Search results for "Heavy neutrino"
showing 10 items of 14 documents
Flavour in heavy neutrino searches at the LHC
2012
Heavy neutrinos at the TeV scale have been searched for at the LHC in the context of left-right models, under the assumption that they couple to the electron, the muon, or both. We show that current searches are also sensitive to heavy neutrinos coupling predominantly to the tau lepton, and present limits can significantly constrain the parameter space of general flavour mixing.
Bounds on Neutrino-Scalar Yukawa Coupling
2015
General neutrino-scalar couplings appear in many extensions of Standard Model. We can probe these neutrino-scalar couplings by leptonic decay of mesons and from heavy neutrino search. Our analysis improves the present limits to $|g_e|^2<1.9\times 10^{-6}$ and $|g_\mu|^2<1.9\times 10^{-7}$ at 90\% C.L. for massless scalars. For massive scalars we found for the first time the constraints for $g^2_{\alpha}$ couplings to be $10^{-6}-10^{-1}$ respectively for scalar masses between below 1 MeV and for 300 MeV.
Search for heavy neutrinos at the NA48/2 and NA62 experiments at CERN
2018
© The Authors, published by EDP Sciences. The NA48/2 experiment at CERN has collected large samples of charged kaons decaying into a pion and two muons for the search of heavy nuetrinos. In addition, its successor NA62 has set new limits on the rate of charged kaon decay into a heavy neutral lepton (HNL) and a lepton, with = e, µ, using the data collected in 2007 and 2015. New limits on heavy neutrinos from kaon decays into pions, muons and positrons are presented in this report.
Search for heavy neutrinos in K + → μ + ν μ decays
2017
The NA62 experiment recorded a large sample of K+→μ+νμ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2×10−6 to 10−5 have been set on the squared mixing matrix element |Uμ4|2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/ c2 . The result extends the range of masses for which upper limits have been set on the value of |Uμ4|2 in previous production search experiments.
Search for heavy neutrinos with the T2K near detector ND280
2019
This paper reports on the search for heavy neutrinos with masses in the range 140<MN<493 MeV/c2 using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are N→ℓ±απ∓ and N→ℓ+αℓ−β(−)ν(α,β=e,μ). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heav…
Search for a right-handed gauge boson decaying into a high-momentum heavy neutrino and a charged lepton in pp collisions with the ATLAS detector at s…
2019
A search for a right-handed gauge boson WR, decaying into a boosted right-handed heavy neutrino NR, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton–proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb$^{−1}$. The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared to the expected signal. No significant d…
Beyond the Minimal Standard Model
2011
The GSW theory is a great step forward in our understanding of electroweak interactions because it allows the well-known extremely successful theory of quantized electrodynamics and the theory of the weak CC and NC interactions to be cast into one unified, renormalizable local gauge theory. Renormalizability, in particular, is a very desirable property of the theory because it makes covariant perturbation theory a reasonable and well-defined approximation method for calculating physical quantities beyond the lowest order diagrams. Nevertheless, this model, very likely, is not the corner stone of a final theory of weak and electromagnetic interactions. It contains very many parameters which …
The seesaw path to leptonic CP violation
2016
Future experiments such as SHiP and high-intensity $e^+ e^-$ colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below $M_Z$. We show that the measurement of the mixing to electrons and muons of one such state could imply the discovery of leptonic CP violation in the context of seesaw models. We quantify in the minimal model the CP discovery potential of these future experiments, and demonstrate that a 5$\sigma$ CL discovery of leptonic CP violation would be possible in a very significant fraction of parameter space.
Double beta decay in left-right symmetric models
1996
Left-right symmetric models provide a natural framework for neutrinoless double beta ($\znbb$) decay. In the analysis of $\znbb$ decay in left-right symmetric models, however, it is usually assumed that all neutrinos are light. On the other hand, heavy {\it right-handed} neutrinos appear quite naturally in left-right symmetric models and should therefore not be neglected. Assuming the existence of at least one right-handed heavy neutrino, absence of $\znbb$ decay of $^{76}$Ge currently provides the following limits on the mass and mixing angle of right-handed W-bosons: $m_{W_R}\ge 1.1 $ TeV and $\tan(\zeta) \le 4.7 \times 10^{-3}$ for a particular value of the effective right-handed neutrin…
Heavy neutrino searches at the lhc with displaced vertices
2013
Sterile neutrinos with masses in the range (1-100) GeV, have been searched for in a variety of experiments. Here, we discuss the prospects to search for sterile neutrinos at the LHC using displaced vertices. Two different cases are discussed: (i) the standard model extended with sterile neutrinos and (ii) right-handed neutrinos in a left-right symmetric extension of the standard model. A dedicated displaced vertex search will allow to probe parts of the parameter space not accessible to other searches, but will require large luminosity in both cases.