Search for the Supersymmetric Partner of the Top Quark in Dilepton Events Produced in $p\bar{p}$ Collisions at $\sqrt{s}$ PDF Download
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Languages : en
Pages : 206
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Supersymmetric partners of top quarks, stops, will be pair produced at the Fermi National Accelerator Laboratory in proton-antiproton collisions at a center-of-mass energy √s= 1.8TeV if kinematically accessible. Within the framework of the Minimal Supersymmetric extension of the Standard Model, the stop quarks are assumed to decay into a lepton, a bottom quark and a supersymmetric neutrino, sneutrino. Thus the experimental signature of stop presence in the data would be two opposite electric charge leptons, hadronic jets and substantial energy imbalance in the detector due to the escaping, undetected sneutrinos. We searched a total of ∫ Ldt = 107.2 pb-1 of data collected by the Collider Detector at Fermilab experiment. No evidence of a stop signal has been found which allows us to calculate a 95% con dence level upper limit on the number of stop-originated events in the data of this size. We have translated this into a 95% con dence level exclusion region in the stop versus sneutrino mass plane.
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Category :
Languages : en
Pages : 206
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Book Description
Supersymmetric partners of top quarks, stops, will be pair produced at the Fermi National Accelerator Laboratory in proton-antiproton collisions at a center-of-mass energy √s= 1.8TeV if kinematically accessible. Within the framework of the Minimal Supersymmetric extension of the Standard Model, the stop quarks are assumed to decay into a lepton, a bottom quark and a supersymmetric neutrino, sneutrino. Thus the experimental signature of stop presence in the data would be two opposite electric charge leptons, hadronic jets and substantial energy imbalance in the detector due to the escaping, undetected sneutrinos. We searched a total of ∫ Ldt = 107.2 pb-1 of data collected by the Collider Detector at Fermilab experiment. No evidence of a stop signal has been found which allows us to calculate a 95% con dence level upper limit on the number of stop-originated events in the data of this size. We have translated this into a 95% con dence level exclusion region in the stop versus sneutrino mass plane.
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Languages : en
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We present the results of a search for pair production of the supersymmetric partner of the top quark (the stop quark ≈1) decaying to a b-quark and a chargino {tilde {chi}}1{sup {+-}} with a subsequent {tilde {chi}}1{sup {+-}} decay into a neutralino {tilde {chi}}1°, lepton l, and neutrino [nu]. Using a data sample corresponding to 2.7 fb−1 of integrated luminosity of p{bar p} collisions at √s = 1.96 TeV collected by the CDF II detector, we reconstruct the mass of candidate stop events and fit the observed mass spectrum to a combination of standard model processes and stop quark signal. We find no evidence for {tilde t}1{bar {tilde t}}1 production and set 95% C.L. limits on the masses of the stop quark and the neutralino for several values of the chargino mass and the branching ratio [Beta]({tilde {chi}}1{sup {+-}} → {tilde {chi}}1°l{sup {+-}}[nu]).
Author: William Johnson
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ISBN: 9781124219684
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Languages : en
Pages :
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We search for pair production of the supersymmetric partner of the top quark, the stop quark, decaying to a b-quark and a chargino with a subsequent decay into a neutralino, lepton, and neutrino. Using 2.7 fb−1 of [square root]s=1.96 TeV proton on antiproton collision data collected by the CDF II experiment, we reconstruct the mass of candidate stop events and fit the observed mass spectrum to a combination of standard model processes and stop signal. No evidence of stop pair production is found, therefore we set 95% C.L. limits on the masses of the stop and the neutralino for several values of the chargino mass and the branching ratio B(X̃±/1[right arrow]X̃01l±v).
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Languages : en
Pages : 17
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We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy (square root)s = 1.96 TeV. This search was conducted within the framework of the R-parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of 1 fb−1 collected by the CDF experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence level in the stop quark versus sneutrino mass plane are set. Stop quark masses up to 180 GeV/c2 are excluded for sneutrino masses around 45 GeV/c2, and sneutrino masses up to 116 GeV/c2 are excluded for stop quark masses around 150 GeV/c2.
