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New Opportunities in Jet Physics at Colliders Felix Ringer Lawrence Berkeley National Laboratory University of Amsterdam, Nikhef, 03/15/18 Motivation A New Factorization for Jets Jet Substructure Jet

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SLIDE 1

New Opportunities in Jet Physics at Colliders

Lawrence Berkeley National Laboratory University of Amsterdam, Nikhef, 03/15/18 Felix Ringer

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

2

The Large Hadron Collider at CERN

Aerial view of the world’s largest and highest energy particle accelerator 17mi tunnel CMS detector accelerating protons and heavy ions

√s = 13 TeV

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

3

Collimated sprays of particles in the detector

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

4

What are jets?

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Pythia 8

√s = 13 TeV 5

What are jets?

  • Azimuthal angle φ
  • Pseudorapidity η = − ln tan θ/2

beam ATLAS detector

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SLIDE 6

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

6

What are jets?

Pythia 8, FastJet

√s = 13 TeV pjet

T > 20 GeV

R = 0.4

  • Jet algorithm, e.g. anti-kT

and recursively merge the particles with the smallest distance

dij = min 1 p2

T i

, 1 p2

T j

! (ηi − ηj)2 + (φi − φj)2 R2

Define a distance between all particles

  • Pioneering work Sterman,

Weinberg `77 Cacciari, Salam, Soyez `08

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SLIDE 7

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

R 7

What are jets?

  • Jet algorithm, e.g. anti-kT

and recursively merge the particles with the smallest distance Pythia 8, FastJet

√s = 13 TeV pjet

T > 20 GeV

R = 0.4

dij = min 1 p2

T i

, 1 p2

T j

! (ηi − ηj)2 + (φi − φj)2 R2

Define a distance between all particles is the radius of the jet

R

  • Pioneering work Sterman,

Weinberg `77 Cacciari, Salam, Soyez `08

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

8

Quantum chromodynamics

  • The Lagrangian
  • The coupling constant

L = ¯ ψ ( i∂µγµ − m ) ψ + gs ¯ ψγµ Ta ψ Aa

µ − 1

4F µν

a F a µν

Confinement Asymptotic freedom

  • Theory of the strong interaction between quarks and gluons

αs = g2

s

4π

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

9

QCD factorization

dσpp→hX dηdpT = fa/p ⊗ fb/p ⊗ Hc

ab ⊗ Dh c

Fragmentation functions

X Hc

ab

Scale dependence governed by DGLAP e.g.

µ d dµDh

i =

X

j

Pji ⊗ Dh

j

Perturbatively calculable Parton distribution functions

  • Hadron production pp → h + X

fa/p fa/p

Dh

c

Non-perturbative but universal

Collins, Soper, Sterman `80s -`90s

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

10

  • Jet production

QCD factorization

pp → jet + X X dσpp→jetX dηdpT = fa/p ⊗ fb/p ⊗ Hab Hab

Jet algorithm and radius dependent

X Hc

ab

fa/p fa/p

Dh

c

fa/p fa/p

Collins, Soper, Sterman `80s -`90s

R

NLO

A ln R + B + O(R2/R2

0)

dσpp→hX dηdpT = fa/p ⊗ fb/p ⊗ Hc

ab ⊗ Dh c

Fragmentation functions Perturbatively calculable Parton distribution functions

  • Hadron production pp → h + X

Non-perturbative but universal

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Why do we care about jets?

11

  • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT
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SLIDE 12

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Why do we care about jets?

12

  • Constrain non-perturbative quantities

e.g. parton distribution functions

Harland-Lang, Martin, Thorne `17

Impact of LHC jet data: for

g(x) x → 1

percentage difference

  • wrt. baseline

fit without jets

pp → jetX

  • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT
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SLIDE 13

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Why do we care about jets?

13

  • Precision test of the standard model, e.g. measure properties of the Higgs
  • Constrain non-perturbative quantities

e.g. parton distribution functions

H → b¯ b

e.g.

boost

98% jets 2% e, µ, γ

Higgs decay channels

  • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT

Jet mass distribution

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SLIDE 14

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Why do we care about jets?

