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FLASY2011 Short Baseline Neutrino Anomalies and Future Probes Sanjib Kumar Agarwalla (Sanjib.Agarwalla@ific.uv.es) IFIC/CSIC, University of Valencia, Spain Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 p.1/32 Definition of

  1. FLASY2011 Short Baseline Neutrino Anomalies and Future Probes Sanjib Kumar Agarwalla (Sanjib.Agarwalla@ific.uv.es) IFIC/CSIC, University of Valencia, Spain Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.1/32

  2. Definition of Short Baseline Short-baseline means : L/E ∼ 1 (m/MeV or km/GeV) It covers a wide range of experiments Radioactive ν e / ¯ ν e Source experiments ( L/E ∼ 1 m/1 MeV) Reactor ¯ ν e experiments ( L/E ∼ 5 m/5 MeV) Accelerator produced ν experiments ( L/E ∼ 1 km/1 GeV) Atmospheric Neutrinos in IceCube ( L/E ∼ 1000 km/1 TeV) Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.2/32

  3. Short Baseline Experiments ν e disappearance search (reactor experiments) ¯ Bugey-3 (at 15, 40 & 95 m), Bugey-4, ROVNO, Gösgen, Krasnoyarsk, ILL Also, Chooz and Palo Verde at L ≃ 1 km ν e disappearance search KARMEN and LSND ν e -carbon cross section estimates GALLEX & SAGE radioactive source experiments Appearance searches ( ν µ → ν e , ¯ ν µ → ¯ ν e ) LSND, MiniBooNE, KARMEN, NOMAD ν µ disappearance limits CDHS, MiniBooNE, Atmospheric neutrinos Neutral Current measurement of MINOS Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.3/32

  4. Short-baseline ν oscillation Recent results from short-baseline neutrino experiments hint towards high ∆ m 2 ∼ 0.1–10 eV 2 oscillation Are they pointing towards Sterile neutrinos or something else? Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.4/32

  5. Positive Indications LSND : L = 30 m, < E ν ¯ µ > = 40 MeV 3 . 8 σ excess of ¯ ν e events in a beam of ¯ ν µ PRL 75 (1995) 2650; PRC 54 (1996) 2685; PRL 77 (1996) 3082; PRD 64 (2001) 112007 MiniBooNE : L = 541 m, < E ν µ ,ν ¯ µ > = 700 MeV A 2 . 8 σ excess of ¯ ν e events in the anti-neutrino mode above 475 MeV , consistent with LSND PRL 103 (2009) 111801; PRL 105 (2010) 181801 Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.5/32

  6. Positive Indications Recent Reactor Anomaly Reanalysis of reactor fluxes in Mueller et al., (arXiv:1101.2663) shows 2.5% upward shift in flux Overall reduction in predicted flux compared to existing data can be interpreted as oscillations at baselines of order 10–100 m (arXiv:1101.2755) Gallium Anomaly There is a deficit of ν e measured in the radioactive source experiments of the GALLEX and SAGE detector Suggests possible ν e disappearance at 2.7 σ (arXiv:1006.3244) Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.6/32

  7. Negetive Indications : Tensions In MiniBooNE, no oscillation in the ν -mode for energies above 475 MeV PRL 98 (2007) 231801 An unexplained 3 σ excess of ν e events in the ν -mode of MiniBooNE below 475 MeV PRL 102 (2009) 101802 No hint of steriles in MiniBooNE ν µ / ¯ ν µ disappearance PRL 103 (2009) 061802 Strong limit on ν µ disappearance from CDHS PLB 134 (1984) 281 No trace of steriles in atmospheric and solar neutrino data in the required parameter range PRD 76 (2007) 093005 Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.7/32

  8. 3+1 SBL oscillations Add one sterile ν with three active ones at the eV scale SBL approximation : ∆ m 2 21 ≈ ∆ m 2 31 ≈ 0 and x ij ≡ ∆ m 2 ij L/ 4 E ν e ) = 4 | U e 4 | 2 | U µ 4 | 2 sin 2 x 41 ≡ sin 2 2 θ µe sin 2 x 41 P (¯ ν µ → ¯ 41 = 0.57 eV 2 and sin 2 2 θ µe = 0.0097 using LSND, MB- ¯ Example Fit : ∆ m 2 ν , KARMEN (Karagiorgi et al., arXiv:0906.1997) P ( ν e → ν e ) = 1 − 4 | U e 4 | 2 (1 − | U e 4 | 2 ) sin 2 x 41 ≡ 1 − sin 2 2 θ ee sin 2 x 41 41 = 1.78 eV 2 and sin 2 2 θ ee = 0.089 using all reactor data Example Fit : ∆ m 2 with new fluxes (J. Kopp et al., arXiv:1103.4570) No CPV : can’t reconcile ¯ ν (LSND, MB) and ν (MB) data Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.8/32

