June 6, 2007

Report of the 2006 External Review Committee
for the Institute for Cosmic Ray ResearchCommittee members:
B. Barish, J. Cronin, W. Hofmann, K. Kodaira, K. Nakai,
H. Sugawara (chairman), A. Suzuki, Y. Tanaka

The committee reviewed the scientific activities of the Institute for Cosmic Ray Research(ICRR). The hearing session was held on October 19 and 20 of 2006 at the Kashiwa campus
with all the committee members attending. The schedule of the hearing session is listed inappendix B.

The committee evaluated some of the completed, on-going and future projects. It

also makes some comments on ICRR organizational issues.

1. Summary

A. General research environment to which ICRR is currently exposed

The committee understands that the current emphasis of scientific research in general is towards
its applications, not only in Japan, but worldwide. Cosmic ray physics and astro-particle physics
are among the least interesting fields for those who are exclusively interested in the industrial
applications of science and technology. The main problem for basic research is the generally
negative attitude towards fundamental science. The huge Japanese national budget deficit also
is affecting the minds of government officials who hesitate to invest in basic science.

The lack of appropriate funding for rather expensive scientific projects is often attributed toorganizational or structural problems in the university system. This structural issue is important,but it could be corrected if the interested parties can reach an agreement.

This will be

discussed in section 3 of this report.

Another point the committee wants to make is that many of the ICRR projects should beinternational collaborations.

In order to facilitate international collaborations ICRR needs tonourish an environment in which varieties of ideas and approaches can be incorporated. The
committee, therefore, recommends that ICRR hire more Japanese women researchers, as well
as more women and men foreign researchers.

B. Summary of review of individual projects
The committee highly appreciates the contributions to the scientific community over the last
several years of Super-Kamiokande and K2K. The properties of neutrinos have been muchclarified, although there still remain some important parameters to be fixed in future experiments,
such as θ13 or the CP parameter “δ”.

Super-Kamiokande must be ready to observe the next nearby supernova explosion by making it
more sensitive to neutrons and it should also be prepared for the next generation of long
baseline neutrino experiments (T2K). The committee is happy to learn that ICRR is working hard
towards this goal.

Understanding the properties of dark matter, or just finding what it is, profoundly affects particle
physics and cosmology. In principle we should be free of any prejudice about what it could be,
but in practice the design of the detector needs some guidelines and it is probably acceptable tofollow the currently popular idea of dark matter being the neutralino. The XMASS project, which
is being designed along this line, is a fine one. The committee acknowledges the R&D activitiesof this project and it appreciates that the plan of splitting the project into two stages is areasonable procedure.

AGASA has provided the community a controversial, but potentially exciting set of data on thehighest end of the cosmic ray spectrum. Currently, the most sensitive detector is the Auger
South; it is five times more sensitive than the Telescope Array (TA). The committee understands
that the two detectors are complementary in that they use different methods of spectrum
measurements: the TA uses a scintillator that is sensitive to the electromagnetic component
and Auger uses a water tank that primarily is more sensitive to the muon component. The
committee recommends that the TA group should not exclude the possibility of joining
international collaboration at certain stage unless some phenomenon which is unique to thenorthern hemisphere permits them to stay independent.

The committee is not unanimous in judging the rather ambitious Ashra detector (described in thenext section). It is certainly tantalizing to have an all-sky detector, but sensitivity is an importantelement too. The Ashra may be restricted to observe gamma rays from AGN, but not much else.
The committee was impressed, however, by the ongoing R&D which is going rather well.

CANGAROO I and II provided rather controversial data and it was worth the effort in provoking
the community. CANGAROO III could still contribute to this field, but it needs further
improvement of the mirrors. The committee recommends strengthening the group by
internationalizing the project further.

The committee acknowledges the air shower array in Tibet would, after its upgrading, contributesignificantly to the observation of gamma ray with the energies of 100 TeV or higher. This effort
is in contrast to the other gamma ray detectors, which emphasize the importance of reducing thethreshold value. The committee recommends that the Tibet Array should also emphasize
research determining the primary cosmic ray components. This is a classic problem, but it still isan unsolved important issue.

