Frontiers in Physics and Astrophysics Fermi Lecture 7 –Higgs Particle, Supersymmetry, Future
Barry C Barish 12-December-2019 Fermi Lecture 7 1 Enrico Fermi
Fermi Lecture 7 2 Enrico Fermi Lectures 2019-2020 Frontiers of Physics and Astrophysics
• Explore frontiers of Physics and Astrophysics from an Experimental Viewpoint • Some History and Background for Each Frontier • Emphasis on Large Facilities and Major Recent Discoveries • Discuss Future Directions and Initiatives ------• Thursdays 4-6 pm • Oct 10,17,24,one week break, Nov 7 • Nov 28, Dec 5,12,19 Jan 9,16,23 • Feb 27, March 5,12,19 Fermi Lecture 7 3 Frontiers Fermi Lectures 2019-2020 - Barry C Barish • Course Title: Large Scale Facilities and the Frontiers of Physics • The Course will consist of 15 Lectures, which will be held from 16:00 to 18:00 in aula Amaldi, Marconi building, according to the following schedule: • 10 October 2019 - Introduction to Physics of the Universe 17 October 2019 - Elementary Particles 24 October 2019 - Quarks 7 November 2019 – Particle Accelerators 28 November 2019 – Big Discoveries and the Standard Model 5 December 2019 – Weak Force Carriers – Z, W: and Higgs Mechanism 12 December 2019 – Higgs Discovery, Supersymmetry?, Future?? 19 December 2019 – Introduction/History of Neutrinos 9 January 2020 – Neutrino(2) 16 January 2020 – Neutrinos(3) 23 January 2020 – Neutrinos (4) 27 February 2020 – Gravitational Waves (1) 5 March 2020 – Gravitational Waves (2) 12 March 2020 – Particle Astrophysics / Experimental Cosmology 19 March 2020 – Future Perspectives • All Lectures and the supporting teaching materials will be published by the Physics Department. Fermi Lecture 7 4 Frontiers 7 Constituents and Forces in the Standard Model
Discovery, Features
Fermi Lecture 6 5 Frontiers 7 Supersymmetry
u c t u c t
d s d s Squarks Quarks b b
e e
e e
Sleptons Leptons
The Generations of Matter The Generations of Smatter
Fermi Lecture 7 6 Frontiers 7 Future Collider Proposals
Fermi Lecture 7 7 Frontiers 7 Next Set of Lectures: Neutrinos
Next Set of Lectures NEUTRINOS Particle Physics Astrophysics Cosmology
Fermi Lecture 6 8 Frontiers 7 The Higgs Mechanism 1964
Fermi Lecture 7 9 Frontiers 7 1964
Tom Kibble Gerry Guralnik Carl Hagen François Englert Robert Brout
Peter Higgs
Fermi Lecture 7 10 Frontiers 7 The Higgs Mechanism for ‘theorists.’
Spontaneous symmetry breaking: massless Nambu- Goldstone boson ‘eaten’`eaten’ by by massless massless gaugegauge bosonboson
Accompanied by massive particle 11 Frontiers 7 1) If Higgs bosons produced, what will we see? Production Rates Decay Fraction
gg ⟶ H ⟶ ZZ ⟶gllllg ⟶ H qq ⟶ qqH
gg ⟶ H ⟶ gg
• Highest production rate: gg ⟶ H • Easiest decays to see: ZZ and gg
Fermi Lecture 7 12 Frontiers 7
2) What other processes can result in four charged leptons?
One main background: qq ⟶ ZZ ⟶ llll
Plus a small background from “fake” leptons: qq ⟶ Zqq ⟶ ll“ll”
Fermi Lecture 7 13 Frontiers 7 3) Differentiate signal from background.
For the background, the two Z bosons have basically random momenta.
In both cases. the detected leptons came from the Z decay
For the signal, the Z bosons come from the decay of the Higgs boson.
