star results high-p t , electro-magnetic and heavy flavor probes
DESCRIPTION
STAR Results High-p T , Electro-Magnetic and Heavy Flavor Probes. Manuel Calder ón de la Barca UC Davis for the STAR Collaboration. Outline. Di -hadron correlations: Interaction of jet with bulk Dh - Df Correlations: charged and identified - PowerPoint PPT PresentationTRANSCRIPT
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STAR Results
High-pT, Electro-Magnetic and Heavy Flavor Probes
Manuel Calderón de la Barca
UC Davisfor the STAR
Collaboration
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Outline
Di-hadron correlations: Interaction of jet with bulk - Correlations: charged and identified Systematics of h-h correlations vs pT trig, assoc,
mid-forward . Hard Probes: Comparison to calculable
processes Photons : Direct in d+Au collisions Heavy Flavor Production
Charm cross section e-h correlations: b contribution to non-photonic electrons Midrapidity (1s+2s+3s) production in p+p
-h correlations in p+p
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- Correlations: Background Near-side long range
correlation in STAR, nucl-ex/0509030 near side “ridge”
How do structures, yields, evolve… Centrality, kinematics
(wide pt ranges), particle identification?
Little guidance from theory: data driven approach
Phys. Rev. C73 (2006) 064907
mid-central AuAupt < 2 GeV
d+Au, 40-100% Au+Au, 0-5%
3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig)
0.8< pt < 4 GeVnucl-ex/0607003See Poster by Ron Longacre
/√
ref
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Study near-side yields
Study away-side correlated yields and shapes
Components near-side jet peak
near-side ridge
v2 modulated background
- Component Picture
Strategy: Subtract from projection: isolate ridge-like correlation Definition of “ridge yield”: ridge yield := Jet+Ridge() Jet()Can also subtract large .
3<pt,trigger<4 GeV
pt,assoc.>2 GeVAu+Au 0-10%
preliminary
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The “Ridge” + “Jet” yield vs Centrality
3<pt,trigger<4 GeV
pt,assoc.>2 GeV
Au+Au 0-10%
preliminary preliminaryJet+Ridge ()Jet ()Jet)
yie
ld
,
)
Npart“Jet” yield constantwith Npart
See Talk by Jörn Putschke
Reminder from pT<2 GeV:
elongated structure already in minbias AuAu elongation in p-p to elongation in AuAu.
PRC 73, 064907 (2006)
p+p. low pT
Number corr. Au+Au. low pT
pT corr.
/√
ref
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Jet + Ridge
Charged hadrons: ridge yield increased vs. Npart,K0
s both have increase of near-side yield with centrality in Au+Au, K0
s: ratio of yields in central Au+Au/d+Au ~ 4-5ridge yield of K0
S < ridge yield of -> “ridge” yield increases with centrality -> “jet” yield is constant vs Npart
same yield as in d+Au
,K0s Near-side associated yield vs
centrality, Au+Au
See Talk by Jana Bielcikova
Jet
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STAR preliminary
Central AuAu: Ridge, Jet Yield vs pT, trig pT, assoc
pt,assoc. > 2 GeV
Ridge yield ~ constant
(slightly decreasing) vs. pT
trig
RidgeJet
“Jet spectrum” much harder than
inclusive
gets harder w/ increasing
pt,trigger
“Ridge spectrum” close to
inclusive
~ independent of pt,trigger
Central
Ridge Persists up to highest pT trig
See Talk by Jörn Putschke
STAR preliminary
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Measure hadron triggered fragmentation functions: Dh1,h2(zT) zT=pT
assoc/pT
trig
Similarity between AuAu and dAu after ridge subtraction
Are the AuAu results with the ridge subtracted the same as dAu, EVEN at low pT?
Near-side zT Distributions: “Jet”
Preliminary
See Talk by Mark Horner
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Near-side zT distributions similar to dAu
no 50% dilution from thermal coalescence triggers?
