%NuFACT02 - Plenary Session
%Terrestrial Sources of Neutrinos%Author: Markoff 
 
 
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\begin{document} 
 
%\title[Terrestrial sources]{Neutrino experiments using terrestrial sources} 
\title[Terrestrial sources]{Status and prospects of neutrino  
oscillations: terrestrial sources} 
 
\author{D.M. Markoff}  
\address{North Carolina State University, Physics Dept., Box 8202,  
Raleigh, NC 27695-8202, USA}  
  
%\ead{Diane_Markoff@ncsu.edu}  
  
\begin{abstract}  
 
By exploring the oscillation mixing angle {\em vs.}  
mass difference allowed regions, terrestrial based  
experiments have advanced  
our understanding of the $\nu$ oscillation solutions  
proposed by the measurements of neutrinos produced in the sun and  
in the atmosphere.   
This paper reviews the contribution of reactor anti-neutrino  
experiments and of accelerator neutrino experiments to the  
development of these theories. 
Selected experiments are briefly described,  
the results are presented and the impact on our understanding  
of neutrino oscillations is discussed.  
  
\end{abstract}  
  
%\maketitle  
  
\section{Introduction}  
Since the 1950's,  
terrestrial neutrino sources have played a major role in  
the study of neutrino properties  
with the first direct observation of these elusive  
particles at a reactor facility, and with the differentiation of muon and  
electron neutrino flavors at an accelerator facility.  
An important subset of terrestrial neutrino experiments  
developed primarily to test the $\nu$ flavor  
oscillation theories proposed to  
explain the solar neutrino problem, (associated with a deficit  
of $\nu_e$ flux)  
the atmospheric anomaly, (now associated with a  
deficit of measured $\nu_\mu$ flux)  
and the zenith angle dependence of the measured spectra.  
  
For neutrino flavor oscillation, a mixing matrix  
links the flavor basis states and the mass eigenstates. 
The probability for one  
neutrino flavor to oscillate to a second flavor, assuming  
two state mixing, is given by  
\begin{equation}  
\label{probability}  
P_{\nu_{\ell^{}} \rightarrow \nu_{\ell^\prime} } = {\sin ^2{2\theta}}  
                  \sin ^2{ \left( \frac{1.27 \Delta m^2 L}{E} \right) }  
\end{equation}  
where $\theta$ is the mixing angle between  
the first and second mass eigenstates,  
$\Delta m^2 \equiv |m_1^2 - m_2^2|$  
is the difference in the square of the masses in units of eV$^2$,  
$L$ is the path length traveled in meters,  
and $E$ is the neutrino energy in MeV.   
For mixing between three $\nu$ states, the 3 by 3 mixing matrix  
depends on mixing angles, $\theta_{12},\theta_{13},$ and $\theta_{23}$,  
and the oscillation probability has the same oscillatory dependence on  
the corresponding mass differences $\Delta m^2_{12},\Delta m^2_{13}$  
and $\Delta m^2_{32}$.  The importance of the mixing angles 
extends to symmetry violations in the lepton sector, since 
CP violation occurs only for $\theta_{ij}=0$ and $\Delta m^2_{ij} \neq 0$ 
for all pairs, $i,j$.  
  
The ratio, $\frac{L}{E}$ in Equation \ref{probability}, 
sets the $\Delta m^2$ sensitivity scale.  
When designing terrestrial source experiments, there may be  
flexibility to choose  the $\nu$ energy and flavors,  
and the detector baseline distance for probing  
specific two-state mixing. 
Terrestrial sources may be shut off to study background contributions  
or varied under known conditions for detecting a modulated signal.  
An important, yet obvious, consequence of controlling and  
characterizing the $\nu$ source, is  
that the spectra calculations and measurements,  
are independent of the solar and atmospheric models.   
  
