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 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,bb*IL fL(xL,H +/-)
from HER tails: BH, bb ~ bH,bb*IH + fH(xL,H +/-)
Beam-gas (bremsstrahlung + Coulomb)
HEB only: BHbg ~ aH*IH + bH*IH2 (aH , bH > 0)
LEB only: BLbg ~ aL*IL + bL*IL2 (aL , bL > 0)
beam-gas cross term: BLHbg ~ cLH * IL * IH (LEB+HEB, out of collision)
BI: LER injection (trickle) background
BLT (exp. signature somewhat similar to bremsstrahlung)

4. Proposed operational procedure: colliding beam measurements (1)

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 (> 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 (> 0.30 A, 0.25 A steps)
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 : A, 0.20 A steps, “no” LEB
no HER bunches in buckets (LFB permitting), 1.5 mA in LER bunch 0
7’ per setting + 5’ at the highest current (IFR)
Vary IL : A, 0.25 A steps, “no” HEB
no LER bunches in buckets (LFB permitting), 1.5 mA in HER bunch 0
at topmost (or 2 topmost) LER current(s), trickle then coast
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 (> 0.30 A, 0.5 A steps)
Keep IL ~ constant (1.85 A), vary IH (> 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’
Setup ’
Collision fixed LER current ’
IL = 1200 mA, vary IH 7 x 10’
IL = 1850 mA , vary IL 7 x 13’ + 5’
Collision fixed HER current ’
IH = mA , vary IL 7 x 10’
IH = 1350 mA , vary IL 7 x 10’
Pedestals ’
HER single-beam scan 7 x 10’ + 5’ ’
LER single-beam scan 7 x 10’ + 2 x 5’ + 5’ 90’
Repeat middle & top points of single-beam scans (H, L) 40’
Non-colliding scans ’
IH = mA , vary IL 4 x 10’
IL = mA , vary IH 4 x 10’

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 7’+5’ (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)
+ aH*IH + bH*IH2 (from single-beam HER data)
+ aL*IL + bL*IL2 (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