Jet Quenching in the light of Experimental perturbative QCD - PowerPoint PPT Presentation

Jet Quenching in the light of perturbative QCD Korinna Zapp Jet Quenching in the light of Experimental perturbative QCD findings Analytical approach MC approach Korinna Zapp Conclusions in collaboration with F. Krauss and U. Wiedemann Institute for Particle Physics Phenomenology Birmingham Particle Physics Seminar 09. 05. 2012

Outline Jet Quenching in the light of perturbative QCD Korinna Zapp Experimental findings Experimental findings Analytical approach MC approach Conclusions Analytical approach MC approach Conclusions

Differential jet cross section Jet Quenching in the light of perturbative QCD Korinna Zapp Experimental findings Analytical approach MC approach Conclusions ATLAS, arXiv:1112.6297

Fragmentation function Jet Quenching in the light of perturbative QCD Korinna Zapp F(z) 3 ATLAS 10 s = 7 TeV Experimental ∫ findings -1 L dt = 36 pb 2 10 Analytical approach 10 MC approach 400 GeV < p < 500 GeV T jet Conclusions Data Pythia6 AMBT1 1 Pythia6 MC09 Pythia6 Perugia 2010 Herwig+Jimmy Herwig++ 2.4.2 Herwig++ 2.5.1 -1 10 Sherpa Pythia8 8.145 4C (MC-Data)/Data (%) (MC-Data)/Data (%) 60 60 40 40 20 20 0 0 -20 -20 -40 -40 -60 -60 -2 -2 -1 -1 10 10 10 10 z z z = p jet · p track p 2 jet ATLAS, Eur. Phys. J. C 71 (2011) 1795

Jet shapes Jet Quenching in the light of perturbative QCD Korinna Zapp 1.1 (r) anti-k jets R = 0.6 Experimental Ψ t findings 1 80 GeV < p < 110 GeV T Analytical 0.9 | y | < 2.8 approach ATLAS 0.8 MC approach -1 ∫ Data L dt = 3 pb 0.7 Conclusions PYTHIA-Perugia2010 HERWIG++ 0.6 ALPGEN 0.5 PYTHIA-MC09 1.1 DATA / MC 1.05 1 0.95 0.9 0.1 0.2 0.3 0.4 0.5 0.6 r � (∆ φ ) 2 + (∆ y ) 2 r = ATLAS, Phys. Rev. D 83 (2011) 052003

Jets in Pb+Pb Jet Quenching in the light of perturbative QCD Korinna Zapp Experimental findings Analytical approach MC approach Conclusions tracks: p ⊥ > 2 . 6 GeV calorimeter cells: E ⊥ > 0 . 7 / 1 GeV A J = E ⊥ 1 − E ⊥ 2 E ⊥ 1 + E ⊥ 2 E ⊥ 1 > 100 GeV E ⊥ 2 > 25 GeV ◮ clear energy asymmetry between jets ◮ jet axis largely unchanged ATLAS, Phys. Rev. Lett. 105 (2010) 024901

Heavy ion challenge Jet Quenching in the light of perturbative QCD Korinna Zapp Experimental findings Analytical approach MC approach Conclusions ◮ jet reconstruction challenging due to large background ◮ maybe look for more robust observables. . .

Single-inclusive hadron suppression Jet Quenching in the light of perturbative QCD Korinna Zapp d N AA / d p ⊥ spectrum in A+A Experimental R AA ( p ⊥ ) = = findings � N coll � d N pp / d p ⊥ � N coll � × spectrum in p+p Analytical approach MC approach 5 10 -2 AA ) (GeV/c) R Conclusions Pb-Pb s = 2.76 TeV 4 10 NN 0 - 5% Pb-Pb s = 2.76 TeV NN 3 scaled pp reference 70 - 80% 10 T dp 0-5% η 2 1 ) / (d 10 70-80% ch 10 N 2 ) (d 1 T p π 1/(2 10 -1 evt -2 10 1/N -3 10 -4 10 -5 10 -6 10 -7 10 0.1 -8 10 0 5 10 15 20 0 5 10 15 20 p (GeV/c) p (GeV/c) T T ALICE, Phys. Lett. B 696 (2011) 30

