Auniﬁedpictureforin-mediumjetevolutioninpQCD Edmond...

A unified picture for in-medium jet evolution in pQCD

Edmond IancuIPhT Saclay & CNRS

with P. Caucal, A. H. Mueller and G. Soyez (PRL 120 (2018) 232001 + w.i.p.)

June 19, 2013

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

200 500 100 1000

fixing ωc

θmax=1, kt,min=0.25 GeVθmax=1, kt,min=0.25 GeVanti-kt(R=0.4), |y|<2.8anti-kt(R=0.4), |y|<2.8

solid: q̂ =1.5, L=4, α- s=0.25solid: q̂ =1.5, L=4, α- s=0.25dashed: q̂ =2.67, L=3, α- s=0.25dashed: q̂ =2.67, L=3, α- s=0.25dotted: q̂ =0.96, L=5, α- s=0.25dotted: q̂ =0.96, L=5, α- s=0.25

R AA

pt [GeV]

nuclear modification factor RAA

ATLASours

JETSCAPE, Texas A&M, Jan 2019 In-medium jet evolution in pQCD Edmond Iancu 1 / 23

Outline

Jet evolution in a quark-gluon plasma at weak coupling

Two types of radiation...

vacuum-like: bremsstrahlung (parton virtualities)

medium-induced radiation : BDMPS-Z (collisions in the plasma)

... which are separately well understood

They can be factorized within controlled approximations in pQCD

The “vacuum-like” radiation too is modified by the medium(constraints on the associated phase-space)

Probabilistic picture allowing for Monte-Carlo implementation

Encouraging preliminary results (jet RAA, fragmentation function)


Jet evolution in a quark-gluon plasma

The leading particle (LP) is produced by a hard scattering

It subsequently evolves via radiation (branchings) ...

Bremsstrahlung triggered by the parton virtualities

... and via collisions off the medium constituents, leading to...

transverse momentum broadening: ∆k2⊥ ' q̂∆t

additional, medium-induced, radiation

wash out the colour coherence (destroy interference pattern)JETSCAPE, Texas A&M, Jan 2019 In-medium jet evolution in pQCD Edmond Iancu 3 / 23

Jets in the vacuum

tf 'ω

k2⊥' 1

ωθ2

dP ' αsCRπ

dω

ω

dθ2

θ2

Formation time tf : the time it takes the daughter partons to lose theirquantum coherence (overlap in transverse direction)

Determined by the virtuality Q2 of the original parton: tf ∼ E/Q2

Log enhancement for soft (ω � E) and collinear (θ � 1) gluons

Parton cascades: successive emissions are ordered in

energy (ωi < ωi−1), by energy conservation

angle (θi < θi−1), by color coherence

Double-logarithmic approximation (DLA): strong double ordering


Lund plot for vacuum emissions at DLA

Strong ordering in both energies and angles:[αs ln(E/ω) ln(θ̄/θ)

]nE � ω1 � ω2 � · · · � ω & θ̄ � θ1 � θ2 � · · · � θ

θ̄: the maximal angle allowed for the first emission

Each emission (ωi, θi): a point in the phase-space diagram

E

ω4

ω3

ω2

ω1

θ1

θ2 θ3

θ4

θ̄

0.1 1 10 100

ω [GeV]

0.01

0.1

θ

(ω1, θ1)

(ω2, θ2)

(ω3, θ3)

(ω4, θ4)

(E, θ̄)

k 2⊥=ω2θ 2

=Λ2

VACUUM PHASE SPACE

Evolution stopped by hadronisation: k⊥ ' ωθ & ΛQCD


Medium-induced radiation

In medium: collisions introduce a lower limit on the transverse momentum ...

tf =ω

k2⊥

& k2⊥ & q̂tf

tf .√ω

q̂

... hence an upper limit on the formation time !

Effective only so long as tf < L (medium size), hence for ω ≤ ωc ≡ q̂L2

Two types of emissions occurring inside the medium (tf < L):

vacuum-like: k2⊥ � q̂tf , or tf �

√ω/q̂

medium-induced: k2⊥ ' q̂tf , or tf '

√ω/q̂


Mini-jets from multiple branching

dP ∼ αsdω

ω

L

tf(ω)∼ αs

√q̂L2

ω

dω

ω(BDMPS-Z)

Multiple branching becomes important when ω . ωbr ≡ α2s q̂L

2

Soft primary gluons with ω . ωbr occur event by event

In turn, they generate mini-jets via democratic branchings: x ∼ 1−x

energy transmitted to many soft quanta which thermalize: ω ∼ Ttypical energy loss by the jet ∆E ∼ ωbr, large fluctuations


