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arXiv · 0904.1733

ZYAM and $\bf v_2$: Underestimating jet yields from dihadron azimuth correlations

Thomas A. Trainor
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Abstract

Dihadron azimuth correlations can provide combinatoric access to jet structure in nuclear collisions. To isolate true jet yields a background must be subtracted, including a constant offset and a contribution from "elliptic flow" (azimuth quadrupole measured by $v^2_2$). The principle of "zero yield at minimum" (ZYAM) has been introduced to determine the constant offset. Independent measurements determine $v_2^2$. This analysis demonstrates that the ZYAM concept is invalid (offset typically overestimated) and $v_2^2$ is also overestimated by conventional measurements. Jet yields are thus substantially underestimated in more-central A-A collisions, and the "away-side" azimuth peak (back-to-back jet correlations) is strongly distorted, leading to incorrect inference of "Mach shocks."

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Thomas A. Trainor. 2009-04-12. ZYAM and $\bf v_2$: Underestimating jet yields from dihadron azimuth correlations. https://doi.org/10.1103/physrevc.81.014905

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