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Neutrinos: a door to

physics Beyond the Standard Model




The aim of the BSM-Nu project is to address the neutrino physics in a comprehensive way in order to extract hints of new physics. The project federates the different teams of P2IO active on the subject in order to share and depeen our expertise and with the ambition of enlarging further our community.


The BSM-Nu project proposes to federate all the actors of neutrino physics inside the P2IO perimeter in order to meet the challenges, both in terms of critical mass and physics expertise, of the next generation of neutrino experiments. The project cover different laboratories and experiments, as well as, different communities (particle and nuclear physicists, phenomenologists, engineers).

The enterprise of characterizing the nature of neutrinos, a royal road to the search of BSM physics, requires a collective effort able to integrate the results from oscillation experiments, both at accelerators and reactors, from neutrino-less double-beta decay searches and from coherent elastic neutrino-nucleus scattering.

These various experimental efforts share common issues related with the development of high-performing detectors and complex analysis techniques for the minimization and evaluation of backgrounds and systematic uncertainties. The BSM-Nu project will allow to share and deepen the expertise on these items, as well as, to enlarge the community through outreach and through the education of a new generation of physicists with a comprehensive view of the neutrino field.



The complete characterization of the new physics explaining the existence of neutrino mass, requires a comprehensive approach to the study of neutrino properties. Moreover the new generation of experiments on the subject will push such study into the precision era by exploiting detectors of unprecedented size and complexity and requiring very sophisticated analysis techniques. The neutrino community needs a change of gear in order to keep-up with these challenge in terms of expertise and (wo)man-power. The BSM-Nu project proposes to meet such challenges by working along the following lines.

The measurement or the constraint of the key parameters of the standard 3-flavor paradigm—with emphasis on the estimation on the uncertainties—but also the study of phenomena outside this basic scheme, such as non-standard neutrino interactions and deviations from the SM of the weak interactions.
There are in particular some subjects where BSM-Nu can have a remarkable impact on neutrino physics, often achievable only by combining data from different searches.
  • A delicate point in the precision measurements of neutrino oscillations is related to the evaluation of the systematic uncertainties. BSM-nu proposes an original approach, consisting of the comparison (cross-validation and, eventually, combination) of the results from the near detectors of the two large next-generation LBL experiments, DUNE and T2HK. This comparison will allow, initially, to validate the results of the two experiments and, subsequently, to combine the oscillation measurements, with a focus on the systematics and the correlation between experiments.
  • Phenomena that lie outside the 3-flavor paradigm, like non-standard neutrino interactions and / or sterile neutrinos, complicate the interpretation of the results. It is very important therefore to constraint adequately these phenomena or to clarify unambiguously their existence, which would imply new physics. A feature of NSIs is that they are represented in all generality by an additional effective term in the Langrangian density that affects neutrino flavor transitions in a wide range of phenomena. In particular, NSIs can show off both at the energy scale of future LBL experiments or at that, much smaller, of CENNS. A combined study of these two classes of experiments is quite rare in the landscape of neutrino-physics projects.
  • In the context of CENNS, BSM-Nu aims at developing a special technology in terms of background control which can really make the difference and enable the detection of this phenomenon at nuclear reactors on a few-year time scale. We remind that, in spite of the remarkable discovery of CENNS performed by the COHERENT collaboration with neutrinos in some tens-of-MeV energy range, only the detection at nuclear reactors emitting ∼ MeV neutrinos can fully deploy the new-physics potential of this phenomenon.
  • As far as neutrino-less double-beta decay (0νββ) is concerned, BSM-Nu will develop a technology potentially able to limit the contribution of the external γ background to a level below 10−4 counts/(keV kg y) in bolometric experiments, even below the end point of the natural γ radioactivity spectrum at 2615 keV. This could change completely the prospects of CUPID-like next generation experiments, leading to reconsider 130 Te as a viable isotope for 0νβ β search, despite the 0νββ signal is located at 2530 keV for this isotope. The impact would be major, as the uniquely high isotopic abundance of 130 Te (34%) make this candidate as the ideal one for practical purposes.
  • The development, commissioning and data-analysis of an innovative near detector indispensable to reconstruct, with adequate precision, the hadronic final state produced in neutrino interactions. The detector includes a new :

a. advanced pixelled plastic-scintillator detector;
b. and, for the first time, a TPC with a large-surface instrumented with resistive Micromegas detectors.

The concept will be fully tested with the T2K near detector, thus estabilishing the basis of the design of the 3DST, one of the DUNE near detectors.

  •  The construction and the operation, for the first time, of active shields in bolometric experiments directly facing the bolometric arrays inside the experimental space at millikelvin temperatures. These shields will not use phonons as detection mediators, but, more conventionally, electron-hole pairs (for CENNS) and scintillation light (for 0νββ), but they will be designed to work at 10–20 mK at which macro-bolometers are usually operated.
One important aim of the project will be the enlarging of the community in view of the renewed interest in neutrino physics and the wide variety of topics to be covered, both in terms of physics analysis and detector development. The formation will be a crucial tool to this aim.
Moreover the project aims to create a unified neutrino community in the P2IO area starting from teams active in different experiments. The various groups of the BSM-Nu consortium have developed know-how on topics like nuclear physics in neutrino interactions, statistical tools for combination of experiments, extremely low radioactive-background detectors. Such items are typically common to various neutrino experiments thus the first aim of the BSM-Nu project is to share such expertise between the various participating groups and explore further topics which are of interest for multiple experiments.
This project aims at financing several PhD and postdoc fellowships. A characteristic of the BSM-Nu is that the research activities of the fellows will span over at least two different topics among those covered by the project, with a joint supervision in order to assure a complementary formation. The purpose is to form a new generation of neutrino physicists with a wide culture and a unitary vision of the most pressing problems of this discipline.
Another element of the formation is a rich program of seminars spread over the participating laboratories. In order to enable a more strict collaboration between the different actors of neutrino physics (engineers, particle and nuclear physicists, phenomenologists), the BSM-Nu group will make a special effort to setup seminars with educational purposes and at the boundaries between different expertises.
In order to reach the described, unprecedented level of sensitivity, the next-geeration neutrino-oscillation and 0νββ experiments are characterized by a huge size, not only in terms of detector dimensions but also in terms of needed funding and international collaboration. It becomes therefore crucial to build a consortium in the P2IO perimeter to assure a proper critical mass and a visible impact of our teams in those experiments.


Web site from A.Sene (CEA, IRFU)


#39 - Last update : 10/12/2020


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