Searcharxiv⌕ Search

arXiv subjects

C. Royon

Publications and source records attributed to C. Royon.

At least 91 records · Page 5Linked to original sources
arXiv2007

Diffractive $χ$ Production at the Tevatron and the LHC

We present predictions for the diffractive production of $χ$ mesons in the central rapidity region usually covered by collider detectors. The predicted cross sections are based on the Bialas-Landshoff formalism for both exclusive and inclusive production and makes use of the DPEMC Monte-Carlo simulation adapted with kinematics appropriate for small-mass diffractive production. We compare generator-level results with a CDF measurement for exclusive $χ$ production, and study background and other scenarios including the contribution of inclusive $χ$ production. The results agree with the Tevatron data and are extrapolated, highlighting the exclusive $\chic$ production at LHC energies. A possible new measurement at the Tevatron using the DØforward detectors is investigated, taking advantage of the dominance of exclusive production for high enough diffractive mass fraction.

hep-ph↗
arXiv2006

Diffraction at HERA, the Tevatron and the LHC

In these lectures, we present and discuss the most recent results on inclusive diffraction from the HERA and Tevatron colliders and give the prospects for the future at the LHC. Of special interest is the exclusive production of Higgs boson and heavy objects ($W$, top, stop pairs) which will require a better understanding of diffractive events and the link between $ep$ and hadronic colliders, as well as precise measurements and analyses of inclusive diffraction at the LHC in particular to constrain further the gluon density in the pomeron.

hep-ph↗
arXiv2006

Tevatron-for-LHC Report of the QCD Working Group

The experiments at Run 2 of the Tevatron have each accumulated over 1 inverse femtobarn of high-transverse momentum data. Such a dataset allows for the first precision (i.e. comparisons between theory and experiment at the few percent level) tests of QCD at a hadron collider. While the Large Hadron Collider has been designed as a discovery machine, basic QCD analyses will still need to be performed to understand the working environment. The Tevatron-for-LHC workshop was conceived as a communication link to pass on the expertise of the Tevatron and to test new analysis ideas coming from the LHC community. The TeV4LHC QCD Working Group focussed on important aspects of QCD at hadron colliders: jet definitions, extraction and use of Parton Distribution Functions, the underlying event, Monte Carlo tunes, and diffractive physics. This report summarizes some of the results achieved during this workshop.

hep-ph↗
arXiv2006

A global analysis of inclusive diffractive cross sections at HERA

We describe the most recent data on the diffractive structure functions from the H1 and ZEUS Collaborations at HERA using four models. First, a Pomeron Structure Function (PSF) model, in which the Pomeron is considered as an object with parton distribution functions. Then, the Bartels Ellis Kowalski Wusthoff (BEKW) approach is discussed, assuming the simplest perturbative description of the Pomeron using a two-gluon ladder. A third approach, the Bialas Peschanski (BP) model, based on the dipole formalism is then described. Finally, we discuss the Golec-Biernat-Wüsthoff (GBW) saturation model which takes into account saturation effects. The best description of all avaible measurements can be achieved with either the PSF based model or the BEKW approach. In particular, the BEKW prediction allows to include the highest $β$ measurements, which are dominated by higher twists effects and provide an efficient and compact parametrisation of the diffractive cross section. The two other models also give a good description of cross section measurements at small $x$ with a small number of parameters. The comparison of all predictions allows us to identify interesting differences in the behaviour of the effective pomeron intercept and in the shape of the longitudinal component of the diffractive structure functions. In this last part, we present some features that can be discriminated by new experimental measurements, completing the HERA program.

hep-ph↗
arXiv2006

Pomeron structure functions from HERA to Tevatron and LHC

The proton diffractive structure function $F_2^{D(3)}$ measured in the H1 and ZEUS experiments at HERA are analysed in terms of perturbative QCD in the perspective of the QCD extrapolation to the Tevatron and the LHC. It is shown that both data sets can be well described by a QCD analysis in which point-like parton distributions, evolving according to the next-leading DGLAP equations, are assigned to the leading and sub-leading Regge exchanges. For present data from H1 and ZEUS the gluon distributions are found to be quite different and we give the corresponding sets of quark and gluon parton distributions for the Pomeron, extracted from the two experiments. An extrapolation to the Tevatron range is compared with CDF data on single diffraction. Conclusions on factorization breaking between HERA and Tevatron critically depend on whether H1 (strong violation) or ZEUS (compatibility at low $β$) fits are taken into account. Using the double Pomeron formulation in central diffractive dijet production we show that the Tevatron mass fraction is much sensitive to the high $β$ tail of the gluon in the Pomeron, suggesting a new way of handling the otherwise badly known gluon distribution in the Pomeron. Extrapolation of the fits to very high $Q^2$ are given since they will be relevant for QCD and diffraction studies at the LHC.

