Hard Probes at ATLAS. Zvi Citron. (for the ATLAS Collabora9on) Moriond, 28 March Zvi Citron

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1 בס"ד Hard Probes at ALAS (for the ALAS Collabora9on) Moriond, 8 March 4

2 HI at ALAS In addi9on to the high energy + rogram, LHC and ALAS have a robust Heavy Ion rogram Muon sectrometry, calorimetry, and charged tracking are well suited for HI and included Pb+Pb runs at s=.76 ev +Pb collsions at s=5. ev in 3 Moriond, 8 March 4

3 Hard Probes in Pb+Pb Electroweak Bosons Do not interact with the QCD medium standard candles for energy loss Production exected to scale with <N coll > Check QCD redictions Check for modification, effects of nuclear PDF Hadrons, Jets Access to quarks, glouns Interact with the QCD medium Modification of color sensitive objects in the medium Quantify and understand where energy goes, what haens in medium interactions Moriond, 8 March 4 3

for energy loss Production exected to scale with <N coll > Check QCD

initial state effects in novel collision energy, geometry Coming soon

Modification of color sensitive objects in the medium Quantify and

4 Hard Probes in Pb+Pb and +Pb! Electroweak Bosons Do not interact with the QCD medium standard candles for energy loss Production exected to scale with <N coll > Check QCD redictions Check for modification, effects of nuclear PDF Focus on initial state effects in novel collision energy, geometry Coming soon Hadrons, Jets Access to quarks, glouns Interact with the QCD medium Modification of color sensitive objects in the medium Quantify and understand where energy goes, what haens in medium interactions Is there a medium in +Pb? Does jet roduction match exectations? Moriond, 8 March 4 4

5 Color Neutral Bosons Isolated Photons Isolation E Select isolated direct hotons High statistics, significant bkg htts://cdsweb.cern.ch/record/4593 Moriond, 8 March 4 5

6 Color Neutral Bosons Isolated Photons Wè μ+ν Isolation E Measured Events / 4. GeV 4 ALAS Preliminary µ +, -8%.< η <.4 3 Pb+Pb =.76 ev - Ldt.4 nb Data W µν W τν Z µ µ QCD htts://cdsweb.cern.ch/record/ miss Reconstruct W from muon and missing as neutrino roxy Significant statistics, some bkg Moriond, 8 March 4 6

7 Color Neutral Bosons Isolated Photons Wè μ+ν Isolation E Measured Events / 4. GeV 4 ALAS Preliminary µ +, -8%.< η <.4 3 Pb+Pb ] - dm [GeV dn =.76 ev - Ldt.4 nb Data W µν W τν Z µ µ QCD ALAS Pb+Pb =.76 ev Data L int =.5 nb Zè ee Z ee - counts Oosite sign: 77 Same sign: 4 Zè μμ Z µ µ 3 4 Simulation miss m ee m µµ Phys. Rev. Lett., 53 (3) Reconstruct di-leton air Low statistics but very clean Moriond, 8 March 4 7

8 Binary Scaling! Isolated Photons htts://cdsweb.cern.ch/record/4593 Moriond, 8 March 4 8

9 Binary Scaling! Isolated Photons Wè μ+ν W µ,fiducial N events N 9 coll N ALAS Preliminary 5 5 ± W (Data) ± W (PYHIA LO*) ± W (POWHEG NLO) + W (Data) Pb+Pb W (Data) =.76 ev - Ldt.4 nb N art htts://cdsweb.cern.ch/record/645 Moriond, 8 March 4 9

10 Binary Scaling! Isolated Photons Wè μ+ν W µ,fiducial N events N 9 coll N ALAS Preliminary Z ll y <.5 N 9 N events coll N 6 Zè ll ALAS Pb+Pb =.76 ev Data L int =.5 nb Z All - Z ee Z ll Z µµ 5 4 Phys. Rev. Lett., 83 (3) 5 ± W (Data) ± W (PYHIA LO*) ± W (POWHEG NLO) + W (Data) W Z <GeV (Data) Pb+Pb =.76 ev Z < - Ldt.4 nb Z >3GeV - <3GeV N art 3 4 N art Moriond, 8 March 4

