The mass spectrum of muon pairs in the range 5 to 15 GeV is studied in the inclusive reaction p+nucleus→μ++μ−+anything. The ϒ and continuum distribution are presented as is the A dependence of the continuum. Comparison with a parton-annihilation model yields a sea-quark distribution.

We report final results of a series of measurements of continuum dimuon production in proton-nucleus collisions at Fermilab. New results with 6 times more statistics are included. A full description of the apparatus and methods used in the analysis of this series of measurements is given. The sea quark distribution of the nucleon is determined within the context of Drell-Yan and quantum-chromodynamic description of dilepton production in hadron collisions.

The production of the ϒ family in proton-nucleus collisions is clarified by a sixfold increase in statistics. Constraining ϒ,ϒ′ masses to those observed at DORIS we find the statistical significance of the ϒ′′ to be 11 standard deviations. The dependence of ϒ production on pt, y, and s is presented. Limits for other resonance production in the mass range 4-18 GeV are determined.

We present proton-nucleus dimuon-production cross sections for masses between 4 and 15 GeV, center-of-mass rapidities between -0.23 and 0.6 and incident energies of 200, 300, and 400 GeV. The data confirm scaling to the 20% level. The dependence of continuum 〈pT〉 on beam energy is also presented.

We present measurements of the production symmetric high-mass hadron and pion pairs by protons of 200, 300, and 400 GeV, incident on a beryllium target. The two-particle invariant cross section for pion production can be described by the function E1E2d6σdp13dp23=(1.7×10−28)pt−8.4(1−xt)14 cm2/GeV4 (where pt is the mean pt of the two hadrons). Functions of the same form have been used in describing single-pion inclusive production. Equality of the exponents of pt in the two processes is observed, confirming the role of smearing contributions to single-hadron cross sections.

Nucleon structure functions obtained from neutrino and anti-neutrino scattering on iron nuclei at high energies (Ev=30 to 250 GeV) are presented. These results are compared with the results of other lepton-nucleon scattering experiments. The structure functions are used to test the validity of the Gross-Llewellyn-smith sum rule, which measures the number of valence quarks in the nucleons, and to obtain leading and second order QCD fits.

The energy dependence of the cross section for neutrino- and antineutrino-nucleon charged-current interactions has been determined from data taken in Fermilab's dichromatic neutrino beam. σνE=(0.669±0.003±0.024)×10−38 cm2/GeV and σν¯E=(0.340±0.003±0.02)×10−38 cm2/GeV are found. These results are higher than some previous measurements.

Measurements of flux-normalized neutrino and antineutrino total charged-current cross sections (σ) in the energy range 45<E<205 GeV are presented. We see no evidence for the anomalous sharp rise in σν¯σν reported by earlier authors. The neutrino cross section rises linearly with energy and with σE about 18% smaller than other measurements below 10 GeV. The average antineutrino slope at 55 GeV is consistent with measurements at low energy; however, a (20 ± 10)% increase is indicated over our energy range.

We present results on flux-normalized neutrino and antineutrino cross sections near y=0 from data obtained in the Fermilab narrow-band beam. We conclude that values of σ0=dσdy|y=0 are consistent with rising linearly with energy over the range 45<~Eν<~20.5 GeV. The separate averages of ν and ν¯, each measured to 4%, are equal to well within the errors. The best fit for the combined data gives σ0E=(0.719±0.035)×10−38 cm2/GeV at an average Eν of 100 GeV.

We report a measurement of the electroweak parameters sin2θw and ϱ based on the ratios of neutral current to charged current events measured in the Fermilab narrow-band neutrino beam at energies of 30–240 GeV. The data are fully corrected for radiative effects, heavy-quark production, and other effects. The best value for sin2θw obtained, sin2θw=0.239±0.011, is consistent with the most recent values fromW andZ production, as well as from other neutrino experiments.

