A New Angle on Jet Substructure

Transcription

1 A New Angle on Jet Substructure Jesse Thaler Kavli IPMU January 13, 2017 Jesse Thaler A New Angle on Jet Substructure 1

2 Jet Substructure Boosting the Search for New Phenomena [Thursday & Today] = = = = =- Pushing the Boundaries of Quantum Field Theory [Next Monday & Tuesday] Jesse Thaler A New Angle on Jet Substructure 2

3 Last Time t 70% 173 GeV++ H 60% 125 GeV micro-jet 65% W/Z 70% b 80/91 GeV 4.2 GeV++ Jets from the c 1.3 GeV++ Standard Model u,d,s 100 MeV++ ++ = plus gluonic radiation g 0++ Jesse Thaler A New Angle on Jet Substructure 3

4 Last Time t 70% 173 GeV++ Substructure Toolbox: Jet Grooming H 60% W/Z 70% 125 GeV 80/91 GeV micro-jet 65% b 4.2 GeV++ Jet Discrimination c 1.3 GeV++ Jets from the vs. Standard Model u,d,s 100 MeV++ g 0++ Jesse Thaler A New Angle on Jet Substructure 4

5 W/Z Tagging in 2016 Soft Drop [Larkoski, Marzani, Soyez, JDT, 2014; see also Dasgupta, Fregoso, Marzani, Salam, 2013] Trimming [Krohn, JDT, Wang, 2009] vs. N-subjettiness before grooming, after decorrelation [JDT, Van Tilburg, 2010, 2011; Dolen, Harris, Marzani, Rappoccio, Tran, 2016] D2 after grooming [Larkoski, Moult, Neill, 2014; based on Larkoski, Salam, JDT, 2013] Jesse Thaler A New Angle on Jet Substructure 5

6 W/Z Tagging in 2016 Can we understand these choices from first principles QCD? Can we construct improved vs. algorithms for 2017? Soft Drop [Larkoski, Marzani, Soyez, JDT, 2014; see also Dasgupta, Fregoso, Marzani, Salam, 2013] N-subjettiness before grooming, after decorrelation [JDT, Van Tilburg, 2010, 2011; Dolen, Harris, Marzani, Rappoccio, Tran, 2016] Trimming [Krohn, JDT, Wang, 2009] D2 after grooming [Larkoski, Moult, Neill, 2014; based on Larkoski, Salam, JDT, 2013] Jesse Thaler A New Angle on Jet Substructure 6

7 W/Z Tagging in 2016 Can we understand these choices from first principles QCD? Can we construct improved vs. algorithms for 2017? Soft Drop Yes! Key realization: Discrimination different before/after grooming [Larkoski, Marzani, Soyez, JDT, 2014; see also Dasgupta, Fregoso, Marzani, Salam, 2013] N-subjettiness Yes! Systematic basis for jet substructure observables before grooming, after decorrelation [JDT, Van Tilburg, 2010, 2011; Dolen, Harris, Marzani, Rappoccio, Tran, 2016] Trimming [Krohn, JDT, Wang, 2009] D2 after grooming [Larkoski, Moult, Neill, 2014; based on Larkoski, Salam, JDT, 2013] Jesse Thaler A New Angle on Jet Substructure 6

8 Punchline: W/Z Tagging in 2017? Soft Collinear z s C-Soft ) ) ) θ cc θ 12 z cs θ cc Ê 1 Ê 2 Probability Density Stable & Performant N 2 (2) Pythia R=1.0,p T >500GeV,m[80,100]GeV Z Light Quark Gluon Ê N 2 = N2 [Moult, Necib, JDT, 2016] X i<j<k Z-like q/g-like p Ti p Tj p Tk min n(r ij R jk ) 2,(R jk R ki ) 2,(R ki R ij ) 2o, X 2 X p Ti p Tj Rij 2 i<j i p Ti Jesse Thaler A New Angle on Jet Substructure 7

