10062016 CERN NEUTRINO PHYSICS Guido Altarelli Memorial Isabella

10/06/2016, CERN NEUTRINO PHYSICS Guido Altarelli Memorial Isabella Masina (Univ. of Ferrara, Italy)

NEUTRINO PHYSICS Nr of published papers by GA on neutrinos: (20+4 rev)/131 + many summary talks at conferences and lectures

Ferruccio Feruglio (19) Isabella Masina (5) Luca Merlo (4) Davide Meloni (3) E. Stamou (1) R. Franceschini (1) G. Blankenburg (1) C. Hagedorn (1) L. Yin (1)

Neutrino timeline 1998 2004 2012 First period (6) Second period (10) Abelian flavour symmetries and GUT Discrete flavor symmetries Third period (4) Which direction?

GA interest on neutrinos started in ‘ 94 (introductory talk at Neutrino Telescopes) What was known : 1) Nr of light neutrinos (below 45 Ge. V) 2) Direct limits on mass 3) Cosmology (DM) 4) Non-observation of 0 nbb decay 5) two anomalies… = 3 [‘ 89 LEP]

Solar deficit of newith respect to the Standard Solar Model seen by: Homestake ‘ 69, Kamiokande ‘ 87, SAGE ‘ 89, GALLEX ’ 91 Solution in terms of ne – nm oscillations [Pontecorvo Gribov ‘ 69]: 3 possibilities, of which 2 based on MSW effect [‘ 78] SMA “The value in brackets for sin 22 q is considered less plausible from a theoretical point of view because of the small mixings observed for quarks (although no real understanding of the CKM mixing matrix of quarks exist sofar)” [1994, GA] LMA

Atmospheric deficit of (nm/ne) with respect to MC expectations seen by: Kamiokande, IMB, Soudan in the 80’s Solution in terms of nm – nt oscillations: “This evidence does not appear to be really compelling so far” (1994, GA)

Two breakthroughs 1997: SSM confirmed (sound speed in sun interior by helioseismology) solar deficit more robust neutrino mass non vanishing [confirmed by SNO in 2001]

Two breakthroughs 1997: SSM confirmed (sound speed in sun interior by helioseismology) solar deficit more robust neutrino mass non vanishing [confirmed by SNO in 2001] 1998 June: SK compelling evidence of atmospheric oscillations neutrino mass non vanishing + large mixing!! e-like m-like SK

Neutrino masses and (at least) one large mixing angle are interesting new inputs beyond the SM GA hopes about neutrinos “It is a window on the physics of GUTs in that the extreme smallness of neutrino masses can only be explained in a natural way if lepton number is violated. ” “The pattern of neutrino masses and mixings can provide new clues on the long standing problem of quark and lepton mass matrices. ” [GA, talk at Neutrino ‘ 99]

VIDEO from the Concluding talk at Neutrino 2004 (from 10: 20 to 15: 15) http: //webcast. in 2 p 3. fr/videos-2613

GA principles about neutrinos - 1

GA principles about neutrinos - 2

GA principles about neutrinos - 3

GA principles about neutrinos - 4

First period: abelian flavor symmetries and GUT SK results Try simplest first 2000 1998 9907532 9807353 0007254 9812475 9809596 3 papers with F Feruglio 2002 2004 0210342

ϑ 23=π/4 ϑ 12=π/4 or 0 (and neglecting ϑ 13 ) B=IH A, B, C (neglecting Δm 2 sol) C=degenerate in the basis where charged leptons and W interactions are flavor diagonal A=NH Models of Neutrino Masses from Oscillations with Maximal Mixing [AF ph/9809596] GA favourite texture

GA favourite texture from the seesaw in the basis where charged leptons and W interactions are flavor diagonal and considering matrices at LO no strong hierarchy M 33≠ 0 v = V 2/M det 23 =0 x=O(1) large L-mixing in m. D large atm mixing and large mass splitting (solar oscillations not specified at LO, need NLO)

A Simple Grand Unification View of Neutrino Mixing and Fermion Mass Matrices [AF hep-ph/9812475] GA favourite easily embedded in SU(5) Assume minimal SU(5) field content + 3 n. R To be corrected by 45 for 2° generation SO(10) remnant Small mixings for up and small L-mixings for down small VCKM Large R-mixing for down Large L-mixing for ch. lept Transferred to neutrinos

