\documentclass[12pt]{article} \usepackage[dvips]{graphicx,color} \usepackage[light,first,bottomafter]{draftcopy} \usepackage{rotating} \draftcopyName{Draft 0.1}{215} \def\baselinestretch{1.2} \parskip 5pt plus 1pt \topmargin -0.5in \evensidemargin 0.0in \oddsidemargin 0.0in \textheight 8.5in \textwidth 6.5in \usepackage{amssymb} % uniform parameters! \def\mdmatm{\Delta m^2_{32}} \def\dmatm{$\mdmatm$} \def\mdmsol{\Delta m^2_{21}} \def\dmsol{$\mdmsol$} \def\numunue{$\nu_\mu \rightarrow \nu_e$} \def\anumunue{$\bar\nu_\mu \rightarrow \bar\nu_e$} \def\meV{e\mbox{V}} \def\eV{$\meV$} \def\MeV{M\eV} \def\GeV{G\eV} \begin{document} \begin{titlepage} \begin{center} \noindent{\large \bf Neutrino Oscillation Experiments for Precise Measurements of Oscillation Parameters and Search for \numunue{} Appearance and CP Violation. } \end{center} \begin{center} M. Diwan, W. Marciano, B. Viren, D. Beavis, N. Samios, R. Palmer\\ {\sl Department of Physics Brookhaven National Laboratory Box 5000, Upton, NY 11973-5000 } \smallskip T. Roser, W. Weng, S. Kahn, Z. Parsa, H. Kirk, R. Fernow \\ {\sl Center for Accelerator Physics, Brookhaven National Laboratory Box 5000, Upton, NY 11973-5000 } \smallskip W. Frati, J.R. Klein, K. Lande, A.K. Mann\\ {\sl R. Van Berg and P. Wildenhain University of Pennsylvania Philadelphia, PA 19104-6396 } \smallskip \smallskip R. Corey\\ {\sl South Dakota School of Mines and Technology Rapid City, S.D. 57701} \smallskip D.B.~Cline, K.~Lee, B.~Lisowski, P.F.~Smith \\ {\sl Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 USA} \smallskip A.~Badertscher, A.~Bueno, L.~Knecht, G.~Natterer, S.~Navas, A.~Rubbia \\ {\sl Institut für Teilchenphysik, ETHZ, CH-8093 Z\"urich, Switzerland} \smallskip R.F.~Burkart, W.~Burgett, E.J.~Feynves \\ {\sl Department of Physics, University of Texas at Dallas, Richardson, TX 75083 USA} \smallskip J.G.~Learned \\ {\sl Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96822 USA} \noindent V. Palladino \\ {\sl Universita di Napoli ``Federico II", 80138 Napoli, Italy} \smallskip I.~Mocioiu, R.~Shrock \\ {\sl C.N.~Yang Institute for Theoretical Physics, State University of New York, Stony Brook, NY 11974 USA} \smallskip C.~Lu, K.T.~McDonald \\ {\sl Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 USA} March 5, 2002 \end{center} \vspace{.2in} \end{titlepage} BLANK PAGE \newpage \begin{abstract} The possibility of making a low cost, very intense source of high energy protons using the Brookhaven AGS as well as the forthcoming new large underground detectors either at the national underground science laboratory (NUSL) in Homestake, South Dakota or at the waste isolation pilot plant (WIPP) in Carlsbad, New Mexico, allows us to propose a program of experiments that will address fundamental aspects of neutrino oscillations and CP-invariance violation. This program of experiments is unique because of the extra-long terrestrial baseline of more than 2500 km from Brookhaven National Laboratory to the underground laboratories in the West, the high intensity of the proposed conventional neutrino beam, and the possibility of constructing a very large array of water Cerenkov detectors with total mass approaching 1 Megaton. As part of this program we will also consider experiments at moderately long baselines ($\sim$400~km) using other detector technologies that can yield valuable and complementary information on neutrino oscillations. This letter of intent focuses on the design and construction of the necessary AGS upgrades and the new neutrino beam which will initially use a proton beam of power $\sim$0.5~MW; the power will be eventually upgraded to 1 MW in a later phase. \end{abstract} %\vspace{.5in} %\pagenumbering{roman} %\tableofcontents \newpage %\pagenumbering{arabic} \section{ Introduction} \vspace{1ex} This is a letter of intent to build a new high intensity neutrino beam at BNL in two phases. The first phase will involve AGS upgrades consisting of an addition to the present LINAC to yield a total LINAC energy of 400 \MeV, and an accumulator ring with permanent magnets mounted in the AGS tunnel. This will allow AGS injection at 2.5 \GeV and the resultant AGS cycle time will be 1 Hz. At 28 \GeV, the intensity should be $1.2 \times 10^{14}$ protons per pulse and the power 0.53 MW. The second phase will require new power supplies for the AGS and booster magnets for rapid cycling, an RF upgrade, and additional shielding; these will produce an AGS cycle time of 2.5 Hz and 1.3 MW power. The new intense proton beam will be used to produce a conventional horn focussed neutrino beam directed at far detectors. We propose to send the beam to two different distances: the very long distance of 2540 km (2880 km) to the Homestake (WIPP) laboratory, and a much shorter distance of 400 km in upstate New York where there are many possible locations for a new detector. It is now well known that the strongest evidence for neutrino oscillations so far comes from astrophysical observations of atmospheric neutrinos with $\mdmatm = (1.6 - 4.0) \times 10^{-3} \meV^2$ and maximal mixing and solar neutrinos with $\mdmsol \sim (2 -10) \times 10^{-5} \meV^2$ and the LMA solution for solar neutrinos~\cite{unkown}. The observation by the LSND experiment~\cite{unknown} will soon be re-tested at Fermilab by the mini-Boone experiment, therefore we will not discuss it in the following. There are several accelerator based experiments (K2K, MINOS, and CNGS) currently in data-taking or construction phase designed to confirm the atmospheric neutrino signatures for oscillations. There is now a consensus that there are four main goals in this field that should be addressed soon by accelerator neutrino