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Beam energy dependence of π and οΏ½οΏ½ production in Au + Au collisions at RHIC
Ning YuCentral China Normal Universityfor the STAR Collaboration
2017/2/7 17:10-17:30
Outline
β― Introduction
β― STAR Experiment
β― Results and Discussions
β― Summary
Ning Yu, Quark Matter 2017@Chicago 1/20
2017/2/7 17:10-17:30
QCD Phase DiagramLHC,RHIC
Future FAIR Experiment
K. Fukushima and C. SasakiProg. Part. Nucl. Phys, 72, (2013) 99
β― High temperature: QGP propertiesβ― High baryon density:
ΓΌ Critical point and phase boundaryΓΌ Possible new phase structure : quarkyonic matter
Phase transition
Correlations of nucleons
Light nuclei
Ning Yu, Quark Matter 2017@Chicago 2/20
2017/2/7 17:10-17:30
Light Nuclei Formation in HI Collisionsβ― Light (anti)nuclei with small binding energy (π), such as π and οΏ½οΏ½ with binding
energy π = 2.2 MeV, are formed via final-state coalescence
πΈ(π)π(π)π(
= π΅( πΈ-π)π-π)π-
.
πΈ/π)π/π)π/
(0.
β π΅( πΈ-π)π-π)π-
(
, π(= π΄π-
β― In thermodynamics, π΅( is related to the nucleon freeze-out correlation volume π6or baryon density
π΅( β π680(, π΅9 =6π)π /-π>
π-9π6
, π /- =π/π-
β― Light nuclei may serve as probes of space-momentum density and correlation of nucleons at freeze-out. We will focus on π (οΏ½οΏ½) in this talk.
LΓ‘szlΓ³ P. Csernai, Joseph I. Kapusta Phys. Reps, 131,223(1986)B. Monreal, et. al. PRC60,031901(1999), PRC60,051902(1999)
Ning Yu, Quark Matter 2017@Chicago 3/20
2017/2/7 17:10-17:30
Energy Dependence of π©π¨Most Central
β― The size of the fireball increase from low to high collision energy, π΅9 decrease with energy
β― The behavior of π΅9 is different at high energy
β― Is there any structure in the
energy dependence of π©π, from high energy to low energy ?
β― Is there any centrality dependence of π©π?
β― Is there any difference of π©πbetween deuteron and anti-
deuteron?PHENIX, PRL. 94, 122302 (2005).
Ning Yu, Quark Matter 2017@Chicago 4/20
1 10 100Collision Energy ππ΅π΅οΏ½ (GeV)
2017/2/7 17:10-17:30
RHIC Beam Energy Scan
ππποΏ½ (GeV) 7.7 11.5 14.5 19.6 27 39 62.4 200Neve(M) 4 11 27 40 71 133 67 480ππ©(MeV) 420 315 260 205 155 115 72 20
β― BES-I Au+Au collisions at π HHοΏ½ = 7.7, 11.5, 14.5, 19.6, 27, 39 and 62.4 GeVΓΌ Search for conjectured QCD critical
point ΓΌ Search for the first order phase
transitionΓΌ Search for the onset of key QGP
signatures
STAR Collaboration, arXiv:1007.2613
J. Cleymans, H. Oeschler, K. Redlich, and S. WheatonPRC 73,034905 (2006)
Ning Yu, Quark Matter 2017@Chicago 5/20
2017/2/7 17:10-17:30
Solenoidal Tracker At RHICTime Projection ChamberοΌTPCοΌ
ΓΌ Charged Particle Tracking
ΓΌ Momentum reconstruction
ΓΌ Particle identification from ionization
energy loss (dE/dx)
ΓΌ Pseudorapidity coverage |Ξ·| < 1.0
Time Of Flight (TOF)
ΓΌ Particle identification m2
ΓΌ Pseudorapidity coverage |Ξ·| < 0.9
Ning Yu, Quark Matter 2017@Chicago 6/20
2017/2/7 17:10-17:30
Particle Identification
Z (d) 0.4β 0.3β 0.2β 0.1β 0 0.1 0.2 0.3 0.4
Cou
nts
0
0.5
1
1.5
2
310Γ
DATASign.+Backgr.Sign.Backgr.
deuteron 39 GeV 0-5% < 0.8 GeV/c
T0.6 < p
)4/c2 (GeV2m2.5 3 3.5 4 4.5
Cou
nts
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
310Γ
DATASign.+Backgr.Sign.Backgr.
deuteron 39 GeV 0-5% < 2.8 GeV/c
T2.4 < p
π§> = logππΈ ππ₯βππΈ ππ₯β >
OO
π9 = π9π9π‘9
πΏ9 β 1
BB : Bethe-BlochH. Bichsel, Nucl. Instrum. Meth. A 562, 154 (2006).
