Outlook on Underground Science Thomas Bowles Los Alamos National Laboratory / University of Washington American Physical Society Meeting Philadelphia April 5, 2003 Nuclear Physics

The Reach of Underground Science A Remarkably Wide Range of Science and Engineering Issues Can Be Addressed Underground Nuclear Physics Neutrino Physics* Particle Physics* Astrophysics* Geophysics + Geobiology + National Security* Education and Outreach In order to fully exploit this potential requires the construction of a National Underground Science and Engineering Laboratory (NUSEL) * Requires depth to eliminate radiactive backgrounds + Requires underground environment

Neutrino Experiments Neutrino Physics - redefining our view of the world –Recent results from SuperKamiokande, SNO, and KamLAND demonstrate conclusively that neutrinos have mass and oscillate between different flavors (e, ,  ) –These results come from large underground detectors in Japan (SuperK and KamLAND) and Canada (SNO) Nuclear Physics Photomultipliers

Neutrino Properties Nuclear Physics What We Don’t Know – Are neutrinos their own antiparticles? (Majorana ) – What is the absolute scale for neutrino mass? – Is the mass scale normal ordered or inverted hierarchy? – Are there sterile neutrinos? – What are the elements of the MNS mixing matrix? – Is CP / CPT violated in the neutrino sector? –Why is the neutrino sector so different than the quark sector? What We Know – Neutrinos have mass and oscillate – Oscillation parameters (  m 2 and tan 2  ) known to ~ 30% – Neutrino masses are small 50 meV < m < 2.8 eV (90% CL) Neutrinos account for at least as much mass in the Universe as the visible stars

Rare Decays / Interactions Double beta decay – Allowed 2 decay : (A,Z)  (A, Z-2) + 2 e – + 2 e – 0 decay : (A,Z )  (A, Z-2) + 2 e – Requires neutrino mass Requires lepton number violation Requires Majorana neutrino Current experiments have sensitivity m < 300 meV Nuclear Physics _ Search for the source of dark matter – Dark matter may be Weakly Interacting Massive Particles (WIMPs) – Our galaxy is moving through the dark matter with a velocity of 270 km/s – WIMP interactions result in recoil nuclei with energies of few tens of keV – Many experiments are underway to search for WIMPs New generation of experiments now being proposed to reach into the range predicted by SUperSYmettry New generation of experiments now being proposed to reach meV mass range from solar/atmospheric

Particle Physics – Search for baryon number violation New generation of proton decay experiments proposed: – LANND - 70 kton liquid argon TPC – UNO, HyperKamiokande Water Cerenkov detectors in US, Japan with lifetime limits on proton decay: DecayPresentProjected (UNO-15 yr) p  e +  o 5 x yr2 x yr p  K x yr2 x yr Nuclear Physics – Atmospheric neutrinos – Long-baseline neutrino oscillations Brookhaven AGS to UNO at NUSEL – < 1% measurement of  m 2 32, sin 2 2  23 – Sensitive to sin 2 2  13 > – Good sensitivity to CP violation 60,000 events per year in UNO – Including 400  events per year Provides good sensitivity to oscillation parameters

Astrophysics at NUSEL Improve our understanding of solar and stellar processes Future solar neutrino experiments will provide direct measurements of the flux of solar neutrinos with E < 5 MeV – Provides test of the Standard Solar Model (p-p, 7 Be, CNO ’s) CNO ’s power initial convective stage during first 10 8 years of solar burning CNO rate tests initial core metallicity Nuclear Physics Future supernova neutrino experiments will provide important information: – Supernova dynamics – Role of neutrino physics in nucleosynthesis – High event rates for galactic supernova (10 kpc): ~ 1000 SNO events, 9000 SuperK events ~ 140,000 UNO events

Nuclear Astrophysics at NUSEL Improve our understanding of the nuclear reactions in solar and stellar processes Nuclear cross section measurements at a high- intensity, underground accelerator facility – Depth is required to suppress cosmic ray backgrounds in measurements of extremely small cross sections of solar fusion. Improve our understanding of nucleosynthesis of the heavy elements in supernova Nuclear Physics

Geosciences at NUSEL Understand characteristics and recovery of water, energy, and mineral resources Develop models and predictive capabilities for water movement, waste storage, … Develop and test techniques for environmental remediation of contaminated wastewater, soil, … Nuclear Physics Understand fractures in rock – Rock strength – Fluid flow – Heat flow – Chemical transport – Ore formation – Faults and earthquakes Need ability to instrument extensive u/g volume: – Generally working mines only allow restricted access for limited periods of time – To make significant progress requires: Continuous access Access to heterogeneous structures Access to large-scale formations Active experiments with heating, chemical tracers, water, … Instrumentation throughout mine Data over very extended periods of time (decades) Extensive diamond coring Deep drilling starting from deepest location possible

Geosciences and Neutrino Physics Search for geophysical antineutrinos – Primary thermal driver of the Earth comes from the radioactive decay of the U and Th chains – Geophysical data provides only indirect estimate of the total amount of U and Th in the Earth Nuclear Physics – There exist different theories of the heating of the Earth’s core, including the possibility of a nuclear reactor in a liquid nickel core – Neutrino experiments are starting to provide the first direct measurements of the total amount of U and Th in the Earth!

