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Overview of jet physics results from ALICE Filip Krizek on behalf of the ALICE collaboration Nuclear Physics Institute of CAS krizek@ujf.cas.cz February 2019 Jets in heavy-ion collisions Hard scattered partons produce collimated sprays of

slide-1
SLIDE 1

Overview of jet physics results from ALICE

Filip Krizek

  • n behalf of the ALICE collaboration

Nuclear Physics Institute of CAS krizek@ujf.cas.cz

February 2019

slide-2
SLIDE 2

Jets in heavy-ion collisions

◮ Hard scattered partons produce

collimated sprays of particles

◮ Jet is a phenomenological object

defined by an algorithm

◮ Well understood theoretically in

pQCD in elementary reactions

◮ Jet quenching in presence of

Quark-Gluon plasma

p+p

  • F. Krizek

2

CMS, Phys. Rev. Lett. 107 (2011) 132001

slide-3
SLIDE 3

Jets in ALICE

◮ Charged jets: tracks |η| < 0.9, 0◦ < ϕ < 360◦, pconst

T

> 150 MeV/c ◮ Jet reconstruction: .. anti-kT algorithm (FastJet package [1]) For given jet R, charged jet acceptance is ..... |ηjet| < 0.9 − R

[1] Cacciari et al., Eur. Phys. J. C 72 (2012) 1896.

  • F. Krizek

3

slide-4
SLIDE 4

Quantification of medium-induced jet modification

◮ Inclusive observables (pT spectra, high-pT hadron-jet correlations) ◮ Quantification of jet shapes by functions which depend on

4-momenta of constituents (angularity, pTD, jet mass,. . . ) λκ

β =

  • i∈constituents

pT,i pT,jet κ ∆R jet,i R β .................[1]

◮ Clustering history (grooming, N-subjettiness)

[1] A. J. Larkoski, J. Thaler, and W. J. Waalewijn, JHEP 11 (2014) 129

  • F. Krizek

4

slide-5
SLIDE 5

Selection of jets using fragmentation bias

) c (GeV/

jet

A

ch

ρ

  • raw

T,ch jet

p =

T,ch jet

p

  • 40
  • 20

20 40 60 80 100

  • 1

) c (GeV/

jet

η d

T,ch jet

p d

ch jet

N

2

d

evt

N 1

coll

N 1

  • 10

10

  • 9

10

  • 8

10

  • 7

10

  • 6

10

  • 5

10

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1 Inclusive c > 5 GeV/

T

p Leading track c > 10 GeV/

T

p Leading track =2.76 TeV

NN

s ALICE Pb-Pb Centrality: 0-10% Charged Jets = 0.3 R

T

k Anti- | < 0.5

jet

η | c > 0.15 GeV/

track T

p

ALI−PUB−64210

◮ Hard scattering, rare process embedded in large background ◮ Correction of jet transverse momentum for mean background energy density [1] preco,ch

T,jet

= pch,raw

T,jet

− ρ × Ajet where Ajet is jet area and ρ = median kT jets {pT,jet/Ajet} ◮ Spectrum of reconstructed jets at low pT is dominated by combinatorial jets ◮ Suppression of combinatorial jets by high-pT jet constituent requirement results in fragmentation bias on jets

[1] Cacciari et al., Phys. Lett. B 659 (2008) 119.