Mini-jets from multiple branching

dP ∼ αsdω

ω

L

tf(ω)∼ αs

√q̂L2

ω

dω

ω(BDMPS-Z)

Multiple branching becomes important when ω . ωbr ≡ α2s q̂L

2

Soft primary gluons with ω . ωbr occur event by event

Energy loss at large angles: a natural explanation for di-jet asymmetry

J.-P. Blaizot, E. I., Y. Mehtar-Tani, PRL 111, 052001 (2013)JETSCAPE, Texas A&M, Jan 2019 In-medium jet evolution in pQCD Edmond Iancu 7 / 23

Intra-jet nucler modifications

Medium-induced radiation propagates at large angles, outside the jet cone

The LHC data also show nuclear modifications for the energy distributioninside the jet cone

[GeV] T

p1 10 210

)

Tp(

DR

0.5

1

1.5

2

2.5

< 158 GeVjet

Tp 126 <

< 251 GeVjet

Tp 200 <

< 398 GeVjet

Tp 316 <

=0.4 jetsR tk | < 2.1 anti-jet

y|ATLAS

, 0-10%-1 = 5.02 TeV, 0.49 nbNNsPb+Pb, -1 = 5.02 TeV, 25 pbs , pp

z2−10 1−10 1

)z(

DR

0.5

1

1.5

2

2.5

< 158 GeVjet

Tp 126 <

< 251 GeVjet

Tp 200 <

< 398 GeVjet

Tp 316 <

=0.4 jetsR tk | < 2.1 anti-jet

y|ATLAS

, 0-10%-1 = 5.02 TeV, 0.49 nbNNsPb+Pb, -1 = 5.02 TeV, 25 pbs , pp

Can vacuum-like radiation be modified by the medium ?


Vacuum-like emissions (VLE)P. Caucal, E.I., A. H. Mueller and G. Soyez, arXiv:1801.09703 (PRL)

A jet initiated by a colorless qq̄ antenna (decay of a boosted γ or Z)

just to simplify the arguments about color coherence

The antenna propagates through the medium along a distance L

Emissions (tf = 1ωθ2 ) can occur either inside (tf ≤ L), or outside (tf > L)


VLEs inside the medium

For ω ≤ ωc, the medium introduces an upper limit on tf :

tf .√ω

q̂≤ L

No emission within the range√ω

q̂<

1

ωθ2< L

End point of VETOED at

ωc = q̂L2 , θc =1√q̂L3

VLEs in medium occur like in vacuum, but with a smaller phase-space

typical values: q̂ = 1 GeV2/fm, L = 4 fm, ωc = 50 GeV, θc = 0.05

Energy loss & p⊥-broadening during formation are negligible


Color (de)coherence

In vacuum, wide angle emissions (θ > θqq̄) are suppressed by color coherence

the gluon has overlap with both the quark and the antiquark

In medium, color coherence is washed out by collisions after a time tcoh

q̂∆t &1

(θqq̄∆t)2=⇒ ∆t & tcoh =

1

(q̂θ2qq̄)

1/3

(Mehtar-Tani, Salgado, Tywoniuk; Casalderrey-Solana, E. I., 2010–12)


Color (de)coherence

In vacuum, wide angle emissions (θ > θqq̄) are suppressed by color coherence

the gluon has overlap with both the quark and the antiquark

In medium, color coherence is washed out by collisions after a time tcoh

tcoh =1

(q̂θ2qq̄)

1/3� L if θqq̄ � θc ' 0.05

Angular ordering could be violated for emissions inside the medium


Angular ordering strikes back

But this is not the case for the VLEs !

θ > θqq̄ & tf =1

ωθ2> tcoh =⇒ tf &

√ω

q̂: not a VLE

Wide angle VLEs (θ > θqq̄) have tf � tcoh, hence they are suppressed

Emissions at smaller angles (θ < θqq̄) can occur at any time

Color decoherence via collisions plays no role for the VLEsJETSCAPE, Texas A&M, Jan 2019 In-medium jet evolution in pQCD Edmond Iancu 12 / 23

Vacuum-like cascades at DLA

Previous arguments extend to a sequence of angular-ordered VLEs

rigorous in the double-logarithmic approximation

Formation time for the cascade ≈ that of the last gluon

a typical VL cascade has a formation time � L

After formation, gluons propagate in the medium along a distance ∼ Ladditional sources for medium-induced radiation... and for vacuum-like emissions outside the medium


