Office of Nuclear Physics - draft 2 revised

The Office of Nuclear Physics supports world-class scientific research at national laboratory and university research facilities located across the United States. This research requires continuing major investments in equipment and facilities in order to maintain forefront research capabilities. Listed below are proposed new initiatives and ongoing projects:

Line Item Projects:

12 GeV Upgrade
Location: Thomas Jefferson National Accelerator Facility	*TPC:* $310 Million	Project Status:* CD-2: Approved 11/09/07
Description: The proposed 12 GeV Upgrade will double the Continuous Electron Beam Accelerator Facility's (CEBAF's) beam energy from the current operating value of 6 GeV to 12 GeV to provide much more precise data on the structure of protons and neutrons. Specifically, the upgrade will enable scientists to address one of the great mysteries of modern physics – the mechanism that “confines” quarks together. New supercomputing studies indicate that force fields called “flux-tubes” may be responsible, and a 12 GeV electron beam is required to excite them, which should lead to the creation of never-before-seen particles. Jefferson Laboratory is proposing to upgrade the accelerator, construct a new hall and beam-line, and upgrade and/or add new equipment in the existing experimental halls. The Upgrade has the support of a large and active user community (~1,200 scientists from 29 countries). The scientific program and technical concept of the 12 GeV Upgrade has been thoroughly reviewed by the Department of Energy/National Science Foundation Nuclear Science Advisory Committee, which recommends the 12 GeV Upgrade as one of its highest priorities in the 2002 Long-Range Plan. In addition, the Office of Science’s Facilities for the Future of Science, A Twenty Year Outlook, identifies the 12 GeV Upgrade as a near-term rank seventh priority facility. This plan, endorsed by Secretary Abraham at his November 10, 2003 press conference, was developed with input from all the relevant stakeholders throughout the physical sciences and outlines the Office of Science’s future scientific initiatives and priorities.

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Electron Beam Ion Source (EBIS)

Location:
Brookhaven National Laboratory

TPC:
$14.8 Million

Project Status*:
CD-3: Approved 9/29/06

Description:
The flagship user facility at Brookhaven National Laboratory (BNL) is the Relativistic Heavy Ion Collider (RHIC), unique in the world for its ability to discover a heretofore-unknown state of nuclear matter called quark-gluon plasma. The operation of RHIC supports the scientific mission of the DOE by providing a world-class facility for Nuclear Physics Research. The quark-gluon plasma is created through the collision of heavy ions accelerated to nearly the speed of light. This process is started at the RHIC pre-injector. The present pre-injector for heavy ions for RHIC uses the Tandem Van de Graaff, built around 1970.

The EBIS project will provide a new heavy ion pre-injector for RHIC based on a high charge state heavy ion source, a Radio Frequency Quadrupole (RFQ) accelerator, and a short Linear Accelerator (Linac). The highly successful development of an Electron Beam Ion Source at BNL now makes it possible to replace the present pre-injector that is based on electrostatic Tandems with a reliable, low maintenance Linac-based pre-injector.

Linac-based pre-injectors are presently used at most accelerator and collider facilities with the exception of RHIC, where the required gold beam intensities could only be met with a Tandem until the recent EBIS development. EBIS produces high charge state ions directly, eliminating the need for two stripping foils required with the Tandem. Unstable stripping efficiency of these foils is a significant source of luminosity degradation in RHIC. The high reliability and flexibility of the new Linac-based pre-injector will lead to increased integrated luminosity at RHIC and is an essential component for the long-term success of the RHIC facility. This new pre-injector based on an EBIS also has the potential for significant future intensity increases and can produce heavy ion beams of all species including uranium beams and could also be used to produce polarized 3He beams. These capabilities will be critical to the future luminosity upgrades and electron-ion collisions in RHIC.

The replacement of the existing ion source at BNL with the proposed EBIS offers additional capabilities to NASA in the operation of the NASA Space Radiation Laboratory (NSRL) at BNL. NASA is contributing a total of $4,500,000 in funding to accelerate the project profile and decrease project duration. The Total Project Cost presented above represents the cost to DOE only.