beams: \begin{enumerate} \item Precise determination of \dmatm{} and definitive observation of oscillatory behavior. \item Detection of \numunue{} in the appearance mode. If the measured $\Delta m^2$ for this measurement is near \dmatm{} then this appearance signal will show that $\left|U_{e3}\right|^2 (= \sin^2\theta_{13})$ from the neutrino mixing matrix in the standard parameterization is non-zero. \item Detection of the matter enhancement effect in \numunue{} in the appearance mode. This effect will also allow us to measure the sign of \dmatm{}; i.e. which neutrino is heavier. \item Detection of CP violation in neutrino physics. The neutrino CP-violation in Standard Model neutrino physics comes from the phase multiplying $\sin \theta_{13}$ in the mixing matrix. This can be detected by observing an asymmetry in the oscillation rates \numunue{} versus \anumunue{}. \end{enumerate} In the following we will briefly describe how all of these goals can be achieved under reasonable assumptions for the various parameters using the new intense AGS based beam and the long and very long baselines. In the first section of this letter of intent we describe the physics purpose of the new beam sent along a baseline of 2540 km, results for 2880 km are similar. The second section describes the physics case for the shorter distance of 400 km. The third section briefly discusses the design and construction of the AGS upgrades. And the last section describes the construction of the new neutrino beam. \section{Very Long Baseline Experiment} \vspace{1ex} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/spec15.eps} \caption{Wide band horn focussed neutrino spectrum for 28 \GeV{} protons. Spectrum of neutrinos are calculated at various angles with respect to the 200 m decay tunnel axis at the AGS and at a distance of 1 km from the target.} \label{bnlspec} \end{center} \end{figure} \begin{figure}[htbp] \begin{center} \includegraphics*[width=\textwidth]{figs/e734mu_theta.eps} % \includegraphics*[width=0.49\textwidth]{figs/e734mu_energy.eps} \caption{Measured and calculated $\theta_\mu$ and $E_\mu$ distributions of $\nu_\mu n \rightarrow \mu^- p$.} \label{fig:e734mu} \end{center} \end{figure} The calculated energy distributions of a $\nu_{\mu}$ beam produced by 28 \GeV{} protons is shown in Fig.~\ref{bnlspec}~\cite{e889}. The $0^\circ$ calculation has been shown consistent with neutrino beam data~\cite{e734}. The spectrum peaks at about 1 \GeV{} with a total spread at half intensity of about 1 \GeV{}. Further work on the optimization of this spectrum for the very long baseline experiment is on going. We calculate the event rate without oscillations assuming a 0.5 MW proton beam power with 28 \GeV{} protons ($1.1 \times 10^{14}$ ppp), a 0.5 MT fiducial mass detector and 5 years of running. Because the AGS can run in a parasitic mode to RHIC we expect to get beam for as much as $1.8\times 10^7$ sec per year. However, we conservatively assume only $1.0\times 10^7$ sec per year here. Using these parameters and the relevant cross section, we calculate that the number of quasi-elastic charged current muon neutrino events in a detector located at 2540 km will be $\sim 5700$ in five years running. The number of neutrino events of all types will be approximately twice this number. This large statistics combined with the long baseline makes many of the following measurements possible and exciting. The angular distribution of the muons from the quasi-elastic process $\nu_{\mu} + n \rightarrow \mu^- + p$ produced by the 0 degree beam in Fig.~\ref{bnlspec} are shown in Fig.~\ref{fig:e734mu}; the principal background, $\nu_{\mu} + n \rightarrow \mu^- + p + \pi$ is also shown. A variety of strategies are possible to reduce this background further in a water Cerenkov detector; we will discuss them in later updates of this proposal. Up to Fermi momentum effects, knowing the direction of an incident $\nu_{\mu}$ accurately and measuring the angle of the observed muon allows the energy of the $\nu_{\mu}$ to be calculated. This method has been used by the currently running K2K experiment \cite{k2k}. The known capability of large water Cerenkov detectors indicates that at energies lower than 1 \GeV{} the $\nu_\mu$ energy resolution will be dominated by Fermi motion and nuclear effects. The contribution to the resolution from water Cerenkov track reconstruction depends on the photo-multiplier tube coverage. With adequate coverage, greater than $\sim$ 10\%, we expect that the reconstruction resolution should be adequate for our purposes. In the following we assume a 10\% resolution on the $\nu_\mu$ energy. This is consistent with the resolution achieved by the K2K experiment. The range of $\mdmatm \sim 1.24{E_\nu\mbox{[\GeV{}]} \over L\mbox{[km]}}$ covered by the proposed experiment using the beam in Fig. \ref{bnlspec} extends to the low value of about $5 \times 10^{-4} \ \meV^2$. The lower end of this extensive range of values is considerably below the corresponding values for other proposed long baseline terrestrial experiments~\cite{minos,cngs}. If the value of \dmatm{} turns out to be towards the lower end ($\sim 10^{-3}$) of its current range or if the value of \dmsol{} turns out to be towards its high end ($\sim$ $10^{-4} \meV^2$) then there will be large and very interesting interference effects in the very long baseline experiment. Extra-long neutrino flight paths open the possibility of observing multiple nodes (minimum intensity points) of the neutrino oscillation probability in the disappearance experiment. Observation of one such pattern will for the first time directly demonstrate the oscillatory nature of the flavor