Directed Flow in STAR Fixed target Experiment€¦ · X. Luo, J. Phys.: Conf. Ser. 599, 012023...
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Results (GeV) NN s 3 4 5 6 7 10 20 30 y=0 /dy | 1 dv 0 0.1 0.2 0.3 10-40 % Λ Λ p p + K - K s 0 K φ (FXT) Λ (FXT) s 0 K p (FXT) p (E895) (FXT) + π (FXT) - π Directed Flow in STAR Fixed target Experiment D. Tlusty, for the STAR Collaboration The STAR Collaboration drupal.star.bnl.gov/STAR/presentations Abstract Some QGP signatures, such as number-of-constituent-quarks scaling of v 2 , can be seen to persist down to √s NN = 7.7 GeV, while others, such as suppression R CP , show a turn-on behavior. Fixed target collisionsin STAR allow the center- of-mass energy to go as low as 4.5GeV. This would provide an opportunity to measure such signatures down to an energy range that can serve as a clean "control" energy in which only a pure hadron gas is expected. In this poster we will present Directed flow of strange hadrons K 0 S and . References [1] L. Adamczyk et al . (STAR Collaboration), Phys. Rev. Lett. 112, 162301 (2014) [2] A. M. Poskanzer, S. A. Voloshin, Phys. Rev. C 58, 1671 (1998) [3] P. Chung et al . (E895 Collaboration), Phys. Rev. Lett. 86, 2533 (2001) Motivation STAR Beam Energy Scan (BES-I) results suggest a softening of the equation of state (EOS) which hints at critical fluctuations To help clarify these hints, STAR needs to access energies below 7.7 GeV where we expect no QGP formation Hence we need to switch from the collider mode to fixed-target mode for collisions below √s NN < 7.7 GeV at RHIC Goals of Beam Energy Scan 1) Observe the disappearance of QGP signatures 2) Find evidence of the possible first-order phase transition 3) Find the possible Critical point Directed Flow Experimental Setup First directed flow v 1 results of 2015 STAR Fixed target test run were presented. v 1 of both K 0 S and Λ follow the trend from the STAR Beam Energy Scan. v 1 of protons is consistent with the trend from E895 experiment [3] The FXT program extends BES-II down to √ = 3.0 GeV 9 e - e + π - π + K + K - t d p 3 He e - e + π - π + K + p d t Directed flow describes the sideward motion of the particles within the reaction plane Generated during the nuclear passage time (2R/γ ≈ 0.1 fm/c) Therefore probes the very earliest stage of the collision dynamics Calculated as Particle Identification (PID) with STAR Time Projection Chamber (TPC) and Time of Flight (TOF) - outstandingfor FXT The target foil was held 2 cm below of the beam axis The foil was 1 mm thick Event Plane Reconstruction [2] = tan -1 Q centered y Q centered x ! Q x = X i (y lab - y c.m. )p (i) T cos φ (i) Q y = X i (y lab - y c.m. )p (i) T sin φ (i) A Ψ 3 − 2 − 1 − 0 1 2 3 0 20 40 60 80 100 v observed 1 = hcos(φ - A corrected )i centering ⌦ cos( A - R ) ↵ = s ⌦ cos( A - B ) ↵⌦ cos( A - C ) ↵ hcos( B - C )i Event Plane Resolution = 0.85 ± 0.03 for K 0 S (10-25%) = 0.81 ± 0.03 for Λ (10-30%) CM y 1 − 0.5 − 0 0.5 1 1 v 0.6 − 0.4 − 0.2 − 0 0.2 0.4 0.6 CM y 1 − 0.5 − 0 0.5 1 1 v 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0 0.1 0.2 0.3 0.4 0.5 v 1 = v observed 1 hcos( A - R )i K 0 S (10-25%) Λ(10-30%) K 0 S or Λ taken from Subevent B Summary STAR Preliminary STAR Preliminary STAR Preliminary STARPreliminary STARPreliminary φ angle in LAB R Reaction Plane angle v 1 = hcos(φ - R )i Event plane reconstructed from protons and deuterons from Subevent A Flattening using Fourier expansion v 1 of Both K 0 S and Λ follow the trend from the STAR Beam Energy Scan and protons are consistent with the trend from E895 [3] Open symbols are reflected Open symbols are reflected Fitting range Y = 0 - 1.5 Fitting range Y = 0 - 1.5
Transcript of Directed Flow in STAR Fixed target Experiment€¦ · X. Luo, J. Phys.: Conf. Ser. 599, 012023...
