Status of Sterile Neutrinos Carlo Giunti

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1 Status of Sterile Neutrinos Carlo Giunti INFN, Sezione di Torino, and Dipartimento di Fisica Teorica, Università di Torino Neutrino Unbound: NOW 0, Neutrino Oscillation Workshop 9-6 September 0, Conca Specchiulla, Otranto, Italy C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

2 Beyond Three-Neutrino Mixing ν τ ν s ν µ ν e ν ν 3 ν 4 ν 5 ν m 3 m m m 4 m 5 logm ν s m SOL 3ν-mixing m ATM m SBL C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

3 Sterile Neutrinos from Physics Beyond the SM Neutrinos are special in the Standard Model: the only neutral fermions In extensions of SM neutrinos can mix with non-sm fermions ( ) ( ) ( ) νl φ SM: L L = Φ = iσ l Φ 0 Symmetry v/ = L φ Breaking 0 SM singlet L L Φ can couple to new singlet chiral fermion field fr related to physics beyond the SM Known examples: light ν R from see-saw NOW0], SUSY (axino, modulino,...), extra dimensions (KK modes), mirror world NOW0],... Dirac mass term L L ΦfR Majorana mass term f C R f R f R is often called Right-Handed Neutrino: f R ν R C. Giunti Status of Sterile Neutrinos 5 Sep 0 3/3

4 Sterile Neutrinos Light anti-ν R are called sterile neutrinos ν c R ν sl (left-handed) Sterile means no standard model interactions Active neutrinos (ν e,ν µ,ν τ ) can oscillate into sterile neutrinos (ν s ) Observables: Disappearance of active neutrinos (neutral current deficit) Indirect evidence through combined fit of data (current indication) Short-baseline anomalies 3ν-mixing: m m 3 m 4... ν ν ν 3 ν 4... ν e ν µ ν τ ν s... C. Giunti Status of Sterile Neutrinos 5 Sep 0 4/3

5 In this talk I consider sterile neutrinos with mass scale ev in light of short-baseline LSND, MiniBooNE, Reactor Anomaly, Gallium Anomaly. Other possibilities (not incompatible): Very light sterile neutrinos with mass scale ev: important for solar neutrino phenomenology [Das, Pulido, Picariello, PRD 79 (009) 0730] [de Holanda, Smirnov, PRD 83 (0) 30] Heavy sterile neutrinos with mass scale ev: could be Warm Dark Matter [Kusenko, Phys. Rept. 48 (009) ] [Boyarsky, Ruchayskiy, Shaposhnikov, Ann. Rev. Nucl. Part. Sci. 59 (009) 9] NOW0] C. Giunti Status of Sterile Neutrinos 5 Sep 0 5/3

6 Effective SBL Oscillation Probabilities in 3 Schemes ( ) m P να ν β = sin ϑ αβ sin 4 L 4E ( ) m P να ν α = sin ϑ αα sin 4 L 4E Perturbation of 3ν Mixing sin ϑ αβ = 4 U α4 U β4 No CP Violation! sin ϑ αα = 4 U α4 ( U α4 ) U e4, U µ4, U τ4, U s4 U e U e U e3 U e4 sin ϑ αα U = U µ U τ U µ U τ U µ3 U τ3 U µ4 U τ4 U s U s U s3 U s4 SBL U α4 sin ϑ αα 4 C. Giunti Status of Sterile Neutrinos 5 Sep 0 6/3

7 Effective SBL Oscillation Probabilities in 3 Schemes φ kj = m kj L/4E η = arg[u e4u µ4 U e5 U µ5] P ( ) ν µ ( ) ν e = 4 U e4 U µ4 sin φ 4 4 U e5 U µ5 sin φ 5 () 8 U µ4 U e4 U µ5 U e5 sinφ 4 sinφ 5 cos(φ 54 η) P ( ) ν α ( ) ν α = 4( U α4 U α5 )( U α4 sin φ 4 U α5 sin φ 5 ) 4 U α4 U α5 sin φ 54 [Sorel, Conrad, Shaevitz, PRD 70 (004) ; Maltoni, Schwetz, PRD 76 (007) ; Karagiorgi et al, PRD 80 (009) 07300; Kopp, Maltoni, Schwetz, PRL 7 (0) 0980; Giunti, Laveder, PRD 84 (0) ; Donini et al, arxiv:5.530; Conrad, Ignarra, Karagiorgi, Shaevitz, Spitz, arxiv:7.4765] NOW0] More parameters: 7 (vs 3 in 3) CP violation 33? NOW0] C. Giunti Status of Sterile Neutrinos 5 Sep 0 7/3