We report an improved measurement of the inverse muon decay process, ν μ +e→ μ − + ν e , at the Fermilab Tevatron. The rate of this reaction with respect to the ν μ -N charged current interaction is measured to be (0.1245±0.0057(stat.)±0.0031 (sys.)) × 10 −2 . The measurement confirms the standard model predictions for the Lorentz structure of the weak current, the helicity of the neutrino, and the energy dependence of the cross section.

This paper reports on measurements of the total cross section for the inclusive reaction vμ+N, as a function of incident energy. Neutrinos and antineutrinos with energy in the range 3

We present measured hadron energy distributions for the reactions ν(ν¯)+N→ν(ν¯)+hadrons at high energy, as well as for the similar charged-current interactions. Insofar as possible, the determination of these distributions avoids any a priori assumptions about either the neutral-current or the charged-current interactions. We further analyze the neutral-current distributions within the framework of specific models, particularly the scaling model, to obtain a positive-helicity component P=0.36±0.10, which lies between pure V−A and pure V or A, and a coupling strength of g0=0.31±0.03 relative to the charged-current interaction. These coupling parameters agree well with the predictions of the Weinberg-Salam model with sin2θW=0.33±0.07.

The CCFR Collaboration presents a measurement of scaling violations of the nonsinglet structure function and a comparison to the predictions of perturbative QCD. The value of ΛQCD, from the nonsinglet evolution with Q2>15 GeV2 and in the modified minimal-subtraction renormalization scheme, is found to be 210±28(stat)±41(syst) MeV.

We have measured the strange-quark content of the nucleon, ηs=−0.08+0.012, and the Kobayashi-Maskawa matrix element ‖Vcd‖=0.220−0.018+0.015 using a sample of 1797 νμ- and ν¯μ-induced μ−μ+ events with Pμ≥9 GeV/c and 30≤Eν≤600 GeV. The data are consistent with the slow-rescaling hypothesis of charm production in ν-N scattering and within this formalism yield a value of the charm-quark mass parameter mc=1.31−0.48+0.64 GeV/c2. .AE

A high-statistics study by the Columbia-Chicago-Fermilab-Rochester Collaboration of opposite-sign dimuon events induced by neutrino-nucleon scattering at the Fermilab Tevatron is presented. A sample of 5044 νμ and 1062 ν¯μ induced μ∓μ± events with Pμ1≥9 GeV/c, Pμ2≥5 GeV/c, 30≤Eν≤600 GeV, and 〈Q2〉=22.2 GeV2/c2 is observed. The data support the slow-rescaling model of charm production with a value of mc=1.31±0.24 GeV2/c2. The first measurement of the Q2 dependence of the nucleon strange quark distribution xs(x) is presented. The data yield the Cabibbo-Kobayashi-Maskawa matrix element ‖Vcd‖=0.209±0.012 and the nucleon fractional strangeness content ηs=0.064−0.007+0.008.

In a sample of 670 000 charged-current neutrino events, 101 μ−μ− events have been observed, with 30 GeV<Eν<600 GeV and Pμ>9 GeV/c for both muons. After background subtraction, 18.5±13.9 events remain, yielding a prompt rate of (5.5±4.1)×10−5 per charged-current event. A sample of 124 000 antineutrino events yields 15 μ+μ+ events, giving 6.4±4.2 events after background subtraction and a prompt rate of (1.0±0.7)×10−4 per charged-current event. The numbers and kinematic distributions of these events are consistent with standard model sources.

We present results for the reactions νp→μ−π+p and νp→μ−K+p at energies above 5 GeV. The average cross section for the first reaction between 15 and 40 GeV is (0.80±0.12) × 10−38 cm2 and for events with Mπ+p<1.4 GeV is (0.55±0.08) × 10−38 cm2. The ratio of the cross section for the second reaction to that for the first is 0.017±0.010.

