2,130 research outputs found
Inclusive Diffraction at HERA
New precision measurements of inclusive diffractive deep-inelastic ep
scattering interactions, performed by the H1 and ZEUS collaborations at the
HERA collider, are discussed. A new set of diffractive parton distributions,
determined from recent high precision H1 data, is presented.Comment: 5 pages, to appear in the proceedings of the 31st Intl. Conference on
High Energy Physics ICHEP 2002, Amsterdam, July 200
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
Dynamical Parton Distributions of the Nucleon up to NNLO of QCD
A new generation of (unpolarized) dynamical parton distribution functions of
the nucleon is determined. After introducing basic elements of perturbative
QCD, the dynamical model is discussed and compared with the approach to parton
distributions used by most other groups ("standard"). Parton distributions sets
(with uncertainties) at different orders (LO, NLO, NNLO), using different
factorization schemes (\overline{MS}, DIS) and different treatments of heavy
quark masses (FFNS, VFNS) are extracted and compared. The astrophysical
implications of the dynamical predictions are outlined before focusing on
collider phenomenology. There, the relevance and perturbative stability of the
longitudinal structure function of the nucleon is studied, and the role of
heavy quark flavors in high-energy colliders is analyzed. In addition, it is
shown how isospin violations in the nucleon help to explain the so-called
"NuTeV anomaly".Comment: Ph.D. Thesis, 98 page
Is There a Significant Excess in Bottom Hadroproduction at the Tevatron?
We discuss the excess in the hadroproduction of B mesons at the Tevatron. We
show that an accurate use of up-to-date information on the B fragmentation
function reduces the observed excess to an acceptable level. Possible
implications for experimental results reporting bottom quark cross sections,
also showing an excess with respect to next-to-leading order theoretical
predictions, are discussed.Comment: 5 pages, Latex, 4 figures. Submitted to Phys. Rev. Let
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
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
Consequences of t-channel unitarity for the interaction of real and virtual photons at high energies
We analyze the consequences of t-channel unitarity for photon cross sections
and show what assumptions are necessary to allow for the existence of new
singularities at for the and total
cross sections. For virtual photons, such singularities can in general be
present, but we show that, apart from the perturbative singularity associated
with , no new ingredient is needed to
reproduce the data from LEP and HERA, in the Regge region.Comment: 10 pages, LaTeX2e with kluwer.sty, 7 figures. Talk presented at the
Second International "Cetraro" Workshop & NATO Advanced Research Workshop
"Diffraction 2002", Alushta, Crimea, Ukraine, August 31 - September 6, 200
Excited Leptons at the CERN Large Hadron Collider
We analyze the potential of the CERN Large Hadron Collider (LHC) to search
for excited spin-1/2 electrons and neutrinos. Assuming a SU(2)_L X U(1)_Y
invariant model, we study in detail the single production of excited electrons
and neutrinos and respective backgrounds through the reactions p p -> e+ e- V
and e+- \nu V with V=photon, W, or Z. We show that the LHC will be able to
tighten considerably the direct constraints on these possible new states,
probing excited lepton masses up to 1-2 TeV depending on their couplings to
fermions and gauge bosons.Comment: 15 pages, 7 figure
DGLAP evolution extends the triple pole pomeron fit
We show that the triple pole pomeron model \cite{CMS} provides an initial
condition for a DGLAP evolution \cite{DGLAP} that produces a fit to high
experimental DIS data. We obtain good for initial scales down to 3
GeV. Values of the initial scale smaller than 1.45 GeV are ruled out at
the 90% confidence level.Comment: 8 pages, 6 figures, uses RevTex 4. Typos corrected, some points
clarifed and 1 figure adde
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
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