# Presentation: 693400

## The Azimuthal Anisotropy of Electrons from Heavy Flavor Decays in √sNN=200 GeV Au-Au Collisions at PHENIX

- Shingo Sakai for PHENIX Collaborations
- (Univ. of Tsukuba)

## OutLine

- Motivation
- Method of electron v2 measurement
-    from heavy flavor decay
- Results
- Compare with model
- B meson contribution
- Expected D meson v2
- Summary

- SQM2006 (Shingo Sakai)

- 2006/3/26

## Why heavy flavor v2 ?

- π,K,K0s,p,Λ, Ξ ;
-  ( light quark->u,d,s )
-   v2 scales approximately with
-   the number of valence quark of hadrons
-    -> indicate partonic level flow
-    for u,d,s
- if charm quark also flow
-   - partonic level thermalization
-   - high density @ the early stage of collision

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
The motivation of this measurement is two. One is heavy flavoe flow and the other is energy loss. The right figure shows the identified particle v2 scaled with number of quarks. These v2 are well scaled and that means the v2 already develop in partonic level. If charm quark flow it indicates that the partonic level thermalization and high density @ the early stage of collision.
The bottom figure show the Raa for the quarks. The model predict that the heavy flavor energy loss is small compared with light quark. V2 is thought that the reflect energy loss therefore if heavy flavor energy loss is smaller, smaller v2 might be expected compared with light quarks v2 @ high pT.

## Heavy flavor study @ PHENIX

-  Electron sources
-      charm decay
-             beauty decay
-         Dalitz decays
-             Di-electron decays
-             Photon conversions
-             Kaon decays
-             Thermal dileptons
-  Subtract photonic electrons following methods
- “Cocktail subtraction” – calculation of “photonic” electron background from all known sources
- “Converter subtraction”– extraction of “photonic” electron background by special run with additional converter
-  (brass, X = 1.7%)

- photonic

- non-photonic

- SQM2006 (Shingo Sakai)

- 2006/3/26

## Non-photonic electron v2 measurement

***converter method***
- _Measure inclusive electron v2 with/without converter_
- Then separate non-photonic & photonic e v2
-       Non-converter ;  Nnc = Nγ+Nnon-γ =>  (1+RNP)v2nc = v2**γ** + RNPv2**non-γ**
-       Converter  ; Nc = R *Nγ+Nnon-γ  =>  (R +RNP) v2c = R v2**γ** + RNPv2**non-γ**
-            R  -- ratio of electrons with & without converter
-            v2nc --- inclusive e v2 measured with non-converter run
-            v2c  --- inclusive e v2 measured with converter run
-             v2**γ** --- photonic e v2,
-             v2**non-γ** --- non photonic e v2
***cocktail method***
- Determined _photonic electron v2 with simulation_
- Then subtract it from _electron v2 measured with _
- _non-converter run_
-            v2**non-γ** =  {(1+RNP)v2nc - v2γ} }/RNP

- Run04: X=0.4%

- Run02: X=1.3%

- Non-pho./pho.

- (QM05 F. Kajihara)

- SQM2006 (Shingo Sakai)

- 2006/3/26

## Electron v2 measurement @ PHENIX 

-  Electron v2 is measured by R.P. method
-  R.P. --- determined with BBC
-  Tracking (pT,φ) --- DC + PC
-  electron ID --- RICH & EMCal

**dN/d(********-********) = N**** ****(1 + 2****v****2****obs****cos(2(********-********)))**

-  (E-p/p/sigma) distribution

- eID @ RICH

**B.G. **

- After subtract B.G.

- Fig : Energy (EMcal) & momentum matching
-         of electrons identified by RICH.
-         Clear electron signals around E-p/p = 0

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
Energy (EMcal) & momentum matching

## Inclusive electron v2 (in/out converter)

-  inclusive electron v2
-    in / out converter
-  clear difference between
-     converter in / out
-  converter in electron v2
-     include large photonic
-     component

- SQM2006 (Shingo Sakai)

- 2006/3/26

## Inclusive electron & photonic electron v2

- inclusive e v2
- (w.o. converter)

- photonic e v2

-  inclusive & photonic electron v2
-       pT < 1.0 GeV/c --- conv. method
-       pT > 1.0 GeV/c --- simulation
-  inclusive electron v2 is smaller
-     than photonic electron v2
-    => non-photonic electron v2
-    is smaller than photonic electron v2

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
Inclusive electron v2 

## Non-photonic electron v2

-  non-photonic electron v2
-     pT < 1.0 GeV/c --- conv. method
-     pT > 1.0 GeV/c --- cock. method
-  Indication for reduction of v2 at pT > 2 GeV/c ; Bottom contribution??
-  Compared with quark
- coalescence model prediction.
- with/without charm quark flow
- (Greco, Ko, Rapp: PLB 595 (2004) 202)
-  Below 2.0 GeV/c ;
- consistent with _charm quark _
- _flow_ model.
-  indicate charm quark flow

