Multiparton Interactions and Rescattering (2009)
Corke, Richard, Sjöstrand, Torbjörn
The concept of multiple partonic interactions in hadronic events is vital for the understanding of both minimum-bias and underlying-event physics. The area is rather little studied, however, and...
Pythia 8, the C++ rewrite of the commonly-used Pythia event generator, is now available in a first full-fledged version 8.1. The older Pythia 6.4 generator in Fortran 77 is still maintained, for now,...
PYTHIA 8 Status Report ∗ (2008)
PYTHIA 8, the C++ rewrite of the commonly-used PYTHIA event generator, is now available in a first full-fledged version 8.1. The older PYTHIA 6.4 generator in Fortran 77 is still maintained, for now,...
QCD Physics Lessons of Z^0 Decays (2007)
Introduction New QCD physics results continue to pour out from the Aleph, Delphi, L3, Opal and Sld collaborations. Increased statistics, improved detectors and refined data analyses make for more...
Low- and High-Mass Components of the Photon Distribution Functions (2007)
Torbjörn Sjöstrand, Gerhard A. Schuler
Introduction This is a brief presentation of ref. 1. Related references may be found on the non-perturbative constraints on the photon structure function 2 , on photoproduction 3 and on flfl physics...
A Brief Introduction to PYTHIA 8.1 (2007)
Sjöstrand, Torbjörn, Mrenna, Stephen, Skands, Peter
The PYTHIA program is a standard tool for the generation of high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard process to a complex...
A Brief Introduction to PYTHIA 8.1 (2007)
Sjöstrand, Torbjörn, Mrenna, Stephen, Skands, Peter
The PYTHIA program is a standard tool for the generation of high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard process to a complex...
The structure of events in high-energy collisions is complex and not predictable from first principles. Event generators allow the problem to be subdivided into more manageable pieces, some of which...
hep-ph/0611247 CERN-LCGAPP-2006-06 November 2006 Monte Carlo Generators (2006)
Torbj Orn Sj, Torbjörn Sjöstrand
The structure of events in high-energy collisions is complex and not predictable from first principles. Event generators allow the problem to be subdivided into more manageable pieces, some of which...
PYTHIA 6.3 Physics and Manual (2003)
Sjöstrand, Torbjörn, Lönnblad, Leif, Mrenna, Stephen, Skands, Peter
The PYTHIA program can be used to generate high-energy-physics `events', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as...
PYTHIA 6.2 Physics and Manual (2001)
Sjöstrand, Torbjörn, Lönnblad, Leif, Mrenna, Stephen
The PYTHIA program can be used to generate high-energy-physics `events', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as...
QCD Signatures of Narrow Graviton Resonances in Hadron Colliders (2001)
Bijnens, J, Eerola, Paule Anna Mari, Maul, M, Mansson, A, Sjöstrand, Torbjörn
We show that the characteristic p_\perp spectrum yields valuable information for the test of models for the production of narrow graviton resonances in the TeV range at LHC. Furthermore, it is...
PYTHIA 6.2 - Physics and Manual (2001)
Torbjörn Sjöstrand, Leif Lönnblad, Lu Tp, Stephen Mrenna
The Pythia program can be used to generate high-energy-physics `events', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide...
gamma-gamma Interactions from Real to Virtual Photons (2000)
A `complete' framework for gamma-gamma / gamma*-gamma / gamma*-gamma* interactions is presented. The emphasis is on providing a model for gamma-gamma physics at all photon virtualities, including the...
QCD Radiation off Heavy Particles (2000)
An algorithm for an improved description of final-state QCD radiation is introduced. It is matched to the first-order matrix elements for gluon emission in a host of decays, for processes within the...
Recent improvements in the PYTHIA event generator are summarized: new hard subprocesses, gamma*-gamma* physics, QCD final-state showers, and more.
A Toy Model of Colour Screening in the Proton (2000)
Dischler, Johann, Sjöstrand, Torbjörn
In hadronic collisions, the mini-jet cross section is formally divergent in the limit pT -> 0. We argue that this divergence is tamed by some effective colour correlation length scale of the hadron....
High-Energy-Physics Event Generation with PYTHIA 6.1 (2000)
Sjöstrand, Torbjörn, Edén, P, Friberg, C, Lönnblad, L, Miu, G, Mrenna, S, ...
PYTHIA version 6 represents a merger of the PYTHIA 5, JETSET 7 and SPYTHIA programs, with many improvements. It can be used to generate high-energy-physics `events', i.e. sets of outgoing particles...
High-Energy-Physics Event Generation with PYTHIA 6.1 (2000)
Sjöstrand, Torbjörn, Edén, Patrik, Friberg, Christer, Lönnblad, Leif, Miu, Gabriela, Mrenna, Stephen, ...