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Facility for Rare Isotope Beams (formerly referred to as Rare Isotope Accelerator (RIA))
Location: To Be Determined	*TPC:* $425 – $550 Million (Not Baselined)	Project Status:* CD-0: Approved 2/9/04
Description: A facility for rare isotope beams (FRIB) is proposed to provide intense beams of rare isotopes for a wide variety of studies in nuclear structure, nuclear astrophysics, and fundamental symmetries. This facility could impact the study of the origin of the elements and the evolution of the cosmos, and offers an opportunity for exploring the limits of nuclear existence and identifying new phenomena, with the possibility that a more broadly applicable theory of nuclei will emerge. The facility would offer new glimpses into the origin of the elements by leading to a better understanding of key issues by creating exotic nuclei that, until now, have existed only in nature’s most spectacular explosion, the supernova. The original concept of this facility, formerly referred to as the Rare Isotope Accelerator (RIA) facility, was to use a powerful superconducting driver linac to provide intense beams from protons to uranium on a variety of production targets to optimize the yield of a desired rare isotope. As part of the alternative analysis, in 2005 the Office of Nuclear Physics and the National Science Foundation (NSF) charged the National Research Council (NRC) of the National Academies to assess the scientific case for a rare istope beam facility in an international context. The NRC concluded that a complementary, lower-cost, next-generation, radioactive-beam facility represents a unique opportunity to explore the nature of nuclei under conditions that only exist otherwise in supernovae and to challenge current understanding of nuclear structure. The report also concluded that the science addressed by a U.S. world-class facility for rare isotope beams, most likely based on a heavy-ion driver using a linear accelerator, should be a high priority for the United States. The Office of Nuclear Physics and NSF also charged the Nuclear Science Advisory Committee (NSAC) to perform an evaluation of the scientific ‘reach’ and technical options for the development of a world-class facility in the United States for rare isotope beam studies within a constrained funding envelope, and in the context of existing and planned research capabilities world-wide. The final NSAC report states that as a result of technical advances, a world-class facility with a subset of capabilities can be built at approximately half the cost of RIA, employing a superconducting linac.

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Major Items of Equipment (MIE):

Fundamental Neutron Physics Beam-line (FNPB)
*Location:* Oak Ridge National Laboratory	*TEC:* $9.2 Million	*Project Status: CD-3:** Approved 04/1/05
Description: The FNPB directly supports the Nuclear Physics mission and addresses the Office of Science Strategic program goal to understand the structure of nuclear matter, the processes of nuclear astrophysics, and the nature of the cosmos. The project includes the fabrication of a beam-line that can accommodate a wide variety of individual experiments. The beam-line will consist of neutron guides, choppers, secondary choppers, shielding, and an external experimental building, along with the necessary utilities, safety, and radiation protection equipment, as well as appropriate ancillary equipment.

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Gamma Ray Energy Tracking In-beam Nuclear Array
Location: Lawrence Berkeley National Laboratory	*TEC:* $17 Million	Project Status:* CD-3: Approved 10/31/07
Description: The Gamma Ray Energy Tracking In-beam Nuclear Array (GRETINA) detector will represent the next-generation gamma ray instrumentation, rotating among the Nuclear Physics low-energy accelerator facilities, optimizing their scientific productivity. GRETINA will provide significant gains in sensitivity in addressing several high priority scientific topics highlighted in the Nuclear Science Advisory Committee Long Range Plan, including studying how weak binding and extreme proton-to-neutron asymmetries affect nuclear properties and how the properties of nuclei evolve with changes in excitation energy and angular momentum. GRETINA will consist of 10 detector modules, each consisting of 3-segmented Ge detectors assembled in a common cryostat with a liquid nitrogen Dewar.

