Associated W and Higgs boson photoproduction and other electroweak photon induced processes at the LHC

Experimental prospects for studying at the LHC photon-proton interactions at center of mass energies up to and above 1 TeV are discussed. Cross sections are presented for many electroweak and beyond the Standard Model processes. Selection strategies based on photon interaction tagging techniques are discussed. Assuming a typical LHC multipurpose detector, the production of single top associated to a W, and anomalous top signals and their irreducible backgrounds are presented after applying detector acceptance cuts. The associated photoproduction of Higgs and W bosons has a typical cross section of 20 fb. The possibility of observing this reaction is investigated for topologies with signal-to-noise ratio close to unity. Comment: 8 pages, 8 tables, 6 figures. Summary talk given at the Workshop on "High-energy photon collisions at the LHC", April 22-25, 2008, CERN, Switzerland. To appear in the proceeding

Detection of two-photon exclusive production of supersymmetric pairs at the LHC

The detection of pairs of sleptons, charginos and charged higgs bosons produced via photon-photon fusion at the LHC is studied, assuming a couple of benchmark points of the MSSM model. Due to low cross sections, it requires large integrated luminosity, but thanks to the striking signature of these exclusive processes the backgrounds are low, and are well known. Very forward proton detectors can be used to measure the photon energies, allowing for direct determination of masses of the lightest SUSY particle, of selectrons and smuons with a few GeV resolution. Finally, the detection and mass measurement of quasi-stable particles predicted by the so-called sweet spot supersymmetry is discussed. Comment: 9 pages, 5 tables, 8 figures. Talk given at the Workshop on "High-energy photon collisions at the LHC", April 22-25, 2008, CERN, Switzerland. To appear in the proceeding

Single top quark photoproduction at the LHC

High-energy photon-proton interactions at the LHC offer interesting possibilities for the study of the electroweak sector up to TeV scale and searches for processes beyond the Standard Model. An analysis of the W associated single top photoproduction has been performed using the adapted MadGraph/MadEvent and CalcHEP programs interfaced to the Pythia generator and a fast detector simulation program. Event selection and suppression of main backgrounds have been studied. A comparable sensitivity to |V_{tb}| to those obtained using the standard single top production in pp collisions has been achieved already for 10 fb^{-1} of integrated luminosity. Photoproduction at the LHC provides also an attractive framework for observation of the anomalous production of single top due to Flavour-Changing Neutral Currents. The sensitivity to anomalous coupling parameters, k_{tu\gamma} and k_{tc\gamma} is presented and indicates that stronger limits can be placed on anomalous couplings after 1 fb^{-1}

The Fragmentation of Quarks in DIS and Strangeness in Photoproduction in

Deep Inelastic scattering (DIS) data, taken in 1993 by the H1 experiment at HERA. The fragmentation function of the quark is examined in the Breit frame of reference and compared with e + e \Gamma data. The measured area, peak and width of the fragmentation function shows that the kinematic evolution variable equivalent to the e + e \Gamma squared centre of mass energy is the invariant square of the four-momentum transfer. The comparison of the differential K 0 s cross-section with the measured inclusive charged particle cross-section shows the contribution of strangeness in photoproduction events. Comparisons of the measured cross-sections with QCD based Monte Carlo models including leading order matrix elements and fragmentation effects are presented. 1. ep Collider Kinematics The HERA collider at DESY, which delivered the first ep interactions in 1992, has opened new kinematical domains in deep inelastic lepton-nucleon scattering in both the small x (Bjorken scaling vari..

OPAL Physics Note PN461 6 October New Particle Searches in e

In this note we report preliminary results of searches for scalar quarks, charginos, neutralinos, heavy long-lived charged particles, anomalous photonic events, excited leptons, leptoquarks, and the single production of top quarks. The analyses combine about 165 pb -1 of data collected with the OPAL detector at # s 200--209 GeV, the highest e e - energy yet achieved. No significant evidence for new physics is observed