both semi-leptonic and fully hadronic (no leptons) final states, we perform cut-based as well as multivariate analyses (MVA) to estimate the signal significance at the 13 TeV run of the LHC. We find that a cut-based anal…
Presented are complete electroweak (EW) corrections at ${\cal O}(αα_{\mathrm s}^{\mathrm 2})$ to top-squark pair production at the Large Hadron Collider (LHC) within the framework of the Minimal Supersymmetric Standard Model (MSSM). At this order, effects from the interference of EW and QCD contributions have to be taken into account. Also photon-induced top-squark production is considered as additionnal partonic channel which arises from the non-zero photon density in the proton. Furthermore, the impact of MSSM parameters on the EW corrections is analyzed.
We analyze the appearance of the trilinear squark-Higgs couplings $x_q$ in Green functions in the Higgs sector of the MSSM and in threshold corrections to the SM. The results are constraints on maximal powers of $x_q$ in QCD-related loop corrections. In practice these often imply all-order resummations of leading or subleading $x_q$ contributions in SM-parametrized expressions. We present a variety of all-order resummation relations for $Δλ$ which include such $x_q$-enhanced terms and different orders in Yukawa and gauge couplings. We contrast which terms cannot be resummed.
We study the compatibility of a light bottom squark M_{\tilde b}< O(10 GeV) in the unconstrained MSSM. We consider the one-loop radiative corrections which are large for a heavy gluino (> O(150 GeV)). We then consider the renormalization group flow up to the Grand Unified scale. For most regions of the parameter space with a light sbottom we find colour and charge breaking minima. Only a small window in gluino mass and tan(beta) is consistent with all bounds. This is alleviated by a light gluino, which is however only marginally experimentally allowed.
We investigate the decays of third generation scalar quarks in the Minimal Supersymmetric extension of the Standard Model, focusing on the three-body modes. We calculate the partial widths of the decays of heavier top and bottom squarks into the lighter ones and a fermion pair [through virtual vector boson, Higgs boson or gaugino exchanges] and the partial widths of the three-body decays of both top squarks into bottom quarks and a pair of fermion and scalar fermion [we consider the case of lighter $\tildeτ$ or $\tilde{b}$ states] and into a bottom quark, the lightest neutralino and a $W$ or a…
We present the detailed analytical and numerical investigations of the one-loop radiative corrections of all quarks and squarks in the MSSM to the lightest chargino pair production via $γγ$ fusion at the future NLC. The numerical corrections show that the cross sections of the subprocess and the parent process are typically enhanced by several percent. We studied also the effects induced by the CP violating complex phases stemming from squark and chargino mass matrices in the MSSM at one-loop level.
The presence of a light b-squark (with mass about 4 GeV) and gluino (with mass about 15 GeV) might explain the observed excess in b-quark production at the Tevatron. Though provocative, this model is not excluded by present data. The light supersymmetric particles can induce large flavor-changing effects in radiative decays of B mesons. We analyse the decays B->X_s gamma and B->X_{sg} in this scenario and derive restrictive bounds on the flavor-changing quark-squark-gluino couplings.
The requirement that the MSSM remain an acceptable effective field theory up to energies beyond the weak scale constrains the sparticle spectrum, and hence the permissible ranges of cold dark matter neutralino-proton cross sections. Specifically, squarks are generally much heavier than sleptons if no tachyons are to appear before the GUT scale ~10^16 GeV, or even before 10 TeV. We display explicitly the allowed ranges of effective squark and slepton masses at the weak scale, and the cross-section ranges allowed if the MSSM is to remain valid without tachyons up to 10 TeV or the GUT scale. The …
We present a calculation of the two-loop quark-squark-gluino contributions to pseudoscalar Higgs boson production via gluon fusion in the MSSM. We regularize the loop integrals using the Pauli-Villars method, and obtain explicit and compact analytic results based on an expansion in the heavy particle masses. Our results - valid when the pseudoscalar Higgs boson is lighter than squarks and gluinos - can be easily implemented in computer codes for an efficient and accurate determination of the pseudoscalar production cross section.
