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Les Houches 'Physics at Tev Colliders 2003' QCD/SM Working Group: Summary Report

M. Dobbs, S. Frixione, E. Laenen, A. De Roeck, K. Tollefson, J. Andersen, C. Balazs, A. Banfi, S. Berge, W. Bernreuther, T. Binoth, A. Brandenburg, C. Buttar, Q-H. Cao, G. Corcella, A. Cruz, I. Dawson, V. Del Duca, V. Drollinger, L. Dudko, T. Eynck, R. Field, M. Grazzini, J. P. Guillet, G. Heinrich, J. Huston, N. Kauer, N. Kidonakis, A. Kulesza, K. Lassila-Perini, L. Magnea, F. Mahmoudi, E. Maina, F. Maltoni, M. Nolten, A. Moraes, S. Moretti, S. Mrenna, P. Nadolsky, Z. Nagy, F. Olness, I. Puljak, D. A. Ross, A. Sabio-Vera, G. P. Salam, A. Sherstnev, Z. G. Si, T. Sjostrand, P. Skands, E. Thome, Z. Trocsanyi, P. Uwer, S. Weinzierl, C. P. Yuan, G. Zanderighi

TL;DR

This report surveys advances in QCD/SM predictions for TeV colliders, emphasizing Monte Carlo tools, multiple interactions, and underlying-event modelling to sharpen SM backgrounds for Higgs and new-physics searches. It compares PYTHIA and PHOJET in soft, minimum-bias regimes, introduces a correlated multi-parton framework with flavor, momentum and color structure, and provides LHC energy extrapolations. The work also probes underlying-event dynamics via Run 2 Tevatron data using transverse-region correlations and discusses strategies to model QCD backgrounds for $t\bar{t}$ analyses. Overall, the contributions bridge phenomenology and experiment to enable precision SM tests and robust background estimation at high-energy colliders.

Abstract

This report documents the results obtained by the Working Group on Quantum Chromodynamics and the Standard Model for the Workshop `Physics at TeV Colliders'', Les Houches, France, 26 May - 6 June 2003. After a Monte Guide description, the first contributions report on progress in describing multiple interactions, important for the LHC, and underlying events. An announcement of a Monte Carlo database, under construction, is then followed by a number of contributions improving parton shower descriptions. Subsequently, a large number of contributions address resummations in various forms, after which follow studies of QCD effects in pion pair, top quark pair and photon pair plus jet production. After a study of electroweak corrections to hadronic precision observables, the report ends by presenting recent progress in methods to compute finite order corrections at one-loop with many legs, and at two-loop.

Les Houches 'Physics at Tev Colliders 2003' QCD/SM Working Group: Summary Report

TL;DR

This report surveys advances in QCD/SM predictions for TeV colliders, emphasizing Monte Carlo tools, multiple interactions, and underlying-event modelling to sharpen SM backgrounds for Higgs and new-physics searches. It compares PYTHIA and PHOJET in soft, minimum-bias regimes, introduces a correlated multi-parton framework with flavor, momentum and color structure, and provides LHC energy extrapolations. The work also probes underlying-event dynamics via Run 2 Tevatron data using transverse-region correlations and discusses strategies to model QCD backgrounds for analyses. Overall, the contributions bridge phenomenology and experiment to enable precision SM tests and robust background estimation at high-energy colliders.

Abstract

This report documents the results obtained by the Working Group on Quantum Chromodynamics and the Standard Model for the Workshop `Physics at TeV Colliders'', Les Houches, France, 26 May - 6 June 2003. After a Monte Guide description, the first contributions report on progress in describing multiple interactions, important for the LHC, and underlying events. An announcement of a Monte Carlo database, under construction, is then followed by a number of contributions improving parton shower descriptions. Subsequently, a large number of contributions address resummations in various forms, after which follow studies of QCD effects in pion pair, top quark pair and photon pair plus jet production. After a study of electroweak corrections to hadronic precision observables, the report ends by presenting recent progress in methods to compute finite order corrections at one-loop with many legs, and at two-loop.

Paper Structure

This paper contains 28 sections, 6 equations, 20 figures, 1 table.

Table of Contents

  1. FOREWORD
  2. LES HOUCHES GUIDEBOOK TO MONTE CARLO GENERATORS FOR HADRON COLLIDER PHYSICS
  3. MULTIPLE INTERACTIONS AND BEAM REMNANTS
  4. Introduction
  5. Correlated Parton Densities
  6. Colour Correlations
  7. Conclusion
  8. DESCRIBING MINIMUM BIAS AND THE UNDERLYING EVENT AT THE LHC IN PYTHIA AND PHOJET
  9. Introduction
  10. PYTHIA Model for Hadron Collisions
  11. PHOJET
  12. Minimum Bias Interactions
  13. KNO Distribution
  14. Pseudorapidity Distribution
  15. The Underlying Event
  16. ...and 13 more sections

Figures (20)

  • Figure 1: (a) The initial state of a baryon, with the valence quarks colour-connected via a central string junction J. (b) Example of a topology with initiators connected at random. (c) Alternative with the junction in the remnant.
  • Figure 2: KNO distributions for NSD p$\overline{\text{p}}$ collisions at $\sqrt{\text{s}}$ = 546 GeV: (a) simple scenario and (b) complex scenario distributions compared to data.
  • Figure 3: KNO distributions for NSD p$\overline{\text{p}}$ collisions at $\sqrt{\text{s}}$ = 1.8 TeV: (a) double Gaussian model with different core-sizes, and (b) PHOJET1.12 compared to the data Alexopoulos:1998biMatinyan:1998ja.
  • Figure 4: Charged particle density distributions,dN$_{ch}$/d$\eta$, for NSD p$\overline{\text{p}}$ at $\sqrt{\text{s}}$ = 900 GeV collisions comparing the data Ansorge:1989kn to (a) PYTHIA6.214 with various p$_{t_{min}}$ and (b) PHOJET1.12.
  • Figure 5: Average charged particles multiplicity in the transverse region showing PYTHIA6.214 - MSTP(82)=4 with (a) different values of PARP(82) (i.e. p$_{t_{min}}$) and (b) different values of PARP(84) (core-size).
  • ...and 15 more figures