Summary and Conclusions John Ellis King’s College London & CERN

Open Questions beyond the Standard Model What is the origin of particle masses? due to a Higgs boson? Why so many types of matter particles? What is the dark matter in the Universe? Unification of fundamental forces? Quantum theory of gravity? LHC

The basis for everything at the LHC Producing new particles –e.g., Higgs Possible signals –e.g., boosted jets Backgrounds –e.g., jets, pile-up Cosmic rays –forward production

Soft QCD Underlying event (M t, M W ): –Pile-up, colour reconnection, … Important for some BSM signatures: RPV, long-lived, … Interesting in own right: –Total σ, single, multiple rapidity gaps, Exclusive Higgs production: 420m, CPV? Near-side ridge: cf, heavy ions? Forward particles: cosmic rays

QCD Theory Lund string vs clusters: “no new ideas in 30 years” –Continuing work towards universal MC tunes Which experimental measurements would help make better event generators? From soft to hard: –Showers with Catani-Seymour dipoles –Matrix element-parton shower matching: differences for Higgs p T –Boosted jets

Hard QCD Many perturbative QCD calculations to NNLO Precision important for discovery & interpretation –New input from string methodology ✓ over many orders, to p T > 2 TeV Measurement of α s Unsung PDF heroes BUT: convergence for gg  H? –Better scheme than MSbar? ISR? e.g., for dark matter search

Hot and Dense Nuclear Matter Explore QCD thermodynamics: –QGP, CSB, deconfinement, … Signatures: –Particle abundances: few protons? –Strangeness enhancement –Direct photon production: T LHC = 1.37 T RHIC –J/Ψ, ϒ suppression, recombination –Elliptic flow v 2, etc.: small η –Jet quenching

Quark-Hadron Phase Diagram As energy density increases: –Nuclear liquid (A)  meson gas (B)  “perfect” liquid (C)  gas asymptotically at higher T? (D) A B C D B C D

Multiverse of Little Bangs Thermalization at speed of light Initial conditions, fluid properties Various v n : hydrodynamics AdS/CFT “bound”: η ≥ 1/4π –RHIC: η < (3 to 6)/4π –LHC: η < (2 to 3)/4π Jet quenching Dijet energy asymmetry Near-side ridge(s): collective effects in pp, p-Pb?

Electroweak Measurements Impressive progress at LHC M t comparable to TeVatron BUT: challenges for M W : –pile-up, low-x PDFs, material, … First measurement of sin 2 θ W = ± Single boson production cross section large?

Electroweak Measurements Diboson production  constraints on couplings –BUT: need more accurate diboson σ calculation Limited sensitivity to tribosons Parameterize vertices using L eff Run at low pile-up?

Electroweak Theory From LEP paradox to LHC paradox –Light Higgs + nothing else? –If something light, why no indirect evidence? If nothing light, is light Higgs unnatural? Electroweak and Higgs coupling measurements complement searches for New Physics

Top Physics Interesting, independently of electroweak theory Added interest in view of EW –Does top have partner: stop? T 5/3, … Why are t and H living dangerously? –Coincidence that (M h, M t ) close to stability boundary?

Top Measurements Many production LHC: –ttbar, single t, t + W/H, 4t? What do we know so far? –V tb ~ 1 –δM t ~ 0.5%, LHC to improve (but colour reconnection, etc.) –Spin measurements Puzzle of AFB: –Measure A l –A LHC

Flavour Physics CKM picture works very well Dominates over new physics – modes of CPV –In K 0, B 0, B ±, B s systems –D 0 ? New LHCb results  Also rare decays: B s  μ + μ - Any new physics at TeV scale must copy CKM –Minimal flavour violation

LHC Not just LHCb, also CMS & ATLAS B s  μ + μ - : important constraint on BSM –Need to push down to SM error –Measure B d  μ + μ - –Is B s  τ + τ - observable? B  K*μ + μ - : A FB zero crossing point ~ SM LHCb upgrade in 2018: –40 MHz, trigger in software –L = 2 × 10 33, 50/fb –Aim at φ s, D SM level, …

B Factories Measurements of sin 2β with error ~ LHCb/3 World leaders for α = , γ = 67 ± 11 B  Xγ and B  τν constrain NP Some puzzles: –B  D*τν 3σ from SM SuperKEKB: luminosity × 40 Complementarity to LHCb Some unique capabilities: –Decays to νν; c and τ decays

The (G)AEBGHKMP’tH Mechanism The only one who mentioned a massive scalar boson

But the Higgs Boson Englert & Brout Guralnik, Hagen & Kibble Higgs Also Goldstone in global case

A Phenomenological Profile of the Higgs Boson First attempt at systematic survey

Higgsdependence Day!

