1 Probing the Forces between Quarks with Photon Beams Ryan Roussel Nuclear Physics Mentor: Dr. Richard Jones

2 Why do we want to study quarks? Quarks make up 99% of all matter and little is known about how they are assembled into the neutrons and the protons which make up all matter. The question is, how does the nucleus stay together when all the positively charged protons are repelling each other? The Strong Force binds these particles together, in a way that is not completely understood yet.

3 The Particles of the Standard Model

4 Quarks Up,Charm,Top 2/3 positive charge 2/3 positive chargeDown,Strange,Bottom 1/3 negative charge 1/3 negative charge Quarks have color charge. Quarks have color charge. Quarks in groups of three are called baryons and a quark/anti-quark pair is called a meson. Quarks in groups of three are called baryons and a quark/anti-quark pair is called a meson.

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6 Anti-Matter All particles have an anti-particle with equal mass but opposite charge. All particles have an anti-particle with equal mass but opposite charge. When anti-matter particles and particles collide they annihilate and create pure energy. When anti-matter particles and particles collide they annihilate and create pure energy. The opposite can also happen, out of energy a The opposite can also happen, out of energy a pair of particles can come out.

7 Force Carrying Particles The interchanges of these particles is the cause of these fundamental forces Photon(γ)- Force carrying particle for the electromagnetic force. Photon(γ)- Force carrying particle for the electromagnetic force. Weak bosons (W +,W -,Z)- Force carrying particles for the weak nuclear force Weak bosons (W +,W -,Z)- Force carrying particles for the weak nuclear force

8 Graviton(G)- undiscovered particle theorized to be the source of gravity the weakest force by far. Graviton(G)- undiscovered particle theorized to be the source of gravity the weakest force by far. Gluon(g)- particle responsible for the strong force, responsible for keeping the quarks in hadrons together Gluon(g)- particle responsible for the strong force, responsible for keeping the quarks in hadrons together Force Carrying Particles(Cont.)

9 Strong Force and the Gluon The Strong force is the attraction between quarks in the nucleon when they exchange gluons. This force overwhelms the residual electromagnetic repulsion from like charged quarks. It forms a strong attraction between quarks, keeping them together.

10 Color Charge The unique feature of the strong force is the existence of color charge. All quarks have color charge, anti-quarks have anti-color charge and gluons have a combination of both giving 8 different colored gluons. Quarks exchange gluons madly, thus a color force field forms. When quarks move away from each other a concentrated stream of exchanged gluons forms, until another quark/anti-quark pair forms.

11 The GlueX Experiment One of the main mysteries of the subatomic world is the properties of the gluon and how it holds the quarks together in the nucleus. Probing deep into this question is the GlueX experiment at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia. This facility has the ability to excite the gluon bond between the two quarks in a meson(one quark and one anti-quark). Using a concentrated beam of photons the scientists in collaboration together are able to study the bond between quarks.

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13 Reaction Inside Detector Photon Hydrogen Atoms Recoil Proton Debris Meson Meson Decay

14 Diamond Wafer Photon Production To produce the photons needed for the experiment an electron beam is fired at a diamond wafer. The atoms in the diamond get energized and release a photon packet, many atoms do this at the same time producing a photon beam. The electrons are then directed away using a magnet. The diamond is supported by tungsten wires.

15 Diamond Configuration with Tungsten Wires

16 Problem Facing Photon Creation One of the problems that occurs during photon creation is the oscillation of the diamond wafer. The diamond is supported by the tension in the tungsten wires. The diamond wafer and string system oscillates due to outside equipment. The main purpose for using the Jefferson Lab is the precision beam of photons that the facility has. If the object that is creating the beams oscillates the accelerator loses it’s precision.

17 Proposed Solution to the Problem Increasing the frequency will lower the amplitude and lessen the deflection. Photons Diamond Normal (No oscillation)Low Frequency High Amplitude High Frequency Low Amplitude

18 Sources To read more… Particleadventure.org symmetrymagazine.org itp.uzh.ch Picture Sources htm startswithabang.com/?p= &org=NSF

19 Questions?