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Brooke Haag UC Davis

Multi-hadron Triggered Azimuthal Correlations in Au+Au Collisions at √s NN = 200 GeV. Outline Introduction / Analysis Technique Motivation & explanation of multi-hadron triggers Results Away side yields for different p T trigger bins: 10 to 12 GeV & 12 to 15 GeV

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Brooke Haag UC Davis

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  1. Multi-hadron Triggered Azimuthal Correlations in Au+Au Collisions at √sNN = 200 GeV • Outline • Introduction / Analysis Technique • Motivation & explanation of multi-hadron triggers • Results • Away side yields for different pT trigger bins: 10 to 12 GeV & 12 to 15 GeV • Ratios of Cluster triggers to di-hadron triggers • Away side yields (dAu) for pT trigger bins: 8 to 10 GeV & 12 to 15 GeV • Cone radius study -- preview • Conclusions and Outlook Brooke Haag UC Davis STAR Analysis Meeting - BNL October 15-19, 2007

  2. Introduction • Fragmentation function D(z) depends on z defined as pT/ET,jet • Current method of Di-hadron correlation is insensitive to true fragmentation functions • Try multi-hadron (cluster) trigger • Better constrain ET,jet ~ pT(trig), better approximation of fragmentation function • Gain statistics STAR, Phys. Rev. Let. 97 (2006),162301 STAR Analysis Meeting - BNL - Oct. 2007

  3. R Seed Associated track R Seed Associated track Secondary Seeds Analysis Technique • Collect arrays of seed and associated tracks with a minimum seed pT cut (5.0 GeV) and a minimum associated pT cut • Define a cone radius (R=0.3) • pT trigger = pT sum of all the associated tracks (secondary seeds) in that cone • Plot  between the highest pT seed in the cone and associated tracks • Subtract flat background for Au+Au • Extract Yields: pT (trigger) = 8 to 10 GeV, 10 to 12 GeV & 12 to 15 GeV pT (assoc) = 3 to 4, … ,10 to 11 GeV Di-hadron correlation Multi-hadron trigger STAR Analysis Meeting - BNL - Oct. 2007

  4. dN/d - jet pT, 12 to 15 GeV, associated pT, 3 to 4 GeV AuAu 0-12% • Plot  between the highest pT seed in the cone and associated tracks • Subtract flat background for Au+Au • Extract Yields: pT (trigger) = 8 to 10 GeV, 10 to 12 GeV, & 12 to 15 GeV pT (assoc) = 3 to 4, … ,10 to 11 GeV Near side Away side STAR Analysis Meeting - BNL - Oct. 2007

  5. R Seed Associated track Secondary Seed Combinatorial Background • pT seed > 5.0 GeV • Vary minimum secondary seed pT to test effect of combinatorial background in AuAu • 2.0 GeV • 3.0 GeV • 4.0 GeV STAR Analysis Meeting - BNL - Oct. 2007

  6. Comparison of single vs. cluster trigger statistics - d+Au Minimum secondary seed cut = 2.0 GeV 291 66 Multi-hadron triggers Di-hadron correlation • gain statistics by allowing clusters to add up to pT(trig), not just requiring a single particle to carry pT(trig) STAR Analysis Meeting - BNL - Oct. 2007

  7. Away side yields Minimum secondary seed cut = 2.0 GeV 10 GeV < pT trig < 12 GeV 12 GeV < pT trig < 15 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers = 0.83 Fraction of Multi-hadron triggers to Single+Multi triggers =0.86 • Multi-hadron and Di-hadron curves match well for 10 < pT trig <12 GeV • Multi-hadron and Di-hadron curves don’t match as well for 12 < pT trig <15 GeV, especially at lower pT assoc, likely effect of random clusters STAR Analysis Meeting - BNL - Oct. 2007

  8. Away side yields Minimum secondary seed cut = 3.0 GeV 10 GeV < pT trig < 12 GeV 12 GeV < pT trig < 15 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers = 0.59 Fraction of Multi-hadron triggers to Single+Multi triggers =0.64 • Multi-hadron and Di-hadron curves match well in both pT trigger bins • Fraction of Multi-hadron triggers decreases as secondary seed cut increases STAR Analysis Meeting - BNL - Oct. 2007

  9. Away side yields Minimum secondary seed cut = 4.0 GeV 10 GeV < pT trig < 12 GeV 12 GeV < pT trig < 15 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers = 0.36 Fraction of Multi-hadron triggers to Single+Multi triggers =0.21 • Multi-hadron and Di-hadron curves match well for 12 < pT trig < 15 GeV • For 10 < pT trig < 12 GeV, Multi-hadron triggers have slightly higher yield than Di-hadrons, possible effect of minimum seed/secondary seed cuts • Fraction of Multi-hadron triggers decreases as secondary seed cut increases STAR Analysis Meeting - BNL - Oct. 2007

