In order to correct for dectector acceptance, Monte Carlo simulations have been embedded into the data and passed through reconstruction in order to determine the particle efficiencies. The efficiency is (#MC Tracks Reconstructed)/(#MC Tracks Total). The following function is used to fit the efficiencies:
|Efficiency = A exp[-(b/pt)c] + d(pt)|
At multiplicities much lower than Au+Au collisions at 200 GeV, the Cu+Cu 22 GeV collisions have negligible variation in efficiency by centrality. Thus the min-bias efficiencies are used for all centralities.
For Reference the Cu+Cu 62.4 GeV Refmult borders are given below in comparison with Au+Au 200 GeV
|Centrality||CuCu22 Refmult||AuAu200 Refmult|
|5%||≥ 86||≥ 510|
|10%||≥ 72||≥ 431|
|20%||≥ 51||≥ 312|
|30%||≥ 35||≥ 217|
|40%||≥ 24||≥ 146|
|50%||≥ 16||≥ 94|
|60%||≥ 10||≥ 56|
|70%||≥ 6||≥ 30|
|80%||≥ 4||≥ 14|
The embedding used is from the Cu+Cu 62.4 GeV Dataset for π±, K+, and for protons. The K+ minbias efficiency has been used for K- as well. As a the Au+Au 200 GeV embedding from Run 5 for K- is shown to demonstrate that there is negligible difference between K+ and K- efficiencies (even in a different collision - as long as the appropriate refmult cuts are made).
Since the K+ and K- efficiencies demonstrate that there is negligible difference at these multiplicities even between Cu+Cu 62.4 GeV and Au+Au 200 GeV the latter is used for the p efficiency.
[Note: While there was embedding available for the Cu+Cu 200GeV Dataset, it was not used since it employes an updated tracker in reconstruction which wasn't used in the Cu+Cu 22 GeV dataset.]
Primary Tracks have been corrected for energy loss in material (mostly before reaching the TPC) with the pion mass assumption. For Kaons, protons and antiprotons, futher correction is needed.