The committee appreciates highly the extremely productive activities of Sloan Digital Sky Survey(SDSS). This is one of the most successful international and interdisciplinary projects. The
committee also appreciates the Japanese contribution led by Fukugita. Among many importantscientific achievements it is gratifying that the determination of cosmological parameters,
especially of the value of the cosmological constant, has been given an independent check on
the WMAP results.

The last frontier of astronomical observations is that of gravitational waves. The committee
appreciates the R&D effort of the Japanese group led by ICRR, especially on the cryogenic
system. Although the committee’s role is not to survey the ICRR future plans, it strongly
recommends that ICRR seriously consider working with other institutes and possibly withinternational participation on the construction of interferometer system with cryogenics.

２． Evaluation of Individual Projects

A. Super-Kamiokande, K2K and T2K

Super-Kamiokande

From 2000 to 2006 Super-Kamiokande (SK) had two shutdowns due to a November 2001 chain
implosion accident: one in 2001-2002 (1 year) and the other in 2005-2006 (~10 months). SK wasreconstructed first to half the original PMT density and then to the full level. The committee
congratulates ICRR on the full recovery of SK in such a short time, made possible by theexcellent, hard work of the ICRR group.

After the discovery of neutrino oscillations in 1998, the study of atmospheric neutrinos from 2000
to 2006 with larger statistics has produced further results on neutrino oscillations, specifically theprecise determination of oscillation parameters, the discrimination between νμ to ντ and νμ toνsterile oscillations, the L/E dependence of oscillations, and the appearance of ντ.

As for the study of solar neutrinos, the comparison of solar neutrino fluxes between SK and SNO
charged-current measurements,

which was done in 2001, gave direct evidence for solar

neutrino oscillations. This has solved the long-standing mystery of the “solar neutrino problem”.
In 2002 global analysis, combining the precise measurements of SK with other solar neutrino
experiments, showed that the LMA (Large Mixing Angle) solution is the most favorable one with
99% C.L.

The committee finds that Super-Kamiokande made critical contributions in understanding thenature of neutrinos and continues to produce essential physics. The committee expects further
outcomes in the next decade by (1) searching for the finite θ13 in atmospheric neutrino
measurements; (2) measuring the spectrum distortion of solar neutrinos, precisely to pin down
oscillation parameters; (3) improving the proton decay life time for various decay modes; (4)watching supernova explosions; and (5) searching for supernova relic neutrinos with a thermal
neutron tagging by loading 0.2% GdCl3 into the detector water.

We also recommend studying mega-ton detectors, not only for future underground experiments,
but also for neutrino-beam experiments.

K2K

K2K was the first accelerator-based long baseline neutrino oscillation experiment, launched in
1999 and finished in 2004.

The ICRR group, as one of the host institutes for K2K, wasresponsible for the operation and the analysis of the K2K main detector, Super-Kamiokande, andfor the construction, operation and analysis of the 1k ton water Cherenkov near detector (1KT).
K2K confirmed the neutrino oscillation in the νμ disappearance mode with 4.3 σ significance. In
the analysis 1KT played an essential role in achieving that significance by providing precise
measurements of neutrino flux normalization and energy spectrum especially in the low energy
region (<1 GeV).

K2K also set the first upper bound on the mixing relevant to the νe appearance with anaccelerator-based experiment. The dominant contributions from background events are π0’s
produced in νμ neutral current interactions (NC). 1KT measured the cross section ratio of σ(νμNC1π0)/σ(νμ CC) with ~10% precision. This ratio was indispensable for evaluating the expectedbackground rate.

In summary, the committee emphasizes that K2K successfully finished and achieved its physics
goal. It provided universal knowledge on the nature of neutrinos, such as the definite
confirmation of finite neutrino masses. On top of that it should be noted that K2K established theexperimental procedure for long base-line neutrino oscillations based on accelerators.

T2K

The T2K project is the second generation long base-line experiment in which very high-intensity
neutrino beams are produced using high intensity proton beams from J-PARC. The primary
physics goals are to observe the νe appearance and to measure the νμ disappearance precisely.
The neutrino beamline is under construction and aiming to start the experiment in April 2009.
Since the T2K beam is more than 50 times more intense than the K2K beam, θ13 can besearched down to 20 times smaller than the CHOOZ limit, and the oscillation parameters of θ23
and Δm232 will be precisely measured. If the evidence of finite θ13 value is obtained, it will open
further studies of the neutrino mass matrix and the CP phase in the lepton sector. The committee
recommends that T2K should be promoted to one of the highest priority projects in ICRR.