Nuclear power fission product decays produce electron anti-neutrinos with low  
energies, $E_{\bar{\nu}{_e}} < 10$~MeV.  Therefore,  
the reactor source oscillation experiments involve the detection  
of only $\bar{\nu}{_e}$ in a disappearance measurement since the   
energies are too low to produce leptons in a charged current reaction  
and the mu and tau antineutrinos are too low in energy to be above  
the background.   
Reactor experiments are sensitive to mixing angle  
$\sin^2{2\theta} \approx {\sin^2{2\theta_{13}}} $  
and easily achieve sensitivities of $\Delta m^2 \sim 10^{-3}$,  
with detector distances on the order of 1~km, and with larger distances  
are capable of reaching the smaller $\Delta m^2$ range suggested by  
solar neutrino measurements.   
The reactor $\bar{\nu}{_e}$ source is isotropic.  Therefore for good  
sensitivity, the detector mass must grow with $L^2$, limiting  
the practical range of baseline distances.  
  
Accelerator sources can produce muon neutrinos in a wide range of  
intermediate to high energies on the order of 20~MeV to 30~GeV.  
These experiments with detectors at different baseline ranges,  
therefore probe a wide range of mixing angles and the  
larger mass difference region associated with $\nu_\mu$ oscillations.  
Long baseline measurements are primarily sensitive to the  
$\Delta m^2_{32}, \sin^2{2\theta_{23}}$ mixing parameters.  
A 500~MeV neutrino source can be used to probe $\Delta m^2 \sim 0.1$  
with the detector located at a distance of 1~km, and the 100~km  
range is needed to probe the $\Delta m^2 \sim 10^{-3}$ region.  
A collimated $\nu$ beam allows for reasonable detector sizes  
even at large distances.  
  
The above general characteristics of reactor and accelerator  
$\nu$ sources show the complementarity of the two approaches in the  
mixing angles, $\sin^2{2\theta_{ij}}$, and allowed $\Delta m^2$  
regions that can be probed.  
Note that considered here are baseline distances less than $\sim 500$~km  
for the reactor experiments and intermediate baseline accelerator  
experiments where matter effects from the Earth are negligible.   
  
For an extensive review of reactor experiments, please refer  
to the article by Bemporad, Gratta and Vogel\cite{reactor_rev},  
and the chapter by F. Boehm  
in an exhaustive set of articles on neutrino physics  
collected in one book\cite{aspects_reactor}.  
In addition, the chapter   
by D.O. Caldwell provides a detailed review  
of accelerator based neutrino physics\cite{aspects_accelerator}.  
  
\section{Reactor Neutrino Experiments}  
Reactor experiments are based on the detection of  
$\bar{\nu}{_e}$ from the beta decay  
of fission products of uranium ($^{235}$U, $^{238}$U)  
and plutonium ($^{239}$Pu, $^{241}$Pu) isotopes.   
As can be seen from Equation \ref{probability}, in a disappearance  
measurement, the oscillation  
parameters modify both the total neutrino flux and the  
energy spectrum detected at distance, $L$.    
Note that the oscillation-induced spectral distortion  
lessens at the limits of the experiment sensitivity to $\Delta m^2$ 
and in the limits of no-oscillation.   
  
The reactor power spectrum (derived from the fuel composition  
and thermal power history provided by the nuclear power company),  
the fission rates and the $\beta$-decay  
spectra are used to determine the neutrino spectrum and total yield,  
about $6\times 10^{20} \bar{\nu}_e $/s for a 3~GW thermal source.  
Each of these processes is well known and the neutrino yield  
can be determined to a few percent or better. 
Anti-neutrinos above 1.5~MeV are produced primarily in  
high Q-value, short-lived decays, and track well with the  
reactor power.   
These calculations have been validated with the  
null results from early reactor  
oscillation experiments (discussed below) at short baselines including  
multiple baseline comparisons. 
  
The $\bar{\nu}{_e}$ is detected by  
inverse beta decay $\bar{\nu}{_e} + p \rightarrow n + e^+$,  
where coincidence measurements are possible for background reduction.  
The neutrino energy spectrum is deduced from the positron spectrum, 
$E_{\bar{\nu}} \approx E_{e^+} + (M_{n} - M_{p}) + m_{e^+}$ and has 
a threshold of 1.8~MeV. 
The deposited energy of the positron comprises the prompt signal,  
and the delayed signal comes from the characteristic 2.2~MeV photon  
emitted in the subsequent capture of the neutron  
($n + p \rightarrow d + \gamma$).  Muon induced  
spallation neutrons produced in the surrounding rock create  
the most difficult background signals to discriminate against.  
 
