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Status of J/ Trigger Simulations for

d+Au Running

Trigger Board MeetingDec5, 2002MC & TU

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Simulations & Datasets

Background Studies: HIJING d+Au, min bias, plain GSTAR simulations: 90k events

Full BEMC was in but only ½ used

J/: 1 decay in e+e-/event + GSTAR: 100k events

flat in rapidity and pT

using simple generator for y and pT

Gaussian y distribution ( = 1) Exponential in pT (slope 600 MeV/c)

Use GSTAR data from BEMC, BBC only

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Assumptions for Run Conditions

d+Au Collisions: L = 1 1028 cm-2 s-1

inel = 2.3 b Interaction Rate = 23 kHz 5.3 10-6 J/ into e+e- in one unit at midrapidity 41 10-6 J/ into e+e- total L2 runs with 1kHz

ADCs of all towers available calibration ADC E available BBC timing info available rough vertex z

L0 one EMC patch > threshold

patch = 4x4 towers available: patch sum and highest tower in patch

optional (?): count of patches above threshold

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L0 Simulation Results I

BBC triggers fires in 93% of all min bias HIJING events

BBC triggered events

all HIJING events

21 kHz BBC rate

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J/ Acceptance

Acceptance = Both Electrons with pMC>1 hit a BEMC tower.

Accepted/Thrown = 0.051

Accepted (in 0< < 1) /Thrown (in 0 < < 1 ) = 0.114

Raw (input) Accepted

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L0 Simulation Results II

How many patches in the event have high tower > 1 (1.5) GeV ?

1 high patch

2 high patches

High tower

1 GeV 4.8 24.2

0.75

1.5 GeV 13.9 195.6

0.18

Sum of patch

1 GeV 2.8 7.9

0.94

1.5 GeV 6.2 38.4

0.37

Rejection power of non-J/ eventsJ/ efficiency (wrt those in acceptance)

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L2 Trigger: Getting the invariant mass quickly

• p1 = (EEMC-12-m2)½ EEMC

• p2 = (EEMC-22-m2)½ EEMC

• cos x1x2/(|x1| |x2|)

• m2 2 p1 p2 (1 – cos )

Pro: • simple, fast (no trig function)• avoids ambiguity

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L2 Energy Resolution

Cluster 3 highest towers in a 3x3 patch

2 tower vs. 3 tower cluster: L2 Mass RMS changes from 668 to 311 MeV

<Ee - Ecl> = 40 MeVRMS = 248 MeV

Resolution ~ 17%/E

Conclusion: need clustering algorithm for L2optimum: 3 tower cluster

3 towercluster

no clustering single tower

3 tower cluster

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cos Resolution

J/ flat in and pt J/ realistic kinematics

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L2 Mass Resolution

Several contributions: Mass approximation

Negligible Cluster Energy

RMS = 248 MeV Cluster cos()

~tails

Realistic simulations: RMSmass = 311 MeV 99.9% contained in 31

GeV mass window

Thrown massL2 Mass, real E, real cos()L2 Mass, cluster E, real cos()L2 Mass, real E, cluster cos()L2 Mass, cluster E and cos()

Here: MC z-vertex used (know from earlier studies that effect is small)

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L2 Simulation Results

How many tower pairs in the event have mass > 1 , 1.5, 2 GeV ?

L0 High Tower Energy

L2 Mass Threshold

Rej. , Eff.

L0 & L2

Increase in Seff, or stat. Gain

1 GeV 1 GeV 32.4

0.699

15.8

1 GeV 2 GeV 50.7

0.698

24.7

1.5 GeV 1.5 GeV 299.6

0.18

9.4

2 3 GeV

0.008

Rejection power of non-J/ eventsJ/ efficiency (w.r.t. those in acceptance)

Note: factors independent of 1 or 2 patch L0 trigger but NOT L0 rate

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L2 Mass & Cos(), Background

L2 Mass cut reduces background, keeps efficiency at ~70% Note correlation between mass and opening angle:

lowest mass pairs must come from cos () ~ 1

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Next Step: Isolation Cuts?

Try to exploit shower topology. Electromagnetic showers should deposit their energy mainly in one tower.

All BG towersPhotonsPionsKaonsKaonsProtons

i high towertowers

itowers

E E

E

electrons background

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Trigger and Sample Rates

Input: 41 10-6 21 kHz = 0.86 Hz in acceptance: 0.86 Hz 0.051 = 44 10-3 Hz

L0 with 1 GeV cut: 1 patch: 21 kHz/4.8 = 4.4 kHz event rate 2 patch: 21 kHz/24 = 0.9 kHz event rate

L2 (1 kHz): 1kHz/2 (rejection) = 500 Hz L2 trigger rate 1 patch: 1kHz/4.4kHz 23% 2 patch: 100%

J/ rate after L2: 1 patch: 44 10-3 Hz 0.23 0.7 50/500 = 0.7 10-3 Hz 2 patch: 44 10-3 Hz 0.7 50/500 = 3 10-3 Hz for 106 sec 700 – 3000 J/ s

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Conclusions Prospects for J/ Trigger look promising Achieve reasonable efficiency at L0 and L2

Tower Energy > 1 GeV, L2 Mass > 2 GeV gives r ~ 24 at L0 (recall BBC rates is ~21 kHz) r ~ 50 at L0 & L2, (simple Mass threshold increases r x 2)L2 eff ~ 70%

Statistical gain of 25 over no trigger case.

Steps to finalize algorithm: Isolation cuts (3x3 sum tested, 5x5 sum, 7x7 sum ?) Test 2 Different Tower Thresholds, e.g. Tower1>1.5, Tower2>1 GeV

Implement trigger in L2 CPU’s next week Note: Trigger fits in very nicely with Jeff’s proposed trigger scheme. Worth reiterating: already a proof-of-principle would teach us a lot!!