14

  • Precision test of the standard model, e.g. measure properties of the Higgs
  • Constrain non-perturbative quantities

e.g. parton distribution functions

H → b¯ b

e.g.

boost

98% jets 2% e, µ, γ

Higgs decay channels

  • Search for physics beyond the standard model

e.g. boosted hadronically decaying Jet mass distribution

  • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT

Z0

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SLIDE 15

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Why do we care about jets?

15

  • Probe of the quark-gluon plasma in heavy-ion collisions
  • Precision test of the standard model, e.g. measure properties of the Higgs
  • Constrain non-perturbative quantities

e.g. parton distribution functions

  • Search for physics beyond the standard model

e.g. boosted hadronically decaying

  • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT

Z0

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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Can we use jets as precision probes?

16

  • Can theory predictions match the experimental precision?

pp → jet + X

  • Can we understand jet substructure from

first principles in QCD?

ATLAS, CERN-EP-2017-157

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SLIDE 17

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

  • Motivation
  • A new factorization theorem for jets
  • Outlook and conclusions

17

Outline

  • A look inside: Jet substructure
  • Jet mass
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SLIDE 18

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

18

Outline

  • Motivation
  • A new factorization theorem for jets
  • Outlook and conclusions
  • A look inside: Jet substructure
  • Jet mass
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SLIDE 19

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

19 CMS Phys.Rev. C96 015202 (2017)

Jet production at the LHC

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e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Jet production at the LHC

20

pT

R = 0.2 R = 0.3 R = 0.4

CMS Phys.Rev. C96 015202 (2017)

NLO 1990

Ellis, Kunszt, Soper `90

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SLIDE 21

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

21

pT

R = 0.2 R = 0.3 R = 0.4

CMS Phys.Rev. C96 015202 (2017)

NLO 1990

Ellis, Kunszt, Soper `90

NNLO 2016 …

Currie, Glover, Pires `16

Jet production at the LHC

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SLIDE 22

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

22

Jet production at NNLOl

ATLAS-CONF-2017-048 µ = pmax

T

µ = pT

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SLIDE 23

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

A new factorization theorem for jets

23 dσpp→hX dpT dη = X

a,b,c

fa ⊗ fb ⊗ Hc

ab ⊗ Dh c

µ d dµDh

i =

X

j

Pji ⊗ Dh

j

Evolution Factorization Hadron

Kang, FR, Vitev `16

pT vs. ΛQCD

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SLIDE 24

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

A new factorization theorem for jets

24 dσpp→jetX dpT dη = X

a,b,c

fa ⊗ fb ⊗ Hc

ab ⊗ Jc

dσpp→hX dpT dη = X

a,b,c

fa ⊗ fb ⊗ Hc

ab ⊗ Dh c

µ d dµDh

i =

X

j

Pji ⊗ Dh

j

Evolution Jet Factorization Hadron

+O(R2/R2

0)

pT vs. ΛQCD pT vs. pT R

Kang, FR, Vitev `16

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SLIDE 25

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

A new factorization theorem for jets

25 dσpp→jetX dpT dη = X

a,b,c

fa ⊗ fb ⊗ Hc

ab ⊗ Jc

dσpp→hX dpT dη = X

a,b,c

fa ⊗ fb ⊗ Hc

ab ⊗ Dh c

µ d dµJi = X

j

Pji ⊗ Jj µ d dµDh

i =

X

j

Pji ⊗ Dh

j

Evolution Jet Factorization Hadron

+O(R2/R2

0)

pT vs. ΛQCD pT vs. pT R

Kang, FR, Vitev `16

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SLIDE 26

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The semi-inclusive jet function

26

where Initiating parton Jet

  • The siJF describes how a parton is transformed

into a jet with radius and carrying an energy fraction

R z

LO NLO

Kang, FR, Vitev `16

NLO

pT = pc

T

pc

T

pc

T

pc

T

pT = pc

T

pT 6= pc

T

Jc(z, pT R, µ) z = pT /pc

T

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e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The semi-inclusive jet function

27

scheme

MS

  • Renormalization group (RG) equation:

resummation of αn

s lnn R

µ d dµJi = X

j

Pji ⊗ Jj µ = pT µJ = pT R

DGLAP for semi-inclusive jet function

  • NLO result

= ↵s 2⇡ ✓1 ✏ + ln ✓ µ2 p2

T R2

◆◆ [Pqq(z) + Pgq(z)] J(1)

q

(z, pT R, µ)

