A brief introduction to PYTHIA 8.1

Abstract

The fortran version of the AcerDET package has been published in [1], and used in the multiple publications on the predictions for physics at LHC. The package provides, starting from list of particles in the event, the list of reconstructed jets, isolated electrons, muons, photons and reconstructed missing transverse energy. The AcerDET represents a simplified version of the package called ATLFAST, used since several years within ATLAS Collaboration. In the fast simulation implemented in AcerDET, some functionalities of ATLFAST are absent, but the most crucial detector effects are implemented and the parametrisations are largely simplified. Therefore it is not representing details neither of ATLAS nor CMS detectors.This short paper documents a new C++ implementation of the same algorithms as used in [1]. We believe that the package can be well adequate for some feasibility studies of the high p T physics at LHC and at planned ppFCC. The further evolution of this code is planned.[1] E. Richter-Was, AcerDET: A Particle level fast simulation and reconstruction package for phenomenological studies on high p(T) physics at LHC , hep-ph/0207355. Nature of physical problem: A particle level fast simulation and reconstruction package. The package provides, starting from the list of particles in the event, list of reconstructed jets, isolated electrons, muons and photons and reconstructed missing transverse energy. The algorithmic part is just rewritten from fortran version of the package AcerDET-1.0 [1]. The default input is generated event in format of HepMC structure [2], output is in form of ROOT file [4], containing tree with reconstructed objects and set of control histograms. Distribution version includes also example of the main program for execution with PYTHIA 8.2 generator [3]. Implemented set of parametrisations is not representing in details ATLAS or CMS detectors, some of them are simple and can be considered rather as place-holders for future adaptation of any detector. Nevertheless, we believe that the package will be well adequate for some feasibility studies on the high p T physics at LHC.[1]. E. Richter-Was, AcerDET: A Particle level fast simulation and reconstruction package for phenomenological studies on high p(T) physics at LHC , hep-ph/0207355;

Light stop searches at the LHC in events with one hard photon or jet and missing energy

“…Pythia has been run with power showers and including stop fragmentation and hadronization [25] before decayt 1 → c +χ 0 1 . The Pythia output has been fed into the fast detector simulation PGS [26], in order to simulate the most important detector effects.…”

Mid-rapidity charged hadron transverse spherocity in pp collisions simulated with Pythia

“…But, other approaches suggest that the phenomenon can be produced by initial state effects [10][11][12]. For instance, Pythia 8.180 [13] gives an effect reminiscent of the collective flow well known from heavy-ion collisions [14]. This flow-like behavior is attributed to multi-parton interactions (MPI) and color reconnection (CR) [15].…”

KS0 and Λ production in charged particle jets in p–Pb collisions at sZhang1 2014Nuclear Physics A5020View full textAdd to dashboardCite

“…2. The results are obtained in the 0 − 10% event multiplicity class with p ch T,jet > 10 GeV/c and > 20 GeV/c and compared to the inclusive V 0 in data and in PYTHIA8 [16] simulations. The ratios in jets do not depend on the jet radii and do not vary with p T,jet .…”

“…This effect is qualitatively similar to the enhancement observed in Pb-Pb collisions [12] that has been discussed in terms of collective flow [13], which could be presented in small systems like pp collisions [14], and/or parton recombination [15]. To discriminate between hard and soft processes contributing to the baryon and meson production, we study the Λ/K 0 S ratio within jets and compare it to inclusive distributions measured in p-Pb and minimum-bias simulations generated by PYTHIA8 (tune 4C) [16] for pp collisions at √ s = 5.02 TeV.…”