Status of MC activities A. Bressan

Outlook ESC – EIC Software Consortium Activities Perspectives

EIC R&D and software development Physics Software Physics Event Generator Detector Simulation Physics Performance Detector Design Detector R&D

Global objectives Interfaces and integration connect existing frameworks / toolkits identify the key pieces for a future EIC toolkit collaborate with other R&D consortia Planning for the future with future compatibility workshop to discuss new scientific computing developments and trends incorporating new standards validating our tools on new computing infrastructure Organizational efforts with an emphasis on communication build an active working group and foster collaboration documentation about available software maintaining a software repository workshop organization

Few specific activities/progress GEANT4 – 4 EIC Makoto Asai (Standford), spokesperson the GEANT4 collaboration will be the contact person in order with to progress on item needed by EIC and presently not enough developed: RICH … GEANT4 is considered the standard for apparatus simulation (even fast simulation by switching off showers and applying fast modelisations) GEOMETRY DESCRIPTION The standard for geometrical description has be chosen in May by ESC after some discussion in previous meetings; this will be GDML: “We recognize that the GDML format is currently the only de-facto standard that can be used natively used by Geant4 and ROOT applications. Many other applications that do not build directly on this format do still have converter to at least export to this format” The problem that GDML doesn’t supports the definition of Sensitive detectors (SDs) will be solved by defining them in a separate file. INPUTS: both Google standard ProMC and HepMC

PYTHIA 8 & DEEP INELASTIC SCATTERING DIS not implemented initially in Pythia 8: “In particular, there is no provision for 𝑒𝑝 collisions or for incoming photon beams, neither on their own nor as flux around an electron.” Very recently simulation of DIS events can be achieved using DIRE (Stefan Hoeche, Stefan Prestel) in conjunction with PYTHIA 8.2 The DIRE parton shower combines dipole-shower ideas in the spirit of ARIADNE with the careful handling of collinear enhancements in classical parton showers. As such, it is a full-fledged replacement of the PYTHIA8 parton showers for lepton-lepton, lepton-hadron and hadron-hadron collisions, including a detailed treatment of mass effects. News: The latest version of DIRE is 2.000, published on May 2nd 2017. This version is compatible with PYTHIA versions 8.226 or higher. The code now allows for NLO corrections to the parton shower evolution, for lepton-lepton, lepton-hadron or hadron-hadron collisions (i.e. DGLAB). If you use these NLO functionalities, please cite arXiv:1705.00742 and arXiv:1705.00982. Ongoing work to validate it by comparing to HERMES and COMPASS results are promising. Both ProMC and HepMC available as outputs BASE MC for RC developments

PYTHIA 8 & DEEP INELASTIC SCATTERING COMPASS, 𝜇p 160-0 GeV EIC, ep 20-100 GeV

HERACLES AND DJANGHO Event Generation of ep Interactions at HERA Including Radiative Processes by H. Spiesberger (Mainz) DJANGOH simulates deep inelastic lepton-proton scattering including both QED and QCD radiative effects. DJANGOH is an interface of the Monte Carlo programs HERACLES and LEPTO (parton cascades can be generated also with the help of ARIADNE) There is an established collaboration with H. Spiesberger to validate DJANGHO for COMPASS Discussions to established a collaboration for implementing a MonteCarlo generator that includes radiative corrections for the EIC (within the ESC Consortium) also started and looking promising

Calculate radiative corrections for transverse polarized observables to measure TMDs and polarized exclusive observables. Provide proof that the MC phase space constrains on the hadronic final state is equal to calculating radiative corrections for each polarized and unpolarized semi-inclusive hadronic final state independently. Define a software framework and develop a library based on this framework, which integrates the radiative corrections depending on polarization and other determining factors in a wrapper-software.

Status and Plans We have defined Pythia 8 + DIRE as the standard generator for the future EIC Work to check the possibility to combine Pythia 8 and (HERACLES/DJANGOH) philosophy just started Two mains steps are needed: Provide the new methods to calculate cross-sections including the RC corrections Provide the methods to generate events which include photon-radiations according to HERACLES both from incoming or outgoing leptons as well as from the partons A starting point could be trough the use of the lepton PDFs flag PDF:lepton (default = on) Use parton densities for lepton beams or not. If off the colliding leptons carry the full beam energy, if on part of the energy is radiated away by initial-state photons. In the latter case the initial-state showers will generate the angles and energies of the set of photons that go with the collision. In addition one collinear photon per beam carries any leftover amount of energy not described by shower emissions. If the initial-state showers are switched off these collinear photons will carry the full radiated energy.