8 LSND [PRL 75 (995) 650; PRC 54 (996) 685; PRL 77 (996) 308; PRD 64 (00) 07] ν µ ν e L 30m 0MeV E 00MeV Beam Excess Beam Excess p(ν _ µ ν_ e,e )n p(ν _ e,e )n other L/E ν (meters/mev) m (ev /c 4 ) Karmen Bugey 90% (L max -L <.3) 99% (L max -L < 4.6) CCFR NOMAD sin θ 3.8σ excess m LSND 0.eV ( m A m S ) C. Giunti Status of Sterile Neutrinos 5 Sep 0 8/3

9 MiniBooNE Neutrinos [PRL 98 (007) 380; PRL (009) 80] ν µ ν e L 54m 00MeV E 3GeV Events / MeV Data ν e from µ ν e from K 0 ν e from K π 0 misid Nγ dirt other Total Background QE E ν (GeV) no ν µ ν e signal corresponding to LSND ν µ ν e signal (E > 475MeV) low-energy anomaly C. Giunti Status of Sterile Neutrinos 5 Sep 0 9/3

MiniBooNE Antineutrinos - 009-0 [PRL 3 (009) 80; PRL 5 (0) 880] ν µ ν e L 54m 00MeV E 3GeV agreement with LSND ν µ ν

10 MiniBooNE Antineutrinos [PRL 3 (009) 80; PRL 5 (0) 880] ν µ ν e L 54m 00MeV E 3GeV agreement with LSND ν µ ν e signal (E > 475MeV) similar L/E but different L and E = oscillations C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

11 MiniBooNE ν - Neutrino 0-6 June agreement with LSND signal is sadly vanishing C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

12 MiniBooNE ν and ν - arxiv: [ev ] m 4 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] MB LOW 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) 4 3 sin ϑ eµ reactors Fit of low-energy excess is marginal It requires m4 0.4eV * <P νµ νe > E [MeV] MiniBooNE ν e exp (,0.04): best fit (0.06,0.7) (0.0,0.4) (0.003,0.7) (0.003,4) Neutrino energy reconstruction problem? [Martini, Ericson, Chanfray, arxiv:.4745] C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

13 ICARUS [arxiv:9.0] NOW0] νµ νe L = 730 km < E < 30 GeV 3 3 < observed νe events 3.7 background νe events (CNGS) E < 9 3 ev L C. Giunti Status of Sterile Neutrinos 5 Sep 0 3/3

14 Reactor Electron Antineutrino Anomaly [Mention et al, PRD 83 (0) ] [update in White Paper, arxiv: new reactor ν e fluxes [Mueller et al, PRC 83 (0) 05465] [Huber, PRC 84 (0) 0467] R = 0.930±0.04 R Reactor Rates Bugey3 5 Bugey3 40 Bugey3 95 Bugey4 ROVNO Gosgen 38 Gosgen 45 Gosgen 65 ILL Krasno 33 Krasno 9 Krasno 57 Average Rate [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] L [m] C. Giunti Status of Sterile Neutrinos 5 Sep 0 4/3

15 Gallium Anomaly Gallium Radioactive Source Experiments Tests of the solar neutrino detectors GALLEX (Cr, Cr) and SAGE (Cr, Ar) Detection Process: ν e 7 Ga 7 Gee ν e Sources: e 5 Cr 5 Vν e e 37 Ar 37 Clν e p(measured)/p(predicted) GALLEX Cr SAGE Cr GALLEX Cr SAGE Ar E 0.7MeV L GALLEX =.9m L SAGE = 0.6m R B = 0.86±0.05 [SAGE, PRC 73 (006) , nucl-ex/054] C. Giunti Status of Sterile Neutrinos 5 Sep 0 5/3

16 Deficit could be due to overestimate of σ(ν e 7 Ga 7 Gee ) Calculation: Bahcall, PRC 56 (997) 339 3/ MeV 3/ 7 Ga 5/ 0.75 MeV / 7 Ge 0.33 MeV σ G.S. from T / ( 7 Ge) =.43±0.03days [Hampel, Remsberg, PRC 3 (985) 666] σ G.S. ( 5 Cr) = cm (±0.004) 3σ ( σ( 5 Cr) = σ G.S. ( 5 Cr).669 BGT BGT ) 500 BGT G.S. BGT G.S. Contribution of Excited States only 5%! C. Giunti Status of Sterile Neutrinos 5 Sep 0 6/3

