Measurements of the muon charge asymmetry in inclusive pp to WX production at sqrt(s) = 7 TeV are presented. The data sample corresponds to an integrated luminosity of 4.7 inverse femtobarns recorded with the CMS detector at the LHC. With a sample of more than twenty million W to mu nu events, the statistical precision is greatly improved in comparison to previous measurements. These new results provide additional constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10E-3 to 10E-1. These measurements and the recent CMS measurement of associated W + charm production are used together with the cross sections for inclusive deep inelastic ep scattering at HERA in a next-to-leading-order QCD analysis. The determination of the valence quark distributions is improved, and the strange-quark distribution is probed directly through the leading-order process g + s to W + c in proton-proton collisions at the LHC.
Summary of the final results for muon charge asymmetry $\mathcal{A}$ with the muon $p_{T}>25$ GeV. The first uncertainty is statistical and the second is systematic. The theoretical predictions are obtained using the FEWZ 3.1 MC tool interfaced with the NLO CT10, NNPDF2.3, HERAPDF1.5, and MSTW2008CPdeut PDF sets. The PDF uncertainty is at 68% C.L. The values are expressed as percentages.
Summary of the final results for muon charge asymmetry $\mathcal{A}$ with the muon $p_{T}>35$ GeV. The first uncertainty is statistical and the second is systematic. The theoretical predictions are obtained using the FEWZ 3.1 MC tool interfaced with the NLO CT10, NNPDF2.3, HERAPDF1.5, and MSTW2008CPdeut PDF sets. The PDF uncertainty is at 68% C.L. The values are expressed as percentages.
Covariance matrix (statistical and systematic uncertainties combined) with the muon $p_{T}>25$ GeV. The units are in $10^{-4}$.
Double parton scattering is investigated in proton-proton collisions at sqrt(s) = 7 TeV where the final state includes a W boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 inverse femtobarns, collected with the CMS detector at the LHC. Observables sensitive to double parton scattering are investigated after being corrected for detector effects and selection efficiencies. The fraction of W + 2-jet events due to double parton scattering is measured to be 0.055 +/- 0.002 (stat.) +/- 0.014 (syst.). The effective cross section, sigma[eff], characterizing the effective transverse area of hard partonic interactions in collisions between protons is measured to be 20.7 +/- 0.8 (stat.) +/- 6.6 (syst.) mb.
Visible cross section for W+2 jet: one muon $(p_{T} > 35.0~GeV/c~\ |\eta|~<~2.1)$ missing transverse energy $> 30.0 GeV$ Transverse Mass (W) $> 50.0 GeV$ excatly two jets $(p_{T} > 20.0~GeV/c \; |\eta|~<~2.0)$.
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Inclusive ep double differential cross sections for neutral current deep inelastic scattering are measured with the H1 detector at HERA. The data were taken with a lepton beam energy of 27.6 GeV and two proton beam energies of Ep = 460 and 575 GeV corresponding to centre-of-mass energies of 225 and 252 GeV, respectively. The measurements cover the region of 6.5 *10^{-4}<=x<= 0.65 for 35<=Q^2<=800 GeV^2 up to y = 0.85. The measurements are used together with previously published H1 data at Ep = 920 GeV and lower Q2 data at Ep = 460, 575 and 920 GeV to extract the longitudinal proton structure function FL in the region 1.5<=Q^2 <=800 GeV^2.
The neutral current reduced cross section at Q^2=35 GeV^2 for a proton energy of 460 GeV.
The neutral current reduced cross section at Q^2=45 GeV^2 for a proton energy of 460 GeV.
The neutral current reduced cross section at Q^2=60 GeV^2 for a proton energy of 460 GeV.
The neutral current e+/-p cross section has been measured up to values of Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated luminosity of 187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) = 318GeV. Differential cross sections in x and Q2, the exchanged boson virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method and greatly increased amount of data allows a finer binning in the high-x region of the neutral current cross section and leads to a measurement with much improved precision compared to a similar earlier analysis. The measurements are compared to Standard Model expectations based on a variety of recent parton distribution functions.
Double differential cross section for Q^2=725 GeV^2.
Double differential cross section for Q^2=875 GeV^2.
Double differential cross section for Q^2=1025 GeV^2.
The production of jets associated to bottom quarks is measured for the first time in PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair. Jet spectra are reported in the transverse momentum (pt) range of 80-250 GeV, and within pseudorapidity abs(eta < 2). The nuclear modification factor (R[AA]) calculated from these spectra shows a strong suppression in the b-jet yield in PbPb collisions relative to the yield observed in pp collisions at the same energy. The suppression persists to the largest values of pt studied, and is centrality dependent. The R[AA] is about 0.4 in the most central events, similar to previous observations for inclusive jets. This implies that jet quenching does not have a strong dependence on parton mass and flavor in the jet pt range studied.
The b-jet yield as a function of pT is for the 0-100% centrality class of PbPb collisions. The yields are scaled by the equivalent number of minimum bias events sampled and by TAA.
The b-jet yield as a function of pT is for the 0-10% centrality class of PbPb collisions. The yields are scaled by the equivalent number of minimum bias events sampled and by TAA.
The b-jet yield as a function of pT is for the 10-30% centrality class of PbPb collisions. The yields are scaled by the equivalent number of minimum bias events sampled and by TAA.
