The magnetic form factor of the neutron, G(n,M), from the deuteron(electron,electron\u27neutron)proton reaction

We measured the d(e,e\sp\primen)p cross-section at three values of Q\sp2: 0.255, 0.176 and 0.109 (GeV/c)\sp2. The electrons were detected with the OHIPS magnetic spectrometer, and the neutrons were detected in a liquid mineral oil scintillator array. The measurement were made at a fixed neutron angle of \theta\sb{n} = 57\sp\circ; the Q\sp2 values were obtained by varying the incident electron energy and the scattering angle. These cross sections are sensitive primarily to the neutron magnetic form factor at these quasifree kinematics. The efficiency of the neutron detector was determined by the associated particle technique with the d($\gamma$,pn) reaction for each of the three neutron kinetic energies. The value of G\sbsp{M}{n} extracted from the cross sections are consistent with the dipole parametrization at the two higher momentum transfers; at the lowest momentum transfer the value of G\sbsp{M}{n} is 10% higher than the dipole model. This enhancement at low momentum transfer is consistent with previous measurements

Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

Constraints are presented on the total width of the recently discovered Higgs boson, ΓH, using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1fb−1at a center-of-mass energy √s=7TeVand 19.7fb−1at √s=8TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of ΓH\u3c22MeVat a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of mH=125.6GeV

Search for pair-produced resonances decaying to jet pairs in proton–proton collisions at √s=8TeV

Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4fb−1of integrated luminosity from proton–proton collisions at a center-of-mass energy of 8TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. The first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350GeV at 95% confidence level. Previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835GeV

Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies

Measurements of two-particle angular correlations between an identified strange hadron (K0Sor Λ/Λ) and a charged particle, emitted in pPb collisions, are presented over a wide range in pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 35nb−1, were collected at a nucleon–nucleon center-of-mass energy (√sNN) of 5.02TeV with the CMS detector at the LHC. The results are compared to semi-peripheral PbPb collision data at √sNN=2.76TeV, covering similar charged-particle multiplicities in the events. The observed azimuthal correlations at large relative pseudorapidity are used to extract the second-order (v2) and third-order (v3) anisotropy harmonics of K0Sand Λ/Λparticles. These quantities are studied as a function of the charged-particle multiplicity in the event and the transverse momentum of the particles. For high-multiplicity pPb events, aclear particle species dependence of v2and v3is observed. For pT\u3c2GeV, the v2and v3values of K0Sparticles are larger than those of Λ/Λparticles at the same pT. This splitting effect between two particle species is found to be stronger in pPbthan in PbPbcollisions in the same multiplicity range. When divided by the number of constituent quarks and compared at the same transverse kinetic energy per quark, both v2and v3for K0Sparticles are observed to be consistent with those for Λ/Λparticles at the 10% level in pPbcollisions. This consistency extends over a wide range of particle transverse kinetic energy and event multiplicities

Study of W boson production in pPb collisions at √sNN=5.02TeV

The first study of W boson production in pPb collisions is presented, for bosons decaying to a muon or electron, and a neutrino. The measurements are based on a data sample corresponding to an integrated luminosity of 34.6nb−1at a nucleon–nucleon centre-of-mass energy of √sNN=5.02TeV, collected by the CMS experiment. The W boson differential cross sections, lepton charge asymmetry, and forward–backward asymmetries are measured for leptons of transverse momentum exceeding 25GeV/c, and as a function of the lepton pseudorapidity in the |ηlab| \u3c2.4range. Deviations from the expectations based on currently available parton distribution functions are observed, showing the need for including W boson data in nuclear parton distribution global fits

Determination of the top-quark pole mass and strong coupling constant from the t t-bar production cross section in pp collisions at sqrt(s) = 7 TeV

The inclusive cross section for top-quark pair production measured by the CMS experiment in proton–proton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, m[pole over t], or the strong coupling constant, α[subscript S]. With the parton distribution function set NNPDF2.3, a pole mass of 176.7[+3.8 over −3.4] GeV is obtained when constraining α[subscript S] at the scale of the Z boson mass, m[subscript Z], to the current world average. Alternatively, by constraining m[pole over t] to the latest average from direct mass measurements, a value of α[subscript S](m[subscript Z])= 0.1151[+0.0033 over −0.0032] is extracted. This is the first determination of α[subscript S] using events from top-quark production

Search for lepton-flavour-violating decays of the Higgs boson

The first direct search for lepton-flavour-violating decays of the recently discovered Higgs boson (H) is described. The search is performed in the H →μτeand H →μτhchannels, where τeand τhare tau leptons reconstructed in the electronic and hadronic decay channels, respectively. The data sample used in this search was collected in pp collisions at a centre-of-mass energy of √s=8TeVwith the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 19.7fb−1. The sensitivity of the search is an order of magnitude better than the existing indirect limits. A slight excess of signal events with a significance of 2.4 standard deviations is observed. The p-value of this excess at MH=125GeVis 0.010. The best fit branching fraction is B(H →μτ) =(0.84+0.39−0.37)%. A constraint on the branching fraction, B(H →μτ) \u3c1.51%at 95% confidence level is set. This limit is subsequently used to constrain the μ–τYukawa couplings to be less than 3.6 ×10−3

Search for narrow high-mass resonances in proton–proton collisions at √s=8TeVdecaying to a Z and a Higgs boson

A search for a narrow, high-mass resonance decaying into Z and Higgs (H) bosons is presented. The final state studied consists of a merged jet pair and a τpair resulting from the decays of Z and Hbosons, respectively. The analysis is based on a data sample of proton–proton collisions at a center-of-mass energy of 8TeV, collected with the CMS experiment in 2012, and corresponding to an integrated luminosity of 19.7fb−1. In the resonance mass range of interest, which extends from 0.8 to 2.5TeV, the Z and H bosons are produced with large momenta, which implies that the final products of the two quarks or the two τleptons must be detected within a small angular interval. From a combination of all possible decay modes of the τleptons, production cross sections in a range between 0.9 and 27.8fb are excluded at 95% confidence level, depending on the resonance mass

Search for excited quarks in the γ+jet final state in proton–proton collisions at √s=8TeV

A search for excited quarks decaying into the γ+jetfinal state is presented. The analysis is based on data corresponding to an integrated luminosity of 19.7fb−1collected by the CMS experiment in proton–proton collisions at √s=8TeVat the LHC. Events with photons and jets with high transverse momenta are selected and the γ+jetinvariant mass distribution is studied to search for a resonance peak. The 95% confidence level upper limits on the product of cross section and branching fraction are evaluated as a function of the excited quark mass. Limits on excited quarks are presented as a function of their mass and coupling strength; masses below 3.5TeV are excluded at 95% confidence level for unit couplings to their standard model partners

Search for quark contact interactions and extra spatial dimensions using dijet angular distributions in proton–proton collisions at √s=8TeV

A search is presented for quark contact interactions and extra spatial dimensions in proton–proton collisions at √s=8TeVusing dijet angular distributions. The search is based on a data set corresponding to an integrated luminosity of 19.7fb−1collected by the CMS detector at the CERN LHC. Dijet angular distributions are found to be in agreement with the perturbative QCD predictions that include electroweak corrections. Limits on the contact interaction scale from a variety of models at next-to-leading order in QCD corrections are obtained. A benchmark model in which only left-handed quarks participate is excluded up to a scale of 9.0 (11.7)TeV for destructive (constructive) interference at 95% confidence level. Lower limits between 5.9 and 8.4TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed–Dimopoulos–Dvali model of extra spatial dimensions