Neutrino masses and mixings: Status of known and unknown 3 Parameters

Capozzi, F.; Lisi, E.; Marrone, A.; Montanino, D.; Palazzo, A.

doi:10.1016/j.nuclphysb.2016.02.016

Neutrino masses and mixings: Status of known and unknown 3 Parameters

F. Capozzi (Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via F. Marzolo 8, Padova, Italy; Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Padova, Via F. Marzolo 8, Padova, Italy) ; E. Lisi (Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, Via E. Orabona 4, Bari, Italy) ; A. Marrone (Dipartimento Interateneo di Fisica “Michelangelo Merlin”, Università di Bari, Via G. Amendola 173, Bari, Italy; Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, Via E. Orabona 4, Bari, Italy) ; D. Montanino (Dipartimento di Matematica e Fisica “Ennio de Giorgi”, Università del Salento, Via Arnesano, Lecce, Italy; Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Lecce, Via Arnesano, Lecce, Italy) ; A. Palazzo (Dipartimento Interateneo di Fisica “Michelangelo Merlin”, Università di Bari, Via G. Amendola 173, Bari, Italy; Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, Via E. Orabona 4, Bari, Italy)

Within the standard 3ν mass–mixing framework, we present an up-to-date global analysis of neutrino oscillation data (as of January 2016), including the latest available results from experiments with atmospheric neutrinos (Super-Kamiokande and IceCube DeepCore), at accelerators (first T2K $\overline{ν}$ and $NO ν A$ ν runs in both appearance and disappearance modes), and at short-baseline reactors (Daya Bay and RENO far/near spectral ratios), as well as a reanalysis of older KamLAND data in the light of the “bump” feature recently observed in reactor spectra. We discuss improved constraints on the five known oscillation parameters ( $δ m^{2}$ , $| Δ m^{2} |$ , $\sin^{2} θ_{12}$ , $\sin^{2} θ_{13}$ , $\sin^{2} θ_{23}$ ), and the status of the three remaining unknown parameters: the mass hierarchy [ $sign (\pm Δ m^{2})$ ], the $θ_{23}$ octant [ $sign (\sin^{2} θ_{23} - 1 / 2)$ ], and the possible CP-violating phase δ. With respect to previous global fits, we find that the reanalysis of KamLAND data induces a slight decrease of both $δ m^{2}$ and $\sin^{2} θ_{12}$ , while the latest accelerator and atmospheric data induce a slight increase of $| Δ m^{2} |$ . Concerning the unknown parameters, we confirm the previous intriguing preference for negative values of $\sin δ$ (with best-fit values around $\sin δ ≃ - 0.9$ ), but we find no statistically significant indication about the $θ_{23}$ octant or the mass hierarchy (normal or inverted). Assuming an alternative (so-called LEM) analysis of $NO ν A$ data, some δ ranges can be excluded at $> 3 σ$ , and the normal mass hierarchy appears to be slightly favored at $\sim 90 %$ C.L. We also describe in detail the covariances of selected pairs of oscillation parameters. Finally, we briefly discuss the implications of the above results on the three non-oscillation observables sensitive to the (unknown) absolute ν mass scale: the sum of ν masses Σ (in cosmology), the effective $ν_{e}$ mass $m_{β}$ (in beta decay), and the effective Majorana mass $m_{β β}$ (in neutrinoless double beta decay).

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      "value": "Within the standard 3\u03bd mass\u2013mixing framework, we present an up-to-date global analysis of neutrino oscillation data (as of January 2016), including the latest available results from experiments with atmospheric neutrinos (Super-Kamiokande and IceCube DeepCore), at accelerators (first T2K <math><mover><mrow><mi>\u03bd</mi></mrow><mo>\u203e</mo></mover></math> and <math><mrow><mi>NO</mi></mrow><mi>\u03bd</mi><mi>A</mi></math> \u03bd runs in both appearance and disappearance modes), and at short-baseline reactors (Daya Bay and RENO far/near spectral ratios), as well as a reanalysis of older KamLAND data in the light of the \u201cbump\u201d feature recently observed in reactor spectra. We discuss improved constraints on the five known oscillation parameters (<math><mi>\u03b4</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup></math>, <math><mo>|</mo><mi>\u0394</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>|</mo></math>, <math><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>\u2061</mo><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>12</mn></mrow></msub></math>, <math><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>\u2061</mo><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>13</mn></mrow></msub></math>, <math><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>\u2061</mo><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>23</mn></mrow></msub></math>), and the status of the three remaining unknown parameters: the mass hierarchy [<math><mtext>sign</mtext><mo>(</mo><mo>\u00b1</mo><mi>\u0394</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math>], the <math><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>23</mn></mrow></msub></math> octant [<math><mtext>sign</mtext><mo>(</mo><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>\u2061</mo><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>23</mn></mrow></msub><mo>\u2212</mo><mn>1</mn><mo>/</mo><mn>2</mn><mo>)</mo></math>], and the possible CP-violating phase \u03b4. With respect to previous global fits, we find that the reanalysis of KamLAND data induces a slight decrease of both <math><mi>\u03b4</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup></math> and <math><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>\u2061</mo><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>12</mn></mrow></msub></math>, while the latest accelerator and atmospheric data induce a slight increase of <math><mo>|</mo><mi>\u0394</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>|</mo></math>. Concerning the unknown parameters, we confirm the previous intriguing preference for negative values of <math><mi>sin</mi><mo>\u2061</mo><mi>\u03b4</mi></math> (with best-fit values around <math><mi>sin</mi><mo>\u2061</mo><mi>\u03b4</mi><mo>\u2243</mo><mo>\u2212</mo><mn>0.9</mn></math>), but we find no statistically significant indication about the <math><msub><mrow><mi>\u03b8</mi></mrow><mrow><mn>23</mn></mrow></msub></math> octant or the mass hierarchy (normal or inverted). Assuming an alternative (so-called LEM) analysis of <math><mrow><mi>NO</mi></mrow><mi>\u03bd</mi><mi>A</mi></math> data, some \u03b4 ranges can be excluded at <math><mo>&gt;</mo><mn>3</mn><mi>\u03c3</mi></math>, and the normal mass hierarchy appears to be slightly favored at <math><mo>\u223c</mo><mn>90</mn><mtext>%</mtext></math> C.L. We also describe in detail the covariances of selected pairs of oscillation parameters. Finally, we briefly discuss the implications of the above results on the three non-oscillation observables sensitive to the (unknown) absolute \u03bd mass scale: the sum of \u03bd masses \u03a3 (in cosmology), the effective <math><msub><mrow><mi>\u03bd</mi></mrow><mrow><mi>e</mi></mrow></msub></math> mass <math><msub><mrow><mi>m</mi></mrow><mrow><mi>\u03b2</mi></mrow></msub></math> (in beta decay), and the effective Majorana mass <math><msub><mrow><mi>m</mi></mrow><mrow><mi>\u03b2</mi><mi>\u03b2</mi></mrow></msub></math> (in neutrinoless double beta decay)."
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Published on:: 23 February 2016
Publisher:: Elsevier
Published in:: Nuclear Physics B , Volume 908 C (2016)

Pages 218-234
DOI:: https://doi.org/10.1016/j.nuclphysb.2016.02.016
Copyrights:: The Authors
Licence:: CC-BY-3.0

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