\subsection{Early Experiments: Short Baselines}  
%In 1956, the group lead by Reines and Cowan constructed  
%a neutrino detector near the Savannah River  
%reactor facility and were the first to directly detect neutrinos  
%(antineutrinos actually, though they hadn't realized it at  
%the time) using methods similar to current experiments\cite{reines}.  
In 1977, scientists at the Institut-Laue-Langevin (ILL) research  
reactor in France, placed at a distance of 8.7~m  
from the reactor core, 
a liquid scintillator positron detector surrounded by $^3$He  
proportional counters to detect the neutrons.   
The measured neutrino spectrum matched the  
calculated spectrum, excluding the high mass region  
$\Delta m^2 \geq 0.15$~eV$^2$ for mixing angles $\sin^2{2 \theta}>0.25$.  
  
The detector was moved to Goesgen, Switzerland, and improvements enabled  
pulse shape discrimination to remove fast neutron background events.  
With the detector placed sequentially at distances of 38, 46, and 65~m,  
no evidence for neutrino oscillations was observed with an  
uncertainty of $6\%$.  The exclusion  
region was extended to $\Delta m^2 \sim 3 \times 10^{-2}$~eV$^2$.  
  
In the early 1990's, the 2800 MW reactor at Bugey, France, was the source  
for detectors located at 15, 40, and 95~m.  The identical detectors consisted  
of prismatic cells of $^6$Li-loaded liquid scintillator material for  
short neutron capture times (30~$\mu$s).   
Prompt $e^+$ events were separated from $n$ capture events 
($^6$Li$+n \rightarrow ^3$H$ + \alpha$) using pulse shape discrimination.  
No evidence for oscillations  
was seen with an absolute normalization of 5\%, and sensitivity to  
$\Delta m^2 \sim 10^{-2}$.  
  
Two short-baseline experiments   
measured deuteron disintegration via the charged current  
($\bar{\nu}{_e} + d \rightarrow e^+ + n + n$) and through the  
neutral current ($\bar{\nu}{_e} + d \rightarrow \bar{\nu}{_e} + p + n$)  
interaction.  As expected, these experiments showed no  
indication of oscillations\cite{reactord_1,reactord_2}.  
  
\subsection{CHOOZ and Palo Verde: Intermediate Baselines}  
The next reactor experiments, CHOOZ and Palo Verde, were designed  
specifically to probe for $\nu_e$-$\nu_\mu$  
oscillations in the allowed region of  
$\Delta m^2 \sim 10^{-3}$ suggested by the atmospheric neutrino  
measurement results at the time of detector construction.  
  
The Palo Verde detector was built 12~m underground,  
about 32 meter-water-equivalent (mwe), and was located  
either 0.89~km or 0.75~km from three generating reactor cores  
that comprise the Palo Verde Nuclear Generating Station in Arizona, USA.  
The CHOOZ neutrino experiment was conveniently constructed in  
an existing underground cavity (300 mwe) at a distance of 1.11 km and  
0.998 km from the two reactor cores of the  
\'{E}lectricit\'{e} de France  
power station located in the Ardennes.  
  
Both experiments consist of gadolinium loaded liquid scintillator,  
and are based on a coincidence measurement of a prompt  
$\e^+ $ and annihilation $\gamma \gamma$ signal and delayed  
$n$ capture in Gd  
producing a cascade of $\gamma$-rays with a total energy of 8~MeV.  
The detector design for each experiment was dictated by the  
background suppression needs resulting in different detector  
construction.  
Analysis methods included flux and spectra comparisons for full and  
reduced power ranges at the different generating stations and taking  
into account the different source distances.  
  
