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Lino Miramonti

Neutrinos and (Anti)neutrinos from Supernovae and from the Earth in the Borexino detector. Lino Miramonti. 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics. Lino Miramonti. June 9-14, 2003, Nara Japan. The main goal of Borexino is the direct observation and measurement

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Lino Miramonti

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  1. Neutrinos and (Anti)neutrinos from Supernovae and from the Earth in the Borexino detector Lino Miramonti 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  2. The main goal of Borexino is the direct observation and measurement of the solar 7Be-ν flux Unsegmented detector featuring 300 tons of ultra-pure liquid scintillator viewed by 2200 photomultipliers PC + PPO (1,5 g/l) r = 0.88 g cm-3 n = 1.505 Threshold: 250 keV (due to 14C) Energy Resolution: FWHM  12% @ 1 MeV Spatial Resolution:  10 cm @ 1 MeV 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  3. In 100 tons of fiducial volume we expect ~ 30 events per day (for LMA) via the ES on e- :νe + e- → νe + e- • Requirements for a 7Be solar νe detector: • Ultra-low radioactivity in the detector : • 10-16 g/g level for U and Th. • 10-14 g/g level for K • Shielding from environmental γ rays • Muon veto and underground location • Low energy threshold • Large fiducial mass 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  4. antineutrino detection By far the best method to detect antineutrino is the classic Cowan Reines reaction of capture by proton in a liquid scintillator: The electron antineutrino tag is made possible by a delayed coincidence of the e+ and by a 2.2 MeV γ-ray emitted by capture of the neutron on a proton after a delay of ~ 200 µs Threshold The entire scintillator mass of 300 tons may be utilized One of the few sources of correlated background is muon induced activities that emit β-neutron cascade. However, all such cases have lifetimes τ < 1 s. Thus they can be vetoed by the muon signal. At LNGS µ reducing factor ~ 106 Borexino µ veto ~ 1/5000 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  5. Others possible goals with Borexino detector: Supernova neutrinos Geo-neutrinos Neutrinos from artificial sources Long-Baseline Reactor 51Cr & 90Sr 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  6. What Can We Learn from a Galactic Supernova Neutrino Signal? NEUTRINO PHYSICS ν absolute mass from time of flight delay νoscillations from spectra (flavor conversion in SN core, in Earth) CORE COLLAPSE PHYSICS explosion mechanism proto nstar cooling, quark matter black hole formation ASTRONOMY FROM EARLY ALERT some hours of warning before visible supernova 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  7. In a liquid scintillator detector, the electron antineutrino on proton reactions constitute the majority of the detected Supernova neutrino events. Nevertheless The abundance of carbon in PC provides an additional interesting target for neutrino interactions. C9H12 Pseudocumene [PC] (1,2,4-trimethylbenzene) • All of the reactions on 12C can be tagged in Borexino: • The CC events have the delayed coincidence of a β decay following the interaction (τ~ qq 10 ms). • The NC events have a monoenergetic γ ray of 15.1 MeV 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  8. We consider 300 tons of PC and a Type II Supernova at 10 kpc (galactic center) • Essentially all gravitational energy (Eb = 3 1053 ergs) is emitted in neutrinos. • The characteristic neutrino emission time is about 10 s. • The total emitted energy is equally shared by all 6 neutrino flavors. • Energy hierarchy rule: Supernova neutrino energy spectra 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  9. cross sections Measurements of cross-sections for 12C(νe,e-)12N and 12C(ν,ν’)12C* have been performed at KARMEN, at LAMPF and by LSND. Since 12N and 12B are mirror nuclei, the matrix elements and energy-independent terms in the cross-section are essentially identical. Only the Coulomb correction differs when calculating the capture rates of the anti-νe. Cross sections for CC on p, ES, CC and NC on 12C. 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  10. SN ν events in Borexino from a SN at 10kpc (Eb = 3 1053 ergs) ES 4.82 events The νμ and the ντ are more energetic than νe. νμandντ dominate the neutral-current reactions 12C(ν,ν’)12C with an estimated contribution of around 90 %. β-inv. 79 events 0.65 events CC In order to exploit these aspects, a liquid scintillator SN neutrino detector needs to be able to cleanly detect the 15.1 MeV γ ray. This implies that the detector require a large volume to contain this energetic γ ray. Reactions on 12C 3.8 events 0.4 events 1.5 events NC 20.6 events Total ~ 110 events 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  11. Simulated spectrum from supernova neutrino in Borexino 2.2 MeV γ rays low energy By studying the arrival time of neutrinos of different flavors from a SN, mass limit on νµ and ντ down to some 10 of eV level can be explored The time delay, in Borexino, is obtained by measuring the time delay between NC events and CC events high energy 15.1 MeV γ rays Continuum of e+ from inverse β decay 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  12. Geoneutrinos Earth emits a tiny heat flux with an average value ΦH~ 80 mW/m2. Integrating over the Earth surface: HE ~ 40 TW(about 20000 nuclear plants) It is possible to study the radiochemical composition of the Earth by detecting antineutrino emitted by the decay of radioactive isotopes. Confirming the abundance of certain radioelements gives constrain on the heat generation within the Earth. 