# Presentation: 642144

## Beauty in the Universe

## Innermost Space

- High Energy Particle Physics is a study of the smallest pieces of matter.
- It investigates the deepest and most fundamental aspects of nature.
- It investigates (among other things) the nature of the universe immediately after the Big Bang.
- It also explores physics at temperatures not common for the past 15 billion years (or so).

## Periodic Table

- Helium

- Neon

*All* atoms are made
- of protons, neutrons
- and electrons

## t

- b

- c

- s

- u

- d

- While quarks have similar electric charge, they have vastly different masses (but zero size!)

## Slide 6

## Mysteries of the Quantum Universe

- Why three dimensions?

- What gives particles their mass?

- Are there new forces and symmetries that we don’t yet know?

- Are the forces and particles of which we do know just different faces of a deeper, unifying principle?

## =e2/ħc

- =e2/ħc

## Fermi National Accelerator Laboratory(a.k.a. Fermilab)

- Begun in 1968
- First beam 1972 (200, then 400 GeV)
- Upgrade 1983          (900 GeV)
- Upgrade 2001             (980 GeV)

- Jargon alert:  1 Giga Electron Volt
- (GeV) is 100,000 times more energy
- than the particle beam in your TV.
- If you made a beam the hard way,
- it would take 1,000,000,000 batteries

## Slide 10

##   The Main Injector upgrade was completed in 1999.

**Increasing ‘Violence’ **
**of Collision **

**Expected**
**Number**
**of**
**Events**

**Run II**

**Run I**

**Increased reach **
**for discovery physics**
**at highest masses**

**Huge statistics **
**for precision physics**
**at low mass scales**

**Formerly rare processes**
**become high statistics**
**processes**

- 1

- 10

- 100

- 1000

****  The Main Injector upgrade was completed in 1999.
- 		 ****  The new accelerator increases the number of
-                       possible collisions per second by 10-20.
- 			     ****  DØ and CDF have undertaken massive
-                                        upgrades to utilize the increased
-                                              collision rate.
**	****	****	****	****                  ******  Run II began March 2001

## How Do You Detect Collisions?

- Use one of two large multi-purpose particle detectors at Fermilab (DØ and CDF).
- They’re designed to record collisions of protons colliding with antiprotons at nearly the speed of light.
- They’re basically cameras.
- They let us look back in                                     time.

## Typical Detector (Now)

- 30’

- 30’

- 50’

- Weighs 5,000 tons
- Can inspect 10,000,000 collisions/second
- Will record 50 collisions/second
- Records approximately 10,000,000 bytes/second
- Will record 1015  (1,000,000,000,000,000) bytes in the next run (1 PetaByte).

## Remarkable Photos

- This collision is the most violent
- ever recorded (and fully understood).  It required that
- particles hit within 10-19 m or
- 1/10,000 the size of a proton

- In this collision, a top and
- anti-top quark were created,
- helping establish their existence

## Slide 15

## Modern Cosmology

- Approximately 15 billion years ago, all of the matter in the universe was concentrated at a single point
- A cataclysmic explosion (of biblical proportions perhaps?) called the *Big Bang* caused the matter to fly apart.

- In the intervening years, the universe has been expanding, cooling as it goes.

## Now 
(13.7 billion years)

**Now **
**(13.7 billion years)**

**Stars form**
**(1 billion years)**

**Atoms form **
**(380,000 years)**

**Nuclei form **
**(180 seconds)**

**??? (Before that)**

**Nucleons form    **
**(10****-10**** seconds)**

**Quarks differentiate             (10****-34**** seconds?)**

## Back to the 

- Mysteries of the Quantum Universe

- Why three dimensions?

- What gives particles their mass?

- Are there new forces and symmetries that we don’t yet know?

- Are the forces and particles of which we do know just different faces of a deeper, unifying principle?

- Back to the
- Mysteries

## Undiscovered!

- In 1964, Peter Higgs postulated a physics
-   mechanism which gives all particles their mass.
- This mechanism is a field which permeates the
-    universe.
- If this postulate is correct, then one of the
-   signatures is a particle (called the *Higgs Particle*).
-   Fermilab’s Leon Lederman co-authored a book
-   on the subject called *The God Particle*.

