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 Full document on the web H Estimated Production Trigger H Implementation, Efficiency and Rejection Simulations and Tests in d+Au and Prospects for Measurements in Plans and Beam Use

3 Production Rates are H per event, into e + e -, per unit rapidity at y=0 H Ok, how many do we see? W Acceptance, centrality selection, offline cuts…  J/  : Requiring E electron >1.2 reduces the signal MinbiasTop 5%Top 10%Top 20% J/  1.35 x x x x ’’ 4.96 x x x x  1.18 x x x x  ’+  ’’ 4.31 x x x x 10 -7

4 Production Rates II J/  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:   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: - f AB (hard fraction) - 1 unit  4  - Acceptance (3/4 Barrel) - momentum cut

5 Simulations for 200 Background H Hijing Signal  Pythia; settings tuned for J/ , modifications for Processed Background and signal in Mixed 1 quarkonium event with 1 Hijing event H Done at ZEBRA bank level (M. Run algorithms H Hijing dataset : Background Rejection Power H Hijing + quarkonium : Trigger Efficiency

6 EMC Topology Trigger  Divide  into 6 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 Efficiency Rejection Cutting at E= 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 10 3 keeping the efficiency above 80%.

14  Trigger Performance  RCuts L0L2 High- Tower ADC Cluster Energy Cos  Mass Efficiency Balanced Rejection Trigger works beautifully. Large rejection power and good Efficiency. 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 Hz L2 Rate is ~ 3 Hz Low rate. L2 Rate can be reduced by ~3 keeping efficiency high Room to move.

17 Heavy Quarks in Run IV: Charm  J/  Trigger works only in peripheral H Very well suited for UPC (F. Yield is small (2% in % Background rate is high H Would require 14% of STAR’s Given this, enhancement of only a factor of We will not request a dedicated trigger.  J/  Analysis will rely on large minbias and central data sets. H 50 x 10 6 minbas + 50 x 10 6 central  3  signal + 5  signal in central W Based on very conservative estimates on background rejection (significance ~ e/h)

18 Heavy Quarks in Run IV: Trigger looks promising H Efficiency can be kept above 85% H Rates are low!! W Take advantage of full luminosity O Same applies to ALL rare triggers (High-Tower) W Shift crews need to be FAST. W Will rely on L3 Express stream for quick turnaround W Conservative estimate: ~100 Upsilons in 2004   has never been measured in heavy ions 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 .