Status of Light Sterile Neutrinos Carlo Giunti INFN, Torino, Italy - PowerPoint PPT Presentation

Status of Light Sterile Neutrinos Carlo Giunti INFN, Torino, Italy EPS-HEP2019 2019 European Physical Society Conference on High Energy Physics 10-17 July 2019, Ghent, Belgium C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 1/20

Short-Baseline Neutrino Oscillation Anomalies Reactor Anomaly: ¯ ν e → ¯ ν x ( ∼ 3 σ ) Gallium Anomaly: ν e → ν x ( ∼ 3 σ ) 1.20 Bugey−3 Daya Bay Krasnoyarsk RENO Bugey−4+Rovno91 Double Chooz Nucifer Rovno88 1.1 GALLEX SAGE Chooz Gosgen+ILL Palo Verde SRP 1.10 Cr1 Cr R = N exp N cal 1.00 1.0 R = N exp N cal GALLEX SAGE 0.90 Cr2 Ar 0.9 0.80 R = 0.934 ± 0.024 0.8 0.70 10 2 10 3 10 R = 0.84 ± 0.05 L [m] 0.7 m L osc = 4 π E . . . . . . LSND Anomaly: ¯ ν µ → ¯ ν e ( ∼ 4 σ ) ∆ m 2 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 C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 2/20

Efgective 3+1 SBL Oscillation Probabilities SBL U e 1 U e 2 U e 3 U e 4 U s 1 U s 2 U s 3 43 41 L experiments! ATM [de Gouvea et al, PRD 91 (2015) 053005, PRD 92 (2015) 073012, arXiv:1605.09376; Palazzo et al, PRD 91 (2015) 073017, PLB 757 (2016) 142; Kayser et al, JHEP 1511 (2015) SOL [Long, Li, Giunti, PRD 87, 113004 (2013) 113004] 4 E U s 4 P SBL 4 E 41 L P SBL Disappearance Appearance ( α � = β ) � ∆ m 2 � � ∆ m 2 � ≃ sin 2 2 ϑ αβ sin 2 ≃ 1 − sin 2 2 ϑ αα sin 2 ( − ) ( − ) ( − ) ( − ) ν α → ν β ν α → ν α sin 2 2 ϑ αα = 4 | U α 4 | 2 � 1 − | U α 4 | 2 � sin 2 2 ϑ αβ = 4 | U α 4 | 2 | U β 4 | 2 ◮ ∆ m 2 SBL = ∆ m 2 41 ≃ ∆ m 2 42 ≃ ∆ m 2   ◮ CP violation is not observable in SBL     U µ 1 U µ 2 U µ 3 U µ 4 U =       U τ 1 U τ 2 U τ 3 U τ 4   ◮ Observable in LBL accelerator exp. sensitive to ∆ m 2 ◮ 6 mixing angles ◮ 3 Dirac CP phases ◮ 3 Majorana CP phases 039, JHEP 1611 (2016) 122] and solar exp. sensitive to ∆ m 2 C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 3/20

Short-Baseline Reactor Neutrino Oscillations no spectral distortion Chooz near detectors ATM 1.20 Bugey−4 Rovno88 Gosgen Krasnoyarsk Nucifer Rovno91 Bugey−3 ILL SRP 1.10 1.00 P ν e →ν e R 0.90 DC DB DB DC E ≈ 4MeV − sin 2 2 ϑ ee = 0.1 R 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 10 1 L [m] SBL � 0 . 5 eV 2 ≫ ∆ m 2 ∆ m 2 ◮ SBL oscillations are averaged at the Daya Bay, RENO, and Double = ⇒ C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 4/20