changing phenomenon. The nodes occur at distances $L_n = 1.24 (2n-1) E_{\nu}/\mdmatm$, $n= 1,2,3, $ \ldots. In Fig. \ref{nodes}, as an example, we show the flight path $L$ versus $E_{\nu}$ relationship of the nodes for $\Delta m^2 = 0.003 {\rm e\mbox{V}}^2$, a value close to the value measured in atmospheric neutrino experiments \cite{kajita}. An advantage of having a very long baseline is that the multiple node pattern is detectable over a broad range of $\Delta m^2$. This is demonstrated in figures \ref{wcnodesa} and \ref{wcnodesb} which shows the disappearance of muon type neutrino events as a function of neutrino energy measured via the muon momentum and angle in quasi-elastic events; the plots do not contain background. For \dmatm{} as small as 0.001 $e\mbox{V}^2$ the oscillation effects will be very large. Even in the presence of background we expect that the statistical error on \dmatm{} will be small ($\sim$ 0.5 \%) and the systematic error from the energy scale of the detector will dominate the total error. \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/node.eps} \caption{Nodes of neutrino oscillations as a function of oscillation length and energy for $\mdmatm = 0.003 \meV^2$. Matter effects are ignored} \label{nodes} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/numu-matter_numu_2540_0_0.8_1.0_0.04_5.0_2.6.eps} \caption{Spectrum of detected quasi-elastic events in a 0.5 MT detector at 2540 km from BNL. We have assumed 0.5 MW of beam power and 5 years of running. The top data points are without oscillations and bottom are with oscillations. This plot is for $\mdmatm = 0.0026 \meV^2$. The error bars correspond to the statistical error expected in the bin. A 10 \% energy resolution is assumed; this corresponds to the expected resolution due to both nuclear effects and the muon momentum reconstruction in the detector.} \label{wcnodesa} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/numu-matter_numu_2540_0_0.8_1.0_0.04_5.0_1.0.eps} \caption{Spectrum of detected quasi-elastic events in a 0.5 MT detector at 2540 km from BNL. We have assumed 0.5 MW of beam power and 5 years of running. The top data points are without oscillations and bottom are with oscillations. This plot is for $\mdmatm = 0.001 \meV^2$. The error bars correspond to the statistical error expected in the bin. A 10 \% energy resolution is assumed; this corresponds to the expected resolution due to both nuclear effects and the muon momentum reconstruction in the detector.} \label{wcnodesb} \end{center} \end{figure} The oscillation of \numunue{} is discussed is several recent papers \cite{marciano, irina}. This oscillation in vacuum is described fully by the following equation: \begin{eqnarray} \label{eq:label} P(\nu_\mu\to\nu_e) & = & 4(s^2_2s^2_3c^2_3 +J_{CP}\sin\Delta_{21}) \sin^2\frac{\Delta_{31}}{2} \nonumber \\ & & +2(s_1s_2s_3c_1c_2c^2_3 \cos\delta -s^2_1s^2_2s^2_3c^2_3) \sin \Delta_{31} \sin \Delta_{21} \label{eq9} \\ & & +4(s^2_1c^2_1c^2_2c^2_3 +s^4_1s^2_2s^2_3c^2_3 -2s^3_1s_2s_3c_1c_2c^2_3 \cos\delta -J_{CP} \sin\Delta_{31}) \sin^2\frac{\Delta_{21}}{2} \nonumber \\ & & +8(s_1s_2s_3c_1c_2c^2_3 \cos\delta - s^2_1s^2_2s^2_3c^2_3) \sin^2 \frac{\Delta_{31}}{2} \sin^2 \frac{\Delta_{21}}{2} \nonumber \end{eqnarray} where \begin{equation} \label{eq:blah} J_{CP} \equiv s_1s_2s_3c_1c_2c^2_3\sin\delta \label{eq6} \end{equation} $J_{CP}$ is an invariant that quantifies CP violation in the neutrino sector. The formula for $P(\bar\nu_\mu\to\bar\nu_e)$ is the same as above except that the $J_{CP}$ terms have opposite sign. Please see attached preprint (hep-ph/0108181) for definitions of symbols but note that $\Delta_{31}$ is the atmospheric term and $\Delta_{21}$ is the solar. The vacuum oscillations for a baseline of 2540 km are illustrated in Fig.~\ref{cpasym} as a function of energy for both muon and anti-muon neutrinos. The main feature of the oscillation is due to the term linear in $\sin^2\frac{\Delta_{31}}{2}$. The oscillation probability rises for lower energies due to the terms linear in $\sin^2 \frac{\Delta_{21}}{2}$. The interference terms involve CP violation and they create an asymmetry between neutrinos and anti-neutrinos. The vacuum oscillation formula and Fig.~\ref{cpasym} show that the CP asymmetry also grows as $1/E$ in the 0.5-3.0 \GeV{} region. Because of this effect it is argued that the figure of merit for measuring CP violation is independent of the baseline. For very long baselines although the statistics for the same size detector at a given energy are poorer by one over the square of the distance, the CP asymmetry is larger linearly in distance. \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/cpasym.eps} \\ \caption{Probability of \numunue{} and \anumunue{} oscillations at 2540 km assuming a $45^o$ CP violation phase. It can be seen that the CP asymmetry between $\nu_\mu$ and $\bar\nu_\mu$ increases for lower energies because the CP asymmetry is proportional to $\mdmsol L /E$ which increases for lower energies. } \label{cpasym} \end{center} \end{figure} The vacuum oscillation formulation must be modified to include the effect of matter \cite{irina}. The \numunue{} probability in the presence of matter is shown in Figs.~\ref{pnumunuea} and \ref{pnumunueb}. When compared to Fig.