# Presentation: 325738

## Systematic measurementsof light vector mesons in RHIC-PHENIX

- Yoshihide Nakamiya
- Hiroshima University, Japan
- for the PHENIX collaboration
- Quark Matter 2008, Jaipur, India

- ~ Contents ~
-     Topics in this talk
-     PHENIX experiment
-     Results
-     Summary

## Topics in this talk

-                - as a probe of the chiral phase transition
-                - in the low pT region

- Question 1 : Have we observed changes in line shape and/or yield?

- _Topics in this talk_

- _ __Mass Line Shape_
- Possible modification of line shape of the invariant mass distribution for **** is expected to be observed.
-     Effects are small and can’t be detected with current statistics and
-        signal to background ratio.

- _Yield difference between ____e__+__e__-__ and ____ K__+__K__-_
- Branching ratio between e+e- and K+K- may be sensitive to mass modification, since Mphi is approximately 2 ****** **MK.
- Compare yields of e+e- and  K+K-

## Topics in this talk (Cont’d)

-                - as a probe of medium effects
-                - at relatively high pT

- Question 1 : Does the particle yield suppression depend on mass or
-                      on quark number ?
-                       Nuclear modification factor RAA of the  meson
-                          is compared to proton results.
- Question 2 : Does RAA of mesons have a mass or flavor dependence?
-                       RAA of several mesons are compared to each other.
-                           (, , ,, ...)

- <Baseline> Results of p+p and d+Au are also shown.

- _Topics in this talk (Cont’d)_

- pT/mT spectra of  and  in several decay channels
- Nuclear modification factors (RAA and RdA) as functions of pT

- Systematic measurements give information about properties of the medium:

- We are trying to answer the following questions:

## Electron, hadron and photon in PHENIX

- _PHENIX acceptance_
-     -0.35 < η < 0.35
-     2 x 90°in azimuthal angle for two arms
-  _Event selection_
-     BBC
- _Electron ID _
-     RICH
-     EMCal

- _photon ID _
-     EMCal

- _Hadron ID_
-     TOF
-     EMCal-TOF

****** ****e****+****e****-**

****** ****K****+****K****-**

****** ********+********-************, **************

## Results for p+p and d+Au as baseline measurement

## d+Au

- _Extended ____K__+__K__-__ analysis_

-  K+K- measurements have been extended to both higher and lower pT using new methods, i.e. no kaon ID and single kaon ID methods.
- The three independent kaon analyses are consistent with each other.

**0-20%**

- 

- p+p

**M.B.**

- _Consistency between ____K__+__K__-__ and ____e__+__e__-_

**In p+p, spectra of e****+****e****-**** and K****+****K****-**** show reasonable agreement!**

## p+p

- ___Measurements of ____ in wide p__T__ range _

- Spectra show good agreement among several decay channels.

- pT spectra of are measured  for several decay modes in d+Au and p+p.

- d+Au

- 

## RdA of  and  mesons in 200 GeV

- RdA does not show suppression in central arm.
-   and  results are consistent with 0 and .

- As a baseline check, RdA is calculated for  and  and compared to other mesons.

- RdA 

- RdA 

**0-20%**

**M.B.**

**0-20%**

**M.B.**

## ,  ratios in p+p and d+Au 200 GeV  

-   and  ratio have little or no pT dependence at pT >2.0 GeV/c.

- 

- 

******/********0**** in** ***p+p   *****Run5 @ √s =     200 GeV = 0.81 ± 0.02(stat) ± 0.07(syst)**
******/********0**** in** ***d*****+Au***** *****Run3 @ √s****NN**** = 200 GeV = 0.94 ± 0.08(stat) ± 0.12(syst)**

- dAu

- pp

- dAu

- pp

- pp

## Topic 1 

- Chiral symmetry restoration

## Yield comparison between e+e- and  K+K- 

- _Yield comparison between ____e__+__e__-__ and ____ K__+__K__-__ _

- Question 1’: Have we observed changes of **yield** between e+e- and K+K- ?

- Have we observed changes of **spectra** between e+e- and K+K- ?

- Comparison of integrated yield is not enough, because
- mass modification effects depend  on the pT region.
- Low pT mesons tend to decay inside the hot/dense matter

- Now, we should ask

- In addition,
- To determine the integrated yield, an extrapolation to lower pT is needed.
- There is a large uncertainty in the calculation.

