TwoParticle Correlation in e e Collisions at 912 GeV with ALEPH Archived Data 1 TwoParticle Correlation in ee with ALEPH archived data Anthony Badea Austin Baty YenJie Lee ID: 763755
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Two-Particle Correlation in e +e- Collisions at 91.2 GeV with ALEPH Archived Data 1 Two-Particle Correlation in e+e- with ALEPH archived data Anthony Badea, Austin Baty, Yen-Jie Lee, Christopher McGinn, Michael Peters, Jesse ThalerMassachusetts Institute of Technology Gian Michele InnocentiCERNPaoti Chang, Tzu-An ShengNational Taiwan University Marcello Maggi Universita degli Studi di Bari 2 nd JETSCAPE Winter School and Workshop 2019Texas A&M University
Motivation 2Two-Particle Correlation in e+e - with ALEPH archived data pppPbPbPb?e+e-Ridge observed in small systems, possible explanations: Initial state effect (CGC)Final state effect due to mini-QGPMPIsEscape mechanism…Similarity between e+e-, pp and AAEvent multiplicity per participant dN/dη(y)Study of high multiplicity event with well-defined initial condition:No complication from hadron structure, Gluon ISRNo multi-parton interaction QGP Escape
Remarkable similarity between e +e- and AA collisions3 Two-Particle Correlation in e+e- with ALEPH archived dataAuAue+e-ppCharged Hadron dN/dη Total Charged Particle Multiplicity Per Participant
ΔΦ correlation with large η gapTwo-Particle Correlation in e+e- with ALEPH archived data 42<|Δη|<4.8 ΔΦProjectionLarge EventMultiplicitySmall N(Event Multiplicity)ΔΦProjection JHEP 09 (2010) 091> 35 particles
Modeling e+ e- collisions with AMPTTwo-Particle Correlation in e+e- with ALEPH archived data5AMPT J.L Nagle et. al PRC 97, 024909 (2018)
Modeling two strings configuration with AMPT Two-Particle Correlation in e+e- with ALEPH archived data 6AMPT J.L Nagle et. al PRC 97, 024909 (2018)
Superconducting Magnet (1.5T) Hadron CalorimeterTime ProjectionChamberMuon ChamberInner Tracking ChamberElectromagnetic CalorimeterThe ALEPH Detector7Two-Particle Correlation in e+e- with ALEPH archived dataLEP1 e+e- data at Z pole (91 GeV)Charged particles multiplicity: : pT>0.2 GeV and |η|<1.74Thrust axis and jets are reconstructed by tracks + calorimeters <1010-2020-30>30>35Charged Particle Multiplicity
Hadronic Event Selection 8Two-Particle Correlation in e+e - with ALEPH archived dataTrack Selection:Number of TPC hits for a charged tracks >= 4|d0| < 2 cm|z0|< 10 cm|cosθ|<0.94 (corresponding to |η|<1.74)pT> 0.2 GeV (pT with respect to beam axis)NTPC >=4x2/ndf < 1000.Neutral Hadron Selection:ECAL / HCAL objectsE> 0.4 GeV|cosθ|<0.98Event Selection:Number of good charged particles >= 5 (including charged hadrons and leptons)Number of good ch+neu. Particles >= 13Echarged > 15 GeV |cos(θsphericity)|<0.82 <1010-2020-30>30>35Charged Particle Multiplicity
Event Shape: Thrust 9Two-Particle Correlation in e+e - with ALEPH archived datae+e- Thrust Axis
Unfolded Thrust Distribution 10Two-Particle Correlation in e+e- with ALEPH archived dataTypical e+e- annihilation events are more pencil-likePencil-like: T~1 Spherical: T~0.5Thrust (T)
High Multiplicity Event in e+ e- Collisions (1)11 Two-Particle Correlation in e+e- with ALEPH archived data 55 TracksT=0.71Highest multiplicity event in ALEPH LEP1 data
High Multiplicity Event in e+ e- Collisions (2)12 Two-Particle Correlation in e+e- with ALEPH archived data 44 TracksT=0.57
High Multiplicity Event in e+ e- Collisions (3)13 Two-Particle Correlation in e+e- with ALEPH archived data 39 TracksT=0.98
Charged Particle Multiplicity 14Two-Particle Correlation in e+e- with ALEPH archived dataPYTHIA6 (dots) gives reasonable description of multiplicity distribution in the ALEPH LEP1 archived dataSlight under-predicting the the high multiplicity tailNote that PYTHIA8 (default) significantly under-predict the high multiplicity tail (not shown)
