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December 19, 2003

Prof. Douglas Michael

Department of Physics

California Institute of Technology

Pasadena, California 91125

Prof. Stanley Wojcicki

SLAC, Bin 63

2575 Sand Hill Road

Menlo Park CA 94025

Dear Doug and Stan,

Thank you for your submissions and Doug\'s presentation at the recent
meeting of the Fermilab Physics Advisory Committee (PAC). The Committee
had the following comments:

*Neutrino physics is an important component of the Laboratory's program,
and its importance is likely to grow in the future. The NuMI/MINOS
program is the highest priority after Run II. The Laboratory is
currently going through a long-range planning process, and the Committee
eagerly awaits its report. Any discussion of neutrino physics at the
Laboratory should be consistent with the long-range plan. Moreover,
future neutrino physics experiments will require high intensity proton
beams, and the possible reach of and costs associated with the necessary
improvement of the accelerator complex are not known at this moment.
Recommendations in this report are made in this context.*

The PAC went on to discuss the issues of proton availability:

*The Committee received the [Report to the Fermilab Director by the
Proton Committee]{.underline} and a presentation on planning after the
proton team report entitled "Toward a Proton Plan," as well as the
impact statements from Laboratory Divisions. These present a
comprehensive picture of the demands for protons vs. time for the
Laboratory's experimental program. They also outline the limitations of
the accelerator complex to deliver protons, as well as a large number of
improvements to eliminate or mitigate these limitations and possibly
provide enough protons. The Accelerator Division is making an ambitious
effort to meet the needs. They have made remarkable progress towards
meeting the short-term demands, but many further improvements are
required to meet present and future demands.*

*The Committee urges the Laboratory to continue its program to improve
the performance of the proton delivery complex, in the short term in
order to deliver at least 510^20^ protons to MiniBooNE, and in the
longer term in order to deliver at least 2.510^20^protons/year for
MINOS. Both experiments will benefit from larger numbers of protons, as
will a possible future off-axis experiment. The ability to run a Booster
neutrino program concurrently with NuMI may also be of interest.
Progress towards meeting proton demands is crucial to the present and
any future Laboratory experiments. The Committee looks forward to a
report on further progress at its next meeting and to a report on plans
for continued improvements by its Aspen meeting.*

Turning more particularly to MINOS, the Committee said:

*The Committee congratulates the Laboratory and the collaboration on the
good progress on NuMI/MINOS. The far detector is complete and taking
data; excavation is complete and civil construction is almost done.
Integration of the NuMI beamline into the Main Injector complex went
very smoothly, despite the logistical difficulties involved. The project
is on schedule and within budget; operations are scheduled to begin in
February 2005.*

*In addition to commissioning the far detector and completing
construction of the near detector, the MINOS collaboration has been
actively participating and assisting in Booster operations and future
planning. This is to be applauded and encouraged to continue.*

*The present Fermilab long-range plan calls for four years of physics
running starting in April 2005; the goal for the first year is to reach
the rate of 2.510^20^ p.o.t. per year. MINOS is requesting that the
Laboratory commit to five years of physics running and total protons on
target of 2510^20^; this would require an increase in the proton
intensity by roughly a factor of three over the course of the decade.
This increase is motivated by the fact that the precision of the MINOS
oscillation parameter measurement depends strongly on the central value
of m~23~^2^. Recent experiments have narrowed the allowed range for this
parameter to (1.3--3)10^-3^ eV^2^ at 90% CL, at the low end of the
targeted range when MINOS was proposed in 1995. To observe the
oscillation maximum for this mass difference at the MINOS location
requires MINOS to run at the lowest available neutrino energy. Lower
neutrino energy corresponds to lower neutrino flux, and the neutrino
interaction cross section also scales with energy. These factors are
multiplicative, resulting in lower event rates for MINOS. The MINOS
oscillation measurements remain statistically limited even up to
2510^20^ protons on target, so the additional flux would allow them to
reduce their measurement errors significantly.*

*The Committee appreciates these arguments and wishes to underscore the
importance of delivering the maximum possible number of protons on
target to MINOS in order to maximize the physics, which is of
fundamental importance. The Committee looks forward to hearing more from
the Laboratory about the plans to develop a coherent proton upgrade
project, based on the recommendations of the Proton Committee report, as
well as the evolution of the central value of m~23~^2^. In the meantime,
the Committee defers any specific recommendation until more is known
about the plans for proton capability upgrades.*

It is good to have the very high priority of the neutrino program in
general, and MINOS in particular, reaffirmed in the PAC comments. As is
the PAC, I am also impressed by the progress on the NuMI/MINOS project,
and am hopeful about the prospects for exceeding our current beam
commitments. As you know, the Laboratory is working on understanding how
best to enhance the capability of the proton source. We will be in a
much better position at the time of the Aspen PAC meeting to revise our
estimates and commitments for our neutrino programs. Between now and
then, your continued participation in discussions as we firm up our
planning should be valuable and is welcome.

Continued good luck to you!

Sincerely,

Michael Witherell

cc: K. Stanfield

H. Montgomery

S. Holmes

J. Appel