Centrality Categorization for $R_{p(d)+A}$ in High-Energy Collisions

20 May 2014, 16:30
spectrum (darmstadtium)



Board: C-14
Poster Initial State Physics Poster session


Dr Darren McGlinchey (University of Colorado)


High energy proton- and deuteron-nucleus collisions provide an excellent tool for studying a wide array of physics effects, many of which are expected to have a significant dependence on the impact parameter of the collision, which is related to the collision centrality. We detail a method, employed by PHENIX, for determining centrality classes in $p(d)+A$ collisions via cuts on the produced charge particle multiplicity in the nucleus-going (-3.9<$\eta$<-3.0) direction. Using a Glauber Monte Carlo simulation we are able to map the centrality classes to geometric quantities of interest, along with corresponding systematic uncertainties. Within this framework we calculate the centrality bias-correction factors on the nuclear modification factor $R_{p(d)+A}$ due to correlations between a measured process and the multiplicity in the nucleus-going direction. These bias-correction factors are tested further using the HIJING MC generator, confirming that for $d+$Au collisions at $\sqrt{s_{NN}}=200$ GeV the corrections are small and vary by less than 5% (10%) for hadron production at midrapidty up to $p_{T}$=10(20) GeV/$c$. In contrast, we find that the bias correction factors for $p+$Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are an order of magnitude larger and exhibit a strong dependence on hadron $p_T$, which likely is due to the larger effect of multiparton interactions.
On behalf of collaboration: PHENIX

Primary author

Dr Darren McGlinchey (University of Colorado)

Presentation Materials