9 Grooming From First Principles [More details on Monday] Jesse Thaler A New Angle on Jet Substructure 8

10 Trimming from First Principles? extensively used by ATLAS [Krohn, JDT, Wang, ; diagram from ATLAS, ] Trimmed Jet Mass: 3 TeV quark jets q ρ/σ dσ / dρ Pythia 6 Simulation Trimming R sub = 0.3, z cut = 0.05 R sub = 0.3, z cut = ρ = m 2 /(p t 2 R 2 ) [Dasgupta, Fregoso, Marzani, Salam, ] Jesse Thaler A New Angle on Jet Substructure 9

11 Trimming from First Principles? extensively used by ATLAS [Krohn, JDT, Wang, ; diagram from ATLAS, ] Trimmed Jet Mass: 3 TeV quark jets q ρ/σ dσ / dρ Pythia 6 Simulation Trimming R sub = 0.3, z cut = 0.05 R sub = 0.3, z cut = 0.1 First-principles QCD (MLL) Trimming R sub =0.3, z cut =0.05 R sub =0.3, z cut = Analytically understand Sudakov peak, kink, and plateau ρ = m 2 /(p t 2 R 2 ) ρ = m 2 /(p t 2 R 2 ) [Dasgupta, Fregoso, Marzani, Salam, ] Jesse Thaler A New Angle on Jet Substructure 9

12 Soft Drop Declustering Original Jet [Larkoski, Marzani, Soyez, JDT, 2014; see also Butterworth, Davison, Rubin, Salam, 2008; Dasgupta, Fregoso, Marzani, Salam/Powling, 2013] Jesse Thaler A New Angle on Jet Substructure 10

13 Soft Drop Declustering Original Jet Clustering Tree = [Larkoski, Marzani, Soyez, JDT, 2014; see also Butterworth, Davison, Rubin, Salam, 2008; Dasgupta, Fregoso, Marzani, Salam/Powling, 2013] Jesse Thaler A New Angle on Jet Substructure 10

14 Soft Drop Declustering Groomed Jet Groomed Clustering Tree = [Larkoski, Marzani, Soyez, JDT, 2014; see also Butterworth, Davison, Rubin, Salam, 2008; Dasgupta, Fregoso, Marzani, Salam/Powling, 2013] Jesse Thaler A New Angle on Jet Substructure 11

15 Soft Drop Declustering Groomed Jet Groomed Clustering Tree = zg 1 zg θg zg > zcut θg β [We ll study zg next Tuesday] [Larkoski, Marzani, Soyez, JDT, 2014; see also Butterworth, Davison, Rubin, Salam, 2008; Dasgupta, Fregoso, Marzani, Salam/Powling, 2013] Jesse Thaler A New Angle on Jet Substructure 11

16 Soft Drop Declustering Groomed Jet Groomed Clustering Tree = zg 1 zg θg zg > zcut θg β [We ll study zg next Tuesday] More Grooming β β < 0 β = 0 β > 0 Less Grooming β Jesse Thaler A New Angle on Jet Substructure 11

17 Calculating Groomed Mass? mg Simulated LHC Data R=1, p t >3 TeV z cut =0.1 Pythia8, parton plain jet β=2 β=1 β=0 β= C 1 (2) mg 2 /pt 2 More Grooming Less Grooming β β < 0 β = 0 β > 0 β [Larkoski, Marzani, Soyez, JDT, 2014] Jesse Thaler A New Angle on Jet Substructure 12

18 Calculating Groomed Mass? mg Simulated LHC Data R=1, p t >3 TeV z cut =0.1 Pythia8, parton plain jet β=2 β=1 β=0 β=-0.5 First-principles QCD (MLL) R=1, p t >3 TeV z cut =0.1 plain jet β=2 β=1 β=0 β=-0.5 Analytic solid: mult. em. Sudakov factor Kink from zcut C 1 (2) mg 2 /pt C 1 (2) mg 2 /pt 2 More Grooming Less Grooming β β < 0 β = 0 β > 0 β [Larkoski, Marzani, Soyez, JDT, 2014] Jesse Thaler A New Angle on Jet Substructure 12

