1 / 34

Neutrinos at the SNS (Spallation Neutron Source)

Supper Neutrino Source. Neutrinos at the SNS (Spallation Neutron Source). Yu.Efremenko. ORNL. 0. A little bit of Modern Neutrino History Why Low Energy Neutrinos are Good 2. Some Proposed Neutrino Experiments at SNS.

wells
Download Presentation

Neutrinos at the SNS (Spallation Neutron Source)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Supper Neutrino Source Neutrinos at the SNS (Spallation Neutron Source) Yu.Efremenko ORNL 0. A little bit of Modern Neutrino History Why Low Energy Neutrinos are Good 2. Some Proposed Neutrino Experiments at SNS

  2. The Earliest Neutrino Conference that has Transparencies posted on the WEB is Neutrino 1998 Lets Look Back in Time • From the opening talk by • P.Ramond(Florida) Ten Years later Yes !!! dm122 = 7.58·10-5eV2sin2(2θ12)=0.87 SNO & KamLAND Yes !!! dm322 = 2.4·10-3 eV2sin2 (2θ23)=1.00 SuperK, K2K, MINOS MiniBoone left door open for some exotic scenarios Two out of three done!!!!!

  3. Now We Have New Set of Experimental Challenges We have a long list of neutrino properties to study. Neutrino Mass –> KATRIN + Set of Double Beta Experiments θ13 -> DoubleChooz, Daya Bay, T2K, NOVA CP phase–> Long Baseline experiments At the same time we have to look at what role neutrinos are playing in our Universe. To do so we have to better understand neutrino interactions with nuclei!

  4. Man Made Neutrino Sources Stop Pion Facilities 10<En<53 MeV Very interesting region. It is nicely coincides with neutrino energies produced during the Super Novae Explosion Nuclear reactors En<10 MeV H.E. “accelerators” En >100 MeV In E-M LSN~L galaxy In Neutrinos LSN~ 3000 L galaxy

  5. SN neutrino spectra, 0.1 s post-bounce Core-collapse supernovae • Destruction of massive star initiated by the Fe core collapse • 1053 ergs of energy released • 99% carried by neutrinos • A few should happen every century in our Galaxy, but the last one observed was over 300 years ago (recently discovered ~150 years old remnants of SN in M.W. G1.9+0.3) • Dominant contributor to Galactic nucleosynthesis • Neutrinos and the weak interaction play a crucial role in the mechanism, which is not well understood SN 1987a Anglo-Australian Observatory

  6.  reactions and nucleosynthesis  opacities Electron capture and core collapse • Neutrinos interactions are believed to be crucial in the delayed mechanism • Realistic treatment of  opacities is required for supernova models • Neutrino reactions with nuclei ahead of the shock may alter the entropy & composition of in fall [Bruenn & Haxton (1991)]. • Neutrino reactions may have an important influence on nucleosynthesis in the r process: setting the neutron-to-proton ratio and altering the abundance pattern [Haxton et al. (1997)]. • Electron capture and the charged-current ne reaction are governed by the same nuclear matrix element: • ne + A(Z,N)  A(Z+1,N-1) + e- • New calculations using a hybrid model of SMMC and RPA predict significantly higher rates for N>40 • Supernovae models w/ new rates: • shock starts deeper and weaker but less impedance • Many ingredients • Charged-current reactions on free nucleons (and nuclei) • Neutral-current scattering • A coherent scattering • e-e scattering •  scattering •  annihilation Neutrinos and Core Collapse SN The weak interaction plays a crucial role in supernova ! We need good understanding of neutrino interactions !