  10. Ratios:Single+Multi-hadron triggers to Di-hadrons - 10 GeV < pT trig < 12 GeV - Min. secondary seed cut = 2.0 GeV Min. secondary seed cut = 3.0 GeV Min. secondary seed cut = 4.0 GeV STAR preliminary STAR preliminary STAR preliminary RatioCluster Analysis/di-hadron Analysis • Ratios (statistical errors only) fall around unity and are relatively flat. No significant variation with increasing secondary seed cut. • The single+multi-hadron triggers sample same kinematics as di-hadron correlations. STAR Analysis Meeting - BNL - Oct. 2007

  11. Ratios:Single+Multi-hadron triggers to Di-hadrons - 12 GeV < pT trig < 15 GeV - Min. secondary seed cut = 2.0 GeV Min. secondary seed cut = 3.0 GeV Min. secondary seed cut = 4.0 GeV STAR preliminary STAR preliminary STAR preliminary RatioCluster Analysis/di-hadron Analysis • Excluding lowest pT associated bins affected by random clusters, ratios (statistical errors only) fall around unity and are relatively flat. No significant variation with increasing secondary seed cut. • The single+multi-hadron triggers sample same kinematics as di-hadron correlations. STAR Analysis Meeting - BNL - Oct. 2007

  12. Away side yields - dAuMinimum secondary seed cut = 2.0 GeV 8 GeV < pT trig < 10 GeV 12 GeV < pT trig < 15 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers = 0.39 Fraction of Multi-hadron triggers to Single+Multi triggers = 0.67 • Run out of statistics with increasing pT associated, especially in higher pT trig bin. STAR Analysis Meeting - BNL - Oct. 2007

  13. Away side yields - AuAu cone radius study Minimum secondary seed cut = 2.0 GeV 8 GeV < pT trig < 10 GeV 8 GeV < pT trig < 10 GeV R = 0.3 R = 0.1 STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers =0.72 Fraction of Multi-hadron triggers to Single+Multi triggers = 0.25 • Vary radius to study effect of combinatoric background. • Fraction of Multi-hadron triggers decreases with smaller cone radius. STAR Analysis Meeting - BNL - Oct. 2007

  14. Conclusions and Outlook • Investigated Multi-hadron triggers as a method of better approximating fragmentation functions • Multi-hadron triggers and Di-hadron correlations mostly give very similar results • Also ratios of Single+Multi-hadron trigger yields to di-hadron yields show slopes not different, kinematics not very different • Multi-hadron triggers yield the same physics as di-hadron correlations with improved statistics • Method is promising, more work is needed • Pythia simulations to understand expectations for multi-hadron trigger yields • Study yields for different jet cone radii • Look at higher pT trigger > 15 GeV STAR Analysis Meeting - BNL - Oct. 2007

  15. Backup Slides

  16. Away side yields Minimum secondary seed cut = 2.0 GeV 8 GeV < pT trig < 10 GeV 10 GeV < pT trig < 12 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers =0.72 Fraction of Multi-hadron triggers to Single+Multi triggers = 0.83 STAR Analysis Meeting - BNL - Oct. 2007

  17. Away side yields Minimum secondary seed cut = 3.0 GeV 8 GeV < pT trig < 10 GeV 10 GeV < pT trig < 12 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers =0.24 Fraction of Multi-hadron triggers to Single+Multi triggers = 0.59 STAR Analysis Meeting - BNL - Oct. 2007

  18. Away side yields Minimum secondary seed cut = 4.0 GeV 10 GeV < pT trig < 12 GeV 8 GeV < pT trig < 10 GeV STAR preliminary STAR preliminary Fraction of Multi-hadron triggers to Single+Multi triggers =0.04 Fraction of Multi-hadron triggers to Single+Multi triggers = 0.36 STAR Analysis Meeting - BNL - Oct. 2007

  19. Ratios:Single+Multi-hadron triggers to Di-hadrons - 8 GeV < pT trig < 10 GeV - Min. secondary seed cut = 2.0 GeV Min. secondary seed cut = 3.0 GeV Min. secondary seed cut = 4.0 GeV STAR preliminary STAR preliminary STAR preliminary RatioCluster Analysis/di-hadron Analysis STAR Analysis Meeting - BNL - Oct. 2007

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