The forward production of charm states in 350 GeV p-Fe interactions has been studied via the production of prompt single muons with momentum p ≳ 20 GeV/ c . The data indicate equal production of single μ + and μ − events. The observed momentum distributions can be fit with the hypothesis that D mesons are produced with an invariant cross section proportional to (1 − x F ) 5.0±0.8 exp[−(2 ± 0.3) P t ] and do not favor a large diffractive cross section predicted by intrinsic charm models. Extrapolation of the distributions to x F = 0 yields a total D D production cross section of 22.6 ± 2.1(±3.6)ωb/nucleon on the assumption of a linear A dependence and 8% average semileptonic branching ratio of charm states.

We report a precise measurement of the weak mixing angle from the ratio of neutral current to charged current inclusive cross-sections in deep-inelastic neutrino-nucleon scattering. The data were gathered at the CCFR neutrino detector in the Fermilab quadrupole-triplet neutrino beam, with neutrino energies up to 600 GeV. Using the on-shell definition, ${\rm sin ~2\theta_W} \equiv 1 - \frac{{\rm M_W} ~2}{{\rm M_Z} ~2}$, we obtain ${\rm sin ~2\theta_W} = 0.2218 \pm 0.0025 ({\rm stat.}) \pm 0.0036 ({\rm exp.\: syst.}) \pm 0.0040 ({\rm model})$.

We have studied D* production mechanisms using data from a photoproduction experiment at the Fermilab Tagged Photon Spectrometer. A large sample of charged D*’s was selected via the clean signature of the cascade decay D*→D0π+ and subsequently D0→K−π+ or D0→K−π+π0. The cross section for the process γp→(D*++anything)p at an average energy of 105 GeV was measured to be 88±32 nb. Only (11±7)% of D*’s were found to be consistent with being accompanied solely by a D¯* or a D¯; the remaining events contain additional particles. The distribution of the production angle of the D* in the photon-fragmentation-system center of mass is strongly anisotropic and consistent with the form f(θ*)=cos4θ*. We set a limit on the associated-production-process cross section σ(γp→(D¯*−+anything)Λc) x)<60 nb (90% C.L.).

Inelastic and elastic $J/\psi$ photoproduction on hydrogen are investigated at a mean energy of 105 GeV. The inelastic cross section with $E_{\psi} / E_{\gamma}$ < 0.9 is significantly lower than the corresponding result for muoproduction on iron targets, but is consistent with a second-order perturbative QCD calculation.

We present a measurement of the cross sections for the associated production of a $W$ boson with at least one heavy quark jet, $b$ or $c$, in proton-antiproton collisions. Data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron \ppbar Collider at $\sqrt{s}=1.96$ TeV are used to measure the cross sections differentially as a function of the jet transverse momenta in the range 20 to 150 GeV. These results are compared to calculations of perturbative QCD theory as well as predictions from Monte Carlo generators.

We present a measurement of the distribution of the variable $\phi^*_\eta$ for muon pairs with masses between 30 and 500 GeV, using the complete Run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4 fb$^{-1}$ at $\sqrt{s}$ = 1.96 TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable $\phi^*_\eta$ probes the same physical effects as the $Z/\gamma^*$ boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the $\phi^*_\eta$ distributions for dilepton masses away from the $Z\rightarrow \ell^+\ell^-$ boson mass peak. The data are compared to QCD predictions based on the resummation of multiple soft gluons.

We present a measurement of the electron 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 data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.

We measure the forward-backward asymmetry in the production of $\Lambda_b^0$ and $\overline \Lambda_b^0$ baryons as a function of rapidity in $p \overline p $ collisions at $\sqrt s =1.96$ TeV using $10.4$ fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. The asymmetry is determined by the preference of $\Lambda_b^0$ or $\overline \Lambda_b^0$ particles to be produced in the direction of the beam protons or antiprotons, respectively. The measured asymmetry integrated over rapidity $y$ in the range $0.1<|y|<2$ is $A=0.04 \pm 0.07 {\rm (stat)} \pm 0.02 {\rm (syst)}$.

