Beam Energy Scan at RHIC

Hiroshi Masui / University of Tsukuba,!
Quark Gluon Plasma and Future Directions in Heavy
Ion Physics at RHIC and LHC,
4th joint meeting of APS-DNP and JPS,
Hawaii, Oct 7-11

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

1 /20

Outline• Introduction‣ RHIC Beam Energy Scan (BES) phase-I• Review selected results• Future upgrade for BES phase-II‣ RHIC luminosity upgrade, sPHENIX & STAR upgrade• Summary

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

2 /20

RHIC Beam Energy Scan (BES)
http://www.bnl.gov/bnlweb/pubaf/pr/photos/2012/07/RHIC_Graphics_Fig1-HR.jpg• Cross-over transition at µ =0
B

‣ from 1st principle Lattice QCD

calculations• If phase transition is 1st orderat high baryon density, theend point is QCD critical point• Beam energy scan → reachhigh baryon density

critical point ?
First orderphase transition ?

• Goals of BES at RHIC:‣ Search for turn-off QGP signals‣ Search for signals of 1st orderphase transition‣ Search for signals of QCD criticalpoint
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

3 /20

RHIC heavy ion collisions√
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
(GeV
)
200
130
62.4
39
27
22.5
19.6
14.5
11.5

• Beam Energy Scan (BES) phase-I(year 2010, 2011)‣ 7.7, 11.5, (14.5), 19.6, 27, 39, 62.4 GeV• 14.5 GeV has just taken this year

7.7
Test
run

9.2 GeV

Au+Au

Cu+Cu

d+Au

He+Au

5 GeV

U+U (193 GeV) & Cu+Au

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

4 /20

PHENIX & STAR experiments
STAR
TOF

MTD
TPC

EMCal

HFT

• Good acceptance in STAR
• Fast trigger, good forward
counters in PHENIX• Similar PID capabilities
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

5 /20

Where are we in QCD phase diagram ?

Beam Energy Scan at the Relativistic Heavy The
IonBeamCollider7
Energy Scan at the Relativistic Heavy Ion Collider

2760 GeV(b) LGT CP Predictions 200 GeV
200
62.4 GeV
39 GeV(a) Chemical Freeze-out Data
200

27 GeV19.6 GeV
11.5 GeV
7.7 GeV

Tkin (MeV)

Temperature Tch (MeV)

250

150

150

100

100

5% Au+Au collisions at RHIC

S. Datta, et al.,NPA904-905, 883c(13)50Z. Fodor and S. Katz, JHEP04, 50(04)50

A. Andronic, et al., NPA834, 237(10)J. Cleymans, et al., PRC73, 34905(06)(TC = 170 MeV)STAR Preliminary

0
10

100

1000

10

100

0

0.1

Baryonic
ChemicalBaryon chemical
potentialµB (MeV)Potential µB (MeV)

1000
0.2
0.3

0.4

0.5

0.6

0.7

〈 β 〉 (c)Figure 4. Kinetic freeze-out temperature (Tkin ) versus the average collective flow in the trare 3. (a) Chemical freeze-out temperature (Tch ) versus
chemicalpotential(µB ) forobtained
directionbaryonic(hbi) in highenergy heavy-ion
collisions
different collision centralities. At each c
a statistical model [20, 19] fit to yields of hadrons
produced
0-5%
centralAu+Au
atperipheral collisions and thoseenergy,the datain
pointswithlower hbi
values collisions
correspond toBlargerhbi values
correspond to
centralcollisions.
C. The yellow bands are the empirical results fromfittingexperimental
dataacquiredprior to the• RHIC BES phase-I covers up to ~ 400 MeV in µ

-I program‣byChemicala statistical model.
(b) The positionsof the QCD
pointchemicalfrom two different
freeze-out
temperature&critical
baryonpotential frome gauge theory
calculationsin the Tch versus µB planearemshown.
particleratiofits to them distributions of p, K, and p (as shown in the representative plot inTat midrapidity at RHIC for various collision energies are shown in Fig. 4. Also shop‣ Kinetic freeze-out temperature
fromresultspT spectra
the corresponding
from Pb+Pb collisions at sNN = 2.76 TeV from ALICELHC [33]. The Tkin values in central collisions are lower than the corresponding va
d lead to further development, understanding,and refinementof thestatisticaldecreases
models.
TchMasui(shownin Fig.
althoughthe differenceHawaii,
lower
beam energies.
At all thH.
/ Univ.
of 3)
Tsukuba,
APS-DNP/JPS
Oct at
7-11,
2014
6 /20

with increasing centrality even for the lowest-energy system. Similarly, as already discussed in the context of Fig. 2,
at high enough pT the suppression is the same at 62.4 and
200 GeV, at all centralities. This is remarkable because thepower nPRL109,of the fit
to the(2012)
spectra changes approximately by
PHENIX:152301

RAA (200 GeV) <RAA (62 GeV) < RAA (39 GeV) (though by
a very modest amount). Also shown in Fig. 8 are the PHENIX
experimental measurements that, within the global systematic
uncertainties, are consistent with the theoretical calculations.
These results highlight the need for p + p reference data at
PHENIX:
PRC86,
064901 (2012)both 39 and 62.4 GeVfrom thesame experiment.
In addition,

Nuclear modification factor RAA
1.6

AuAu, π0, |η|<0.35|
sNN = 39 GeV
sNN = 62.4 GeV
sNN = 200 GeV

162.4 GeV PHENIX data/our estimat e
Global sys.= ± 29.4%

1.2

39 GeV PHENIX data/FNAL data
Global sys.= ± 19%

1

RAA

0.5

J/ψ → µµ, 1.2 <|y| < 2.2

0.8

0

0.6
0

100

200

300

400

Npart

0.4

FIG. 3 (color online). Nuclear modification factor averaged forpT > 6 GeV=c. Uncertainties are shown as error bars (statistical), boxes (sum of pT -uncorrelated and Ncoll ), boxes around one(types B and C and uncertainties from the p þ p-collisionreference).

301-5

200 GeVGlobal sys.= ± 9.2%

1.4

T

RAA (p > 6 GeV/c)

1.5

6
(t
c
th
U
C
s
th

0.2
0
0

50

100

150

200

250

300

350

400

Npart

√
FIG. 6. (Color online) J /ψ RAA at sNN = 39, 62.4, and 200 GeV[4]. The solid error bars are the quadrature sum of the statistical andtype A systematic uncertainties, and the boxes represent the correlated(type B) systematic uncertainties. The global systematic uncertainties
are quoted in the legend for each energy’s results.

• Parton energy loss in colored medium‣ π0 RAA is suppressed in most central 0-10% at √sNN = 39 GeV

064901-- Results in Cu+Cu 22.5 GeV show enhancement in pT = 4 GeV/c‣ J/ψ RAA is also suppressed at 39 GeV, similar with 62.4 and 200 GeV
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

p
p
C

7 /20

Elliptic flow v2

PHYSICAL REVIEW C 88, 014902 (IC FLOW OF IDENTIFIED HADRONS IN Au + . . .

