Speaker
Description
Studying its path-length dependence is crucial for understanding the mechanisms of parton energy loss in the Quark-Gluon Plasma (QGP) [1]. A path-length asymmetry along impact parameter direction ($x$) exists for hard probes in heavy-ion collisions at finite rapidity, as the QGP bulk is tilted in reaction plane, while the hard scattering profile is not [2]. Previous measurements of $v_1$ (= $\langle p_x/p_T \rangle$) of $D^0$-mesons have demonstrated sensitivity of hard produced partons to this path-length asymmetry [2,3]. Measurements of jet $v_1$ will provide access to path-length dependent energy loss of partons in the QGP. The jet $v_1$ measurements do not get contributions from event-by-event geometry fluctuations, unlike measurements relative to the second order event plane. Measurements therefore of in- and out-of-plane yield ratios of hard probes in events with different second-order eccentricities offer complementary information on this effect in the QGP.
In this talk we present the first measurement of inclusive charged jet and high-$p_T$ charged hadron $v_1$ in Au+Au and Ru+Ru, Zr+Zr (isobar) collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV by STAR. Jet $p_{\mathrm{T}}$ and radius dependence of jet $v_1$ will be shown. We will also present an evaluation of the initial path-length asymmetry from the tilted bulk, utilizing models describing the measured pseudorapidity dependence of particle production in asymmetric collisions and discuss future opportunities with event shape engineering (ESE) for the first order anisotropy. In addition, measurements of ratios of in-and out-of-plane yields of high momentum probes in events selected to have different second order eccentricities, using ESE, in Au + Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV will be shown.
[1] ALICE Collaboration Phys. Lett. B 851 138584 (2024); C. Beattie et al. Phys. Lett. B 836 137596 (2023)
[2] S. Chatterjee, P. Bozek, Phy. Rev. Lett 120, 192301 (2018); A. Adil, M. Gyulassy Phys. Rev. C 72, 034907 (2005)
[3] STAR Collaboration, Phys. Rev. Lett 123, 162301 (2019)
| Category | Experiment |
|---|---|
| Collaboration (if applicable) | STAR |