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Results
(GeV)NNs3 4 5 6 7 10 20 30
y=0
/dy
|1
dv
0
0.1
0.2
0.3
10-40 %
Λ Λ p p
+ K - Ks0 K φ (FXT)Λ (FXT)s
0 Kp (FXT) p (E895)
(FXT)+π (FXT)-π
DirectedFlowinSTARFixedtargetExperiment
D. Tlusty, for the STAR Collaboration
The STAR Collaborationdrupal.star.bnl.gov/STAR/presentations
AbstractSomeQGPsignatures,suchasnumber-of-constituent-quarksscalingofv2,canbeseentopersistdownto√sNN =7.7GeV,whileothers,suchassuppressionRCP,showaturn-onbehavior.FixedtargetcollisionsinSTARallowthecenter-of-massenergytogoaslowas4.5GeV.Thiswouldprovideanopportunitytomeasuresuchsignaturesdowntoanenergyrangethat canserveasaclean"control"energyinwhichonlyapurehadrongasisexpected.InthisposterwewillpresentDirectedflowofstrangehadronsK0S and.
References[1] L. Adamczyk et al. (STAR Collaboration), Phys.Rev.Lett.112, 162301(2014)[2] A. M. Poskanzer, S. A. Voloshin, Phys. Rev. C 58, 1671 (1998)[3] P. Chung et al. (E895 Collaboration), Phys. Rev. Lett. 86, 2533 (2001)
Motivation
STARBeamEnergyScan(BES-I)resultssuggestasofteningoftheequationofstate(EOS)whichhintsatcriticalfluctuations
Tohelpclarifythesehints,STARneedstoaccessenergiesbelow7.7GeV whereweexpectnoQGPformation
Henceweneedtoswitchfromthecollidermodetofixed-targetmodeforcollisionsbelow√sNN <7.7GeV atRHIC
Goals of Beam Energy Scan1) Observe the disappearance of QGP
signatures 2) Find evidence of the possible first-order
phase transition 3) Find the possible Critical point
Directed Flow
Experimental Setup
Firstdirectedflowv1 resultsof2015STARFixedtargettestrunwerepresented.
v1ofbothK0S andΛ followthetrendfromtheSTARBeamEnergyScan.
v1ofprotonsisconsistentwiththetrendfromE895experiment[3]
TheFXTprogramextendsBES-IIdownto√𝑠𝑁𝑁 =3.0GeV
Why a Fixed-Target (FXT) Program?¾ STAR Beam Energy Scan (BES-I) results suggest a
softening of the equation of state (EOS) and hints at critical fluctuations
¾ To help clarify these hints, STAR needs to access energies below 7.7 GeV where we expect no QGP formation
¾ At these lower energies the luminosity of RHIC is too low, making it impractical to take data in collider mode
3Kathryn Meehan -- UC Davis -- RHIC & AGS Users Meeting 2016
The goals of BES-I:1) Observe the
disappearance of QGP signatures
2) Find evidence of the possible first-order phase transition
3) Find the possible Critical Point
X. Luo, J. Phys.: Conf. Ser. 599, 012023 (2015). [arXiv:1501.03010].
P. Shanmuganathan for the STAR Collaboration, Quark Matter 2015.
Gold Target Installed for Run 14Run 14 details:
¾ Fixed Target 3.9 GeV data taken concurrently with 14.5 GeV Au + Au collider events
¾ The target foil is held 2 cm below of the beam axis. ¾ The foil is 1 mm thick (4%).
8Kathryn Meehan -- UC Davis -- RHIC & AGS Users Meeting 2016
Out of time pile-upof electron-capture Au halo nuclei
Gold Target Installed for Run 14Run 14 details:
¾ Fixed Target 3.9 GeV data taken concurrently with 14.5 GeV Au + Au collider events
¾ The target foil is held 2 cm below of the beam axis. ¾ The foil is 1 mm thick (4%).
