Status of Light Sterile Neutrinos Carlo Giunti INFN, Torino, Italy EPS-HEP 07 07 European Physical Society Conference on High Energy Physics Venezia, Italy, 5- July 07 C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4
Indications of SBL Oscillations Beyond 3ν C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 3/4 LSND [PRL 75 (995) 650; PRC 54 (996) 685; PRL 77 (996) 308; PRD 64 (00) 07] ν µ ν e 0 MeV E 5.8 MeV Well-known and pure source of ν µ p + target π + at rest µ + + ν µ µ + at rest e + + ν e + ν µ ν e + p n + e + Well-known detection process of ν e 3.8σ excess L 30 m But signal not seen by KARMEN at L 8 m with the same method [PRD 65 (00) 0]
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 4/4 m (ev /c 4 ) Karmen Bugey CCFR NOMAD - - 90% (L max -L <.3) 99% (L max -L < 4.6) -3 - - sin θ m SBL 3 ev m ATM.5 3 ev m SOL
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 5/4 MiniBooNE L 54 m ν µ ν e [PRL (009) 80] 00 MeV E 3 GeV ν µ ν e [PRL (03) 680] LSND signal LSND signal Purpose: check LSND signal. Different L and E. Similar L/E (oscillations). No money, no Near Detector. LSND signal: E > 475 MeV. Agreement with LSND signal? CP violation? Low-energy anomaly!
Gallium Anomaly Gallium Radioactive Source Experiments: GALLEX and SAGE ν e Sources: e + 5 Cr 5 V + ν e e + 37 Ar 37 Cl + ν e E 0.75 MeV E 0.8 MeV Test of Solar ν e Detection: ν e + 7 Ga 7 Ge + e R =N exp N cal 0.7 0.8 0.9.0. GALLEX SAGE Cr Cr R = 0.84 ± 0.05 L GALLEX =.9 m GALLEX SAGE Cr Ar L SAGE = 0.6 m m SBL ev m ATM m SOL.9σ deficit [SAGE, PRC 73 (006) 045805; PRC 80 (009) 05807; Laveder et al, Nucl.Phys.Proc.Suppl. 68 (007) 344, MPLA (007) 499, PRD 78 (008) 073009, PRC 83 (0) 065504] C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 6/4
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 7/4 Reactor Electron Antineutrino Anomaly [Mention et al, PRD 83 (0) 073006] New reactor ν e fluxes [Mueller et al, PRC 83 (0) 05465; Huber, PRC 84 (0) 0467] P ν e νe 0.70 0.80 0.90.00..0 Bugey 4 Rovno9 E 4MeV sin ϑ ee = 0. m 4 = 0. ev m 4 = 0.5 ev m 4 =.0 ev Rovno88 Bugey 3 Gosgen ILL 3 L [m] Krasnoyarsk SRP Nucifer R DC DB DC R DB.8σ deficit m SBL 0.5 ev m ATM m SOL
ε C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 8/4 NEOS [arxiv:6.0534] Events /day/0 kev Data/Prediction Data/Prediction 60 50 40 30 0..0 (a) (b) Prompt Energy [MeV] Data signal (ON-OFF) Data background (OFF) MC 3ν (H-M-V) MC 3ν (Daya Bay) NEOS/H-M-V Systematic total 7 6 5 4 3 3 4 5 6 7 8 Neutrino Energy [MeV] 0.9. 3 4 5 6 7 (c) NEOS/Daya Prompt BayEnergy [MeV] Systematic total.0 (.73 ev, 0.050) (.3 ev, 0.4) 0.9 3 4 5 6 7 Prompt Energy [MeV] 3 Hanbit Nuclear Power Complex in Yeong-gwang, Korea. Thermal power of.8 GW. Detector: a ton of Gd-loaded liquid scintillator in a gallery approximately 4 m from the reactor core. The measured antineutrino event rate is 976 per day with a signal to background ratio of about.