First emission outside the medium

The respective formation time is necessarily large: tf & L

In-medium sources with θ � θc lose coherence in a time tcoh � L

First outside emission can violate angular ordering

re-opening of the angular phase-space

Subsequent “outside” emissions obey angular-ordering, as usual

Vetoed region + lack of angular-ordering for the first “outside” emission


Gluon distribution at DLA

Double differential distribution in energies and emission angles:

T (ω, θ) ≡ ωθ2 d2N

dωdθ2

0.02

0.05

0.2

0.4

0.01

0.1

0.1 1 10 100

θ

ω [GeV]

0.02

0.05

0.2

0.4

0.01

0.1

0.1 1 10 100

0.8525 1

E=200 GeV, θqq=0.4, α- s=0.3, q̂ =2 Gev2/fm, L=3 fm

T/Tvac

E = 200 GeV, θqq̄ = 0.4

q̂ = 2 GeV2/fm, L = 3 fm

T/Tvac = 0 in the excluded region

T/Tvac = 1 inside the medium andalso for ω > ωc and any θ

T/Tvac < 1 outside the mediumat small angles . θc

T/Tvac > 1 outside the mediumat large angles ∼ θqq̄


Jet fragmentation function at DLA

D(ω) ≡ ωdN

dω=

∫ θ2qq̄

Λ2/ω2

dθ2

θ2T (ω, θ)

0.02

0.05

0.2

0.4

0.01

0.1

0.1 1 10 100

θ

ω [GeV]

0.02

0.05

0.2

0.4

0.01

0.1

0.1 1 10 100

0.8525 1

E=200 GeV, θqq=0.4, α- s=0.3, q̂ =2 Gev2/fm, L=3 fm

T/Tvac

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1 10 100

solid: Λ=100 MeVdashed: Λ=200 MeV

D(ω

)/D

vac(ω

)ω [GeV]

q̂ =1 Gev2/fm,L=3 fmq̂ =2 Gev2/fm,L=3 fmq̂ =2 Gev2/fm,L=4 fm

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1 10 100

E=200 GeV, θqq- =0.4, α- s=0.3

Slight suppression at intermediate energies (from 3 GeV up to ωc)

the phase-space is reduced by the vetoed regionthe amount of suppression increases with L and q̂


Jet fragmentation function at DLA

D(ω) ≡ ωdN

dω=

∫ θ2qq̄

Λ2/ω2

dθ2

θ2T (ω, θ)

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1 10 100

solid: Λ=100 MeVdashed: Λ=200 MeV

D(ω

)/D

vac(ω

)

ω [GeV]

q̂ =1 Gev2/fm,L=3 fmq̂ =2 Gev2/fm,L=3 fmq̂ =2 Gev2/fm,L=4 fm

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1 10 100

E=200 GeV, θqq- =0.4, α- s=0.3

Significant enhancement at low energy (below 2 GeV)

reopening of the phase-space by the first emission outside the medium

Related proposal by Mehtar-Tani and Tywoniuk, arXiv:1401.8293JETSCAPE, Texas A&M, Jan 2019 In-medium jet evolution in pQCD Edmond Iancu 16 / 23

Monte Carlo implementation(P. Caucal, E.I., A. H. Mueller and G. Soyez, in preparation)

So far, conceptually simple, but DLA approximations are very crude:

no energy conservation (small-x, gluons only), fixed couplingno k⊥-broadening, no medium-induced radiation

Factorization remains true when assuming strong angular ordering alone

Probabilistic (Markovian) description separately for

vacuum-like parton cascades with angular orderingmedium-induced cascades with BDMPS-Z branching rates

MC implementation: convolution of three showers:

vacuum cascade inside the medium but outside the vetoed regionmedium-induced cascade (in energy)vacuum cascade outside the medium, down to the hadronisation line

Leading parton selected according to the cross-section for pp→ 2 partons


Monte Carlo implementation(P. Caucal, E.I., A. H. Mueller and G. Soyez, in preparation)

So far, conceptually simple, but DLA approximations are very crude:

no energy conservation (small-x, gluons only), fixed couplingno k⊥-broadening, no medium-induced radiation

Leading-logarithmic approximation (angular ordering), with obvious benefits

full splitting functions, running coupling, quarks and gluons, Nc = 3

Gaussian k⊥-broadening ascribed by handreconstruction of the geometry in 3 dimensionsenergy loss: partons with angles θ > θ̄ are leaving the jetno angular ordering for the first emission outside the mediumall the partons inside the medium can act as sources for it

