F. Hautmann
We discuss prospects for Monte Carlo event generators incorporating the dynamics of transverse momentum dependent (TMD) parton distribution functions. We illustrate TMD evolution in the parton branching formalism, and present Monte Carlo applications of the method.
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Transverse Momentum Dependent (TMD) parton distributions are a very powerful concept for the description of low and high transverse momentum effects in high energy collisions. The Parton Branching (PB) method provides TMD distributions which can be used in parton shower simulations, as already implemented in \cascade\ Monte Carlo event generator. This report gives a description of the work done during the DESY summer student program 2021, young scientists from very different time zones connecting from remote twice a day for 8 weeks, to develop a method, PS2TMD, that allows to determine effecti…
We present studies of double longitudinal spin asymmetries in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator, which includes quark intrinsic transverse momentum within the generalized parton model based on the fully differential cross section for the process. Additionally, we apply Bessel-weighting to the simulated events to extract transverse momentum dependent parton distribution functions and also discuss possible uncertainties due to kinematic correlation effects.
The Parton Branching (PB) Method describes the evolution of transverse momentum dependent parton densities (TMDs). The obtained TMDs can be used in Monte Carlo generators to describe physical observables. We give an overview of recent developments, in particular the new application of PB TMDs in Drell-Yan + jets production, the four-flavor and five-flavor schemes for heavy quark contributions, and the inclusion of QED corrections in the PB evolution.
The CASCADE3 Monte Carlo event generator based on Transverse Momentum Dependent (TMD) parton densities is described. Hard processes which are generated in collinear factorization with LO multileg or NLO parton level generators are extended by adding transverse momenta to the initial partons according to TMD densities and applying dedicated TMD parton showers and hadronization. Processes with off-shell kinematics within $k_t$-factorization, either internally implemented or from external packages via LHE files, can be processed for parton showering and hadronization. The initial state parton sho…
We present studies of double longitudinal spin asymmetries in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator, which includes quark intrinsic transverse momentum within the generalized parton model based on the fully differential cross section for the process. Additionally we employ Bessel-weighting to the MC events to extract transverse momentum dependent parton distribution functions and also discuss possible uncertainties due to kinematic correlation effects.
We revisit the model-independent decomposition of the gluon correlator, producing T-even and T-odd gluon transverse momentum distributions (TMDs), at leading twist. We propose an expansion of the gluon correlator, using a basis of four tensors (one antisymmetric and three symmetric), which are expressed through generators of the $U(2)$ group acting in the two-dimensional transverse plane. One can do clear interpretations of the two transversity T-odd TMDs with linear polarization of gluons: symmetric and asymmetric under permutation of the transverse spin of the nucleon and the transverse mome…
The theoretical description of Drell-Yan (DY) transverse momentum spectra over wide kinematic regions in energy, mass and transverse momentum requires not only fixed-order perturbative QCD calculations but also soft-gluon QCD resummations to all orders of perturbation theory. The latter are traditionally accomplished either by Parton Showers (PS) with Monte Carlo event generators or by (different versions of) analytical procedures. In this work we focus on issues involved in the matching of the fixed-order calculation and resummation, especially in the moderate to low mass and $p_{\bot}$ regio…
We present the Monte Carlo generator Sartre for simulating diffractive exclusive vector meson production and DVCS in electron-proton, electron-ion, and hadron-hadron collisions.
We describe a simple algorithm that calculates the distributions of electrons and positrons under multiphoton beamstrahlung at a future linear collider. The evolution equation as given by Chen is solved by a Monte Carlo algorithm. Explicit multiple beamstrahlung photons are generated. We present first results from an implementation of beamstrahlung into the Monte Carlo event generator {\tt WOPPER}, that calculates the QED radiative corrections to the process $e^+e^- \to 4$~fermions through resonating W pairs.
We discuss a practical formulation of backward evolution for the CCFM small-$x$ evolution equation and show results from its implementation in the new Monte Carlo event-generator CASCADE.