(a)

0.1 7.7 GeV

Au+Au, 0-80%
η-sub EP

STAR: PRC88, 014902 (2013)11.5 GeV

19.6 GeV

39 GeV62.4 GeV

v2/nq

0.05
0
0.1 27 GeV
0.05
0
0

0.5

1

1.5

20

0.5 1 1.5 2 0(m -m0)/nq (GeV/c2)

0.5

1

1.5

2

T

of constituent quark (NCQ) scaling - partonic d.o.f•(b)Number
0.1‣

7.7 GeV11.5 GeV
19.6 GeV
Au+Au, 0-80%
Hold separately
for particles and anti-particles
η-sub EP

0.05 more statistics in high mT-m0 at lower energies‣ NeedH. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 20148 /20

v2; particles vs anti-particles

STAR: PRL110, 142301 (2013),
110, 142301(2013)(2013)
PRC88, 014902

The Beam Energy Scan at the Relativistic Heavy
Ion
ColliderHybridmodel:
PRC86, 044903 (2012)

P H Y S I C A L R E V I E W L E T T ENJL
RS
model: PRL112, 012301 (2014)

wee
5 AP

0-80% Au + Au Collisions at RHIC

Most of the published theoretical calculations ca
Ξ -Ξ
0.04
Au+Au, 0%-80%
(a)
(b)
p-p
η-sub EP
duce
the
basic
pattern
but fail to quantitatively reExp. data Hybrid model
Exp. data NJL model
Λ-Λ
p
the
v2 difference[25–28]. So far, non
0.03
p measured
p
K+-K
0.04
K
π+-π
Λ
Λ
theorycalculations describes
the observed ord
π
K
K
0.02
the
particles.
Therefore,ππmore accurate calculatio
theory are needed to distinguish between the
0.02
0.01
possibilities. Other possible reasons for the obs
%
þ
that
the
!
v
ðp
Þ
is
larger
than
the
!
v2 ðp
2 T
0
0
Coulomb repulsion of !þ by the midrapidity net(only
at200low 300pT ) andthe100chiralmagnetic
effect
0
20
40
60
0
100
400 0
200
300
400
baryon-density
matterPotential[29]. Simulations
have to bsNN (GeV)
Baryonic ChemicalµB (MeV)out to quantify if those effects can expl
(color online). The difference in v2 between particles
observations.
8. Theasmeasureddifference in integrated v2 between particles and their corre! Figure
d their corresponding antiparticles (X)(see legend)a
In Ref. [21], the study of the centrality depen
pﬃﬃﬃﬃﬃﬃﬃﬃ Relative differencev2 pions
betweenparticles
andanti-particles(filled triangles),kaons (opensquares),Ls (open triangles), and proto
Au ofcollisions.
The
on of sNN for 0%–80% central Au þ antiparticles:"v2 for protons and antiprotons is extended to incircles),
all shown
as a function of baryonic chemical potential and collision energy for 0–80%
lines in theincreaseplot are fits witha power-law
function.
The
in lower
beam
energies
if different production rates for protons and antipr[83, errors.
84]. Only statistical error bars are shown. Panels (a) and (b) show the compar
ars depict the combined statistical andcollisions
systematica functionof centrality
could cause the observe‣ Difference increasemodel
linearlywithchemicalpotential
calculations
frombaryon
Refs. [86] and[87, 88], respectively.
ences. It was observed that the differences, "‣ Reasonable agreement with hybrid significant
hydro model→ baryon stopping ?
at all centralities.
pﬃﬃﬃﬃﬃﬃﬃﬃ
Thev2 ðmTanisotropy% m0 Þ andpossible
NCQstudied
scalingile in Au
þAu
collisions
at
s
¼
200
GeV
a
earlier,
there
are
two
types
of
azimuthalthatarecommonly
in hNN‣ NJL model also qualitatively reproduce the dataandantiparticles
se
NCQ scaling can be observed forparticles
andflow investigatedcollisions,directed(v1 ) and ellipticfor
flowparticles(v2 ). In thissubsection,
we concen
Figure3to showsvHawaii,
as mostaOctfunctionof the reduced
tr2therticles, the observed difference in vv2 . at
lower
beam
The
v2Masuicoefficienthas
provenAPS-DNP/JPS
be one of
discussed
the
dyn
H.
/ Univ. of
Tsukuba,
7-11, 2014 probes of
9 /20

•

-

+

200

v2(part.) - v2(anti-part.)2

v2(X)-v (X)

0.06

39

27 19.6

11.5

7.7 (GeV)

200

39

27 19.6

11.5

7.7 (GeV)

RV=1.1

RV=0.5

The Beam Energy Scan at the Relativistic Heavy Ion Collider

22

Charge separation w.r.t.
event
plane
PHYSICAL REVIEWPRL 113, 052302 (2014)
STAR: PRL103, 251601 (2009), PRL113, 052302 (2014),
ALICE: PRL110, 012301 (2013)
5

5

0

0

-5

-5

-10

(a)-101062.4 GeV Au+Au 10

5

5

0

0

-5

(c) -5

5200 GeV Au+Au

0

30

30

27 GeV Au+Au

20

opposite charge
same charge

10

κ=1
κ = 1.5
κ=2

-5

(b)

UrQMD (κ =1)-10
2

39 GeV Au+Au

(d)

β

RP

[γ ≡ 〈cos(φα+φ -2ψ )〉] × 104

10

104 × (HSS - HOS)

2.76 TeV Pb+Pb

10

incre
and
deter

60 - 80%

19.6 GeV Au+Au

20

30 - 60%

1

0

Au+Au

-1

Pb+Pb

10

(e)

(f)

0

10 - 30%

0
0

20

40

60

80 0

40

11.5 GeV Au+Au 40

30

30

20

20

10

0.5
20

40

60

7.7 GeV Au+Au
0

10

(g)

0
80

60

40

20

0
0 80

80

W
the N
and
resou
by th
of Sc
Braz
Russ
Chin
the C
CSIR
the N
Mini
of C

(h)
60

40

20

0

Collision centrality (% Most Central)

10

102

10

3

sNN (GeV)• Chiral magnetic effect + Local parity violationp
FIG.
4. HSS − HOS , as a function of beam energy for three
Figure 14. The three-point correlator (g) as a function of centrality for Au+Au collisions at sNN=p
7.7-200 GeV. Also shown are the corresponding results for Pb+Pb collisions at sNN = 2.76 TeV from
centrality bins in Au þ Au collisions. The default values (dotted
ALICE at the LHC [125]. Note that the vertical scales are different for the different rows. The plottedcurves) are for Hκ¼1, and the solid (dash-dotted) curves areNN
systematic errors (shaded rectangles) reflect the extra conditions of DpT > 0.15 GeV/c and Dh > 0.15
obtained with κ ¼ 1.5 (κ ¼ 2). For comparison, the results forto suppress HBT + Coulomb effects.
Au þ Au collisions at 200 GeV [11] and Pb þ Pb collisions at‣ Signal ~ 0 in √s= 7.7 - 19.6 GeV

measurements below 20 GeV‣ Need better estimate of κ & precision
2.76 TeV [16] are also shown. The systematic errors of the STAR

