Speakers
Description
A path length asymmetry along impact parameter direction ($x$) exists for hard probes in heavy-ion collisions at finite rapidity, as the Quark Gluon Plasma (QGP) bulk is tilted in reaction plane, while the hard scattering profile is not~\cite{ref1}. Jet $v_1$ and $\langle p_x \rangle$ measurements provide access to path length dependent energy loss of partons in the QGP. Such a measurement has several advantages. Energy loss can be measured without measurements in p+p collisions. Event-by-event fluctuations in geometry and energy loss do not contribute to $v_1$ (and $\langle p_x \rangle$), unlike to the elliptic anisotropy, $v_2$. Non-flow contributions are also minimal as measurements use reaction plane determined from spectators.
In this talk we present the first measurement of jet $v_1$ and $\langle p_x \rangle$ in heavy-ion collisions using Au+Au and Ru+Ru, Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV by STAR. Centrality, jet $p_{\mathrm{T}}$ and radius dependence of the observables will be shown. We will also present an evaluation of the initial path length asymmetry utilizing models describing the measured pseudorapidity dependence of particle production in asymmetric collisions. The measurements open up a new avenue to study path length dependent energy loss of partons in QGP and its mass, flavor and fragmentation dependences.
| Category | Experiment |
|---|---|
| Collaboration | STAR |
