1 / 52

The Previous Results and Future Possibilities of KamLAND

The Previous Results and Future Possibilities of KamLAND. Kazumi Tolich Stanford University 2/6/2007. Outline. KamLAND Previous Reactor Neutrino Result Previous Geoneutrino Result Future Possibilities Full Energy Analysis Solar Neutrinos Supernova. KamLAND.

quilla
Download Presentation

The Previous Results and Future Possibilities of KamLAND

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. The Previous Results and Future Possibilities of KamLAND Kazumi Tolich Stanford University 2/6/2007

  2. Outline • KamLAND • Previous Reactor Neutrino Result • Previous Geoneutrino Result • Future Possibilities • Full Energy Analysis • Solar Neutrinos • Supernova

  3. KamLAND Introduction to the KamLAND experiment

  4. KamLAND Collaboration T. Ebihara,1 S. Enomoto,1 K. Furuno,1 Y. Gando,1 K. Ichimura,1 H. Ikeda,1 K. Inoue,1 Y. Kibe,1 Y. Kishimoto,1 M. Koga,1 Y. Konno,1 Y. Minekawa,1 T. Mitsui,1 K. Nakajima,1 K. Nakajima,1 K. Nakamura,1 K. Owada,1 I. Shimizu,1 J. Shirai,1 F. Suekane,1 A. Suzuki,1 K. Tamae,1 S.Yoshida,1 J. Busenitz,2 T.Classen,2 C. Grant,2 G. Keefer,2 D.S.Leonard,2 D. McKee,2 A. Piepke,2 B.E. Berger,3 M.P. Decowski,3 D.A. Dwyer,3 S.J. Freedman,3 B.K. Fujikawa,3 F. Gray,3 L. Hsu,3 R.W. Kadel,3 C. Lendvai,3 K.-B. Luk,3 H. Murayama,3 T. O’Donnell,3 H.M. Steiner,3 L.A. Winslow,3 C. Jillings,4 C. Mauger,4 R.D. McKeown,4 C. Zhang,4 C.E. Lane,5 J. Maricic,5 T. Miletic,5 J.G. Learned,6 S. Matsuno,6 S. Pakvasa,6 G.A. Horton-Smith,7 A. Tang,7 K. Downum,8 G. Gratta,8 K. Tolich,8 M.Batygov,9 W. Bugg,9 Y. Efremenko,9 Y. Kamyshkov,9 A.Kozlov,9 O. Perevozchikov,9 H.J. Karwowski,10 D.M.Markoff,10 W. Tornow,10 J.S. Ricol,11 F. Piquemal,11 and K.M. Heeger,12 1. Research Center for Neutrino Science, Tohoku University, Sendai 980-8578, Japan 2. Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA 3. Physics Department, University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 4. W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125, USA 5. Physics Department, Drexel University, Philadelphia, Pennsylvania 19104, USA 6. Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA 7. Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA 8. Physics Department, Stanford University, Stanford, California 94305, USA 9. Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 10. Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA and Physics Departments at Duke University, North Carolina State University, and the University of North Carolina at Chapel Hill 11. CEN Bordeaux-Gradignan, IN2P3-CNRS and University Bordeaux I, F-33175 Gradignan Cedex, France 12. Department of Physics, University of Wisconsin at Madison, Madison, Wisconsin, USA

  5. KamLAND Location • KamLAND was designed to measure reactor anti-neutrinos. • KamLAND is surrounded by nuclear reactors in Japan. KamLAND

  6. 1km (2700 m.w.e) Overburden KamLAND Detector Electronics Hut Steel Sphere of 8.5m radius Inner detector 1325 17” PMT’s 554 20” PMT’s 34% coverage 1 kton liquid-scintillator Transparent balloon of 6.5m radius Buffer oil Water Cherenkov outer detector 225 20” PMT’s

  7. Detecting Anti-neutrinos with KamLAND Delayed Prompt • KamLAND (Kamioka Liquid scintillator Anti-Neutrino Detector) 2.2 MeVg 0.5 MeV e- e+ 0.5 MeV n p • Inverse beta decay ne + p → e+ + n p d ne • The positron loses its energy then annihilates with an electron. • The neutron first thermalizes then gets captured on a proton with a mean capture time of ~200ms. • Neutrino energy can be estimated by the kinetic energy of the positron plus 1.8MeV.

  8. Major Background Events for Antineutrino Detection • Accidentals: uncorrelated events due to the radioactivity in the detector mimicking the inverse beta decay signature. • 13C(,n): 210Po (introduced as 222Rn) emits an particle, which reacts with naturally occurring 13C (~1.1% of C). • 1H(n,n)1H: the neutron collides with protons (prompt) and later captures on a proton (delayed). • 12C(n,n)12C: the neutron excites a 12C producing a 4.4 MeV  (prompt), and later captures on a proton (delayed). • 13C(,n)16O: the 16O* de-excites with a 6 MeV (prompt), and the neutron later captures on a proton (delayed).