[1]
[2]
[3]
[4]
[5]
[6]
[7]

data (filled boxes) bear the same meaning as those in Fig. 2.
H. Masui / Univ.UrQMD
of Tsukuba,
APS-DNP/JPS
Oct 7-11,
calculations
with κ ¼Hawaii,
1 are also
shown2014
as solid shaded
10 /20 [8]Di-electron mass spectra
STAR, QM2014• Chiral symmetry restoration,
thermal radiation‣ STAR measured di-electron

spectra in √sNN = 19.6 - 200
GeV‣ Excess in Mee < 1.1 GeV/c2(LMR) observed at all energies‣ In-medium modification of ρ

spectral function describe LMR
enhancement‣ No energy dependence of LMR

excess• Need more statistics below
20 GeVH. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201411 /20informative. We define the slope Fnet-p based on expressing 130
the rapidity dependence of directed flow for all protons as½v1 ðyÞ%p ¼ rðyÞ½v1 ðyÞ%p̄ þ ½1 − rðyÞ%½v1 ðyÞ%net-p , where rðyÞis theobserved rapidity dependence of the ratio of
STAR: PRL112, 162301 (2014)

Directed flow v10

H. Stöcker / Nuclear Physics A 750 (2005) 121–147

H. Stocker:
NPA750 (2005) 121-147

10-40% Centrality-0.02(a) antiproton-0.04√sNN (GeV)

y=0

dv 1/dy|(b) proton

13.7

PHYSICAL REVIEW C 89, 054913 (2014)

EXAMINATION OF DIRECTED FLOW AS A SIGNAL FOR . . .

0.01

4.3 6.1

Fig. 7. Measured SIS and AGS proton (dpx /dy)-slope data compared to a three-fluid hydro calculation. A linear
extrapolation of the AGS data indicates a collapse of flow at ELab ≈ 30 A GeV, i.e., for the lowest SPS- and theupper FAIR-energies at GSI [59].

J. Steinheimer et al,
PRC89, 054923(2014)

02(c) net10 proton

10

0.01

0

Data
UrQMD

10

√ sNN (GeV)

10 2

8. Directed flow v1 of protons versus rapidity at 40 A GeV Pb + Pb collisions [60] as measured by NA49 for
FIG. 4 (color online). Directed flow slope (dv1 =dy) near Fig.
three centrality
bins:(dots),
mid-central(squares) andsolidandlines are polynomial
FIG.
7. central(Coloronline)Comparison
ofperipheral
results (triangles).
for pure The
hydro
fits
to
the
data
[60].
The
protonantiflowisobserved
in
the
NA49
experiment
even
at
near
centralmidrapidity versus beam energy for intermediate-centrality
hybrid model calculations with a first order EOS. Shown is the slopecollisions, whichis in contrast to the UrQMD-model involving no phase transition (Fig. 9).
of v1 of protons and antiprotons around midrapidity compared to
Au+Au. Panels (a), (b) and (c) report measurement for antiexperimental data.
protons, protons, and net protons, respectively, along with Recently,
substantial support for this prediction has been obtained by the low energy
UrQMD‣calculations
subject
to
the
same
cuts
and
fit
conditions.
40
A
GeV
SPS
data of thewith
NA49 Collaboration[60]prediction(cf. Fig. 8). These data clearly show
Non-monotonic behavior, trendtheisfirstfromsimilar
early
below.
Also theoverallmagnitude
seems toproton“antiflow”
aroundmid-rapidity,
in contrast
to be
thestrongly
AGS data as well as
Systematic uncertainties are shown as shaded bars. Dashedto theoverestimated.
UrQMD calculations involving no phase transition (Fig. 9). Thus, at bombarding
curves areasmooth
fit
to
guide
the
eye.
‣ Recent more realistic hybrid calculation can’t reproduce the data

2301-5• Possible signature of first order phase transition
V. DISCUSSION
FIG. 6. (Color online) Slope of v1 of (a) negatively charged pions

observedAPS-DNP/JPS
in previous studies[21,24–26],
the hybrid
H. Masui / Univ. ofAs
Tsukuba,
Hawaii,Oct 7-11,
2014

12 /20Azimuthal sensitive HBTEmission duration and expansion/lifetime
PHENIX, QM2014
24

STAR: arXiv:1403.4972 [nucl-ex]
0.4E895 (-0.6<y<0.6, 7.4-29.7%)

0.35STAR (-0.5<y<0.5, 10-30%)

UrQMD(2+1)D hydro EOS-Q(2+1)D hydro EOS-HεF

CERES (-1<y<-0.5, 10-25%)(2+1)D hydro EOS-I(2+1)D hydro MC-KLN

STAR (-1<y<-0.5, 10-30%)
STAR (0.5<y<1, 10-30%)

0.3(2+1)D hydro MC-GLB

0.25

π ±- π ±kT = 0.15-0.6 GeV/c

0.2
0.15
0.1

 



0.05
0
10

3

2

10

sNN [GeV]

10

7: (Color online) The dependence of the kinetic freeze-out eccentricity of pions on collision energy in mid-central Au+Au collisionsSTAR) and Pb+Au collisions (CERES) for three rapidity regions and with ⟨kT ⟩ ≈ 0.31 GeV/c. For clarity, the points for forward andrd rapidity from STAR are offset slightly. Error bars include only statistical uncertainties. Several (2+1)D hydrodynamical models andD calculations are shown. Model centralities correspond to the data. The trend is consistent with a monotonic decrease in eccentricity
am energy.

centricities at kinetic freeze-out in Fig. 27 were maderQMD in cascade mode and so do not incorporate thisal between string fragments.
hould be noted that none of the models predict all
ables simultaneously. The UrQMD model, while ites the freeze-out shapes well, matches the momentum
observables less well. And the hydrodynamic models,
hey are able to describe the momentum space pT specd v2 results, do less well at predicting the eccentricity
ends observed in HBT analyses. The availability of
new experimental results provide an important opporto further constrain models.