  • F. Krizek

5

slide-6
SLIDE 6

Hadron-jet coincidence measurement

[1] ALICE, JHEP 09 (2015) 170

) c (GeV/

reco,ch T,jet

p

40 − 20 − 20 40 60 80 100 120

  • 1

) c (GeV/

reco,ch T,jet

p d

jet

η d N

2

d

trig

N 1

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 10

TT{8,9} 0.005 ± Integral: 1.644 TT{20,50} 0.009 ± Integral: 1.651

= 2.76 TeV

NN

s 0-10% Pb-Pb = 0.4 R charged jets,

T

k Anti-

Statistical errors only

ALICE < 0.6 ϕ ∆ − π

ALI−PUB−93509

TT = trigger track TT{X,Y} means X < pT,trig < Y GeV/c

preco,ch

T,jet

= pch, raw

T,jet

−ρ×Ajet ◮ Hadron-jet correlation allows to suppress combinatorial jets including

multi-parton interaction without imposing fragmentation bias

◮ Data driven approach allows to measure jets with large R and low pT ◮ In events with a high-pT trigger hadron, analyze recoiling away side jets [1]

|ϕtrig − ϕjet − π| < 0.6 rad

◮ Assuming uncorrelated jets are independent of trigger pT

  • F. Krizek

6

slide-7
SLIDE 7

∆recoil in Pb–Pb at √sNN = 2.76 TeV

∆recoil = 1 Ntrig d2Njet dpch

T,jetdη

  • pT,trig∈TT{20,50}

− 1 Ntrig d2Njet dpch

T,jetdη

  • pT,trig∈TT{8,9}

⋄ Link to theory... 1 NAA

trig

d2NAA

jet

dpch

T,jetdηjet

  • pT,trig∈TT

=

  • 1

σAA→h+X · d2σAA→h+jet+X dpch

T,jetdηjet

  • pT,h∈TT

) c (GeV/

ch T,jet

p

20 30 40 50 60 70 80 90 100

  • 1

) c (GeV/

recoil

∆

4 −

10

3 −

10

2 −

10

= 0.2 R = 0.4 R = 0.5 R Correlated uncertainty Shape uncertainty ALICE TT{8,9} − TT{20,50} < 0.6 ϕ ∆ − π = 2.76 TeV s 0-10% Pb-Pb charged jets

T

k Anti-

ALI−PUB−93501

◮ ∆recoil corrected for background

smearing of jet pT + detector effects

◮ Medium effects

∆IAA = ∆Pb-Pb

recoil /∆pp recoil

Need pp reference at the same √s

ALICE, JHEP 09 (2015) 170

  • F. Krizek

7

slide-8
SLIDE 8

∆IAA and ∆recoil ratio in Pb–Pb

) c (GeV/

ch T,jet

p

10 20 30 40 50 60 70 80 90 100

PYTHIA recoil

∆ /

PbPb recoil

∆ =

AA

I ∆

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 ALICE data Shape uncertainty Correlated uncertainty = 2.76 TeV

NN

s 0-10% Pb-Pb

Hadron Trigger Threshold

= 0.5 R charged jets,

T

k Anti- < 0.6 ϕ ∆ − π TT{8,9} − TT{20,50} ALICE

ALI−PUB−93497

R = 0.5

) c (GeV/

ch T,jet

p

10 20 30 40 50 60 70 80 90 100

=0.5) R (

recoil

∆ =0.2)/ R (

recoil

∆

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 ALICE data Shape uncertainty Correlated uncertainty PYTHIA Perugia: Tune 2010 & 2011

Hadron Trigger Threshold

= 2.76 TeV

NN

s 0-10%, Pb-Pb charged jets

T

k Anti- < 0.6 ϕ ∆ − π ALICE TT{8,9} − TT{20,50}

ALI-PUB-93521

◮ Left: ∆IAA with Reference ∆PYTHIA

recoil

from PYTHIA Perugia 10 Suppression of the recoil jet yield

◮ Right: Observable sensitive to lateral energy distribution in jets

Red band: variation in the observable calculated using PYTHIA tunes No evidence for significant energy redistribution w.r.t. PYTHIA

ALICE, JHEP 09 (2015), 170

  • F. Krizek

8

slide-9
SLIDE 9

Jet broadening and the transport coefficient ˆ q

ˆ q ≡

  • k2

⊥

  • L

= 1 L

  • d2k⊥

(2π)2 k2

⊥P (k⊥)

