Report on the

RSVP Detector Capabilities, Simulation,

and Backgrounds Review

January 11-13, 2005

New York University

### Executive Summary

The KOPIO and MECO experiments address important fundamental questions
and are of great interest to the particle physics community. Both
experiments involve risk, since they must achieve excellent background
rejection in the face of extremely difficult experimental environments.
After hearing detailed presentations on the simulations that underlie
the sensitivity and background estimates of both experiments, the review
committee is satisfied that both experiments have reasonable prospects
of meeting their goals. However, we cannot at this time provide
assurance that either will do so. We do find that steps can be taken to
clarify and subsequently reduce the risks, and we urge the RSVP project
and the KOPIO and MECO collaborations to give high priority to taking
these steps as soon as possible. These steps include developing software
to carry out more realistic simulations and making measurements of
critical beam and detector parameters. The high priority measurements
will require a significant level of effort not only from the
collaborations, but also the staff of the BNL Alternating Gradient
Synchrotron (AGS). Some will require operating the AGS at high
intensity. (These measurements require high intensity per pulse, not
large integrated intensity.)

KOPIO seeks to measure the K~L~×Ø branching fraction. The experimental
signature of this mode is difficult to say the least, since only two
photons from the decay are observable. The technique employed by KOPIO
requires an extraordinary level performance from its photon veto system
(10^8^ rejection for s from other sources), which must operate in a very
intense neutral beam environment. To make the necessary time-of-flight
measurement of K~L~ momentum, narrow microbunching of the beam with good
extinction between microbunches is needed. While KOPIO has done a good
job addressing many issues via simulation, a clear inadequacy of the
simulations is the lack of detector digitization and realistic event
reconstruction. An increased level of manpower devoted to software and
simulations is clearly needed. We recommend that, as soon as possible,
KOPIO:

-   Develop a detector Monte Carlo with full digitization of detector
    signals, and realistic event reconstruction starting from "raw data"
    in order to validate background estimates.

-   Develop a fully engineered design for the barrel photon veto, build
    a full-scale prototype, and subject it to beam tests to validate
    that it achieves the required performance.

-   Perform tests with the AGS to measure beam microbunch width and
    inter-bunch extinction at full intensity (at least 70 Tp/spill) and
    to demonstrate the necessary bunch widths and extinction are
    achieved.

-   Design the neutral beam and shielding, install it, and perform beam
    tests (using specialized detectors) to establish that the properties
    of the beam (e.g., n halo) meet the requirements of the experiment.

KOPIO projects 12,000 hours of data-taking to be needed for a branching
fraction measurement of 12% if K~L~×Ø occurs at 310^11^. Based on
current information, the committee finds this to be a reasonable
estimate. However, we emphasize that (1) a short early run with only a
partial detector can make an interesting physics measurement because it
would have sensitivity to non-Standard Model physics, and (2) once a
K~L~×Ø signal is established, the precision of the branching fraction is
expected to improve only with the square root of running. Thus, KOPIO's
success depends upon achieving the required beam and detector
performance and meeting it goals for background rejection, rather than
meeting a particular target for total running time.

MECO seeks to perform a stringent test of separate lepton number
conservation by looking for the conversion of a muon to electron in the
field of a nucleus at the level of 210^17^ (w.r.t. NN). Reaching this
goal requires achieving an extraordinary level of extinction between
beam bunches (10^9^). The experiment utilizes a large and complex series
of superconducting magnets and detector elements (including a straw
tracker) that must operate in vacuum. While MECO has done a good job
addressing many issues via simulation, a clear inadequacy of the
simulations is the lack of detector digitization and realistic event
reconstruction. An increased level of manpower devoted to software and
simulations is clearly needed. We recommend that, as soon as possible,
MECO:

-   Develop a detector Monte Carlo with full digitization of detector
    signals, and realistic event reconstruction starting from "raw data"
    to validate background estimates.

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-   Perform tests with the AGS to demonstrate the required extinction
    when running at 8 GeV with intensity of at least 20 Tp/spill.

-   Continue to develop more realistic simulations of the full
    target/transport channel/detector chain to further explore exotic
    background scenarios.

In addition, the committee recommends that [both]{.underline} KOPIO and
MECO:

-   Develop deliverables-based schedules with performance milestones,
    which include the steps recommended in this report planned for
    completion as early as possible.

