arXiv subjects
Publications and source records attributed to L. Favart.
A new method of extracting diffractive parton distributions is presented which avoids the use of Regge theory ansatz and is in much closer relation with the factorization theorem for diffarctive hard processes.
The Very Forward Proton Spectrometer (VFPS) of the H1 experiment at HERA is collecting data since 2005. The fiber detectors in the Roman pots located at 218 and 222m downstream from the H1 interaction point, tag and measure diffractively scattered protons with a high acceptance in the $\xpom$ range [0.01, 0.025]. The experimental set up and the spectrometer tagging performance using diffractive events collected during 2006 and 2007 are discussed.
Results are given on the measurements of the hard diffractive interactions at HERA $ep$ collider. The structure of the diffractive exchange in terms of partons and the factorisation properties are discussed, in particular by comparing the QCD predictions for dijets and $D^*$ with measurements both in the photo and electroproduction regimes.
The skewing factor, defined as the ratio of the imaginary parts of the amplitudes $Im A(γ^* p \to γ^* p)/Im A(γ^* p \to γp)$ is extracted for the first time from the data using recent Deeply Virtual Compton Scattering (DVCS) and the inclusive inelastic cross section measurements at DESY-HERA. The results values are compared to theoretical predictions for NLO QCD and the colour dipole approach.
Recent results on the Deeply Virtual Compton Scattering (DVCS) and prompt photon productions from H1 and ZEUS experiments on the $ep$ collider HERA are presented. A new DVCS cross section measurements of the H1 Collaboration, for photon virtualities $Q^2>4$ GeV$^2$ and photon-proton c.m.s. energy $30<W<140$ GeV, are discussed and compared to NLO QCD calculations encoding Generalized Parton Distributions (GPDs) and to Colour Dipole model predictions. For the first time the cross section dependence is reported on the momentum transfer squared at the proton vertex, $t$. Prompt photon production in deep inelastic scattering and photoproduction are presented both in the inclusive case and in the presence of a jet. The results are compared to NLO QCD predictions.
A review is given of the measurements of the hard diffractive interactions in recent years from two high-energy colliders, the HERA $ep$ collider and the Tevatron $p\bar{p}$ collider. The structure of the diffractive exchange in terms of partons, the factorisation properties and the ratio of diffractive to non-diffractive cross sections are discussed.
In this note, we present a new generator for Deeply Virtual Compton Scattering processes. This generator is based on formalism of Generalized Partons Distributions evolved at Next Leading Order (NLO). In the following we give a brief description of this formalism and we explain the main features of the generator for the elastic reactions, as well as for proton dissociation.
The Deeply Virtual Compton Scattering (DVCS) $γ^* p \to γp$ cross section has been measured with the H1 detector at HERA with an increased precision and in an extended kinematic domain: at photon virtualities $4<Q^2<80$ GeV$^2$, and photon-proton c.m.s. energy $30<W<140$ GeV. The measurement is compared to NLO QCD calculations and to Colour Dipole model predictions.
We show the role played by QCD evolution and skewedness effects in the DVCS cross section at large $Q^2$ within the color dipole description of the process at photon level. The dipole cross section is given by the saturation model, which can be improved by DGLAP evolution at high photon virtualities. We investigate both possibilities as well as the off-forward effect through a simple phenomenological parametrisation. The results are compared to the recent ZEUS DVCS data.
We investigate the deeply virtual Compton scattering (DVCS) in the color dipole approach, implementing the dipole cross section through the saturation model, which interpolates successfully between soft and hard regimes. The imaginary and real part of the DVCS amplitude are obtained and the results are compared to the available data.
A great interest for diffraction has been generated these last years by the HERA data. They give us the first opportunity to understand high energy diffractive physics in terms of a fundamental theory, i.e. QCD. A review of the main results from H1 and ZEUS in this field is presented and the relation with the proton structure function at small x-Bjorken values is discussed.
Results on Deeply Virtual Compton Scattering at HERA measured by the H1 and ZEUS Collaborations are presented. The cross section, measured for the first time, is reported for by H1 and ZEUS for $Q^2$ above a few GeV$^2$ in the low $x$ region. The measured cross section is discussed and compared to different predictions.
Results on Deeply Virtual Compton Scattering at HERA measured by the H1 and ZEUS Collaborations are presented. The cross section, measured for the first time, is reported for $Q^2 > 2 GeV^2$, $30 < W < 120 GeV$ and $|t| < 1 GeV^2$.
Results on Deeply Virtual Compton Scattering at HERA measured by the H1 and ZEUS Collaborations are presented. The cross section, measured for the first time, is reported for Q^2 > 2 GeV^2.
A new, very forward proton spectrometer (VFPS) with large acceptance is proposed to be installed in the proton beam of the H1 experiment after the luminosity upgrade in the year 2000. The spectrometer, located at 220 m downstream of the interaction point is based on the Roman Pot technique and consists of two stations situated in the cold section of the proton beam line. Physics motivations and a brief description of the proton spectrometer are presented.
Brief review of the diffractive physics at HERA, stressing QCD aspects.
It is shown that a significant measurement of the longitudinal structure function $F_L(x,Q^2)$ can be performed at HERA, for $Q^2 = 2 GeV^2$ and $Q^2 = 5 GeV^2$ and for x around $10^{-4}$, using radiative events with hard photon emission collinear to the incident lepton beam, under the present running conditions and with an integrated luminosity of 10 $pb^{-1}$. The influence of experimental conditions is discussed.
Review of prospects for discovery of new physics signals at LEP2. The areas covered include SUSY, exotic fermions, BESS models, leptoquarks, virtual effects and CP violating observables.