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Advances in G4-Based Simulation for PEP-II Beam Backgrounds: Status, Validation, and Future Tasks

This document outlines the status and future plans for the G4-based simulation of PEP-II beam backgrounds, crucial for understanding and mitigating beam-related interactions and backgrounds. Key contributors have improved models, including the Bertini cascade and high precision neutron packages, while validating nuclear interaction models and vacuum chamber geometries. Future tasks include enhancing the simulation geometry, magnetic field modeling, and generating necessary plots to support ongoing research in collision environments. Collaboration among teams continues to ensure accuracy in results and predictions.

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Advances in G4-Based Simulation for PEP-II Beam Backgrounds: Status, Validation, and Future Tasks

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  1. G4 simulation: status and validation strategy Goals Contributors Status Needed plots Future tasks MDI meeting

  2. EMC clusters HER LER Luminosity Beam-beam 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 by* MDI meeting

  3. 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 MDI meeting

  4. 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 MDI meeting

  5. Status • Generators: • bbbrem: validated, deployed (WL) • bhlumi: validated, deployed (NB) • Nuclear interaction modeling: • e/g 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) MDI meeting

  6. 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 • combined check of optics and apertures • minor aperture differences between G4 and TURTLE at front face of forward Q2 septum MDI meeting

  7. slope: 40mm/mr dx(z=-789 cm) O(1) TRANSPORT: 36 mm/mr dx’(z=+771 cm) (radians) 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) MDI meeting

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

  9. 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*s) from TURTLE simulation with updated apertures • subsystem occupancy plots MDI meeting

  10. Extra slides MDI meeting

  11. 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 MDI meeting

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