Fermi Lecture 7 14 15 Frontiers 7 Experimentally searching for the Higgs • The ambitious U.S. initiative - The Superconducting Super Collider (SSC)
• The cost was ~ $10B and had a highest energy of 20 TeV to pursue the Higgs Boson and new physics “beyond” the Standard Model.
• Killed by newly elected Congress in 1993. Fermi Lecture 7 16 Frontiers 7 Experimentally searching for the Higgs • Fortunately, there was already a large tunnel at CERN (though considerably smaller than SSC).
• The 27 km ring is filled with superconducting magnets cooled to just above absolute zero.
• Large Hadron Collider (LHC) costs about $10B over 20 years. Note: Hadrons are particles containing quarks.
• ATLAS and CMS projects involve
over 3,000 physicists Fermi Lecture 7 17 The Large Hadron Collider LHC is located at CERN The LHC collides protons CERN is located near Geneva Center of Mass E=14 TeV ~7X Fermilab Part of CERN is in France Very high luminosity ~100X Fermilab Goal: discover Higgs+SUSY+???
Fermi Lecture 7 18 Frontiers 7 CERN Large Hadron Collider – Aerial View
Fermi Lecture 7 19 Frontiers 7 The CERN Large Hadron Collider
Fermi Lecture 7 20 The Large Hadron Collider
Above Ground
Below Ground
Fermi Lecture 7 21 The Large Hadron Collider
Magnetic field at 7 TeV: 8.33 Tesla Operating temperature: 1.9 K Number of magnets: ~9300 Number of main dipoles: 1232 Number of quadrupoles: ~858 Number of correcting magnets: ~6208 Number of RF cavities: 8 per beam; Field strength at top energy ≈ 5.5 MV/m Power consumption: ~120 MW
Fermi Lecture 7 22 How Do We Get 7 TeV Protons?
~7 TeV final beam energy
LINAC→PSB→PS→SPS→LHC
~450 GeV
~25 GeV
~1011 protons/beam ~2 GeV
~1 GeV
23 24 The Energy has been increased toThe 13-14 GeV
Fermi Lecture 7 25 Fermi Lecture 7 26 Fermi Lecture 7 27 LHC Detectors
Fermi Lecture 7 28 Frontiers 7 The Atlas and CMS Detectors at LHC
Fermi Lecture 7 29 Frontiers 7
30 Frontiers 7
Fermi Lecture 7 31 Frontiers 7
Fermi Lecture 7 32 Frontiers 7
Fermi Lecture 7 33 Fermi Lecture 7 34 Fermi Lecture 7 35 36 Frontiers 7 LHC – Tunnel and Superconducting Magnets
Fermi Lecture 7 37 Frontiers 7 Movie of a collision
Fermi Lecture 7 38 Frontiers 7 H → gg
Fermi Lecture 7 39 Frontiers 7 Same event, different angle
Fermi Lecture 7 40 Frontiers 7 H → ZZ →
Fermi Lecture 7 41 Frontiers 7 H → ZZ → eeee
Fermi Lecture 7 42 Fermi Lecture 7 43 Fermi Lecture 7 44 Frontiers 7 H → gg
ATLAS
V 10000
e Selected diphoton sample
G
2 Data 2011+2012
8000 /
Sig+Bkg Fit (m =126.8 GeV)
H s
t Bkg (4th order polynomial) n e 6000
v ATLAS Preliminary
E H®gg
4000
s = 7 TeV, Ldt = 4.8 fb-1 2000 ò s = 8 TeV, òLdt = 20.7 fb-1
g 500
k 400
b
d 300 e
t 200
t i
F 100
-
CMS
0 s
t -100 n
e -200 v 100 110 120 130 140 150 160 E 45 mgg [GeV] Fermi Lecture 7 46 Fermi Lecture 7 47 Fermi Lecture 7 48 Frontiers 7 Higgs boson summary
• Two different experiments (ATLAS and CMS) find a new particle with a mass of 125.6 GeV/c2.
• This is a spin 0 boson, with properties consistent with the Standard Model Higgs boson.
• The existence of this particle confirms the point of view that mass is an acquired property (through coupling to the Higgs field) and not an intrinsic property of particles.
