We study the effect of soft gluon emission in the hadroproduction of gluino-gluino and squark-antisquark pairs at the next-to-leading logarithmic (NLL) accuracy within the framework of the minimal supersymmetric model. We present the calculation of the one-loop soft anomalous dimension matrices controlling the colour evolution of the underlying hard-scattering processes. The numerical results for resummed cross sections for proton-proton collisions at the Large Hadron Collider are discussed in detail.
We present results for a combined resummation of soft and Coloumb gluon corrections in squark-antisquark production at the LHC, including the non-trivial interference of the two effects and the contribution of squark-antisquark bound states below threshold. The total correction to the next-to-leading order approximation is found to be sizeable, and amounts to 5-14 % in the squark mass region 200 GeV-2 TeV. The scale dependence of the total cross section is also reduced.
We study the effect of soft gluon emission in the hadroproduction of squark-antisquark and gluino-gluino pairs at the next-to-leading logarithmic (NLL) accuracy within the framework of the minimal supersymmetric model. The one-loop soft anomalous dimension matrices controlling the colour evolution of the underlying hard-scattering processes are calculated. We present the resummed total cross sections and show numerical results for proton-proton collisions at 14 TeV. The size of the NLL contribution to the cross section and the reduction of the scale dependence of the theoretical predictions du…
We consider the resummation of soft gluon emission for squark-antisquark pair-production at the LHC at next-to-next-to-leading-logarithmic (NNLL) accuracy in the framework of the minimal supersymmetric standard model. We present the analytical ingredients needed for the calculation and provide numerical predictions for the LHC at centre-of-mass energies of 7 and 14 TeV. We find a significant reduction in the scale uncertainty and a considerable increase in the prediction of the total cross section. Compared to the next-to-leading order prediction, the corrections increase the cross section by …
We consider the resummation of soft and Coulomb gluons for pair-production processes of heavy coloured particles at hadron colliders, and discuss recent results on the construction of a basis in colour space that diagonalizes the soft function to all orders in perturbation theory and the determination of the two-loop soft anomalous dimension needed for NNLL resummations. We present results for the combined NLL resummation of soft gluon and Coulomb-gluon effects for squark-antisquark production at the LHC.
We report on the resummation of soft-gluon emissions for squark-antisquark production at next-to-next-to-leading-logarithmic (NNLL) accuracy. We will put particular emphasis on the one loop hard matching coefficients required to perform the resummation. Furthermore we will discuss the numerical effect of the different ingredients in the corrections. We find a significant reduction in the scale uncertainty and a considerable increase in the prediction of the total cross section at the central scale. Compared to the next-to-leading order prediction, the corrections increase the cross section by …
We present the calculation of the electroweak corrections for squark-antisquark pair production at the LHC within the Minimal Supersymmetric Standard Model. Taking into account all possible chirality and light-flavor configurations, we evaluate the NLO EW corrections, which are of O(a_s^2 a), as well as the subleading tree-level contributions of O(a_s a) and O(a^2). Numerical results are presented for several scans in the SUSY parameter space and relevant differential distributions are investigated. The impact of the electroweak corrections is nonnegligible and strongly depends on the chiralit…
We present NNLO cross sections for squark- antisquark production at the LHC. We have calculated new analytic expressions for the scale dependent scaling functions at one and two loop.
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.
We consider the resummation of soft gluon emission for squark and gluino hadroproduction at next-to-leading-logarithmic (NLL) accuracy in the framework of the minimal supersymmetric standard model. We present analytical results for squark-squark and squark-gluino production and provide numerical predictions for all squark and gluino pair-production processes at the Tevatron and at the LHC. The size of the soft-gluon corrections and the reduction in the scale uncertainty are most significant for processes involving gluino production. At the LHC, where the sensitivity to squark and gluino masses…
We analyze effects of the CP violating interactions on associated gluino-squark production in the MSSM at hadron colliders. Depending on the sparticle masses, the hadronic cross sections can be enhanced up to 9.5 % for a 500 GeV gluino at the LHC energies.
In the light gluino scenario, squarks in the 100 GeV mass region can be copiously produced at the Tevatron without a second heavy particle. Their subsequent dijet decay into quark plus gluino leads to non-scaling structure in the inclusive jet X_T distribution. The expected behavior is similar to recent observations.
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…
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.
