Angular Correlations with ALICE Jan Fiete Grosse-Oetringhaus, CERN for the ALICE collaboration EPS-HEP, Vienna Muon-hadron correlations (p-Pb) Event shape engineering (Pb-Pb) Identified particle femtoscopy (Pb-Pb)

Typical Two-Particle Correlation Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus2 Near-side jet + resonances,... (  ~ 0,  ~ 0) Away-side jet (  ~ , elongated in  ) 2 < p T,trig < 4 GeV/c 1 < p T,assoc < 2 GeV/c 40% lowest multiplicity p-Pb  1/N trig d 2 N assoc /d  d  As you probably know, there is more…  (rad) here:  =  lab p-Pb ALICE, PLB719 (2013) 29

Observed in high-multiplicity pp collisions Well known feature from Pb-Pb collisions (  collective flow) Somehow expected in p-Pb, still surprising, in particular the amplitude 3 The Near-Side Ridge Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus CMS, PLB718 (2013) % of MB N offline,trk > 110 pp CMS, JHEP09(2010) % of MB ALICE, PLB708 (2012) 249 p-Pb 10% of MB Pb-Pb here:  =  lab pp p-Pb Pb-Pb

Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus4 The Double Ridge Subtraction to “isolate” ridge from jet –No ridge seen in % and similar to pp – 0-20%60-100% =  (rad)   (rad)   (rad)  ALICE, PLB719 (2013) 29 here:  =  lab Two ridges ! p-Pb Quantified by Fourier coefficients v n of the  distribution v 2,v 3 vs. event class

v n coefficients –Significant v 2 and v 3 Multi-particle correlation –v 2 {4} = v 2 {6} = v 2 {8} Particle species dependence –Mass ordering of v 2 {p} and v 2 {  } for –Similar for K and  5 Quantification of Ridges Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Features reminiscent of Pb-Pb collisions  strong hints that similar effects at play in p-Pb and Pb-Pb collisions PRL110, (2013)arXiv: PLB 726 (2013) 164PLB 742 (2015) 200 v 2 vs. p T v 2 vs. multiplicity p-Pb What happens in the forward region (large  )?

 s NN = 5.02 TeV y lab – y cms = ±0.465 L int = 5 – 5.8 nb -1 One sided muon arm Beam configurations: 6 p-Pb Collisions in ALICE Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Time Projection Chamber Inner Tracking System (ITS) Muon TrackerMuon Trigger V0 Scintillator p Pb  arm p-Pb: “p going” Pb p  arm Pb-p: “Pb-going” y cms = 0 y lab = 0 Absorber p-Pb

Hadrons at mid rapidity (|  | < 1.0) and forward inclusive muons (-4 <  < -2.5) Tracklets –Straight line using first two layers of ITS – ~ 0.75 GeV/c –Cross-checked with reconstructed tracks (lower statistics) Inclusive muons –Composition varies as a function of p T –Higher p T : dominated by heavy flavour Sample split into multiplicity classes (V0, 2.8 < η < 3.9 and -3.7 < η < -2.7) –Symmetric for both beam configurations –0-20% = high multiplicity | % low multiplicity 7 Forward-Central Correlations Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Layer 1 Layer 2 Heavy flavor Pion Kaon Other Particle fraction vs. p T arXiv: p-Pb

8 Correlations Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus p-going directionPb-going direction 0-20% % Near-side ridge extends out to  ~ 5 (and  ~ ±4) No ridge in low multiplicity Ridge in high multiplicity arXiv: p-Pb

Subtraction déjà vu… Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus9 – = arXiv: p-Pb 0-20% %

Subtracted Correlations Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus10 p-going direction Pb-going direction n = 1 n = 2 n = 3 Double ridge in both beam directions 2 nd coefficient dominates arXiv: p-Pb

Calculate inclusive  v 2 (factorization) p-going < Pb-going (16% difference) AMPT (for inclusive  ) –Similar trend For p T > 2 GeV/c heavy flavour > 60% –v 2 HF (AMPT) ~ 0 –v 2 HF (data) > 0? or different particle composition? 11 v2v2 Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus arXiv: p-Pb

After discussing potential collective effects in small systems let’s shift gears… … and have a look at news about collectivity from Pb-Pb 12Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus

Large event-by-event variation of v n Final-state v 2 correlated with initial-state eccentricities  2 (hydro with small  /s) Proposed by Schukraft, Timmins, Voloshin (PLB719 (2013) 394) –Split events by event-by-event v 2 (Q vector) Q vector from 2 different detectors –TPC in |  | < 0.4  q 2 TPC –V0C (-3.7 <  < -1.7)  q 2 V0C Event studied in 0.5 < |  | < 0.8 –p T spectra –v 2 (scalar product method) 13 Event Shape Engineering Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Pb-Pb nucl-ex/ M no. of particles arXiv:

Does the selection work? –Select on q 2 TPC  check q 2 V0C v 2 changes p T independent –q 2 TPC vs. q 2 V0C  selection bias 14 q 2 Selection Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Large q 2  large v 2 Small q 2  small v 2 (all centralities in backup) Selected / Inclusive vs. p T q 2 selects global event property v 2 vs. p T Pb-Pb P(q 2 V0C ) vs. q 2 V0C Unbiased Small q 2 TPC Large q 2 TPC arXiv:

p T spectra for , K, p Change observed with q 2 selection –p T dependent effect –Harder spectra for large q 2 –Softer spectra for small q 2 –Magnitude depends on mass Events with large q 2 have also larger radial flow? 15 p T Spectra Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus  K p large q 2 TPC small q 2 TPC Selected / Inclusive  K p Let’s test this question… Pb-Pb arXiv:

Quantification of radial flow – Reproduce basic features of hydro-dynamic modeling – Main parameters expansion velocity  T and temperature T Quantify change of spectra – Fixed T, allow change of  T –  T is 0.41%±0.03% larger than inclusive in the large q 2 selection –  T is 0.22%±0.03% smaller than inclusive in the small q 2 selection 16 Blast-Wave Fit Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Blast-Wave: PRC 48, 2462 (1993) q 2 vector (  eccentricity) correlated with radial flow (  pressure gradient) Pb-Pb p T spectra ratio vs. p T large q 2 TPC arXiv:

Pb-Pb  s NN = 2.76 TeV 1D radii separate for , K ±, K 0, pbar, p pairs Monotonic decrease with increasing pair transverse mass Can be described by hydro with hadronic phase (HKM model) –HKM: ideal hydro, gradual decoupling (hydrokinetic), UrQMD 17 Femtoscopic radii for , K, p Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Advertisement 0-10% 10-30% 30-50% ALICE paper: arXiv: HKM: Nucl.Phys. A929 (2014) 1 Pb-Pb Approximate m T scaling for K and p Hadronic phase important R inv vs.

Muon-hadron correlations at forward rapidities in p-Pb –Double ridge extends over 10 units of pseudorapidity –Inclusive muon v 2 larger on Pb-going side than p-going side –AMPT comparison suggests HF v 2 > 0 or different particle composition Event Shape Engineering in Pb-Pb –Divide event sample based on event-by-event q vector –q vector shown to be a global event property –Initial state 2 nd order eccentricity and pressure gradients correlated 18 Summary Angular Correlations with ALICE - Jan Fiete Grosse-Oetringhaus Results constrain the role of initial state and hydrodynamic expansion in the modeling of p-Pb and Pb-Pb collisions

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