ρ 0 vector meson elliptic flow (v 2 ) in Au + Au collisions at √s NN = 200 GeV in STAR at RHIC
Au+Au collisions at GeV by the STAR experiment sNN = 200 · 2019. 10. 18. · Measurement of...
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Measurement of semi-inclusive +jet and π 0 +jet distributions in central Au+Au collisions at GeV by the STAR experiment γ dir s NN = 200 Nihar Ranjan Sahoo, for the STAR Collaboration Shandong University, Qingdao, China Email Id: [email protected] The STAR Collaboration: https://drupal.star.bnl.gov/STAR/presentations/ Jet Jet Abstract MTD TOF Magnet upVPD BBC EEMC BEMC TPC § Special High Tower trigger for π 0 /γ event [BEMC] § Discrimination between π 0 γγ and γ dir § By Transverse Shower Profile (TSP) method § Using Barrel Shower Maximum Detector [BSMD] 2. STAR detector setup 1. Motivation 5. Summary and outlook • First γ dir +jet and π 0 +jet measurement at RHIC within 9 < E T trig < 15 GeV is presented in central Au+Au collisions at center of mass energy 200 GeV • Recoil jet with jet radius 0.2 is strongly suppressed at high jet p T whereas a noticeable recovery of jet energy loss is observed at jet radius 0.5 for both the γ dir and π 0 trigger cases • Recoil jet suppression is seen to be independent of E T trig ; whereas γ dir +jet and π 0 +jet show similar level of suppression. • The measurement within 15 < E T trig < 20 GeV for γ dir +jet is ongoing • Jet quenching is an important signature of the hot and dense QCD matter produced in heavy-ion collisions [1]. • A direct photon (γ dir ) produced in coincidence with a recoil jet (γ dir +jet) is a good probe to study the parton energy loss in the QGP [2]. • Comparison between γ dir+ jet vs π 0 +jet provides quantitative understanding of parton energy loss in the QCD medium • Energy loss as a function of path length, color factor, parton energy, etc. • Redistribution of lost energy inside the medium [Jet radius] 1 - 0.5 - 0 0.5 1 h 3 - 2 - 1 - 0 1 2 3 f 0 2 4 6 8 10 [GeV/c] T p -Trigger Event g Au+Au 200 GeV [Run14], Event number=37362, Run number=15098037 - Trigger g 3. Analysis details γ rich trigger event Full analysis chain: 1. Discrimination between π 0 /γ rich -triggered events Transverse Shower Profile method [4] 2. Recoil jets from high-tower-triggered events (SE) Using FastJet package [3]; Recoil jet region:[π-π/4, π+π/4]; Jet radius = 0.2 and 0.5; |η jet | < 1-R 3. Subtraction of uncorrelated jet background in recoil region Based on h+jet analysis[5], event-mixing technique 4. Correction for detector and heavy-ion background fluctuations effects 5. Conversion from γ rich +jet to γ dir +jet [4] Using π 0 +jet yield and purity of γ dir 6. Major sources of systematic uncertainty Unfolding, mixed-event normalization region, detector effects, γ dir background subtraction [contributes only to γ dir +jet] Purity of direct photon for different trigger E T trig bins γ rich trigger events: enriched-γ dir trigger events with some admixture of photons from π 0 . 8 10 12 14 16 18 20 [GeV] trig T E 10 15 20 25 30 35 sample rich γ Background (%) in STAR Preliminary Au+Au 200 GeV [year 2014], 0%-15% Uncertainty σ 1 ± References 1. J. Adams et al. (STAR Collaboration), Nucl. Phys. A 757, 102 (2005) 2. X.