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

Transcription

1 Lecture 3: Results of measurements in - and heavy ion collisions Brian. A Cole, Columbia University June 4, 3

2 - ev ALAS arxiv: submitted to EPJC dy [b/gev]!/d d systematic uncertainties NLO QCD (C) # non-ert. corr. arxiv: $ L - dt =. b s =.76 ev anti-k t R =.6! ) y <.3 (! 9.3 " y <.8 (! ) 6.8 " y <. (! ) 3. " y <. (! ). " y <.8 (! ) -3.8 " y < 3.6 (! ) " y < 4.4 (! ) ALAS

3 ALAS arxiv: submitted to EPJC - ev dy [b/gev]!/d d systematic uncertainties NLO QCD (C) # non-ert. corr. 3 4 $ L - dt =. b s =.76 ev anti-k t R =.4! ) y <.3 (! 9.3 " y <.8 (! ) 6.8 " y <. (! ) 3. " y <. (! ). " y <.8 (! ) -3.8 " y < 3.6 (! ) " y < 4.4 (! ) ALAS 3

4 NLOJet++, non-erturbative corrections NLOJet is arton-level NLO QCD weighted event generator. Non-erturbative corrections due to arton shower, hadronizatio, UE calculated by PYHIA Dominated by out-of-cone loss Dominated by additional PS s Non-erturbative correction.3.. s =.76 ev R=.4 anti-k t y <.3 Pythia 6 AMBB CEQ6L Pythia 6 AUEB LO** Pythia 6 Perugia Pythia 8 4C Herwig++.5. UE7- Pythia 6 AUEB CEQ6L Uncertainty Non-erturbative correction.3.. Pythia 6 AMBB CEQ6L Pythia 6 AUEB LO** Pythia 6 Perugia Pythia 8 4C Herwig++.5. UE7- Pythia 6 AUEB CEQ6L Uncertainty.9.8 ALAS Simulation.9.8 s =.76 ev R=.6 anti-k t y <.3 ALAS Simulation 3 4! 3 4! 4

5 Ratio wrt NLO QCD (C).5 NLOJet++ - data comarisons y <.3.5.3! y < ! y <..5.5.! y < ! Ratio wrt NLO QCD (C) ! y <.8.8! y < ! y < ! ALAS " L - dt =. b s =.76 ev anti-k t R =.6 Data with statistical uncertainty Systematic uncertainties NLO QCD # non-ert. corr. max (C, "= ) POWHEG# PYHIA tune AUEB Born (C, "= ) POWHEG# PYHIA tune Perugia Born (C, "= ) Relative uncertainty [%] NLO QCD (C) s =.76 ev anti-k R=.6 t y < otal Scale choice PDF! S ALAS Simulation! MC and data systematic uncertainties Relative uncertainty [%] ! L dt =. b s =.76 ev otal JER JES 3 4 R=.6 anti-k t y <.3 Unfolding Others ALAS! 5

6 - ev GeV] dy [b /! / d 7 ALAS (3) s = 76 GeV, y < ALAS inclusive cross-sections 3 ALAS () s = 7 GeV, y <.3 CMS () s = 7 GeV, y <.5 CDF (8) s = 96 GeV, y <. D (8) s = 96 GeV, y <.4 UA (99) s = 63 GeV, " <.85 UA (985) s = 546 GeV, " <.85 UA (985) s = 546 GeV, " <.4 4 6

7 - ev ] dy [b GeV d! / d 3 (/") ALAS inclusive cross-sections see inlay - ALAS (3) s = 76 GeV, y <.3 ALAS () s = 7 GeV, y <.3 CMS () s = 7 GeV, y <.5 CDF (8) s = 96 GeV, y <. D (8) s = 96 GeV, y <.4 UA (99) s = 63 GeV, # <.85 UA (985) s = 546 GeV, # <.85 UA (985) s = 546 GeV, # <.4 = Different!, y ranges, algorithms, sizes,... x / s 7

8 - ev Measured using PC tracks + EMCal anti-k, R =. (left),.4 (right) Comared to two different NLO calculations one NLO + hadronization 8

9 - ev (analytic) hadronization and (N)NLO make ~ equal contributions to (N)LO calculation. 9

10 Heavy ion collisions

11 he starting oint Reconstruct (unsubtracted) Pb+Pb event Here, for demonstration, with kt algorithm!but the kt algorithm is roblematic because the background s eat edges of real s

12 he underlying event

13 he underlying event (ALAS) 3

14 he underlying event (ALAS) 4

15 he underlying event (ALAS) 5

16 ALAS erformance Jet is considered not fake if within R =.: R =.4 track (rec. from tracks w/ > 4 GeV), hoton, or electron with > 7 GeV 6

17 he underlying event (ALAS) For the student: why gamma dist s? 7

18 he underlying event (ALAS) Imortant: subtracting the correct average energy reserves energy scale. Fluctuations on mean affect resolution. 8

