Combination of inclusive and differential tt‾\mathrm{t}\overline{\mathrm{t}} charge asymmetry measurements using ATLAS and CMS data at s=\sqrt{s} = 7 and 8 TeV

This paper presents combinations of inclusive and differential measurements of the charge asymmetry ($A_{\mathrm{C}}$) in top quark pair ($\mathrm{t}\overline{\mathrm{t}}$) events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV corresponding to integrated luminosities of about 5 and 20 fb$^{-1}$ for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are $A_{\mathrm{C}}^{\mathrm{LHC7}} = 0.005 \pm0.007 \text{ (stat)}\pm0.006 \text{ (syst)}$ at 7 TeV and $A_{\mathrm{C}}^{\mathrm{LHC8}} = 0.0055 \pm0.0023\text{ (stat)}\pm0.0025\text{ (syst)}$ at 8 TeV. These values, as well as the combination of $A_{\mathrm{C}}$ measurements as a function of the invariant mass of the $\mathrm{t}\overline{\mathrm{t}}$ system at 8 TeV, are consistent with the respective standard model predictions.Comment: Replaced with the published version. Figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/TOP-15-016 (CMS Public Pages) and https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2016-16 (ATLAS pages

Measurements of identified particles at intermediate transverse momentum in the STAR experiment from Au+Au collisions at sqrt{s_{NN}}=200 GeV

Data for Au+Au collisions at sqrt{s_{NN}}=200 GeV are analyzed to determine the ratios of identified hadrons ($\pi$, $K$, $p$, $\Lambda$) as functions of collision centrality and transverse momentum ($p_T$). We find that ratios of anti-baryon to baryon yields are independent of $p_T$ up to 5 GeV/c, a result inconsistent with results of theoretical pQCD calculations that predict a decrease due to a stronger contribution from valence quark scattering. For both strange and non-strange species, strong baryon enhancements relative to meson yields are observed as a function of collision centrality in the intermediate $p_T$ region, leading to $p/\pi$ and $\Lambda$/K ratios greater than unity. The increased $p_T$ range offered by the $\Lambda$/K$^{0}_{S}$ ratio allows a test of the applicability of various models developed for the intermediate $p_{T}$ region. The physics implications of these measurements are discussed with regard to different theoretical models.Comment: Submitted to PR

Combination of Differential D^{*\pm} Cross-Section Measurements in Deep-Inelastic ep Scattering at HERA

H1 and ZEUS have published single-differential cross sections for inclusive D^{*\pm}-meson production in deep-inelastic ep scattering at HERA from their respective final data sets. These cross sections are combined in the common visible phase-space region of photon virtuality Q2 > 5 GeV2, electron inelasticity 0.02 < y < 0.7 and the D^{*\pm} meson's transverse momentum pT (D^*) > 1.5 GeV and pseudorapidity |eta(D^*)| < 1.5. The combination procedure takes into account all correlations, yielding significantly reduced experimental uncertainties. Double-differential cross sections d2s /dQ2dy are combined with earlier D^{*\pm} data, extending the kinematic range down to Q2 > 1.5 GeV2. Perturbative next-to-leadingorder QCD predictions are compared to the results.Comment: 37 pages, 14 figures, 9 tables, published: JHEP 09(2015)14

Combination of Measurements of Inclusive Deep Inelastic e±pe^{\pm}p Scattering Cross Sections and QCD Analysis of HERA Data

A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current $e^{\pm}p$ scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb$^{-1}$ and span six orders of magnitude in negative four-momentum-transfer squared, $Q^2$, and Bjorken $x$. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in $\alpha_s(M_Z)=0.1183 \pm 0.0009 {\rm(exp)} \pm 0.0005{\rm (model/parameterisation)} \pm 0.0012{\rm (hadronisation)} ^{+0.0037}_{-0.0030}{\rm (scale)}$. An extraction of $xF_3^{\gamma Z}$ and results on electroweak unification and scaling violations are also presented.Comment: 159 pages, 83 figures. Updated version as accepted for publication. Small corrections and reordering of table

