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 correlated in a non-trivial way even in an unconstrained setup. In this work, phenomenology of the bottom and the top squarks is studied at the Large Hadron Collider which exploits such a possibility with a particular emphasis on bottom squark decaying to top squark and $W$ boson. Possibility of reconstructing multiple $W$ bosons in the final state is identified to be the key in probing the squark mixing angles. Further entanglement of the electroweak gaugino-higgsino sector is also not impossible in scenarios based on phenomenological MSSM while for highly constrained scenarios like minimal supergravity/constrained MSSM such entanglements are trivially forced upon.
We calculate the total cross sections for squark production at future photon-proton and photon-electron colliders in R-parity violating MSSM. The Lambda-prime couplings offer several ways of producing single squarks at photon colliders. The results are discussed and compared with those of the existing colliders.
Supersymmetry predicts the identity of Yukawa and gauge couplings in the QCD sector: quark-squark-gluino = squark-squark-gluon = quark-quark-gluon. We examine whether the quark-squark-gluino Yukawa coupling can be determined, by methods complementary to LHC, by analyzing squark-gluino final states at a TeV e+e- collider.
Current mass limits allow the possibility that squarks may be produced in large numbers at the next generation of linear $e^+e^-$ colliders. In this paper we investigate the prospects for precision studies of squark masses at such colliders. We assume that squarks are lighter than gluinos, and discuss both direct and cascade decay scenarios. By exploiting the clean environment and polarizable beams of linear $e^+e^-$ colliders, we find that squark mass determinations at the level of a few GeV are possible in a large part of the parameter space.
The theoretical status of squark and gluino production at present and future hadron colliders is reviewed. I shall concentrate on the evaluation of SUSY-QCD corrections to the production cross sections and their phenomenological implications.
Strong mixing between right-handed strange and beauty squarks is a possible solution to the CP violation discrepancy in $B\to ϕK_S$ decay as recently suggested by the Belle data. In this scenario, thanks to the strong mixing one of the strange-beauty squarks can be as light as 200 GeV, even though the generic supersymmetry scale is at TeV. In this work, we study the production of this light right-handed strange-beauty squark at hadronic colliders and discuss the detection in various decay scenarios. Detection prospect at the Tevatron Run II is good for the strange-beauty squark mass up to abou…
We present the cross-sections for the hadroproduction of squarks and gluinos in next-to-leading order of supersymmetric QCD. The four possible final states squark-antisquark, squark-squark, gluino-gluino and squark-gluino are analysed for the hadron colliders Tevatron and LHC. The dependence of the cross-sections on the renormalization and factorization scale is reduced significantly. The shape of the transverse-momentum and rapidity distributions remains nearly unchanged when the next-to-leading order SUSY-QCD contributions are included. The size of the corrections at the central scale, given…
We study the production cross sections for squarks and gluinos in collision of longitudinally polarized hadrons. The corresponding polarized partonic cross sections are computed in leading order supersymmetric QCD. The resulting asymmetries are evaluated for the polarized proton collider RHIC, as well as for hypothetical polarized options of the Tevatron and the LHC. These asymmetries turn out to be sizable over a wide range of supersymmetric particle masses, thus potentially opening a window to detailed sparticle spectroscopy at future polarized hadron colliders.
We investigate the potentials of future high energy lepton-proton colliders to detect supersymmetric particles in the charged current type $lp\to\tildeν_l\tilde qX$, $l=e,μ$, reactions. We also study their decays by using the mass spectrum given in the Technical Design Report of ATLAS Collaboration (SUGRA Point 6 corresponding to large $tanβ$).
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.
The determination of the full SUSY QCD corrections to the production of squarks and gluinos at hadron colliders is reviewed. The inclusion of the NLO corrections stabilizes the theoretical predictions of the various production cross sections significantly and leads to sizeable enhancements of the most relevant cross sections. We discuss the phenomenological consequences of the results on present and future experimental analyses. Finally we investigate the impact of the corrections on the transverse momentum and rapidity distributions.
