Measurement of high-p T azimuthal anisotropy in charged hadron production from 2.76 TeV PbPb collisions at CMS Victoria Zhukova (MIT) for the CMS Collaboration Quark Matter Conference, Washington DC 14 th Aug, 2012 Quark Matter 2012, Washington DC 1 Victoria Zhukova
Jet Quenching and Azimuthal Anisotropy Path length (L) dependence of jet energy loss ( Δ E) jet energy loss ( Δ E~L α Fourier decomposition of charged hadron yields: ∞ d 3 N d 2 N p T dp T d η d φ = 1 X 2 v n = km ( p T , η ) cos [ n ( φ − Ψ pp p T dp T d η (1 + m )]) 2 π k =1 Azimuthal anisotropy (v 2, v 3, v 4 ) of high p T jets Quark Matter 2012, Washington DC 2 Victoria Zhukova
Physics Motivation • CMS (* preliminary) PbPb s = 2.76 TeV NN 2 µ * Z (0-100%) p > 20 GeV/c ∫ -1 1.8 L dt = 7-150 b T µ µ W (0-100%) p > 25 GeV/c T 1.6 Isolated photon (0-10%) b-quarks (0-100%) Δ E~L α 1.4 (via secondary J/ ) ψ 1.2 α = 1 for pQCD, collisional AA 1 R α = 2 for pQCD, radiative 0.8 α = 3 for AdS/CFT 0.6 0.4 Initial Conditions: Charged particles (0-5%) 0.2 -Glauber 0 0 20 40 60 80 100 p (m ) (GeV) -Color Glass Condensate T T Phys. Usp. B 52, 659 (2009) Phys. Lett. B (2012) 710 256 Nucl. Phys. A784, 426 (2007) Phys. Rev. Lett. (2011) 106 312301 Phys. Rev. C 82, 024908 (2011) Eur. Phys. J. C. (2012) 72 1945 Phys. Rev. C 84, 034904 (2011) JHEP 1205 (2012) 063 Phys. Rev. C 83, 024908 (2011) Quark Matter 2012, Washington DC 3 Victoria Zhukova
CMS Detector CMS Detector Hadronic calorimeters Hadronic Calorimeter EM Calorimeter Tracker Unprecedented kinematic range and acceptance Quark Matter 2012, Washington DC 4 Victoria Zhukova
High p T Single Track Trigger • Full 2011 HI Data set: L int = 150 µ b -1 • Single-Track High-p T Triggers (Total # of events: ~1.55M with p T > 20 GeV/c ) All triggers are at least 95% efficient (0-40%) Trigger Efficiency 1 0.8 0.6 CMS Preliminary Trigger Thresholds: p > 12 GeV/c 0.4 T > 14 GeV/c p T p > 20 GeV/c T Centrality: 40 - 100% 0.2 | | < 1 η 0 18 20 22 24 26 28 30 10 12 14 16 max p (GeV/c) T Quark Matter 2012, Washington DC 5 Victoria Zhukova
Event Plane Formalism Event Plane ) m 1 5 b = 6 . 0 f m = 0 . 2 3 8 Experimentally observable, used to ε f part ( y estimate the true participant plane. 1 0 x' y' 5 Ψ R 0 - 5 - 1 0 v 2 Coefficient = 2 . 4 0 4 f m σ x' = 3 . 0 6 6 f m σ y' - 1 5 - 1 5 - 1 0 - 5 0 5 1 0 1 5 x ( f m ) ( ) { } v 2 EP cos 2 ' / R % EP 1 Need to CMS PbPb s =2.76 TeV 0.9 NN Resolution Correction Factor correct for Ψ EP 0.8 resolution (R). 0.7 0.6 0.5 0.4 Resolution Correction: (3-subevent method) " ! HF- (-5 < -3) 0.3 " ! HF+ (3 < 5) 0.2 2 Subevent 0.1 0 0 10 20 30 40 50 60 70 80 90 100 Centrality (%) Four-particle Cumulant Quark Matter 2012, Washington DC 6 Victoria Zhukova
