896 research outputs found
The alignment of the C3 Accelerator Structures with the Rasnik alignment system
The Rasnik 3-point alignment system, now widely applied in particle physics
experiments and in the instrumentation of gravitational wave experiments, can
be used as N-point alignment system by daisy chain N individual 3-point
systems. The conceptual implementation of Rasnik chains in C3 is presented. The
proper operation of a laser diode and a CMOS image sensor in liquid nitrogen
has been verified. Next plans for testing a small but complete system, immersed
in liquid nitrogen, are presented
Search for supersymmetry in events with opposite-sign dileptons and missing transverse energy using an artificial neural network
In this paper, a search for supersymmetry (SUSY) is presented in events with two opposite-sign isolated leptons in the final state, accompanied by hadronic jets and missing transverse energy. An artificial neural network is employed to discriminate possible SUSY signals from a standard model background. The analysis uses a data sample collected with the CMS detector during the 2011 LHC run, corresponding to an integrated luminosity of 4.98  fb-1 of proton-proton collisions at the center-of-mass energy of 7 TeV. Compared to other CMS analyses, this one uses relaxed criteria on missing transverse energy (E̸T>40  GeV) and total hadronic transverse energy (HT>120  GeV), thus probing different regions of parameter space. Agreement is found between standard model expectation and observations, yielding limits in the context of the constrained minimal supersymmetric standard model and on a set of simplified model
Erratum: Search for anomalous t¯t production in the highly-boosted all-hadronic final state
Erratum to: JHEP09(2012)02
Search for narrow resonances using the dijet mass spectrum in pp collisions at sqrt(s) = 8 TeV
Results are presented of a search for the production of new particles decaying to pairs of partons (quarks, antiquarks, or gluons), in the dijet mass spectrum in proton-proton collisions at sqrt(s) = 8 TeV. The data sample corresponds to an integrated luminosity of 4.0 inverse femtobarns, collected with the CMS detector at the LHC in 2012. No significant evidence for narrow resonance production is observed. Upper limits are set at the 95% confidence level on the production cross section of hypothetical new particles decaying to quark-quark, quark-gluon, or gluon-gluon final states. These limits are then translated into lower limits on the masses of new resonances in specific scenarios of physics beyond the standard model. The limits reach up to 4.8 TeV, depending on the model, and extend previous exclusions from similar searches performed at lower collision energies. For the first time mass limits are set for the Randall-Sundrum graviton model in the dijet channel
Determination of the top-quark pole mass and strong coupling constant from the ttbar production cross section in pp collisions at sqrt(s) = 7 TeV
The inclusive cross section for top-quark pair production measured by the CMS experiment in proton-proton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, , or the strong coupling constant, . With the parton distribution function set NNPDF2.3, a pole mass of 176.7 GeV is obtained when constraining at the scale of the Z boson mass, , to the current world average. Alternatively, by constraining to the latest average from direct mass measurements, a value of = 0.1151 is extracted. This is the first determination of using events from top-quark production
Search for the associated production of the Higgs boson with a top-quark pair
A search for the standard model Higgs boson produced in association with a top-quark pair (t tbar H) is presented, using data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns and 19.7 inverse femtobarns collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H to hadrons, H to photons, and H to leptons. The results are characterized by an observed t tbar H signal strength relative to the standard model cross section, mu = sigma/sigma[SM], under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is mu = 2.8 +/- 1.0 for a Higgs boson mass of 125.6 GeV
Erratum to: Search for the associated production of the Higgs boson with a top-quark pair
Erratum to: JHEP09(2014)08
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