f, ks, , and x production at 200 gev d+au collisions from star
DESCRIPTION
F, Ks, , and X production at 200 GeV d+Au collisions from STAR. Xiangzhou Cai, Yugang Ma, Hai Jiang, Jingguo Ma for the STAR Collaboration Shanghai INstitute of Applied Physics (SINAP) University of California, Los Angeles (UCLA) Lawrence Berkeley National Laboratory (LBNL). Outline - PowerPoint PPT PresentationTRANSCRIPT
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR Ks, and production at 200 GeVd+Au collisions from STAR
Xiangzhou Cai, Yugang Ma, Hai Jiang, Jingguo Mafor the STAR Collaboration
Shanghai INstitute of Applied Physics (SINAP)University of California, Los Angeles (UCLA)
Lawrence Berkeley National Laboratory (LBNL)
PAs: Lee Barnby, Xiangzhou Cai, Magali Estienne, Hai Jiang, Camelia Mironov, Lijuan Ruan, Frank Simon, Nu Xu, Haibin Zhang
Outline
•Motivations for measuring Ks, and •Analysis details of dAu analysis (Ks, , , K*, Kink-K)
•Spectra, fit function and comparison
•Rcp, RdAu, Cronin effect and recombination model
•Summary
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR Motivation & Introduction
1) Particle dependence of RAA/Rcp and
v2 from Au+Au collisions is observed. How about RAA/Rcp in dAu? particle
type or mass dependence? (Rcp for
Ks, , and ). 2) The Cronin effect has been considered as due to initial parton scattering. Should the Cronin effect be influenced by the final state particle formation dynamics? 3) Transverse momentum production: <pT> versus multiplicity
m~1019 MeV/c2 ; m~1116 MeV/c2; mKs~498 MeV/c2
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR production in AuAu and ppproduction in AuAu and pp
200 GeV meson production from both AuAu and pp collisions are analysed by Jingguo Ma.200 GeV meson production from dAu is also necessary for further understanding: production mechanism particle dependence of nuclear modification factor
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
dAu 200GeV STAR MuDst P03a:
MinBias and Combined
Event
Trigger ID: 2001 or 2003
Primary Vertex Position: -50cm<z<50cm
Track
nFitPts: > 15
|eta|: < 1.0
Kaon Pt range: 0.1GeV < Pttrack < 4.0GeV
Data Sets and Event Cuts
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR Centrality definition of dAu
1)dE/dx identify stable charged particles in a certain momentum range.2)Unstable particles identified by decay topology or event mixing method.
Multiplicity FTPC East in d+Au collisions
40-100%
20-40%
0-20%
STAR Preliminary
Three Multiplicity Bins are defined by the Nch per event in FTPC East
After cut: ~ 10 Million events
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
Event Selection:
|VertexZ| < 50cm, with Primary vertex found, good run
After cuts, # of Events ~ 10M
Decay mode:
Ks =>+ - (68.6%)
- - (99.9%)
p+ + - (63.9%)
=>+ - (49.1%)
K* => (100%)
Ks, , are reconstructed using topology cuts, like decay length, dca-v0-primV
Daughter tracks are NOT identified when pt>1.1 GeV/c, but v0 can be identified at much higher pT.
,K*: event mixing
p+
Decay point
-
Primary Vertex
-
-
Decay point
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
• Ks and are V0 particles: decay length: Ks = 2.69 cm = 7.89 cm • In TPC, neutral Ks and are reconstructed from charged
particles: p, K and (See above sketch).
Topology Cuts (See the right sketch)• |vertexZ|<50cm• DcaV0: between two daughter tracks < 0.7cm• DcaImpact (distance between V0 and Primary vertex) <
0.75 cm () , and < 0.6cm (Ks)• Decay length (distance between primary vertex and V0
decay point) > 2 cm (Ks and )
-
p+
Ks and reconstruction & Topology cuts
Primary Vertex
Ks
-
+
Primary Vertex
Decay point Decay point
DcaV0
Decay length
DcaImpact
Track 1
Track 2
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
Measurements in dAu collisionsMass = 1019.4±0.5MeV/c2, FWHM=7.31.1 MeV/c2
K+K- pair invariant mass
background subtracted
Phi
For 40~100% centrality bin at |y|<0.5 and 0.4<pt<1.3GeV/c. Red line is the same-event distribution. Black line is the normalized mixed-event distribution.
Invariant mass distribution of meson
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
pp collisionsMeasured Mass=1019 MeV/c2, FWHM=7.10.3 MeV/c2
Misidentified KsPhi
K+K- pair invariant mass
background subtracted
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STARSTAR Invariant mass plots
|y|<1
0.4 <pt< 6.0
|y|<1
0.4 <pt< 6.0|y|<1
0.6 <pt< 5.0
|y|<0.5
0.4 <pt< 1.3
• Without background subtraction
• Ks, , : topology cuts;
• : event mixing
• The quality of signals are pretty good.
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAREfficiency Correction of Ks and
The efficiency increases with Pt and becomes flat when Pt is up to 2GeV/c2
The error bar of each efficiency correction is less than 5%.Weak multiplicity dependence. The difference of efficiency correction between different centrality bins is small than the error.