By doing so, dangerous surprises may be avoided later. If serious
problems are found early, there will be a much better chance that
solutions can be found and implemented in time to avoid major
degradation of the experiment.

Finally, the scenario described to us for AGS running during RHIC
data-taking, while perhaps conservative, would provide only a marginal
amount of RSVP running per year. We urge BNL to make it a high priority
to maximize AGS slow spill running during RHIC operation. Also, both
KOPIO and MECO should benefit if data-taking is structured to provide
the longest possible runs in alternate years, rather than shorter runs
based on an equal division of available running each year.

### Introduction

The RSVP Project Office organized this review to address the reliability
of estimates of the sensitivity and background rejection of the KOPIO
and MECO experiments. The membership of the review committee is listed
in Appendix 1. The charge to the committee is included as Appendix 2.
The agenda for the three-day meeting conducted at New York University
can be found in Appendix 3.

The committee reached consensus on its conclusions and recommendations
during the review and presented them in a closeout report at the end of
the review. The Executive Summary essentially presents the contents of
the closeout report. In the body of this report, we provide additional
discussion for each experiment of a number of topics that are important
in assessing their status and prospects.

### Discussion of KOPIO Issues

#### Running Time and Beam Fluxes

KOPIO proposes to run for 12,000 hours at the AGS with extracted proton
intensity of 100 Tp/spill (1 Tp = 110^12^ protons). The highest
demonstrated AGS intensity is 70 Tp/spill. KOPIO's ultimate sensitivity
could be less than expected if fluxes prove to be less than estimated.
This could occur either as a failure to reach 100 Tp/spill from the AGS,
or from K~L~ flux per proton in the neutral beam being less than
estimated. To the extent that KOPIO can optimize spill parameters with
any given proton intensity, the sensitivity of the experiment degrades
more slowly than linear with decreased intensity. A run with an
optimized spill at 70 Tp/spill provides sensitivity only about 15% worse
than running at 100 Tp/spill for the same duration. This is fortunate
since significant effort will be needed to achieve 100 Tp/spill.

KOPIO's estimate of K~L~ flux produced at 42 in 25.5 GeV proton
interactions with a thick Pt target is based on measurements of the
E-802 charged-particle fluxes produced by 14.6 GeV/c protons. The yield
at 42 is scaled to the desired proton energy using small-angle
charged-particle production data at 23.1 GeV/c. Similarly, the K~L~ flux
from Pt is estimated using the A-dependence of the measured yields from
Be, Al, Cu, and Au targets. While these procedures are reasonable, there
are uncertainties associated with them. The KOPIO collaboration quotes a
20% uncertainty in the resulting K~L~ flux.

Thus, shortfalls in both proton intensity and K~L~ flux per proton are
possible. This illustrates the importance of the fact that KOPIO's
success does not hinge upon making a branching fraction measurement with
high precision. Rather, it rests upon convincingly establishing a signal
for K~L~×Ø and making a moderately precise branching fraction
measurement, which in principle should be possible with significantly
less than 12,000 hours of data taken with less than 100 Tp/spill.

#### Microbunched Beam and Extinction

KOPIO requires beam microbunches of width less than 200 psec spaced by
40 nsec with extinction between microbunches of one part in 10^3^. This
should be achievable. We are encouraged by a 2002 AGS experimental
observation of 240 psec wide bunches using a single 93 MHz cavity. We
are also encouraged by a 2004 experiment, at 4.5 MHz, that observed an
extinction of one part in 10^5^, far better than needed. But we are
concerned that (1) neither result was obtained at high intensity, and
(2) the extinction result was observed at a much lower frequency.

During normal acceleration, protons are rapidly lost if they are not in
an rf bucket. But during a flat top, protons can persist outside of an
rf bucket. KOPIO requires higher frequency bunching than is used in
normal AGS acceleration. So it is planned, after acceleration (at 4.5
MHz), to de-bunch after acceleration, and re-bunch at the higher
frequency (25 MHz). Since the energy is constant during this procedure,
protons could, in principle, survive between rf buckets. The extinction
could be spoiled by problems either in the re-bunching, or by any
mechanism that moves protons out of a bucket into the continuum. Noise
in the rf during bunching might do the former. Energy loss from scraping
on an extraction septum or collimator could do the latter, as could a
longitudinal instability. Either mechanism could be worse at higher
intensities. Such problems seem more likely at the higher bunching
frequency, since the protons need to migrate a shorter distance into the
inter-bunch region. Such problems might be worse with a very long flat
top (5 sec), as planned by KOPIO, that leaves more time for the bunching
to spoil.