A Simple Grand Unification View of Neutrino Mixing and Fermion Mass Matrices [AF hep-ph/9812475] GA favourite easily embedded in SU(5) and derived from U(1) flavor symmetry (in susy) After flavor symmetry breaking Large mixings (SMA)

First period: abelian flavor symmetries and GUT 02/99 Neutrino telescopes SNO results SK results 1998 2004 9907532 9807353 0210342 0007254 9812475 3 AFM papers 9809596

Large n mixing from small quark and lepton mixings [AFM hep/ph 9907532] L/R mixings in matrices at GUT scale could be ALL small (nice for SO(10)) Neglecting 1 st but not 2 nd generation X=O(1) large atm mixing and det 23 suppressed “The seesaw mechanism has created large mixing from almost nothing” In addition: - both SMA and LMA possible U(1)x. U(1) flavor model in SU(5) renormalization effects

From Minimal to Realistic Supersymmetric SU(5) Grand Unification [AFM hep-ph/0007254] a ”realistic” example of SUSY SU(5) GUT model, with an additional U(1) flavour symmetry 1) not plagued by the need of large fine tunings (doublet-triplet splitting via MDM) and 2) that leads to an acceptable phenomenology: - coupling unification - an acceptable pattern for fermion masses and mixing angles (LMA) - a proton decay rate compatible with present limits

Models of Neutrino Masses: Anarchy versus Hierarchy [AFM hep-ph/0210342] comparison of U(1)-inspired textures from Anarchy to Hierarchy

First period: abelian flavor symmetries and GUT Kamland SNO: LMA Dm 212 at 10% & sin 2 q 12 ≈ 1/3 02/99 Neutrino telescopes improved bound Ue 3 < 0. 23 SNO results SK results 1998 2004 9907532 9807353 9809596 0007254 9812475 0210342

Second period: (non-abelian) discrete flavor symmetries and GUT or extra-dimensions “special” models and deviations from them based on A 4 (or S 4), GUT and/or extra dim 2004 0504165 0402155 A F 0512103 AF A F Masina 2008 2011 0610165 0800090 A F Lin A F Hagedorn & orbifolding SUSY SU(5) 0512202 A Franceschini Le-Lm-Lt 09050620 A Meloni 09031940 A F Merlo S 4 e BM 08091041 A Meloni CPV 10122697 A Blankenburg SO(10) & type-II

Can Neutrino Mixings Arise from the Charged Lepton Sector? [AFM hep-ph/0402155] large First approximation to data BM: A) B) TBM: Models possible but unnatural Possible to have BM from Un and small corrections from Ue correlations among neutrino observables U e 3 expected of O(dsol)

Tri-Bimaximal Neutrino Mixing from Discrete Symmetry [AF hep-ph/0504165, many other…] TBM fits better data [Harrison Perkins Scott] The most general mass matrix invariant under 2 -3 symmetry and under S belonging to A 4 Predictions of these “special models”: ϑ 23 nearly maximal ϑ 13 < 0. 05 [Altarelli, 2005]

Third period: which direction? Daya Bay, REN 0… measure of q 13≈0. 15 no path clear: try comparisons 2011 1205. 4670 AF Merlo Stamou BM 1205. 5133 AF Merlo review Special models revisited 1305. 1001 1207. 0587 AF Masina Merlo A Meloni Non susy SO(10) GUT U(1) flavor Normal models revisited

Unfortunately ϑ 13 ≈ 0. 15 and the hint non-maximal ϑ 23 does not indicate any precise direction Moderate hierarchy better than Anarchy NORMAL SPECIAL The problem is the lack of predictiveness Extensions to GUT possible and not too complicated BM better than TBM The problem is not so much that q 13 is large but that there is no hint from quarks for them [GA, Corfu 2014] Extension to GUTs possible (many existence proofs) but rather complicated

[GA, Status of neutrino mass and mixing, 1404. 3859] As already happened in the past, hopefully future experiments might help to find the path: - Discriminating between NH, IH, DEG - Assessing the value of q 23 - Measuring the CPV phase

THANKS TO GUIDO Long & high distance vision Methodology Accent Clearness Humour Enthousiasm Kindness Aesthetic sense Affability

THANKS TO GUIDO for having shared with us your way of being a scientist