19 vs. Events / 4 GeV Soft Drop 600 Data Top (W j) Top (q j) Top (g j) Other bkgs fb (8 TeV) CMS Preliminary Normalised Entries ATLAS Simulation s=8 TeV Truth η < < p Truth T < 350 GeV anti-k t R=1.0 jets Trimmed (f =5%,R =0.2) cut sub Trimming W-jets (in W WZ) Multijets (leading jet) Gaussian fit to signal 1σ Fit Window G G W = 0.59 QCD = % Window G G = 0.65 = 0.1 W QCD 0.06 Pull β=0 [GeV] M SD [CMS, JME ] [ATLAS, ] M [GeV] Both grooming strategies give good signal isolation Jesse Thaler A New Angle on Jet Substructure 13

20 Scorecard 0.3 quark jets (Pythia 6 MC) m [GeV], for p t = 3 TeV, R= Soft Drop Trimming * ρ/σ dσ / dρ Trimmer (z cut =0.1, R sub =0.2) Pruner (z cut =0.1) mmdt (y cut =0.11, µ=0.67) mmdt (z cut =0.1, µ=0.67) * Soft drop with β = 0 = mmdt with μ = 1 Both have primary kink at ρ = m /(p t R ) [Dasgupta, Fregoso, Marzani, Salam, ] * Trimming has secondary kink at (Pruning also has similar behavior) Jesse Thaler A New Angle on Jet Substructure 14

21 Axes or Axes-Free? Jesse Thaler A New Angle on Jet Substructure 15

22 Discrimination with Axes Dimensionless kinematics: N-subjettiness = Requires a definition of subjet axes (i.e. minimizing over all axes possibilities) [JDT, Van Tilburg, , ; see also Kim, ] [related work in Stewart, Tackmann, Waalewijn, ] Jesse Thaler A New Angle on Jet Substructure 16

23 Discrimination without Axes Dimensionless kinematics: Energy Correlation Functions = 3 Axes-free probe for substructure; not immediately obvious how it works [Larkoski, Salam, JDT, ; Larkoski, Moult, Neill, , ; see also Banfi, Salam, Zanderighi, hep-ph/ ; Jankowiak, Larkoski, ] Jesse Thaler A New Angle on Jet Substructure 17

24 vs. Events / 0.05 Data MC N-subjettiness CMS Preliminary CMS Data G Bulk G Bulk (2 TeV) WW (MADGRAPH) (2 TeV) ZZ(MADGRAPH) W' (2 TeV) WZ (MADGRAPH) QCD PYTHIA8 65 GeV < M P < 105 GeV fb (13 TeV) τ 21 Normalised Entries 0.22 ATLAS Simulation 0.2 s=8 TeV η Truth <1.2 Truth 350 < p M Cut T < 500 GeV anti-k R=1.0 jets t Trimmed (f =5%,R =0.2) cut sub [CMS, JME ] [ATLAS, ] Energy Correlator: D2 W-jets (in W WZ) Multijets (leading jet) G & T W = 50% (β=1) D 2 Can we understand this behavior from first principles? Jesse Thaler A New Angle on Jet Substructure 18

25 N-subjettiness Behavior τ2 τ1 1.0 q/g Bkgd W/Z Signal Parametric separation between 1 and 2 prong jets Jesse Thaler A New Angle on Jet Substructure 19

26 N-subjettiness Behavior with Grooming τ2 τ1 1.0 q/g Bkgd W/Z Signal Parametric separation between 1 and 2 prong jets even after removing soft peripheral radiation Jesse Thaler A New Angle on Jet Substructure 20

27 Scorecard Soft Drop Trimming * N-subjettiness before grooming D2 after grooming * (also works after grooming) Not just good discrimination, but stability to choice of cuts Jesse Thaler A New Angle on Jet Substructure 21

