The production of Z bosons is studied in the dimuon and dielectron decay channels in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV, using data collected by the CMS experiment at the LHC. The PbPb data sample corresponds to an integrated luminosity of about 150 inverse microbarns, while the pp data sample collected in 2013 at the same nucleon-nucleon centre-of-mass energy has an integrated luminosity of 5.4 inverse picobarns. The Z boson yield is measured as a function of rapidity, transverse momentum, and collision centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic nucleon-nucleon collisions, is found to be 1.06 +/- 0.05 (stat) +/- 0.08 (syst) in the dimuon channel and 1.02 +/- 0.08 (stat) +/- 0.15 (syst) in the dielectron channel, for centrality-integrated Z boson production. This binary collision scaling is seen to hold in the entire kinematic region studied, as expected for a colourless probe that is unaffected by the hot and dense QCD medium produced in heavy ion collisions.
The measured Z boson production cross section in pp collisions as a function of the Z boson pT for the dimuon decay channel in |y|<2.0.
The measured Z boson production cross section in pp collisions as a function of the Z boson pT for the dielectron decay channel in |y|<1.44.
The measured Z boson production cross section in pp collisions as a function of the Z boson rapidity for the dimuon decay channel.
The ratio between the prompt psi(2S) and J/psi yields, reconstructed via their decays into muon pairs, is measured in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV. The analysis is based on PbPb and pp data samples collected by CMS at the LHC, corresponding to integrated luminosities of 150 inverse microbarns and 5.4 inverse picobarns, respectively. The double ratio of measured yields, (N[psi(2S)]/N[J/psi])[PbPb] / (N[psi(2S)]/ N[J/psi])[pp], is computed in three PbPb collision centrality bins and two kinematic ranges: one at midrapidity, abs(y) < 1.6, covering the transverse momentum range 6.5 < pt < 30 GeV/c, and the other at forward rapidity, 1.6 < abs(y) < 2.4, extending to lower pt values, 3 < pt < 30 GeV/c. The centrality-integrated double ratio changes from 0.45 +/- 0.13 (stat) +/- 0.07 (syst) in the first range to 1.67 +/- 0.34 (stat) +/- 0.27 (syst) in the second. This difference is most pronounced in the most central collisions.
Double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, as a function of centrality, for the midrapidity analysis bin.
Double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, as a function of centrality, for the forward rapidity analysis bin.
Double ratio of measured yields, $(N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{\mathrm{PbPb}} / (N_{\psi\mathrm{(2S)}} / N_{J/\psi})_{pp}$, integrated over centrality, for the midrapidity and forward rapidity analysis bins.
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pt) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 inverse femtobarns. The measured cross sections are compared to predictions from Monte Carlo generators, MADGRAPH + PYTHIA and SHERPA, and to next-to-leading-order calculations from BLACKHAT + SHERPA. The differential cross sections are found to be in agreement with the predictions, apart from the pt distributions of the leading jets at high pt values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.
The cross section measurement as a function of the exclusive jet multiplicity, for jet multiplicities of up to 6.
The cross section measurement as a function of the inclusive jet multiplicity, for jet multiplicities of up to 6.
The differential cross section measurement as a function of the transverse momentum of the first leading jet.
The first observation of $Z$ boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of $\sqrt{s_{NN}}=5~\text{TeV}$ is presented. The data sample corresponds to an integrated luminosity of $1.6~\text{nb}^{-1}$ collected with the LHCb detector. The $Z$ candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above $20~\text{GeV}/c$. The invariant dimuon mass is restricted to the range $60-120~\text{GeV}/c^2$. The $Z$ production cross-section is measured to be \begin{eqnarray*} \sigma_{Z\to\mu^+\mu^-}(\text{fwd})&=&13.5^{+5.4}_{-4.0}\text{(stat.)}\pm1.2\text{(syst.)}~\text{nb} \end{eqnarray*} in the direction of the proton beam and \begin{eqnarray*} \sigma_{Z\to\mu^+\mu^-}(\text{bwd}) & =&10.7^{+8.4}_{-5.1}\text{(stat.)}\pm1.0\text{(syst.)}~\text{nb} \end{eqnarray*} in the direction of the lead beam, where the first uncertainty is statistical and the second systematic.