Ning Yu, Quark Matter 2017@Chicago 7/20
2017/2/7 17:10-17:30
Efficiency and Acceptance
πUVW πX = πZexp βπ8πX
^_+ πππ(2)
πUde πX = πZexp βπ8πX
^_
πUde πX =ThenumberofTOFMatchedTracks
ThenumberofTPCTracks
Ning Yu, Quark Matter 2017@Chicago 8/20
2017/2/7 17:10-17:30
Correctionsβ― Energy Loss
β― Background in π analysis
π πX = π΄ + π΅ 1 +πΆπX9
{
- No centrality dependence of energy loss- Energy loss of π and οΏ½οΏ½ are the same- The energy loss for all the collision energy are the
same except 14.5 GeV (different material budget)
Ning Yu, Quark Matter 2017@Chicago 9/20
2017/2/7 17:10-17:30
Deuteron Spectraβ― Mid-rapidity ( π¦ β€ 0.3) transverse
momentum distribution of π from
Au+Au Collision
β― Dash line: blast-wave function fits1 2 3 4
5
4
3
2
1
111.5 GeV
1 2 3 4
5
4
3
2
1
114.5 GeV
1 2 3 4
6β10
5β10
4β10
3β10
2β10
1β10
1
19.6 GeV
1 2 3 4
6
5
4
3
2
1
1
27 GeV
1 2 3 4
6
5
4
3
2
1
1
39 GeV
1 2 3 4
6β
10
5β
10
4β10
3β
10
2β10
1β10 62.4 GeV
1 2 3 4
6
5
4
3
2
1 200 GeV
1 2 3 4
6
5
4
3
2
1β
4 2Γ 0-10%
3 2Γ10-20%
2 2Γ20-40%
1 2Γ40-60%
0 2Γ60-80%
(GeV/c)T
Transverse Momentum p
Deuteron from Au+Au Collision
)2
/Ge
V2
dy)
(c
TN
/(d
p2
)dT
pΟ
1/(
2
1 2 3 4
5β
10
4β10
3β
10
2β10
1β10
17.7 GeV
STAR Preliminary
d9ππXππX
β οΏ½ πdππXπΌZπXsinhπ
π πΎ8πXcoshπ
π
οΏ½
Z
Ning Yu, Quark Matter 2017@Chicago 10/20
2017/2/7 17:10-17:30
Anti-Deuteron Spectra
1 2 3 4
6
5
4
3
11.5 GeV
1 2 3 4
6
5
4
3
14.5 GeV
1 2 3 46β10
5β10
4β10
3β10
2β10 19.6 GeV
1 2 3 46
5
4
3
2
27 GeV
1 2 3 46
5
4
3
2
39 GeV
1 2 3 4
6β
10
5β
10
4β10
3β
10
2β10
1β10
62.4 GeV
1 2 3 4
6
5
4
3
2
1
200 GeV
1 2 3 4
6
5
4
3
2
1β
4 2Γ 0-10%
3 2Γ10-20%
2 2Γ20-40%
1 2Γ40-60%
0 2Γ60-80%
(GeV/c)T
Transverse Momentum p
Anti-Deuteron from Au+Au Collision
)2
/Ge
V2
dy)
(c
TN
/(d
p2
)dT
pΟ
1/(
2
1 2 3 4
6β
10
5β
10
4β10
3β
10
d9ππXππX
β οΏ½ πdππXπΌZπXsinhπ
π πΎ8πXcoshπ
π
οΏ½
Z
STAR Preliminary
β― Mid-rapidity ( π¦ β€ 0.3) transverse
momentum distribution of οΏ½οΏ½ from
Au+Au Collision
β― Dash line: blast-wave function fits
Ning Yu, Quark Matter 2017@Chicago 11/20
2017/2/7 17:10-17:30
ππ» and π»πππ, π·
β© Part
Nβ¨100 200 300
( G
eV/c
)β©
T pβ¨
1
1.5
219.6 GeV 27 GeV 39 GeV62.4 GeV 200 GeV
Au+Au Anti-Deuteron
β© Part
Nβ¨100 200 300
( G
eV/c
)β©
T pβ¨
1
1.5
27.7 GeV 11.5 GeV 14.5 GeV 19.6 GeV27 GeV 39 GeV 62.4 GeV 200 GeV
Au+Au Deuteron
STAR Preliminary STAR Preliminary
39 GeV π οΏ½οΏ½ π, πΎ, πβ
Cent. π»πππ(MeV) π·(c) πX (GeV/c) πX (GeV/c) π»πππ(MeV) π·(c) πX (GeV/c)0-10% 99Β±12 0.45Β±0.02 1.35Β±0.09 1.39Β±0.09 118Β±11 0.48Β±0.04 0.85Β±0.0510-20% 110Β±14 0.43Β±0.02 1.32Β±0.09 1.35Β±0.05 120Β±11 0.46Β±0.03 0.83Β±0.0520-40% 135Β±23 0.39Β±0.02 1.23Β±0.08 1.23Β±0.08 126Β±11 0.41Β±0.03 0.79Β±0.05