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 9/4 NEOS Spectrum 90% CL 95% CL 99% CL [ev ] m 4 + 3 sin ϑ ee Best Fit: m 4 =.3 ev sin θ 4 = 0.04 χ no osc. χ min = 6.5.σ anomaly
Beyond Three-Neutrino Mixing: Sterile Neutrinos C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4 m. ν 5. ν s ν 4 m SBL ν s ev ν 3 ν ν matm msol ν e ν µ ν τ.5 3 ev 7.4 5 ev Terminology: means: a ev-scale sterile neutrino a ev-scale massive neutrino which is mainly sterile
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4 Effective 3+ SBL Oscillation Probabilities Appearance (α β) ( ) m P SBL ( ) sin ϑ ν ( ) αβ sin 4 L α ν β 4E Disappearance ( ) m P SBL ( ) sin ϑ ν ( ) αα sin 4 L α ν α 4E sin ϑ αβ = 4 U α4 U β4 sin ϑ αα = 4 U α4 ( U α4 ) U e U e U e3 U e4 U µ U µ U µ3 U µ4 U = U τ U τ U τ3 U τ4 U s U s U s3 U s4 SBL 6 mixing angles 3 Dirac CP phases 3 Majorana CP phases CP violation is not observable in SBL experiments! Observable in LBL accelerator exp. sensitive to matm [de Gouvea et al, PRD 9 (05) 053005, PRD 9 (05) 0730, arxiv:605.09376; Palazzo et al, PRD 9 (05) 07307, PLB 757 (06) 4; Gandhi et al, JHEP 5 (05) 039, JHEP 6 (06) ] and solar exp. sensitive to msol [Long, Li, CG, PRD 87, 3004 (03) 3004] [Palazzo, EPS-HEP 07]
3+ Appearance-Disappearance Tension ν e DIS sin ϑ ee 4 U e4 ν µ ν e APP ν µ DIS sin ϑ µµ 4 U µ4 sin ϑ eµ = 4 U e4 U µ4 4 sin ϑ ee sin ϑ µµ [Okada, Yasuda, IJMPA (997) 3669; Bilenky, CG, Grimus, EPJC (998) 47] ν µ ν e is quadratically suppressed! [ev ] m 4 PrGlo7 σ σ ν e Dis ν µ Dis Dis App 4 3 PrGlo7 = Pragmatic Global Fit 07 [Gariazzo, CG, Laveder, Li, arxiv:703.00860] χ NO = 47.4 6.σ anomaly Best Fit: m4 =.7 ev U e4 = 0.00 U µ4 = 0.05 χ min /NDF = 595./579 GoF = 3% χ PG /NDF PG = 7./ GoF PG =.7% Similar tension in 3+, 3+3,..., 3+N s [CG, Zavanin, MPLA 3 (05) 650003] sin ϑ eµ C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4
Effects of MINOS, IceCube and NEOS C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 3/4 ( ) ν µ ( ) ν µ PrGlo6A PrGlo6A + MINOS PrGlo6A + IceCube PrGlo6A + MINOS + IceCube = PrGlo6B ( ) ν e ( ) ν e PrGlo6A PrGlo6A + MINOS + IceCube = PrGlo6B PrGlo6A + MINOS + IceCube + NEOS = PrGlo7 m 4 [ev ] [ev ] m 4 MINOS IceCube sin ϑ µµ NEOS sin ϑ ee IceCube effect in agreement with Collin, Arguelles, Conrad, Shaevitz, PRL 7 (06) 80
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 4/4 The Race for the Light Sterile ( ) ν e ( ) ν e PrGlo7 σ σ PrGlo7 σ σ [ev ] [ev ] m 4 m 4 DANSS (yr, 95% CL) Neutrino 4 (yr, 95% CL) PROSPECT phase (3yr, ) PROSPECT phase (3yr, ) SoLiD phase (yr, 95% CL) SoLiD phase (3yr, ) STEREO (yr, 95% CL) sin ϑ ee CeSOX shape (95% CL) CeSOX rate (95% CL) CeSOX rate+shape (95% CL) BEST (σ) IsoDAR@KamLAND (5yr, ) C ADS (5yr, ) KATRIN (90% CL) sin ϑ ee
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 5/4 ( ) ν µ ( ) ν e ( ) ν µ ( ) ν µ SBN (3yr, ) nuprism () JSNS () SBN (3yr, ) KPipe (3yr, ) [ev ] [ev ] m 4 m 4 PrGlo7 σ σ 4 3 sin ϑ eµ PrGlo7 σ σ sin ϑ µµ
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 6/4 Preliminary Bound from MINOS & MINOS+ [Whitehead, EPS-HEP 07] Flanagan @ PPC07 PrGlo7 σ σ m 4 [ev ] MINOS 90% CL MINOS 99% CL MINOS 99.73% CL () MINOS & MINOS+ 90% CL sin ϑ µµ
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 7/4 Preliminary Bound from DANSS [Danilov, EPS-HEP 07] ion with current statistics -- Svirida @ WIN07 PrGlo7 σ σ ) in: [ev ] m 4 e y DANSS Preliminary 95%CL Compilation of allowed regions from arxiv:5.00 [physics.ins-det] DANSS 95% CL s sin ϑ ee
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 8/4 ) χ i ( Events 5000 Events 5000 500 000 Reactor Antineutrino 5 MeV Bump Entries / 50 kev 5000 Full uncertainty Reactor uncertainty ILL+Vogel Integrated (Data - MC) / MC 0. 0. 0 0. 3 4 5 6 7 8 Prompt Energy (MeV) (Data - MC) / MC 0. 0. 0 Data / Predicted 0.5 MeV.4..0 Data No oscillation Reactor flux uncertainty Total systematic uncertainty Best fit: sin θ 3 = 0.090 0.8 0. 0.6 3 4 5 6 7 8 3 4 5 6 7 8 Prompt Energy Visible Energy (MeV) Ratio to Prediction (Huber + Mueller) contribution χ.. 0.9 0.8 4 0 4 4 6 8 4 6 8 4 6 8 Prompt Energy (MeV) 3 4 5 6 Local p-value ( MeV windows) [RENO, arxiv:5.05849] [Double Chooz, arxiv:406.7763] [Daya Bay, arxiv:508.0433] Cannot be explained by neutrino oscillations (SBL oscillations are averaged in Double Chooz, Daya Bay, RENO). Very likely due to theoretical miscalculation of the spectrum. 3% effect on total flux, but if it is an excess it increases the anomaly! No post-bump complete calculation of the neutrino fluxes. Saclay-Huber flux calculation uncertainty is about.5%. Increasing the flux uncertainty is a game that one can play, but there are only guesses, e.g. about 5%. [Hayes and Vogel, 06] Better to exclude the reactor rates from the global fit. [suggestion of Pedro Machado at WIN 07]
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 9/4 Global Fit Without Reactor Rates [ev ] [ev ] m 4 m 4 PrGlo7 σ σ ν e Dis ν µ Dis Dis App 4 3 PrGlo7wrr σ σ ν e Dis ν µ Dis Dis App 4 3 sin ϑ eµ sin ϑ eµ The Reactor Antineutrino Anomaly has small impact on the global fit.