We examine the prospects of detecting sfermions at a gamma gamma collider. Once produced, a slepton can decay into a pair of quarks (jets) through R-parity violating interactions. Similarly, a squark may decay into a lepton-quark pair. Analyzing the corresponding Standard Model backgrounds, namely 4-jet and dilepton plus dijet final states respectively, we show that the sfermion can be detected almost right upto the kinematic limit and its mass determined to a fair degree of accuracy. Similar statements also hold for nonsupersymmetric leptoquarks and diquarks.
We report on the study of soft gluon effects in the production of squarks and gluinos at hadron colliders. Close to production threshold, the emission of soft gluon results in the appearence of large logarithmic corrections in the theoretical expressions. In order to resum these corrections at next-to-leading-logarithmic accuracy appropriate one-loop anomalous dimensions have to be calculated. We present the calculation of the anomalous dimensions for all production channels of squarks and gluinos and provide numerical predictions for the Tevatron and the LHC.
We discuss a potential of studying the production and the decay of the lightest top squark (t-tilde_1) in the framework of the supersymmetric standard model at a future e^+e^- collider. In particular, we consider the process t-tilde_1 -> t chi^0_1 (with chi^0_1 being the lightest neutralino) followed by t -> bW. It is shown that, by the study of the angular distribution of the bottom quark (as well as the production cross section of the top squark), properties of chi_1^0 can be extracted. We also discuss that, if chi^0_1 is gaugino-like, the neutralino mixing parameters (i.e., the so-called mu…
Within the supergravity framework, sleptons are expected to be considerably lighter than squarks if gluinos and squarks are approximately degenerate. This can lead to a significant enhancement in leptonic branching ratio for neutralinos, and sometimes, charginos. Using ISAJET 7.0/ISASUSY 1.0, we evaluate the multilepton signals from cascade decays of gluinos and squarks produced at the Fermilab Tevatron $p\bar p$ collider assuming squark and slepton masses are related as in supergravity models. We find observable cross sections for spectacular event topologies: $m$-lepton + $n$-jet + $\eslt$ e…
We have determined the theoretical predictions for the cross-sections of squark and gluino production at $\ppb$ and $pp$ colliders (Tevatron and LHC) in next-to-leading order of supersymmetric QCD. By reducing the dependence on the renormalization/factorization scale considerably, the theoretically predicted values for the cross-sections are much more stable if these higher-order corrections are implemented. If squarks and gluinos are discovered, this improved stability translates into a reduced error on the masses, as extracted experimentally from the size of the production cross-sections. Th…
In the case with a large splitting between the squark and slepton masses, the supersymmetric identities which enforce the equality of the gauge and gaugino couplings are violated in the effective theory below the squark mass threshold. We compute the full one-loop (s)quark corrected slepton production cross-sections. We find that the one-loop corrected slepton production cross-sections can depend on the squark mass strongly, up to 9% *log_{10}(M_{\tilde{Q}}/m_{\tilde{l}}). We investigate the squark mass sensitivity of the slepton cross-section measurements at a future linear collider. For sneu…
In supersymmetry (SUSY) the flavor mixing between top-squark (stop) and charm-squark (scharm) induces the flavor-changing neutral-current (FCNC) stop decay $\tilde t_1 \to c \tilde χ^0_1$. Searching for this decay serves as a probe of soft SUSY breaking parameters. Focusing on the stop pair production followed by the FCNC decay of one stop and the charge-current decay of the other stop, we investigate the potential of detecting this FCNC stop decay at the Fermilab Tevatron, the CERN Large Hadron Collider (LHC) and the next-generation $e^+e^-$ linear collider (LC). We find that this decay may n…
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 lighter superpartner of the top quark ($\tt_1$) may be considerably lighter than squarks of the first two generations, and hence may be accessible to Tevatron collider searches, even if the other squarks and the gluino are too heavy. For the range of $m_{\tt_1}$ of interest at the Tevatron, the $\tt_1$ decays to a chargino via $\tt_1 \to b\tw_1$ if this is kinematically allowed; otherwise, the flavor-changing loop decay $\tt_1 \to c\tz_1$ dominates. In the latter case, $\tt_1$ production is signalled by jet(s) plus $\eslt$ events. If, instead, the chargino decay is allowed, $1\ell + b$-$je…
