Experimenting with Quarks

Prof. Richard JonesUniversity of Connecticut,

Storrs

Science Symposium, Darien High School, May 28, 2008

Science Symposium, Darien High School, May 29, 2008 2

Ordinary matter

cup of coffeeatoms

electrons + nuclei neutrons + protons

quarks

Elementary particles: electrons quarks

neutron

proton

Science Symposium, Darien High School, May 29, 2008 3

What makes things stick?

• Opposite charges attract

• What about these guys?

electrons (-) nucleus (+)

protons (+) neutrons (0) !!

The strong nuclear force

nuclear gluenuclear glue

The electromagnetic force

Science Symposium, Darien High School, May 29, 2008 4

Can we actually “see” elementary particles?

• not exactly…

Science Symposium, Darien High School, May 29, 2008 5

Thomas Jefferson National Accelerator

• racetrack accelerator

• accelerates electrons to

6 GeV

• upgrading to12 GeV

• experiments

Science Symposium, Darien High School, May 29, 2008 6

Why are quarks difficult to see?

• How were electrons first seen?• make a glass vacuum tube• apply force using electric

potential of several kV• electrons rip free from atoms• electric current flows

The world’s first particle accelerator

Science Symposium, Darien High School, May 29, 2008 7

What makes seeing quarks interesting?

• J.J Thompson: "Could anything at first sight seem more

impractical than a body which is so small that its mass is an insignificant fraction of the mass of an atom of hydrogen?"

• Can we try it again with quarks?• people tried, no success

Science Symposium, Darien High School, May 29, 2008 8

• 99% of the mass of ordinary matter is locked up in particles composed of quarks

• mass is energy – E = mc2

• all of this energy is stored safely in the nuclei of the ordinary elements

• can additional energy be pumped in and converted to more mass?

What makes seeing quarks interesting?

new exotic particles

Science Symposium, Darien High School, May 29, 2008 9

Two quarks on a string

• So what happens when you pull on a quark inside a proton?

• N. Isgur, 1988: What happens if you stretch the string, and then pluck it?

theoretical simulationcourtesy of D. Leinweber

1. the quark begins to move2. a glue string forms3. the string stretches 4. the quark slows down5. the quark snaps back – denied!

Science Symposium, Darien High School, May 29, 2008 10

The GlueX experiment

Science Symposium, Darien High School, May 29, 2008 11

The GlueX experimentTime line for experiment• 1997 – first meeting• 1999 – initial proposal• 2002 – mature proposal• 2003 – project adopted by DOE• 2006 – mature design• 2009 – construction starts• 2014 – commissioning • 2017 – first results!

UConn responsibility

Science Symposium, Darien High School, May 29, 2008 12

Prototyping detectors

Science Symposium, Darien High School, May 29, 2008 13

Prototyping detectors

Science Symposium, Darien High School, May 29, 2008 14

The Competition

• China – Beijing Electron-Positron Collider• BES experiment

• Europe – FAIR Antiproton Accelerator• PANDA experiment

• Japan – JPARC Proton Accelerator• several multi-GeV beam lines• proposals in preparation

Science Symposium, Darien High School, May 29, 2008 15

Status and Outlook

• Funding is approved for GlueX• Construction should begin soon• Lots of opportunities for students

at all levels• Exciting discoveries await!