Jet Yields From Dihadron Correlations in PbPb Collisions at 2.76 TeV

Measurements made using the CMS detector at the LHC of dihadron correlations of charged particles produced in PbPb collisions at nucleon-nucleon center-of-mass energy of 2.76 TeV are presented. The results are studied over a broad range of relative pseudorapity (∆η) and the full relative azimuthal angle (∆φ). The observed two-dimensional correlation structure in ∆η and ∆φ is characterized by a narrow peak at (∆η, ∆φ) ≈ (0,0) from jet-like correlations, which sits upon a long-range “ridge” structure that persists out to at least |∆η| = 4, and is assumed to be due to hydrodynamic flow. On the “away” side (|∆φ| ≈ π), the jet contribution is spread out quite evenly in ∆η and thus not easily distinguishable from the flow signal. The jet yields of both the near side and the away side are measured. The near-side jet yield is measured by directly subtracting off the ridge contribution. On the away side, where it is not so simple to separate the two, a new method for distinguishing the jet yield from the flow signal is presented along with its results.