PYTHIA version 6 represents a merger of the PYTHIA 5, JETSET 7 and SPYTHIA programs, with many improvements. It can be used to generate high-energy-physics `events', i.e. sets of outgoing particles...
High-Energy-Physics Event Generation with PYTHIA 6.1 (2000)
Sjöstrand, Torbjörn, Edén, P, Friberg, C, Lönnblad, L, Miu, G, Mrenna, S, ...
PYTHIA version 6 represents a merger of the PYTHIA 5, JETSET 7 and SPYTHIA programs, with many improvements. It can be used to generate high-energy-physics `events', i.e. sets of outgoing particles...
Effects of Longitudinal Photons (2000)
Friberg, Christer, Sjöstrand, Torbjörn
The description of longitudinal photons is far from trivial, and their phenomenological importance is largely unknown. While the cross section for direct interactions is calculable, an even more...
Total Cross Sections and Event Properties from Real to Virtual Photons (2000)
Friberg, Christer, Sjöstrand, Torbjörn
A model for total cross sections with virtual photons is presented. In particular gamma*-p and gamma*-gamma* cross sections are considered. Our approach extends on a model for photoproduction, where...
Report of the QCD Working Group (2000)
Ballestrero, A, Bambade, P, Bravo, S, Cacciari, M, Costa, M, De Boer, Wim, ...
The activities of the QCD working group concentrated on improving the understanding and Monte Carlo simulation of multi-jet final states due to hard QCD processes at LEP, i.e. quark-antiquark plus...
Third General Meeting of the LEP2 Workshop (2000)
Boudjema, F, Knowles, I G, Melé, Barbara, Nason, P, Sjöstrand, Torbjörn
Standard process. QCD. Event generators for QCD.
Recent Progress in PYTHIA (2000)
PYTHIA is a general-purpose event generator for multiparticle production in high-energy physics. After a general introduction and program news survey, some areas of recent physics progress are...
PYTHIA version 7-0.0 - a proof-of-concept version (2000)
Marc Bertini, Leif Lönnblad, Torbjörn Sjöstrand
This document describes the rst proof-of-concept version of the Pythia7 program. Pythia7 is a complete re-write of the Pythia program in C++. It is mainly intended to be a replacement for the...
Total Cross Sections and Event Properties from Real to Virtual Photons (2000)
Christer Friberg, Torbjörn Sjöstrand
A model for total cross sections with virtual photons is presented. In particular p and cross sections are considered. Our approach extends on a model for photoproduction, where the total cross...
Effects of Longitudinal Photons (2000)
Christer Friberg, Torbjörn Sjöstrand
The description of longitudinal photons is far from trivial, and their phenomenological importance is largely unknown. While the cross section for direct interactions is calculable, an even more...
QCD Interconnection Studies at Linear Colliders (1999)
Khoze, Valery A., Sjöstrand, Torbjörn
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...
QCD Interconnection Effects (1999)
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...
QCD Interconnection Effects (1999)
Sjöstrand, Torbjörn, Khoze, V A
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...
QCD Interconnection Effects (1999)
Sjöstrand, Torbjörn, Khoze, Valery A.
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...
QCD Interconnection Effects (1999)
Sjöstrand, Torbjörn, Khoze, V A
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...
Jet Production by Virtual Photons (1999)
Friberg, Christer, Sjöstrand, Torbjörn
The production of jets is studied in collisions of virtual photons, gamma*-p and gamma*-gamma*, specifically for applications at HERA and LEP2. Photon flux factors are convoluted with matrix elements...
Jet Production by Real and Virtual Photons (1999)
Friberg, Christer, Sjöstrand, Torbjörn
The production of jets is studied in collisions of virtual photons, specifically for applications at HERA. Photon flux factors are convoluted with matrix elements involving either direct or resolved...
Some thoughts on how to match Leading Log Parton Showers with NLO Matrix Elements (1999)
Friberg, Christer, Sjöstrand, Torbjörn
We propose a scheme that could offer a convenient Monte Carlo sampling of next-to-leading-order matrix elements and, at the same time, allow the interfacing of such parton configurations with a...
QCD Interconnection Studies at Linear Colliders (1999)
Valery A. Khoze, Torbjörn Sjöstrand, Infn Laboratori, Nazionali Frascati
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...
PYTHIA and HERWIG for Linear Collider Physics (1999)
Torbjörn Sjöstrand, Michael H. Seymour
An overview is given of general-purpose event generators, especially Pythia and HERWIG. The current status is summarized, some recent physics improvements are described, and planned future projects...
QCD Interconnection Effects (1999)
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...
Recent Progress in PYTHIA (1999)
PYTHIA is a general-purpose event generator for multiparticle production in high-energy physics. After a general introduction and program news survey, some areas of recent physics progress are...