  9. Phys. Rev. Lett. 94, 081801 (2005) “Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion” 425 citation as of last week! Neutrino Oscillation Results Phys. Rev. Lett. 90, 021802 (2003) “First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance” 1269 citations as of last week! The most cited paper in physics in 2003 The 2nd most cited paper in all sciences in 2003

  10. Neutrino Oscillations in Vacuum • The weak interaction neutrino eigenstates may be expressed as superpositions of definite mass eigenstates • The electron neutrino survival probability can be estimated as a two flavor oscillations:

  11. Δr < 2m 0.5μs < ΔT < 1000μs 2.6MeV < Ee+, p < 8.5MeV 1.8MeV < E, d < 2.6MeV Veto after muons Rp, Rd < 5.5m Selecting Reactor Anti-neutrino Events Delayed Prompt 2.2 MeVg 0.5 MeV e+ 0.5 MeV

  12. Dataset and Rate Analysis • From March 9 2002 to January 11 2004. • 365.2 ± 23.7 expected reactor antineutrinos with no oscillation. • 17.8 ± 7.3 expected background events. • 258 candidate events. • The average survival probability is 0.658 ± 0.044(stat) ± 0.047(syst). • We confirmed antineutrino disappearance at 99.998% C.L. (~4).

  13. Prompt Energy Distribution • KamLAND saw an antineutrino energy spectral distortion at 99.6% significance.

  14. Shape distortion is the key factor in determining m2. Oscillation Analysis Shape + Rate Shape Only

  15. Average Distance, L0 KamLAND L0 = 180 km 80% of total flux comes from reactors 140 to 210km away.

  16. L0/E Observed/No Oscillation Expected Would the data come back up again???

  17. Geoneutrino Result Nature 436, 499-503 (28 July 2005) “Experimental investigation of geologically produced antineutrinos with KamLAND”

  18. Convection in the Earth • The mantle convection is responsible for the plate tectonics and earthquakes. • The mantle convection is driven by the heat production in the Earth. Image: http://www.dstu.univ-montp2.fr/PERSO/bokelmann/convection.gif

  19. Heat from the Earth • Heat production rate from U, Th, and K decays is estimated from chondritic meteorites to be 19TW. • Heat flow is estimated from bore-hole measurements to be 44 or 31TW. • Models of mantle convection suggest that the radiogenic heat production rate should be a large fraction of the total heat flow. • Problem with • Mantle convection model? • Total heat flow measured? • Estimated radiogenic heat production rate?

  20. Geoneutrino Signal Inverse Beta Decay Threshold •  decays in U and Th decay chains produce antineutrinos. • Geoneutrinos can serve as a cross-check of the radiogenic heat production rate. • KamLAND is only sensitive to antineutrinos above 1.8MeV • Geoneutrinos from K decay cannot be detected with KamLAND.

  21. Δr < 1m* 0.5μs < ΔT < 500μs* 1.7MeV < E,p< 3.4MeV 1.8MeV < E,d< 2.6MeV Veto after muons Rp, Rd < 5m* ρd>1.2m* Selecting Geoneutrino Events Delayed Prompt 2.2 MeVg 0.5 MeV e+ 0.5 MeV *These cuts are tighter compared to the reactor antineutrino event selection cuts because of the excess background events for lower geoneutrino energies.

  22. Geoneutrino Candidate Energy Distribution Expected total Expected total background 127 ± 13 Candidate data 152 events Expected reactor 80.4 ± 7.2 Expected (,n) 42 ± 11 Measured Accidental 2.38 ± 0.01 Expected U 14.8± 0.7 Expected Th 3.9 ± 0.2 Data from March, 2002 to October, 2004.

  23. How Many Geoneutrinos? chondritic meteorites Expected 3 U geoneutrinos 18 Th geoneutrinos 28 U + Th geoneutrinos

  24. Geoneutrinos Reactor neutrinos Future Possibility IFull Energy Analysis My Thesis in Progress

  25. Combined Analysis • Combined analysis probes lower energy reactor anti-neutrinos and should improve m2 measurement. • We will possibly observe the re-reappearance of reactor antineutrinos. • Better understanding of reactor spectrum might improve the geoneutrino measurement. Re-reappearance?

  26. Previous and Planned Cuts • Geoneutrino event selection cuts are tighter due to the low energy accidental background. • Combined analysis requires consolidation of the difference in the event selection cuts.

  27. Real and Visible Energies • Ereal is the particle’s real energy. • Evisible is determined from the amount of optical photons detected, including quenching and Cerenkov radiation effects. • The model of Evisible/Ereal as a function of Ereal fits calibration data very well. • Previous analyses were done in positron real energy, having to convert background energies (such as ’s) into effective positron real energies. 12C(n,)13C 1H(n,)2H 60Co Fit to our model 65Zn 68Ge 203Hg

  28. Expected Prompt Energy Spectra Accidentals Reactor neutrinos (,n) Th geoneutrinos U geoneutrinos *Scaled approximately to the number of events expected.

