How and Why to go Beyond the Discovery of the Higgs Boson

Transcription

1 How and Wy to go Beyond te Discovery of te Higgs Boson Jon Alison University of Cicago ttp://ep.ucicago.edu/~jonda/comptonlectures.tml

2 Lecture Outline April 1st: Newton s dream & 20t Century Revolution April 8t: Mission Barely Possible: QM + SR April 15t: Te Standard Model April 22nd: Importance of te Higgs April 29t: Guest Lecture May 6t: Te Cannon and te Camera May 13t: Te Discovery of te Higgs Boson May 20t: Problems wit te Standard Model May 27t: Memorial Day: No Lecture June 3rd: Going beyond te Higgs: Wat comes next? 2

3 Reminder: Last Week Quantum Mecanics + Space-time leads us to expect: Planck scale ~ weak scale ~ Hubble scale We observe: Planck scale weak scale Hubble scale Current teory accounts for uge difference w/implausible cancellation Need modifications QM or Space-time to avoid fine tuning 3

4 Reminder: Last Week Quantum Mecanics + Space-time leads us to expect: Problems associated to eac fundamental scale. Planck Scale: Planck scale ~ weak scale ~ Hubble scale Wat replaces spacetime? ( Quantum Gravity ) Weak Scale: We observe: Wy is Gravity so weak? ( Hierarcy Problem ) Hubble Scale: Wy is te universe so big? ( Cosmological Constant Problem ) Planck scale weak scale Hubble scale Current teory accounts for uge difference w/implausible cancellation Need modifications QM or Space-time to avoid fine tuning 4

5 Today s Lecture Going beyond te Higgs Discovery: Wat comes next? 5

6 Focus: Problem associated w/weak scale (In principle) Failure WW scattering ~unexplored LHC Standard Model (After Higgs Discovery) Standard Model (Before Higgs Discovery) Directly Probed Experimentally GeV 1 (10 36 m) 10 3 GeV 1 (10 19 m) GeV 1 (10 25 m) Planck ( p scale G N ) weak scale observable universe Most tractable now: - Currently directly probing tis scale wit te LHC - Understand te pysics at tis scale incredibly well Working teory tats been verified experimentally observable universe 6

7 Focus: Problem associated w/weak scale (In principle) Reminder: Vacuum Standard fluctuations Model (After of Higgs mass Discovery) (mh²) Failure WW scattering ~unexplored GeV 1 (10 36 m) Planck ( p scale G N ) Top LHC 10 3 GeV 1 (10 19 m) Standard Model (Before Higgs Discovery) Directly Probed Experimentally ~ Λ² mh GeV 2 Very different mh² type = problem tan we discussed 554 `Pl before: weak scale Naturalness Problem: + 30 digits - Teory is fully logically consistent 2 Most - Need tractable bizarre now: (un-natural) coice 453 of input parameters `Pl - Currently directly probing 30 digits tis scale wit te LHC Un-like - Understand situation te before pysics Higgs at were tis scale teory incredibly broke down well P(ωω ωω) Working > teory 1 / Inconsistent tats been mass verified description experimentally GeV 1 (10 25 m) observable universe observable universe 7

8 Wat scale do we need Modification? mh² = + ~ (weak-scale)² mh²classical ~ Λ² Can avoid need for fine tuning only if Λ ~ weak-scale. Need canges to stop vacuum fluctuations below: 10 3 GeV 1 (10 19 m) new particle X mx ~ 1000 GeV (Pencil metapor: analogous to te pencil glue/string) 8

9 Naturalness Problems in History Same type of problems ave occurred before in istory of pysics Same types of arguments for scale of new pysics worked Example: Energy stored in te electric field around electron electric field r E r Naively seems infinite e Energy of electron at rest: ~ me Introduce cut off Need Λ α/e to avoid fine tuning 9

10 Naturalness Problems in History Same type of problems ave occurred before in istory of pysics Same types of arguments for scale of new pysics worked Example: Energy stored in te electric field around electron Naturalness requires new pysics kick in Λ α/me Picture of point like electron must break down at tis scale e Exactly wat appens! e e + At scale Λ~1/me start seeing particle-anti-particle cloud Solution was Anti-particles : - Direct result of extension of Space-time (adding QM) - Doubled te number of particles in te teory 10

