Abstract
Directional sensitivity to nuclear recoils would provide a smoking gun for a possible discovery of dark matter in the form of WIMPs (Weakly Interacting Massive Particles). A hint of ...directional dependence of the response of a dual-phase argon Time Projection Chamber (TPC) was found in the SCENE experiment. Given the potential importance of such a capability in the framework of dark matter searches, a new dedicated experiment, ReD (Recoil Directionality), was designed by the Global Argon Dark Matter Collaboration, in order to scrutinise this hint. A small dual-phase argon TPC was irradiated with neutrons produced by the p(
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Li,
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Be)n reaction using the 15 MV TANDEM accelerator of the INFN - Laboratori Nazionali del Sud, Catania, Italy, so as to produce argon nuclear recoils in the range (20 - 100) keV of interest for dark matter searches. Energy and direction of nuclear recoils are inferred by the detection of the elastically-scattered neutron by a set of scintillation detectors. Events were selected by gating of the associated
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Be, which is detected by a telescope of Si detectors.
The Recoil Directionality (ReD) Experiment Sanfilippo, S; Agnes, P; Albergo, S ...
Journal of physics. Conference series,
11/2022, Letnik:
2374, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Directional sensitivity to nuclear recoils would provide a smoking gun for a possible discovery of dark matter in the form of WIMPs (Weakly Interacting Massive Particles). A hint of directional ...dependence of the response of a dual-phase argon Time Projection Chamber (TPC) was found in the SCENE experiment. Given the potential importance of such a capability in the framework of dark matter searches, a new dedicated experiment, ReD (Recoil Directionality), was designed by the Global Argon Dark Matter Collaboration, in order to scrutinize this hint. Prior to the irradiation with a neutron beam, the ReD TPC underwent a long campaign of characterization and optimization: some selected results are presented in this contribution.
In the direct searches for Weakly Interacting Massive Particles (WIMPs) as Dark Matter candidates, the sensitivity of the detector to the incom- ing particle direction could provide a smoking gun ...signature for an interesting event. The SCENE collaboration firstly suggested the possible directional de- pendence of a dual-phase argon Time Projection Chamber through the columnar recombination effect. The Recoil Directionality project (ReD) within the Global Argon Dark Matter Collaboration aims to characterize the light and charge re- sponse of a liquid Argon dual-phase TPC to neutron-induced nuclear recoils to probe for the hint by SCENE. In this work, the directional sensitivity of the de- tector in the energy range of interest for WIMPs (20-100 keV) is investigated with a data-driven analysis involving a Machine Learning algorithm.
A double-phase argon Time Projection Chamber (TPC), with an active mass of 185 g, has been designed and constructed for the Recoil Directionality (ReD) experiment. The aim of the ReD project is to ...investigate the directional sensitivity of argon-based TPCs via columnar recombination to nuclear recoils in the energy range of interest (20-200 keV\(_{nr}\)) for direct dark matter searches. The key novel feature of the ReD TPC is a readout system based on cryogenic Silicon Photomultipliers, which are employed and operated continuously for the first time in an argon TPC. Over the course of six months, the ReD TPC was commissioned and characterised under various operating conditions using \(\gamma\)-ray and neutron sources, demonstrating remarkable stability of the optical sensors and reproducibility of the results. The scintillation gain and ionisation amplification of the TPC were measured to be \(g_1 = (0.194 \pm 0.013)\) PE/photon and \(g_2 = (20.0 \pm 0.9)\) PE/electron, respectively. The ratio of the ionisation to scintillation signals (S2/S1), instrumental for the positive identification of a candidate directional signal induced by WIMPs, has been investigated for both nuclear and electron recoils. At a drift field of 183 V/cm, an S2/S1 dispersion of 12% was measured for nuclear recoils of approximately 60-90 keV\(_{nr}\), as compared to 18% for electron recoils depositing 60 keV of energy. The detector performance reported here meets the requirements needed to achieve the principal scientific goals of the ReD experiment in the search for a directional effect due to columnar recombination. A phenomenological parameterisation of the recombination probability in LAr is presented and employed for modeling the dependence of scintillation quenching and charge yield on the drift field for electron recoils between 50-500 keV and fields up to 1000 V/cm.
The callosotomy on drug-resistant epileptic seizures may abolish or reduce their frequency and may modified the morphology of different kind of seizures. Our series is composed of 36 patients. ...Drop-attacks and complex partial seizures (CP) were present in all patients, generalized tonic-clonic seizures (GTC) in 16 (44.4%) and simple partial seizures (SP) and myoclonic attacks (MY) in 6 patients each. We found two kinds of modifications: a) lateralization of hypotonia which becomes hemisomatic, with lateral bending to the hypotonic side; b) different way of falling, due not only to the lateralization of hypotonia but also to the gradual impairment of muscle tone. Modifications in CP mainly concerned automatisms, which disappeared in 39.1% of patients, while 34.8% of them had a significant reduction in automatisms; this reduction consisted in simplification of automatic movements and in shorter duration of seizures.
Thirty-six drug-resistant epileptic patients submitted to callosotomy were studied. Anterior callosotomy was performed in 27 patients, total two-stage callosotomy was performed in 8 patients and 1 ...patient had only posterior callosotomy. We found mutism in 10 patients (2 after complete callosotomy and 8 after anterior section). The patients did not speak, but the comprehension was present: they were able to carry out orders and to write. Their attitude to the environment was characterized by complete indifference. The mutism was always transient, lasting from 4 to 25 days (mean 7 days). Regression of mutism was always complete. We think that this complication should be chiefly attributed mainly to surgical manipulation, even if it is impossible to completely exclude a multi-factorial etiology.
EEG Patterns after callosotomy Quattrini, A; Papo, I; Cesarano, R ...
Journal of neurosurgical sciences
41, Številka:
1
Journal Article
Recenzirano
In 36 patients with drug-resistant epilepsy submitted to anterior callosotomy (27 cases), to two-stage total callosotomy (8 cases) and to posterior callosotomy (1 case) the EEG variations concerning ...background activity, focal activity and sharp-waves (SW) bisynchronous activity were evaluated. EEG modifications observed after callosotomy are the following: background rhythm tends to be better organised as spectral analysis demonstrated, this finding usually coincide with reduction of bisynchronous discharges. It appears that improvement in background activity cannot be correlated with outcome, but it seems to be to some extent since at the same time cognitive functions also seem to improve; however, this last aspect need to be checked in much larger series. The number and location of EEG foci do not change, but they appear to be more active; this is likely to depend only on the concomitant reduction of bisynchronous activity. No correlation seems to exist between the number and the location of foci, which are generally multiple. Lateralization of bisynchronous discharges as well as the reduction of their frequency and duration were observed. However, the clinical course is quite different: in some patients we have achieved good clinical responses in others postoperative results were poor. Lateralization of bisynchronous discharges is never absolute, on the grounds that in prolonged recordings bisynchronous discharges are nearly always present. Bisynchronous discharges in some cases are alternatively predominant in both hemispheres even within minutes or seconds. It was observed that after certain time, generally some months, lateralized discharges tend to generalize again, confirming that corpus callosum is replaced in discharge diffusion by other structures (brain-stem, diencephalon).
Colloidal inks, comprised of silica microspheres with tailored attractive interactions between them, have been directly assembled via a robotically controlled deposition technique. 3D periodic ...lattices, whose periodicity far exceeds the dimensions of the colloidal building blocks (see Figure for a cross‐sectional image), were created through layer‐ by‐layer patterning of parallel rods.
