Speaker
Description
Jets and their modifications due to partonic energy loss provide a powerful tool to study the properties of the QGP created in ultrarelativistic heavy ion collisions. For correlation studies of jet energy loss, two complementary trigger object choices offer access to the initial hard parton’s energy: On the one hand, direct-photon–tagged jets are a self-generated tomographic medium probe, unaffected by the medium and hence with an unbiased in-medium path length. They are also expected to exhibit a different flavor-dependence of energy loss, since high-$p_T$ direct photons are primarily produced with a quark recoil. On the other hand, reconstructed jets offer the promise of path length control or Jet Geometry Engineering through cut parameters. Previously, $A_J$ measurements at STAR observed significant imbalance for anti-$k_T$ di-jets with a resolution parameter R = 0.4 and a “hard-core” selection using only constituents with $p_T$ above 2.0 GeV/c and a neutral high tower with $E_T$ > 5.5 GeV. When soft constituents are included, this imbalance is found restored to the balance of the p+p reference inside the original jet cone, indicative of milder modification due to more surface-biased production.
We present a study of correlated hadrons and semi-inclusive recoil jets coincident with direct photons and neutral pions with 9 < $E_T^{trig}$ < 20 GeV, as well
as with respect to to the dijet selection from the above $A_J$ measurement. A
comparison between the two measurements, and a comparison to similar measurements at RHIC and the LHC establishes new systematic input into the flavor- and path-length dependence of light flavor energy loss in the QGP.
| Preferred Track | Jets and High pT Hadrons |
|---|---|
| Collaboration | STAR |
