New Opportunities in Jet Physics at Colliders Felix Ringer - PowerPoint PPT Presentation

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 Mass Conclusions The Large Hadron Collider at CERN Aerial view of the world’s largest and highest energy particle accelerator 17mi tunnel accelerating protons and heavy ions √ s = 13 TeV CMS detector 2

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Collimated sprays of particles in the detector 3

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions What are jets? 4

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions What are jets? ATLAS detector beam Pythia 8 √ s = 13 TeV • Azimuthal angle φ • Pseudorapidity η = − ln tan θ / 2 5

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions What are jets? Pythia 8, FastJet √ s = 13 TeV R = 0 . 4 • Pioneering work Sterman, Weinberg `77 p jet T > 20 GeV • Jet algorithm, e.g. anti-k T Cacciari, Salam, Soyez `08 Define a distance between all particles ( η i − η j ) 2 + ( φ i − φ j ) 2 ! 1 , 1 d ij = min p 2 p 2 R 2 T i T j and recursively merge the particles with the smallest distance 6

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions What are jets? Pythia 8, FastJet √ s = 13 TeV R = 0 . 4 • Pioneering work Sterman, Weinberg `77 p jet T > 20 GeV • Jet algorithm, e.g. anti-k T Cacciari, Salam, Soyez `08 Define a distance between all particles ( η i − η j ) 2 + ( φ i − φ j ) 2 ! 1 , 1 d ij = min p 2 p 2 R 2 T i T j and recursively merge the particles R with the smallest distance is the radius of the jet R 7

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Quantum chromodynamics • Theory of the strong interaction between quarks and gluons • The Lagrangian µ − 1 ψγ µ T a ψ A a L = ¯ ψ ( i ∂ µ γ µ − m ) ψ + g s ¯ 4 F µ ν a F a µ ν • The coupling constant α s = g 2 s 4 π Confinement Asymptotic freedom 8

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions QCD factorization Collins, Soper, Sterman `80s -`90s • Hadron production pp → h + X D h f a/p Perturbatively calculable c d σ pp → hX H c = f a/p ⊗ f b/p ⊗ H c ab ⊗ D h ab c d η dp T X f a/p Parton distribution functions Fragmentation functions Non-perturbative but universal Scale dependence governed by DGLAP e.g. µ d dµD h X P ji ⊗ D h i = j j 9

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions QCD factorization Collins, Soper, Sterman `80s -`90s • Hadron production pp → h + X D h f a/p Perturbatively calculable c d σ pp → hX H c = f a/p ⊗ f b/p ⊗ H c ab ⊗ D h ab c d η dp T X f a/p Parton distribution functions Fragmentation functions Non-perturbative but universal • Jet production pp → jet + X R d σ pp → jet X f a/p = f a/p ⊗ f b/p ⊗ H ab d η dp T H ab Jet algorithm and X radius dependent f a/p NLO A ln R + B + O ( R 2 /R 2 0 ) 10

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Why do we care about jets? • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT 11

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Why do we care about jets? • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT • Constrain non-perturbative quantities e.g. parton distribution functions Impact of LHC jet data: for g ( x ) x → 1 pp → jet X percentage difference wrt. baseline fit without jets Harland-Lang, Martin, Thorne `17 12

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Why do we care about jets? • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT • Constrain non-perturbative quantities e.g. parton distribution functions • Precision test of the standard model, e.g. measure properties of the Higgs 2% e, µ, γ e.g. H → b ¯ b boost 98% jets Higgs decay channels Jet mass distribution 13

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Why do we care about jets? • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT • Constrain non-perturbative quantities e.g. parton distribution functions • Precision test of the standard model, e.g. measure properties of the Higgs • Search for physics beyond the standard model e.g. boosted hadronically decaying Z 0 2% e, µ, γ e.g. H → b ¯ b boost 98% jets Higgs decay channels Jet mass distribution 14

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Why do we care about jets? • Jets are inherently interesting. They are emergent phenomena and can teach us about QFT • Constrain non-perturbative quantities e.g. parton distribution functions • Precision test of the standard model, e.g. measure properties of the Higgs • Search for physics beyond the standard model e.g. boosted hadronically decaying Z 0 • Probe of the quark-gluon plasma in heavy-ion collisions 15

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Can we use jets as precision probes? pp → jet + X • Can theory predictions match the experimental precision? • Can we understand jet substructure from first principles in QCD? ATLAS, CERN-EP-2017-157 16

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions Outline • Motivation • A new factorization theorem for jets • A look inside: Jet substructure • Jet mass • Outlook and conclusions 17

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − Outline • Motivation • A new factorization theorem for jets • A look inside: Jet substructure • Jet mass • Outlook and conclusions 18

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − Jet production at the LHC CMS Phys.Rev. C96 015202 (2017) 19

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − Jet production at the LHC R = 0 . 4 R = 0 . 2 R = 0 . 3 p T CMS Phys.Rev. C96 015202 (2017) NLO 1990 Ellis, Kunszt, Soper `90 20

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − Jet production at the LHC R = 0 . 4 R = 0 . 2 R = 0 . 3 p T CMS Phys.Rev. C96 015202 (2017) NLO 1990 NNLO 2016 … Ellis, Kunszt, Soper `90 Currie, Glover, Pires `16 21

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − Jet production at NNLOl µ = p max µ = p T T ATLAS-CONF-2017-048 22

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − A new factorization theorem for jets p T vs. Λ QCD Factorization Evolution d σ pp → hX µ d Hadron X X dµD h P ji ⊗ D h f a ⊗ f b ⊗ H c ab ⊗ D h i = = j c dp T d η j a,b,c Kang, FR, Vitev `16 23

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − A new factorization theorem for jets p T vs. Λ QCD p T vs. p T R Factorization Evolution d σ pp → hX µ d Hadron X X dµD h P ji ⊗ D h f a ⊗ f b ⊗ H c ab ⊗ D h i = = j c dp T d η j a,b,c d σ pp → jet X Jet X f a ⊗ f b ⊗ H c + O ( R 2 /R 2 0 ) ab ⊗ J c = dp T d η a,b,c Kang, FR, Vitev `16 24

Motivation A New Factorization for Jets Jet Substructure Jet Mass Conclusions e + e − A new factorization theorem for jets p T vs. Λ QCD p T vs. p T R Factorization Evolution d σ pp → hX µ d Hadron X X dµD h P ji ⊗ D h f a ⊗ f b ⊗ H c ab ⊗ D h i = = j c dp T d η j a,b,c d σ pp → jet X µ d Jet X X f a ⊗ f b ⊗ H c + O ( R 2 /R 2 0 ) dµJ i = P ji ⊗ J j ab ⊗ J c = dp T d η j a,b,c Kang, FR, Vitev `16 25