The ICRR group is responsible for maintaining and producing data from the main detector,
Super-Kamiokande. The development of new electronics is in progress and will be replaced in2008. This is to ensure the long-term stability of detector operation, which is required by T2K.
The committee endorses this decision and recommends completion of the development onschedule so that there will be enough commissioning time.

It is also recommended that ICRR take a leading role in the calibration and data analysis ofSuper-Kamiokande. The analysis of νe appearance requires background rejection far beyond thewell-established e-like event selections, which have been used in the standard atmospheric
neutrino analysis. This imposes much better understanding and more precise calibrations of the
SK detector performance. Studies to establish the analysis procedure for the systematic errorestimation, such as those of fiducial mass, particle identification and so on, should be initiated assoon as possible in order to obtain physics results in a timely manner.

B. XMASSThe XMASS experimental search for the dark-matter candidate is the most interesting challenge
in solving the fundamental puzzle in cosmology, astrophysics and particle physics. It is also
aiming at the detection of double beta decays and low energy solar neutrinos. With the 100 kg
liquid-Xenon fiducial mass and 5 year exposure, XMASS has a sensitivity of about 10-45 cm2 forspin independent interactions.

For the dark matter search this improves the current best limit of CDMS-II by 2 orders ofmagnitude. In case the upper limit is obtained, it will constrain SUSY models and will extend
our understanding of the nature of dark matter, combined with astrophysics observations andaccelerator search for SUSY particles.

The experiment will detect recoils from interactions of neutralino (a WIMP candidate) with nuclei
in a liquid-Xe detector. The ingenious idea of using the liquid-Xe detector for detection of
low-energy recoils (<500 keV) in extremely rare events has been tested successfully with aprototype small detector (3 kg fiducial volume). The committee understands that the physics
target of XMASS with the 800 kg liquid-Xenon is strong, and endorses it as one of major projects
of ICRR.

One of the key technical issues is to construct and operate the detector in a cryogenic
environment.

The XMASS group demonstrated this capability in the prototype detector.

Another key issue in achieving this goal is to reduce background events. The XMASS groupaddresses this issue by:(1) developing low background photomultiplier tubes,(2) self-shielding property of liquid-Xenon detector is realized by giving capability of resolving
vertex position,(3) purification of liquid-Xenon, especially removing krypton by distillation. The photomultipliertubes have almost reached the required quality level of low radioactivity.

The ‘self-shielding’ technology was developed and was shown to be effective in reducing
low-energy background in the energy region less than 500 keV in the central fiducial region.

In the last several years R&D studies with the 3 kg prototype detector demonstrated that thevertex resolution was well reproduced by simulation, and that the Kr contamination was reduced
by a factor of ~1000 with distillation. Other background activities from U and Th are still higher
than the required level by a factor of 10~30. The committee urges the XMASS group to prove
the possibility of reducing U and Th contaminations inside liquid Xenon. Much experience
suppressing background from outside has accumulated at the Kamioka mine through the
Kamiokande, the Super-Kamiokande and the KamLAND experiments.
sources of background such as the

For the possible

85

Kr contamination in Xe liquid and internal radioactivities in

the photomultipliers, R&D studies have been done on greatly reducing the background during
the process of system construction.

The committee judged that the feasibility to enter the construction stage of the 800 kg liquid-Xe
detector (100 kg fiducial volume) has been well demonstrated; consequently, the committee
recommends that XMASS proceed to the first stage of XMASS experiment at the earliest
opportunity. Although the XMASS project is planned in two stages, the first-stage detector
would already reach the world’s best sensitivity with improvement of two orders of magnitudes
from the present limit. The XMASS at Kamioka is competing with the SuperCDMS at SNOLAB
and WARP at Gran Sasso. Early start of the first stage is very important.