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 0/4 Global Fit Without Reactor Rates and Gallium Data [ev ] [ev ] m 4 m 4 PrGlo7 σ σ ν e Dis ν µ Dis Dis App 4 3 PrGlo7wrrwg σ σ ν e Dis ν µ Dis Dis App 4 3 sin ϑ eµ sin ϑ eµ Given the current constraints, only the LSND signal is crucial for a positive indication in favor of active-sterile SBL oscillations.
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4 Daya Bay Reactor Fuel Evolution [Daya Bay, arxiv:704.08] [Tsang @ EPS-HEP 07] Fission fraction (%) Reactor ν e flux produced by the β decays of the fission products of 35 U, 38 U, 39 Pu, 4 Pu. 0 90 80 70 60 50 40 30 0 35 U 39 Pu 38 U 4 Pu Others 0 0 5000 000 5000 0000 Burn-up (MWD/TU) Cross section per fission: σ f = F i σ f,i i=35,38,39,4 Effective fission fractions: σf [ 43 cm / fission] 6.05 6.00 5.95 5.90 5.85 5.80 5.75 5.70 F 35, F 38, F 39, F 4. 0.63 0.60 Best fit Average F 35 0.57 0.54 Model (Rescaled) Daya Bay 0.5 0.4 0.6 0.8 0.30 0.3 0.34 0.36 F 39
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 /4 9 σ39 [ 43 cm / fission] 5.5 5.0 4.5 4.0 3.5 3.0 Daya Bay Huber model w/ 68% C.L. σ38 = (. ±. 0) 43 σ4 = (6. 04 ± 0. 60) 43 C.L 68% 95% 99.7% 5. 5.6 6.0 6.4 6.8 7. σ 35 [ 43 cm / fission] 4 χ 4 9 Best fit: suppression of σ f,35. Equal fluxes suppression: χ /NDF = 7.9/ disfavored at.8σ. Equal fluxes suppression corresponds to SBL oscillations, but theoretical flux uncertainties must be taken into account.
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 3/4 With theoretical flux uncertainties: Daya Bay χ min NDF GoF 35 U 4.6 7 7% OSC 9.6 7 % σ f / σ f th 0.75 0.85 0.95.05.5 35 OSC All Reactors χ min NDF GoF 35 U 9.4 3 60% [CG, Laveder, Li, in preparation] OSC 8.7 3 58% L 3 Nucifer ILL Bugey 4 Bugey 3 5 Rovno9 Rovno88 I Rovno88 I Rovno88 S Rovno88 S SRP 8 SRP 4 Rovno88 S Krasnoyarsk87 33 Krasnoyarsk99 34 Gosgen 38 Bugey 3 40 Gosgen 46 Krasnoyarsk94 57 Gosgen 65 Krasnoyarsk87 9 Bugey 3 95 RENO Double Chooz Daya Bay 0.344 Daya Bay 0.33 Daya Bay 0.3 Daya Bay 0.3 Daya Bay 0.99 Daya Bay 0.87 Daya Bay 0.74 Daya Bay 0.5 Palo Verde Chooz
C. Giunti Status of Light Sterile Neutrinos EPS-HEP 07 7 July 07 4/4 Conclusions Exciting indications of sterile neutrinos (new physics!) at the ev scale: LSND ν µ ν e signal (caveat: single experimental signal). Gallium ν e disappearance (caveat: overestimated detector efficiency?). Reactor νe disappearance (caveat: flux calculation dependence). Vigorous experimental program to check conclusively in a few years: ν e and ν e disappearance with reactors and radioactive sources. ν µ ν e transitions with accelerator neutrinos. ν µ disappearance with accelerator neutrinos. Independent tests through effect of m 4 in β-decay and ββ 0ν -decay. Cosmology: strong tension with N eff = and m 4 ev. It may be solved by a non-standard cosmological mechanism. Possibilities for the next years: Reactor and source experiments νe and ν e observe SBL oscillations: big excitement and explosion of the field. Otherwise: still marginal interest to check the LSND appearance signal. In any case the possibility of the existence of sterile neutrinos related to New Physics beyond the Standard Model will continue to be studied (e.g kev sterile neutrinos).