star fixed-target results from = 4.5 gev au+au and · 2017-09-26 · star fixed-target results from...

STAR Fixed-Target Results from 𝑺𝑵𝑵 = 4.5 GeV Au+Au and 𝑺𝑵𝑵 = 4.9 GeV Al+Au Collisions

Muhammad Usman AshrafFor the STAR Collaboration

Tsinghua University, Beijing, P. R. China

September 23 Muhammad Usman Ashraf 1

Outlineq Goals of the BES-I Programq Physics Motivation of FXT program.q Introduction to the Fixed-Target (FXT)

Programq Results from Au+Au FXT Collisions

at 𝑆$$ = 4.5 GeV q Results from Al+Au FXT Collisions

at 𝑆$$ = 4.9 GeVq Future upgrades and the FXT programq Summary


STAR: arXiv:1007.2613

Goals of the BES Program


qBES phase I at RHICØStudy the onset of de-

confinement and phase boundary

ØSearch for the QCD critical point

ØTurn-off of QGP signalsØSoftening of the equation of

stateØFind evidence of the

possible first-order phase transition

qSystematic study of Au+Au collisions at 7.7, 11.5, 14.5, 19.6, 27, 39 GeV(BES Phase-I)

Motivation for the Fixed-Target Program


q NA49 has reported that the onset of deconfinement may occur at 7 GeV, the low end of BES range.

q How to achieve low energy?

Ø By installing a target inside the beam pipe and using RHIC beam as a projectile.

Ø It can extend the µ& range from 400 MeV to about 720 MeV

Ø Provide control measurements for searches of the critical point and onset of deconfinement

Need to probe lower energies!

M. Stephanov. J. Physics G.: Nucl. Part. Phys. 38 (2011) 124147 Need

datahere!

STAR PRELIMINARY

FXT

κσ2

Preliminary HADES result, Quark Matter 20170-10%(QM 2017)

Systematic uncertainties included

à FXT measurements needed to determine shape of kσ2

observable at lower energies

5

Peak behavior predicted in critical region:

Control Measurements for CEP Signatures

September 23 Muhammad Usman Ashraf

àGold foil is 1mm thick with about a 4% interaction probability

à1.3M Au+Au events with top 30% centrality trigger

àtarget is outside of the STAR TPC at ~211 cm

Fixed-Target Geometry


Results from FXT Au+Au Collisions

at 𝑺𝑵𝑵 = 4.5 GeV


Centrality Determination for Au+Au Collisions at 𝑺𝑵𝑵 = 4.5 GeV

Top5%

q nGoodTracks are those tracks which pass through basic QA cuts.

q Pileup has been removed by multiplicity cut.

q 15%-30% centralities are biased toward the more central collisions. This biasing is minimal for more central events.


STAR preliminary

FXT PID & Acceptance

9

Ke+e-π

p

d

t

3HeK

π

PID with Time-of-Flight DetectorPID with TPC

|p|/q (GV/c) |p|/q (GV/c)

dE/d

x (k

eV/c

m) 1/β

p T(G

eV/c

)

y y

TPC TPC

π π

e- e+ K Kp

dt

(GeV/c)π pp T (GeV

/c)

q In STAR, the acceptance for particles and anti-particles is the same. This is not normally true for an experiment with a dipole magnet.

Particle Reconstruction in Au+Au at 𝑺𝑵𝑵 = 4.5 GeV 𝐾() Λ

𝛯+

STAR preliminary STAR preliminary

STAR preliminary

π ,K, p are identified by dE/dx in TPC. Secondary vertex reconstruction.


