Exploring the QGP with Jets at ALICE

Exploring the QGP with Jets at ALICE Oliver Busch University of sukuba Oliver Busch HI café, okyo 217/1 1

jets in pp collisions jets in heavy-ion collisions jet nuclear modification factor event plane dependence collision energy dependence strangeness production in jets jet mass Oliver Busch HI café, okyo 217/1 2

Introduction Oliver Busch HI café, okyo 217/1 3

Jets: seeing quarks and gluons jet: collimated bunch of hadrons quasi-free parton scattering at high Q 2 : the best available experimental equivalent to quarks and gluons Oliver Busch HI café, okyo 217/1 4

Jet fragmentation initial hard scattering: high-p partons cascade of gluons: parton shower at soft scale (O(ΛQCD)): hadronization in heavy-ion collisions, jets probe the medium at a variety of scales Oliver Busch HI café, okyo 217/1 5

Establish correspondence between detector measurements / final state particles / partons two types of jet finder: - iterative cone - sequential recombination (e.g. anti-k) resolution parameter R Jet reconstruction hep-ph/82.1189 Oliver Busch HI café, okyo 217/1 6

Jets at ALICE (run 1) charged particle tracking: - Inner racking System (IS) - ime Projection Chamber (PC) - full azimuth, η <.9 p > 15 MeV/c jet trigger with EMCal and RD `charged (tracking) jets and `full jets Electromagnetic Calorimeter (EMCal) : - neutral particles - Δφ = 17, η <.7 cluster E > 3 MeV full jets from charged particle tracking and EM energy: conceptually different and complementary to traditional approach 7

Jet Cross Section in pp Collisions Oliver Busch HI café, okyo 217/1 8

Full jets in pp at = 2.76 ev good agreement with NLO pqcd calculations for R =.2 and R =.4 reference for Pb-Pb at same energy R =.2 R =.4 Phys. Lett. B 722 (213) 262 Oliver Busch HI café, okyo 217/1 9

CMS: jets at = 7 ev single inclusive jet cross sections compared to NLO pqcd: agreement over 14 orders of magnitude comparable theoretical and experimental uncertainties complementary jet p reach of the LHC experiments PRD 87 (212) 1122 Oliver Busch HI café, okyo 217/1 1

pp charged jet cross-sections inclusive charged jet cross section in minimum bias collisions at = 5.2 ev: well described by POWHEG NLO calculations cross section ratio: well described by PYHIA and POWHEG reference for run 2 Pb-Pb collisions at same snn dη (mb c/gev) σ/dp 2 d 1 1 1 2 3 1 1 4 pp s = 5.2 ev ALICE POWHEG (UE subtracted) PYHIA6 (Perugia-211) PYHIA8 (Monash-213) ALICE Preliminary σ(r=.2)/σ(r=.4).9.8.7.6 pp s = 5.2 ev anti-k, η <.5 jet track,ch p >.15 GeV/c ALICE Preliminary anti-k, R=.2.5 MC/Data 5 1 1.4 1.2 1 η p <.7 jet track,ch >.15 GeV/c.4.3.2.1 ALICE POWHEG (UE subtracted) PYHIA6 (Perugia-211) PYHIA8 (Monash-213).8.6 1 2 3 4 5 6 jet,ch p (GeV/c) 1 2 3 4 5 6 jet,ch p (GeV/c) ALI PREL 11383 Oliver Busch HI café, okyo 217/1 11

Jets and Quark-Gluon Plasma Oliver Busch HI café, okyo 217/1 12

QCD phase transition in heavy-ion collisions at ultra-relativistic energies, a quasi macroscopic fireball of hot, strongly interacting matter in local thermal equilibrium is created lattice QCD predicts phase transition to deconfined, chirally symmetric matter HotQCD, PRD 9, 9453 energy density from the lattice: rapid increase around C, indicating increase of degrees of freedom (pion gas quarks and gluons) C = 154 +/- 9 MeV EC = 34 +/- 45 MeV/fm 3 Oliver Busch HI café, okyo 217/1 13

