4,548 research outputs found
Bose-Einstein Correlations in e+e- -> W+W- at a Linear Collider
We show that the most popular method to simulate Bose-Einstein (BE)
interference effects predicts negligible correlations between identical pions
originating from the hadronic decay of different W's produced in e+e- -> W+W-
-> 4 jets at typical linear collider energies.Comment: 5 pages, 2 eps figures, Proccedings of the Workshop "Physics Studies
for a Future Linear Collider", QCD Working Group, 2000, DESY 123
Exclusive vector meson production at HERA from QCD with saturation
Following recent predictions that the geometric scaling properties of deep
inelastic scattering data in inclusive gamma*-p collisions are expected also in
exclusive diffractive processes, we investigate the diffractive production of
vector mesons. Using analytic results in the framework of the BK equation at
non-zero momentum transfer, we extend to the non-forward amplitude a
QCD-inspired forward saturation model including charm, following the
theoretical predictions for the momentum transfer dependence of the saturation
scale. We obtain a good fit to the available HERA data and make predictions for
deeply virtual Compton scattering measurements.Comment: 10 pages, 5 figures, full analysis including the charm contribution
and J/PSI production. Conclusions confirme
Radial excitations of Q-balls, and their D-term
We study the structure of the energy-momentum tensor of radial excitations of
Q-balls in scalar field theories with U(1) symmetry. The obtained numerical
results for the excitations allow us to study in detail
patterns how the solutions behave with N. We show that although the fields and
energy-momentum tensor densities exhibit a remarkable degree of complexity, the
properties of the solutions scale with N with great regularity. This is to best
of our knowledge the first study of the D-term d1 for excited states, and we
demonstrate that it is negative --- in agreement with results from literature
on the d1 of ground state particles.Comment: 11 pages, 12 figure
Non-Singlet QCD Analysis of the Structure Function F_2 in 3-Loops
First results of a non--singlet QCD analysis of the structure function
in 3--loop order based on the non--singlet world data are
presented. Correlated errors are determined and their propagation through the
evolution equations is performed analytically. The value for is
determined to be compatible with results from other
QCD analyses. Low moments for , and with
correlated errors are calculated which may be compared with results from
lattice simulations.Comment: 1 Latex file, 1 style file, 2 figures Current World average on
alpha_s adde
Pentaquark searches at FOCUS
We find no evidence for high-energy photoproduction of pentaquarks at 1540
MeV/, 1862 MeV/, or 3099 MeV/ using decay modes ,
, and , respectively.Comment: Proceedings from talk at 2004 DPF Meeting at University of
California, Riversid
Exclusive diffractive processes at HERA within the dipole picture
We present a simultaneous analysis, within an impact parameter dependent
saturated dipole model, of exclusive diffractive vector meson (J/psi, phi and
rho) production, deeply virtual Compton scattering and the total gamma* p cross
section data measured at HERA. Various cross sections measured as a function of
the kinematic variables Q^2, W and t are well described, with little
sensitivity to the details of the vector meson wave functions. We determine the
properties of the gluon density in the proton in both longitudinal and
transverse dimensions, including the impact parameter dependent saturation
scale. The overall success of the description indicates universality of the
emerging gluon distribution and proton shape.Comment: 48 pages, 28 figures, the final version to appear in Physical Review
Exclusive photoproduction of meson in and reactions
The amplitude for is calculated in a pQCD -
factorization approach. The total cross section for this process is compared
with HERA data. Total cross section, as a function of photon-proton energy and
photon virtuality, is calculated. We also discuss the ratio of /
and the dependence on the mass of the strange quark. The amplitude
for is used to predict the cross section for exclusive
photoproduction of meson in proton-proton collisions. Absorption effects
are included. The results for RHIC, Tevatron and LHC energies are presented.Comment: 10 pages, 5 figure
- …