B. Webber - University of Pennsylvania

B. Webber
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B. Webber
University of Pennsylvania
United States

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High Energy Physics - Phenomenology (49)
High Energy Physics - Experiment (14)
High Energy Physics - Theory (2)
Computer Science - Computation and Language (1)
Nuclear Theory (1)

Publications Authored By B. Webber

We compute the leading-order evolution of parton distribution functions for all the Standard Model fermions and bosons up to energy scales far above the electroweak scale, where electroweak symmetry is restored. Our results include the 52 PDFs of the unpolarized proton, evolving according to the SU(3), SU(2), U(1), mixed SU(2) x U(1) and Yukawa interactions. We illustrate the numerical effects on parton distributions at large energies, and show that this can lead to important corrections to parton luminosities at a future 100 TeV collider. Read More

Many language technology applications would benefit from the ability to represent negation and its scope on top of widely-used linguistic resources. In this paper, we investigate the possibility of obtaining a first-order logic representation with negation scope marked using Universal Dependencies. To do so, we enhance UDepLambda, a framework that converts dependency graphs to logical forms. Read More

We study the impact of including quark- and gluon-initiated jet discrimination in the search for strongly interacting supersymmetric particles at the LHC. Taking the example of gluino pair production, considerable improvement is observed in the LHC search reach on including the jet substructure observables to the standard kinematic variables within a multivariate analysis. In particular, quark and gluon jet separation has higher impact in the region of intermediate mass-gap between the gluino and the lightest neutralino, as the difference between the signal and the standard model background kinematic distributions is reduced in this region. Read More

We show that in studies of light quark- and gluon-initiated jet discrimination, it is important to include the information on softer reconstructed jets (associated jets) around a primary hard jet. This is particularly relevant while adopting a small radius parameter for reconstructing hadronic jets. The probability of having an associated jet as a function of the primary jet transverse momentum ($p_T$) and radius, the minimum associated jet $p_T$ and the association radius is computed upto next-to-double logarithmic accuracy (NDLA), and the predictions are compared with results from Herwig++, Pythia6 and Pythia8 Monte Carlos (MC). Read More

We compute the resummed hadronic transverse-energy ($E_T$) distribution due to initial-state QCD radiation in the production of a Standard Model Higgs boson of mass 126 GeV by gluon fusion at the Large Hadron Collider, with matching to next-to-leading order calculations at large $E_T$. Effects of hadronization, underlying event and limited detector acceptance are estimated using aMC@NLO with the Herwig++ and Pythia 8 event generators. Read More

Authors: K. Agashe, R. Erbacher, C. E. Gerber, K. Melnikov, R. Schwienhorst, A. Mitov, M. Vos, S. Wimpenny, J. Adelman, M. Baumgart, A. Garcia-Bellido, A. Loginov, A. Jung, M. Schulze, J. Shelton, N. Craig, M. Velasco, T. Golling, J. Hubisz, A. Ivanov, M. Perelstein, S. Chekanov, J. Dolen, J. Pilot, R. Pöschl, B. Tweedie, S. Alioli, B. Alvarez-Gonzalez, D. Amidei, T. Andeen, A. Arce, B. Auerbach, A. Avetisyan, M. Backovic, Y. Bai, M. Begel, S. Berge, C. Bernard, C. Bernius, S. Bhattacharya, K. Black, A. Blondel, K. Bloom, T. Bose, J. Boudreau, J. Brau, A. Broggio, G. Brooijmans, E. Brost, R. Calkins, D. Chakraborty, T. Childress, G. Choudalakis, V. Coco, J. S. Conway, C. Degrande, A. Delannoy, F. Deliot, L. Dell'Asta, E. Drueke, B. Dutta, A. Effron, K. Ellis, J. Erdmann, J. Evans, C. Feng, E. Feng, A. Ferroglia, K. Finelli, W. Flanagan, I. Fleck, A. Freitas, F. Garberson, R. Gonzalez Suarez, M. L. Graesser, N. Graf, Z. Greenwood, J. George, C. Group, A. Gurrola, G. Hammad, T. Han, Z. Han, U. Heintz, S. Hoeche, T. Horiguchi, I. Iashvili, A. Ismail, S. Jain, P. Janot, W. Johns, J. Joshi, A. Juste, T. Kamon, C. Kao, Y. Kats, A. Katz, M. Kaur, R. Kehoe, W. Keung, S. Khalil, A. Khanov, A. Kharchilava, N. Kidonakis, C. Kilic, N. Kolev, A. Kotwal, J. Kraus, D. Krohn, M. Kruse, A. Kumar, S. Lee, E. Luiggi, S. Mantry, A. Melo, D. Miller, G. Moortgat-Pick, M. Narain, N. Odell, Y. Oksuzian, M. Oreglia, A. Penin, Y. Peters, C. Pollard, S. Poss, H. B. Prosper S. Rappoccio, S. Redford, M. Reece, F. Rizatdinova, P. Roloff, R. Ruiz, M. Saleem, B. Schoenrock, C. Schwanenberger, T. Schwarz, K. Seidel, E. Shabalina, P. Sheldon, F. Simon, K. Sinha, P. Skands, P. Skubik, G. Sterman, D. Stolarski, J. Strube, J. Stupak, S. Su, M. Tesar, S. Thomas, E. Thompson, P. Tipton, E. Varnes, N. Vignaroli, J. Virzi, M. Vogel, D. Walker, K. Wang, B. Webber, J. D. Wells, S. Westhoff, D. Whiteson, M. Williams, S. Wu, U. Yang, H. Yokoya, H. Yoo, H. Zhang, N. Zhou, H. Zhu, J. Zupan