  29. Expected Delayed Energy Spectra n-capture on p Accidentals *Scaled approximately to number of events expected

  30. Expected t Spectra Previous Geoneutrino Analysis Cut n-capture on p Accidentals *Scaled approximately to number of events expected

  31. Time Variation of Reactor Neutrino Flux • Shika reactor ~90km (half of L0) away turned on from May 26 2005 to July 4 2006. • Shika contributed 14% of total flux. • May help distinguish LMA I and LMA II.

  32. Prompt Energy Delayed Energy t Time Probability Density Functions • Expected prompt energy spectra and time variation of reactor neutrino flux were used in the previous analyses. • Expected delayed energy and t spectra will be added to distinguish accidental background.

  33. Future Possibility II7Be Solar Neutrino Detection http://www.noaanews.noaa.gov/stories2005/images/sun-soho011905-1919z.jpg

  34. p + p  2H + e+ + e p + e- + p  2H + e 99.75% 0.25% 2H + p  3He 86% 14% 3He + 3He   + 2p 3He +   7Be 99.89%0.11% 7Be + e- 7Li + e 862keV & 383keV 7Be + p  8B 7Li + p   +  8B  8Be + e+ + e 8Be   +  7Be e flux is much greater than 8B e flux! Solar Neutrinos from the p-p Chain Reactions

  35. Solar Neutrino Spectrum We expect to see a few hundred events per day. Solar Neutrino Flux at the surface of the Earth with no neutrino oscillations. Uses the solar model, BS05(OP).

  36. 7Be Solar Neutrino Detection • Solar  scatters off e-. • The electron recoil energy is From e From  &  *Detection resolution is not included.

  37. Current Radioactivity in KamLAND After fiducial volume cut is applied

  38. Test Removal of Reducible Background • Distillation removed 222Rn by a factor of 104 to105. • Heating and distillation reduced the 212Pb activity by a factor of 104 to 105. • Distillation reduced the 40K concentration in PPO by a factor of 102. • Distillation reducednatKr by a factor of 105 to 106.

  39. 14C Total BG 85Kr 40K Expected Energy Spectra after the Purification

  40. Purification System Constructed • The purification system is being commissioned right now. • We have done some testing and are fixing bugs. • We should be able to start the full purification operations soon. From October 2006

  41. Future Possibility IIISupernova Detection http://upload.wikimedia.org/wikipedia/commons/4/43/Supernova-1987a.jpg

  42. Expected Signals • For a “standard supernova” (d = 10 kpc, E=3x1053 ergs, equal luminosity in all neutrino flavors), we expect to see (no neutrino oscillations): • ~310 events • ~20 events • ~60 events • ~45 events • ~20 events • ~10 events • ~300 events (0.2 MeV threshold) • There should be 300 e+ events above 10 MeV, with an initial rate of 100 Hz (exponential decay with ~3s time constant). • The proton scattering events (low visible energy) provide a determination of both luminosity of all neutrino flavors and temperature. * J. F. Beacom et al.

  43. Expected Proton Scattering Events Realistic energy threshold after purification of scintillator dN/dEvisible [1/MeV] Evisible [MeV] * J. F. Beacom et al.

  44. Supernova Trigger • 8 high energy inverse beta decay events (>~9MeV) within ~0.8s causes a supernova trigger. • With the supernova trigger, the trigger switches to a pre-determined supernova mode. • The supernova mode has a lower energy threshold (~0.6MeV) in order to detect low energy events (especially ν + p → ν + p.) • The energy threshold could be lowered after the purification.

  45. Conclusions • KamLAND has been producing some impressive results. • I am analyzing the full energy range, reactor neutrinos and geoneutrinos simultaneously, to improve sensitivity. • The planned purification of scintillator will be followed by the solar neutrino phase. • If there is a supernova explosion, KamLAND is the only detector that can possibly detect the proton scattering events.

  46. Questions?

  47. Total Heat Flow from the Earth Bore-hole Measurements • Conductive heat flow measured from bore-hole temperature gradient and conductivity • Deepest bore-hole (12km) is only ~1/500 of the Earth’s radius. • Total heat flow 44.21.0TW (87mW/m2), or 311TW (61mW/m2) according to more recent evaluation of same data despite the small quoted errors. Image: Pollack et. al

  48. Radiogenic Heat • U, Th, and K concentrations in the Earth are based on measurement of chondritic meteorites. • Chondritic meteorites consist of elements similar to those in the solar photosphere. • The predicted radiogenic total heat production is 19TW. • Th/U ratio of 3.9 is known better than the absolute concentrations of Th and U.

  49. Reference Earth Model Flux • ~20% from nearby crust (within ~30km). • ~20% from outside of a ~4000km radius. • ~25% from the mantle.

  50. MSW Effect in the Sun • e’s experience MSW effect in the Sun. • For 7Be e’s, Possible sin22 For E = 862keV & m2=7.9x10-5eV2

More Related