-N. Wang, Z. Huang, and I. Sarcevic, Phys. Rev. Lett. 77, 231 (1996) 3. M. Cacciari, G. P. Salam, and G. Soyez, Eur. Phys. J. C (2012) 72:1896 4. L. Adamczyk et al. (STAR Collaboration), Phys. Lett. B 760 (2016) 689-696 5. L. Adamczyk et al. (STAR Collaboration), Phys. Rev. C 96 (2017) no.2, 024905 We present the semi-inclusive measurement of charged jets recoiling from direct-photon and π0 triggers in central Au+Au collisions at 200 GeV center of mass energy, using a dataset with integrated luminosity 13 nb−1 recorded by the STAR experiment in 2014. The photon and π0 triggers have 9 < E T trig < 15 GeV. Charged jets are reconstructed with the anti-k T algorithm with resolution parameters R=0.2 and 0.5. A mixed Event technique developed previously by STAR is used to correct the recoil jet yield for uncorrelated background, enabling recoil jet measurements over a broad p T,jet range with large jet radius. We report the corrected semi-inclusive recoil jet yields for both triggers and compare them to those for p+p collisions. These measurements have different trigger bias, in terms of both the path-length distribution and quark/gluon mix of the recoil jet population, and their corrected recoil spectra are compared. 4. Results and discussion 6 - 10 5 - 10 4 - 10 3 - 10 2 - 10 1 - 10 1 10 ] -1 ) [(GeV/c) jet h d reco,ch T,jet /(d p jets N 2 ) d trig (1/N Au+Au 200 GeV, 0-15% = 0.2 jet R T anti-k +jet 0 p < 11 GeV [SE] T trig 9 < E < 15 GeV [SE] T trig 11 < E ME = 0.5 jet R 10 - 0 10 20 30 A) [GeV/c] × r - raw,ch T,jet (= p reco,ch T,jet p 1 10 ME SE 10 - 0 10 20 30 A) [GeV/c] × r - raw,ch T,jet (= p reco,ch T,jet p 6 - 10 5 - 10 4 - 10 3 - 10 2 - 10 1 - 10 1 10 ] -1 ) [(GeV/c) jet h d reco,ch T,jet /(d p jets N 2 ) d trig (1/N Au+Au 200 GeV, 0-15% = 0.2 jet R T anti-k +jet rich g < 11 GeV [SE] T trig 9 < E < 15 GeV [SE] T trig 11 < E ME = 0.5 jet R 10 - 0 10 20 30 A) [GeV/c] × r - raw,ch T,jet (= p reco,ch T,jet p 1 10 ME SE 10 - 0 10 20 30 A) [GeV/c] × r - raw,ch T,jet (= p reco,ch T,jet p STAR Preliminary STAR Preliminary γ rich +jet: SE and ME π 0 +jet: SE and ME γ dir +jet vs π 0 +jet: Recoil jet suppression for R jet = 0.2 and 0.5 5 10 15 20 25 1 − 10 1 PYTHIA AA I Au+Au 200 GeV, 0-15% = 0.5 jet R T anti-k STAR Preliminary < 11 GeV trig T 9 < E 5 10 15 20 25 [GeV/c] ch T,jet p 1 − 10 1 PYTHIA AA I < 15 GeV trig T 11 < E +jet 0 π +jet dir γ Caption- I AA PYTHIA as a function of p T,jet ch for γ dir - (red band) and π 0 -trigger (blue band) recoil charged jet. Top: 9 < E T trig < 11 GeV. Bottom: 11 < E T trig < 15 GeV. Lighter and darker bands represent systematic and statistical uncertainties, respectively. Right and left panels represent R jet =0.2 and 0.5, respectively. A clear difference between recoil-jet spectra for different trigger E T : 9 < E T trig < 11 GeV vs. 11 < E T trig < 15 GeV. Recoil jet p T is suppressed with respect to PYTHIA8. γ dir +jet: downward arrow represents upper limit in the yield at: p T,jet ch = 11 GeV/c for 9 < E T trig <11 GeV, p T,jet ch = 15 GeV/c for 11 < E T trig <15 GeV. Caption- γ rich +jet :The reconstructed jet p T, jet reco distributions are shown for the same event (SE) and mixed event (ME) for two triggers E T trig bins: 9-11 GeV and 11-15 GeV. Left and right panels represent for R jet =0.2 and 0.5, respectively. Lower panels shows the ratio between SE and normalized ME. Recoil charged jets dominate (above ~10 GeV/c) over uncorrelated jet background from mixed events for different E T trig bins and jet radii. A clear