This report summarizes the work of the Energy Frontier Top Quark working group of the 2013 Community Summer Study (Snowmass). Read More

We point out that QCD coherence effects can help to identify the colour structure of possible new physics contributions to the anomalously large forward-backward asymmetry in top quark pair production. New physics models that yield the same inclusive asymmetry make different predictions for its dependence on the transverse momentum of the pair, if they have different colour structures. From both a fixed-order effective field theory approach and Monte Carlo studies of specific models, we find that an s-channel octet structure is preferred. Read More

The leading-order accurate description of top quark pair production, as usually employed in standard Monte Carlo event generators, gives no rise to the generation of a forward--backward asymmetry. Yet, non-negligible -- differential as well as inclusive -- asymmetries may be produced if coherent parton showering is used in the hadroproduction of top quark pairs. In this contribution we summarize the outcome of our study of this effect. Read More

We derive generating functions, valid to next-to-double logarithmic accuracy, for QCD jet rates according to the inclusive forms of the kt, Cambridge/Aachen and anti-kt algorithms, which are equivalent at this level of accuracy. We compare the analytical results with jet rates and average jet multiplicities from the SHERPA event generator, and study the transition between Poisson-like and staircase-like behaviour of jet ratios. Read More

We propose a method for reconstructing the mass of a particle, such as the Higgs boson, decaying into a pair of tau leptons, of which one subsequently undergoes a 3-prong decay. The kinematics is solved using information from the visible decay products, the missing transverse momentum, and the 3-prong tau decay vertex, with the detector resolution taken into account using a likelihood method. The method is shown to give good discrimination between a 125 GeV Higgs boson signal and the dominant backgrounds, such as Z decays to tau tau and W plus jets production. Read More

Coherent QCD radiation in the hadroproduction of top quark pairs leads to a forward--backward asymmetry that grows more negative with increasing transverse momentum of the pair. This feature is present in Monte Carlo event generators with coherent parton showering, even though the production process is treated at leading order and has no intrinsic asymmetry before showering. In addition, depending on the treatment of recoils, showering can produce a positive contribution to the inclusive asymmetry. Read More

We review the methods developed for combining the parton shower approximation to QCD with fixed-order perturbation theory, in such a way as to achieve next-to-leading-order (NLO) accuracy for inclusive observables. This has made it possible to generate fully-simulated hadronic final states with the precision and stability of NLO calculations. We explain the underlying theory of the existing methods, MC@NLO and POWHEG, together with their similarities, differences, achievements and limitations. Read More

These are the proceedings of the "Workshop on Precision Measurements of alphas" held at the Max-Planck-Institute for Physics, Munich, February 9-11, 2011. The workshop explored in depth the determination of alphas(mZ) in the MS-bar scheme from the key categories where high precision measurements are currently being made, including DIS and global PDF fits, tau-decays, electroweak precision observables and Z-decays, event-shapes, and lattice QCD. These proceedings contain a short summary contribution from the speakers, as well as the lists of authors, conveners, participants, and talks. Read More

