Search for pair production of second-generation scalar leptoquarks in pp collisions at √s = 7 TeV

A search for pair production of second-generation scalar leptoquarks in the final state with two muons and two jets is performed using proton-proton collision data at √s = 7 TeV collected by the CMS detector at the LHC. The data sample used corresponds to an integrated luminosity of 34 pb?1. The number of observed events is in good agreement with the predictions from the standard model processes. An upper limit is set on the second-generation leptoquark cross section times β2 as a function of the leptoquark mass, and leptoquarks with masses below 394 GeV are excluded at a 95% confidence level for β = 1, where β is the leptoquark branching fraction into a muon and a quark. These limits are the most stringent to date.     

Search for pair production of first-generation scalar leptoquarks in pp collisions at √s = 7 TeV

A search for pair production of first-generation scalar leptoquarks is performed in the final state containing two electrons and two jets using proton-proton collision data at √s = 7 TeV. The data sample used corresponds to an integrated luminosity of 33 pb?1 collected with the CMS detector at the CERN LHC. The number of observed events is in good agreement with the predictions for the standard model background processes, and an upper limit is set on the leptoquark pair production cross section times β2 as a function of the leptoquark mass, where β is the branching fraction of the leptoquark decay to an electron and a quark. A 95% confidence level lower limit is set on the mass of a first-generation scalar leptoquark at 384 GeV for β = 1, which is the most stringent direct limit to date.     

Measurement of the top quark mass in dileptonic top quark pair decays with √s = 7 TeV ATLAS data

The top quark mass in dileptonic top quark pair decays was measured using 4.7 fb^–1 of √s = 7 TeV proton-proton (pp) collision data recorded by the ATLAS experiment at the LHC in 2011. The event topology is characterized by the presence of two charged leptons, at least two neutrinos and several jets, two of which originate from bottom quarks. Using the template method and the m _?b observable, defined as the average invariant mass of the two charged lepton plus b-jet pairs in each event, the top quark mass is measured to be 173.09 ± 0.64(stat) ± 1.50(syst) GeV. This proceeding is based on a preliminary result, which has been superseded meanwhile.     

Measurement of dijet angular distributions and search for quark compositeness in pp collisions at √s = 7 TeV

Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at √s = 7 TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36 pb?1. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With a modified frequentist approach, a lower limit on the contact interaction scale for left-handed quarks of Λ? = 5.6 TeV (Λ? = 6.7 TeV) for destructive (constructive) interference is obtained at the 95% confidence level.     

Search for production of heavy particles decaying to top quarks and invisible particles in pp collisions at √s = 1.96 TeV

We present a search for a new particle T' decaying to top quark via T' → t + X, where X is an invisible particle. In a data sample with 4.8 fb(-1) of integrated luminosity collected by the CDF II detector at Fermilab in pp collisions with √s = 1.96 TeV, we search for pair production of T' in the lepton + jets channel, pp → tt + X + X → ?νbqq'b + X + X. We interpret our results primarily in terms of a model where T' are exotic fourth generation quarks and X are dark matter particles. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600 GeV/c2, the dark matter particle mass being anywhere below m(T'). The data are consistent with standard model expectations, and we set 95% confidence level limits on the generic production of T'T' → tt + X + X. For the dark matter model we exclude T' at 95% confidence level up to m(T') = 360 GeV/c2 for m(X) ≤ 100 GeV/c2.     

Production of low transverse energy clusters in pp collisions at √s=0.2–0.9 TeV and their interpretation in terms of QCD jets

The production of transverse energy clusters in minimum bias proton-antiproton collisions at the CERN SPS Collider is studied with the UA1 detector over a new range of centre of mass energies (√s = 0.2−0.9 TeV). This study is intended to investigate how low in transverse momentum perturbative QCD is able to describe the dynamics of hadron collisions. We observe that clusters with transverse energy in excess of a few GeV exhibit properties in agreement with QCD expectations for parton scattering, supporting their interpretation in terms of jet production. We find that the jet-event rate represents a sizeable fraction of the inelastic rate and is increasing with √s over the measured energy range.     

