Searches For Squarks And Gluinos At Cdf And D0 Detectors

This contribution reports on preliminary measurements on searches for squarks and gluinos at CDF and D0 detectors in p{bar p} collisions at {radical}s = 1.96 TeV. The analyses are performed using event topologies with multiple jets and large missing energy in the final state. The mSUGRA scenario and R-parity conservation is assumed. No excess with respect to the Standard Model predictions is observed and new limits on the gluino and squark masses are extracted.

This contribution reports on preliminary measurements of searches for squarks and gluinos at CDF and D0 detectors in p{bar p} collisions at (square root)s = 1.96 TeV using 1 fb−1 of data. The analyses are optimized for event topologies with multiple jets and large missing transverse energy in the final state. No excess with respect to the Standard Model predictions is observed and new limits on the gluino and squark masses are extracted in a mSUGRA scenario with R-parity conservation.

This thesis reports on two searches for the production of squarks and gluinos, supersymmetric partners of the Standard Model (SM) quarks and gluons, using the CDF detector at the Tevatron (square root)s = 1.96 TeV p{bar p} collider. An inclusive search for squarks and gluinos pair production is performed in events with large E{sub T} and multiple jets in the final state, based on 2 fb−1 of CDF Run II data. The analysis is performed within the framework of minimal supergravity (mSUGRA) and assumes R-parity conservation where sparticles are produced in pairs. The expected signal is characterized by the production of multiple jets of hadrons from the cascade decays of squarks and gluinos and large missing transverse energy E{sub T} from the lightest supersymmetric particles (LSP). The measurements are in good agreement with SM predictions for backgrounds. The results are translated into 95% confidence level (CL) upper limits on production cross sections and squark and gluino masses in a given mSUGRA scenario. An upper limit on the production cross section is placed in the range between 1 pb and 0.1 pb, depending on the gluino and squark masses considered. The result of the search is negative for gluino and squark masses up to 392 GeV/c2 in the region where gluino and squark masses are close to each other, gluino masses up to 280 GeV/c2 regardless of the squark mass, and gluino masses up to 423 GeV=c2 for squark masses below 378 GeV/c2. These results are compatible with the latest limits on squark/gluino production obtained by the D0 Collaboration and considerably improve the previous exclusion limits from direct and indirect searches at LEP and the Tevatron. The inclusive search is then extended to a scenario where the pair production of sbottom squarks is dominant. The new search is performed in a generic MSSM scenario with R-parity conservation. A specific SUSY particle mass hierarchy is assumed such that the sbottom decays exclusively as {tilde b}1 --> b{sub {tilde {chi}}1°}. The expected signal for direct sbottom pair production is characterized by the presence of two jets of hadrons from the hadronization of the bottom quarks and E=T from the two LSPs in the final state. The events are selected with large E{sub T} and two energetic jets in the final state, and at least one jet is required to be associated with a b quark. The measurements are in good agreement with SM predictions for backgrounds. The results are translated into 95% CL exclusion limits on production cross sections and sbottom and neutralino masses in the given MSSM scenario. Cross sections down to 0.1 pb are excluded for the sbottom mass range considered. Sbottom masses up to 230 GeV/c2 are excluded at 95% CL for neutralino masses below 70 GeV/c2. This analysis increases the previous CDF limit by more than 40 GeV/c2. The sensitivity of both the inclusive and the exclusive search is dominated by systematic effects and the results of the two analyses can be considered as conclusive for CDF Run II. With the new energy frontier of the newly commissioned Large Hadron Collider in Geneva, the experience from Tevatron will be of crucial importance in the developing of effective strategies to search for SUSY in the next era of particle physics experiments.

A search for squarks and gluinos is performed in the topology of multijet events accompanied by large missing transverse energy in 2.1fb−1 of p{bar p} collision data collected using the D0 detector at the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV. About half of this dataset is specifically analyzed for events involving at least one tau lepton decaying hadronically in addition. No deviation from the Standard Model expectation is observed and the analyses are combined to set limits on the squark and gluino masses and on parameters of minimal supergravity.

Abstract: We present preliminary results on a search for squarks and gluinos in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV and based on 1.1 fb-1 of data collected by the CDF detector in the Tevatron Run II. Events with multiple jets of hadrons and large missing transverse energy in the final state are studied within the framework of minimal supergravity and assuming R-parity conservation. No excess with respect to Standard Model predictions is observed and new limits on the gluino and squark masses are extracted.

We report on D0 searches for scalar quarks ({tilde q}) and gluinos ({tilde g}), the superpartners of quark and gluons, in topologies involving jets and missing transverse energies. Data samples obtained with D0 detector from p{bar p} collisions at a center-of-mass energy of 1.96 TeV corresponding to an integrated luminosities of 1-4 fb−1 were analyzed. No evidence for the production of such particles were observed and lower limits on squarks and gluino masses were set.

Based on 7.1 pb−1 of single interaction event data collected by the DO Detector at Fermilab during the 1992--1993 p{bar p} collider run at (square root)s = 1.8 TeV, results are presented of a search for supersymmetric partners of the quark and gluon, the squark and gluino, using missing E{sub T} and jets as the signature. Limits are set on the squark and gluino masses in the context of the Minimal Supersymmetric Standard Model including the effect of cascade decays of the squark and gluino.

A search for squarks and gluinos performed by the CDF and D0 collaborations is presented. The sample taken during the RunII of the Fermilab TeVatron collider at (square root)s = 1.96 TeV is used. Supersymmetry (SUSY) is one of the most promising ways to solve crucial problems of the Standard Model (SM). This spacetime symmetry links bosons to fermions by introducing supersymmetric partners (sparticles) to all SM particles: squarks and gluinos are SUSY partners of quarks and gluons. The mass difference between the squark mass eigenstates depend on the mass of the corresponding quark. Hence squarks are (to a good approximation) mass degenerate for the two first generations whereas a (potentially) large mixing may appear for the third family, leading to a light stop. The former case corresponds to squarks and gluinos searches whereas dedicated searches for stop are performed for the latter.

We report on a search for squarks and gluinos in p{anti p} collisions at (square root) s= 1.8 TeV using the D0 detector at Fermilab. Data corresponding to 79.2 " 4.2 pb−1 were examined for events with large missing transverse energy, three or more jets, and the absence of isolated leptons. No events were observed significantly in excess of Standard Model background predictions, and we place limits on the Minimal Supergravity parameters M0 and M12.