We consider the problem of reconstructing energies, momenta, and masses in collider events with missing energy, along with the complications introduced by combinatorial ambiguities and measurement errors. Typically, one reconstructs more than one value and we show how the wrong values may be correlated with the right ones. The problem has a natural formulation in terms of the theory of Riemann surfaces. Read More

We review the physics basis, main features and use of general-purpose Monte Carlo event generators for the simulation of proton-proton collisions at the Large Hadron Collider. Topics included are: the generation of hard-scattering matrix elements for processes of interest, at both leading and next-to-leading QCD perturbative order; their matching to approximate treatments of higher orders based on the showering approximation; the parton and dipole shower formulations; parton distribution functions for event generators; non-perturbative aspects such as soft QCD collisions, the underlying event and diffractive processes; the string and cluster models for hadron formation; the treatment of hadron and tau decays; the inclusion of QED radiation and beyond-Standard-Model processes. We describe the principal features of the ARIADNE, Herwig++, PYTHIA 8 and SHERPA generators, together with the Rivet and Professor validation and tuning tools, and discuss the physics philosophy behind the proper use of these generators and tools. Read More

Fermion masses may arise via mixing of elementary fermions with composite fermions of a strong sector in scenarios of strongly-coupled electroweak symmetry breaking. The strong sector may contain leptoquark states with masses as light as several hundred GeV. In the present study we focus on the scalar modes of such leptoquarks since their bosonic couplings are determined completely and hence their production cross sections only depend on their masses. Read More

This is the user's manual of MC@NLO 4.0. This package is a practical implementation, based upon the Fortran HERWIG and Herwig++ event generators, of the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements consistently into a parton shower framework. Read More

We present the calculations necessary to obtain next-to-leading order QCD precision with the Herwig++ event generator using the MC@NLO approach, and implement them for all the processes that were previously available from Fortran HERWIG with MC@NLO. We show a range of results comparing the two implementations. With these calculations and recent developments in the automatic generation of NLO matrix elements, it will be possible to obtain NLO precision with Herwig++ for a much wider range of processes Read More

I discuss the calculation of QCD jet rates in e+e- annihilation as a testing ground for parton shower simulations and jet finding algorithms. Read More

A method is proposed for determining the masses of the new particles N,X,Y,Z in collider events containing a pair of effectively identical decay chains Z to Y+jet, Y to X+l_1, X to N+l_2, where l_1, l_2 are opposite-sign same-flavour charged leptons and N is invisible. By first determining the upper edge of the dilepton invariant mass spectrum, we reduce the problem to a curve for each event in the 3-dimensional space of mass-squared differences. The region through which most curves pass then determines the unknown masses. Read More

We examine the effects of invisible particle emission in conjunction with QCD initial state radiation (ISR) on quantities designed to probe the mass scale of new physics at hadron colliders, which involve longitudinal as well as transverse final-state momenta. This is an extension of our previous treatment, arXiv:0903.2013, of the effects of ISR on global inclusive variables. Read More

We compute the resummed hadronic transverse energy (E_T) distribution due to initial-state QCD radiation in vector boson and Higgs boson production at hadron colliders. The resummed exponent, parton distributions and coefficient functions are treated consistently to next-to-leading order. The results are matched to fixed-order calculations at large E_T and compared with parton-shower Monte Carlo predictions at Tevatron and LHC energies. Read More

Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300/fb of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10/fb of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. Read More

A simple method is proposed for determining the masses of new particles in collider events containing a pair of decay chains (not necessarily identical) of the form Z -> Y+1, Y -> X+2, X -> N+3, where 1,2 and 3 are visible but N is not. Initial study of a possible supersymmetric case suggests that the method can determine the four unknown masses in effectively identical chains with good accuracy from samples of a few tens of events. Read More

The Tevatron experiments have recently excluded a Standard Model Higgs boson in the mass range 160 - 170 GeV at the 95% confidence level. This result is based on sophisticated analyses designed to maximize the ratio of signal and background cross-sections. In this paper we study the production of a Higgs boson of mass 160 GeV in the gg -> H -> WW -> l nu l nu channel. Read More

We present results of CHARYBDIS2, a new Monte Carlo simulation of black hole production and decay at hadron colliders in theories with large extra dimensions and TeV-scale gravity. The main new feature of CHARYBDIS2 is a full treatment of the spin-down phase of the decay process using the angular and energy distributions of the associated Hawking radiation. Also included are improved modelling of the loss of angular momentum and energy in the production process as well as a wider range of options for the Planck-scale termination of the decay. Read More