Uncorrected Thrust Distributions 15Two-Particle Correlation in e+e- with ALEPH archived dataN: # of charged particles with pT>0.2 GeV and |η|<1.74High multiplicity events are more sphericalInclusive NN<1010≤N<2020≤N<30N≥30N≥35
Uncorrected Thrust Distributions 16 Two-Particle Correlation in e+e- with ALEPH archived dataN: # of charged particles with pT>0.2 GeV and |η|<1.74High multiplicity events are more spherical, reasonable description from PYTHIAInclusive NN<1010≤N<2020≤N<30N≥30N≥35
Beam Axis Analysis 17 Two-Particle Correlation in e+e- with ALEPH archived data e+e- Identical measurement as performed in pp, pA and AA collisions in various experimentsSoft radiation
Beam Axis Analysis 18 Two-Particle Correlation in e+e- with ALEPH archived data Pseuodorapidity ( η ) and azimuthal angle (Φ) are calculated with respect to the beam pipee+e- Φ η
Beam Axis A nalysis19 Two-Particle Correlation in e+e- with ALEPH archived data e + e - Φ 1 Δη = η 1 - η 2 Search for ridge signal with beam axis: enhance number of charged particle pairs with large Δη gap and similar Φ ( small ΔΦ = Φ 1 - Φ 2 ) Ex: Sensitive to “pressure driven expansion” of the medium in the direction perpendicular to the beam axis Φ 2 New results since QM2018 will be presented in Anthony’s talk
Beam Axis Analysis 20 Two-Particle Correlation in e+e- with ALEPH archived data e+e- No ridge signal is found in beam axis analysis , which is mainly sensitive to perturbative physics (+ parton shower)See Anthony’s talk
Thrust Axis Analysis 21 Two-Particle Correlation in e+e- with ALEPH archived data e+e- Thrust axis analysis to follow the “direction of color string”Thrust Axis
Thrust Axis Analysis 22 Two-Particle Correlation in e+e- with ALEPH archived data e+e- Thrust Axis Φ η Pseuodorapidity ( η ) and azimuthal angle ( Φ ) are calculated with respect to the Thrust Axis Thrust axis analysis to follow the “direction of color string”
Thrust Axis Analysis 23 Two-Particle Correlation in e+e- with ALEPH archived data e+e- Thrust Axis Φ 1 Δη = η 1 - η 2 Φ 2 Search for ridge signal with thrust axis : enhance number of charged particle pairs with large Δη gap and similar Φ ( small ΔΦ = Φ 1 - Φ 2 ) Thrust axis analysis to follow the “direction of color string” Pseuodorapidity ( η ) and azimuthal angle ( Φ ) are calculated with respect to the Thrust Axis
Event Mixing in Thrust Axis Analysis 24Two-Particle Correlation in e+e- with ALEPH archived datae+e-Signal Event Matched Evente+e- Thrust axis of the signal eventUse the signal event Thrust axis to calculate the particle (η,Φ) distributions.Problem: (η,Φ) distributions of the mixed event will not match with the spectra in the signal events in the multiplicity binIdea: Reweight the mixed event (η,Φ) distribution to match the average (η,Φ) distributions in the multiplicity binThrust axis of the signal event
Two-Particle Correlation F unction25Two-Particle Correlation in e+e- with ALEPH archived dataEvent 1 Event 2 same event pairsmixed event pairs Signal pair distribution: Background pair distribution: Δη = η 1 -η 2 Δφ = φ 1 -φ 2 Associated hadron yield per trigger: Δη = η 1 -η 2 Δφ = φ 1 -φ 2 Beam Axis Reweight the mixed event to match the signal event η - Φ distributions
Correlation Function with Thrust Axis 26Two-Particle Correlation in e+e- with ALEPH archived dataALEPH e+e-10≤N<20 Thrust axisCMS ppInclusive Beam axisCorrelation function with Thrust Axis as reference become much more similar to the beam axis result in pp collisions (with many caveats / differences)
Correlation Function with Thrust Axis 27 Two-Particle Correlation in e+e- with ALEPH archived dataALEPH e+e-10≤N<20 Thrust axisNarrower away side peak in high multiplicity eventsALEPH e+e-N≥35 Thrust axis