• Non%monotonicity'magniﬁed'with'(Rout)2'–'(Rside)2''• Rside/Rlong'indicaDve'of'expansion/lifeDme'

global fit method has been developed.
2014%05%20'
R.'Soltz'for'PHENIX'%'Quark'Ma<er'2014'
A wide variety of HBT measurements have been performed
and the comparison of results at different energies is greatly
improved. In the azimuthally integrated case, the beam energy
dependence of the radii generally agree with results from otherexperiments, but show a much smoother trend than the earlier
data which were extracted from a variety of experiments withvariations in analysis techniques. The current analyses additionally contribute data in previously unexplored regions ofcollision energy. The transverse mass dependence is also consistent with earlier observations and allows one to conclude
that all kT and centrality bins exhibit similar trends as a function of collision energy.
The energy dependence of the volume of the homogeneity regions is consistent with a constant mean free path atfreeze-out, as is the very flat energy dependence of Rout . This
scenario also explains the common dependence of Rside andRlong on the cube root of the multiplicity that is observed at
Masui/ Univ.
of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014
higher energy. For 7.7 and 11.5H.
GeV,
Rside appears
to deviate• First order phase transition → small freeze-out eccentricity‣ STAR results show monotonic energy dependence

•

VII.

Non-monotonic behavior on (Rout)2-(Rside)2, Rside/Rlong‣ (Rout)2-(Rside)2 ~ emission duration, Rside/Rlong ~ proxy of sound speed
CONCLUSIONS

two-pion HBT analyses that have been presented proey measurements in the search for the onset of a firsthase transition in Au+Au collisions as the collision en-

13 /20Net-proton & net-charge fluctuations
PRL 112, 032302 (2014)

STAR: PRL112, 032302 (2014)
1.2

P H Y S I C A L R E V I E W PRL
L E113,
T T E092301
R S (2014)

week ending
P24HJANUARYY S I C A 2014
L REVIEW

STAR: PRL113, 092301 (2014)the κσ 2 and Sσ2 from(a) UrQMD
Net-charge[23] (not shown in the figures)
10
1.0
Au+Au
closely follows the dataat the lower beam energies of 7.7|η| < 0.5
SkellamDistribution
0.8
and 11.5 GeV. Their values are, in general, larger compared
70%-80%
to data for the higher beam energies.
0.6
0%-5%
10
The current data provide the most relevant measurements
0.4
Net proton
over the widest range in μB (20–450 MeV) to date for the
0.2 0.4<p <0.8 (GeV/c),|y|<0.5
T
CP search, and for comparison with the baryon number
1.2
susceptibilities
from QCD to understand the(b)
0.6 computed
various features of the QCD phase structure [6,16,17]. The
1.0
0.4
deviations ofSσ and κσ 2 below the Skellam expectation
0.8
p+p data
are qualitatively
0.2 consistent with a QCD-based model which
Au+Au
70%-80%0.6
includes a CP [33]. However, the UrQMD model which
Au+Au 0%-5%0
Au+Au 0%-5% (UrQMD)
does not include
a CP also shows deviations from the
0.4
Ind. Prod. (0-5%)(c)Skellam expectation.
Hence, conclusions on the existence
1.05
of CP can 5be made only after comparison to QCD
1.00
0calculations with
CP behavior which include the dynamics
0-5%
associated withfinite corre0.95-5 heavy-ion collisions, such as70-80%
0-5% NBD
lation length and freeze-out effects.
70-80% NBD
0.90-100-5% Poisson
In summary,measurements of the higher moments
and70-80%
Poisson0.85-15 (Sσ and κσ 2 ) of the net-proton distributions
their products
5 6
20 30
200
10
100
5 6 7 8 10
20
30 40
200
100
at
midrapidity
(jyj
<
0.5)
within
0.4
<
p
<
0.8
GeV=c
in
T
Colliding Energy sNN (GeV)√sNN(GeV)pﬃﬃﬃﬃﬃﬃﬃﬃ
Au þ Au collisions over a wide range of sNN and μB havebeen presented
to searcha possible CP
and signals
FIG. 4 (color
online). forBeam-energy
dependenceof (a)of
σ 2a=M,
FIG. 4 (color online). Collision energy and centrality depende2
phase(b)transitiontheκσcollisions.
observables
showaSσ, andin(c), after allThese
corrections,for most
centralnce of the net proton Sσ and κσ 2 from Au þ Au and p þ p(0%–5%)
peripheral(70–80%)whichbins. are
The not
errorreprobars arecentrality
and andenergydependence,collisions at RHIC. Crosses, open squares, and filled circles
the capstransport
represent model
systematic
errors. Results
from
ducedstatisticalby eitherandnon-CP
calculations
or by
are for the efficiency corrected results of p þ p, 70%–80%, andﬃﬃﬃﬃﬃﬃﬃ
ﬃp
the Poisson
and NBDare superimposed.
valuesa hadronresonancegas baselines
model. For
sNN > 39 The
GeV,
Sσ of
0%–5% Au þ Au collisions, respectively. Skellam distributions
2
for the Poisson baseline are always unity.
for corresponding collision centralities are shown in the top
and κσκσ2 values
are similar for central, peripheral Au þ Au
panel. Shaded hatched bands are the results from UrQMD [22].
collisions, and p þ p collisions. Deviations for both κσ 2
In the middle and lower panels, the shaded solid bands are theand Sσfrom HRG and Skellam expectations
are observed
are always
unity. For
ﬃﬃﬃﬃﬃﬃﬃﬃ for the Poisson baselines
pvalues
expectations assuming independent proton and antiproton profor peripheralsNN ≤ 27 GeV.
The themeasurements
reasonably
collisions
κσ 2 values areshowalmost no
duction. The width of the bands represents statistical uncertainH. Masui / Univ.
of
Tsukuba,
Hawaii,Oct 7-11,2014
described
by assuming
independent
production
Naboveandthevariation
as APS-DNP/JPS
a functionof beamenergyand of
lie
Sσ

σ2
M

κ σ2

Sσ

(S σ)/Skellamκσ2

Au+Au Collisions at RHIC

• Sensitive to fluctuations induced by QCD critical point• Largest deviation around 19.6 GeV for net-proton• Need more precise measurementsLE

hadron yie
chemical fresonanceorder corre
thermal equfreeze-out
data on m
obtained [4analyses [4results for c
extracted
151 MeV aerrors in thfunction of
the statistiments. Mor
this is the fi
moments hout condit
freeze-out
analysis ar[25,46]. Th
to freeze-ou
investigatio
In summcharge mulof centralienergies fr
These data
QCD phase
We observ
with increa
is observed

14 /20RHIC luminosity improvementswith electron coolingand long buncheswith electron cooling

BES-I• Electron cooling will be available for BES-II‣ Electron cooling: by a factor of 3-10 increase in 5-20 GeV‣ Electron cooling + long bunches: by a factor of 2-5
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201415 /20effectively a first stage implementation of the tracking detector considered for ePHENIX aan Electron Ion Collider [3].

