Aldo Ianni, LNGS for the Borexinocollaboration Sept. 29th, 2011

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1 Aldo Ianni, LNGS for the Borexinocollaboration Sept. 29th, 2011

2 First Borexino proposal: 1991 Main goal: real time measurement of sub-mev solar neutrinos Why? To solve the Solar Neutrino Puzzle (missingsolarneutrinos) Tounderstandbetter the Solar Standard Model How? Bymeansof a massive organicliquidscintillator

3 The Sun shines by burning H fuel 4p 4 He+2e + +2 e +( )MeV

4 Hydrogen burning: pp-chain ~0.4% ~85% ~15% ~0.02%

6 Solar Neutrino Spectrum pp(0.6%) 7 Be(7%) 13 N(14%) 15 O(15%) pep(1.1%) 8 B(14%) 17 F(17%)

7 use 100 tonsoforganicscintillator C 9 H 12 aimtodetect 7 Be monoenergeticneutrinosabove 250 kev N e f <s>

8 10 4 g/mev 25% coverage 20% PMTs QE Yield = 500 p.e./mev

9 No event-by-eventsignature Anyprocesswhichproducesan electron is a source of background Naturalradioactivityfromintrinsicimpurities ( 238 U, 232 Th, 210 Pb, 40 K ) The reduction of background events is a key issue

With 238 U and 232 Th at the levelof 10-16 g/g and exploiting offline background reductiononeexpects ~ 24 cpd soilhas ~ ppm level Otherbackground ( 85 Kr, 39 Ar, 210 Pb, 40 K)

10 With 238 U and 232 Th at the levelof g/g and exploiting offline background reductiononeexpects ~ 24 cpd soilhas ~ ppm level Otherbackground ( 85 Kr, 39 Ar, 210 Pb, 40 K) sourcesmustalsobereduced In 1991 best sensitivitywith ICP-MS whichcouldbeachievedforu and Thwas at the levelof g/g A prototypeforborexino, the Counting Test Facility, wasbuilt and operational in 1994 to prove the feasibilityof the experiment

11 Counting Test Facility

14 Borexinofilled and operational in May 2007 after 16 yearsof work

15 U and Thradiopurity at the levelof g/g 7 Be solar neutrino measurement at the levelof ~4% Day-nightasymmetryfor 7 Be solarneutrinos: ±0.012(stat)±0.007(syst) 8 B solar neutrino measurement at ~16% First observationofgeoneutrinos at 4s First indicationofpepsolarneutrinos Strongestbound on CNO neutrinos Searchforcosmogenicradioactiveisotopes in liquidscintillators Searchfor rare processes neutrino magnetic moment electron antineutrinosfrom the sun

16 solar neutrino signal in 100tons FM correspondsto ~ Bq/kg U[Th] at the levelof g/gcorrespondsto [ ]Bq/kg U/Th in soil ~ 12/4Bq/kg Rn in Borexino FM ~ Bq/kg Rn in air ~ 10 Bq/kg at STD

17 Calibration system gsources bsources a neutrons 57 Co 139 Ce 203 Hg 85 Sr 54 Mn 65 Zn 60 Co 40 K 14 C 214 Bi 214 Po np nc Energy [MeV] , SSS ALSO: 228 Th external source

19 Data reduction No muons + no correlated FV (<3m) FV( z <1.7m) Pulseshape

20 Spectrumofneutrinos + background

24 Since 2005 a new recalculation of the sun s metallicity has raised a strong tension between helioseismology and the SSM data HZ SNO + Borexino LZ data HZ LZ 1,3 scontours 1,2,3 scontours

25 Electron antineutrinos from 238 U and 232 Th decays in the crust and mantle The present paradigm: predicts a chondriticth/u ratio of about 4 for the whole Earth predicts a radiogenic contribution to the total heat from the Earth (~ 46 TW) of about 50% Our goal is to probe the standard paradigm More than one detector measurements are needed

26 anti- p n e + g DR prompt-delayed < 1m Dt prompt-delayed ~ 256ms target LS ~ p

27 Reactors in the World: main source of background Borexino KamLAND

28 Bestfitparametersfromlikelihoodan alysis 68%, 90% and 99.73% C.L. Max radiogenic Minradiogenic BSE 1s(3s)

29 Tackle down CNO neutrinos by reducing 210 Bi contamination Water Extraction purification in progress Nitrogen stripping has reduced 85 Kr and this improves 7 Be measurement and allows to probe pp neutrinos Improve statistics for geoneutrinos Put forward a program to use a neutrino artificial source ( 51 Cr) in Borexino for sterile neutrino search neutrino-electron interaction at 1 MeV scale

After 16 years of work Borexino is in data taking since 2007 Borexinohasperformed the first measurementof 7 Be solarneutrino flux at ~5% level in 2011 Borexinohasperformed the first measurementof 8 B