LEP1 Data vs PYTHIA6 N≥3028Two-Particle Correlation in e+e- with ALEPH archived dataProjectionHint of near-side peak in dataConsistent with PYTHIA6 without final state effectsContribution from multi-jet correlation and reconstruction effectsPYTHIA6 reference limited by archive MC statistics(ZYAM subtracted)1.6<|Δη|<3.0(Long range)
LEP1 Data vs PYTHIA6 N≥ 35 29Two-Particle Correlation in e+e- with ALEPH archived dataProjection(ZYAM subtracted)1.6<|Δη|<3.0(Long range)Hint of near-side peak in dataConsistent with PYTHIA6 without final state effectsContribution from multi-jet correlation and reconstruction effectsPYTHIA6 reference limited by archive MC statistics
Thrust Axis Analysis 30 Two-Particle Correlation in e+e- with ALEPH archived data e+e- “Perturbative QCD physics” still comes in the Thrust axis analysis (Jets) One possibility to suppress jet component is to apply a | η| selectionThrust Axis
Thrust Axis Analysis with “Barrel Particles” 31 Two-Particle Correlation in e+e- with ALEPH archived data e+e- Thrust Axis Remove particles at large η (in the leading and subleading jet) by requiring | η | < 1.6 Enhance the contribution of soft radiation soft radiation Jet Veto “Perturbative QCD physics” still comes in the Thrust axis analysis (Jets) One possibility to suppress jet component is to apply a | η | selection
LEP1 Data vs LEP1 MC N≥35 32 Two-Particle Correlation in e+e- with ALEPH archived dataProjectionHint of near-side peak in dataConsistent with PYTHIA6 w/o final state effectsContribution from multi-jet correlation and reconstruction effectPYTHIA6 reference limited by archive MC statistics
LEP1 Data vs LEP1 MC N≥35 33 Two-Particle Correlation in e+e- with ALEPH archived dataProjection|η| < 1.6Hint of near-side peak in dataConsistent with PYTHIA6 w/o final state effectsContribution from multi-jet correlation and reconstruction effectPYTHIA6 reference limited by archive MC statistics
Future plan 34Two-Particle Correlation in e+e- with ALEPH archived dataNear term:ZYAM: Change to fit (as opposite to the current local minimum)Correct for the Thrust reco effectsExtract associated yield upper limit from data (See Anthony Badea’s talk)New ideas:Collinear drop algorithm for correlation analysisRe-analyze large thrust region (jet core)Possibility to have a more detail look at the jet structure fluctuation in e+e-Azimuthal angle correlation of particles inside the jet coneFragmentation function vs. multiplicityD and B meson measurement vs. multiplicity…M(Kπ) (GeV)D0→KπD0→KK
Summary 35Two-Particle Correlation in e+e - with ALEPH archived dataThe first two-particle correlation analysis in e+e- performed in bins of event multiplicity up to N = 35 - 55No significant ridge signal is observed in beam axis analysisThrust axis and jet region veto are employed to enhance the signal from soft radiationsNo significant difference between ALEPH LEP1 data and PYTHIA6 observedNo evidence of the final state effect in the probed event multiplicity ranges: An important reference of the ridge signal observed in pp, pA, dA and AA collisionsBELLE Data (~11 GeV) and LEP2 Data analyses (up to ~208 GeV) ongoing… stay tuned!
MIT Team 36Two-Particle Correlation in e+e - with ALEPH archived dataAnthony Badea Austin Baty Gian Michele Innocenti Yen-Jie LeeChristopher McGinn Michael Peters Jesse ThalerDemonstrating the value of open data Looking forward to LEP2 data analysis!
Acknowledgement 37Two-Particle Correlation in e+e - with ALEPH archived dataWe would like to thank Roberto Tenchini and Guenther Dissertori from the ALEPH collaboration for the useful comments and suggestions on the use of ALEPH archived data.We would like to thank Wei Li, Maxime Guilbaud, Wit Busza and Yang-Ting Chen for the useful discussions on the analysis.The MIT group's work was supported by US DOE-NP