We illustrate a study based on a veto technique to match parton showers and matrix elements in the Cascade Monte Carlo event generator, and present a numerical application to gluon matrix elements for jet production.
We have written the Exclusive Hadronic Monte Carlo Event (ExHuME) generator. ExHuME implements the perturbative QCD calculation of Khoze, Martin and Ryskin of the process pp-> p+X+p, where X is a centrally produced colour singlet system.
ISAJET is a Monte Carlo event generator for $pp$, $\bar pp$, and $e^+e^-$ interactions at high energies. This document summarizes the physics underlying the program and describes how to use it.
The choice of a factorization scheme suitable for Monte Carlo simulations of NLO initial state parton showers is discussed in this contribution.
A Monte Carlo event generator is presented. An original algorithm is developed to simulate electron-positron scattering at energies and momentum transferred much more than the electron mass. The first-order electroweak radiative corrections are included completely. Higher order corrections are taken into account by means of electron structure functions.
We present some results concerning the Bose-Einstein effect in asymmetric sources in Monte Carlo generators. A comparison of LEP data, standard JETSET predictions and results from the weight method is given. Possible generalization of the weight factors to an asymmetric form is considered.
A new Monte-Carlo generator including real radiated photons in DIS on polarized and unpolarized targets is presented. Analytical and numerical tests are performed and discussed in details.
EDDE is a Monte Carlo event generator, under construction, for different Exclusive Double Diffractive Events. The program is based on the extended Regge-eikonal approach for "soft" processes. Standard Model and its extensions are used for "hard" fusion processes. An interface to PYTHIA, CMSJET and CMKIN is provided.
We present results obtained with the new Monte Carlo event generator Herwig++. In its first version (1.0), Herwig++ is capable of simulating e+e- Annihilation events. We compare results for different distributions with a vast amount of available data from e+e- annihilation.
EDDE is a Monte Carlo event generator for different Exclusive and Semi-Inclusive Double Diffractive processes. The program is based on the extended Regge-eikonal approach for "soft" processes. Standard Model and its extensions are used for "hard" fusion processes.
We briefly review various methods of implementing the Bose - Einstein effect into Monte Carlo generators. The weight methods are discussed in more detail; in particular, our method employing a clustering algorithm is applies for the process e^+e^- -> W^+W^-. New results for the multiplicity distributions are presented.
This article provides an introduction to the principles of particle physics event generators that are based on the Monte Carlo method. Following some preliminaries, instructions on how to build a basic parton-level Monte Carlo event generator for the hard interaction are given through exercises. Indications on how to proceed to full event simulations are given.
With Run II of the LHC having started, the need for high precision theory predictions whose uncertainty matches that of the data to be taken necessitated a range of new developments in Monte-Carlo Event Generators. This talk will give an overview of the progress in recent years in the field and what can and cannot be expected from these newly written tools.
The Monte Carlo generator MERADGEN 1.0 for the simulation of radiative events in parity conserving doubly-polarized Moller scattering has been developed. Analytical integration wherever it is possible provides rather fast and accurate generation. Some numerical tests and histograms are presented.
We present a method which incorporates the Bose-Einstein effect into Monte Carlo generators for multiple production by weighting the events. Various aspects of weight calculations are discussed in detail. We show that our method allows to describe reasonably well a sample of data and we outline the future tests and applications.
We review the main features of Monte Carlo generators for top quark phenomenology and present some results for t-tbar and single-top signals and backgrounds at the LHC.
ISAJET 7.69 is now available, replacing version 7.64 and several intermediate versions. This document contains the release notes and current manual.
A new version of the Monte Carlo event generator DPMJET is presented. It is a code system based on the Dual Parton Model and unifies all features of the DTUNUC-2, DPMJET-II and PHOJET 1.12 event generators. DPMJET-III allows the simulation of hadron-hadron, hadron-nucleus, nucleus-nucleus, photon-hadron, photon-photon and photon-nucleus interactions from a few GeV up to the highest cosmic ray energies.