Cou

nts

E895 data

K0S →π+ + π- Λ→ p + π

Ξ→ Λ+ π → (p + π) + π

0-5% 0-5%

0-30% 0-7%FWHM = 5.13 MeV

𝐾() -> π+ + π - Λ -> p + π

𝛯+ -> Λ + π -> (p + π) + πE895: PhysRevLett.91. (2003) 202301

Open symbols are reflected

π-

E895: Phys. Rev. C 68 (2003) 054905

E802: Phys. Rev. C 57 (1998) R466

E877: Phys. Rev. C 62 (2000) 024901

qAmplitudes and widths of the rapidity densities are consistent with results from the AGS experiments

Gaussian Fit

Systematic uncertainties Shown for STAR and E895


0-8% Central

0-4% Central

0-5% Central

0-5% Central

Pion Spectra and dN/dy Distribution

mT-m0 and dN/dy spectra of 𝑲𝑺𝟎 and Λ in Au+Au at 𝑺𝑵𝑵 = 4.5 GeV


(GeV/c)S0K-mTm

0 0.5 1 1.5 2 2.5

-2dy

(GeV

/c)T

/dm2)dN Tmπ2

ev1/(

N

10−10

9−10

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210 -1.5 < y < -1.25

-1.25 < y < -1.0

-1.0 < y < -0.75

-0.75 < y < -0.5

-0.5 < y < -0.25

STAR preliminary

Top 5%𝑲𝑺𝟎

)2 (GeV/cΛ-mTm0 0.5 1 1.5 2 2.5

-2dy

(GeV

/c)T

/dm2)dN Tmπ2

ev1/(

N

10−10

9−10

8−10

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6−10

5−10

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3−10

2−10

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1

10

-1.5 < y < -1.25

-1.25 < y < -1.0

-1.0 < y < -0.75

-0.75 < y < -0.5

-0.5 < y < -0.25

spectra Au+Au 4.5 GeVΛ-mT mΛ

STAR preliminary

ΛTop 5%

cmsy - y2− 1.5− 1− 0.5− 0 0.5 1 1.5 2

dN/dy

02468

101214 FXT STAR @ 4.5 GeVS

0K E917 @ 4.30 GeV+K E917 @ 4.30 GeV-K

)/2 E917 @ 4.30 GeV-+K+(K

STAR preliminary

Top 5%

cmy - y2− 1.5− 1− 0.5− 0 0.5 1 1.5 2

)/dy

ΛdN

(

02468

10121416 FXT STAR @ 4.5 GeVΛ

E891 @ 4.9 GeVΛ E877 @ 4.9 GeVΛ

STAR preliminary

Gaussian Fitting


Statistical Error only


Statistical Error only

Amplitudes and widths of rapidity density, dN/dy, are in a good agreement with AGS experiments.

Particle Yield comparison in Au+Au at 𝑺𝑵𝑵 = 4.5 GeV with different experiments

q The excitation function of integrated yield, dN/dy, at mid-rapidity, scaled by the average number of participants.

q 𝐾() points are scaled by factor of 10.q STAR data are in a good agreement with various AGS and CERN experiments.


§ E895: Phys. Rev. C 68 (2003) 054905

§ E895: NPA 698 (2002) 495c § E802: NPA 610 (1996) 139c § E877: Phys. Rev. C 63 (2001)

014902§ E891: PLB 382 (1996) 35 E896:

Phys. Rev. Lett. 88, 062301§ NA44: Phys. Rev. C 66 (2002)

044907 § NA49: JPG 30 (2004) S701§ NA49: Phys. Rev. Lett. 93 (2004)

022302 § Phys. Rev. Lett. 93 (2004) 022302 § NA57: JPG:NPP32 (2006) 2065§ WA98: Phys. Rev. C 67 (2003)

014906

PRELIMINARY

p π-

π+

10-30%10-25%

10-30%

STAR PRELIMINARY

STAR PRELIMINARY

STAR PRELIMINARY




Statistical errors only




q Proton flow is “positive”.q Pion flow is “negative”.q π+ flow is twice that of π-

flow.*15-30% centrality bias is not corrected.

Directed flow of protons and pions in Au+Au Collisions at 𝒔𝑵𝑵 = 4.5 GeV

𝑲𝑺𝟎

STAR PRELIMINARY


10-25%

slope near mid-rapidity-0.022 +- 0.015 Λ

STAR PRELIMINARY


10-30%

slope near mid-rapidity0.094 +- 0.015




qdv1/dy|y=0 of 𝐾() (mesons) is negative.qdv1/dy|y=0 of Λ (baryons) is positive.q*15-30% centrality bias is not corrected.