Fermi Lecture 7 49 Frontiers 7 Is it a Higgs Boson?
• Is it a single fundamental particle? • Does it have zero intrinsic angular momentum (spin=0)? • Does it have even parity? • Is it electrically neutral? • Does it interact with fermions as predicted? • Probability is directly proportional the the fermion mass. • Does it interact with W and Z bosons as predicted? • Tied the relationship between EM and Weak forces.
Fermi Lecture 7 50 Frontiers 7 Interaction Strengths
• Studies from both the LHC (CERN) and Tevatron (Fermilab) • LHC collided protons with protons at energies of 7 – 8 TeV • Tevatron collided protons with anti-protons at an energy of 2 TeV
• Analyses are like before, but for specific decays • Select events one would expect for a specific Higgs production and decay. • Discriminate that signal from the backgrounds. • Measure the signal rate. • Does it agree with theory? Fermi Lecture 7 51 Higgs Interaction Strengths
Fermi Lecture 7 52 Frontiers 7
• Straight blue line gives the standard model predictions.
• Range of predictions in models with extra dimensions -- yellow band, (at most 30% below the Standard Model
• The red error bars indicate the level of precision attainable at the ILC for each particle
53 Frontiers 7 Testing Spin and Parity • After discriminating signal from background, find distributions that discriminated between different spin and parity hypotheses: SpinParity = 0+, 0-, or 2+ ?
Fermi Lecture 7 54 Spin and Parity Results
Fermi Lecture 7 55 Frontiers 7 Is it the ‘simple’ Higgs or multiple Higgs or??
• Investigate the properties of the Higgs boson in more detail (e.g. decay paths, coupling to other particles, etc).
• Are there other Higgs-like particles? The Standard Model assumes a Higgs field with fourfold symmetry, but there are other models that include more Higgs terms.
• Other interesting physics problems to study at the LHC. Physics beyond the Standard Model?
Fermi Lecture 7 56 Frontiers 7 Summary
• The Standard Model describes the fundamental particles and three of the four forces. • Matter is made from quarks and leptons, which come in three copies of increasing mass. • Ordinary matter is made from the lightest copies. • Forces are caused by exchanging force carrier particles. • The non-zero Higgs field gives mass to particles that interact with it. Fermi Lecture 7 57 Break
Supersymmetry, etc
Fermi Lecture 7 58 Frontiers 7
What about Super- symmetry?
Fermi Lecture 7 59 Frontiers 7 Quote from Ed Witten in preface of Gordon Kane’s book “Supersymmetry”
“Supersymmetry, if it holds in nature, is part of the quantum structure of space and time… Discovery of supersymmetry would be one of the real milestones in physics… Indeed, supersymmetry is one of the basic requirements of string theory… Discovery of supersymmetry would surely give string theory an enormous boost… The search for supersymmetry is one of the great dramas in present day physics.”
Fermi Lecture 7 60 Frontiers 7 Supersymmetry
• In Quantum Mechanics, there is a connection between Global transformations and conserved quantities:. o Translational Invariance → Linear momentum conservation o Rotational Invariance → Angular momentum conservation Emmy Noether o Translations in time → Energy conservation
Noether’s theorem – Symmetries (invariances) naturally lead to conserved quantities
Fermi Lecture 7 61 Frontiers 7 What is Supersymmetry ? There are two types of particles in nature: fermions and bosons.
Fermions have half units of spin, and tend to shy away from each other, like people who always stay in single rooms at the fermion motel.
Bosons have zero or integer units of spin, and like to be with each other, like people who stay in shared dormitories at the boson inn.