The ν¯μ charged-current total cross section has been measured with the Fermilab 15-ft bubble chamber plus the external muon identifier and internal "picket fence." Beam monitoring information used for the flux calculation was obtained from Blair et al., whose detector operated in the same dichromatic beam. The present result, averaged over ν¯μ energies from 5 to 250 GeV, is σE=(0.340±0.019±0.022)×10−38 cm2/(GeV nucleon) for an isoscalar target.

We present a measurement of the forward--backward asymmetry in top quark-antiquark production using the full Tevatron Run II dataset collected by the D0 experiment at Fermilab. The measurement is performed in lepton+jets final states using a new kinematic fitting algorithm for events with four or more jets and a new partial reconstruction algorithm for events with only three jets. Corrected for detector acceptance and resolution effects, the asymmetry is evaluated to be 10.6+-3.0 %. Results are consistent with the standard model predictions which range from 5.0% to 8.8%. We also present the dependence of the asymmetry on the invariant mass of the top quark--antiquark system and the difference in rapidities of top quark and antiquark.

The production of top quark-antiquark pair events in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the $t\bar{t}$ pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified to originate from a $b$ quark. The data sample corresponds to 9.7 fb$^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.

We determine the fraction of events with double parton (DP) scattering in a single ppbar collision at sqrt{s}=1.96 TeV in samples of photon + 3 jet and photon + b/c jet + 2 jet events collected with the D0 detector and corresponding to an integrated luminosity of about 8.7 fb^{-1}. The DP fractions and effective cross sections (sigma_eff) are measured for both event samples using the same kinematic selections. The measured DP fractions range from 0.21 to 0.17, with effective cross sections in the photon + 3 jet and photon + b/c jet + 2 jet samples of sigma_eff^incl = 12.7 +- 0.2 (stat) +- 1.3 (syst) mb and sigma_eff^HF = 14.6 +- 0.6 (stat) +- 3.2 (syst) mb, respectively.

We present measurements of the forward-backward asymmetry in the angular distribution of leptons from decays of top quarks and antiquarks produced in proton-antiproton collisions. We consider the final state containing a lepton and at least three jets. The entire sample of data collected by the D0 experiment during Run II of the Fermilab Tevatron Collider, corresponding to 9.7 inverse fb of integrated luminosity, is used. The asymmetry measured for reconstructed leptons is $A_{FB}^l = \big(2.9 \pm 2.1(stat.) ^{+1.5}_{-1.7}(syst.) \big)$%. When corrected for efficiency and resolution effects within the lepton rapidity coverage of $|y_l|<1.5$, the asymmetry is found to be $A_{FB}^l = \big(4.2 \pm 2.3(stat.) ^{+1.7}_{-2.0}(syst.) \big)$%. Combination with the asymmetry measured in the dilepton final state yields $A_{FB}^l = \big(4.2 \pm 2.0(stat.) \pm 1.4(syst.) \big)$%. We examine the dependence of $A_{FB}^l$ on the transverse momentum and rapidity of the lepton. The results are in agreement with predictions from the next-to-leading-order QCD generator \mcatnlo, which predicts an asymmetry of $A_{FB}^l = 2.0$% for $|y_l|<1.5$.

We have examined the inclusive production of nonstrange particle resonances in νp interactions using the Fermilab 15-ft bubble chamber. A sample of 2437 charged-current events with visible longitudinal momentum greater than 10 GeV/c was obtained. The ρ0 and Δ++(1232) are seen. An overall rate of 0.21±0.04 ρ0 per event is found. For five-prong events, the rate is 0.44±0.08 ρ0 per event. The ρ0Z distribution falls rapidly for Z greater than 0.4. The production of Δ++ is seen clearly in events with an identified proton. No evidence is seen for Δ0 production. An upper limit of 0.34 is placed on the ratio of ηπ0 (90% confidence level).