  7. ADONIS or HALO SN 1987A Supernova Neutrino Observations High statistic measurement of neutrino signal from SN will provide wealth of information about SN dynamics • An accurate understanding of neutrino cross sections is important for SN neutrino detectors. • Nuclei of interest: C, O, Fe, Pb

  8. Diffuse Supernovae Neutrino (DSN) Detection While waiting for SN to happen in the Milky Way we can search for diffuse SN flux From: C.Lunardini, astro-ph/0610534 • Several proposals are aiming to be sensitive enough to see DSN: • GADZOOKS • HyperKamiokande • UNO • MEMHYS • LENA • LANNDD • GLACIER

  9. Atmospheric Neutrino Background for DSN Water Cherenkov detectors: SuperK 92 kton·y Irreducible background from atmospheric neutrino interactions: limit discovery potential. Detectors with Neutron Detection Capabilities: Antineutrino Channel with neutron detection will eliminate such a background From LENA proposal: Phys.Rev.D75:023007 there is claim of background free window from 10 till 25 MeV However background from neutral current reactions have not been considered yet. We need good understanding of neutrino Carbon and neutrino Oxygen interactions!!!

  10. So far it is a green field. Only n-C interactions have been accurately studiedexperimentally. There are ~ 40% accurate data for d,Fe,I v-d is well understood theoretically and indirectly has been measured by SNO Neutrino Nuclear Interactions at Low MeV Range are: Important for understanding of supernovae mechanism Important for neutrino detection from SN Important for Calculations of backgrounds for DSN Have a general interest for the nuclear theory It is important to provide accurate v-A measurements for wide range of isotopes

  11. Early interest in low energy neutrino nucleus cross sections: Twenty five years later, same scientist is still interested in neutrino-nucleus cross sections

  12. A Z0 A D.Z. Freedman PRD 9 (1974) A. Drukier & L. Stodolsky, PRD 30, 2295 (1984)‏ Horowitz et al. astro-ph/0302071 Straight-forward to calculate “Huge” cross section > 10-39 cm2 Neutrino Coherent Scattering Detectable only via very low energy (~10keV) nuclear recoil Never observed Important for supernova dynamics (neutrino opacity)

  13. What Physics Could be Learned From Neutrino Coherent Scattering? K. Scholberg, Phys. Rev D 73 (2006) 033005 Basically, any deviation from SM is interesting... - Weak mixing angle: could measure to ~few % (new channel)‏ - Non Standard Interactions (NSI) of neutrinos: could significantly improve constraints - Neutrino magnetic moment: hard, but conceivable It is difficult to do it on Nuclear Reactors because of the continues flux and very low recoil energies

  14. New Facility -SNS

  15. SNS LINAC:  x ~1000  Repeat 60/sec. Accumulator Ring: 1 GeV Similar pulse structure to ISIS  greatly suppressed backgrounds Presently being commissioned. 0.5 MW power has been achieved last week Eventual operation > 1 MW (~FY09) ~7x1012p / spill (~10x ISIS)

  16. Accelerator

  17. Target

  18. p  Neutrino Production at SNS CAPTURE ~99% e Fragments -   2200 nsec A + DAR e+ ~ 1 GeV +   26 nsec  Fragments Specific benefits of neutrinos at SNS • Well known neutrino spectra (DAR) • Separate neutrinos of different flavors by time cut • Very high neutrino intensities ~ 1015n/sec • Pulsed Structure

  19. protons 60 m Potential Locations for Neutrino Experiments at theSpallation Neutron Source proposed site inside target building • 20 m2 x 6.5 m (high) • Close to target ~ 20 m • 2x107n/cm2/s • q=165 to protons • lower backgrounds The SNS Target hall There are multiple sites available outside of target building.

  20. protons 60 m 2.8·1020 protons delivered on target in two week period 1020 neutrino produced Background Studies • Space for prototype development • Neutron detectors Power ~ 0.4 MW • 60 tons of steel Now: Background, shielding & protoype studies p~2 C neutrons Particle id Counts gammas -2 2 4 6 0 Pulse height Time (s)

  21. Proton beam (RTBT) n-SNS BL18 ARCS Possible Concept of Shielded Enclosure for Neutrino Experiments • Total volume = 130 m3 4.5m x 4.5m x 6.5m (high) • Heavily-shielded • 60 m3 steel ~ 470 tons 1 m thick on top 0.5 m thick on sides • Active veto • ~70 m3 instrumentable • Configured to allow 2 simultaneously operating detectors of up to 40 tons A coherent scattering 43 m3 liquid detector Segmented detector for solids Prototypes for SN detectors