19 ALAS erformance ( data) x4 Data-driven evaluation of underlying event fluctuations ] 3x4 ] or "[E 7x7 "[E x7 Data E 7x7 HIJING E 3x4 Data E 3x4 HIJING E 3x4 E - $ E # ALAS Pb+Pb - s NN =.76 ev & L dt = 4 mb [ev] FCal!E truth " [!E ]/E or truth #/E!E $.4.3 anti-k t R =. truth " [!E ]/E + fit, -% truth " [!E ]/E + fit, 6-8% truth " [!E ]/E.. $!E #/E $!E #/E truth truth, -%, 6-8% or truth #/E!E $.4 ALAS simulation R =.4.3 anti-k t truth " [!E ]/E + fit, -% truth " [!E ]/E + fit, 6-8% HIJING MC evaluation of erformance.. $!E #/E $!E #/E truth truth, -%, 6-8% Efficiency %, -% %, 6-8% %', -% %', 6-8% truth E Efficiency %, -% %, 6-8% %', -% %', 6-8% truth E truth E truth E 9

20 An examle Pb+Pb event Even more central collision, more asymmetric di

21 ALAS di asymmetry measurement AJ = E E E +E E > GeV E > 5 GeV st indication of medium modifications of LHC

22 Pb+Pb Jet Sectra R=. R=.4 Unfolded (SVD) and efficiency corrected For these results, no absolute normalization awaiting absolute energy scale uncertainty

23 Jet yields: centrality deendence If factorization holds yields should vary with centrality " Ncoll Comare yields between centrality bins using Rc R CP ALAS Preliminary R =.4 anti-k t Pb+Pb! L dt s NN - = 7 µb =.76 ev 5-6 % 3-4 % R CP = N coll N evt N coll N evt dn cent d dn d 6 8 Overall energy scale divides out in ratio % - %

24 Systematic errors Black band: fully correlated systematics Red boxes: artially correlated systematics Error bars:! of diagonal element of unfolding statistical covariance matrix R =.4 Jet Rc Phys. Lett. B 79 (3) -4 4

25 Centrality deendence of Rc R CP R CP.9 ALAS Preliminary < 89 < < 44 GeV < 3 GeV "N! art anti-k t R =.4 5 < 9 < < 58 GeV < 37 GeV R CP R CP "N! art 67 < < 77 GeV "N! art Pb+Pb s NN =.76 ev - # L dt = 7 µb 58 < < 8 GeV "N! art Study centrality evolution for fixed Rc vs Nart!Smooth turn on of suression between eriheral and central collisions. 5

26 Jet radius deendence of Rc R CP ALAS Preliminary - % Centrality 58 < 89 < < 8 GeV < 3 GeV Pb+Pb! L dt s NN - = 7 µb =.76 ev Significant cancellation of correlated errors. /R CP R R CP.8.6 Pb+Pb s NN =.76 ev -! L dt = 7 µb - % R =.3 R =.4 R = < < 58 GeV < < 44 GeV R =. R =.3 R =.4 R =.5.8 ALAS Preliminary Evaluate radius deendence of Rc Modest but significant variation of Rc Less suression for larger R!An indication of broadening? 6

27 ALICE: suression 7

28 ALICE: shaes More evidence for low hadron 8

29 Hard scattering rate control: Z Z"e+e- event dislay Z"#+#- event dislay 9

30 Hard scattering rate control: Z Phys. Rev. Lett., 3 (3) Comare Pb+Pb Z raidity distributions (minimum-bias) and sectra to PYHIA scaled to NNLO calculations No nuclear PDFs! Nuclear PDF effects <~ % 3

31 Differential suression Measure yields in 8 bins of $% with resect to the ellitic event lane Here for R =. s, 6 < < 8 GeV!UE subtraction corrected for ellitic flow modulation in calorimeter # "! 3

32 Differential suression Observe non-zero v for (R =.) values > GeV! quenching clearly sensitive to initial geometry out to very high 3

33 Jet v() v.6.4 -! L dt =.4 nb 5 - % Pb+Pb =.76 ev s NN anti-k t R =. - % ALAS reliminary - 3 %. v % 4-5 % 5-6 % Do rough comarison of, charged v at high lot. for /5-% lot.3 for > %!As good as could be exected 33

34 Differential suression R "!. 5 - % - % - 3% ALAS reliminary anti-k t R =. #/8 < #/4 < 3#/8 < "! "! "! < #/4 < 3#/8 < #/ Pb+Pb s NN =.76 ev - $ L dt =.4 nb R "!. 3-4% 4-5% 5-6% Evaluate ratio of yields in different $% bins to the yield in < $% < "/8. RAA($%)/RAA(-"/8)! ~5% change in single suression between in-lane, high 34

35 Inclusive fragmentation Unfolded for and charged article resolution We are well along or started on all of these Dzq N dn chg dz,z chg { D q N dn chg d 35

36 Inclusive fragmentation () R =.4 First observation of modified arton shower in inclusive s!not only seeing left over unquenched s. 36

37 Inclusive fragmentation (3) ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=.4 > GeV -%/6-8% ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=.4 > GeV -%/6-8% ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=.4 > GeV -3%/6-8% ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=.4 > GeV 3-4%/6-8% ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=.4 > GeV 4-5%/6-8% ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=.4 > GeV 5-6%/6-8% Check that the modification is not due to the measurement of! D()!D() shows similar modifications.8 37

