The results of searches for charginos, neutralinos and sleptons in data collected by the four LEP experiments up to center-of-mass energies of 209 GeV have been used to extract limits on the mass of ...the lightest neutralino within a constrained MSSM and the mSUGRA model.
TileCal is the barrel hadronic calorimeter of the ATLAS experiment presently in an advanced state of installation and commissioning at the LHC accelerator. The complexity of the experiment, the ...number of electronics channels and the high rate of acquired events requires a detailed commissioning of the detector, during the installation phase of the experiment and in the early life of ATLAS, to verify the correct behaviour of the hardware and software systems. This is done through the acquisition, monitoring, reconstruction and validation of calibration signals as well as processing data obtained with cosmic ray muons. To assess the detector status and verify its performance a set of tools has been developed spanning from the hardware detector verification tests and the online monitoring to the offline reconstruction. Tools allowing for a fast and semi-automated analysis of the result have been developed and the system includes web interfaces to allow for remote monitoring and data quality assessment.
We present a study of events with Z bosons and jets produced at the Fermilab Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV. The data sample consists of nearly 14,000 ...Z/G* -> e+e- candidates corresponding to the integrated luminosity of 340 pb-1 collected using the D0 detector. Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross section have been measured for n = 1 to 4 jet events. Our measurements are found to be in good agreement with a next-to-leading order QCD calculation and with a tree-level QCD prediction with parton shower simulation and hadronization.
We report on a search for second generation leptoquarks LQ_2 which decay into a muon plus quark in p\bar{p} collisions at a center-of-mass energy of sqrt{s} = 1.96 TeV in the D0 detector using an ...integrated luminosity of about 300 pb-1. No evidence for a leptoquark signal is observed and an upper bound on the product of the cross section for single leptoquark production times branching fraction beta into a quark and a muon was determined for second generation scalar leptoquarks as a function of the leptoquark mass. This result has been combined with a previously published D0 search for leptoquark pair production to obtain leptoquark mass limits as a function of the leptoquark-muon-quark coupling, lambda. Assuming lambda=1, lower limits on the mass of a second generation scalar leptoquark are m{LQ_2}>274 GeV and m{LQ_2}>226 GeV for beta=1 and beta=1/2, respectively.
A search for the pair production of scalar top quarks, or stops, has been performed in 360 pb-1 of data from p pbar collisions at a center-of-mass energy of 1.96 TeV, collected by the D0 detector at ...the Fermilab Tevatron collider. The stop decay mode considered is stop into c chi, where chi is the lightest supersymmetric particle. The topology analyzed therefore consists of a pair of acoplanar heavy-flavor jets with missing transverse energy. The data show good agreement with the standard model expectation, and a 95% C.L. exclusion domain in the stop and chi mass plane has been determined, extending the domain excluded by previous experiments.
We present a search for a neutral particle, pair-produced in p-pbar collisions at sqrt(s)=1.96 TeV, which decays into two muons and lives long enough to travel at least 5 cm before decaying. The ...analysis uses ~380 pb^-1 of data recorded with the D0 detector. The background is estimated to be about one event. No candidates are observed, and limits are set on the pair production cross section times branching fraction into dimuons + X for such particles. For a mass of 10 GeV and lifetime of 4x10^-11 s, we exclude values greater than 0.14 pb (95% C.L.). These results are used to limit the interpretation of NuTeV's excess of di-muon events.
A search for direct production of scalar bottom quarks (sb) is performed with 310 pb-1 of data collected by the DO experiment in ppbar collisions at sqrt(s)=1.96 TeV at the Fermilab Tevatron ...Collider. The topology analyzed consists of two b jets and an imbalance in transverse momentum due to undetected neutralinos chi0_1, with chi0_1 assumed to be the lightest supersymmetric particle. We find the data consistent with standard model expectations, and set a 95% C.L. exclusion domain in the (m_sb,m_chi0_1) mass plane, improving significantly upon the results from Run I of the Tevatron.
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