Jet from QM2014
Shingo Sakai @ LNF-INFN

1

At the beginning …
This presentation is based on QM 2014



Measurement of jets in Pb-Pb collisions with ALICE

Measurements of jet suppression with ATLAS2

R. Alex for CMS collaboration

Measurement of momentum flow relative to the dijet system in PbPb & pp
collsions

E. Appelt

Studies of dijet & photon-jet properties in pp, pPb, & PbPb collisions withCMSK. Jung for ATLAS collaboration

Jet and charged hadron RAA in pPb collisions with CMS
D. V. Perepelitsa for ATLAS collaboration

B-jet RAA in Heavy-ion collisions with CMSA. Angerami for ATLAS collaboration

Centrality and rapidity dependence of inlusive jet production in √sNN=5.02
TeV p+pB with ATLASS. Aiola for ALICE collaboration

D. Gulhan for CMS collaboration

Experimental results on jets in ultra-relativistic nuclear collisions
Y. J. Lee

Introduction (1) A strong suppression of particle production in H.I.C was observed at RHIC (0.2 TeV) Particle productions in H.I.C at LHC (2.76 TeV) strong suppression up to 100 GeV/c (charged particle)
 heavy flavours (charm & beauty) productions are strongly suppressed photon, Z and W productions are scaled binary collisions of pp
3

Introduction (2)π, K, p …

Parton hard scattering
Q2 >> 1 GeV2

Scattered partons interact with
Medium => energy loss

Fragmentation

hadrons
Single particle RAA(in previous slide)
Jet measurement allow to access parton level4

Jets spectrum in Pb-Pb

 Suppression of Jet in Pb-Pb collisions in Pb-Pb collisions w.r.t pp collisions
 y dependence of jet production
 forward rapidity, the spectrum becomes steeper dominated by hard scattering with outgoing quarks (different parton shower)
5

Jets in Pb-Pb

 Strong suppression up to 400 GeV in most central (0-5%, 0-10%)
 Indication of centrality dependence of RAA: RAA(0-10%) < RAA(10-30%)
 Indication of energy recover in large R: RAA(R=0.2) < RAA(R=0.4):
6

Comparison with models

7 Models: realistic geometry, initial state conditions, hadronization
 are in good agreement with measurements (0-10% & 10-30%)
 detail of models
JEWEL: arXiv: 1212.1599
 YaJEM: PRC78,034908, PRC84,067902

y dependence of Jet production

 forward rapidity: different production in mid-rapidity spectrum is steeper in large y not significant y dependence of suppression up to y=28

Path length dependence of Jet RAAoutin energy loss: expect path length dependence out-plane: longer length 0-5%: zero v2 ? path length almost same in-out plane 30-50%: indication non-zero v29

Lower energy & lower pT

10 Strong suppression of jets at pT > 30 GeV/c at 2.76 TeV Pb-Pb
 Jets in 0.2 TeV Au-Au collisions
 observed suppression at low pT (<30 GeV/c)
 note: R = 0.4
 ATLAS RAA (R=0.4) ~0.5 at pT > 50 GeV/c

b jet production in Pb-Pb collisions

11

 heavy flavour production: mainly initial hard scattering
 good probe to study the medium
 production is understood by pQCD
 NLO: Flavor creation, Flavour excitation & Gluon splitting Strong suppression of b jet in most central (0-10%) collisions
 indication of beauty energy loss in Pb-Pb collisions

Flavour dependence ?

 no mass order of energy loss at high pT of jets (>80 GeV/c)
 comparison D meson & non-prompt J/ψ (pT~10 GeV/c) indicatesmass dependence of energy loss measurement of low pT heavy-flavour jets is important12Jet Fragmentation at LHC
 Fragmentation function of jet(100 <pT < 300 GeV/c)

 ratio between central (0-10%)
and peripheral (60-80%)/ or pp collisions
 low pT particles are enhanced
in central collisions

13

Photon-h correlations in Au-Au

 high pT associate hadrons (small ξ)
are suppressed w.r.t pp
 low pT associate hadrons (large ξ)are enhanced w.r.t. pp
 lost energy goes to low pT particle

14

Photon-jet correlations in Pb-Pb

 photon penetrate the matter unbiased trigger
 low pT jet enhanced especiallytriggered with high pT γ

15

Jet production in p-Pb

 RpPb of Jet is unity (R = 0.2 & R = 0.4)
 no Cold Nuclear Matter effects
 No modification of jet shape: R(0.2)/R(0.4) in pp & pPb are consistent16

Jet production in p-Pb & Pb-Pbb jetInclusive

 RpPb of Jet is unity up to 400 GeV/c: inclusive & b jets inclusive & b jet RAA strongly suppress up to 250 – 300 GeV/c
 strong suppression of jets in Pb-Pb is mainly due to final stateinteraction with medium
17Jet production in p-Pb

 RpPb of Jet is unity in ALICE, ATLAS & CMS: good agreement
 However, charged particles RpPb show enhancement at high pT in CMS & ATLAS high pT charged particle: leading particle of jet => large fraction in jet might be expected similar trend in Jet ?
 pp references are different in ALICE & ATLAS (QM discussion)18

y dependence RpPb is unity in all rapidity range in MB19y dependence in diﬀerent centrality

 y dependence of RpPb
 most central: looks like suppression
 energy loss due to path length ?
 peripheral: looks like enhancement
20

y>0pPb

Summary Strong suppression of jet production up to 400 GeV/ccentrality dependence Not observed y dependence
 Path length dependence
 b-jet also strongly suppress: same order of inclusive jet Low pT particle / jet enhancement observe in FF & awayside No modification of Jet in p-Pb (RpPb = 1)

No R dependence (R=0.2 vs. R=0.4)
 In MB, RpPb = 1 in rapidity
 Centrality dependence Most central: suppression at high pT
 Peripheral: enhancement at high pT21