# Presentation: 183793

## -meson v2 studies in Cu+Cu collisions at 200GeV

- Xinghua Shi (LBNL/SINAP)
- Jinhui Chen (SINAP)
- Bedanga Mohanty (VECC)

## Cut used and data-sets from TPC

**Track cut in the analysis**
** ****Kaon: nFitPts >= ****15**** **
** ****nFitPts/nPossmax >= ****0.52 **
** ****0.1**** < pT < ****2.0**** GeV/c **
** ****|eta| < ****1.0**
** ****dipangle >= ****0.04**** **
** ****Phi candidates: |y| < ****1.0**
**PID cut**
** ****Kaon: | nSigma | < ****2.00**

**Event cut in Cu+Cu collisions at 200GeV**
**Trigger Id : ****66007                                                   **
**Trigger Setup : ****cuProductionMinBias**
**                         ****cuProductionHighTower**
**Production : ****P06ib**
**Number of events after all Cuts :**** **
**cuProductionMinBias ~**** ****15.1M**** ****(0-60%)**
**cuProductionHighTower ~**** ****5.4M**** ****(0-60%)**
**Centrality bins **
**  ****10% : ****140         ****20% : ****103        ****30% : ****74**
**   ****40% : ****53          ****50% : ****37          ****60% : ****25**
**Vertex cuts : |Vz| < ****30 ****cm**

**1**

##  Reaction-plane from FTPC

**Event cut**
** ****Trigger Id : ****66007                                                   **
** ****TriggerSetup :**
** ****cuProductionMinBias**
** ****Production : ****P06ib**
** ****Vertex cuts : |Vz| < ****30 ****cm  **
**PID cut**
** ****Kaon: | nSigma | < ****2.00**
**Track cut**
** ****5**** =< nFitPts < ****11**** **
** ****nFitPts/nPossmax >= ****0.52 **
** ****0.1**** < pT < ****2.0**** GeV/c **
** ****2.5****<|eta| < ****4.0**
** ****dipangle >= ****0.04**** **
** ****Phi candidates: |y| < ****1.0**

**              **

** ****2**

**Why we use FTPC reactionplane?**
**1.The non-flow correlation and auto correlation effects are smaller from FTPC reactionplane**
**2.Comparing the v2 results from FTPC reactionplane with TPC reactionplane can help us understand the non-flow effects.**
**3.To check the v2 results in low pt. **

## Weighting Corrections

-     Due to detector acceptance effects, the phi angle distribution isn't isotropic.
-    To correct those effects, more weight is given to the particles that are detected at the place where the least particle are detected. We are compensating for the “blind spots” of the FTPC.

**3**

## Shifting Corrections

**2.Shifting Corrections:**
- Even with the weighting method, the event plane distribution we obtain isn't isotropic. We can, however, flatten that distribution by shifting it.

-     (n=1,2,3,4...... )

**4**

*           **Reference:    J.Barrette et al.  Nucl-ex/9707002*

**Reaction-plane from West and East FTPC**

**Before weight corrections**
**Before shifting**
**After shifting**
**Fit with a line**

**Before weight corrections**
**Before shifting**
**After shifting**
**Fit with a line**

** ****5**

**Before weight corrections**
**Before shifting**
**After shifting**
**Fit with a line**

**(a)**

**(b)**

**(c)**

**(a)West:cos****△****Ψ****:0.342405 **
**cos****△****Ψ**** error:0.0012**
**(b)East:cos****△****Ψ**** ****:0.230437**
**cos****△****Ψ**** ****error:0.0027**
**(c)Full:cos ****△****Ψ**** ****:0.292285   **
**cos****△****Ψ**** error:0.0015**

## Resolution

**If the whole event is divided into two sub-events a and b with equal multiplicity to calculate the reaction plane resolution.The event plane resolution is calculated by:**

**6**

## Analysis in Cu+Cu at 200GeV 0-60%(FTPC_reaction plane)

**7**

## -meson v2 in Cu+Cu at 200GeV

**8**

**1.At low pt, ********-****meson v2 might be negative**** ****value in Cu+Cu collisions.**
**2. The elliptic flow is a function of pt in Cu+Cu collisions.**

## Next steps

-      1)To combine reactionplane from W-FTPC
-     with E-FTPC after they are both flattened.   Then do  meson v2.
-    2) To analysis both M.B. Cu+Cu and HT
-     Cu+Cu data from FTPC reactionplane.
- 3) Try to split the centrality to 0-10% and
-     10-60%.** **

**9**