1,067 research outputs found
Structure function results from H1
New structure function results from H1 are presented. The measurements cover
a huge kinematical range for Q^2, the four momentum transfer squared, from
0.35, GeV^2 to 30,000, GeV^2, and for Bjorken x between \sim 5\cdot 10^{-6} and
0.65. At Q^2>100, GeV^2, full HERA, I data have been analyzed. The data are
compared with a new QCD analysis. The impact of the HERA, I data on the parton
density functions is discussed.Comment: 8 page
Internal Jet Structure in Dijet Production in Deep-Inelastic Scattering
The internal jet structure in dijet production in deep-inelastic scattering
is measured with the H1 detector at HERA. Jets with transverse energies
E(T,breit) > 5 GeV are selected in the Breit frame employing kt and cone jet
algorithms in the kinematic region of squared momentum transfers of 10 < Q^2 <
120 GeV^2 and x-Bjorken values of 0.0002 < x < 0.008. Jet shapes and subjet
multiplicities are measured as functions of a resolution parameter. The
corrected data are well described by QCD models. It is observed that jets are
more collimated with increasing transverse jet energies and decreasing
pseudo-rapidities, i.e. towards the photon direction. Comparisons with OPAL
data show that jet shapes of jets measured in photon-photon collisions are very
similar to those measured in ep collisions.Comment: 4 pages, 3 figures, to be published in the proceedings of 7th
International Workshop on Deep Inelastic Scattering and QCD (DIS 99),
Zeuthen, Germany, 19-23 Apr 199
Diffractive Physics at HERA
Brief review of the diffractive physics at HERA, stressing QCD aspects.Comment: Contribution to the INPC98 proceeding, 5 pages, 6 figure
Structure Functions in Deep Inelastic Lepton-Nucleon Scattering
Latest results on structure functions, as available at the Lepton-Photon
Symposium 1999, are presented. This report focusses on three experimental
areas: new structure function measurements, in particular from HERA at low x
and high Q2; results on light and heavy flavour densities; determinations of
the gluon distribution and of alpha_s. As the talk was delivered at a historic
moment and place, a few remarks were added recalling the exciting past and
looking into the promising future of deep inelastic scattering.Comment: 27 pages, latex, 15 figures, Talk at Lepton-Photon Symposium,
Stanford, August 199
Predicting F2D(3) from the dipole cross-section
We employ a parameterisation of the proton dipole cross section previously
extracted from electroproduction and photoproduction data to predict the
diffractive structure function F2D(3)(Q^2, beta, xpom). Comparison with HERA H1
data yields good agreement.Comment: 5 pages,4 figures, Latex2e, uses espcrc1.sty. Presented at "Hadron
99" Beijing, August 1999. Reference added, erroneous citation correcte
Open Charm Production at HERA
Measurements of charmed particle cross sections at HERA in the
photoproduction and deep inelastic regimes are reviewed. The status of the
comparison with perturbative QCD calculations is discussed.Comment: Presented at the Ringberg Workshop on ``New Trends in HERA Physics
2001'' 17-22 June 2001. 12 pages, 11 figure
The total cross section and elastic diffraction
The empirical scaling law, wherein the total photoabsorption cross section
depends on the single variable , provides
empirical evidence for saturation in the sense of for at fixed . The
total photoabsorption cross section is related to elastic diffraction in terms
of a sum rule. The excess of diffractive production over the elastic component
is due to inelastic diffraction that contains the production of hadronic states
of higher spins. Motivated by the diffractive mass spectrum, the generalized
vector dominance/color dipole picture (GVD/CDP) is extended to successfully
describe the DIS data in the full region of , all , where
the diffractive two-gluon-exchange mechanism dominates.Comment: 4 pages, Latex using espcrc2.sty, 1 figure using 1 eps file.
Presented at QCD2002, Montpellier, France, July 200
Deep inelastic diffractive scattering at HERA
Recent high precision measurements of deep inelastic diffractive scattering
at HERA are presented in an increased region of phase space. Current models for
diffractive photon dissociation are compared to the data.Comment: 6 pages, 6 figures, talk presented at QCD03, Montpellier, France,
July 2-9, 200
Minireview of Leptoquark Searches
Direct and indirect leptoquark searches at colliders are reviewed.Comment: 4 pages, 2 figures, to be published in the proceedings of the
International Conference on High Energy Physics 2002, Amsterdam, 24-31 July
200
Hard exclusive production of two pions: Dipion mass distributions in gamma* N -->pi pi N and gamma* gamma --> pi pi
The leading twist parametrization of dipion mass distribution in hard
exclusive reactions is proposed. Its parameters are related to quark
distributions (usual and skewed) in the pion and to distributions amplitudes of
mesons (, , etc.). We show that measurements of the shape of dipion
mass distribution in hard exclusie reactions can give important information
about partonic structure of the pion. The expression for the amplitude of the
reaction near the threshold in terms of singlet
quark distribution in the pion is presented.Comment: Talk given at 7th International Workshop on Deep Inelastic Scattering
and QCD (DIS 99), Zeuthen, Germany, 19-23 Apr 1999. Minor typos are correcte
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