# Run14 Au+Au: jet-hadron correlations relative to the event plane - Paper Page

Title:
Jet-hadron correlations with respect to the event plane in \sNN = 200 GeV Au+Au collisions in STAR

Abstract:
We present the dependence of azimuthal angular correlations of charged tracks with the axis of a reconstructed jet relative to second order event plane for \AuAu collisions at \sNN = 200 GeV in STAR.  Partonic interactions are dependent upon the path-length traversed through the medium, so medium modifications to a jet should be path-length dependent.  Studying jets differentially to the event plane allows for a path-length dependent measurement of these medium modifications.  The event plane is the experimental estimate of the reaction plane defined as the plane formed by the impact parameter and the beam direction.  The reaction place fit (RPF) method is implemented to remove the flow modulated background.  Associated track yields and gaussian width calculations are performed in three angular bins of the jet axis relative to the event plane.   Results from the 20-50\% most central events for $15 < \ptJet < 20$ and $20 < \ptJet < 40$ \GeV are shown by the track yields in EP bins. Potential effects are further quantified by taking ratios of the track yields in EP bins.  No dependence on the results is seen within uncertainties for jets with transverse momentum ranging from 15 to 40 \GeV.   This finding is consistent with the observation from ALICE at \sNN = 2.76 TeV.

Conclusion:
The measurement of jet-hadron correlations relative to the event plane for the 20-50\% most central events for \AuAu collisions at \sNN = 200 GeV in STAR is reported.  Partonic interactions are directly related to the distance traversed in the medium, so the expectation is any modifications via the medium to the jet should be path-length dependent.  The angle of the jet measured with respect to the event plane is correlated on average with the jets' path-length through the medium.  We maximize this average path-length of the away-side jet by surface biasing the near-side trigger jet.  This work utilizes the RPF background subtraction method to remove the reaction plane dependent background while reducing uncertainties and assumptions associated with prior background subtraction techniques.  Associated yields, their ratios, and jet peak widths are extracted for each event plane orientation and compared.  With the current statistics, the associated yields and jet peak widths show no event plane dependence.  The ratios taken of the associated yields attempt to quantify the differences, but they do not deviate significantly from 1.0.  The lack of an event plane dependence therefore indicates that any dependence of these modifications on the average path-length is less than our experimental uncertainties.  The lack of event plane dependence was also seen in jet-hadron and h-h correlations by ~\cite{Nattrass:2016cln}, and jet-hadron correlations by ALICE Experiment ~\cite{Acharya_2020} at \sNN = 2.76 TeV energies.  This is also seen in a di-jet asymmetry measurement relative to the event plane as predicted by JEWEL ~\cite{Milhano:2015mng}.  In these calculations, they reported that not only energy loss fluctuations, but also hard fluctuations which did not arise from jet-medium interactions played a more important role than path-length dependence \cite{Milhano:2015mng}.

PA's:
Joel Mazer, Rutgers
Tanmay Pani, Rutgers
Sevil Salur, Rutgers

Target Journal:
PRC

GPC:
(to be determined)

Paper draft:
v2
v2.1_21-04-09

Analysis Note:
finishing porting new info in, will be posted soon

Analysis Code:
(to be posted on cvs (git?) soon)
github pages:
1) https://github.com/joelmazer/star-jetframework
2) https://github.com/joelmazer/Centrality

Presentation to JetCorr:
April 1, 2021

Presentation to PWGC: (to be scheduled) Friday - April 23rd, 2021

Public Presentations:
- Jet Workshop - June 27, 2018 - talk presentation:
"Jet-hadron correlations and the need for a precise background subtraction method"

- Hot Quarks, September 2018 - talk presentation:  "Jet-hadron correlations relative to the event plane at RHIC with STAR"

- 13th International Workshop on High-pt Physics in the RHIC/LHC era - March 2019 - talk presentation:  "Event plane dependence of jet quenching studied via azimuthal correlations and differential jet shape in Au+Au collisions at \sqrt{s_{NN}} GeV with the STAR detector at RHIC"

- 13th International Workshop on High-pt Physics in the RHIC/LHC era - March 2019 - proceedings: "Event plane dependence of jet quenching studied via azimuthal correlations and differential jet shape in Au+Au collisions at \sqrt{s_{NN}} GeV with the STAR detector at RHIC"

Preliminary Plots
- preliminary plots page

Figures:
1. Event plane resolution

2. Example: raw jet-had dphi correlation with signal+BG, BG and RPF background fit, for 15-20 GeV/c jets and 1.0-1.5 GeV/c associated hadrons

3. Example: background subtracted jet-had dphi correlation, for 15-20 GeV/c jets and 1.0-1.5 GeV/c associated hadrons

4. Associated yields for 15-20 GeV/c jets

5. Associated yields for 20-40 GeV/c jets

6. Jet peak widths for 15-20 GeV/c jets

7. Jet peak widths for 20-40 GeV/c jets

8. Associated yield ratios for 15-20 GeV/c jets

9. Associated yield ratios for 20-40 GeV/c jets

Groups: