GLA2011 Very Short Baseline Neutrino Oscillation Experiments using - PowerPoint PPT Presentation

GLA2011 Very Short Baseline Neutrino Oscillation Experiments using Cyclotron Decay-at-Rest Sources Sanjib Kumar Agarwalla (Sanjib.Agarwalla@ific.uv.es) IFIC/CSIC, University of Valencia, Spain Sanjib K. Agarwalla, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.1/25

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 ν s or something else? Short-baseline means : L/E ∼ 1 (m/MeV or km/GeV) LSND : L = 30 m, < E ν ¯ µ > = 40 MeV 3 . 8 σ excess of ¯ ν e events in a beam of ¯ ν µ 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 Sanjib K. Agarwalla, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.2/25

SBL ν oscillation continued.. No oscillation in the ν -mode for energies above 475 MeV An unexplained 3 σ excess of ν e events in the ν -mode of MiniBooNE below 475 MeV No hint of steriles in MiniBooNE ν µ / ¯ ν µ disappearance 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) Gallex-Sage reduced calibration source rate also suggesting possible ν e disappearance Sanjib K. Agarwalla, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.3/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.4/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.5/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.6/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.7/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.8/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.9/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.10/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.11/25

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, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.12/25

Appearance wave in LENA 50 kt LENA (Appearance mode) [ With Osc/Full Transmutation ] 0.01 Bin and fit IBD data with reconstructed L/E 0.009 (3+1) fit : Karagiorgi et al., arXiv:0906.1997 0.008 0.007 (3+1) 41 = 0.57 eV 2 & sin 2 2 θ µe = 0.0097 ∆ m 2 0.006 0.005 (3+2) fit : J. Kopp et al., arXiv:1103.4570 (3+2) 0.004 0.003 Event ratio Accessible L range : 20–120 m 0.002 DAR energy range : 20–52.8 MeV 0.001 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 L/E [m/MeV] SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984 Oscillation wave is dramatic in the long LENA detector and can provide a powerful handle to discriminate between (3+1) and (3+2) schemes Sanjib K. Agarwalla, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.13/25

Appearance Event Rates ∆ 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 Intrinsic ¯ ν e Fiducial Mass Radius Length Signal Signal (A : 1103.4570) (B : 0906.1997) Background 50 kt 13.58 m 100 m 12985 32646 1450 25 kt 10.78 m 79.37 m 7787 18356 875 10 kt 7.94 m 58.48 m 3753 7964 443 5 kt 6.3 m 46.42 m 2080 4044 261 Signal and beam background events in 5 to 50 kt LENA Total 4 × 10 21 ¯ ν µ (100 kW source), efficiency 90% ν e beam contamination is 4 × 10 − 4 The intrinsic ¯ Sanjib K. Agarwalla, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.14/25

DAR-LENA ¯ ν µ → ¯ ν e Sensitivity σ σ DAR−LENA 5 DAR−LENA 5 (2 dof) (2 dof) 5 kt 5 kt 1 1 10 kt 10 kt 10 10 25 kt 25 kt 50 kt 50 kt 10 kW (1 year) 100 kW (1 year) [eV ] [eV ] 2 2 ν ν ( ) ( ) MiniBooNE + LSND MiniBooNE + LSND 99% CL (2 dof) 99% CL (2 dof) 0 0 2 2 ∆ m ∆ m 10 10 −1 −1 Appearance mode Appearance mode 10 10 −4 −3 −2 −1 −4 −3 −2 −1 10 10 10 10 10 10 10 10 2 2 θ 2 2 θ sin sin µ e µ e SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984 5 kt LENA combined with a small 10 kW DAR source can test the LSND/MiniBooNE anti- neutrino signal at 5 σ CL in 3+1 model in 1 yr Sanjib K. Agarwalla, GLA2011, Jyvaskyla, Finland, 07/06/11 – p.15/25