trigger dependence can been seen. 0 5 10 15 20 25 [GeV/c] ch T,jet p 4 - 10 3 - 10 2 - 10 1 - 10 -1 ) [GeV/c] jet h d ch T,jet /(dp jet 2 dN trig 1/N Au+Au, 0-15% =0.5 jet , R T anti-k < 30 GeV/c const T p +jet 0 p PYTHIA < 15 GeV trig T 11 < E < 11 GeV trig T 9 < E STAR Preliminary π 0 +jet: Recoil jet p T spectra γ dir +jet: Recoil jet p T spectra Caption- Fully corrected semi- inclusive γ dir trigger recoil charged jet p T , jet spectra for the above two E T trig bins. Dashed lines are PYTHIA8 expectation. Left panel (R=0.2) and Right panel (R=0.5). Systematic (lighter band) and statistical (darker band) uncertainty. γ dir +jet: Downward arrow represents the large uncertainty.
Transcript of Au+Au collisions at GeV by the STAR experiment sNN = 200 · 2019. 10. 18. · Measurement of...
Measurement of semi-inclusive +jet and π0+jet distributions in central Au+Au collisions at GeV by the STAR experiment
γdirsNN = 200
Nihar Ranjan Sahoo, for the STAR Collaboration Shandong University, Qingdao, China
Email Id: [email protected] The STAR Collaboration: https://drupal.star.bnl.gov/STAR/presentations/
JetJet
Abstract
MTD TOF Magnet upVPD BBC EEMCBEMC TPC
§ Special High Tower trigger for π0/γ event [BEMC] § Discrimination between π0 γγ and γdir
§ By Transverse Shower Profile (TSP) method § Using Barrel Shower Maximum Detector [BSMD]
2. STAR detector setup1. Motivation
5. Summary and outlook• First γdir+jet and π0+jet measurement at RHIC within 9 < ETtrig < 15 GeV is presented in central Au+Au collisions at
center of mass energy 200 GeV• Recoil jet with jet radius 0.2 is strongly suppressed at high jet pT whereas a noticeable recovery of jet energy loss is
observed at jet radius 0.5 for both the γdir and π0 trigger cases• Recoil jet suppression is seen to be independent of ET
trig; whereas γdir+jet and π0+jet show similar level of suppression.• The measurement within 15 < ET
trig < 20 GeV for γdir+jet is ongoing
• Jet quenching is an important signature of the hot and denseQCD matter produced in heavy-ion collisions [1].
• A direct photon (γdir) produced in coincidence with a recoiljet (γdir+jet) is a good probe to study the parton energy lossin the QGP [2].
• Comparison between γdir+jet vs π0+jet provides quantitativeunderstanding of parton energy loss in the QCD medium
• Energy loss as a function of path length, colorfactor, parton energy, etc.
• Redistribution of lost energy inside themedium [Jet radius]
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3. Analysis details
γrich trigger event
Full analysis chain:
1. Discrimination between π0/γrich-triggered events
Transverse Shower Profile method [4]
2. Recoil jets from high-tower-triggered events (SE)
Using FastJet package [3]; Recoil jet region:[π-π/4,
π+π/4]; Jet radius = 0.2 and 0.5; |ηjet| < 1-R
3. Subtraction of uncorrelated jet background in recoil region
Based on h+jet analysis[5], event-mixing technique
4. Correction for detector and heavy-ion background
fluctuations effects
5. Conversion from γrich+jet to γdir+jet [4]
Using π0+jet yield and purity of γdir
6. Major sources of systematic uncertainty
Unfolding, mixed-event normalization region, detector
effects, γdir background subtraction [contributes only to γdir+jet]
Purity of direct photon for different trigger ETtrig bins
γrich trigger events: enriched-γdir trigger events with someadmixture of photons from π0.