Kang, FR, Vitev `16

is the jet radius

R

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e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

28

The semi-inclusive jet function

5 10 15 20 0.01 0.1 1

Jg(z, pT R) pT = 250 GeV

5 10 15 20 0. z z

z 1 0.1 0.01 5 10 15 20

initial condition for the evolution

Kang, FR, Vitev `16

µ = pT µJ = pT R

energy fraction

Jg(z, pT R)

is the jet radius

R

Vogt `04 (Pegasus), Anderle, FR, Stratmann `15

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e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

29

The semi-inclusive jet function

z 1 0.1 0.01 5 10 15 20

NLLR

R=0.7 R=0.3 R=0.05

Jg(z, pT R) pT = 250 GeV

Jg(z, pT R)

µ = pT µJ = pT R

initial condition for the evolution energy fraction is the jet radius

R

Vogt `04 (Pegasus), Anderle, FR, Stratmann `15 Kang, FR, Vitev `16

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e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

30

The semi-inclusive jet function

z 1 0.1 0.01 5 10 15 20

NLLR

R=0.7 R=0.3 R=0.05

Jg(z, pT R) pT = 250 GeV

Jg(z, pT R)

is the jet radius

R

Kang, FR, Vitev `16

5 10 15 20 0.01 0.1 1

Dπ

g (z, pT )

DSS ‘14

z z

z 0.1 0.01 5 10 15 20

Dh

g (z, pT )

DSS ‘07 1

µ = pT µJ = pT R

initial condition for the evolution energy fraction

Vogt `04 (Pegasus), Anderle, FR, Stratmann `15

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SLIDE 31

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

31

The semi-inclusive jet function

z 1 0.1 0.01 5 10 15 20

NLLR

R=0.7 R=0.3 R=0.05

Jg(z, pT R) pT = 250 GeV

Jg(z, pT R)

use evolved functions in the factorization

µ = pT µJ = pT R

initial condition for the evolution energy fraction is the jet radius

R

Vogt `04 (Pegasus), Kang, FR, Vitev `16 Anderle, FR, Stratmann `15

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e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Comparison to LHC data

32

pT

R = 0.2 R = 0.3 R = 0.4

CMS Phys.Rev. C96 015202 (2017) = X

a,b,c

fa ⊗ fb ⊗ Hab

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SLIDE 33

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Comparison to LHC data

33

pT

R = 0.2 R = 0.3 R = 0.4

CMS Phys.Rev. C96 015202 (2017)

0.5 1 1.5 100 200 300 R = 0.2 100 200 300 R = 0.3 100 200 300 R = 0.4 anti-kT , √s = 2.76 TeV |η| < 2

dσdata,Res/dσNLO pT

Kang, FR, Vitev `16 = X

a,b,c

fa ⊗ fb ⊗ Hab X

a,b,c

fa ⊗ fb ⊗ Hc

ab ⊗ Jc

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SLIDE 34

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Threshold resummation

34 Liu, Moch, FR `17, `18

DR = σ(R) σ(R = 0.5)

CMS, PRD 90 (2014) 072006

  • Threshold logarithms

H ⊗ J αn

s

ln2n(1 − z) 1 − z z → 1

  • partonic threshold

Sterman `87; Catani, Trentadue `89

in

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SLIDE 35

e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Threshold resummation

35 Liu, Moch, FR `17, `18

DR = σ(R) σ(R = 0.5)

CMS, PRD 90 (2014) 072006

  • Threshold logarithms

H ⊗ J αn

s

ln2n(1 − z) 1 − z z → 1

  • partonic threshold

Sterman `87; Catani, Trentadue `89

in

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SLIDE 36

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

36

Outline

  • Motivation
  • A new factorization theorem for jets
  • Outlook and conclusions
  • A look inside: Jet substructure
  • Jet mass
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SLIDE 37

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

A look inside: Jet substructure

37

  • Precision probe of QCD
  • Fragmentation functions (collinear and TMD)

Hadron

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SLIDE 38

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Hadron

38

  • Precision probe of QCD
  • Fragmentation functions (collinear and TMD)
  • Quark-gluon tagging