We have no specific reason to believe that such mechanisms will be
present, and thus no reason to believe that the required extinction will
not be obtained. But the tests made to date do not guarantee that
problems will not be encountered when the KOPIO rf systems are used at
high intensity and slow extraction. Better simulation is promised, and
is clearly desirable, but instabilities are hard to predict. We thus
believe it is important to build the proposed system, and test it at
high intensity, as soon as possible.

Therefore, we recommend that KOPIO, as soon as possible:

-   Perform tests with the AGS to measure beam microbunch width and
    inter-bunch extinction at full intensity (at least 70 Tp/spill) and
    to demonstrate the necessary bunch widths and extinction are
    achieved.

#### Software and Simulations

KOPIO employs a mixture of simulation tools to address various beam and
detector issues, including GEANT3, GEANT4, FLUKA, and others. The tools
employed represent state-of-the-art and appropriate choices. Signal and
background issues are addressed primarily with a "parameterized" Monte
Carlo called FASTMC. While this is a standard approach at an early stage
of an experiment, KOPIO has reached the point where more realism is
needed if subtle issues of background rejection, such as the effects of
noise hits upon reconstruction efficiencies, are to be reliably
addressed.

FASTMC provides a first pass effort to account for signal inefficiencies
resulting from the construction of higher-level event parameters such as
tracks and clusters in a high rate environment. Nevertheless, we are
concerned that unaccounted for losses associated with forming clean
Pre-radiator tracks and linked calorimeter clusters will be significant.
KOPIO is beginning to account for reconstruction and rate-related
losses, which in aggregate now correspond to a loss of 57%. Additional
losses being considered, such as Pre-radiator cluster splitting, are
coming in each at several percent, further eroding the signal
efficiency. These trends have been seen in previous rare decay
experiments such as the KTeV experiment where unaccounted-for
reconstruction losses and rate effects corresponded to a factor of two
loss of final signal efficiency for K~L~^0^ee with respect to initial
projections at a stage similar to the state of KOPIO today. Similar
losses in KOPIO, compared to current estimates, seem quite plausible to
us. Therefore, it is of the utmost importance to develop more realistic
simulations which provide full digitization of detector signals, so for
instance the interference between hits can be correctly modeled, and to
develop realistic reconstruction algorithms that operate on the
realistic "raw data." We recommend that KOPIO, as soon as possible:

-   Develop a detector Monte Carlo with full digitization of detector
    signals, and realistic event reconstruction starting from "raw data"
    in order to validate background estimates.

Manpower currently devoted to simulations was reported to be 4.5 FTEs.
The committee did not probe this estimate, but notes that it includes a
number of 0.5 FTE contributions, so that the number of persons focusing
on these issues is quite small. A significantly higher level of effort
will be required to implement our recommendation, and to develop an
appropriate analysis framework to provide collaboration-wide access to
MC and data analysis tools.

#### Background Rejection 

Background rejection is the critical issue in the KOPIO experiment.
KOPIO has invested significant effort in developing a strategy based on
both kinematic information and photon vetos to deal with all identified
backgrounds using their fast Monte Carlo. The most important background
sources are K~L~ and K~L~e. The signal-to-background level is estimated
to be 0.42 for events with both photons measured in the Pre-radiator,
giving an angle measurement, and about 0.28 for events with only one
photon striking the Pre-radiator (assuming K~L~×Ø occurs at 310^11^).

The Photon Veto system presents a particular vulnerability, owing to the
exceptional performance requirements in terms of photon inefficiency and
low energy threshold in the presence of high rates associated with a
very intense neutral beam. Current estimates of photon inefficiency are
based on E949 below 200 MeV and on FLUKA for energies above 200 MeV.
However, the E949 beam and geometry are significantly different than
that of KOPIO. We are concerned that KOPIO's much larger system,
operating in a significantly different beam environment, poses many
difficult challenges.

Great care should be taken to closely couple the simulations and the
engineering design. We are especially concerned about mechanical
supports and mechanical joins or gaps in the barrel and forward detector
subsystems such as: the \"projective\" seams between cylindrical barrel
Shashlyk modules, seams at the supports between forward Pre-radiator
modules, and supports at the mechanical interface to outer Photon Veto
modules added in the cylindrical barrel design. All regions should be
studied as a function of photon energy in GEANT3/4 simulations with a
realistic geometry description of the mechanical components and with
statistics sufficient to characterize their effect on veto inefficiency
and signal reconstruction.

