Search for new physics in events with same-sign dileptons and b jets in pp collisions at root s=8 TeV

A search for new physics is performed using events with isolated same-sign leptons and at least two bottom-quark jets in the final state. Results are based on a sample of proton-proton collisions collected at a center-of-mass energy of 8TeV with the CMS detector and corresponding to an integrated luminosity of 10.5 fb(-1). No excess above the standard model background is observed. Upper limits are set on the number of events from non-standard-model sources and are used to constrain a number of new physics models. Information on acceptance and efficiencies is also provided so that the results can be used to confront an even broader class of new physics models

Search for supersymmetry in final states with missing transverse energy and 0, 1, 2, or >= 3 b-quark jets in 7 TeV pp collisions using the variable alpha(T)

A search for supersymmetry in final states with jets and missing transverse energy is performed in pp collisions at a centre-of-mass energy of root s = 7 TeV. The data sample corresponds to an integrated luminosity of 4.98 fb(-1) collected by the CMS experiment at the LHC. In this search, a dimensionless kinematic variable, alpha(T), is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. The search is performed in a signal region that is binned in the scalar sum of the transverse energy of jets and the number of jets identified as originating from a bottom quark. No excess of events over the standard model expectation is found. Exclusion limits are set in the parameter space of the constrained minimal supersymmetric extension of the standard model, and also in simplified models, with a special emphasis on compressed spectra and third-generation scenarios

Search for a heavy bottom-like quark in pp collisions at root s=7 TeV

A search for pair-produced bottom-like quarks in pp collisions at root s = 7 TeV is conducted with the CMS experiment at the LHC. The decay b' -> tW is considered in this search. The b'(b) over bar' tW-(t) over barW(+) process can be identified by the distinctive signature of trileptons and same-sign dileptons. With a data sample corresponding to an integrated luminosity of 34 pb(-1), no excess above the standard model background predictions is observed and a b' quark with a mass between 255 and 361 GeV/c(2) is excluded at the 95% confidence level. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved

Study of the underlying event at forward rapidity in pp collisions at root s=0.9, 2.76, and 7 TeV

The underlying event activity in proton-proton collisions at forward pseudorapidity (-6.6 < eta < -5.2) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/d(eta), for events with a charged-particle jet produced at central pseudorapidity (vertical bar eta(jet)vertical bar < 2) to the forward energy density for inclusive events. This forward energy density ratio is measured as a function of the central jet transverse momentum, p(T), at three different pp centre-of-mass energies (root s = 0.9, 2.76, and 7 TeV). In addition, the root s evolution of the forward energy density is studied in inclusive events and in events with a central jet. The results are compared to those of Monte Carlo event generators for pp collisions and are discussed in terms of the underlying event. Whereas the dependence of the forward energy density ratio on jet p(T), at each root s separately can be well reproduced by some models, all models fail to simultaneously describe the increase of the forward energy density with root s in both inclusive events and in events with a central jet

Measurement of Wγ and Zγ production in pp collisions at s=7 TeV

AbstractA measurement of Wγ and Zγ production in proton–proton collisions at s=7 TeV is presented. Results are based on a data sample recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 36 pb−1. The electron and muon decay channels of the W and Z are used. The total cross sections are measured for photon transverse energy ETγ>10 GeV and spatial separation from charged leptons in the plane of pseudorapidity and azimuthal angle ΔR(ℓ,γ)>0.7, and with an additional dilepton invariant mass requirement of Mℓℓ>50 GeV for the Zγ process. The following cross section times branching fraction values are found: σ(pp→Wγ+X)×B(W→ℓν)=56.3±5.0(stat.)±5.0(syst.)±2.3(lumi.) pb and σ(pp→Zγ+X)×B(Z→ℓℓ)=9.4±1.0(stat.)±0.6(syst.)±0.4(lumi.) pb. These measurements are in agreement with standard model predictions. The first limits on anomalous WWγ, ZZγ, and Zγγ trilinear gauge couplings at s=7 TeV are set

Measurement of the production cross section for Z gamma -> nu(nu)over-bar gamma in pp collisions at root s=7 TeV and limits on ZZ gamma and Z gamma gamma triple gauge boson couplings

A measurement of the Z gamma -> nu(nu) over bar gamma cross section in pp collisions at root s = 7 TeV is presented, using data corresponding to an integrated luminosity of 5.0 fb(-1) collected with the CMS detector. This measurement is based on the observation of events with an imbalance of transverse energy in excess of 130 GeV and a single photon in the absolute pseudorapidity range vertical bar eta vertical bar nugamma production cross section is measured to be 21.1 +/- 4.2(stat.)+/- 4.3(syst.)+/- 0.5(lum.)fb, which agrees with the standard model prediction of 21.9 +/- 1.1 fb. The results are combined with the CMS measurement of Z gamma production in the l(+)l(-)gamma final state (where l is an electron or a muon) to yield the most stringent limits to date on triple gauge boson couplings. vertical bar h(3)(Z)vertical bar < 2.7 x 10(-3), vertical bar h(4)(Z)vertical bar < 1.3 x 10(-5) for ZZ gamma and vertical bar h(3)(gamma)vertical bar < 2.9 x 10(-3), vertical bar h(4)(gamma)vertical bar < 1.5 x 10(-5) for Z gamma gamma couplings

Measurement of the ratio of the 3-jet to 2-jet cross sections in pp collisions at s=7 TeV

AbstractA measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum, HT, in the range 0.2<HT<2.5 TeV is presented. The data have been collected at a proton–proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb−1. Comparisons are made between the data and the predictions of different QCD-based Monte Carlo models for multijet production. All models considered in this study are consistent with the data for HT>0.5 TeV. This measurement extends to an HT range that has not been explored before