The goal of the experiment to observe the neutralino as the most probable candidate; this issolely based on a theoretical prediction of super-symmetry. Consequently, the neutralino
dark-matter search is a highly risky mission. Nevertheless, the fundamental importancecompensates the risk, and the experimental effort has to be highly encouraged.

Thecommittee recommends concentration of efforts on the dark matter search, leaving otherexperiments (double beta decay and solar neutrino studies) for the second stage.

C. Telescope Array (including AGASA) and Ashra

Telescope Array (TA)The Telescope Array (TA) project was proposed to confirm the data obtained by AGASA and to
study the origin of the ultrahigh-energy cosmic rays. It was unfortunate, however, that the TA
proposal took a long time before approval of its funding. Auger project started much earlier with alarger scale. For reexamination of such a crucial data it is certainly important to have two ormore independent experiments. Extensive efforts by Auger and TA would be required for detailed
studies of the events, probably under international cooperation.

Committee understands that Telescope Array is a hybrid detector in the Northern Hemispherewith an acceptance of the surface array of 1200 km2sr.

This is to be compared to theacceptance of the Auger Observatory in the Southern Hemisphere of 7000 km2sr.

The TA is not yet operating, but from a technical point of view, there is no reason to doubt thatafter the usual initial problems with any large system, the TA will work very well. The sensitivityof the TA is about one fifth of Auger South.
The northern region has a more uniform magnetic field because it does not include the center ofthe galaxy and the flux from the northern sky is significantly different from that in the south. This
will make a northern detector more insensitive to the magnetic disturbances from which southern
detectors would suffer.
We note that in the next two years Auger South also will be reporting an elongation rate from 1017
to ~ 1020 eV.

The Auger collaboration will be submitting a proposal for an array covering 10000

km2 with an acceptance of about 23000 km2sr. It is not clear that this proposal will be accepted.
Data from Auger South may strengthen the case for a large northern array. It would seem that
the ICRR should consider joining a collaborative effort to develop a very large northern array
concentrating on the very highest energies. And, for the participation in international activities,
the most important question from scientific viewpoint is ‘what are original and unique Japanesecontributions?’ ICRR is considering the possibility of a major international collaboration in thenorthern detector after careful examination of the results from TA and Auger.

AGASA

There have been many discussions of the apparently different results between AGASA and the
HiRes experiments. The first difference is that the reported flux of AGASA is larger than that of
HiRes in the energy region where there are good statistics. The second is that AGASA with its
published calibration has about 11 events above 1020 eV, indicating the lack of a GZK cutoff.
The first difference is most easily accounted for by a shift in energy scale of either AGASA or
HiRes by about 30% or a shift of either by 15%. AGASA certainly measures well the parameter
S(600) (density of particles in the shower plane 600 meters from the axis).

The methodology for the measurement of S(600) is sound. However, the conversion from S(600)to energy involves simulations using hadronic interaction models in a domain of unknown
physics, which might be in error by some 30%.

However, it is important to note that theabsolute fluorescence efficiency has a systematic error of at least 16%. Also, the publishedspectrum from HiRes uses mono data, which are prone to significant errors in the geometricalreconstruction. The exact difference between AGASA and HiRes awaits the completion of the
HiRes stereo data, which has not been published. Also there are a number of experiments thatare measuring the absolute fluorescence efficiency with much greater precision. This could
lead to a significant shift in energy scale of fluorescence experiments. It is entirely possible thatthe differences between AGASA and HiRes will be greatly reduced. If the energy scales of
AGASA and HiRes are brought into agreement, the excess of events beyond the GZK cutoff is
not statistically different for the two experiments. The ICRR should take pride in the AGASA
experiment, which has been well executed.

Ashra

Despite of the fact that the project is ‘not authorized‘ as an ICRR project, the group has madeinnovative developments for a new step of gamma-ray astronomy by a personal effort being
supported by the JST fund. Ashra is a unique detector covering a broad field of view (80 % offull sky) with fine directional resolution (of about 1 arc-minutes), which allows simultaneous
monitor and observation of transient phenomena by high-energy gamma-rays as well as opticallight. The group emphasizes observation of the gamma-ray burst (GRB) to start with, andvarious possibilities are discussed. It is also notable that the all-sky long-term observation
enables Ashra to detect very rare events, such as those at ultra-high energy. The possibility tofind high-energy tau-neutrino coming out from the earth after lepton flavor oscillation of cosmic
neutrino is interesting, though it would appear only once a year or so.

