Prospects for Neutrino Physics at the Spallation Neutron Source

1. Prospects for Neutrino Physics at the Spallation Neutron Source Vince Cianciolo, ORNL for the nSNS Collaboration Carolina Neutrino Workshop 2004

2. Neutrino!   + + A e+ e p - ~99% LINAC:  x ~1000  Accumulator Ring: Capture The Spallation Neutron Source • Proton beam current: 1 mA • Proton beam energy: 1 GeV • Protons/pulse: ~1.61014 • Pulse rate: 60 Hz • Pulse length: 380 ns (FWHM) • Operating hours/year: 5000 • Proton target material: Mercury • Neutrinos/pulse/flavor: ~1.61013 • Neutrino-target interactions/year: few thousand Repeat 60/sec. Carolina Neutrino Workshop 2004

3. Decays with t1/2 = t1/2 = 26 ns Decays with t1/2 = t1/2 = 2.2 ms p m Time Structure • Next pulse arrives in 16,000,000 ns! • Turning the detector on for only a few ms after each pulse reduces cosmic-ray background by ~ x2,500. • 2.3 km water-equivalent. • Leaving the detector off for the first ms after a pulse effectively eliminates machine-related backgrounds. • Also eliminates clean neutral-current events. • Whether sufficient background rejection can be achieved w/o this cut (through shielding and detector techniques) is under study. Carolina Neutrino Workshop 2004

4. SNS neutrino spectra Supernova neutrino spectra, 100 ms post-bounce Energy Spectra • Neutrino spectra at stopped-pion facilities have significant overlap with the spectra of neutrinos generated in a supernova explosion! Carolina Neutrino Workshop 2004

5. National Research Council Report by the Committee on the Physics of the Universe Scientific Motivation • Core-collapse supernovae. • Neutrino detector calibration. • Nuclear structure (complement to RIA). Carolina Neutrino Workshop 2004

6. Core Collapse Supernovae • Most spectacular explosions in the universe. (R. Hix) • Birthplace of most “heavy” elements – we are stardust. • The core of a supernova is so dense it is black to neutrinos. Since there are so many of them they play a crucial role in the explosion and the accompanying nucleosynthesis. • Knowledge of nA cross-sections for A<120 is crucial when attempting to make accurate supernova models. Carolina Neutrino Workshop 2004

7. Neutrino Detector Calibration • Large-scale detectors exist or are proposed to measure supernovae neutrinos. • In order to make full use of their data, calibrations of neutrino interactions in the detector materials are required. • Integral cross-sections insufficient. • Differential cross-sections (vs. energy, angle) are crucial. • Neutral-current interactions also very important. Carolina Neutrino Workshop 2004

8. Nuclear Structure • nA cross section measurements provide important information to constrain nuclear structure models. • Reasonable extrapolations away from measured nuclei can be made for ~DN<8, DP<8 (up to shell boundaries). • The plot shows extrapolation regions relative to 8 of the ~36 feasible target materials. • Rather complete coverage in a few years! Carolina Neutrino Workshop 2004

9. nSNS Goal:Precision nA Cross Section Measurements • Build a facility that will allow a total cross section measurement with s<10% in one year. Carolina Neutrino Workshop 2004

10. Feasibility • A suitable location has been identified. • Floor-loading calculations have been performed. • Total capacity = 545 tons. • Allows for 1 meter ceiling, ½ meter walls. • Together with SNS time structure, active veto provides sufficient rejection of cosmic-ray background. • SNS management has provided encouraging response and is empanelling a review committee. Carolina Neutrino Workshop 2004

11. Bunker, Active Veto • Active veto (e > 99%) required to reduce cosmic muons. • Time structure plus passive shield reduces cosmogenic and machine-related neutron backgrounds sufficiently. • 1m thick ceiling;½-m thick walls • 4.5 x 4.5 x 6.5 m3 total vol.  3.5 x 3.5 x 5.5 m3 inside shield. • Remaining volume large enough to house two 10-ton fiducial target/detectors. S Shielding Veto Detector 2 20 t Detector 1 20 t Carolina Neutrino Workshop 2004

12. e Segmented Detector • Designed to handle metals or other solid targets. • Targets – thin wall pipes, easily replaced. • Active detector – straw gas tubes. • Mass of the sensitive part of the detector is less than target mass. • Reconstruct tracks and count # of fired tubes: • sE ~ 30% • sQ ~ 15 degrees • Particle ID through e.g., # of fired tubes, track linearity, energy deposition. Carolina Neutrino Workshop 2004

13. Homogeneous Detector • “Standard” technology • mBoone • Suitable for transparent liquid targets, e.g., d, C, N, O, I, Br, Pb • Light detection by PMT or PD • ~38% PMT coverage allows for either scintillator or Cerenkov detection. Carolina Neutrino Workshop 2004

14. Timescale • Commissioning could reasonably begin when machine power approaches design value (end of CY08). Carolina Neutrino Workshop 2004

15. http://www.phy.ornl.gov/workshops/nusns/vSNSstudy.pdf Collaboration • Robust collaboration. • >30 members, more welcome! • Next collaboration meeting to be held June 11-12 at ORNL. • Assembled study report that discusses all elements of this talk in greater detail. • Will form the basis for input to the APS Neutrino Working Group • Copies available at back of room, on the web. Carolina Neutrino Workshop 2004

16. Conclusions • The SNS provides a unique opportunity to study low-energy (10’s of MeV) nA interactions. • Pulsed time structure. • Intensity. • Building a nA facility at the SNS is feasible. • Sufficient intensity. • Suitable location. • SNS Management encouragement. • Addresses broad range of physics interests. • Understanding the supernova explosion mechanism. • Calibration of neutrino detectors. • Nuclear structure complementary to RIA. Carolina Neutrino Workshop 2004

17. Neutrino oscillations at the SNSORLAND Redux • If MiniBoone confirms LSND result, the SNS would be a logical place to follow up. • Low backgrounds due to absorption of the vast majority of nes in mercury target. • If nSNS goes forward there will already be a near detector to quantify the remaining backgrounds. • Very precise measurement of oscillation parameters possible. Carolina Neutrino Workshop 2004