CHOOZ and Palo Verde saw no evidence for $\nu$ oscillations.   
The ratio of the number of expected $\bar{\nu}_e$  
to the number detected was reported as $1.01 \pm 0.04$ for the CHOOZ  
experiment\cite{CHOOZ_results} and $1.04 \pm 0.08$ for the Palo Verde  
experiment\cite{PaloVerde_results}.  
These results indicate that atmospheric neutrino oscillations  
are primarily $\nu_\mu$ to $\nu_\tau$ and not $\nu_\mu$ to   
$\nu_e$ in the range $\Delta m^2 > 10^{-3}$.  
This is consistent with the subsequent results from  
SuperK\cite{superk_results}.  
 In addition, the CHOOZ result puts an important stringent upper limit of  
$\sin^2 {\theta_{13}} < 0.1$ at 90\% confidence level in the  
large $\Delta m^2$ region\cite{CHOOZ_results}. 
  
\subsection{KamLAND: Long Baselines}  
  
The Kamioka mine site (where both the Kamiokande and Super Kamiokande  
experiments were constructed) is strategically located  
140 to 200~km away from over 16 reactors in Japan and Korea.  
With an average baseline distance of 190 km, the Kamioka Liquid  
scintillator Anti-Neutrino Detector, KamLAND is the first  
terrestrial $\nu$ experiment to be sensitive to an  
allowed region including the Large Mixing Angle (LMA) oscillation solution  
($\Delta m^2 \sim 10^{-5}$~eV$^2$) suggested by solar  
$\nu$ experiments\cite{sno_results}.  
  
KamLAND positioned at 2700 mwe, is a 1~kton liquid scintillator  
viewed by 1879 photomultiplier tubes (PMTs)  
surrounded by a water \v{C}erenkov veto detector viewed with  
225 PMTs.  The usual $e^+ n$ coincidence signal  
is detected in the liquid scintillator with  
$n$ background suppression from fiducial volume cuts  
and cuts based on $\mu$ events.  
For experimental details, please  
see the KamLAND paper in these proceedings\cite{kamland}. 
For a no-oscillation result, the excluded region will  
eliminate the LMA solution from further consideration. 
If KamLAND observes a deficit of antineutrinos,  
then (assuming CPT invariance) this important result will provide the most  
stringent restraints in the $\Delta m^2$ allowed region  for  
$\nu_e \rightarrow \nu_x$ oscillations.   
 
\subsection{Next generation}  
If KamLAND fails to see oscillations at the LMA mass limits, then  
another round of experiments will be needed to study the high range of the  
Large Mixing Angle region.  
Such a reactor experiment has been proposed in Germany.  The Heilebron  
experiment would strategically be located in a salt mine (480-640~mwe)  
near several reactors with distances about 10-20 km. The detector would  
be a 100 - 1000 kton scintillator depending on the sensitivity  
needed\cite{Heilebron}.  
In addition, the upper range of $\Delta m^2$ could be reached  
with very long baseline experiments (see below).  
  
\section{Accelerator Neutrino Experiments}  
  
Accelerator neutrinos originate from the decay of pions and  
kaons produced in the bombardment of a fixed target  
with high-energy protons.  
The beam is primarily $\nu_\mu + \bar{\nu}{_\mu}$  
with a small percentage of $\nu_e + \bar{\nu}_e$.   
Each flavor is generated with a different average energy.  
  
Accelerator experiments focus primarily on the disappearance of  
$\nu_\mu$ or the appearance of $\nu_\tau$, and thus  
are well suited for atmospheric neutrino oscillation studies.  
Disappearance studies of $\nu_e$ is very difficult since less  
than 1\% of the neutrinos produced are  
electron neutrinos.  This neutrino beam contribution must  
be understood in order to study $\nu_\mu \rightarrow \nu_e$ appearance  
in very sensitive measurements. 
Essentially no electron antineutrinos are produced, so that  
$\bar{\nu}_e$ appearance can readily be studied.  
For $\nu_\mu$ disappearance experiments, a near detector calibrates  
the neutrino beam with intensity and $\nu$ spectra measurements. 
Meson detectors are used to monitor the beam.   
Beam simulations to characterize the $\nu$ source is sufficient for 
$\nu_\tau$ appearance measurements, and a near detector is not required. 
Note that the threshold for $\tau$ production is 3~GeV, and therefore  
$\nu_\tau$ appearance can only be studied at the higher energy accelerator  
facilities.  
  