The main question on this project may be, while it claims to do everything, does it do any thing
better than existing experiments? It seems to the committee that to make a success more humanresources and funds may be required to finish it.

As an all-sky optical burst monitor, it is to our knowledge unique and the chance of capturing
GRB light curves during the full burst is exciting.

Sensitivity is a bit on theedge, so it is open how many bursts this detector will see. As an all-sky VHE gamma ray
detector, its sensitivity - especially for bursts - is better than Milagro or Tibet. A lot of people
would be very happy to have an all-sky TeV burst monitor. The relatively high threshold will,
however, limit this detector to nearby AGNs. For DC sources we believe most of the work will

be done by H.E.S.S., MAGIC and VERITAS, but Ashra may still add a handful of sources, inparticular off the by then well-studied Galactic plane.

As a UHE cosmic ray observatory, this detector will see a few events with very high angularresolution. The committee would be surprised if this produces new physics.

The committee is most uncertain, but Ashra, as a UHE neutrino monitor, may be in a regime
where it is competitive but not leading. Overall, the committee is sure Ashra would produce
some nice physics, and there is some potential for surprises. The unique features of Ashra as asurvey/monitoring telescope would provide prompt information of any flushing event useful for
detailed analyses with other telescopes.

Collaboration of Ashra with telescopes such as

Subaru, H.E.S.S. as well as other detectors should be encouraged.

D. CANGAROO

High-energy gamma-ray astronomy is a rapidly developing field and the ICRR group was amongits pioneers. CANGAROO was the first modern Cherenkov telescope operating in the southernhemisphere and its initial results – such as the discovery of high-energy gamma-ray emission
from the supernova remnant RX J1713-3946 – have contributed much to stimulate the field andmotivated the construction of the CANGAROO III telescope system, as well as other instruments,
such as H.E.S.S.

Some of the spectacular claims by CANGAROO I and II have since been

retracted, with the apparent gamma-ray signals being traced to poorly understood features of theimage analysis. The improved analysis techniques developed for CANGAROO III are, however,paving the way to reestablish confidence in CANGAROO analysis and their results. Comparedto other instruments, such as H.E.S.S. in the southern hemisphere (which started operation
shortly after CANGAROO III) or VERITAS in the north (which was completed in Fall 2006),
CANGAROO III provides reduced sensitivity by a factor of about 3. This can be traced to thefact that the first of its four telescopes has an inferior camera and is not operated anymore, andthat the mirrors of all telescopes have undergone severe degradation, both concerning theirreflectivity and spot characteristics.

In addition, the smaller dish area (compared to othertelescope systems) and the location at sea level result in an increased energy threshold.
CANGAROO human resources, both at ICRR and in the collaboration as a whole, appear
marginal.

Without question, it is highly desirable to operate, besides H.E.S.S. in Namibia, anothergamma-ray instrument in the southern hemisphere, providing redundancy and cross checks andallowing the recording of transient gamma-ray emission from variable sources such as AGN
without long observation gaps. For CANGAROO to play this role in the longer term, resources
need to be invested in the replacement of mirrors and the upgrade of the camera and electronics
of the first telescope. Concerning the mirror replacement, some additional R&D is required, since
no straight-forward technical solution is at hand. The collaboration should be strengthened, inparticular seeking international partners; the committee realizes, however, that this may provedifficult at the current time. The committee supports and encourages attempts to seek funding for
the upgrade of CANGAROO. In the medium to long-term future participation in the developing
multinational efforts towards development of a next-generation instrument is recommended, as
compared to smaller-scale national activities.

E. Tibet

The Tibet AS-gamma Experiment, in collaboration with Chinese scientists, is the only operating
air shower array at high altitude.

They have a beautiful apparatus:

they can measureasymmetries at the fraction of a percent level. The current emphasis is on the detection ofhigh-energy gamma rays in the range 3-100 TeV and decomposition of primary particles aroundthe "knee region".

The committee has reviewed the results obtained so far, as well as thepotential of the experiment.