11 No Sign of npdf Modification in Differential Yields (yet) Wè μ+ν 9 coll N N events dn dη ALAS Preliminary - - W µ ν 9 coll N N events dn dη ALAS Preliminary + W + µ + ν Pb+Pb - Ldt.4 nb Data =.76 ev MRS LO* MSW NLO -8% Uncorr. uncertainty Corr. uncertainty Pb+Pb Data =.76 ev - Ldt.4 nb MRS LO* MSW NLO -8% Uncorr. uncertainty Corr. uncertainty Data/NLO η µ η - Data/NLO η µ η + htts://cdsweb.cern.ch/record/645 Moriond, 8 March 4

12 No Sign of npdf Modification in Differential Yields (yet) 9 coll N N events dn dη Data/NLO Pb+Pb - Ldt.4 nb Data =.76 ev MRS LO* MSW NLO -8% Wè μ+ν ALAS Preliminary - - Uncorr. uncertainty Corr. uncertainty W µ ν η µ η - 9 coll N N events dn dη Data/NLO Pb+Pb Z ll Ldt.4 nb Data =.76 ev dn dy MRS LO* MSW NLO N events % 4 ALAS Preliminary Uncorr. uncertainty Corr. uncertainty W + µ + ν Zè ll ALAS Pb+Pb =.76 ev Data L int =.5 nb Centrality -8% η Z ll Model µ η + Data Model Model is LO y shae scaled to NNLO total cross-section - y Z Phys. Rev. Lett., 83 (3) Moriond, 8 March 4

13 Jet Nuclear Modification Factor R CP ALAS anti-k t R =.4 Pb+Pb L dt s NN - = 7 µb =.76 ev 5-6 % 3-4 % - % - % R CP R CP ALAS 38 < < 44 GeV 89 < < 3 GeV R CP N art R CP = N eriheral Coll central N Coll anti-k t R =.4 5 < < 58 GeV 9 < < 37 GeV N art N art Inclusive jet roduction measured Increasing suression with centrality Roughly flat in for central events R CP R CP 67 < < 77 GeV Pb+Pb L dt 58 < =.76 ev - = 7 µb d N central jets / dyd d N eriheral jets / dyd < 8 GeV N art Phys. Lett. B 79 (3) -4 Moriond, 8 March 4 3

14 Internal Jet Structure R D(z) = D(z) central /D(z) eriheral z = article jet cos( Δη + Δϕ ) D(z) are background subtracted and unfolded Enhancement at low z Suression at intermediate z No change at high z - leading article unaffected? htt://cdsweb.cern.ch/record/47936 Moriond, 8 March 4 4

15 Charged Hadrons in +Pb R Pb.6.4. ALAS Preliminary - +Pb L µb = int =5. ev -9% -<y*<.5 Glauber R Pb formed using + baseline interolated from.76 and 7 ev collisions Enhancement seen to GeV Higher with more statistics coming soon.8 otal systematic uncertainty htts://cdsweb.cern.ch/record/64333 Moriond, 8 March 4 5

16 Jets in +Pb R CP. -%/6-9% -%/6-9% Centrality,, and y deendent jet roduction/relative suression Maybe only centrality and deendence? R CP %/6-9%.8.6 anti-k t, R=.4 ALAS Preliminary +Pb, 5. ev, = 3 nb L int. 3-4%/6-9% < y* < < y* < < y* < < y* < < y* < < y* < -3.6 cosh(y*) htts://cdsweb.cern.ch/record/644 Moriond, 8 March 4 6

17 Jets in +Pb Centrality,, and y deendent jet roduction/relative suression Maybe only centrality and deendence? R Pb formed using Pythia in lieu of true + baseline Suression is only relative within centrality bins! R Pb PYHIA R R Pb CP PYHIA R R Pb Pb CP %/6-9% < y* < +.8 -% -%/6-9% -.3 < y* < +.3 -% -9% -3% 6-9% %/6-9%.8 -. < y * < -.8 PYHIA R R CP Pb R CP < y* < -. anti-k ALAS t, R=.4 Preliminary -. < y* < -.8 ALAS +Pb, Preliminary 5. ev, L int = 3 nb - +Pb, anti-k t <, y* R=.4 ev, < -3.6 = 3 nb L int %/6-9% < y * < < y* < < y* < < y* < anti-k -3.6 < y* < t, R=.4 ALAS for Aroval. 6-9% -. < y* < < y* < Pb, 5. ev, L int = 3 nb 5 PYHIA R Pb cosh(y*) -% - htts://cdsweb.cern.ch/record/644 Moriond, 8 March 4 7