17 BGT 75 BGT G.S. BGT 500 BGT G.S. Krofcheck et al. PRL 55 (985) 5 Haxton PLB 43 (998) Frekers et al. PLB 706 (0) 34 7 Ga(p,n) 7 Ge < ±0.03 Shell Model 0.9 ± Ga( 3 He, 3 H) 7 Ge 0.039± ±0.06 Haxton: [Haxton, PLB 43 (998) ] a sophisticated shell model calculation is performed... for the transition to the first excited state in 7 Ge. The calculation predicts destructive interference between the (p, n) spin and spin-tensor matrix elements Does Haxton argument apply also to ( 3 He, 3 H) measurements?.7σ discrepancy of BGT 500 /BGT G.S. measurements! Anyhow, new 7 Ga( 3 He, 3 H) 7 Ge data support Gallium Anomaly! C. Giunti Status of Sterile Neutrinos 5 Sep 0 7/3

18 SUN&KamLAND ϑ 3 bound on U e4 [Giunti, YF Li, PRD 80 (009) 3007; Palazzo, PRD 83 (0) 303, Palazzo, PRD 85 (0) 07730] NOW0] 3 with simplifying assumptions: U µ4 = U τ4 = 0, no CP violation U e = c c 3 c 4 U e = s c 3 c 4 U e3 = s 3 c 4 U e4 = s 4 U s = c c 3 s 4 U s = s c 3 s 4 U s3 = s 3 s 4 U s4 = c 4 P νe ν e ( s3 )( ) s 4 P ν ν e ν e P νe ν s s4 ( ) P ν ν e ν s V = c 3 c 4 V CC c 3 s 4 V NC = ( U e U e )V CC ( U s U s )V NC C. Giunti Status of Sterile Neutrinos 5 Sep 0 8/3

19 red band: SUN and KL blue band: TK and MINOS before Daya Bay and RENO [Palazzo, PRD 85 (0) 07730] ( 4) 8 6 With DYBRENO Without [Giunti, Laveder, Li, Liu, Long, Sep 0] % C.L.( ) 90.00% C.L. 68.7% C.L.( ) log(sin 4) C. Giunti Status of Sterile Neutrinos 5 Sep 0 9/3

20 Global ν e and ν e Disappearance m 4 [ev ] [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] m 4 [ev ] [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] 95% C.L. Gallium Reactors ν e C Sun Combined sin ϑ ee GALREAν ecsun 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) sin ϑ ee ν e C N g.s. e KARMEN LSND [Conrad, Shaevitz, PRD 85 (0) 0307] [Giunti, Laveder, PLB 706 (0) 00] C. Giunti Status of Sterile Neutrinos 5 Sep 0 0/3

21 Testable Implications: β Decay [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] [(Q T) K(T)] / (Q T) T Q [ev] (sin ϑ ee, m 4 [ev ]) ( 0., 7.59 ) ( 0., ) ( 0.07, 0.9 ) ( 0.05, 0.46 ) relative deviation of Kurie plot (Q T) K(T) Q T [ev ] m 4 sin ϑ ee GALREAν ecsun [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) KATRIN: NOW0] C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

22 Testable Implications: (ββ) 0ν Decay χ [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] 99.73% EXO 99% 95.45% 90% 68.7% GALREAνeCSUN KK 3 (4) m ββ [ev] m ββ = k U ek m k m (4) ββ = U e4 m 4 caveat: possible cancellation with m (3ν IH) ββ NOW0] C. Giunti Status of Sterile Neutrinos 5 Sep 0 /3

23 Global 3 Fit: Disappearance Constraints ν e disappearance experiments: sin ϑ ee = 4 U e4 ( U e4 ) 4 U e4 ν µ disappearance experiments: sin ϑ µµ = 4 U µ4 ( U µ4 ) 4 U µ4 ν µ ν e experiments: sin ϑ eµ = 4 U e4 U µ4 4 sin ϑ ee sin ϑ µµ Upper bounds on sin ϑ ee and sin ϑ µµ = strong limit on sin ϑ eµ [Okada, Yasuda, Int. J. Mod. Phys. A (997) ] [Bilenky, Giunti, Grimus, Eur. Phys. J. C (998) 47] C. Giunti Status of Sterile Neutrinos 5 Sep 0 3/3