Geomicrobiology at NUSEL Study life in extreme conditions Microbial life exists in deep, hot rock! Nuclear Physics Applications in geomicrobiology – New microbes may be of benefit to medicine – Microbes may be efficient means for environmental remediation – Outstanding questions: How long has life at depth been sequestered? What are the connections between life at the surface and life in deep rock? Are there unknown microbes at depth? What are the limiting conditions for life at depth? What can life at depth teach us about extraterrestrial life? – Deep rock may have been shelter for life at early times – 200 M yr old bacteria at WIPP shown to be viable

Additional Aspects of NUSEL National security –Ultra low-level counting Background reductions of possible Provides new capabilities and flexibility: – Nuclear forensics – Theatre defense applications – Industrial applications - Single Event Upsets – Improved capabilities for environmental applications Education and Outreach: –The public has great interest in the science that will be carried out at NUSEL. Research will include E&O as an integral part Nuclear Physics

Depth Issues at NUSEL Experiment Requirements Ultra-low level experiments  decay, dark matter, reactor/SN/solar Great depth, modest to large size High-energy experiments Proton decay, long-baseline, atmospheric Moderate depth, large size Geophysics / Geomicrobiology 3-D from surface to great depth Heterogeneous,  T, H 2 O National Security Modest depth, small size Ultra low-level counting facility Great depth, moderate size for R&D on experiments Nuclear Physics

NUSEL at Homestake Nuclear Physics

NUSEL at San Jacinto Nuclear Physics

WIPP as an Underground Laboratory Nuclear Physics

An Extension to SNO Nuclear Physics

Comparison of Underground Labs Nuclear Physics

The Best Site Homestake provides the optimal site in the US 600 km of existing drifts down to great depths (8000’) A tremendous amount of existing infrastructure Large hoisting capabilities Extremely strong rock Dedicated operation of a deep u/g science laboratory Ability to take sea-containers directly u/g Ability to excavate UNO-size cavity in 2-3 years Ability to excavate large chambers at depth 15 MVA of power substations, 860,000 cfm HVAC, … Complex geology throughout site Provides ideal conditions for geoscience / geomicrobiology Minimal risk in excavation (109 yrs of experience) Location appropriate for long-baseline experiments Nuclear Physics

Homestake - A Unique Opportunity Nuclear Physics Geosciences proposing Earthlab at Homestake

The Status of NUSEL Homestake planned closure on 1/1/02 announced 9/11/00 UW Long Range Plan workshop starts NUSL-Homestake effort Committee on Underground Scientific Laboratory recommends Homestake as preferred site NSAC Long Range Plan recommends construction of a deep u/g lab as the highest priority for near-term construction HEPAP Long Range Plan NRC Committee on Physics of the Universe NRC Neutrino Facilities Assessment Committee NeSS ‘02 workshop held in September participants – NSAC sends support letter for Homestake to NSF and DOE Unanimous agreement of working group leaders to construct NUSEL Strong interest in NSF Physics, Geology, Biology Divisions Nuclear Physics Support for NUSEL: Compelling Science Case for NUSEL Established and Vetted Homestake Recommended as the Best Site April NUSEL consortium formed Homestake proposal submitted to NSF June 2001 San Jacinto proposal submitted to NSF September 2001 Established Interim Homestake-NUSEL Collaboration – Revised Homestake proposal being prepared: –Much improved use of lifts –Preserves prime area at 4850 for megadetector construction –No shaft extension or major drift excavations required –Proposal will be completed this summer

The Status of Homestake Mine is secure, Barrick is positive about NUSL Indemnification is still a major issue – Continuing to carry out environmental remediation – Carrying out maintenance on hoists, replaced hoist ropes – Continues to employ ≈ 35 people on site – Continued operations to keep mine available for NUSEL – Costs Barrick ~ $200K/month with no reimbursement Strong support from the SD governor, senators and congressmen, local legislature, and neighboring states. Proposal needs to be approved by NSF Science Board. Indemnification needs to be resolved. NSF and OMB need to resolve issues/priorities on funding Funding possible in FY05 ??? Nuclear Physics – Barrick working with the state of SD to reach agreement If all goes well, we will be able to return to the site of the first oservation of solar neutrinos by Davis et al. with a major new science facility. Thar’s more gold in them thar hills than what comes out of the ground.