Theory of Neutrinos: a White Paper

Abstract

During 2004, four divisions of the American Physical Society commissioned a study of neutrino physics to take stock of where the field is at the moment and where it is going in the near and far future. Several working groups looked at various aspects of this vast field. The summary was published as a main report entitled "The Neutrino Matrix" accompanied by short 50 page versions of the report of each working group. Theoretical research in this field has been quite extensive and touches many areas and the short 50 page report [1] provided only a brief summary and overview of few of the important points. The theory discussion group felt that it may be of value to the community to publish the entire study as a white paper and the result is the current article. After a brief overview of the present knowledge of neutrino masses and mixing and some popular ways to probe the new physics implied by recent data, the white paper summarizes what can be learned about physics beyond the Standard Model from the various proposed neutrino experiments. It also comments on the impact of the experiments on our understanding of the origin of the matter-antimatter asymmetry of the Universe and the basic nature of neutrino interactions as well as the existence of possible additional neutrinos. Extensive references to original literature are provided.

Neutrinoless double b decay with small neutrino masses

“…Therefore, new interactions must be added to the SM in order to allow for 0νβ β . We illustrate the different 2 Operators involving leptons and quarks with no gauge bosons generate neutrino masses at 1 to 4 loops [25,26,15,27] and may receive enhancements from top Yukawa couplings. possibilities diagrammatically in Figure 4, where only one LNV vertex is considered at a time.…”

“…The remarkable observation of neutrino oscillations (see [1] and [2,3] for recent reviews and [4 -8] for fits including latest data on θ 13 ) has provided the first evidence for neutrino masses. On the other hand, the invisible decay width of the Z-boson tells us that there are only three species of light active neutrinos (lighter than about 45 GeV and interacting with full gauge strength).…”

Interim Design Report

“…Neutrino masses are not accounted for in the Standard Model of particle physics. It is not hard to modify the Standard Model Lagrangian to accommodate neutrino masses [17]. Indeed, one can write down several different "Standard Neutrino Model" (SνM) Lagrangians that render neutrinos massive that are consistent with the available data.…”

“…Attempts to understand the underlying physics behind the pattern of lepton mixing provide some guidance [17,26,27]). Such attempts often make predictions regarding the specific values for the different parameters or, perhaps more generically, make predictions regarding relations among different oscillation parameters.…”

Lepton flavour violating signature in supersymmetric U(1)′ seesaw models at the LHC

“…In this paper, we wish to explore another possibility which can provide richer collider signatures. A sumpersymmetric seesaw model [2] associated with an additional gauge symmetry U(1) [3] would be one of such examples.…”