Shower Monte Carlo event generators have played an important role in particle physics. Modern experiments would hardly be possible without them. In this talk I discuss how QCD physics is incorporated into the mathematical structure of these programs and I outline recent developments including matching between events with different numbers of hard jets and the inclusion of next-to-leading order effects.
We present the EpIC Monte Carlo event generator for exclusive processes sensitive to generalised parton distributions. EpIC utilises the PARTONS framework, which provides a flexible software architecture and a variety of modelling options for the partonic description of the nucleon. The generator offers a comprehensive set of features, including multi-channel capabilities and radiative corrections. It may be used both in analyses of experimental data, as well as in impact studies, especially for future electron-ion colliders.
CASCADE is a full hadron level Monte Carlo event generator for e-p, gamma-p and p-p_bar processes, which uses the CCFM evolution equation for the initial state cascade in a backward evolution approach supplemented with off-shell matrix elements for the hard scattering. A detailed program description is given, with emphasis on parameters the user wants to change and common block variables which completely specify the generated events.
We discuss the implementations of the Bose-Einstein effect from asymmetric sources in Monte Carlo generators. A comparison of LEP data with results from the PYTHIA/JETSET code with the standard procedure imitating the effect and with the results from the weight method (with weights depending in various ways on components of momenta differences) is presented. We show that in this last method one can reproduce the experimental hierarchy of the source radii.
The Monte Carlo generator {\sc Major} 1.5 simulates the production and decay of heavy Majorana neutrinos via lepton mixing or exchange of `light' right-handed $W$-bosons in deep inelastic scattering, i.e. $e^{\pm} p \rightarrow {N} X \rightarrow{e}^{\pm} W^{\mp} X$ or $ν_e Z X$. Physics and programming aspects are described in this manual.
A method to construct Monte-Carlo event generators at arbitrarily non-leading order is explained for the case of a non-gauge theory. A precise and correct treatment of parton kinematics is provided. Modifications of the conventional formalism are required: parton showering is not exactly the same as DGLAP evolution, and the external line prescription for the hard scattering differs from the LSZ prescription. The prospects for extending the results to QCD are discussed.
TAUOLA is a Monte Carlo generator dedicated to generating tau-lepton decays and it is used in the analysis of experimental data both at B-factories and LHC. TAUOLA is a long-term project that started in the 90's and has been under development up to now. In this note we discuss the status of the predominant hadronic tau-lepton decays into two ($Br \simeq 25.52\%$) and three pions ($Br \simeq 18.67\%$).
We discuss the theoretical approach and practical algorithms for simulation of radiative events in elastic ep-scattering. A new Monte Carlo generator for real photon emission events in the process of elastic electron-proton scattering is presented. We perform a few consistency checks and present numerical results.
We present the Monte Carlo generator tuning strategy followed, and the tools developed, by the MCnet CEDAR project. We also present new tuning results for the Pythia 6.4 event generator which are based on event shape and hadronisation observables from e+e- experiments, and on underlying event and minimum bias data from the Tevatron. Our new tunes are compared to existing tunes and to Peter Skands' new "Perugia" tunes.
ExDiff is a Monte Carlo event generator for simulation of Exclusive Diffractive processes in proton-proton collisions. The present version includes reactions: elastic scattering $pp\to pp$ at 7, 8, 13, 14~TeV; $pp\to p+R+p$, $R = f_0(1710),\, f_2(1950)$ at 13~TeV. In the future versions many processes of Central Exclusive Diffractive Production will be added.
We present the description of HIPPOPO (Hadron Induced Particle Production Off Pomeron Outpour), a computer code aimed at the simulation of hadron production in hadron-hadron collisions at high energies via the multipomeron exchange mechanism. We briefly remind the theoretical inputs from the Quark-Gluon String Model and give a detailed description of program components.
We discuss three implementations of the CCFM evolution equations in event generator programs. We find that some of them are able to describe observables such as forward jet rates in DIS at HERA, but only if the so-called consistency constraint is removed. We also find that these results are sensitive to the treatment of non-singular terms in the gluon splitting function.