sPHENIX upgrade for BES-II• Possible configurations in

OUTER HCAL

year 2019INNER HCAL

• Option 1: EMCAL+VTX• Option 2

BABAR MAGNET‣ Option 1+ Additional silicon

Acceptance:- |η| < 1
- Full azimuth

EMCAL

trackers•

Option 3

BEAMPIPE
VTX‣ Option 1+ TPC
OUTER HCALOUTER HCAL

INNER HCAL

INNER HCALBABAR MAGNETBABAR MAGNET

EMCAL

EMCAL

TPC

OUTER SILICON
TRACKER
BEAMPIPE

BEAMPIPE
VTX

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 2014

VTX

16 /20STAR upgrade for BES-II
inner TPC upgrade
Event Plane Detector• Event Plane Detector, 1.8 < |η| < 5‣ Trigger, event plane, centrality- suppress backgrounds on flow measurements, independent centrality determination• inner TPC upgrade‣ increase TPC acceptance from 1 to 1.5 in η
‣ improve dE/dx resolution → better PID
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201417 /20BES-II white papers

NOTES:
1. MATERIAL: BLACK DELRIN OR EQUIV.

http://www.phenix.bnl.gov/phenix/WWW/publish/
dave/sPHENIX/BES_II_whitepaper.pdf

https://drupal.star.bnl.gov/STAR/system/files/BES_WPII_ver6.9_Cover.pdf

Studying the Phase
Diagram of QCD
Matter at RHIC

Beam Energy Scan II (2018–2019)PHENIX Collaboration White Paper
NOTES:
1. MATERIAL: BLACK DELRIN OR EQUIV.

NOTES:
1. MATERIAL: BLACK DELRIN OR EQUIV.

A STAR white paper summarizing
the current understanding anddescribing future plans

OUTER HCAL

INNER HCALBABAR MAGNET

01 June 2014

EMCAL

BEAMPIPEVTXOUTER HCALOUTER HCAL

INNER HCAL

INNER HCALBABAR MAGNETBABAR MAGNET

EMCAL

EMCAL

TPC

OUTER SILICON
TRACKER
BEAMPIPE

BEAMPIPE
VTX

VTX

Version 1: March 1, 2014

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201418 /20Projections for BES-II; fluctuations
Higher order cumu
Physics Goals for the BES II

Fluctuations
andAnalysisof Higher
Moments
The Beam Energy
Scan at theRelativistic
Heavy
Ion CollidersPHENIX
Net-proton
Au+Au 0-5% Central

STAR

curr
achi

κσ2

1

0.5
sPHENIX 2019 BES-2
UrQMD
STAR 2010-11 BES

0

10

2

10
Beam Energy (s1/2)
NN

Figure 26. Collision energy dependence of net-proton ks2 from central 0-5% (filledth4oFigure 3.3: Estimates for sPHENIX sensitivity
to measurementof net proton
for Auerror+Au
70-80% (open-squares)
Au+Au collisions
at RHIC.ks
The2 verticalbars are statisticalpcorrespondto systematic
errors.andThe yellow
solidband represents
central Au+Au
collcollisions as a function of s NN are shownon theleft panel,similarestimatesfor 0-5%STAR
futu
from UrQMD
simulations. The
shaped bandshows
the estimatedare shown on the right panel. Both estimates
are compared
thegreen
publishedSTAR
results
from statistical errors
8th oassuming the requested events listed in Table 2.
the first beam energy scan. See text forPhase-II,details.

• Net-proton moments‣ By a factor of 2-4 improvements on statistical precision below 20 GeV

statisticalerrors for
sPHENIX(withTPC)InandSTAR
3.5.1‣ Similar
Net Proton
Fluctuations
increased
sensitivity to
the criticality.
addition,
we will also study the higher m
the net-kaons.

With the benefit of a TPC, describedH.inMasui
Section
2.4,
sPHENIX
will Hawaii,
have Octthe7-11,capability
to 19 /20
/ Univ. of
Tsukuba,
APS-DNP/JPS
2014

Summary• Success of RHIC Beam Energy Scan phase-I‣ Several observables show a hint of possible turn-off signature of QGP- Turn-off/onset of QGP ? → BES phase II, future FAIR, J-PARC heavy ion programs‣ Non-monotonic behavior of directed flow and asHBT radii- 1st order phase transition ? → Quantitative and systematic model comparisons‣ Possible non-monotonic behavior of conserved charge fluctuations- QCD critical point ? → Precision measurements & Lattice QCD calculation• We need precision measurements below 20 GeV‣ BES phase-II in 2018, 2019

‣ Significant improvements on statistical precisions by RHIC luminosity& sPHENIX/STAR detector upgrades‣ BES-II white papers- sPHENIX: http://www.phenix.bnl.gov/phenix/WWW/publish/dave/sPHENIX/
BES_II_whitepaper.pdf- STAR: https://drupal.star.bnl.gov/STAR/system/files/BES_WPII_ver6.9_Cover.pdf
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201420 /20Back up

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201421 /200 0.5 1 of
1.5 v220 for
0.5 anti-particles
1 1.5 2 0 0.5 1 1.5
NCQ scaling(m -m )/n (GeV/c )T(b)0.1 7.7 GeV

Au+Au, 0-80%
η-sub EP

0

2

q

2

STAR: PRC88, 014902 (2013)11.5 GeV

19.6 GeV

39 GeV62.4 GeV

v2/nq

0.05
0
0.1 27 GeV
0.05
0
0

0.5

1

1.5

20

0.5 1 1.5 2 0(m -m0)/nq (GeV/c2)

0.5

1

1.5

2

T

. (Color online) The NCQ-scaled elliptic flow, v2 /nq versus (mT − m0 )/nq , for 0%–80% central Au + Au collisions for) and corresponding antiparticles (b). Only statistical error bars are shown. The dashed lines show the results of simultan7) to all particles except the pions.
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201422 /20CME signal

STAR: PRL103, 251601 (2009), PRL113, 052302 (2014),
PRL110,(2014)012301 (2013)
PHYSICAL REVIEWPRLALICE:
113, 052302
60 - 80%
50-5UrQMD (κ =1)

104 × (HSS - HOS)

-10
2

κ=1
κ = 1.5
κ=230 - 60%

1

0

Au+Au

-1

Pb+Pb

10 - 30%

LETTERS

week ending
1 AUGUST 2014

increase the statistics by a factor of 10 for the low energies
and if we can reduce the uncertainty associated with
κ. )i = v2 F⌘determination
hcos ( 1 of
+ the2value2of RPH,
thankOperations Group and RCF at BNL,
⌘ We
hcos
( 1the RHIC
2 )i = F + H,
the NERSC Center at LBNL, the KISTI Center in Korea,
andCMEthe Open
Science Grid consortium for providingH:
contribution,
resources and support. This work was supported in partFby
: backgroundcontribution,
: parameter
the Offices of NP and
HEP within the U.S.
DOE, Officeof Science; the U.S. NSF; CNRS/IN2P3; FAPESP CNPq of
Brazil; the Ministry of Education and Science of theRussian Federation; NNSFC, CAS, MoST, and MoE ofChina; the Korean Research Foundation; GA and MSMT of
the Czech Republic; FIAS of Germany; DAE, DST, andCSIR of India; the National Science Centre of Poland;
the National Research Foundation (NRF-2012004024); theMinistry of Science, Education and Sports of the Republicof Croatia; and RosAtom of Russia.