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Large-Area Time-of-Flight System for STAR

Location:
Brookhaven National Lab

TEC:
$4.8 Million

Project Status*:
Construction Start in FY 2006

Description:
The Solenoidal Tracker at RHIC (STAR) community proposes to install a 23k-channel multi-gap resistive plate chamber (MRPC) time-of-flight (TOF) system at the outer radius of the time projection chamber (TPC), the area now occupied by the central trigger barrel (CTB). The detector will cover the full azimuth and from -0.9 < h < 0.9. MRPC technology is a major new detector technology developed at CERN for the ALICE experiment. STAR has been conducting successful R&D for STAR-specific MRPC detectors since 2000. The technology and test results are described in the proposal. Prototype detectors operated successfully in STAR in Runs 3, 4, and 5 (2002-2005).

The parallel plate detectors are made from 2, 0.7 mm and 5, 0.55 mm-thick glass plates separated by 6, 0.22 mm gaps. An electric potential of 14 kV is applied across the plates. The chambers operate in a highly electro-negative gas, primarily Freon r134a. Charged particles traversing the plates create electron avalanches in the gas gaps which are seen in 3.15 cm x 6.3 cm copper pick-up pads. The signals are amplified, discriminated, then recorded by the CERN HPTDC chip with a 25 ps least-significant-bit precision.

The proposed TOF system will double STAR’s particle identification (PID) reach to 95% of all charged particles within the acceptance of the TOF detector. Seamless hadron particle identification from 0.1 < pT <~10 GeV/c over the full azimuth and -0.9 < h < 0.9 by the combination of time of flight and dE/dx at relativistic rise from the TPC will provide a crucial tool for the detailed study of the equation of state, hadronization, and jets in heavy-ion collisions. The enhanced PID capability is essential for STAR’s heavy flavor physics program and for investigations of chiral properties of resonance particles in dense matter through measurement of their leptonic decays. For example, the proposed TOF detector will allow STAR to make a precise measurement of the D⁰ production cross section in a normal running period. The identification of electrons below 2 GeV/c, by combining the TOF and the TPC dE/dx measurements, is critical for the measurement of resonances such as r, f, and J/y . The proposed TOF system will enable studies of identified-particle correlations and fluctuations over broad scales of pT, rapidity, and azimuth. These studies will open new opportunities in STAR, event-by-event analysis, possibly addressing the nature of the fluctuations induced by temperature variations and mini-jet scattering in the dense medium.

The new detector will be realized in two parallel fabrication projects, one in China and one in the U.S. Six Chinese universities and research institutions joined the STAR collaboration in 2001. The Chinese STAR Collaboration will take the responsibility for MRPC production in China. The Chinese group will manufacture and test 4032, 6-channel MRPC modules using Chinese funds, and will be responsible for delivering MRPC modules to the U.S. The U.S project will install the modules in aluminum trays, 32 per tray, build and install the read-out electronics, and test the completed detector trays. Both Chinese and U.S institutions will be responsible for installing and commissioning the detector in STAR.

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Large Hadron Collider Detector Upgrade for Heavy Ion Physics

Location:
CERN Geneva , Switzerland

TEC:
$5 - $16 Million
(Not Baselined)

Project Status*:
CD-0: Approved 11/23/05

Description:
Discoveries at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory have motivated a unique U.S-led research program at the Large Hadron Collider (LHC) at the Organisation Européanne pour la Recherche Nucléaire ( CERN ) that proposes upgrades to the existing detectors at the LHC. The LHC energy exceeds that of RHIC by a factor of 30. As a result, significantly different conditions and changes are expected at the LHC relative to RHIC in key parameters controlling the properties of the Quantum ChromoDynamic (QCD) matter generated in the fiery cores of ion-ion collisions; in particular, higher energy density and longer lifetime. RHIC measurements have established that the “perfect fluid” is remarkably dense and that high momentum processes provide novel and sensitive tools for characterizing its properties. As the mechanisms for the unexpectedly rapid thermalization and nearly perfect liquid flow of the matter produced in RHIC collisions are only partially understood, it remains to be seen if similar conditions apply to the even hotter matter that should be produced at LHC. The LHC will provide a larger variety of “rare” processes and more penetrating “jets” (a collection of particles flowing in the same direction) with significantly greater abundances. However, all the detector systems presently under construction at the LHC were designed prior to the RHIC discoveries and thus generally need supplementary capabilities to fully exploit the measurements of “jets” emanating from collisions between heavy ions. Thus, the LHC offers an outstanding scientific opportunity for U.S. scientists to extend its strategies employed at RHIC to gain complementary information about the properties of matter in the unexplored realms of density and temperature.