8 10 12 14 16 18 20 [GeV]trig
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Au+Au 200 GeV [year 2014], 0%-15% Uncertaintyσ1±
References1. J. Adams et al. (STAR Collaboration), Nucl. Phys. A 757, 102 (2005)2. X.-N. Wang, Z. Huang, and I. Sarcevic, Phys. Rev. Lett. 77, 231 (1996)3. M. Cacciari, G. P. Salam, and G. Soyez, Eur. Phys. J. C (2012) 72:18964. L. Adamczyk et al. (STAR Collaboration), Phys. Lett. B 760 (2016) 689-6965. L. Adamczyk et al. (STAR Collaboration), Phys. Rev. C 96 (2017) no.2, 024905
We present the semi-inclusive measurement of charged jets recoiling from direct-photon and π0 triggers in central Au+Au collisions at 200 GeV center of mass energy, using a dataset with integratedluminosity 13 nb−1 recorded by the STAR experiment in 2014. The photon and π0 triggers have 9 < ETtrig < 15 GeV. Charged jets are reconstructed with the anti-kT algorithm with resolutionparameters R=0.2 and 0.5. A mixed Event technique developed previously by STAR is used to correct the recoil jet yield for uncorrelated background, enabling recoil jet measurements over a broadpT,jet range with large jet radius. We report the corrected semi-inclusive recoil jet yields for both triggers and compare them to those for p+p collisions. These measurements have different trigger bias,in terms of both the path-length distribution and quark/gluon mix of the recoil jet population, and their corrected recoil spectra are compared.
4. Results and discussion
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ME
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T,jet (= preco,ch
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T,jet (= preco,ch
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T,jet (= preco,ch
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STAR Preliminary STAR Preliminary
γrich+jet: SE and MEπ0+jet: SE and ME
γdir+jet vs π0+jet: Recoil jet suppression for Rjet = 0.2 and 0.5
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Caption- IAAPYTHIA as a function ofpT,jetch for γdir- (red band) and π0-trigger(blue band) recoil charged jet. Top: 9 <ETtrig< 11 GeV. Bottom: 11 < ETtrig< 15GeV. Lighter and darker bandsrepresent systematic and statisticaluncertainties, respectively. Right andleft panels represent Rjet=0.2 and 0.5,respectively.
A clear difference between recoil-jet spectra for different trigger ET: 9 < ETtrig < 11 GeV vs. 11 <
ETtrig < 15 GeV. Recoil jet pT is suppressed with respect to PYTHIA8. γdir+jet: downward arrow
represents upper limit in the yield at: pT,jetch = 11 GeV/c for 9 < ET
trig <11 GeV, pT,jetch = 15 GeV/c
for 11 < ETtrig <15 GeV.
Caption- γrich+jet :The reconstructed jet p T, jetreco distributions
are shown for the same event (SE) and mixed event (ME) fortwo triggers ETtrig bins: 9-11 GeV and 11-15 GeV. Left andright panels represent for Rjet =0.2 and 0.5, respectively. Lowerpanels shows the ratio between SE and normalized ME.
Recoil charged jets dominate (above ~10 GeV/c) overuncorrelated jet background from mixed events for differentETtrig bins and jet radii. A clear trigger dependence can beenseen.
0 5 10 15 20 25 [GeV/c]ch
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π0+jet: Recoil jet pT spectra γdir+jet: Recoil jet pT spectraCaption- Fully corrected semi-inclusive γdir trigger recoil charged jetpT, jet spectra for the above two ETtrigbins. Dashed lines are PYTHIA8expectation. Left panel (R=0.2) andRight panel (R=0.5). Systematic(lighter band) and statistical (darkerband) uncertainty. γdir+jet: Downwardarrow represents the large uncertainty.
