Search for new physics in the multijet and missing transverse momentum final state in proton-proton collisions at √s=8 Tev

Peer reviewe

Search for a non-standard-model Higgs boson decaying to a pair of new light bosons in four-muon final states

Results are reported from a search for non-standard-model Higgs boson decays to pairs of new light bosons, each of which decays into the mu(+)mu(-) final state. The new bosons may be produced either promptly or via a decay chain. The data set corresponds to an integrated luminosity of 5.3 fb(-1) of proton-proton collisions at root s = 7 TeV, recorded by the CMS experiment at the LHC in 2011. Such Higgs boson decays are predicted in several scenarios of new physics, including supersymmetric models with extended Higgs sectors or hidden valleys. Thus, the results of the search are relevant for establishing whether the new particle observed in Higgs boson searches at the LHC has the properties expected for a standard model Higgs boson. No excess of events is observed with respect to the yields expected from standard model processes. A model-independent upper limit of 0.86 +/- 0.06 fb on the product of the cross section times branching fraction times acceptance is obtained. The results, which are applicable to a broad spectrum of new physics scenarios, are compared with the predictions of two benchmark models as functions of a Higgs boson mass larger than 86 GeV/c(2) and of a new light boson mass within the range 0.25-3.55 GeV/c(2). (C) 2013 CERN. Published by Elsevier B.V. All rights reserved

Searches for Higgs bosons in pp collisions at root s=7 and 8 TeV in the context of four-generation and fermiophobic models

Searches are reported for Higgs bosons in the context of either the standard model extended to include a fourth generation of fermions (SM4) with masses of up to 600 GeV or fermiophobic models. For the former, results from three decay modes (tau tau, WW, and ZZ) are combined, whilst for the latter the diphoton decay is exploited. The analysed proton-proton collision data correspond to integrated luminosities of up to 5.1 fb(-1) at 7 TeV and up to 5.3 fb(-1) at 8 TeV. The observed results exclude the SM4 Higgs boson in the mass range 110-600 GeV at 99% confidence level (CL), and in the mass range 110-560 GeV at 99.9% CL. A fermiophobic Higgs boson is excluded in the mass range 110-147 GeV at 95% CL, and in the range 110-133 GeV at 99% CL. The recently observed boson with a mass near 125 GeV is not consistent with either an SM4 or a fermiophobic Higgs boson. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved

Search for new physics in final states with a lepton and missing transverse energy in pp collisions at the LHC

This Letter describes the search for an enhanced production rate of events with a charged lepton and a neutrino in high-energy pp collisions at the LHC. The analysis uses data collected with the CMS detector, with an integrated luminosity of 5.0 fb(-1) at root s = 7 TeV, and a further 3.7 fb(-1) at root s = 8 TeV. No evidence is found for an excess. The results are interpreted in terms of limits on a heavy charged gauge boson (W') in the sequential standard model, a split universal extra dimension model, and contact interactions in the helicity-nonconserving model. For the last, values of the binding energy below 10.5 (8.8) TeV in the electron (muon) channel are excluded at a 95% confidence level. Interpreting the l(nu) final state in terms of a heavy W' with standard model couplings, masses below 2.90 TeV are excluded. DOI: 10.1103/PhysRevD.87.07200

Studies of jet mass in dijet and W/Z plus jet events

Invariant mass spectra for jets reconstructed using the anti-k(T) and Cambridge-Aachen algorithms are studied for different jet "grooming" techniques in data corresponding to an integrated luminosity of 5 fb(-1), recorded with the CMS detector in proton-proton collisions at the LHC at a center-of-mass energy of 7 TeV. Leading-order QCD predictions for inclusive dijet and W/Z+jet production combined with parton-shower Monte Carlo models are found to agree overall with the data, and the agreement improves with the implementation of jet grooming methods used to distinguish merged jets of large transverse momentum from softer QCD gluon radiation

Search for Top-Quark Partners with Charge 5/3 in the Same-Sign Dilepton Final State