11 Potential Solutions vacuum fluctuations vs Planck scale ~ weak scale Planck scale weak scale Compositeness Higgs made of smaller particles Weak scale not fundamental / Similar to size of te proton New underlying pysics responsible for Higgs/Higgs potential New forces / New matter Extra dimensions Planck scale is really at te weak scale Gravity appears weak b/c gravitons can propagate in extra dim. Go troug example of ow works in detail Supersymmetry Has been a favorite witin te field Vacuum corrections suppressed below weak scale 11

12 Modification of Space-time Distance measured in quantum numbers: x y = - y x x² = 0 Can only take one step Super Symmetry Extra Quantum Dimension Doubles number of particles: - Standard Model particles - Super-partners w/step in extra dimension Super electron Our familiar 4D Space-time electron Measured in normal numbers x y = y x All regular rules of QFT apply / Symmetry relating particles/super particles 12

13 Modification of Space-time Distance measured in quantum numbers: x y = - y x x² = 0 Can only take one step Super Symmetry Extra Quantum Dimension Super electron Our familiar 4D Space-time electron - Havent seen super-partners Doubles - Could number anoter of example particles: of long-distance illusion: - Standard eg: difference Model particles between forces - Idea: Super-partners going to w/step sort in enoug extra dimension distances start seeing symmetry - To avoid fine-tuning needs to appen around weak scale Measured in normal numbers x y = y x All regular rules of QFT apply / Symmetry relating particles/super particles 13

14 How Does Tis Help? ~(weak-scale)² ~(weak-scale)² SM particle mh² = mh²classical Super-particle 14

15 Super Symmetry at te LHC Super-top Quantum Dimension stop - mχ0 proton proton Super-top ttbar + MeT searc t p 210 m~ t [GeV] 1 t 95% CL t p t Super-poton p - Massive t p t b b f W - Stable - Weakly interacting W f f 00 Perfect candidate for Dark Matter f

16 e Interaction Strengts e q e α = 1/137 γ e αweak = 1/50 Z q αstrong = 1/10 gluon Did not ave to appen! - Not put in by and - Could be coincidence - Seems like strong sign we are te rigt track 16

17 Searcing For Solutions at te LHC 17

18 Higgs as Window to New Pysics Go troug examples of eac of tese Higgs boson directly related to all potential solutions Problem fundamentally related to Higgs field Higgs Boson is te arbinger of te Higgs field (ow we study it) Compositeness: - Deeper origin for sape of potential (probe experimentally wit events) Potential Energy of Higgs Field Extra Dimensions: Excited Graviton SuperSymmetry: new particle(s) 3

19 Enanced Higgs Production Signal: Graviton (mg) b b b b Event Selection: Reconstructed te event from te observed b-jets - Work backward from 4b 2 G - Study te reconstructed graviton mass 19

20 Signal: 0 ncertainty Events/10 GeV Graviton (mg) Data/Bkgd Enanced Higgs Production ATLAS 10 Data -1 s = 13 TeV, 2016, 10.1 fb Multijet tt Signal Region: Resolved G(300) 10 b b b b Preliminary Event Selection: G(800) 10 SM 500 Stat+Syst Uncertainty Reconstructed 1 te event from te observed b-jets - Work backward from 4b 2 G 0 - Study te reconstructed graviton mass m 4j [GeV] 20

21 Modified Higgs Couplings Expect contributions from new pysics to correct iggs mass: If new pysics interacts wit te electro-magnetic: γ new pysics strong force: g Modifies rate a wic iggs bosons decay to potons. γ Modifies rate a wic iggs bosons are produced at LHC g 21

22 Modified Higgs Couplings Expect contributions from new pysics to correct iggs mass: Wy detailed Higgs measurements are so important: If new pysics interacts wit te electro-magnetic: g H g κg t H γ W κγ Modifies rate a wic iggs γ bosons decay to potons. κ g γ γ 1 ATLAS and CMS LHC Run 1 new pysics or strong force: ATLAS+CMS ATLAS CMS 68% CL 95% CL Best fit SM expected Modifies rate a wic iggs bosons are produced at LHC g κ γ g 22

