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Geo-neutrinos: combined KamLAND and Borexino analysis, and future

Geo-neutrinos: combined KamLAND and Borexino analysis, and future. 4° Neutrino Geoscience Takayama 21-23 March 2013. 1° Neutrino Geoscience Honolulu 14-16 December 2005. Fabio Mantovani – University of Ferrara & INFN. Summary. An historical perspective How to look into the deep Earth?

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Geo-neutrinos: combined KamLAND and Borexino analysis, and future

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  1. Geo-neutrinos: combined KamLAND and Borexino analysis, and future 4° Neutrino Geoscience Takayama 21-23 March 2013 1° Neutrino Geoscience Honolulu 14-16 December 2005 Fabio Mantovani – University of Ferrara & INFN

  2. Summary An historical perspective How to look into the deep Earth? Why the refined local and global models are important? New Borexino and KamLAND results: theory vs experiments Multi-site “view” of the mantle

  3. Geo-neutrinos: anti-neutrinos from the Earth U, Th and 40K in the Earth release heat together with anti-neutrinos, in a well fixed ratio: Earth emits (mainly) antineutrinos whereas Sun shines in neutrinos. A fraction of geo-neutrinos from U and Th (not from 40K) are above threshold for inverse b on protons: Different components can be distinguished due to different energy spectra: e. g. anti-n with highest energy are from Uranium. Signal unit: 1 TNU = one event per 1032 free protons per year

  4. Geo-neutrinos born on board of the Santa Fe Chief train In 1953 G. Gamow wrote to F. Reines: “It just occurred to me that your background may just be coming from high energy beta-decaying members of U and Th families in the crust of the Earth.” F. Reines answered to G. Gamow: “Heat loss from Earth’s surface is 50 erg cm−2 s−1. If assume all due to beta decay than have only enough energy for about 108 one-MeV neutrinos cm−2 and s.”

  5. Model with an uniform distribution of U in the continental crust: Krauss et al. (Nature 1984) BSE model with different U distribution between crust and mantle: • 2° x 2° crustal model with BSE constraint (papers after 2004) Rothschild et al. (1991) • Raghavan et al. (1998) KamLAND and Borexino measurements Geoneutrino signal: an historical perspective Models assuming uniform U distribution in the Earth: Eder (Nucl. Phys. 1966) Marx (Cz. J. Phys 1969) Kobayashi (GRL 1991)

  6. Expected signal in SNO+ (2013-14) • 82 % from crust • 18 % from mantle Expected signal in KamLAND (2002) • 75 % from crust • 25 % from mantle Expected signal in Borexino (2007) • 75 % from crust • 25 % from mantle Reconstruction of geo-n direction with Gd, Li and B loaded LS is being investigated by several groups. (See Shimizu, Domogatsky et al., Hochmuth et al.) Expected signal in Hawaii • 28 % from crust • 72 % from mantle See Jocher et al. 2013 John Learned talk – Saturday 23 March – 10.00 @ NGS13 How to look into the deep Earth?

  7. ? arXiv:1204.1923v1 [hep-ph] Apr 2012

  8. ROC • Discrimination of OC and CC • Thickness and extension of the main continental reservoirs • U and Th abundance of the crustal layers • Evaluation of the uncertainties LOC (~500 x 500 km) • Refined geophysical model of the crust • Main tectonic structures • Direct and detailed survey of U and Th content • Hierarchy of uncertainties sources Modeling geo-neutrino signal For each element (U, Th) the expected geo-neutrino signal S in one site on the Earth’s surface is the sum of three contributions:

  9. A refined local model for Kamioka A world wide reference model* predicts for KamLAND: Inputs used for the refinement • Use a geochemical study of the Japan Arc exposed upper crust (166 samples distinguishing 10 geological classes) • Use detailed (± 1 km) measurements of Conrad and Moho depth • Use selected values for abundances LC • Build a new crustal map of the Japan Arc (scale ¼° x ¼°) • Consider possible effect of the subducting platebelow Japan * Mantovani et al. – Phys. Rev. D 69 – 2004 - hep-ph/0309013

  10. Local contribution to geo-n signal in KamLAND Different local sources of geo-n are investigated and the expected signals are estimated: The local expected signal is 17.7 ± 1.4 TNU to compare with 16.4 TNU For a fixed element the 1s uncertainties are independent We assume DS(U) and DS(Th) totally correlated

  11. Local contribution to geo-n signal in Borexino A world wide reference model predicts for Borexino: Inputs used for the refinement • The geophysical structure of the crust is modeled using data of CROP seismic sections and from 38 deep oil and gas wells. • We identify 6 reservoirs: 4 of sediments, UC and LC. • Representative samples of the sedimentary cover were collected and measured by using ICP-MS • U and Th contentmeasured in samples collected from outcropson Alps is adopted for UC and LC

  12. A refined local model for Borexino The main results of this study are about the thickness of layers and their composition. The local expected signal calculated signal is SAfter = 9.7 ± 1.3 TNU to compare with SBefore = 15.0 TNU.

  13. We need to evaluate the uncertainties of the geophysical crustal model • New compilations of U and Th abundances are published • An updated 1°x1° map of the sediments is available • New approach based on seismic arguments can be used in the evaluation of U and Th abundances (and their uncertainties) in MC and LC The Rest Of the Crust Why do we need a refinement of the crustal model? Main inputs for calculating geo-nsignal from the crust: • The CRUST2.0 crustal model (Laske G. et al. 2001). • For each of the 16200 tiles density and thickness of sediments, upper, middle and lower crust are given. • Values of the U and Th mass abundance in each layer taken by review papers (Plank & Langmuir 98, Rudnick & Gao 03). Yu Huang talkFriday 22 March – 14.00 @ NGS13

  14. These expected signals can be compared with the data published in 2013 by KamLAND and Borexino collaborations. Measured geoneutrino signal [TNU] KamLAND 2013 31.1 ± 7.3 Borexino 2013 38.8 ± 12.0 Theory vs experiments 1 Fiorentini et al. 2012; 2 Huang et al. 2013

  15. Measured geoneutrino signals in the last years Expected signal* Two independent experiments, far ~104 km each other, measure a geo-n signal in good agreement with the expectation. Expected signal* *Fiorentini et al. 2012 arXiv:1204.1923v2 + Huang et al. 2013

  16. Multi-site “view” of the mantle Preliminary Preliminary 1 Fiorentini et al. 2012; 2 Huang et al. 2013

  17. For a fixed m(U) , the highest and lowest signal is obtained with these U distributions: m(U) maximal amount of U tolerated by crustal models the remaining U mass homogeneously distributed in the mantle minimal amount of U tolerated by crustal models the remaining U mass displaced on the bottom of the mantle Geo-n, global U mass and radiogenic heat power For a fixed site on Earth’s surface the expected geo-n signal from U depends on its global mass m(U) and its distribution inside the Earth:

  18. Geological implications of new KL and BX results Region allowed by a BSE model with a global m(U) = 0.8 ± 0.1 1017 kg and Th/U = 3.9. The graph is site dependent: • the “slope” is universal • the intercept depends on the site (crust effect) • the width depends on the site (crust effect)

  19. Implications of KL and BX on terrestrial radiogenic heat mW / m2 New results based on ~40.000 measurements in deep bore-holes (55% more than used in previous estimates) Heat loss through the sea floor is estimated by half space model. For the first time the global terrestrial heat power from U and Th is measured in two different locations Preliminary

  20. Waiting SNO+… See you for Neutrino Geoscience in 2020! 4° Neutrino Geoscience Takayama 21-23 March 2013 1° Neutrino Geoscience Honolulu 14-16 December 2005

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