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Planning for the summer: How do we trigger?

Planning for the summer: How do we trigger?. Assumptions Running conditions Hardware Algorithms & Rates Scaled from Star Note 0347 Prescaling?. Assumptions http://www.agsrhichome.bnl.gov/RHIC/luminosity/lumratetable.html. For vacuum, “expected” = “current” Vacuum level from Bill C.

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Planning for the summer: How do we trigger?

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  1. Planning for the summer:How do we trigger? Assumptions Running conditions Hardware Algorithms & Rates Scaled from Star Note 0347 Prescaling?

  2. Assumptions http://www.agsrhichome.bnl.gov/RHIC/luminosity/lumratetable.html • For vacuum, “expected” = “current” • Vacuum level from Bill C. • Bunches reach IP every 105 nsec • for summer, most will be empty

  3. Hardware • CTB • In place, working • Timing bit timing not adjusted • timing bit probably not usable • MWC • Noisy • Timing not adjusted • probably not usable • possible veto (low efficiency) • Logic • Level 0: there, working • Level 2: questionable • probably requires major effort

  4. Physics Rates • If maximum luminosity is 0.002 of design, what can we do? • Assume 106 seconds (10 days) of running at 5*10-4 of design luminosity • What are the rates (in STAR acceptance)? • ** F acceptance depends on K momenta • This includes MWC acceptance • without MWC divide by ~ 4

  5. Cosmics • Rate reaching TPC (16 m2) • ~ 2,000 Hz (E>~ 2 GeV) • CTB gate ( 40 nsec/105 nsec) • 760 Hz • 6 bunches out of 60 • 76 Hz • Need ~ 10 X better • CTB timing bit ~ 3X better • probably unavailable • topology cut • tracks must pass through most of TPC • select horizontal events

  6. Topology Cuts • Divide f into 4 sectors • (view looking down beampipe) • 2-5 track triggers must include hits in opposite sectors • Orient vertically or diagonally • diagonal better for cosmics • current cabling is vertical • vertical rejection should give ~X5 rejection • Cosmic rate ~ 15 Hz

  7. Beam Gas • Vacuum levels and profiles somewhat uncertain • Combine currents + current vacuum ~ match SN347 • 6/60 bunches --> 10X decrease • No MWC • 10X increase ??? • 53 Hz

  8. Other Triggers • Beam induced backgrounds • RHIC Note 22 (A.J. Stevens) • More likely to mimic semi-central collisions • rate should be low • Need data • Grazing Nuclear Collisions • SN347 rate: 0.04 Hz • No MWC: X10 • 0.4 Hz • Photonuclear Interactions • SN347 Rate: 0.12 Hz • No MWC: X10 • 1.2 Hz

  9. Rates • Summary: • Total ~ 70 Hz • 7X too high • Uncertainty ~ X3 • prescale as needed

  10. Conclusions • Summer luminosities will be very low. Despite this, some signals should be visible: • r0 p+ p- is very likely • f  K+K and gg e+e- should also be possible • Beam gas is largest background • Cosmics are second • With accessible hardware and algorithms, trigger rate ~ 70 Hz • Will need prescaling • Physics should still be accessible

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