β― ππ» decrease fromcentral to peripheralcollision
β― ππ» of π and π areconsistent within error
β― B.W. can describe bothπ and π, πΎ, π withsimilar parameters
β STAR Collaboration, arXiv:1701.07065 (submitted to PRC)
Ning Yu, Quark Matter 2017@Chicago 12/20
2017/2/7 17:10-17:30
Integral Yield π π΅ π πβ
β― ππ π /ππ¦ is smaller at higher energy: baryon stoppingβ― ππ(π)/ππ¦ increases with increasing energy: baryon pair productionβ― ποΏ½οΏ½οΏ½οΏ½ scaled ππ/ππ¦ for π show weak centrality dependence, for π
increase slightly from peripheral to central collision
β© Part
Nβ¨100 200 300
]β© P
art
Nβ¨Γ
dN
/dy/[
0.5
6β10
5β10
4β10
3β10
11.5 GeV 14.5 GeV 19.6 GeV 27 GeV39 GeV 62.4 GeV 200 GeV
Au+Au Anti-Deuteron
β© Part
Nβ¨100 200 300
]β© P
art
Nβ¨Γ
dN
/dy/[
0.5
3β10
2β10
7.7 GeV 11.5 GeV 14.5 GeV 19.6 GeV
27 GeV 39 GeV 62.4 GeV 200 GeV
Au+Au Deuteron
STAR Preliminary STAR Preliminary
Ning Yu, Quark Matter 2017@Chicago 13/20
2017/2/7 17:10-17:30
Antiparticle to Particle Ratios
β― π οΏ½οΏ½ /π π ratio decreases as a function of collision centralityβ― π οΏ½οΏ½ /π π ratio decreases with decreasing energy
β© Part Nβ¨100 200 300
)/N(d
)d
N(
0
0.2
0.4
0.6
0.8 200 GeV 2Γ39 GeV
4Γ19.6 GeV PHENIX 200 GeV
STAR Preliminary
PHENIX, PRL. 94, 122302 (2005).
Ning Yu, Quark Matter 2017@Chicago 14/20
2017/2/7 17:10-17:30
π΅(π )/π΅(π) Ratio vs. Energy
The lines are from thermal model predictionA. Andronic, P. Braun-Munzinger, J. Stachel, H. Stocker, PLB697 (2011)203
(GeV)NNs10 210 310
Parti
cle
Rat
io
4β10
3β10
2β10
1β10
1STAR 0-10% d/p
p/dSTAR 0-10% SIS d/pEOS802 d/pNA49 d/pPHENIX d/p
p/dPHENIX ALICE d/p
Thermal Prediction
5 MeVΒ±T = 163
β― The N(π)/π(π) ratios by thermal model prediction are consistentwith the data from SIS energies up to LHC
β― A temperature of π = 163 Β± 5 MeV can be extracted from π(π)/π(π)and π(οΏ½οΏ½)/π(οΏ½οΏ½)
π(π)π(π) ~
πΎ9 π> πβπΎ9 π- πβ
ποΏ½οΏ½X
π(οΏ½οΏ½)π(οΏ½οΏ½) ~
πΎ9 π> πβπΎ9 π- πβ
π0οΏ½οΏ½X
STAR Preliminary
Ning Yu, Quark Matter 2017@Chicago 15/20
2017/2/7 17:10-17:30
π /ππ and π οΏ½/ποΏ½π Ratiosβ― In thermal model with GCE (grand canonical
ensemble), π π9β and οΏ½οΏ½ οΏ½οΏ½9β should be the same if iso-spin effect can be neglected
π π =
12 ln
οΏ½οΏ½ οΏ½οΏ½9βπ π9β
β― The π /π can also be obtained by π π =
12 ln
πΒ‘
π0
The results are close to zero implying smalliso-spin effect
10 210
2d/p
0.2
0.4
0.6
0.8
3β10Γ
2d/p2
p/d
p err.