STAR Preliminary
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
Spectra for MinBias Phi production in dAuexp fit covering low pt end and power-law fit covering high pt region.Double exponential fit can reproduce the experimental data better than other two functions.
Comparison of different Fits
21
)0()0(
)1(2
T
mmt
T
mmt
eaaedy
dN
Double exponential fit:
T1: ~300MeV; T2: 1.0~1.5GeV;
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STARSTAR Spectra and fits
pT: 0.4 – 6 GeV/c. With efficiency correction (including vertex efficiency). Statistical errors only. cross point: pT~(2~4)GeV/c2.Recombination model may fit spectra well … TT(low pt)+TS(middle pt)+SS(high pt)
double exp fit
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STARSTAR Spectra comparison
Different measurements are consistent within STAR!
From Camelia
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STARSTAR
- + bar minbias : dN/dy = 0.0268 ± 0.0007
+ bar minbias (inclusive) : dN/dy =
0.339 ± 0.007
If assuming 0- and ~ 10% - ,
Then feed-down from
~ 0.056 ( 17% )
Consistent with the feed-down in Consistent with the feed-down in AuAu ~ 15% AuAu ~ 15% (Hui, Magali’s SQD paper)
spectra and feed-down contribution to
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STARSTAR dN/dy vs. <Nch>
• , Ks, , increase with <Nch> in dAu and AuAu collisions.
dAu Minbias
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STARSTAR <pt> vs. <Nch>
<pt>: shows no dependence of <Nch> within error bar, but and are different.
dAu Minbias
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STARSTAR Rcp definition
We select three data samples:
“Central”: centrality 0-20%
“Semi-central”: centrality 20-40%
“Peripheral”: centrality 40-100%
Then we calculate the ratios Central/Peripheral as function of pT at different rapidities.
Rcp = (d2N/dpTd) cent/ d2N/dpTd) peri
Many corrections and systematics cancel out.
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STARSTAR Rcp of , Ks, ,
•Mesons (Ks, K, ) have the same Rcp for dAu and AuAu collisions
•Baryons (, ) have the same Rcp too, but higher than mesons.Particle production at intermediate pT region is dividing by the particle’s type,
not the mass. Recombination model works!Recombination model works!•Recombination modelRecombination model can explain the difference of Rcp between mesons and baryons for both dAu and AuAu. How? nucl-th/0403001, nucl-th/0401001
TTTT TSTS SSSS
TTTTTT TTS+TSSTTS+TSS SSSSSS
AuAu 200 GeVdAu 200 GeV
STAR: and K* behave like mesons, despite of the large mass: ReComb prediction
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR From Fragmentation to Recombination
• With more partons around: multiple parton fragmentation (higher twist)
• If phase space is filled with partons, recombine/coalesce them into hadrons.
• Use just the lowest Fock state, i.e. valence quarks:
qqqB qqM
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STARSTARRecombination model of Hwa and Yang
Nucl-th/0403001, PRL, in press
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STARSTARRecombination model of Hwa and Yang (contd)
Nucl-th/0404066
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STARSTAR v2 Scaling
Baryons are pushed further in PT
Perfect scaling for all measured hadrons,some deviation for pions (from decays)
P. Sorensen
P. Sorensen
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STARSTAR Nuclear modification factor RdAu
The behavior of the many-body systems we study (A-A or d-A) can be “calibrated” with a “simple system” like p-p .
Borrowing from “Cronin effect” studies, we compare particle production in d-A to the scaled production in p-p:
RdAu = (d2NdAu/dpTd) / (Ncoll d2Npp/dpTd )
With Ncoll being the estimated number of binary collisions as d “goes through” the Au nuclei.
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STARSTAR RdAu
• RdAu of is closer to that of p and k than that of p
•Particle production at intermediate pT region is sorted by the particle’s type, not the mass
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STARSTAR Comparison with pA collision
s =27.4GeV
P.B Straub,PRL 68, 452(1992)Rw/Be at pA collisions
W: tungsten Be: beryllium
s =38.8GeV
RRw/Bew/Be : : Mesons Mesons (2 quarks):(2 quarks):
Kaon and Kaon and ~ 1.5; ~ 1.5; Baryons Baryons (3 quarks):(3 quarks):
protonproton ~ 2.5 ~ 2.5
Particle-type Particle-type dependence also!dependence also!
~1.4
~1.5
~2.5
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相对论重离子碰撞与低能强子物理研讨会 , 2004/8/3-7, 威海
STARSTAR
1) Measure productions and <pt> for various particles (Ks, , K*, Kink-K) in dAu collisions;
2) Double exponential function can fit the , Ks, and spectra better than others;
3) dN/dy of scales linearly with number of charged particles;
4) RdAu and Rcp in dAu are grouped into mesons and baryons; it indicates particle production is dividing by the particle type rather than particle mass as shown by the parton recombination model.
5) Final state effect based on recombination model works for the spectra and Rcp at dAu collisions;
6) Rcp plots show no suppression indicating that the suppression in Au+Au arises from additional effects.
SummarySummary
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STARSTAR
The EndThe End
Thank you!Thank you!
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STARSTAR Spectra and fits
Ks yield is lower than TOF_K and kink at the low pt, but the shapes are same.
Neutral K* in mt exp fit
Charge K* in power-law fit
K* from Lijuan, Haibin Kink from Camelia
TOF_K from Lijuan