We present a phenomenological study of top squarks (~t_1,2) and bottom squarks (~b_1,2) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, μand M_1. In particular we focus on the CP phase dependence of the branching ratios of (~t_1,2) and (~b_1,2) decays. We give the formulae of the two-body decay widths and present numerical results. We find that the effect of the phases on the (~t_1,2) and (~b_1,2) decays can be quite significant in a large region of the MSSM parameter space. This could have important implications for (~t_1,2) and (~b_1,2) searches and the …
Current searches for the top squark mostly focus on the decay channels of $\tilde{t}_1 \rightarrow t χ_1^0$ or $\tilde{t}_1 \rightarrow b χ_1^\pm \rightarrow bW χ_1^0$, leading to $tt/bbWW+\not\mathrel{E}_T$ final states for top squark pair production at the LHC. In supersymmetric scenarios with light gauginos other than the neutralino lightest supersymmetric particle (LSP), different decay modes of the top squark could be dominant, which significantly weaken the current top squark search limits at the LHC. Additionally, new decay modes offer alternative discovery channels for top squark searc…
We discuss the associated W+/- H-/+ production in p p collision for the Large Hadron Collider. A complete one-loop calculation of the loop-induced subprocess g g -> W+/- H-/+ is presented in the framework of the Minimal Supersymmetric Standard Model (MSSM), and the possible enhancement of the hadronic cross section is investigated under the constraint from the squark direct-search results and the low-energy precision data. Because of the large destructive interplay in the quark-loop contributions between triangle-type and box-type diagrams, the squark-loop contributions turn out to be comparab…
The effects of loop contributions to the electroweak precision observables and m_h in the MSSM with non-minimal flavour violation (NMFV) are analyzed, including the mixing between third and second generation squarks. The mixing-induced shift in M_W can amount to 140 MeV and to 70x10^{-5} in sin^2 θ_{eff} for extreme values of squarks mixing, allowing to set limits on the NMFV parameters. The corrections for m_h are usually small and can amount up to O(5 GeV) for large flavour violation.
The production of the lightest Higgs boson, $h^0$, in association with the lightest stop, $\tilde{t}_{1}$, in the Minimal Supersymmetric Standard Model, is an interesting channel, as its cross section can be higher than Higgs production in association with top quarks. Furthermore, the $\tilde{t}_{1}\tilde{t}^{*}_{1}h^{0}$ production rate is highly dependent on various Supersymmetric parameters. The mass, mixings, couplings and production cross sections relevant to the $\tilde{t}_{1}\tilde{t}^{*}_{1}h^{0}$ channel have been studied in the past. Here, we complement these analyses by performing a…
We calculate the rate for $Υ$ decay into a pair of bottom squarks as a function of the masses of the bottom squark and the gluino. Data from decays of the $Υ$ states could provide significant new bounds on the existence and masses of these supersymmetric particles.
The lightest CP-even Higgs boson $h$ in the minimum supersymmetric standard model (MSSM) has a mass upper bound depending on the top quark and squark masses. An $e^+e^-$ collider with enough energy and luminosity to produce $h+Z$ at measurable rates up to the maximum $h$ mass would cover the entire MSSM parameter space, if $h+A$ production was also searched for. We explore the energy and/or luminosity needed for various top quark and squark masses. For $m_t=150$\,GeV and 1\,TeV SUSY mass scale, a 230\,GeV collider with 10\,fb$^{-1}$ luminosity would suffice.