Regarding 100 TeV or higher gamma-ray astronomy, the committee takes the point of view that it
would be very important for the Tibet array to continue this effort since other detectors, such as
air Cerenkov telescopes, emphasize the lower energy region and try to lower the thresholdenergy. The currently planned upgrade of gamma-ray identification is very important.

The high-altitude array has an advantage in disentangling the classic problem of primary
composition. The recent advancement of model simulations is noticed. The key issue is thesystematic uncertainties, which would be difficult to squeeze.

The committee, therefore,suggests that they have a workshop to discuss whether the proposed upgrading is indeed
sufficient. It is also recommended that the workshop will also discuss what the future of thisproject should be.

F. SDSSThe Sloan Digital Sky Survey (SDSS) is a project to undertake a photometric survey of about ahalf of the northern sky and a follow-up spectroscopic survey of over one million astronomical

objects, complete within precisely defined criteria. The production observation started in early
2000, and SDSS-I ended in June 2005. This survey extended the volume of the well-studied
universe by a factor of more than 100. The accumulated comprehensive data were made public
as DR5 in July 2006. The SDSS data were and are being used for a wide variety of studies inastronomy and astrophysics. The representative issues are the large-scale structure of galaxy
distribution over a very large volume of the universe, detailed characteristics of properties ofgalaxies and quasars, gravitational-lens phenomena, Galaxy structure, and lowest-massmain-sequence stars.

The contribution of the 6-member Japanese Promotion Group (JPG) was mostly to photometric
instrumentation, which included (1) the design, construction, and verification of the mosaic CCD
camera with its readout electronics and pipeline, and optical filters, and (2) the initial design ofthe target selection for spectroscopy.

The general success of SDSS should be attributed

largely to the solid achievement of the 3 ICRR members in JPG, in addition to the strong initiativeand commitment of the JPG leader, Prof. Fukugita, who promoted the total SDSS Projectthroughout all the phases. Over one hundred SDSS papers carrying the names of the ICRR
members were published in international refereed journals. The most valuable contribution of the
SDSS group was the confirmation of the validity of the Λ CDM cosmology model withhigh-quality quantitative data for the middle z-range with the discovery of the acoustic peak in the
point correlation function. In summary, the SDSS activities by ICRR members in last years
were well rewarded and are highly evaluated.

Now that the initial mission by ICRR members was realized, the SDSS-II program for theremaining spectroscopic targets shall be pursued with much less commitment of ICRR, andscience results shall be harvested from SDSS database by the larger community. The huge
SDSS database is now mirrored at the NAOJ (National Astronomical Observatory of Japan) Data
Center (according to previous recommendation of this Review Committee), and is open to Asian
researchers. It is recommended that ICRR, jointly with NAOJ, actively advertise the availabilityof the SDSS database to a wide range of researches in astronomy and astrophysics. The
Japanese science community may make better use of the SDSS data in combination withobservation programs of the Subaru Telescope and the IR/X-ray Satellites.

G. Gravitational waves and the proposed LCGT project

Direct detection of gravitational waves is a major goal in physics and astronomy worldwide.

Albert Einstein predicted gravitational waves in 1916. Strong evidence for their existence wasprovided in the binary pulsar timing experiment (PSR 1913+16) of Hulse and Taylor, and we
expect direct detection will follow within the next decade. Large investments have been and arebeing made worldwide toward detection with large scale interferometers in Japan, Germany, Italy
and the U.S. The TAMA interferometer was the first large scale interferometer to become
operational for science and did several initial measurements. It has been surpassed by the
LIGO interferometers and others which are much larger and more ambitious.

LIGO is in the midst of a major data run at design sensitivity for the initial interferometers andcould possibly detect gravitational waves in the near term, but most expectations are that it will
require a major upgrade, called Advanced LIGO, to make actual detections. That upgrade has
been approved and proposed for funding by the NSF; it is included in the President’s FY08
budget and likely will be approved for funding by Congress this year.

If so, the time-scale toreach design sensitivity for an operational Advanced LIGO is about 2013 (or somewhat later).

