3 research outputs found

    Measurement of charged particle multiplicities in pp collisions at sqrt(s) = 7 TeV in the forward region

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    Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of s√=7 TeV in different intervals of pseudorapidity η. Charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the η ranges −2.5<η<−2.0 and 2.0<η<4.5. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of η. In general, the models underestimate charged particle production

    Search for chargino-neutralino production in p(p)over-bar collisions at root s=1.96 TeV

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    We present a search for associated production of the chargino and neutralino supersymmetric particles using up to 1.1 fb(-1) of integrated luminosity collected by the CDF II experiment at the Tevatron p (p) over bar collider at root s=1.96 TeV. We analyze events with a large transverse momentum imbalance and either three charged leptons or two charged leptons of the same electric charge. The numbers of observed events are consistent with standard model expectations. Upper limits on the production cross section are derived in different theoretical models

    Observation of the heavy baryons Sigma(b) and Sigma(b)*

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    We report an observation of new bottom baryons produced in p (p) over bar collisions at the Tevatron. Using 1.1 fb(-1) of data collected by the CDF II detector, we observe four Lambda(0)(b)pi(+/-) resonances in the fully reconstructed decay mode Lambda(0)(b)->Lambda(+)(c)pi(-), where Lambda(+)(c)-> pK(-)pi(+). We interpret these states as the Sigma((*)+/-)(b) baryons and measure the following masses: m(Sigma b)(+)=5807.8(-2.2)(+2.0)(stat.)+/- 1.7(syst.) MeV/c(2), m(Sigma b)(-)=5815.2 +/- 1.0(stat.)+/- 1.7(syst.) MeV/c(2), and m(Sigma(*)(b))-m(Sigma(b))=21.2(-1.9)(+2.0)(stat.)(-0.3)(+0.4)(syst.) MeV/c(2)
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