Phys.Rev. C70 (2004) 024905
Measure hadron triggered fragmentation functions: Dh1,h2(zT) zT=pT
assoc/pT
trig
Ratio AuAu/dAu
Similarity between AuAu and dAu after ridge subtraction
See Talk by Mark Horner
Near-side zT Distributions: “Jet”
Preliminary
• 8<pTtrig<15 GeV/c
STAR PRL 97 162301
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Away-Side: pTtrig Dependence
0-12%
1.3 < pTassoc < 1.8
GeV/c
4.0 < pTtrig < 6.0 GeV/c 6.0 < pT
trig < 10.0 GeV/c
Away-side: Structures depend on range of
pT.
becomes flatter with increasing pT
trig
yield increases
3.0 < pTtrig < 4.0 GeV/c
AuAu 0-12%
Central contribution to away-side
becomes more significant with
harder pTtrig => fills dip
PreliminaryAway side
See Talk by Mark Horner
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High zT for hard triggers shows “standard” suppression (~0.2)
Larger yields seen at low zT or low pT
trig bulk response
Deviation from suppression depends on pT
trig
Away-side: zT Distributions
Preliminary
2.5 < pTtrig < 4.0 GeV/c never reaches the 0.250.06 IAA
away-side suppression for pTtrig>8 GeV/c (STAR PRL 97,
162301)See Talk by Mark Horner
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Correlation from FTPC to MTPC
Trigger: 3<pTtrig<4 GeV/c, A.FTPC: 0.2<pT
assoc< 2 GeV/c, A.TPC: 0.2<pTassoc< 3 GeV/c
Near-side correlation: consistent with zero
Away-side correlations are very similar!
Energy loss picture is the same for mid- and forward ?
Need quantitative calculations for correlations analyses!
AuAu 0-10%AuAu 0-5%
AuAu 60-80%
STAR Preliminary
2.7<|ηassoc|<3.9
See Talk by Levente Molnar
STAR Preliminary
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Hard Probes: 0’s and in STAR EMCal 0s in p+p preliminary result from
subset of year 5 data good agreement with pQCD
+ KKP fragmentation disfavors Kretzer FFs
d+Au
direct photons and d+Au double ratio:
(incl/0) / (decay/0) = 1 + dir/ decay
direct signal consistent with NLO pQCD baseline results for Au+Au
analysis No discrepancy between
STAR & PHENIX.
See Talk by Martijn Russcher
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dNNcc/dy from p+p to A+A
D0, e±, and μ± combined fit Advantage: Covers ~95% of cross
section Mid-rapidity dNN
cc/dy vs Nbin NN
ccfollows binary scaling Charm production from initial state
(as expected) Higher than FONLL prediction in pp
collisions.
See Talk by Chen Zhong
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Checking STAR electrons Discrepancy between STAR
and PHENIX Investigated method to estimate
Photonic background. No issues found.
Reanalyzed from scratch pp results change by ~25% dAu results change by ~10% AuAu results do not change
Within systematics Still difference btw. STAR &
PHENIX RAA still slightly below most c+b
calculations. Future: low material run
Improve uncertainty on background Issue remains: no information on
contribution from beauty.
• PHENIX hep-ex/0609010
• STAR, submitted to PRL
• STAR Au+Au 0-5%
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Can we tell how much beauty?
Use e-h Correlation Large B mass compared
to D Semileptonic decay: e
gets larger kick from B. Broadened e-h
correlation on near-side. Extract B contribution
Use PYTHIA shapes Con: Model dependent Pro: Depends on decay
kinematics well described
Fit ratio B/(B+D)See Talk by Xiaoyan Lin
e-h from Be-h from DFit
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p+p 200 GeV
B contribution to NP electrons vs. pT Fit e-h correlation with
PYTHIA Ds and Bs
Non-zero B contribution
Contribution consistent with FONLL Model dependent
(PYTHIA) Depends mainly on
kinematics of D/B decay (not on Fragmentation).
Dominant systematic uncertainty: photonic background
rejection efficiency Additional uncertainties
under studySee Talk by Xiaoyan Lin
Beauty !
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More Beauty: signal in p+p
Large dataset sampled in Run VI Luminosity limited trigger Analyzed 5.6 pb-1, with corrections.