38 Jet fragmentation: R deendence >85 GeV.3.3 Check that the -%/6-8%.... modification is.9.9 not due to underlying event z fluctuations ALAS Preliminary.6.6 Pb+Pb s NN =.76 ev Pb+Pb.5 - L Use different int =.4 nb.5.4 anti-k R=..4 >85 GeV.3.3 -%/6-8% sizes:.... R =., Obtain the same results as R =.4!Observed modifications are robust R D(z) ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb anti-k R=. R D(z) ) R D( ALAS Preliminary Pb+Pb s NN =.76 ev - =.4 nb - anti-k R=.3 >9 GeV -%/6-8% ALAS Preliminary s NN =.76 ev - =.4 nb anti-k R=.3 >9 GeV -%/6-8% z 38

39 Periheral &- momentum balance central (/N! ) dn /dx.5 PYHIA+Data Data 4-8% R=. Pb+Pb s =.76 ev NN =.3 nb - (/N! ) dn /dx.5 PYHIA+Data Data -4% R=. Pb+Pb s =.76 ev NN =.3 nb - (/N! ) dn /dx.5 PYHIA+Data Data -% R=. Pb+Pb s =.76 ev NN =.3 nb - (/N! ) dn /dx.5 PYHIA+Data Data -% R=. Pb+Pb s =.76 ev NN =.3 nb - R =..5 ALAS Preliminary.5 ALAS Preliminary.5 ALAS Preliminary.5 ALAS Preliminary x x x x (/N! ) dn /dx.5 PYHIA+Data Data 4-8% R=.3 Pb+Pb s =.76 ev NN =.3 nb - (/N! ) dn /dx.5 PYHIA+Data Data -4% R=.3 Pb+Pb s =.76 ev NN =.3 nb - (/N! ) dn /dx.5 PYHIA+Data Data -% R=.3 Pb+Pb s =.76 ev NN =.3 nb - (/N! ) dn /dx.5 PYHIA+Data Data -% R=.3 Pb+Pb s =.76 ev NN =.3 nb - R =.3.5 ALAS Preliminary.5 ALAS Preliminary.5 ALAS Preliminary.5 ALAS Preliminary x Plot distribution of x hoton background airs subtracted unfolded for energy resolution!substantial change in &- balance x x J = /γ x 39

40 Pb+Pb Z- measurement dn Z+ ) Z /! d( N Z 3 ALAS Preliminary Pb+Pb s NN =.76 ev,l Z int - =.5 nb Anti-k Jet R=.4, >5, >6 GeV, / >5/6 PYHIA: Mean=.84±. Pb+Pb: Mean=.68±.5±.3 -% Centrality Arbitrary Units.6.4. Z.5 3 #" Z / Z- measurements have less background than &-, but smaller rate! st results dn Z+ ) Z /! d( N Z 3 ALAS Preliminary Pb+Pb s NN =.76 ev,l - =.5 nb Anti-k Jet R=.4, >5, >6 GeV, / >5/6 PYHIA: Mean=.84±. Z int Pb+Pb: Mean=.8±.7±.8-8% Centrality Arbitrary Units.6.4. Z.5 3 #" / Z 4

41 Di (and gamma-) acolanarity ) dn/d"! (/N evt ) dn/d"! (/N evt ) dn/d"! (/N evt ) dn/d"! (/N evt Pb+Pb Data + Data HIJING+PYHIA "!.5 3 "!.5 3 "!.5 3 "! Is the lack of k broadening in the resence of significant quenching a death knell for leading arton models of energy loss? 4

42 Di acolanarity, R =. Look at di acolanarity w/ R =. s! small UE effects! <NO> broadening 4

43 /d #" ) dn (/N Periheral PYHIA+Data Data 4-8% R=. - =.3 nb ALAS Preliminary &- angular distribution /d #" ) dn (/N PYHIA+Data Data -4% R=. - =.3 nb ALAS Preliminary /d #" ) dn (/N PYHIA+Data Data -% R=. - =.3 nb ALAS Preliminary /d #" ) dn (/N central PYHIA+Data Data -% R=. - =.3 nb ALAS Preliminary R = #".5 3 #".5 3 #".5 3 #" /d #" ) dn (/N PYHIA+Data Data 4-8% R=.3 - =.3 nb ALAS Preliminary /d #" ) dn (/N PYHIA+Data Data -4% R=.3 - =.3 nb ALAS Preliminary /d #" ) dn (/N PYHIA+Data Data -% R=.3 - =.3 nb ALAS Preliminary /d #" ) dn (/N PYHIA+Data Data -% R=.3 - =.3 nb ALAS Preliminary R = #".5 3 #".5 3 #" ake leading in hemishere oosite hotons with 6 < < 9 GeV Jets with > 5 GeV, R =. and.3!distribution of $% eaked at ".5 3 #"!For following, aly cut $% - " < 7"/8 43