30 After 16 years of work Borexino is in data taking since 2007 Borexinohasperformed the first measurementof 7 Be solarneutrino flux at ~5% level in 2011 Borexinohasperformed the first measurementof 8 B solarneutrinos in a liquidscintillator at 16% level in 2010 Borexinohasperformed the first observationofgeoneutrinos at 4s in 2010 Borexinohasprovided the first indicationofpepsolarneutrinos at 97% CL in 2011 Borexinoisperforming a purificationcampaing and entering in a secondphasewherewehopeto tackle down the CNO and ppsolar neutrino fluxes Borexinoaimstosearchfor sterile neutrinoswithanartificial source at 10 PBqlevel

31 References on BOREXINO results Technicalpapers Detector: NIM A 600 (2009) Purification and fluidhandling: NIM A 587, (2008) Physicsresults 7 Be evidence: PL B (2008) 7 Be at 10% + f pp /f CNO : PRL 101, (2008) 8 B neutrinos: PRD 82 (2010) Limits on violationofpauliforbiddentransitions on 12C: PR C 81 (2010) Electron antineutrinosfrom the sun: PLB 696 (2011) 7 Be at 5%: acceptedby PRL Day-nightasymmetry: arxiv: Seasonalmodulationofcosmicmuons: arxiv:

32 Spares

$A referencemodel: the Bulk SilicateEarth Earth global compositionfromchondriticmeteorites Usegeochemicalargumentsto account for loss and fractioningduringplanetformation$

33 A referencemodel: the Bulk SilicateEarth Earth global compositionfromchondriticmeteorites Usegeochemicalargumentsto account for loss and fractioningduringplanetformation Obtaincompositionof primitive mantlebeforecrustformation BSE gives total m(u) and a(th):a(u):a(k)~4:1:12000 m BSE (U) ~ kg; m Mantle (U) ~ m BSE (U) m Crust (U)

34 U chain and correlated Bi-Po events

35 Hydrogen burning: CNO chain This cycle accounts for only ~0.7% of solar luminosity ~10-2

abundances in the crust HPE Weuse 2 2 meshmodelwithdifferentlay ers

36 The Earth scrust Weknowfor a factthat the CrustcontainsHeatProducingEl ements (HPE) Empiricaldeterminationof abundances in the crust HPE Weuse 2 2 meshmodelwithdifferentlay ers (UC, MC, LC) CRUST 2.0 model 200 km scale m C (U) ~ kg L (U) ~ s -1 H (U) ~ 3 TW a

37 Source locations in Borexino A: underneath WT D=825 cm No changetopresent configuration B: inside WT D = 700 cm Needtoremove shielding water C: center Majorchange Canbedone at the end of solarneutrinophysics C B A

38 Besides the inversebetadecaygoldenchannelborexinohas a uniqueopportunityfortagging SN neutrinosbymeansof neutrino protonelasticscatteringneutralcurrentinteraction Borexino data show that the background forthischannelabove 200 kevis at the levelof 10% with 30 eventsexpectedfor a standard SN at 10 kpc

Rateof 7 Be(0.862 MeV) = 46±1.5(stat) +1.5-1.

39 Rateof 7 Be(0.862 MeV) = 46±1.5(stat) (sys) cpd/100tons No flavorchangehypothesisrejected at 5s Fiducial Volume systematics: % Energy scale systematics: 2.7 %

40 ratepep: 3.13 ±0.05(stat)±0.31(syst) cpd/100tons Nullhypothesisrejected at 97% C.L. CNO upper bound: data/ssm < % C.L.

41 Tagging 11 C cosmogenic nuclei

42 LOW allowed area at 3s Allowed regions: 68.27% C.L % C.L % C.L. Global fitforsolar neutrino measurement in the oscillationhypothesis

Geo- luminosity and flux 40 K : 26 10 24 s -1 232 Th : 5.3 10 24 s -1 238 U : 6.

43 Geo- luminosity and flux 40 K : s Th : s U : s -1 L(geo- ) ~ s K [19 ppb] 232 Th [55 ppb] 238 U [15 ppb] Forcomparison L (Sun) ~ s -1 L (SN electron anti- ) ~ s -1

44 Spectroscopyofgeo- signal Geo- spectrum Geo- effectivespectrum 232 Th 238 U 238 U

LOW ENERGY SOLAR NEUTRINOS WITH BOREXINO. Lea Di Noto on behalf of the Borexino collaboration

LOW ENERGY SOLAR NEUTRINOS WITH BOREXINO Lea Di Noto on behalf of the Borexino collaboration Vulcano Workshop 20 th -26 th May 2018 [cm -2 s -1 MeV -1 ] SOLAR NEUTRINOS Electrons neutrinos are produced