Sterile neutrino oscillations. Antonio Palazzo

Transcription

1 MPP Retreat Bayrischzell 0/01/014 Sterile neutrino oscillations Antonio Palazzo MPI für Physik (München)

2 Outline The standard 3ν framework Beyond three neutrino families Ongoing research activity Conclusions

3 The 3ν mass spectrum NH or IH? ν 3 ν e ν µ ν τ +Δm δm = 7.5 x 10-5 ev Δm =.4 x 10-3 ev ν ν 1 δm -Δm mi sub-ev ν 3 NMH and absolute mass at the center of intense investigation 3

4 The 3ν mixing matrix Dirac CP-violating phase δ U is non-real if δ (0, π) Explicit form θ 3 ~ 41 º θ 13 ~ 9 º θ 1 ~ 34 º CPV at the center of neutrino research program 4

5 Beyond three neutrino families One of the most simple extensions of the SM involves sterile neutrinos, i.e. singlets of the SM gauge group ν s s have been investigated in several contexts: - GUT scale: see-saw models of neutrino mass generation and leptogenesis - TeV scale: possible production at colliders and impact on EWPOs - kev scale: dark matter candidate - ev scale: anomalies in very-short-baseline oscillation experiments - sub-ev scale: solar neutrino energy spectrum anomaly I will focus on ev scale: light neutrinos 5

6 Light Sterile Neutrinos: A White Paper arxiv: v1 [hep-ph] 18 Apr 01 K. N. Abazajian a, 1 M. A. Acero, S. K. Agarwalla, 3 A. A. Aguilar-Arevalo, C. H. Albright, 4, 5 S. Antusch, 6 C. A. Argüelles, 7 A. B. Balantekin, 8 G. Barenboim a, 3 V. Barger, 8 P. Bernardini, 9 F. Bezrukov, 10 O. E. Bjaelde, 11 S. A. Bogacz, 1 N. S. Bowden, 13 A. Boyarsky, 14 A. Bravar, 15 D. Bravo Berguño, 16 S. J. Brice, 5 A. D. Bross, 5 B. Caccianiga, 17 F. Cavanna, 18, 19 E. J. Chun, 0 B. T. Cleveland, 1 A. P. Collin, P. Coloma, 16 J. M. Conrad, 3 M. Cribier, A. S. Cucoanes, 4 J. C. D Olivo, S. Das, 5 A. de Gouvêa, 6 A. V. Derbin, 7 R. Dharmapalan, 8 J. S. Diaz, 9 X. J. Ding, 16 Z. Djurcic, 30 A. Donini, 31, 3 D. Duchesneau, 3 H. Ejiri, 33 S. R. Elliott, 34 D. J. Ernst, 35 A. Esmaili, 36 J. J. Evans, 37, 38 E. Fernandez-Martinez, 39 E. Figueroa-Feliciano, 3 B. T. Fleming a, 18 J. A. Formaggio a, 3 D. Franco, 40 J. Gaffiot, R. Gandhi, 41 Y. Gao, 4 G. T. Garvey, 34 V. N. Gavrin, 43 P. Ghoshal, 41 D. Gibin, 44 C. Giunti, 45 S. N. Gninenko, 43 V. V. Gorbachev, 43 D. S. Gorbunov, 43 R. Guenette, 18 A. Guglielmi, 44 F. Halzen, 46, 8 J. Hamann, 11 S. Hannestad, 11 W. Haxton, 47, 48 K. M. Heeger, 8 R. Henning, 49, 50 P. Hernandez, 3 P. Huber b, 16 W. Huelsnitz, 34, 51 A. Ianni, 5 T. V. Ibragimova, 43 Y. Karadzhov, 15 G. Karagiorgi, 53 G. Keefer, 13 Y. D. Kim, 54 J. Kopp a, 5 V. N. Kornoukhov, 55 A. Kusenko, 56, 57 P. Kyberd, 58 P. Langacker, 59 Th. Lasserre a,, 40 M. Laveder, 60 A. Letourneau, D. Lhuillier, Y. F. Li, 61 M. Lindner, 6 J. M. Link b, 16 B. L. Littlejohn, 8 P. Lombardi, 17 K. Long, 63 J. Lopez-Pavon, 64 W. C. Louis a, 34 L. Ludhova, 17 J. D. Lykken, 5 P. A. N. Machado, 65, 66 M. Maltoni, 31 W. A. Mann, 67 D. Marfatia, 68 C. Mariani, 53, 16 V. A. Matveev, 43, 69 70, 39 N. E. Mavromatos, A. Melchiorri, 71 D. Meloni, 7 O. Mena, 3 G. Mention, A. Merle, 73 E. Meroni, 17 M. Mezzetto, 44 G. B. Mills, 34 D. Minic, 16 L. Miramonti, 17 D. Mohapatra, 16 R. N. Mohapatra, 51 C. Montanari, 74 Y. Mori, 75 Th. A. Mueller, 76 H. P. Mumm, 77 V. Muratova, 7 A. E. Nelson, 78 J. S. Nico, 77 E. Noah, 15 J. Nowak, 79 O. Yu. Smirnov, 69 M. Obolensky, 40 S. Pakvasa, 80 18, 5 O. Palamara, M. Pallavicini, 81 S. Pascoli, 8 L. Patrizii, 83 Z. Pavlovic, 34 O. L. G. Peres, 36 H. Pessard, 3 F. Pietropaolo, 44 M. L. Pitt, 16 M. Popovic, 5 J. Pradler, 84 G. Ranucci, 17 H. Ray, 85 S. Razzaque, 86 B. Rebel, 5 R. G. H. Robertson, 87, 78 W. Rodejohann a, 6 S. D. Rountree, 16 C. Rubbia, 39, 5 O. Ruchayskiy, 39 P. R. Sala, 17 K. Scholberg, 88 T. Schwetz a, 6 M. H. Shaevitz, 53 M. Shaposhnikov, 89 R. Shrock, 90 S. Simone, 91 M. Skorokhvatov, 9 M. Sorel, 3 A. Sousa, 93 D. N. Spergel, 94 J. Spitz, 3 L. Stanco, 44 I. Stancu, 8 A. Suzuki, 95 T. Takeuchi, 16 I. Tamborra, 96 J. Tang, 97, 98 G. Testera, 81 X. C. Tian, 99 A. Tonazzo, 40 C. D. Tunnell, 100 R. G. Van de Water, 34 L. Verde, 101 E. P. Veretenkin, 43 C. Vignoli, 5 M. Vivier, R. B. Vogelaar, 16 M. O. Wascko, 63 J. F. Wilkerson, 49, 10 W. Winter, 97 Y. Y. Y. Wong a, 5 T. T. Yanagida, 57 O. Yasuda, 103 M. Yeh, 104 F. Yermia, 4 Z. W. Yokley, 16 G. P. Zeller, 5 L. Zhan, 61 and H. Zhang 6 1 University of California, Irvine Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México 3 Instituto de Fisica Corpuscular, CSIC and Universidad de Valencia 4 Northern Illinois University 5 Fermi National Accelerator Laboratory 6 University of Basel a Section editor b Editor and corresponding author (pahuber@vt.edu and jmlink@vt.edu) 6

