1. Xiaochun He Georgia State University For the PHENIX collaboration
f Meson Measurements at Forward/Backward Rapidity at RHIC with PHENIX Detector
Xiaochun He
Georgia State University
For the PHENIX collaboration
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

2. X. He, WPCF2017, Amsterdam, Netherlands
A few things about f
f is the lightest bound state of strange quarks (ss) with hidden strangeness (m = GeV). It decays into K+K- with a branching ratio of 49.2%, and into the dilepton pairs e+e- (B.R. 2.97x10-4) and m+m- (B.R. 2.86x10-4). Its lifetime is about 45 fm/c.
Unlike u and d quarks, s quark is not present as valence quark in the initial state. f production is suppressed in elementary collisions because of the OZI rule. However, in an environment with many s quarks, f can be produced readily through coalescence, bypassing the OZI rule.
In the early stage of high-energy collisions, strangeness is produced in flavor creation (ggss, qq->ss) and flavor excitation (gsgs, qsqs). Strangeness is also created during the subsequent partonic evolution via gluon splittings (gss). These processes tend to dominate the production of high pT strange hadrons.
At low pT, nonperturbative processes dominate the production of strange hadrons. The detailed production mechanism is still an open issue.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

3. Why Is This Work Interesting?
The forefront effort in high energy nuclear physics community over the past three decades is to create and characterize the properties of the quark-gluon plasma in relativistic heavy ion collisions. Extensive results have been produced both from the RHIC and the LHC experiments.
It is well known that the medium created in heavy ion collisions is HOT/DENSE and it FLOWS collectively at partonic (quarks and gluons) level.
There are great successes of probing the medium properties with heavy quarks (charm and beauty) and jets, together with theoretical studies based on perturbative quantum chromodynamics (QCD).
However, huge uncertainties still exist in understanding the soft particle production given the limited theoretical guidance (i.e. non-perturbative QCD regime). More data is needed in order to constrain phenominological models.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

4. It has been proposed in the last century (1982)
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

5. A Complementary QGP Probe
φ meson is an excellent probe for studying QGP (in Au+Au collisions) because it is sensitive to several aspects of the collision, including modifications of strangeness production in bulk matter. Owing to its small inelastic cross section for interacting with nonstrange hadrons, the φ meson is less affected by late hadronic rescattering and should reflect the initial evolution of the system.
The lepton decay channel is of particular interest because of the absence of strong interactions between muons and the surrounding hot hadronic matter.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

6. X. He, WPCF2017, Amsterdam, Netherlands
In this talk, I will start with a brief summary of f measurements in central rapidity, which is then followed with f results (in dimuon decay channel) in the forward and backward rapidities in p+p, d+Au, Cu+Au collisions in the PHENIX experiment at RHIC.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

7. X. He, WPCF2017, Amsterdam, Netherlands
Large rapidity coverage: 1.2<|y|<2.2 and |y|<0.35
PHENIX recorded p+p, p+Au, p+Al, d+Au, He+Au, Cu+Au and Au+Au sNN = 200 GeV and p+p sNN = 510 GeV.
PHENIX Detector
Central Arms:
U,J/y, y’  e+e-
D  X+e
,,𝜙  e+e- ,K+K-
𝑥~5× 10 −3
Shadowing region
Muon Arms:
U,J/y  +-
D  X+
,,𝜙  +-
p, d, Cu, Au Au
𝑥~8× 10 −2
Anti-shadowing region e+ e- m+ m-
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

8. X. He, WPCF2017, Amsterdam, Netherlands
(from Mate’s talk on Monday)
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

9. Nuclear Modification Factor – RAA’
or other final state particles, like f, p
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

10. Nuclear Modification Factors in the Most Central Au+Au Collision
QCD dynamics is very hard to study !!!
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