The $\nu$ flavors are identified through the charged  
current (CC) interaction,  
namely with the capture of a neutrino producing the  
lepton partner, $\ell$,  
and a residual nucleus ($\nu_{\l} + N \rightarrow \l + N^{\prime}$).   
The long baseline experiments may  
include detecting neutral current (NC) reactions for overall rate  
comparisons, and CC to NC event ratio differences between  
near and far detectors.  
  
\subsection{CHORUS and NOMAD: Intermediate Baselines}  
  
%Intermediate baseline experiments at high-energy accelerator.  
  
The Neutrino Oscillation MAgnetic Detector, NOMAD, and  
the CERN Hybrid Oscillation Research apparatUS, CHORUS,  
were designed to search for $\nu_\mu \rightarrow \nu_\tau$  
oscillations, and  
take advantage of neutrinos produced at the CERN proton synchrotron  
which accelerates protons onto a Be target.  The neutrino beam  
is primarily $\nu_{\mu}$ with an average  
energy of 24~GeV with about 6\% $\bar{\nu}_{\mu}$ at an average  
energy of 19~GeV.   
One detector is positioned just downstream of the other in the same  
experimental hall located approximately  
600~m from the neutrino source.  These experiments are  
therefore sensitive to the large $\Delta m^2 _{\mu \tau}$ region.   
  
In NOMAD, the identification of ${\tau^-}$ production is through the  
kinematic criteria that requires identifying the leptonic or  
hadronic decay particles, measuring their momentum, and analyzing  
the transverse momentum.  For momentum analysis, the 2.7 ton fiducial  
volume $\nu$ target region is located within a uniform magnetic  
field (0.4~T) perpendicular to the beam axis creating a particle  
drift chamber.   
  
The CHORUS detector, which contains 770~kg of emulsion,  
identifies $\tau$ events through the  
identification of kinks in the particle tracks produced by  
the $\tau^-$ decay to a negative hadron, electron or muon.  
To reduce background events,   
the track kink must satisfy specific distance and energy criteria  
depending on the leptonic or hadronic decay of the $\tau^-$.  
Alternating layers of scintillating fiber trackers  
initially identify vertex and track positions  
to be studied in the emulsion sheets. A hadron spectrometer  
with fiber trackers measures track momenta.  
The energy is measured with a lead scintillating fiber calorimeter.  
  
Both experiments failed to see oscillations $\nu_\mu$ to $\nu_\tau$.  
CHORUS and NOMAD provide consistent null results in the large  
$\Delta m^2$ region, and with 90\% confidence level (CL),  
put an upper limit on the oscillation probability of  
$P_{\mu \tau} < 3 \times 10^{-4}$  
and exclude $\nu_\mu \rightarrow \nu_\tau$ mixing 
down to $\sin^2{2\theta} \sim 10^{-4}$ with similar limits 
for $\nu_e \rightarrow \nu_\tau$ mixing\cite{NOMAD+CHORUS}. 
These limits reinforce the small $\Delta m^2$,  
$\nu_\mu$ to $\nu_\tau$ oscillation  
explanation of the atmospheric anomaly.  
  
\subsection{LSND and KARMEN: $\bar{\nu}_e$ Appearance}  
  
The Liquid Scintillator Neutrino Detector, LSND, and the  
KArlsruhe-Rutherford Medium Energy Neutrino, KARMEN, experiments  
are designed to detect the appearance  
of $\bar{\nu}{_e}$ from $\bar{\nu}_{\mu}$ beams  
($< E_\nu > \sim 35$~MeV) produced  
in the beam stop of intermediate-energy (800~MeV) proton accelerators.  
The protons are accelerated onto a water or lead target at the  
Los Alamos Meson Facility for LSND, and onto a   
Ta + D$_2$O target at the  
ISIS spallation facility at the Rutherford Appelton Laboratory for KARMEN.  
Pions, produced in the target, decay in flight into muons,  
$\pi^+ \rightarrow \mu^+ + \nu_\mu$, and the muons subsequently  
decay at rest, $\mu^+ \rightarrow e^+  +  \bar{\nu}{_\mu} + \nu_e$.  
%The small $\bar{\nu}_e$ contamination is on the order of $10^{-4}$.  
Both experiments measured $\bar{\nu}{_e}$ production from the coincidence  
signal from the inverse beta decay reaction,  
$\bar{\nu}{_e} + p \rightarrow e^+ + n$, observed in liquid scintillator  
material.  
  
