The HIGGS BOSON Discovery:

What it Reveals and Where it Leads

UCSC Institute of Arts & Sciences ”LASER”

Discussion Series

November 5 2013

Bruce SchummUCSC/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 nucleiWhy 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

Main Architect:

Richard “Dick” Feynman

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.

“photon"

Electron #2

Electron#2

Electron #1

Electron #1

x (position)

t (time)

N.B.: These things are collectively know as “field quanta”

WHY IS THE WEAK FORCE WEAK?

Z

Electron #2

Electron#2

Electron #1

Electron #1

x (position)

t (time)

R = Range of InfluenceM = Exchanged object mass

R 1/M

Z mass = 80 “GeV”

For this mass

R 10-18 meters, or about 1/1000 of a proton radius!

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 TheoryVery difficult to test (“Planck length” 10-35 m, or about 10-20 of a proton radius

Our leading framework for unifying strong and Electroweak forces

Every known particle (including Higgs) has “supersymmetric partner”

In fact, there are (at least) five HiggsIn Supersymmetric models.

If the one we’ve found is one of these, its properties would be subtly different than expected

The search is on!

A WORD ON SUPERSYMMETRY

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 HIGGS BOSON: WHAT IS IT?IS IT REALLY THE HIGGS? CMS 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 cross-cultural 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 WildeFor the gory details… including how abstract math comes into, and is indispensable to, our fundamental description of nature