Authors: H. Jung1, A. De Roeck2, Z. J. Ajaltouni3, S. Albino4, G. Altarelli5, F. Ambroglini6, J. Anderson7, G. Antchev8, M. Arneodo9, P. Aspell10, V. Avati11, M. Bahr12, A. Bacchetta13, M. G. Bagliesi14, R. D. Ball15, A. Banfi16, S. Baranov17, P. Bartalini18, J. Bartels19, F. Bechtel20, V. Berardi21, M. Berretti22, G. Beuf23, M. Biasini24, I. Bierenbaum25, J. Blumlein26, R. E. Blair27, C. Bombonati28, M. Boonekamp29, U. Bottigli30, S. Boutle31, M. Bozzo32, E. Brucken33, J. Bracinik34, A. Bruni35, G. E. Bruno36, A. Buckley37, A. Bunyatyan38, H. Burkhardt39, P. Bussey40, A. Buzzo41, M. Cacciari42, F. Cafagna43, M. Calicchio44, F. Caola45, M. G. Catanesi46, P. L. Catastini47, R. Cecchi48, F. A. Ceccopieri49, S. Cerci50, S. Chekanov51, R. Chierici52, M. Ciafaloni53, M. A. Ciocci54, V. Coco55, D. Colferai56, A. Cooper-Sarkar57, G. Corcella58, M. Czakon59, A. Dainese60, M. Dasgupta61, M. Deak62, M. Deile63, P. A. Delsart64, L. Del Debbio65, A. de Roeck66, C. Diaconu67, M. Diehl68, E. Dimovasili69, M. Dittmar70, I. M. Dremin71, K. Eggert72, R. Engel73, V. Eremin74, S. Erhan75, C. Ewerz76, L. Fano77, J. Feltesse78, G. Ferrera79, F. Ferro80, R. Field81, S. Forte82, F. Garcia83, A. Geiser84, F. Gelis85, S. Giani86, S. Gieseke87, M. A. Gigg88, A. Glazov89, K. Golec-Biernat90, K. Goulianos91, J. Grebenyuk92, V. Greco93, D. Grellscheid94, G. Grindhammer95, M. Grothe96, A. Guffanti97, C. Gwenlan98, V. Halyo99, K. Hamilton100, F. Hautmann101, J. Heino102, G. Heinrich103, T. Hilden104, K. Hiller105, J. Hollar106, X. Janssen107, S. Joseph108, A. W. Jung109, H. Jung110, V. Juranek, J. Kaspar, O. Kepka, V. A. Khoze, Ch. Kiesling, M. Klasen, S. Klein, B. A. Kniehl, A. Knutsson, J. Kopal, G. Kramer, F. Krauss, V. Kundrat, K. Kurvinen, K. Kutak, L. Lonnblad, S. Lami, G. Latino, J. I. Latorre, O. Latunde-Dada, R. Lauhakangas, V. Lendermann, P. Lenzi, G. Li, A. Likhoded, A. Lipatov, E. Lippmaa, M. Lokajicek, M. Lo Vetere, F. Lucas Rodriguez, G. Luisoni, E. Lytken, K. Muller, M. Macri, G. Magazzu, A. Majhi, S. Majhi, P. Marage, L. Marti, A. D. Martin, M. Meucci, D. A. Milstead, S. Minutoli, A. Nischke, A. Moares, S. Moch, L. Motyka, T. Namsoo, P. Newman, H. Niewiadomski, C. Nockles, E. Noschis, G. Notarnicola, J. Nystrand, E. Oliveri, F. Oljemark, K. Osterberg, R. Orava, M. Oriunno, S. Osman, S. Ostapchenko, P. Palazzi, E. Pedreschi, A. V. Pereira, H. Perrey, J. Petajajarvi, T. Petersen, A. Piccione, T. Pierog, J. L. Pinfold, O. I. Piskounova, S. Platzer, M. Quinto, Z. Rurikova, E. Radermacher, V. Radescu, E. Radicioni, F. Ravotti, G. Rella, P. Richardson, E. Robutti, G. Rodrigo, E. Rodrigues, M. Rogal, T. C. Rogers, J. Rojo, P. Roloff, L. Ropelewski, C. Rosemann, Ch. Royon, G. Ruggiero, A. Rummel, M. Ruspa, M. G. Ryskin, D. Salek, W. Slominski, H. Saarikko, A. Sabio