Gluino Pair Production Research Articles

Phenomenology of QCD threshold resummation for gluino pair production at NNLL

Abstract We examine the impact of threshold resummation for the inclusive hadronic production cross section of gluino pairs at next-to-next-to-leading-logarithmic accuracy, compared to the exact next-to-leading-order cross section and the next-to-next-to-leading-order approximation. Here, we apply formulas derived recently in the classical Mellin-space formalism. Moreover, we give the analytic input for the alternative momentum-space formalism and discuss the crucial points of the numeric implementation. We find that soft resummation keeps the hadronic cross section close to the fixed next-to-leading-order result.

Same-sign diboson signature from supersymmetry models with light Higgsinos at the LHC.

In supersymmetric models with light Higgsinos (which are motivated by electroweak naturalness arguments), the direct production of Higgsino pairs may be difficult to search for at the LHC due to the low visible energy release from their decays. However, the wino pair production reaction W2(±)Z4→(W(±)Z1,2)+(W(±)W1(∓)) also occurs at substantial rates and leads to final states including equally opposite-sign and same-sign diboson production. We propose a novel search channel for LHC14 based on the same-sign diboson plus missing ET final state which contains only modest jet activity. Assuming gaugino mass unification, and an integrated luminosity ≳100 fb(-1), this search channel provides a reach for supersymmetry well beyond that from usual gluino pair production.

Pure gravity mediation of supersymmetry breaking at the Large Hadron Collider

Supersymmetric theories which can allow for a 125 GeV Higgs mass and also solve the naturalness and susy flavor problems now require a fair degree of complexity. Here we consider the simplest possibility for supersymmetry near the weak scale, but with the requirement of naturalness dropped. In "pure gravity mediation", all supersymmetric particles except for the gauginos lie at tens to thousands of TeV, with the gauginos obtaining loop suppressed masses automatically by anomaly mediation and higgsino threshold corrections. The gauginos are the lightest superpartners, and we investigate the current collider constraints on their masses, as well as the future reach of the LHC. We consider gluino pair production with a jets + missing energy signature, as well as events with disappearing charged tracks caused by charged winos decaying into their neutral partners. We show that presently, gluino masses less than about 1 TeV and wino masses less than about 300 GeV are excluded, and that the 14 TeV LHC can probe gluino masses up to about 2 TeV and wino masses up to 1 TeV.

Search for pair production of massive particles decaying into three quarks with the ATLAS detector in $ \sqrt{s}=7\;\mathrm{TeV} $ pp collisions at the LHC

AbstractA search is conducted for hadronic three-body decays of a new massive coloured particle in$ \sqrt{s}=7\;\mathrm{TeV} $ppcollisions at the LHC using an integrated luminosity of 4.6 fb−1collected by the ATLAS detector. Supersymmetric gluino pair production in the context of a model withR-parity violation is used as a benchmark scenario. The analysis is divided into two search channels, each optimised separately for their sensitivity to high-mass and low-mass gluino production. The first search channel uses a stringent selection on the transverse momentum of the six leading jets and is performed as a counting experiment. The second search channel focuses on low-mass gluinos produced with a large boost. Large-radius jets are selected and the invariant mass of each of the two leading jets is used as a discriminant between the signal and the background. The results are found to be consistent with Standard Model expectations and limits are set on the allowed gluino mass.

QCD threshold corrections for gluino pair production at hadron colliders

Abstract We present the complete threshold enhanced predictions in QCD for the total cross section of gluino pair production at hadron colliders at next-to-next-to-leading order. Thanks to the computation of the required one-loop hard matching coefficients our results are accurate to the next-to-next-to-leading logarithm. In a brief phenomenological study we provide predictions for the total hadronic cross sections at the LHC and we discuss the uncertainties arising from scale variations and the parton distribution functions.

Search for three-jet resonances in pp collisions at [formula omitted

Results are reported from a search for the production of three-jet resonances in pp collisions at a center-of-mass energy s=7 TeV. The study uses the data sample collected by the CMS experiment at the LHC in 2011, corresponding to an integrated luminosity of 5.0 fb−1. Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed for the presence of resonances in the three-jet invariant mass spectrum. No evidence for a narrow resonance is found in the data, and limits are set on the cross section for gluino pair production in an R-parity-violating supersymmetry model, for gluino masses greater than 280 GeV. Assuming a branching fraction for gluino decay into three jets of 100%, gluino masses below 460 GeV are excluded at 95% confidence level. These results significantly extend the range of previous limits.

Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS detector

This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb^-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.

