Experimenting with Quarks

Experimenting with Quarks

Prof. Richard JonesUniversity of Connecticut,

Storrs

Science Symposium, Darien High School, May 28, 2008

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Ordinary matter

cup of coffeeatoms

electrons + nuclei neutrons + protons

quarks

Elementary particles: electrons quarks

neutron

proton

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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

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Can we actually “see” elementary particles?

• not exactly…

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Thomas Jefferson National Accelerator

• racetrack accelerator

• accelerates electrons to

6 GeV

• upgrading to12 GeV

• experiments

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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

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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

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• 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

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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!

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The GlueX experiment

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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

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Prototyping detectors

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Prototyping detectors

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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

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Status and Outlook

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

at all levels• Exciting discoveries await!