Samples of inclusive photon+2 jet and photon+3 jet events collected by the D0 experiment with an integrated luminosity of about 1fb^-1 in ppbar collisions at sqrt{s}=1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (pT) of the photon+leading jet system (jets are ordered in pT) and pT of the other jet for photon+2 jet, or pT sum of the two other jets for photon+3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well described by predictions provided by the PYTHIA MPI models with pT-ordered showers and by SHERPA with the default MPI model. The photon+2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet pT.

We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb-1 per experiment. The measured cross section is $\sigma_s = 1.29^{+0.26}_{-0.24}$ pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is $1.8 \times 10^{-10}$, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.

We present the first measurement of the form factor ratios g1/f1 (direct axial-vector to vector), g2/f1 (second class current) and f2/f1 (weak magnetism) for the decay Xi0 -> Sigma+ e- anti-nu/e using the KTeV (E799) beam line and detector at Fermilab. From the Sigma+ polarization measured with the decay Sigma+ -> p pi0 and the e- - anti-nu/e correlation, we measure g1/f1 to be 1.32 +0.21-0.17(stat.) +/- 0.05(syst.), assuming the SU(3)f (flavor) values for g2/f1 and f2/f1. Our results are all consistent with exact SU(3)f symmetry.

An experiment to measure the electromagnetic form factor of the negative π meson has been carried out at Fermilab by elastically scattering 100-GeV/c pions from the atomic electrons in a liquid-hydrogen target. We find that the elastic differential scattering cross section is characterized by a root-mean-square pion charge radius of 0.56±0.04 fm. This paper described our experimental design, measurement resolutions, event triggering logic, event reconstruction, experimental corrections, and form-factor results.

We have measured the electromagnetic form factor of the charged pion by direct scattering of 100-GeV/c π− from stationary electrons in a liquid-hydrogen target at Fermilab. The deviations from the pointlike pion-scattering cross section may be characterized by a root-mean-square charge radius for the pion of 〈rπ2〉12=0.56±0.04 F.

We present the first measurements of the differential cross section $d\sigma/dp_{T}^{\gamma}$ for the production of an isolated photon in association with at least two $b$-quark jets. The measurements consider photons with rapidities $|y^\gamma| < 1.0$ and transverse momenta $30 < p_{T}^{\gamma} < 200$~\GeV. The $b$-quark jets are required to have $p_T^{jet}>15$ GeV and $| y^{jet}| < 1.5$. The ratio of differential production cross sections for $\gamma+2~b$-jets to $\gamma+b$-jet as a function of $p_{T}^{\gamma}$ is also presented. The results are based on the proton-antiproton collision data at $\sqrt{s}=$1.96~\TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next-to-leading order perturbative QCD calculations as well as predictions based on the $k_{T}$-factorization approach and those from the SHERPA and PYTHIA Monte Carlo event generators.

We study $\Lambda$ and $\bar{\Lambda}$ production asymmetries in $p \bar{p} \rightarrow \Lambda (\bar{\Lambda}) X$, $p \bar{p} \rightarrow J/\psi \Lambda (\bar{\Lambda}) X$, and $p \bar{p} \rightarrow \mu^\pm \Lambda (\bar{\Lambda}) X$ events recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV. We find an excess of $\Lambda$'s ($\bar{\Lambda}$'s) produced in the proton (antiproton) direction. This forward-backward asymmetry is measured as a function of rapidity. We confirm that the $\bar{\Lambda}/\Lambda$ production ratio, measured by several experiments with various targets and a wide range of energies, is a universal function of "rapidity loss", i.e., the rapidity difference of the beam proton and the lambda.

We measure the forward-backward asymmetries $A_{\rm FB}$ of charged $\Xi$ and $\Omega$ baryons produced in $p \bar{p}$ collisions recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV as a function of the baryon rapidity $y$. We find that the asymmetries $A_{\rm FB}$ for charged $\Xi$ and $\Omega$ baryons are consistent with zero within statistical uncertainties.

