1. The HIGGS BOSON Discovery: What it Reveals and Where it Leads
UCSC Institute of Arts
& Sciences ”LASER”
Discussion Series
November
Bruce Schumm
UCSC/SCIPP
Why we need strong force to be non-abelian: force needs to grow with distance so that only color-neutral objects are
Possible for stable matter. Only for this reason does the weaker electromagnetic, and not the strong force, dominate the properties of
Matter. Otherwise, the scale for `chemical’ reactions would be MeV, not eV. It’s very difficult to imagine how life would have eveolved
In a universe that required MeV radiation to support its biology!!

2. THE “FOUR FORCES OF NATURE”
The Universe is only an interesting place because of causation – the capability of objects to exert influence on one another.
Current evidence tells us that this influence is brought about through four modes of interaction:
Gravity – that persistent tug
Electromagnetism – pretty much everything we sense
Nuclear interaction (weak) – nuclear -decay (obscure)
Nuclear interaction (strong) – holds together nuclei
Why the quotes? There really aren’t four of them. Nor is the term “force” is general enough to specify their role in nature…

3. UNIFICATION
Physicist in the shower:
“Hmmm… there’s but one universe.
Why should it have four forces?
One force would make a lot more sense.”
Unification
But… they’re all so different!
Let’s start with electromagnetism and the weak nuclear force
It’s from the resulting unified theory of the “electroweak force” that the Higgs boson arises

4. WHAT – ME WORRY?
Does anyone really care about
the Weak Nuclear Force?
Solar burning cycle (proton + proton  Deuterium + other junk)
Heavy elements (i.e. anything heavier than Hydrogen)
Medical physics (beta decay tracers)
BTW: If the Weak Nuclear Force were much stronger, the sun would burn too fast

5. Relativistic Quantum Field Theory
Main Architect:
Richard “Dick” Feynman
“photon"
Electron #2
Electron#2
Electron #1
x (position)
t (time)
In a nutshell: Objects influence one another by tossing things around.
For Electromagnetism, that “thing” is just the photon
For the Weak Nuclear Force, there are three: the W+, W-, and Z bosons.
N.B.: These things are collectively know as “field quanta”

6. WHY IS THE WEAK FORCE WEAK?
R = Range of Influence
M = Exchanged object mass
R  1/M
Z mass = 80 “GeV”
For this mass
R  meters, or about 1/1000 of a proton radius!
So it’s not really weak, you’re just very unlikely to get close enough! Z
Electron #2
Electron#2
Electron #1
x (position)
t (time)

7. THE PROBLEM:
Massive force particles don’t work with quantum field theory
THE SOLUTION:
The Higgs Mechanism
All-pervasive Higgs field is “sticky”, and gives particles inertia that is in every way like mass, but really isn’t (“effective mass”).
So force (and matter!) particles can have mass
And oh… by the way… if there is such a field, there needs to be at least one particle associated with it  Higgs Boson

8. THE HUNT IS ON (SINCE THE 1960s)
CERN

9. WE’RE ALL IN THIS TOGETHER

10. THE HIGGS BOSON: WHAT IS IT?

11. THE ATLAS DETECTOR

12. (SemiConductor Tracker)
THE ATLAS SCT
(SemiConductor Tracker)

13. SEARCHING FOR THE HIGGS (H)
Candidate event for the production of a Higgs that falls apart right away into two Z bosons
H  Z Z
(with each Z then falling apart into two stable particles)

14. OK – WHAT NOW??!!
We vanquished Electro-Weak Unification What about the other forces?
1) Mix in the strong nuclear force?
e.g. Supersymmetry, with “shadow world” of partner particles, including dark matter candidate  Testable
2) And then mix in gravity
String Theory
Very difficult to test (“Planck length”  m, or about of a proton radius

15. A WORD ON SUPERSYMMETRY
Our leading framework for unifying strong and Electroweak forces
Every known particle (including Higgs) has “supersymmetric partner”
In fact, there are (at least) five Higgs
In Supersymmetric models.
If the one we’ve found is one of these, its properties would be subtly different than expected
The search is on!

16. THE NEXT GREAT MACHINE ?
SUPERSYMMETRY
???????

18. OK – WHAT NOW??!!

19. THE HIGGS BOSON: WHAT IS IT?

20. IS IT REALLY THE HIGGS? ATLAS SAYS…
The answer you should get if it is indeed the Higgs
What ATLAS sees for various expected decays of the Hoggs

21. The “yeah it’s a Higgs” line
THE HIGGS BOSON: WHAT IS IT?
IS IT REALLY THE HIGGS? CMS SAYS…
The “yeah it’s a Higgs” line

22. SO, THANKS FOR YOUR ATTENTION AND FOREBEARANCE
So in the end, what about this Higgs thingy?
Won’t end warfare, address climate change, redefine our relationship with our natural environment
Is a profound confirmation of a remarkable prediction
Raises as many questions as it answers
How precisely does it hew to expectations?
What is this “Higgs Potential”
What does it tell us about the formation of the universe
Its prediction and production stand, I believe, as one of the greatest triumphs of human intellect and cross-cultural collaboration.

23. THE HIGGS BOSON: WHAT IS IT?

24. “Freezing out” of the Higgs field leads to faster-than-light expansion
INFLATION

25. SHAMELESS PLUG
“For people who like this sort of thing, this is the sort of thing they like”
Oscar Wilde
For the gory details… including how abstract math comes into, and is indispensable to, our fundamental description of nature