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 University of California, Los Angeles Lawrence Berkeley National Laboratory. Outline - PowerPoint PPT PresentationTRANSCRIPT
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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 University of California, Los Angeles
Lawrence Berkeley National Laboratory
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, particle dependence of Cronin effect
•Summary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
Pt range: 0.1GeV < Pttrack < 4.0GeV
Data Sets and Event Cuts
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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%
Three Multiplicity Bins are defined by the Nch per event in FTPC East
After cut: ~ 10 Million events
STAR STAR
Preliminary
Preliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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 len
DcaImpact
Track 1
Track 2
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAR
K+ K- Branching Ratio = 0.49
Both K+ and K- come from the same eventSignal
K+ and K- come from different event
Background
Mixed event is supposed to contain everything of significance to the correlation analysis except the correlation itself.
Calculate the invariant mass of every possibleK+K- pairs and accumulate the signal toreconstruct in each (y, pt) bin.
Event Mixing Method
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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.
STAR STAR
Preliminary
Preliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTARAcceptance and
Efficiency
4
Embedding method: Generate tracks with certain pT and rapidity distribution.
(SimTrack) Generate Monte-Carlo tracks in STAR geometry
(MCTrack)Acceptance =
TPC response simulator generates hits Monte-Carlo hits are embedded in the real data Reconstruct the “embedded events” using the same chain as
real data production (RecTrack) Tracking efficiency extraction
Efficiency = Total correction factor
Correction = Acceptance * Efficiency*Branching Ratio
SimTrack
MCTrack
MCTrack
cTrackRe
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAREfficiency Correction of Ks and
The efficiency increases with Pt and becomes flatWeak multiplicity dependence. The difference of efficiency correction between different centrality bins is small than the error bars.
STAR STAR
Preliminary
Preliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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 funtions.
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;
STAR STAR PreliminaryPreliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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 necessary for further understanding: production mechanism particle dependence of nuclear modification factor
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
STAR STAR PreliminaryPreliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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 SQM paper)
spectra and feed-down contribution to
STAR STAR PreliminaryPreliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAR Spectra comparison
Different measurements are consistent within STAR!
From Camelia
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAR dN/dy vs. <Nch>
• , Ks, , increase with <Nch> in dAu and AuAu collisions.
dAu Minbias
STAR STAR PreliminaryPreliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAR <pt> vs. <Nch>
<pt>: shows no dependence of <Nch> within error bar, but and are different.
dAu Minbias
STAR STAR PreliminaryPreliminary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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.
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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/Coalescence model works!Recombination/Coalescence model works!They can explain the difference of Rcp between mesons and baryons for both dAu and AuAu. (Z.M.Ko et al., R.C.Hwa et al….)
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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.
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAR
1) Measure the productions and <pt> for various particles (Ks, ) in dAu collisions
2) Double exponential function can fit the , Ks, and spectra better than others, dN/dy scale linearly with the number of charged particles
3) RdAu and Rcp in dAu are grouped into mesons and baryons it indicates that the particle production is dividing by particle type rather than particle mass as predicted by the parton recombination/quark coalescence model.
4) Rcp plots show no suppression indicating that the suppression in Au+Au maybe arises from additional effects
SummarySummary
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTAR
The EndThe End
Thank you!Thank you!
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
STARSTARRecombination model of Hwa and Yang
Nucl-th/0403001, Nucl-th/0404066
++- in d+Au P in d+Au
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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
International CCAST Workshop on QCD & RHIC Physics, Aug. 13, 2004
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