It should be stressed that observations of gravitational waves is the beginning, not the end of this
topic. Such observations will open two important subjects: testing general relativity, even in thestrong field limit, and opening a new astronomical window, gravitational wave astronomy.
Therefore, the strategy in Japan is probably best served if a sensitive instrument can be built andmade operational on the time scale of entering into these new scientific fields.
The Large-scale Cryogenic Gravitational-wave Telescope, LCGT, is a proposed next generationinterferometer that will have sensitivity comparable to the Advanced LIGO design (expected to
be operational in seven years). The LCGT interferometer configuration is similar to that of theAdvanced LIGO, having arms 3 km long, but with some features that could give improved
performance: 1) the facility will be built about 200 m underground, significantly reducing seismic
and perhaps environmental noise; 2) the test masses in the two arms will incorporate sapphirecryogenic mirrors operating at 20 degrees Kelvin.
The unique feature of the LCGT design is its use of a cryogenic system to suppress thermal
noise.

Sapphire was chosen for the substrate material because of its optical thermal

conductivity and measured high Q values at low temperatures.

A test interferometer, theCryogenic Laser Interferometer Observatory (CLIO), has100 m arms and sapphire test masses.
The CLIO project has operated with all mirrors cooled down to 20 K degrees, but there were heatflow issues; These have been fixed and the heat flow has been reduced. CLIO is being tested
to improve the performance of the interferometer. Due to the reduced seismic backgrounds

underground, the 100 m CLIO interferometer promises to exceed LIGO and Virgo sensitivities atvery low frequencies.
The LCGT was proposed to cost $130 million, but funding proposals in both FY2006 and FY2007
were not approved. The reorganization of funding in Japan for large projects for fundamental
research was an important contributing factor. The LCGT group remains committed and themembers are actively pursuing their goals. LCGT has sought and received strong support fromthe international GW detector community, anticipating that LCGT will become an important partof a global network doing gravitational wave astronomy.
A new proposal is being submitted for FY2008, stressing international collaboration.

The

Japanese efforts in this area are unique (cryogenic). They also are important members of thelarger international community and collaboration.

The potential science in the field ofgravitational waves is truly exciting and ground breaking, including both profound tests of generalrelativity and a new way to observe the universe.
Our committee could not perform a technical review of LCGT in the limited time available, but wecan confirm that the goal of developing a cryogenic detector is unique and that this project could
enable Japan to play a very important role in the evolution of an exciting new field of physics andastronomy.
H. Theory

The tiny theory group at ICRR is not only contributing to the experimental activities of the institute,but it also is contributing much to the understanding of particle physics and astrophysics, working
with the researchers outside the institute. The theoretical framework which is popular at thepresent stage of physics (the so-called standard model or supersymmetric version of it withgravity) is not so powerful in predicting what to expect in certain experiments, due mostly to theappearance of too many parameters. This largely results from the lack of understanding offlavor physics.

It is, therefore, hard to design a detector for finding something with somecertainty. However, the group is making much effort to contribute towards this goal. The time may
be coming that theorists should reconsider the validity of standard cosmology (due to thediscovery of dark energy and dark matter) and/or the standard particle theory (due to LHC or ILC
results which may be coming soon). Critical review of the existing theoretical scheme may benecessary at this stage. The committee strongly encourages the theoretical effort leading tosuggestions for future experimental developments."

３． Comments on the organization of ICRRIn the review, some of the organizational difficulties of ICRR as an inter-university institute havebecome evident.

Typical examples are the CANGAROO and AGASA-TA projects. In these cases Japanese
teams pioneered new fields through very interesting discoveries and kept leading positions for awhile, but when other foreign groups joined the research field, the Japanese teams were not able
to compete with them.

This could be attributed to weak funding. Even so, theinternationalization of the projects could have been more robustly pushed forward.

The main financial difficulty (which did not exist before 2005) is that all the university-affiliatedresearch laboratories must submit their budget proposals through the university management.
Before 2005 they were able to submit their budget more or less directly to the ministry. The
purpose of the change was to increase the autonomy of each university. However, the result isthat institutes such as ICRR must compete with other institutes within the university. In addition,
ICRR is open to all users, not just those within the university. ICRR interests could be in conflictwith the interests of the university.