18 Jets in +Pb Centrality,, and y deendent jet roduction/relative suression Maybe only centrality and deendence? R Pb formed using Pythia in lieu of true + baseline Suression is only relative within centrality bins! PYHIA R R Pb CP R Pb PYHIA R R Pb Pb CP %/6-9% < y* < +.8 -% -%/6-9% -.3 < y* < +.3 -% -9% -3% 6-9% %/6-9%.8 -. < y * < -.8 PYHIA R R CP Pb R CP < y* < -. anti-k ALAS t, R=.4 Preliminary -. < y* < -.8 ALAS +Pb, Preliminary 5. ev, L int = 3 nb - +Pb, anti-k t <, y* R=.4 ev, < -3.6 = 3 nb L int %/6-9% < y * < < y* < < y* < < y* < anti-k -3.6 < y* < t, R=.4 ALAS for Aroval. 6-9% -. < y* < < y* < Pb, 5. ev, L int = 3 nb 5 PYHIA R Pb cosh(y*) -% - htts://cdsweb.cern.ch/record/644 Moriond, 8 March 4 8

Summary Many more results from Pb+Pb collisions Charged ar9cle sectra, heavy flavor, jet- boson correlatoins, more jet roer9es (see M. Sousta s talk!

19 Summary Many more results from Pb+Pb collisions Charged ar9cle sectra, heavy flavor, jet- boson correlatoins, more jet roer9es (see M. Sousta s talk!) On the ath to understanding interac9ons of high momentum robes with the color medium as well as nailing down ini9al state effects Intriguing results from +Pb and more to come soon! 9 Moriond, 8 March 4

20 Backu Information Moriond, 8 March 4

21 Photon+jet Fully unfolded and corrected data htts://cdsweb.cern.ch/record/47335 x Jγ = J γ Moriond, 8 March 4

76 ev,l jet int - =.5 nb Anti-k Jet R=.3, >5, >6 GeV, / >5/6 PYHIA: Mean=.8±. Z Pb+Pb: Mean=.76±.6±.6-8% Centrality jet Z Arbitrary Units.6.4..5 3 φ.5.5.5 3 jet Z /.

22 and Z+jet Low statistics but intriguing qualitative observation dn Z+jet ) Z / jet d( N Z 3 ALAS Preliminary Pb+Pb =.76 ev,l jet Z int - =.5 nb Anti-k Jet R=.3, >5, >6 GeV, / >5/6 PYHIA: Mean=.8±. Pb+Pb: Mean=.6±.4±.4 -% Centrality jet Z dn Z+jet Arbitrary Units.6.4. ) Z / jet d( N Z 3 ALAS Preliminary Pb+Pb =.76 ev,l jet int - =.5 nb Anti-k Jet R=.3, >5, >6 GeV, / >5/6 PYHIA: Mean=.8±. Z Pb+Pb: Mean=.76±.6±.6-8% Centrality jet Z Arbitrary Units φ jet Z /.5 3 φ jet Z / Fully unfolded and corrected data Back-to-back correlation reserved Reduction in the momentum ratio of jet / Z boson htts://cdsweb.cern.ch/record/4794 Moriond, 8 March 4

23 Boson+Jet ALAS-CONF-- Consistent results from jet correlations with hoton and Z Reduction in momentum ratio Reduction in jet yield er boson htts://cdsweb.cern.ch/record/47335, htts://cdsweb.cern.ch/record/4794 Moriond, 8 March 4 3

24 Phys.Lett. B77 () Centrality Sectators Particiants Precise control over Pb+Pb collision geometry! <N art > -5% 38 ± % 5-% 33 ± % -% 6 ± % -4% 58 ± 3% 4-8% 46 ± 6% Binary Collisions <N coll > 683 ± 8% 38 ± 8% 93 ± 7% 44 ± 7% 78 ± 9% Moriond, 8 March 4 4

25 ΣE Pb Centrality definition ALAS +Pb, Preliminary - = 5. ev, L int = µb 4 3 ] - [GeV Pb dn/dσe /N evt ALAS Preliminary - +Pb, = 5. ev, L int = µb Pb ΣE Pb ΣE Pb-going FCal (side A ) is used to characterize event centrality, it is more sensitive to nuclear geometry FCal ΣE Pb is divided into centrality intervals: -%, -5%, 5-%, -%, -3%, 3-4%, 4-6%, 6-9% 9-% is excluded due to larger systematic uncertainties on event comosition and reconstruction efficiency -6 Moriond, 8 March 4 5 E