QCD matter at LHC direct photons: prompt photons from hard scattering + thermal radiation from QCD matter low-p inverse slope parameter: eff = 297 ± 12 stat. ± 42 syst. MeV/c indicates initial temperature way above C Phys. Lett. B 754 (216) 235 Oliver Busch HI café, okyo 217/1 14

Partons in heavy-ion collisions hard partons are produced early and traverse the hot and dense QGP expect enhanced parton energy loss : `jet quenching (mostly) due to medium-induced gluon radiation vacuum expectation calculable by pqcd : calibrated probe of QGP jets sensitive to properties of the medium (energy density,, mean free path, coupling... )... but also jet-medium interaction not trivial (strong / weak coupling, parton mass / type, fireball dynamics...) JE collaboration, PRC 9, 1499 15

Hadrons in heavy-ion collisions high-p hadrons proxy for jet jet quenching for charged hadrons, Pb-Pb collisions at snn = 2.76 ev PLB 72 (213) 25 1 ALICE Pb-Pb s NN = 2.76 ev charged particles, η <.8 R AA hadron observables biased towards leading fragment study the effect for fully reconstructed jets 1 1 ALI DER 1571 1 2 3 4 5 p (GeV/c) -5% 7-8% Oliver Busch HI café, okyo 217/1 16

Underlying event jet reconstruction in heavy-ion collisions : difficult due to the high underlying event background not related to hard scattering correct spectra for background fluctuations and detector effects via unfolding not possible down to lowest jet p central jet area ~.5 (R =.4) peripheral 17

Jet nuclear modification factor full jet RAA at snn = 2.76 ev, R =.2 strong suppression observed, similar to hadron RAA parton energy not recovered inside jet cone increase of suppression with centrality Phys.Lett. B746 (215) 1 JEWEL: PLB 735 (214) YaJEM:PRC 88 (213) 1495 weak p dependence JEWEL and YaJEM jet quenching models reproduce suppression Oliver Busch HI café, okyo 217/1

Jet azimuthal anisotropy Oliver Busch HI café, okyo 217/1 19

Reaction plane dependence different medium thickness in- and out-of plane sensitive to path length dependence of jet quenching: pqcd radiative E-loss : ~L 2 collisional E-loss : ~L strong coupling (ADS/CF) : ~L 3 Oliver Busch HI café, okyo 217/1 2

Local background subtraction account for flow-modulation of background via event-by-event fit and subtraction of local background density unfolding to account for background fluctuations : separately for spectra in- and out-of-plane (ϕ) (GeV/c) 2 15 Pb-Pb s NN Single event = 2.76 ev ALICE ρ ch 1 Phys. Lett. B753 (216) 511 5.15 < p < 5 GeV/c, η <.9, track track ρ (ϕ) ch ρ ρ (1+2v cos(2[ϕ-ψ ])) 2 EP, 2 ρ (1+2v cos(3[ϕ-ψ ])) 3 EP, 3 1 2 3 4 5 6 ϕ (rad) Oliver Busch HI café, \ okyo 217/1 21

Jet v2: results quantify azimuthal asymmetry via 2 nd Fourier harmonic ch jet v2 central collisions: 1.5-2 sigma from v2 ch jet = consistent with, but maybe hint for effect of initial density fluctuations? non-zero v2 ch jet in semi-central collisions -5% 3-5% {EP, η >.9 } ch jet v 2.2.1 ch jet v 2-5%, Stat unc. Syst unc. (shape) Syst (correlated) Syst unc. (correlated) ALICE Pb-Pb s NN = 2.76 ev R =.2 anti-k, η <.7 jet {EP, η >.9 } ch jet v 2.2.1 ch jet v 2 3-5%, Stat unc. Syst unc. (shape) Syst (correlated) Syst unc. (correlated) ALICE Pb-Pb s NN = 2.76 ev R =.2 anti-k, η <.7 jet (a) p >.15 GeV/c, p > 3 GeV/c, track, lead 2 3 4 5 6 7 8 9 1 ch jet p (GeV/c) Phys. Lett. B753 (216) 511 (b) p >.15 GeV/c, p > 3 GeV/c, track, lead 2 3 4 5 6 7 8 9 1 ch jet p (GeV/c) Oliver Busch HI café, okyo 217/1 22