Avoiding Di-Jet Correlations φ EP- EP+ To calculate v2 : v 2 + with EP- and v 2 - with EP+ gap Particles from the positive η region are correlated with the event plane calculated in V 2 - V 2 + the negative η region. Event Planes: EP+ (3< η <5) EP- (-5< η <-3) η -5 -3 3 5 0 Hadronic Forward Calorimeters used for determining the Event Plane. This minimizes systematic effects that result from back-to-back di-jets Quark Matter 2012, Washington DC 7 Victoria Zhukova
η -Gap Study 0.3 {EP} 10 - 20% 20 - 30% 0 - 10% 2 v 0.25 p (GeV/c) -1 -1 -1 -1 -1 CMS L CMS L CMS L CMS L CMS L = 150 = 150 = 150 = 150 = 150 b b b b b µ µ µ µ µ T 0.2 int int int int int PbPb PbPb PbPb PbPb PbPb s s s s s = 2.76 TeV = 2.76 TeV = 2.76 TeV = 2.76 TeV = 2.76 TeV NN NN NN NN NN 2.4 - 3.2 0.15 CMS Preliminary CMS Preliminary CMS Preliminary CMS Preliminary CMS Preliminary 1.6 - 1.8 0.1 1.0 - 1.1 9.6 - 12.0 0.05 35.2 - 48.0 0 0.3 {EP} 30 - 40% 40 - 50% 50 - 60% 2 v 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 Δ η Δ η Δ η gap gap gap Based on this study we conclude that the gap size of 3 is sufficient to suppress most of the back-to-back di-jet effects Quark Matter 2012, Washington DC 8 Victoria Zhukova
η -Gap Study 0.3 {EP} 10 - 20% 20 - 30% 0 - 10% 2 v 0.25 p (GeV/c) -1 -1 -1 -1 -1 CMS L CMS L CMS L CMS L CMS L = 150 = 150 = 150 = 150 = 150 b b b b b µ µ µ µ µ T 0.2 int int int int int PbPb PbPb PbPb PbPb PbPb s s s s s = 2.76 TeV = 2.76 TeV = 2.76 TeV = 2.76 TeV = 2.76 TeV NN NN NN NN NN 2.4 - 3.2 0.15 CMS Preliminary CMS Preliminary CMS Preliminary CMS Preliminary CMS Preliminary 1.6 - 1.8 0.1 1.0 - 1.1 9.6 - 12.0 0.05 high p T 35.2 - 48.0 0 0.3 {EP} 30 - 40% 40 - 50% 50 - 60% 2 v 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 Δ η Δ η Δ η gap gap gap Based on this study we conclude that the gap size of 3 is sufficient to suppress most of the back-to-back di-jet effects Quark Matter 2012, Washington DC 9 Victoria Zhukova
v 2 as a function of p T (| η |<1) 0-10% 10-20% 20-30% 30-40% 40-50% 50-60% 0 . 2 5 0 . 2 5 0 . 2 5 0 - 1 0 % 1 0 - 2 0 % 2 0 - 3 0 % - 1 CMS L = 150 b µ i n t 0 . 2 0 PbPb s = 2.76 TeV . 2 0 . 2 N N 0 . 1 5 0 . 1 5 0 . 1 5 CMS 2011 | | < 1 η 2 CMS 2010, | |<0.8 η v 0 . 1 0 . 1 0 . 1 ATLAS ALICE, | η |<0.8 0 . 0 5 0 . 0 5 0 . 0 5 0 0 0 - 0 . 0 5 - 0 . 0 5 - 0 . 0 5 1 0 2 0 3 0 4 0 5 0 1 0 2 0 3 0 4 0 5 0 1 0 2 0 3 0 4 0 5 0 0 . 2 5 0.25 0.25 3 0 - 4 0 % 50-60% 4 0 - 5 0 % 0 . 2 0.2 0.2 0 . 1 5 0.15 0.15 2 v 0 . 1 0.1 0.1 0 . 0 5 0.05 0.05 0 0 0 - 0 . 0 5 -0.05 -0.05 1 0 2 0 3 0 4 0 5 0 10 20 30 40 50 10 20 30 40 50 p (GeV/c) p (GeV/c) p (GeV/c) PRL 109, 022301(2012) T T T -First v 2 measurements for p T > 20GeV/c -Gradual decrease of v 2 above p T ~ 10 GeV/c Quark Matter 2012, Washington DC 10 Victoria Zhukova