Directed flow of 𝑲𝑺𝟎 and Λ in Au+AuCollisions at 𝒔𝑵𝑵 = 4.5 GeV

STAR BES10-40%

STAR FXT10-25%

STAR PRELIMINARY



E895: PRL 84 (2000) 5488STAR: PRL 112 (2014) 162301

q First π results shown for this 𝑠$$ = 4.5 GeV. qThe mesons continue the trend of negative flow seen at higher

energies.

*15-30% centrality bias is not corrected

Directed Flow Comparison Across Experiments and Energies


q First π results shown for this energy range. qThe mesons continue the trend of negative flow seen at higher

energies.qProtons and Lambdas are consistent with positive flow indicative of

compression.

Directed Flow Comparison Across Experiments and Energies

BES-IICollider

E895: Phys. Rev. Lett. 84 (2000) 5488STAR: Phys. Rev. Lett. 112 (2014) 162301

*15-30% centrality bias is not corrected

STAR FXT10-25%

FXTSTAR PRELIMINARY

Elliptic Flow of Pions and Protons

FXT BES-IICollider

STAR PRELIMINARY

STAR PRELIMINARY

STAR PRELIMINARYE895: Phys. Rev. Lett. 83 (1999) 1295

p

Statistical Errors Only




0-30%

0-30%

q First measurement of pion elliptic flow for this energy range.

q Proton v2 shows good agreement with E895.

q *15-30% centrality bias is not corrected.

STAR PRELIMINARY

CERES: JPG30 (2004) S1371ALICE: PRL 110 (2013) 152301

STAR: PRC92 (2015) 21901

FXT BES-II

Systematic and statistical errors shown


q FXT measurement continues the decreasing trend towards lower energies and is in a good agreement with UrQMD.

Dynamical Relative Charge Number Fluctuations

Pion HBT Results STAR PRELIMINARY

STAR PRELIMINARY

E895: Phys. Rev. Lett. 84 (2000) 2798E866: Phys. Rev. C 66 (2002) 054096

STAR BES: Phys. Rev. C 92 (2015) 14904E895: Phys. Rev. Lett. 84 (2000) 2798E866: Phys. Rev. C 66 (2002) 054096 ALICE: Phys. Lett. B 696 (2011) 328

0-10% Central

0-15% Central

STAR PRELIMINARY

0.1 GeV/c < pT < 0.3 GeV/c

0.15 GeV/c < pT < 0.8 GeV/c

GeV/c2





0-10% Central

q Consistent with results from AGS experiments.

q In the FXT regime, as the collision energy rises, compression reduces the source size and increases the baryon density.

q The BES collider regime shows increased longitudinal expansion.

q First pion dv1/dy results obtained for this energy range. They continue the trend of negative flow for mesons.

q First pion v2 results obtained for this energy.

q First 𝜈dyn result obtained for this energy range.

q Spectra and yields, HBT radii, proton dv1/dy, and proton v2 results are consistent with results from AGS experiments.

à STAR operates well in FXT mode!


Conclusions from First FXT Run at 𝒔𝑵𝑵 = 4.5 GeV

Results from FXT Al+Au Collisions

at 𝑺𝑵𝑵 = 4.9 GeV


Centrality Determination for Al+Auat 𝑺𝑵𝑵 = 4.9 GeV

Top5%

q 3.4 M Al+Au events collected with the top 30% centrality.

q It is not a beam pipe study.

q Pileup has been removed by multiplicity cut.


