NA62 sensitivity to heavy neutral leptons in the low scale seesaw model

The sensitivity of beam dump experiments to heavy neutral leptons depends on the relative strength of their couplings to individual lepton flavours in the Standard Model. We study the impact of present neutrino oscillation data on these couplings in the minimal type I seesaw model and find that it significantly constrains the allowed heavy neutrino flavour mixing patterns. We estimate the effect that the DUNE experiment will have on these predictions. We then discuss implication that this has for the sensitivity of the NA62 experiment when operated in the beam dump mode and provide sensitivity estimates for different benchmark scenarios. We find that the sensitivity can vary by almost two orders of magnitude for general choices of the model parameters, but depends only weakly on the flavour mixing pattern within the parameter range that is preferred by neutrino oscillation data.Comment: 29 pages, 8 figures, 3 tables, version accepted by JHE

Searching for New Long Lived Particles in Heavy Ion Collisions at the LHC

We show that heavy ion collisions at the LHC provide a promising environment to search for new long lived particles in well-motivated New Physics scenarios. One advantage lies in the possibility to operate the main detectors with looser triggers, which can increase the number of observable events by orders of magnitude if the long lived particles are produced with low transverse momentum. In addition, the absence of pileup in heavy ion collisions can avoid systematic nuisances that will be present in future proton runs, such as the problem of vertex mis-identification. Finally, there are new production mechanisms that are absent or inefficient in proton collisions. We show that the looser triggers alone can make searches in heavy ion data competitive with proton data for the specific example of heavy neutrinos in the Neutrino Minimal Standard Model, produced in the decay of B mesons. Our results suggest that collisions of ions lighter than lead, which are currently under discussion in the heavy ion community, are well-motivated from the viewpoint of searches for New Physics.Comment: Version accepted by Physical Review Letters for publication as a Letter. 6 pages, 3 figure

Dissociation between spatial and temporal integration mechanisms in Vernier fusion

AbstractThe visual system constructs a percept of the world across multiple spatial and temporal scales. This raises the questions of whether different scales involve separate integration mechanisms and whether spatial and temporal factors are linked via spatio-temporal reference frames. We investigated this using Vernier fusion, a phenomenon in which the features of two Vernier stimuli presented in close spatio-temporal proximity are fused into a single percept. With increasing spatial offset, perception changes dramatically from a single percept into apparent motion and later, at larger offsets, into two separately perceived stimuli. We tested the link between spatial and temporal integration by presenting two successive Vernier stimuli presented at varying spatial and temporal offsets. The second Vernier either had the same or the opposite offset as the first. We found that the type of percept depended not only on spatial offset, as reported previously, but interacted with the temporal parameter as well. At temporal separations around 30–40ms the majority of trials were perceived as motion, while above 70ms predominantly two separate stimuli were reported. The dominance of the second Vernier varied systematically with temporal offset, peaking around 40ms ISI. Same-offset conditions showed increasing amounts of perceived separation at large ISIs, but little dependence on spatial offset. As subjects did not always completely fuse stimuli, we separated trials by reported percept (single/fusion, motion, double/segregation). We found systematic indications of spatial fusion even on trials in which subjects perceived temporal segregation. These findings imply that spatial integration/fusion may occur even when the stimuli are perceived as temporally separate entities, suggesting that the mechanisms responsible for temporal segregation and spatial integration may not be mutually exclusive

Perspectives to find heavy neutrinos with NA62

The sensitivity of beam dump experiments to heavy neutrinos depends on the relative size of their mixings with the lepton flavours in the Standard Model. We study the impact of present neutrino oscillation data on these mixing angles in the minimal type I seesaw model. We find that current data significantly constrains the allowed heavy neutrino flavour mixing patterns. Based on this, we discuss the implications for the sensitivity of the NA62 experiment to heavy neutrinos when operated in the beam dump mode. We find that NA62 is currently the most sensitive experiment in the world for heavy neutrino masses between that of the kaon and the $D$-mesons. The sensitivity can vary by almost two orders of magnitude if the heavy neutrinos exclusively couple to the tau flavour, but depends only comparably weakly on the flavour mixing pattern within the parameter range preferred by light neutrino oscillation data.Comment: Contribution to the proceedings of the 53rd Rencontres de Moriond on Electroweak Interactions and Unified Theories (2018). 6 pages, 2 figure