28 The Power of Power Counting Jesse Thaler A New Angle on Jet Substructure 22

29 Textbook QCD x z 1 z θ 2 2 n 2 n 1 Splitting Function 1 2 At leading log order: Cq = 4/3 Cg = 3 See end of talk for quark/gluon tagging dp i ig ' 2α s π C i dθ θ Collinear singularity dz z Soft singularity Jesse Thaler A New Angle on Jet Substructure 23

30 Power Counting Modes 1-prong background (quark or gluon) 2-prong signal (W or Z) Soft Collinear z s Soft Collinear z s C-Soft } } θ cc } θ cc θ 12 z cs } θ cc C S C CS S energies 1 z s 1 z cs z s SX CC SX CC C1C2 or CCS angles 1 1 Jesse Thaler A New Angle on Jet Substructure 24

31 Power Counting D2: Background = 3 Setting β = 1 Soft Collinear z s CCC CCS CSS } θ cc CC CS Jesse Thaler A New Angle on Jet Substructure 25

32 Power Counting D2: Background = 3 Setting β = 1 Soft Collinear z s CCC CCS CSS } θ cc CC CS if soft dominates Jesse Thaler A New Angle on Jet Substructure 25

33 Power Counting D2: Background Without grooming, D2 unstable to mass cut (hard to do sideband analysis) = 3 Soft Collinear Setting β = 1 z s Probability Density } θ cc D 2 (2) forlightquarks Pythia R=1.0,p T >500GeV for β = 1 m [40,60]GeV m [60,80]GeV CCC m [80,100]GeV CCS CSS m [100,120]GeV D 2 (2) CC CS if soft dominates Jesse Thaler A New Angle on Jet Substructure 26

34 Background after Grooming Collinear CCC ) θ cc = 3 CC Probability Density GroomedD 2 (2) forlightquarks Pythia8.219,SoftDrop: =0,z cut =0.1 R=1.0,p T >500GeV m SD [40,60]GeV m SD [60,80]GeV m SD [80,100]GeV m SD [100,120]GeV D 2 (2) After grooming, D2 background distribution is parametrically stable Jesse Thaler A New Angle on Jet Substructure 27

35 Signal/Background Separation Collinear CCC ) θ cc = 3 CC Collinear C-Soft } } θ cc C1C2CS C1C2C θ 12 z cs } θ cc C1C2 Signal parametrically distinct Jesse Thaler A New Angle on Jet Substructure 28

36 Scorecard ATLAS R2D2 Tagger 1 / QCD G & T ATLAS s = 8 TeV anti-k t R=1.0 jets Trimmed (f =5%,R =0.2) cut sub < 1.2, 350 GeV < p < 500 GeV T Performance in W bosons from tt (POWHEG+Pythia) vs. inclusive multijets (Pythia) Monte Carlo Predicted wta 21 C (=1) 2 (=1) D 2 Soft Drop Trimming * Measured (Medium WP) 2 10 Stat. Syst. Uncertainty Measured (Tight WP) Stat. Syst. Uncertainty Better N-subjettiness before grooming D2 after grooming * [ATLAS, ] G & T W (also works after grooming) *unstable before grooming Theoretically sound W/Z tagging strategies for the LHC Jesse Thaler A New Angle on Jet Substructure 29

37 Systematic Catalog of Axes-Free Observables Jesse Thaler A New Angle on Jet Substructure 30

38 Punchline: W/Z Tagging in 2017? Soft Collinear z s C-Soft ) ) ) θ cc θ 12 z cs θ cc Ê 1 Ê 2 Probability Density Stable & Performant N 2 (2) Pythia R=1.0,p T >500GeV,m[80,100]GeV Z Light Quark Gluon Ê N 2 = N2 [Moult, Necib, JDT, 2016] X i<j<k Z-like q/g-like p Ti p Tj p Tk min n(r ij R jk ) 2,(R jk R ki ) 2,(R ki R ij ) 2o, X 2 X p Ti p Tj Rij 2 i<j i p Ti Jesse Thaler A New Angle on Jet Substructure 31