Not yet fully realistic for phenomenology:over-simplified medium description: no expansion, no hydro, just q̂no hadrons, just partons


MC: preliminary results

Focus on 2 observables:

nuclear modification factor RAAratio of FFs in AA and pp

Various choices for q̂, L and αs,med


Medium-induced radiation alone

Initial parton with energy E ≡ pt0 generating a medium-induced cascade

Left: fragmentation function (or spectrum) D(ω) = ω dNdω

pronounced leading-particle peak so long as E � ωs = α2sωc

BDMPS-Z spectrum D(ω) ∝ 1√ωat ω < ωc

0

1

2

3

4

5

6

7

8

0.1 1 10 100 1000

q̂ =1.5 GeV2/fm, L=4 fm, α-s=0.25q̂ =1.5 GeV2/fm, L=4 fm, α-s=0.25

R=1.0, θmax=1.5R=1.0, θmax=1.5

ωc

ωsω0

D(p

t)

constituent pt [GeV]

Fragmentation function varying pt0

pt=5 GeVpt=10 GeVpt=20 GeVpt=50 GeVpt=100 GeVpt=200 GeVpt=500 GeV

0

1

2

3

4

5

6

7

8

0.1 1 10 100 1000

0

5

10

15

20

25

30

1 10 100 1000

q̂ =1.5 GeV2/fm, L=4 fm, α- s=0.25q̂ =1.5 GeV2/fm, L=4 fm, α- s=0.25

aver

age

Ener

gy lo

ss [

GeV

]

initial pt [GeV]

average energy loss

R=0.2R=0.4R=0.8R=1.0

0

5

10

15

20

25

30

1 10 100 1000


Medium-induced radiation alone

Initial parton with energy E ≡ pt0 generating a medium-induced cascade

Right: average energy loss by the jet + its fluctuations

〈∆E〉 becomes independent of E when E � ωs

sizeable dependence upon the jet opening angle for R ≤ 0.8

0

1

2

3

4

5

6

7

8

0.1 1 10 100 1000

q̂ =1.5 GeV2/fm, L=4 fm, α-s=0.25q̂ =1.5 GeV2/fm, L=4 fm, α-s=0.25

R=1.0, θmax=1.5R=1.0, θmax=1.5

ωc

ωsω0

D(p

t)

constituent pt [GeV]

Fragmentation function varying pt0

pt=5 GeVpt=10 GeVpt=20 GeVpt=50 GeVpt=100 GeVpt=200 GeVpt=500 GeV

0

1

2

3

4

5

6

7

8

0.1 1 10 100 1000

0

5

10

15

20

25

30

1 10 100 1000

q̂ =1.5 GeV2/fm, L=4 fm, α- s=0.25q̂ =1.5 GeV2/fm, L=4 fm, α- s=0.25

aver

age

Ener

gy lo

ss [

GeV

]

initial pt [GeV]

average energy loss

R=0.2R=0.4R=0.8R=1.0

0

5

10

15

20

25

30

1 10 100 1000


Boldly adding the data: RAA

Not a fit: just a set of “reasonable” values for the physical parameters

“Uncontrolled parameters” = kinematical cuts: kt,min ≡ Λ, θmax ≡ θ̄

results are remarkably robust

Right plot: RAA depends upon the medium only via ωc = q̂L2/2

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

200 500 100 1000

varying uncontrolled params

q̂ =1.5, L=4, α- s=0.25q̂ =1.5, L=4, α- s=0.25anti-kt(R=0.4), |y|<2.8anti-kt(R=0.4), |y|<2.8

solid: θmax=1, kt,min=0.25 GeVsolid: θmax=1, kt,min=0.25 GeVdashed: vary kt,min (0.15, 0.5)dashed: vary kt,min (0.15, 0.5)dotted: vary θmax (0.75, 1.5)dotted: vary θmax (0.75, 1.5)

R AA

pt [GeV]


ATLASours

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

200 500 100 1000

fixing ωc



R AA

pt [GeV]


ATLASours


Boldly adding the data: RAA

Not a fit: just a set of “reasonable” values for the physical parameters

Left plot: fixing θc, that is, the product q̂L3

results are changing, as expected

Right plot: RAA depends upon the medium only via ωc = q̂L2/2

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

200 500 100 1000

fixing θc



R AA

pt [GeV]


ATLASours

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

200 500 100 1000

fixing ωc



R AA

pt [GeV]