The partial widths are determined for squark decays to gluinos and quarks, and gluino decays to squarks and quarks, respectively. The widths are calculated including one-loop SUSY-QCD corrections. The corrections amount to $+$30\% to $+$50\% for squark decays and $-$10\% to $+$10\% for gluino decays. We have derived the results in the \DR ~and \MS ~renormalization schemes, and we have demonstrated explicitly that the one-loop effective $qqg$ and $q\sq\gl$ couplings are equal in the limit of exact supersymmetry.
We perform the resummation of soft-gluon emissions for squark and gluino production at next- to-next-to-leading-logarithmic (NNLL) accuracy. We include also the one-loop hard matching coefficients as well as Coulomb corrections to second order, using Mellin-moment methods. We study the characteristics of this resummation in detail for a centre-of-mass (CM) energy of 8 TeV at the LHC, and for squark and gluino masses up to 2.5 TeV. We find significant enhancing effects for all four processes of squark- and gluino-pair production. Scale dependence is generally reduced compared to NLL resummation…
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 study the implication of finite squark and gluino decay widths for threshold resummation of squark and gluino production cross sections at the LHC. We find that for a moderate decay width (Gamma/m < 5%) higher-order soft and Coulomb corrections are appropriately described by NLL calculations in the zero-width limit including the contribution from bound-state resonances below threshold, with the remaining uncertainties due to finite-width effects of a similar order as the ambiguities of threshold-resummed higher-order calculations.
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…
We consider scenarios with large flavour violating entries in the squark mass matrices focusing on the mixing between second and third generation squarks. These entries govern both, flavour violating low energy observables on the one hand and squark and gluino decays on the other hand. We first discuss the constraints on the parameter space due to the recent data on B mesons from the B factories and Tevatron. We then consider flavour violating squark and gluino decays and show that they can still be typically of order 10% despite the stringent constraints from low energy data. Finally we brief…
We calculated the electroweak contributions to the hadronic production of a squark in association with a gluino within the Minimal Supersymmetric Standard Model (MSSM). Presented are complete next-to-leading order electroweak (NLO EW) corrections at O(alpha_s^2 alpha), which include real photon and real quark radiation processes. Also considered are photon induced tree level O(alpha_s alpha) contributions.
We review the theoretical status of squark and gluino hadroproduction and provide numerical predictions for all squark and gluino pair-production processes at the Tevatron and at the LHC, with a particular emphasis on proton-proton collisions at 7 TeV. Our predictions include next-to-leading order supersymmetric QCD corrections 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 provide an estimate of the theoretical uncertainty due to scale variation and the parton distribution f…
Under the assumption of gaugino mass unification at a high scale, chargino and neutralino masses depend on the value of the gluino mass, which itself becomes a function of squark masses through self-energy corrections. We demonstrate that this leads to combined bounds on squark and gluino masses from the limits on chargino, neutralino and Higgs boson masses obtained in the CERN LEP-1 and LEP-1.5 runs. These bounds turn out to be comparable to those obtained from direct searches at the Fermilab Tevatron and may be expected to improve as LEP energies go higher.
In the presence of a light singlino-like LSP in the NMSSM, the missing transverse energy - MET - signature of squark/gluino production can be considerably reduced. Instead, a pair of Higgs bosons is produced in each event. We propose benchmark points for such scenarios, which differ in the squark and gluino masses, and in their decay cascades. Events for these points are simulated for the run II of the LHC at 13 TeV centre of mass energy. After cuts on the transverse momenta of at least four jets, and requiring two tau-leptons from one Higgs decay, we find that the invariant mass of two b-jets…
We explain how physics in the kaon sector proves useful in setting constraints in models where the gluino mass is below 2 TeV, while the other supersymmetric particles are in the range $\sim(3-10)$ TeV. We also discuss the signals of these models at colliders, in particular at the LHC.