Squarks and gluinos have been searched for at hadron colliders in events with multiple jets and missing transverse energy. No excess has been observed to date, and from a comparison of experimental cross section limits and theoretical cross section predictions one can deduce lower bounds on the squark and gluino masses. We present an improved analysis of squark and gluino mass bounds which is based on state-of-the-art cross section calculations including the summation of large threshold corrections. For illustration, we consider experimental data obtained by the CDF collaboration at the Fermil…
We study neutral and charged Higgs boson production in association with stop and sbottom squarks at the Large Hadron Collider, within the Supergravity inspired Minimal Supersymmetric Standard Model. The phenomenological relevance of such reactions is twofold. Firstly, they constitute a novel production mechanism of Higgs particles, either through a decay of a heavier (anti)squark into a lighter one or via a Higgs bremsstrahlung process. Secondly, their production rates are extremely sensitive to the values assumed by the five input parameters of the model, this possibly allowing one to put str…
We calculate squared helicity amplitudes for non-diagonal and mixed squark pair production at hadron colliders, taking into account not only loop-induced QCD diagrams, but also previously unconsidered electroweak channels, which turn out to be dominant. Mixing effects are included for both top and bottom squarks. Numerical results are presented for several SUSY benchmark scenarios at both the CERN LHC and the Fermilab Tevatron, including the possibilities of light stops or sbottoms. The latter should be easily observed at the Tevatron in associated production of stops and sbottoms for a large …
The scalar partners of top and bottom quarks are expected to be the lightest squarks in supersymmetric theories, with potentially large cross sections at hadron colliders. We present predictions for the production of top and bottom squarks at the Tevatron and the LHC, including next-to-leading order corrections in supersymmetric QCD and the resummation of soft gluon emission at next-to-leading-logarithmic accuracy. We discuss the impact of the higher-order corrections on total cross sections and transverse-momentum distributions, and provide an estimate of the theoretical uncertainty due to sc…
We analyse the prospect of extending the reach for squarks and gauginos via associated production at a $\sqrt{s} = 100$ TeV proton-proton collider, given 3 ab$^{-1}$ integrated luminosity. Depending on the gluino mass, the discovery reach for squarks in associated production with a gluino can be up to 37 TeV for compressed spectra (small gluino-LSP mass splitting), and up to 32 TeV for non-compressed spectra. The discovery reach for Winos can be up to between 3.5 and 6 TeV depending on squark masses and Wino decay kinematics. Binos of up to 1.7 TeV could similarly be discovered. Squark-gaugino…
The exchange of electroweak gauginos in the $t-$ or $u-$channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. We discuss the potential for detection of such rapidity gap events at the Large Hadron Collider (LHC). We present an analysis with full event simulation using PYTHIA as well as Herwig++, but without detector simulation. We analyze the transverse energy deposited between the jets from squark decay, as well as the probabili…
We study the prospect of determining the decay properties of the gluino in the supersymmetric (SUSY) standard model at a 100 TeV future hadron collider. We consider the case where the neutral Wino is the lightest superparticle. In this case, the long-lived charged Wino can be used to eliminate standard model backgrounds, which enables us to study the details of superparticles. We show that, based on the analysis of the numbers of high $p_T$ leptons, boosted $W$-jets, and $b$-tagged jets, we may determine the gaugino species and the quark flavors in the gluino decay. With such determinations, w…
We study the pair production of neutral Higgs bosons through gluon fusion at hadron colliders in the framework of the Minimal Supersymmetric Standard Model. We present analytical expressions for the relevant amplitudes, including both quark and squark loop contributions, and allowing for mixing between the superpartners of left- and right-handed quarks. Squark loop contributions can increase the cross section for the production of two CP-even Higgs bosons by more than two orders of magnitude, if the relevant trilinear soft breaking parameter is large and the mass of the lighter squark eigensta…
This dissertation addresses the question of how to detect light top squarks at the upgraded Fermilab Tevatron collider. After a brief introduction to supersymmetry, the basic phenomenology of the light stop is reviewed and the current experimental situation is surveyed. The analysis presented here is based on collider event simulations. The main decay modes accessible to the Tevatron are studied, feasible discovery channels are identified, and recipes for experimental analysis are proposed. It is found that stops with masses up to the top quark mass are liable to detection under these schemes …