24 ν e and ν e Disappearance [ev ] m 4 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] 99% C.L. Bugey3 Bugey4Rovno GosgenILL Krasnoyarsk ν e C Gallium SUN 3 New Reactor ν e Fluxes [Mueller et al., PRC 83 (0) 05465] [Mention et al., PRD 83 (0) ] [Huber, PRC 84 (0) 0467] KARMEN LSND ν e C N g.s. e [Conrad, Shaevitz, PRD 85 (0) 0307] [Giunti, Laveder, PLB 706 (0) 00] SUN&KamLAND ϑ 3 [Giunti, YF Li, PRD 80 (009) 3007] [Palazzo, PRD 83 (0) 303] [Palazzo, PRD 85 (0) 07730] [Giunti, Laveder, Li, Liu, Long, Sep 0] sin ϑ ee C. Giunti Status of Sterile Neutrinos 5 Sep 0 4/3

25 ν µ and ν µ Disappearance [ev ] m 4 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] 99% C.L. CDHSW (984): ν µ ATM: ν µ ν µ MINOS (0): ν µ sin ϑ µµ ATM constraint on U µ4 [Maltoni, Schwetz, PRD 76 (007) ] MINOS constraint on U µ4 [Giunti, Laveder, PRD 84 (0) ] To be included: MiniBooNE/SciBooNE limit on SBL ν µ disappearance [arxiv:8.03] To be included: AMANDA/Ice Cube limit on SBL ν µ and ν µ disappearance [Esmaili, Halzen, Peres, arxiv:6.6903] NOW0] C. Giunti Status of Sterile Neutrinos 5 Sep 0 5/3

26 3 3 3σ ν e Dis ν µ Dis Dis App 0 MiniBooNE data [ev ] m 4 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] GoF = 9.3% PGoF = 0.00% missing new ICARUS constraint (added later) 4 3 sin ϑ eµ 3 & 3: Appearance-Disappearance tension Tension reduced in 3NSI [Akhmedov, Schwetz, JHEP (0) 5] No tension in 3CPTV [Barger, Marfatia, Whisnant, PLB 576 (003) 303] [Giunti, Laveder, PRD 8 (0) 09306, PRD 83 (0) ] C. Giunti Status of Sterile Neutrinos 5 Sep 0 6/3

27 3 3 is preferred to 3 only if there is CP-violating difference of ν µ ν e and ν µ ν e transitions 0 MiniBooNE antineutrino data indicated neutrino-antineutrino difference in 0 it was reasonable and useful to consider 3 neutrino-antineutrino difference almost disappeared with 0 MiniBooNE antineutrino data in 0 3 is reduced to 3 by Okkam razor shaving C. Giunti Status of Sterile Neutrinos 5 Sep 0 7/3

28 3 Global Fit without ICARUS 3 GLO LOW 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) 3 GLO HIG 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) [ev ] m 4 DIS APP 4 3 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] [ev ] m 4 DIS APP 4 3 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] sin ϑ eµ No Osc. GoF = 0.07% 3 GoF = 9.3% PGoF = 0.00% sin ϑ eµ No Osc. GoF = 0.75% 3 GoF = 30% PGoF = 0.6% C. Giunti Status of Sterile Neutrinos 5 Sep 0 8/3

29 3 Global Fit with ICARUS 3 GLO LOWICARUS 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) 3 GLO HIGICARUS 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) [ev ] m 4 DIS APP 4 3 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] [ev ] m 4 DIS APP 4 3 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] sin ϑ eµ No Osc. GoF = 0.0% 3 GoF = 9.9% PGoF = 0.0% sin ϑ eµ No Osc. GoF = 0.87% 3 GoF = 3% PGoF = 0.7% C. Giunti Status of Sterile Neutrinos 5 Sep 0 9/3