We study the discovery reach of the gluino ($\widetilde{g}$) and the lightest stop squark ($\widetilde{t}_1$) with baryonic R-parity violation (UDD type) in the context of Minimal Supersymmetric Standard Model (MSSM) at the 14 TeV run of the LHC. We consider the gluino pair production process followed by its decay to a top quark and a real or virtual stop squark. The top quark produced from the decay of the gluino can have sufficient transverse momentum to appear as a single fat jet. We apply the jet substructure technique to tag such a hadronically decaying boosted top quark and find that glu…
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 ${\tilde u}_{1,2}$ can have large branching ratios for the decays into $c {\tildeχ_1^0}$ and $t {\tildeχ_1^0}$ at the same time, leading to QFV signals '$p p \to c \bar t\, (t \bar c)$ + missing-$E_T$ + $X$' with a significant rate. The observation of this remark…
We investigate the electroweak phase transition in the presence of a large CP violation in the squark sector of the MSSM. When the CP violation is large, scalar-pseudoscalar mixing of the Higgs bosons occurs and a large CP violation in the Higgs sector is induced. It, however, weakens first-order phase transition before the mixing reaches the maximal. Even when the CP violation in the squark sector is not so large that the phase transition is strongly first order, the phase difference between the broken and symmetric phase regions grows to O(1), which leads to successful baryogenesis, when the…
We calculate cross sections for mixed stop-sbottom pair production at the LHC, analogous to single-top production, a weak process involving the W-t(i)-b(j) vertex. While coupling-suppressed relative to QCD same-flavor squark pair production, the signal is distinctive due to heavy-flavor tagging along with a possible same-sign lepton pair in the final state. SUSY backgrounds can often be suppressed many orders of magnitude by taking advantage of distinct kinematic differences from the signal. Measuring the rate of this process would add significant additional information to that gathered from o…
We present an analysis of the production and two-photon decay of the lightest CP-even Higgs boson of the Minimal Supersymmetric Standard Model (MSSM) at the Large Hadron Collider (LHC). A rather general model is considered, without supergravity constraints. All parameters of the model are taken into account, we especially study the dependence of the cross section on the squark masses, on the bilinear parameter $μ$ and the trilinear supersymmetry breaking parameter $A$. Non-zero values of these parameters lead to significant mixing in the squark sector, and, thus, affect the masses of Higgs bos…
We analyze effects of the CP-odd soft phases in the MSSM on the pair-productions of colored superpartners in pp collisions at the LHC energies. We find that, among all pair-production processes, those of the scalar quarks in the first and second generations are particularly sensitive to the CP-odd phases, more precisely, to the phases of the gluinos and neutralinos. We compute pair-production cross sections, classify various production modes according to their dependencies on the gluino and neutralino phases, perform a detailed numerical analysis to determine individual as well as total cross …
We study the two-body decays of the gluino at full one-loop level in the Minimal Supersymmetric Standard Model with quark-flavour violation (QFV) in the squark sector. The renormalization is done in the $\overline{\rm DR}$ scheme. The gluon and photon radiations are included by adding the corresponding three-body decay widths. We discuss the dependence of the gluino decay widths on the QFV parameters. The main dependence stems from the $\tilde c_R - \tilde t_R$ mixing in the decays to up-type squarks, and from the $\tilde s_R - \tilde b_R$ mixing in the decays to down-type squarks due to the s…
Processes of the form $pp\to anything \to X_i X_j \to x\bar{x} + y\bar{y} (+ \slashchar{E})$ are studied via a technique that may be viewed as an adaptation of time-honoured Dalitz plot analyses. $X_i$ and $X_j$ are new heavy states (with $i,j=1...n$), which may be identical or distinct; and $x\bar{x}$ and $y\bar{y}$ are necessarily distinct Standard Model (SM) fermion pairs whose invariant masses can be measured. A Dalitz-like plot of said invariant masses, $M(x\bar{x})$ {\it vs.$$} $M(y\bar{y})$, exhibits a topology connected to the masses and specific decay chains of $X_i$ and $X_j$. Aside …
The inflation within the MSSM is proposed, where the inflaton field is a combination of the Higgs, squark and slepton states. While the inflationary phase is fully governed by the electron Yukawa superpotential coupling, the fields' condensates float along the flat $D$-term trajectory. This predicts the MSSM parameter $\tan β\simeq 13.1$ determined via the value of the curvature perturbation amplitude. The values of the scalar spectral index and the tensor-to-scalar ratio are predicted to be $n_s\simeq 0.966$ and $r=0.00118$. The postinflation reheating of the Universe proceeds by the radiativ…
We calculate the CP-violating effects in the top quark semi-leptonic three body decays induced by the supersymmetric CP-odd phase of the top squark trilinear soft breaking term $\arg(A_t)$. The light top squark mass is assumed to be close to the top quark mass $m_{\tilde{t}}\sim m_t$. The CP-conserving phase is provided by the $χ^+$ and $χ^0$ cut. We find that the partial rate asymmetry is in the 0.1% level. In the most favorable parameter region the decay rate asymmetr can reach up to 0.55%.
