**Hadronic Hose Review -- October 2000**

**Physics Comments:**

The Hadronic Hose (HH) will noticeably improve the MINOS physics results
by decreasing both the statistical and systematic errors. The
improvements, although not dramatic, enhance the capability of the
experiment to investigate more complicated oscillation scenarios and to
differentiate between oscillation and non-oscillation physics. The
improvement in sensitivity will enable MINOS to more effectively
determine the specific type of oscillations occurring and measure the
oscillation parameters. Furthermore, the decreased errors will improve
the quality of the oscillation fit, which will lead to a more convincing
understanding of the oscillation phenomena and will allow more changes
in the configuration with shorter runs.

The HH is especially important due to the ongoing K2K long baseline
neutrino oscillation experiment in Japan. K2K will, presumably, have
established a clear deficit in the ν~μ~ flux by the time that MINOS
begins taking data in 2003. However, MINOS, due to its much higher event
rate, will be capable of not only observing a deficit, but also of
determining the cause of the deficit in a definitive manner. Therefore,
this precision measurement capability is the hallmark of the MINOS
experiment and provides a strong motivation for building the HH.

The HH has several important effects on neutrino flux:

-   It increases the ν~μ~ flux by 25% for neutrino energies below 6 GeV
    at the far detector, when the low energy horn configuration is used.
    This low energy beam option is especially important at the energies
    where existing results on neutrino mass difference suggest ν~μ~ =\>
    ν~τ~ oscillations should occur. The flux increase is even larger for
    neutrinos whose energies are greater than 6 GeV.

-   It reduces the errors in the far/near flux ratio determination that
    are sensitive to hadronic production models.

-   It reduces the flux errors that occur from misalignment of the
    focusing horns and other beamline components.

-   It increases the ν~e~ background by a factor of two, but this is
    compensated by the previously mentioned increase in statistics,
    giving no change to the experimental sensitivity for the ν~μ~ =\>
    ν~e~ appearance measurement.

-   It does not impact the need for better information on secondary
    particle production.

Comments about increasing flux:

In the case of the low energy MINOS beam, most relevant to the SuperK
signal region, the statistical error will be decreased due to the 25%
increase in neutrino flux in the critical region below 6 GeV. The HH
increases the flux because pions that would hit the decay pipe wall are
now channeled along the pipe and thus have a greater probability to
decay. This focusing also affects higher energy pions, and for the low
energy horn configuration increases the flux below 16 GeV by more than
50%. While the neutrinos above \~10 GeV may not be important in directly
determining neutrino oscillation parameters, their interactions will
serve as an important check on beam and detector systematics.

Since event rates in the near detector will be much higher than those in
the far detector, a small amount of "HH off" data in the near detector
could be useful in comparison to "HH on" data, in checking systematic
effects.

The combined effects of the increase in the neutrino flux and the
reduced systematic errors with the HH can be seen from studies done for
ν~μ~ =\> ν~τ~ oscillations with sin^2^2θ = 1.0 and ∆m^2^ = 0.003 eV^2^.
In this case a combined systematic and statistical error on ∆m^2^ of
0.0001 eV^2^ is obtained after an exposure of 14.5 kiloton-yrs with the
HH and the same error level is reached in 22.7 kiloton-yrs without the
HH for the same number of 120 GeV protons on target. In addition, Monte
Carlo studies where a large number of "MINOS experiments" was simulated
concluded that a larger number of these "experiments" has false minima
in the chi-squared distribution with the HH off than with the HH on, and
that the fit resolutions are better with the HH on. In these studies
spectral distortions corresponding to the production model uncertainty
were included in the simulation.

Comments about flux ratio uncertainty from models:

The hadronic production models used to predict the secondary beam
distributions for the calculation of the neutrino flux have significant
uncertainties in the phase space relevant to the MINOS beam. The MINOS
collaboration has calculated the expected ν~μ~ flux in their near and
far detectors for four different production models (GFLUKA, BMPT, MARS
and Malensek) which characterize three sets of production data: (1)
Atherton et al. (CERN 80-07, 1980), (2) Barton et al. (Phys. Rev. 27,
(1983) 2580) and (3) NA56/SPY (Eur. Phys. J. C10, (1999) 605). The
calculations from the different models result in somewhat different flux
yields with the agreement in most cases being about 25%. For
disappearance measurements, the systematic error associated with these
model differences will be decreased because the additional focusing of
the HH makes the fluxes seen by the near and far detectors much more
similar. In this type of measurement the spectrum observed in the near
detector is used to predict the neutrino flux in the far detector. As
the acceptance of the two detectors is not the same, the comparison
depends on precise knowledge of the neutrino beam kinematics, which is
coupled to understanding the production of secondary particles in the
beam. The HH reduces the acceptance differences of the far and near
detectors, thus reducing the dependence of the disappearance measurement
on the production models. For the low energy beam option, the HH reduces
the production model uncertainty in the far/near flux prediction by a
factor of two.

