We present a measurement of the muon charge asymmetry from the decay of the $W$ boson via W to mu nu using 7.3 fb^{-1} of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider at sqrt{s} = 1.96 TeV. The muon charge asymmetry is presented in two kinematic regions in muon transverse momentum and event missing transverse energy: (p^{\mu}_{T} > 25 GeV, \met > 25 GeV) and (p^{\mu}_{T} > 35 GeV, \met > 35 GeV). The measured asymmetries are compared with theory predictions made using three parton distribution function sets. The predictions do not describe the data well for p^{\mu}_{T} > 35 GeV, \met > 35 GeV, and larger values of muon pseudorapidity.
We present the first measurement of the inclusive three-jet differential cross section as a function of the invariant mass of the three jets with the largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96 TeV. The measurement is made in different rapidity regions and for different jet transverse momentum requirements and is based on a data set corresponding to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at the Fermilab Tevatron Collider. The results are used to test the three-jet matrix elements in perturbative QCD calculations at next-to-leading order in the strong coupling constant. The data allow discrimination between parametrizations of the parton distribution functions of the proton.
We present the first combined measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations, based on the recently proposed quantity $R_{\Delta \phi}$. The variable $R_{\Delta \phi}$ measures the fraction of the inclusive dijet events in which the azimuthal separation of the two jets with the highest transverse momenta is less than a specified value for the parameter $\Delta \phi_{\rm max}$. The quantity $R_{\Delta \phi}$ is measured in $p\bar{p}$ collisions at $\sqrt{s}=1.96\,$TeV, as a function of the dijet rapidity interval, the total scalar transverse momentum, and $\Delta \phi_{\rm max}$. The measurement uses an event sample corresponding to an integrated luminosity of $0.7\,$fb$^{-1}$ collected with the D0 detector at the Fermilab Tevatron Collider. The results are compared to predictions of a perturbative QCD calculation at next-to-leading order in the strong coupling with corrections for non-perturbative effects. The theory predictions describe the data, except in the kinematic region of large dijet rapidity intervals and large $\Delta \phi_{\rm max}$.
We present measurements of the differential cross section $d\sigma/dp_{T}^{\gamma}$ for the associated production of a $c$-quark jet and an isolated photon with rapidity $|y^{\gamma}|< 1.0$ and transverse momentum $30 < p_{T}^{\gamma} < 300$ GeV. The $c$-quark jets are required to have $|y^{jet}| < 1.5$ and $p_{T}^{jet} >15$ GeV. The ratio of differential cross sections for photon+ c and photon+ b production as a function of $p_{T}^{\gamma}$ is also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=$1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the $k_{T}$-factorization approach, and to predictions from the Sherpa and Pythia Monte Carlo event generators.
We present a measurement of the ratio of multijet cross sections in pp-bar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R3/2, has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the PYTHIA event generator do not agree with the data, while SHERPA provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects, gives a good description of the data.
We measure the ratio of cross sections, {\sigma}(ppbar -> Z + b jet)/{\sigma}(ppbar -> Z + jet), for associated production of a Z boson with at least one jet. The ratio is also measured as a function of the jet transverse momentum, jet pseudorapidity, Z boson transverse momentum, and the azimuthal angle between the Z boson and the closest jet for events with at least one b jet. These measurements use data collected by the D0 experiment in Run II of Fermilab's Tevatron ppbar Collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of 9.7 fb$^{-1}$. The results are compared to predictions from next-to-leading order calculations and various Monte Carlo event generators.
We present a measurement of the elastic differential cross section $d\sigma(p\bar{p}\rightarrow p\bar{p})/dt$ as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of $\approx 31 nb^{-1}$ collected with the D0 detector using dedicated Tevatron $p\bar{p} $ Collider operating conditions at sqrt(s) = 1.96 TeV and covers the range $0.26 <|t|< 1.2 GeV^2$. For $|t|<0.6 GeV^2$, d\sigma/dt is described by an exponential function of the form $Ae^{-b|t|}$ with a slope parameter $ b = 16.86 \pm 0.10(stat) \pm 0.20(syst) GeV^{-2}$. A change in slope is observed at $|t| \approx 0.6 GeV^2$, followed by a more gradual |t| dependence with increasing values of |t|.
We report on the analysis of Charmonium and Bottomium states produced in p-Si interactions at s =38.7 GeV . The data have been collected with the open geometry spectrometer of the E771 Experiment at the FNAL High Intensity Lab. J ψ , ψ′ and γ total cross sections as well as the ratio B(ψ′ → μμ)σ(ψ′) (B( J ψ → μμ)σ( J ψ )) have been measured. Results are compared with theoretical predictions and with results at other energies.
We study the process of associated photon and jet production, p+pbar --> photon + jet + X, using 8.7 fb^-1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider at a center-of-mass energy sqrt{s}=1.96 TeV. Photons are reconstructed with rapidity |y^gamma| <1.0 or 1.5<|y^{gamma}| < 2.5 and transverse momentum pT^gamma GeV. The highest-p_T jet is required to be in one of four rapidity regions up to |y^{jet}|< 3.2. For each rapidity configuration we measure the differential cross sections in pT_gamma separately for events with the same sign (y^{gamma} y^{jet}}>0) and opposite sign (y^{gamma} y^{jet}<=0) of photon and jet rapidities. We compare the measured triple differential cross sections, d^3 sigma / d pT_gamma y^{gamma} y^{jet}, to next-to-leading order (NLO) perturbative QCD calculations using different sets of parton distribution functions and to predictions from the SHERPA and PYTHIA Monte Carlo event generators. The NLO calculations are found to be in general agreement with the data, but do not describe all kinematic regions.
The production of $\Xi(1321)^{-}$ and $\overline{\Xi}(1321)^{+}$ hyperons in inelastic p+p interactions is studied in a fixed target experiment at a beam momentum of 158 GeV/textitc. Double differential distributions in rapidity y and transverse momentum $p_{T}$ are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both $\Xi^{-}$ and $\overline{\Xi}^{+}$. The rapidity and transverse momentum spectra are compared to transport model predictions. The $\Xi^{-}$ mean multiplicity in inelastic p+p interactions at 158~\GeVc is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.