Supersymmetry says that for every fermion in Nature there must be a boson and vice-versa. Supersymmetric particles have not been observed (yet) so they must be heavier - SUSY must be broken by some mechanism
Fermi Lecture 7 62 Frontiers 7
Finding symmetries are now a guiding principle in new physical theories
Propose a new symmetry of nature: Supersymmetry • Spin ½ Fermions (quarks, leptons) → spin 0 boson superpartner • Spin 1 Bosons → spin ½ fermion superpartner
SUSY is not an exact symmetry • Mass of SUSY particles ≠ Mass of normal particles
Fermi Lecture 7 63 Fermi Lecture 7 64 Frontiers 7
SPIN ½ SPIN 0 FERMIONS BOSONS
u c t u c t
d s d s Squarks Quarks b b
e e
e e
Sleptons Leptons
The Generations of Matter The Generations of Smatter
Fermi Lecture 7 65 Frontiers 7
BOSONS
FERMIONS Gravitino WWZ+−0 Photino Gluino
Fermi Lecture 7 66 Frontiers 7 What about the Higgs Boson?
Higgs Boson Higgsino
Higgsino Higgs Boson
A further non-interacting “singlet” Higgs and Higgsino can even explain the origin of Higgs mass itself
Fermi Lecture 7 67 Frontiers 7 Eliminates needed Fine Tuning The Standard Model The SUSY Standard Model acts requires fine-tuning to one like a Digital radio that part in a trillion trillion to eliminates nearly all the fine- work! - it is rather like fine- tuning – however a few % tuning the knobs on an old tuning remains (SFK, Kane 98) fashioned radio
Fermi Lecture 7 68 Frontiers 7 Supersymmetric Particles Candidate for the Dark Matter
SUSY provides an excellent candidate for dark matter: the spin ½ partner to the photon which is the lightest SUSY particle and is cosmologically stable called the photino! g
Fermi Lecture 7 69 Frontiers 7 Supersymmetry could explain Inflation SUSY provides the basis for cosmological theories in which the Universe naturally inflates to its present size, and explain how the microwave background radiation appears isotropic
For example a SUSY version of the Standard Model with extra Higgs singlets has been constructed that explains inflation, large scale structure, the origin of Higgs mass, and the origin of right-handed neutrino mass (Bastero-Gi,SFK, Di Clemente)70 Frontiers 7 Grand Unification
Strong
Weak
Electromagnetic
Fermi Lecture 7 71 Frontiers 7 SUSY particles
Interactions are the same -- e.g. squarks interact via strong interaction Fermi Lecture 7 72 Frontiers 7 Strong Theoretical Motivations for SUSY
• SUSY cancels divergences in the Standard Model
• SUSY provides a theoretical route to include gravity in “standard model”, and it is needed in string / M-theory
Fermi Lecture 7 73 Frontiers 7
• SUSY allows for unification of the
forces 1/Strength
• The lightest SUSY particle Log Energy GeV (LSP) is a candidate for dark matter o In most models, the lightest Neutralino Supersymmetric particle is stable Fermi Lecture 7 74 Frontiers 7 SUSY Experimentally
• Baryon number and Lepton number are not conserved by all of the renormalizable couplings in the theory. o Normal” particles and “SUSY” particle have opposite R-parity o R-Parity conserved (assumed!) o R-parity conservation → stable LSP (lightest supersymmetric particle)
• LSP Leading Candidate: Neutralino, neutral weakly interacting particle o Missing energy in event, key signature! o Measure missing transverse momentum/energy Fermi Lecture 7 75 Fermi Lecture 7 76 Fermi Lecture 7 77 78 79 Fermi Lecture 7 80 Fermi Lecture 7 81 End
Outlook: Future Particle Accelerators
Fermi Lecture 7 82 Particle Accelerators Livingstone’s Diagram: Collider Era
Fermi Lecture 7 83 Direct discovery of Very rare events
should be somewhat improved at FCC-ee (5 TeraZ)
Fermi Lecture 7 84 Direct discovery of right-handed neutrinos
For the very small mixing typical of Type-I see-saw, the RH neutrino is 2 -12 very close to sterile (|U| = mv/M (10 for M=50 GeV)
Fermi Lecture 7 85 RightElectroweak-handedeigenstatesneutrinos
풆 풆 R R R Q= -1 풗풆 L 풗 L 풗 L Q= 0 풆 R R R
I = 1/2 I = 0
Right handed neutrinos are singlets no weak interaction no EM interaction no strong interaction
can’t produce them can’t detect them -- so why bother? –
Also called ‘sterile’
Fermi Lecture 7 86 Particle Accelerators Proposed International Linear Collider - Japan
Higgs Factory Electron Positron 250 Gev Center of Mass (expandable)
Fermi Lecture 7 87 What will e+e- Collisions Contribute?
