William Lockman UC Santa Cruz May 6, 2005MDI meeting G4 simulation: status and validation strategy Goals Contributors Status Needed plots Future tasks

William Lockman May 6, 2005MDI meeting Goals of the simulation Tool for remediating interactions of beam related backgrounds Degraded electrons from beam-gas interactions (Coulomb, Bremstrahlung) Debris from Bhabha scattering (gamma-nuclear, electro-nuclear) In BaBar detector components DCH, EMC most vulnerable (from B. Peterson plenary, Feb. 2004) Prediction of backgrounds in 2005/6 IP upgrade relative to current levels Changes to B1, Q1 fields to ameliorate parasitic losses, reduce  y * HER LER Luminosity Beam-beam EMC clusters

William Lockman May 6, 2005MDI meeting G4-based simulation of PEP beam backgrounds What has been added to the G4 simulation: improved interaction physics models: Bertini cascade model (hadronics) “high precision” package for neutrons (thermalization, capture) Bhabha generators: bbbrem (forward beam Bremsstrahlung) bhlumi (small angle radiative) Geometry: detailed model of vacuum chambers and magnets through Q5 neutron counters Magnetic fields: B1, Q1, Q2, Q4, Q5 main fields correctors solenoid fringe field outside measurement grid Analysis packages: BgsUser: MC truth, TURTLE, GHits (G4) - ntp666 PepBkgMon: Trigger, digis ntp300

William Lockman May 6, 2005MDI meeting Contributors Coordination of G4-based simulation:- W. Lockman Machine lattice & apertures (TURTLE): - T. Fieguth, R. Barlow bhabha generators (bbbrem, bhlumi):- N. Blount, WL PEP beam line geometry:- M. Bondioli, G. Calderini, WL PEP beam line magnetic field model:- G. Bower, WL hadronics:- D. Wright Analysis ntuples:- WL Validation: optics and apertures:- WL, GRB, TF, GC SVT analysis:- Brian Petersen DCH analysis:- M. Cristinziani DRC analysis:- D. Aston, GRB, J. Va’vra EMC analysis:- C. Edgar neutron physics:- GRB

William Lockman May 6, 2005MDI meeting Status Generators: bbbrem: validated, deployed (WL) bhlumi: validated, deployed (NB) Nuclear interaction modeling: e/  nuclear processes added HP package deployed neutron fission and capture added Bertini cascade model validated and deployed neutron thermalization, capture, n-alpha processes being validated (GRB) n+p -> Dg (in DRC water tank) 10B5 + n -> 7Li3 + 4He2 (in neutron counters)

William Lockman May 6, 2005MDI meeting Status Vacuum chamber geometry: detailed models of Q2 septa important source of backgrounds LER complete through Q5 HER complete through Q4 validated visually against CAD model and drawings vrml fly-through x-ray cross section plots G4 vs. TURTLE LER vacuum chamber hit comparison comparison combined check of optics and apertures minor aperture differences between G4 and TURTLE at front face of forward Q2 septum

William Lockman May 6, 2005MDI meeting Status Magnets and fields: B1, Q1, Q2, Q4, Q5, correctors, solenoid field+fringe validated against: magbends (repaired a sign error in SKEW QUAD SK1 rotation) TURTLE (beam ellipse study) Transport (launch angle study)launch angle study  x(z=-789 cm)  x’(z=+771 cm) (radians) slope: 40mm/mr O(1) TRANSPORT: 36 mm/mr

William Lockman May 6, 2005MDI meeting Status Analysis ntuple: common framework for single-beam and luminosity related background studies by subsystems experts with access to Monte Carlo information: Monte Carlo information Truth TURTLE GHit Trigger and raw data information Samples: Data Monte Carlo forward beam Bremsstrahlung (bbbrem) forward beam Bremsstrahlung radiative Bhabha (bhlumi) radiative Bhabha LER coulomb and Bremsstrahlung scattered TURTLE rays Subsystems: please analyze see planning documentplanning document

William Lockman May 6, 2005MDI meeting Needed plots/data samples Single beam: LER, HER single beam vacuum chamber dose rates from TURTLE simulation HER rays for G4 studies subsystem occupancy plots Colliding beam: Bhabha vacuum chamber dose rates (E*  ) from TURTLE simulation with updated apertures subsystem occupancy plots

William Lockman May 6, 2005MDI meeting Extra slides

William Lockman May 6, 2005MDI meeting Future Monte Carlo tasks TURTLE rays: corresponding to PEP-II upgrade lattice Geometry: Add missing SVT material outside the tracking volume flat cables matching cards improve model of B1/Q1 synchrotron masks Add Q5 HER forward and backward vacuum chambers replace cloned parts of the vacuum chamber Follow updates to real vacuum chamber: forward Q2 septum Q4/Q5 HER Add IFR shielding wall Magnetic fields: inside permanent magnet Samarium cobalt