hep-ph↗
arXiv2006

Diffractive SUSY particle production at the LHC

We give detailed predictions for diffractive SUSY Higgs boson and top squark associated productions at the LHC via the exclusive double pomeron exchange mechanism. We study how the SUSY Higgs cross section and the signal over background ratio are enhanced as a function of tangent beta in different regimes. The prospects are particularly promising in the ``anti-decoupling'' regime, which we study in detail. We also give the prospects for a precise measurement of the top squark mass using the threshold scan of central diffractive associated top squark events at the LHC.

hep-ph↗
arXiv2006

Small-x QCD effects in forward-jet and Mueller-Navelet jet production

We investigate small-x QCD effects in forward-jet production in deep inelastic scattering in the kinematic regime where the virtuality of the photon and the transverse momentum of the jet are two hard scales of about the same magnitude. We show that the data from HERA published by the H1 and ZEUS collaborations are well described by leading-logarithmic BFKL predictions. Parametrizations containing saturation effects expected to be relevant at higher energies also compare well to the present data. We extend our analysis to Mueller-Navelet jets at the LHC and discuss to what extent this observable could test these small-x effects and help distinguishing between the different descriptions.

hep-ph↗
arXiv2006

Hard diffraction at the LHC and the Tevatron using double pomeron exchange

We use a Monte Carlo implementation of recently developped models of inclusive and exclusive diffractive $W$, top, Higgs and stop productions to assess the sensitivity of the LHC experiments. We also discuss how the Tevatron experiments could test the models and measure the gluon density in the pomeron, which is needed to make precise predictions at the LHC.

hep-ph↗
arXiv2005

High mass diffraction at the LHC

We use a Monte Carlo implementation of recently developped models of exclusive diffractive W, top, Higgs and stop productions to assess the sensitivity of the LHC experiments.

hep-ph↗
arXiv2005

Threshold scans in Central Diffraction at the LHC

We propose a new set of measurements which can be performed at the LHC using roman pot detectors. The method exploits excitation curves in central diffractive pair production, and is illustrated using the examples of the W boson and top quark mass measurements. Further applications are mentioned.

hep-ph↗
arXiv2005

Confronting next-leading BFKL kernels with proton structure function data

We propose a phenomenological study of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach applied to the data on the proton structure function F_2 measured at HERA in the small-x_{Bjorken} region. In a first part we use a simplified ``effective kernel'' approximation leading to few-parameter fits of F_2. It allows for a comparison between leading-logs (LO) and next-to-leading logs (NLO) BFKL approaches in the saddle-point approximation, using known resummed NLO-BFKL kernels. The NLO fits give a qualitatively satisfactory account of the running coupling constant effect but quantitatively the chi squared remains sizeably higher than the LO fit at fixed coupling. In a second part, a comparison of theory and data through a detailed analysis in Mellin space (x_{Bjorken} -> omega) leads to a more model independent approach to the resummed NLO-BFKL kernels we consider and points out some necessary improvements of the extrapolation at higher orders.

hep-ph↗
arXiv2004

Physics at the CLIC Multi-TeV Linear Collider

This report summarizes a study of the physics potential of the CLIC e+e- linear collider operating at centre-of-mass energies from 1 TeV to 5 TeV with luminosity of the order of 10^35 cm^-2 s^-1. First, the CLIC collider complex is surveyed, with emphasis on aspects related to its physics capabilities, particularly the luminosity and energy, and also possible polarization, γγand e-e- collisions. The next CLIC Test facility, CTF3, and its R&D programme are also reviewed. We then discuss aspects of experimentation at CLIC, including backgrounds and experimental conditions, and present a conceptual detector design used in the physics analyses, most of which use the nominal CLIC centre-of-mass energy of 3 TeV. CLIC contributions to Higgs physics could include completing the profile of a light Higgs boson by measuring rare decays and reconstructing the Higgs potential, or discovering one or more heavy Higgs bosons, or probing CP violation in the Higgs sector. Turning to physics beyond the Standard Model, CLIC might be able to complete the supersymmetric spectrum and make more precise measurements of sparticles detected previously at the LHC or a lower-energy linear e+e- collider: γγcollisions and polarization would be particularly useful for these tasks. CLIC would also have unique capabilities for probing other possible extensions of the Standard Model, such as theories with extra dimensions or new vector resonances, new contact interactions and models with strong WW scattering at high energies. In all the scenarios we have studied, CLIC would provide significant fundamental physics information beyond that available from the LHC and a lower-energy linear e+e- collider, as a result of its unique combination of high energy and experimental precision.

hep-ph↗
arXiv2004

Saturation and forward jets at HERA

We analyse forward-jet production at HERA in the framework of the Golec-Biernat and Wusthoff saturation models. We obtain a good description of the forward jet cross sections measured by the H1 and ZEUS collaborations in the two-hard-scale region kT ~ Q >> Lambda_QCD with two different parametrisations with either significant or weak saturation effects. The weak saturation parametrization gives a scale compatible with the one found for the proton structure function F_2. We argue that Mueller-Navelet jets at the Tevatron and the LHC could help distinguishing between both options.

hep-ph↗