Vera, T. Sako, G. P. Salam, V. A. Saleev, C. Sander, G. Sanguinetti, A. Santroni, Th. Schorner-Sadenius, R. Schicker, I. Schienbein, W. B. Schmidke, F. Schwennsen, A. Scribano, G. Sette, M. H. Seymour, A. Sherstnev, T. Sjostrand, W. Snoeys, G. Somogyi, L. Sonnenschein, G. Soyez, H. Spiesberger, F. Spinella, P. Squillacioti, A. M. Stasto, A. Starodumov, H. Stenzel, Ph. Stephens, A. Ster, D. Stocco, M. Strikman, C. Taylor, T. Teubner, R. S. Thorne, Z. Trocsanyi, M. Treccani, D. Treleani, L. Trentadue, A. Trummal, J. Tully, W. K. Tung, M. Turcato, N. Turini, M. Ubiali, A. Valkarova, A. van Hameren, P. Van Mechelen, J. A. M. Vermaseren, A. Vogt, B. F. L. Ward, G. Watt, B. R. Webber, Ch. Weiss, Ch. White, J. Whitmore, R. Wolf, J. Wu, A. Yagues-Molina, S. A. Yost, G. Zanderighi, N. Zotov, M. zur Nedden
Affiliations: 1DESY, U. Antwerp, 2CERN, U. Antwerp, 3DESY, U. Antwerp, 4DESY, U. Antwerp, 5DESY, U. Antwerp, 6DESY, U. Antwerp, 7DESY, U. Antwerp, 8DESY, U. Antwerp, 9DESY, U. Antwerp, 10DESY, U. Antwerp, 11DESY, U. Antwerp, 12DESY, U. Antwerp, 13DESY, U. Antwerp, 14DESY, U. Antwerp, 15DESY, U. Antwerp, 16DESY, U. Antwerp, 17DESY, U. Antwerp, 18DESY, U. Antwerp, 19DESY, U. Antwerp, 20DESY, U. Antwerp, 21DESY, U. Antwerp, 22DESY, U. Antwerp, 23DESY, U. Antwerp, 24DESY, U. Antwerp, 25DESY, U. Antwerp, 26DESY, U. Antwerp, 27DESY, U. Antwerp, 28DESY, U. Antwerp, 29DESY, U. Antwerp, 30DESY, U. Antwerp, 31DESY, U. Antwerp, 32DESY, U. Antwerp, 33DESY, U. Antwerp, 34DESY, U. Antwerp, 35DESY, U. Antwerp, 36DESY, U. Antwerp, 37DESY, U. Antwerp, 38DESY, U. Antwerp, 39DESY, U. Antwerp, 40DESY, U. Antwerp, 41DESY, U. Antwerp, 42DESY, U. Antwerp, 43DESY, U. Antwerp, 44DESY, U. Antwerp, 45DESY, U. Antwerp, 46DESY, U. Antwerp, 47DESY, U. Antwerp, 48DESY, U. Antwerp, 49DESY, U. Antwerp, 50DESY, U. Antwerp, 51DESY, U. Antwerp, 52DESY, U. Antwerp, 53DESY, U. Antwerp, 54DESY, U. Antwerp, 55DESY, U. Antwerp, 56DESY, U. Antwerp, 57DESY, U. Antwerp, 58DESY, U. Antwerp, 59DESY, U. Antwerp, 60DESY, U. Antwerp, 61DESY, U. Antwerp, 62DESY, U. Antwerp, 63DESY, U. Antwerp, 64DESY, U. Antwerp, 65DESY, U. Antwerp, 66DESY, U. Antwerp, 67DESY, U. Antwerp, 68DESY, U. Antwerp, 69DESY, U. Antwerp, 70DESY, U. Antwerp, 71DESY, U. Antwerp, 72DESY, U. Antwerp, 73DESY, U. Antwerp, 74DESY, U. Antwerp, 75DESY, U. Antwerp, 76DESY, U. Antwerp, 77DESY, U. Antwerp, 78DESY, U. Antwerp, 79DESY, U. Antwerp, 80DESY, U. Antwerp, 81DESY, U. Antwerp, 82DESY, U. Antwerp, 83DESY, U. Antwerp, 84DESY, U. Antwerp, 85DESY, U. Antwerp, 86DESY, U. Antwerp, 87DESY, U. Antwerp, 88DESY, U. Antwerp, 89DESY, U. Antwerp, 90DESY, U. Antwerp, 91DESY, U. Antwerp, 92DESY, U. Antwerp, 93DESY, U. Antwerp, 94DESY, U. Antwerp, 95DESY, U. Antwerp, 96DESY, U. Antwerp, 97DESY, U. Antwerp, 98DESY, U. Antwerp, 99DESY, U. Antwerp, 100DESY, U. Antwerp, 101DESY, U. Antwerp, 102DESY, U. Antwerp, 103DESY, U. Antwerp, 104DESY, U. Antwerp, 105DESY, U. Antwerp, 106DESY, U. Antwerp, 107DESY, U. Antwerp, 108DESY, U. Antwerp, 109DESY, U. Antwerp, 110DESY, U. Antwerp

