Correcting Correlation Function Measurements

Abstract

Correlation functions measured as a function of $\Delta \eta ,\Delta \varphi$ have emerged as a powerful tool to study the dynamics of particle production in nuclear collisions at high energy. They are however subject, like any other observables, to instrumental effects which must be properly accounted for to extract meaningful physics results. We compare the merits of several techniques used towards measurement of these correlation functions in nuclear collisions. We discuss and distinguish the effects of finite acceptance, and detection efficiency that may vary with collision parameters such as the position of the event in the detector and the instantaneous luminosity of the beam. We focus in particular on instrumental effects which break the factorization of the particle pair detection efficiency, and describe a technique to recover the robustness of correlation observables. We finally introduce a multi-dimensional weight method to correct for efficiencies that vary simultaneously with particle pseudo rapidity, azimuthal angle, transverse momentum, and the collision vertex position. The method can be generalized to account for any number of "event variables" that may break the factorability of the pair efficiency.

19 pages, 12 figures, Corrected various tempos. Replotted 2D figures to reduce their size for faster upload

References in corpus (4)

• Observation of long-range near-side angular correlations in proton-lead collisions at the LHC
• K/pi Fluctuations at Relativistic Energies
• Delta- phi Delta- eta Correlations in Central Au+Au Collisions at sqrt{s_{NN}} = 200 Gev
• Momentum conservation and correlation analyses in heavy-ion collisions at ultrarelativistic energies

Cited by in corpus (16)

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• Flow dominance and factorization of transverse momentum correlations in Pb-Pb collisions at the LHC
• General balance functions of identified charged hadron pairs of $(\pi ,\mathrm{K},\mathrm{p})$ in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV
• Evolution of the longitudinal and azimuthal structure of the near-side jet peak in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV
• Identity Method Revisited
• Beam-energy dependence of identified two-particle angular correlations in Au+Au collisions at RHIC
• Balance functions of (un)identified hadrons in Pb--Pb, p--Pb, and pp collisions at the LHC
• Effect of centrality bin width corrections on two-particle number and transverse momentum differential correlation functions
• Correction methods for finite-acceptance effects in two-particle correlation analyses
• Differential Correlation Measurements with the Identity Method
• Two-particle transverse momentum correlations in pp and p-Pb collisions at energies available at the CERN Large Hadron Collider
• Balance functions of charged hadron pairs $(\pi ,K,p)\otimes (\pi ,K,p)$ in Pb--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$2.76 TeV
• Method for High Accuracy Multiplicity Correlation Measurements