P (k⊥) =

  • d2x⊥e−ik⊥x⊥WR (x⊥)

WR (x⊥) ≡ expectation value of the Wilson loop

k L q

◮ Strongly coupled plasma (AdS CFT) : P (k⊥) is Gaussian ◮ Weakly coupled plasma (perturbative thermal field theory) :

P (k⊥) is a Gaussian with a power-law P (k⊥) ∝ 1/k4

⊥ tail emerging

from single hard Moli` ere scatterings off QGP quasi-particles ⇒ Use recoil jets to search for QGP quasi-particles [1] by looking at enhancement in large angle deflections w.r.t. reference pp

...........

  • F. Krizek

9

[1] D’Eramo et al., JHEP 05 (2013) 031.

slide-10
SLIDE 10

Search for large-angle single hard Moli` ere scatterings

ϕ ∆

1.6 1.8 2 2.2 2.4 2.6 2.8 3

) ϕ ∆ ( Φ

0.02 0.04 0.06 Hadron trigger TT{8,9} − TT{20,50} TT{20,50} TT{8,9} ALICE = 2.76 TeV

NN

s 0-10% Pb-Pb = 0.4 R charged jets,

T

k Anti- c < 60 GeV/

reco,ch T,jet

p 40 <

ALI−PUB−93873

ALICE, JHEP 09 (2015), 170

For recoil jets in 40 < pch

T,jet < 60 GeV/c define

Φ (∆ϕ) = 1 Ntrig d2Njet dpch

T,jetd∆ϕ

  • TT{20,50}

− 1 Ntrig d2Njet dpch

T,jetd∆ϕ

  • TT{8,9}

Quantify the rate of large angle scatterings Σ (∆ϕthresh) = π−∆ϕthresh

π/2

Φ (∆ϕ) d∆ϕ

  • F. Krizek

10

slide-11
SLIDE 11

Σ (∆ϕthresh) in Pb–Pb and PYTHIA

thresh

ϕ ∆

0.1 0.2 0.3 0.4 0.5 0.6 0.7

)

thresh

ϕ ∆ ( Σ

0.01 0.02 0.03 Pb-Pb PYTHIA + Pb-Pb ALICE = 2.76 TeV

NN

s 0-10% Pb-Pb = 0.4 R charged jets,

T

k Anti- c < 60 GeV/

reco,ch T,jet

p 40 < TT{8,9} − TT{20,50}

Statistical errors only

ALI−PUB−93885

thresh

ϕ ∆

0.1 0.2 0.3 0.4 0.5 0.6 0.7

PYTHIA

)

thresh

ϕ ∆ ( Σ /

Data

)

thresh

ϕ ∆ ( Σ

1 2 ALICE = 2.76 TeV

NN

s 0-10% Pb-Pb = 0.4 R charged jets,

T

k Anti- c < 60 GeV/

reco,ch T,jet

p 40 < TT{8,9} − TT{20,50} ) sys 0.36( ± ) stat 0.641( ± 0.527 − Slope =

Statistical errors only

ALI−PUB−93889

◮ Raw data are compared with PYTHIA smeared with detector response

and embedded into real events

◮ Ratio < 1 corresponds to the suppression of recoil jet yield ◮ Shape of the ratio depends on underlying processes ◮ Fit of the ratio by a linear function gives a slope consistent with zero ⇒

No evidence for medium-induced Moli` ere scattering

◮ To be further studied in Run3 with more statistics and for lower jet pTs

ALICE, JHEP 09 (2015), 170

  • F. Krizek

11

slide-12
SLIDE 12

QGP signatures in small systems

◮ Indication of collective effects in pp and p–Pb

(rad) ϕ ∆

  • 1

1 2 3 4 η ∆

  • 2
  • 1

1 2 )

  • 1

(rad ϕ ∆ d η ∆ d

assoc

N

2

d

trig

N 1 0.75 0.80 0.85 c < 4 GeV/

T,trig

p 2 < c < 2 GeV/

T,assoc

p 1 < = 5.02 TeV

NN

s p-Pb (0-20%) - (60-100%)

ALI−PUB−46246

◮ Is there jet quenching in p–Pb?

