# Presentation: 063886

## Life as a High Energy Physicistmade possible by E.O. Lawrence

- John Krane, Ph.D.
- Iowa State University

-  Who am I?
-  What is HEP?
-  Accelerators and detectors
-  Interactions and what   we measure
-  What keeps us coming  back to work
-  What we actually do at work

## Who am I?

- Lived in Sioux Falls, SD from 1975 until college
- College at USD, majoring in
- Business Administration -- Management
- Physics
- Graduate School at University of Nebraska -- Lincoln
- Solid State Physics, then High Energy Physics - Ph.D. 1998
- Research Associate at Iowa State University
- Living “in residence” at Fermilab, member of the D0 Collaboration

- /

- John Krane, ISU

- December 10, 2001

## What is High Energy Physics?

- The events that occurred in the first “moments” of the universe fall in the realm of HEP.
- By recreating the conditions of those moments (but with much less material!) we strive to understand nature at its most fundamental level.

|  | Typical
Size | Very Small
Size |
| --- | --- | --- |
| Typical
Energies | Classical
Physics | Quantum
Physics |
| Very High
Energies | RelativisticPhysics | High Energy
(Particle)Physics |

- John Krane, ISU

- December 10, 2001

## Particle Types 

- Protons constituents
- Quarks
- Gluons
- Electrons
- Photons
- Neutrinos
- Exotic particles

- Ye olde “planetary model” of atoms

- +

- -

- How does one study these particles?!  It is onlypossible with high energies...started with cosmic rays

**e****-**

**e****-**

**e****-**

**e****-**

****

- John Krane, ISU

- December 10, 2001

## The Accelerator

- Near Chicago, IL
- TeVatron has 1km radius
- Construction startedin 1968

- 1 TeV = 1 trillion electron-Volts
- ...convenient units for us

- John Krane, ISU

- December 10, 2001

## The TeVatron

- The particle beams are a thousand times thinner than a human hair
- 1 TeV ~ 1 erg ~ energy of a mosquito landing
- Three circular accelerators and two linear accelerators create and collide proton and antiproton particle beams

- John Krane, ISU

- December 10, 2001

## Compare to...the BeVatron

- Construction began 1949
- Top energy: 6 Billion eV
- Discovered antiproton

- E.O. Lawrence with an
- early 37.5 inch version

- 6 ft

- John Krane, ISU

- December 10, 2001

## The DO Collaboration

- 18 countries
- 79 Univ. & institutes
- 399 people
*(Regular people!)*

**/**

- John Krane, ISU

- December 10, 2001

## Compare to...

- This collaboration built a 60 inch cyclotronat Berkeley

- John Krane, ISU

- December 10, 2001

## The DO Detector

- Most modern detectors possess three basic design modules:
- Tracking
- Calorimetry
- Muon ID and tracking

**/**

- John Krane, ISU

- December 10, 2001

## What are we detecting?

- At their most basic, all detectors work via ionization or photon creation
- Charged particles pass through “active” material (l Ar, Si wafers, scintillating fibers)
- Near each molecule, the particle can liberate an electron
- These ionization electrons are collected on charged plates

- John Krane, ISU

- December 10, 2001

## What does an interaction look like?

- Beams traveling into and out of the screen
- Tracker finds many ion traces
- Calorimeter energy represented by “lego blocks”

- Muon detector (not shown)finds two tracks: the blue lines.

- John Krane, ISU

- December 10, 2001

## What we measure

**What we measure**

- Azimuthal angle
- Transverse momentum (pT) = energy * sin()
- Neglect most particle masses
- Relative angles  invariant mass

**beam**

**beam**

**Polar angle******

- John Krane, ISU

- December 10, 2001

## A Cross Section Measurement

- A “cross section” is really an observation frequency
-   or
- The cross section for particle jets

**number of observations**

**number of opportunities**

- John Krane, ISU

- December 10, 2001

## The Top Quark Discovery

- Decay modesand “signatures”

- p

- p

- t

- b

- W

- q

- q

- W

- b

- t

- l

- n

- John Krane, ISU

- December 10, 2001

## Analogy of a Signature

**Analogy of a Signature**

- Imagine a game with a curtain hiding an unseen structure...
- Consider these different cases:

- John Krane, ISU

- December 10, 2001

## Studying distributions

- Let’s say you can’t play the game one roll at a time...
- 							...and you only get a few shots
- Essentially, this is what we do in an HEP analysis!

**?**

**Observation of the Top Quark**
**Phys. Rev. Letters {74} 2632 (1995)**
- Had 17 top quark events.

- John Krane, ISU

- December 10, 2001

## Looking for the Higgs

- Origin of mass
- Most sensitive channel is
- ...followed by decay of H to bb and decay of W to e or  and a 
- Two “jets” with associated , and an extra e or 
- We might get ~10 events, with ~40 background

**q**

**q**

**W***

**W**

**H**

- John Krane, ISU

- December 10, 2001

## Work in Progress

**Work in Progress**

- t discovered 1994,mass is 174300 MeV
- Neutrinos (n) have non-zero mass 1998
-  discovered 2000
- 			5-15 years?

- H130?

- Note: I personally am more interested in the force carriers (g, , etc.)

- John Krane, ISU

- December 10, 2001

## Why do we care?

- We are curious and our questions are large
- HEP is a handle on the first moments, cosmology
- Current theories become inconsistent at high energies, gravity
- The tools we need become useful to others
- Accelerators used in cancer treatment, diagnosis
- Particle detectors for imaging of internal organs
- Parallel computing
- www created at a HEP lab for our use
- Today’s abstract knowledge is tomorrows industry
- Quantum physics (transistors, lasers)
- Superconductivity (MRI, mag-lev)
- Molecular manipulation (plastics and pharmaceuticals)
- Electricity...

- “Cool.  But what’s the point of putting letters in your little boxes?”

- John Krane, ISU

- December 10, 2001

## What do we do, daily?

- Design and build the hardware
- Operate the data acquisition system
- Analyze the data
- Develop theories to explain or predict observations
- Manage efforts of any of the above
- Some mix of things

- John Krane, ISU

- December 10, 2001

## Summary

**Summary**

- Educational path that brought me to HEP
- Defined particle physics, and showed you the tools we use (accelerators, really big detectors)
- Illustrated how to understand quantum-level physics with macroscopic instruments
- Listed recent accomplishments in HEP and what our work means to everyone else
- Showed you a few things physicists do

**If it were not for E. O. Lawrence, we ****would still be working with cosmic rays...**

- John Krane, ISU

- December 10, 2001