The LSND detector located 30~m and $12^{\circ}$ off-axis from the target,  
consisted of 167 tons of mineral oil with a diluted scintillator that  
allowed the detection of both scintillation and \v{C}erenkov light.   
In contrast, KARMEN was located 18~m and $90^{\circ}$ off-axis from  
the target and consisted of 56 tons of Gd loaded scintillator segmented  
into 512 modules.  
These designs resulted in different sensitivities  
to $\Delta m^2$, methods of background suppression,  
position and energy resolutions, and detector efficiencies.  
  
LSND observed $\bar{\nu}{_\mu}$ to $\bar{\nu}{_e}$ oscillations  
in the large $\Delta m^2$ region where the small $\sin^2{2\theta}<  0.1$  
region is not ruled out by reactor results.  
The LSND signal above background is quoted as  
$87.9 \pm 22.4 \pm 6.0$ events with an oscillation  
probability of $(0.264\pm 0.067 \pm 0.045)\%$\cite{LSND_results}.  
KARMEN2 (data from 1997-2001) measured 15 events with an  
expected background of $15.8 \pm 0.5$ events: no oscillation evidence.  
KARMEN provides the most stringent constraints on the LSND results,  
with a limit on the  
LSND range to $0.3$eV$^2 < \Delta m^2 < 2$eV$^2$\cite{KARMEN_results}.  
A joint detailed statistical analysis of original data  
shows incompatibility of the two measurements each at the 60\%CL 
for an overall 36\% CL and areas  
of statistical compatibility only at  
$\Delta m^2 < 1$~eV$^2$\cite{LSND+KARMEN}.  
  
This is the only positive oscillation result for accelerator experiments,  
and implies a third $\Delta m^2$ range that is different  
from the solar and atmospheric values.  To accommodate this  
additional mass difference range, a number of theories have been  
developed including the postulation of a fourth but sterile neutrino flavor,  
$\nu_s$, so that the 3 weak interacting $\nu$ flavor constraint set by  
the width of the Z boson is satisfied.   
   
\subsection{K2K and MINOS: Long Baselines}  
  
A wide-band $\nu$ beam with energy $1-2$~GeV from the %12~GeV  
proton synchrotron at KEK, in Japan, is directed at SuperK,  
at a distance of 250~km and with a beam aiming accuracy of about  
1~mrad.   
In this KEK to Kamioka (K2K) experiment, SuperK serves as the far detector  
in a $\nu_\mu$ disappearance measurement. 
%with event selection using  
%GPS (Global Positioning System) signals for beam timing synchronization.  
Assuming a $\Delta m^2 = 5 \times 10^{-3}$~eV$^2$, a 1~GeV neutrino  
would be near the first minimum after traveling a distance of 250~km.  
For $10^{20}$ protons on target at KEK,  
the rate is $\sim$200 events at SuperK  
and the expected background is 5 atmospheric events/day. 
The near detector at 300~m is a 1 kton water \v{C}erenkov detector  
with the same PMT arrangement (40\% coverage) as SuperK,  
followed by a  
scintillating fiber detector for tracking, a lead glass array  
for tagging electromagnetic showers and a $\mu$ range detector  
to measure energy and momentum of muons from CC $\nu_\mu$ events.  
  
The K2K data recorded so far measured 56 events with an expected  
number for the case of no-oscillations  
of 80 events;  results inconsistent with no-oscillations at 99\% CL.  
The best fit to the measured spectrum gives  
$\Delta m^2 = 2.7 \times 10^{-3}$~eV$^2$ with $\sin^2{2 \theta} = 1$,  
and is consistent with the SuperK atmospheric results\cite{K2K_results}.  
  