Comparison to previous results ALICE + CMS single particles, ALAS full jets : different energy scales! non-zero v2 up to high p CMS, PRL 19 (212) 22 ALAS, PRL 111 (213) 152 ALICE, Phys. Lett. B753 (216) 511 ALICE, Phys. Lett. B719 (213) 18 jet, v 2 part v 2.3.2 ALICE Pb-Pb = 2.76 ev s NN R =.2 anti-k, η <.7 jet ch jet v 2-5%, Stat unc. Syst unc. (shape) Syst unc. (correlated) calo jet 5-1% part ALAS v 2 CMS v 2 { η >3} -1% part ALICE v 2 { η >2} -5% jet, v 2 part v 2.3.2 ALICE Pb-Pb = 2.76 ev s NN R =.2 anti-k, η <.7 jet ch jet v 2 3-5%, Stat unc. Syst unc. (shape) Syst unc. (correlated) ALAS v 2 calo jet 3-5% part CMS v 2 { η >3} 3-5% part ALICE v 2 { η >2} 3-5%.1.1 (a) p >.15 GeV/c, p > 3 GeV/c, track, lead 5 1 15 part jet p, p (GeV/c) (b) p >.15 GeV/c, p > 3 GeV/c, track, lead 5 1 15 part jet p, p (GeV/c) Oliver Busch HI café, okyo 217/1 23

Comparison to JEWEL good agreement with JEWEL in semi-central collisions clear indication of path-length dependence of energy loss ch jet v 2.2 ch jet v 2 ch jet v 2-5%, JEWEL -5%, Stat unc. Syst unc. (shape) Syst unc. (correlated) ALICE Pb-Pb s NN = 2.76 ev R =.2 anti-k, η <.7 jet ch jet v 2.2 ch jet v 2 ch jet v 2 3-5%, JEWEL 3-5%, Stat unc. Syst unc. (shape) Syst unc. (correlated) ALICE Pb-Pb s NN = 2.76 ev R =.2 anti-k, η <.7 jet.1.1 (a) lead p >.15 GeV/c, p, track 2 3 4 5 6 7 8 9 1 ch jet p (GeV/c) > 3 GeV/c (b) lead p >.15 GeV/c, p, track 2 3 4 5 6 7 8 9 1 ch jet p (GeV/c) > 3 GeV/c Phys. Lett. B753 (216) 511 Oliver Busch HI café, okyo 217/1 24

Jet Nuclear Modification Factor at snn = 5.2 ev Oliver Busch HI café, okyo 217/1 25

LHC run 2 increased CMS energy for Pb-Pb collisions from 2.76 5.2 ev quenching strength ~ s ~ ε 3/4 expect (modest) increase in ε, measure energy density dependence of jet quenching note: RAA also depends on parton input spectrum : at higher s, flatter spectrum larger RAA /dη ch dn 2 part N 14 12 1 8 6 4 pp(pp), INEL ALICE CMS UA5 PHOBOS ISR pa(da), NSD ALICE PHOBOS AA, central ALICE CMS ALAS PHOBOS PHENIX BRAHMS SAR NA5.155(4) s.13(2) s 2 1 2 1 3 1 η <.5 4 1 s NN (GeV) Oliver Busch HI café, okyo 217/1 26