It is shown that if the sneutrino is the second lightest SUSY particle, then the decay products of squarks and gluinos produced at the TEVATRON collider tend to have i) more leptons, ii) smaller number of jets and iii) two or more carriers of missing E_T. This may relax the existing limits on the squark and gluino masses. This effect is likely to be even more striking as these limits improve with accumulation of data. Numerical results for signal cross sections are presented and compared with the ones obtained without a light sneutrino. The possibilities of accommodating this scenario in model…
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 present cross section predictions for squark and gluino production at the LHC, in association with up to two additional hard jets. These cross sections can be very large in comparison to the inclusive Born rates. Because hadron collider experiments utilize hard jets in the reconstruction of cascade decays or as a way to separate squark and gluino production, the understanding of these processes is crucial. We show to what degree hard jet radiation can be described by shower algorithms and point out how tuning these showers, for example to top quark pair production, could help reduce theoret…
Soft supersymmetry breaking appears in the weak-scale effective action but is usually generated at higher scales. For these models the structure of the renormalization group evolution down to the electroweak scale leaves only part of the squark-gluino and slepton-gaugino mass planes accessible. Our observations divide these physical mass planes into three wedges: the first can be reached by all models of high-scale breaking; the second can only be populated by models with a low mediation scale; in the third wedge squarks and gluinos would have to be described by an exotic theory. All usual ben…
We present the hard matching coefficients for squark and gluino hadroproduction. The hard matching coefficients follow from the next-to-leading order cross section near threshold and are an important ingredient for performing threshold resummation at next-to-next-to-leading logarithmic accuracy. We discuss the calculation, list the analytical results and study the numerical impact of these corrections. We find that the impact of the hard matching coefficients can be considerable, with the largest effect observed for final states involving gluinos.
The physical pole and running masses of squarks and gluinos have recently been related at two-loop order in a mass-independent renormalization scheme. I propose a general method for improvement of such formulas, and argue that better accuracy results. The improved version gives an imaginary part of the pole mass that agrees exactly with the direct calculation of the physical width at next-to-leading order. I also find the leading three-loop contributions to the gluino pole mass in the case that squarks are heavier, using effective field theory and renormalization group methods. The efficacy of…
We present predictions for the total cross sections for pair production of squarks and gluinos at the LHC including a combined NNLL resummation of soft and Coulomb gluon effects. The NNLL corrections can be up to 25% relative to previous NLL results and reduce the theoretical uncertainties to the 10% level.
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 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…
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 consider single squark production in $p\overline{p}$ collisions at $\sqrt{s}=1800$ Gev in the light gluino scenario, where production is dominated by the parton subprocess $qg\rightarrow \tilde{q}\tilde{g}\rightarrow q\tilde{g}\tilde{g}$. Computed are the total production cross-sections as well as the contribution of such production to the dijet mass distribution. We compare our cross-sections to the experimental data from the CDF collaboration with integrated luminosity of $19 pb^{-1}$.
The next-to-leading order QCD corrections to the production of gluino pairs at the Tevatron are presented in this paper. Similar to the production of squark-antisquark pairs, the dependence of the cross section on the renormalization/factorization scale is reduced considerably by including the higher-order corrections. The cross section increases with respect to the lowest-order calculation which, in previous experimental analyses, had been evaluated at the scale of the invariant energy of the partonic subprocesses.
We discuss the supersymmetric O(alpha_s) QCD corrections to e+ e- -> squark_i + antisquark_j (i,j = 1,2) and to squark_i -> q' + chargino_j, q + neutralino_k (i,j = 1,2; k = 1...4) within the Minimal Supersymmetric Standard Model. In particular we consider the squarks of the third generation stop_i and sbottom_i including the left-right mixing. In the on-shell scheme also the mixing angle has to be renormalized. We use dimensional reduction (which preserves supersymmetry) and compare it with the conventional dimensional regularization. A detailed numerical analysis is also presented.
An analysis of the cross section for hadronic production of gluino-squark pairs close to threshold is presented. Within the framework of non-relativistic QCD a significant enhancement compared to fixed order perturbation theory is observed which originates from the characteristic remnants of the gluino-squark resonances below the nominal pair threshold. The analysis includes all colour configurations of S-wave gluino-squark pairs, i.e. triplet, sextet and 15 representation. Matching coefficients at leading order are separately evaluated for all colour configurations. The dominant QCD correctio…
We present completely general next-to-leading order predictions for squark and gluino production at the LHC, based on the fully automated MadGolem tool. Without any assumptions on the mass spectrum we predict production rates and examine the structure of the massless and massive quantum corrections. This allows us to quantify theory uncertainties induced by the spectrum assumptions commonly made. Going beyond total rates we compare general fixed-order distributions to resummed predictions from jet merging. As part of this comprehensive study we present the MadGolem treatment of ultraviolet, in…
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…
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.
