2,941 research outputs found
Jets in Deep Inelastic Scattering and High Energy Photoproduction at HERA
Recent results on jet production in neutral current deep inelastic scattering
and high energy photoproduction at the HERA electron-proton-collider are
briefly reviewed. The results are compared to QCD expectations in NLO and
determinations using these data are summarized.Comment: 12 pages, 10 figures, talk given at the 9th Adriatic Meeting
"Particle Physics and the Universe" in Dubrovnik/Croatia, 4.-24.9.200
Regge Analysis of Diffractive and Leading Baryon Structure Functions from DIS
In this paper we present a combined analysis of the H1 data on leading baryon
and diffractive structure functions from DIS, which are handled as two
components of the same semi-inclusive process. The available structure function
data are analyzed in a series of fits in which three main exchanges are taking
into account: pomeron, reggeon and pion. For each of these contributions, Regge
factorization of the correspondent structure function is assumed. By this
procedure, we extract information about the interface between the diffractive,
pomeron-dominated, region and the leading proton spectrum, which is mostly
ruled by secondary exchanges. One of the main results is that the relative
reggeon contribution to the semi-inclusive structure function is much smaller
than the one obtained from a analysis of the diffractive structure function
alone.Comment: ps file, 22 pages, 5 figures. Totally revised version with major
changes, to appear in Physical Review
Regge residues from DGLAP evolution
We show that combining forward and backward evolution allows to extract the
residues of the triple-pole pomeron and of the other singularities for 10
GeV GeV. In this approach, the essential singularity
generated by the DGLAP evolution is considered as a numerical approximation to
a triple-pole pomeron. Using an analytical expression for the form factors, we
reproduce the experimental data with a of 1.02. This proves the
compatibility between Regge theory and DGLAP evolution. The method used here
enables us to evaluate the uncertainties on the gluon distribution which prove
to be large at small and small .Comment: 11 pages, 9 figures, RevTeX 4, Submitted to Phys. Re
MICROMEGAS chambers for hadronic calorimetry at a future linear collider
Prototypes of MICROMEGAS chambers, using bulk technology and analog readout,
with 1x1cm2 readout segmentation have been built and tested. Measurements in
Ar/iC4H10 (95/5) and Ar/CO2 (80/20) are reported. The dependency of the
prototypes gas gain versus pressure, gas temperature and amplification gap
thickness variations has been measured with an 55Fe source and a method for
temperature and pressure correction of data is presented. A stack of four
chambers has been tested in 200GeV/c and 7GeV/c muon and pion beams
respectively. Measurements of response uniformity, detection efficiency and hit
multiplicity are reported. A bulk MICROMEGAS prototype with embedded digital
readout electronics has been assembled and tested. The chamber layout and first
results are presented
The impact of new neutrino DIS and Drell-Yan data on large-x parton distributions
New data sets have recently become available for neutrino and antineutrino
deep inelastic scattering on nuclear targets and for inclusive dimuon
production in pp pd interactions. These data sets are sensitive to different
combinations of parton distribution functions in the large-x region and,
therefore, provide different constraints when incorporated into global parton
distribution function fits. We compare and contrast the effects of these new
data on parton distribution fits, with special emphasis on the effects at large
x. The effects of the use of nuclear targets in the neutrino and antineutrino
data sets are also investigated.Comment: 24 pages, 13 figure
Novel features of diffraction at the LHC
Interest and problems in the studies of diffraction at LHC are highlighted.
Predictions for the global characteristics of proton-proton interactions at the
LHC energy are given. Potential discoveries of the antishadow scattering mode
and diffractive scattering conjugated with high-- jets are discussed.Comment: 10 pages, 7 figures, journal version, 1 figure added, extended
introductio
Multi-jet cross sections in deep inelastic scattering at next-to-leading order
We present the perturbative prediction for three-jet production cross section
in DIS at the NLO accuracy. We study the dependence on the renormalization and
factorization scales of exclusive three-jet cross section. The perturbative
prediction for the three-jet differential distribution as a function of the
momentum transfer is compared to the corresponding data obtained by the H1
collaboration at HERA.Comment: 5 pages, 3 figure
Light Gluino Constituents of Hadrons and a Global Analysis of Hadron Scattering Data
Light strongly interacting supersymmetric particles may be treated as
partonic constituents of nucleons in high energy scattering processes. We
construct parton distribution functions for protons in which a light gluino is
included along with standard model quark, antiquark, and gluon constituents. A
global analysis is performed of a large set of data from deep-inelastic lepton
scattering, massive lepton pair and vector boson production, and hadron jet
production at large values of transverse momentum. Constraints are obtained on
the allowed range of gluino mass as a function of the value of the strong
coupling strength alpha_s(M_Z) determined at the scale of the Z boson mass. We
find that gluino masses as small as 10 GeV are admissible provided that
alpha_s(M_Z) \ge 0.12. Current hadron scattering data are insensitive to the
presence of gluinos heavier than ~ 100 - 150 GeV.Comment: 31 pages, 12 figures, RevTe
Evidence for Factorization Breaking in Diffractive Low-Q^2 Dijet Production
We calculate diffractive dijet production in deep-inelastic scattering at
next-to-leading order of perturbative QCD, including contributions from direct
and resolved photons, and compare our predictions to preliminary data from the
H1 collaboration at HERA. In contrast to recent experimental claims, evidence
for factorization breaking is found only for resolved, and not direct, photon
contributions. No evidence is found for large normalization uncertainties in
diffractive parton densities. The results confirm theoretical expectations for
the (non-)cancellation of soft singularities in diffractive scattering as well
as previous results for (almost) real photoproduction.Comment: 4 pages, 3 figure
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