Production mechanisms of charm hadrons in the string model (1998)
Norrbin, Emanuel, Sjöstrand, Torbjörn
In the hadroproduction of charm in the context of string fragmentation, the pull of a beam remnant at the other end of a string may give a charm hadron more energy than the perturbatively produced...
New and Old Jet Clustering Algorithms for Electron-Positron Events (1998)
Moretti, Stefano, Lönnblad, Leif, Sjöstrand, Torbjörn
Over the years, many jet clustering algorithms have been proposed for the analysis of hadronic final states in $e^+e^-$ annihilations. These have somewhat different emphasis and are therefore more or...
Soft-Particle Spectra as a Probe of Interconnection Effects in Hadronic $W^{+} W^{-}$ Events (1998)
Khoze, V A, Sjöstrand, Torbjörn
Cross-talk between the W^+ and W^- sources of hadron production at LEP2 offers a hope to learn about basic properties of QCD, but at the same time threatens high-precision measurements of the W boson...
New and Old Jet Clustering Algorithms for Electron-Positron Events (1998)
Stefano Moretti, Leif Lönnblad, Torbjörn Sjöstrand
Over the years, many jet clustering algorithms have been proposed for the analysis of hadronic final states in e + e \Gamma annihilations. These have somewhat different emphasis and are therefore...
W Production in an Improved Parton-Shower Approach (1998)
Gabriela Miu, Torbjörn Sjöstrand
In the description of the production properties of gauge bosons (W \Sigma , Z 0 , fl ) at colliders, the lowest-order graph normally is not sufficient. The contributions of higher orders can be...
Modelling Bose-Einstein correlations at LEP 2 (1997)
Leif Lonnblad, Torbjörn Sjöstrand
We present new algorithms for simulating Bose--Einstein correlations among final-state bosons in an event generator. The algorithms are all based on introducing Bose--Einstein correlations as a shift...
A scenario for high-energy $\gamma\gamma$ interactions (1996)
Schuler, G A, Sjöstrand, Torbjörn
A real photon has a complicated nature, whereby it may remain unresolved or fluctuate into a vector meson or a perturbative q-qbar pair. In gamma-gamma events, this gives three by three combinations...
A scenario for high-energy gamma-gamma interactions (1996)
Schuler, Gerhard A., Sjöstrand, Torbjörn
A real photon has a complicated nature, whereby it may remain unresolved or fluctuate into a vector meson or a perturbative q-qbar pair. In gamma-gamma events, this gives three by three combinations...
Determination of the mass of the W boson (1996)
Kunszt, Zoltán, Stirling, J W, Ballestrero, A, Banerjee, S, Blondel, A, Campanelli, M, ...
Previous studies of the physics potential of LEP2 indicated that with the design luminosity of 500 inverse picobarn one may get a direct measurement of the mass of the W-boson with a precision in the...
Knowles, I G, Webber, Bryan R, Todorova, S, Thompson, J C, Seymour, Michael H, Sarkar, S, ...
This report is a survey on QCD Event Generator issues of relevance for LEP 2. It contains four main sections: a summary of experience from LEP 1, extrapolations to LEP 2 energies, Monte Carlo...
Knowles, I G, Sjöstrand, Torbjörn, Blondel, A, Böhrer, A, Buchanan, C D, Charlton, D G, ...
This report is a survey on QCD Event Generator issues of relevance for LEP 2. It contains four main sections: a summary of experience from LEP 1, extrapolations to LEP 2 energies, Monte Carlo...
Gamma-gamma physics at LEP2 (1996)
Aurenche, Patrick, Schuler, G A, Bawa, A C, Boudinov, E, Buijs, A, Cacciari, M, ...
This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the following topics: structure functions, equivalent photon approximation, tagging conditions etc, soft and...
Parton distributions of the virtual photon (1996)
Schuler, G A, Sjöstrand, Torbjörn
We propose a generic ansatz for the extension of parton distributions of the real photon to those of the virtual photon. Alternatives and approximations are studied that allow closed-form...
Parton Distributions of the Virtual Photon (1996)
Schuler, Gerhard A., Sjöstrand, Torbjörn
We propose a generic ansatz for the extension of parton distributions of the real photon to those of the virtual photon. Alternatives and approximations are studied that allow closed-form...
$\gamma\gamma$ event generators (1996)
Lönnblad, L, Wright, A, Walker, R, Sjöstrand, Torbjörn, Schuler, G A, Ranft, J, ...
The report from the working group on '\gamma\gamma Event Generators' of the LEP 2 workshop
$\gamma\gamma$ event generators (1996)
Lönnblad, L, Seymour, Michael H, Boudinov, E, Butterworth, J, Engel, R, Finch, A, ...
The report from the working group on '\gamma\gamma Event Generators' of the LEP 2 workshop
Parton Distributions of the Virtual Photon (1996)
Gerhard A. Schuler, Torbjörn Sjöstrand
We propose a generic ansatz for the extension of parton distributions of the real photon to those of the virtual photon. Alternatives and approximations are studied that allow closed-form...
