Borexino Source Experiment G. Ranucci On behalf of the Borexino - PowerPoint PPT Presentation

Borexino Source Experiment G. Ranucci On behalf of the Borexino Collaboration SNAC11 ,Blacksburg, VA 27 September 2011 27/09/2011 Gioacchino Ranucci ‐ SNAC11

The idea to use a neutrino source in Borexino and in other underground experiments dates d i th d d i t d t back to at least 20 years – N.G.Basov,V.B.Rozanov, JETP 42 (1985) – Borexino proposal, 1991 (Sr90) Bx – J.N.Bahcall,P.I.Krastev,E.Lisi, Phys.Lett.B348:121 ‐ 123,1995 J N Bahcall PI Krastev E Lisi Phys Lett B348:121 123 1995 – N.Ferrari,G.Fiorentini,B.Ricci, Phys. Lett B 387, 1996 (Cr51) Bx – I.R.Barabanov et al., Astrop. Phys. 8 (1997) – Gallex coll. PL B 420 (1998) 114 Done (Cr51) G ll ll PL B 420 (1998) 114 D (C 51) – A.Ianni,D.Montanino, Astrop. Phys. 10, 1999 (Cr51 and Sr90) Bx – A.Ianni,D.Montanino,G.Scioscia, Eur. Phys. J C8, 1999 (Cr51 and Sr90) Bx – SAGE coll. PRC 59 (1999) 2246 Done (Cr51 and Ar37) – SAGE coll. PRC 73 (2006) 045805 – C.Grieb,J.Link,R.S.Raghavan, Phys.Rev.D75:093006,2007 g y – V.N.Gravrin et al., arXiv: nucl ‐ ex:1006.2103 – C.Giunti,M.Laveder, Phys.Rev.D82:113009,2010 – C.Giunti,M.Laveder, arXiv:1012.4356 C.Giunti,M.Laveder, arXiv:1012.4356 27/09/2011 Gioacchino Ranucci ‐ SNAC11

The physics case with a source experiment • Neutrino magnetic moment • Neutrino ‐ electron non standard interactions • Probe ν • Probe ν e ‐ e weak couplings at 1 MeV scale e weak couplings at 1 MeV scale • Probe sterile neutrinos at 1eV scale • Probe neutrino vs anti ‐ neutrino oscillations on 10m scale 10m scale 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Anomalies/hints for Δ m 2 ≅ 1eV 2 Anomalies/hints for Δ m ≅ 1eV Workshop on Beyond Three Family Neutrino Oscillations Family Neutrino Oscillations a ) The LSND/Miniboone (anti ‐ ν and ν) anomalies / LNGS 3 ‐ 4 May 2011 b ) The reactor anomaly arXiv:1101.2755 sin 2 2 θ ee = 0.1 Δ m 2 = 0.4 eV 2 Rate only analysis R t l l i sin 2 2 θ ee = 0.1 Δ m 2 = 1.5 eV 2 Rate+shape c ) The Gallium anomaly R=0.86 from Gallex and Sage source tests arXiv1006.3244 Giunti and Laveder sin 2 2 θ ee = 0.5 Δ m 2 = 2.24 eV 2 d ) Indications from cosmology and BBN of more than 3 neutrinos 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Borexino at Gran Sasso: low energy neutrino real time detection Stainless Steel Sphere: 2212 photomultipliers Scintillator: Scintillator: 1350 m 3 1350 3 270 t PC+PPO in a 150 μ m thick nylon vessel Design based on the principle of graded shielding Nylon vessels: N l l Water Tank: Inner: 4.25 m γ and n shield Outer: 5.50 m μ water Č detector μ water Č detector 208 PMTs in water Neutrino 2100 m 3 electron scattering ν e −> ν e 20 legs 20 legs Carbon steel plates Gioacchino Ranucci - SNAC11 27/09/2011

UMass Gioacchino Ranucci - SNAC11 27/09/2011

Borexino achievements � High precision (better than 5%) 7 Be flux � 7 Be day night (absence) � 7 Be day ‐ night (absence) � Unambiguous geo ‐ neutrino detection � 8 Be with a 3 MeV threshold � First indication of pep solar neutrinos and tight upper limit on CNO neutrinos (Borexino talks at the recent TAUP) All above thanks to the accurate energy ‐ position calibration of the detector volume detector volume The perfect knowledge of the detector performances witnessed by this impressive list of achievements is the solid ground upon which this impressive list of achievements is the solid ground upon which the proposal for the source test in Borexino is built 27/09/2011 Gioacchino Ranucci ‐ SNAC11

7 Be Solar neutrinos in Borexino hep ‐ ex/1104 1816v1 hep ‐ ex/1104.1816v1 +1.6 7 Be = 46.0 ± 1.5 cpd/100 tons p / ‐ 1.5 210 Bi Bi pep & CNO 85 Kr pp pp Now removed! 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Solar neutrino survival probability p y “Ultimate” validation of the MSW ‐ LMA survival probability curve 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Position and energy calibration • On and off axis calibrations sources • Rn, AmBe Rn, AmBe • 57 Co, 139 Ce, 208 Hg, 85Sr, 54 Mn 65 Zn 40 K 60 Co Mn, Zn, K, Co The knowledge of the detector and The knowledge of the detector and of its performance makes it the ideal “environment” for a series of source test to shed light on the hints of a test to shed light on the hints of a new neutrino oscillation mass scale involving steriles Initially external location, later in the Initially external location, later in the center 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Source location in Borexino Source location in Borexino • A: underneath WT A d th WT – D=825 cm – No change to present g p configuration • B: inside WT B C – D = 700 cm 00 – Need to remove shielding water g • C: center – Major change – Remove inner vessels l – To be done at the end of solar Neutrino physics eut o p ys cs A 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Source position A Source position A 27/09/2011 Gioacchino Ranucci ‐ SNAC11

