44 research outputs found
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
A Measurement of the Proton Structure Function
A measurement of the proton structure function is reported
for momentum transfer squared between 4.5 and 1600 and
for Bjorken between and 0.13 using data collected by the
HERA experiment H1 in 1993. It is observed that increases
significantly with decreasing , confirming our previous measurement made
with one tenth of the data available in this analysis. The dependence is
approximately logarithmic over the full kinematic range covered. The subsample
of deep inelastic events with a large pseudo-rapidity gap in the hadronic
energy flow close to the proton remnant is used to measure the "diffractive"
contribution to .Comment: 32 pages, ps, appended as compressed, uuencoded fil
The Prevention of Respiratory Syncytial Virus Infection in Children: Focus on Palivizumab
From industrial relations to manpower planning: the transformations of Singapore's industrial relations
First measurement of the charged current cross-section at HERA
The cross section of the charged current process e â p â v e + hadrons is measured at HERA for transverse momenta of the hadron system larger than 25 GeV. The size of the cross section exhibits the W propagator
Scale influence on the energy dependence of photon - proton cross-sections
The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energy W is studied using low Q 2 < 0.01 GeV 2 e + p interactions collected by the H1 experiment at HERA. The value of the largest transverse momentum of a charged particle in the photon fragmentation region is used to define the hard scale. The slope of the W dependence of the cross section is observed to increase steeply with increasing transverse momentum. The result is compared to measurements of the Q 2 evolution of the W dependence of the virtual photon-proton cross section. Interpretations in terms of QCD and in terms of Regge phenomenology are discussed
Bose-Einstein correlations in deep inelastic e p scattering at HERA
Two-particle correlations in invariant mass are studied separately for
like-sign and unlike-sign charged particles produced in deep inelastic
positron-proton scattering in a new kinematical domain. The data were taken
with the H1 detector at the HERA storage ring in 1994, in which 27.5 GeV
positrons collided with 820 GeV protons at a centre of mass energy sqrt{s}=300
GeV. The observed enhancement of the like-sign correlations at low invariant
masses is related to the dimensions of the hadronic source. The data are
compared to different QCD models where the hadronization is performed with the
string-fragmentation model. Results are presented for the first time separately
for diffractive and non-diffractive scattering, in domains of four-momentum
transfer, Bjorken-x, and hadronic center of mass energy, and in intervals of
charged particle multiplicity. The observed source radii do not differ strongly
from those measured in lower energy lepton-nucleon inelastic scattering, and
e^+e^- annihilation.Comment: 36 pages, 10 Figure