There is another governmental funding system called “Kakenhi” whereby individual researchers
can submit a proposal. Some of the ICRR projects depend on this kind of funding. This system
can support a unique and original project with short-term funding (say, $1-10mil for 3-6 years) tobuild a facility. Unfortunately, after several years of construction there is no guarantee that theoperation and management of the facility can be funded when the experiment or observation
starts.

Because cosmological and astrophysical research is inherently global international

cooperation is an important element of the ICRR programs.

In the case of international

programs, the expenditures for the operation of facilities (telescopes) and for traveling abroadneed to be much more than the case of domestic programs. A more important fact is that any
international cooperative research will typically last longer than the 3 to 6 year period of“Kakenhi”.

Before 2005 ICRR had long been successful as an inter-university research organization withmany research programs, in spite of having only a small number of staffs. Human resources forresearch activities in every program were supported by outside universities, and research funds
for inter-university activities came directly from Monbusho at the request of the institute.
However, in the new system ICRR has to ask the University of Tokyo to support inter-university

expenditures.

KEK was founded as the first inter-university research organization, which is not affiliated withany university. KEK built KEK-PS, TRISTAN, and KEKB. Recently, INS, which used to belong
to the University of Tokyo, moved to KEK to build J-PARC. National Astronomical Observatoryof Japan (NAOJ) also separated from the University of Tokyo to build Subaru. Similarly, ICRR
could move out of the university to build the MEGATON-class water Cherenkov Detector.
Certainly, there is a merit to remaining with a university and the decision must be made withcaution.

We know that Monkasho recently established a committee to discuss funding for research
institutes, especially the ones affiliated with universities. ICRR management should follow thecommittee’s activity closely.

Appendix
A. Affiliation of Members of the 2006 ICRR External Review Committee

Name
Barry C. Barish

James W. Cronin

Affiliation
California Institute of Technology
Depts. of Physics and Astronomy & Astrophysics
University of Chicago

Werner Hofmann

Max-Planck-Institut für Kernphysik

Keiichi Kodaira

The Graduate University for Advanced Studies

Kozi Nakai

Tokyo University of Science

Hirotaka Sugawara

Hayama Center for Advanced Studies,
The Graduate University for Advanced Studies

Atsuto Suzuki

High Energy Accelerator Research Organization (KEK)

Yasuo Tanaka

Max-Planck-Institut für Extraterrestrische Physik

B. Program for the ICRR External Review meeting
Oct. 19th, 2006

9:00-9:30
9:30-10:00
10:00-10:40
10:40-10:50
10:50-11:20
11:20-11:30

Overview ・・・・・・・・・・・Y.Suzuki
Closed session
Super-Kamiokande ・・・・・・・・M.Nakahata(Questions & Answers)
K2K & T2K ・・・・・・・・・・・

M.Shiozawa(Questions & Answers)

11:30-12:00

Closed session

12:00-13:00

Working lunch (at the Cafeteria)

13:00-13:20

XMASS ・・・・・・・・・・・・・ S.Moriyama

13:20-13:30
13:30-14:15
14:15-14:30(Questions & Answers)
CANGAROO・・・・・・・・・・・

M.Mori(Questions & Answers)

14:30-15:00

Closed session (coffee)

15:00-15:45

Tibet ・・・・・・・・・・・・・・ M.Takita

15:45-16:00
16:00-16:45
16:45-17:00
17:00-18:00
19:00-(Questions & Answers)
TA (including AGASA) ・・・・・・・M.Fukushima(Questions & Answers)
Closed session
Dinner (at Crest Hotel Kashiwa)

Oct 20th, 2006

9:00-9:20
9:20-9:30
9:30-10:05

Ashra・・・・・・・・・・・・・・・M.Sasaki(Questions & Answers)
SDSS ・・・・・・・・・・・・・・ M.Fukugita(presented by N.Yasuda)

10:05-10:15(Questions & Answers)

10:15-10:45

Closed session (coffee)

10:45-11:20

Theory ・・・・・・・・・：：・・・ M.Kawasaki

11:20-11:30
11:30-12:15
12:15-12:30(Questions & Answers)
Gravitational Wave ・・・・：：・・ K.Kuroda(Questions & Answers)

12:30-13:00

Closed session

13:00-14:00

Working lunch (at the Cafeteria)

14:00-

Closed session