Monte-Carlo generator for e+e- annihilation into lepton and hadron pairs with precise radiative corrections (original) (raw)
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Study of the process e+e-→π+π-γ with the CMD-3 detector at the e+e- collider VEPP-2000
EPJ Web of Conferences
Existing Monte-Carlo generators with radiative corrections to the e+e-→π+π- process are usually developed under the assumption that pions can be treated as pointlike particles. We study the e+e-→π+π-γ process with final-state radiation and test this assumption using simulated events from the MCGPJ generator based on the scalar QED hypothesis. In order to increase a fraction of events with FSR, the analysis was performed in the energy region to the left from the ρ-meson peak (660÷785 MeV) that is based on the integrated luminosity of about 8.4 pb-1. The experimental data for the photon energy spectrum agree with the simulation results at 1% level.
Computer Physics Communications, 1994
Based on QCD-inspired models for multiple jets production, we developed a Monte Carlo program to study jet and the associated particle production in high energy pp, pA and AA collisions. The physics behind the program which includes multiple minijet production, soft excitation, nuclear shadowing of parton distribution functions and jet interaction in dense matter is briefly discussed. A detailed description of the program and instructions on how to use it are given.
Radiative corrections for pion and kaon production at e+ e− colliders of energies below 2 GeV
Journal of High …, 1997
Processes of electron-positron annihilation into charged pions and kaons are considered. Radiative corrections are taken into account exactly in the first order and within the leading logarithmic approximation in higher orders. A combined approach for accounting exact calculations and electron structure functions is used. An accuracy of the calculation can be estimated about 0.2%.
Photon radiation in e^+e^-\;\rightarrow \;$$ e + e - → hadrons at low energies with carlomat_3.1
The European Physical Journal C
We present a sample of results for the cross sections of several processes of low energetic e + e − annihilation into final states containing pions accompanied by one or two photons, or a light lepton pair. The results, which have been obtained with a new version of a multipurpose Monte Carlo program carlomat, labelled 3.1, demonstrate new capabilities of the program which, among others, include a possibility of taking into account either the initial or final state radiation separately, or both at a time, and a possibility of inclusion of the electromagnetic charged pion form factor for processes with charged pion pairs. We also discuss some problems related to the U (1) electromagnetic gauge invariance.
WWGENPV 2.0 — A Monte Carlo event generator for four-fermion production at e+e− colliders
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The Monte Carlo program WWGENPV, designed for computing distributions and generating events for four-fermion production in e + e − collisions, is described. The new version, 2.0, includes the full set of the electroweak (EW) tree-level matrix elements for double-and single-W production, initial-and final-state photonic radiation including p T /p L effects in the Structure Function formalism, all the relevant non-QED corrections (Coulomb correction, naive QCD, leading EW corrections). An hadronisation interface to JETSET is also provided. The program can be used in a three-fold way: as a Monte Carlo integrator for weighted events, providing predictions for several observables relevant for W physics; as an adaptive integrator, giving predictions for cross sections, energy and invariant mass losses with high numerical precision; as an event generator for unweighted events, both at partonic and hadronic level. In all the branches, the code can provide accurate and fast results.
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Monte Carlo event generators (MCEGs) are the indispensable workhorses of particle physics, bridging the gap between theoretical ideas and first-principles calculations on the one hand, and the complex detector signatures and data of the experimental community on the other hand. All collider physics experiments are dependent on simulated events by MCEG codes such as Herwig, Pythia, Sherpa, POWHEG, and MG5_aMC@NLO to design and tune their detectors and analysis strategies. The development of MCEGs is overwhelmingly driven by a vibrant community of academics at European Universities, who also train the next generations of particle phenomenologists. The new challenges posed by possible future collider-based experiments and the fact that the first analyses at Run II of the LHC are now frequently limited by theory uncertainties urge the community to invest into further theoretical and technical improvements of these essential tools. In this short contribution to the European Strategy Upda...
Pion pair production with higher order radiative corrections in low energy e+e−e^+e^-e+e− collisions
The European Physical Journal C - Particles and Fields, 2002
The complete O(α) QED initial state (IS), final state (FS) and initial-final state (IFS) interference corrections to the process e + e − → π + π − are presented. Analytic formulae are given for the virtual and for the real photon corrections. The total cross section (σ), the pion angular distribution (dσ/d cos Θ) and the π + π − invariant mass distribution (dσ/ds ′) are investigated in the regime of experimentally realistic kinematical cuts. It is shown that in addition to the full O(α) corrections also the O(α 2) and leading log O(α 3) photonic corrections as well as the contributions from IS e + e − pair production have to be taken into account if at least per cent accuracy is required. For the data analysis we focus on an inclusive treatment of all photons. The theoretical error concerning our treatment of radiative corrections is then estimated to be 2 per mill for both the measurement of the total cross section and the π + π − invariant mass distribution. In addition we discuss the model uncertainty due to the pion substructure. Altogether the precision of the theoretical prediction matches the requirements of low energy e + e − experiments like the ones going on at DAΦNE or VEPP-2M.
Studies of hadronic event structure in e + e - annihilation from 30 to 209 GeV with the L3 detector
Physics Reports-review Section of Physics Letters, 2004
In this Report, QCD results obtained from a study of hadronic event structure in high energy e + e − interactions with the l3 detector are presented. The operation of the lep collider at many different collision energies from 91 GeV to 209 GeV offers a unique opportunity to test QCD by measuring the energy dependence of different observables. The main results concern the measurement of the strong coupling constant, α s , from hadronic event shapes and the study of effects of soft gluon coherence in charged particle multiplicity and momentum distributions. 5 interfaced to the Jetset or Pythia fragmentation and decay routines. In addition, Ariadne uses Jetset or Pythia routines to generate the initial qq system and ISR. Only the string fragmentation is used here. In the Ariadne perturbative phase, there are two main parameters that affect the parton configuration most: the parton shower scale parameter Λ AR and the parton shower cut-off parameter p min t . The relevant fragmentation parameters are the same as those in the Jetset PS model.
A Monte Carlo program for generating hadronic final states in electron-positron annihilations
Computer Physics Communications, 1985
Title of program: EPOS particles in the final state(30 or 40 particles are not uncommon at W = 35 GeV) [1]. The complexity of this phenomenon needs Catalogue number: ACDM a theoretical framework for describing and understanding the basic physical mechanism involved. Program obtainable from: CPC Program Library, Queen's Uni-The present program is an event generator of hadronic final versity of Belfast, N. Ireland (see application form in this issue) states based on the Fire-String theory and has been shown to reproduce very well all the features experimentally observed [2]. Computers on which the program is operable: CDC 7600/CYBER 875/VAX 780 Method of solution The program is based on the Monte Carlo method and its Operating system: 7000 SCOPE 2.1.4 (CDC)/NOS-BE Level generates events with weight = I using the Fire-String theory 587/VAX-VMS [2]. The notion of Fire-String comes from the description of hadronic matter in terms of bound states (bags) of quarks and Programming language: FORTRAN antiquarks in the theoretical framework named Quark-Geometro-Dynamics [3]. In this approach to the dynamics of high High speed storage required: 50 Kwords on CDC's and a peak energy physics one can define a highly excited quark-antiquark value of 240 Kwords on the VAX bound state with a cylindrical structure, called Fire-string (FS). The evolution of the FS and its decay modes are responsible for No. of bits in a word: 60 (CDC), 32 (VAX) the deposition of hadrons in the final states. All these physical ideas have been implemented in the No. of lines in combined program and test deck: 3938 present program.