## Higgs:  An Analogy

## Hunting for Higgs

- For technical reasons, we look for Higgs bosons in association with a W or Z boson.

- b jet

- electron

- neutrino
- (MET)

- In the region where the Higgs boson is expected, we expect it to decay nearly-exclusively into b-quarks

## Symmetries

- Translational

- Rotational

## More Complex Symmetries

- In a uniform gravitational field, a ball’s motion is independent of vertical translation.
- The origin from where potential energy is chosen is irrelevant.

- The equations of motion are “symmetric under vertical or horizontal translations.”

## Complex Familiar Symmetries

*r*

*r*1

*r*2

*y*

## Complex Familiar Symmetries

*r*

- Translations:
-    *x*  *x* + *x*
*   **y*  *y* + *y*

## Complex Familiar Symmetries

*r*

*r*1

*r*2

*y*

*y*

- Reflections:
-    *x*  -*x*
*   **y*  -*y*

## Complex Familiar Symmetries

*r*

*r*1

*r*2

- Rotations:
-    *** ** ***

## Complex Familiar Symmetries

*r*

*r*1

*r*2

- Charge Flip:
-    *q ** ****q*

## Complex Familiar Symmetries

*r*

*r*1

*r*2

- Bottom Line:
- Electromagnetic force exhibits a symmetry under:
-    Translation
-    Rotation
-    Reflection
-    Charge Congugation
-    (and many others)

## Fermions and Bosons

- Fermions:
-   matter particles
-  1⁄2  integer spin
- Bosons:
-   force particles
-   integer spin

## Unfamiliar Symmetries

- One possible symmetry that is not yet observed is the interchange of fermions (spin 1⁄2 particles) and bosons (integral spin particles)

- Equation = Fermions + Bosons

- Equation = Fermions + Bosons

- Known equation

- Interchanged equation   (pink  green)

## Unfamiliar Symmetries

- One possible symmetry that is not yet observed is the interchange of fermions (spin 1⁄2 particles) and bosons (integral spin particles)

- Equation = Fermions + Bosons

- Known equation

-                + Fermions + Bosons

-                + Fermions + Bosons

- This New Symmetry is called SuperSymmetry (SUSY)

## SUSY Consequence

- SUSY quark    “squark”
- SUSY lepton   “slepton”
- SUSY boson   “bosino”

## The Golden Tri-lepton SuperSymmetry Signature

- This is the easiest to observe signature for SUSY.
- No excess yet observed.

## The Conundrum of Gravity

- Why is gravity so much weaker       (~10-35×) the other forces?
- Completely unknown
- One possibility is that gravity can access more dimensions than the other forces

## The Dimensionality of Space Affects a Force’s Strength

- Gauss Law

- 2D

- 3D

## Are More Dimensions Tenable?

- Newton’s Law of Gravity
- Clearly indicates a 3D space structure.
*	**	**	**	**Or does it?*

## Nature of Higher Dimensions

- What if the additional dimensions had a different shape?
- What if the additional dimensions were small?

## Access to Additional Dimensions

- What if gravity alone had access to the additional dimensions?

## Access to Additional Dimensions

- What if gravity alone had access to the additional dimensions?

## A Model with “n” Dimensions.

- Gravity communicating with these extra dimensions could produce an unexpectedly large number of electron or photon pairs.
- Thus, analysis of the production rate of electrons and photon provides sensitivity to these extra dimensions.
- Large energies are required to produce such pairs.

## Once again there are interesting events! (way out on the mass tail.)

-  		 ee pair			    pair

## Data-Model Comparison

## Data-Model Comparison

## Summary

- Particle physics allows us to study some of the deepest mysteries of reality.
- We know a whole bunch of stuff.
- The things we don’t know, we’re studying like mad.
- The mysteries mentioned here are unsolved.  We need help.

- Send students.

## www-d0.fnal.gov/~lucifer/PowerPoint/Teacher_Colloquium.ppt

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