The LHC is slated to turn on by 2008 and plans to run eight months of proton-proton collisions and around one month of lead-lead collisions per year. There are currently three detectors under fabrication at the LHC that plan on participating in the heavy-ion program: A Large Ion Collider Experiment (ALICE), the Compact Muon Solenoid ( CMS ) and A Toroidal LHC ApparatuS (ATLAS) detector. ALICE is a special purpose detector being constructed by non-DOE entities specifically for relativistic heavy ion physics. Both the CMS and ATLAS detectors possess good detection capabilities for proton collisions that could be adapted with some additions to their core designs to contribute to the heavy-ion program. That is, all three experiments are planning to acquire heavy ion data during appropriate running periods at CERN .

To accomplish its mission, the NP program is proposing to participate in the LHC heavy ion program and support upgrades in one to three experiments (ALICE, ATLAS and CMS ) by adding new instrumentation and/or contributing data processing hardware.

There are three logical alternatives for addressing the needed capabilities to characterize high energy density matter using high momentum processes at the LHC.

Alternative 1a: The ALICE-USA collaboration is a group of 14 U.S. institutions that proposes to build a large area electromagnetic calorimeter ( EMC ) to complement and extend the ALICE high momentum program. The ALICE detector is the only detector under construction at the LHC that is optimized to study collisions of heavy nuclei. The integration of the proposed EMC into ALICE draws together the excellent tracking and particle identification capabilities of the other detector subsystems to provide the best characterization of energetic “jets” and their correlations with a wide variety of other measurements. This alternative can pursue a wider program and is better prepared to respond to new opportunities, owing to its more sophisticated detector and flexible data acquisition and trigger systems.

Alternative 1b: A “mini” ALICE EMC is also being considered. It is similar to Alternative 1a except it would have less detector modules and thus, its scientific coverage would entail roughly one quarter of Alternative 1a.

Alternative 2: The CMS -USA collaboration is a medium-sized group of 4 United States (U.S.) institutions headed by the Massachusetts Institute of Technology (MIT) that proposes to use the existing electromagnetic and hadronic calorimeter in the CMS experiment. Since the CMS was optimized for the proton-proton collider program, this alternative has less performance and flexibility compared to Alternative 1. However, when operated during the heavy ion run, its primary advantage is the availability of calorimetry with full azimuthal coverage and larger “pseudo rapidity” coverage. A major part of the pre-proposal requires the acquisition of two out of a total of eight “slices” of the CMS online computer farm since the highly specialized triggering requirements for heavy ion collisions are extremely exacting on real time computing.

Alternative 3: ATLAS-USA collaboration is presently a small group of U.S. researchers that propose to use the existing electromagnetic and hadronic calorimeter in the ATLAS experiment that has similar capabilities to the CMS alternative two. The emphasis is placed on high momentum signatures, which are better matched to the ATLAS design concepts than “soft” low momentum measurements which are covered by option one. No major changes are required to the detector presently under construction, nor to the trigger and data acquisition system. The fabrication of a small Zero Degree Calorimeter similar in the design now used by all four RHIC experiments is proposed.

Alternative 4: Do nothing. The study of high energy density matter is an international effort in which U.S. leadership is preeminent. No involvement at the LHC will preclude U.S. scientists to be partners in the discoveries to be gleaned at the higher energy density frontiers offered by LHC.

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Neutrinoless Double Beta Decay Project

Location:
TBD

TPC:
$15-$75 Million
(Not Baselined)

Project Status*:
CD-0: Approved 11/23/05

Description:
Joint Project between the Office of Nuclear Physics and the Office of High Energy Physics

Among the several broad areas of study in nuclear physics and high energy physics is the utilization of low-energy processes and selected nuclei as “laboratories” to provide insight into fundamental interactions and particles often studied at much higher energies. This thrust includes the physics of neutrinos, motivating such important projects as the Super-Kamiokande experiment that studied atmospheric neutrinos, the Sudbury Neutrino Observatory (SNO) solar neutrino experiment, the experiment using the Kamioka Large Anti-Neutrino Detector (KamLAND) to study reactor neutrinos, and the MiniBooNE experiment at Fermi National Laboratory.

