APS News

Four Divisions in Sweeping Attack on Neutrinos

By Ernie Tretkoff

The APS Divisions of Astrophysics, Nuclear Physics, Physics of Beams, and Particles and Fields have begun a sweeping study of neutrino physics. The study, which is still in its early stages, will cover everything from astrophysical neutrinos to accelerator experiments.

Recent discoveries, especially the compelling evidence for neutrino oscillation, prompted these APS divisions to embark on the study in order develop a coherent plan to guide further neutrino research. Study organizers hope to have a final report by the end of the summer.

"I think neutrino physics is genuinely exciting," said Boris Kayser, who co-chairs the study with Stuart Freedman. "Really beautiful experiments have gotten convincing evidence that neutrinos change from one flavor to another, and that means they have nonzero masses. This does raise some very interesting physics questions, and we want to go ahead and answer those questions, but we need to have a coherent plan for doing that."

The study aims to lay a plan to answer some of the open questions in neutrinos physics. According to Kayser, a few of these important questions are: How many neutrino species exist? Are there sterile neutrinos? Are neutrinos their own anti-particle? What is the scale of the neutrino mass? What physics is responsible for neutrino masses and mixing? Do neutrino interactions violate CP? The study members hope to come to a consensus, if possible, about what measurements should be made to answer these questions. According to the charge of the study "the study will lay the groundwork for the choices that must be made during the next few years."

The study will not evaluate or rank specific proposals, but will investigate what physics questions are most important and what are the most promising ways to search for answers. Funding agencies may then consider those guidelines when allotting funds to various proposals, said Kayser.

The study is divided into six working groups, each focused on a particular experimental approach. The working groups are: Solar and atmospheric neutrino experiments; Reactor neutrino experiments; Superbeam experiments and development; Neutrino factory and beta beam experiments and development; Neutrinoless double beta decay and direct searches for neutrino mass; and What cosmology/astrophysics and neutrino physics can teach each other.

"The most interesting aspects of this study may be understanding how the different experimental approaches of the different groups fit together." said Ed Blucher, one of the leaders of the reactor working group.

The study began with a kickoff meeting at Argonne in December. Most working groups are still in preliminary stages. All groups have had their first meeting and have selected questions the group hopes to answer; some groups have already outlined their report. The study organizing committee and the working group leaders will meet in April to determine whether the study is on track.

At the APS April Meeting there will be a Town Meeting on "Our Neutrino Future," that will include a talk by Freedman on the status of the study and opportunity for discussion.

The final report, which will be completed this summer, will include contributions from individual working group members, a summary for each working group, and an integrated summary of the whole study.

"We need to have a coherent plan, and if possible, it should enjoy at least some degree of community consensus. Now that is very nontrivial to achieve," said Kayser. "This is very hard, and also very important, so we're going to try."

Kayser also hopes the study will do some outreach, possibly in the form of a glossy brochure for the general public, or a "neutrinofest" conference, in which scientists would give talks to a general audience, with a large media presence, to convey the excitement of neutrino research.

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Editor: Alan Chodos
Associate Editor: Jennifer Ouellette