H, W ±, Z, t¯ t

using e.g. jet mass

98% jets

light quark jets, gluons jets, 
 b-jets, tau-jets

A look inside: Jet substructure

  • Tagging of boosted objects

√s = 7 TeV

ATLAS, JHEP 1205 (2012) 128

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SLIDE 39

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

A look inside: Jet substructure

39

  • Understand the radiation pattern inside jets
  • Perform additional measurement on the jets

v

dσpp→jetX dpT dη = X

abc

fa ⊗ fb ⊗ Hc

ab ⊗ Jc + O(R2/R2 0)

dσpp→(jet v)X dpT dηdv = X

abc

fa ⊗ fb ⊗ Hc

ab ⊗ Gc(v) + O(R2/R2 0)

such as the jet mass

pT vs. pT R

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W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

40

First example: the jet fragmentation function

A look inside: Jet substructure

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SLIDE 41

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The jet fragmentation function l

41

zh = ph

T /pT

pp → (jeth)X

  • First reconstruct a jet and then identify the hadrons inside the jet

Kang, FR, Vitev `16

where

Ji(z, pT R, µ)

standard collinear FFs matching coefficients

Gh

q (z, zh, pT R, µ) =

X

j

Jij(z, zh, pT R, µ) ⊗ Dh

j (zh, µ)

Procura, Stewart `10, Jain, Procura, Waalewijn `11, Arleo et al. `14, Kaufmann, Mukherjee, Vogelsang`15 see also:

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SLIDE 42

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The jet fragmentation function l

42

zh = ph

T /pT

pp → (jeth)X

  • First reconstruct a jet and then identify the hadrons inside the jet

where standard collinear FFs matching coefficients

Ji(z, pT R, µ) Gh

q (z, zh, pT R, µ) =

X

j

Jij(z, zh, pT R, µ) ⊗ Dh

j (zh, µ)

  • resummation again via DGLAP

µ d dµGh

i (z, zh, pT R, µ) =

X

j

Pji(z) ⊗ Gh

j (z, zh, pT R, µ)

αn

s lnn R

Kang, FR, Vitev `16 Procura, Stewart `10, Jain, Procura, Waalewijn `11, Arleo et al. `14, Kaufmann, Mukherjee, Vogelsang`15 see also:

slide-43
SLIDE 43

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The jet fragmentation function l

43

zh = ph

T /pT

pp → (jeth)X

  • First reconstruct a jet and then identify the hadrons inside the jet

where standard collinear FFs matching coefficients

  • resummation again via DGLAP

2x DGLAP

µ = pT µJ = pT R 1 GeV Dh

i

Gh

i

Hi

ab

Ji(z, pT R, µ) Gh

q (z, zh, pT R, µ) =

X

j

Jij(z, zh, pT R, µ) ⊗ Dh

j (zh, µ)

µ d dµGh

i (z, zh, pT R, µ) =

X

j

Pji(z) ⊗ Gh

j (z, zh, pT R, µ)

αn

s lnn R

Kang, FR, Vitev `16 Procura, Stewart `10, Jain, Procura, Waalewijn `11, Arleo et al. `14, Kaufmann, Mukherjee, Vogelsang`15 see also:

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SLIDE 44

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Phenomenology

44 Kang, FR, Vitev `16

small-z requires additional resummation

see Anderle, Kaufmann, FR, Stratmann `16 ATLAS-CONF-2015-022 CMS, JHEP 10 (2012) 087 Arleo, Fontannaz, Guillet, Nguyen `14 Kaufmann, Mukherjee, Vogelsang `15

  • Light charged hadrons
  • Photons

Kaufmann, Mukherjee, Vogelsang `16

  • Heavy flavor mesons

Chien, Kang, FR, Vitev, Xing `15

  • Quarkonia

Kang, Qiu, FR, Xing, Zhang `17 Bain, Dai, Hornig, Leibovich, Makris, Mehen `16 Baumgart, Leibovich, Mehen, Rothstein `14 Bain, Dai, Hornig, Leibovich, Makris, Mehen `16 Bain, Dai, Leibovich, Makris, Mehen `17 Neill, Scimemi, Waalewijn `16 Kang, FR, Vitev `16 Makris, Neill, Vaidya `17 Anderle, Kaufmann, Stratmann, FR, Vitev `17

