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STAR Results High-p T , Electro-Magnetic and Heavy Flavor Probes

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

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STAR Results High-p T , Electro-Magnetic and Heavy Flavor Probes

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  1. STARResultsHigh-pT, Electro-Magnetic and Heavy Flavor Probes Manuel Calderón de la Barca UC Davis for the STAR Collaboration

  2. Outline • Di-hadron correlations: Interaction of jet with bulk • Dh-Df Correlations: charged and identified • Systematics of h-h correlations vs pT trig, assoc, mid-forward h. • Hard Probes: Comparison to calculable processes • Photons : Direct g 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 • g-h correlations in p+p

  3. Dh-Df Correlations: Background d+Au, 40-100% Au+Au, 0-5% Phys. Rev. C73 (2006) 064907 • 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 mid-central AuAu pt < 2 GeV Dr/√rref 0.8< pt < 4 GeV nucl-ex/0607003 See Poster by Ron Longacre 3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig)

  4. Dh-Df Component Picture     3<pt,trigger<4 GeV pt,assoc.>2 GeV • Study near-side yields • Study away-side correlated yields and shapes • Components • near-side jet peak • near-side ridge • v2 modulated background Au+Au 0-10% preliminary Strategy:Subtract  from  projection: isolate ridge-like correlation Definition of “ridge yield”: ridge yield := Jet+Ridge()  Jet() Can also subtract large .

  5. The h “Ridge” + “Jet” yield vs Centrality Jet+Ridge ()Jet () Jet) preliminary yield,) Npart 3<pt,trigger<4 GeV pt,assoc.>2 GeV Au+Au 0-10% preliminary “Jet” yield constant with Npart p+p. low pT Number corr. Au+Au. low pT pT corr. Reminder from pT<2 GeV: h elongated structure already in minbias AuAu f elongation in p-p  to h elongation in AuAu. Dr/√rref See Talk by Jörn Putschke PRC 73, 064907 (2006)

  6. L,K0sNear-side associated yield vs centrality, Au+Au Jet + Ridge Jet Charged hadrons: ridge yield increased vs. Npart L,K0s both have increase of near-side yield with centrality in Au+Au L, K0s: ratio of yields in central Au+Au/d+Au ~ 4-5 ridge yield of K0S < ridge yield of L -> “ridge” yield increases with centrality -> “jet” yield is constant vs Npart same yield as in d+Au See Talk by Jana Bielcikova

  7. Central AuAu: Ridge, Jet Yield vs pT, trig pT, assoc STAR preliminary STAR preliminary Ridge Jet pt,assoc. > 2 GeV Central “Jet spectrum” much harder than inclusive gets harder w/ increasing pt,trigger “Ridge spectrum” close to inclusive ~ independent of pt,trigger Ridge yield ~ constant (slightly decreasing) vs. pT trig Ridge Persists up to highest pT trig See Talk by Jörn Putschke

  8. Near-side zT Distributions: “Jet” Preliminary • Measure hadron triggered fragmentation functions: • Dh1,h2(zT) • zT=pTassoc/pTtrig • Similarity between AuAu and dAu after ridge subtraction Are the AuAu results with the ridge subtracted the same as dAu, EVEN at low pT? See Talk by Mark Horner

  9. Preliminary Near-side zT Distributions: “Jet” • Measure hadron triggered fragmentation functions: • Dh1,h2(zT) • zT=pTassoc/pTtrig • Ratio AuAu/dAu • Similarity between AuAu and dAu after ridge subtraction • 8<pTtrig<15 GeV/c • STAR PRL 97 162301 Near-side zT distributions similar to dAu no 50% dilution from thermal coalescence triggers? Phys.Rev. C70 (2004) 024905 See Talk by Mark Horner

  10. Away-Side: pTtrig Dependence Preliminary Away-side: • Structures depend on range of pT. • becomes flatter with increasing pTtrig • yield increases 1.3 < pTassoc < 1.8 GeV/c AuAu 0-12% Central contribution to away-side becomes more significant with harder pTtrig => fills dip 6.0 < pTtrig < 10.0 GeV/c 3.0 < pTtrig < 4.0 GeV/c 4.0 < pTtrig < 6.0 GeV/c 0-12% Away side See Talk by Mark Horner

  11. Away-side: zT Distributions Preliminary • High zT for hard triggers shows “standard” suppression (~0.2) • Larger yields seen at low zT or low pTtrig • bulk response • Deviation from suppression depends on pTtrig 2.5 < pTtrig < 4.0 GeV/c never reaches the 0.250.06 IAA away-side suppression for pTtrig>8 GeV/c (STAR PRL 97, 162301) See Talk by Mark Horner

