PHOTOS interface in C++: Technical and physics documentation

By N. Davidson, T. Przedzinski, Z. Was. Computer Physics Communications, 2016

496 citations recorded by the source corpus.

Abstract For five years now, PHOTOS Monte Carlo for bremsstrahlung in the decay of particles and resonances has been available with an interface to the C++ HepMC event record. The main purpose of the present paper is to document the technical aspects of the PHOTOS Monte Carlo installation and present version use. A multitude of test results and examples are distributed together with the program code. The PHOTOS C++ physics precision is better than its FORTRAN predecessor and more convenient steering options are also available. An algorithm for the event record interface necessary for process dependent photon emission kernel is implemented. It is used in Z and W decays for kernels of complete first order matrix elements of the decays. Additional emission of final state lepton pairs is also available. Physics assumptions used in the program and properties of the solution are reviewed. In particular, it is explained how the second order matrix elements were used in design and validation of the program iteration procedure. Also, it is explained that the phase space parameterization used in the program is exact. Program summary Program title: Photos++ Catalogue identifier: AEYF_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEYF_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 53720 No. of bytes in distributed program, including test data, etc.: 1297747 Distribution format: tar.gz Programming language: C++. Computer: PC. Operating system: Linux, MacOS. RAM: Bytes. Libraries take less than 2 MB. Memory complexity is O ( n ) with around 2–4 MB for events with 10 k particles. Classification: 11.1, 11.2. Nature of problem: Algorithm described in this paper can be used to add final state radiation to the event generated by external software using selected event record format. It can also be used on a sample of events loaded from data file. User can define parts of the decay tree on which algorithm can be invoked. The influence of the next-to-leading-order corrections, along with other options regarding electron–positron pair, muon pair and photon emission, can be studied. Solution method: The event record is traversed and a list of all decaying particles is created. Decays where program is not supposed to act and decays excluded by the user are removed from the list. The photon and pair adding algorithm is invoked separately on each remaining decay. If one or more particle is added to the decay, the kinematic of the whole decay tree is updated. Restrictions: Application of the algorithm strongly depends on the content on the event record. Insufficient precision or missing information may deteriorate quality of the results of the algorithm or prevent algorithm from working on the event or its parts. See Section 2 for more details. Running time: 10-30 s per 100k events for small events (less than 1k particles). The complexity strongly depends on the event content and user selection of excluded decays. The theoretical pessimistic complexity of the algorithm is O ( n 2 ) . However, such cases are highly unrealistic. In our tests, the average complexity is around O ( n 1.2 ) .

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7b5eb23a352739184c95f9ceb166638b1b18b2d6

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Nuclear and High Energy Physics

Citations in the corpus

Measurement of the W boson mass (2021, methodology): “The logarithm of this energy difference as described by Pythia, Herwig, and an alternative configuration of Pythia with the final-state radiation modelled by Photos [58] is shown in figure 9.”
Electron and photon energy calibration with the ATLAS detector using 2015-2016 LHC proton-proton collision data (2018, methodology): “52 [17] was used for QED emissions from electroweak vertices and charged leptons.”
Muon reconstruction and identification efficiency in ATLAS using the full Run 2 $pp$ collision data set at $\sqrt{s}=13$ TeV (2020, methodology): “52 [20, 21] was used to simulate the effect of final-state radiation.”
Test of lepton universality in beauty-quark decays (2021, methodology): “Bremsstrahlung emission in the decay of particles is simulated using the Photos software in the default configuration [158], which is observed to agree with an independent quantum electrodynamics calculation at the level of 1% [5].”
Search for doubly charged Higgs boson production in multi-lepton final states with the ATLAS detector using proton–proton collisions at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepac (2017, methodology): “Photos ++ version 3.52 [52] was used for photon emissions from electroweak vertices and charged leptons.”
Performance of the ATLAS muon triggers in Run 2 (2020, background): “52) [8, 9] to simulate the effects of final-state radiation.”
Observation of an exotic narrow doubly charmed tetraquark (2021, unknown): “Decays of unstable particles are described by EvtGen [102], in which final-state radiation is generated using Photos [103].”
Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector (2015, unknown): “Photon radiation from charged leptons for all samples is provided by Photos [76].”