The Linked Dipole Chain Monte Carlo

We present an implementation of the Linked Dipole Chain model for deeply inelastic ep scattering into the framework of the Ariadne event generator. Using this implementation we obtain results both for the inclusive structure function as well as for exclusive properties of the hadronic final state. (The original publication was based on results from an implementation containing an error. In this revised version this error has been corrected, some of the beyond leading-log assumptions have been revised and so have some of the results.)Comment: 26 page

Is BFKL ruled out by the Tevatron gaps between jets data ?

We have performed a detailed phenomenological investigation of the hard colour singlet exchange process observed at the Tevatron in events that have a large rapidity gap between outgoing jets. We include the effects of multiple interactions to obtain a prediction for the gap survival factor. Comparing the data on the fraction of gap events with the prediction from BFKL pomeron exchange we find agreement provided that a constant value of alpha_s is used in the BFKL calculation. Moreover, the value of alpha_s is in line with that extracted from measurements made at HERA.Comment: 5 pages, 5 figures. Talk given at the Tevatron Run 2 QCD and Weak Boson Physics workshop, Nov 4-6 199

Diffractive vector boson production at the Tevatron

The diffractive production of vector bosons at the Tevatron is studied. We take a hard pomeron flux and use the H1 parton density functions extracted from their measurement of F_2^{D(3)}. To this we add a reggeon exchange contribution. We find that the ratio of diffractive to non-diffractive W boson production is in good agreement with the CDF data. We note that the poorly understood reggeon contribution might be as large as the pomeron contribution in the kinematic range of the data. We also note that our pomeron exchange contribution is much smaller than earlier predictions due to our use of a hard pomeron flux. All our results have been obtained using the lowest order matrix elements and we have compared to the results obtained using a modified version of Herwig which is capable of generating a wide variety of diffractive scattering processes. Gap survival is estimated using Pythia and is found to be around 60%. We make predictions which could be compared to future measurements of diffractive Drell-Yan production.Comment: 11 pages, 4 figure

K0s-K0s correlations in 7 TeV pp collisions from the ALICE experiment at the LHC

Identical neutral kaon pair correlations are measured in 7 TeV pp collisions in the ALICE experiment. K0s-K0s correlation functions are formed in 3 multiplicity X 4 kT bins. The femtoscopic kaon source parameters Rinv and lambda are extracted from these correlation functions by fitting a (femtoscopy) X (PYTHIA) model to them, PYTHIA accounting for the non-flat baseline found in pp collisions. Source parameters are obtained from a fit which includes quantum statistics and final-state interactions of the a0/f0 resonance. K0s-K0s correlations show a systematic increase in Rinv for increasing multiplicity bin and decreasing Rinv for increasing kT bin as seen in pi-pi correlations in the pp system, as well as seen in heavy-ion collisions. Also, K0s-K0s correlations are observed to smoothly extend this pi-pi Rinv behavior for the pp system up to about three times higher kT than the kT range measured in pi-pi correlations.Comment: Proceedings of the Quark Matter 2011 Conference, 4 pages, 5 figure

Wroclaw neutrino event generator

A neutrino event generator developed by the Wroclaw Neutrino Group is described. The physical models included in the generator are discussed and illustrated with the results of simulations. The considered processes are quasi-elastic scattering and pion production modelled by combining the $\Delta$ resonance excitation and deep inelastic scattering.Comment: Talk given at 2nd Scandanavian Neutrino Workshop (SNOW 2006), Stockholm, Sweden, 2-6 May 2006. 3 pages, 6 figure

How low can SUSY go? Matching, monojets and compressed spectra

If supersymmetry (SUSY) has a compressed spectrum then the current mass limits from the LHC can be drastically reduced. We consider a possible 'worst case' scenario where the gluino and/or squarks are degenerate with the lightest SUSY particle (LSP). The most sensitive searches for these compressed spectra are via the final state LSPs recoiling against initial state radiation (ISR). Therefore it is vital that the ISR is understood and possible uncertainties in the predictions are evaluated. We use both MLM (with Pythia 6) and CKKW- L (with Pythia 8) matching and vary matching scales and parton shower properties to accurately determine the theoretical uncertainties in the kinematic distributions. All current LHC SUSY and monojet analyses are employed and we find the most constraining limits come from the CMS Razor and CMS monojet searches. For a scenario of squarks degenerate with the LSP and decoupled gluinos we find $M_{\tilde{q}}>340$ GeV. For gluinos degenerate with the LSP and decoupled squarks, $M_{\tilde{g}}>500$ GeV. For equal mass squarks and gluinos degenerate with the LSP, $M_{\tilde{q},\tilde{g}}>650$ GeV.Comment: References added, version submitted to ep

Matching parton showers to NLO computations

We give a prescription for attaching parton showers to next-to-leading order (NLO) partonic jet cross sections in electron-positron annihilation. Our method effectively extends to NLO the scheme of Catani, Krauss, Kuhn, and Webber for matching between m hard jets and (m+1) hard jets. The matching between parton splitting as part of a shower and parton splitting as part of NLO matrix elements is based on the Catani-Seymour dipole subtraction method that is commonly used for removing the singularities from the NLO matrix elements.}Comment: 45 pages, new introduction, more detailed discussion of the Sudakov reweightin

Monte Carlo studies of the jet activity in Higgs + 2 jet events

Tree-level studies have shown in the past that kinematical correlations between the two jets in Higgs+2-jet events are direct probes of the Higgs couplings, e.g. of their CP nature. In this paper we explore the impact of higher-order corrections on the azimuthal angle correlation of the two leading jets and on the rapidity distribution of extra jets. Our study includes matrix-element and shower MC effects, for the two leading sources of Higgs plus two jet events at the CERN LHC, namely vector-boson and gluon fusion. We show that the discriminating features present in the previous leading-order matrix element studies survive.Comment: 12 pages, 10 figures. Version to appear on JHEP. Figs. 5-8 replaced with colour version

Generic User Process Interface for Event Generators

Generic Fortran common blocks are presented for use by High Energy Physics event generators for the transfer of event configurations from parton level generators to showering and hadronization event generators.Comment: Physics at TeV Colliders II Workshop, Les Houches, France, May 2001 14 pages, 6 figure