A measurement is presented of inelastic photo- and electroproduction of J/psi mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J/psi mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a k_T factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.
Measured differential photoproduction cross section as a function of the squared transverse momentum of the J/PSI.
Measured differential photoproduction cross section as a function of the elasticity of the J/PSI.
Measured photoproduction cross section as a function of the photon-proton centre of mass energy W.
The production of jets is studied in deep-inelastic e+p scattering at low negative four momentum transfer squared 5<Q^2<100 GeV^2 and at inelasticity 0.2<y<0.7 using data recorded by the H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb^-1. Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q^2 and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction xi. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling alpha_s.
Inclusive Jet Cross Section ${\rm\frac{d\sigma_{jet}}{dQ^2}}$.
2-Jet Cross Section ${\rm\frac{d\sigma_{2-jet}}{dQ^2}}$.
3-Jet Cross Section ${\rm\frac{d\sigma_{3-jet}}{dQ^2}}$.
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.
The production of neutral strange hadrons is investigated using deep-inelastic scattering events measured with the H1 detector at HERA. The measurements are made in the phase space defined by the negative four-momentum transfer squared of the photon 2 < Q^2 < 100 GeV^2 and the inelasticity 0.1 < y < 0.6. The K_s and Lambda production cross sections and their ratios are determined. K_s production is compared to the production of charged particles in the same region of phase space. The Lambda - anti-Lambda asymmetry is also measured and found to be consistent with zero. Predictions of leading order Monte Carlo programs are compared to the data.
Visible cross section for the production of K0S and LAMBDA(BAR).
Ratio of strange baryon to meson production.
Ratio of K0S to charged hadron production.
The production of jets is studied in deep-inelastic ep scattering at large negative four momentum transfer squared 150<Q^2<15000 GeV^2 using HERA data taken in 1999-2007, corresponding to an integrated luminosity of 395 pb^-1. Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q^2, jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurements is alpha_s(M_Z) = 0.1168 +/-0.0007 (exp.) +0.0046/-0.0030 (th.) +/-0.0016(pdf).
Normalised inclusive jet cross section in bins of $Q^{2}$.
Normalised 2-jet cross section in bins of $Q^{2}$.
Normalised 3-jet cross section in bins of $Q^{2}$.
The production of isolated photons in deep-inelastic scattering $ep\to e \gamma X$ is measured with the H1 detector at HERA. The measurement is performed in the kinematic range of negative four-momentum transfer squared $4<Q^2<150 $~GeV$^2$ and a mass of the hadronic system $W_X>50$ GeV. The analysis is based on a total integrated luminosity of 227~pb$^{-1}$. The production cross section of isolatedphotons with a transverse energy in the range $3 < E_T^\gamma < 10$ GeV and pseudorapidity range $-1.2 < \eta^\gamma < 1.8$ is measured as a function of $E_T^\gamma$, $\eta^\gamma$ and $Q^2$. Isolated photon cross sections are also measured for events with no jets or at least one hadronic jet. The measurements are compared with predictions from Monte Carlo generators modelling the photon radiation from the quark and the electron lines, as well as with calculations at leading and next to leading order in the strong coupling. The predictions significantly underestimate the measured cross sections.
Measured inclusive isolated photon cross section.
Measured total cross section for isolated photons plus no-jets and 1-jet.
Differential cross section as a function of the photon ET.
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 inelastic production of J/psi mesons in e p collisions has been studied with the ZEUS detector at HERA using an integrated luminosity of 109 pb-1. The J/psi mesons were identified using the decay channel J/psi -> mu+ mu-. The measurements were performed in the kinematic range 2 < Q^2< 80 Gev^2, 50 < W < 250 Gev, 0.2 < z <0.9 and -1.6 < Ylab < 1.3, where Q^2 is the virtuality of the exchanged photon, W is the photon-proton centre-of-mass energy, z is the fraction of the photon energy carried by the J/psi meson in the proton rest frame and Ylab is the rapidity of the J/psi in the laboratory frame. The measured cross sections are compared to theoretical predictions within the non-relativistic QCD framework including colour-singlet and colour-octet contributions, as well as to predictions based on the kT-factorisation approach. Calculations of the colour-singlet process generally agree with the data, whereas inclusion of colour-octet terms spoils this agreement.
Integrated cross section for the process E P --> E J/PSI X.
Differential cross section as a function of Z.
Differential cross section as a function of W.
Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2. The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s) = 318 GeV using the ZEUS detector and correspond to an integrated luminosity of 82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential dijet and trijet cross sections are presented as functions of jet transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections, is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.) {+0.0064}_{-0.0046}(th.)
Inclusive trijet cross section as a function of the jet transverse energy in the Breit frame for the jet with the highest transverse energy.
Inclusive trijet cross section as a function of the jet transverse energy in the Breit frame for the jet with the second highest transverse energy.
Inclusive trijet cross section as a function of the jet transverse energy in the Breit frame for the jet with the third highest transverse energy.
A measurement of the beauty production cross section in ep collisions at a centre-of-mass energy of 319 GeV is presented. The data were collected with the H1 detector at the HERA collider in the years 1999-2000. Events are selected by requiring the presence of jets and muons in the final state. Both the long lifetime and the large mass of b-flavoured hadrons are exploited to identify events containing beauty quarks. Differential cross sections are measured in photoproduction, with photon virtualities Q^2 < 1 GeV^2, and in deep inelastic scattering, where 2 < Q^2 < 100 GeV^2. The results are compared with perturbative QCD calculations to leading and next-to-leading order. The predictions are found to be somewhat lower than the data.
Muons and jets from beauty photoproduction, pseudorapidity.
Muons and jets from beauty photoproduction, muon transverse momentum.
Muons and jets from beauty photoproduction, leading jet transverse momentum
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