~\ref{cpasym} we can see that matter will enhance (suppress) neutrino (anti-neutrino) conversion at high energies and will also lower (increase) the energy at which the oscillation maximum occurs. The effect is opposite (enhancement for anti-neutrinos and suppression for neutrinos) if the sign of \dmatm{} is negative. The matter enhancement effect in neutrino oscillations has been postulated for a long time without experimental confirmation~\cite{wolfenstein}. Detection of such an effect by measuring a large asymmetry between neutrino and anti-neutrino oscillations or by measuring the spectrum of electron neutrinos is a major goal for neutrino physics. This measurement will also yield the sign of \dmatm{}. Figures \ref{nuenodes} and \ref{lm12} show the spectrum of electron type neutrinos that will be detected at 2540 km. The signal for $\sin^2 2 \theta_{13} \sim 0.04$ will be about 100 events. The background for this signal will come from the intrinsic contamination of $\nu_e$ particles in the beam as well as neutral current events producing $\pi^0$s. This background will be examined in detail in a future update to this proposal. From past experience using this beam, we expect that the total background in the signal region can be reduced to about 0.5\% of the charged current muon neutrino events. The advantages of the very long baseline are in obtaining a large enhancement at higher energies and creating a nodal pattern in the appearance spectrum. Both of these can be used to further improve the sensitivity of the experiment. The very long baseline experiment has a great advantage if \dmsol{} is found to be somewhat larger within its allowed range $(2-10) \times 10^{-5} \meV^2$. This is shown in Fig.~\ref{lm12}. The differences in the electron neutrino spectra are striking within Figs.~\ref{nuenodesa} and \ref{nuenodesb},\ref{lm12}. To understand CP violation, the effect of matter enhancement must be clearly understood and subtracted from any observation. If CP violation is large and the signal to \numunue{} is also large then it is possible to measure CP violation with just the neutrino beam. As shown in Fig.~\ref{cpasym} the effects of CP violation grow linearly as energy is decreased (or the baseline increased). For a very long baseline experiment it is possible to compare the signal strength in the $\pi/2$ node versus the $3\pi/2$ or higher nodes. Such a comparison will yield a measurement of CP violation. Any such measurement of CP must be augmented by data using an anti-neutrino beam. Such a program of measurements will require large statistics. This proposal has the flexibility to obtain much larger data sets because the detector will eventually be upgraded to its final configuration with 1 MT of mass and the AGS accelerator complex can be upgraded up to 4 MW of beam power. It is also possible that the conventional neutrino beam which we propose here will be replaced by a neutrino factory based on a muon storage ring. %\begin{figure} %\epsfig{file=cpasymat.ps,width=6in} \\ %\caption{Probability of $\nu_\mu \to \nu_e$ %and $\bar\nu_\mu \to \bar\nu_e$ oscillations at 2540 km %assuming a $45^o$ Cp violation phase %including the effects of matter. %} %\label{cpasymat} %\end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/numunue0.eps} \caption{Probability of $\nu_\mu$ oscillating into $\nu_e$ after 2540 km. The parameters assumed are listed in the figures. This plot assumes that there is no CP violation in the neutrino mixing matrix.} \label{pnumunuea} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/numunue45.eps} \caption{Probability of $\nu_\mu$ oscillating into $\nu_e$ after 2540 km. The parameters assumed are listed in the figures. This plot assumes a CP violation phase of $45^o$. } \label{pnumunueb} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/nue-matter_numu_2540_0_0.8_1.0_0.04_5.0_2.6.eps} \caption{Spectrum of detected quasi-elastic electron neutrino charged current events in a 0.5 MT detector at 2540 km from BNL. We have assumed 0.5 MW of beam power and 5 years of running. This plot is for $\mdmatm = 0.0026 \meV^2$. We have assumed $\sin^2 2 \theta_{13} = 0.04$. The error bars correspond to the statistical error expected in the bin. A 10 \% energy resolution is assumed; this corresponds to the expected resolution due to both nuclear effects and the electron momentum reconstruction in the detector.} \label{nuenodesa} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/nue-matter_numu_2540_0_0.8_1.0_0.04_5.0_1.0.eps} \caption{Spectrum of detected quasi-elastic electron neutrino charged current events in a 0.5 MT detector at 2540 km from BNL. We have assumed 0.5 MW of beam power and 5 years of running. This plot is for $\mdmatm = 0.001 \meV^2$. We have assumed $\sin^2 2 \theta_{13} = 0.04$. The error bars correspond to the statistical error expected in the bin. A 10 \% energy resolution is assumed; this corresponds to the expected resolution due to both nuclear effects and the electron momentum reconstruction in the detector.} \label{nuenodesb} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/nue-matter_numu_2540_0_0.8_1.0_0.04_10.0_2.6.eps} \caption{ Spectrum of detected quasi-elastic electron neutrino events in a 0.5 MT detector at 2540 km from BNL. We have assumed 0.5 MW of beam power and 5 years of running. This plot is for $\mdmatm = 0.0026 \meV^2$ and $\mdmsol = 0.0001 \meV^2$. We have assumed $\sin^2 2 \theta_{13} = 0.04$. The error bars correspond to the statistical error expected in the bin. A 10 \% energy resolution is assumed; this corresponds to the expected resolution due to both nuclear effects and the electron momentum reconstruction } \label{lm12} \end{center} \end{figure} \subsection{Detectors for the very long baseline experiment} The conversion of Homestake Gold Mine in Lead, South Dakota, into the National Underground Science Laboratory (NUSL), tentatively to take place in 2002, will provide a unique opportunity for a program of extra-long baseline neutrino oscillation experiments. As explained above these will be possible because of the