Run 2 jet cross section and RAA jet cross section and nuclear modification factor at snn = 5.2 ev stronger suppression in more central collisions, slight increase with p ALI-PREL-11355 ALI-PREL-113513 Oliver Busch HI café, okyo 217/1

snn dependence of RAA charged jet RAA at snn = 5.2 ev compared to: ALICE full jet RAA at 2.76 ev (R =.2) ALAS jet RAA (R =.4) different jet energy scales comparable RAA: effect of flattening of the spectrum compensated by stronger suppression ALI-PREL-114186 28

Strangeness Production in Jets Oliver Busch HI café, okyo 217/1 29

Identified hadrons in heavy-ion collisions baryons / meson RAA a probe of gluon / quark energy loss? R AA would expect stronger radiative energy loss for gluons than for quarks - subtle cancellations? - hadron observable biased towards hard fragmentation? 1.8.6.4.2 Phys. Rev. C 93, 34913 ALICE -5% Pb-Pb - π + +π + - K +K p + p Charged s NN =2.76 ev study jets to improve our ALI DER 86149 understanding of parton energy loss: - PID in reconstructed jets mitigates fragmentation biases - enhanced sensitivity to medium effects measuring soft particles in jets 2 4 6 8 1 12 14 16 18 2 (GeV/c) note: medium effects likely strongest at scales of ~ medium emperature (J.G. Milhano, K. C. Zapp, hep-ph/1512.819,. Renk, Phys. Rev. C 81, 1496, B. Mueller, hep-ph/11.4258) p Oliver Busch HI café, okyo 217/1 3

Strange hadron reconstruction neutral strange particles reconstructed via decay topology ( V ): signal extraction from invariant mass distributions Oliver Busch HI café, okyo 217/1 31

Strangeness production in nuclear collisions Inclusive strangeness production in Pb-Pb: Baryon / Meson ratio enhanced - collective effects? - parton recombination? - jet fragmentation? Phys. Rev. Lett. 111 (213) 2231 measurement of identified particles in jets helps to constrain hadronisation and energy loss scenarios 32

Strangeness in jets candidate - jet matching (V in jet cone) jet R =.2, acceptance η V <.7 candidate - bulk matching: underlying event V signal extraction from invariant mass distributions correct for efficiency and feed-down subtract underlying event from spectra Oliver Busch HI café, okyo 217/1 33

Underlying event subtraction subtract underlying event contribution to K S, Λ spectra in jets various methods with different sensitivity to acceptance, event plane correlations, presence of additional jets, apply a correction to account for background density fluctuations Oliver Busch HI café, okyo 217/1 34

(Λ+Λ)/2K s ratio in jets Pb-Pb collisions at snn = 2.76 ev jet R =.2 p jet > 1 GeV/c (2 GeV/c) leading constituent bias p leading > 5 GeV/c to reject fake jets S (Λ + Λ)/2K 2 1.8 1.6 1.4 1.2 ALICE Preliminary Pb Pb, s NN in jets, p in jets, p = 2.76 ev, 1 % jet,ch jet,ch > 1 GeV/c > 2 GeV/c feed-down uncertainty inclusive Λ/K, ALICE, S ( 5 %, y <.5) V no significant jet p jet dependence ratio in jets significantly lower than for inclusive case 1.8.6.4 η <.7 V anti-k t, R =.2 η <.5 jet,ch p track p leading track > 5 GeV/c > 15 MeV/c.2 ALI PREL 93799 2 4 6 8 1 12 (GeV/c) Oliver Busch HI café, okyo 217/1 35 p

Comparison to p-pb compare Pb-Pb results to reference from p-pb collisions at 5.2 ev: agreement within uncertainties ongoing efforts to improve systematics for lowest K S, Λ p p-pb Λ)/2K (Λ + S 2 1.8 1.6 1.4 1.2 ALICE Preliminary Pb-Pb Pb Pb, s NN in jets, p in jets, p = 2.76 ev, 1 % jet,ch jet,ch > 1 GeV/c > 2 GeV/c feed-down uncertainty inclusive Λ/K, ALICE, S ( 5 %, y <.5) V 1.8.6.4 η <.7 V anti-k t, R =.2 η <.5 jet,ch p track p leading track > 5 GeV/c > 15 MeV/c.2 ALI-PREL-8712 ALI PREL 93799 2 4 6 8 1 12 (GeV/c) p Oliver Busch HI café, okyo 217/1 36

