A new anti-neutrino detection technique based on positronium tagging with plastic scintillators

The main signature for anti-neutrino detection in reactor and geo-neutrino experiments based on scintillators is provided by the space-time coincidence of positron and neutron produced in the Inverse Beta Decay reaction. Such a signature strongly suppresses backgrounds and allows for measurements performed underground with a relatively high signal-to-background ratio. In an aboveground environment, however, the twofold coincidence technique is not sufficient to efficiently reject the high background rate induced by cosmogenic events. Enhancing the positron-neutron twofold coincidence efficiency has the potential to pave the way future aboveground detectors for reactor monitoring. We propose a new detection scheme based on a threefold coincidence, between the positron ionization, the ortho-positronium (o-Ps) decay, and the neutron capture, in a sandwich detector with alternated layers of plastic scintillator and aerogel powder. We present the results of a set of dedicated measurements on the achievable light yield and on the o-Ps formation and lifetime. The efficiencies for signal detection and background rejection of a preliminary detector design are also discussed.Comment: 18 pages, 10 figure

Measurement of ortho-Positronium Properties in Liquid Scintillators

Pulse shape discrimination in liquid scintillator detectors is a well-established technique for the discrimination of heavy particles from light particles. Nonetheless, it is not efficient in the separation of electrons and positrons, as they give rise to indistinguishable scintillator responses. This inefficiency can be overtaken through the exploitation of the formation of ortho-Positronium (o-Ps), which alters the time profile of light pulses induced by positrons. We characterized the o-Ps properties in the most commonly used liquid scintillators, i.e. PC, PXE, LAB, OIL and PC + PPO. In addition, we studied the effects of scintillator doping on the o-Ps properties for dopants currently used in neutrino experiments, Gd and Nd. Further measurements for Li-loaded and Tl-loaded liquid scintillators are foreseen. We found that the o-Ps properties are suitable for enhancing the electron-positron discrimination.Comment: 4 pages, 1 figure. Contribution to proceedings of the Low Radioactivity Techniques 2013 Workshop at LNGS, Assergi (AQ), Italy, April 10-12 201

First operation of a liquid Argon TPC embedded in a magnetic field

We have operated for the first time a liquid Argon TPC immersed in a magnetic field up to 0.55 T. We show that the imaging properties of the detector are not affected by the presence of the magnetic field. The magnetic bending of the ionizing particle allows to discriminate their charge and estimate their momentum. These figures were up to now not accessible in the non-magnetized liquid Argon TPC.Comment: 9 pages, 3 figure

A compact light readout system for longitudinally segmented shashlik calorimeters

The longitudinal segmentation of shashlik calorimeters is challenged by dead zones and non-uniformities introduced by the light collection and readout system. This limitation can be overcome by direct fiber-photosensor coupling, avoiding routing and bundling of the wavelength shifter fibers and embedding ultra-compact photosensors (SiPMs) in the bulk of the calorimeter. We present the first experimental test of this readout scheme performed at the CERN PS-T9 beamline in 2015 with negative particles in the 1-5~GeV energy range. In this paper, we demonstrate that the scheme does not compromise the energy resolution and linearity compared with standard light collection and readout systems. In addition, we study the performance of the calorimeter for partially contained charged hadrons to assess the $e/\pi$ separation capability and the response of the photosensors to direct ionization.Comment: To appear in Nuclear Instruments and Methods in Physics Research,

First results from a Liquid Argon Time Projection Chamber in a Magnetic Field

A small liquid argon Time Projection Chamber (LAr TPC) was operated for the first time in a magnetic field of 0.55 Tesla. The imaging properties of the detector were not affected by the magnetic field. In a test run with cosmic rays a sample of through going and stopping muons was collected. The chamber with the readout electronics and the experimental setup are described. A few selected events were reconstructed and analyzed and the results are presented. The magnetic bending of the charged particle tracks allows the determination of the electric charge and the momentum, even for particles not fully contained in the drift chamber. These features are e.g. required for future neutrino detectors at a neutrino factory.Comment: 35 pages, 25 figures, version with full resolution figures at available at http://neutrino.ethz.ch/GLACIER

‘Mapping’ health state utility values from non-preference-based measures : a systematic literature review in rare diseases