While simulations will be an important input to the design process,
confidence can only come from an experimental demonstration that a fully
engineered (i.e., buildable) system will achieve the photon
inefficiency. Therefore, the committee recommends that KOPIO, as soon as
possible:

-   Develop a fully engineered design for the barrel photon veto, build
    a full-scale prototype, and subject it to beam tests to validate
    that it achieves the required performance.

[Detector and veto rate considerations.]{.underline}

KOPIO requires a high level of background rejection from veto systems
that must operate in a very challenging rate environment, which results
from kaon decays and from soft particles associated with the intense
neutral beam. Reducing detector rates to acceptable levels hinges on
designing the beam and associated shielding to minimize beam halo and
soft particle fluxes so that they are not the dominant sources of
detector rates (as compared to kaon decays).

Realistic simulations are an important part of the design process for
the beam and shielding. There are a number of areas where KOPIO could
benefit from more detailed simulations. For example:

1.  The contour of the carbon fiber composite beam pipe could be
    optimized. (The pipe will both intercept outer halo neutrons and
    degrade their spectrum since carbon is a good moderator.)

2.  Neutrons in the detector volume can be moderated by hydrogenic and
    light materials. (There will also be neutron capture, with the
    attendant capture gammas. In some detectors these low energy gammas
    can cause singles rate and correlated rate problems via single and
    double Compton scattering. Their implications for detector
    performance should be evaluated.)

3.  All moderate and low energy fluxes should be checked for potential
    detector impact, particularly on veto inefficiency/deadtime. These
    fluxes are not reliably modeled by GEANT3 with GHEISHA or FLUKA.
    (For GEANT4 neutron transport options, GEANT4 experts should be
    consulted.)

The next line of defense against high rates is excellent timing from the
veto systems. KOPIO has made well-motivated and elegant detector
technology choices to provide the required timing performance. However,
of particular concern is the performance of the Beam Catcher, which must
function in a 10+ GHz beam of neutrons. The design of the Beam Catcher
has been validated in low intensity beam tests, but there have yet to be
high intensity tests that can challenge the requirement of 3 nsec
double-pulse resolution. A demonstration of this timing performance,
short of an actual beam test, would be an important next step in
reducing the technical risk associated with the veto systems. Also of
concern is the role that the Pre-radiator must play as a veto system.
The Pre-radiator system is the only KOPIO veto system with projective
readout, which exacerbates rate effects. In contrast the Barrel Veto,
Calorimeter, and Beam Catcher are \"pixelized\" with a tower geometry,
which significantly reduces the maximum rate/channel. The KOPIO
collaboration should work expeditiously to develop a strategy to
explicitly use Pre-Radiator data to form veto objects so that the
associated signal losses can be understood, and possibly mitigated with
design changes at this early stage.

While detailed simulations are critical for successful beam and
shielding design, due to the high risk associated with the neutral beam,
and the experience of many previous rare kaon decay experiments which
found that beam backgrounds were their limiting factor, it would be wise
to design and build the neutral beam as soon as possible, and test its
actual performance. Therefore, the committee recommends that KOPIO, as
soon as possible:

-   Design the neutral beam and shielding, install it, and perform beam
    tests (using specialized detectors) to establish that the properties
    of the beam (e.g., n halo) meet the requirements of the experiment.

We note that having the actual beam would also make it possible at an
early stage to remove the uncertainties (discussed earlier) in the K~L~
flux. It would also provide perhaps the only appropriate test beam in
the world for the Beam Catcher.

# Discussion of MECO Issues

#### 

#### Running Time and Beam Fluxes

MECO proposes to run for 10^7^ sec (about 2800 hours) with 40 Tp/spill
from the AGS, after the running required to commission the experiment
has been completed. This would provide a single event sensitivity of
210^17^. This depends on achieving an extremely high /p ratio, several
orders of magnitude higher than any previous experiment. This is a
feature of the capture of pions by the graded solenoid that MECO
employs. Muon flux estimates depend not only on the capture, but also on
the cross section for low-energy pion production by 8 GeV protons, which
is not well-known, and estimates of the stopping probability and capture
probability.

