Transcript Higgs_LASER_11-5-13

The HIGGS
BOSON Discovery:
What it Reveals
and Where it Leads
UCSC Institute of Arts
& Sciences ”LASER”
Discussion Series
November 5 2013
Bruce Schumm
UCSC/SCIPP
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…
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
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
Relativistic Quantum Field Theory
t (time)
Main Architect:
Electron#2
Richard “Dick” Feynman
Electron #1
In a nutshell: Objects influence
one another by tossing things
around.
“photon"
For Electromagnetism, that
“thing” is just the photon
x (position)
Electron #1
Electron #2
For the Weak Nuclear Force,
there are three: the W+, W-,
and Z bosons.
N.B.: These things are collectively know as “field quanta”
WHY IS THE WEAK FORCE WEAK?
t (time)
Electron#2
R = Range of Influence
M = Exchanged object mass
R  1/M
Electron #1
Z mass = 80 “GeV”
Z
For this mass
R  10-18 meters, or about
1/1000 of a proton radius!
x (position)
Electron #1
Electron #2
So it’s not really weak,
you’re just very unlikely to
get close enough!
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
THE HUNT IS ON (SINCE THE 1960s)
CERN
WE’RE ALL IN THIS TOGETHER
THE HIGGS BOSON: WHAT IS IT?
THE ATLAS DETECTOR
THE ATLAS SCT
(SemiConductor Tracker)
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)
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” 
10-35 m, or about 10-20 of a proton radius
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!
THE NEXT GREAT MACHINE ?
SUPERSYMMETRY
???????
OK – WHAT NOW??!!
THE HIGGS BOSON: WHAT IS IT?
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
THE
HIGGSTHE
BOSON:
WHAT
IT?
IS IT
REALLY
HIGGS?
CMSIS
SAYS…
The “yeah it’s
a Higgs” line
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 crosscultural collaboration.
THE HIGGS BOSON: WHAT IS IT?
“Freezing out” of the Higgs field
leads to faster-than-light expansion
INFLATION
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