Strange particle spectra in jets spectra of K S and Λ particles in jets: more differential observable to increase sensitivity to potentially modified fragmentation (c/gev) ) dn/dp 2 1/(N jets πr 1 1 1 Pb Pb, = 2.76 ev, 1 % s NN ALICE Preliminary p Ks, stat. unc. (Λ+Λ)/2, stat. unc. syst. unc. jet,ch > 1 GeV/c (c/gev) ) dn/dp 2 1/(N jets πr 1 1 1 Pb Pb, = 2.76 ev, 1 % s NN ALICE Preliminary p Ks, stat. unc. (Λ+Λ)/2, stat. unc. syst. unc. jet,ch > 2 GeV/c 2 1 1 3 ALI PREL 112782 η V <.7 anti-k t, R =.2 η <.5 p track p jet,ch leading track > 5 GeV/c > 15 MeV/c 2 3 4 5 6 7 8 9 1 p (GeV/c) 2 1 1 3 ALI-PREL-112794 η V <.7 anti-k t, R =.2 η <.5 p track p jet,ch leading track > 5 GeV/c > 15 MeV/c 2 3 4 5 6 7 8 9 1 (GeV/c ) Oliver Busch HI café, okyo 217/1 37 p

Comparison to PYHIA K S spectra in jets follow similar slope as predicted by PYHIA simulations Λ shape different? More reliable reference needed! (c/gev) ) dn/dp 2 1/(N jets πr 1 1 1 Pb Pb, = 2.76 ev, 1 % s NN ALICE Preliminary p jet,ch Ks, stat. unc., (x 1.5) (Λ+Λ)/2, stat. unc. syst. unc. s full markers K, (x 1.5) open markers (Λ+Λ)/2 PYHIA 8 - tune Monash PYHIA 6 - tune Perugia 211 PYHIA 6 - tune Perugia NoCR p jet smeared with true σ (δp > 1 GeV/c jet ) (c/gev) ) dn/dp 2 1/(N jets πr 1 1 1 Pb Pb, = 2.76 ev, 1 % s NN ALICE Preliminary p jet,ch Ks, stat. unc., (x 1.5) (Λ+Λ)/2, stat. unc. syst. unc. s full markers K, (x 1.5) open markers (Λ+Λ)/2 PYHIA 8 - tune Monash PYHIA 6 - tune Perugia 211 PYHIA 6 - tune Perugia NoCR p jet smeared with true σ (δp > 2 GeV/c jet ) 2 1 1 3 ALI PREL 112798 η V <.7 anti-k t, R =.2 η <.5 p track p jet,ch leading track > 5 GeV/c > 15 MeV/c 2 3 4 5 6 7 8 9 1 p (GeV/c ) 2 1 1 3 ALI PREL 11282 η V <.7 anti-k t, R =.2 η <.5 p track p jet,ch leading track > 5 GeV/c > 15 MeV/c 2 3 4 5 6 7 8 9 1 p (GeV/c ) Oliver Busch HI café, okyo 217/1 38

Jet Mass Oliver Busch HI café, okyo 217/1 39

Oliver Busch HI café, okyo 217/1 4

Mass and virtuality invariant mass of jet constituents, related to virtuality of initial parton parton from hard scattering produced off-shell in vacuum: virtuality decreases at each emission in medium, virtuality can rise due to scatterings quenching observable (A. Majumder, J. Putschke, nucl-th 148.344) soft constituents far from jet axis within cone larger mass few hard constituents smaller mass 41

