Zero yield at minimum (ZYAM) method and v(2): Underestimating jet yields from dihadron azimuth correlations

Dihadron azimuth correlations can provide combinatoric access to jet structure in nuclear collisions. To isolate true jet yields a combinatoric 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. Separate measurements determine v(2)(2). This analysis suggests that the ZYAM offset is usually substantially overestimated, and v(2)(2) is overestimated by conventional analysis methods. Therefore, jet yields may be substantially underestimated in more-central A-A collisions, and the away-side azimuth peak (back-to-back jet correlations) may be distorted leading to questionable inferences of Mach shocks.