From Discovery to Measurement Mass measurements: ± 0.3 GeV Signal strengths ~ SM in many channels Frontiers: –VBF significance 2σ in several channels, 3σ combined –Decay to ττ emerging, limits on ττ (μτ, eτ) –Decay to bbbar emerging (CMS, Tevatron) –Indirect evidence for ttbar coupling (search for ttbar + H/W, Zγ)

Couples like Higgs of Standard Model No indication of any significant deviation from the Standard Model predictions JE & Tevong You, arXiv:

The Particle Higgsaw Puzzle Is LHC finding the missing piece? Is it the right shape? Is it the right size?

What is it? –Higgs or …? What else is there? –Supersymmetry …? What next? –A Higgs factory or …? Some Questions Supersymmetric model fits

What is it ? Does it have spin 0 or 2? Is it scalar or pseudoscalar? Is it elementary or composite? Does it couple to particle masses? Quantum (loop) corrections? What are its self-couplings?

Does the ‘Higgs’ have Spin Two ? Discriminate spin 2 vs spin 0 via angular distribution of decays into γγ JE & Hwang: arXiv: JE, Fok, Hwang, Sanz & You: arXiv: Monte Carlo simulations %

Pseudoscalar 0 - disfavoured at > 99% CL The ‘Higgs’ is probably a scalar

Global Analysis of Higgs-like Models Rescale couplings: to bosons by a, to fermions by c Standard Model: a = c = 1 JE & Tevong You, arXiv: b bbarτ γ W Z Global No evidence for deviation from SM

It Walks and Quacks like a Higgs Do couplings scale ~ mass? With scale = v? Red line = SM, dashed line = best fit JE & Tevong You, arXiv: Global fit

Loop Corrections ? ATLAS sees excess in γγ, CMS sees deficit Loop diagrams ~ Standard Model? JE & Tevong You, arXiv:

What is it ? Beyond any Reasonable Doubt Does it have spin 0 or 2? –Simple spin 2 couplings excluded Is it scalar or pseudoscalar? –Pseudoscalar strongly disfavoured Is it elementary or composite? –No significant deviations from Standard Model Does it couple to particle masses? –Prima facie evidence that it does Quantum (loop) corrections? –γγ coupling > Standard Model? What are its self-couplings? Hi-lumi LHC or …?

A or The? Others? –Upper limits on couplings of massive H’ –Extra singlet? 2HDM? Fermiophobic? MSSM? Non-SM decays? –Invisible decays? SM4? μμ? ττ? aa? H ±± ? VV scattering? –Closure test Another way? Other scenarios? –Precision of BSM predictions? Will the HL-LHC be enough?

Completing the Holy Trinity Hierarchy possible only in theory that can be calculated over many magnitudes of energy “Renormalizable” Theorem: (1) vectors (2) fermions (3) scalars Need to specify: (1) group (2) representations (3) symmetry breaking (1) = SU(3) × SU(2) × U(1) [so far] (2) = Singlets + doublets + triplets Finally: (3) A scalar and the mechanism of symmetry breaking Cornwall, Levin & Tiktopoulos; Bell; Llewellyn-Smith

Theoretical Constraints on Higgs Mass Large M h → large self-coupling → blow up at low-energy scale Λ due to renormalization Small: renormalization due to t quark drives quartic coupling < 0 at some scale Λ → vacuum unstable Vacuum could be stabilized by Supersymmetry Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:

Theoretical Confusion High mortality rate among theories (M H, M t ) close to stability bound Λ close to Weinberg upper bound Split SUSY? High-scale SUSY? Modify/abandon naturalness? Does Nature care? String landscape? SUSY anywhere better than nowhere SUSY could not explain the hierarchy New ideas needed!

To Sherlock Holmes: “Is there any other point to which you would wish to draw my attention?” Holmes: "To the curious incident of the dog in the night-time." To Holmes: "The dog did nothing in the night-time." Holmes: "That was the curious incident.” We have many clues: Waiting for our Holmes: maybe a string player? The Dog(s) that did not Bark

No convincing models Anarchy works just fine! Normal or inverted hierarchy? Majorana or Dirac masses? (*) CP violation? (*) (*) Important in principle for leptogenesis, but not sufficient to calculate it Main competition weak-scale baryogenesis? Seesaw mass scale accessible at LHC? Neutrino Models

Neutrino Experiments Hierachy of masses? ‘Holy Grail’ of CP violation? –ESS 400 MeV ν source, Water Č Sterile neutrinos? –LSND, MiniBooNE, reactor anomaly Possible experiments: –IsoDAR, ICARUS/NESSIE (CERN) Towards another ‘Holy Grail’? –Cosmic neutrino background using Mcu of Tritium

Astroparticle Physics Focus on dark matter  LHC Interesting other topics: –VHE ν’s in IceCube –Inflation (Planck): Higgs boson? Dark matter: axions or WIMPs? –Strong CP problem not same naturalness problem as M h –ADMX experiment probing dark matter parameter space

Cosmological Inflation in Light of Planck A scalar in the sky?

