332 research outputs found
The Layout of the photon collider at the ILC
One of the interaction regions at the linear colliders should be compatible
both with e+e- and gamma-gamma, gamma-electron modes of operation. In this
paper, the differences in requirements and possible design solutions are
discussed.Comment: Talk at LCWS06, Bangalore, India, March 2006, to be published in
Indian Journal of Physics; 3pp, Latex, 1 .eps figur
Parametrisation of F_2^gamma at low Q^2 and of sigma(gamma,gamma) and sigma(gamma^*,gamma) at high energies
A parametrisation of the real photon structure function F_2^gamma in the low
Q^2, low x region is formulated. It includes both the VMD and the QCD
components, the latter suitably extrapolated to the low Q^2 region and based on
arbitrary parton distributions in the photon. The parametrisation used together
with the GRV and GRS' parton densities describes reasonably well the existing
high energy data on F_2^gamma, sigma(gamma,gamma) and the low Q^2 data on
sigma(gamma^*, gamma). Predictions for sigma(gamma,gamma) and for sigma(gamma^*
,gamma) for energies which may become accessible in future linear colliders are
also given.Comment: 21 pages, 11 figure
Spin dependent structure function at small and small
Theoretical expectations concerning the low and low behaviour of
are summarized and compared with the recent SMC data.Comment: 4 pages, plain LATEX, 1 eps figure; contribution to 3rd UK
Phenomenology Workshop on HERA Physics, St. John's College, Durham, UK,
September 199
Deep Inelastic Lepton-Nucleon Scattering at HERA
Data from the HERA collider experiments, H1 and ZEUS, have been fundamental
to the rapid recent development of our understanding of the partonic
composition of the proton and of QCD. This report focuses on inclusive
measurements of neutral and charged current cross sections at HERA, using the
full available data taken to date. The present precision on the proton parton
densities and the further requirements for future measurements at the Tevatron
and LHC are explored. Emphasis is also placed on the region of very low
Bjorken-x and Q^2. In this region, the `confinement' transition takes place
from partons to hadrons as the relevant degrees of freedom and novel or exotic
QCD effects associated with large parton densities are most likely to be
observed. Finally, prospects for the second phase of HERA running are
discussed.Comment: 13 pages, 15 figures, to appear in Proceedings of the XXI
International Symposium on lepton and Photon Interactions at High Energies,
Fermilab, August 200
Comment on the recent COMPASS data on the spin structure function g_1
We examine the recent COMPASS data on the spin structure function g_1
singlet. We show that it is rather difficult to use the data in the present
form in order to draw conclusions on the initial parton densities. However, our
tentative estimate is that the data better agree with positive rather than
negative initial gluon densities.Comment: 8 pages, 1 figur
Testing the Noncommutative Standard Model at a Future Photon Collider
Extensions of the Standard Model of elementary particle physics to
noncommutative geometries have been proposed as a low energy limit of string
models. Independent of this motivation, one may consider such a model as an
effective field theory with higher-dimensional operators containing an
antisymmetric rank-two background field. We study the signals of such a
Noncommutative Standard Model (NCSM) and analyze the discovery potential of a
future photon collider, considering angular distributions in fermion pair
production.Comment: 13 pages RevTeX, Feynman diagrams and figures included, references
added, typographical errors in Feynman rules corrected (all results remain
unchangend, since correct Feynman rules were used in the calculations), to
appear in Phys. Rev.
Accessing the Longitudinally Polarized Photon Content of the Proton
We investigate the QED Compton process (QEDCS) in longitudinally polarized
lepton-proton scattering both in the elastic and inelastic channels and show
that the cross section can be expressed in terms of the polarized equivalent
photon distribution of the proton. We provide the necessary kinematical
constraints to extract the polarized photon content of the proton using this
process at HERMES, COMPASS and eRHIC. We also discuss the suppression of the
major background process coming from virtual Compton scattering. We point out
that such an experiment can give valuable information on in the
small , broad region at the future polarized collider eRHIC and
especially in the lower , medium region in fixed target experiments.Comment: Version to appear in PR
A polarized version of the CCFM equation for gluons
A derivation for a polarized CCFM evolution equation which is suitable to
describe the scaling behavior of the the unintegrated polarized gluon density
is given. We discuss the properties of this polarized CCFM equation and compare
it to the standard CCFM equation in the unpolarized case.Comment: 15 pages, 6 figures, RevTeX, some minor typos corrected, version to
appear in Phys. Rev.
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