16 research outputs found

    Measurement of the inclusive energy spectrum in the very forward direction in proton-proton collisions at root s=13 TeV

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    Inclusive-jet photoproduction at HERA and determination of alpha(s)

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    Jet-radius dependence of inclusive-jet cross sections in deep inelastic scattering at HERA

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    Differential inclusive-jet cross sections have been measured for different jet radii in neutral current deep inelastic ep scattering for boson virtualities Q^2 > 125 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb^-1. Jets were identified in the Breit frame using the k_T cluster algorithm in the longitudinally inclusive mode for different values of the jet radius R. Differential cross sections are presented as functions of Q^2 and the jet transverse energy, E_T,B^jet. The dependence on R of the inclusive-jet cross section has been measured for Q^2 > 125 and 500 GeV^2 and found to be linear with R in the range studied. Next-to-leading-order QCD calculations give a good description of the measurements for 0.5 500 GeV^2: alpha_s(M_Z) = 0.1207 +- 0.0014 (stat.) -0.0028 +0.0030 (exp.) -0.0023 +0.0022 (th.). The variation of alpha_s with E_T,B^jet is in good agreement with the running of alpha_s as predicted by QCD

    Search for Pentaquarks Decaying to Xi-pi in Deep Inelastic Scattering at HERA

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    Measurement of the proton structure function F-2 and the total gamma*p cross-section at low Q(2) and low x

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    The ZEUS-experiment at HERA has significantly enhanced the kinematic coverage for low Q(2) and low x inelastic e(+)p --> e(+) X scattering with an upgrade of the ZEUS-detector in 1995 which extends the acceptance for small positron scattering angles. The upgrade included the modification of the beam pipe with low mass exit windows and the installation of a small electromagnetic sampling calorimeter, the Beam Pipe Calorimeter (BPC), to explore the region in Q(2) of 0.11 less than or equal to Q(2) less than or equal to 0.65 GeV2. A shift of two rear uranium calorimeter (RCAL) modules and the small rear tracking detector (SRTD) closer to the beam together with a data sample taken with a shifted event vertex extended the Q(2) coverage of the main detector down to 0.6 GeV2. Both data sets have been used to measure the proton structure function F-2 and the total virtual photonproton gamma*p cross-section. Results are presented for 0.11 less than or equal to Q(2) less than or equal to 6.10 GeV2 and 2.10(-6) less than or equal to x less than or equal to 7.10(-4) along with a comparison to various models

    Jet shapes at HERA

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    The shape of jets produced in quasi-real photon-proton interactions and deep inelastic positron-proton scattering (DIS) at high Q(2) (Q(2) > 100 GeV2) has been measured with the ZEUS detector at HERA. Jets with transverse energies E-T(jet) > 14 GeV and pseudorapidities (eta(jet)) in the range -1 collisions, and are similar to those in e(+)e(-) interactions

    D* and J/psi inelastic photoproduction at HERA

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    Cross sections of D* and J/Psi inelastic photoproduction were measured by the ZEUS detector at HERA collider. Comparisons of the data with calculations in NLO pQCD and SHA QCD approaches were made

    Forward transverse energy flow and forward jets at low x

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    Transverse energy flow and forward jet cross sections at low values of x(Bj) are measured with the ZEUS detector at HERA in order to study the underlying parton dynamics (DGLAP versus BFKL). The energy how has been compared to different model simulations, but hadronization effects are too large to draw a firm conclusion. The measured jet cross section for 10(-4) < x(Bj) < 5.10(-3) is for the lower x(Bj)-bins larger than that of NLO QCD DGLAP calculations but lies still below a more qualitative BFKL prediction

    QCD fits to ZEUS and fixed target structure function data

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    Preliminary results are presented on the gluon density at low x obtained from a QCD analysis of ZEUS 1994 F-2 structure function data combined with those from NMC. Also given are estimates of the experimental error on the e(+) p NC Born cross section at large x and Q(2). This estimate is obtained from propagation of the statistical and systematic errors on fixed target structure functions

    Searches at HERA for excited fermions, contact interactions, a heavy neutrino, and: a HERA excess?

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    Results are presented on a number of searches for new physics in ep collisions at HERA using the ZEUS and HI detectors. Limits are presented on the production of elicited fermions, contact interactions, as well as a heavy right handed neutrino and W-R boson. Also presented are ZEUS results on the excess of events at high x and Q(2)
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