Search results for "NAK"
showing 10 items of 469 documents
On Fibrations Between Internal Groupoids and Their Normalizations
2018
We characterize fibrations and $$*$$ -fibrations in the 2-category of internal groupoids in terms of the comparison functor from certain pullbacks to the corresponding strong homotopy pullbacks. As an application, we deduce the internal version of the Brown exact sequence for $$*$$ -fibrations from the internal version of the Gabriel–Zisman exact sequence. We also analyse fibrations and $$*$$ -fibrations in the category of arrows and study when the normalization functor preserves and reflects them. This analysis allows us to give a characterization of protomodular categories using strong homotopy kernels and a generalization of the Snake Lemma.
Neutrino counting experiments and non-unitarity from LEP and future experiments
2020
Non-unitarity of the neutrino mixing matrix is expected in many scenarios with physics beyond the Standard Model. Motivated by the search for deviations from unitary, we study two neutrino counting observables: the neutrino-antineutrino gamma process and the invisible $Z$ boson decay into neutrinos. We report on new constraints for non-unitarity coming from the first of this observables. We study the potential constraints that future collider experiments will give from the invisible decay of the Z boson, that will be measured with improved precision.
Heavy Neutrinos and Lepton Flavour Violation in Left-Right Symmetric Models at the LHC
2012
We discuss lepton flavour violating processes induced in the production and decay of heavy right-handed neutrinos at the LHC. Such particles appear in left-right symmetrical extensions of the Standard Model as the messengers of neutrino mass generation, and can have masses at the TeV scale. We determine the expected sensitivity on the right-handed neutrino mixing matrix, as well as on the right-handed gauge boson and heavy neutrino masses. By comparing the sensitivity of the LHC with that of searches for low energy LFV processes, we identify favourable areas of the parameter space to explore the complementarity between LFV at low and high energies.
Dirac neutrinos from flavor symmetry
2013
We present a model where Majorana neutrino mass terms are forbidden by the flavor symmetry group Delta(27). Neutrinos are Dirac fermions and their masses arise in the same way as that of the charged fermions, due to very small Yukawa couplings. The model fits current neutrino oscillation data and correlates the octant of the atmospheric angle with the magnitude of the lightest neutrino mass, with maximal mixing excluded for any neutrino mass
Search for heavy neutral lepton production in K+ decays
2018
A search for heavy neutral lepton production in $K^+$ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the $10^{-7}$ to $10^{-6}$ level are established on the elements of the extended neutrino mixing matrix $|U_{\ell 4}|^2$ ($\ell=e,\mu$) for heavy neutral lepton mass in the range $170-448~{\rm MeV}/c^2$. This improves on the results from previous production searches in $K^+$ decays, setting more stringent limits and extending the mass range.
10.8 Conclusion
2008
Analysis of the Lepton Mixing Matrix from Neutrino Oscillation Experiments
1988
An analysis of experimental results in the framework of simultaneous oscillations of three neutrino flavours is used, in a combined fit, to constrain the elements of the 3×3 unitary lepton mixing matrix and to obtain limits on the three lepton mixing angles αeμ αeτ and αμτ. No evidence for mixing is found.
Present Knowledge of the Lepton Mixing Matrix from Neutrino Oscillation Experiments
1986
An analysis of experimental results in the framework of simultaneous oscillations of three neutrino flavours is used, in a combined fit, to constrain the elements of the 3 × 3 unitary lepton mixing matrix and to obtain limits on the three lepton mixing angles αeμ, αe τ and αμτ.
Pasākumu daudzveidība LU Bibliotēkā Raiņa bulvārī: grāmatas atvēršanas svētki, dzeja, diskusijas
2017
Rakstā atspoguļoti pasākumi, kas norisinājās LU Bibliotēkā Raiņa bulvārī 2017. gadā: LU Bibliotēkas veidotās izstādes atklāšanas pasākums, veltīts Reformācijas jubilejai, grāmatas "Filipa evaņģēlijs" atvēršanas svētki, literārs pasākums kopā ar rakstniekiem Tomu Treibergu un Evu Mārtužu, Muzeju nakts pasākums u. c. notikumi.
Neural substrates for processing chemosensory information in snakes.
2002
Snakes interact with their chemical environment through their olfactory and vomeronasal systems. The present report summarizes advances on neural substrates for processing chemosensory information. First, the efferent and centrifugal afferent connections of the main and accessory olfactory bulbs were reinvestigated. Second, the afferent and efferent connections of the nucleus sphericus, the main target of the accessory olfactory bulb, were characterized. The nucleus sphericus gives rise to a very small projection to the hypothalamus, but it does project to other telencephalic structures where olfactory and vomeronasal information could converge. Third, the intra-amygdaloid circuitry and the…