Analysis Meeting,November 9-11, 2003

Manuel Calderón de la Barca Sánchez

Heavy Flavor Working Group

Heavy Flavor in ‘04:

Prospects for J/.

Heavy Flavor in ‘04:

Prospects for J/.

2

Status of Studies for 2004 Run

Full document on the web http://www.star.bnl.gov/protected/heavy/www/proposals/oni

um.pdf

Estimated Production Rates Trigger

Implementation, Efficiency and Rejection Power

Simulations and Tests in d+Au and p+p Prospects for Measurements in Au+Au Plans and Beam Use

3

Production Rates Rates are

per event, into e+e-, per unit rapidity at y=0

Ok, how many do we see? Acceptance, centrality selection, offline cuts… J/: Requiring Eelectron>1.2 reduces the signal

Minbias Top 5% Top 10% Top 20%

J/ 1.35 x 10-4 6.21 x 10-4 5.54 x 10-4 4.46 x 10-4

’ 4.96 x 10-6 2.28 x 10-5 2.03 x 10-5 1.64 x 10-5

1.18 x 10-7 5.43 x 10-7 4.84 x 10-7 3.89 x 10-7

’+’’ 4.31 x 10-8 1.98 x 10-7 1.77 x 10-7 1.42 x 10-7

4

Production Rates IIJ/ Yield:24 J/ e+e-, p>1.2 GeV per 1M min-bias events

98 J/ e+e-, p>1.2 GeV per 1M 10% central events

Yield:0.046 e+e-, p>3 GeV per 1M min-bias events

0.19 e+e-, p>3 GeV per 1M 10% central events(Triggered event ~ central)

Include:- fAB (hard fraction)- 1 unit 4- Acceptance (3/4 Barrel)- momentum cut

5

Simulations for Au+Au @ 200 GeV Background

Hijing Minbias Signal

Pythia; settings tuned for J/, modifications for

Processed Background and signal in GSTAR Mixed 1 quarkonium event with 1 Hijing

eventDone at ZEBRA bank level (M. Potekhin)

Run algorithmsHijing dataset : Background Rejection PowerHijing + quarkonium : Trigger Efficiency

6

EMC Topology Trigger Divide into 6

sections Find a tower above

a threshold Look in the 3

opposite sections in

If another tower above threshold, trigger.

7

J/ Trigger: L0 Efficiency and Rejection

Eff

icie

ncy

Rej

ectio

n

Cutting at E=1.2-1.4 GeV is the region where we can work.Less than that:

•Tower calibration•No rejection power

More than that:•Little signal left. Efficiency is 10% at 1.6 GeV

8

J/ Trigger: L0 Efficiency and Rejection

No free lunch:

High rejection only for peripheral events.

Most signal in central events.

98% of the yield is in top 60% central.

9

Trigger: L0 Efficiency and Rejection

Compare 2 approaches at L0, the topology trigger and the single High-Tower trigger.

10

Trigger: 1/Rejection vs Efficiency

High-Tower trigger at L0 gives better efficiency for the same rejection power. Decision: use High-Tower at L0 for the upsilon trigger.

11

J/: L0 & L2 Efficiency and Rejection

Most of the work is done by the topology trigger.Again, high rejection only for peripheral events.

12

J/: L0 & L2 Efficiency and Rejection

For central collisions, every event fires

Trigger works for low multiplicity, where yield is small.Not much to gain…

13

Trigger: L2 Efficiency and Rejection

Using High-Tower at level 0 and L2 fast invariant mass:Sample the parameter space of the triggers in tandem.

Minimum Bias Central

Can achieve rejections of 103 keeping the efficiency above 80%.

14

Trigger Performance

R Cuts

L0 L2

High-Tower ADC

ClusterEnergy

Cos Mass

Efficiency 0.95 300 10 4.5 0 7

Balanced 0.90 833 10 5.0 -0.2 6

Rejection 0.85 2174 10 5.0 0 8

Trigger works beautifully. Large rejection power and goodEfficiency.The problem is that there is not much signal!Need Luminosity!!

15

Putting it all together: J/ Rates

Rejection is good only in peripheral trigger.

Yield is small in peripheral. Trigger enhances by only a factor ~2 there.

Killer: Would require 14% of STAR’s bandwidth

Simply take minbias and central triggers, obtain a good sample.

}

16

Rates

Trigger enhances yield by more than a factor of 10.Trigger works!

Even at the highest L,L0 Rate is ~100 HzL2 Rate is ~ 3 HzLow rate.

L2 Rate can be reduced by ~3 keeping efficiency highRoom to move.

17

Heavy Quarks in Run IV: Charm J/ Trigger works only in peripheral

Very well suited for UPC (F. Meissner) Yield is small (2% in 100-60% bin) Background rate is high

Would require 14% of STAR’s bandwidth Given this, enhancement of only a factor of 2. We will not request a dedicated trigger. J/ Analysis will rely on large minbias and central

data sets.50 x 106 minbas + 50 x 106 central

3 signal + 5 signal in central Based on very conservative estimates on

background rejection (significance ~ e/h)

18

Heavy Quarks in Run IV: Beauty

Trigger looks promisingEfficiency can be kept above 85%Rates are low!!

Take advantage of full luminosity Same applies to ALL rare triggers (High-Tower)

Shift crews need to be FAST. Will rely on L3 Express stream for quick

turnaround Conservative estimate: ~100 Upsilons in 2004

has never been measured in heavy ions before

Next step, implementation and testing online. (Hank, Falk, Tonko, Chris)

19

Effect of Cos Cut

Topology trigger, limit by /3,Limits J/ p to ~ 5 GeV/c.

L2 cut on cos < -0.2 is still quite safe for .