Home page for Experimental Nuclear Physics @ University of Maryland: Projects


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Current Experiments

EXO: Neutrinoless Double Beta Decay in Xenon
Radiative Decay of the Neutron
E906: Drell-Yan Production at Fermilabof the Neutron
The G0 Experiment G0-00-006 
Neutron Electromagnetic Form Factors
Electroproduction of Hypernuclei
E96001-Eta Production 

Past Work

E94918 ("t20")
E93018 (ee'K)
SAMPLE@MIT BATES and SAMPLE with Deuterium
E91011 (pi0 production)


Detector space frames in Hall A @ JLAB 
Pb-Glass shower counters in Hall A @ JLAB 
Aerogel Cerenkov detector in Hall A @ JLAB 
G0 Detector Package in Hall A @ JLAB 
RICH detector in Hall A @ JLAB 


In the last ten years neutrino physicists have found compelling evidence that neutrinos have a tiny mass. However, the value of the neutrino mass remains a mystery, with the current upper limit set at 2.2 eV. The existence of non-zero neutrino mass raises the possibility that the neutrino may be its own anti-particle, which is a basic prediction of many grand unification theories. Both the particle/anti-particle question and the value of the neutrino mass can be addressed by searching for a rare type of radioactive decay known as neutrinoless double beta decay. Our group is collaborating on the EXO experiment, which will soon be the largest double beta decay experiment ever attempted (by about a factor of ten). EXO represents an opportunity to make a significant discovery in fundamental physics in the next few years. We are also constructing a liquid xenon laboratory here at Maryland to develop new experimental techniques to apply towards double beta decay research in the future.

Go to the EXO main web page at Stanford University
Go to the (protected) EXO elog

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Radiative Decay of the Neutron at NIST

The theory of quantum electrodynamics predicts that beta decay of the neutron into a proton, electron, and antineutrino should be accompanied by a continuous spectrum of soft photons. While this inner bremsstrahlung branch has been previously measured in nuclear beta decay and electron capture decay, it has never been observed in free neutron decay, until just recently by a group at NIST in Gaithersburg, Maryland in a pilot experiment.  Phase II of the experiment will improve this first measurement by a factor of 10 or more.

Go to the NIST group's web page
Go to the main NIST web site

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Fermilab E906:  Measurement of quark properties in nuclei using Drell-Yan production

Nearly all of the visible mass of universe comes from protons and neutrons at the core of atomic nuclei, yet their internal structure is still not well understood.  One specific poorly understood aspect of the proton is how anti-up and anti-down quarks are distributed in its quark-gluon sea, and how these distributions might change in nuclei. Hints from earlier experiments indicate that there is an asymmetry in these distributions that could influence other high energy experiments carried out with nuclear targets.  A new Fermilab experiment, E906, will use the Drell-Yan process (two protons annihilate and create two muons).   The experiment, which is being led by a group at Argonne National Laboratory, is planned to run in (or before) 2009. Our group has recently joined.

Results from prior experiments can be found at the E866 web site.
Go to the E906 web page

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    The goal of the G0 experiment is to measure parity-violating asymmetries in elastic electron- nucleon scattering, as a function of momentum transferred to the nucleon. This momentum dependence translates into probing deeper and deeper into the interior of the nucleon. The parity-violating asymmetries are sensitive to the interference of the neutral weak (Z-exchange) and electromagnetic forces, resulting in a direct measure of the neutral weak structure of the nucleon. When combined with known information about the electromagnetic nucleon structure, it is possible to decompose the proton's charge and magnetic structure into contributions from up, down and strange quarks. From quasi-elastic scattering on deuterium, we also get information on the anapole structure of the nucleon. 
    During Fall 2002, we are embarking on the first engineering run of the full detector system in Hall C at Jefferon Laboratory in Newport News, VA. The first data taking will measure asymmetries at very forward electron angles,  where scattered protons are detected. Then the detector will be turned around and backward scattered electrons will be detected from hydrogen and deuterium targets.

Go to the G0 main web page at the Jefferson Laboratory
Click here for a the main G0 web page at the University of Illinois.

