32 research outputs found
Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant
Jet event rates in deep inelastic ep scattering at HERA are investigated
applying the modified JADE jet algorithm. The analysis uses data taken with the
H1 detector in 1994 and 1995. The data are corrected for detector and
hadronization effects and then compared with perturbative QCD predictions using
next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2)
is determined evaluating the jet event rates. Values of alpha_S(Q^2) are
extracted in four different bins of the negative squared momentum
transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the
renormalization group equation to these several alpha_S(Q^2) values results in
alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys.
J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4
Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA
Deep--inelastic scattering events with a leading baryon have been detected by
the H1 experiment at HERA using a forward proton spectrometer and a forward
neutron calorimeter. Semi--inclusive cross sections have been measured in the
kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T
<= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV,
or a neutron with energy E' >= 160 GeV. The measurements are used to test
production models and factorization hypotheses. A Regge model of leading baryon
production which consists of pion, pomeron and secondary reggeon exchanges
gives an acceptable description of both semi-inclusive cross sections in the
region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading
neutron data are used to estimate for the first time the structure function of
the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.
Jets and energy flow in photon-proton collisions at HERA
Properties of the hadronic final state in photoproduction events with large transverse energy are studied at the electron-proton collider HERA. Distributions of the transverse energy, jets and underlying event energy are compared to \overline{p}p data and QCD calculations. The comparisons show that the \gamma p events can be consistently described by QCD models including -- in addition to the primary hard scattering process -- interactions between the two beam remnants. The differential jet cross sections d\sigma/dE_T^{jet} and d\sigma/d\eta^{jet} are measured
Разработка интерактивной моделирующей системы технологии низкотемпературной сепарации газа
We present a study of J ψ meson production in collisions of 26.7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J ψ mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of σ(ep → J ψ X) = (8.8±2.0±2.2) nb is determined for 30 GeV ≤ W γp ≤ 180 GeV and Q 2 ≲ 4 GeV 2 . Using the flux of quasi-real photons with Q 2 ≲ 4 GeV 2 , a total production cross section of σ ( γp → J / ψX ) = (56±13±14) nb is derived at an average W γp =90 GeV. The distribution of the squared momentum transfer t from the proton to the J ψ can be fitted using an exponential exp(− b ∥ t ∥) below a ∥ t ∥ of 0.75 GeV 2 yielding a slope parameter of b = (4.7±1.9) GeV −2
Multijet event rates in deep inelastic scattering and determination of the strong coupling constant
Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant αs(M2Z) is determined evaluating the jet event rates. Values of αs(Q2) are extracted in four different bins of the negative squared momentum transfer Q2 in the range from 40 GeV2 to 4000 GeV2 . A combined fit of the renormalization group equation to these several αs(Q2) values results in αs(M2Z) = 0.117 ± 0.003 (stat)+0.009-0.013 (sys) + 0.006 (jet algorithm)
Dijet event rates in deep inelastic scattering at HERA
Di-jet event rates have been measured for deep-inelastic scattering in the
kinematic domain ~5 < Q^2 < ~100 GeV^2 and ~10^(-4) < x_Bj < ~10^(-2), and for
jet transverse momenta squared p_t^2 > ~Q^2. The analysis is based on data
collected with the H1 detector at HERA in 1994 corresponding to an integrated
luminosity of about 2 pb^(-1). Jets are defined using a cone algorithm in the
photon-proton centre of mass system requiring jet transverse momenta of at
least 5 GeV. The di-jet event rates are shown as a function of Q^2 and x_Bj.
Leading order models of point-like interacting photons fail to describe the
data. Models which add resolved interacting photons or which implement the
colour dipole model give a good description of the di-jet event rate. This is
also the case for next-to-leading order calculations including contributions
from direct and resolved photons.Comment: 22 pages, 5 figures, 1 table, submitted to Eur. Phys. J., corrected
author lis
Measurement of dijet cross-sections at low Q**2 and the extraction of an effective parton density for the virtual photon
The triple-differential dijet cross-section, d^3 sigma_{ep}/dQ2 dE_t2
dxgjets, is measured with the H1 detector at HERA as a function of the photon
virtuality Q^2, the fraction of the photon's momentum carried by the parton
entering the hard scattering, xgjets, and the square of the mean transverse
energy, E_t2, of the two highest E_t jets. Jets are found using a longitudinal
boost-invariant k_T clustering algorithm in the gamma* p center of mass frame.
The measurements cover the ranges 1.6 < Q^2 < 80 GeV$^2 in virtuality and 0.1 <
y < 0.7 in inelasticity y. The results are well described by leading order QCD
models which include the effects of a resolved component to the virtual photon.
Models which treat the photon as point-like fail to describe the data. An
effective leading order parton density for the virtual photon is extracted as a
function of the photon virtuality, the probing scale and the parton momentum
fraction. The x_gamma and probing scale dependences of the parton density show
characteristic features of photon structure, and a suppression of this
structure with increasing Q^2 is seen.Comment: 32 pages, 10 figures, 4 tables, submitted to Eur. Phys. J.