A search for the production of heavy partners of the top quark with charge 5/3 is performed in events with a pair of same-sign leptons. The data sample corresponds to an integrated luminosity of 19.5 fb(-1) and was collected at root s = 8 TeV by the CMS experiment. No significant excess is observed in the data above the expected background, and the existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level, assuming they decay exclusively to tW. This is the first limit on these particles from the LHC, and it is significantly more restrictive than previous limits

Search for fractionally charged particles in pp collisions at root s=7 TeV

A search is presented for free heavy long-lived fractionally charged particles produced in pp collisions at root s = 7 TeV. The data sample was recorded by the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb(-1). Candidate fractionally charged particles are identified by selecting tracks with associated low charge measurements in the silicon tracking detector. Observations are found to be consistent with expectations for background processes. The results of the search are used to set upper limits on the cross section for pair production of fractionally charged, massive spin-1/2 particles that are neutral under SU(3)(C) and SU(2)(L). We exclude at 95% confidence level such particles with electric charge +/- 2e/3 with masses below 310 GeV, and those with charge +/- e/3 with masses below 140 GeV

Searches for long-lived charged particles in pp collisions at root s=7 and 8 TeV

Results of searches for heavy stable charged particles produced in pp collisions at root s = 7 and 8 TeV are presented corresponding to an integrated luminosity of 5.0 fb(-1) and 18.8 fb(-1), respectively. Data collected with the CMS detector are used to study the momentum, energy deposition, and time-of-flight of signal candidates. Leptons with an electric charge between e/3 and 8e, as well as bound states that can undergo charge exchange with the detector material, are studied. Analysis results are presented for various combinations of signatures in the inner tracker only, inner tracker and muon detector, and muon detector only. Detector signatures utilized are long time-of-flight to the outer muon system and anomalously high (or low) energy deposition in the inner tracker. The data are consistent with the expected background, and upper limits are set on the production cross section of long-lived gluinos, scalar top quarks, and scalar tau leptons, as well as pair produced long-lived leptons. Corresponding lower mass limits, ranging up to 1322 GeV/c(2) for gluinos, are the most stringent to date

Measurement of the elliptic anisotropy of charged particles produced in PbPb collisions at root s(NN)=2.76 TeV

The anisotropy of the azimuthal distributions of charged particles produced in root s(NN) = 2.76 TeV PbPb collisions is studied with the CMS experiment at the LHC. The elliptic anisotropy parameter, upsilon(2), defined as the second coefficient in a Fourier expansion of the particle invariant yields, is extracted using the event-plane method, two- and four-particle cumulants, and Lee-Yang zeros. The anisotropy is presented as a function of transverse momentum (p(T)), pseudorapidity (eta) over a broad kinematic range, 0.3 < p(T) < 20 GeV/c, vertical bar eta vertical bar < 2.4, and in 12 classes of collision centrality from 0 to 80%. The results are compared to those obtained at lower center-of-mass energies, and various scaling behaviors are examined. When scaled by the geometric eccentricity of the collision zone, the elliptic anisotropy is found to obey a universal scaling with the transverse particle density for different collision systems and center-of-mass energies. DOI: 10.1103/PhysRevC.87.01490

Search for the standard model Higgs boson produced in association with a W or a Z boson and decaying to bottom quarks

A search for the standard model Higgs boson (H) decaying to b (b) over bar when produced in association with a weak vector boson (V) is reported for the following channels: W(mu nu)H, W(e nu)H, W(tau nu)H, Z(mu mu)H, Z(ee)H and Z(nu nu)H. The search is performed in data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at root s = 7 TeV and up to 18.9 fb(-1) at root s = 8 TeV, recorded by the CMS experiment at the LHC. An excess of events is observed above the expected background with a local significance of 2.1 standard deviations for a Higgs boson mass of 125 GeV, consistent with the expectation from the production of the standard model Higgs boson. The signal strength corresponding to this excess, relative to that of the standard model Higgs boson, is 1.0 +/- 0.5