Double-differential dijet cross sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of dijet mass and rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5/fb, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross sections are presented at the particle level. Cross sections are measured up to 5 TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6. The cross sections are compared with next-to-leading-order perturbative QCD calculations by NLOJET++ corrected to account for non-perturbative effects. Comparisons with POWHEG predictions, using a next-to-leading-order matrix element calculation interfaced to a parton-shower Monte Carlo simulation, are also shown. Electroweak effects are accounted for in both cases. The quantitative comparison of data and theoretical predictions obtained using various parameterizations of the parton distribution functions is performed using a frequentist method. An example setting a lower limit on the compositeness scale for a model of contact interactions is presented, showing that the unfolded results can be used to constrain contributions to dijet production beyond that predicted by the Standard Model.
Measured double-differential dijet cross sections for the range 0.0 <= y* < 0.5 and jet radius parameter R = 0.4. The statistical uncertainties from data and MC simulation have been combined. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
Measured double-differential dijet cross sections for the range 0.5 <= y* < 1.0 and jet radius parameter R = 0.4. The statistical uncertainties from data and MC simulation have been combined. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
Measured double-differential dijet cross sections for the range 1.0 <= y* < 1.5 and jet radius parameter R = 0.4. The statistical uncertainties from data and MC simulation have been combined. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
We report measurements of Upsilon meson production in p+p, d+Au, and Au+Au collisions using the STAR detector at RHIC. We compare the Upsilon yield to the measured cross section in p+p collisions in order to quantify any modifications of the yield in cold nuclear matter using d+Au data and in hot nuclear matter using Au+Au data separated into three centrality classes. Our p+p measurement is based on three times the statistics of our previous result. We obtain a nuclear modification factor for Upsilon(1S+2S+3S) in the rapidity range |y|<1 in d+Au collisions of R_dAu = 0.79 +/- 0.24 (stat.) +/- 0.03 (sys.) +/- 0.10 (pp sys.). A comparison with models including shadowing and initial state parton energy loss indicates the presence of additional cold-nuclear matter suppression. Similarly, in the top 10% most-central Au+Au collisions, we measure a nuclear modification factor of R_AA=0.49 +/- 0.1 (stat.) +/- 0.02 (sys.) +/- 0.06 (pp sys.), which is a larger suppression factor than that seen in cold nuclear matter. Our results are consistent with complete suppression of excited-state Upsilon mesons in Au+Au collisions. The additional suppression in Au+Au is consistent with the level expected in model calculations that include the presence of a hot, deconfined Quark-Gluon Plasma. However, understanding the suppression seen in d+Au is still needed before any definitive statements about the nature of the suppression in Au+Au can be made.
Invariant mass distributions of electron pairs in the region $|y_{ee}| < 0.5$, p+p.
Invariant mass distributions of electron pairs in the region $|y_{ee}| < 0.5$, d+Au.
(a) $B_{ee} \times d\sigma/dy$ vs. $y$ for p+p collisions and for d+Au collisions (scaled down by 103).
We present a measurement of the $W$ boson production charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center of mass energy of 1.96 TeV, using 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum is determined using a neutrino weighting method, and the asymmetry is measured as a function of the $W$ boson rapidity. The measurement extends over wider electron pseudorapidity region than previous results, and is the most precise to date, allowing for precise determination of proton parton distribution functions in global fits.
${\it CP}$-folded $W$ charge asymmetry for data and predictions from MC@NLO using NNPDF2.3 PDFs tabulated in percent (%) for each $|y_W|$ bin. The $\langle|y_W|\rangle$ is calculated as the cross section weighted average of $y_W$ in each bin from RESBOS with photos. For data, the first uncertainty is statistical and the second is systematic. The uncertainties on the prediction come from both the PDF uncertainties and $\alpha_s$ uncertainties. The numbers in this table are the revised data published on 10th December 2014 (after the journal publication).
Correlation coefficients between central values of asymmetry in different $|y_W|$ bins.
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 inverse femtobarns and was collected at sqrt(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.
The distribution of HT for all channels combined after the full selection except for the HT requirement itself.
Expected and observed 95% CL limits on the $\mathrm{T}_{5/3}$ production cross section times the branching fraction for decay to same-sign dileptons.
The distribution of HT for all channels combined, after the requirement of same- sign dileptons, the Z-boson veto, and a requirement of at least two jets.
Measurements of transverse-single-spin asymmetries ($A_{N}$) in $p$$+$$p$ collisions at $\sqrt{s}=$62.4 and 200 GeV with the PHENIX detector at RHIC are presented. At midrapidity, $A_{N}$ is measured for neutral pion and eta mesons reconstructed from diphoton decay, and at forward rapidities, neutral pions are measured using both diphotons and electromagnetic clusters. The neutral-pion measurement of $A_{N}$ at midrapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, where the valence quark distributions are probed, the data exhibit sizable asymmetries. In comparison with previous measurements in this kinematic region, the new data extend the kinematic coverage in $\sqrt{s}$ and $p_T$, and it is found that the asymmetries depend only weakly on $\sqrt{s}$. The origin of the forward $A_{N}$ is presently not understood quantitatively. The extended reach to higher $p_T$ probes the transition between transverse momentum dependent effects at low $p_T$ and multi-parton dynamics at high $p_T$.
Neutral pion $A_N$ at $\sqrt{s} = 62.4$ GeV as a function of $x_F$ in pseudorapidity $3.1 < |\eta| < 3.5$, with statistical and systematic uncertainties.
Neutral pion $A_N$ at $\sqrt{s} = 62.4$ GeV as a function of $x_F$ in pseudorapidity $3.5 < |\eta| < 3.8$, with statistical and systematic uncertainties.
Neutral pion $A_N$ at $\sqrt{s}$ = 62.4 GeV as function of transverse momentum $p_T$.
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