2. Stellar Neutrino Studies at the Spallation Neutron Source (Oak Ridge) (SNS) 2 NuFact 03 - June 10 th Or study of neutrino nucleus cross sections at veeery low energy

3. Pre supernovae Evolutionary stages of a 25 MSUN star: Stage Temperature (K) Duration of stage Hydrogen burning 4 x 10 7 7 x 10 6 years Helium burning 2 x 10 8 5 x 10 5 years Carbon burning 6 x 10 8 600 years Neon burning 1.2 x 10 9 1 year Oxygen burning 1.5 x 10 9 6 months Silicon burning 2.7 x 10 9 1 day Core collapse 5.4 x 10 9 1/4 second

4. Supernovae Recorded explosions visible to naked eye: Year (A.D.) Where observed Brightness 185 Chinese Brighter than Venus 369 Chinese Brighter than Mars or Jupiter 1006 China, Japan, Korea, Europe, Arabia Brighter than Venus 1054 China, SW India, Arabia Brighter than Venus 1572 Tycho Nearly as bright as Venus 1604 Kepler Brighter than Jupiter 1987 Ian Shelton (Chile)

5. Explosion Collapse and re-bound(1-4) creates a shock wave(5) propagating outward from center of core(6), meeting in falling outer core material Shock stalls due to neutrino escape & nuclear dissociation Deleptonisation of the core creates intensive neutrino flux (99% of energy) Neutrino interactions behind the shock reheat the shock and drive it outwards(7) Measuring 56 Fe( e,e - ) 56 Co provides valuable data to guide shock formation models. Other cross sections, 28 Si, should also play an important role. 5

6. Energy in supernovae Total energy – 10 53 erg Light – 1-2% Neutron star kick ~1% 98% of the energy is emitted by neutrinos !!!!

7. -Process Nucleosynthesis in Supernovae “ process nucleosynthesis” could be an important new dramatically altering the r-process (push through waiting nuclei) “ process nucleosynthesis” can produce rare isotopes - 180 Ta, 138 La, 19 F, 10,11 B These isotopes cannot be produced at other sites and thus form “fingerprints” 181 Ta(  ’ n) 180 Ta 138 Ba( e,e - ) 138 La 20 Ne(  ’ n) 19 Ne 19 F 12 C(  ’ p) 11 B, 12 C(  ’ pn) 10 B

8. Conclusion: Neutrinos are important For Super Novae explosion mechanism SN dynamics Nucleosynthesis of heavy elements. To understand those we need to know: Neutrino oscillations parameters. Neutrino interactions in the range of SN energies The last one is important contribution to the nuclear theory

9. SN neutrino energies In this region of energy only three nucleus has been measured: d(40%), C(10%), and Fe(50%), and only carbon – published. Core collapse of ~25 solar mass star

10. The Spallation Neutron Source ORNL 1.3 GeV proton accelerator Accumulator ring 2 MW Mercury target

11. SNS parameters Primary proton beam energy - 1.3 GeV Intensity - 9.6  10 15 protons/sec Pulse duration - 380ns(FWHM) Repetition rate - 60Hz Total power - 2 MW Liquid Mercury target Number of neutrino produced ~ 3  10 22 /year This is a neutrino factory already under construction !!!

12. Present status First beam - 2006, full power - 2008

13. Neutrino Production at SNS Hg ++ -- 99.6% ++   e  -- e+e+ e-e- 94% 0.13 0.09 e, , , >> e   e p SNS

14. Energy Time Actual spectra of neutrinos from SNS Short pulses with the energy similar to SN neutrino spectra

15. The SNS will produce 3.2x10 15 neutrinos/sec in 60Hz pulses It will be the most intense, pulsed, low energy neutrino source in the world! The pulsed source drastically reduces backgrounds from cosmic rays. Reduction is equivalent to 1 km of rock overburden. Beam time structure allows separation of  from  and e Spectra of ,   and e are well known e is highly suppressed SNS is a Unique Neutrino Source

16. Reaction Cross section for these energy is small !!! e e -  e e -  e -   e - e 12 C  12 Ngs e - e 12 C  e 12 C *  12 C   12 C * e p  ne + e 56 Fe  56 Co e - 0.297  10 -43 cm 2 0.050  10 -43 cm 2 0.92  10 -41 cm 2 0.45  10 -41 cm 2 0.27  10 -41 cm 2 7.2  10 -41 cm 2 ~2.5  10 -40 cm 2 However SNS will deliver ~ 3 10 22 neutrinos per year At such flux Carbon at 20 meters yields ~ ¼ interaction per kilogram per year

17. Location of detectors at SNS Neutrino emission from the target is isotropic Extra advantage for small detector – less background from cosmic rays. Not exceedingly close to the target, as some shielding is required to reduce flux of energetic neutrons from spallation target. Closer => Smaller and Cheaper Closer => Smaller and Cheaper

18. SNS Target Building Property of BES branch of DOE Neutron beams and users have high priority Our advantage: we do not need beam line ! We do not want beam line ! We need a spot on the floor not far away from the target Potential location ~ 20 m from the target

19. What do we plan? We propose to built protected enclosure At 20 meters from the SNS Bunker with active veto large enough to have two 10-20 t detectors. 4.5  4.5  6.5 meter outside 2.5  2.5  5.5 meters inside Two detectors placed one on the top of other First one Homogeneous “Simple”, light collection technique. Liquid, transparent targets Second Segmented: More challenging, modular structure with replaceable targets. Detector should have enough mass to provide ~ 1k events per year. Plan is to run one new target every year. First target will be Iron.

20. Liquid targets 2 d, 12 C, 16 O, 127 I Hermetic vessel with good PMT coverage Concept of homogenous detector 300, 8” PMTs 40% of photocathode coverage ~ 15 t fiducial mass 3 m

21. Metal or other solid targets 51 V, 27 Al, 9 Be, 11 B, 52 Cr, 56 Fe, 59 Co, 209 Bi, 181 Ta Active detector – gas tubes Energy measurement - by range Concept of segmented detector e Expected resolution for tubes 10mm and 0.5 mm at 30 MeV is ~ 25% Detector size for 20 t fiducial mass is – 3.0  2.3  2.3 Expected event rate (for iron target)~16/day: Good separation from neutrons

22. Background estimations SNS neutrons. Extra shielding and absorbers will eliminate low energy neutrons Time cut will remove high energy neutrons Cosmic Ray Background: SNS duty factor is 4  10 -4 Active hermetic veto will cut another 99% 1 meter of steel overburden will kill hadronic component Our estimations shows that expected number of untagged neutrons events in the detector is - 5 /day. This is already below expected neutrino event rates Extra factor is expected from PID in detectors.

23. Formal Proposal -January 2004 Detector R&D and design-2003-2006 (applying for ORNL LDRD money right now) Detector Construction begins- FY 2006 Shielding Enclosure Erection- 2007 Detectors Installation Completed- January 2008 Detectors Commissioning- Summer 2008. (SNS) 2 Schedule

24. SNS Conclusion We have a unique opportunity to established program for neutrino- nucleus cross section at very lower energy This will be modest by $, long range program This program will influence Cosmology, Nuclear Astrophysics, and Nuclear theory This program should be done !!! Ideas and collaborators are welcome SNS 2