We study the signal from the pair production of $t$-squarks at the Tevatron under the assumption that their two-body decay to charginos as well as their three-body decay to $W$ bosons is kinematically forbidden. In this case, the stop dominantly decays via $\widetilde{t_1}\rightarrow c\tz_1$, so that the signal consists of two charm jets together with $\eslt$. We reevaluate this signal using ISAJET~7.01, and show that if the stop mass is below about 100 GeV, there should be as many as 50-70 events in the accumulated data sample of the CDF and D0 experiments even if the LSP is as heavy as 50 Ge…
We examine the stau-neutralino coannihilation (CA) mechanism of the early universe. We use the minimal supergravity (mSUGRA) model and show that from measurements at the Large Hadron Collider one can predict the dark matter relic density with an uncertainty of 6% with 30 fb-1 of data, which is comparable to the direct measurement by Wilkinson Microwave Anisotropy Probe. This is done by measuring four mSUGRA parameters m0, m1/2, A0 and tan(beta) without requiring direct measurements of the top squark and bottom squark masses. We also provide precision measurements of the gaugino, squark, and li…
The branching fraction for the decays of gluinos to third generation quarks is expected to be enhanced in classes of supersymmetric models where either third generation squarks are lighter than other squarks, or in mixed-higgsino dark matter models constructed to be in concordance with the measured density of cold dark matter. In such scenarios, gluino production events at the CERN Large Hadron Collider should be rich in top and bottom quark jets. Requiring b-jets in addition to missing transverse energy should, therefore, enhance the supersymmetry signal relative to Standard Model backgrounds…
We study the production and decays of top squarks (stops) at the Tevatron collider in models of low-energy supersymmetry breaking. We consider the case where the lightest Standard Model (SM) superpartner is a light neutralino that predominantly decays into a photon and a light gravitino. Considering the lighter stop to be the next-to-lightest Standard Model superpartner, we analyze stop signatures associated with jets, photons and missing energy, which lead to signals naturally larger than the associated SM backgrounds. We consider both 2-body and 3-body decays of the top squarks and show that…
If the lighter top squark has no kinematically allowed two-body decays that conserve flavor, then it will form hadronic bound states. This is required in models that are motivated by the supersymmetric little hierarchy problem and obtain the correct thermal relic abundance of dark matter by top-squark-mediated neutralino annihilations, or by top-squark-neutralino co-annihilations. It is also found in models that can accommodate electroweak-scale baryogenesis within minimal supersymmetry. I study the prospects for detecting scalar stoponium from its diphoton decay mode at the Large Hadron Colli…
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 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…
Presented are complete next-to-leading order electroweak (NLO EW) corrections to top-squark pair production at the Large Hadron Collider (LHC) within the Minimal Supersymmetric Standard Model (MSSM). At this order, also effects from the interference of EW and QCD contributions have to be taken into account. Moreover, photon-induced top-squark production is considered as an additional partonic channel, which arises from the non-zero photon density in the proton.
The exchange of electroweak gauginos in the $t-$ or $u-$channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. We discuss the potential for detection of such rapidity gap events at the Large Hadron Collider (LHC). Our numerical analysis is divided into two parts. First, we evaluate in a simplified framework the rapidity gap signal at the parton level. The second part covers an analysis with full event simulation using PYTHIA as we…
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.
We discuss a decay rate asymmetry of the top squark, which is induced by a new source of CP violation intrinsic in the supersymmetric standard model. Although new sources of CP violation in this model are severely constrained from the electric dipole moment of the neutron, an unsuppressed CP-violating phase can still coexist with a top squark whose mass is accessible by near-future colliders. Then the dominant decay mode of the top squark has a width different from its CP conjugate process. The magnitude of this $CP$ asymmetry becomes of order $10^{-3}$.
Supersymmetry predicts that gauge couplings are equal to the corresponding gaugino-sfermion-fermion Yukawa couplings. This prediction can be tested for the QCD sector of the MSSM by studying the processes eplus+eminus -> squark+antisquark+gluon and eplus+eminus -> squark+antiquark+gluino at a future linear collider. We present results for these processes at next-to-leading order in alpha_s in the framework of the MSSM. We find sizable SUSY-QCD corrections. The renormalization scale dependence is significantly reduced at next-to-leading order.