length of the baseline, 2540 km from the Brookhaven National Laboratory (BNL) to Lead, South Dakota. It is proposed that the NUSL facility will accommodate an array of detectors with total mass approaching 1 Megaton. Most of these will be water Cerenkov detectors that can observe neutrino interactions in the desired energy range with sufficient energy and time resolution \cite{3m}. An alternative to Homestake also exists at the waste isolation pilot plant (WIPP) located in an ancient salt bed at a depth of $\sim 700 m$ near Carlsbad, New Mexico. The distance from BNL to WIPP is about 2880 km. The cosmic ray background will be higher at WIPP because the facility is not as deep as Homestake which has levels as deep as $\sim 2500 m$. The increased background, although undesirable, is not an insurmountable problem. However, the mechanical design of a large cavity in a salt bed has to be very different because of the slow movement of salt that causes a cavity to slowly collapse in a salt mine. In this LOI we will not address the detailed issues of detector design and cost. Currently, a study is in progress to site the LANNDD, 70 KT liquid Argon detector there. The key issue at this stage is one of safety and a proposal to the DOE to study this is in preparation. In Figure \ref{landd}, we show the LANNDD detector in a possible underground location at WIPP. One advantage of the WIPP Site is that, it is owned by the DOE and now has a program of underground science. % There are other advantages, but we %do not view the WIPP Site as a NUSL such as Homestake is %heading towards. We note that the recent Neutrino Factory Study at BNL identified the WIPP Site as one possible location for a far detector, and the current BNL neutrino beam could use the same concept. The LANNDD detector concept includes a detector for neutrino physics, in addition to the search for proton decay and other astroparticle Physics goals. Currently, the ICARUS detector at the Gran Sasso is being constructed with a 3KT detector as a goal. The operation of this detector will provide key information for the eventual construction of LANNDD and for the neutrino physics identified in the LOI. \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/lanndd.eps} \caption{Schematic of the WIPP underground site and a location for the LANNDD detector. A water Cerenkov detector array could also be accommodated at the WIPP site. } \label{landd} \end{center} \end{figure} \vspace{1ex} \section{Long Baseline Experiment} A dedicated experiment to detect \numunue{} appearance signature in the \dmatm{} region of 0.003 $\meV^2$ needs to have low background from the intrinsic $\nu_e$ contamination as well as neutral current events that produce $\pi^0$s which can mimic the $\nu_e$ QE CC signature. This can be achieved by placing a fine grained detector 1.5 degrees off-axis from the BNL neutrino beam. As originally pointed out by the E889 collaboration \cite{e889} at angles larger than the divergence of the pion beam the neutrino spectrum is almost independent of the pion energy and has a narrow spectrum peaking at 1 \GeV{} (See Fig.~\ref{bnlspec}). If the value of $\mdmatm = 0.003 \meV^2$ is known with good precision then the detector could be placed at 412 km which is at the point of the first maximum for oscillations. This is shown in figure \ref{400km}. At this distance and energy the effect of matter enhancement is small and a very sensitive experiment for \numunue{} appearance could be performed with a high resolution fine grained detector such as a 10 kT liquid argon calorimeter \cite{Rubbia77}, with maximum performance achieved if the detector is immersed in a large magnetic field \cite{lanndd}. We calculate the number of events in a 1.5 degree off-axis beam in a 10 kT liquid Argon detector assuming 0.5 MW of beam power and 5 years of running. In the absence of oscillations there will be about 2000 quasi-elastic muon neutrino events. The total number of events including neutral current events will be about 1.5 times this number. If $\mdmatm = 0.003 \meV^2$ the number of muon quasi-elastic events will drop to only $\sim$200. If $\sin^2\theta_{13} = 0.01$ then the number of electron neutrino quasi-elastic events will be about 40. The background from the electron neutrino contamination in the beam and the neutral current $\pi^0$ will be spread widely in energy, but the signal of 60 events will be in the peak of the neutrino spectrum. It has been shown in previous studies that the high energy resolution of the liquid Argon detector as well as the granularity should make it possible to reduce the neutral current background to a negligible level. The intrinsic electron neutrino background in the AGS neutrino beam is known to be at 0.5 \% level \cite{e889}. A complete study of the sensitivity of this approach will be presented in an update to this proposal. \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/numu-matter_numu_400_0_0.8_1.0_0.04_5.0_3.0.eps} \caption{Spectrum of neutrinos at 1.5 degrees with and without oscillations with $\mdmatm = 0.003 \meV^2$ and full mixing.} \label{400km} \end{center} \end{figure} The viability of a large liquid argon detector is presently being demonstrated by the ICARUS collaboration \cite{ICARUS} in cosmic-ray tests of a 300-ton module located on the Earth's surface. Fig.