We calculate the full one-loop SUSY-QCD corrections to stop annihilation into gluons and light quarks including the Sommerfeld enhancement effect and discuss their impact on the neutralino relic density in the MSSM.
The Minimal Supersymmetric Standard Model (MSSM) is under intense scrutiny at the LHC and in dark matter searches. Interestingly, scenarios with light squarks of the third generation remain not only viable, but also well motivated by the observed Standard-Model-like Higgs boson mass and dark matter relic density. The latter often requires important contributions from squark pair annihilation. Following up on previous work, we present in this paper a precision analysis of squark pair annihilation into quarks at next-to-leading order of QCD including Sommerfeld enhancement effects. We discuss al…
We study the effect of squark-generation mixing on gluino decays in the Minimal Supersymmetric Standard Model (MSSM). We show that due to the effect the quark-flavor violating (QFV) gluino decay branching ratio B(gluino -> c bar{t} (t bar{c}) + neutralino_1) can be very large (up to ~50%) in a significant part of the MSSM parameter space despite the very strong experimental constraints on QFV from B meson observables. This could have an important impact on the search for gluinos and the determination of the MSSM parameters at LHC.
The present paper deals with a next-to-leading order analysis of the radiative $B \to K^* γ$ decay. Working in the PQCD approach developed by Szczepaniak {\it et al.}, we compute the correction, coming from a single gluon exchange with the spectator, to the essential form factor. Since the branching ratio gets much above the experimental data, although in agreement with other theoretical models predictions, we take into consideration the effects of complex flavour couplings in the squark sector. Finally, we discuss these SUSY implications on the branching ratio and direct CP asymmetry values a…
We study the decays of top squarks and bottom squarks in the Minimal Supersymmetric Standard Model with complex parameters A_t, A_b and mu. In a large region of the supersymmetric parameter space the branching ratios of stop_1 and sbottom_1 show a pronounced phase dependence. This could have an important impact on the search for stop_1 and sbottom_1 at a future linear collider and on the determination of the supersymmetric parameters.
Recent experimental and theoretical progress regarding B --> K(*) l+ l- decays led to improved bounds on the Wilson coefficients C_9 and C_10 of four-fermion operators of the |Delta B|=|Delta S|=1 effective Hamiltonian. We analyze the resulting implications on squark flavor violation in the MSSM and obtain new constraints on flavor-changing left-right mixing in the up-squark-sector. We find the dimensionless flavor mixing parameter (delta^u_23)_LR, depending on the flavor-diagonal MSSM masses and couplings, to be as low as \lesssim 0.1. This has implications for models based on radiative flavo…
In full one-loop generality and in next-to-leading order in QCD, we study rare top to Higgs boson flavour changing decay processes $t\to q h$ with $q=u,c$ quarks, in the general MSSM with R-parity conservation. Our primary goal is to search for enhanced effects on $Br(t\to q h)$ that could be visible at current and high luminosity LHC running. To this end, we perform an analytical expansion of the amplitude in terms of flavour changing squark mass insertions that treats both cases of hierarchical and degenerate squark masses in a unified way. We identify two enhanced effects allowed by various…
Because of their Yukawa interactions, third generation squarks may be substantially lighter than those of the first two generations. Assuming that $\tb_1 \to b\tz_1$ and $\tz_1$ escapes experimental detection, we show that experiments at the Main Injector upgrade (integrated luminosity of $2 fb^{-1}$) of the Tevatron should be sensitive to $b$-squark masses up to 210 GeV for $m_{\tz_1} \leq 120$ GeV. For integrated luminosities of $10 fb^{-1}$ (25 $fb^{-1}$) the sbottom mass reach increases by 20 GeV (35 GeV). If the channel $\tb_1 \to b\tz_2$ is also accessible, the reach becomes model-depend…
We present the Fortran code SDECAY, which calculates the decay widths and branching ratios of all the supersymmetric particles in the Minimal Supersymmetric Standard Model, including higher order effects. Besides the usual two-body decays of fermions and gauginos and the three-body decays of charginos, neutralinos and gluinos, we have also implemented the three-body decays of top squarks, and even the four-body decays of the top squark; the important loop-induced decay modes are also included. The QCD corrections to the two-body decays involving strongly interacting particles and the dominant …