26 Glauber and Glauber-Gribov models o model Nart distribution we used: standard Glauber with σ NN cross section = 7±5mb Glauber-Gribov color fluctuation models, with <σ NN > cross section = 7±5mb In Glauber-Gribov model: σ tot is considered frozen for each event arameter Ω controls the amount of fluctuations Ω is extracted from exerimental data:.55 [PLB633 (6) 45 5] and. [PLB 7 (3) ] P H (σ NN )..5 ALAS Preliminary +Pb = 5. ev Glauber-Gribov Ω=.55 Glauber-Gribov Ω=. P(N art ) - - ALAS Preliminary +Pb = 5. ev standard Glauber Glauber-Gribov Ω=.55 Glauber-Gribov Ω= σ NN [mb] N art Moriond, 8 March 4 6 E

27 Constructing FCal ΣE Pb resonse E distribution modeled by PYHIA simulated taking into account FCal resonse in +Pb configuration and were aroximated by Gamma(k,θ) distributions counts 3 ALAS Preliminary PYHIA 8, 5. ev counts 3 ALAS Preliminary PYHIA 6, 5. ev fit to gamma function = 3.44 =.4, θ k fit to gamma function =.677 =.3, θ k FCal A E FCal A E Convolution of N art Gamma(k,θ) was taken as Gamma(k(N art ),θ(n art )) We allowed: k(n art ) = k +k *(N art -); θ(n art ) = θ +θ *(log(n art -)); In WN : k(n art ) = k*n art ; θ(n art ) = θ; E resonse for N art was weigthed according to Glauber or Glauber-Gribov model and fitted to the data Moriond, 8 March 4 7 E

28 FCal E distribution fits ] - [GeV Pb dn/dσe /N evt ALAS Preliminary +Pb, L int = µb = 5. ev - dn evt /de obtained by summing the gamma distributions over different N art values weighted by P(N art ) -6 Glauber Glauber Glauber-Gribov, Ω =.55 Glauber-Gribov, Ω =. Fits to the measured E Pb distributions show reasonable agreement over 3 orders of magnitude in E distribution. fit / data Glauber-Gribov, Ω =.55 Glauber-Gribov, Ω =. 5 5 Pb ΣE Moriond, 8 March 4 8 E

29 N art for different Glauber models art N 3 5 ALAS Simulation Preliminary +Pb, - L int = µb = 5. ev % -% -3% 3-4% 4-6% 6-9% Glauber Glauber-Gribov Ω =.55 Glauber-Gribov Ω =. -5% -% -9% centrality Results roduced with models are different Standard Glauber has highest fluctuations of roduced E er articiant Glauber-Gribov Ω=. has less E fluctuation and therefore gives highest N art Moriond, 8 March 4 9 E

Charged Hadron Suression R CP Aarent flattening at highest measured

30 Charged Hadron Suression R CP Aarent flattening at highest measured High charged article suression. ALAS Preliminary Pb+Pb =.76eV Data + - =.5nb L int R CP = N eriheral Coll central N Coll d N central / dyd d N eriheral / dyd η <.5 Increase hinted at in RHIC (5-6)% data, / dramatically (6-8)% measured (3-4)% / (6-8)% (-5)% / (6-8)% R At limit that HI ( AA ) eriheral +, generally R CP >R AA Moriond, 8 March 4 3

31 Heavy Quark Measurement with µ Inclusive muon sectrum dominated by heavy flavor decays Decomose muons (4< <4 GeV) into those from HF and background c(r) = loss ID + r S balance Scattering angle significance Moriond, 8 March 4 3

Heavy Quark Yield d d N d evt N -3-4 -5 ALAS Preliminary Pb+Pb =.76 ev <.

76 ev -6-7 -% -% -4% 4-6% 6-8% R CP hadrons 4 5 6 7 8 9 3 4.4 -% / 6-8%.

Fully correlated systematics R CP = N eriheral Coll central N Coll d N central

32 Heavy Quark Yield d d N d evt N ALAS Preliminary Pb+Pb =.76 ev <.5 - L dt = 7!b Muon R CP..8.6 η <.5 Pb+Pb =.76 ev % -% -4% 4-6% 6-8% R CP hadrons % / 6-8%. -% / 6-8% - -4% / 6-8% L dt = 7 µb 4-6% / 6-8% ALAS Preliminary Boxes: Fully correlated systematics R CP = N eriheral Coll central N Coll d N central HF / dyd d N eriheral HF / dyd Roughly flat in Somewhat different from inclusive hadrons HF acting heavy? Moriond, 8 March 4 3

