1. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Geoneutrinos in Borexino Marco G. Giammarchi & Lino Miramonti Dip. di Fisica dell’Universita’ and Infn Milano Introduction to Borexino Radiopurity in Borexino Physics Test results Borexino and Geoneutrinos

2. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano

3. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Borexino Borexino is located under the Gran sasso mountain which provides a shield against cosmic rays (residual flux = 1  /m 2 hour); The core of the detector is shielded by successive layers of increasingly pure materials Core of the detector: 300 tons of liquid scintillator contained in a nylon vessel of 4.25 m radius (PC+PPO); 1 st shield: 1000 tons of ultra-pure buffer liquid (pure PC) contained in a stainless steel sphere of 7 m radius; 2 nd shield: 2400 tons of ultra-pure water contained in a cylindrical dome; 2214 photomultiplier tubes pointing towards the center to view the light emitted by the scintillator; 200 PMTs mounted on the SSS pointing outwards to detect light emitted in the water by muons

4. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Nylon vessels installation

5. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Nylon vessels installed and inflated (May 2004)

6. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Experimental Hall In Gran Sasso (Hall C) Stainless Steel Sphere (SSS) PMTs ready to be mounted Optical fiber istallation

7. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Final closure of the Inner detector (2004)

8. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Monocromatic ! E =862 keV  SSM =4.8x10 9 /sec/cm 2 “ window” (0.25-0.8 MeV)  =10 -44 cm 2 expected rate (LMA hypothesis) is 35 counts/day in the neutrino window

9. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Radiopurity constraints To lower the threshold down to 250 keV, it is mandatory to reach very high radiopurity levels in the active part of the detector ; This translates into the following requirements on the most critical contaminants ( 238 U, 232 Th, 40 K, 210 Po, 210 Pb, 39 Ar, 85 Kr) : Intrinsic contamination of the scintillator for what concerns isotopes belonging to the U and Th chain < 10 -16 g/g; Intrinsic contamination of the scintillator for what concerns 40 K < 10 -14 g/g; Contamination of the buffer liquid in U and Th chain < 10 -14 g/g; Contamination of the nylon vessel for what concerns the U and Th chain < 10 -12 g/g; Constraints on N 2 used to sparge scintillator: <0.14 ppt of Kr in N 2 (0.2  Bq 85 Kr/m 3 N 2 ) Constraints on N 2 used to sparge scintillator: <0.36 ppm of Ar in N 2 (0.5  Bq 39 Ar/m 3 N 2 ) Each of these points required careful selection and clean handling of materials, + implementation of purification techniques Contamination of the external water in U and Th chain < 10 -10 g/g; 14 C / 12 C <10 -18 in the scintillator

10. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Counting Test Facility (CTF) 100 PMTs 4 tons of scintillator 4.5m thickness of water shield Muon-veto detector CTF high mass and very low levels of background contamination make it a unique detector to search for rare or forbidden processes with high sensitivity CTF campaigns 1.CTF1: 95-97 2.CTF2: 2000 (pxe) 3.CTF3: 2001 still ongoing CTF is a prototype of BX. Its main goal was to verify the capability to reach the very low-levels of contamination needed for Borexino

11. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Physics results of the Counting Test Facility of Borexino (CTF)

12. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Limits on electron stability [ Phys. Lett. B 525 (2002) 29] - Non-conservation of electric charge would lead to electron decay via two processes: e   +, e   + + - search for the decay e   + (256keV line) -  > 4.6 x 10 26 y (90% C.L.) - currently world best limit (quoted on the PdG) Neutrino magnetic moment [Physics Letters B 563 (2003) 35 - a non-zero  would increase the e scattering cross-section by the term; - this effect becomes dominant at low energy -  < 5.5 x 10 -10  B (90% C.L.) - it is the best limit with low energy neutrino 1.e- scattering 2. 14 C spectrum 3.Residual radioactive bkg

13. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Limits on nucleon decay into invisible channels [Physics Letters B 563 (2003) 23] - different channels were considered in which a single nucleon or a pair of nucleons bounded in C or O nuclei decay with the emission of invisible particles (neutrinos, majorons…) - the obtained limits are comparable or improve previous limits; Limits on Heavy neutrino mixing in 8 B decay [JETP Lett. Vol. 78 No 5 (2003)261] - If heavy neutrinos H with m > 2 m e are emitted in 8 B reaction in the sun then the decay H  L + e + + e - should be observed; - CTF significantly improves limits on (m H - ׀U eH ׀ 2 ) parameter space; Limits on Pauli Esclusion Principle [Europ. Physical Journal C37 (2004) 421] - we look for non-Paulian transitions in 12 C and 16 O nuclei from 1P shell to a filled 1S 1/2 shell; - the obtained limits significantly improves (up to three order of magnitude) previous limits Other papers are under preparation: “Constraints on the solar anti-neutrino flux obtained with the BX prototype”  < 3x10 5 cm -2 s -1 (90% C.L.) first limit at low energy

14. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Earth emits a tiny heat flux with an average value of Φ H ~ 60 mW/m 2 Integrating over the Earth surface: H E ~ 30 TW Giving constrain on the heat generation within the Earth. Detecting antineutrino emitted by the decay of radioactive isotopes It is possible to study the radiochemical composition of the Earth

15. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano 238 U and 232 Th chains have 4 β with E > 1.8 MeV : end.point [Th-chain] 228 Ac< 2.08 MeV [Th-chain] 212 Bi< 2.25 MeV [U-chain] 234 Pa< 2.29 MeV [U-chain] 214 Bi< 3.27 MeV Anti-neutrino from 40 K are under threshold The terrestrial antineutrino spectrum above 1.8 MeV has a “2-component” shape. high energy component coming solely from U chain and low energy component coming with contributions from U + Th chains This signature allows individual assay of U and Th abundance in the Earth

16. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Borexino is located in the Gran Sasso underground laboratory (LNGS) in the center of Italy: 42°N 14°E Calculated anti-ν e flux at the Gran Sasso Laboratory (10 6 cm -2 s -1 ) UThTotal (U+Th)Reactor BKG CrustMantleCrustMantle 3.30.953.00.778.00.39 Data from the International Nuclear Safety Center (http://www.insc.anl.gov) Background from nuclear Reactors Earth data from F. Mantovani et al., Phys. Rev. D 69 (2004) 013001

17. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Pb concentration measured in the Counting Test Facility Background from Po-210 Alpha particles reacting on C-13: Pb-210 related background negligible Only significant source of background are nuclear reactors Accidental rate also negligible (< 10% of reactors background)

18. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano The number expected events in Borexino are: The background will be: Predicted accuracy of about 30% in 5 years of data taking

19. Honolulu 16/Dec/2005 Marco G. Giammarchi, Infn Milano Following August 2002 accident, Borexino activity has suffered from severe restrictions especially for what concerns fluid handling operations; In spite of this, the detector installation has continued and was completed in 2004; Following this, it was possible to start the re-commissioning of all ancillary plants which had been stopped three years ago; the re- commissioning is currently taking place; We expect to start filling the detector with scintillator in June 2006; We expect to start data-taking with the filled detector in november 2006 Conclusion and outlook Borexino is a low background high sensitivity underground detector which is located on continental crust and can give important information on geoneutrino fluxes.