39 Back to Basics: What is a Measurement? Ê energy flowing to infinity Stress-Energy Flow Operator: Ê(θ,φ,v) lim t ˆn i T 0i (t,vtˆn) Also charge flow operators, but not IRC safe in a particular direction at a particular speed [Sveshnikov, Tkachov, hep-ph/ ; see also Mateu, Stewart, JDT, ] Jesse Thaler A New Angle on Jet Substructure 32

40 Back to Basics: What is a Measurement? Energy Correlators: Decomposition for any IRC safe observable All N-tuples N Energies Angular Weighting (symmetric, vanishes for θij 0) Completely general, but useful for jets? [Tkachov, hep-ph/ ] Jesse Thaler A New Angle on Jet Substructure 33

41 1-point Correlator The most basic jet observable: Using dimensionless quantities 1-point: Jesse Thaler A New Angle on Jet Substructure 34

42 2-point Correlators 2-point: Similar information to jet mass Soft Collinear z s soft dominated β = 2 thrust a.k.a. m 2 /pt 2 ) θ cc equal weight β = 1 width a.k.a. broadening, girth collinear dominated β = 0.5 Les Houches Angularity [see also Berger, Kucs, Sterman, hep-ph/ ; Ellis, Vermilion, Walsh, Hornig, Lee, ; Larkoski, Salam, JDT, ; Larkoski, Neill, JDT, ; Larkoski, JDT, Waalewijn, ; Soyez, JDT, Freytsis, Gras, Kar, Lönnblad, Plätzer, Siodmok, Skands, Soper, ] Jesse Thaler A New Angle on Jet Substructure 35

43 3-point Correlators 3-point: used for D2 Probe of hierarchical jet substructure [Moult, Necib, JDT, ] Jesse Thaler A New Angle on Jet Substructure 36

44 N-point Correlators 2e 4 Systematic jet dissection n = 2, 3, 4, v = 1, 2, 3,, n choose 2 β =, 0.5, 1, 2, collinear dominated soft dominated [Moult, Necib, JDT, ] Jesse Thaler A New Angle on Jet Substructure 37

45 New Discriminants Jesse Thaler A New Angle on Jet Substructure 38

46 New Boosted W/Z Discriminants Rule of thumb: boost invariance along jet axis (i.e. same angular scaling in numerator and denominator) Lesson: Signal robust to grooming, but background can change when soft modes removed [Moult, Necib, JDT, ] Jesse Thaler A New Angle on Jet Substructure 39

47 W/Z Tagging before Grooming () () - - (B overlaps S) Jesse Thaler A New Angle on Jet Substructure 40 () (B overlaps S)

48 W/Z Tagging after Grooming () () - - () Jesse Thaler A New Angle on Jet Substructure 41

49 Performance Follows Power Counting Better Before Grooming After Grooming Z vs. q Quark Mistag Zvs.LightQuark Pythia y=x D 2 (2) M 2 (2) N 2 (2) D 2 (1,2) R=1.0,p T >500GeV,m[80,100]GeV Quark Mistag y=x D 2 (2) M 2 (2) N 2 (2) D 2 (1,2) Z vs. Light Quark (Groomed) Pythia8.219, SoftDrop: =0,z cut =0.1 R=1.0,p T >500GeV,m SD [80,100]GeV Z Efficiency Z Efficiency Z vs. g Gluon Mistag y=x (2) D 2 (2) M 2 (2) N 2 (1,2) Zvs.Gluon D 2 Pythia 8.219, R=1.0, p T >500GeV,m[80,100]GeV Gluon Mistag y=x D 2 (2) M 2 (2) N 2 (2) D 2 (1,2) Z vs. Gluon (Groomed) Pythia8.219,SoftDrop: =0,z cut =0.1 R=1.0,p T >500GeV, m SD [80,100]GeV Z Efficiency Z Efficiency (Note, groomed mass gives x3-5 better background rejection by itself) Jesse Thaler A New Angle on Jet Substructure 42

