shingo sakai for the phenix collaborations (univ. of tsukuba)
DESCRIPTION
The azimuthal anisotropy of electrons from heavy flavor decays in √S NN = 200 GeV Au-Au collisions by PHENIX. Shingo Sakai for the PHENIX collaborations (Univ. of Tsukuba). Why heavy flavor v 2 ?. (1)π,K,K 0 s ,p,Λ, Ξ,d ( light quark->u,d,s ) v 2 scales approximately with - PowerPoint PPT PresentationTRANSCRIPT
DNP/JPS 1
The azimuthal anisotropy of electrons from heavy flavor decays in √SNN = 200 GeV Au-Au collisions by PHENIX
Shingo Sakai for the PHENIX collaborations(Univ. of Tsukuba)
DNP/JPS 2
Why heavy flavor v2 ?
(1)π,K,K0s,p,Λ, Ξ,d ( light quark->u,d,s )
v2 scales approximately with
the number of valence quark of hadrons
-> indicate partonic level flow
if charm quark flow - partonic level thermalization - high density @ the early stage of collision
(2) Heavy flavor energy loss - v2@high pT reflects energy loss
- if heavy flavor energy loss is small, smaller v2 @ high pT might be expected compared with light quarks v2
M. Djordjevic, M. Gyulassy, R. Vogt, S. Wicks. nucl-th/0507019
DNP/JPS 3
Heavy flavor study @ PHENIX
Elecron 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
DNP/JPS 4
Electron v2 measurement @ PHENIX
e-
Electron v2 is measured by R.P. method
R.P. --- determined with BBCTracking (pT,φ) --- DC + PCelectron ID --- RICH & EMCal
dN/d(-) = N (1 + 2v2obscos(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
DNP/JPS 5
Non-photonic electron v2 measurementconverter methodSeparate non-photonic & photonic e v2 by usingNon-converter run & converter run
Non-converter ; Nnc = Nγ+Nnon-γ => (1+RNP)v2nc = v2γ + RNPv2non-γ Converter ; Nnc = R *Nγ+Nnon-γ => (R +RNP) v2c = R v2γ + RNPv2non-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 v2γ --- photonic e v2, v2non-γ --- non photonic e v2
cocktail methodDetermined photonic electron v2 with simulation Then subtract it from electron v2 measured with non-converter run
v2non-γ = {(1+RNP)v2 - v2γ} }/RNP
Run04: X=0.4%
Run02: X=1.3%
Non-pho./pho.
(QM05 F. Kajihara)
DNP/JPS 6
Inclusive electron & photonic electron v2
inclusive e v2
photonic e v2
Non photonicsignal
Photonic b.g.
- inclusive electron v2 (pho. + non-pho.) &
photonic electron v2
pT < 1.0 GeV/c --- converter method
pT > 1.0 GeV/c --- cocktail method
- inclusive electron v2 is smaller than
photonic electron v2
- Above 1.0 GeV/c, non-photonic electron
contribution is more than 50 % !
DNP/JPS 7
Charm quark flow ?
-pT dependence of non-photonic electron v2 after subtracting photonic electron from inclusive electron v2
-Compared with quark coalescence model prediction. D -> e v2 with/without charm quark flow
(Greco, Ko, Rapp: PLB 595 (2004) 202)
*Due to light quark has finite v2, D meson has
non-zero v2 though charm quark v2 = 0
Below 2.0 GeV/c ; consistent with charm quark flow calculation
Greco, Ko, Rapp: PLB 595 (2004) 202
DNP/JPS 8
D v2 from non-photonic electron v2 (1)
access D meson v2 from non-photonic electron v2 below 2 GeV/c (due to large error & uncertainty B meson contribution above 2 GeV/c)
(1) Assume D meson v2 as; v2 D = a * fv2(pT) fv2(pT) = pi v2 fv2(pT) = kaon v2 fv2(pT) = proton v2 fv2(pT) = D v2 (y_T scailing)
(2) Calculate D -> e (PYTHIA)(3) D v2 is given as weight to get e v2 (4) chi-squared test with “measured” non-photonic electron v2 below 2 GeV/c χ2 = Σ{(v2 non-γ- v2 D->e)/σv2 }2
(3) Find chi-squared minimum of a
experiment simulation
fv2(pT) = pi v2 fv2(pT) = kaon v2
fv2(pT) = proton v2 fv2(pT) = D v2 (y_T scal.)ch
i2
chi2
chi2
chi2
a(%) a(%)
a(%) a(%)
DNP/JPS 9
D v2 from non-photonic electron v2 (2)
-D meson v2 after scaling with chi2 minimum value (achi2_mim) for each D meson shape (fv2(pT))
v2 D = achi2_mim * fv2(pT)
fv2(pT) = pi v2 fv2(pT) = kaon v2 fv2(pT) = proton v2 fv2(pT) = D v2 (y_T scailing)
-D (= achi2_mim * fv2(pT)) -> e v2
compared with “measured” non-photonic electron v2
D meson v2 after scaling with
chi2 minimum value (achi2_mim) for each fv2(pT)
DNP/JPS 10
Simulation of B->e v2
D & B v2 (assume D & B v2 same)
D -> e
B -> e (B v2 flat @ high pT)
B -> e (B v2 decrease @ high pT )
- B meson v2 same as D meson v2
decrease @ high pT
flat @ high pT
- Clear difference electron v2
from B & D
-If B meson v2 is
(1) Smaller v2 than D meson
(2) decreasing @ high pT
(3) B->e overcome D->e
around 3~4 GeV/c
Non-photonic e v2 might be
reduced.
pT
v 2
DNP/JPS 11
Conclusion
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
Access D meson v2 from non-photonic electron v2 assuming D meson v2 shape as pion, Kaon, proton & D meson from y_T scailing.
DNP/JPS 12
Back up slides
DNP/JPS 13
y_T scailing
0 1 2 3 4 5
v 2
0.00
0.05
0.10
0.15
0.20
0.25
0.30 s 200 GeVNNAu Au
0SKp
fsTy
5 < Centrality < 30 %
K
(STAR)
(PHENIX)
(STAR)
(PHENIX)
(PHENIX)
DNP/JPS 14
Photon Converter (Brass: 1.7% XPhoton Converter (Brass: 1.7% X00))
Yield of conversion electron can be determined by the radiation length (X0) of material amount.
We know precise X0 of each detector material, but don’t the total effective value (+ air etc.).
However, we can measure the yield of conversion electron by inserting of converter.
Then, the photonic electron is subtracted from inclusive.
Advantage is small systematic error even in low pT region.
Photonic Subtraction-Converter Method
Ne Inclusive electron yield
Material amounts: 0
1.1% 1.7%
Dalitz : 0.8% X0 equivalent
0
With converterConversion in converter
W/O converter
0.8%
Non-photonic
Conversion from known material
? %
Photonic
F. Kajihara (session CC 7)