⋄ ∆E ∝ ˆ qL2

BDMPS, Nucl. Phys. B483 (1997) 291

⋄ ˆ q|pPb = 1

7 ˆ

q|PbPb

K.Tywoniuk, Nucl.Phys. A 926 (2014) 85–91

⋄ ∆E = (8 ± 2stat) GeV/c medium-induced E transport to R > 0.5 in Pb–Pb

ALICE, JHEP 09 (2015) 170

  • F. Krizek

12

CMS, JHEP 09 (2010) 091 ALICE, Phys.Lett. B 719 (2013) 29–41

slide-13
SLIDE 13

Event Activity biased jet measurements in p–Pb at LHC

Jet RpPb in p–Pb at √sNN = 5.02 TeV Event Activity from ET in Pb-going direction −4.9 < η < −3.2

RpPb =

dNcent

jets /dpT

TpPb · dσpp/dpT

◮ RpPb depends on rapidity range

Caveats:

◮ TpPb assume Event Activity

correlated with geometry (Glauber modeling)

◮ Conservation laws and fluctuations

Kordell, Majumder, arXiv:1601.02595v1

Alternative: Hadron-jet conditional yields

  • F. Krizek

13

slide-14
SLIDE 14

Semi-inclusive hadron-jet observables and TAA

Calculable at NLO pQCD [1] 1 NAA

trig

d2NAA

jet

dpch

T,jetdηjet

  • pT,trig∈TT
  • measured

=

  • 1

σAA→h+X · d2σAA→h+jet+X dpch

T,jetdηjet

  • pT,h∈TT
  • from theory

In case of no nuclear effects 1 NAA

trig

d2NAA

jet

dpch

T,jetdηjet

  • pT,trig∈TT

=

  • 1

σpp→h+X · d2σpp→h+jet+X dpch

T,jetdηjet

  • pT,h∈TT

× TAA TAA ❅ ❅ ❅

◮ This coincidence observable is self-normalized, no requirement of

TAA scaling

◮ No requirement to assume correlation between Event Activity and

collision geometry, no Glauber modeling

[1] D. de Florian, Phys.Rev. D79 (2009) 114014

  • F. Krizek

14

slide-15
SLIDE 15

∆recoil in p–Pb at √sNN = 5.02 TeV

Raw spectrum

) c (GeV/

reco,ch T,jet

p

10 20 30 40 50 60 70 80 90

1 −

) c (GeV/

recoil

∆ and

jet

η d

reco,ch T,jet

p d

jets

N

2

d

trig

N 1

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1 = 5.02 TeV

NN

s Pb − ALICE p 20% ZNA − = 0.4 R charged jets,

T

k Anti- < 0.96 *

jet

y 0.03 < − < 1.36; *

TT

y 0.43 < − < 0.6 ϕ ∆ − π TT{12,50} : 1.84 Integral TT{12,50} TT{6,7} : 1.83 Integral TT{6,7} = 0.94 )

Ref

c (

recoil

∆ Statistical errors only

ALI−PUB−160376

.......Fully corrected

) c (GeV/

ch T,jet

p

20 30 40 50

1 −

) c (GeV/

recoil

∆

4 −

10

3 −

10

2 −

10

1 −

10 1 100 × 10 × 1 × = 5.02 TeV

NN

s Pb − p 0.465 − =

NN

y = 0.4 R charged jets,

t

k Anti- < 0.6 ϕ ∆ − π TT{6,7} − TT{12,50} MB 20 % − ZNA 0 100 % − ZNA 50

  • Syst. uncert.