One of the exciting recent scientific realizations from these and other neutrino experiments is that neutrinos are transformed from one type into another as they travel from their source to a detector, a quantum mechanical phenomenon called “neutrino oscillation”. The fact that neutrinos oscillate requires that they have a non-zero mass. However, from several lines of evidence, it is known that neutrino masses must be very small. The small mass of the neutrino leaves open another intriguing possibility, that neutrinos are their own antiparticle. Such a property could have far-reaching consequences in fundamental and particle physics, and even cosmology. Precision experiments that exploit the process of neutrinoless double beta decay provide possibly the best opportunity to address both of these crucial questions: what are the masses of the neutrinos, and are they their own antiparticle.

Two neutrons inside a nucleus can spontaneously transform into two protons and two electrons (thus, double beta) in order to conserve charge and two antineutrinos to conserve lepton number. Electrons, neutrinos and their antiparticles are leptons and lepton number is a conserved quantum number. This means that since neutrons are not leptons the decay products must have the total lepton number equal zero. Researchers believe that a variation of this process might occur that violates lepton number in which no neutrinos are emitted (thus, neutrinoless decay). In this case, a virtual neutrino might be emitted by one neutron and absorbed by the second neutron or they could be annihilated. This process has never been observed. If discovered, neutrinoless double beta decay could: (1) provide an independent verification of the existence of neutrino mass along with a measure of its absolute scale and mass hierarchy; (2) establish the nature of the neutrino wherein it is its own antiparticle; and (3) indicate violation of a fundamental symmetry, lepton number conservation.

The rate at which neutrinoless double beta decay occurs is proportional to the effective weighted mass of the neutrino among its three flavors. Experiments exploiting this process offer the most sensitive means to determine an absolute scale for the neutrino mass for the foreseeable future. A handful of nuclei have been identified as having the most favorable characteristics to maximize the possibility of detecting and quantifying this rare process.

Experimental Alternative 1: CUORE (Cryogenic Underground Observatory for Rare Events)
The CUORE experiment involves a collaboration of ten European laboratories and universities, along with LBNL, the University of South Carolina, LLNL, and the University of California (Berkeley), and is led by the University of Milan in Italy. The experiment would be at the Gran Sasso underground laboratory in Italy. CUORE utilizes the isotope 130Te, which is abundant enough in natural tellurium that isotopic separation is not required to mount a 780-kg(TeO2) class experiment. An upgrade path could require the enriched isotope. The main technical components would be detector modules of the isotopic crystals, electronics, data acquisition, cryogenics and shielding.

Experimental Alternative 2: EXO (Enriched Xenon Observatory)
The EXO experiment involves a collaboration of Stanford University, Stanford Linear Accelerator Collider (SLAC), the University of Alabama, Colorado State University and several foreign institutions. This experiment would employ the separated isotope 136Xe, which is a good candidate for the planned detector, a Time Projection Chamber, and a technique for extracting and identifying the residual atom of barium.

Experimental Alternative 3: Majorana
The Majorana experiment is being planned by a collaboration of eleven U.S. laboratories and universities (the University of Washington, Pacific Northwest National Laboratory, LBNL and Los Alamos National Laboratory are principle institutions), and institutions in Russia, Canada, and Japan. This experiment would utilize ~180 kg of the separated isotope of germanium, 76Ge. This experiment benefits from a deep underground site. The approach is scalable to reach lower values or limits of the effective neutrino mass.

Experimental Alternative 4: Do nothing.
Neutrinoless double beta decay is the only process feasible for determining whether the neutrino is its own antiparticle. If it is, then neutrinoless double beta decay also provides the most sensitive method to measure the neutrino mass or determine an upper limit for its value. If the project is not done, these two high priority goals of the U.S. nuclear and particle physics programs may eventually be answered in European experiments without major U.S. participation, resulting in the loss of U.S. leadership in this high priority science field, and the concomitant loss of potential technical spin offs and training of next generation scientists.