nGoodTracks

Pileup

STAR preliminary

Data

Multiplicity0 50 100 150 200 250

Events

1

10

210

310

410

510

To

p 5

%T

op

10

%T

op

15

%T

op

20

%T

op

25

%T

op

30

%

Pil

e U

p

= 4.9 GeVNNsSTAR Al+Au GlauberPile Up

Particle Reconstruction in Al+Au at 𝑺𝑵𝑵 = 4.9 GeV

Al+Au at 𝑺𝑵𝑵 = 4.9 GeV, 0-5%

à K0S→π+ + π-

àΛ → p + π-

q π ,K, p are identified with TPC dE/dxq Secondary vertex reconstruction

𝐾() ΛSTAR preliminary STAR preliminary


0-5%0-5%

mT-m0 and dN/dy spectra of 𝑲𝑺𝟎 and Λ in Al+Au at 𝑺𝑵𝑵 = 4.9 GeV


)2 (GeV/cΛ-mTm0 0.5 1 1.5 2 2.5

-2dy

(GeV

/c)T

/dm2)dN Tmπ2

ev1/(

N

10−10

9−10

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

-1.5 < y < -1.25

-1.25 < y < -1.0

-1.0 < y < -0.75

-0.75 < y < -0.5

-0.5 < y < -0.25

STAR preliminary

Top 5%

(GeV/c)S0K-mTm

0 0.5 1 1.5 2 2.5

-2dy

(GeV

/c)T

/dm2)dN Tmπ2

ev1/(

N

12−10

11−10

10−10

9−10

8−10

7−10

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3−10

2−10

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10

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-1.5 < y < -1.25

-1.25 < y < -1.0

-1.0 < y < -0.75

-0.75 < y < -0.5

-0.5 < y < -0.25

STAR preliminary

Top 5%

Λ𝑲𝑺𝟎

cmsy - y1.5− 1− 0.5− 0 0.5 1

)/dy

S0dN

(K

012345678

STAR Al+Au @ 4.9 GeVS0K Si+Au @ 5.39 GeV+K Si+Au @ 5.39 GeV-K

)/2 Si+Au @ 5.39 GeV-+K+(K

Au+Au 4.5 GeV

STAR preliminarySTAR data Top 5%

AGS data Top 7%

cmy - y1− 0.5− 0 0.5 1 1.5

)/dy

ΛdN

(

00.5

11.5

22.5

33.5

44.5

5 FXT STAR Al+Au @ 4.9 GeVΛ

STAR preliminary

Uncertainties are Statistical only

Amplitudes and widths of rapidity density, dN/dy, are In a good agreement with AGS experiments.

Uncertainties are Statistical only

Comparison of mT-m0 spectra and dN/dy with Au+Au and Al+Au

Ø mT-m0 Spectra and dN/dy in Different rapidity bins for FXT Au+Au collisions at 𝑺𝑵𝑵 = 4.5 GeV and Al+Au collisions at 𝑺𝑵𝑵 = 4.9 GeV.

Ø Errors are statistical only.à Solid line fit to data and dashed

line is extrapolation with fitting function.


)2 (GeV/cS0K-mTm

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

-2dy

(GeV

/c)T

/dm2)d

NTmπ2

ev1/(

N

10−10

9−10

8−10

7−10

6−10

5−10

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1

10

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-1.5 < y < -1.25

-1.25 < y < -1.0

-1.0 < y < -0.75

-0.75 < y < -0.5

-0.5 < y < -0.25

STAR preliminary

Open marker for Au+Au Solid marker for Al+Au

Top 5%

)2 (GeV/cΛ-mTm0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

-2dy

(GeV

/c)T

/dm2)d

NTmπ2

ev1/(

N

10−10

9−10

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10

1

10

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-1.5 < y < -1.25

-1.25 < y < -1.0

-1.0 < y < -0.75

-0.75 < y < -0.5

-0.5 < y < -0.25

STAR preliminary

Open marker for Au+Au Solid marker for Al+Au

Top 5%Λ𝑲𝑺𝟎

cmy - y2.5− 2− 1.5− 1− 0.5− 0 0.5 1 1.5 2 2.5

)/dy

ΛdN

(

02468

10121416 FXT STAR Au+Au @ 4.5 GeVΛ

E891 Au+Au @ 4.9 GeVΛ E877 Au+Au @ 4.9 GeVΛ FXT STAR Al+Au @ 4.9 GeVΛ

STAR preliminary

https://arxiv.org/pdf/1609.05102.pdfStar Note 0644 : Technical Design Report for the iTPC Upgrade Star Note 0666 : An Event Plane Detector for STAR

inner TPC upgrade

Event Plane Detector

endcap TOF

iTPC Upgrade:ü Improved dE/dx resolutionü Better momentum resolutionü Extends η coverage from

1.0 to 1.5 ü pT >60 MeV/cü Ready in 2019

EndCap TOF Upgrade:ü Mid-rapidity coverage is criticalü Needed for PID at mid-rapidityü -1.6<η<-1.1ü Allows higher energy range of

FXT programü Ready in 2019

EPD Upgrade:ü Better triggerü Reduces backgroundü Improves event plane

resolutionü 2.1<|η|<5.1ü Ready in 2018


The STAR Upgrades and the FXT program

q Detector upgrades required to extend STAR FXT up to 7.7 GeV, an overlap energy with the collider mode.

