Critical Review on Neutrino Anomalies Carlo Giunti INFN, Torino, Italy Neutrinos: the Quest for a New Physics Scale CERN, 27-31 March 2017 C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 1/49
Indications of SBL Oscillations Beyond 3 ν C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 2/49
LSND [PRL 75 (1995) 2650; PRC 54 (1996) 2685; PRL 77 (1996) 3082; PRD 64 (2001) 112007] ν µ → ¯ ¯ ν e 20 MeV ≤ E ≤ 52 . 8 MeV ◮ Well-known and pure source of ¯ ν µ → µ + + ν µ at rest p + target → π + − − − µ + − at rest e + + ν e + ¯ − − → ν µ L ≃ 30 m ν e + p → n + e + ¯ Well-known detection process of ¯ ν e ◮ ≈ 3 . 8 σ excess ◮ But signal not seen by KARMEN at L ≃ 18 m with the same method [PRD 65 (2002) 112001] C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 3/49
10 2 ∆ m 2 (eV 2 /c 4 ) 10 Karmen CCFR Bugey 1 NOMAD -1 10 90% (L max -L < 2.3) 99% (L max -L < 4.6) -2 10 -3 -2 -1 10 10 10 1 sin 2 2 θ SBL � 3 × 10 − 2 eV 2 ≫ ∆ m 2 ATM ≃ 2 . 5 × 10 − 3 eV 2 ≫ ∆ m 2 ∆ m 2 SOL C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 4/49
MiniBooNE L ≃ 541 m 200 MeV ≤ E � 3 GeV ν µ → ¯ ¯ ν e ν µ → ν e [PRL 110 (2013) 161801] [PRL 102 (2009) 101802] LSND signal LSND signal ◮ Purpose: check LSND signal. ◮ LSND signal: E > 475 MeV. ◮ Different L and E . ◮ Agreement with LSND signal? ◮ Similar L / E (oscillations). ◮ CP violation? ◮ No money, no Near Detector. ◮ Low-energy anomaly! C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 5/49
Gallium Anomaly Gallium Radioactive Source Experiments: GALLEX and SAGE e − + 51 Cr → 51 V + ν e e − + 37 Ar → 37 Cl + ν e ν e Sources: E ≃ 0 . 75 MeV E ≃ 0 . 81 MeV ν e + 71 Ga → 71 Ge + e − Test of Solar ν e Detection: 1.1 GALLEX SAGE Cr1 Cr 1.0 R = N exp N cal GALLEX SAGE Cr2 Ar 0.9 0.8 R = 0.84 ± 0.05 0.7 ≈ 2 . 9 σ deficit � L � GALLEX = 1 . 9 m � L � SAGE = 0 . 6 m [SAGE, PRC 73 (2006) 045805; PRC 80 (2009) 015807; Laveder et al, Nucl.Phys.Proc.Suppl. 168 (2007) 344, SBL � 1 eV 2 ≫ ∆ m 2 ∆ m 2 ATM ≫ ∆ m 2 MPLA 22 (2007) 2499, PRD 78 (2008) 073009, SOL PRC 83 (2011) 065504] C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 6/49
◮ Deficit could be due to overestimate of σ ( ν e + 71 Ga → 71 Ge + e − ) ◮ Calculation: Bahcall, PRC 56 (1997) 3391 3 / 2 − 0 . 500 MeV 5 / 2 − 0 . 175 MeV 1 / 2 − 71 Ge 0 . 233 MeV 3 / 2 − 71 Ga ◮ σ G.S. from T 1 / 2 ( 71 Ge) = 11 . 43 ± 0 . 03 days [Hampel, Remsberg, PRC 31 (1985) 666] σ G.S. ( 51 Cr) = 55 . 3 × 10 − 46 cm 2 (1 ± 0 . 004) 3 σ � � 1 + 0 . 669 BGT 175 + 0 . 220 BGT 500 ◮ σ ( 51 Cr) = σ G.S. ( 51 Cr) BGT G.S. BGT G.S. ◮ Contribution of excited states only 5%! C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 7/49