• Decompose measured correlation
to CME (H) and background (F)contributions

0.5

0- based on A. Bzdak et al, Lect. Notes Phys.

[1]871,
C. Vafaand(2013)
E. Witten, Phys. Rev. Lett. 53, 535 (1984).
503[2] T. D. Lee, Phys. Rev. D 8, 1226 (1973).
sNN (GeV)
T. D. Lee and
C. Wick, Phys.
Rev. D 9, 2291 (1974).
assumeγ isG. linearly
proportional
to v2
‣ [3]
[4] D. E. Kharzeev, L. D. McLerran, and H. J. Warringa, Nucl.
FIG. 4. HSS − HOS , as a function of beam energy for three
Phys. A803, 227 (2008).
centrality bins in Au þ Au collisions. The default values (dotted[5] D. Kharzeev, Phys. Lett. B 633, 260 (2006).
curves) are for Hκ¼1, and the solid (dash-dotted) curves are[6] D. Kharzeev and A. Zhitnitsky, Nucl. Phys. A797, 67
obtained with κ ¼ 1.5 (κ ¼ 2). For comparison, the results for
H. Masui
Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201423 /20Au þ Au collisions at 200 GeV [11] and Pb þ Pb collisions
at / Univ. of(2007).
10

102

10

3

two highest energies. The initial states in the PHSD andand 200 GeV). However, v1 (y) for antiprotons agrees with the
HSD are simulated on an event-by-event basis taking into
data only for the highest energies where baryon-antibaryon
account fluctuations in the position of the initially colliding
pairs are dominantly produced by hadronization. This becomes
nucleons and fluctuations in the reaction plane. This procedureevident from a comparison to the HSD results with v1 (y) ≈ 0.
is identical to that in the study of the elliptic flow in Ref. [44].
The shape of the v1 (y) distribution for antiprotons starts
The average impact parameter for the selected events is
progressively
to differ from the measured data if we proceed√b = 7 fm. In the simulations the experimental acceptancefrom sNN = 11.5 to 7.7 GeV. In the lower energy range
NATIONDIRECTED. . . [39].
PHYSICAL
014903(2014)
P.T THE
Konchakovski
etPUZZLEal, for
PRC90,
014903(2014)
0.2V.
!OF
p
!
2 GeV/cis takenFLOW
into accountallIN
hadrons
DIRECTED
FLOW
AS C
A 90,
SIGNALFOR...
the EXAMINATION
HSD and PHSD OF
results
get very REVIEW
close whichindicates

Directed flow, model calculations
proton b = 2 fm
Au+Au,

pion π-antiproton

0.02

200 GeV

0.02
0
-0.02

p
p
π+
π-

v1

30 40 50 6070

v1

62.4 GeV

0.02
03FD: crossover
39 GeV 3FD: hadrons

-0.02

1

0

-0.02

4

5 6 7 8 910

20sNN [GeV]
27 GeV. (Color online) Particle abundance at midrapidity calcucentral
0.02 collisions (b = 2 fm) in the 3FD model with anpure hadronic
phase (dashed lines) and for the case of a0transition(solid lines). The experimental data are the same
-0.02
19.6 GeV
1.
0.02

-0.02

v1 (y) = F y + Cy 3 ,

STAR
STAR

(2)

7.7an
GeV
to 0.02
obtainestimate of the uncertainty in extracting thecoefficient F . The error bars in Fig. 3 just stem from the0
different fitting procedures. Note that the energy axis
√ in Fig. 3
is -0.02
extended by adding experimental results for sNN = 62
and 200 GeV [39]. This representation is more delicate as-0.04
compared
to v1 (y)0 in Fig.1 2. For-1protons-1
0 there 1is a qualitative-1
0
1
agreement of the yHSD and PHSD results
withtheexperimentyymeasurements: the slope F > 0 at low energies, however,exceedingthe experimental
values bydistributions
up to√a factorofofthe
about
FIG. 8. (Color
online) Rapidity
directed flow
2; the slope crosses the line F = 0 at sNN ∼ 20 GeV,
for
protons, antiprotons, and positive and negative pions from 10
which is twice larger than the experimental crossing point,
toand
40%
centralAu+online)Auand
collisions
differentenergies
FIG.
6. (Color
Slope
v1 of
(a) negatively
charged
pions
then
stays
negative
almostof atconstant
withcollision
further
calculated
withinthe
3FDmodel.
The
experimental
data
are
from
the
and
(b)
protonsandantiprotons
aroundmidrapidity
extracted
fromenergy increase. However, the absolute values of the calculated
theCollaboration
hybridinmodel
calculations
with
a bag
model
crossoverSTAR
The
dashedlines
correspondtoofa hadronic
protonslopesthis[39].
highenergyrange
areon theleveland−(0.01–0.02),
while
the
measured
ones
are
about
−0.005.
The
EOS.
We
comparewithstandard
UrQMD
andexperimental
data
EoS while the solid lines stand for a crossover transition.
standard
UrQMD model results, as cited in the experimental[11,12,23].
paper [39] and in the more recent theoretical work [40], aredisplayed inaccurate
Fig. 3 by calculations
the wide and requirenarrow shaded
areas, memory
Therefore,
very high
The fulldependence
the from
model
respectively.
Thesebeam
resultsenergy
for protons
are close forto those
and
CPU
time
and,
accordingly,
calculations
for hybrid
a first-orderthe results
HSD model
andmidrapidity
essentially overestimate
thenegatively
slope for chargedof thev1 slopes fortransition
EoS∼30have
notbeen completed
yet. In
particular, forenergiesGeV
butenergy are
becomenegativepionsbelow
and protons
andat higher
antiprotons
shown
in Figs. 6(a)

v1

-0.02

0.02
3

pions

v1

0

STAR
PHSD
HSD

the dominance of hadronic reaction channels (absorption andrecreation).
The direct flow distributions for negative and0.04
positive pions are close
to each other andantiprotons
also begin to disagree
protons0.02
withexperiment in theSTAR
same range of low STAR
collision energies as
for antiprotons
(see
Fig.
2).
Again
the
PHSD
results are very0close to the experimental measurements at higher energies-0.02the 27
while
HSD
GeVresults deviate more sizeably, thus stressing
the role of partonic degrees of freedom in the entire collision
dynamics. The clear
overestimation of the p̄ and π − slopes at
19.6 GeV√
s0.02
NN = 7.7 GeV demonstrates that the heavy-ion dynamics
is not 0yet fully understood within the string/hadron picture at
the lower energies.
-0.02
The characteristic slope of hadronic
the v1 (y) distributions at
1
midrapidity, dv
|
=
F
,
is
presented
in Fig. 3 for all cases
crossoverdy y=0considered in Fig. 2. In a first approximation the v1 flow in the
0.02 11.5 GeV
center-of-masssystem may be well fitted by a linear function
v1 (y) 0= F y within the rapidity interval −0.5 < y < 0.5. A
cubic equation is also used,