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 …
We study the flavour changing neutral Higgs boson decays that can be induced from genuine supersymmetric particles at the one-loop level and within the context of the Minimal Supersymmetric Standard Model. We consider all the possible flavour changing decay channels of the three neutral Higgs bosons into second and third generation quarks, and focus on the Supersymmetric-QCD corrections from squark-gluino loops which are expected to provide the dominant contributions. We assume here the more general hypothesis for flavour mixing, where there is misalignment between the quark and squark sectors…
I present results for the finite renormalization of the Cabibbo-Kobayashi-Maskawa (CKM) matrix induced by gluino--squark diagrams in the MSSM with non-minimal sources of flavour violation. Subsequently I derive bounds on the flavour--off--diagonal elements of the squark mass matrices by requiring that the radiative corrections to the CKM elements do not exceed the experimental values. The constraints on the associated dimensionless quantities $δ^{d LR}_{ij}$, $j>i$, are stronger than the bounds from flavour-changing neutral current (FCNC) processes if gluino and squarks are heavier than 500$ \…
We investigate the choice of the renormalization and factorization scales for the production of squarks and gluinos at the Fermilab Tevatron collider as a function of the produced sparticle masses. We determine a scale to be used in leading-order perturbative QCD calculations optimized such that the normalization of the next-to-leading order cross section is reproduced. Use of this optimal scale permits at least a partial implementation of next-to-leading order contributions in leading order Monte Carlo simulations. We provide next-to-leading order predictions of the production cross sections …
Supersymmetric models with a Dirac gluino have been shown to be considerably less constrained from LHC searches than models with a Majorana gluino. In this paper, we generalize this discussion to models with a "Mixed Gluino", that acquires both Dirac and Majorana masses, as well as models in which electroweak gauginos contribute to squark production. Our primary interest is the degree of suppression of the cross section for first generation squarks compared with a gluino with a pure Majorana mass. We find that not all Majorana masses are alike -- a Majorana mass for the gluino can suppress the…
We propose an inclusive analysis of a stransverse mass (m_{T2}) using a hemisphere method for supersymmetry studies at the LHC . The hemisphere method is an algorithm to group collinear and high p_T particles and jets, assuming that there are two of such groups in a event. The m_{T2} is defined as a function of the unknown LSP mass, two hemisphere momenta, and missing transverse momentum. The kinematical end point of the m_{T2} distribution provides information on the squark and gluino masses. We perform a Monte Carlo simulation to study the inclusive m_{T2} distribution at the LHC. We show th…
In this work we explore the 7 TeV LHC implication on light top squark (stop) and investigate discovery limits at both 8 and 14 TeV LHC using same-sign dilepton signature. We consider a simplified spectrum with gluino pair production followed by heavy gluino decay into on-shell stop and top quark in pair. The light stop is then assumed to uniquely decay into c\tildeχ_1^0, bW^+\tildeχ_1^0 or t\tildeχ_1^0. The same-sign dilepton search at 7 TeV LHC places a lower bound of about 800 GeV on the gluino mass in this scenario. We find that the 8 TeV LHC with 30 fb^{-1} luminosity can reach 960 (900) G…
We present state-of-the-art cross section predictions for the production of supersymmetric squarks and gluinos at the upcoming LHC run with a centre-of-mass energy of $\sqrt{s} = 13$ and $14$ TeV, and at potential future $pp$ colliders operating at $\sqrt{s} = 33$ and $100$ TeV. The results are based on calculations which include the resummation of soft-gluon emission at next-to-leading logarithmic accuracy, matched to next-to-leading order supersymmetric QCD corrections. Furthermore, we provide an estimate of the theoretical uncertainty due to the variation of the renormalisation and factoris…
The ATLAS Collaboration announced a 3$σ$ excess in the leptonic-$Z+jets+\met$ channel. We show that such an excess can be interpreted in the extension of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) with a heavy Dirac gluino and light squarks. The abundant $Z$ bosons can be produced by light squark pair productions with the subsequent decays $\tilde{q} \to q \tildeχ_2^0 \to q Z \tildeχ_1^0$. We investigate the relevant parameter space by considering the constraints from both the ATLAS and CMS direct SUSY searches. Our model can provide sufficient $Z$-signal events in large paramet…
A status report is given of the calculations of next-to-leading-order ($N=1$) supersymmetric QCD corrections to the production of squarks and gluinos in $p\bar{p}/pp$ collisions. The implementation of these SUSY-QCD corrections leads to more stable theoretical predictions and to a substantial increase of the production cross-sections. In addition we give a discussion of the use of the $\overline{MS}$ scheme for renormalizing the coupling constants in the QCD sector of ($N=1$) supersymmetric theories.
