Measurement of the charge ratio of atmospheric muons with the CMS detector

We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interactions in the atmosphere, using data collected by the CMS detector both at ground level and in the underground experimental cavern at the CERN LHC. Muons were detected in the momentum range from 5 GeV/c to 1 TeV/c . The surface flux ratio is measured to be 1.2766±0.0032(stat.)±0.0032(syst.), independent of the muon momentum, below 100 GeV/c. This is the most precise measurement to date. At higher momenta the data are consistent with an increase of the charge ratio, in agreement with cosmic ray shower models and compatible with previous measurements by deep-underground experiments.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC

Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (η) and azimuthal angle (ϕ). Short-range correlations in Δη, which are studied in minimum bias events, are characterized using a simple “independent cluster” parametrization in order to quantify their strength (cluster size) and their extent in η (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb[superscript −1] data set at 7 TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate p [subscript T] of 1–3 GeV/c, 2.0 < |Δη| < 4.8 and Δϕ ≈ 0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or p[−over]p collisions

Search for supersymmetry in pp collisions at 7 TeV in events with jets and missing transverse energy

A search for supersymmetry with R-parity conservation in proton–proton collisions at a centre-of-mass energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 pb[superscript -1] collected by the CMS experiment at the LHC. The search is performed in events with jets and significant missing transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary background, from standard model multijet production, is reduced by several orders of magnitude to a negligible level by the application of a set of robust kinematic requirements. With this selection, the data are consistent with the standard model backgrounds, namely t [bar over t], W + jet and Z + jet production, which are estimated from data control samples. Limits are set on the parameters of the constrained minimal supersymmetric extension of the standard model. These limits extend those set previously by experiments at the Tevatron and LEP colliders.European Organization for Nuclear ResearchUnited States. Dept. of EnergyNational Science Foundation (U.S.

Search for microscopic black hole signatures at the Large Hadron Collider

A search for microscopic black hole production and decay in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 pb[superscript −1]. Events with large total transverse energy are analyzed for the presence of multiple high-energy jets, leptons, and photons, typical of a signal expected from a microscopic black hole. Good agreement with the standard model backgrounds, dominated by QCD multijet production, is observed for various final-state multiplicities and model-independent limits on new physics in these final states are set. Using simple semi-classical approximation, limits on the minimum black hole mass are derived as well, in the range 3.5–4.5 TeV. These are the first direct limits on black hole production at a particle accelerator.European Organization for Nuclear ResearchNational Science Foundation (U.S.)United States. Dept. of Energ

Measurement of the differential dijet production cross section in proton–proton collisions at √s = 7 TeV

A measurement of the double-differential inclusive dijet production cross section in proton–proton collisions at √s = 7 TeV is presented as a function of the dijet invariant mass and jet rapidity. The data correspond to an integrated luminosity of 36 pb[superscript −1], recorded with the CMS detector at the LHC. The measurement covers the dijet mass range 0.2 TeV to 3.5 TeV and jet rapidities up to |y|=2.5. It is found to be in good agreement with next-to-leading-order QCD predictions.United States. Dept. of EnergyNational Science Foundation (U.S.

Searches for heavy Higgs bosons in two-Higgs-doublet models and for t → c h decay using multilepton and diphoton final states in p p collisions at 8 TeV

Searches are presented for heavy scalar (H) and pseudoscalar (A) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of pp collisions collected with the CMS experiment at the LHC at a center-of-mass energy of root s = 8 TeV and corresponding to an integrated luminosity of 19.5 fb(-1). The decays H - GT hh and A - GT Zh, where h denotes an SM-like Higgs boson, lead to events with three or more isolated charged leptons or with a photon pair accompanied by one or more isolated leptons. The search results are presented in terms of the H and A production cross sections times branching fractions and are further interpreted in terms of 2HDM parameters. We place 95% C.L. cross section upper limits of approximately 7 pb on sigma B for H - GT hh and 2 pb for A - GT Zh. Also presented are the results of a search for the rare decay of the top quark that results in a charm quark and an SM Higgs boson, t - GT ch, the existence of which would indicate a nonzero flavor-changing Yukawa coupling of the top quark to the Higgs boson. We place a 95% C.L. upper limit of 0.56% on B(t - GT ch)

Final states with 3rd generation quarks @ 13 TeV (resonant or not)

A wide variety of new physics models gives rise to final states with third-generation quarks. This note presents new results for some of these models using 13 TeV proton-proton collisions at the CERN LHC. Direct production of third-generation supersymmetric superpartners and vector-like quarks are discussed. Also the searches looking for resonances with third-generation quarks are covered. None of the searches discussed here shows an indication of new physics and the new exclusion limits are presented

SUSY searches for EWK Production of Gauginos and Sleptons at the LHC

The searches for direct electroweak production of supersymmetric particles produced in proton-proton collisions at the LHC are presented. The focus is on gaugino and slepton production, which yield final states with two or more leptons. A wide variety of complimentary searches are discussed with none of them shows any indication for physics beyond the standard model

W cross section measurement in the electron channel in pp collisions at [the square root of sigma]= 7 TeV

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.In title on title page, "the square root of sigma" appears as the mathematical symbol, and "sigma" appears as the lower-case Greek letter. Cataloged from PDF version of thesis.Includes bibliographical references (p. 165-172).From March until November 2010 the Compact Muon Solenoid 36 pb-1 of pp collisions at [the square root of sigma]= 7 TeV. One of the first precision Model that can be performed with this data is the measurement cross section and the charge asymmetry in the cross section. measurements are performed in the electron decay channel. The experiment recorded tests of the Standard of the W-production In this thesis, both results obtained are: [sigma](W -> ev) = 10.48 ± 0.03(stat.) 0.15(syst.) ± 0.09(th.) ± 0.42(lumi.)nb [sigma](W+ -> e+v, U(W+ - ez) = 1.430 ± 0.008(stat.) ± 0.022(syst.) ± 0.029(th.) [sigma](W- ->e-v) The measurements agree with state-of-the-art NNLO QCD calculations with the latest parton distribution functions.by Pieter Bruno Bart Everaerts.Ph.D

Commissioning and performance of the CMS silicon strip tracker with cosmic ray muons

During autumn 2008, the Silicon Strip Tracker was operated with the full CMS experiment in a comprehensive test, in the presence of the 3.8 T magnetic field produced by the CMS superconducting solenoid. Cosmic ray muons were detected in the muon chambers and used to trigger the readout of all CMS sub-detectors. About 15 million events with a muon in the tracker were collected. The efficiency of hit and track reconstruction were measured to be higher than 99% and consistent with expectations from Monte Carlo simulation. This article details the commissioning and performance of the Silicon Strip Tracker with cosmic ray muons