Light gravitino production in association with gluinos at the LHC

We study the jets plus missing energy signature at the LHC in a scenario where the gravitino is very light and the gluino is the next-to-lightest supersymmetric particle and promptly decays into a gluon and a gravitino. We consider both associated gravitino production with a gluino and gluino pair production. By merging matrix elements with parton showers, we generate inclusive signal and background samples and show how information on the gluino and gravitino masses can be obtained by simple final state observables.

Supersoft supersymmetry is super-safe

We show that supersymmetric models with a large Dirac gluino mass can evade much of the jets plus missing energy searches at the LHC. Dirac gaugino masses arise from ``supersoft'' operators that lead to finite one-loop suppressed contributions to the scalar masses. A little hierarchy between the Dirac gluino mass 5--10 times heavier than the squark masses is automatic and technically natural, in stark contrast to supersymmetric models with Majorana gaugino masses. At the LHC, colored sparticle production is suppressed not only by the absence of gluino pair (or associated) production, but also because several of the largest squark pair production channels are suppressed or absent. We recast the null results from the present jets plus missing energy searches at the LHC for supersymmetry onto a supersoft supersymmetric simplified model. Assuming a massless lightest supersymmetric particle, we find the strongest bounds are as follows: 748 GeV from a $2j+{\mathrm{E\ensuremath{\llap{\not\;}}}}_{T}$ search at ATLAS ($4.7\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$) and 684 GeV from a combined jets plus missing energy search using ${\ensuremath{\alpha}}_{T}$ at CMS ($1.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$). In the absence of a future observation, we estimate the bounds on the squark masses to improve only modestly with increased luminosity. We also briefly consider the further weakening in the bounds as the lightest supersymmetric particle mass is increased.

NLL soft and Coulomb resummation for squark and gluino production at the LHC

Abstract We present predictions of the total cross sections for pair production of squarks and gluinos at the LHC, including the stop-antistop production process. Our calculation supplements full fixed-order NLO predictions with resummation of threshold logarithms and Coulomb singularities at next-to-leading logarithmic (NLL) accuracy, including bound-state effects. The numerical effect of higher-order Coulomb terms can be as big or larger than that of soft-gluon corrections. For a selection of benchmark points accessible with data from the 2010-2012 LHC runs, resummation leads to an enhancement of the total inclusive squark and gluino production cross section in the 15-30% range. For individual production processes of gluinos, the corrections can be much larger. The theoretical uncertainty in the prediction of the hard-scattering cross sections is typically reduced to the ±10% level.

A heavier gluino from t–b–τ Yukawa-unified SUSY

Supersymmetric models with t–b–τ Yukawa coupling unification and unified gaugino masses at the GUT scale—with μ>0—show a mild preference for light gluino masses mg˜≲500 GeV. This range of mg˜ is now essentially ruled out by LHC searches. We show that a heavier gluino with mg˜∼0.5–3 TeV can also be compatible with excellent t–b–τ Yukawa coupling unification in supersymmetric models with non-universal Higgs masses (NUHM2). The gluino in such models is the lightest colored sparticle, while the squark sector displays an inverted mass hierarchy with mq˜∼5–20 TeV. We present some LHC testable benchmark points for which the lightest Higgs boson mass mh≃125 GeV. We also discuss LHC signatures of Yukawa-unified models with heavier gluinos. We expect gluino pair production followed by decay to final states containing four b-jets plus four W-bosons plus missing ET to occur at possibly observable rates at LHC.

Impact of LHC searches on NLSP top squark and gluino mass

We explore the implications of 7 TeV LHC searches for a scenario in which one of the stops is the next-to lightest supersymmetric particle (NLSP). The NLSP stop (\tilde{t}_1) is assumed to decay exclusively into neutralino and charm quark. We consider processes where the stops are pair produced together with a hard QCD jet. We also consider stop quarks from gluino decays, \tilde{g}\to t\tilde{t}_1^\ast+\bar{t}\tilde{t}_1. We show that the monojet ATLAS and CMS searches corresponding to 1 fb^{-1} of integrated luminosity are sensitive to stop masses of up to 160 GeV, with the 20% neutralino-stop coannihilation region essentially ruled out for M_{\tilde{t}_1}\lesssim 140 GeV. The region M_{\tilde{t}_1}\lesssim 130 GeV is excluded with even relatively larger mass difference, M_{\tilde{t}_1}-M_{\tilde{\chi}_1^0}\sim 40 GeV, by the multi-jets search. The b-jet and same-sign dilepton searches are sensitive to a heavier gluino because they only pick up gluino pair production events followed by top quarks decaying into b-jets and same-sign dileptons, respectively. We find that the LHC data places a lower limit on the gluino mass in this scenario of about 600 GeV (700 GeV) from b-jets (same-sign dileptons) searches.