BGT 175 BGT 500 BGT G.S. BGT G.S. Krofcheck et al. 71 Ga( p , n ) 71 Ge < 0 . 056 0 . 126 ± 0 . 023 PRL 55 (1985) 1051 Haxton Shell Model 0 . 19 ± 0 . 18 PLB 431 (1998) 110 Frekers et al. 71 Ga( 3 He , 3 H) 71 Ge 0 . 039 ± 0 . 030 0 . 202 ± 0 . 016 PLB 706 (2011) 134 ◮ The 71 Ga( 3 He , 3 H) 71 Ge data confirm the contribution of the two excited states. ◮ Haxton: “The calculation predicts destructive interference between the ( p , n ) spin and spin-tensor matrix elements” ◮ It is unlikely that the deficit is caused by an overestimate of the cross section. ◮ Possible explanations: ◮ Statistical fluctuations. ◮ Experimental faults. ◮ Short-baseline oscillations. C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 8/49
Reactor Electron Antineutrino Anomaly [Mention et al, PRD 83 (2011) 073006] New reactor ¯ ν e fluxes [Mueller et al, PRC 83 (2011) 054615; Huber, PRC 84 (2011) 024617] 1.20 Bugey−3 Daya Bay ILL Palo Verde Rovno91 Bugey−4 Double Chooz Krasnoyarsk RENO SRP 1.10 Chooz Gosgen Nucifer Rovno88 R = N exp N cal 1.00 0.90 0.80 R = 0.940 ± 0.024 0.70 10 2 10 3 10 L [m] ≈ 2 . 5 σ deficit C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 9/49
1.20 Bugey−4 Rovno88 Gosgen Krasnoyarsk Nucifer Rovno91 Bugey−3 ILL SRP 1.10 1.00 P ν e →ν e R DC 0.90 DB DB DC R E ≈ 4MeV − sin 2 2 ϑ ee = 0.1 0.80 2 = 0.1 eV 2 ∆ m 41 2 = 0.5 eV 2 ∆ m 41 2 = 1.0 eV 2 ∆ m 41 0.70 10 2 10 3 1 10 L [m] SBL � 0 . 5 eV 2 ≫ ∆ m 2 ∆ m 2 ATM ≫ ∆ m 2 SOL C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 10/49
5 MeV Bump Data (a) Near 20000 Full uncertainty 15000 Events / 0.2 MeV Entries / 250 keV Reactor uncertainty Data 15000 ILL+Vogel MC 10000 10000 Integrated 5000 5000 Ratio to Prediction 1.2 (Huber + Mueller) 1.1 1 (Data - MC) / MC 0.9 0.2 0.8 0.1 1 4 (1 MeV windows) contribution − 1 10 Local p-value 0 2 − 2 10 ) ∼ χ i 0 3 10 − 0.1 ( − 4 2 10 − − 2 1 2 3 4 5 6 7 8 − 5 χ 10 4 − 6 10 − Prompt Energy (MeV) 2 4 6 8 Prompt Energy (MeV) [RENO, arXiv:1511.05849] [Daya Bay, arXiv:1508.04233] ◮ It is correlated with the reactor activity. ◮ Cannot be explained by neutrino oscillations. ◮ Very likely due to theoretical miscalculation of the spectrum. ◮ ∼ 3% effect on total flux. ◮ It seems to be an excess! C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 11/49
