The production of leading neutrons, where the neutron carries a large fraction x_L of the incoming proton's longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb^{-1}. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6 < Q^2 < 100 GeV^2, Bjorken scaling variable 1.5x10^{-4} < x < 3x10^{-2}, longitudinal momentum fraction 0.32 < x_L < 0.95 and neutron transverse momentum p_T < 0.2 GeV. The leading neutron structure function, F_2^{LN(3)}(Q^2,x,x_L), and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of Q^2, x and x_L. Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function.

10.1140/epjc/s10052-010-1369-4

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Measurement of beauty and charm photoproduction using semi-muonic decays in dijet events at HERA

The European Physical Journal C (2012)

F. D. Aaron C. Alexa V. Andreev S. Backović A. Baghdasaryan

Measurements of cross sections for beauty and charm events with dijets and a muon in the photoproduction regime at HERA are presented. The data were collected with the H1 detector and correspond to an integrated luminosity of 179 pb^{-1}. Events with dijets of transverse momentum P_T^{jet1} > 7 GeV and P_T^{jet2} > 6 GeV in the pseudorapidity range -1.5< \eta^{jet} < 2.5 in the laboratory frame are selected in the kinematic region of photon virtuality Q^2 < 2.5 GeV^2 and inelasticity 0.2 < y < 0.8. One of the two selected jets must be associated to a muon with P_T^{\mu} > 2.5 GeV in the pseudorapidity range -1.3 < \eta^{\mu} < 1.5. The fractions of beauty and charm events are determined using the impact parameters of the muon tracks with respect to the primary vertex and their transverse momentum relative to the axis of the associated jet. Both variables are reconstructed using the H1 vertex detector. The measurements are in agreement with QCD predictions at leading and next-to-leading order.

Pseudorapidity

Charm (quantum number)

10.1140/epjc/s10052-012-2047-5

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Measurement of inclusive and dijet D∗ meson cross sections in photoproduction at HERA

The European Physical Journal C (2012)

F. D. Aaron C. Alexa V. Andreev S. Backović A. Baghdasaryan

The inclusive photoproduction of D\ast mesons and of D\ast-tagged dijets is investigated with the H1 detector at the ep collider HERA. The kinematic region covers small photon virtualities Q2 < 2 GeV2 and photon-proton centre-of-mass energies of 100 < Wgp < 285 GeV. Inclusive D\ast meson differential cross sections are measured for central rapidities |eta(D\ast)| < 1.5 and transverse momenta pT (D\ast) > 1.8 GeV. The heavy quark production process is further investigated in events with at least two jets with transverse momentum pT (jet) > 3.5 GeV each, one containing the D\ast meson. Differential cross sections for D\ast-tagged dijet production and for correlations between the jets are measured in the range |eta(D\ast)| < 1.5 and pT (D\ast) > 2.1 GeV. The results are compared with predictions from Monte Carlo simulations and next-to-leading order perturbative QCD calculations.

Perturbative QCD

D meson

10.1140/epjc/s10052-012-1995-0

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INELASTIC SCATTERING OF DEUTERONS ON CARBON AT 8.9-GeV/c. (IN RUSSIAN)

Yad.Fiz. (1983)

V.G. Ableev L.N. Strunov A. Filipkowski G.G. Vorob'ev I.U. Khristova

Carbon fibers

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Diffractive photoproduction of J/ψ mesons with large momentum transfer at HERA

Physics Letters B (2003)

Å. Aktas V. Andreev T. Anthonis A. Astvatsatourov A. Babaev

The diffractive photoproduction of J/psi mesons is measured with the H1 detector at the ep collider HERA using an integrated luminosity of 78 pb^-1. The differential cross section d sigma(gamma p -> J/psi Y) / d t is studied in the range 2 < |t| < 30 GeV^2, where t is the square of the four-momentum transferred at the proton vertex. The cross section is also presented as a function of the photon-proton centre-of-mass energy W in three t intervals, spanning the range 50 < W < 200 GeV. A fast rise of the cross section with W is observed for each t range and the slope for the effective linear Pomeron trajectory is measured to be alpha^\prime= -0.0135 \pm 0.0074 (stat.) \pm 0.0051 (syst.) GeV^-2. The measurements are compared with perturbative QCD models based on BFKL and DGLAP evolution. The data are found to be compatible with s-channel helicity conservation.

Perturbative QCD

Pomeron

Helicity

Momentum transfer

10.1016/j.physletb.2003.06.056

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Citations (55)

DEVELOPMENT OF THE ALFA-3C FACILITIES DESIGNED FOR THE SEARCH FOR SUPEREXCITED MULTI - QUARK STATES OF LIGHT NUCLEI AND SOME EXPERIMENTAL RESULTS. (IN RUSSIAN)

V.G. Ableev L.N. Strunov G.G. Vorob'ev A. Parfenov I.M. Sitnik

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