NPE in Au+Au 62.4 GeV - current results and prospects for run 16

Updated on Tue, 2015-05-12 07:49. Originally created by kikola on 2015-04-16 03:09.

general information

NPE spectra and v2 results from Au+Au 62.4 GeV run 2010

Slides 18 - 21 in Recent Open Heavy Flavor Results from STAR (RHIC & AGS Annual Users' Meeting 2014)

Prospects for NPE meausrements in Au+Au 62.4 GeV in run 16

(based on inputs from Mustafa Mustafa and James Dunlop)

Attached are ratio plots from theory calculations. The total charm cross-section is down by a factor of 4-5. However the pT dependence is not trivial.

The pT of charm quarks is, consequentially, harder at 200 GeV. For R_cp measurement it means a factor of 15-20 drop in cross-section in the interesting pT region (4-10 GeV/c).
For NPE v2 the harder spectra at 200 GeV implies that the NPE cross-section is down by a factor of 10 at low electron pT due to the feed down from higher pT.

Regarding the background, the NPE background is down by only a factor of 2 (with some pT dependence) from 200 to 62GeV.

Taking the projections for top energy of min/max = 2.2 nb^-1/ 3.6 nb^-1 /week (take the middle, say 3 nb^-1) at 200 GeV, then scaling down by E^2, would expect
~1.5 nb^-1 in such a run, delivered. Take 70% live, ~1 nb^-1.

So a factor of 5 or so possible vs. what was triggered in Run 10, also perhaps somewhat better with a narrower vertex distribution.
Not clear whether that pushes us over the top to make the HT trigger useful. It is unlikely, especially with the worse NPE S:B with the HFT.