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