  12. Correlation from FTPC to MTPC Trigger: 3<pTtrig<4 GeV/c, A.FTPC: 0.2<pTassoc< 2 GeV/c, A.TPC: 0.2<pTassoc< 3 GeV/c 2.7<|ηassoc|<3.9 AuAu 0-10% AuAu 0-5% AuAu 60-80% STAR Preliminary STAR Preliminary Near-side correlation: consistent with zero Away-side correlations are very similar! Energy loss picture is the same for mid- and forward h? Need quantitative calculations for correlations analyses! See Talk by Levente Molnar

  13. Hard Probes: p0’s and g in STAR d+Au • direct photons and d+Au • double ratio: • (incl/0) / (decay/0) = 1 + dir/ decay • direct g signal consistent with NLO pQCD • baseline results for Au+Au analysis • No discrepancy between STAR & PHENIX. • EMCal 0s in p+p • preliminary result from subset of year 5 data • good agreement with pQCD + KKP fragmentation • disfavors Kretzer FFs See Talk by Martijn Russcher

  14. dsNNcc/dy from p+p to A+A • D0,e±, and μ± combined fit • Advantage: Covers ~95% of cross section • Mid-rapidity dsNNcc/dy vs Nbin • sNNccfollows binary scaling • Charm production from initial state (as expected) • Higher than FONLL prediction in pp collisions. See Talk by Chen Zhong

  15. Checking STAR electrons • STAR, submitted to PRL • PHENIX hep-ex/0609010 • 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. • STAR Au+Au 0-5%

  16. Can we tell how much beauty? e-h from B e-h from D Fit • 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

  17. 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 study Beauty ! p+p 200 GeV See Talk by Xiaoyan Lin

  18. More Beauty:  signal in p+p STAR Preliminary p+p 200 GeV • e+e- Minv • Unlike-Sign Pairs • Like-Sign Pairs STAR Preliminary p+p 200 GeV e+e- Minv Background Subtracted • Large dataset sampled in Run VI • Luminosity limited trigger • Analyzed 5.6 pb-1, with corrections. • Measure (1s+2s+3s) ds/dy at y=0 See Talk by Pibero Djawotho

  19. Mid-rapidity (1s+2s+3s) Cross section • Integrate yield at mid-rapidity: |y|<0.5 • (1s+2s+3s) BR * ds/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 Preliminary p+p 200 GeV Counts ds/dy (nb) y See Talk by Pibero Djawotho

  20. Towards g-jet: (g,p0)-h Df Correlation analysis p+p p0 Mixed Photon Use “shower-shapes” in EMC: Create two samples Enriched photon sample (mix g, p0) Enriched p0 sample (almost pure p0) Reduction in near angle peak in Photon sample Away-side yields only slightly reduced Effect more prominent for larger Ettrigger See Talk by Subhasis Chattopadhyay

  21. Spectra for g-tagged Events Use g-enriched sample: plot away-side pT-spectra for photon-tagged events Matches charged hadron spectra in direct photon events from HIJING. Promising for future g-jet studies: RHIC II See Talk by Subhasis Chattopadhyay

  22. Conclusions and Outlook xie xie ! • Near Side: Broadening along Dh. (“Jet”+”h Ridge”) • “ridge” yield: steep increase with centrality, • “jet” yield: constant with centrality, increasing with pTtrig • After subtraction of long range Dh, D(zT) similar to dAu. • Unmodified “jet” after subtraction? • Away side: • Central: contribution to Df=p increases with harder pTtrig, 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 g: Signal in d+Au matches pQCD • Charm s • 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. • g-h correlations: First g-jet measurement. • , g-h : First steps towards RHIC II. xie xie !

  23. Backup

  24. Df Correlation, strange particle triggers, Au+Au 200 GeV See Talk by J. Bielcikova trigger: baryon/meson baryon/antibaryon Selection criteria: 3.0 GeV/c < pTtrigger < 3.5 GeV/c 1 GeV/c < pTassociated < 2 GeV/c |h| < 1 STAR preliminary STAR preliminary STAR preliminary STAR preliminary correlation functions before elliptic flow subtraction correlation functions after elliptic flow subtraction syst. error due to v2 uncertainty ~ 25%

  25. Direct photons for correlation analysis Standard methods used for extraction of photons: Statistical method by Reconstruction of inclusive photons Subtract photons from decay of p0 , h etc. Cannot be used for correlation. Method: Enhance g using difference in shower shapes.. Compare correlation functions between g-enriched (narrow EM showers) p0-enriched (broader EM showers) mixed PHOTON p0

  26. Associated pT Dependence Preliminary • 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 pTassoc pTtrig see talk by M. Horner 7

  27. 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

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