30 Cosmology N s = number of thermalized sterile neutrinos (not necessarily integer) [Melchiorri, Tamborra, NOW0] CMB and LSS in ΛCDM: N s =.3±0.9 m s < 0.66eV (95% C.L.) [Hamann, Hannestad, Raffelt, Tamborra, Wong, PRL 5 (0) 830] N s =.6±0.9 m s < 0.70eV (95% C.L.) [Giusarma, Corsi, Archidiacono, de Putter, Melchiorri, Mena, Pandolfi, PRD 83 (0) 503] N s = 0.±0.59 [Cyburt, Fields, Olive, Skillman, AP 3 (005) 33] BBN: N s = [Izotov, Thuan, ApJL 7 (0) L67] 0.35 N s at 95% C.L. [Mangano, Serpico, PLB 70 (0) 96] CMBLSSBBN: N s = (95% C.L.) [Hamann, Hannestad, Raffelt, Wong, JCAP 9 (0) 034] Standard ΛCDM: 3 allowed, 3 disfavored C. Giunti Status of Sterile Neutrinos 5 Sep 0 30/3

31 Combined Oscillation and Cosmology Fit [Archidiacono, Fornengo, Giunti, Melchiorri, arxiv:7.655] 5 P( m4 [ev ]) 4 3 [ev ]) P( m m4 [ev ] Mass Hierarchy: m 4 m 3,m,m = m 4 Cosmology: m 4 < 0.73eV (95% Bayesian CL) 0 0. m [ev ] 4 m 4 Oscillation Cosmology: 0.85 < m 4 <.8eV (95% Bayesian CL) C. Giunti Status of Sterile Neutrinos 5 Sep 0 3/3

32 Conclusions Short-baseline neutrino oscillation anomalies = sterile neutrinos Short-Baseline ν µ ν e Signal is not feeling well: MiniBooNE 0 antineutrino data are similar to neutrino data (LSND signal diminished and low-energy anomaly appeared) Probably there is no CP violation = no need of 3 The decrease of MiniBooNE-LSND agreement is discouraging Better experiments are needed to clarify situation NOW0] Short-Baseline ν e and ν e Disappearance is in good health: Reactor νe anomaly is alive and exciting Gallium νe anomaly strengthened by new cross-section measurements Many promising projects to test short-baseline νe and ν e disappearance in a few years with reactors, radioactive sources and accelerators [Ianni, Link, NOW0] Independent tests through effects of m4 in β-decay and (ββ) 0ν -decay C. Giunti Status of Sterile Neutrinos 5 Sep 0 3/3

33 Backup Slides C. Giunti Status of Sterile Neutrinos 5 Sep 0 33/3

34 Reactor ν e Disappearance [ev ] m 4 [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] REA 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) sin ϑ ee C. Giunti Status of Sterile Neutrinos 5 Sep 0 34/3

35 m 4 [ev ] [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] Gallium ν e Disappearance m 4 [ev ] [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] GAL Haxton 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) 3 sin ϑ ee GAL Frekers et al. 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) 3 sin ϑ ee No Osc. χ min 4.8 NDF 4 GoF 0.5 % 3 χ min 4.8 NDF GoF 9. % m4 [ev ].4 sin ϑ ee 0.50 No Osc. χ min 7. NDF 4 GoF 0. % 3 χ min 7.9 NDF GoF.9 % m4 [ev ].09 sin ϑ ee 0.30 C. Giunti Status of Sterile Neutrinos 5 Sep 0 35/3

36 m 4 [ev ] Reactor ν e and Gallium ν e Disappearance [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] m 4 [ev ] [Giunti, Laveder, YF Li, QY Liu, HW Long, Sep 0] REA GAL Haxton 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) sin ϑ ee REA GAL Frekers et al. 68.7% C.L. (σ) 90.00% C.L % C.L. (σ) 99.00% C.L % C.L. (3σ) sin ϑ ee No Osc. χ min 45.6 NDF 4 GoF 3.3 % 3 χ min 30.8 NDF 40 GoF 85 % m4 [ev ].95 sin ϑ ee 0.6 No Osc. χ min 48.9 NDF 4 GoF.5 % 3 χ min 3. NDF 40 GoF 80 % m4 [ev ].95 sin ϑ ee 0.6 C. Giunti Status of Sterile Neutrinos 5 Sep 0 36/3

Status of Light Sterile Neutrinos Carlo Giunti

C. Giunti Status of Light Sterile Neutrinos EPS-HEP 05 3 July 05 /5 Status of Light Sterile Neutrinos Carlo Giunti INFN, Sezione di Torino and Dipartimento di Fisica, Università di Torino giunti@to.infn.it