Reactor Antineutrino 5 MeV Bump [RENO, arXiv:1511.05849] [Daya Bay, arXiv:1508.04233] oscillations (SBL oscillations are averaged in RENO, DC, DB). miscalculation of the spectrum. an excess it increases the anomaly! [Double Chooz, arXiv:1406.7763] uncertainty due to unknown [Hayes and Vogel, ARNPS 66 (2016) 219] of the neutrino fmuxes. (Data - MC) / MC 0.2 ◮ Cannot be explained by neutrino 0.1 0 0.1 − ◮ It is likely due to a theoretical 1 2 3 4 5 6 7 8 Prompt Energy (MeV) ◮ Heretic solution: detector energy Data / Predicted Data 1.4 0.25 MeV No oscillation Reactor flux uncertainty nonlinearity. [Mention et al, PLB 773 (2017) 307] Total systematic uncertainty 1.2 2 Best fit: sin 2 θ = 0.090 13 1.0 ◮ ∼ 3 % efgect on total fmux, but if it is 0.8 ◮ No post-bump complete calculation 0.6 1 2 3 4 5 6 7 8 Visible Energy (MeV) ◮ Nominal Huber-Mueller fmux calculation uncertainty: ∼ 2 . 7 % . ◮ Post-bump estimate of the fmux forbidden decays: ∼ 5 % . C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 5/20

Reactor Fuel Evolution RENO decays of the fjssion products of 235 U 238 U 239 Pu 241 Pu F 235 F 238 F 239 F 241 Daya Bay F 235 ◮ Reactor ¯ ν e fmux produced by the β 0.63 0.60 0.57 0.54 0.51 6.05 σ f [ 10 − 43 cm 2 / fission] 6.00 5.95 ◮ Efgective fjssion fractions: 5.90 5.85 5.80 Best fit Model (Rescaled) ◮ Cross section per fjssion (IBD yield): 5.75 Average Daya Bay 5.70 � σ f = F k σ f , k 0.24 0.26 0.28 0.30 0.32 0.34 0.36 F 239 k = 235 , 238 , 239 , 241 F 239 100 0.35 0.3 0.25 Fission fraction (%) 235 U 90 Data 6 239 Pu / fission] Model (scaled by -6.0%) 80 238 U Best fit 70 241 Pu Identical spectra 5.9 60 Others 2 50 cm 40 -43 5.8 [10 30 20 f y 10 5.7 0.5 0.55 0.6 0.65 0 0 5000 10000 15000 20000 F Burn-up (MWD/TU) 235 C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 6/20

[Giunti, Li, Littlejohn, Surukuchi, PRD 99 (2019) 073005, arXiv:1901.01807] dF 239 Daya Bay Data 6.1 Daya Bay Fit RENO Data 6.0 RENO Fit 5.9 f σ 5.8 5.7 0.26 0.28 0.30 0.32 0.34 F 239 10 10 Daya Bay 9 9 RENO Prediction 8 8 7 7 6 6 2 χ 5 f 5 σ Δ 4 4 3 3 2 2 1 1 0 0 5.6 5.8 6.0 6.2 6.4 − 2.5 − 2.0 − 1.5 − 1.0 d /dF σ σ f f 239 σ f + d σ f � � σ f ( F 239 ) = ¯ F 239 − F 239 C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 7/20

[Giunti, Li, Littlejohn, Surukuchi, arXiv:1901.01807] 235+239: 235+OSC: OSC: 235: Daya Bay Daya Bay and RENO RENO 0.980 5.0 235 235+239 235+OSC 239 OSC 239+OSC σ 239 [10 − 43 cm 2 /fission] 0.965 4.5 HM σ f / σ f 0.950 4.0 0.935 Combined 3.5 1 σ 2 σ 0.920 3 σ 0.25 0.27 0.29 0.31 0.33 0.35 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 F 239 σ 235 [10 − 43 cm 2 /fission] r 235 = 0 . 985 ± 0 . 015 ν e = 0 . 939 ± 0 . 024 P ¯ ν e → ¯ χ 2 / NDF = 9 . 0 / 15 GoF = 88 % χ 2 / NDF = 16 . 3 / 15 GoF = 37 % � r 235 = 0 . 923 ± 0 . 015 � r 235 = 0 . 938 ± 0 . 029 r 239 = 0 . 975 ± 0 . 032 ν e = 0 . 986 ± 0 . 022 ν e → ¯ P ¯ χ 2 / NDF = 8 . 7 / 14 GoF = 85 % χ 2 / NDF = 8 . 8 / 14 GoF = 85 % C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 8/20

oscillations (OSC). [Giunti, Ji, Laveder, Li, Littlejohn, JHEP 1710 (2017) 143, arXiv:1708.01133] reactor antineutrino fmux calculations must be corrected (most likely the 1. The 5 MeV bump 2. The fuel evolution data model-independent information ratios of spectra at difgerent distances ◮ Daya Bay and RENO favor a suppression of the 235 U fmux (235) over ◮ However, a better fjt is obtained with the hybrid model 235+OSC. ◮ Moreover, the addition of other reactor data favors oscillations or, better, 235 U and/or 239 U fmux suppression plus oscillations. ◮ Even if there are short-baseline neutrino oscillations, it is likely that the 235 U fmux) to fjt: ◮ The search for short-baseline neutrino oscillations needs ⇑ C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 9/20