Low- and high-mass components of the photon distribution functions (1995)
Sjöstrand, Torbjörn, Schuler, G A
Four new parton distributions of the photon are presented, with a description of theory choices, properties and applications.
Low- and high-mass components of the photon distribution functions (1995)
Sjöstrand, Torbjörn, Schuler, G A
Four new parton distributions of the photon are presented, with a description of theory choices, properties and applications.
PYTHIA 5.7 and JETSET 7.4 physics and manual (1995)
This is the latest edition of the physics description and manual of the PYTHIA and JETSET programs for event generation in High Energy Physics.
PYTHIA 5.7 and JETSET 7.4 physics and manual (1995)
This is the latest edition of the physics description and manual of the PYTHIA and JETSET programs for event generation in High Energy Physics.
Low- and high-mass components of the photon distribution functions (1995)
Schuler, G A, Sjöstrand, Torbjörn
The structure of the general solution of the inhomogeneous evolution equations allows the separation of a photon structure function into perturbative (``anomalous") and non-perturbative...
Low- and high-mass components of the photon distribution functions (1995)
Schuler, Gerhard A., Sjöstrand, Torbjörn
The structure of the general solution of the inhomogeneous evolution equations allows the separation of a photon structure function into perturbative (``anomalous") and non-perturbative...
Low- and High-Mass Components of the Photon Distribution Functions (1995)
Lu Tp, Torbjörn Sjöstrand, Gerhard A. Schuler
Four new parton distributions of the photon are presented, with a description of theory choices, properties and applications. * To appear in the Proceedings of the International Europhysics...
Soft Photoproduction Physics (1995)
Several topics of interest in soft photoproduction physics are discussed. These include jet universality issues (particle flavour composition), the subdivision into event classes, the buildup of the...
γp and γγ QCD Physics at High Energies (1995)
The challenge of flp and flfl studies is a complexity in excess of that encountered elsewhere in particle physics. In order to construct a complete and consistent model of all main phenomena, several...
Low- and High-Mass Components of the Photon Distribution Functions (1995)
Lu Tp, Gerhard A. Schuler, Torbjörn Sjöstrand
The structure of the general solution of the inhomogeneous evolution equations allows the separation of a photon structure function into perturbative ("anomalous") and non-perturbative...
$\gamma$-$\gamma$ and $\gamma$-p events at high energies (1994)
Schuler, G A, Sjöstrand, Torbjörn
A real photon has a complicated nature, whereby it may remain unresolved or fluctuate into a vector meson or a perturbative q-qbar pair. Based on this picture, we previously presented a model for...
Colour correlations and multiplicities in top events (1994)
Khoze, V A, Sjöstrand, Torbjörn
In events of the type e+ e- -> t tbar -> b W+ bbar W-, particle production could depend in a non-trivial way on the kinematics of the process. Energetic perturbative gluon radiation can be generated...
$\gamma$-$\gamma$ and $\gamma$-p events at high energies (1994)
Schuler, G A, Sjöstrand, Torbjörn
A real photon has a complicated nature, whereby it may remain unresolved or fluctuate into a vector meson or a perturbative q-qbar pair. Based on this picture, we previously presented a model for...
Does the W Mass Reconstruction Survive QCD Effects? (1993)
Sjöstrand, Torbjörn, Khoze, Valery A.
In the hadronic decay mode of a pair of W bosons, $\text{e}~+\text{e}~- \to \text{W}~+ \text{W}~- \to \text{q}_1 \overline{\text{q}}_2 \text{q}_3 \overline{\text{q}}_4$, QCD interference effects can...
On Colour Rearrangement in Hadronic W$^+$W$^-$ Events (1993)
Sjöstrand, Torbjörn, Khoze, Valery
We discuss the possibility of colour rearrangement in $\ee \to \W^+ \W^- \to \q_1 \qbar_2 \q_3 \qbar_4$ events, i.e.\ that the original colour singlets $\q_1 \qbar_2$ and $\q_3 \qbar_4$ may be...
Summary and theoretical basis (1991)
Reya, E, Zerwas, Peter M, Berends, F A, Bordes, G, Cavanna, F, Del Águila, F, ...
Bambah, B A, Chrin, J, De Boer, Wim, Fuster, J A, Gary, J W, Hahn, M, ...
Dedicated to the Memory of (1937)
Torbjörn Sjöstrand, Stephen Mrenna, Peter Skands, Bo Andersson
The Pythia program can be used to generate high-energy-physics ‘events’, i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide...
Dedicated to the Memory of (1937)
Lu Tp, Torbjörn Sjöstrand, Stephen Mrenna, Peter Skands, Bo Andersson
Abstract: The Pythia program can be used to generate high-energy-physics ‘events’, i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to...