33 Qin and Müller QM Jets as a Probe of the Medium A artonic A artonic jet shower jet shower in medium E, rad L out E, rad L in R E J coll E L ( R) E E ( R) L g Leading arton: Partonic jet shower in vacuum comosed of: Add the Leading Parton and Radiated Gluons medium: coll E g E transfer to medium via elastic collsions Gluons radiated due to medium interactions broad E g E transfer to medium via elastic collsions Shunted out of jet cone from multile scattering Moriond, 8 March 4 33

34 Full Jet Reconstruction Anti-k t (R=..6) reconstruction algorithm Event-by-event background subtraction: Anti-k t reconstruction rior to a background subtraction Underlying event estimated for each longitudinal layer and ƞ slice Jets corrected for flow contribution to background Underlying event fluctuations rejected by matching jets to track jets or electron/hoton Moriond, 8 March 4 34

Di-Jet Asymmetry ) dn/da (/N J evt 4 3 4-% ) dn/da (/N J evt 4 3-4% ) dn/da (/N J evt 4 3 -% ) dn/da (/N J evt 4 3 =.76

35 Di-Jet Asymmetry ) dn/da (/N J evt % ) dn/da (/N J evt 4 3-4% ) dn/da (/N J evt 4 3 -% ) dn/da (/N J evt 4 3 =.76 ev -% ALAS Pb+Pb - L int =.7!b A J A J A J A J ) dn/d (/N evt ) dn/d (/N evt ) dn/d (/N evt ) dn/d (/N evt Pb+Pb Data + Data HIJING+PYHIA Full jet reconstruction with anti-k t algorithm (R=.4) Azimuthal correlation consistent in all systems +, MC, and eriheral Pb +Pb consistent asymmetry eaked at zero Central Pb+Pb has eak away from zero Momentum balance from hard scattering not ket within di-jets Phys. Rev. Lett. 5, 533 () Moriond, 8 March 4 35

36 Jet Cone Size Deendence R CP.5 ALAS 89 < < 3 GeV Pb+Pb L dt s NN - = 7 µb =.76 ev Is lost energy hiding in larger cones? Vary cone sizes (R) in anti-k t algorithm R deendence seen at lower % % % - % R =. R =.3 R =.4 R =.5 Phys. Lett. B 79 (3) -4 Moriond, 8 March 4 36

37 Jet Cone Size Deendence R CP ALAS 89 <. /R CP R R CP 5-6 % 3-4 % - % - % < 3 GeV Pb+Pb L dt Pb+Pb s L dt NN s NN - = 7 µb =.76 ev R =. R =.3 R =.4 R =.5 Phys. Lett. B 79 (3) -4 - = 7 µb =.76 ev ALAS Is lost energy hiding in larger cones? Vary cone sizes (R) in anti-k t algorithm R deendence seen at lower % R =.3 R =.4 R =.5 Moriond, 8 March 4 37

38 dn d Azimuthal Distribution of Jets = A( + v cos[( )]) Jet v is not Jet hydrodynamic flow Rather, a look at the jets as a function of the amount of medium they traverse Δϕ jet v % anti- R =. - % ALAS k t jet v % L dt =.4 nb 3-4 % Pb+Pb =.76 ev. jet v % 5-6 %.4. Phys. Rev. Lett., 53 (3) 5 5 Moriond, 8 March

39 dn d Azimuthal Distribution of Jets = A( + v cos[( )]) Jet v is not Jet hydrodynamic flow Rather, a look at the jets as a function of the amount of medium they traverse Δϕ jet v % anti- R =. - % ALAS k t jet v % L dt =.4 nb 3-4 % Pb+Pb =.76 ev. v Z boson v.. -. Z y. ALAS Pb+Pb =.76 ev Data L int =.5 nb Centrality: -8% v. -. Z Phys. Rev. Lett., 53 (3) - v N art jet v % 5 5 Moriond, 8 March %

Lecture 3: Results of jet measurements in p-p and heavy ion collisions. Brian. A Cole, Columbia University June 14, 2013

Lecture 3: Results of jet measurements in p-p and heavy ion collisions. Brian. A Cole, Columbia University June 14, 2013 Lecture 3: Results of measurements in - and heavy ion collisions Brian. A Cole, Columbia University June 4, 3 - cross-sections @.76 ev ALAS arxiv: 34.4739 submitted to EPJC dy [b/gev]!/d d 8 6 4 5 9 6