• elementary particles • well-defined • energy, • angular momentum • uses full COM energy • produces particles democratically • can mostly fully reconstruct events
Fermi Lecture 7 88 Extra dimensions and the Higgs?
Precision measurements of Higgs coupling can reveal extra dimensions in nature
•Straight blue line gives the standard model predictions. • Range of predictions in models with extra dimensions -- yellow band, (at most 30% below the Standard Model • The red error bars indicate the level of precision attainable at the ILC for each particle
Fermi Lecture 7 89 LHC --- Superconducting Magnet
Fermi Lecture 7 90 ILC - Superconducting RF Cryomodule
Fermi Lecture 7 91 Particle Accelerators Proposed CEPC Collider - Chinah
Fermi Lecture 7 92 IFF funding bid succeeds at first round → start might be in 2030
Fermi Lecture 7 93 The Future Circular Colliders CDR and cost review to appear Q4 2018 for ESU International collaboration to Study Colliders fitting in a new ~100 km infrastructure, fitting in the Genevois • Ultimate goal: 16 T magnets 100 TeV pp-collider (FCC-hh) → defining infrastructure requirements Two possible first steps: • e+e- collider (FCC-ee) High Lumi, ECM =90-400 GeV The way by FCC-ee is the fastest and • HE-LHC 16T 27 TeV cheapest way to 100 TeV, also produces the most physics. in LEP/LHC tunnel Preferred scenario presented in the CDR. Possible addition: https://cerncourier.com/cern-thinks-bigger/ • p-e (FCC-he) option Its also a good start for a C!
Fermi Lecture 7 94 Status of FCC CDR
First ideas in 2010-11 Study kicked off in 2014 Draft CDR circulating for authorship and last substantial comments (1260 authors today) CDR Publication date : 10/12/2018 for ESPP Update Vol.1 : Physics Opportunities Vol.2 : The lepton collider (FCC-ee) Vol.3 : The hadron collider (FCC-hh) (includes e-h option) Vol.4: HE-LHC Common ~100 km infrastructure @ CERN Civil engineering, electricity, cooling, ventilation, cryogenics R&D for SC magnets (up to highest affordable field) To be approved and initiated a.s.a.p. Staged approach for collider and physics 1st step: high-luminosity and precision e+e- collider (FCC-ee) Phase A: 88 → 240 GeV (Z, W, Higgs) Phase B: 345 → 365 GeV (Higgs, top) (significant RF upgrade) 2nd step : high-energy pp collider (FCC-hh, 100 - 150 TeV?) e-p option (FCC-eh)
At least 60 years of the most sensitive and versatile search for solutions to the mysteries of Universe (BAU, Dark matter & Energy, Neutrino masses, Flavour etc.)
From European Strategy in 2013: “ambitious post-LHC accelerator project” Fermi Lecture 7 95 M. Aleksa
FCC-ee physics start at the end of HL-LHC
Fermi Lecture 7 96 TheParticleParticle Future AcceleratorsAcceleratorsCircular Colliders CDRNext and Big cost Advance?Proposed review FCC Plasma to Collider appear Wakefield - CERNQ4 2018 Acceleration for ESU International collaboration to Study Colliders fitting in a new ~100 km infrastructure, fitting in the Genevois • Ultimate goal: 16 T magnets 100 TeV pp-collider (FCC-hh) → defining infrastructure requirements Two possible first steps: • e+e- collider (FCC-ee)
High Lumi, ECM =90-400 GeV • HE-LHC 16T 27 TeV in LEP/LHC tunnel Possible addition: • p-e (FCC-he) option
Fermi Lecture 7 97 End
Fermi Lecture 7 98