The experimental measurement of $B(b \to sγ)$ imposes important constraints on the charged Higgs boson mass in the MSSM. If squarks are in the few TeV range, the charged Higgs boson mass in the MSSM must satisfy $m_{H^{\pm}} \gsim 440$ GeV. For lighter squarks, then light charged Higgs bosons can be reconciled with $B(b \to sγ)$ only if there is also a light chargino. In the MSSM if we impose $m_{χ^{\pm}_1}>90$ GeV then we need $m_{H^{\pm}} \gsim 110$ GeV. We show that by adding bilinear R--Parity violation (BRpV) in the tau sector, these bounds are relaxed. The bound on $m_{H^{\pm}}$ in the M…
Chirally enhanced supersymmetric QCD corrections to FCNC processes are investigated in the framework of the MSSM with generic sources of flavor violation. These corrections arise from flavor-changing self-energy diagrams and can be absorbed into a finite renormalization of the squark-quark-gluino vertex. In this way enhanced two-loop and even three-loop diagrams can be efficiently included into a leading-order (LO) calculation. Our corrections substantially change the values of the parameters delta^{d,LL}_{23}, delta^{d,LR}_{23}, delta^{d,RL}_{23}, and delta^{d,RR}_{23} extracted from Br[B->X_…
We analyze higher order decay modes of the lightest top squark $\tilde{t}_1$ in the Minimal Supersymmetric extension of the Standard Model (MSSM), where the lightest SUSY particle (LSP) is assumed to be the neutralino $χ_1^0$. For small $\tilde{t}_1$ masses accessible at LEP2 and the Tevatron, we show that the four-body decay mode into the LSP, a bottom quark and two massless fermions, $\tilde{t}_1 \ra b χ_1^0 f\bar{f}'$, can dominate in a wide range of the MSSM parameter space over the loop-induced decay into a charm quark and the LSP, $\tilde{t}_1 \ra c χ_1^0$. This result might affect the e…
In the general MSSM, first and second generation squarks and gluinos may be sufficiently light to be produced and studied at $e^+e^-$ colliders operating in the 0.5-1 TeV energy range. After a reminder that the MSSM is {\it not} the same as mSUGRA, we provide a brief overview of these possibilities within this more general framework
The main production mechanism for supersymmetric Higgs particles at hadron colliders crucially depends on the size of their Yukawa couplings to bottom quarks. For sufficiently large tan(beta) the total cross section for some of the neutral Higgs bosons in the MSSM is dominated by bottom-quark fusion. After an introduction to bottom-associated Higgs production, we discuss the complete O(alpha) electroweak and O(alpha_s) strong corrections for the bb-fusion channel in the MSSM. Choosing proper renormalization and input-parameter schemes, an improved Born approximation, constructed from previousl…
We present a calculation of the two-loop bottom-sbottom-gluino contributions to Higgs boson production via gluon fusion in the MSSM. The calculation is based on an asymptotic expansion in the masses of the supersymmetric particles, which are assumed to be much heavier than the bottom quark and the Higgs bosons. We obtain explicit analytic results that allow for a straightforward identification of the dominant contributions in the NLO bottom corrections. We emphasize the interplay between the calculations of the masses and the production cross sections of the Higgs bosons, discussing sensible c…
We compute the order alpha_s^3 (next-to-leading) corrections to the Wilson coefficients of the Delta F=2 effective Hamiltonian in the Minimal Supersymmetric Standard Model with completely arbitrary soft terms. These results are relevant for phenomenological studies of neutral meson mixings in the presence of large squark mass splittings, in particular in hierarchical scenarios of supersymmetry. These corrections achieve a considerable reduction of the uncertainty related to the matching scale ambiguity, and are therefore numerically relevant. We briefly analyze the effect of certain mass split…
In this article we study the MSSM with stops and Higgs scalars much lighter than gluinos and squarks of the first two generations. In this setup, one should use an effective field theory with partial supersymmetry in which the gluino and heavy squarks are integrated out in order to connect SUSY parameters (given at a high scale) to observables in the stop sector. In the construction of this effective theory, valid below the gluino mass scale, we take into account $O(α_3)$ and $O(Y_{t,b}^2)$ effects and calculate the matching as well as the renormalization group evolution. As a result, the runn…