Implications of a 125 GeV Higgs scalar for the LHC supersymmetry and neutralino dark matter searches

The ATLAS and CMS collaborations have reported an excess of events in the $\ensuremath{\gamma}\ensuremath{\gamma}$, $Z{Z}^{*}\ensuremath{\rightarrow}4\ensuremath{\ell}$ and $W{W}^{*}$ search channels at an invariant mass $m\ensuremath{\simeq}125\text{ }\text{ }\mathrm{GeV}$, which could be the first evidence for the long-awaited Higgs boson. We investigate the consequences of requiring ${m}_{h}\ensuremath{\simeq}125\text{ }\text{ }\mathrm{GeV}$ in both the minimal supergravity and 2-parameter nonuniversal Higgs supersymmetric models. In minimal supergravity, large values of trilinear soft breaking parameter $|{A}_{0}|$ are required, and universal scalar ${m}_{0}\ensuremath{\gtrsim}0.8\text{ }\text{ }\mathrm{TeV}$ is favored so that we expect squark and slepton masses typically in the multi-TeV range. This typically gives rise to an ``effective supersymmetric'' type of sparticle mass spectrum. In this case, we expect gluino pair production as the dominant sparticle creation reaction at LHC. For ${m}_{0}\ensuremath{\lesssim}5\text{ }\text{ }\mathrm{TeV}$, the superpotential parameter $\ensuremath{\mu}\ensuremath{\gtrsim}2\text{ }\text{ }\mathrm{TeV}$ and ${m}_{A}\ensuremath{\gtrsim}0.8\text{ }\text{ }\mathrm{TeV}$, greatly restricting neutralino annihilation mechanisms. These latter conclusions are softened if ${m}_{0}\ensuremath{\sim}10--20\text{ }\text{ }\mathrm{TeV}$ or if one proceeds to the 2-parameter nonuniversal Higgs model. The standard neutralino abundance tends to be far above WMAP-measured values unless the neutralino is Higgsino-like. We remark upon possible nonstandard (but perhaps more attractive) cosmological scenarios which can bring the predicted dark matter abundance into accord with the measured value, and discuss the implications for direct and indirect detection of neutralino cold dark matter.

Whplus missing-ETsignature from gaugino pair production at the LHC

In SUSY models with heavy squarks and gaugino mass unification, the gaugino pair production reaction pp-> \tw_1^\pm\tz_2 dominates gluino pair production for m_{\tg}\agt 1 TeV at LHC with \sqrt{s}=14 TeV (LHC14). For this mass range, the two-body decays \tw_1\to W\tz_1 and \tz_2\to h\tz_1 are expected to dominate the chargino and neutralino branching fractions. By searching for \ell b\bar{b}+MET events from \tw_1^\pm\tz_2 production, we show that LHC14 with 100 fb^{-1} of integrated luminosity becomes sensitive to chargino masses in the range m_{\tw_1}\sim 450-550 GeV corresponding to m_{\tg}\sim 1.5-2 TeV in models with gaugino mass unification. For 10^3 fb^{-1}, LHC14 is sensitive to the Wh channel for m_{\tw_1}\sim 300-800 GeV, corresponding to m_{\tg}\sim 1-2.8 TeV, which is comparable to the reach for gluino pair production followed by cascade decays. The Wh+MET search channel opens up a new complementary avenue for SUSY searches at LHC, and serves to point to SUSY as the origin of any new physics discovered via multijet and multilepton + MET channels.

A Higgs mass shift to 125 GeV and a multi-jet supersymmetry signal: Miracle of the flippons at the [formula omitted] LHC

We describe a model named No-Scale F-SU(5) which is simultaneously capable of explaining the dual signals emerging at the LHC of (i) a 124–126 GeV Higgs boson mass mh, and (ii) tantalizing low-statistics excesses in the multi-jet data which may attributable to supersymmetry. These targets tend to be mutually exclusive in more conventional approaches. The unified mechanism responsible for both effects is the introduction of a rather unique set of vector-like multiplets at the TeV scale, dubbed flippons, which (i) can elevate mh by around 3–4 GeV via radiative loop corrections, and (ii) flatten the running of the strong coupling and color-charged gaugino, resulting in a prominent collider signal from production of light gluino pairs. This well-motivated theoretical framework maintains consistency with all key phenomenological constraints, and all residual parameterization freedom may in principle be fixed by a combination of the two experiments described. We project that the already collected luminosity of 5 fb−1 may be sufficient to definitively establish the status of this model, given appropriate data selection cuts.

