Speaker
Description
Jet-medium interactions in heavy-ion collisions are expected to generate a characteristic hydrodynamic response consisting of a forward wake front and a backward diffusion wake. Direct observation of the depletion of soft hadrons behind the jet characteristic of the diffusion wake has proven difficult due to background and overlapping jet induced structures. Recent theory suggests that dijets with a finite pseudorapidity separation provide a clean handle: the diffusion wake of the recoiling jet is shifted in rapidity, allowing for the measurement of the corresponding depletion in soft hadrons via asymmetry in jet-hadron correlations [1]
.
We present a novel search for this signal in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions at STAR, compared against dijets from $\sqrt{s}=200$~GeV $p$+$p$ collisions, where QGP is not expected to form. Jets are reconstructed with the anti-$k_{T}$ algorithm and dijet events are grouped by rapidity gap between the leading and subleading jet axes. By comparing per-dijet associated jet-hadron correlations for large and small gap dijets, we construct a rapidity asymmetry observable using soft hadrons that suppresses contributions from the underlying event and radial flow. The distribution of associated hadrons $\Delta N_{AA}$, defined as
$\Delta N_{AA} = \int d\Delta\phi \left[\frac{dN_{AA}}{d\Delta\phi d\Delta\eta} - \frac{dN_{pp}}{d\Delta\phi d\Delta\eta} \right]$,
is constructed for dijet events with and without a finite rapidity gap. The difference is taken between $\Delta N_{AA}$ for dijets with a rapidity gap and dijets without a rapidity gap to arrive at the final observable. A track $p_{\rm{T}}$ range of $1.0$ GeV/$c < p_{\rm{T}}< 2.0$ GeV/$c$ is applied to suppress contribution to the signal from radial flow. We report preliminary results and assess sensitivity to diffusion wake driven depletion structures, providing new constraints on jet induced medium response at RHIC.
[1] Z.~Yang and X.-N.~Wang, Rapidity Asymmetry of Jet--Hadron Correlation as a Robust Signal of Diffusion Wake Induced by Dijets in High-Energy Heavy-Ion Collisions, Phys. Rev. Lett. 135, 072302 (2025).
| Is this an experimental talk? | Yes |
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| Is this on behalf of a collaboration? | Yes |
| Which collaboration? | STAR Collaboration |
| Are you willing to present as a poster if it is not selected for oral presentation? | Yes |