4,959 research outputs found

    LHC Reach for Gauge Mediated Supersymmetry Breaking Models Via Prompt Photon Channels

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    We evaluate the supersymmetry reach of the Large Hadron Collider within the gauge-mediated low energy supersymmetry breaking framework, assuming that a neutralino is the second lightest sparticle and that it decays promptly into a gravitino which escapes detection. We find that the maximum reach is obtained via a search for inclusive \gamma\gamma+\eslt events coming dominantly from chargino and neutralino production. Assuming an integrated luminosity of 10~fb−1fb^{-1}, we find that LHC experiments will be able to probe values of the model parameter \Lambda \alt 400 TeV, corresponding to mtg⁥≀2.8m_{\tg} \leq 2.8 TeV. A measure of the model parameter Λ\Lambda may be possible from the photon pTp_T spectrum.Comment: 10 page Revtex file plus 4 EPS figure

    Analysis of Long-Lived Slepton NLSP in GMSB model at Linear Collider

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    We performed an analysis on the detection of a long-lived slepton at a linear collider with s=500\sqrt{s}=500 GeV. In GMSB models a long-lived NLSP is predicted for large value of the supersymmetry breaking scale F\sqrt{F}. Furthermore in a large portion of the parameter space this particle is a stau. Such heavy charged particles will leave a track in the tracking volume and hit the muonic detector. In order to disentangle this signal from the muon background, we explore kinematics and particle identification tools: time of flight device, dE/dX and Cerenkov devices. We show that a linear collider will be able to detect long-lived staus with masses up to the kinematical limit of the machine. We also present our estimation of the sensitivity to the stau lifetime.Comment: Minor changes, Ref. 10 fixed. 12 pages, RevTex, 4 eps figure

    Viable Supersymmetric Models with an Inverted Scalar Mass Hierarchy at the GUT Scale

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    Supersymmetric models with an inverted mass hierarchy (IMH: multi-TeV first and second generation matter scalars, and sub-TeV third generation and Higgs scalars) have been proposed to ameliorate phenomenological problems arising from flavor changing neutral currents (FCNCs) and CP violating processes, while satisfying conditions of naturalness. Models with an IMH already in place at the GUT scale have been shown to be constrained in that for many model parameter choices, the top squark squared mass is driven to negative values. We delineate regions of parameter space where viable models with a GUT scale IMH can be generated. We find that larger values of GUT scale first and second generation scalar masses act to suppress third generation scalars, leading to acceptable solutions if GUT scale gaugino masses are large enough. We show examples of viable models and comment on their characteristic features. For example, in these models the gluino mass is bounded from below, and effectively decouples, whilst third generation scalars remain at sub-TeV levels. While possibly fulfilling criteria of naturalness, these models present challenges for detection at future pp and e^+e^- collider experiments.Comment: 16 page REVTEX file with 6 PS figure

    Yukawa Unified Supersymmetric SO(10) Model: Cosmology, Rare Decays and Collider Searches

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    It has recently been pointed out that viable sparticle mass spectra can be generated in Yukawa unified SO(10) supersymmetric grand unified models consistent with radiative breaking of electroweak symmetry. Model solutions are obtained only if tan⁥ÎČ∌50\tan\beta \sim 50, ÎŒ<0\mu <0 and positive DD-term contributions to scalar masses from SO(10) gauge symmetry breaking are used. In this paper, we attempt to systematize the parameter space regions where solutions are obtained. We go on to calculate the relic density of neutralinos as a function of parameter space. No regions of the parameter space explored were actually cosmologically excluded, and very reasonable relic densities were found in much of parameter space. Direct neutralino detection rates could exceed 1 event/kg/day for a 73^{73}Ge detector, for low values of GUT scale gaugino mass m1/2m_{1/2}. We also calculate the branching fraction for b→sÎłb\to s \gamma decays, and find that it is beyond the 95% CL experimental limits in much, but not all, of the parameter space regions explored. However, recent claims have been made that NLO effects can reverse the signs of certain amplitudes in the b→sÎłb\to s\gamma calculation, leading to agreement between theory and experiment in Yukawa unified SUSY models. For the Fermilab Tevatron collider, significant regions of parameter space can be explored via bbˉAb\bar{b}A and bbˉHb\bar{b}H searches. There also exist some limited regions of parameter space where a trilepton signal can be seen at TeV33. Finally, there exist significant regions of parameter space where direct detection of bottom squark pair production can be made, especially for large negative values of the GUT parameter A0A_0.Comment: Added comparison to Blazek/Raby results and added Comments on de Boer et al. b->s gamma result

    Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

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    The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

    Combined search for the quarks of a sequential fourth generation