ALICE Preliminary

ALI−PREL−118028

Event Activity selected by - ZNA zero degree neutron calorimeter η ≈ 10 ...................................... - V0A scintillator array η ∈ (2.8, 5.1) ...................................... both detectors are located in Pb-going direction ∆recoil = 1 Ntrig d2Njet dpch

T,jetdη

  • pT,trig∈TT{12,50}

− 1 Ntrig d2Njet dpch

T,jetdη

  • pT,trig∈TT{6,7}

ALICE, Phys. Lett. B 783 (2018) 95–113.

  • F. Krizek

15

slide-16
SLIDE 16

Ratios of Event Activity biased ∆recoil distributions

) c (GeV/

ch T,jet

p

15 20 25 30 35 40 45 50

100% ZNA − 50 recoil

∆

/

20% ZNA − recoil

∆

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

TT{6,7} − TT{12,50} = 0.4 R charged jets,

T

k Anti- < 0.97 *

jet

y 0.03 < − < 1.36; *

TT

y 0.43 < − < 0.6 ϕ ∆ − π

  • Syst. uncert.

spectrum jet shift c 0.4 GeV/ = 5.02 TeV

NN

s Pb − ALICE p

ALI−PUB−160424

ZNA

) c (GeV/

ch T,jet

p

15 20 25 30 35 40 45 50

100% V0A − 50 recoil

∆

/

20% V0A − recoil

∆

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

TT{6,7} − TT{12,50} = 0.4 R charged jets,

T

k Anti- < 0.97 *

jet

y 0.03 < − < 1.36; *

TT

y 0.43 < − < 0.6 ϕ ∆ − π

  • Syst. uncert.

spectrum jet shift c 0.4 GeV/ = 5.02 TeV

NN

s Pb − ALICE p

ALI−PUB−160434

V0A

Ratio RCP = ∆recoil|0−20 % ∆recoil|50−100 % compatible with unity

ALICE, PLB 783 (2018) 95–113.

ch T,jet

p

15 20 25 30 35 40 45 50

in log scale

recoil

∆

1 −

10 1

s

Low EA: b

ch T,jet

p − exp a High EA: b s +

ch T,jet

p − exp a

b s − = exp

CP

R

◮ Medium-induced spectrum shift ¯

s for high relative to low Event Activity p–Pb ¯ s = (−0.06 ± 0.34stat ± 0.02syst) GeV/c for V0A ¯ s = (−0.12 ± 0.35stat ± 0.03syst) GeV/c for ZNA ¯ s = (8 ± 2stat) GeV/c in Pb–Pb

ALICE, JHEP 09 (2015) 170

◮ Medium-induced charged energy transport out of

R = 0.4 cone is less than 0.4 GeV/c (one sided 90% CL)

  • F. Krizek

16

slide-17
SLIDE 17

Jet shapes in pp and central Pb–Pb collisions

ALICE, Medium modification of the shape of small-radius jets in central Pb–Pb collisions at √sNN = 2.76 TeV JHEP 10 (2018) 139

◮ Angularity

g =

  • i∈jet

pT,i pT,jet |∆Rjet,i|

∆Rjet,i = angle between jet constituent and jet axis; pT,i = jet constituent transverse momentum

◮ Momentum dispersion

pTD =

  • i∈jet p2

T,i

  • i∈jet pT,i

pT,i denotes jet constituent transverse momentum Underlying event corrected for by area-derivatives method [1]

[1] G.Soyez et al., Phys.Rev.Lett. 110 (2013) 162001

  • F. Krizek

17

slide-18
SLIDE 18

Jet shapes in pp and Pb–Pb (0–10% centrality)

0.02 0.04 0.06 0.08 0.1 0.12 5 10 15 20 25 30 35

g /d

jets

N d

jets

N 1/

ALICE data PYTHIA Perugia 2011 PYTHIA 8 Tune 4C = 7 TeV s pp = 0.2 R charged jets,