Reactor Spectral Ratios in favor of SBL oscillations Martinez-Soler, Schwetz, arXiv:1803.10661] [PLB 787 (2018) 56, arXiv:1804.04046] DANSS-2018 [Gariazzo, Giunti, Laveder, Li, arXiv:1801.06467] [Dentler, Hernandez-Cabezudo, Kopp, Machado, Maltoni, NEOS [PRL 118 (2017) 121802 (arXiv:1610.05134)] 2018 model independent indication 1 2 3 4 5 6 7 10 1.1 NEOS/Daya Bay (c) Data/Prediction Systematic total 0.76 1.0 Ratio Down/Up 0.72 2 (1.73 eV , 0.050) 2 (2.32 eV , 0.142) 0.9 ⋅ ⋅ 1 2 3 4 5 6 7 10 0.68 Prompt Energy [MeV] DANSS No−Oscillations 10 0.64 NEOS+DANSS−2018 Oscillations Best Fit 1 σ 2 σ 1.0 2.0 3.0 4.0 5.0 6.0 7.0 3 σ Positron Energy [MeV] 2 [eV 2 ] 1 ∆ m 41 NEOS: ∼ 1 . 7 σ DANSS-2018: ∼ 2 . 7 σ 2 σ NEOS Combined: ∼ 3 . 5 σ DANSS−2018 10 − 1 10 − 4 10 − 3 10 − 2 10 − 1 | U e 4 | 2 C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 10/20

New DANSS results @ EPS-HEP 2019 [Danilov @ EPS-HEP 2019] Ratio of positron energy spectra at down and up detector positions 10 (Full data set) NEOS+DANSS−2018 1 σ Preliminar y 2 σ 3 σ 2 [eV 2 ] 1 Δ M 2 =1.33 eV 2 , ∆ m 41 Sin 2 (2 θ )=0.03 ∆Χ 2 =4.3 Δ M 2 =0.35 eV 2 , Sin 2 (2 θ )=0.15 ∆Χ 2 =7.8 DANSS−2019 Best Fit 2 σ - The best 4 ν point ( Δ M 2 =0.35eV 2 , Sin 2 (2 θ )=0.15, ∆Χ 2 =7.8) Solar 2 σ NEOS bound has CL of 1.8σ. DANSS−2018 - Best point in old data ( Δ M 2 =1.33 eV 2 ) is also shown 10 − 1 10 − 4 10 − 3 10 − 2 10 − 1 | U e 4 | 2 ◮ The DANSS-2019 best fjt has too large mixing. ◮ The agreement between NEOS and DANSS has diminished. ◮ Reactor indications in favor of SBL oscillations seem to be fadind away. ◮ We wait independent checks of PROSPECT, STEREO and SoLiD. C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 11/20

The Gallium Anomaly Revisited [Kostensalo, Suhonen, Giunti, Srivastava, arXiv:1906.10980] ◮ New JUN45 shell-model calculation of the cross section of ν e + 71 Ga → 71 Ge + e − 10 10 Reactors 1 σ 2 σ 3 σ 2 [eV 2 ] 2 [eV 2 ] 1 1 ∆ m 41 ∆ m 41 90% CL Gallium − JUN45 Bahcall 68.27% CL (1 σ ) Haxton 90.00% CL 95.45% CL (2 σ ) Frekers 99.00% CL JUN45 99.73% CL (3 σ ) 10 − 1 10 − 1 10 − 3 10 − 2 10 − 1 10 − 3 10 − 2 10 − 1 | U e 4 | 2 | U e 4 | 2 C. Giunti − Status of Light Sterile Neutrinos − EPS-HEP2019 − Ghent − 13 July 2019 − 12/20