Geo-neutrinos Status and Prospects

Transcription

1 Geo-neutrinos Status and Prospects SNOLAB Grand Opening Workshop May 2012 e+ νe W u pu Steve Dye Hawaii Pacific University d d u d n

2 Outline Radiogenic heat/thermal evolution Radiogenic heat/geo-neutrinos Detecting geo-neutrinos Geo-neutrino data Geo-neutrino analyses Project updates Prospects

3 Planetary Power Aq = Mh Mc( T/ t) Surface heat flow- Aq Internal heating- Mh Heat to change temperature- Mc( T/ t) Temperature change rate: T/ t = Aq/Mc (Mh/Aq 1) Planetary Urey ratio - U = Mh/Aq

4 Surface Heat Flow Pollack et al., 1993 Added for Davies, Davies, 2010 mw m-2 Heat flow probethermal conductivity, dt/dx Heat conductionq = -k dt/dx Total Flow Aq = 47 ±2 TW

5 Internal Heating Geology predicts TW of radioactive power Mass loss rate dm/dt = -(6-15) tonne y-1? ~20% escapes to space as geo-neutrinos ~80% remains to heat planet Other known sources of internal heating small Internal heating Mh = TW

6 Thermal Evolution of Earth Temperature change rate: T/ t = Aq/Mc (Mh/Aq 1) U = Mh/Aq U>1 T U<1 T Surface heat flow- Aq = 47 ±2 TW (Davies, Davies, 2010) Internal heating- Mh = 13 to 34 TW (various models) Planetary Urey ratio - U = Mh/Aq = 0.28 to 0.70 Geology predicts a cooling planet

7 Earth Heating Elements 238 U 206Pb +8α +6e +6ν e MeV 235 U 207Pb +7α +4e +4ν e MeV 232 Th 208Pb +6α +4e +4ν e MeV 40 K 40Ca +e +ν e MeV (89.3%) 40 K +e 40Ar +ν e MeV (10.7%) Uranium Thorium Potassium h(μw/kg) x 10-1 (1) -1 l(kg μs ) x 10 U, Th, K produce heat and geo-neutrinos

8 Geo-neutrino Intensity Spectra [ A, Z ] [ A, Z + 1] + e + ν e + Qβ per decay we = (Qβ + me Eν e ) [ 2 pe = (Qβ + me Eν e ) ] 2 1/ 2 me dn( Eν e ) / deν e we Eν e 2 pe2γ 1eπη Γ( γ + iη ) 2 γ = 1 α 2 ( Z + 1) 2 η = α ( Z + 1) we pe Internal heating and geo-neutrinos connected

9 Antineutrino Interactions Electron elastic scattering Inverse β-decay νe + e - νe + e - νe + p n + e+ Electron target Proton target No energy threshold Cross-section σ(eν)~4.0x10-45 Eν1 cm2 e- Ethresh 1.80 MeV Cross-section σ(eν)~9.5x10-44 (Eν-1.3)2 cm2 W Z0 p νe e+ νe e- νe u d u u d d n

10 Cross Sections ν e + e ν e + e Tmax = Eν e 1 + me 2 Eν e 2 2 E T m T ν 44 σ e ( Eν e ) = 0.43 x Tmax + ( x + 1) 2 e 1 (1 max )3 x( x + 1) e max 10 3 Eν e 2 Eν2e ν e + p e+ + n ( ) σ p ( Eν e ) = 9.52( Eν e ) 2 1 me2 Eν e Te = Eν e me

11 Cross Sections Nue-bar elastic scattering observed by Reines, Gurr, Sobel in 1976 Sensitivity below 1.8 MeV; no tag 4 e- / p+ in CH2 LS Resolve e- direction to find signal? Nue-bar quasi-elastic scattering used by Reines and Cowan in 1950 s Coincidence counting; weak direction Works great for geo-nue-bars Uncertainties small

12 Detected Spectra

13 Inverse-β Interaction Kinematics transverse n Initialptrans= 0 νe pν Finalptrans= 0 p θe ' longitudinal e+ Batygov Watanabe θn pν θe e+

