A new approach for the ortho-positronium lifetime determination in a vacuum cavity

Currently, the experimental uncertainty for the determination of the ortho-positronium (o-Ps) decay rate is at 150 ppm precision; this is two orders of magnitude lower than the theoretical one, at 1 ppm level. Here we propose a new proof of concept experiment aiming for an accuracy of 100 ppm to be able to test the second-order correction in the calculations, which is $\simeq 45\left(\frac{\alpha}{\pi}\right)^2\approx 200$ ppm. The improvement relies on a new technique to confine the o-Ps in a vacuum cavity. Moreover, a new method was developed to subtract the time dependent pick-off annihilation rate of the fast backscattered positronium from the o-Ps decay rate prior to fitting the distribution. Therefore, this measurement will be free from the systematic errors present in the previous experiments. The same experimental setup developed for our recent search for invisible decay of ortho-positronium is being used. The precision will be limited by the statistical uncertainty, thus, if the expectations are fulfilled, this experiment could pave the way to reach the ultimate accuracy of a few ppm level to confirm or confront directly the higher order QED corrections. This will provide a sensitive test for new physics, e.g. a discrepancy between theoretical prediction and measurements could hint the existence of an hidden sector which is a possible dark matter candidate.Comment: 12 pages, 8 Figures, prepared for the proceedings of the PSAS2018 conference, Vienna (Austria

Sensitivity potential to a light flavor-changing scalar boson with DUNE and NA64μ\mu

In this work, we report on the sensitivity potential of complementary muon-on-target experiments to new physics using a scalar boson benchmark model associated with charged lepton flavor violation. The NA64$\mu$ experiment at CERN uses a 160-GeV energy muon beam with an active target to search for excess events with missing energy and momentum as a probe of new physics. At the same time, the proton beam at Fermilab, which is used to produce the neutrino beam for the Deep Underground Neutrino Experiment (DUNE) will also produce a high-intensity muon beam dumped in an absorber. Combined with the liquid Argon Near Detector, the system could be used to search for similar scalar boson particles with a lower energy but higher intensity beam. We find that both NA64$\mu$ and DUNE could cover new, unexplored parts of the parameter space of the same benchmark model, providing a complementary way to search for new physics

Movement-related beta and gamma synchronization of the supplementary and primary motor cortex measured in epilepsy patients during longterm video EEG monitoring with subdural electrodes [Abstract]

Introduction: Exploration of sensorimotor integration processes during movement regulation is crucial to understand the pathophysiology of movement disorders and the effect of neuromodulation therapy. In Parkinson’s disease, dysfunction of supplementary motor cortex (SMA) has a primary role in evoking typical symptoms. In this study we detected post-movement beta (PMBS) and gamma synchronization of the SMA and primary motor cortex with electrocorticography (ECoG) in patients with epilepsy. PMBS is an electrophysiological indicator of sensorimotor integration, its parameters alter differently in several movement disorders. Methods: ECoG in 3 patients with epilepsy was recorded during invasive preoperative long-term video EEG monitoring through subdural strip and grid electrodes placed on the SMA and lobulus paracentralis and the representation field of the hand area in the primary motor cortex. Patients were requested in the interictal period to repeat short flexions of each thumb thirty times voluntarily; the trials were averaged with respect to the offset of the brisk movements. Time-frequency analysis of power was performed with multitaper method. Results: Post-movement synchronization could be detected mainly in the gamma frequency band above SMA and in the beta band above primary motor cortex. Latencies of post-movement synchronization varied in the SMA and primary motor cortex. Conclusions: Activity of the SMA in the two hemispheres cannot be detected with electroencephalography or magnetoencephalography. In our study we showed the first time that post-movement synchronization appears mainly in the gamma band in the SMA. Evaluation of the latencies supports the hypothesis that post-movement synchronization indicates a motor network activity

Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment

We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment

Spectroscopy Apparatus for the Measurement of The Hyperfine Structure of Antihydrogen

The ASACUSA CUSP collaboration at the Antiproton Decelerator (AD) of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. We describe here the latest developments on the spectroscopy apparatus developed to be coupled to the antihydrogen production setup (CUSP).Comment: Proceedings of the 11th International Conference on Low Energy Antiproton Physics (LEAP 2013) held in Uppsala, Sweden, 10 to 15 June, 201

Search for Axionlike and Scalar Particles with the NA64 Experiment

We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as shielding, and would be observed either through their $a(s)\to\gamma \gamma$ decay in the rest of the HCAL detector or as events with large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to $2.84\times10^{11}$ electrons on target allowing to set new limits on the $a(s)\gamma\gamma$-coupling strength for a(s) masses below 55 MeV.Comment: This publication is dedicated to the memory of our colleague Danila Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys. Rev. Let