Inflationary Models in Light of Planck Planck CMB observations consistent with inflation Tilted scalar perturbation spectrum: n s = ± BUT strengthened upper limit on tensor perturbations: r < 0.10 Challenge for simple inflationary models Starobinsky R 2 to rescue? Similar predictions from Higgs inflation

If at first you don’t succeed … … postulate a new particle: –QM and Special Relativity:Antimatter –Nuclear spectra:Neutron –Continuous spectrum in β decay:Neutrino –Nucleon-nucleon interactions:Pion –Absence of lepton number violation:Second neutrino –Flavour SU(3):Ω - –Flavour SU(3):Quarks –FCNC:Charm –CP violation:Third generation –Strong dynamics:Gluons –Weak interactions:W ±, Z 0 –Renormalizability:H –Dark matter:WIMP/axion?

WIMP Searches Direct search for dark matter scattering: –Spin-independent and –dependent σ limits from XENON100, COUPP –CoGeNT & DAMA well excluded –3 CDMS candidates (~ threshold, compatibility with XENON100?) Cf, monojet searches at LHC: –LHC wins for interactions with quarks and gluons XENON, DARWIN, EURECA

Indirect WIMP Searches Rising positron fraction? –Require large boost factor –Limits from γ rays –No antiproton signal Fermi γ 130 GeV: 4.6 σ (3.3 σ with look-elswhere effect) –Need σ > SUSY? –Seen from earth’s limb! –Test with HESS-II et al. Falsify WIMP hypothesis?

What else is there? Supersymmetry Successful prediction for Higgs mass –Should be < 130 GeV in simple models Successful predictions for couplings –Should be within few % of SM values Naturalness, GUTs, string, … (???)

Data Electroweak precision observables Flavour physics observables g μ - 2 Higgs mass Dark matter LHC MasterCode: O.Buchmueller, JE et al. Deviation from Standard Model: Supersymmetry at low scale, or …?

5 1 Favoured values of gluino mass significantly above pre-LHC, > 1.5 TeV Gluino mass Yesterday’s update of Buchmueller, JE et al: arXiv: CMSSM

Towards universal mass limits in SUSY Many searches in specific scenarios: –CMSSM, “natural”, (over)simplified models Combination may be less model-dependent Buchmueller & Marrouche

What Next: A Higgs Factory? To study the ‘Higgs’ in detail: The LHC –Rethink LHC upgrades in this perspective? A linear collider? –ILC up to 500 GeV –CLIC up to 3 TeV (Larger cross section at higher energies) A circular e+e- collider: LEP3, … –A photon-photon collider: SAPPHiRE A muon collider

Future Accelerators (What) precision, (how) high energy, neutrinos? Which is THE top priority accelerator? –Precision: HL-LHC, ILC/CLIC, TLEP, MC, γγ –Energy: HE-LHC, VHE-LHC, CLIC, MC –Neutrinos: from superbeam (ESS) to ν factory HL-LHC is not a done deal, needs high-tech: –11T dipoles, 13T quads, 500m HTS link, crab cavities Worldwide collaborative R&D needed No decision before LHC 13/14 TeV results

Higgs Factory Summary ICFA Higgs Factory Workshop Fermilab, Nov Best precision

Predictions of current best fits in simple SUSY models Current uncertainties in SM calculations [LHC Higgs WG] Comparisons with –LHC –HL-LHC –ILC –TLEP Don’t decide before HE-LHC Impact of Higgs Factory? Supersymmetric model fits

European Strategy Europe’s top priority should be the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around This upgrade programme will also provide further exciting opportunities for the study of flavour physics and the quark- gluon plasma. CERN should undertake design studies for accelerator projects in a global context, with emphasis on proton-proton and electron- positron high-energy frontier machines. These design studies should be coupled to a vigorous accelerator R&D programme, including high-field magnets and high-gradient accelerating structures, in collaboration with national institutes, laboratories and universities worldwide.

European Strategy … The initiative from the Japanese particle physics community to host the ILC in Japan is most welcome, and European groups are eager to participate. Europe looks forward to a proposal from Japan to discuss a possible participation. CERN should develop a neutrino programme to pave the way for a substantial European role in future long-baseline experiments. Europe should explore the possibility of major participation in leading long-baseline neutrino projects in the US and Japan.

Big Accelerator Laboratories Roles in Research/Innovation/Training/Outreach: –Push forward frontiers of technology as well as science –Stimulate young people to study STEM subjects –Society needs to realize and appreciate science Sustained commitment, global collaboration, information sharing in pursuit of common goals Need accelerator projects in all regions –Do not underestimate the issues involved –Propose and discuss in international context Remember the last ‘green-field’ project

Conversation with Mrs Thatcher: 1982 What do you do? Think of things for the experiments to look for, and hope they find something different Wouldn’t it be better if they found what you predicted? Then we would not know how to proceed!