NEOS [arXiv:1610.05134] 10 Prompt Energy [MeV] ε (a) 60 7 − 1 10 6 ◮ Hanbit Nuclear Power Complex in Events /day/100 keV 50 5 − 10 2 4 3 40 Yeong-gwang, Korea. − 3 10 2 1 2 3 4 5 6 7 8 12 30 Neutrino Energy [MeV] Data signal (ON-OFF) ◮ Thermal power of 2.8 GW. 20 Data background (OFF) ν MC 3 (H-M-V) 10 ν MC 3 (Daya Bay) ◮ Detector: a ton of Gd-loaded 1 2 3 4 5 6 7 8 NEOS/H-M-V (b) Data/Prediction liquid scintillator in a gallery 1.1 Systematic total approximately 24 m from the 1.0 reactor core. 0.9 1 2 3 4 5 6 7 10 1.1 NEOS/Daya Bay (c) ◮ The measured antineutrino event Data/Prediction Systematic total rate is 1976 per day with a signal 1.0 to background ratio of about 22. 2 (1.73 eV , 0.050) 2 (2.32 eV , 0.142) 0.9 ⋅ ⋅ 1 2 3 4 5 6 7 10 Prompt Energy [MeV] C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 12/49
] 10 2 [eV NEOS Spectrum RAA allowed 90% CL 90% CL 41 95% CL 2 m 99% CL 95% CL ∆ 99% CL 2 [eV 2 ] 1 + Excluded NEOS 90% CL 1 ∆ m 41 Bugey-3 90% CL Daya Bay 90% CL s − 1 10 10 − 1 − − 2 1 10 10 1 10 − 3 10 − 2 10 − 1 1 θ 2 sin 2 14 sin 2 2 ϑ ee 2-D χ 2 Analysis Raster Scan [NEOS, arXiv:1610.05134] Best Fits: χ 2 no osc. − χ 2 min = 6 . 5 sin 2 2 θ 14 = 0 . 05 ∆ m 2 41 = 1 . 7 eV 2 sin 2 2 θ 14 = 0 . 04 ∆ m 2 41 = 1 . 3 eV 2 ≈ 2 . 1 σ anomaly C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 13/49
Beyond Three-Neutrino Mixing: Sterile Neutrinos m . . . . . . ν 5 ν s 2 ν 4 ν s 1 � 1 eV 2 ∆ m 2 SBL ν 3 ≃ 2.5 × 10 − 3 eV 2 ∆ m 2 ATM ν 2 ≃ 7.4 × 10 − 5 eV 2 ∆ m 2 SOL ν 1 ν e ν µ ν τ Terminology: a eV-scale sterile neutrino means: a eV-scale massive neutrino which is mainly sterile C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 14/49
Four-Neutrino Schemes: 2+2, 3+1 and 1+3 m m m m m m ν 4 ν 2 ν 2 ∆ m 2 ∆ m 2 ∆ m 2 ν 4 ν 4 ν 3 SOL SOL ATM ν 1 ν 1 ∆ m 2 ∆ m 2 ν 3 ATM ATM ν 2 ∆ m 2 SOL ν 1 ν 3 ∆ m 2 ∆ m 2 ∆ m 2 ∆ m 2 ∆ m 2 ∆ m 2 SBL SBL SBL SBL SBL SBL ν 3 ν 2 ∆ m 2 SOL ∆ m 2 ∆ m 2 ν 1 ν 4 ATM ATM ν 2 ν 2 ∆ m 2 ∆ m 2 ∆ m 2 ATM ν 4 ν 4 SOL SOL ν 3 ν 1 ν 1 ν 3 2+2 3+1 1+3 C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 15/49
2+2 Four-Neutrino Schemes m m ν 4 ν 2 ∆ m 2 ∆ m 2 SOL ATM ν 1 ν 3 ∆ m 2 ∆ m 2 SBL SBL ν 4 ν 2 ∆ m 2 ∆ m 2 ATM SOL ν 3 ν 1 ◮ After LSND (1995) 2+2 was preferred to 3+1, because of the 3+1 appearance-disappearance tension [Okada, Yasuda, IJMPA 12 (1997) 3669; Bilenky, CG, Grimus, EPJC 1 (1998) 247] ◮ This is not a perturbation of 3- ν Mixing = ⇒ Large active–sterile oscillations for solar or atmospheric neutrinos! C. Giunti − Review on Neutrino Anomalies − Neutrinos: the Quest for a New Physics Scale − 27 March 2017 − 16/49
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