****

- Thus, pT-dependent information is essential for comparison.

- Low pT

****

- High pT

## Au+Au

- Errors are too large to make any clear statement about the comparison of spectra for e+e- and 

**40-92%**

**20-40% **

- _Spectra comparison between ____e__+__e__-__ and ____ K__+__K__-__ _

**M.B.**

## Topic 2 

- Nuclear modification factors

## K+K- in Au+Au is also extended to higher mT

- ___K__+__K__-__ in Au+Au is also extended to higher m__T_

-  K+K- measurement has been extended to higher mT using no kaon ID method.
- mT region is extended   to ~ 5 GeV.

- The two independent hadron decay analyses are consistent with each other in Au+Au.

## Is RAA suppression carried by mass or quark number?

**R****AA**** of******** meson (m********=1019 MeV/c****2****)**

**R****AA**** of proton (m****p****=938 MeV/c****2****)**

**Comparison between ******** and p:**

-      60-93%

- _Is R__AA__ suppression carried by mass or quark number?_

- RAA of  in central collisions is lower than in peripheral at high pT.
- RAA of protons is nearly independent of centrality.

- Difference of RAA between   and proton suggests that energy loss occurs at the partonic level.

**Question 1 : Is particle yield suppression carried by mass or quark number ?**** **

****** ****R****AA**** shows a different trend as compared to the proton.**

## mesons in Au+Au

- ___mesons in Au+Au_

-  Measurement of  mesons up to 10 GeV/c is made.

- Background estimate is improved in ωπ0γ analysis

- Background and shape are carefully estimated.

- pT spectra of  are measured for several centralities and at high pT.

**0-20%**

**20-60%**

**60-92%**

**M.B.**

**Details are in M.Ouchida’s **
**poster**

## Mass dependence of RAA between mesons

- _Mass dependence of R__AA__ between mesons_

-  meson has a different RAA for pT < 5 GeV/*c*.

**Question 2 : Does R****AA**** of mesons have a mass or a flavor dependence?**

## Summary

-                - as a probe of chiral phase transition
-                - in low pT region

- Question 1 : Have we observed changes of line shape, yield, and/or spectra?
- Answer 1 : We are still trying to quantify the difference.
- 	    Improvement of statistics and signal to background ratio
-                   in the next run will improve existing measurements.

- <Topic 2 > Particle yield suppression of light vector mesons in medium
-                - as a probe of medium effect
-                - at relatively high pT

- Question 1 : Is particle yield suppression carried by mass or quark number ?
- Answer 1 : Difference between RAA of  meson vs proton suggests that
-                    energy loss occurs at the partonic level .
- Question 2 : Does RAA of mesons have a mass or flavor dependence ?
- Answer 2 :  meson has a different RAA compared to other mesons 

- _Summary_

## Thank you for inviting me to Quark Matter 2008 !

*Thank you for inviting me to Quark Matter 2008 !*
*I’d like to say thanks to all participants and collaborators*

## Back up

## Yield and temperature for φ mesons  

-  information is not enough to determine the difference between
-  e+e- and K+K-.
- Need a careful check of mT spectra.

- _Yield and temperature for φ mesons  _

## The invariant mass spectra for φ mesons

_******__*** ***__***e***__***+***__***e***__***-***__** p+p**__**  **_

_******__*** ***__***e***__***+***__***e***__***-***__** d+Au**_

_******__***e***__***+***__***e***__***-***__** Au+Au**_

- φ

- φ

_******__***K***__***+***__***K***__***-***__** **__**(double PID) **__**d+Au**_

_******__*** ***__***K***__***+***__***K***__***-***__** **__**(double PID) **__**Au+Au**_

## The invariant mass spectra for φ mesons

_**The invariant mass spectra for φ mesons**_

**************************no PID) AuAU**

**************************single PID) pp**

**********************no PID) pp**

**********************no PID) dAu**

## The invariant mass spectra for ω mesons

- _The invariant mass spectra for ω mesons_

_******__*** ***__***e***__***+***__***e***__***-***__** p+p  **_

_******__***e***__***+***__***e***__***-***__** d+Au  **_

_******__***e***__***+***__***e***__***-***__** Au+Au **_

- ω

- ω

_******__******__******__******__******__******__** **__**p+p  **_

_******__***0***__******__***  ***__**p+p  **_

_******__***0***__******__**Au+Au  **_