27/09/2011 Gioacchino Ranucci ‐ SNAC11

Sources � Activity: several 1000 ν evts within 1 year � E >250 keV ( 14 C background) � E >250 keV ( C background) � Half-life ≥ 1 month � Compact � Limited heat � Limited heat � Efficient shielding � Low impurities level 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Proposed at the workshop Beyond 3 ν at Gran Sasso in May and in arXiv:1107.2335 y 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Originally 51Cr proposed by Raju Raghavan h ~36 kg of 38% enriched 50 Cr g 190 W/MCi from 320 keV γ ’s 7 μ Sv/h (must be < 200) Done two times for Gallex at 35 MW reactor with effective thermal neutrons flux of ~5.4E13 cm ‐ 2 s ‐ 1 2 1 SAGE coll., PRC 59 (1999) 2246 ~1.8 MCi Gallex coll., PL B 420 (1998) 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Transport container 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Cr51 Gallex source Cr51 Gallex source 27/09/2011 Gioacchino Ranucci ‐ SNAC11

27/09/2011 Gioacchino Ranucci ‐ SNAC11

The case of ν e The case of ν e Cr source in Borexino 51 Cr source in Borexino Bi Bismuth210 th210 CNO CNO Be7 Source events Wi d Window 0.250 ‐ 0.700 KeV 0 250 0 700 K V Background : solar neutrinos + Bismuth210 27/09/2011 Gioacchino Ranucci ‐ SNAC11

37 Ar ν source Ar ν e source 37 Ar( τ =50.55 days) 37 813 keV (9.8%) 811 keV (90.2%) 37 Cl From irradiation of CaO using fast neutrons 40 Ca(n, α ) 37 Ar Used in SAGE with ~0.4 MCi ~16 W/MCi from 2.6 keV X ‐ rays Gaseous source Mentioned here for “historical” reasons SAGE coll., PRC 73 (2006) 045805 27/09/2011 Gioacchino Ranucci ‐ SNAC11

90Sr ‐ 90Y ν source e τ Sr = 28.79 years τ Y = 3.8 days 90 Sr Inverse beta decay <E>=2±0 2MeV <E> 2±0.2MeV < σ >=7.2 ⋅ 10 ‐ 45 cm 2 90 Y 7.25 kg/MCi Product of nuclear fission ~6700 W/MCi 6700 W/MCi Used in thermoelectric generators Used in thermoelectric generators including Bremsstrahlung Known technology for 0.2 MCi sources 27/09/2011 Gioacchino Ranucci ‐ SNAC11

27/09/2011 Gioacchino Ranucci ‐ SNAC11

3 27/09/2011 Gioacchino Ranucci ‐ SNAC11

Spatial profile of detected events for a monoenergetic 120 source (Cr51) in the tunnel Δ m 2 sin 2 2 θ 100 8 0.07 8 0 07 80 1 0.1 no oscillation 60 Ideal case Ideal case no spatial resolution 40 no background 20 0 400 500 600 700 800 900 1000 1100 1200 1300 1400 Cmfrom the source 27/09/2011 Gioacchino Ranucci ‐ SNAC11

How to exploit the rate and waves information Oscillometry measurements ‐ Standard way to convey the predicted sensitivity of an oscillation Standard way to convey the predicted sensitivity of an oscillation experiment • Exclusion plots exploiting Exclusion plots exploiting o Rate only (usual approach) o Rate plus waves (specificity of the present case) o Obtained through the likelihood ratio method, testing against the oscillation hypothesis simulated data which instead are produced unaffected by oscillations instead are produced unaffected by oscillations o Practically derived by comparing the corresponding χ 2 (average data with no oscillation ‐ model with oscillation) ( g ) with the desired quantile (90%, 99%, 99.73%) of the χ 2 distribution with two degrees of freedom 27/09/2011 Gioacchino Ranucci ‐ SNAC11

‐ Complementary, less used approach: • Discovery plots to determine the existence of the effect, exploiting again only the rate or the rate+waves combination o Obtained through the likelihood ratio method, but Obt i d th h th lik lih d ti th d b t testing against the no oscillation hypothesis simulated data which instead are produced as simulated data which instead are produced as affected by oscillations o Practically derived by comparing corresponding χ 2 (average data with oscillation ‐ model with no oscillation) with the desired quantile (90%, 99%, 99.73%) of the χ 2 distribution with two degrees of 2 di t ib ti 99 73%) f th ith t d f freedom o The determination of the oscillation parameters is o The determination of the oscillation parameters is also carried out o Exclusion and discovery contours are practically similar ‐ At high Δ m 2 effectively rate only analysis (in both cases)