We compare the prospects for observing theories with Majorana or Dirac gauginos at a future 100 TeV proton-proton collider. Calculating the expected discovery and exclusion regions, we find that for heavy gluino masses the squark discovery reach is significantly reduced in Dirac gluino models relative to the Majorana case. However, if the squark and gluino masses are close the reach is similar in both scenarios. We also consider the electroweak fine tuning of theories observable at such a collider, and the impact of existing constraints from flavour and CP violating observables. Models with Ma…
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.
Until now the focus within the direct search for supersymmetry has mainly been on flavour diagonal observables. Recently lepton flavour violating signals at future electron positron colliders have been studied. There is now an opportunity to analyse the relations between collider observables and low-energy observables in the hadronic sector. In a first work in this direction, we study flavour violation in the squark decays of the second and third generations taking into account results from B physics, in particular from the rare decay b ->s gamma. Correlations between various squark decay mode…
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.
The scalar partner of the top quark is relatively light in many models of supersymmetry breaking. We study the production of top squarks (stops) at the Tevatron collider and their subsequent decay through baryon-number violating couplings such that the final state contains no leptons. Performing a detector-level analysis, we demonstrate that, even in the absence of leptons or missing energy, stop masses upto 210 \gev/c^2 can be accessible at the Tevatron.
We derive a factorization formula for the production of pairs of heavy coloured particles in hadronic collisions near the production threshold that establishes factorization of soft and Coulomb effects. This forms the basis for a combined resummation of Coulomb and soft corrections, including the non-trivial interference of the two effects. We develop a resummation formalism valid at NNLL accuracy using the momentum-space approach to soft gluon resummation. We present numerical results for the NLL resummed squark-antisquark production cross section at the LHC and Tevatron, including also the c…
In compressed supersymmetry, a light top squark naturally mediates efficient neutralino pair annihilation to govern the thermal relic abundance of dark matter. I study the LHC signal of same-sign leptonic top-quark decays from gluino and squark production, which follows from gluino decays to top plus stop followed by the stop decaying to a charm quark and the LSP in these models. Measurements of the numbers of jets with heavy-flavor tags in the same-sign lepton events can be used to confirm the origin of the signal. Summed transverse momentum observables provide an estimate of an effective sup…
The invariant mass distribution of the di-photons from the decay of the lighter scalar Higgs boson(h) to be carefully measured by dedicated h search experiments at the LHC may be distorted by the di-photons associated with the squark-gluino events with much larger cross sections in Gauge Mediated Supersymmetry Breaking (GMSB) models. This distortion if observed by the experiments at the Large Hadron Collider at 7 TeV or 14 TeV, would disfavour not only the standard model but various two Higgs doublet models with comparable h - masses and couplings but without a sector consisting of new heavy p…
We discuss the three-body decays stop_1 -> W^+ b neutralino_1, stop_1 -> H^+ b neutralino_1, stop_1 -> b slepton_i neutrino_l, and stop_1 -> b sneutrino_l l^+$ ($l =e,μ,τ$) of the lighter top squark within the minimal supersymmetric standard model. We give the complete analytical formulas for the decay widths and present a numerical study in view of an upgraded Tevatron, the CERN LHC, and a future lepton collider demonstrating the importance of these decay modes.
We study the hadroproduction of two neutral Higgs bosons in the minimal supersymmetric extension of the standard model, which provides a handle on the trilinear Higgs couplings. We include the contributions from quark-antiquark annihilation at the tree level and those from gluon-gluon fusion, which proceeds via quark and squark loops. We list compact results for the tree-level partonic cross sections and the squark loop amplitudes, and we confirm previous results for the quark loop amplitudes. We quantitatively analyze the hadronic cross sections at the CERN Large Hadron Collider assuming a fa…
We investigate the production of Higgs particles in association with the supersymmetric scalar partners of the top quark at proton colliders. In the minimal supersymmetric extension of the Standard Model, the cross sections for the production of the lightest neutral Higgs boson in association with top squark pairs can be rather large, substantially exceeding the rate for the associated Higgs boson production with top quarks. If the lightest top squark is not much heavier than the top quark, this process will enhance the potential of the CERN Large Hadron Collider to discover the lightest neutr…
A Fortran-program for the production cross-sections of squarks and gluinos at hadron colliders is described. It includes full next-to-leading order SUSY-QCD corrections to all possible final states ($\squark\squarkbar, \gluino\gluino, \squark\gluino, \squark\squark$). The program allows to calculate total cross-sections as well as differential distributions in the transverse momentum p_t and the rapidity y of one of the outgoing particles. In addition cuts in p_t and y can easily be implemented.
