# Presentation: 708243

## Meson Production in d  Au Collisions at  √s = 200 GeV

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Outline

**Physics motivation**
**PHENIX experiment**
**Particle identification**
**Data analysis**
****** ****meson reconstruction**
** ****Corrections    **
**Results ( ************ K****+****K****-**** and ************ e****+****e****-****)**
**Summary and outlook**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Physics motivation

_****__** **__**mesons**_
**Chiral symmetry restoration and medium effects**
**     ****- mass shift, width broadening**
**     ****- branching ratios in K****+****K****-**** and e****+****e****-**** decay channel**
**     ******** ****Simultaneous measurement of ************ K****+****K****-  ****and   ************ e****+****e****-**
**Strangeness production**
**    ****- ******** meson yield**
**Particle production mechanism**
**    ****- R****cp****, elliptic flow**
_**Au – Au & d – Au collisions**_
**Distinguish between hot and cold partonic matter**
**Evolution of medium properties with density and temperature**
**Probing nuclear effects**
**        **

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## PHENIX Setup

**Minimum-bias**
**|z****Vertex****| < 30 cm**
**N****evt**** = 54 M**** **
**        **

**Tracking :**** DC – PC1       – PC3**
**    ****Momentum **

_**PHENIX Setup**_

**Collision vertex and centrality:**
-  **Beam-beam Counter**

_****____ __**e**__**+**__**e**__**-**_

-  **Electron identification: RICH + EMC**
**  ****|********| < 0.35, ********= 90****o****, both arms **

_****__****__****__****__****_
**Kaon identification: **** **
**TOF: |********| < 0.35, ******** = 45****o**** **
**PbSc (East):  |********| < 0.35, ******** = 45****o**
**PbSc (West): |********| < 0.35, |********| = 90****o**

**K****-**

**K****+**

**K****+****K****-**

**K****+****K****-**

**K****+     ****K****-**

********** ****e****+****e****-**
**ERT_Electron trigger**
**|z****vertex****| < 30 cm**
**N****evt**** (ERT) = 31M**
****** ****1.9 G Minimum bias**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Kaon identification

_**Kaon identification**_

**Time  of flight (TOF):**
**0.3 < p (GeV/c) < 2**
******t**** = 130 ps**

**PbSc East and West:**
**0.3 < p(GeV/c) < 1.0**
******t**** ~ 450 ps**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Electron identification

**Electron PID cuts**
**NRICH PMT ******** 2**
**0.5<E/p<1.5 **
**E - from EMC**
**p  from tracking**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Data analysis and corrections

**Same event K****+****K****-**** and e****+****e****-**** invariant mass distributions (R).**
**Combinatorial background (CB)**
**     ******** ****Event mixing within same centrality and Z****vertex**
**        ******** ****Normalization to 2****√N****++****N****—**
**Signal = R - CB**
**Acceptance correction:**
**     ******** ****PHENIX Single particle Monte-Carlo simulation**
**         ****- ****Event generation + Detector hit + Detector response + offline analysis**
**           **
**Other experimental quality control correction:**
**     ******** ****Run (time) dependent corrections**
**      **
**      **

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Invariant mass distributions

- _Invariant mass distributions_

- Mixed
- Background

**Counts per 10 MeV/c****2**

- e+e- invariant mass (GeV/c2)

********** ****K****+****K****-**** @ d – Au, ****√****s****NN**** = 200 GeV**
**K****+**** and K****-**** are selected from TOF**

********** ****e****+****e****-**** @ d – Au, ****√****s = 200 GeV**

**S ~ 120**
**S/B = 1/4**

****** ****= 4.409 ****± 0.711 MeV/c****2**

**Counts per 1 MeV/c****2**** bin**

- Hot Quarks 2004, Taos Valley

##  meson transverse mass spectra (I)

**m****T****(GeV/c****2****)**

******e+e-**

**1/2********m****T ****dN/dm****T****dy**** ****(GeV/c****2****)****-2**

**PHENIX Preliminary**

**PHENIX Preliminary**

**Fitted with exponential function in m****T**

**dN/dy=0.056********0.015(stat) ********50%(syst)**
**T=326 ********94(stat) ********  53%(syst) MeV**

**PHENIX Preliminary**

**PHENIX Preliminary**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

##   meson transverse mass spectra (II)

_**SPS  result**_

_**Central Pb-Pb 158 A GeV**_
** ********49:**
** ************  ****K****+****K****-****  T = 305 MeV     **
** ****dN/dy ~ 2.35 **

**NA50: **
**********************   ****T = 227 MeV         **
**No specific quote of dN/dy**
**Integrating the m****T**** spectrum gives**
** ****dN/dy ~ 13**

**D. Rohrich et al, J Phys. G 27 (2001) 355**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Minimum-bias mT distribution of 

- 1/2mT dN/dmTdy (GeV/c2)-2

_**Minimum-bias m**__**T**__** distribution of **__****_

- MT(GeV/c2)

**Overall fit**
**dN/dy~ 0.0485**
**T~408**
******2****/DOF=6.7/7**

**dN/dy**

**T**

** ******** ****yields in d-Au collisions  in K****+****K****-**** **
**and e+e- channels are consistent with**
**each other**

**K****+****K****-**

**K****+****K****-**

**e****+****e****-**

**e****+****e****-**

********** ****K****+****K****-**

**********e****+****e****-**

**PHENIX Preliminary**

**PHENIX Preliminary**

**PHENIX Preliminary**

- Hot Quarks 2004, Taos Valley

## Comparison between  yields in d-Au and Au-Au collisions( K+K- )

_**Comparison between **__****__** yields in d-Au and Au-Au collisions**__**(**__****__****__** K**__**+**__**K**__**-**__** )**_

** ****yield increases  from d-Au to Au-Au system**

**Inverse slope remains **
**constant in Au-Au and **
**d-Au  collisions.**

**(Preliminary)**

**(Preliminary)**

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Invariant mass spectra from TOF and PbSc analysis

-   **Factor of ~4 more statistics  is now available by including**
**      ****the PbSc detectors in east and west arm.**
**  ****Scope of centrality dependence studies.**

_**Invariant mass spectra from TOF and PbSc analysis**_

**        **

**Full east arm ( TOF + PbSc)**

**West arm (PbSc)**

_**Work in progress**_

_**Work in progress**_

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Summary

**First simultaneous measurement of ************ K****+****K****-**** and ************ e****+****e****-**** in ****d-Au**** collisions at RHIC.   **
**     **_****__****__** **__**K**__**+**__**K**__**- **__** **_

**dN/dy=0.056********.015(stat) ********50%(syst)**
**T=326 ********94(stat) ********53%(syst) MeV**

_****__****__** **__**e**__**+**__**e**__**-**_

****** ****Consistent with each other within errors.**

_** **_**     ******** ****yield jumps from d-Au minimum-bias to Au-Au peripheral **
**      ****collisions. Then  it increases slowly upto Au-Au mid-central,**
**      ****finally saturates.**_** **_

**(PHENIX Preliminary**_**)**_

**(PHENIX Preliminary**_**)**_

- Hot Quarks 2004, Taos Valley

**Notes:**

Show also NA50 low-mass spectrum?

## Outlook

**Extended ************ K****+****K****-**** measurement in d-Au collisions with kaons identified with PbSc modules.**
**     ********  ****Total yield increases by almost a factor of 4.**
**     ********  ****Better understanding of the systematics is possible.**
**     ********  ****Centrality dependence of******** yield **
**     ********  ****Particle ratio**
**     ********  ****R****cp**** measurements.**

- Hot Quarks 2004, Taos Valley