23 Modified Higgs Couplings Expect contributions from new pysics to correct iggs mass: new pysics by construction, cannot avoid: Higgs interaction: One of te reasons Di-Higgs is a so important Modifies Di-Higgs production 23

24 Measuring Higgs Potential Energy of Higgs field: Higgs potential V ( )= µ Expanding about minimum: V ( )! V (v + ) V = V 0 + v v V = V m2 2 + m2 2v 2 v m 2 2v 2 4 µ p v ~ weak scale Higgs mass term λ -production λ4 -production - Sape of potential gives relationsip between λ and m, v - Measuring λ important probes te sape of te Higgs potential - production interesting because it measures λ Standard Model: = m2 2v 2 24

25 Measuring Higgs Potential ATLAS Preliminary Teory 500 µb 1 80 µb Need muc more data tan we currently ave to see 1 σ [pb] Standard Model Total Production Cross Section Measurements Status: August 2016 Energy 10of 6 Higgs field: Higgs potential 81 pb 10 V ( 5 )= 1 µ pb 1 81 pb Expanding about minimum: V ( )! V (v + ) 10 3 top quarks: ~10 events/s V = V 0 + v v V = V m2 2 + m2 2v v Higgs mass term pb 1 ~1000 λ Run 1,2 -production s =7,8,13TeV W bosons: 4 khz 1 event/s m 2 SM production total 2v 2 4 λ4 -production - Sape of potential pp gives relationsip between λ and m, v ~40 fb W Z t t t WW H Wt WZ~4/our ZZ t ~ (1e-3 t-can - Measuring λ important probes te sape of te Higgs potential t tw t tz Hz) s-can SM -production - production interesting because it measures λ VBF VH t th 2.0 fb 1 LHC pp s =7TeV µ p Data fb 1 LHC pp s =8TeV Data 20.3 fb 1 LHC pp s =13TeV v ~ weak scale Data fb 1 Standard Model: = m2 2v 2 25

26 Outlook for te Future Wat we migt know by

27 Future LHC Program Now Run I Run II Run III Run IV - 8 TeV - 20/fb - Get to 300/fb of TeV data - Up to 75 interactions per crossing /fb of TeV data - Pile-up of up to increase in size of dataset 150 increase in dataset size 27

28 Future LHC Program 25 Interactions Now Run I Run II Run III Run IV - 8 TeV - 20/fb - Get to 300/fb of TeV data - Up to 75 interactions per crossing /fb of TeV data - Pile-up of up to increase in size of dataset 150 increase in dataset size 28

29 Draft version 1.0 Future LHC Program ATLAS NOTE Future: 200 Interactions! 25 Interactions February 26, 2013 Now Study of te spin of te Higgs-like particle in te H! WW ( )! e µ cannel wit 20.7 fb 1 of s = TeV data collected wit te ATLAS detector Te ATLAS Collaboration Run II Future LHC Simulation Run I Abstract Recently, te ATLAS collaboration reported te observation of a new neutral particle in te searc for te Standard Model Higgs boson. Te measured production rate of te new particle is consistent wit te Standard Model Higgs boson wit a mass of about 125 GeV, but its oter pysics properties are unknown. Presently, te only constraint on te spin of tis particle stems from te observed decay mode to two potons, wic disfavours a spin-1 ypotesis. Tis note reports on te compatibility of te observed excess in te H WW ( ) e µ searc arising from eiter a spin-0 or a spin-2 particle wit positive carge-parity. Data collected in 2012 wit te ATLAS detector favours a spin-0 signal, and results in te exclusion of a spin-2 signal at 95% confidence level if one assumes a qq X production fraction larger tan 25% for a spin-2 particle, and at 91% confidence level if one assumes pure gg production. - 8 TeV - 20/fb Run III - Get to 300/fb of TeV data - Up to 75 interactions per crossing 30 increase in size of dataset Run IV /fb of TeV data - Pile-up of up to increase in dataset size c Copyrigt 2013 CERN for te benefit of te ATLAS Collaboration. Reproduction of tis article or parts of it is allowed as specified in te CC-BY-3.0 license. 29

30 Higgs at te LHC Uncertainty(%) on µ (Br) Run I: ~30/fb / 7-8 TeV Run II-II: ~300/fb / TeV Run IV: ~3000/fb / TeV Br(Inv) γγ WW ZZ ττ bb µ µ Zγ 30