T

k Anti- c 60 GeV/ ≤

ch T,jet

p ≤ 40 ALICE 0.02 0.04 0.06 0.08 0.1 0.12

g

0.6 0.8 1 1.2 1.4 1.6

Data/MC

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 2 3 4 5 6 7

D

T

p /d

jets

N d

jets

N 1/

ALICE data PYTHIA Perugia 2011 PYTHIA 8 Tune 4C ALICE data PYTHIA Perugia 2011 PYTHIA 8 Tune 4C = 7 TeV s pp = 0.2 R charged jets,

T

k Anti- c 60 GeV/ ≤

ch T,jet

p ≤ 40 ALICE 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

D

T

p

0.6 0.8 1 1.2 1.4 1.6

Data/MC

0.02 0.04 0.06 0.08 0.1 0.12 5 10 15 20 25 30 35

g /d

jets

N d

jets

N 1/

ALICE data PYTHIA Perugia 2011 PYTHIA 8 Tune 4C = 2.76 TeV

NN

s Pb − 10% Pb − = 0.2 R charged jets,

T

k Anti- c 60 GeV/ ≤

ch T,jet

p ≤ 40 ALICE 0.02 0.04 0.06 0.08 0.1 0.12

g

0.5 1 1.5 2

Data/MC

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 2 3 4 5 6 7

D

T

p /d

jets

N d

jets

N 1/

ALICE data PYTHIA Perugia 2011 PYTHIA 8 Tune 4C ALICE data PYTHIA Perugia 2011 PYTHIA 8 Tune 4C = 2.76 TeV

NN

s Pb − 10% Pb − = 0.2 R charged jets,

T

k Anti- c 60 GeV/ ≤

ch T,jet

p ≤ 40 ALICE 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

D

T

p

0.5 1 1.5 2

Data/MC

...................................................

  • pp collisions at √s=7 TeV

...................................................

  • Pb–Pb collisions at √sNN=2.76 TeV

◮ Anti-kT track-based jets with R = 0.2 and 40 < pch

T,jet < 60 GeV/c

◮ Fully corrected on detector effects and underlying event ◮ pp: jet shapes well reproduced by PYTHIA ◮ Pb–Pb: decrease in mean angularity ⇒ jets are more collimated

Pb–Pb: increase in mean pTD ⇒ jets are more hard Pb–Pb: qualitatively consistent with more quark-like fragmentation

ALICE, JHEP 10 (2018) 139

  • F. Krizek

18

slide-19
SLIDE 19

Jet substructure from iterative declustering

ALI-PREL-147982 ALI-PREL-147990

◮ Grooming aims to select hard splittings within jet shower Soft Drop: z > zcut ◮ zg filled with z of the first splitting where z > 0.1 ◮ nSD the number of splittings that fulfill z > 0.1 when we follow the hardest branch ◮ pp reproduced by PYTHIA

  • F. Krizek

19

Lund plot maps jet shower splittings in plane opening angle θ and pT fraction z = min(pT,1, pT,2) pT,1 + pT,2

...............................................................

  • pp collisions at √s=7 TeV
slide-20
SLIDE 20

Iterative declustering in Pb–Pb (0–10% centrality)

  • F. Krizek

20

ALI-PREL-148233

splittings with θ < 0.1

ALI-PREL-148229

splittings with θ > 0.2

ALI-PREL-155677

◮ Raw spectra compared to PYTHIA smeared by detector effects and embedded to raw Pb–Pb events ◮ Anti-kT jets R = 0.4 and 80 < pch