slide-45
SLIDE 45

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

45

The hadron transverse momentum dependent (TMD) spectrum inside jets

A look inside: Jet substructure

slide-46
SLIDE 46

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The TMD spectrum in jets

46

  • Measure the relative transverse momentum of the

hadron wrt. to the jet axis

zh

longitudinal and transverse momentum

j⊥

,

Kang, Liu, FR, Xing `17 Kang, Prokudin, FR, Yuan `17

standard TMD fragmentation functions as for SIDIS and e+e−

  • Test of universality and TMD evolution
  • Constrain gluon TMD fragmentation function
  • Azimuthal asymmetries at RHIC - Collins effect

see also: Neill, Scimemi, Waalewijn `17

slide-47
SLIDE 47

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The TMD spectrum in jets

47

  • Measure the relative transverse momentum of the

hadron wrt. to the jet axis

zh

longitudinal and transverse momentum

j⊥

,

Kang, Liu, FR, Xing `17 Kang, Prokudin, FR, Yuan `17 ATLAS, EPJC 71 (2011) 1795

5 10 15 20 0.5 1 1.5 2 2.5 3

√s = 7 TeV, |η| < 1.2, R = 0.6 pT [25, 40], < zh >= 0.08

2j⊥F(zh, pT , j⊥) j⊥

siTMDFF ATLAS

20

standard TMD fragmentation functions as for SIDIS and e+e−

  • Test of universality and TMD evolution
  • Constrain gluon TMD fragmentation function
  • Azimuthal asymmetries at RHIC - Collins effect

see also: Neill, Scimemi, Waalewijn `17

slide-48
SLIDE 48

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

48

Related observables: jet shapes Inclusive subjet distribution

A look inside: Jet substructure

slide-49
SLIDE 49

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Measuring subjets

49

  • Recluster particles inside the jet with a smaller jet parameter
  • Longitudinal and transverse energy profile of jets

r < R

Kang, FR, Waalewijn `17

pT pr

T

zr = pr

T /pT

where

slide-50
SLIDE 50

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

50

  • Recluster particles inside the jet with a smaller jet parameter
  • Longitudinal and transverse energy profile of jets

r < R

zr = pr

T /pT

where

pT pr

T

0.1 < zr < 0.2

trigger Pythia 8, FastJet

Measuring subjets

Kang, FR, Waalewijn `17 Figures: Yayun He

slide-51
SLIDE 51

W ± e+e−

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

51

Upcoming measurements from ALICE

Measuring subjets

Subjet function Gjet

q (z, zr, pT R, µ) ∼ Pqq(zr) + Pqg(zr)

  • Measure the QCD the splitting functions r ∼ R

pT pr

T

Kang, FR, Waalewijn `17

slide-52
SLIDE 52

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

52

Outline

  • Motivation
  • A new factorization theorem for jets
  • Outlook and conclusions
  • A look inside: Jet substructure
  • Jet mass
slide-53
SLIDE 53

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Measuring the mass of a jet

53

  • Quark-gluon discrimination
  • Tagging of boosted objects
  • Jet mass for inclusive jet production

m2

J =

⇣ X

i∈J

pi ⌘2 pp → (jet m2

J)X

ATLAS, JHEP 1205 (2012) 128

√s = 7 TeV

Kang, Lee, FR `18 CMS, PRL 119 (2017) 111802

pT > 500 GeV, |η| < 2.5

Kang, Lee, Liu, FR `18

slide-54
SLIDE 54

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Measuring the mass of a jet

54

  • Large underlying event contribution

Multi parton interactions, pileup …

  • Jet mass for inclusive jet production

m2

J =

⇣ X

i∈J

pi ⌘2 pp → (jet m2

J)X

mJ

soft radiation

  • Quark-gluon discrimination
  • Tagging of boosted objects

Kang, Lee, FR `18 Kang, Lee, Liu, FR `18

slide-55
SLIDE 55

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The soft drop grooming algorithm

55

  • Soft drop grooming

Larkoski, Marzani, Soyez, Thaler `14

z < zcutRβ

ij

Soft threshold zcut Distance Rij =

p ∆η2 + ∆φ2/R

  • Recursively remove soft branches from the

clustered jet as long as

β

Angular exponent

slide-56
SLIDE 56

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The soft drop grooming algorithm