~\ref{icarus2} shows an example of the detailed tracking information obtainable with this technology. \begin{figure}[htp] % h = here, t = top, b = bottom, p = new page \begin{center} \includegraphics*[width=\textwidth]{figs/icarus6.eps} \parbox{5.5in} % change 5.5in to \hsize for full-width caption {\caption[ Short caption for table of contents ] {\label{icarus2} An event from the recent cosmic-ray test run of ICARUS \cite{ICARUS}, showing excellent track resolution over long drift distances in zero magnetic field. }} \end{center} \end{figure} A magnetized liquid argon detector would give the maximal discrimination against backgrounds in a neutrino beam, would enhance the ability to perform CP violation experiments, and would permit use of a beam that contains both neutrino and antineutrinos. An R\&D experiment is proposed to use a prototype liquid argon detector in a magnetic field to determine the sign of electrons via analysis of their electromagnetic showers up to several \GeV{}. \section{AGS Upgrade} \vspace{1ex} The preliminary design of the AGS upgrades and the new neutrino beam have been produced by the AGS department to reach an AGS power of 0.47 MW in its first phase. In this phase the LINAC will be improved to inject protons to the booster at 400 \MeV{} (at present it is 200 \MeV{}), and the booster energy increased to 2.5 \GeV{} from 1.8 \GeV{}. The addition of a fixed field accumulator storage ring between the booster and the AGS main ring will increase the AGS input beam from the present 4 booster pulses per AGS acceleration to 6 booster pulses per AGS acceleration and, at the same time, increase the AGS frequency from 0.6 Hz to 1.0 Hz. The AGS power increase would be from 0.14 to 0.47 MW. Figures~\ref{page3} to \ref{page10} show the proposed additions. The new accumulator will be in the same tunnel as the AGS. Figure \ref{page4} shows the present and proposed AGS injection modes. The AGS intensity upgrades and parameters are shown in Table~\ref{agsupg}. The location of the accumulator ring in the AGS tunnel is shown in Figs.~\ref{page9} and \ref{page10} and the accumulator parameters given in Table~\ref{page8}. The fixed field magnets of the accumulator ring will be essentially copies of the magnets produced for a similar purpose at Fermilab. We have consulted Bill Foster at Fermilab to design and calculate the cost of the accumulator ring proposed here. The tentative cost estimates for the various upgrades and improvements are shown in Table \ref{agscost}, separated into two relatively independent phases of roughly equal cost. It is possible to rearrange the order in which the improvements are made. A partial study of the options is shown in Table~\ref{agsupg}. Three options are shown: \begin{enumerate} \item only the LINAC is improved, \item only the accumulator is added, \item both are done. \end{enumerate} Some AGS and booster power supply upgrades are assumed along with the accumulator. A detailed study of space charge, intensity, injection energies, rep rate, power and cost needs to be made to make a much more specific proposal for this upgrade. This would come about with approval of the present letter of intent. \begin{table} \begin{tabular}{|l|l|l|l|l|l|} \hline & Now & 400 \MeV{} & \multicolumn{2}{c|}{2.5 \GeV{} Accumulator} & AGS to \\ & & LINAC & & 400 \MeV{} LINAC & 2.5 Hz \\ \hline LINAC Energy (\MeV{}) & 200 & 400 & 200 & 400 & 400 \\ Booster Intensity (ppp) & $1.5\times 10^{13}$ & $2.0\times 10^{13}$ & $1.5\times 10^{13}$ & $2.0\times 10^{13}$ & $2.0\times 10^{13}$ \\ Booster energy (\GeV{}) & 1.8 & 1.8 & 2.5 & 2.5 & 2.5 \\ Booster Cycles & 4 & 4 & 6 & 6 & 6 \\ AGS energy (\GeV{}) & 24 & 28 & 28 & 28 & 28 \\ AGS Intensity (Tp/sec) & 36 & 48 & 90 & 120 & 300 \\ AGS Rep Rate (Hz) & 0.6 & 0.6 & 1.0 & 1.0 & 2.5 \\ AGS Current ($\mu$ A) & 5.6 & 7.7 & 14 & 19 & 48 \\ AGS Intensity (ppp) & $6\times 10^{13}$ & $8\times 10^{13}$ & $9\times 10^{13}$ & $12\times 10^{13}$ & $12\times 10^{13}$ \\ AGS power (kW) & 140 & 215 & 390 & 530 & 1300 \\ \hline \end{tabular} \caption{AGS Intensity Upgrade Plan.} \label{agsupg} \end{table} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/page3.eps} \caption{Layout of the AGS facility with the addition of the super conducting LINAC.} \label{page3} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/page9.eps} \caption{Placement of the permanent magnet accumulator ring inside the AGS tunnel.} \label{page9} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=0.8\textwidth]{figs/page10.eps} \caption{Placement of the permanent magnet accumulator ring inside the AGS tunnel. Satellite view.} \label{page10} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=\textwidth]{figs/page4.eps} \caption{Time sequence of injecting pulses into the AGS. Top picture shows that at the moment 4 booster pulses are injected into the AGS during the period when the AGS magnets are at low field. In the new proposed configuration in the bottom picture the booster will inject 6 pulses into the accumulator which will store the beam until the AGS is at low field and then transfer the beam into the AGS.} \label{page4} \end{center} \end{figure} %\begin{figure} %\epsfig{file=page8.eps,width=6in} %\caption{Parameters of the accumulator ring.} %\label{page8} %\end{figure} \begin{table} \begin{center} \begin{tabular}{ll} Max. Kinetic Beam Energy & 2.5 \GeV{} \\ Rigidity & 13 Tm \\ Circumference & 819.07 m \\ Number of Superperiods & 25 \\ Number of FODO Cells & 50 \\ Number of (Combined-Function) Dipoles & 100 \\ Dipoles Length/Field & 3.25 m/ 0.25 T \\ Length of FODO Cell & 16.45 m \\ Length of straight sections & 8.22 m \\ Phase Advance per FODO Cell & 72 degrees \\ & \\ Vacuum Chamber x/y & 150 mm/ 75 mm \\ Acceptance Geometric x/y & 234/58 $\pi$ mm mrad \\ Acceptance Normalized \@ 2.5 \GeV{} x/y & 744/184 $\pi$ mm mrad \\ Space Charge limit: & \\ (100 $\pi$ mm mrad, $\delta \nu = 0.3$, 2.5 \GeV{}, debunched) & $3.5\times 10^{14}$ ppp \\ & \\ Betatron Tunes x/y & 10.3/10.5 \\ Chromaticities x/y & -11.7/-12.7 \\ Beta Max. x/y & 24.7 m/24.3 m \\ Beta Min. x/y & 7.8m/7.5 m \\ Dispersion Max. & 1.8 m \\ Transition Gamma & 9.6 \\ \end{tabular} \caption{Parameters of the permanent magnet accumulator ring.