An iterative method to estimate the combinatorial background

Abstract

The reconstruction of broad resonances is important for understanding the dynamics of heavy ion collisions. However, large combinatorial background makes this objective very challenging. In this work an innovative iterative method which identifies signal and background contributions without input models for normalization constants is presented. This technique is successfully validated on a simulated thermal cocktail of resonances. This demonstrates that the iterative procedure is a powerful tool to reconstruct multi-differentially inclusive resonant signals in high multiplicity events as produced in heavy ion collisions.PACS. 29. Experimental methods and instrumentation for elementary-particle and nuclear physics -29.85.-c Computer data analysis

Correlated pion-proton pair emission off hot and dense QCD matter

“…The distributions of pairs are binned as follows: 150 MeV/c wide bins in p T from 0 to 1350 MeV/c and one additional 250 MeV/c wide bin up to 1600 MeV/c, 10 bins in laboratory rapidity from 0 to 1.8 with increasing bin size, 50 bins in pair invariant mass (M inv ) from the πp threshold to 1900 MeV/c 2 , 10 equal bins from -1 to 1 in cos θ, where θ is the angle of the pion in the rest frame of the pair with respect to the motion of the pair in the center-of-mass frame of the collision. The background is obtained using a procedure which splits iteratively the total measured sample in correlated and uncorrelated pion-proton pairs using the random track rotation technique described in details in [47]. The procedure accounts for the detector pair acceptance and efficiency and a correlation of tracks with respect to the orientation of the event plane.…”

“…One important challenge of such measurements in heavy systems as Au+Au is the large abundance of uncorrelated pions and protons which dominate the pair spectrum and has to be subtracted in order to access the true correlated signal. For such a purpose, an iterative technique, which improves the identification of the combinatorial background compared to the most commonly used mixed event-technique has been developed and applied in this work [47].…”