Single and Pair Production of Neutral Electroweak Gauge Bosons at LEP

Recent LEP results on single and pair production of neutral electroweak gauge bosons are reviewed. QED and Electroweak gamma-e Compton scattering at LEP covers gamma-e center-of-mass energies sqrt{shat} in the range from about 20 GeV to 170 GeV, and leads to single production of on-shell gamma, off-shell gamma*, and Z bosons, also known as ``Zee'' process. The latter two final states have been observed for the first time by the OPAL collaboration, while the measurement of the scattered on-shell gamma's by L3 represents the highest energies at which QED Compton scattering has been studied so far. These processes can be used to set limits on excited electrons. Pair production of gamma* and/or Z at the e+e- center-of-mass energy sqrt{s}=183 GeV has been studied by the DELPHI, L3, and OPAL collaborations. The combination of these experiments yields the first significant measurement of Z pair production. With more statistics at higher energies, interesting limits on anomalous gammaZZ and ZZZ couplings can be derived from this process.Comment: 6 pages, 10 figures, talk given at ICHEP-98, Vancouve

Discovery potential at the LHC: channels relevant for SM Higgs

The discovery potential of Standard Model Higgs searches at the LHC at 14 TeV center-of-mass energy is reviewed. Decay channels such as $H\to\gamma\gamma$, $H\to ZZ^{\star}\to 4\ell$, $H\to WW^{\star}$ and $H\to \tau\tau$ are considered. Results are based on the most recent full GEANT-based simulations performed by the ATLAS and CMS experiments.Comment: 5 pages, three figures, Proceedings of ISMD08 Conference, Hamburg, Germany, September 200

Status of 2+1 flavor, 32^3x64 domain wall fermion simulations

We describe details of 1/a ~ 2.2Gev, L ~ 3 fm dynamical domain wall fermion simulations which will allow us to do a more systematic continuum extrapolation in combination with existing simu- lations. Details of the simulations such as algorithm choices and machine performance, as well as results of basic measurements are presented. These configurations are presently being generated on the QCDOC machine at Edinburgh and the DOE QCDOC machine at Brookhaven as part of a joint project with LHPC.Comment: 7 pages, presented at the 25th International Symposium on Lattice Field Theory, 30 Jul - 4 Aug 2007, Regensburg, German

Search for Physics beyond Standard Model at HERA

Recent results on searches for signals of physics beyond Standard Model at the ep collider HERA are reviewed. Limits obtained for contact interaction models, large extra dimensions and finite quark radius are presented. Searches for excited-fermion resonances yield unique limits on excited electrons and neutrinos. Finally, measurement of W production cross section in ep collision is presented.Comment: 3 pages, 5 figures, proceedings prepared for SUSY08 conference, to be published by AI

Electroweak Physics at HERA

Neutral-current (NC) and charged-current (CC) deep inelastic scattering (DIS) interactions have been studied in electron-proton and positron-proton collisions with longitudinally polarised lepton beams using the H1 and ZEUS detectors at HERA. Measurements of the polarised inclusive cross-sections are presented and compared to the Standard Model (SM) expectations. The extraction of several electroweak parameters using a combined EW-QCD fit of unpolarised data is also discussed.Comment: 7 pages, 7 figures, Presented at 41th Rencontres de Moriond, Electroweak Interactions and Unified Theories, La Thuile, Italy, March 11 - 18, 200

Combination and QCD analysis of charm and beauty production cross-section measurements in deep inelastic epep scattering at HERA

Measurements of open charm and beauty production cross sections in deep inelastic $ep$ scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon $2.5$ GeV$^2<Q^2<2000$ GeV$^2$ and Bjorken scaling variable $3\cdot10^{-5}<x_{\text{Bj}}<5\cdot10^{-2}$. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as $m_c(m_c) = 1.290^{+0.046}_{-0.041}\text{(exp/fit)}^{+0.062}_{-0.014}\text{(model)}^{+0.003}_{-0.031}\text{(parameterisation)}$ GeV and $m_b(m_b) = 4.049^{+0.104}_{-0.109}\text{(exp/fit)}^{+0.090}_{-0.032}\text{(model)}^{+0.001}_{-0.031} \text{(parameterisation)}$~GeV.Comment: 58 pages, 22 figures, submitted to EPJ