56

  • Soft drop grooming

Larkoski, Marzani, Soyez, Thaler `14

1 − z z

z < zcutRβ

ij

Soft threshold zcut Distance Rij =

p ∆η2 + ∆φ2/R Rij β

Angular exponent

  • Recursively remove soft branches from the

clustered jet as long as

slide-57
SLIDE 57

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The soft drop grooming algorithm

57

  • Soft drop grooming

Larkoski, Marzani, Soyez, Thaler `14

z < zcutRβ

ij

Soft threshold zcut Distance Rij =

p ∆η2 + ∆φ2/R β

Angular exponent

  • Recursively remove soft branches from the

clustered jet as long as

slide-58
SLIDE 58

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

The soft drop grooming algorithm

58

  • Soft drop grooming

Larkoski, Marzani, Soyez, Thaler `14

  • Recursively remove soft branches from the

clustered jet as long as

  • The mass of the remaining constituents is

referred to as the “soft drop groomed jet mass”

mJ

mgr

J

Soft threshold zcut

β

Distance

z < zcutRβ

ij

Rij = p ∆η2 + ∆φ2/R

Angular exponent

slide-59
SLIDE 59

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Jet mass factorization

59

  • The ungroomed case

Gi(z, pT R, mJ, µ) = X

j

Hi→j(z, pT R, µ) Ci(mJ, pT , µ) ⊗ Si(mJ, pT , R, µ)

Kang, Lee, FR `18 Kang, Lee, Liu, FR `18

slide-60
SLIDE 60

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Jet mass factorization

60

  • The ungroomed case
  • The groomed case

mJ

mgr

J

Gi(z, pT R, mJ, µ) = X

j

Hi→j(z, pT R, µ) Ci(mJ, pT , µ) ⊗ Si(mJ, pT , R, µ) Gi(z, pT R, mgr

J , zcut, µ) =

X

j

Hi!j(z, pT R, µ) S62gr

i

(pT , R, zcut, µ) Ci(mgr

J , pT , µ) ⊗ Sgr i (mgr J , pT , R, zcut, µ)

Hc(pT )

RG evolution

Sgr

i (mJ, zcut)

Ci(mJ) Sgr

i (mgr J , zcut)

Ci(mgr

J )

Joint resummation

  • f logarithms in R, mJ, zcut

Kang, Lee, FR `18 Kang, Lee, Liu, FR `18

slide-61
SLIDE 61

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

61

  • The ungroomed case

Non-perturbative shift

ATLAS, JHEP 05 (2012) 128 Kang, Lee, Liu, FR `18

slide-62
SLIDE 62

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

62

Non-perturbative shift

  • The ungroomed case
  • The groomed case

ATLAS, JHEP 05 (2012) 128 ATLAS, arXiv: 1711.08341 Kang, Lee, Liu, FR `18

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 −4

1 σresum dσ/d log10(m2 J/p2 T)

4.5−4−3.5−3−2.5−2−1.5−1

Groomed dijet β = 1

−4.5−4−3.5−3−2.5−2−1.5−1

β = 2

log10(m2

J/p2 T)

log10(m2

J/p2 T)

√s = 13 TeV, anti-kT, R = 0.8 pT > 600 GeV, |η| < 1.5 soft drop, zcut = 0.1, β = 0 NLL NLL + NP(Ω = 1) ATLAS

slide-63
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Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

63

Outline

  • Motivation
  • A new factorization theorem for jets
  • Outlook and conclusions
  • A look inside: Jet substructure
  • Jet mass
slide-64
SLIDE 64

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Jets at a future Electron Ion Collider

64

Dedicated workshop for jets at the EIC eRHIC July, BNL

  • Constrain gluon spin contribution
  • Jet mass and shapes
  • Medium properties in cold nuclear matter
  • Back-to-back correlations
  • …

JLEIC

slide-65
SLIDE 65

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions

Conclusions

65

The new factorization for jets has enabled

  • Precision phenomenology using resummation
  • Jet substructure calculations from first principles
  • Groomed jet observables

and it has many applications in the future machine learning

  • Jets at the EIC
  • Combination with modern techniques of
  • …