err.p
Au+Au 0-10%
(GeV)NNs10 210
/ T
QΒ΅ 0.5β
0
2BES d/p-
Ο/+ΟBES -
Ο/+ΟNA49 Initial Iso-spin
STAR Preliminary
NA49, PRC 94, 044906 (2016)
Ning Yu, Quark Matter 2017@Chicago 16/20
2017/2/7 17:10-17:30
π©π v.s. ππ» and Collision Centrality
β― The values of π΅9 increase as a function of πXand decrease with collision centrality : collective expansion
β― π΅9 π are smaller than that of π΅9 π , antiβbaryon freeze out at a larger source
π΅9 = π Β£ exp π πX β π
NA44, EPJ C. 23, 237 (2002)
)2 - m (GeV/cTm0.5 1 1.5
)3/c2
(GeV
2B
1
2
3
4
3β10Γ
(d) 0-10%2B(d) 10-20%2B(d) 20-40%2B(d) 40-60%2B
)2 - m (GeV/cTm0.5 1 1.5
)3/c2
(GeV
2B
) 0-10%d(2B) 10-20%d(2B) 20-40%d(2B) 40-60%d(2B
Au+Au 39 GeV
STAR Preliminary
Ning Yu, Quark Matter 2017@Chicago 17/20
(GeV)NNs4 5 6 7 8 10 20 30 40 100 200
)3/c2
(GeV
2B
3β10
E864(d) Au+PbE866(d) Au+AuE877(d) Au+AuNA49(d) Pb+PbPHENIX(d) Au+Au
) Au+AudSTAR() Au+AudPHENIX(
/ A = 0.65 GeV/cT
pSTAR 0-10%(d) Au+Au
) Au+AudSTAR 0-10%(
Average of p+p and p+A
Central CollisionSTAR Preliminary
2017/2/7 17:10-17:30
Coalescence Parameters v.s. Collision Energy
β― π΅9 decrease with collision energy. A minimum around sHHοΏ½ = 20 GeV :change of EOS?!
β― π΅9 π values are systematically lower than that of π΅9(π) implying emitted source of anti-baryons is larger than those of baryons
arXiv:1410.2559
β βπ β ππ
Ning Yu, Quark Matter 2017@Chicago 18/20
2017/2/7 17:10-17:30
Discussionβ― Is there any structure in energy
dependence of π΅9, from high
energy to low energy ? (BES: Yes)
β― Is there any centrality dependence
of π΅9? (Yes)
β― Is there any difference of π΅9between deuteron and anti-
deuteron? (Yes) (GeV)NNs4 5 6 7 8 10 20 30 40 100 200
)3/c2
(GeV
2B
3β10
E864(d) Au+PbE866(d) Au+AuE877(d) Au+AuNA49(d) Pb+PbPHENIX(d) Au+Au
) Au+AudSTAR() Au+AudPHENIX(
/ A = 0.65 GeV/cT
pSTAR 0-10%(d) Au+Au
) Au+AudSTAR 0-10%(
Average of p+p and p+A
Central CollisionSTAR Preliminary
Ning Yu, Quark Matter 2017@Chicago 19/20
2017/2/7 17:10-17:30
Summaryβ― STAR systematic results of π(οΏ½οΏ½) production (ππ/ππ¦, ππ ) from Au + Au collisions
at ππποΏ½ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV
β― Coalescence parameterπ΅9forπ and οΏ½οΏ½ are extracted. π΅9(π) and π΅9(οΏ½οΏ½) are found to
be different in the most central collisions
β― Similar to the π HBT and net-proton high moment, around sHHοΏ½ = 20 GeV, π΅9reaches a minimum implying EOS changes around the energy
β― High statistics data are needed for future studies, especially at the high net-baryon
density, i.e., low collision energy region
Ning Yu, Quark Matter 2017@Chicago 20/20
Thank you
2017/2/7 17:10-17:30 Ning Yu, Quark Matter 2017@Chicago 21/20
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