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E96001 : Eta electroproduction in the Delta region and the proton's quadrupole structure

    Proton recoil polarization in the p(e,e'p)eta reaction will be used to study the S11(1535) resonance, which dominates this reaction, and the nondominant P11(1440) and D13(1520) resonances. Recoil polarization provides unique sensitivities to nondominant multipoles that are very difficult to extract form cross section data alone. The proposal has been approved but the experiment has not yet been scheduled. 

Find more information on E96001 .

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E93038: Measurement of the Neutron Electromagnetic Form Factors

     The neutron electric form factor can be extracted from neutron recoil polarization measurements using the d(e,e'n)p reaction in quasi-elastic kinematics. Equivalent information can be found using a polarized target and polarized beam. The electric form factor gives detailed information about the internal charge distribution of the neutron. Two experiments were completed at Jefferson Lab in early 2002. Another, E02-013 , was completed in 2007, and the data are presently being analyzed. 
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E98108: Kaon electroproduction at high momentum transfer

    This experiment is a higher momentum extension to E93018, which ran in Hall C at JLab in the mid 1990's. By using the Hall A spectrometers it is possible to extend measurements of Kaon electroproduction to higher momentum transfer, Q2 = 2-3 (GeV/c)2 . These measurements provide precise data for models that attempt to describe the production of nucleon excited states which arise from the production of a pair of strange-antistrange quarks. These experiments complement those taken in the CLAS detector in Hall B because they provide very precise information at specific kinematics. 
 A related measurement is the production of hypernuclear states by electroproduction of kaons. In hypernuclei, one neutron or proton is replaced by a strange baryon. Production of these states allows one to learn about the origin of the force between two baryons as it arises from the interacting quarks and gluons. 

Find more information on E98108 and the Hall A Hypernuclear program.

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E94018 ("t20"): Deuteron tensor polarization and electromagnetic structure

    The deuteron is a spin 1 object, and as a result has three components to its electromagnetic structure: charge monopole, charge quadrupole and magnetic dipole. Polarization measurements are required to separate the three components. E94018 recently provided new information on the charge distribution of the deuteron through a measure of its tensor polarization in elastic electron scattering. 

Here are two recent publications: 
D. Abbott et al., Phys. Rev. Lett. 84, 5053 (2000)
D. Abbott et al., Euro. Phys. Jour A 7, 421 (2000)

More information about the experiment can be found at the JLAB t20 web page

This experiment was the thesis project of Kenneth Gustafsson. Kenneth's thesis can be found here.

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E93-018 (ee'K): Kaon electroproduction

    Very little data currently exists on the electroproduction of strange baryons. These data help  constrain models that attempt to describe the flavor dependence of nucleon excited states.  E93018 provides precise new data on the reactions p(e,e'K)L and p(e,e'K)S, separated into its longitudinal and transverse components. The U Md group developed the aerogel Cerenkov detector needed to identify Kaons in the SOS spectrometer in Hall C. 

This experiment was the thesis project of Rick Mohring. A gzipped-PS version of his thesis can be found here.

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    Like G0, the SAMPLE experiment at the MIT-Bates Lab measured parity-violating electron scattering, although SAMPLE was specifically focused on backward angle scattering at low energy, which isolates the magnetic structure of the proton. The deuterium portion, completed in 1999 provided the first experimental access to the proton's anapole moment. The combined measurements seem to indicate that strange quark effects are small, but that the proton's anapole structure is more complicated than previously thought. We also carried out a third measurement, quasielastic scattering from deuterium at half the beam energy of theprevious two data sets, to verify our earlier results and provide the first information on how the axial form factor might change with momentum transfer.  

The hydrogen portion of the experiment was completed in 1998 and the results are in D. Spayde et al., Phys. Rev. Lett 84, 1106 (2000).  The 1998 SAMPLE hydrogen measurement was the thesis project of Damon Spayde. Damon's thesis can be found here.

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E91011: Pion electroproduction in the Delta region and the proton's quadrupole structure 

    Angular distributions of proton recoil polarization for the p(e,e'p)pi0 reaction for kinematics dominated by intermediate excitation of the delta resonance are sensitive to small quadrupole amplitudes, often described as deformation, and to nonresonant multipoles that are difficult to obtain from cross section data alone. The experiment was performed at Jefferson Laboratory from May 15 through July 31, 2000 and comprehensive results were published in Physical Review C. 

Go here for more information about E91011.

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Last modified: October 02, 2002


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