Single-inclusive hadron suppression Jet Quenching in the light of perturbative QCD Korinna Zapp 1.6 1.6 1.6 CMS PbPb η s = 2.76 TeV, | |<1.0 1.4 NN 1.4 1.4 Experimental findings 1.2 1.2 1.2 T and lumi. uncertainty AA 1 1 1 Analytical AA R 0.8 0.8 0.8 approach 0.6 0.6 0.6 MC approach 0.4 0.4 0.4 Conclusions 0.2 0.2 0.2 70-90% 50-70% 30-50% 1 2 3 4 56 10 20 30 100 1 2 3 4 56 10 20 30 100 1 2 3 4 5 10 20 30 100 p (GeV/c) p (GeV/c) p (GeV/c) T T T 1.2 1.2 1.2 1 1 1 0.8 0.8 0.8 AA 0.6 0.6 0.6 R 0.4 0.4 0.4 0.2 0.2 0.2 10-30% 5-10% 0-5% 0 0 0 1 2 3 4 56 10 20 30 100 1 2 3 4 56 10 20 30 100 1 2 3 4 5 10 20 30 100 p (GeV/c) p (GeV/c) p (GeV/c) T T T CMS, Eur. Phys. J. C (2012) 72:1945

Heavy ion collisions Jet Quenching in the light of perturbative QCD ◮ high multiplicity Korinna Zapp ◮ nuclei large objects (radius ∼ 7 fm) Experimental findings ◮ expect extended system with very high density Analytical ◮ estimate of initial energy density: ǫ 0 ≃ 5 . 5 GeV approach fm 3 at RHIC and ǫ � 40 GeV MC approach fm 3 at LHC Conclusions ◮ theoretical expectation: nucleons melt around 1 GeV fm 3 → quark gluon plasma ◮ naive picture �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� ◮ jets involve high scale → early production ◮ apparently: interactions in dense medium

Heavy ion collisions Jet Quenching in the light of perturbative QCD ◮ high multiplicity Korinna Zapp ◮ nuclei large objects (radius ∼ 7 fm) Experimental findings ◮ expect extended system with very high density Analytical ◮ estimate of initial energy density: ǫ 0 ≃ 5 . 5 GeV approach fm 3 at RHIC and ǫ � 40 GeV MC approach fm 3 at LHC Conclusions ◮ theoretical expectation: nucleons melt around 1 GeV fm 3 → quark gluon plasma ◮ naive picture �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� �������� ◮ jets involve high scale → early production ◮ apparently: interactions in dense medium

Jet quenching Jet Quenching in the light of perturbative QCD Korinna Zapp Motivation Experimental ◮ ’deep inelastic scattering’ of jet on medium findings ◮ interplay between weakly and strongly coupled regimes Analytical approach ◮ emergence of collectivity from microscopic theory of MC approach individual quanta Conclusions Executive summary of experimental findings ◮ strong suppression of hadron production at large p ⊥ ◮ reduction of jet energy ◮ fragmentation function inside remainder jet looks as in vacuum ◮ jet axis remains unchanged ◮ soft modes get transported to large angles

Jet quenching Jet Quenching in the light of perturbative QCD Korinna Zapp Motivation Experimental ◮ ’deep inelastic scattering’ of jet on medium findings ◮ interplay between weakly and strongly coupled regimes Analytical approach ◮ emergence of collectivity from microscopic theory of MC approach individual quanta Conclusions Executive summary of experimental findings ◮ strong suppression of hadron production at large p ⊥ ◮ reduction of jet energy ◮ fragmentation function inside remainder jet looks as in vacuum ◮ jet axis remains unchanged ◮ soft modes get transported to large angles

Gluon radiation in eikonal limit Jet Quenching in the light of perturbative QCD Korinna Zapp ω , k ⊥ Experimental findings Analytical approach E MC approach Conclusions .............. q ( 1 ) q ( 2 ) q ( N ) ⊥ ⊥ ⊥ L ◮ high energy approximation: E ≫ ω ≫ k ⊥ , q ⊥ ◮ static scattering centres → no collisional energy loss ◮ medium characterised by transport coefficient q = � q 2 ⊥ � ˆ λ Baier, Dokshitzer, Mueller, Peigne, Schiff, Nucl. Phys. B 484 (1997) 265

LPM-effect: heuristic discussion Jet Quenching in the light of perturbative QCD Brownian motion of the gluon: � k 2 ⊥ � = ˆ qL Korinna Zapp gluon decoheres from projectile when relative phase ϕ > 1 Experimental findings � � k 2 qL 2 = ˆ 2 ω = ω c Analytical ⊥ ϕ = 2 ω L approach ω MC approach formation time of the radiated gluon: Conclusions � t f ≃ 2 ω ≃ 2 ω 2 ω N coh = t f ⇒ t f = and k 2 ˆ ˆ λ qt f q ⊥ gluon energy spectrum: � d 2 I coh d 2 I incoh 1 ˆ α s q d ω d z ≃ ∝ d ω d z 2 ω ω N coh radiative energy loss: L ω c d ω ω d 2 I � � qL 2 d ω d z ∝ α s ˆ ∆ E = d z 0 0 Baier, Schiff, Zakharov, Ann. Rev. Nucl. Part. Sci. 50 (2000) 37