The estimation of the pion flux produced by 8 GeV protons on a long gold
target is estimated from measured pion yields from 10 GeV protons on Ta.
The experimental invariant cross sections are scaled to 8 GeV using
several hadronic models. GEANT3 FLUKA and GEANT4 QGSP appear to be the
best suited for this purpose. However, the predicted low-energy pion
multiplicities from these codes do not agree well with thin-target
measurements. MECO uses a conservative estimate of low-energy pion (and
consequently muon) fluxes in their subsequent estimation of beam rates.

While there are uncertainties in the MECO flux estimates, they do not
seem unduly optimistic. Perhaps the most optimistic assumption is 40
Tp/spill from the AGS. Fortunately, some shortfall can be made up by
additional running time.

#### Beam Extinction

MECO requires that the protons be captured in just two rf buckets (the
AGS rf provides 6 buckets, all of which are normally filled), spaced by
1.35 microseconds. In each bucket there would be 210^13^ protons (about
double that in each bunch in normal AGS running, but giving fewer total
protons per fill). MECO requires exceptional extinction between these
two bunches: no more than one part in 10^9^. In order to achieve this,
it is proposed to destabilize unfilled buckets during acceleration and
extraction, and in addition provide an active kicker system in the
extraction line to remove protons between the bunches.

We are encouraged by the experimental observation of extinction as good
as one part in 10^7^ when operating near the MECO energy. This was at
low intensity, but used the same rf as would be used in MECO. We note
also that once the required extinction is achieved, migration into the
intra-bunch region requires relatively long drift and might be expected
to be slow compared with the loss from the destabilization. The use of
the second level of extinction in the external beam line appears sound.

Nevertheless, unexpected instabilities could cause problems, and might
not be apparent until the system is operated at the required intensity.
Since the success of MECO depends on achieving the target level of
extinction, we recommend that MECO, as soon as possible:

-   Perform tests with the AGS to demonstrate the required extinction
    when running at 8 GeV with intensity of at least 20 Tp/spill.

We note that the MECO goal is running with 40 Tp/spill, and of course
tests at that intensity are desirable. However, our understanding is
that due to both technical and administrative reasons, it may be
possible to perform the required tests much earlier if the intensity
does not exceed 22 Tp/spill. Our emphasis is on performing early tests
at an intensity at which MECO could operate viably, even if it is below
the optimal intensity.

#### Software and Simulations

MECO employs a mixture of simulation tools to address various beam and
detector issues. There are multiple issues, which overlap with
background rejection and other issues discussed later in this report.
These include: simulation of the particle fluxes and transport through
the magnetic channel, simulation of the detector performance, and an
analysis framework for the experiment.

MECO has made good use of GEANT3 to simulate particle fluxes from the
production target and graded field solenoid, as well as transport
through the S-shaped collimator and p-absorber. If simulation now turns
to the question of particle trapping/latency in the upstream section,
care will be required to check the numerical accuracy for trajectories

making many turns in the trapping region (as it has been checked already
for particles that transport through the system normally).

Problems involving neutron transport require other tools. Work in other
experiments has shown that that neutron transport from high energy down
to thermal can be simulated consistently (typically to within factors of
1.05 to 2.00 depending on energy, material type, and material depth)
using GEANT/Gcalor or Standalone FLUKA. (These fluxes are not reliably
modeled by GEANT3 with GHEISHA or FLUKA. For GEANT4

neutron transport options, GEANT4 experts should be consulted.)

There are a number of areas where MECO could benefit from more detailed
analysis using these codes. For example, neutrons produced in the
stopping target will be moderated by any hydrogenic and light materials
in the detector. In turn, there will be neutron capture, with associated
capture gammas. In some detector designs these low energy capture gammas
can cause singles rate and correlated rate problems via single and
double Compton scattering. In MECO, the rate of such effects in the
three-layer scintillator shield should be calculated from simulation.

Also if, until now, collimator performance has been evaluated using only
GEANT3 with GHIESHA or (internal) FLUKA, it should be re-simulated with
neutron transport

codes. There may be unexpected problems associated with low energy
neutrons or photons produced in the collimators. In general, all fluxes
transported by the above codes should be checked for unwanted effects,
such as the creation of false signals or increases in the veto deadtime.