The status of the multi-purpose event generator HELAC is briefly presented. The aim of this tool is the full simulation of events within the Standard Model at current and future high energy experiments, in particular the LHC. Some results related to the production of multi-jet final states at the LHC are also discussed.
By using predictions from the Pythia 8 Monte Carlo event generator, we determine the energy-dependent turn-over values (pT0) of the partonic cross section for the simulation of multiparton interactions. Since the observed energy dependence of the pT0 values is not well described by a power-law function, we introduce an additional energy-dependent term, to better describe the experimental observations in the energy range sqrt(s) = 0.3-13 TeV. We obtain a similar level of agreement for predictions using various parton densities.
Monte Carlo event generators are essential components of almost all experimental analyses and are also widely used by theorists and experiments to make predictions and preparations for future experiments. They are all too often used as "black boxes", without sufficient consideration of their component models or their reliability. In this set of three lectures we hope to open the box and explain the physical bases behind the models they use. We focus primarily on the general features of parton showers, hadronization and underlying event generation.
ISAJET is a Monte Carlo program which simulates $pp, \bar pp$ and $e^+e^-$ interactions at high energies. This document summarizes the physics underlying the program and describes how to use it. New features of Version 7.40 include generation of $W+H$ and $Z+H$ events, non-minimal GMSB models, and use of the experimental $α_s(M_Z)$ by default.
A new version of Monte Carlo generator ELRADGEN for simulation of real photon emission in elastic electron-proton scattering is presented. The extensions in the new version include opportunity to deal with polarized particles: longitudinally polarized electron and arbitrary polarized proton. Simulation strategy, specifications of used kinematics, structure of the contributions to the observed cross section, cross-checks, and numerical results for BLAST experimental setup are presented and briefly discussed.
We present a Monte Carlo generator for exclusive vector meson production in charged lepton-proton interactions, l+p --> l+p+V, based on a QCD leading logarithm model calculation according to which the cross section for this process is proportional to the square of the gluon momentum density in the proton. The generator can be used for both fixed target and collider kinematics. Each event is assigned a weight equal to its cross section, so that the independent variables can be generated according to convenient distributions, not necessarily identical to the physics ones.
The status of two Monte Carlo generators, HELAC-PHEGAS, a program for multi-jet processes and VBFNLO, a parton level program for vector boson fusion processes at NLO QCD, is briefly presented. The aim of these tools is the simulation of events within the Standard Model at current and future high energy experiments, in particular the LHC. Some results related to the production of multi-jet final states at the LHC are also shown.
We report on the status of the Monte Carlo event generator WOPPER. Version 1.1 of WOPPER describes four fermion production at LEP-II and beyond with leading logarithmic radiative corrections in the double W pole approximation. These approximations are appropriate for almost all practical purposes, but the inclusion of these finite width effects and radiative corrections is nevertheless indispensable for LEP-II physics.
In this paper we describe a check of the implementation of SANC system generated modules into the framework of the WINHAC Monte Carlo event generator. At this stage of work we limit ourselves to inclusion of complete one-loop electroweak corrections to the charged-current Drell--Yan process. We perform tuned comparisons of the results derived with the aid of two codes: 1) the standard SANC integrator with YFS-inspired treatment of the ISR QED corrections and 2) the WINHAC generator, upgraded with the SANC electroweak modules and downgraded to the O(α) QED corrections. The aim of these comparis…
In the usual factorization theorems, which give predictions only for inclusive cross sections, there is considerable freedom in the choice of the scheme to define the parton distribution functions. These theorems do not directly apply to Monte-Carlo event generators, and more general factorization theorems which give predictions for fully exclusive cross sections are needed. It has been shown that appropriate parton distribution functions are uniquely defined by the showering algorithm. In this paper, we present results of calculations of the Monte-Carlo parton distribution functions in terms …
In this talk I gave a brief summary of leading order, next-to-leading order and shower calculations. I discussed the main ideas and approximations of the shower algorithms and the related matching schemes. I tried to focus on QCD issues and open questions instead of making a inventory of the existing programs.