T,jet < 120 GeV/c

◮ Normalization includes jets with nSD = 0 ◮ Small enhancement of small angle asymmetric splittings + suppression of large angle symmetric splittings: qualitatively expected from color coherence ◮ Shift towards lower number of splittings passing Soft Drop w.r.t. PYTHIA: harder, more quark-like fragmentation (cf. g and pTD)

slide-21
SLIDE 21

Summary

◮ Hadron-jet technique allows to measure jet quenching in heavy-ion

collisions and small systems

◮ does not require the assumption that Event Activity is correlated with

collision geometry

◮ provides systematically well-controlled comparison of jet quenching as a

function of Event Activity

◮ Pb–Pb at √sNN = 2.76 TeV: suppression of recoil jet yield, but no

evidence of intra-jet broadening of energy profile out to R = 0.5

◮ p–Pb at √sNN = 5.02 TeV: no significant quenching effects are observed

when comparing recoil jet yield for low and high Event Activity. At 90% CL, medium-induced charged energy transport out of R = 0.4 cone is less than 0.4 GeV/c ◮ Jets in Pb–Pb are more hard and collimated w.r.t. pp ◮ Suppression of large angle symmetric splittings

  • F. Krizek

21

slide-22
SLIDE 22

Backup slides

slide-23
SLIDE 23

Corrections of raw jet spectra

◮ Background fluctuations:

embedding MC jets or random cones [1] δpt =

i pt,i − A · ρ

◮ Detector response:

based on GEANT + PYTHIA

◮ Response matrix:

two effects are assumed to factorize Rfull

  • prec

T,jet, ppart T,jet

  • =

.δpt

  • prec

T,jet, pdet T,jet

  • ⊗ Rinstr
  • pdet

T,jet, ppart T,jet

  • ◮ R−1

full obtained with Bayesian [2] and

SVD [3] unfolding with RooUnfold [4]

[1] ALICE, JHEP 1203 (2012) 053 [2] D’Agostini, Nucl.Instrum.Meth.A362 (1995) 487 [3] H¨

  • cker and Kartvelishvili, Nucl.Instrum.Meth.A372 (1996) 469

[4] http://hepunx.rl.ac.uk/˜adye/software/unfold/RooUnfold.html ) c (GeV/

ch T

p δ

  • 40
  • 20

20 40 60 80

probability density

  • 6

10

  • 5

10

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1 =2.76 TeV

NN

s Pb-Pb Centrality: 0-10% c > 0.15 GeV/

track T

p Random Cones ALICE c = 4.47 GeV/ σ = 0.2 R c = 7.15 GeV/ σ = 0.3 R

ALI−PUB−64214

part T,ch jet

p )/

part T,ch jet

p

  • det

T,ch jet

p (

  • 1
  • 0.8
  • 0.6
  • 0.4
  • 0.2

0.2

Probability/Bin(0.04)

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 ALICE simulation ) c (GeV/

part T,ch jet

p 30 - 40 50 - 60 70 - 80 = 0.2 R

T

k Anti- c > 0.15 GeV/

track T

p

ALI−PUB−64222

  • F. Krizek

23

slide-24
SLIDE 24

QGP signatures in small systems

◮ Indication of collective effects in p–Pb ◮ Is there jet quenching in p–Pb? ◮ Considerations

⋄ ∆E ∝ ˆ qL2

BDMPS, Nucl. Phys. B483 (1997) 291

⋄ ˆ q|pPb = 1

7 ˆ

q|PbPb

K.Tywoniuk, Nucl.Phys. A 926 (2014) 85–91

⋄ ˆ q|PbPb = (1.9 ± 0.7) GeV2/fm

JET Collaboration, Phys.Rev. C 90, 014909 (2014)

⋄ ˆ q|Cold Nuclear Matter ≈ 0.02 GeV2/fm

W.T.Deng, X.N.Wang, Phys.Rev. C 81, 024902 (2010)

⋄ ∆E = (8 ± 2stat) GeV/c medium-induced E transport to R > 0.5 in Pb–Pb

ALICE, JHEP 09 (2015) 170

(rad) ϕ ∆

  • 1

1 2 3 4 η ∆

  • 2
  • 1

1 2 )