7 Introducing a light sterile neutrino 4ν 3ν U s4 ~ 1 Δm atm Δm sol Δm 14 ~ 1 ev Small mixing of active flavors with the 4 th state 7

8 The reactor and gallium anomalies (unexplained ν e disappearance) N OBS /(N EXP ) pred,new ILL Bugey!3/4 ROVNO Krasnoyarsk Goesgen Bugey3 Goesgen Krasnoyarsk!3 Goesgen Krasnoyarsk! Bugey3 PaloVerde CHOOZ In a ν framework: P ee 1 sin θ new sin m newl 4E Distance to Reactor (m) p(measured)/p(predicted) Mention et al. arxiv:1101:755 [hep-ex] GALLEX Cr1 1.1 SAGE Cr GALLEX Cr SAGE Ar In a 3+1 scheme: P ee =1 4 j>k U eju ek sin m jk L 4E m sol m atm m new SAGE coll., PRC 73 (006) sin θ new U e4 = sin θ 14 8

9 Fitting the anomalies with sterile ν oscillations "# dof "# contours 1 dof "# profile % % % "# dof "# contour (ev ) "m new ! dof "# profile (ev ) "m new ! ! !3 10! sin 10! (! new ) 5 10 "# 10! !3 1 FIG. 6. AllowedMention regionset inal., the PRD sin83 (θ new ) m (011) new plane obtained from the fit of th hypothesis, with sin (θ 13 ) = 0. The left panel is the combination of the reactors an with 51 Cr and 37 Ar radioactive sources. The right panel is the combination of the re data following the method of Ref. [56]. In both cases the ILL energy spectrum info sin θ new 0.1 m new 1 ev Our ILL re-analysis, including only the en- 9

