Inelastic dark matter at the LHC

The dark matter sector may be more complicated than anticipated. An inelastically scattering dark matter with a mass splitting above one MeV will make direct detection experiments hopeless, and render LHC the primary chance for discovery. We perform a model-independent study of inelastic dark matter at the LHC, concentrating on the parameter space with the mass splitting between the excited and ground states of dark matter above a few hundred MeV. The generic signatures of inelastic dark matter at the LHC are displaced pions together with a monojet plus missing energy, and can be tested at the 7 TeV LHC.     

Inelastic diffraction at collider energy

s-channel unitarity strongly constrains the amount of inelastic diffraction at collider energy, and allows to predict its dependence on the impact parameter and to compute useful upper bounds at even higher energies.     

Soft diffraction at the LHC: a partonic interpretation

We present a ‘new generation’ model for high energy proton–proton ‘soft’ interactions. It allows for a full set of multipomeron vertices as well as for including multichannel eikonal scattering. It describes the behaviour of the proton–proton total, σ_tot, and elastic, dσ_el/dt, cross sections together with those for low- and high-mass proton dissociation. Although the model contains a comprehensive set of multipomeron diagrams, it has a simple partonic interpretation. Including the more complicated multipomeron vertices reduces the absorptive effects as compared to the predictions in which only the triple-pomeron vertex is considered. Tuning the model to describe the available ‘soft’ data in the CERN ISR–tevatron energy range, we predict the total, elastic, single- and double-diffractive dissociation cross sections at the LHC energy. An inescapable consequence of including multichannel eikonal and multipomeron effects is that the total cross section is expected to be lower than before: indeed, we find σ_tot≃ 90 mb at the LHC energy. We also present differential forms of the cross sections. In addition, we calculate soft diffractive central production.     

Inelastic diffraction in the quark-glue model

Diffractive dissociation of hadrons is related to the quark-glue picture of their structure. It is shown that the quark-glue model can produce sufficiently large variations of opacities for diffractive eigenstates to account for the experimental value of diffractive cross sections if unitarity is saturated in central glue-glue collisions. This requirement simplifies the collision picture and provides a natural explanation for the observed energy independence of proton opacity in central pp collisions.     

SUSY at the LHC

I discuss part of the program of work towards discoveries at the LHC with seeds for orientation and navigation in the parameter space given an anticipated multitude of excesses at start-up.     

Supersymmetry at the LHC

The success of supersymmetry is beyond any doubt. With the availability of the precise measurement of the dark-matter content of the universe, SUSY models are used as cosmological connection to particle physics. We are now ready to verify this theory directly at the upcoming large hadron collider (LHC). It is possible to use the LHC measurements to reconstruct the SUSY model parameters. These parameters will then be used to calculate the relic density very precisely to be compared with the dark-matter content measured from the astrophysical measurements. In this review, I will summarize various search strategies which will be important to measure supersymmetry parameters in different models in order to establish the cosmological connection.     

Soft diffraction and the elastic slope at Tevatron and LHC energies: a multi-Pomeron approach

We present a formalism for high energy soft processes, mediated by Pomerons, which embodies pion-loop insertions in the Pomeron trajectory, rescattering effects via a two-channel eikonal and high-mass diffractive dissociation. It describes all the main features of the data throughout the ISR to Tevatron energy interval. We give predictions for soft diffractive phenomena at the LHC energy, and we calculate the different survival probabilities of rapidity gaps which occur in various diffractive processes. Received: 1 August 2000 / Published online: 27 October 2000     

Higgs searches at the LHC

We review the prospects for searches of the Standard Model Higgs boson at the LHC, based on detailed studies performed by the ATLAS and CMS Collaborations. The search channels and strategies are described, resulting in the assessment of the discovery potential for the two experiments. We discuss the prospects for measurements in the Higgs sector. To cite this article: A. De Roeck, G. Polesello, C. R. Physique 8 (2007).     

Quantum gravity at the LHC

We study the production of massless gravitons at the LHC and compare our results to those obtained in extra-dimensional models. The signature in both cases is missing energy plus jets. In case of non-observation, the LHC could be used to put the tightest limit to date on the value of the Planck mass.     

Higgs bosons at the LHC

The investigation of the dynamics responsible for electroweak symmetry breaking is one of the prime tasks of the experiments at the CERN Large Hadron Collider (LHC). In this article, the potential of the ATLAS and CMS experiments for the discovery of a standard model Higgs boson and for Higgs bosons in the minimal supersymmetric extension is summarized. Emphasis is put on those studies which have been performed recently by the experimental collaborations using a realistic simulation of the detector performance. This includes a discussion of the search for Higgs bosons using the vector boson-fusion mode, a discussion on the measurement of Higgs boson parameters as well as a detailed review of the MSSM sector for different benchmark scenarios.     

Higgs physics at LHC

The large hadron collider (LHC) and its detectors, ATLAS and CMS, are being built to study TeV scale physics, and to fully understand the electroweak symmetry breaking mechanism. The Monte-Carlo simulation results for the standard model and minimal super symmetric standard model Higgs boson searches and parameter measurements are discussed. Emphasis is placed on recent investigations of Higgs produced in association with top quarks and in vector boson fusion channels. These results indicate that Higgs sector can be explored in many channels within a couple of years of LHC operation, i.e.,L = 30 fb⁻¹. Complete coverage including measurements of Higgs parameters can be carried out with full LHC program.     

On minimum-bias effects at the LHC

In general, minimum-bias triggers planned for experiments at the LHC miss a considerable fraction of the total number of events. We exemplify the rejection rate using the Durham model of soft high-energy interactions to obtain quantitative estimates of the signals arising from the ATLAS scintillation counters positioned in the rapidity intervals 2<|η|<4$2<|\eta |<4$, and also from TOTEM detectors covering the intervals 3.1<|η|<6.5$3.1<|\eta |<6.5$. Typically we find that the expected signal is about half of the total cross section, σtot${\sigma }_{\mathrm{tot}}$. We also calculate the cross section for the so-called zero-bias measurement planned by CMS in the extended rapidity interval −5<η<7$-5<\eta <7$. We emphasize that only models which give satisfactory predictions for the measured minimum-bias or zero-bias cross sections can be used to obtain the value of the total inelastic cross section.