Author: Takashi Ogawa
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Category :
Languages : en
Pages : 145
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A search for the pair production of supersymmetric partner of the top quark in scenario with R-parity violation is presented. The quantum number called R-parity distinguishes particles in standard model from supersymmetric particles. A scalar top quark (stop) is assumed to decay only via R{sub p}-violating supersymmetric coupling into tau lepton and b-quark. To collect events with multiple taus, a new special tau trigger (the lepton plus track trigger) is installed in Run II experiment of the Collider Detector at Fermilab (CDF). The goal of the lepton plus track trigger is to collect generic dilepton ({ell}{ell}, {ell}{tau}, {tau}{tau}) events with lower p{sub T} threshold (8 GeV/c) and without prescale even at high luminosity. The Z {yields} {tau}{tau} event, where one {tau}-lepton decays leptonically and the other hadronically, is a good benchmark to calibrate the lepton plus track trigger and {tau} identification. The data sample of 72 pb{sup -1}, collected using the electron plus track trigger, contains clear a {tau} signal from Z {yields} {tau}{tau} events. The data used in stop search correspond to 200 pb{sup -1}. The lower stop mass bound of 134 GeV/c{sup 2} at a 95% confidence level is obtained. This limit is also directly applicable to the case of the third generation scalar leptoquark (LQ{sub 3}) assuming a 100% branching for the LQ{sub 3} {yields} {tau}b decay mode.
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Languages : en
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A search is presented for supersymmetry in all-hadronic events with missing transverse momentum based on tagging of top quarks. The data sample corresponds to an integrated luminosity of 2.3 inverse femtobarns of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC. Search regions are defined using the properties of reconstructed jets, the presence of bottom and top quark candidates, and an imbalance in transverse momentum. With no statistically significant excess of events observed beyond the expected contributions from the standard model, we set exclusion limits at 95% confidence level on the masses of new particles in the context of simplified models of direct and gluino-mediated top squark production. For direct top squark production with decays to a top quark and a neutralino, top squark masses up to 740 GeV and neutralino masses up to 240 GeV are excluded. Gluino masses up to 1550 GeV and neutralino masses up to 900 GeV are excluded for models of gluino pair production where each gluino decays to a top-antitop quark pair and a neutralino.
Author: Maddalena Giulini
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Category : Jets
Languages : en
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Languages : en
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We report on a search for the supersymmetric partner of the top quark (scalar top) decaying into a charm quark and a neutralino in p{bar p} collisions at √s = 1.96 TeV. The data sample, collected by the CDF II detector at the Fermilab Tevatron, corresponds to an integrated luminosity of 2.6 fb−1. Candidate events are selected by requiring two or more jets and a large imbalance in the transverse momentum. To enhance the analysis sensitivity, at least one of the jets is required to be identified as originating from a charm quark using an algorithm specifically designed for this analysis. The selected events are in good agreement with standard model predictions. In the case of large mass splitting between the scalar top quark and the neutralino we exclude a scalar top quark mass below 180 GeV/c2 at 95% confidence level.
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Category :
Languages : en
Pages : 146
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We search for pair production of the supersymmetric partner of the top quark, the stop quark $̃ar{t}$1, decaying to a b-quark and a chargino X-±1 with a subsequent X-±1 decay into a neutralino X-1 , lepton l, and neutrino . Using 2.7 fb-1 of √s = 1.96 TeV p$ar{p}$ collision data collected by the CDF II experiment, we reconstruct the mass of candidate stop events and t the observed mass spectrum to a combination of standard model processes and stop signal. No evidence of $̃ar{t}$1 $ar{t}$1 production is found, therefore we set 95% C.L. limits on the masses of the stop and the neutralino for several values of the chargino mass and the branching ratio B (X-±1 → X-01 l±v).
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Languages : en
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Results are reported from a search for the top squark $ \tilde{t}_1 $, the lighter of the two supersymmetric partners of the top quark. The data sample corresponds to 19.7 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} =$ 8 TeV collected with the CMS detector at the LHC. The search targets $ \tilde{t}_1 \to \mathrm{b} \tilde{\chi}^{\pm}_1$ and $ \tilde{t}_1 \to \mathrm{t}^{(*)} \tilde{\chi}^0_1$ decay modes, where $\tilde{\chi}^{\pm}_1$ and $\tilde{\chi}^0_1$ are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible $ \tilde{t}_1 $ and $\tilde{\chi}^0_1 $ masses. The highest excluded $ \tilde{t}_1 $ and $ \tilde{\chi}^0_1$ masses are about 700 GeV and 250 GeV, respectively.
