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Background Characterization and Monitoring for BaBar Beam Performance

This document outlines the background characterization and operational procedures for BaBar detectors, focusing on beam-current dependencies and machine-induced backgrounds. It proposes a baseline parametrization involving various beam components and discusses methods for optimizing luminosity, lifetime, and stability during data-taking. The report also addresses the importance of dedicated background monitors and suggests operational guidelines for efficient data collection under varying beam conditions. Addressing open questions and ensuring reproducibility in measurements are also prioritized.

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Background Characterization and Monitoring for BaBar Beam Performance

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  1. Background characterization: MD plan W. Kozanecki • MD goals • Background sources & parametrization • Operational procedures • Open questions

  2. MD goals • 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 (& backgrounds) • specific luminosity • vertical & horizontal spot sizes in LER & HER • loss rates @ collimators in PR12 (HER), PR04 + PR02 (LER)

  3. Proposed baseline parametrization B = BP + BL + Bbb + BHbg + BLbg + BLHbg + BI [+ BLT] = BP(from no-beam data) + dP * L (from colliding-beam data) + Bbb (IbL, IbH) (from colliding-beam data) + aH*IH + bH*IH2 + cH*IH4 (from single-beam HER data) + aL*IL + bL*IL2 + cL*IL4 (from single-beam LER data) + cLH * IL * IH (from 2-beam, non-colliding ?) + BI (differential, trickle – coasting ?) [+ BLT] (LER only, vary VRF?)

  4. Proposed baseline parametrization B = BP + BL + Bbb + BHbg + BLbg + BLHbg + BI [+ BLT] = BP(from no-beam data) + dP * L(from colliding-beam data) + Bbb (IbL, IbH) (from colliding-beam data) + aH*IH + bH*IH2 + cH*IH4 (from single-beam HER data) + aL*IL + bL*IL2 + cL*IL4 (from single-beam LER data) + cLH * IL * IH(from 2-beam, non-colliding ?) + BI(differential, trickle – coasting ?) [+ BLT](LER only, vary VRF ?)

  5. Data: Jan 04 (bef. therrmal outgassing crisis) Background characterization measurements Step 1: Beam-current scans  single-beam terms

  6. Data: Jan 04 • Total occupancy • HER single beam • LER single beam • Beam-beam term • present in all subdetectors • reproducibility! Step 2: L & beam-beam terms EMC cluster multiplicity SVT occupancy (FL1 M01-f)

  7. Proposed operational procedure: general guidelines • BaBar taking data! • Perturb as adiabatically as possible • start with stable machine in delivery mode • avoid acrobatics (delivery  collisions bkg  pedestals  single-beam  non-colliding  pedestals) • At each current setting • optimize tunes • on luminosity (in collision, coasting so lifetime reasonable) • on lifetime (single beam, minimize Touschek for beam-gas measurement) • reset vertical IP angles in both rings • check SLM, SXM & interferometer settings • start a new run (also at trickle-coasting transition) • Pedestal runs • no beam • Reproducibilty: if beam(s) lost, redo last setting

  8. Time request • 2 components • setup & tuning: hard to estimate - make appropriate arrangements! • at least 5' per setting when changing only 1 beam current (requires BaBar shifter "on the ball") • first setup, state changes & aborts more time-consuming (need MCC ops "on the ball") • Babar data taking • in 2004: 7' per setting (no trickle), dominated by pin-diode stabilization needs • can we shorten it? • what do diamonds need? • what does data taking need? • what do pin diodes need? • From actual experience • in 2004: • planned 8h for data taking & BBR transitions only (w/o setup & mishaps) • used 16 h, but with more complicated procedure • 2006 request: comparable DAQ time  RQ 2 shifts (8:30 am - 12 am) • recovery should be easier than from an acc. phys. MD

  9. To be clarified • Prerequisites • stabilized vacuum • in particular: is PR02 NEG 8020 really quiet ? • Babar encouraged to sample single-beam data whenever possible in the next few days (+ analyze it quickly) • ‘routine’ running in LER & HER with fulll RF complement • decent stored-beam & trickle backgrounds during preceding owl shift • Minimize data-taking time • diamond/diode settling time? • best trigger rmix to enhance background fraction ? • When (not) to trickle? • Need volunteer(s) to analyze data - incl. CsI & BLM!

  10. Spare slides

  11. Proposed operational procedure: colliding beam measurements • Setup: save configs & orbits; check fbcks; change BBR L1 config. • Keep IL ~ constant, vary IH (> 0.25 A, 0.25 A steps) • 2 regimes (to help separate Lumi & beam-beam contributions) • IL ~ 1.6 A (60% of peak LER current, moderate beam-beam) • no trickle (coast during data taking, trickle LER back up while filling HER) • ~ 7’ steps (dominated by pin-diode stability?) • IL ~ 2.7 A (or max. LER current that can be sustained stably) • to measure trickle contribution differentially, for each HER current setting: • trickle LER + HER (~ 5’) • coast LER + HER (~ 5’) • Keep IH ~ constant, vary IL (> 0.30 A, 0.35 A steps) • 2 regimes (to help separate Lumi & beam-beam contributions) • IH ~ 1.0 A (60% of peak HER current, moderate beam-beam) • no trickle (coasting during data taking, trickle HER back up when filling LER) • IH ~ 1.6 A (or max. sustainable HER current, assuming full RF complement) • to measure trickle contribution differentially, for each LER current setting: • trickle LER + HER (~ 5’) • coast LER + HER (~ 5’) • Pedestal run

  12. Proposed operational procedure: single-beam measurements • Vary IH : 0.25-1.6 A, 0.25 A steps, no LEB • no trickle at low current, 7’ per setting • at topmost (or 2 topmost) HER current(s), trickle then coast (5+5') • Vary IL : 0.3-2.7 A, 0.35 A steps, no HEB • no trickle at low current , 7’ per setting • at topmost (or 2 topmost) LER current(s), trickle then coast (5+5') • 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 (1.35 A), vary IL (> 0.30 A, 0.6 A steps) • Keep IL ~ constant (2.35 A), vary IH (> 0.25 A, 0.5 A steps) • Operational aspects • Separate beams: X = 2 * 1 mm, Y = 2 * 400 microns ? • 7’ per setting, no trickle (measure HEB lifetime change) • Pedestal run

  13. Total time estimates (ONLY data taking + BBR on-off): 690' • Setup 15’ • Collision scan @ fixed LER current 160’ • IL = 1600 mA, vary IH 7 x 10’ • IL = 2700 mA , vary IH 7 x 13’ • Collision scan @ fixed HER current 190’ • IH = 1000 mA , vary IL 8 x 10’ • IH = 1600 mA , vary IL 8 x 13’ • Pedestals 5’ • HER single-beam scan 5 x 10’ + 2 x 13' 80’ • LER single-beam scan 6 x 10’ + 2 x 13' 90’ • Repeat middle & top points of single-beam scans (H, L) 50’ • Non-colliding scans 90’ • IH = 1350 mA , vary IL 5 x 10’ • IL = 2350 mA , vary IH 4 x 10’ • Pedestals 5’

  14. 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)

  15. Proposed operational procedure: colliding beam measurements (1) • 2000 & 2002 procedure:

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