Results: ppb jet mass in ppb collisions at snn = 5.2 ev, charged jets with R=.4 overall well described by PYHIA with some tension in the tails (c 2 /GeV).2 6 < p (GeV/c) < 8, ch jet ALICE Preliminary (c 2 /GeV).2 8 < p (GeV/c) < 1, ch jet (c 2 /GeV) 1 < p (GeV/c) < 12, ch jet.2 p-pb s = 5.2 ev NN dn dm ch jet 1 N jets.1 dn dm ch jet 1 N jets.1 Anti-k, R =.4 dn dm ch jet 1 N jets.1 Systematic p-pb PYHIA Perugia 211 2 4 6 8 1 12 14 16 18 (GeV/c 2 ) ALI PREL 113418 M ch jet 2 4 6 8 1 12 14 16 18 2 22 (GeV/c 2 ) M ch jet 2 4 6 8 1 12 14 16 18 2 22 24 (GeV/c 2 ) M ch jet Data/PYHIA 4 3 2 6 < p (GeV/c) < 8, ch jet ALICE Preliminary PYHIA Perugia 211 Data/PYHIA 4 3 2 8 < p (GeV/c) < 1, ch jet p-pb = 5.2 ev s NN Anti-k, R =.4 Data/PYHIA 4 3 2 1 < p (GeV/c) < 12, ch jet p-pb / PYHIA(5.2eV) (Sys p-pb) / PYHIA(5.2eV) 1 1 1 2 4 6 8 1 12 14 16 18 (GeV/c 2 ) ALI DER 113422 M ch jet 2 4 6 8 1 12 14 16 18 2 22 (GeV/c 2 ) M ch jet 2 4 6 8 1 12 14 16 18 2 22 24 (GeV/c 2 ) M ch jet 42

Results: Pb-Pb jet Mass in Pb-Pb collisions at snn = 2.76 ev fully corrected for detector effects and background fluctuations via 2D unfolding (c 2 /GeV) dn dm ch jet 1 N jets.2.1 6 < p (GeV/c) < 8, ch jet ALICE Preliminary (c 2 /GeV) dn dm ch jet 1 N jets.2.1 8 < p, ch jet (GeV/c) < 1 Anti-k, R =.4 (c 2 /GeV) dn dm ch jet 1 N jets.2.1 1 < p, ch jet Pb-Pb -1% Systematic Pb-Pb (GeV/c) < 12 = 2.76 ev s NN 2 4 6 8 1 12 14 16 18 2 22 (GeV/c 2 ) ALI-PREL-11339 M ch jet 5 1 15 2 25 (GeV/c 2 ) M ch jet 5 1 15 2 25 (GeV/c 2 ) M ch jet Oliver Busch HI café, okyo 217/1 43

Results: Pb-Pb jet Mass in Pb-Pb collisions at snn = 2.76 ev fully corrected for detecor effects and background fluctuations via 2D unfolding (c 2 /GeV) dn dm ch jet 1 N jets.2.1 6 < p (GeV/c) < 8, ch jet ALICE Preliminary (c 2 /GeV) dn dm ch jet 1 N jets.2.1 8 < p, ch jet (GeV/c) < 1 Anti-k, R =.4 (c 2 /GeV) dn dm ch jet 1 N jets.2.1 1 < p, ch jet (GeV/c) < 12 Pb-Pb -1% s NN = 2.76 ev Systematic Pb-Pb ppb s NN = 5.2 ev Systematic p-pb 2 4 6 8 1 12 14 16 18 2 22 (GeV/c 2 ) ALI-DER-114292 M ch jet 5 1 15 2 25 (GeV/c 2 ) M ch jet 5 1 15 2 25 (GeV/c 2 ) M ch jet small s dependence is expected (quark / gluon composition) compare the ratio Pb-Pb / ppb to the ratio in PYHIA at the 2 energies 44