Simulation of the detector performance plays a critical role in
background estimates. Presentations at the review described the status
of simulations of the straw tracker, the calorimeter, and the cosmic ray
veto. Our concerns focus on the straw tracker, which provides the
ultimate background rejection through the precision measurement of
electron momentum. The issue is whether the high rate environment
introduces problems that have not been fully simulated. An effort has
been made to include such effects, but without a full MC simulation
which digitizes detector signals and correctly deals with cases such as
two hits close in time on the same wire, coupled with a realistic
pattern reconstruction algorithm, we are not confident that possible
pathological topologies have not been overlooked, or that inefficiencies
(after all cuts) may not prove to be larger than expected. Therefore,
the committee recommends that MECO, as soon as possible:

-   Develop a detector Monte Carlo with full digitization of detector
    signals, and realistic event reconstruction starting from "raw data"
    in order to validate background estimates.

Closely related to implementing this recommendation is the matter of
establishing a framework that integrates Monte Carlo, reconstruction,
and data analysis code and makes it accessible to the full
collaboration. MECO's plan for such a framework, described to the
committee, is a good one. However, a significant infusion of manpower
will be needed to implement it. We were told that current
software/simulation manpower is 4-5 FTEs, while about 7.5 FTEs are
needed. The estimate for what is needed is reasonable.

#### Background Rejection

The signature of a signal in MECO is the appearance of a 105.1 MeV
electron coming from the stopping target. The most serious potential
background comes from radiative pion capture. This background will be
rendered insignificant by the pulsed beam structure with 10^-9^
inter-bunch extinction. Failure to achieve this extinction would
seriously limit the experiment. Thus, we have already emphasized the
importance of demonstrating this level of extinction as soon as
possible.

The other important backgrounds come from the muons themselves and from
cosmic rays. Here one can be guided both from the experience of the
previous SINDRUM-II experiment and from simulation. The intrinsic
background from muon decay in orbit is suppressed by good momentum
resolution for the electron in the vacuum straw tracker. The advertised
resolution, which is dominated by multiple scattering in the straws, is
adequate. The concern that needs to be addressed through more realistic
simulations is the possible mis-measurement of electron momentum that
could result from pattern reconstruction errors that become possible in
the presence of very high rates. I.e., noise hits can corrupt the "real"
hits. Also, it is at least possible that realistic pattern recognition
algorithms do not provide the expected efficiency in the presence of
high rates. MECO has addressed these issues within their existing
simulation framework, but more realistic simulations are needed. This
has been addressed by our earlier recommendation for developing full
detector digitization in the Monte Carlo and pattern recognition
algorithms that operate on the MC-generated raw data.

An efficient cosmic-ray veto shield will reduce the cosmic ray
background to a negligible level. This can be verified in the
experiment, since cosmic-ray background events should extend well beyond
105 MeV. The presentation at this review on the cosmic ray veto system
and the associated simulations left the committee with confidence that
this is unlikely to be a problem for MECO.

In summary, the required background rejection depends on achieving the
target extinction and the projected detector performance, especially for
the tracking system. The needed extinction should be demonstrated as
soon as possible. More realistic simulations can address the tracking
issues.

#### Detector Performance

The MECO detector technologies are well suited to the low-mass, speed,
and resolution requirements of this very challenging experiment. MECO is
not inventing new technology to meet these requirements, but rather is
pushing existing tracking and calorimetry techniques into new regimes.
Operating straws and lead-tungstate crystals in vacuum present
significant engineering challenges. The collaboration has addressed many
of these, but several remain. Notable among the challenges is the
effective cooling of the crystal calorimeter and readout in vacuum
without the introduction of substantial dead material, and the operation
of the straw readout in vacuum subject to a high radiation field. Before
production begins on these key detector systems, fully engineered
prototypes should be operated in vacuum to understand cooling of
calorimeter systems, and possible damage mechanisms of the straw
readout. Of particular concern for the straw readout are etching of the
straw conductive surfaces by fast gases in a radiation field, and
degradation of the straw mechanical properties in the high radiation
field.

MECO has initiated a detailed simulation of the detector systems and has
presented plausible arguments that the spectrometer systems have
sufficient pattern recognition capability and resolution to suppress
known backgrounds to the design level. Much work remains to be done to
assess and account for reconstruction losses associated with rate
effects and detector deadtime, particularly in the straw tracking
system. This is addressed by our recommendation concerning full MC
digitization of detector signals and realistic reconstruction
algorithms. The review committee notes that the performance of the muon
veto shield system may be over-specified, since the estimated background
contribution from cosmic ray muons is far less than other sources.
Relaxing the performance of the muon veto system may reduce deadtime
(caused by beam related processes) from this veto system and possibly
lower costs to the project.