  22. wave-length shifting fibers read out by multi-anode PMT Bunker 1.5 cm iron extruded scintillator 1 cm x 10 cm x 4.5 m • Efficiencies • muons ~99% muons • 7.6 MeV gamma = 0.005% • neutron =0.07% Cosmic Ray Veto Sensitive to cosmic muons Blind for gammas from (n , gamma) capture

  23. Veto R&D • In collaboration with MECO • 100 x 4.5-m planks extruded for SNS 23

  24. Homogeneous Experiment • 3.5m x 3.5m x 3.5m steel vessel (43 m3) • 600 PMT’s (8” Hamamatsu R5912)  Fiducial volume 15.5 m3 w/ 41% coverage • Robust well-understood design • dE/E ~ 6% • dx ~ 15-20 cm • dq ~ 5 - 7 • First experiments: • 1300 events/yr ne+12C12N+e- (mineral oil) • 450 events/yr ne+16O 16F+e- (water) • 1000 events/yr nx+2H  p+n+ nx (heavy water)

  25. dE/E = 6.8% at 50 MeV less if corrected for position Performance Geant4 Monte Carlo simulations ongoing • dE/E ~ 6% • dx ~ 15-20 cm • dq ~ 5 - 7 • Neutron discrimination? • Layout and coverage • More compact photosensors • 60% of mass lost to fiducial cut

  26. Standard Model Tests μ+ e+ + e + μ. e + 12C  e- + 12N g.s. • Shape of the e spectrum from  decay is sensitive to scalar and tensor components of the weak interaction SNS expected 1-yr operation L=0.11 KARMEN upper limit Armbruster et al., PRL81 (1998) • We could substantially improve the limit on L with only 1 year of data L=0

  27. Segmented Experiment corrugated metal target straw tube 16 mm anode wire • Target - thin corrugated metal sheet (e.g. 0.75 mm-thick iron) • Total mass ~14 tons, 10 tons fiducial • Other good metal targets: Al, Ta, Pb • Detector • 1.4x104 gas proportional counters (straw tube) • 3m long x 16mm diameter • 3D position by Cell ID & charge division • PID and Energy by track reconstruction • Expected Statistic • 1100 events/yr ne+FeCo+e- • 1100 events/yr ne+AlSi+e- • 4900 events/yr ne+Pb Bi+e-

  28. Slow charge collection e broad timing problematic narrow time (ms) Straw tube R&D • Currently testing prototypes Diameters between 10-16 mm Lengths ranging up to 2 m Gases (Ar-CO2, Isobutene, CF4) • Measure resolution with cosmic muons Energy, position, time • How much can time resolution be improved using pulse shape information? • Simulations to improve the fast neutron discrimination.

  29. The CLEAR (Coherent Low Energy A Recoils) Experiment

  30. CLEAR A. Curioni

  31. Background for CLEAR Expect ~190 events/year in 20 kg of xenon >3 keVr SNS neutronics group calculation of neutron spectrum + Fluka sim through shielding (T. Empl) + Xe detector sim (J. Nikkel)‏ + scaling using measured fluxes

  32. Sterile Neutrinos Neutrino Oscillations Test CP Violation Osc-SNS • MiniBooNE/LSND-type detector • Higher PMT coverage (25% vs 10%) • Mineral oil + scintillator (vs pure oil) • Faster electronics (200 MHz vs 10 MHz) • Located ~60m upstream of the beam dump/target, this location reduces DIF background ~ 60m

  33. Oscillation Event Rates Expected for LSND best fit point of : sin22 =0.004 dm2 = 1

  34. Summary & Outlook • Understanding of neutrino interactions are important for: • Physics of Supernova • Calculation of response of Large Neutrino Detectors to Milky Way Supernova • Calculation of backgrounds from DSN • The combination of high flux and favorable time structure at the SNS is very attractive for diverse program of neutrino studies • New Proposals like CLEAR and Osc-SNS appeared recently • We welcome new ideas and participation • See http://www.phy.ornl.gov/nusns

More Related