Neutrino oscillations with radioactive sources and large detectors Wladyslaw H. Trzaska on behalf of: Yu.N. Novikov, T. Enqvist, A.N. Erykalov, F. v.Feilitzsch, J. Hissa, K. Loo, D.A. Nesterenko, F. Thorne, J.D. Vergados and M. Wurm

Sources of neutrinos for oscillation studies Sun Power reactors Accelerators – Super-beams – Neutrino factory – Beta-beams – Decay at rest neutrino sources (produced with an ~800 MeV p) Sanjib K. Agarwalla GLA2011 Radioactive sources NNN11W.H.Trzaska2

Beta Decay vs. Electron Capture Beta decay: – Emission of two particles – Each particle with a wide energy spectrum Electron capture: – Emission of one particle – Monoenergetic electron neutrinos NNN11W.H.Trzaska3

Possible sources of monoenergetic electron neutrinos NNN11W.H.Trzaska4 NuclideT 1/2 (d) Q (keV) E (keV) E e,max (kev) Irradiatio n material intensity (kg-1 s - 1) 37 Ar Ar8.3 x Cr Cr2.3 x Se Se1.1 x Sn Sn8.0 x Sm Sm2.0 x Yb Yb1.1 x 10 15

51 Cr NNN11W.H.Trzaska5 90.1% E ν = 747 keV

62 PBq 51 Cr source for GALLEX NIMA 378 (1996) kg of enriched Cr containing ~14 kg of 50 Cr Produced by Kurchatov Institute (CrO 3 ) Electrolyzed in Saclay to obtain metal tubes Tubes were crushed into coarse chips ~1 mm 3 Chips were put inside 12 irradiation cells Cells were placed around the reactor core Siloé reactor at Grenoble was specially reconfigured for this 23.8 days irradiation Activated chromium was sealed in a tungsten shield with 8.5 cm thick walls The source resided in the center of the GALLEX detector between June 23 and October 10, 1994 irradiating the gallium target with neutrino intensity well above the solar neutrino background. Fall 1996  2 nd irradiation  69 PBq NNN11W.H.Trzaska6

75 Se NNN11W.H.Trzaska7 94.5% E ν = 450 keV

Oscillation length vs. energy NNN11W.H.Trzaska8 Fermilab plot 0.085(51) Double Chooz

(ν x,e - ) scattering cross section as a function of neutrino energy [keV] NNN11W.H.Trzaska9

BOREXINO spectrum NNN11W.H.Trzaska10

Neutrino oscillometry Simultaneous measurement of θ 13 and L 32 L 32 ≈ detector length/height E ν [keV] ≈ L 32 [m] Calculated scenarios – LENA (100 m tall) + 75 Se  θ 13 and L 32 – LScint (R > 3 m) + 51 Cr  sterile neutrinos Next step – antineutrino oscillometry NNN11W.H.Trzaska11

source Distance to top Horizontal axis = Our calculations are based on this kind of scenario: 75 Se 6 x 120 days E ν =450 keV 14 C thr:200 keV Be-7 neutrinos ≈ 100 m NNN11W.H.Trzaska12

75 Se: 6 x 120 days with different sin 2 (2θ 13 ) With solar Be-7 background No systematics NNN11W.H.Trzaska13

If 14 C background could be reduced NNN11W.H.Trzaska14

Detector length is essential! NNN11W.H.Trzaska15

Hunt for θ 13 16ANT'11Wladyslaw H. Trzaska

Following slides show cumulative events detected inside of a hemisphere, with a radius = r. Source is put straight to the top of detector. Sterile neutrino examples source r Source: 51 Cr 3 x 28 days E ν =747 keV NNN11W.H.Trzaska17

Example: 3+1 neutrino case Signal Is way above 6sigma statistical level NNN11W.H.Trzaska18

Example: 3+2 neutrino case NNN11W.H.Trzaska19

Some of the candidates for antineutrino oscillometry NNN11W.H.Trzaska20 Requirements: Q β - > 1.8 MeV T 1/2 >10 d and ΔE ν < 500 keV (ΔE ν = E ν keV) Assumed reactor irradiation time: 0.1 year for 113 In and 123 Sb 1 year for 153 Eu E th = 1.8 MeV

154 Eu source T 1/2 = 8.6 years %β - = Q - = MeV – 10.3 % feeding to 123 keV 2 + state in 154 Gd The rest goes to higher excited states – – = MeV NNN11W.H.Trzaska21 E th = 1.8 MeV

144 Ce Pr NNN11W.H.Trzaska22 Phys. Rev. Lett. 107, (2011) Proposed Search for a Fourth Neutrino with a PBq Antineutrino Source

Conclusions Radioactive sources provide attractive and complementary addition to LBNO for the study of neutrino properties via oscillations – Monoenergetic, sub-MeV neutrinos – Very compact, removable source – Entire oscillation curve; not just a 2 point sample The proposed 50 kton, liquid scintillator LENA detector would be well suited for such studies thanks to the low energy threshold, high detection efficiency, and uniquely slender design (100 m high tank!) – Very promising for sterile neutrino studies! NNN11W.H.Trzaska23