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|.
The $d\sigma$/$dt$ differential cross section. The statistical and systematic uncertainties are added in quadrature.
We present measurements of Underlying Event observables in pp collisions at $\sqrt{s}$ = 0.9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum $p_{\rm T, LT}$ in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different $p_{\rm T}$ thresholds: 0.15, 0.5 and 1.0 GeV/$c$. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track $p){\rm T}$ threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed $p_{\rm T}$ in the Transverse region by about 10-30%.
Number density as a function of the leading charged-particle PT at a centre-mass-energy of 900 GeV for events having charged-particle PT > 0.15 GeV. The data is shown for the three azimuthal regions.
Number density as a function of the leading charged-particle PT at a centre-mass-energy of 7000 GeV for events having charged-particle PT > 0.15 GeV. The data is shown for the three azimuthal regions.
Number density as a function of the leading charged-particle PT at a centre-mass-energy of 900 GeV for events having charged-particle PT > 0.5 GeV. The data is shown for the three azimuthal regions.
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.
The measured 3-jet differential cross section for |y|<0.8 and pT>40 GeV.
The measured 3-jet differential cross section for |y|<1.6 and pT>40 GeV.
The measured 3-jet differential cross section for |y|<2.4 and pT>40 GeV.
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.
The normalised differential cross section of the azmiuthal decorrelation variable DELTA for the GAMMA+3JET sample for the PT of the second jet in the range 15 TO 30 GeV.
The normalised differential cross section of the azmiuthal decorrelation variable DELTA for the GAMMA+2JET sample for the PT of the second jet in the range 15 TO 20 GeV.
The normalised differential cross section of the azmiuthal decorrelation variable DELTA for the GAMMA+2JET sample for the PT of the second jet in the range 20 TO 25 GeV.
Bose-Einstein correlations between identical particles are measured in samples of proton-proton collisions at 0.9 and 7 TeV centre-of-mass energies, recorded by the CMS experiment at the LHC. The signal is observed in the form of an enhancement of number of pairs of same-sign charged particles with small relative momentum. The dependence of this enhancement on kinematic and topological features of the event is studied.
The double ratio R_double at 900 and 7000 GeV.
The double ratio R_double at 7000 GeV in different bins of charged particle multiplicity and kT.
The double ratio R_double at 7000 GeV in different bins of charged particle multiplicity and kT.
Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of sqrt(s) = 0.9, 2.36, and 7 TeV, in five pseudorapidity ranges from |eta|<0.5 to |eta|<2.4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7 TeV run in 2010. The multiplicity distribution at sqrt(s) = 0.9 TeV is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with sqrt(s) is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.
Mean multiplicity for charged hadron production for |pseudorapidity| < 2.4.
Fully corrected charged hadron multiplicity spectrum for |pseudorapidity| < 0.5 at a centre-of-mass energy of 900 GeV.
Fully corrected charged hadron multiplicity spectrum for |pseudorapidity| < 1.0 at a centre-of-mass energy of 900 GeV.
Using 7.3 pb-1 of ppbar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable \phistar, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the \phistar distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.
The measured PHI* distributions for the dielectron events corrected back to the particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.
The measured PHI* distributions for the dimuon events corrected back to the particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.
We present a new measurement of the Z/gamma* transverse momentum distribution in the range 0 - 330GeV, in proton-antiproton collisions at sqrt{s}=1.96 TeV. The measurement uses 0.97 fb-1 of integrated luminosity recorded by the D0 experiment and is the first using the Z/gamma*->mu+mu- + X channel at this center-of-mass energy. This is also the first measurement of the Z/gamma* transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/gamma* in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals.
Normalized differential cross section.
Absolute differential cross section produced by multiplying by the measuredtotal cross section (118 pb).
We report on a CDF measurement of the total cross section and rapidity distribution, $d\sigma/dy$, for $q\bar{q}\to \gamma^{*}/Z\to e^{+}e^{-}$ events in the $Z$ boson mass region ($66<M_{ee}<116$GeV/c$^2$) produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$TeV with 2.1fb$^{-1}$ of integrated luminosity. The measured cross section of $257\pm16$pb and $d\sigma/dy$ distribution are compared with Next-to-Leading-Order(NLO) and Next-to-Next-to-Leading-Order(NNLO) QCD theory predictions with CTEQ and MRST/MSTW parton distribution functions (PDFs). There is good agreement between the experimental total cross section and $d\sigma/dy$ measurements with theoretical calculations with the most recent NNLO PDFs.
Total cross section integrated up to ABS(YRAP)=2.9.
Rapiditiy distribution of E+ E- pairs in the mass range from 66 to 116 GeV.
Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at sqrt(s) = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between -2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN(charged)/d(eta) for |eta| < 0.5, are 3.48 +/- 0.02 (stat.) +/- 0.13 (syst.) and 4.47 +/- 0.04 (stat.) +/- 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in p-pbar and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
Measured differential yield of charged hadrons as a function of transverse momentum for pseudorapidities 0.1, 0.3, 0.5 and 0.7 for centre-of-mass energy 900 GeV.
Measured differential yield of charged hadrons as a function of transverse momentum for pseudorapidities 0.9, 1.1, 1.3 and 1.5 for centre-of-mass energy 900 GeV.
Measured differential yield of charged hadrons as a function of transverse momentum for pseudorapidities 1.7, 1.9, 2.1 and 2.3 for centre-of-mass energy 900 GeV.
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