J. Steinheimer etPHYSICAL
al, PRC89,054923(2014)
REVIEW
C 89, 054913(2014)

FIG. 7. (Color online) Comparison of results for pure hydro andhybrid model calculations with a first order EOS. Shown is the slopeof v1 of protons and antiprotons around midrapidity compared toexperimental data.

from below. Also the overall magnitude seems to be strongly
experimental
data and, in the case of charged pions, in0overestimated.
er agreement
than in the HSD and PHSD approaches
-0.02
GeV
1). The purely hadronic11.5EoS
definitely overestimates
V. DISCUSSION
0.02yield at midrapidity in this energy range, whileroton
0with thecrossover transition quite reasonably agrees
As observed in previous studies [21,24–26], the hybrid-0.02
experimental data. Notethat the antiprotons aremodel (and to some extent also standard UrQMD) usually
7.7 GeVproduced
fluid0 [29].
shows a reasonable agreement with experimental particle-1 from-0.5 0 the
0.5 fireball1 -1 -0.5 (baryonless)
0 0.5 1 -1 -0.5
0.5 1
y
y
y
spectra, as well as the second and third order flow coefficients,
tain extent, this may be interpreted as being due toat the energies investigated in this article. Furthermore, it has
son formationof ponline)p̄ in equilibriumin analogy
HSDanFIG. 2. (Color
The directed flowv1 (y) for to
protons,
been shown [6,27–29] that fluid dynamical simulations can
SD approaches
these
are central
not inAufull
tiprotons as wellwhereas negative
pionschannels
from 10 to 40%+ Au√
quite successfully account for the rapidity-even v1 moment,sNN = 7.7
to 200 GeV
at different collisionenergiesfrom EoS’s
um.collisions
The difference
betweenthe twois clearly√ lines)from HSD (dashedand PHSD (solid lines). Experimental data
which is caused by initial state fluctuations.
igher energies sNN ! 20 GeV, where the crossover
are from the STAR Collaboration [39].
The strong deviation of the directed flow of all models, asavorable for all hadronic species rather than only forthe samereasonwehavefailedso
far
to
perform
calculations
and 6(b), respectively.
Both proton and antiproton slopes arecompared to data, noted in the previous section is therefore√¯ "¯ + ) as pointed out in Ref. [70].
ons (p̄,!,for energies
abovefor thesNNwhole= 30examined
GeV. Notethat thechangeof014903-4
overestimatedcollisionenergyrange,
surprising and requires a further discussion about the possible
otherwhileobservables,
analyzedsofar[69–72],
is
below
15%
as
dv1 /dy|y=0 for pions agrees withsources of differences in the v1 extracted from the model as√ the data at lower
comparedtoresultsofprevious
calculations.
B. Directed flow in the 3FD model
collision energies but changes sign at sNN ≈ 10–15 GeV,
compared to the experiment.
The
directed
flow
v
(y)
as
a
functionofrapidityyatwhich is not supported1 by the STAR data. While the difference
One particular difference, for example, lies in the determient works [69–72] an analysis of the major part of bulk
BES-RHIC
bombarding
energiesispresented
in
Fig.
8
for
betweentheinvestigatedequations
of
state
was
alreadyrathernationof the reaction
plane angles
les has been performed: the baryon stopping [69],
H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii,
Oct 7-11,2014 !RP used in Eq. (2). In• PHSD (or HSD) vs hydro with hadronic,
crossover EOS• Hybrid (UrQMD IS + Hydro + UrQMD
hadronic phase) vs hydro only withdifferent freeze-out

24 /20includes four weeks of full energy running split into two weeks of Au+Au and two weeks
of p+ p running. Running at 5 GeV is given a very low priority since a useful data set
would require an impractically long running time. It would take 218 days of running time
to record only 10 million events. Therefore, running at 5 GeV is not included in Table 4.2.

Beam time request for BES-IIAs detailed in Section 3.7, we request a short, of order two weeks, of running for p+ p andpAu+Au at s NN = 200 GeV. This critical pilot data taking would come at a small cost in
running time and help ensure a fully successful program for the full sPHENIX starting in
2021.

PHENIX

Table 4.2: An outline of the PHENIX run request for the BES II program. The running timeis integrated to cover a single year of RHIC running that spans 22 cryo-weeks, or 19 weeksof physics running depending on ramp-up and switching times. Higher priority is given
to the data sets listed first. The number of events refers to good events within the baselinesPHENIX configuration requiring |zvertex | < 10 cm including the PHENIX and RHIC duty
factor. Also included are event estimates with a wider |zvertex | < 30 cm and |zvertex | < 1 m
cut that could be applied if a TPC is installed.

Species

p

s NN

µB

(GeV) (MeV)

Au+Au

p+p

Run Time

Events(M)Events(M)(Days)|zvtx | < 10cm |zvtx | < 30cm |zvtx | < 1 m

315

45

15

45

112.5

13.0

281

23

17

50

125

9.0

376

41

6

17

42.5

19.6

205

4

33

100

2500

200

20

10

1200

3600

9000

10

1.2 pb 1

3.6 pb 1

9 pb 1• Focused on √s

44

STAR

Table 3. Beam Energy Scan Phase-II proposal for 22 weeks of RHIC running in each of the years
2018 and 2019.

Events(M)

11.5

200

The Beam Energy Scan at the Relativistic Heavy Ion Collider

Collision Energy (GeV)µB (MeV) in 0-5% Central Collisions
BES-I (Million Events)
BES-I Event Rate (Million Events/Day)
BES-I Int. Luminosity (1⇥1025 /cm2 s)
e-Cooling Luminosity Improvement Factor
BES Phase-II (Million Events)
Required Beam Time (Weeks)

7.7
420
4
0.25
0.13
4
100
14

9.1
370
–
0.6
0.5
4
160
9.5

11.5
315
12
1.7
1.5
4
230
5.0

14.5
260
20
2.4
2.1
8
300
2.5

19.6
205
36
4.5
4.0
15(4)
400
4.0+

measurements down to the region of the expected highest baryon density, which would be acollision energy of about 8 GeV.
The above paragraph outlines our best understanding of the most important energy ranges
and the necessary energy step sizes. The previous Section (3.1) detailed the required statistics
for the key measurements at each proposed energy. It is assumed that there will be 22
cryo-weeks of RHIC running in each of the years 2018 and 2019. Based on these goals,
requirements, constraints, and assumptions, we have developed a proposal for the BES PhaseII which is summarized in Table 3. The proposed number of weeks of RHIC running at 7.7
GeV has been estimated by considering the corresponding average event rate in the final week
25 of BES-I operations, BES-I luminosity, an electron cooling luminosity improvement factor
mid-way between the optimistic and pessimistic estimates (see Section 3.5), and the numberof events required for the physics program as per Table 2. The proposed number of weeks forbeam energies of 11.5 and 19.6 GeV are obtained using the average numbers for event rate andluminosity over the entire collider running period, and the event statistics as desired in BES
Phase-II (Table 2). There is an additional uncertainty on the rate estimates for the 19.6 GeV
system, and that arises because without an improvement to the trigger, the raw data rate will
exceed the limits of the STAR DAQ system. The situation should be significantly improved
with the help of the cleaner beam after electron cooling, and with the help of the Event Plane
Detector (EPD) upgrade described in Section 3.6. The numbers of weeks proposed for RHIC

