Planning for the summer: How do we trigger?
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Transcript of 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.
Bunches reach IP every 105 nsec for summer, most will be empty
Parameter Design Expected
BeamEnergy
100 GeV/n 70 GeV/n?
Bunches 60 6
Current/bunch
109 ions 5*108 ions
Luminosity(gold)
2*1026/cm2s 4.3*1023/cm2s(0.002 design)
VacuumLevel (@IP)
10-9 Torr Few 10-9 Torr
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
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)?
acceptance depends on K momenta
This includes MWC acceptance without MWC divide by ~ 4
Channel Rate0 + - 8,000 K+K- 300 ** e+e- 250
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
Topology Cuts Divide 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
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
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
Rates
Summary:
Total ~ 70 Hz 7X too high Uncertainty ~ X3
prescale as needed
Cosmics 15 Hz
Beam Gas 53 Hz
Grazing Nuclear 0.4 Hz
Photonuclear 1.2 Hz
Conclusions Summer luminosities will be very
low. Despite this, some signals should be visible: 0 + - is very likely K+K and 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