11. X. He, WPCF2017, Amsterdam, Netherlands
f results in central rapidity
The φ meson exhibits a different suppression pattern compared to lighter mesons (π0 and η) and baryons (protons and antiprotons) in heavy ion collisions. For all centralities, the φ meson is less suppressed than π0 and η in the intermediate pT range (2–5 GeV/c), whereas, at higher pT , φ, π0, and η show similar suppression values.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

12. How about f production in forward and backward rapidities?
Results should be very important to constraining the theoretical model predictions.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

13. f Meson Production in Forward/Backward Rapidity in p+p at 200 GeV
Phys. Rev. D 90, (2014)
Very important for validating the phenomenological models for strangeness production.
Provide baseline measurement for studying nuclear modification of f production in d+Au, p+Au,p+Al, Cu+Cu, Cu+Au and Au+Au collisions at RHIC.
The study of f meson production in p+p collisions is an important tool to study QCD, providing data to tune phenomenological soft QCD models, to compare to hard perturbative QCD calculations and to gain insight into new phenomena, like long-range angular correlations. The results in p+p collision would provide a baseline measurement for studying strangeness production in heavy ion collision.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

14. Nuclear Modification in d+Au
arXiv:
Phys. Rev. C 92, (2015)
The RdAu enhancement (suppression) in the Au-going (d-going) direction is consistent with what is observed by the ALICE collaboration at sNN= 5.02 TeV in p+Pb collisions
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

15. f Meson vs Open & Closed Heavy Flavor
Phys. Rev. C 92, (2015)
phi lifetime is 1.55 x 10^{-22} sec and J/psi mean lifetime is 7.2 x 10^{-21} sec. The hadronic decay mode of J/psi and phi are strongly suppressed because of the OZI rule. This effect strongly increases the lifetime of the particle and thereby gives them very narrow decay width.
Nuclear modification to 𝜙 production as a function of rapidity has a similar trend as the observed in heavy flavor decay leptons. They are less suppressed in comparison with J/y in backward and central rapidity regions.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

16. Nuclear Modification in Cu+Au
Phys. Rev. C 93, (2016)
𝜙 meson production is enhanced over all centralities in the Au-going direction, while a suppression is observed for the most central collisions in the Cu-going direction
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

17. X. He, WPCF2017, Amsterdam, Netherlands
f Meson vs J/y in Cu+Au
Integrated over all centralities, 𝜙 nuclear modification in Cu+Au is consistent with 𝜙 in d+Au collision.
However, J/ψ is suppressed in Cu+Au both in the Cu-going and Au-going directions.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

18. Energy Dependent f Production in p+p Collisions
PHENIX is about to release a new publication about energy-dependent f production in forward/backward rapidities by combining the results published by ALICE at LHC. Extensive comparisons with Monte Carlo event generators available in the market have been done!
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

19. X. He, WPCF2017, Amsterdam, Netherlands
Summary and Outlook
PHENIX has measured f production in p+p, d+Au, Cu+Cu, Cu+Au and Au+Au collisions with a wide rapidity coverage. This talk summarizes the recent results of f production in forward and backward rapidities measured with the PHENIX Muon Arms.
The particle-dependent nuclear modifications in all colliding systems will provide stringent tests of theoretical model predictions.
The data analysis of f production in p+Al, He+Au, and Au+Au in forward and backward rapidities is ongoing and is hoped to be published soon.
Thank you all!
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

20. X. He, WPCF2017, Amsterdam, Netherlands
Backups
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

21. X. He, WPCF2017, Amsterdam, Netherlands
Use the identified particle spectra to extract the thermal medium properties
“Specifically, in-medium modification of the vector spectral function can be deduced from the thermal radiation off the expanding QCD fireball” – Ralf Rapp
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

22. In a big picture – Big Bang Cosmology
Medium energy density approximation by including only those particles with mass less than the medium temperature:
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

23. f Flows in Au+Au Collisions at RHIC
Results at RHIC indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy.
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands

24. Nuclear Modification Factor (d+Au)
6/15/17
X. He, WPCF2017, Amsterdam, Netherlands