Nuclear and Subnuclear Physics
Research in nuclear and nucleon physics is carried out by Professor Timothy Smith. This experimental group does most of its research at MIT-Bates Linear Accelerator Center , using a new detector and series of experiments called
BLAST . Bates has a 1 GeV electron accelerator, which means that BLAST will look at
matter on the scale of 10-15 meters. Dartmouth is a part of an international collaboration of nearly a dozen universities which have built
this new detector. We are leading the software effort for the experiment, and designing a control system for one of the targets.
Above: An artist conception of 3He. There are three quarks in each nucleon and three nucleons in 3He.
One of the most interesting questions which we are probing is, "What is the charge distribution inside of a neutron?" Because a neutron is made of
three quarks, and each quark has a charge, there is a charge distribution even if the total charge of a neutron is zero. This is a very important
experiment for nuclear physics because it is a probe of the spin-spin component of quark-quark binding.
Another experiment we are leading is the search for "pre-existing Delta particles". A "Delta particle" is a nucleon (proton or neutron) which is in a
excited state. Delta particles have been observed in many experiments. However, it has never been clear if the Delta was created by the accelerator, or
Right: What a pre-existing Delta particle would look like in BLAST.
A number of our undergraduate students have had internships at Bates Lab, spending a quarter working on the experiments and detectors. They have run
the detectors and taken data, and each also has their own project. These projects have included mapping the magnetic fields of BLAST, working with the
neutron detectors, and developing programs which control the accelerator. In collaboration with Bates Lab we continue to offer the opportunity for
undergraduate research internships.
Left: Dartmouth students / BLAST interns, sitting inside of BLAST.
We are also developing the control systems for the polarized 3He target at Dartmouth. This target is necessary for a number of experiments
For more information see the Dartmouth Nuclear Physics page.
V. Kubarovsky, et. al (CLAS Collaboration), "Observation of an exotic baryon
with S = +1 in photoproduction from the proton," Phys. Rev. Lett. 92, 032001
S. Taylor, S. Ahmad, J. Distelbrink, G. S. Mutchler, E. Smith and T. Smith,
"The CLAS Start Counter," Nucl. Instrum. Meth. A 462, 484 (2001).