Gluino pair production at the LHC: The threshold

The next-to-leading order analysis of the cross section of hadronic gluino pair production 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 remnant of the 1 S peak below the nominal pair threshold. This enhancement is similar to the corresponding one for top production. However, as a consequence of the larger color factor of the QCD potential the effect is significantly enhanced. The analysis includes all color configurations of S-wave gluino pairs, i.e. singlet, symmetric and antisymmetric octet, decuplet and twenty-seven representation. Matching coefficients involving real and virtual radiation are separately evaluated for all color and spin configurations and initial states. We concentrate on the case of gluino decay rates comparable to the gluino binding energy. The non-relativistic dynamics of the gluino pair is solved by calculating the Greenʼs function in NLO. Numerical results for the Large Hadron Collider at s = 14 TeV and 7 TeV are presented for various characteristic scenarios.

Revisiting combinatorial ambiguities at Hadron Colliders with M T2

We present a method to resolve combinatorial issues in multi-particle final states at hadron colliders. The use of kinematic variables such as MT2 and invariant mass significantly reduces combinatorial ambiguities in the signal, but at a cost of losing statistics. We illustrate this idea with gluino pair production leading to 4 jets $+\met$ in the final state as well as $t\bar{t}$ production in the dilepton channel. Compared to results in recent studies, our method provides greater efficiency with similar purity

First Search for Multijet Resonances ins=1.96 TeVpp¯Collisions

We present the first model independent search for three-jet hadronic resonances within multijet events in $\sqrt{s} = 1.96$ TeV $p\bar{p}$ collisions at the Fermilab Tevatron using the CDF II detector. Pair production of supersymmetric gluinos and squarks with hadronic R-parity violating decays is employed as an example of a new physics benchmark for this signature. Selection criteria based on the kinematic properties of an ensemble of jet combinations within each event help to extract signal from copious QCD background. Our background estimates include all-hadronic $t\bar{t}$ decays that have a signature similar to the signal. No significant excess outside the top quark mass window is observed in data with an integrated luminosity of 3.2 fb$^{-1}$. We place 95% confidence level limits on the production cross section $\sigma(p \bar{p} \rightarrow XX^{'}) \times \rm{BR}$($\widetilde{g}\widetilde{g}$$ \rightarrow 3 {\rm jet}+3 {\rm jet})$ where $X, X' = \widetilde{g}, \widetilde{q}$, or $\widetilde{\bar{q}}$, with $\widetilde{q}$, $\widetilde{\bar{q}} \rightarrow \widetilde{g}$ + jet, as a function of gluino mass, in the range of 77 GeV/$c^2$ to 240 GeV/$c^2$.

Effects of invisible particle emission on global inclusive variables at hadron colliders

We examine the effects of invisible particle emission in conjunction with QCD initial state radiation (ISR) on quantities designed to probe the mass scale of new physics at hadron colliders, which involve longitudinal as well as transverse final-state momenta. This is an extension of our previous treatment, arXiv:0903.2013, of the effects of ISR on global inclusive variables. We present resummed results on the visible invariant mass distribution and compare them to parton-level Monte Carlo results for top quark and gluino pair-production at the LHC. There is good agreement as long as the visible pseudorapidity interval is large enough (eta ~ 3). The effect of invisible particle emission is small in the case of top pair production but substantial for gluino pair production. This is due mainly to the larger mass of the intermediate particles in gluino decay (squarks rather than W-bosons). We also show Monte Carlo modelling of the effects of hadronization and the underlying event. The effect of the underlying event is large but may be approximately universal.

Testing Yukawa-unified SUSY during year 1 of LHC: the role of multiple b-jets, dileptons and missing E T

We examine the prospects for testing SO(10) Yukawa-unified supersymmetric models during the first year of LHC running at \sqrt{s}= 7 TeV, assuming integrated luminosity values of 0.1 to 1 fb^-1. We consider two cases: the Higgs splitting (HS) and the D-term splitting (DR3) models. Each generically predicts light gluinos and heavy squarks, with an inverted scalar mass hierarchy. We hence expect large rates for gluino pair production followed by decays to final states with large b-jet multiplicity. For 0.2 fb^-1 of integrated luminosity, we find a 5 sigma discovery reach of m(gluino) ~ 400 GeV even if missing transverse energy, E_T^miss, is not a viable cut variable, by examining the multi-b-jet final state. A corroborating signal should stand out in the opposite-sign (OS) dimuon channel in the case of the HS model; the DR3 model will require higher integrated luminosity to yield a signal in the OS dimuon channel. This region may also be probed by the Tevatron with 5-10 fb^-1 of data, if a corresponding search in the multi-b+ E_T^miss channel is performed. With higher integrated luminosities of ~1 fb^-1, using E_T^miss plus a large multiplicity of b-jets, LHC should be able to discover Yukawa-unified SUSY with m(gluino) up to about 630 GeV. Thus, the year 1 LHC reach for Yukawa-unified SUSY should be enough to either claim a discovery of the gluino, or to very nearly rule out this class of models, since higher values of m(gluino) lead to rather poor Yukawa unification.