} \label{page8} \end{center} \end{table} \begin{table} \begin{center} \begin{tabular}{|l|r|} \hline Phase I (AGS at 1 Hz) & \\ 300 \MeV{} SRF (116 \MeV{} to 400 \MeV{}) & \$35 M \\ 2.5 \GeV{} AGS accumulator ring & \$25 M \\ AGS Injection at 2.5 \GeV{} & \$ 5 M \\ Total for Phase I 0.53 MW & \$65 M \\ \hline Phase-II (AGS at 2.5 Hz) & \\ AGS power supply & \$32 M \\ AGS RF upgrade & \$8.6 M \\ Booster Power Supply & \$5.5 M \\ AGS Collimation and Shielding & 8.0 M \\ Total for Phase-II 1.3 MW & \$ 54.1 M \\ \hline \end{tabular} \caption{Cost of upgrading the AGS in two phases to 1 MW. The superconducting LINAC upgrade could be delayed to be after the accumulator. In this case phase I could deliver about 0.3 MW at a cost of \$30 M. It is assumed that the target station shielding can be retrieved from existing resources.} \label{agscost} \end{center} \end{table} \section{Neutrino Beam Design} The geographic location of BNL on one side of the continent allows us to send beams to a variety of distances including very long baselines of 2000 km or more. This is shown in Fig. \ref{blines}. The distances from BNL to Lansing, Soudan, Lead (Homestake), and WIPP are 350, 1770, 2540, and 2880 km, respectively. The respective dip angles are 1.7, 7.9, 11.5, and 13.0 degrees. The difficulty of building the beam and the cost increases with the dip angle. For the purposes of this LOI we use the design for a conventional horn focussed neutrino beam. We use the tried and tested design used in previous experiments at BNL including E734 (Fig. \ref{horns}). The design shown uses a water cooled copper target. For much higher intensities this target will have to be redesigned. It is very likely that we can adapt the graphite target design used for NuMI at FNAL for our purposes. We also need to modify the horn focusing to make a wider band beam to increase the neutrino flux in the 4 \GeV{} region. There are a number of ways to optimize the horn design; we will not discuss them here. Our preliminary design for a beam to Homestake is shown in figures \ref{planview} and \ref{eleview}. This can clearly be adapted to any far location in the western direction. Our design addresses a number of issues. At BNL we are constrained to keep the beam line above the water table which is at a shallow depth ($\sim$ 20 m) on Long Island. Therefore the beam has to be constructed on a hill that is built with the appropriate 11.5 degree slope. Fortunately, it is relatively easy, and inexpensive to build such hills on Long Island because of the flat, sandy geology. It is important to keep the height of the hill low so that the costs are not dominated by the construction of the hill. The proton beam must be elevated to the top of the hill to a target station. The cost of the hill can be lowered by bending the proton beam upwards as quickly as possible. We have, however, used the design and bend angle used for the RHIC injection lines for our design because the RHIC injection lines have well known costs. The new fast extracted proton beam line in the U-line tunnel will be a spur off the line feeding RHIC which turns almost due west, a few hundred meters before the horn-target building. In addition to its 90 degree bend, the extracted proton beam will be bent upward through 13.76 degrees to strike the proton target. The downward 11.30 degree angle of the 667.8 ft meson decay region will then be aimed at the 7000 ft. level of the Homestake Laboratory. This will require construction of a 39 meter hill to support the target-horn building, but will avoid any penetration of the water table. At its midpoint (about Lake Michigan) the center of the neutrino beam will be roughly 120 km below the Earth's surface. For a shorter baseline in approximately the same direction as Homestake, for example Lansing NY, we do not have to build the hill, therefore the cost will be lower by a considerable amount. We are considering a number of strategies for combining the proton transport and the target station for two different baselines. A preliminary estimate of the cost without any of the customary burdens is shown in table \ref{bcost}. The costs are based on the the RHIC injector work, as well as the E889 proposal and the neutrino factory study. The table shows that costs can be lowered by reducing the length of the decay tunnel. The conventional construction costs are dominated by the size of the hill which is approximately proportional to the third power of the decay tunnel length. In our cost estimate we assume that we will bury the beam dump underground to reduce the height of the hill. We have also estimated the cost assuming 200 m and 150 m long decay tunnels. The spectra shown in Fig. \ref{bnlspec} are based on a 200 m long tunnel. A shorter tunnel could reduce the intensity at higher energies because of the longer flight paths of parent pions. We will study this optimization further in future updates of this proposal. \begin{figure} \begin{center} \includegraphics*[width=0.9\textwidth]{figs/bnl_near.eps} \includegraphics*[width=0.9\textwidth]{figs/bnl_wipp_lead.eps} \caption{Possibilities for baselines from BNL. The distances from BNL to Lansing, Soudan, Lead (Homestake), and WIPP are 350, 1770, 2540, and 2880 km, respectively. } \label{blines} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=0.8\textwidth]{figs/fig3a19.eps} \caption{The design of the horn focusing system used for the E734 experiment adapted from the E889 proposal.