MINOS, the Main Injector Neutrino Oscillation  
Search, far detector currently under development will be  
located at the Soudan mine, 730~km from FermiLab, where the  
Neutrinos at the Main Injector (NuMI) beam is produced.  With a two-horn  
system to focus the mesons into the decay region, and variable proton  
target locations, NuMI is expected to  
vary the neutrino energy with an average of $<E_{\nu}> = 3,6,12$~GeV.  
The far detector is based on light-tight modules of alternating  
steel plates and scintillator strips forming a 5.4~kton fiducial volume  
monitored with PMTs.  
The near detector located 300~m from the end of the NuMI 
meson decay tunnel, is a 930 ton fiducial volume scintillator  
tracking calorimeter  
segmented like the far detector for high-statistics measurements  
of the $\nu$ beam including energy spectra and $\nu_e$ contamination.  
NuMI expects 120~GeV protons on target by 2004 with MINOS 
taking data by 2005.  
  
If the atmospheric mass difference squared is indeed in  
the range, $\Delta m_{atmos}^2 \approx (2.0 - 5.0) \times 10^{-3}$~eV$^2$,  
then the MINOS experiment will determine the value with an estimated  
uncertainty of 10\% for 10~kton-years of data.   
With the long baseline and $|\Delta m^2_{21}|<<|\Delta m^2_{32}|$,   
MINOS will put a more stringent limit on the allowed range for  
$\Delta m^2_{32}$ and $ \sin^2{2\theta_{23}}$.  
In addition, the comparison of the CC to NC event ratio in the  
near and far detectors may be sensitive to $\nu_\mu \rightarrow \nu_{s}$  
mixing, providing another existence test of sterile neutrinos.  
  
\subsection{Next generation projects}  
  
The Booster Neutrino Experiments (BooNE) are underway at FermiLab  
where an 8~GeV proton beam produces a  
$\nu_\mu + \bar{\nu}_\mu$ beam with energy ranging from 300~MeV to 1.5~GeV.  
The set of BooNE experiments, starting with MiniBooNE, are designed  
to test the same allowed mass region as LSND.  
The detector, located 440~m from the source, is a \v{C}erenkov detector  
with 776 tons of mineral oil viewed by 1275 PMTs. 
%8$''$ PMTs.  
This experiment looks at the appearance of both $\nu_e$ and  
$\bar{\nu}{_e}$ from $\nu_\mu$ and $\bar{\nu}{_\mu}$, respectively,  
requiring a Monte Carlo analysis to determine the expected $\nu$ flux.  
In 2 years of data for $10^{21}$ protons on target, MiniBooNE  
expects $10^5$ $\nu_\mu$ CC events and the LSND oscillation  
predicts 1000 $\nu_\mu \rightarrow \nu_e$ events out of an  
expected 3500 electron like events in the detector\cite{MiniBooNE}.   
As of autumn 2002, MiniBooNE has begun taking data.  
% A. Bararko Nucl Phy B (Proc Suppl) 91, 210 (2001)  
% R Tayloe Proceedings of Neutrino 2002, Munich, Germany, May 25-30, 2002.  
  
Two experiments under development are optimized to study  
$\nu_{\mu} \rightarrow \nu_e$ and $\nu_{\mu} \rightarrow \nu_\tau$  
appearance from the CERN to Gran Sasso (CNGS)  
neutrino beam source located 730~km away with  
an average $\nu$ energy of 17~GeV, and with a  
2\% $\nu_\mu$ and 0.8\% $(\nu_e + \bar{\nu}_e)$ contamination.  
To achieve a mass difference sensitivity of $10^{-3}$~eV$^2$,  
which translates to a position sensitivity of $1~\mu$m,  
the Oscillation Project with Emulsion-tRacking Apparatus  
(OPERA) detects  
$\tau$ decays by identifying track kinks in    
a massive target (2~kton) of alternating layers of Fe and Pb plates and thin  
emulsion sheets in which the emulsion area is more than 300 times   
that of CHORUS.  If OPERA fails to see $\tau$ events, the region  
for $\nu_\mu - \nu_\tau$ mixing with $\Delta m^2 < 1.2 \times 10^{-3}$~eV$^2$  
at maximal mixing and $\sin ^2 {2\theta} < 5.7 \times 10^{-3}$ at large  
$\Delta m^2$ will be excluded at 90\% CL\cite{Europe-accelerators}.  
 