R-symmetry leads to a distinct realisation of SUSY with a significantly modified coloured sector featuring a Dirac gluino and a scalar colour octet (sgluon). We present the impact of R-symmetry on squark production at the 13 TeV LHC. We study the total cross sections and their NLO corrections from all strongly interacting states, their dependence on the Dirac gluino mass and sgluon mass as well as their systematics for selected benchmark points. We find that tree-level cross sections in the R-symmetric model are reduced compared to the MSSM but the NLO K-factors are generally larger in the ord…
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 experim…
We have determined the QCD corrections to the production of squark-antisquark pairs in $p\bar p$ collisions at the Tevatron. If the next-to-leading order corrections are taken into account, the renormalization/factorization scale dependence of the theoretical prediction for the cross section is reduced considerably. The higher order corrections increase the production cross section at the Tevatron by about a factor two if we compare the next-to-leading order prediction at a scale near the squark mass with the lowest order prediction for which, in the experimental analyses, the scale was identi…
In this paper, we present results based on a combination of four inclusive topology searches for supersymmetry (SUSY) from the CMS experiment, and use this to determine universal mass limits on gluino and third-generation squarks in the context of Natural-like SUSY spectra. The class of Natural-like SUSY spectra considered follows the typical Natural SUSY model made up of a gluino, third-generation squarks, and higgsino sparticles, but is extended to more complex spectra containing sleptons. We show that the limits obtained from the combination of inclusive topology searches are far more stabl…
After completion of the LHC8 run in 2012, the plan is to upgrade the LHC for operation close to its design energy sqrt{s}=14 TeV, with a goal of collecting hundreds of fb^{-1} of integrated luminosity. The time is propitious to begin thinking of what is gained by even further LHC upgrades. In this report, we compute an LHC14 reach for SUSY in the mSUGRA/CMSSM model with an anticipated high luminosity upgrade. We find that LHC14 with 300 (3000) fb^{-1} has a reach for SUSY via gluino/squark searches of m(gluino)\sim3.2 TeV (3.6 TeV) for m(squark)\sim m)gluino), and a reach of m(gluino)\sim1.8 T…
The effects of light, long-lived gluinos on $2\to 2$ processes at hadron colliders are examined. Such particles can mediate single squark resonant production via $q\glu\to\sq\to q\glu$ which would significantly modify the dijet data sample. We find that squark masses in the range $130<m_{\tilde q}< 694, 595, 573$ GeV are excluded for gluino masses of $0.4, 1.3, 5.0$ GeV from existing UA2 and Tevatron data on dijet bump searches and angular distributions. Run II of the Tevatron has the capability of excluding this scenario for squark masses up to $\sim 1$ TeV.
We study the constraints on the mass-splitting of the first two generations of left-handed squarks obtained from Delta M_K, epsilon_K and D mixing. The different contributions from gluino, neutralino and chargino diagrams are examined in detail, concluding that it is not justified to neglect electroweak gaugino diagrams if the squark mass matrices contain flavor non-diagonal LL elements. We find that the constraints on the mass-splitting are very strong for light gluino masses. However, if the gluino is heavier than the squarks the constraints on the mass-splitting are much weaker. There are e…
The Z boson can decay to a pair of light gluinos through loop-mediated processes. Based on unitarity of the S-matrix, the imaginary part of the decay amplitude is computed in the presence of a light bottom squark. This imaginary part can provide useful information on the full amplitude. Implications are discussed for a recently proposed light gluino and light bottom squark scenario.
Some variants of the MSSM feature a strip in parameter space where the lightest neutralino is identified as the lightest supersymmetric particle (LSP), the gluino is the next-to-lightest supersymmetric particle (NLSP) and is nearly degenerate with the LSP, and the relic cold dark matter density is brought into the range allowed by astrophysics and cosmology by coannihilation with the gluino NLSP. We calculate the relic density along this gluino coannihilation strip in the MSSM, including the effects of gluino-gluino bound states and initial-state Sommerfeld enhancement, and taking into account…
