M. Mangano

Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions

We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.

Heavy quark correlations in hadron collisions at next-to-leading order

Abstract We present a calculation of the fully exclusive parton cross sections for heavy-quark production at order O(αS3) in QCD. Our result includes the Born cross section for producing a Q Q pair, of order O(αS2), the virtual corrections to the Born cross section, of order O(αS3), and the cross section for producing a Q Q pair plus a light parton, of order O(αS3). We can therefore compute distributions in which correlations among the heavy quarks (and, if present, the associated jet) are correctly taken into account up to order O(αS3). We present some applications of phenomenological interest to top, bottom and charm production at hadron colliders.

Matching matrix elements and shower evolution for top-quark production in hadronic collisions

We study the matching of multijet matrix elements and shower evolution in the case of top production in hadronic collisions at the Tevatron and at the LHC. We present the results of the matching algorithm implemented in the ALPGEN Monte Carlo generator, and compare them with results obtained at the parton level, and with the predictions of the MC@NLO approach. We highlight the consistency of the matching algorithm when applied to these final states, and the excellent agreement obtained with MC@NLO for most inclusive quantities. We nevertheless identify also a remarkable difference in the rapidity spectrum of the leading jet accompanying the top quark pair, and comment on the likely origin of this discrepancy.

Physics potential and experimental challenges of the LHC luminosity upgrade

Abstract.We discuss the physics potential and the experimental challenges of an upgraded LHC running at an instantaneous luminosity of 1035 cm-2s-1. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are discussed. A few examples of the increased physics potential are given, ranging from precise measurements within the Standard Model (in particular in the Higgs sector) to the discovery reach for several New Physics processes.

Top-pair production at hadron colliders with next-to-next-to-leading logarithmic soft-gluon resummation

Incorporating all recent theoretical advances, we resum soft-gluon corrections to the total tcross-section at hadron colliders at the next-to-next-to-leading logarithmic (NNLL) order. We perform the resummation in the well established framework of Mellin N-space resummation. We exhaustively study the sources of systematic uncertainty like renormalization and factorization scale variation, power suppressed effects and missing two- and higher-loop corrections. The inclusion of soft-gluon resummation at NNLL brings only a minor decrease in the perturbative uncertainty with respect to the NLL approximation, and a small shift in the central value, consistent with the quoted uncertainties. These numerical predictions agree with the currently available measurements from the Tevatron and LHC and have uncertainty of similar size. We conclude that significant improvements in the tcross-sections can potentially be expected only upon inclusion of the complete NNLO corrections.

NLL resummation of the heavy quark hadroproduction cross-section

Abstract We compute the effect of soft-gluon resummation, at the next-to-leading-logarithmic level, in the hadroproduction cross section for heavy flavours. Applications to top, bottom and charm total cross sections are discussed. We find in general that the corrections to the fixed next-to-leading order results are larger for larger renormalization scales, and small, or even negative, for smaller scales. This leads to a significant reduction of the scale dependence of the results, for most experimental configurations of interest.

Heavy quarkonium physics

This report is the result of the collaboration and research effort of the Quarkonium Working Group over the last three years. It provides a comprehensive overview of the state of the art in heavy-quarkonium theory and experiment, covering quarkonium spectroscopy, decay, and production, the determination of QCD parameters from quarkonium observables, quarkonia in media, and the effects on quarkonia of physics beyond the Standard Model. An introduction to common theoretical and experimental tools is included. Future opportunities for research in quarkonium physics are also discussed.

Flavor physics of leptons and dipole moments

This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

Theoretical predictions for charm and bottom production at the LHC

A bstractWe present predictions for a variety of single-inclusive observables that stem from the production of charm and bottom quark pairs at the 7 TeV LHC. They are obtained within the FONLL semi-analytical framework, and with two “Monte Carlo + NLO” approaches, MC@NLO and POWHEG. Results are given for final states and acceptance cuts that are as close as possible to those used by experimental collaborations and, where feasible, are compared to LHC data.

THE RESUMMATION OF SOFT GLUONS IN HADRONIC COLLISIONS

Abstract We compute the effects of soft-gluon resummation for the production of high mass systems in hadronic collisions. We carefully analyse the growth of the perturbative expansion coefficients of the resummation formula. We propose an expression consistent with the known leading and next-to-leading resummation results, in which the coefficients grow much less than factorially. We apply our formula to Drell-Yan pair production, heavy flavour production, and the production of high invariant mass jet pairs in hadronic collisions. We find that, with our formula, resummation effects become important only fairly close to the threshold region. In the case of heavy flavour production we find that resummation effects are small in the experimental configurations of practical interest.