The inclusive cross section of top quark-antiquark pairs produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is measured in the lepton$+$jets and dilepton decay channels. The data sample corresponds to 9.7 fb${}^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Employing multivariate analysis techniques we measure the cross section in the two decay channels and we perform a combined cross section measurement. For a top quark mass of 172.5 GeV, we measure a combined inclusive top quark-antiquark pair production cross section of $\sigma_{t\bar{t}} = 7.26 \pm 0.13\,(\mathrm{stat.})\,^{+0.57}_{-0.50}\,(\mathrm{syst.})$ pb which is consistent with standard model predictions. We also perform a likelihood fit to the measured and predicted top quark mass dependence of the inclusive cross section, which yields a measurement of the pole mass of the top quark. The extracted value is $m_t = 172.8 \pm 1.1\,(\mathrm{theo.})\,^{+3.3}_{-3.1}\,(\mathrm{exp.})$ GeV.

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.

We present measurements of the differential cross section dsigma/dpT_gamma for the inclusive production of a photon in association with a b-quark jet for photons with rapidities |y_gamma|< 1.0 and 30<pT_gamma <300 GeV, as well as for photons with 1.5<|y_gamma|< 2.5 and 30< pT_gamma <200 GeV, where pT_gamma is the photon transverse momentum. The b-quark jets are required to have pT>15 GeV and rapidity |y_jet| < 1.5. 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 measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the kT-factorization QCD approach, and those from the Sherpa and Pythia Monte Carlo event generators.

We present a comprehensive analysis of inclusive W(\to e\nu)+n-jet (n\geq 1,2,3,4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb^{-1} dataset collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (p_T) and pseudorapidity (\eta), the scalar sum of the transverse energies of the W boson and all jets (H_T), leading dijet p_T and invariant mass, dijet rapidity separations for a variety of jet pairings for p_T-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for p_T-ordered and angular-ordered jets, and W boson transverse momentum. The mean number of jets in an event containing a W boson is measured as a function of H_T, and as a function of the rapidity separations between the two highest-p_T jets and between the most widely separated jets in rapidity. Finally, the probability for third-jet emission in events containing a W boson and at least two jets is studied by measuring the fraction of events in the inclusive W+2-jet sample that contain a third jet over a p_T threshold. The analysis employs a regularized singular value decomposition technique to accurately correct for detector effects and for the presence of backgrounds. The corrected data are compared to particle level next-to-leading order perturbative QCD predictions, predictions from all-order resummation approaches, and a variety of leading-order and matrix-element plus parton-shower event generators. Regions of the phase space where there is agreement or disagreement with the data are discussed for the different models tested.

We present measurements of direct photon pair production cross sections using 8.5 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron $p \bar p$ collider. The results are presented as differential distributions of the photon pair invariant mass $d\sigma/dM_{\gamma \gamma}$, pair transverse momentum $d \sigma /dp^{\gamma \gamma}_T$, azimuthal angle between the photons $d\sigma/d\Delta \phi_{\gamma \gamma}$, and polar scattering angle in the Collins-Soper frame $d\sigma /d|\cos \theta^*|$. Measurements are performed for isolated photons with transverse momenta $p^{\gamma}_T>18 ~(17)$ GeV for the leading (next-to-leading) photon in $p_T$, pseudorapidities $|\eta^{\gamma}|<0.9$, and a separation in $\eta-\phi$ space $\Delta\mathcal R_{\gamma\gamma} > 0.4$. We present comparisons with the predictions from Monte Carlo event generators {\sc diphox} and {\sc resbos} implementing QCD calculations at next-to-leading order, $2\gamma${\sc nnlo} at next-to-next-to-leading order, and {\sc sherpa} using matrix elements with higher-order real emissions matched to parton shower.

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.