#### Magnetic Field Tolerances and Pathological Trajectories

Magnetic field in the transport solenoid was designed to eliminate
unwanted long-latency (i.e., trapped or nearly trapped) particles by
requiring a graded field in each straight section. The field
specification is conservative and has been confirmed by detailed
calculations to be robust. The committee, however, is still concerned
that there is some risk of a defect in the field, such as a local
minimum. Trapped particles in such field, by being delayed or by
scattering into the acceptance of the detector, could introduce
background since no suppression factor from extinction would apply. In
addition to such trapping, distorted trajectories of particles would
modify the beam profile and hence degrade the effect of the collimators,
which may affect efficiencies and detector rates as well as background
rejection. Therefore, continuing studies should focus on anomalous
trajectories using realistic simulations which assume field defects to
understand their possible effects. Also, serious consideration should be
given to monitoring the field to identify any anomalous features if they
develop, from whatever cause.

While we are impressed with work already done by MECO understand these
issues, and we have no specific reasons to question the results, we
recommend that MECO:

-   Continue to develop more realistic simulations of the full
    target/transport channel/detector chain to further explore exotic
    background scenarios.

## 

## Discussion of Issues Common to KOPIO and MECO

This review focused on the simulations, with emphasis on estimates of
sensitivity and backgrounds. Beam and detector issues are inextricably
related to those estimates, so they were also considered. The committee
did not receive any information on schedules. Nonetheless, to reinforce
our emphasis on giving high priority and immediate attention to some
issues that have potentially far-reaching consequences, the committee
makes one recommendation with respect to the schedules. The committee
recommends that [both]{.underline} KOPIO and MECO:

-   Develop deliverables-based schedules with performance milestones,
    which include the steps recommended in this report planned for
    completion as early as possible.

By doing so, dangerous surprises may be avoided later. If serious
problems are found early, there will be a much better chance that
solutions can be found and implemented in time to avoid major
degradation of the experiment.

## 

There were no presentations at this review on scenarios for AGS slow
spill running for RSVP. Informally, the committee was told by a BNL
representative that, while perhaps conservative, projections are that 15
weeks of 80 hours/week of slow spill AGS running per year are possible
with RHIC (assuming RHIC runs 29 weeks/year). An additional 10 weeks of
120 hours/week without RHIC are also possible. This suggests only 1200
to 2400 hours per year of RSVP running, which must be shared by KOPIO
and MECO.

Short running periods of 2400 hours or less will not only cause RSVP
running to require many calendar years, but will also introduce
considerable inefficiency due to the edge effects associated with
startups. The integrated cost of RSVP running will undoubtedly increase
in such a scenario. While it is outside the scope of this review, it
seems clear that BNL needs to give high priority to maximizing the slow
spill running available during RHIC operation. The success of RSVP may
depend on this.

Additionally, it is important to have a sensible distribution of
available running time between KOPIO and MECO. The specific needs will
depend on the status of the experiments and cannot be predicted today.
However, a good guideline for planning is that long runs, separated by a
period of sufficient duration to analyze the data, will be much more
efficient and useful than short runs of both experiments every year.
That is, alternating full-year KOPIO and MECO runs is likely to be much
better than running both experiments each year.

## 

## Finally, we wish to emphasize the essential role the AGS, and therefore the AGS staff, must play in RSVP. Both KOPIO and MECO require the AGS to achieve challenging performance parameters that have never been achieved in the AGS, and indeed never achieved in any machine. A close working relationship between the collaborations and the AGS will be essential. 

## 

## Appendix 1

### Membership of the Committee

### 

> Prof. Edward Blucher Dr. Cyrus Hoffman
>
> University of Chicago Los Alamos National Lab, ret.
>
> blucher@hep.uchicago.edu choffman9@comcast.com
>
> Dr. Patricia McBride Prof. Jack Ritchie, Chair
>
> Fermilab University of Texas at Austin
>
> mcbride@fnal.gov ritchie@physics.utexas.edu
>
> Prof. Michael Shupe Dr. Robert Tschirhart
>
> University of Arizona Fermilab
>
> shupe@physics.arizona.edu tsch@fnal.gov
>
> Dr. Koji Yoshimura
>
> KEK
>
> koji.yoshimura@kek.jp