The measured Z production cross-sections in proton-lead collisions, measured in the fiducial region defined in the table, in the forward and backward directions. The statistical uncertainty is defined as the 68% confidence interval with symmetric coverage assuming that the number of candidates follows a Poisson distribution.
The forward-backward ratio measured in the overlap region 2.5 < ABS(YRAP) < 4.0. The first uncertainty is statistical, defined as the 68% confidence interval with symmetric coverage. The second uncertainty is systematic and includes the uncertainty on the acceptance correction factor, BETA, for the difference in the detector acceptance of the muons between the forward and backward directions.
Production of prompt J/$\psi$ meson pairs in proton-proton collisions at $\sqrt{s}$ = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 inverse-femtobarns. The two J/$\psi$ mesons are fully reconstructed via their decays into $\mu^+\mu^-$ pairs. This observation provides for the first time access to the high-transverse-momentum region of J/$\psi$ pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/$\psi$ transverse momentum ($p_T^{J/\psi}$) and rapidity (|$y^{J/\psi}$|): |$y^{J/\psi}$| lower than 1.2 for $p_T^{J/\psi}$ greater than 6.5 GeV/c; |$y^{J/\psi}$| in [1.2,1.43] for a $p_T$ threshold that scales linearly with |$y^{J/\psi}$| from 6.5 to 4.5 GeV/c; and |$y^{J/\psi}$| in [1.43,2.2] for $p_T^{J/\psi}$ greater than 4.5 GeV/c. The total cross section, assuming unpolarized prompt J/$\psi$ pair production is 1.49 $\pm$ 0.07 (stat.) $\pm$ 0.13 (syst.) nb. Different assumptions about the J/$\psi$ polarization imply modifications to the cross section ranging from -31% to +27%.
Differential cross section D(SIG)/DM(J/PSI J/PSI) in bins of the J/PSI pair invariant mass, M(J/PSI J/PSI).
Differential cross section D(SIG)/DABS(DELTA(YRAP)) in bins of the absolute rapidity difference between J/PSI mesons, ABS(DELTA(YRAP)).
Differential cross section D(SIG)/DPT(J/PSI J/PSI) in bins of the transverse momentum of the J/PSI pair, PT(J/PSI J/PSI).
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low mass vector meson, $\omega$, $\rho$, and $\phi$, production through the dimuon decay channel at forward rapidity ($1.2<|y|<2.2$) in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The differential cross sections for these mesons are measured as a function of both $p_T$ and rapidity. We also report the integrated differential cross sections over $1<p_T<7$ GeV/$c$ and $1.2<|y|<2.2$: $d\sigma/dy(\omega+\rho\rightarrow\mu\mu) = 80 \pm 6 \mbox{(stat)} \pm 12 \mbox{(syst)}$ nb and $d\sigma/dy(\phi\rightarrow\mu\mu) = 27 \pm 3 \mbox{(stat)} \pm 4 \mbox{(syst)}$ nb. These results are compared with midrapidity measurements and calculations.
Differential cross sections of (OMEGA + RHO) and PHI as functions of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
Differential cross sections of (OMEGA + RHO) and PHI as functions of rapidity. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
N(PHI) / ( N(OMEGA) + N(RHO) ) as a function of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
The ArgoNeuT collaboration presents measurements of inclusive muon neutrino and antineutrino charged current differential cross sections on argon in the Fermilab NuMI beam operating in the low energy antineutrino mode. The results are reported in terms of outgoing muon angle and momentum at a mean neutrino energy of 9.6 GeV (neutrinos) and 3.6 GeV (antineutrinos), in the range $0^\circ < \theta_\mu < 36^\circ$ and $0 < p_\mu < 25$ GeV/$c$, for both neutrinos and antineutrinos.
