The production of beauty and charm quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q^2 < 1000 GeV^2 using an integrated luminosity of 354 pb^{-1}. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of Q^2, Bjorken x, jet transverse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of x and Q^2. The running beauty-quark mass, m_b at the scale m_b, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be 4.07 \pm 0.14 (fit} ^{+0.01}_{-0.07} (mod.) ^{+0.05}_{-0.00} (param.) ^{+0.08}_{-0.05} (theo) GeV.
Differential cross sections for inclusive jet production in beauty events as a function of ET(JET) for ET(JET) > 5 GeV. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
Differential cross sections for inclusive jet production in charm events as a function of ET(JET) for ET(JET) > 4.2 GeV. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
Differential cross sections for inclusive jet production in beauty events as a function of ETARAP(JET) for -1.6 < ETARAP(JET) < 2.2. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
The production of prompt photons is measured in the photoproduction regime of electron-proton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340 pb^-1 collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range 6 < Et < 15 GeV and -1.0 < eta < 2.4, respectively. Cross sections for events with an additional jet are measured as a function of the transverse energy and pseudorapidity of the jet, and as a function of the fractional momenta x_gamma and x_p carried by the partons entering the hard scattering process. The correlation between the photon and the jet is also studied. The results are compared with QCD predictions based on the collinear and on the k_T factorisation approaches.
Measured inclusive prompt photon cross section in the defined phase space.
Measured prompt photon plus jet cross section in the defined phase space.
Bin averaged differential cross section as a function of ET in the defined phase space.
The inclusive production of D*(2010) mesons in deep-inelastic ep scattering is measured in the kinematic region of photon virtuality 100 < Q^2 < 1000 GeV^2 and inelasticity 0.02 < y < 0.7. Single and double differential cross sections for inclusive D* meson production are measured in the visible range defined by |eta(D*)| < 1.5 and p_T(D*) > 1.5 GeV. The data were collected by the H1 experiment during the period from 2004 to 2007 and correspond to an integrated luminosity of 351 pb^{-1}. The charm contribution, F_2^{ccbar}, to the proton structure function F_2 is determined. The measurements are compared with QCD predictions.
Total inclusive cross section for D*+- production.
Single differential cross section DSIG/DPT for D*+- production. The DSYS errors are the uncorrelated and correlated systematicuncertainties respectively.
Single differential cross section DSIG/DETARAP for D*+- production. The DSYS errors are the uncorrelated and correlated systematicuncertainties respectively.
Measurements of the cross sections for charged current deep inelastic scattering in e-p collisions with longitudinally polarised electron beams are presented. The measurements are based on a data sample with an integrated luminosity of 175 pb-1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is given for positively and negatively polarised electron beams. The differential cross-sections dsigma/dQ2, dsigma/dx and dsigma/dy are presented for Q2>200 GeV2. The double-differential cross-section d2sigma/dxdQ2 is presented in the kinematic range 280<Q2<30000 GeV2 and 0.015<x<0.65. The measured cross sections are compared with the predictions of the Standard Model.
Total cross section for CC DIS events for two values of the longitudinal polarization of the electron beam.
Total cross section for CC DIS events as a function of the longitudinal polarization of the electron beam.
Differential cross section DSIG/DQ**2 for the two values of longitudinal polarization of the electron beam.
The semi-inclusive reaction e+ p -> e+ X p was studied with the ZEUS detector at HERA using an integrated luminosity of 12.8 pb-1. The final-state proton, which was detected with the ZEUS leading proton spectrometer, carried a large fraction of the incoming proton energy, xL>0.32, and its transverse momentum squared satisfied pT^2<0.5 GeV^2/ the exchanged photon virtuality, Q^2, was greater than 3 GeV^2 and the range of the masses of the photon-proton system was 45<W<225 GeV. The leading proton production cross section and rates are presented as a function of xL, pT^2, Q^2 and the Bjorken scaling variable, x.
Double differential cross sections as a funtion of PT**2 for the XL range 0.32 TO 0.38. The methods S123 and S456 are the results using different stations of the silicon microstrip detectors.
Double differential cross sections as a funtion of PT**2 for the XL range 0.38 TO 0.44. The methods S123 and S456 are the results using different stations of the silicon microstrip detectors.
Double differential cross sections as a funtion of PT**2 for the XL range 0.44 TO 0.50. The methods S123 and S456 are the results using different stations of the silicon microstrip detectors.
