1. Smashing the Standard Model: Physics at the CERN LHC
Kenneth Johns
University of Arizona

2. Outline Opening remarks – 5 min Standard model and Higgs – 12 min
Destroyed magnets, black hole video
Standard model and Higgs – 12 min
CERN and LHC accelerator – 8 min
ATLAS detector – 5 min
October disaster – 5 min
Higgs – 12 min
Production
Decay
Discovery potential
Other LHC physics and conclusions – 5 min
Total
UA contributions

3. First Beam in the LHC
Sept 10, 2008 in the ATLAS control room

4. First Beam in the LHC
No black hole or stranglet production

5. First Beam in the LHC
No black hole or stranglet production

6. First Malfunction at the LHC
Sept 19, 2008 in the LHC tunnel

7. Physics at the LHC
“There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.” Donald Rumsfeld

8. Fundamental Forces 8

9. Fundamental Particles

10. Fundamental Particles
Or just another pattern to unravel?

11. Standard Model
The Standard Model unifies the strong, weak, and electromagnetic interactions in the sense that they all arise from a local symmetry principle
Local gauge invariance
A minor problem is that the symmetries of the Standard Model do not allow for massive gauge bosons
There are no experimental contradictions to the predictions of the Standard Model, which is complete in that its mathematical structure allows calculations to be carried out
Tested to a high precision (1 part in 1000)

12. Standard Model Local gauge invariance
We first ask is the theory (L) invariant under global gauge transformations?
We next ask is the theory (L) invariant under local gauge transformations?

13. Standard Model
We can make the theory locally gauge invariant by introducing a gauge covariant derivative that includes a gauge field
Now our Lagrangian does remain invariant under local gauge transformations
Using this derivative leads directly to QED!
And tells us that the photon is massless!

14. Standard Model
We could apply the same idea to the weak interaction Lagrangian (SU(2))
We’d find the need for three gauge covariant derivatives containing three gauge bosons
We’d like to identify them as the W+, W-, and Z except they too are massless

15. Standard Model
Spontaneous Symmetry Breaking (SSB) occurs when a Lagrangian is invariant under some symmetry but the ground state (vacuum) is not
Pencil falling
Heisenberg ferromagnet
2008 Nobel Prize to Nambu for discovering SSB

16. Standard Model Higgs mechanism
We have SSB when a Lagrangian is invariant under some symmetry but the ground state (vacuum) is not
If the broken symmetry is a continuous symmetry, then there necessarily exists one or more massless spin 0 particles (Goldstone bosons)
If the broken symmetry is a local gauge symmetry, then the Goldstone bosons get absorbed (eaten) by the massless gauge bosons thereby acquiring mass

17. Standard Model
Consider a charged self-interacting complex scalar field (the Higgs field)
Require the Lagrangian to be locally gauge invariant
For m2 > 0 we have QED of charged scalars
For m2 < 0 we have SSB and a continuum of degenerate vacuum states

18. Standard Model
The Lagrangian for small perturbations about the ground state
A massive scalar (Higgs) with
A massive gauge boson
with
And no massless Goldstone boson

19. Standard Model Summary Massive Higgs Higgs Mechanism Boson Local Gauge
Invariance
Massive
Gauge
Bosons

20. Standard Model
An often used analogy for mass generation

21. Standard Model Successes
Tested from to 1022 cm
No significant deviations (including quantum corrections) at the 10-3 level
Predicted weak neutral currents – discovered
Required the existence of W±, Z – discovered
Necessitated charm and top – discovered
Predicts only 3 neutrino families

22. Standard Model Successes
There are no experimental discrepancies with Standard Model predictions
But no Higgs boson observation either

23. Standard Model Parameters
On the other hand, the Standard Model does contain a lot of parameters

24. Seeking the underlying patterns of matter
The basic constituents of matter are the 6 quarks and the 6 leptons, and the 4 carriers of the fundamental forces. The three quark and lepton generations have very similar properties.
All the particles we know of (protons, neutrons, nuclei, atoms are made from these simple building blocks.
As far as we know, there are no smaller units than quarks and leptons.

25. Fundamental Forces Interactions arise from
Fields (classical field theory)
Exchanged quanta (quantum field theory) 25

26. Fundamental Fermions
There are three families of leptons and quarks 26

27. Fundamental Particles
Or just another pattern to unravel? R L g
Higgs
Graviton

28. So what is this thing called the Standard Model we are trying to smash – and why
Let’s start with the fundamental particles and their interactions
You’ve seen this many times so I won’t linger here

29. One of the goals of physics is to understand the common elements of these forces and particles
Perhaps they can be unified in the sense that electricity and magnetism are unified as electromagnetism
And in fact, in the 1960’s it was shown that the electromagnetic force and weak force had a common origin