Background: In rare disease (RD) studies, generic preference-based patient-reported outcome measures (PROMs) that yield health state utility values (HSUVs) are seldom collected, as they are considered not sensitive enough for these small and heterogeneous patient populations. In such cases, a HSUV can also be obtained by ‘mapping’ a more sensitive ‘source’ (e.g., disease-specific PROM) to a ‘target' preference-based measure (e.g., EuroQol-5 Dimension (EQ-5D)) through a statistical relationship. Objective: This study aimed to systematically review all published studies using ‘mapping’ to derive HSUVs from non-preference-based measures in RDs (i.e. affecting fewer than 1 in 2,000 people), and identify any critical issue related to the main features of RDs. Methods: The following databases were searched during the first half of 2019 without time, study design or language restrictions: MEDLINE (via PubMed), the School of Health and Related Research Health Utility Database (ScHARRHUD) and the Health Economics Research Centre (HERC) database of mapping studies (version 7.0). The keywords combined terms related to ‘mapping’ with ORPHANET’s list of RD indications (e.g., ‘acromegaly’), in additional to ‘rare’ and ‘orphan’. ‘Very rare’ diseases (i.e. with less than 1000 cases or families documented in the medical literature) were excluded from the searches. A predefined, pilot-tested extraction template (in Excel®) was used to collect structured information from the studies. Results: Two groups of studies were identified in the review. The first group (n=19) developed novel mapping algorithms in thirteen different RDs. As a target measure, the majority used EQ-5D, and the others the Short-Form Six-Dimension (SF-6D) and 15D; most studies adopted Ordinary Least Squares (OLS) regression. The second group of studies (n=9) applied previously existing algorithms in non-RDs to comparable RDs, mainly in the field of cancer. The critical issues relating to ‘mapping’ in RDs included the availability of very few studies, the relatively high number of cancer studies, and the absence of research in paediatric RDs. Moreover, the reviewed studies recruited small samples, hindering the cross-validation of algorithms and application of more complex regression models, showed a limited overlap between RD-specific and generic PROMs, and highlighted the presence of cultural and linguistic factors influencing results in multi-country studies. Additionally, few studies explicitly referred to published recommendations for mapping. Lastly, the application of existing algorithms in non-RDs was likely to produce inaccuracies at the bottom of the EQ-5D scale, due to the greater severity of RDs. Conclusions: More research is encouraged to develop algorithms for a broader spectrum of RDs (including those affecting young children), improve mapping study quality, test the generalizability of algorithms developed in non-RDs (e.g., HIV) to rare variants or evolutions of the same condition (e.g., AIDS wasting syndrome), and verify the robustness of results when mapped HSUVs are used in cost-utility models

Underground Neutrino Detectors for Particle and Astroparticle Science: the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER)

The current focus of the CERN program is the Large Hadron Collider (LHC), however, CERN is engaged in long baseline neutrino physics with the CNGS project and supports T2K as recognized CERN RE13, and for good reasons: a number of observed phenomena in high-energy physics and cosmology lack their resolution within the Standard Model of particle physics; these puzzles include the origin of neutrino masses, CP-violation in the leptonic sector, and baryon asymmetry of the Universe. They will only partially be addressed at LHC. A positive measurement of $\sin^22\theta_{13}>0.01$ would certainly give a tremendous boost to neutrino physics by opening the possibility to study CP violation in the lepton sector and the determination of the neutrino mass hierarchy with upgraded conventional super-beams. These experiments (so called ``Phase II'') require, in addition to an upgraded beam power, next generation very massive neutrino detectors with excellent energy resolution and high detection efficiency in a wide neutrino energy range, to cover 1st and 2nd oscillation maxima, and excellent particle identification and $\pi^0$ background suppression. Two generations of large water Cherenkov detectors at Kamioka (Kamiokande and Super-Kamiokande) have been extremely successful. And there are good reasons to consider a third generation water Cherenkov detector with an order of magnitude larger mass than Super-Kamiokande for both non-accelerator (proton decay, supernovae, ...) and accelerator-based physics. On the other hand, a very massive underground liquid Argon detector of about 100 kton could represent a credible alternative for the precision measurements of ``Phase II'' and aim at significantly new results in neutrino astroparticle and non-accelerator-based particle physics (e.g. proton decay).Comment: 31 pages, 14 figure