37 research outputs found

    Effects of electric and magnetic fields on the event reconstruction in the ICARUS T600 detector

    No full text
    In recent years, a number of anomalies in neutrino oscillation scenario were observed, that point out to possible non-standard oscillations which could imply the existence of a fourth (or more) sterile neutrino. Its existence, or absence, calls for a definitive clarification with new data. In particular, the Short Baseline Neutrino program at FNAL, will exploit three Liquid Argon Time Projection Chamber (LAr TPC) detectors along the Booster Neutrino Beamline. Each detector has different mass and a different position: the near detector SBND is the smallest, the intermediate detector MicroBooNE is the medium sized while the biggest one is the far detector, the ICARUS T600. This Ph.D. thesis is focused on the ICARUS T600 detector, the largest LAr TPC ever built, which concluded successfully the operation at LNGS in Italy. Here it was exposed at underground conditions to the CNGS beam to study oscillations. After the CNGS shut down, the detector continued taking data with cosmic rays until it was de-commissioned and transported to CERN, where it is now under refurbishment, before moving to FNAL. In a LAr TPC, when a charged particle crosses the detector, ionizing electrons are drifted towards the wire anode planes, where they are collected providing two spatial coordinates of the track; arrays of PMTs detect scintillation light, providing the measurement of the absolute time of occurrence that, combined with the knowledge of the drift velocity, permits the determination of the third coordinate of the track, that along the drift direction. The goal of the ICARUS reconstruction procedure is to extract, in an accurate way, all the physical information contained in the wire and PMT output signals, to build a complete 3D spatial and calorimetric picture of the event. To have this faithful event reconstruction, it is mandatory to determine wire and drift coordinates accurately and so it is essential to understand everything that could distort the information. The uniformity of electric field is essential in order to ensure a uniform drift velocity and thus the proportionality between drift time and drift coordinate. Electric field distortions may arise by a local accumulation, along the drift path, of positive ions, which are drifted towards the cathode more slowly than the electrons. This accumulation is emphasised by high interaction rate, given for example by high cosmic ray flux. This problem, called space charge, could be present at FNAL, where the ICARUS detector will be placed at shallow depths. In order to understand the influence of this effect in track reconstruction, a data sample is analysed, collected when the detector was at surface condition for a test run in Pavia. In the thesis are described the parameters used to study space charge effects in the ICARUS detector and the obtained results are illustrated. As stated before, the drift coordinate precision is derived by the electrons drifted towards the wire planes and it is affected by several factors, such as the diffusion. To evaluate the diffusion parameter, a dedicated run with different electric field values was performed collecting cosmic rays at the end of LNGS run. The analysis of these data samples is pointed out, considering the dependence of the width of the signal registered by the TPC. The ICARUS Collaboration is also involved in a long time project, called DUNE (Deep Underground Neutrino Experiment): it will be a long baseline experiment, with modular kiloton LAr-TPCs, to be built in the next 20 years. The T600 could be used as Near Detector, once provided with a magnetic field for particle momentum measurements and charged particle identification. The presence of a magnetic field introduces new parameters and possibilities for the reconstruction procedure. In this framework, an algorithm is developed, in order to discriminate between electron neutrino and electron antineutrino, considering their interaction products.In recent years, a number of anomalies in neutrino oscillation scenario were observed, that point out to possible non-standard oscillations which could imply the existence of a fourth (or more) sterile neutrino. Its existence, or absence, calls for a definitive clarification with new data. In particular, the Short Baseline Neutrino program at FNAL, will exploit three Liquid Argon Time Projection Chamber (LAr TPC) detectors along the Booster Neutrino Beamline. Each detector has different mass and a different position: the near detector SBND is the smallest, the intermediate detector MicroBooNE is the medium sized while the biggest one is the far detector, the ICARUS T600. This Ph.D. thesis is focused on the ICARUS T600 detector, the largest LAr TPC ever built, which concluded successfully the operation at LNGS in Italy. Here it was exposed at underground conditions to the CNGS beam to study oscillations. After the CNGS shut down, the detector continued taking data with cosmic rays until it was de-commissioned and transported to CERN, where it is now under refurbishment, before moving to FNAL. In a LAr TPC, when a charged particle crosses the detector, ionizing electrons are drifted towards the wire anode planes, where they are collected providing two spatial coordinates of the track; arrays of PMTs detect scintillation light, providing the measurement of the absolute time of occurrence that, combined with the knowledge of the drift velocity, permits the determination of the third coordinate of the track, that along the drift direction. The goal of the ICARUS reconstruction procedure is to extract, in an accurate way, all the physical information contained in the wire and PMT output signals, to build a complete 3D spatial and calorimetric picture of the event. To have this faithful event reconstruction, it is mandatory to determine wire and drift coordinates accurately and so it is essential to understand everything that could distort the information. The uniformity of electric field is essential in order to ensure a uniform drift velocity and thus the proportionality between drift time and drift coordinate. Electric field distortions may arise by a local accumulation, along the drift path, of positive ions, which are drifted towards the cathode more slowly than the electrons. This accumulation is emphasised by high interaction rate, given for example by high cosmic ray flux. This problem, called space charge, could be present at FNAL, where the ICARUS detector will be placed at shallow depths. In order to understand the influence of this effect in track reconstruction, a data sample is analysed, collected when the detector was at surface condition for a test run in Pavia. In the thesis are described the parameters used to study space charge effects in the ICARUS detector and the obtained results are illustrated. As stated before, the drift coordinate precision is derived by the electrons drifted towards the wire planes and it is affected by several factors, such as the diffusion. To evaluate the diffusion parameter, a dedicated run with different electric field values was performed collecting cosmic rays at the end of LNGS run. The analysis of these data samples is pointed out, considering the dependence of the width of the signal registered by the TPC. The ICARUS Collaboration is also involved in a long time project, called DUNE (Deep Underground Neutrino Experiment): it will be a long baseline experiment, with modular kiloton LAr-TPCs, to be built in the next 20 years. The T600 could be used as Near Detector, once provided with a magnetic field for particle momentum measurements and charged particle identification. The presence of a magnetic field introduces new parameters and possibilities for the reconstruction procedure. In this framework, an algorithm is developed, in order to discriminate between electron neutrino and electron antineutrino, considering their interaction products