8Kathryn Meehan -- UC Davis -- RHIC & AGS Users Meeting 2016
Out of time pile-upof electron-capture Au halo nuclei
Directed%Flow%(v1)%
• Directed%flow%describes%the%sideward%mo1on%of%the%par1cles%within%the%reac1on%plane%
• Generated%during%the%nuclear%passage%1me%(2R/γ%≈%0.1%fm/c)%
• Therefore%probes%the%very%earliest%stage%of%the%collision%dynamics%
v1 = cos! ! !"RP( )
4%
3.9 GeV Au + Au Test Run
9Kathryn Meehan -- UC Davis -- RHIC & AGS Users Meeting 2016
Excellent PID with Time Projection Chamber (TPC) and Time of Flight (TOF) detectors for fixed target events
e- e+
π- π+
K+
p
dt
e- e+
π-π+
K+
K-
td
p
3He
3.9 GeV Au + Au Test Run
9Kathryn Meehan -- UC Davis -- RHIC & AGS Users Meeting 2016
Excellent PID with Time Projection Chamber (TPC) and Time of Flight (TOF) detectors for fixed target events
e- e+
π- π+
K+
p
dt
e- e+
π-π+
K+
K-
td
p
3He
Directedflowdescribesthesidewardmotionoftheparticleswithinthereactionplane
Generatedduringthenuclearpassagetime(2R/γ ≈0.1fm/c)
Thereforeprobestheveryearlieststageofthecollisiondynamics
Calculatedas
ParticleIdentification(PID)withSTARTimeProjectionChamber(TPC)andTimeofFlight(TOF)- outstandingforFXT
Thetargetfoilwasheld2cmbelowofthebeamaxisThefoilwas1mmthick
Event Plane Reconstruction [2]
= tan�1
Qcentered
y
Qcenteredx
!
Qx
=
X
i
(ylab � yc.m.
)p(i)T
cos �(i)
Qy
=
X
i
(ylab � yc.m.
)p(i)T
sin �(i)
Psi1AEntries 24173Mean 0.009859Std Dev 1.814
/ ndf 2χ 330.4 / 307Prob 0.1714
AΨ3− 2− 1− 0 1 2 30
20
40
60
80
100
Psi1AEntries 24173Mean 0.009859Std Dev 1.814
/ ndf 2χ 330.4 / 307Prob 0.1714
vobserved
1
= hcos(� � Acorrected
)i
centering
⌦cos(
A � R)
↵=
s⌦cos(
A � B)
↵ ⌦cos(
A � C)
↵
hcos(
B � C)i
EventPlaneResolution
=0.85± 0.03forK0S (10-25%)= 0.81± 0.03forΛ (10-30%)
CMy
1− 0.5− 0 0.5 1
1v
0.6−
0.4−
0.2−
0
0.2
0.4
0.6CMy
1− 0.5− 0 0.5 1
1v
0.5−0.4−0.3−0.2−0.1−0
0.10.20.30.40.5
v1
=
vobserved
1
hcos(
A � R)i
K0S(10-25%)
Λ(10-30%)
34th
Reimei Workshop
J-PARC, Tokai, Japan
Daniel Cebra
08/August/2016 Slide 22 of 31
Fixed-Target Program 3.0 to 7.7 GeV
The Fixed-Target Program
will extend the reach of
the RHIC BES to higher B.
Goals:
1) Search for evidence of
the first entrance into
the mixed phase
2) Control
measurements for BES
collider program
searches for Onset of
Deconfinement
3) Control
measurements for
Critical Point searches
K0S orΛ takenfromSubeventB
Summary
STARPreliminary
STARPreliminary
STARPreliminary
STARPreliminary
STARPreliminary
� angle in LAB
R Reaction Plane angle
v1 = hcos(� � R)i
EventplanereconstructedfromprotonsanddeuteronsfromSubeventA
FlatteningusingFourierexpansion
v1ofBothK0S andΛ followthetrendfromtheSTARBeamEnergyScanandprotonsareconsistentwiththetrendfromE895[3]
Opensymbolsarereflected
Opensymbolsarereflected
FittingrangeY=0- 1.5
FittingrangeY=0- 1.5