Ratio Pb-Pb / p-pb slope indicates that Pb-Pb distribution is shifted towards smaller masses with respect to ppb Data/PYHIA 4 3 2 6 < p (GeV/c) < 8, ch jet ALICE Preliminary PYHIA Perugia 211 Data/PYHIA 4 3 2 8 < p, ch jet Pb-Pb -1% p-pb (GeV/c) < 1 s = 2.76 ev NN = 5.2 ev s NN Anti-k, R =.4 Data/PYHIA 4 3 2 1 < p, ch jet (GeV/c) < 12 p-pb / PYHIA(5.2eV) Sys p-pb / PYHIA(5.2eV) Pb-Pb / PYHIA(2.76eV) Sys Pb-Pb / PYHIA(2.76eV) 1 1 1 2 4 6 8 1 12 14 16 18 (GeV/c 2 ) ALI DER 113434 M ch jet 2 4 6 8 1 12 14 16 18 2 22 (GeV/c 2 ) M ch jet 2 4 6 8 1 12 14 16 18 2 22 24 (GeV/c 2 ) M ch jet Oliver Busch HI café, okyo 217/1 45

Model comparison data lies in between PYHIA and JEWEL with recoils off Q-PYHIA and JEWEL with recoils on produce too large mass (c 2 /GeV) dn dm ch jet.2 6 < p, ch jet (GeV/c) < 8 ALICE Preliminary (c 2 /GeV) dn dm ch jet.2 8 < p, ch jet (GeV/c) < 1 (c 2 /GeV) dn dm ch jet.2 1 < p (GeV/c) < 12, ch jet Pb-Pb -1% s NN = 2.76 ev PYHIA Perugia 211 s NN = 2.76 ev JEWEL+PYHIA Recoil on -1% PbPb JEWEL+PYHIA Recoil off -1% PbPb jets N 1 jets N 1 jets N 1 Q-PYHIA.1.1.1 2 4 6 8 1 12 14 16 18 2 22 (GeV/c 2 ) ALI DER 11342 M ch jet 5 1 15 2 25 (GeV/c 2 ) M ch jet 5 1 15 2 25 (GeV/c 2 ) M ch jet Q-PYHIA: radiative energy loss modelled by enhanced splitting functions (N. Armesto, L. Cunqueiro, C. A. Salgado, hep-ph/97.114) Oliver Busch HI café, okyo 217/1 46

ALICE in run 2: DCal run 2: DCal upgrade - significantly extended jet acceptance - back-to-back in azimuth (di-jet topology) new avenues for jet physics in ALICE Oliver Busch HI café, okyo 217/1 47

Summary jet cross sections and properties in pp strong jet suppression observed in Pb-Pb collisions first jet nuclear modification factor from run 2 indicates stronger suppression at higher energy non-zero jet v2 indicates path-length dependence of jet quenching strange particles in jets first measurement of jet mass in HI collisions indicate shift to smaller masses first results from run 2 - more to come! Oliver Busch HI café, okyo 217/1 48

- Backup - Oliver Busch HI café, okyo 217/1 49

full jets, pp at 2.76 ev JES uncertainty ~ 3.6% at p jet = 1 GeV/c ALICE jet response Phys. Lett. B 722 (213) 262 JHEP 3 (214) 13 charged jets: Pb-Pb JE resolution at low p dominated by background, at high p by detector effects 5

Jet Structure different observables, e.g. radial moment g, pd comparison to PYHIA pp reference shows collimation of jet core (R=.2) Oliver Busch HI café, okyo 217/1 51 26

Jet Structure : Model Comparison trends reproduced by JEWEL jet quenching model JEWEL: K.C. Zapp, F. Kraus, U.A. Wiedemann, JHEP 133 (213) 8 27 Oliver Busch HI café, okyo 217/1 52

pp charged jet cross-sections measured in minimum bias collisions at = 7 ev good agreement with ALAS charged jet measurements (despite slightly different acceptance and track p range) R =.4 R =.6 PRD 91 (215) 11212 Oliver Busch HI café, okyo 217/1 11