Comments about alignment and other component errors:

An additional benefit of the HH is a lessening of the effect of
transverse misalignment of the horns relative to the incident proton
beam. MINOS studies show that misalignment effects on flux ratios in the
far/near detectors are better tolerated with the HH. For example, with
the HH a 1.0mm transverse horn misalignment produces less than a 2%
fluctuation in the far/near flux ratio. Without the HH such a
fluctuation is observed for a 0.8mm horn transverse offset. Studies also
indicate that the expected 1.5 mm sag in the 72 10m long sections of the
Al HH wire are hardly noticeable.

Comments about ν~e~ background:

The HH, because it also provides stronger focusing for muons in the
decay pipe, produces additional ν~e~ flux from muon decays in the pipe.
This intrinsic ν~e~ flux constitutes a background to the ν~e~ appearance
measurements. Although this increase is not a desirable effect, if
combined with the increase in statistics provided by the HH it does not
seem to reduce the sensitivity of MINOS to ν~e~ appearance measurements.
The increase in the ν~e~/ν~μ  ~event ratio in the far detector for E~ν~
\< 6 GeV is about a factor of two, i.e. from 0.8% to 1.5%. However, the
signal/√(background) remains almost constant since the signal increases
by about 25% with the HH. The same ratios for the near detector are
about a factor of two larger due to the increased phase space available
for decay neutrino flux to subtend the near detector.

Comments about a dedicated secondary particle production experiment:

There is the issue of whether MINOS should embark on a secondary
particle production measurement experiment such as P-907 and how this
affects the need for the HH or vice versa. The MINOS experiment and the
reviewers agree that an experimental determination of particle yields at
values of x~f~ and p~t~ relevant to the MINOS beam configurations would
be of benefit in determining the neutrino flux. Such knowledge would
allow a critical check on the observed event spectrum in the near
detector. It was noted that K2K is having trouble making such a check in
their experiment. The reviewers support both the HH and a P-907 type
experiment; neither obviates the need for the other; both would provide
independent information that may be crucial in understanding neutrino
oscillations or other possible interpretations of the experiment's
observations. Since the near detector is the primary monitor, an
accurate prediction of neutrino interactions in it will require accurate
and relevant production (P-907) data that do not now exist.

**Electrical Comments:**

The committee would like to commend the work that has gone on in the
last several months. The physicists, engineers and technicians have
worked through all of the obstacles that have surfaced. All questions
from the previous review were addressed.

The committee saw a working full size 40-ft section of the hose and
decay pipe. Second generation fixes to further optimize the design were
also discussed.

A prototype pulser was demonstrated on the single length of hose. This
is a good approach and has allowed very good electrical characterization
of the line.

The preliminary design of the power supply looks solid and
completion/installation should not impact the schedule. The cost
estimate looks more than adequate for the system.

Recommendations:

1.  The experiment should produce a good set of specifications for the
    current wave shape that includes both short-term limits on the pulse
    to pulse current as well as long-term limits. These specifications
    should be tied to physics requirements. Spare capacity should be
    built in at this time since getting spare capacity may be difficult
    to add in the future.

2.  Continue working on the prototype pulser with the next generation
    including the final output transformer. This will give the designers
    a good measurement of the total inductance of each of the 72 loads.

3.  A full-scale model (Spice Simulation) will be required to predict
    the operating parameters of the current pulse for the full system.
    This should be started as soon as all inputs are known.

4.  Alternative solutions of the interconnecting transmission line from
    section to section should be investigated. Perhaps a multi-conductor
    cable will reduce costs and sensitivity to moisture.