  • 1

(rad ϕ ∆ d η ∆ d

assoc

N

2

d

trig

N 1 0.75 0.80 0.85 c < 4 GeV/

T,trig

p 2 < c < 2 GeV/

T,assoc

p 1 < = 5.02 TeV

NN

s p-Pb (0-20%) - (60-100%)

ALI−PUB−46246

ALICE, Phys.Lett. B 719 (2013) 29–41

  • F. Krizek

24

slide-25
SLIDE 25

Event Activity in p–Pb at √sNN = 5.02 TeV

(TeV)

ZN

E

20 40 60 80 100 120

Events (a.u.)

2

10

3

10

4

10

5

10

= 5.02 TeV

NN

s ALICE p-Pb Data SNM-Glauber

0-20 % 20-50 % 50-100 %

1 2 3 4 5 6 7 8 5000 10000 15000 20000 25000 30000

ALI−DER−121282

V0A (Pb-side) amplitude (arb. units)

100 200 300 400 500

Events (arb. units)

5 −

10

4 −

10

3 −

10

2 −

10 = 5.02 TeV

NN

s ALICE p-Pb Data NBD-Glauber fit

= 11.0, k = 0.44) µ x NBD (

part

N

0-20% 20-50% 50-100%

10 20 30 40

2 −

10 ALI−DER−119334

Pb-going direction ZNA V0A

η ∈ (2.8, 5.1)

Charged track reconstruction

|η| < 0.9, pT > 150 MeV/c

ITS 6-layered silicon tracker TPC time projection chamber

ALICE, Phys. Rev. C 91 (2015) 064905

✲ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✼

  • F. Krizek

25

slide-26
SLIDE 26

Event Activity assignment in p–Pb

ZNA percentile

10 20 30 40 50 60 70 80 90 100

Probability density

0.01 0.02 0.03

= 5.02 TeV

NN

s Pb − ALICE p MB TT{6,7} TT{12,50}

ALI−PUB−160361

High EA Low EA V0A percentile

10 20 30 40 50 60 70 80 90 100

Probability density

0.01 0.02 0.03

= 5.02 TeV

NN

s Pb − ALICE p MB TT{6,7} TT{12,50}

ALI−PUB−160365

High EA Low EA ◮ High-pT track requirement (TT) biases event to large Event

Activity

◮ Similar Event Activity bias for TT 6–7 GeV/c and

12–50 GeV/c

ALICE, PLB 783 (2018) 95–113.

  • F. Krizek

26

slide-27
SLIDE 27

Ratios of recoil jet yields obtained with different R

) c (GeV/

ch T,jet

p

10 20 30 40 50 60 70 80 90 100

=0.4) R (

recoil

∆ =0.2)/ R (

recoil

∆

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 ALICE data Shape uncertainty Correlated uncertainty PYTHIA Perugia: Tune 2010 & 2011

Hadron Trigger Threshold

= 2.76 TeV

NN

s 0-10%, Pb-Pb charged jets

T

k Anti- < 0.6 ϕ ∆ − π ALICE TT{8,9} − TT{20,50}

ALI-PUB-93546

) c (GeV/

ch T,jet

p

10 20 30 40 50 60 70 80 90 100

=0.5) R (

recoil

∆ =0.2)/ R (

recoil

∆

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 ALICE data Shape uncertainty Correlated uncertainty PYTHIA Perugia: Tune 2010 & 2011

Hadron Trigger Threshold

= 2.76 TeV

NN

s 0-10%, Pb-Pb charged jets

T

k Anti- < 0.6 ϕ ∆ − π ALICE TT{8,9} − TT{20,50}

ALI-PUB-93521

◮ Observable sensitive to lateral energy distribution in jets ◮ Red band: variation in observable calculated using PYTHIA tunes ◮ No evidence for significant energy redistribution w.r.t. PYTHIA up

to jets with R = 0.5

ALICE JHEP 09 (2015), 170