2nd workshop on the implications of HERA for LHC physics. Working groups: Parton Density Functions Multi-jet final states and energy flows Heavy quarks (charm and beauty) Diffraction Cosmic Rays Monte Carlos and Tools Read More

We examine the effects of QCD initial-state radiation on a class of quantities, designed to probe the mass scale of new physics at hadron colliders, which involve longitudinal as well as transverse final-state momenta. In particular, we derive universal functions that relate the invariant mass and energy distribution of the visible part of the final state to that of the underlying hard subprocess. Knowledge of this relationship may assist in checking hypotheses about new processes, by providing additional information about their scales. Read More

This is the user's manual of MC@NLO 3.4. This package is a practical implementation, based upon the HERWIG event generator, of the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements consistently into a parton shower framework. Read More

We re-evaluate the non-perturbative contribution to the thrust distribution in $e^+e^-\to$ hadrons, in the light of the latest experimental data and the recent NNLO perturbative calculation of this quantity. By extending the calculation to NNLO+NLL accuracy, we perform the most detailed study to date of the effects of non-perturbative physics on this observable. In particular, we investigate how well a model based on a low-scale QCD effective coupling can account for such effects. Read More

We present the calculation of the Wt single-top production channel to next-to-leading order in QCD, interfaced with parton showers within the MC@NLO formalism. This channel provides a complementary way of investigating the properties of the Wtb vertex, with respect to the s- and t-channels. We pay special attention to the separation of this process from top quark pair production. Read More

A new release of the Monte Carlo program Herwig++ (version 2.2) is now available. This version includes a number of improvements including: matrix elements for the production of an electroweak gauge boson, W and Z, in association with a jet; several new processes for Higgs production in association with an electroweak gauge boson; and the matrix element correction for QCD radiation in Higgs production via gluon fusion. Read More

In this paper we describe Herwig++ version 2.3, a general-purpose Monte Carlo event generator for the simulation of hard lepton-lepton, lepton-hadron and hadron-hadron collisions. A number of important hard scattering processes are available, together with an interface via the Les Houches Accord to specialized matrix element generators for additional processes. Read More

The discovery of a Standard Model Higgs boson is possible when experimental cuts are applied which increase the ratio of signal and background cross-sections. In this paper we study the pp->H->WW signal cross-section at the LHC which requires a selection of Higgs bosons with small transverse momentum. We compare predictions for the efficiency of the experimental cuts from a NNLO QCD calculation, a calculation of the resummation of logarithms in the transverse momentum of the Higgs boson at NNLL, and the event generator MC@NLO. Read More

A new release of the Monte Carlo program Herwig++ (version 2.1) is now available. This version includes a number of significant improvements including: an eikonal multiple parton-parton scattering model of the underlying event; the inclusion of Beyond the Standard Model physics; and a new hadronic decay model tuned to LEP data. Read More

We explain how angular correlations in leptonic decays of vector bosons and top quarks can be included in Monte Carlo parton showers, in particular those matched to NLO QCD computations. We consider the production of $n$ pairs of leptons, originating from the decays of $n$ electroweak vector bosons or of $n$ top quarks, in the narrow-width approximation. In the latter case, the information on the $n$ $b$ quarks emerging from the decays is also retained. Read More