If the lighter top squark has no kinematically allowed two-body decays that conserve flavor, then it will live long enough to form hadronic bound states. The observation of the diphoton decays of stoponium could then provide a uniquely precise measurement of the top squark mass. In this paper, we calculate the cross section for the production of stoponium in a hadron collider at next-to-leading order (NLO) in QCD. We present numerical results for the cross section for production of stoponium at the LHC and study the dependence on beam energy, stoponium mass, and the renormalization and factori…
We study flavor changing effects on the \ppbchT process at the Large Hadron Collider(LHC), which are inspired by the left-handed up-type squark mixings in the Minimal Supersymmetric Standard Model(MSSM). We find that the SUSY QCD radiative corrections to $bcH^\pm$ coupling can significantly enhance the cross sections at the tree-level by a factor about $1.5 \sim 5$ with our choice of parameters. We conclude that the squark mixing mechanism in the MSSM makes the \ppbchT process a new channel for discovering a charged Higgs boson and investigating flavor changing effects.
We investigate the ability of single top quark production via qq'-> squark->tb and q \bar q'->slepton->t\bar b at the LHC and Tevatron to probe the strength of R-parity violating couplings in the minimal supersymmetric model. We found that given the existing bounds on R-parity violating couplings, single top quark production may be greatly enhanced over that predicted by the standard model, and that both colliders can either discover R-parity violating SUSY or set strong constraints on the relevant R-parity violating couplings. We further found that the LHC is much more powerful than the Tevat…
Within the Minimal Supersymmetric Standard Model we study the three body decay of the lighter top squark into a b-quark, a W-boson and the lightest neutralino and compare this decay with the flavour changing two body decay of the lighter top squark into a c-quark and the lightest neutralino. We do this for scenarios where two body decays at tree level are forbidden for the light top squark. We give the complete analysis for the three body and compare it with the mentioned two body decay. We discuss our numerical results in view of the upgraded Tevatron, the LHC and a 500~GeV $e^+ e^-$ Linear C…
If supersymmetry (SUSY) is realized at the electroweak scale, its underlying structure and breaking mechanism may be explored with great precision by a future linear $e^+ e^-$ collider (LC) with a clean environment, tunable collision energy, high luminosity polarized beams, and additional $e^-e^-$, $eγ$ and $γγ$ modes. In this report we summarize four papers submitted to the ICHEP04 conference about the precise measurements of the top squark parameters and $\tanβ$, the impacts of the CP phases on the search for top/bottom squarks, the Majorana nature and CP violation in the neutralino system, …
We present here the results for Higgs and Supersymmetry prospective searches at the Large Hadron Collider. We show that for one year at high luminosity, Standard Model and MSSM Higgs should be observed within the theoretically expected mass range. MSUGRA and restricted phenomenological MSSM searches lead to discovery of up to 2.5 TeV squarks and gluinos.
We study the potential of the LHC accelerator, and a future 33 TeV proton collider, to observe the production of a light top squark pair in association with the lightest Higgs boson (${\tilde t}_1 {\tilde t}_1 h_1$), as predicted by the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We scan randomly about ten million points of the NMSSM parameter space, allowing all possible decays of the lightest top squark and lightest Higgs boson, with no assumptions about their decay rates, except for known physical constraints such as perturbative bounds, Dark matter relic density consistent with …
A new particle's interactions can be measured at colliders, by observing its associated production with Standard Model particles. We focus on the case of a collider-stable right-handed top squark and study the LHC sensitivities to its couplings to the photon, Z, and the Higgs boson. Such measurements determine the top squark's charge, mixing angle and coupling to the electroweak symmetry breaking sector. Determining these couplings can provide strong evidence for the supersymmetric solution to the hierarchy problem. Our analysis shows that the LHC has great prospects for measuring the photon a…
