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| Mohapatra–Valle | |
|---|---|
| Name | Mohapatra–Valle |
| Field | Particle physics |
| Introduced | 1980s |
| Key persons | Rabindra N. Mohapatra, J. W. F. Valle |
| Applications | Neutrino mass models, lepton number violation, seesaw mechanisms |
Mohapatra–Valle is a theoretical framework in particle physics proposing a class of mechanisms for generating small neutrino masses through extended seesaw structures and lepton-number–violating interactions. It interrelates ideas from the type I seesaw, type II seesaw, and inverse-seesaw approaches and connects to models invoked in studies of grand unification, left–right symmetry, and supersymmetry. The construction has been applied across contexts including neutrinoless double beta decay, lepton flavor violation, and collider phenomenology.
The proposal emerged amid efforts to explain results from the Homestake experiment, GALLEX, SAGE, and later Super-Kamiokande anomalies in solar and atmospheric neutrino fluxes, while reconciling findings from LSND and MiniBooNE. Early motivations drew on the need to embed tiny neutrino masses into frameworks like the Pati–Salam model, SO(10), and left–right models without invoking ultra-heavy right-handed neutrino scales incompatible with collider tests at facilities such as the Large Hadron Collider and proposed International Linear Collider. Connections were explored with proposals by Steven Weinberg, Peter Minkowski, T. Yanagida, Gell-Mann, Ramond and Slansky, and later work by Mohapatra and Senjanović.
The formalism extends the standard type I seesaw Lagrangian by introducing extra gauge-singlet fermions and small lepton-number–violating mass parameters, producing an effective light-neutrino mass matrix via a generalized inverse-seesaw pattern. It typically involves interactions with scalar multiplets from representations present in SO(10), SU(5), or Pati–Salam embeddings and can be implemented in supersymmetric contexts like the Minimal Supersymmetric Standard Model augmented by singlets. The construction employs mass matrices mixing left-handed neutrino fields, heavy right-handed neutrino states, and sterile singlets, yielding suppressed eigenvalues akin to mechanisms in the linear seesaw and inverse seesaw proposals by authors such as Gonzalez-Garcia and Valle. Gauge structure realizations use groups explored by Mohapatra, Senjanović, Foot, Heeger, and model-building techniques parallel to those in Fritzsch-type textures and Casas–Ibarra parameterization treatments.
Predictions include small but potentially observable rates for neutrinoless double beta decay mediated by light and heavy neutrino exchange, altered patterns in neutrino oscillation parameters measured by experiments like T2K, NOvA, DUNE, and JUNO, and possible signals in charged lepton flavor violation channels such as μ→eγ probed by MEG and μ→e conversion searched for by Mu2e and COMET. There are implications for cosmology through contributions to the effective number of neutrino species relevant to Planck and WMAP data, and for baryogenesis via low-scale leptogenesis scenarios connected to work by Fukugita and Yanagida. Collider signatures may include heavy neutral lepton production with displaced vertices at the ATLAS and CMS experiments, resonances akin to those in Z' models when embedded in extended gauge groups, and scalar-sector modifications comparable to expectations from Higgs-portal models.
Constraints derive from global fits to oscillation data compiled by groups such as NuFIT and from direct searches for heavy neutral leptons at LEP, LHCb, ATLAS, and CMS, as well as fixed-target experiments like PS191 and CHARM. Limits on lepton-number–violating processes from GERDA, KamLAND-Zen, and EXO-200 restrict parameter space relevant to the mechanism. Precision electroweak bounds from LEP and flavor constraints from BELLE and BaBar further shape viable model realizations, while cosmological limits from Planck and structure-formation studies impose bounds on sterile states. Ongoing and planned facilities such as DUNE, Hyper-Kamiokande, SHiP, and proposed intensity-frontier programs target key regions of parameter space.
Variants include embedding the mechanism into SO(10) or E6 unified frameworks, supersymmetric extensions like the NMSSM-inspired implementations, and combinations with radiative neutrino mass models (for example those by Ma). Other extensions couple the construction to dark-sector portals involving axion or sterile neutrino dark-matter proposals studied by groups working on warm dark matter and keV sterile neutrinos. Model-building adaptations adopt family symmetries such as A4, S4, and U(1) flavor charges to address mixing-angle patterns explored by King, Altarelli, and Feruglio.
The framework is named for key contributions by Rabindra N. Mohapatra and J. W. F. Valle, building on foundational seesaw work by Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, and the left-right analyses of Mohapatra and Senjanović. Subsequent theoretical and phenomenological development involved researchers including Steve King, Enrique Fernandez-Martinez, Gonzalez-Garcia, Werner Rodejohann, Sergio Pastor, Asimina Arvanitaki, and experimental liaison with collaborations like Super-Kamiokande, SNO, KamLAND, and IceCube. The evolution of the approach paralleled advances in neutrino oscillation discoveries and technological progress at CERN, Fermilab, and underground laboratories such as Gran Sasso and Sudbury.
Category:Neutrino physics Category:Particle physics models