This is the user's manual of MC@NLO 3.3. This package is a practical implementation, based upon the HERWIG event generator, of the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements consistently into a parton shower framework. Read More

We apply the positive-weight Monte Carlo method of Nason for simulating QCD processes accurate to Next-To-Leading Order to the case of e+e- annihilation to hadrons. The method entails the generation of the hardest gluon emission first and then subsequently adding a `truncated' shower before the emission. We have interfaced our result to the Herwig++ shower Monte Carlo program and obtained better results than those obtained with Herwig++ at leading order with a matrix element correction. Read More

A new release of the Monte Carlo program Herwig++ (version 2.0) is now available. This is the first version of the program which can be used for hadron-hadron physics and includes the full simulation of both initial- and final-state QCD radiation. Read More

This document was prepared as part of the briefing material for the Workshop of the CERN Council Strategy Group, held in DESY Zeuthen from 2nd to 6th May 2006. It gives an overview of the physics issues and of the technological challenges that will shape the future of the field, and incorporates material presented and discussed during the Symposium on the European Strategy for Particle Physics, held in Orsay from 30th January to 2nd February 2006, reflecting the various opinions of the European community as recorded in written submissions to the Strategy Group and in the discussions at the Symposium. Read More

A standard file format is proposed to store process and event information, primarily output from parton-level event generators for further use by general-purpose ones. The information content is identical with what was already defined by the Les Houches Accord five years ago, but then in terms of Fortran commonblocks. This information is embedded in a minimal XML-style structure, for clarity and to simplify parsing. Read More

We extend our earlier study of spin correlations in the decay chain $D\to C q$, $C\to B l^{near}$, $B\to A l^{far}$, where $A,B,C,D$ are new particles with known masses but undetermined spins, $l^{near}$ and $l^{far}$ are opposite-sign same-flavour charged leptons and $A$ is invisible. Instead of looking at the observable 2- and 3-particle invariant mass distributions separately, we compare the full three-dimensional phase space distributions for all possible spin assignments of the new particles, and show that this enhances their distinguishability using a quantitative measure known as the Kullback-Leibler distance. Read More

If new particles are discovered at the LHC, it will be important to determine their spins in as model-independent a way as possible. We consider the case, commonly encountered in models of physics beyond the Standard Model, of a new scalar or fermion $D$ decaying sequentially into other new particles $C,B,A$ via the decay chain $D\to C q$, $C\to B l^{near}$, $B\to A l^{far}$, $l^{near}$ and $l^{far}$ being opposite-sign same-flavour charged leptons and $A$ being invisible. We compute the observable 2- and 3-particle invariant mass distributions for all possible spin assignments of the new particles, and discuss their distinguishability using a quantitative measure known as the Kullback-Leibler distance. Read More

A new release of the Monte Carlo program Herwig++ (version 2.0beta) is now available. The main new feature is the extension of the program to include simple hadron-hadron processes including the initial-state parton shower. Read More

This is the user's manual of MC@NLO 3.2. This package is a practical implementation, based upon the HERWIG event generator, of the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements consistently into a parton shower framework. Read More

We match next-to-leading order QCD results for single-top hadroproduction with parton shower Monte Carlo simulations, according to the prescription of the MC@NLO formalism. In this way, we achieve the first practical implementation in MC@NLO of a process that has both initial- and final-state collinear singularities. We show that no difficulties of principle arise from this complication, and present selected results relevant to the Tevatron. Read More

In theories with large extra dimensions and TeV-scale gravity, black holes are copiously produced in particle collisions at energies well above the Planck scale. I briefly review some recent work on the phenomenology of this process, with emphasis on theoretical uncertainties and possible strategies for measuring the number of extra dimensions. Read More

An interesting alternative to supersymmetry (SUSY) for extending physics beyond the Standard Model is a model with universal extra dimensions (UED), in which the SUSY superpartners are replaced by Kaluza-Klein excitations of the Standard Model particles. If new particles are discovered at the LHC, even if their mass spectrum favours SUSY or UED, it will be vital to distinguish between their spin assignments in the two models as far as possible. We extend the method proposed by Barr [hep-ph/0405052] to the UED case and investigate the angular and charge asymmetries of decay distributions for sample mass spectra of both SUSY and UED types. Read More

This is the user's manual of MC@NLO 3.1. This package is a practical implementation, based upon the HERWIG event generator, of the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements consistently into a parton shower framework. Read More