Results from Borexino Davide Franco CNRS-APC NOW 2012 September 9-16, 2012

Davide Franco – APC CNRS – NOW2012 Detector layout and radiopurity Water Tank:  and n shield  water Č detector 208 PMTs in water 2100 m 3 Carbon steel plates Scintillator: 270 t PC+PPO in a 150  m thick nylon vessel Stainless Steel Sphere: 2212 PMTs 1350 m 3 Nylon vessels: Inner: 4.25 m Outer: 5.50 m

Davide Franco – APC CNRS – NOW2012 Detection principles and signature Borexino detects solar via their elastic scattering off electrons in a volume of highly purified liquid scintillator Mono-energetic MeV 7 Be neutrinos: main target Mono-energetic 8B, pep, CNO and possibly pp neutrinos Detection via scintillation light: Very low energy threshold Good position reconstruction Good energy resolution BUT… No direction measurement The induced events can’t be distinguished from other  events due to natural radioactivity RadioIsotopeConcentration or Flux NameSourceRequiredAchieved  cosmic~ < CIntrinsic PC/PPO~ UDust< g/g~ ThOrganometallic (?)(in scintillator)~ PoSurface contam. ~ KrAir (nitrogen)< 1 c/d/100 t= 25±3 Extreme radio-purity of the scintillator is a must!

Davide Franco – APC CNRS – NOW2012 Detector Calibration May 2007 Detector response vs position: 100 Hz 14 C+ 222 Rn in scintillator in >100 positions Quenching and energy scale: Beta: 14 C, 222 Rn in scintillator Alpha: 222 Rn in scintillator Gamma: 139 Ce, 57 Co, 60 Co, 203 Hg, 65 Zn, 40 K, 85 Sr, 54 Mn Neutron: AmBe MC-G4Bx Data Pulse shape of 14 C events LY ~ 500 p.e./MeV Ph.Y. ~ photons/MeV Data - MC

Davide Franco – APC CNRS – NOW Be neutrino (862 keV) 4.6% Phys. Rev. Lett. 107, (2011) live days MC Fit Analytical Fit Systematics

Davide Franco – APC CNRS – NOW2012 Implication of the 7 Be measurement No oscillation 5.0  Assuming MSW-LMA: f 7Be = 0.97± 0.09 f pp = f CNO < 1.7% (95 % C.L.) Pee = 0.51 ± 867 keV no power to resolve low/high metallicity problem  <  b Neutrino magnetic moment limit:

Davide Franco – APC CNRS – NOW2012 The Day-Night Asymmetry A dn = ± (stat) ± (syst) LOW ruled out at 8.5  A neutrino “regeneration” is expected only in the LOW solution

Davide Franco – APC CNRS – NOW B neutrinos with the lowest threshold: 3 MeV 2.6 MeV  ’s from 208 Tl on PMT’s and in the buffer All volume R < 3 m (100 tons) Energy spectrum in Borexino (after  subtraction) Expected 8 B rate in 100 tons of liquid scintillator above 2.8 MeV: 0.26±0.03 c/d/100 tons > 5  distant from the 2.6 MeV  peak S/B ratio < 1/6000!!! live-time: 246 days

Davide Franco – APC CNRS – NOW B neutrino rate measurement raw spectrum  cut FV cut cosmogenic, neutron, 214 Bi and 10 C cuts 208 Tl MeV MeV Rate [c/d/100 tons]0.22±0.04± ±0.02± 0.01  ES exp [10 6 cm −2 s −1 ] 2.4±0.4±0.12.7±0.4±0.2  ES exp /  ES th 0.88± ±0.23

Davide Franco – APC CNRS – NOW2012 First observation of pep neutrinos  + 12 C →  + 11 C + n + p → d +  → 11 B + e + + e Three Fold Coincidence (TFC): space-time veto removes 90% of 11 C paid with 50% loss of exposure 11 C  ~ 30 min

