Neutrinos and nuclei:
An inter-experiment hunt
The MINERvA detector would be constructed just upstream of the MINOS near detector, shown above.
Neutrinos, those tiny, nearly-massless particles that can slip imperceptibly
through solid rock, have puzzled particle physicists since their first
detection in 1956. Collaborations at Fermilab and at other laboratories are
beginning to discover, however, that neutrinos can interact with matter in
ways never thought measurable.
Within the MINOS experiment, neutrinos travel from the near detector at
Fermilab and change, or oscillate, into other types of neutrinos before
reaching the far detector 735 kilometers away in Soudan, Minnesota. But back here
at Fermilab, there's plenty of interaction going on within the steel plates
of the MINOS near detector before the "ghost" particles whiz off to
Minnesota. Since neutrinos are known as the loners of the subatomic world,
there's still a lot to learn about the way they interact with matter. "One
of the interesting ways that neutrinos can interact is with a nucleus as a
whole, not just the smaller particles," said Peter Shanahan of MINOS. This
interaction is called coherent neutrino-nucleus scattering and gives a
different picture of how neutrinos "see" matter.
Because the NuMI neutrino beam is so intense, the MINOS near detector
collects a huge number of events, which makes researchers hopeful that they
might be able to find coherent neutrino-nucleus scattering. In addition,
scientists working on the K2K (KEK to Kamioka) experiment in Japan have
observed a surprisingly low incidence of these interactions based on
predicted values. To intensify the search for this process, the MINERvA
experiment is developing a six-ton, high-precision neutrino detector to
operate just upstream of the MINOS near detector.
MINERvA underwent a combined CD1, CD2, and CD3a DOE review in December.
Experiment co-spokesperson Jorge Morfin said CD3a approval would allow MINERvA to stay on schedule with advance purchasing of components that
have a long lead time. The MINERvA detector would further investigate
neutrino interactions with three different nuclei -- steel, lead, and
graphite, said MINERvA project manager Debbie Harris. The results of these
experiments would help to fine-tune neutrino oscillation measurements at the
far detector.
"We'll be able to look at all the different ways neutrinos interact with
matter in better detail than anyone ever has before," Harris said.
--Christine Buckley
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