50 Boosted Top Discrimination τ 3 ˆn 1 ˆn 2 Axes vs. axes-free? After grooming, identical power counting, similar performance 2e 4 b-quark Mistag Top vs. b-quark(groomed) Pythia8.219,SoftDrop: =0,z cut =0.1 R=1.0,p T >200GeV,m SD >80GeV (2) D 3 (1) 32 (2) N Top Efficiency [Moult, Necib, JDT, ] Jesse Thaler A New Angle on Jet Substructure 43

51 The Next Frontier Jesse Thaler A New Angle on Jet Substructure 44

52 Quark/Gluon Tagging for New Physics Signals quark-enriched Backgrounds gluon-enriched g g g g g g [] = - = ++ + Promising performance in SUSY searches % = = =% [] [Bhattacherjee, Mukhopadhyay, Nojiri, Sakakie, Webber, ] Jesse Thaler A New Angle on Jet Substructure 45

53 Quark/Gluon Tagging for New Physics Signals quark-enriched Backgrounds gluon-enriched g g g g g g [] = - = % = = =% [] ++ () ++ () () () () () Promising performance in SUSY searches but considerable theoretical uncertainties [Bhattacherjee, Mukhopadhyay, Nojiri, Sakakie, Webber, ] Jesse Thaler A New Angle on Jet Substructure 46

54 Key Task for Jet Substructure vs. e + e quarks (CF = 4/3) e + e gluons (CA = 3) Q = 200 GeV R = 0.6 Pythia Herwig Sherpa Vincia Deductor Ariadne5.0. Analytic NLL 5 4 Q = 200 GeV R = 0.6 Pythia Herwig Sherpa Vincia Deductor Ariadne5.0. Analytic NLL p q ( 1 0.5) 3 Q=200 GeV R=0.6 p g ( 1 0.5) 3 Q=200 GeV R= LHA = X i z i p θi LHA = X i z i p θi Well-constrained by LEP measurements Needs more input from experiment (and theory) [Soyez, JDT, Freytsis, Gras, Kar, Lönnblad, Plätzer, Siodmok, Skands, Soper, ] Jesse Thaler A New Angle on Jet Substructure 47

55 Higher-Point Quark/Gluon Discriminants (aka C1) Soft Collinear z s Soft Collinear z s Soft Collinear z s Probability Density U 2 (0.2) Pythia8.219,R=0.6,p T >500GeV Quark Gluon Gluon Rejection % Quark Efficiency Pythia8.219,R=0.6,p T >500GeV x 9/4 () U 1 Mult. U 2 () U 3 () Better U 2 (0.2) Jesse Thaler A New Angle on Jet Substructure 48 [Moult, Necib, JDT, ]

56 Jet Substructure Boosting the Search for New Phenomena [Thursday & Today] = = = = =- Pushing the Boundaries of Quantum Field Theory [Next Monday & Tuesday] Jesse Thaler A New Angle on Jet Substructure 49

57 Solar System Galaxy The Universe Matter/Anti-Matter? Three Generations? Neutrino Masses? Strong CP? Planet Us The TeV Scale Protons Electrons Molecules Cells Hairs Quantum Gravity Grand Unification m m 10 4 m m m Dark Matter? Dark Energy? The Standard Model? Origin of Mass? Higgs Boson! Grand Unification? Quantum Gravity? Inflation? Hierarchy Problem? Jesse Thaler A New Angle on Jet Substructure 50

58 Solar System Galaxy The Universe Matter/Anti-Matter? Three Generations? Neutrino Masses? Strong CP? Planet Us The TeV Scale Protons Electrons Molecules Cells Hairs Quantum Gravity Grand Unification m m 10 4 m m m Dark Energy? Inflation? Dark Matter? The Standard Model Fascinating Dynamics in QCD? Origin of Mass? Higgs Boson! Grand Unification? Hierarchy Problem? Quantum Gravity? Jesse Thaler A New Angle on Jet Substructure 50