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  13. Radioelements (ε is the present natural isotopic abundance) 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  14. The energy threshold of the reaction is 1.8 MeV There are 4 β in the 238U and 232Th chains with energy > 1.8 MeV : The terrestrial antineutrino spectrum above 1.8 MeV has a “2-component” shape. The high energy component coming solely from U chain and The low energy component coming with contributions from U and Th chains. This signature allows individual assay of U and Th abundance in the Earth 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  15. Equation for Heat and neutrinos Luminosity Each element has a fixed ratio H = 9.5 10-8· M(U) + 2.7 10-8 · M(Th) + 3.6 · 10-12 M(K) [W] LAnti-ν = 7.4·104 · M(U) + 1.6·104 · M(Th) + 27 · M(K) [anti-ν/s] Lν = 3.3 · M(K) [ν/s] Everything is fixed in term of 3 numbers: 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  16. The radiogenic contribution to the terrestrial heat is not quantitatively understood. Models have been considered: Primitive Mantle The starting point for determining the distribution of U, Th and K in the present CRUST and MANTLE is understanding the composition of the “Bulk Silicate Earth” (BSE), which is the model representing the primordial mantle prior to crust formation consistent with observation and geochemistry (equivalent in composition to the modern mantle plus crust). BSE concentrations of: U ~ 20 ppb (±20%), have been suggested H M Mantle= 68% M Earth M(U) = 20 ppb · 0.68 · 6·1027g = 8.5·1019g • In the BSE model: • The radiogenic heat production H rate is ~ 20 TW • (~ 8 TW from U, ~ 8.6 TW from Th, ~ 3 TW from K) • The antineutrino production L is dominated by K. L 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  17. During the formation of the Earth’s crust: the primitive mantle was depleted of U, Th and K, while the crust was enriched. Continental Crust: average thickness ~ 40 km Oceanic Crust: average thickness ~ 6 km CC is about 10 times richer in U and Th than OC Measurements of the crust provide isotopic abundance information: With these measurement, it is possible to deduce the average U and Th concentrations in the present depleted mantle. Crust type and thickness data in the form of a global crust map: A Global Crustal Model at 5° x 5° (http://quake.wr.usgs.gov/study/CrustalStructure/) 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  18. Borexino is homed in the Gran Sasso underground laboratory (LNGS) in the center of Italy: 42°N 14°E LNGS Data from the International Nuclear Safety Center(http://www.insc.anl.gov) 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  19. Positron energy spectrum from antineutrino events in Borexino In Borexino are expected: The background will be: (7.6 of them in the same spectral region as the terrestrial anti-ν) U+Th U only European Reactors The characteristic 2-component shape of the terrestrial anti-neutrino energy spectrum make it possible to identify these events above the reactor anti-neutrino background. The reactor anti-neutrino background has a well-known shape it can be easily subtracted allowing the discrimination of the U contribution from the Th contribution. 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  20. The main characteristics that made BOREXINO interesting for neutrino physics are: SUPERNOVAE The very effective ability to detect the high energy gamma peak (15.1 MeV) from NC reactions on 12C thanks to the unsegmented large volume detector. The absence of nuclear plants in Italy gives a very low contribution to the geo antineutrino background. GEONUTRINOS 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

  21. NC reactions on 12C have no spectral information In a low threshold detector like Borexino the ES on proton (NC reaction): can be observed measuring the recoiling protons. In principle, it can furnish spectroscopic information. Furthermore: the total neutrino flux from a SN is 6 times greater than the flux from just anti-νe. The νµ and ντ flavors are more energetic, increasing the total event rate. This provide Borexino with several hundred supernova neutrino interactions draft 1st Yamada Symposium Neutrinos and Dark Matter in Nuclear Physics Lino Miramonti June 9-14, 2003, Nara Japan

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