} \label{horns} \end{center} \end{figure} \begin{figure} \begin{center} \includegraphics*[width=0.8\textwidth]{figs/ap-2.eps} \caption{ The beam line for sending a neutrino beam to Homestake mine, South Dakota. This same beam line can be adapted for any far location in the Western direction.} \label{planview} \end{center} \end{figure} \begin{sidewaysfigure} \begin{center} \includegraphics*[bb=240 30 400 555,width=0.34\textwidth,angle=270]{figs/ap-1.eps} \includegraphics*[bb=240 570 400 740,width=0.34\textwidth,angle=270]{figs/ap-1.eps} \caption{Elevation view of the neutrino beam line to Homestake, South Dakota. For a nearer location a much smaller hill can be constructed. In this beam we assume a decay tunnel length of 200 m. For a shorter tunnel the cost of the hill will reduce as shown in table \ref{bcost}. } \label{eleview} \end{center} \end{sidewaysfigure} \begin{table} \begin{center} \begin{tabular}{|l|l|l|r|} \hline Item & basis & 200 m & 150 m \\ \hline %Proton transport & RHIC injector & \$8.3 M & \$8.3 M \\ Proton transport & RHIC injector & \$11.85 M & \$11.85 M \\ Target/horn & E889 & \$3.0 M & \$3.0 \\ Installation/Beam Dump & New & \$2.67 M & \$2.67 M \\ Decay Tunnel & E889 & \$0.45 M & \$0.45 M \\ Conventional const. (hill) & New & \$8.0 M & \$5.0 M \\ %Conventional const. (other) & E889 & \$6.77 M & \$6.77 M\\ Conventional const. (other) & E889 & \$9.1 M & \$9.1 M\\ \hline Total & & \$35.19 & \$32.19 \\ \hline \end{tabular} \caption{Preliminary cost of building the neutrino beam. The third column is for a beam with 200 meter tunnel. The fourth column is for building the beam with a 150 meter tunnel.} \label{bcost} \end{center} \end{table} \vspace{1ex} \section{ Conclusion} \vspace{1ex} We have outlined the neutrino physics program for an intense new neutrino beam from the Brookhaven AGS. The four goals of accelerator neutrino physics: precise determination of \dmatm{}, detection of \numunue{} appearance, measurement of the matter effect, and detection of CP asymmetries in the neutrino section are all possible for the proposed complex for reasonable values of the oscillation and mixing parameters, some of which are not yet known. Further surprises in neutrino physics should not be discounted, therefore any new facility must have sufficient flexibility to address new challenges. Our proposal allows such flexibility because of the possibility to mount both very long (over 2500 km) and intermediate (400 km) baseline experiments with beam intensity that can be increased in stages. The AGS complex is unique because it can be upgraded simply by decreasing the cycle time of the machine. This ability allows us the flexibility to continuously upgrade the facility to as much as 4 MW~\ref{roser}. In this proposal we have examined upgrades up to 1 MW. The estimated cost of the first phase of the AGS upgrades to reach 0.47 MW, plus the new neutrino beam directed to Homestake is approximately \$95M. With a 30 percent contingency, the total cost is \$122M. It is probable that the first three modules of the detector array will be produced in about five years, so that construction of the AGS upgrades and neutrino beam would be planned for that period and involve an average expenditure of approximately \$30M/yr. For a detector at intermediate baseline the costs will be less. The total yearly cost to the AGS department to provide protons for and maintain the neutrino beam would be about \$9M, approximately equal to the operations expense at present for HEP experiments. Neither the duration of the construction period nor the anticipated cost of the improvements to the BNL AGS complex is large in relation to plans and expenditures now usual for major apparatus in high energy and elementary particle physics. Witness the effort and expense that have rightly gone into the search for CP-invariance violation in the b-quark family alone in the past few years. Moreover, the improvements to the AGS and the new beam will be available for carefully chosen other physics in addition to providing important advances in our understanding of this exciting new frontier of elementary particle physics. \begin{thebibliography}{99} \bibitem{e889} E889 Collaboration, Physics Design Report, BNL No. 52459, April, 1995. \bibitem{3m} 3M Collaboration: Proposal titled: Megaton Modular Multi-Purpose Neutrino Detector, Nov. 26, 2001. \bibitem{k2k} k2k PRL \bibitem{uno} hep-ex/????? \bibitem{short} Shorter flight paths: approximately 730 km from Fermilab to the Soudan Mine and from CERN to the Gran Sasso Underground Laboratory, and 295 km from the proposed JHF to the Kamioka Mine. \bibitem{kajita} See, for example, E.W. Beier, Phys. Lett. {\bf B283}, 446 (1992); T. Kajita and Y. Totsuka, Rev. Mod. Phys. {\bf 73}, 85 (2001). \bibitem{kasuga} S. Kasuga {\it et al.}, Phys Lett. {\bf B374}, 238 (1996). \bibitem{arafume} Jiro Arafune, Masafumi Koike and Joe Sato, Phys. Rev {\bf D56}, 3093 (1997). \bibitem{marciano} William J. Marciano, ar X iv: hep-phy/0108181, vi, 22 Aug 2001. \bibitem{irina} Irina Mociouiu and Robert Schrock, arXiv: hep-ph/0106139v3, 15 Nov. 2001 \bibitem{cline1} D.B.Cline - NIM A 472 (2001) 511 and references within. \bibitem{cline2} D.B.Cline, J.G. Learned, K.T. McDonald and F.Sergiampietri, LANNDD - A Massive Liquid Argon Detector for Proton Decay, Supernova and Solar Neutrino Studies and a Neutrino Factory Detector. Proceedings of the NUFACT'01 Workshop, Tsukuba, Ibaraki, Japan, May 24-30, 2001; Astro-PH/0105442. \bibitem{cline3} Proposal to Study the Feasibility to Site various Neutrino Detectors at WIPP for Neutrino Factories and Super Beams - UCLA, UTD, Princeton, LANL in preparation. \end{thebibliography} \end{document}