  9. 3+2 SBL oscillations Add two sterile neutrinos with three active ones at the eV scale SBL approximation : ∆ m 2 21 ≈ ∆ m 2 31 ≈ 0 and x ij ≡ ∆ m 2 ij L/ 4 E 4 | U e 4 | 2 | U µ 4 | 2 sin 2 x 41 + 4 | U e 5 | 2 | U µ 5 | 2 sin 2 x 51 P (¯ ν µ → ¯ ν e ) = + 8 | U e 4 U µ 4 U e 5 U µ 5 | sin x 41 sin x 51 cos( x 54 + δ ) δ ≡ arg ( U ∗ e 4 U µ 4 U e 5 U ∗ µ 5 ) is the CP -phase 1 − 4(1 − | U e 4 | 2 − | U e 5 | 2 )( | U e 4 | 2 sin 2 x 41 + | U e 5 | 2 sin 2 x 51 ) P ( ν e → ν e ) = 4 | U e 4 | 2 | U e 5 | 2 sin 2 x 54 − ∆ m 2 ∆ m 2 | U e 4 | | U µ 4 | | U e 5 | | U µ 5 | δ/π 41 51 A : arXiv:1103.4570 0.47 0.128 0.165 0.87 0.138 0.148 1.64 B : arXiv:0906.1997 0.39 0.40 0.20 1.10 0.21 0.14 1.1 Global best-fit points for (3+2) model. Mass splittings are shown in eV 2 Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.9/32

  10. What do we need? We have both positive and negative hints for sterile high ∆ m 2 oscillation. Nothing is conclusive !! We need powerful new experiments to have appearance and disappearance searches at high significance involving both neutrinos and anti-neutrinos Combine powerful new multi-kiloton liquid scintil- lator, argon or water detectors with a modest power decay-at-rest neutrino source at short-baseline Observe the L/E dependence of the oscillation wave across the length scales of these detectors SKA, Patrick Huber, arXiv:1007.3228 SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984 Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.10/32

  11. Stopped Pion Source 800 MeV protons from cyclotrons interact in a low-A target (C, H 2 O) producing π + and, at a low level, π − p + X → π ± + X ′ Low-A target is embedded in a high-A, dense material where pions are brought to rest π − & daughter µ − captured before DIF, minimizing ¯ ν e π + decay produces mono-energetic 29.8 MeV ν µ & µ + π + → µ + + ν µ µ + decays at rest, providing Michel spectrum µ + → e + + ν e + ¯ ν µ Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.11/32

  12. Decay At Rest (DAR) Source µ + + ν µ π + → | → e + + ν e + ¯ ν µ ν µ ν µ ) -1 s ν -1 e Φ (MeV 0 10 20 30 40 50 60 E ν (MeV) Provides an equal, high-intensity, isotropic, DAR ν µ , ν e and ¯ ν µ ν e contamination ( 4 × 10 − 4 ) beam with tiny ¯ Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.12/32

  13. Cyclotron : Proton Source Mike Shaevitz, SBNW11, Fermilab Cyclotrons : ideal low-cost source for low energy protons Bunch spacing ∼ few tens of ns, continuous source Average beam power, 10 - 100 kW, prototypes for DAE δ ALUS Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.13/32

  14. Neutrino Source Details 4 × 10 21 per year, per flavor ( ν µ , ¯ ν µ and ν e ), 1 . 6 × 10 18 per year of ¯ ν e ( 4 × 10 − 4 compared to other flavors); Delivered as 100 kW average power, with 200 kW instantaneous power, (50% duty factor allowing equal beam-on and beam-off data sets); 800 MeV protons on target; ± 25 cm smearing (assumed flat) on neutrino production point; 20 m distance from average production point to face of detector fiducial region. p/ π ratio uncertain : conservative 10% correlated normalization error on all flavors 20% normalization error on the π − DIF background No uncertainty in the shape of the energy spectrum Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.14/32

  15. DAR beam interactions 1e−39 ν µ → ¯ ¯ ν e Appearance ν e + p → e + + n (IBD) [ cm ] ¯ 2 1e−40 Cross−section Free protons : Liquid scintillator oil, H 2 O 1e−41 Low kinematic threshold : 1.81 MeV Coincidence tag between prompt positron ν + p n [IBD] ( ) e e , 1e−42 40 40 * ν − and the delayed neutron capture by a proton Ar K ( ) e e , 12 12 ν e , e − C N ( ) g.s. n + p → d + γ (2.2 MeV) after ∼ 250 µ s 1e−43 10 15 20 25 30 35 40 45 50 Neutrino energy [MeV] ν e → ν e Disappearance ν e + 12 C → e − + 12 N g . s . Threshold 17.33 MeV, well measured, ∼ 5 to 10% uncertainty prompt e − , followed within a 60 ms window by e + from β -decay of the 12 N g . s . , mean τ 15.9 ms ν e + 40 Ar → e − + 40 K ⋆ Threshold 4.24 to 5.89 MeV depending on which 40 K ⋆ It has the highest cross-section in the energy range of interest, excellent for Disappearance studies Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.15/32

  16. LENA Scintillation Detector 50 kt Fiducial (Unsegmented) 100 m tall by 30 m diameter Source-to-detector-face = 20 m Low detection threshold Excellent Vertex and Energy Resolution Clear coincidence signal for ¯ ν e IBD events Deep underground location (4000 mwe) Negligible cosmic muon backgrounds Neutrino Energy threshold For appearance : E ν > 20 MeV For disappearance : E ν > 33 MeV Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.16/32

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