NN < 20 GeV‣ One year (2019) request from PHENIX‣ Two year (2018, 2019) request from STAR

H. Masui / Univ. of Tsukuba, APS-DNP/JPS Hawaii, Oct 7-11, 201425 /20BES-II projections
The Beam Energy Scan at the Relativistic Heavy Ion Collider

33

Rcp

Energy Scan at the Relativistic Heavy Ion Collider

The Beam Energy Scan at the Relativistic Heavy Ion Collider

34

v2

35

Figure 21. Number of constituent quark (NCQ) scaled event anisotropy parameter (v2 ) for identified
The Beam
EnergyScanfromat theRelativistic
Heavy
Ion Collider
hadrons, including the f-meson(filledcircles)minimumbias(0-80%)
Au+Au collisions at 7.7
Figure 20. The BES-I RCP data are are shown for p, K, and p for 7.7, 11.5, and 19.6 GeV. The BES
GeV (left) and 11.5 GeV (right). The projections of the statistical errors for the f-meson v2 , from BES
Phase-II projected error bands are for the same energies, 7.7 (red, scaled by 10), 11.5 (blue, scaled by
Phase-II are shown by the shaded bands in both plots. The shapes of the kaon v2 (pT ), dashed line,
60 - 80%dN/dy|/ 10552.8 57.6 60.8 77.2
100), and 19.6 (green, scaled by 1000).
5
4.5
were
used
in
the
estimation.
The Beam Energy Scan at the Relativistic Heavy Ion Collider
37

Di-lepton LMR excess

charge separation

0

LMR Excess Yield / dN/dy|/ (× 10-5)

Directed flow

κ=1

4

BES-II extrapolation
model expectation at BES-II
data

SS

- HOS) × 104

3.5
errors are displayed in Fig.
κ =20
1.5as colored bands. For clarity of presentation, the projected-5
error bands are scaled by κ10= 2(for 7.7 GeV), 100 (for 11.5 GeV), and 1000 (for 19.6 GeV). used in the estimation. As shown in Table32, 100M and 200M useful minimum bias eventsBES II error projection
The-10 error bands are truncated when the error reaches 50%; this represents the expected high are requireded from the Au+Au collisions at 7.7 and 11.5 GeV, respectively. The shape of the
2.5
pT2 limit for each measurement. For intermediate energies the expected error bands can be kaon v is assumed for the estimation up to p ⇡ 3 GeV/c where the scaling has been observed
30 - 60%
2
2Tinterpolated. It is also of interest to consider the inclusive charged hadron RCP measurementin high-energy nuclear collisions at the RHIC energies [34] in both plots. These measurements
1
1.5
(Fig.
12). We have also projected the expected error in BES Phase-II for this measurement,
will
answerdecisively
thequestionhowmuch
f meson flow there is compared to that of lighttherefore, we can report the high pT limits for the inclusive charged hadron RCP are found to1
quark hadrons. Lack of the collectivity of the f meson will provideof 2the
LMR: clear
0.30 < Mevidence
be0 5.2, 5.7, and 6.5 GeV/c for the 7.7, 11.5, and 19.6 GeV systems, respectively.
ee < 0.70 GeV/c
0.5(H

200 GeV: [arXiv:1312.7397]
hadronic interaction dominated medium in the low energy heavy ion
Moreover,
BES: collisions.
STAR Preliminary
Au+Au
Pb+Pb
0
-1
parametersfor40multi-strange
3.1.2. The v2 of f mesons and NCQ scaling for indentified particles This measurement will with such statistics, information of the event anisotropy
7
10
20
60
100hadrons,
200
allow us to quantitatively address10thesuspected
decrease,followedbyanabsence,ofpartonic- 30%such as X and W, can also be extracted.
3sNN (GeV)p

0.5
collectivity
below sNN = 19.6 GeV. High-statistics data with a new event plane detector (asFigure 23.toLeft
panel:
Statistical errorsup
withdiscussed below in section 3.6) are required. It is necessary
makemeasurements
to narrowpT centrality bins for proton dv1 /dy near midrapidity
Three-particle correlators related to CME/LPV These measurements will allow us toat two sample beam energies for BES-I data sets 3.1.3.
= 03 GeV/c with a statistical error of less than 10% on
v2 . From this resolution requirement (blue error bars; the points are arbitrarily placed at
dv1 /dy = 0) and with the proposed BES Phase-II data sets (black error bars). RightFigure
panel:ofThe
same,
27.
This
plot summarizes
our current measurements.
data points
are thetheturn-off
of CME/LPV-like
effects at 7.7TheGeV.
In orderto integral
we can estimate the statistics necessary (see Table 2) for BES Phase-II to reach transverse corroborate the observation
2
but for net-protons.
excess(data-cocktail)and 700
the measured
p multiplicity
foon themeasuredbetween
CME300signalHSSMeV/c
HOSnormalized
by a factor
3 as showninmomenta beyond 2.5 GeV/c even at the lowest energies. This will allow us to test in NCQ reduce the statistical error
minimum-bias events. The grey dotted line below 20 GeV indicates the average normalized eFig. 22, we propose to increase
the event statistics by factors of ten and four at 7.7 and 11.5
scaling10detail for many 10particle species,10including multi-strange particles.
sNN (GeV)
while the grey band indicates the projected uncertainty in the proposed BES Phase-II measurem
The projection of the statistical errors for the f meson
for BEStoPhase-II
areifshown
it is notv2possible
determine
there isbyany
minimum
at all, muchlessrequires
identify where
GeV,
respectively.
This⇠ 50M events for each beam energy (see Table 2).
The purple dotted line shows the expected increase by a factor of two in normalized excess yieldtheshaded
bands
in
both
plots
in
Fig.
21.
The
shapes
of
the
kaon
v
(p
),
dashed
line,
were
it
might
lie
along
the
beam-energy
axis,
for
eithercentralor
peripheral
collisions.
T
2 errorH. Masui / Univ.
of Tsukuba,
Hawaii,Oct 7-11,effect2014(CSE) has also been
The (HH ) difference as a function of beam energy is now shown with
Besidesthe chiral APS-DNP/JPS
magneticWith
effect, thechiral separation
2

SS

OS

3

26 /20