FXT Energy Reach With Upgrades

π

p T(G

eV/c

)

p T(G

eV/c

)

ylabylab

p


CurrentAcceptance

CurrentAcceptance

Acceptancewithupgrades

Acceptancewithupgrades


Need datahere!

BES-IICollider

Preliminary HADES result, Quark Matter 20170-10%(QM 2017)

STAR PRELIMINARY

FXT

Systematic uncertainties included

q 100 M (~2 days) events of Au + Au collisions at 𝑠33 = 3.0 GeV .

q The Event Plane Detector will be ready and available for flow analyses.

q Can obtain a fluctuation measurement at energies below BES-I.

Outlook: FXT Program in Run 18


q iTPC and eTOF upgrades will be available. q Would need 100 million events at each energy, 2 days per energy

(3.5 GeV – 7.7 GeV).q Data rate is limited by DAQ.q Data at 7.7 GeV would provide an overlap energy with the

collider mode.

Outlook: FXT Program in Run 19

C. Blume, J. Phys. G31, S57 (2005).

q Clear signals for 𝐾(), Λ and Ξ+ are observed in Au+Au at 4.5 GeV FXT test run

q Clear signals for 𝐾() and Λare observed in Al+Au at 4.9 GeV FXT test run.

q Have not seen Λ6 and 𝛀, due to low statistics.

q After upgrade we need ~100M events for each energy and hoping to see the Λ6, 𝛀 and Ξ+ .


Strange Particles in FXT and BES-II

Summaryq First FXT run results demonstrate STAR has a capability

to run in the fixed-target as well as in the collider mode. q Higher statistics FXT run in 2018 will allow a kurtosis

measurements at 3 GeV.q Installation of EPD in 2018 will allow to improve flow

measurements.q The FXT program will extend the energy range of the

RHIC BES-II down to √sNN = 3.0 GeV (𝜇B=720 MeV).q With detector upgrades the FXT program can be

extended up to 7.7 GeV, where it overlaps with the collider mode.

q This will also allow more comprehensive and refined measurements.


Thank You!



Back Up

E895_PRL86(2001)2533

STAR PRELIMINARY

E895_PRL86(2001)2533

Slope near mid-rapidity0.09 +/- 0.015

0-18%

Au+Au 3.8 GeV

Au+Au3.8 GeV

E895 trend:/p flow ratio at 4.5 GeV è 0.2

STAR FXT:/p flow ratio at 4.5 GeV è 1.1

Differences:E895 -- <px>STAR-FXT – v1

E895 – 0-18%STAR-FXT 10-25%

p

Λ

KE beam (AGeV)35

Comparison to E895 Λ Flow

Au+Au 4.5 GeV 10-25%

September 23 Muhammad Usman Ashraf

Λ

Λ

pT spectra of 𝑲𝑺𝟎 in Au+Au at 𝑺𝑵𝑵 = 4.5 GeV

Ø 𝐾() Spectra in Different rapidity bins for FXT Au+Au at 𝑺𝑵𝑵 = 4.5 GeV.Ø Statistical errors only.Ø 15-30% trigger is biased towards the most central.à Spectra are extrapolated to high pT with Stefan-Boltzmann fitting function.


(GeV/c)TP0 0.5 1 1.5 2 2.5

-2dy

(GeV

/c)T

/dP2)dN TPπ2

ev1/(

N

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1

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0-5%)-15-10% (x10

)-210-15% (x10)-315-20% (x10)-420-25% (x10)-525-30% (x10

(GeV/c)TP0 0.5 1 1.5 2 2.5

-2dy

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/c)T

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ev1/(

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/c)T

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ev1/(

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[-1.25,-1.00]

STAR preliminary STAR preliminary STAR preliminary

[-1.00,-0.75] [-0.75,-0.50] [-0.50,-0.25]

STAR preliminary

[-1.50,-1.25][-1.75,-1.50]

pT spectra of Λ in Au+Au at 𝑺𝑵𝑵 = 4.5 GeV

Ø Λ Spectra in Different rapidity bins for FXT Au+Au at 𝑺𝑵𝑵 = 4.5 GeV.Ø Statistical errors only.Ø 15-30% trigger is biased towards the most central.à Spectra are extrapolated to high pT with Stefan-Boltzmann fitting function.