The second CNGS experiment, ICARUS  
(Imaging Cosmic and Rare Underground Signals) a 3~kton detector  
with a liquid Argon time projection chamber, will measure  
$\tau$ appearance in the complementary method using kinematic criteria.  
With fiducial volume cuts, particle momentum and energy cuts,  
ICARUS will reach the same sensitivity as OPERA for $\nu_\mu - \nu_\tau$.   
With 1~mm resolution and good particle identification including electrons,  
ICARUS is expected to reach a sensitivity of  
$\sin^2{2\theta_{13}} > 2 \times 10^{-2}$\cite{Europe-accelerators},  
reducing the limits set by CHOOZ. 
Completion of the CNGS beam and detectors is planned for 2006.  
  
\section{What's next?}  
  
The next set of terrestrial source experiments will  
require new $\nu$ beams and detectors to  
improve the sensitivity to $\Delta m_{23}^2$ and $\theta_{23}$  
and in a $\nu_e$ appearance measurement, to $\sin^2{\theta_{13}}$.  
In addition, new measurements may be sensitive to CP violation,  
or to the sign of $\Delta m^2$  
which will shed light on the mass hierarchy of the $\nu$ mass states.  
  
The JHF2K project under construction, 
will direct a $\nu$ beam ($<E> \sim 0.5$~GeV) from  
the JAERI accelerator in Tokai, Japan, initially to the SuperK detector 
located $\sim$300~km away in Kamioka,  
and in the second phase, at the next generation  
large scale (1 Mton) detector (HyperK) in Japan\cite{JHF2K_proposal}.  
Several superbeams as upgrades to current US 
accelerators have been proposed\cite{US_superbeams}. 
New liquid argon based $\nu$ 
detectors are being considered as part of a  
100-1000~km baseline detector system using a  
proposed superbeam neutrino source  
at the Brookhaven National Laboratory in New York\cite{BNL_proposal}. 
Accelerating $\beta$ unstable radioactive isotopes  
to high energies has been proposed to produce an intense  
low-energy $\nu_e$ beam\cite{beta_beam}. 
These and other proposals for
detector and accelerator developments based
on superbeams and neutrino factories 
form the basis of the NuFACT02 conference  
and the topics of these proceedings.  
  
\section{Summary}  
  
So far, the terrestrial neutrino oscillation experiments have  
confirmed and complemented the solar neutrino results, 
$\nu_e$ oscillates to $\nu_\mu$ and $\nu_\tau$ with   
$\Delta m^2 \approx 10^{-5}$ to $10^{-4}$ eV$^2$\cite{sno_results}, 
and the atmospheric neutrino  
results that $\nu _\mu$ oscillates to $\nu_\tau$   
with large $\Delta m^2 \approx 10^{-3}\mathrm{eV}^2$  
\cite{superk_results}.  
The reactor measurements and the intermediate  
baseline accelerator results are consistent with the neutrino oscillation  
solutions and have put important limits on the allowed regions  
of $\Delta m^2$ {\it vs.} $\sin^2{2\theta}$.  KamLAND will  
provide the next reactor experiment result, and with sensitivity 
to the favored LMA solution, will either complete or extend  
the solar neutrino puzzle. 
Soon, MiniBooNE will confirm or refute the LSND large $\Delta m^2$ 
oscillation results and  
provide insights into the existence of a third mixing mass region.  
In the following years, the long baseline experiments will  
help define the
lepton mixing matrix elements and contribute to the determination
of the (as yet unknown) mass hierarchy.  
  
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\end{thebibliography}  
  
  
\end{document}  
