Indiana University

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Thursday, July 16, 2009

Last modified: Thursday, July 16, 2009

IU physicist's study of nucleon interactions funded for NIST lab

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July 16, 2009

BLOOMINGTON, Ind. -- Indiana University nuclear physicist Mike Snow's investigations into the weak interactions of low energy neutrons will advance using equipment funded by the IU Office of the Vice Provost for Research and then put into use at the National Institute of Standards and Technology.

IU's Faculty Research Support Program will provide Snow $90,970 toward equipping a new high-precision neutron spin rotation facility at NIST's Center for Neutron Research in Gaithersburg, Md., so work can continue on parity-odd spin rotation in liquid helium, deuterium and hydrogen targets. Achieving precise measurements in low energy nucleon-nucleon (NN) weak interactions can address issues of fundamental importance in nuclear and particle physics.

"These types of weak interactions remain one of the most poorly understood sectors of the Standard Model and a quantitative description of the weak NN interaction is needed to understand weak interaction phenomena in atomic, nuclear, and hadronic systems," said Snow, who holds a master's degree and a Ph.D. from Harvard. "This new facility will build upon our laboratory's recent search for parity-odd neutron spin rotation in liquid helium, which is the most sensitive measurement of its type ever performed, and make possible more precise experiments in helium, deuterium, and hydrogen targets. This accuracy is expected to be enough to see clearly the effects of quark-quark weak interactions in these systems for the first time."

Believed to be the most elementary constituents of matter, quarks appear to be permanently confined in neutrons and protons by the "strong" interaction. There are also "weak" interactions between quarks which produce mirror-asymmetric effects of known, but very small, size, said Snow, a Department of Physics professor in the IU College of Arts and Sciences who also leads the Weak Interactions Group at the IU Cyclotron Facility. By studying how the weak interactions between protons and neutrons are related to the weak interactions of the quarks inside them, scientists hope to better understand the theory of the strong interaction.

Institutions collaborating with IU in addition to NIST include University of Washington, George Washington University, North Carolina Central University, Georgia State University and Kazakh National University.

"This support from the Faculty Research Support Program will help provide for the main equipment components needed to repeat a measurement in helium, but with higher precision than before, and also to pursue measurements with deuterium and hydrogen," Snow said. "We have already done the first search for this phenomenon in helium and data analysis is nearing completion. Independent of the result of that analysis we plan to conduct a more sensitive measurement at NIST in the future."

Snow said data analysis from the first helium experiment should be complete this fall, with the next NIST measurement expected to be conducted in the next few years after a new slow neutron beamline is constructed there as part of a new cold neutron guide hall.

"This new facility IU is funding will help put the IU nuclear physics experimental group in strong position to take full advantage of the new science made possible by NIST's construction of one of the most intense slow neutron beams for fundamental physics with neutrons in the world," Snow added. "It would also further build upon the several existing IU/NIST collaborations in neutron physics and scattering."

To speak with Snow, please contact Steve Chaplin, University Communications, at 812-856-1896 or

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