5.  Safety aspects of the monitoring system should be evaluated.

**Mechanical Comments:**

The committee is impressed with the effort expended since our last
review.  The testing and continued outfitting of the full-scale mockup
of the HH represents significant progress in resolving wire support and
electrical feedthrough design issues.  These efforts should continue for
optimization of mechanical details, observing effects of\
long term pulsing, and establishing detailed installation procedures.\
\
The required design information necessary for the civil contractor to
proceed with the decay pipe installation is complete.  Existing manpower
allocation appears adequate though the fractional involvement of
individuals of the design team as it is now constituted, could become an
issue if their focus is diverted to other pressing needs.  However,
having a dedicated installation team with experienced people should help
relieve engineering oversight demand during the installation. The costs
both for fabrication and installation are consistent with the complexity
of the design.  Any deviation should be minimal and well within
contingencies provided.\
\
There are no mechanical engineering reasons to prevent the committee
from recommending inclusion of the HH in the NuMI project.

**Management Comments:**

The cost estimate for the HH, the decay pipe cooling and the power
supplies has not changed significantly over the past six months even
after folding in the experience gained in building the prototype cell.
These costs were done carefully and appear solid.  The cost of the civil
work will remain uncertain until negotiations are completed with the
contractor.  The outcome of these negotiations is difficult to predict
and depends on the number of additional weeks needed to accomplish the
changes.  The contract changes are likely to result in a cost that is
more than the original estimates but are unlikely to cause the total
cost to exceed \$3.25M.  The results will be known in the next few
weeks.  If the total cost of the HH project comes in at around \$3M, the
review committee feels that the improvement in physics capability of the
detector makes the HH a very good investment.\
\
Exercises building the prototype cell have helped confirm the schedule
estimates for the work on the hose hardware.  The civil construction
will be stretched by about four weeks.  The work on the HH and the
extension of the civil construction do not appear to impact the overall
NuMI schedule.  The changes to the civil construction\
contract, however, need to be concluded immediately.\
\
There was no organization presented at the review.  The people working
on the project are of high quality and the resources allocated are quite
reasonable.  The effort is fragmented, however, with a lot of people
working part time including the management.  This could well be a threat
to the schedule and could eat up the available float.  Although a \$3M
project is small by Fermilab standards it needs a project manager who
devotes more than half time to the project to ensure success.  The HH
project also needs to be integrated into the NuMI management structure
so that there are clear lines of responsibility and authority.

**Project Summary:**

The HH Project seems to be fairly well engineered.  There are some
questions concerning the pulsing and actual wire supports but no real
problems. Technical assessment would indicate that it is unlikely for
them to have any dramatic problems with the system. The main question is
with respect to costs that will be required by Healy and impact on the
schedule. This is not perfectly known yet but a conservative estimate is
\$3.25M and at\
most a 3-month delay.  The delay may not be real since Healy\'s work
will probably have a slower schedule; adding the HH project will give
Healy an excuse for any delays. The project may have to pay extra to
Healy even without the HH.

Nothing mechanical/electrical is pushing the system technically; this is
not a state-of-the-art project.  It should be straightforward to monitor
the system and know what is working at any time.  The project
engineering, management and oversight looks manageable although it will
need to be increased if the project is to succeed on schedule. The
project needs to be integrated into the full NuMI resource loaded
schedule.\
\
The statistical impact of the HH is not significantly large by itself
but it makes the far/near comparison much more solid.  It may be
important for establishing the credibility of the results since the
predictions of the far spectra will not be as dependent on the primary
production models. The combination of the hose and P907 particle
production results cover complementary systematic uncertainties, so a
hadron production experiment in the right x~f~ and p~t~ regions will be
useful to MINOS in reducing systematic errors. The hose makes the
far/near comparison more robust independent of production spectrum
whereas P907 allows one to understand and check the observed event
spectrum independently in the near and the far detectors.  Also, if
nature is more complicated than simple ν~μ~ =\> ν~τ~ single oscillation,
then having more handles on the systematics will help to sort things
out. The increase in statistics will allow one to do more changes with
shorter runs and the expected oscillation effects should show up with
somewhat less beam.

Anything that reduces systematics in a tough experiment should be done
especially since the cost is on the order of a 3% increase.\
\
The HH project cannot go in later so the decision needs to be made now. 

**Recommendations:**

**\
**The committee recommends that the Hadronic Hose project go ahead.  The
hose would increase the flux by 25% in the critical region below 6 GeV
and reduce the systematic uncertainty in the far/near comparison.  Even
if production spectra measurements were available, the committee feels
that the reduced systematic uncertainties with the hose justifies the 3%
cost increase of NuMI.  The technical risks are minimal but the project
is costly and will likely impose a modest schedule delay.