Background characterization: MD plan

1
Background characterization MD plan
W. Kozanecki

• MD goals
• Background sources
• Operational procedures
• Open questions

2
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 (pins, CsI
  counters, collim. BLMs)
• beam-beam performance
• specific luminosity
• vertical horizontal spot sizes in LER HER
• loss rates _at_ collimators in PR12 (HER), PR04
  PR02 (LER)
• Parasitically measure thermally-induced motion
  of IR components
• using a witness bunch in HER (1mA, feedbacks
  off) when varying LER current, vv
• take advantage of slow current staircase to
  measure thermal time constants
• note this only measures the effect on the OTHER
  beam (e.g. LER ? HER)

3
Background sources

• Luminosity (radiative-Bhabha debris) major
  concern (DCH future)
• BP dP L (strictly linear with L)
• Beam-beam tails
• from LER tails BL, bb bL,bbIL fL(xL,H
  /-)
• from HER tails BH, bb bH,bbIH fH(xL,H
  /-)
• Beam-gas (bremsstrahlung Coulomb)
• HEB only BHbg aHIH bHIH2 (aH , bH gt
  0)
• LEB only BLbg aLIL bLIL2 (aL , bL gt
  0)
• beam-gas cross term BLHbg cLH IL IH
  (LEBHEB, out of collision)
• BI LER injection (trickle) background
• BLT (exp. signature somewhat similar to
  bremsstrahlung)

4
Proposed operational procedure colliding beam
measurements (1)

• 2000 2002 procedure

5
Proposed operational procedure general guidelines

• BaBar taking data!
• Perturb as adiabatically as possible
• start with stable machine in delivery mode
• avoid acrobatics (collisions ? pedestals ?
  single-beam ?
  non-colliding ? pedestals)
• LER Touscheck background a separate, dedicated MD
• At each current setting
• optimize tunes
• on luminosity (in collision, coasting so lifetime
  reasonable)
• on lifetime (single beam, for beam-gas
  measurement)
• reset vertical IP angles in both rings
• check SLM interferometer settings
• start a new run (also at trickle-coasting
  transition)
• Pedestal runs
• 1.5 mA in each ring, non-collidng
• Reproducibilty if beam(s) lost, redo last setting

6
Proposed operational procedure colliding beam
measurements (2)

• Setup save configs orbits check fbcks change
  BBR L1 config.
• Keep IL constant, vary IH (gt 0.30 A, 0.20 A
  steps)
• 2 regimes (to help separate Lumi beam-beam
  contributions)
• IL 1.20 A (2/3 of peak LER current, moderate
  beam-beam)
• no trickle (LER coasting only)
• 7 steps
• IL 1.85 A (or max. sustainable LER current)
• to measure trickle contribution differentially,
  for each HER current setting
• trickle LER ( 5)
• coast LER ( 5) (peak L H currents 5
  additional for IFR high-stat data)
• Keep IH constant, vary IL (gt 0.30 A, 0.25 A
  steps)
• 2 regimes (to help separate Lumi beam-beam
  contributions)
• IH 0.85 A (2/3 of peak HER current, moderate
  beam-beam)
• IH 1.35 A (or max. sustainable HER current,
  assuming 8 stations)
• no trickle, 7 /setting
• Pedestal run
• 1.5 mA in LER bucket 0, 1.5 mA in HER bucket 3400

7
Proposed operational procedure single-beam
measurements

• Vary IH 0.30-1.35 A, 0.20 A steps, no LEB
• no HER bunches in buckets 0-100 (LFB
  permitting), 1.5 mA in LER bunch 0
• 7 per setting 5 at the highest current (IFR)
• Vary IL 0.3-2 A, 0.25 A steps, no HEB
• no LER bunches in buckets 0-100 (LFB permitting),
  1.5 mA in HER bunch 0
• at topmost (or 2 topmost) LER current(s), trickle
  then coast
• 7 per setting 5 at the highest current (IFR)
• Reproducibility check on single beam scans (esp.
  pins)
• repeat middle top points of previous two scans
  (HER, then LER)
• Non-colliding scan (sparse)
• Keep IH constant (1.30 A), vary IL (gt 0.30 A,
  0.5 A steps)
• Keep IL constant (1.85 A), vary IH (gt 0.30 A,
  0.4 A steps)
• Operational aspects
• Separate beams vertically by 2 400 microns
  (feasibility ?)
• Patterns 100 bucket truncation at opposite ends
  of the two trains (YP!)
• 7 per setting
• Pedestal run

8
Total time estimates (ONLY data taking BBR
on-off) 620

1. Setup 10
2. Collision scan _at_ fixed LER current 170
3. IL 1200 mA, vary IH 7 x 10
4. IL 1850 mA , vary IL 7 x 13 5
5. Collision scan _at_ fixed HER current 140
6. IH 850 mA , vary IL 7 x 10
7. IH 1350 mA , vary IL 7 x 10
8. Pedestals 5
9. HER single-beam scan 7 x 10 5 80
10. LER single-beam scan 7 x 10 2 x 5 5
    90
11. Repeat middle top points of single-beam scans
    (H, L) 40
12. Non-colliding scans 80
13. IH 1350 mA , vary IL 4 x 10
14. IL 1850 mA , vary IH 4 x 10
15. Pedestals 5

9
To be clarified

• Likely prerequisites
• routine 8-station running in HER
• decent stored-beam trickle backgrounds during
  preceding owl shift
• Actual trigger rmix to enhance background
  fraction minimize duration tbd by BaBAr trig
  expert
• Run duration/ evts per beam setting 7 (coast
  only) or 75 (trickle/coast), dominated by pin
  diode stability
• Trickle ? coast switch
• Need volunteer(s) to analyze CsI BLM data!

10
Spare slides
11
Proposed baseline parametrization

• B BP Bbb BHbg BLbg BLHbg BLT BI
• a0 (from no-beam data ?)
• dP L (from colliding-beam data)
• Bbb (IbL, IbH) (from colliding-beam data)
• aHIH bHIH2 (from single-beam HER
  data)
• aLIL bLIL2 (from single-beam LER
  data)
• cLH IL IH (from 2-beam, non-colliding
  ?)
• BLT (LER only, vary VRF?)
• BI (differential, trickle coasting ?)

12
DCH 2002
13
TRG 2002
14
EMC 2002