- 1

- 2

- 3

- 0

- SQM2006 (Shingo Sakai)

- 2006/3/26

## B meson contribution to non-γ.e. v2

- D & B v2
-   - assume D & B v2 same
-   - v2 ~ 0.6 pi v2

- D -> e

- B -> e

- pT

- v2

-  Model predict B -> e v2 reduce non-photonic electron v2 @ high pT
-  e v2 from B meson is smeared due to large mass difference

** ****based on quark coalescence model**
** ****c, b reso ; c,b get v2 by elastic scat. in QGP**

- Hendrik, Greco, Rapp
- nucl-th/0508055

**w.o. B meson (c flow)**

**w. B meson (c,b flow)**

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
 w. b meson
w.o. b meson

## D v2 estimate from non-γ e v2

- electron v2

- D meson v2

- Decay

-  Estimate D meson v2 with non-γe v2
-     (below 2.0 GeV/c)
-  Assuming several v2 shape for
-            D meson v2
-              Dv2(pT) = api * pi v2
-              Dv2(pT) = aK * kaon v2
-              Dv2(pT) = ap * proton v2
-  Calculate D -> e
-  chi-squared test with
-       “measured” non-photonic electron v2
-  find chi-squared minimum “a”
-      for pi, K, p (api, aK and ap)

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
Decay 

## Compare D v2 with other hadron v2

-  expected D meson v2 from non-photonic electron v2 (pT < 2.0 GeV/c)
-  smaller than pi v2
-  larger than Deuteron v2 (Mass D meson~ Mass Deuteron)

- π, deuteron v2 --- PHENIX preliminary

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
Π, deuteron v2 --- PHENIX preliminary

## Summary

- Non-photonic electron v2 from heavy flavor decays has been measured
- with RHIC-PHENIX
-  Compare with model calculations assuming charm flow or not
-  =>Out result consistent with charm flow model at low pT
- Compare with PYTHIA calculation.
- D meson v2 --- scaled pion v2
- =>Indicate D meson v2 is smaller than pion v2

-  Non-photonic electron v2 from heavy flavor decays
-      has been measured with RHIC-PHENIX
-  Compare with model calculations assuming
-       charm flow or not
-       Our result consistent with charm flow model below
-       2.0 GeV/c
-  B meson contribution might be reduce non-photonic e v2
-      @ high pT
-  Estimate D meson v2 from non-photonic electron v2
-     assuming D meson v2 shape as pion, Kaon, proton.

- SQM2006 (Shingo Sakai)

- 2006/3/26

- Backup slides

- SQM2006 (Shingo Sakai)

- 2006/3/26

## Azimuthal anisotropy

***Initial spatial anisotropy***

***Momentum space anisotropy***
***      ******of particle emission***

- A powerful probe of the initial state of
- the high energy heavy ion collision
-  Low pT* *
-  pressure gradient of
-     early stage of collision
-  High pT
-  parton energy loss in hot &
-           dense medium

-   dN/dφ ∝ N0(1+2**v****2**cos(2φ))

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
Spatial anisotropy
Thermal equilibrium
The azimuthal anisotropy of particle emission is sensitive to the early stages of system evolution
Probe of jet quenching 
Hydro model 
Measurement of identified particle v2 give up much more
Information of the collision dynamics

## Converter method

- Separate non-photonic & photonic e v2 by using
- Non-converter run & converter run
-           Non-converter ;  Nnc = Nγ+Nnon-γ
-           Converter  ; Nc = R *Nγ+Nnon-γ
-          (1+RNP)v2nc = v2**γ** + RNPv2**non-γ**
-          (R +RNP) v2c = R v2**γ** + RNPv2**non-γ**
-  v2**non-γ****(non-photonic) & **v2**γ****(photonic) ****is **
**“*****experimentally*****”   determined !**

-   R  --- ratio of electrons with & without converter (measured)
-   RNP --- non-photonic/photonic ratio (measured)
-   v2nc --- inclusive e v2 measured with non-converter run (measured)
-  v2c  --- inclusive e v2 measured with converter run (measured)

- SQM2006 (Shingo Sakai)

- 2006/3/26

## Cocktail method

- Then subtract it from electron v2 measured
-  with non-converter run
-            dNe/d = dNpho.e /d + dNnon-pho.e /d
-            v2**non-γ** =  {(1+RNP) v2 - v2γ} } / RNP

- measured

- RNP --- non-photonic/photonic ratio
-             experimentally determined
- v2 --- inclusive electron v2 (without converter)
- v2γ --- photonic electron v2
-             calculated from pi0 (pion) v2

- calculate

- measured

- SQM2006 (Shingo Sakai)

- 2006/3/26

**Notes:**
From F. Kajihara