ExHuME: A Monte Carlo Event Generator for Exclusive Diffraction

We have written the Exclusive Hadronic Monte Carlo Event (ExHuME) generator. ExHuME implements the perturbative QCD calculation of Khoze, Martin and Ryskin of the process pp-> p+X+p, where X is a centrally produced colour singlet system.Comment: 11 pages, 3 figure

Hunting a light CP-violating Higgs via diffraction at the LHC

We study the central diffractive production of the (three neutral) Higgs bosons, with a rapidity gap on either side, in an MSSM scenario with CP-violation. We consider the bb-bar and tautau-bar decay for the light H_1 boson and the four b-jet final state for the heavy H_2 and H_3 bosons, and discuss the corresponding backgrounds. A direct indication of the existence of CP-violation can come from the observation of either an azimuthal asymmetry in the angular distribution of the tagged forward protons (for the exclusive pp -> p+H+p process) or of a sin(2phi) contribution in the azimuthal correlation between the transverse energy flows in the proton fragmentation regions for the process with the diffractive dissociation of both incoming protons (pp -> X+H+Y). We emphasise the advantage of reactions with the rapidity gaps (that is production by the pomeron-pomeron fusion) to probe CP parity and to determine the quantum numbers of the produced central object.Comment: 11 pages, 3 figure

Diffractive gamma-gamma production at hadron colliders

We compute the cross section for exclusive double-diffractive gamma-gamma production at the Tevatron, $p{\bar p} \to p + \gamma\gamma + {\bar p}$, and the LHC. We evaluate both the gluon-gluon and quark-antiquark t-channel exchange contributions to the process. The observation of exclusive gamma-gamma production at the Tevatron will provide a check on the model predictions, and offer an opportunity to confirm the expectations for exclusive double-diffractive Higgs production at the LHC.Comment: 16 pages, 7 figure

Structure of the final states in Higgs production at Hadronic Colliders

We quantify the rate and the signal-to-background ratio for Higgs $\to b\bar{b}$ detection in double-diffractive events at the Tevatron and the LHC. The signal is predicted to be very small at the Tevatron, but observable at the LHC. We exemplify the diagnostic power of hadronic antenna pattern by considering the topology of hadronic flow corresponding to Higgs $\to b\bar{b}$ events.Comment: 4 pages, talk given at XXXI International Symposium on Multiparticle Dynamics, Sept 1-7, 2001, Datong China. URL http://ismd31.ccnu.edu.cn

Rapidity Gap Higgs Signal at the Tevatron and the LHC

We quantify the rate and the signal-to-background ratio for Higgs --> b anti-b detection in double-diffractive events at the Tevatron and the LHC. The signal is predicted to be very small at the Tevatron, but observable at the LHC. We show that the double-diffractive dijet production may serve as a unique gluon factory. This process can be used also as a Pomeron-Pomeron luminosity monitor.Comment: 12 pages, 1 figure, Late

Non-factorizable corrections and effective field theories

We analyze the structure of higher-order radiative corrections for processes with unstable particles. By subsequently integrating out the various scales that are induced by the presence of unstable particles we obtain a hierarchy of effective field theories. In the effective field theory framework the separation of physically different effects is achieved naturally. In particular, we automatically obtain a separation of factorizable and non-factorizable corrections to all orders in perturbation theory. At one loop this treatment is equivalent to the double-pole approximation (DPA) but generalizes to higher orders and, at least in principle, to beyond the DPA. It is known that one-loop non-factorizable corrections to invariant mass distributions are suppressed at high energy. We study the mechanism of this suppression and obtain estimates of higher-order non-factorizable corrections at high energy.Comment: 45 page

QCD Interconnection Studies at Linear Colliders

Heavy objects like the W, Z and t are short-lived compared with typical hadronization times. When pairs of such particles are produced, the subsequent hadronic decay systems may therefore become interconnected. We study such potential effects at Linear Collider energies.Comment: 1+7 pages, 6 figure