14 Coincidence Counting Prompt event Positron Ee Eν 1.8 MeV Evis Eν 0.8 MeV Ionization energy + 2γ Deposition time ~ few ns <Re> ~ 0.4 cm Delayed event Neutron En kev Thermal diffusion Evis depends capture nucleus Deposition time ~ μs <Rn> ~ 5 15 cm Watanabe

15 Antineutrino Detection Antineutrino (Eν>1.8 MeV) interacts with free proton γ νe e- p + n p+ γ e+ γ Prompt event deposits energy of Eν-0.8 MeV Delayed event deposits energy of 2.2 MeV ~10,000 γ/mev PMTs measure position and amount of deposited energy 3-October-2010 Steve Dye, HPU 15

16 238 Geo-neutrino Event Spectrum U 232 1α, 1β 234 Pa 1α, 1β νe 2.3 MeV νe 2.1 MeV 5α, 2β 214 Bi Pb 228 Ac 4α, 2β νe 3.3 MeV νe 2.3 MeV 2α, 3β 206 Th 212 Bi 1α, 1β Th/U in source regions determines spectral shape 208 Pb

17 Neutrino Oscillations- θ13>0 3-ν mixing Pee3ν = 1 {cos 4 (θ13 ) sin 2 (2θ12 ) sin 2 ( 21 ) + sin 2 (2θ13 )[cos 2 (2θ12 ) sin 2 ( 31 ) + sin 2 (2θ12 ) sin 2 ( 32 )]} ji = 1.27( δm 2ji L) / Eν e [ δm 2ji m 2j mi δm31 δm32 >> δm21 Pee 1 cos 4 (θ13 ) sin 2 (2θ12 ) sin 2 ( 21 ) sin 2 ( 2θ13 ) [ Error dominated by solar mixing angle ] ] 024 Pee cos 4 (θ13 ) sin 2 (2θ12 ) + sin 2 (2θ13 ) = Fogli et al., 2011 ; An et al., 2012 ; Ahn et al., 2012

18 Average Oscillation Probability θ13 : 0 º 10 º <Pee> : Lowers reactor & crust flux predictions Using <Pee> overestimates a(u) & a(th) and underestimates Th/U Pronounced at sites enriched in U & Th such as Sudbury basin Perry et al., 2009 Dye, 2012 arxiv: v2

19 Reactor Antineutrino Background Φ(E) OLD- θ13=0 Pν e ν e 1 sin 2 (2θ12 ) sin 2 (1.27 m212 L / Eν e ) N(E) σ(e) Geo ν (Enomoto, Neutrino Sciences 2007) OLD- Japan? Expected reactor signals depend on location

20 Non-neutrino Background Fast neutron background from muons outside veto <1 TNU at Gran Sasso Accidental background 3.4±0.2 TNU KL (2005) 1.3±0.2 TNU BX (2010) Mei and Hime, 2006 Isotope background (β,n) ~0.5 TNU Radon contamination 210 Po 206Pb + α 13 C(α,n)16O <0.3 TNU Abe et al., 2010

21 Existing Gν Detectors KamLAND- Kamioka, Japan 1 kt LS 80% dodecane 20% PC w/ 1.36 g/l PPO ~1800 PMTs 34% solid angle Borexino- Gran Sasso, Italy kt PC w/ 1.5 g/l PPO in PMTs ~30% solid angle ~500 pe/mevvis ~0.17x1031 p ~250 pe/mevvis (5.98±0.12)x1031 p Both existing detectors are in Eurasia at ~40 ⁰ N and separated in longitude by ~120 ⁰

22 Gν Data: Existing Detectors KamLAND Borexino Mar-02 to Nov-09 : 3.49±0.07 TNU-1 Dec-07 to Dec-09 : TNU-1 Total events- 841 Background- 730±32 Geo-nu- 111±43 Gando et al., 2011 Nature Geoscience 4, 647 Total events- 15 Background- 5.3±0.3 Geo-nu- 9.7±3.9 Bellini et al., 2010 Phys. Lett. B 687, 299

