W. KozaneckiMD planning meeting, 20 Jan 04 Background characterization strategy  MD goals  Background sources  Operational procedures  Open questions  Appendix: a few useful links W. Kozanecki

MD planning meeting, 20 Jan 04 MD goals  Main goal: characterize beam-current dependence of  machine-induced backgrounds  all BaBar ‘detectors’: SVT, DCH, EMC, DIRC, IFR + TRG, ODF  dedicated background monitors SVTRAD pin diodes + diamonds CsI counters BLM’s  beam-beam performance  specific luminosity  vertical & horizontal spot sizes in LER & HER  loss collimators in PR12 (HER), PR04 + PR02 (LER)  Parasitically: measure thermally-induced motion of IR components  using a ‘witness’ bunch in HER (1mA) when varying LER current, & vv  take advantage of slow ‘current staircase’ to measure thermal time constants

W. KozaneckiMD planning meeting, 20 Jan 04 Background sources  Beam-gas (bremsstrahlung + Coulomb)  HEB only: B Hbg ~ a H *I H + b H *I H 2 (a H, b H > 0)  LEB only: B Lbg ~ a L *I L + b L *I L 2 (a L, b L > 0)  beam-gas cross term: B LHbg ~ c LH * I L * I H (LEB+HEB, out of collision)  Luminosity (radiative-Bhabha debris)  B P ~ d P * L (strictly linear with L)  Beam-beam tails  from HER tails: B H, bb ~ b H,bb *I H + terms non linear in L, I L /bunch ( & I H /bunch ?)  from LER tails: B L, bb ~ b L,bb *I L + terms non linear in L, I H /bunch ( & I L /bunch ?)  Touscheck  LER only; signature somewhat similar to bremsstrahlung  B LT non-linear with charge density in bunch  B I : LER injection (trickle) background

W. KozaneckiMD planning meeting, 20 Jan 04 Proposed baseline parametrization B = B P + B bb + B Hbg + B Lbg + B LHbg + B LT + B I = a0 (from no-beam data ?) + d P * L (from colliding-beam data) + B bb (I b L, I b H ) (from colliding-beam data) + a H *I H + b H *I H 2 (from single-beam HER data) + a L *I L + b L *I L 2 (from single-beam LER data) + c LH * I L * I H (from 2-beam, non-colliding ?) + B LT (LER only, vary V RF ?) + B I (differential, trickle – coasting ?)

W. KozaneckiMD planning meeting, 20 Jan 04 Proposed operational procedure: colliding beam measurements  Keep I L ~ constant (1.85 A), vary I H (> 0.2 A, 0.2 A steps)  non-trickle  LER trickle ?  Keep I H ~ constant (1.5 A ?), vary I L (> 0.25 A, 0.25 A steps)  non-trickle  LER trickle ?

W. KozaneckiMD planning meeting, 20 Jan 04 Proposed operational procedure: single-beam measurements  Vary I L : A, 0.25 A steps, no HEB  no LER bunches in buckets (LFB permitting)  1.5 mA in HER bunch 3400  Vary I H : A, 0.20 A steps, no LEB  no HER bunches in buckets (LFB permitting)  1.5 mA in LER bunch 3400  Separate beams vertically by 2 * 400 microns (feasibility!)  Keep I L ~ constant (1.85 A), vary I H (> 0.2 A, 0.4 A steps)  Keep I H ~ constant (1.5 A ?), vary I L (> 0.25 A, 0.5 A steps)  LER Touscheck backgrounds  3 possible ways to vary charge density (method tbc)  vary LER RF voltage (  bunch length): clean but delicate  vary transverse size using tunes: easy, but ill-defined conditions  use terser pattern & increase bunch current (1.5 mA/b -> 2.5 mA/ b?)

W. KozaneckiMD planning meeting, 20 Jan 04 Proposed operational procedure: general guidelines  BaBar taking data!  Perturb as adiabatically as possible  start with stable machine in delivery mode  avoid acrobatics (collisions first, then single-beam, then non- colliding...)  change Babar run #s etc while machine is filling  At each current setting:  optimize tunes  on lifetime (single beam, for beam-gas measurement)  on luminosity (in collision)  reset vertical IP angles in both rings  check SLM & interferometer settings  start a new run ?  Witness bunches (single-beam only, conditions permitting)  1.5 mA in bucket 3400 in LER when ramping HER (& vv)  requires additional 100-bucket gap at end of high-current train

W. KozaneckiMD planning meeting, 20 Jan 04 Open questions  Likely prerequisites  ‘routine’ 8-station running in HER  decent stored-beam & trickle backgrounds during preceding owl shift  Trigger rmix ?  Run duration/# evts per beam setting  Data samples  Do we want one (or more) zero-current run(s) for pedestals etc?  Do we really need to measure the cross-term contribution?  Do we really need to measure the trickle contribution?  Reproducibility checks: strategy?  Do we need to change run #  at each current setting?  between trickle & non-trickle?  Touscheck background measurement procedure ?  Need volunteer(s) to analyze CsI & BLM data!

W. KozaneckiMD planning meeting, 20 Jan 04 Learning from the past: a few useful links...  General link for 2002 studies: & follow-up postings  SVT 2002 studies:  DCH grounds/ DIRC studies:  EMC  links tbd  evidence for a luminosity term