Measurement of the integrated luminosities of the data taken by BESⅢ at √s=3.650 and 3.773 GeV

Data sets were collected with the BESⅢ detector at the BEPCⅡ collider at the center-of-mass energy of √s=3.650 GeV during May 2009 and at √s=3.773 GeV from January 2010 to May 2011. By analyzing the large angle Bhabha scattering events, the integrated luminosities of the two data sets are measured to be （44.49±0.02±0.44） pb-1 and （2916.94±0.18±29.17） pb-1, respectively, where the first error is statistical and the second error is systematic.     

Measurement of the B(s)0 lifetime in fully and partially reconstructed B(s)0→D(s)(-)(ϕπ(-))X decays in p¯p collisions at √s=1.96 TeV

We present a measurement of the B(s)(0) lifetime in fully and partially reconstructed B(s)(0)→D(s)(-)(?π(-))X decays in 1.3 fb(-1) collected in pp ˉ collisions at √s=1.96 TeV by the CDF II detector at the Fermilab Tevatron. We measure τ(B(s)(0))=1.518±0.041(stat)±0.027(syst) ps. The ratio of this result and the world average B(0) lifetime yields τ(B(s)(0))/τ(B(0))=0.99±0.03, which is in agreement with recent theoretical predictions.     

Study of Events with an Electron,Muon, and Two Hadron Jets in the Final State with an Integrated Luminosity of a 139 fb–1 in pp Collisions at $$\sqrt s $$ = 13 TeV with the ATLAS Detector at the LHC

Physics of Atomic Nuclei - To investigate the Higgs boson properties in the h → WW* → еνμν decay channel, events with an electron, muon, and two hadron jets in the...     

Semileptonic (lepton,neutrino and jets) <Emphasis Type="Italic">WW</Emphasis>/<Emphasis Type="Italic">WZ</Emphasis> resonances searches at √<Emphasis Type="Italic">s</Emphasis> = 8 and 13 TeV with the ATLAS detector at the LHC

This talk presents the analyses results of the diboson (WW or WZ) resonances production search in pp collisions at √s = 8 and 13 TeV with the ATLAS detector at the LHC with the semileptonic final state. As benchmark signal models Randall-Sundrum bulk model for KK G* → WW and Heavy Vector Triplet model for W′ → WZ and Z′ → WW are used. No significant excess for diboson resonances production is observed and upper limits on the production cross section times branching fraction of G*, W′ and Z′ are determined at 95% CL.     

Study of K*(892)0andФ(1020)meson production in proton–proton and Pb–Pb collisions at√SNN=2.76 TeV

In this paper,we describe a study of charged particle yield as a function of pT for K^*(892)0 and phgr(1020)mesons in proton–proton(pp)and Pb–Pb collisions at√S_NN=2.76 TeV in the central rapidity region of|y|<0.5,in a pT range of 0?1in pp collisions and in a pT range of 0NN=2.76 TeV.It was concluded that the models'predictions for the phgr-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data,and that the difference increased with pT.This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models.For K^*0 mesons,both programs gave almost the same predictions,and with pT in the interval pT>3 GeV c^?1,the predictions were very close to the experimental data.Both models gave higher predictions for the soft pT interval and lower predictions for the hard interactions.The values of the RAA distributions were lower than unity and both models were very close to the ALICE data.It is very interesting that the models were not able to describe the pT distributions,but they gave good predictions for their ratios.This may possibly be due to parton collective behaviors.We observed some additional suppression of K^*0 at low values of pT with respect to phgr-mesons,which may be related to the role of the masses of the particles in soft interactions.The rising trend for R_AAin the region from pT=10 GeV c^?1to 20 GeV c^?1 observed by the ALICE experiment was absent for theФ-mesons.