23 Gν Data Analysis Borexino KamLAND unconstrained fit NU = 65 ; NTh = 33 Th/U ~ 8 ε(u) = ε(th) = Best fit: 9.9(+4.1/-3.4) gν events ε=0.85±0.01 Fixing Th/U=3.9 N(U+Th) = 106±29 Fixing Th/U= ±10.5(stat)±11.5 (sys) TNU systematic > statistical Gando et al., 2011 Nature Geoscience 4, ±25(stat)±2(sys) TNU statistical >> systematic Bellini et al., 2010 Phys. Lett. B 687, 299

24 Gν Analysis- I Observed Gν Observed Gν Predicted Crust Surface heat flux Old value. Revised lower by Coltorti et al., Mh (U+Th) = 20 ± 9 TW Gando et al., 2011 Nature Geoscience 4, 647

25 Gν Analysis- II Increased total signals KL R(U+Th) TNU BX R(U+Th) TNU R(U+Th) >0 at ~4.2σ θ13>0 decreases expected crust KL (Enomoto et al., 2007).54/.59=.92 BX (Coltorti et al., 2011).54/.57=.95 Gando et al., 2011 Add to increase mantle signal Mantle = Total Crust Fiorentini et al., 2012 arxiv: v1

26 Gν Analysis- II Residual mantle signal w/ model comparisons 1.7 Th/U 3.9 Rmantle = 23 ± 10 TNU R>0 at ~2.4σ Geophysical- consistent Geochemical- excluded >90% CL Cosmochemical- constrained Mh(U+Th) > 19 TW (68% CL) No model excluded at ~>2σ Fiorentini et al., 2012 arxiv: v1

27 Gν Analysis- III Method M=N-B C δm = (N + δb2 + δc2)1/2 Assumptions Th/U = 3.9 ; C model MKL= MBX Combined result: consistent w/ GP, GC weakly excludes CC Rmantle = 17 ± 10 TNU Weighted average BX > KL but consistent with BX=KL Dye, 2012 arxiv: v2 Sramek et al., 2012

28 Gν Analysis- III KamLAND (2011) data consistent with models, prefers Mh < Aq Borexino (2010) data consistent with GP and Mh = Aq KL+BX (weighted averages) consistent w/ GP & GC weakly exclude CC Min Mh = 28 ± 13 TW Max Mh = 33 ± 16 TW Dye, 2012 arxiv: v2 Homogeneous mantle DM w/ enriched basement layer

29 Resolving Geological Models- Prospects Crust systematic dominates rate uncertainty Single measurement at continental or existing site does not resolve models Single measurement at oceanic site does resolve models Dye, 2012 arxiv: v2

30 Expected Signals: Existing Sites KL before and after reactor shutdown BX can operate for many years before systematic uncertainty significant

31 Expected Signals: Future & Prospective Sites Continental Observatories Next year!!! + Baksan Mount Elbrus Village Neutrino N E Oceanic Observatory

32 Geo-neutrino Observatory Network Pyhäsalmi Baksan Homestake Sramek et al., 2012

33 Borexino Project Updates doubled statistics and improved FV definition... Data look nice. Aldo Ianni KamLAND acquiring good data but wont publish for a year until reactors come back Kunio Inoue SNO+ Data next year, crust study LENA White paper published in Astropart. Phys.- M. Wurm Baksan Discussing kt detector- V. Sinev Hanohano Discussing 2-3 kt GeoPANO

34 Projection to Year 2020 KamLAND : 9 TNU-1 δm = ± 6 TNU Borexino : 1 TNU-1 δm = ± 10 TNU SNO+ : 3 TNU-1 δm = ± 9 TNU Total : 13 TNU-1 δm = ± 4-5 TNU OR GeoPANO : 3 TNU-1 δm = ± 3 TNU GeoPANO : 6 TNU-1 δm = ± 2 TNU OR Network- Five x 10 TNU-1 δm = ± 3 TNU

35 Gν Summary Observing planetary U & Th; no K or direction Data accumulating in two geo-ν detectors: KL & BX Beginning to address geological models SNO+ next year! First continental observatory 5-y statistical error ±6 TNU (~12% Gν measurement) First measurement of Th/U Oceanic observatory resolves geological models Model resolution possible with network of continental observatories SNO+, LENA, Baksan, Homestake, plus KL & BX