v 2 as a function of p T (1<| η |<2 ) 0-10% 10-20% 20-30% 30-40% 40-50% 50-60% 0-10% 10-20% 20-30% -1 = 150 b CMS L µ int PbPb s = 2.76 TeV 0 . 2 0 . 2 0 . 2 NN 1<| |<2 η 2 CMS 2011 v 0 . 1 0 . 1 0 . 1 ATLAS 0 . 0 0 . 0 0 . 0 20 40 20 40 20 40 40-50% 5 0 - 6 0 % 30-40% 0 . 2 0 . 2 0 . 2 2 v 0 . 1 0 . 1 0 . 1 0 . 0 0 . 0 0 . 0 20 40 20 40 20 40 PRL 109, 022301(2012) p (GeV/c) p (GeV/c) p (GeV/c) T T T Quark Matter 2012, Washington DC 11 Victoria Zhukova
Theory Comparison Data: PRL 109.022301(2012) Theory: B.Betz,M.Gyulassy;arXiv:1201.0281 -Data can constrain different theoretical scenarios Quark Matter 2012, Washington DC 12 Victoria Zhukova
Higher Harmonics Results (v 3 ) GLAUBER 0-10% 10-20% 20-30% 30-40% 40-50% 50-60% CMS Preliminary 0-10% 10-20% 20-30% 0.15 0.15 -1 0.15 L = 150 b µ int PbPb s = 2.76 TeV NN 0.10 0.10 0.10 | |<1 η 3 1<| |<2 η v 0.05 0.05 0.05 0.00 0.00 0.00 0 20 40 0 20 40 0 20 40 5 0 - 6 0 % 30-40% 40-50% 0.15 0.15 0.15 0.10 0.10 0.10 3 v 0.05 0.05 0.05 0.00 0.00 0.00 0 20 40 0 20 40 0 20 40 p ( G e V / c ) p (GeV/c) p (GeV/c) T T T PAS HIN-12-010 NEW RESULTS!!! -Small v 3 signal above 20 GeV/c . Quark Matter 2012, Washington DC 13 Victoria Zhukova
Higher Harmonics Results (v 4 ) GLAUBER 0-10% 10-20% 20-30% 30-40% 40-50% 50-60% CMS Preliminary 10-20% 20-30% 0-10% 0.15 0.15 - 1 0.15 L = 150 b µ i n t = 2.76 TeV PbPb s N N 0.10 0.10 0.10 | |<1 η 4 1<| |<2 η v 0.05 0.05 0.05 0.00 0.00 0.00 20 40 0 20 40 0 20 40 0 50-60% 40-50% 30-40% 0.15 0.15 0.15 0.10 0.10 0.10 4 v 0.05 0.05 0.05 0.00 0.00 0.00 0 20 40 20 40 0 20 40 0 p (GeV/c) p (GeV/c) p (GeV/c) T T T PAS HIN-12-010 NEW RESULTS!!! Quark Matter 2012, Washington DC 14 Victoria Zhukova
v 2 as a function of centrality 1.0 < p < 1.1 GeV/c 3.2 < p < 4.0 GeV/c 14 < p < 16 GeV/c T T T | |<1 0.2 η 0.2 0.2 1<| |<2 η 2 v 0.1 0.1 0.1 -1 CMS L = 150 b µ int PbPb s = 2.76 TeV NN participants 0.0 0.0 0.0 100 200 300 100 200 300 100 200 300 28.8 < p < 35.2 GeV/c 35.2 < p < 48 GeV/c 48 < p < 60.8 GeV/c T T T 0.2 0.2 0.2 2 v 0.1 0.1 0.1 0.0 0.0 0.0 100 200 300 100 200 300 100 200 300 N N N part part part ε part : 0.09 (0-10%) to 0.46 (50-60%) - Significant non-zero v 2 up to p T ~48 GeV/c for all the centralities. - For p T > 48 GeV/c v 2 is consistent with 0 for all the centralities. Quark Matter 2012, Washington DC 15 Victoria Zhukova
Recommend
More recommend