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Neutron Electric Dipole Moment Experiment

Location:
SNS, Oak Ridge National Laboratory

TEC:
$12-18.3M
(Not baselined)

Project Status*:
CD-0: Approved 11/23/05

Description:
The neutron electric dipole moment experiment (EDM) studies the fundamental space-time properties of the neutron, one of the building blocks of the matter that surrounds us. This is done by looking for a very small difference in the precession rate of a neutron placed in magnetic and electric fields when the electric field is oriented either “up” or “down.” Precession is a phenomenon by which the axis of a spinning object "wobbles" when a torque is applied to it. The observation of a different precession rate indicates that the neutron has a significant electric dipole moment and therefore a Charge Parity (CP)-violating preferred arrangement of the quark charges inside the neutron. CP-violation may explain the matter excess in the universe. The proposed major item of equipment (MIE) in support of this experiment will allow the fundamental space-time properties of the neutron to be studied with two orders of magnitude greater sensitivity than ever before. This level of sensitivity does not exist in current and planned experiments and is necessary in order to measure the different rates of precession to sufficient accuracy to constrain existing theoretical models.

The existence of an EDM constrains a wide variety of theories of nuclear and particle physics. The increased sensitivity will permit researchers to achieve greater precision measurements in order to probe CP violation in the strong interaction at sufficient levels needed to help understand the matter/anti-matter asymmetry of the universe.

A promising experimental approach called the superthermal method of ultra cold neutron (UCN) production would uses liquid Helium (LHe) in a novel cryogenic technique to obtain an improved sensitivity of two orders of magnitude better than existing experiments. This first exploitation of liquid helium (LHe) is to produce very high densities of UCN in an experimental bottle by down scattering cold neutrons from He atoms, resulting in a UCN and a phonon. LHe is a very good dielectric. This property of LHe will permit the experimenters to apply very high electric fields to the measurement volume. The cryogenic temperatures will allow for long storage and thereby measuring times of the UCN. These three factors will enable the great improvement in sensitivity. This is currently the only experimental approach being proposed in the U.S.

The EDM experiment looks for a very small change in the precession rate of a neutron placed in a magnetic and electric field when the electric field is oriented “up” or “down”. Thus the experiment is extremely sensitive to small fluctuations of the weak external magnetic field that envelops the UCN. This problem is overcome by the addition of the only other species that can occupy the same volume as the UCN, i.e. 3He, which has a magnetic moment very similar to that of the neutron but can have no EDM at the sensitivity of the experiment. Thus the 3He provides a control measurement for the neutrons. The 3He provides the extra benefit of measuring the precession rate of the neutrons through their highly spin-dependent capture cross section.

The EDM experiment is specifically designed to utilize one of two experimental areas at the Fundamental Neutron Physics Beam-line (FNPB), a Major Item of Equipment (MIE) currently supported by NP and under fabrication at the Spallation Neutron Source (SNS) located at Oak Ridge National Laboratory (ORNL). FNPB is unique in that it will provide the highest peak current of cold and ultra-cold neutrons (UCN) in the world.

Without an EDM experiment, the opportunity to play this leadership role in achieving the necessary measurements to better understand the space-time properties of the neutron (in support of NP’s mission) will be lost. In addition, the return of investment in the FNPB and the scientific benefits anticipated with its construction will be minimized. Alternatives would include doing nothing and not realizing this compelling scientific opportunity, or playing a minor role in existing efforts elsewhere in the world, that do not have the capabilities of the FNPB at the SNS, or the projected sensitivities of the proposed experimental technique.

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* Critical Decision-0, Mission Need; CD-1, Alternative Selection and Cost Range;
CD-2, Performance Baseline; CD-3A, Long-lead Procurements; CD-3, Start of Construction;
CD-4, Start of Operations or Project Close; TEC, Total Estimated Cost; TPC, Total Project Cost