(GeV/c)TP0 0.5 1 1.5 2 2.5

-2dy

(GeV

/c)T

/dP2)dN TPπ2

ev1/(

N

10−10

9−10

8−10

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1

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ev1/(

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ev1/(

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[-1.25,-1.00]


[-1.00,-0.75] [-0.75,-0.50] [-0.50,-0.25]

STAR preliminary

[-1.50,-1.25][-1.75,-1.50]

(GeV/c)TP0 0.5 1 1.5 2 2.5 3 3.5

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STAR preliminary

[-1.25,-1.00]

[-1.00,-0.75] [-0.75,-0.50] [-0.50,-0.25]

[-1.50,-1.25][-1.75,-1.50]

pT spectra of 𝑲𝑺𝟎 in Al+Au at 𝑺𝑵𝑵 = 4.9 GeV

(GeV/c)TP0 0.5 1 1.5 2 2.5 3 3.5 4

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spectra, Al+Au 4.9 GeVS0K

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STAR preliminary

[-1.75,-1.50]

Ø 𝐾() Spectra in Different rapidity bins for FXT Al+Au at 𝑺𝑵𝑵 = 4.9 GeV.Ø Statistical errors only.à Spectra are extrapolated to high pT with Stefan-Boltzmann fitting function.


(GeV/c)TP0 0.5 1 1.5 2 2.5

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[-1.25,-1.00]

[-1.00,-0.75] [-0.75,-0.50] [-0.50,-0.25]

[-1.50,-1.25][-1.75,-1.50]



STAR preliminary

pT spectra of Λ in Al+Au at 𝑺𝑵𝑵 = 4.9 GeV

(GeV/c)TP0 0.5 1 1.5 2 2.5 3 3.5 4

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spectra, Al+Au 4.9 GeVS0K

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STAR preliminary

[-1.75,-1.50]

Ø Λ Spectra in Different rapidity bins for FXT Al+Au at 𝑺𝑵𝑵 = 4.9 GeV.Ø Statistical errors only.à Spectra are extrapolated to high pT with Stefan-Boltzmann fitting function.


(GeV/c)TP0 0.5 1 1.5 2 2.5

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[-1.50,-1.25][-1.75,-1.50]



STAR preliminary (GeV/c)TP

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NTPπ2

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STAR preliminary

[-1.25,-1.00]

[-1.00,-0.75] [-0.75,-0.50] [-0.50,-0.25]

[-1.50,-1.25][-1.75,-1.50]

Net-Proton Directed Flow Slope at Mid-rapidity


q A minimum is observed in the mid-rapidity slope of net proton directed flow.

q The energy range of this minimum is 𝑺𝑵𝑵 = 10-20 GeV.

q According to prediction of hydrodynamic models, this minimum resembles the “softest point”.


Centrality # of Events <Npart> +/- stat +/-sys

0-5% ~267k 335.9 +/- 0.51 +/-0.97

5-10% ~287k 285.9 +/- 0.56 +/-0.88

10-15% ~259k 242.4 +/- 0.53 +/-0.37

15-20% ~204k 203.9 +/- 0.48 +/-0.85

20-25% ~126k 170.3 +/- 0.44 +/-0.46

25-30% ~69k 142.2 +/- 0.43 +/-0.50

Relation between centrality bins and <npart>


Centrality PileUp Efficiency

0-5% 6.014710% 96.871020%

5-10% 2.179419% 95.604648%

10-15% 1.815579% 98.653689%

15-20% 1.578787% 96.707016%

20-25% 1.367026% 92.393202%

25-30% 1.149513% 95.157688%

Trigger efficiencies and pileup for each centrality bin.

star fixed-target results from = 4.5 gev au+au and · 2017-09-26 · star fixed-target results from...

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