ATLASours


Boldly adding the data: FragmentationThe same “canonical” values for the medium parameters as in the “best”description of RAA (ATLAS data from arXiv:1805.05424)

Fixing ωc = q̂L2/2: very small variations (except at very low z)

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

126 < pt < 158 GeV126 < pt < 158 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

158 < pt < 200 GeV158 < pt < 200 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

200 < pt < 251 GeV200 < pt < 251 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

251 < pt < 316 GeV251 < pt < 316 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

316 < pt < 398 GeV316 < pt < 398 GeV

variations at fixed ωc

anti-kt(R=0.4), |y|<2.1

θmax=1, kt,min=0.25 GeV

solid: q̂ =1.5, L=4, α- s=0.25dashed: q̂ =2.67, L=3, α- s=0.25dotted: q̂ =0.96, L=5, α- s=0.25

ratio

PbP

b/pp

z

ATLASours



Fixing θc, that is, q̂L3: very small variations as well ...

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

126 < pt < 158 GeV126 < pt < 158 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

158 < pt < 200 GeV158 < pt < 200 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

200 < pt < 251 GeV200 < pt < 251 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

251 < pt < 316 GeV251 < pt < 316 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

316 < pt < 398 GeV316 < pt < 398 GeV

variations at fixed θc

anti-kt(R=0.4), |y|<2.1



ratio

PbP

b/pp

z

ATLASours



Equally good results when plotted as a function of the constituent pt ...

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2 5 20 50 200 1 10 100

126 < pt < 158 GeV126 < pt < 158 GeV

ratio

PbP

b/pp

pt [GeV]

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2 5 20 50 200 1 10 100

158 < pt < 200 GeV158 < pt < 200 GeV

ratio

PbP

b/pp

pt [GeV]

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2 5 20 50 200 1 10 100

200 < pt < 251 GeV200 < pt < 251 GeV

ratio

PbP

b/pp

pt [GeV]

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2 5 20 50 200 1 10 100

251 < pt < 316 GeV251 < pt < 316 GeV

ratio

PbP

b/pp

pt [GeV]

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2 5 20 50 200 1 10 100

316 < pt < 398 GeV316 < pt < 398 GeV

variations at fixed ωc

anti-kt(R=0.4), |y|<2.1



ratio

PbP

b/pp

pt [GeV]

ATLASours



... but stronger variability with respect to the “uncontrolled parameters” :

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

126 < pt < 158 GeV126 < pt < 158 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

158 < pt < 200 GeV158 < pt < 200 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

200 < pt < 251 GeV200 < pt < 251 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

251 < pt < 316 GeV251 < pt < 316 GeV

ratio

PbP

b/pp

z

ATLASours

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0.005 0.02 0.05 0.2 0.5 0.01 0.1 1

316 < pt < 398 GeV316 < pt < 398 GeV

varying uncontrolled parameters

anti-kt(R=0.4), |y|<2.1

q̂ =1.5, L=4, α- s=0.25

solid: θmax=1, kt,min=0.25 GeVdashed: vary kt,min (0.15, 0.2, 0.35, 0.5)dotted: vary θmax (0.75, 1.5)

ratio

PbP

b/pp

z

ATLASours


Conclusions & perspectives

Vacuum-like emissions inside the medium can be factorized from themedium-induced radiation via systematic approximations in pQCD

Medium effects enter already at leading-twist level :

reduction in the phase-space for VLEs inside the medium

violation of angular ordering by the first emission outside the medium

Angular ordering is preserved for VLEs inside the medium, like in the vacuum

VLEs inside the medium act as sources for medium-induced radiation

Probabilistic picture, well suited for Monte-Carlo implementations

Preliminary MC results, which look promising

qualitative and even semi-quantitative agreement with the LHC datafor jet fragmentation and the nuclear modification factor

Perspectives: more realistic description of the medium, implementation inJETSCAPE


MC: preliminary results (2)

“No quenching”: just VLEs

no energy loss: RAA = 1

suppression in FF at small ξ

“No decoherence”: strict angular ordering(including first “outside” emission)

no effect on energy loss (RAA)

little enhancement at small ξ

“Quenching before VLEs”: no VLEsinside the medium

RAA larger & increasing with pT,jet

Partons created inside the medium via medium-induced emissionssignificantly contribute to the soft radiation outside the medium


Auniﬁedpictureforin-mediumjetevolutioninpQCD Edmond...

Documents

Transcript of Auniﬁedpictureforin-mediumjetevolutioninpQCD Edmond...