We use a subtraction method to construct NLO corrections in a Monte-Carlo event generator for the case of vector boson production in Drell-Yan processes. Our calculations are carried out both for the Bengtsson-Sjostrand-van Zijl (BSZ) algorithm and for a modified algorithm proposed by Collins. In the case of the modified algorithm, we compute the relation between the parton distribution functions and the ones in the MSbar scheme; this relation is the same as the corresponding relation for DIS. For the BSZ algorithm, we show that there is no simple relation.
The transverse polarization of a quark is a degree of freedom that is not taken into account in the most commonly used Monte Carlo generators. For the case "e^+e^- -> hadrons" I show that it is possible to use these generators to simulate processes where the parent quark and antiquark are transversely polarized and the fragmentation process is affected by this polarization. The key point is that it is possible to obtain this without touching the generator code at all. One only works on the parton-level and hadron-level outputs that the Monte Carlo code has produced, modifying them in a correla…
A practical method of calculating weights implementing the Bose - Einstein interference effects is presented. The usefulness of the method is demonstrated for the events generated by the JETSET/PYTHIA code to describe the UA1 proton-antiproton data at 630GeV. A good description of data is achieved with a reasonable value of the Gaussian width of a two-particle weight factor, which is the only free parameter in our calculations.
The structure and algorithms of the Monte-Carlo generator ELRADGEN 2.0 designed to simulate radiative events in polarized ep-scattering are presented. The full set of analytical expressions for the QED radiative corrections is presented and discussed in detail. Algorithmic improvements implemented to provide faster simulation of hard real photon events are described. Numerical tests show high quality of generation of photonic variables and radiatively corrected cross section. The comparison of the elastic radiative tail simulated within the kinematical conditions of the BLAST experiment at MIT…
In this paper a Monte Carlo generator, GaGaRes, is presented which can be used to describe two-photon resonance production in e^+e^- collisions. The program can generate the five lowest-lying C=+1 meson states of any q\bar{q} combination together with the outgoing electron and positron. The dependence on the photon virtualities Q_1^2 and Q_2^2 is fully taken into account. The program also generates the density matrices of the resonance, which form an essential tool in the description of the decay of the resonances. Furthermore, the program is applicable for all tagging conditions.
We present the Monte Carlo event generator {\tt WOPPER} for pair production of $W$'s and their decays at high energy $e^+e^-$ colliders. {\tt WOPPER} includes the effects from finite $W$ width and focusses on the calculation of higher order electromagnetic corrections in the leading log approximation including soft photon exponentiation and explicit generation of exclusive hard photons.
The Monte Carlo program {\tt WWGENPV}, designed for computing distributions and generating events for the four-fermion process $e^+ e^- \to W^+ W^- \to 4f$, is described. It is based on the calculation of the exact tree-level matrix element of the four-fermion reaction and includes initial-state radiation in the leading-log approximation within the structure function approach. The program can be used in a two-fold way: as a Monte Carlo integrator for weighted events, providing predictions for the total cross section, the $W$ invariant-mass distribution, the radiative energy and invariant-mass …
We summarise the motivation for, and the status of, the tools developed by CEDAR/MCnet for validating and tuning Monte Carlo event generators for the LHC against data from previous colliders. We then present selected preliminary results from studies of event shapes and hadronisation observables from e+e- colliders, and of minimum bias and underlying event observables from the Tevatron, and comment on the approach needed with early LHC data to best exploit the potential for new physics discoveries at the LHC in the next few years.
Description of Bhabha-scattering at small angles using the Monte Carlo generator ReneSANCe
该研究利用 Monte Carlo 生成器 ReneSANCe 模拟 240 GeV 与 Z 共振处的小角度 Bhabha 散射，并为满足约 10⁻⁴ 的亮度测量精度确定最小截止角。
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