The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of $61 \pbi$. The dijet cross section has been measured for virtualities of the exchanged virtual photon, $5 < Q^2 < 100 \gev^2$, and $\gamma^{*} p$ centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive k_{T} algorithm in the $\gamma^* p$ frame, were required to have a transverse energy $E^*_{T, \rm jet} > 4 \gev$ and the jet with the highest transverse energy was required to have $E^*_{T,\rm jet} > 5 \gev$. All jets were required to be in the pseudorapidity range $-3.5 < \eta^*_{\rm jet} < 0$. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data.
Total di-jet cross section SIG as a function of Q**2 .
Distribution of D(SIG)/DQ**2 as a function of Q**2 .
Distribution of D(SIG)/DW as a function of W .
Inclusive dijet and trijet production in deep inelastic $ep$ scattering has been measured for $10<Q^2<100$ GeV$^2$ and low Bjorken $x$, $10^{-4}<x_{\rm Bj}<10^{-2}$. The data were taken at the HERA $ep$ collider with centre-of-mass energy $\sqrt{s} = 318 \gev$ using the ZEUS detector and correspond to an integrated luminosity of $82 {\rm pb}^{-1}$. Jets were identified in the hadronic centre-of-mass (HCM) frame using the $k_{T}$ cluster algorithm in the longitudinally invariant inclusive mode. Measurements of dijet and trijet differential cross sections are presented as functions of $Q^2$, $x_{\rm Bj}$, jet transverse energy, and jet pseudorapidity. As a further examination of low-$x_{\rm Bj}$ dynamics, multi-differential cross sections as functions of the jet correlations in transverse momenta, azimuthal angles, and pseudorapidity are also presented. Calculations at $\mathcal{O}(\alpha_{s}^3)$ generally describe the trijet data well and improve the description of the dijet data compared to the calculation at $\mathcal{O}(\alpha_{s}^2)$.
Two jet cross section D(SIG)/DQ**2 as a function of Q**2.
Two jet cross section D(SIG)/DX as a function of X.
Two jet cross section D(SIG)/DET(P=4,RF=CM) as a function of ET(P=4,RF=CM).
Inclusive D* production is measured in deep-inelastic ep scattering at HERA with the H1 detector. In addition, the production of dijets in events with a D* meson is investigated. The analysis covers values of photon virtuality 2< Q^2 <=100 GeV^2 and of inelasticity 0.05<= y <= 0.7. Differential cross sections are measured as a function of Q^2 and x and of various D* meson and jet observables. Within the experimental and theoretical uncertainties all measured cross sections are found to be adequately described by next-to-leading order (NLO) QCD calculations, based on the photon-gluon fusion process and DGLAP evolution, without the need for an additional resolved component of the photon beyond what is included at NLO. A reasonable description of the data is also achieved by a prediction based on the CCFM evolution of partons involving the k_T-unintegrated gluon distribution of the proton.
Visible cross section for inclusive D*+- production.
Visible cross section for inclusive D*+- production.
Visible cross section for inclusive D*+- production with two jets.
The hadronic final states observed with the ALEPH detector at LEP in ${\rm e}^ + {\rm e}^-$ annihilation
Mean charged particle multiplicities at different c.m. energies.
XP distribution at c.m. energy 133.0 GeV.
XP distribution at c.m. energy 161.0 GeV.
Cross sections for e^+p charged current deep inelastic scattering at a centre-of-mass energy of 318 GeV have been determined with an integrated luminosity of 60.9pb^-1 collected with the ZEUS detector at HERA. The differential cross sections dsigma/dQ^2, dsigma/dx and dsigma/dy for Q^2>200 GeV^2 are presented. In addition, d^2sigma/dxdQ^2 has been measured in the kinematic range 280 GeV^2 < Q^2 < 17000 GeV^2 and 0.008 < x < 0.42. The predictions of the Standard Model agree well with the measured cross sections. The mass of the W boson propagator is determined to be M_W=78.9 +/- 2.0 (stat.) +/- 1.8 (syst.) +2.0 -1.8 (PDF) GeV from a fit to dsigma/dQ^2. The chiral structure of the Standard Model is also investigated in terms of the (1-y)^2 dependence of the the double-differential cross section. The structure-function F_2^CC has been extracted by combining the measurements presented here with previous ZEUS results from e^-p scattering, extending the measurement obtained in a neutrino-nucleus scattering experiment to a significantly higher Q^2 region.
The total cross section for Q**2 > 200 GeV**2.
The differential cross section as a function of Q**2.
The differential cross section as a function of X.
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