The measured differential cross sections in muon angle for CC NUMU and NUMUBAR interactions in argon, per argon nucleus. Both statistical and total errors are shown.
The measured differential cross sections in muon momentum for CC NUMU and NUMUBAR interactions in argon, per argon nucleus. Both statistical and total errors are shown.
We measure the inclusive forward-backward asymmetry of the charged-lepton pseudorapidities from top-quark pairs produced in proton-antiproton collisions, and decaying to final states that contain two charged leptons (electrons or muons), using data collected with the Collider Detector at Fermilab. With an integrated luminosity of 9.1 $\rm{fb}^{-1}$, the leptonic forward-backward asymmetry, $A_{\text{FB}}^{\ell}$, is measured to be $0.072 \pm 0.060$ and the leptonic pair forward-backward asymmetry, $A_{\text{FB}}^{\ell\ell}$, is measured to be $0.076 \pm 0.082$, compared with the standard model predictions of $A_{\text{FB}}^{\ell} = 0.038 \pm 0.003$ and $A_{\text{FB}}^{\ell\ell} = 0.048 \pm 0.004$, respectively. Additionally, we combine the $A_{\text{FB}}^{\ell}$ result with a previous determination from a final state with a single lepton and hadronic jets and obtain $A_{\text{FB}}^{\ell} = 0.090^{+0.028}_{-0.026}$.
The leptonic forward-backward asymmetry.
The leptonic pair forward-backward asymmetry.
The leptonic forward-backward asymmetry calculated as the combination of the current asymmetry measurement and a previous CDF measurement.
The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton + jets decay channels using data corresponding to an integrated luminosity of 5.0 inverse femtobarns. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the t t-bar production is determined as a function of the additional jet multiplicity in the lepton + jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
Normalised differential TOP TOPBAR production cross section as a function of the jet multiplicity for jets with PT(JET) > 30 GeV in the dilepton channel. The statistical and main experimental and model systematic uncertainties are displayed.
Normalised differential TOP TOPBAR production cross section as a function of the jet multiplicity for jets with PT(JET) > 60 GeV in the dilepton channel. The statistical and main experimental and model systematic uncertainties are displayed.
Normalised differential TOP TOPBAR production cross section as a function of the jet multiplicity for jets with PT(JET) > 35 GeV in the lepton+jets channel. The statistical and main experimental and model systematic uncertainties are displayed.
The ratio of the top-quark branching fractions $R = B(t \to Wb)/B(t \to Wq)$, where the denominator includes the sum over all down-type quarks (q = b, s, d), is measured in the $t\bar{t}$ dilepton final state with proton-proton collision data at $\sqrt{s}$ = 8 TeV from an integrated luminosity of 19.7 inverse-femtobarns, collected with the CMS detector. In order to quantify the purity of the signal sample, the cross section is measured by fitting the observed jet multiplicity, thereby constraining the signal and background contributions. By counting the number of b jets per event, an unconstrained value of R = 1.014 $\pm$ 0.003 (stat) $\pm$ 0.032 (syst) is measured, in good agreement with the standard model prediction. A lower limit R greater than 0.955 at the 95% confidence level is obtained after requiring R lower than one, and a lower limit on the Cabibbo-Kobayashi-Maskawa matrix element |$V_tb$| greater than 0.975 is set at 95% confidence level. The result is combined with a previous CMS measurement of the t-channel single-top-quark cross section to determine the top-quark total decay width, $\Gamma_t$ = 1.36 $\pm$ 0.02 (stat)$^{+0.14}_{-0.11}$ (syst) GeV.
The measured TOP TOPBAR production cross section.
The measured ratio of branching fractions, R = BR(TOP --> W BOTTOM) / BR(TOP --> W QUARK) where the denominator includes the sum over all down-type quarks (QUARK = BOTTOM, STRANGE, DOWN). The combined measurement and the individual measurements from the three channels considered are presented.
An indirect measurement of the top-quark total decay width.
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