31 Bencmark Coupling Constraints Sensitivity tested in model wit 7 parameters g t κg H κγ H W γ H Z W/Z κz H W W/Z κw g γ 4 fermion couplings: κτ / κµ / κu κt = κc / κd κb Z W/Z W W/Z Allow for decays to new particles 31

32 Higgs at te LHC Uncertainty(%) Text Text Br(Inv) Run II-III: ~300/fb / TeV Run IV: ~3000/fb / TeV κγ κg κ W Coupling modifications in Generic BSM models (M ~ 1 TeV / Satisfies EWK precision fits) κz κl κd apple V apple b apple Singlet Mixing 6% 6% 6% 2HDM 1% 10% 1% Decoupling MSSM % 1.6% < 1.5% Composite 3% (3 9)% 9% Top Partner 2% 2% 3% κ u κµ For 10% deviation 2σ CL 5σ CL 32

33 mstop - mχ0 Direct searc for Super Symmetry ttbar + MeT searc Super-Poton Mass [GeV] t p 210 m~ t [GeV] 1 t imits at 95% CL t p p p t t b W W f f f 00 t b f 000 (b) (c) p p t t ±1 1 b W p p b b 01 ±1 1 t W Super-Top Mass [GeV] 01 33

34 Beyond te LHC Wat we migt know by

35 ~100 km tunnel / Operate in two modes 1st-stage: collide electrons: ee Z 2nd-stage: 100 TeV proton collider 35

36 Similar idea being pursued in Cina ~100 km tunnel / Operate in two modes Would 1st-stage: Also collide operate electrons: in two modes ee Z 2nd-stage: 1st-stage: 100 collide TeV electrons: proton collider ee Z 2nd-stage: 50 TeV proton collider Could be faster time scale if approved 36

37 Beyond te LHC Uncertainty(%) Br(Inv) κγ κg κ W Coupling modifications in Generic BSM models (M ~ 1 TeV / Satisfies EWK precision fits) Run II-II: ~300/fb / TeV Run IV: ~3000/fb / TeV Higgs factory κz κl κd apple V apple b apple Singlet Mixing 6% 6% 6% 2HDM 1% 10% 1% Decoupling MSSM % 1.6% < 1.5% Composite 3% (3 9)% 9% Top Partner 2% 2% 3% κ u κµ For 10% deviation 2σ CL 5σ CL 37

38 100 TeV proton collider Measure Higgs self-coupling to ~10%? 38

39 V ()! ( ) log. (7) reac! S! HH in tese modes is sown in Fig. sould 9. 2 ing or for jet pp substructure tecniques. Additional refinements incr ure of te mixing between te singlet S and te Higgs boson. possibilities are associated wit totally di erent underlying vity,tese at te price of making assumptions on te future detectordynamdesign v)/m (mh /ms symmetry ), so tis mixing is expected to be sizable. S ics for electroweak breaking tan te SM, requiring new pysics m2 100 TeV proton collider Nature of EW pase transition beyond te Higgs around te weak scale. Tey also ave radically di er- s Exclusion ent teoretical implications for naturalness, tecl ierarcy problem and te contours 10000of te two di erent searc strat Boosted Top structure of quantum field teory. s = 100 TeV 1 10 c = 1/3 10 σ [pb] c=1 c = 1/10 1 ave -1? It is possible to exclude neutrali 8 TeV, 20 fb sys,bkg = 20% 10 b neutralino limit. A 1.5 TeV stop could 14 TeV, 300 fb TeV, 3000 fb-1 space. space ste = 100searces TeV -1 Compressed proposed ere also L dt = 3000 fb sys,sig = 20% gg S m 0 (GeV) All of te results presented ere ave 10 not rely on b-tagging or jet substructure te searc sensitivity, at te price 10000of ma LHC m~ (GeV) 18: Question 2 3 te nature 4 5of te 6 Figure of Consider a model Higgs + electroweak singlett pase transition. Mx [TeV] Simplest, but also ardest to discover. 1 39

40 Have only collected ~1% of total LHC dataset Next 5-10 years incredibly unique/interesting time! Bigger rings currently being planned Tank You Jon Alison / STFC Interview