Measure (1s+2s+3s) d/dy at y=0
STAR Preliminaryp+p 200 GeVe+e- Minv
Background Subtracted
See Talk by Pibero Djawotho
e+e- Minv • Unlike-Sign Pairs— Like-Sign Pairs
STAR Preliminaryp+p 200 GeV
19dt pb L
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Mid-rapidity (1s+2s+3s) Cross section
Integrate yield at mid-rapidity: |y|<0.5
(1s+2s+3s) BR * d/dy 91 ± 28 stat ± 22 syst pb-1
(Preliminary)
Consistent with NLO pQCD calculations at midrapidity.
Trigger ready for next run and RHIC II: luminosity limited
STAR Preliminaryp+p 200 GeV
See Talk by Pibero Djawotho
y
d/
dy
(nb
)
Cou
nts
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p+p
Towards -jet: (,0)-h Correlation analysis
See Talk by Subhasis Chattopadhyay
Use “shower-shapes” in EMC: Create two samples
Enriched photon sample (mix , 0)Enriched 0 sample (almost pure 0)
Reduction in near angle peak in Photon sampleAway-side yields only slightly reduced
Effect more prominent for larger Ettrigger
0
MixedPhoton
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Promising for future -jet studies: RHIC II
Spectra for -tagged Events
Use -enriched sample:plot away-side pT-spectra for photon-tagged events
Matches charged hadron spectra in direct photon events from HIJING.
See Talk by Subhasis Chattopadhyay
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Conclusions and Outlook Near Side: Broadening along . (“Jet”+” Ridge”)
“ridge” yield: steep increase with centrality, “jet” yield: constant with centrality, increasing with pT
trig
After subtraction of long range , D(zT) similar to dAu. Unmodified “jet” after subtraction?
Away side: Central: contribution to = increases with harder pT
trig, fills dip
Away side jet shapes at forward rapidities : similar to midrapidity in d+Au and Au+Au
Energy loss picture is similar at forward and mid-rapidity?
Direct Signal in d+Au matches pQCD Charm
Larger than NLO by ~4, Still difference with PHENIX. Beauty:
Non-zero beauty contribution to non-photonic electrons (1s+2s+3s) in p+p: Consistent with pQCD at y=0.
-h correlations: First -jet measurement.
-h : First steps towards RHIC II.
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Backup
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correlation functions before elliptic flow subtraction
correlation functions after elliptic flow subtraction syst. error due to v2 uncertainty ~ 25%
Correlation, strange particle triggers, Au+Au 200 GeV
Selection criteria: 3.0 GeV/c < pT
trigger < 3.5 GeV/c 1 GeV/c < pT
associated < 2 GeV/c || < 1
STAR STAR preliminarypreliminary
STAR STAR preliminarypreliminary
STAR STAR preliminarypreliminary
STAR STAR preliminarypreliminary
trigger: baryon/meson baryon/antibaryontrigger: baryon/meson baryon/antibaryon
See Talk by J. Bielcikova
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Direct photons for correlation analysisStandard methods used for extraction of photons: Statistical method by Reconstruction of inclusive photons Subtract photons from decay of etc.
Cannot be used for correlation.
Method: Enhance using difference in shower shapes..
Compare correlation functions between-enriched (narrow EM showers)0-enriched (broader EM showers)mixed
PHOTON
0
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Associated pT Dependence Centrality : 0 -
12% Associated pT
(rows): 0.3 – 0.8 GeV/c 0.8 – 1.3 GeV/c 1.3 – 1.8 GeV/c 2.0 – 4.0 GeV/c
Triggers (columns): 2.5 – 4.0 GeV/c 3.0 – 4.0 GeV/c 4.0 – 6.0 GeV/c 6.0 – 10.0
GeV/c Detailed cases:
3rd row right column
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pTtrig
pTassoc
Preliminary
see talk by M. Horner
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Heavy Flavor Production e-h Correlations
Understanding features in heavy quark measurements requires experimental measurement of B and D contributions. First try: use non-
photonic electron correlations.
See talk from Xiaoyan Lin