10 The SBL accelerator February 5, :7 WSPC/146-MPLA anomaly S (unexplained ν e appearance in a ν µ beam) LSND Phenomenology of Light Sterile Neutrinos Beam Excess Beam Excess p(ν _ µ ν_ e,e+ )n p(ν _ e,e+ )n.5 0 BooNE Results L/E ν (meters/mev) 07-1 )# e CQE) of events oboone). ve to check MiniBooNE other sin θ eµ 1 4 sin θ ee sin θ µµ 4 U e4 U µ4 Δm (ev /c 4 ) Karmen Bugey 90% (L max -L <.3) 99% (L max -L < 4.6) # m " # LSND e 0 ev ( matm msol) Δm (ev ) C. Giunti Phenomenology of Sterile Neutrinos 16 May 011 5/59 # " # e Mod. Phys. Lett. A Downloaded from ANCK INSTITUTE FOR PHYSICS LIBRARY on 0/8/13. For personal use only. MiniBooNE LSND 90% CL sin (θ) NOMAD (90%) 68% CL 90% CL 95% CL CCFR 99% CL 3σ CL KARMEN 90% CL NOMAD LSND 99% CL NuTeV (90%) CCFR (90%) Excluded at 90% CL sin θ Excluded at 99% CL ICARUS Fig. 1. Regions allowed by the main published experiments sensitive to the accelerator anomaly superimposed to the limits established by the ICARUS experiment. Figure taken from Ref. 9. nary pieces of data, namely the solar neutrino sector experiments together with the new dual-baseline θ 13 -sensitive reactor experiments Daya Bay and RENO, are able to put interesting constraints on the scheme. Finally we draw our conclusions.. The Anomalies.1. The accelerator anomaly 1 10

11 Anomalous & Regular Results Overall picture is not clear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h. Lasserre ICFA-ν

12 The dark radiation anomaly Planck (013) P/Pmax Planck+WP+highL +BAO +H 0 +BAO+H 0 extra relativistic content ~ sigma effect N eff Warnings: ΔN eff >0 driven by tension in H 0 determination (CMB vs Astro) - ΔN eff [0, 1] requires a mechanism hampering νs thermalization - N eff is not specific of sterile neutrinos 1

13 How to shed light onto a confused picture SOX: SHORT DISTANCE OSCILLATIONS W 51Cr source - external 00 events events!m =.0 ev Smoking gun: oscillatory pattern (in energy and/or space) sin (! ) = 0.05 s A promising option: ν source close or inside Borexino SOX: SHORT DISTANCE OSCILLATIONS WITH BOREXINO (II) 51Cr!m =.0 ev sin(!s) = Ce 51Cr distance from source (cm) source - internal source - external sensiti #!$ 150!m =.0 ev sin(!s) = year !!"#$% 00 source sensitivity of events External source - external events 51Cr %&#''$(!$)%*$ %&+,&-$./($013$ #4$&--"$356-7& #4$&--"$89$ #$!"#$ distance from source (cm) Neutrino 01 - Kyoto sensitivity of - external M. Neutrino !"!#$ (cm) distance from center!"!!#$ M. Pallavicini 144Ce source M. of Neutrino 01 - internal sensitivity 51Cr!!"#$% #$ 13 :!4$%";" &<7=60&0$ %&#''$(!$)%*$ %&+,&-$./($013$ #4$&--"$356-7&$*+,&+3*,$ #4$&--"$89$ Several other projects under scrutiny #!$ 500 0

14 Impact of a light sterile neutrino in β-decay m β = Uei m = c i 1c 13c 14m 1 + s 1c 13c 14m + s 13c 14m 3 + s 14m 4 1/ Present Future Mainz Kraus et al., arxiv: KATRIN Formaggio and Barrett, arxiv:

15 Impact of a light sterile in 0νβ-decay m ββ = U eim i = c 1c 13c 14m 1 + s 1c 13c 14m e iα + s 13c 14m 3 e iβ + s 14m 4 e iγ 10 0 Normal Normal Hierarchy 3 ν (best-fit) 1+3 ν (best-fit) Inverted Inverted Hierarchy 3 ν (best-fit) 1+3 ν (best-fit) <m ee > (ev) m light (ev) Mainz KATRIN Barry, Rodejohann, Zhang, arxiv:

16 Conclusion () New info should come within 5 years! Many proposals with capabilities to unambiguously test L/E"1 m/mev oscillatory behavior with low backgrounds! Reactor Neutrinos! Results within 5 years, Modest Cost (-10 M$)! Background mitigation is challenging! Neutrino Generator! Results within 5 years, Modest Cost (<5 M$)! Challenge for the source production and transportation! Neutrino Beam! Longer Term, Higher Cost! Would allow a complete study sterile neutrino phenomenology! Independent tests through -decay and ( )0 -decay Th. Lasserre ICFA-ν