##### List of Observers

> Marv Goldberg, NSF
>
> Alex Firestone, RSVP Project Office
>
> Jon Kotcher, RSVP Project Office
>
> Jack Lightbody, NSF
>
> Bob Palmer, BNL
>
> Bill Willis, RSVP Project Office

**Appendix 2**

### Charge to the Committee

**RSVP Detector Capabilities,**

**Simulations and Backgrounds Review**

**CHARGE**

\[1\] For each of the KOPIO and MECO experiments, determine if the
proposed detectors are capable of achieving the stated sensitivities and
background suppression. Specific questions to address include:

\(a\) What is the current status of the detailed detector design?

> \(b\) Is this design capable of achieving the desired resolutions,
> efficiencies, and hermeticity?

\(c\) What is the current status of the simulation studies?

> \(d\) Do they indicate that acceptable signal and background levels
> can be achieved?
>
> \(e\) How is the field specified in detail in the MECO magnet system,
> and\
> what method is used to determine these specifications?  What is the\
> consequence for the rates and backgrounds if the desired field
> accuracy in\
> various aspects is not achieved?
>
> \(f\) What is the current status of beam studies? In particular, can
> desired extinction levels be achieved?
>
> \(g\) Given the detector status in (a) thru (f) above, how much
> running will be required to achieve the stated sensitivities?

\[2\] If any of the issues in \[1\] above are judged to be currently
inadequate, what does the review committee recommend doing to achieve
the stated sensitivities and background rejection? What additional
resources will be required to accomplish this? What time will be
required to accomplish this?

\[3\] Are there any organizational, personnel, or resource issues which
may hinder achievement of the stated sensitivities? If so, how does the
review committee recommend they be addressed?

### Appendix 3

**Agenda**

  -------------------------------------------------------- --------------
  **Tuesday, 11 January: KOPIO Experiment**                **Time**

  **Morning Session**                                      

  Executive Session (30')                                  08:30-09:00

  KOPIO Overview (Bryman -- 30')                           09:00-10:00

  AGS & Beams (Sivertz -- 30')                             10:00-10:30

  BREAK (15')                                              10:30-10:45

  Detector (Littenberg -- 45')                             10:45-11:30

  Signal & Backgrounds (Jaffe -- 60')                      11:30-12:30

  LUNCH (90')                                              12:30-14:00

  **Afternoon Session**                                    

  Conclusions (Littenberg -- 15')                          14:00-14:15

  Executive Session/Discussion (120')                      14:15-16:15

  Questions to KOPIO, as needed (60')                      16:15-17:15

  ADJOURN                                                  17:15

                                                           

  **Wednesday, 12 January: MECO Experiment**               **Time**

  **Morning Session**                                      

  Executive Session (30')                                  08:30-09:00

  MECO Overview/Sources of background (Molzon -- 45')      09:00-09:45

  Proton Beam & Extinction Requirements (Molzon -- 15')    09:45-10:00

  Production Solenoid Environment (Tumakov -- 30')         10:00-10:30

  BREAK (15')                                              10:30-10:45

  Muon Beam Simulations (Tumakov -- 30')                   10:45-11:15

  Magnetic Field Specifications & Tolerances (20')         11:15-11:35

  Tracker Requirements & Simulations (Hebert -- 40')       11:35-12:15

  LUNCH (90')                                              12:15-13:45

  **Afternoon Session**                                    

  Calorimeter Requirements & Simulations (Djilkibaev --    13:45-14:05
  20')                                                     

  Cosmic Ray Veto Requirements & Simulations (Kane -- 15') 14:05-14:20

  Plans for WBS 1.3.9 Simulations &                        14:20-14:30
  Analysis(Kolomensky--10')                                

  BREAK (20')                                              14:30-14:50

  Executive Session/Discussion (120')                      14:50-16:50

  Questions to MECO, as needed (70')                       16:50-18:00

  ADJOURN                                                  18:00

                                                           

  **Thursday, 13 January**                                 

  Executive Session (30')                                  08:30-09:00

  Answers to Questions from KOPIO (60')                    09:00-10:00

  Answers to Questions from MECO (60')                     10:00-11:00

  BREAK (15')                                              11:00-11:15

  Executive Session (105')                                 11:15-13:00

  Closeout (60')                                           13:00-14:00

  ADJOURN                                                  14:00
  -------------------------------------------------------- --------------