Davide Franco – APC CNRS – NOW2012 o-Ps in scintillators Measurements of the o-Ps mean-life and formation probability in scintillators with the PALS technique D. Franco, G. Consolati, D. Trezzi, Phys. Rev. C83 (2011) Pulse shape induced distortion MC  ~ 3 ns p ~ 50%

Davide Franco – APC CNRS – NOW2012 Multivariate maximum likelihood fit Energy spectral fit Radial fit Pulse shape fit Pulse shape test

Davide Franco – APC CNRS – NOW2012 pep neutrinos: results pep neutrinos: Rate: 3.1 ± 0.6 (stat) ± 0.3 (sys) cpd/100 t Assuming MSW-LMA: Φ pep = 1.6 ± cm -2 s -1 No oscillations excluded at 97% C.L. Absence of pep solar ν excluded at 98% CNO neutrinos: only limits, correlation with 210 Bi; CNO limit obtained assuming SSM CNO rate < 7.1 cpd/100 t (95% c.l.) Assuming MSW-LMA: Φ CNO < cm -2 s -1 (95% C.L.) the strongest limit to date not sufficient to resolve metallicity problem Δχ 2 profile for fixed pep and CNO rates Borexino limit

Davide Franco – APC CNRS – NOW2012 The Borexino Solar neutrino spectroscopy

Davide Franco – APC CNRS – NOW2012 Status and future perspectives Since July 2010, purification campaigns: Nitrogen stripping successful in 85 Kr removal: 85 Kr < 8.8 cpd / 100 t ( : 31.2 ± 5) moderate success in 210 Bi removal by water extraction: 210 Bi : (16 + 4) cpd / 100 t ( : 41.0 ± 2.8) unprecedented 238 U and 232 Th radio-purity: 238 U < g/g and 232 Th < g/g 210 Po natural decreasing: ~5 cpd / t Borexino phase II started: Solar neutrino program: - Improve 7 Be, 8 B → test of MSW - Confirm pep at more than 3 σ - Improve upper limit on CNO → probe metallicity - Attempt direct pp measurement more statistics for an update of geo-neutrino measurement; another long-term scientific goals under discussion (sterile?)

Davide Franco – APC CNRS – NOW2012 A glance at the Borexino physics results Neutrino speed: Measurement of CNGS muon neutrino speed with Borexino, submitted Pep & CNO limit : First evidence of pep solar neutrinos by direct detection in Borexino, Phys. Rev. Lett. 108 (2012) Be ADN: Absence of day--night asymmetry of 862 keV 7Be solar neutrino rate in Borexino and MSW oscillation parameters, Phys. Lett. B 707 (2012) %: Precision measurement of the 7Be solar neutrino interaction rate in Borexino, Phys. Rev. Lett. 107 (2011) Solar antinu limits: Study of Solar and other unknown anti-neutrino fluxes with Borexino at LNGS, Phys. Lett. B696 (2011) Geo-nu: Observation of Geo-Neutrinos, Phys. Lett. B687 (2010) B > 3 MeV: Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector, Phys. Rev. D82 (2010) %: Direct Measurement of the Be-7 Solar Neutrino Flux with 192 Days of Borexino Data, Phys. Rev. Lett. 101 (2008) %: First real time detection of Be-7 solar neutrinos by Borexino, Phys. Lett. B658 (2008) muon modulation + cosmogenics + axions + Pauli principle + magnetic moment + ….

Davide Franco – APC CNRS – NOW2012 Borexino Collaboration Kurchatov Institute (Russia) Dubna JINR (Russia) Heidelberg (Germany) Munich (Germany) Jagiellonian U. Cracow (Poland) Perugia Genova APC Paris Milano Princeton University Virginia Tech. University

Davide Franco – APC CNRS – NOW2012 Backup

Davide Franco – APC CNRS – NOW2012 Geo-neutrinos: results Null hypothesis rejected at 4.2 