17 What if a ν s is discovered in the next 5 years? First concrete extension of the Standard Model; will need scrutiny (other properties beyond mixing? Self interactions and/or with DM) Subleading effects expected in the existing neutrino phenomenology. Impact on standard parameter extraction (NMH and CPV) in current and future experiments. New CPV phases in an enlarged PMNS matrix Impact in cosmology (contribution to radiation and hot dark matter) Impact in astrophysics (supernova explosion) It will seem natural to think that several such particles can exist and may explain other observations: solar spectrum (10-3 ev), DM (kev), baryon asymmetry via leptogenesis and small ν mass (GUT), A major breakthrough with several implications and much work to do in the next 10 years! 17

18 Conclusions The 3ν scheme may not constitute the ultimate description of the ν oscillatory phenomena. Sterile νs may alter the standard picture. Light sterile neutrinos with ev mass offer an option for explaining some laboratory and cosmological anomalies. Matter of intense investigation. Rich ongoing experimental activity. The discovery of a sterile neutrino would be a major breakthrough with several implications/ramifications and much work to do. 18

19 Backup Slides 19

20 013 status of global 3ν oscillation analysis LBL Acc + Solar + KamLAND + LBL Reactors + SK Atm N 4 IH 3 NH Weak preference for δ [π, π] (sin δ < 0) m -5 /10 ev m /10 ev / Some preference for first octant of θ 3 but weaker in IH N sin sin 3 sin 13 No sensitivity to neutrino mass hierarchy Capozzi, Fogli, Lisi, Marrone, Montanino, Palazzo [arxiv: ] 0

21 Disappearance/appearance tension Beam Excess Beam Excess p(ν _ µ ν_ e,e+ )n p(ν _ e,e+ )n other Δm (ev /c 4 ) Karmen Bugey CCFR NOMAD % (L max -L <.3) 99% (L max -L < 4.6) L/E ν (meters/mev) LSND, PRL 75 m(1995) LSND 0650 ev ( matm msol) sin θ Giunti and Laveder, arxiv: C. Giunti Phenomenology of Sterile Neutrinos 16 May 011 5/59 Warning: Theory: In tension with disappearance searches: ν µ ->ν e positive appearance signal incompatible with joint ν e >ν e (positive) & ν µ ->ν µ (negative) searches sin θ eµ 1 4 sin θ ee sin θ µµ 4 U e4 U µ4 Experiments: ~ few %o ~ 0.1 < few % 1

22 New trends in cosmological data ev sterile neutrinos ΔN eff ~ 0.6 m ν ~ 0.4 ev Haman and Hasenkamp [ astro-ph] Similar findings in: Wyman et al. [ hep-ph] Giunti et al. [ astro-ph]

23 A VLSν provides both features 1) Contribution to the absolute ν mass in the sub-ev range ) Only partial thermalization is expected to occur: 0<ΔN eff <1 for Δm 14 [10-3, 10-1 ] ev and U e4 <10 - log 10 ( δm s [ev ]) σ σ 3σ σ 3σ σ log (sin θ ) 10 s 1σ 1σ 1σ ev m a m 41 0, sin Θ sol. upturn 10 3 sin Θ 14 KATRIN 10 sin Θ SBL 10 1 Hannestad, Tamborra, Tram JCAP 107 (01) 05 Mirizzi et al. Phys. Lett. B 76 (013) 8 3

24 4-flavor analysis performed for free θ 13 A.P. [ hep-ph] FIG. 3: Results obtained from the 4-flavor analysis for a free θ 13, whichismarginalizedaway. Thecontoursrefertod.o.f. 90% C.L. (blue thick line) and 99% (red thin line). General degradation of sensitivity in all the three experiments ( m ev ), the parameter θ 13 has no lower bound. This behavior can be easily understood as in this case the two terms in Eq. (8), respectively driven by θ 13 and θ 14, becomes almost identical and a complete degeneracy among the two parameters emerges. In other words, for such values of m 14 all the reactor data could be interpreted in terms of pure θ 14 -driven oscillations without resorting to a non-zero θ 13. In practice, this interpretation is not Entire lobes disappear due to strong degeneracies among θ 13 and θ 14 Degradation less severe in: D-Chooz (Bugey-4 at 15 m as an anchor) Daya-Bay (additional near/near ratio constrain values > 10 - ev ) Noticeable synergy in the global combination 4