The Braidwood Experiment

From: Ed Blucher (
Date: Wed May 10 2006 - 14:52:31 CDT

Dear Dr. Staffin:

    We are writing to express our frustration with the recent decision
of the DOE to deny R&D support to the Braidwood experiment. This
decision was made without benefit of the expected technical comparison
among competing experiments. We believe eliminating this technical
competition will harm the quality of the experiment, wherever it is
ultimately done.

    A precision measurement of sin2(2th13) below the 0.01 level is
recognized as the key next step for understanding neutrino masses and
mixing, and as an important component of the long term neutrino
program. The importance of this measurement has been affirmed by the APS
Neutrino Study, as well as the Neutrino Scientific Assessment Group.

    A measurement of this precision is extremely challenging,
representing more than an order of magnitude improvement over the best
previous experiment. It amounts to measuring the difference in counting
rates at different locations to the level of 0.1%. Our collaboration's
studies showed that reaching this precision in a convincing way requires
an experiment that follows certain basic principles:

- multiple large, spherical detectors that minimize boundary effects
- all detectors protected by an equal and well-understood overburden so
cosmic ray backgrounds are similar
- detectors on the reactor symmetry axis to eliminate reactor flux effects
- a robust shielding system to reduce and measure backgrounds in situ.

The unique features of the Braidwood site allowed our group to design an
experiment incorporating these critical points. We are concerned that
the Daya Bay design does not include these features, and that US groups
may have limited ability to effect changes.

    We believe that thorough peer review of experiments is critical to
the health of the U.S. high energy physics program. Supported
competition between Braidwood and Daya Bay will produce the best and
most cost effective version of this extremely challenging experiment. We
therefore request that R&D funding be awarded to both Daya Bay and
Braidwood, and that a full technical review of both experiments be
carried out.

The Braidwood Collaboration

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