    Characterization of SiPM arrays in different series and parallel configurations

    No full text
    A number of innovative experiments dedicated to neutrino and rare-event physics use liquefied noble-gases both as a target and as a detector. These media have the remarkable property to efficiently produce scintillation photons after the passage of ionizing particles. Scintillation light, which is used for triggering and timing purposes, is traditionally detected by large area Photo-Multiplier Tubes (PMTs) working at cryogenic temperature. Silicon Photo-Multiplier (SiPM) arrays are gradually substituting PMTs in many applications, especially where low voltages are required and magnetic field is present. One of the problems of this devices is the small active area. For this reason we built several prototype arrays made by different SiPM models with a common readout: the basic unit is a device with an active area of (1.2├Ś1.2)cm2 . A fast signal leading edge is crucial to realize devices to be used for triggering and timing. To this purpose we studied different series/parallel electrical configurations to obtain the best timing performance, by operating our custom arrays both at room and cryogenic temperatures

    Platelet-derived extracellular vesicles regulate cell cycle progression and cell migration in breast cancer cells

    No full text
    Platelets have been extensively implicated in the progression of cancer and platelet-derived extracellular vesicles (PEVs) are gaining growing attention as potential mediators of the platelet-cancer interplay. PEVs are shed from platelet membrane in response to extracellular stimuli and carry important biological signals for intercellular communication. In this study we demonstrate that PEVs specifically bind to different breast cancer cells and elicit cell-specific functional responses. PEVs were massively internalized by the metastatic cell lines MDA-MB-231 and SKBR3 and the ductal carcinoma cell line BT474, but not by the MCF-7 cell line. In SKBR3 cells, PEVs decreased mitochondrial dehydrogenase activities and altered cell cycle progression without affecting cell viability. Conversely, PEVs potently stimulated migration and invasion of MDA-MB-231, without affecting the distribution in the different phases of the cell cycle. In all the analyzed breast cancer cells, PEVs triggered a sustained increase of intracellular Ca2+, but only in MDA-MB-231 cells, this was associated to the stimulation of selected signaling proteins implicated in migration, including p38MAPK and myosin light chain. Importantly, inhibition of myosin light chain phosphorylation by a Rho kinase inhibitor prevented PEVs-stimulated migration of MDA-MB-231 cells. Our results demonstrate that PEVs are versatile regulators of cancer cell behavior and elicit a variety of different responses depending on the specific breast cancer cell subtype

    Amyloid precursor protein is required for in vitro platelet adhesion to amyloid peptides and potentiation of thrombus formation

    No full text
    Amyloid precursor protein (APP) is the precursor of amyloid ╬▓ (A╬▓) peptides, whose accumulation in the brain is associated with Alzheimer's disease. APP is also expressed on the platelet surface and A╬▓ peptides are platelet agonists. The physiological role of APP is largely unknown. In neurons, APP acts as an adhesive receptor, facilitating integrin-mediated cell adhesion, while in platelets it regulates coagulation and venous thrombosis. In this work, we analyzed platelets from APP KO mice to investigate whether membrane APP supports platelet adhesion to physiological and pathological substrates. We found that APP-null platelets adhered and spread normally on collagen, von Willebrand Factor or fibrinogen. However, adhesion on immobilized A╬▓ peptides A╬▓1-40, A╬▓1-42 and A╬▓25-35 was completely abolished in platelets lacking APP. By contrast, platelet activation and aggregation induced by A╬▓ peptides occurred normally in the absence of APP. Adhesion of APP-transfected HEK293 to A╬▓ peptides was significantly higher than that of control cells expressing low levels of APP. Co-coating of A╬▓1-42 and A╬▓25-35 with collagen strongly potentiated platelet adhesion when whole blood from wild type mice was perfused at arterial shear rate, but had no effects with blood from APP KO mice. These results demonstrate that APP selectively mediates platelet adhesion to A╬▓ under static condition but not platelet aggregation, and is responsible for A╬▓-promoted potentiation of thrombus formation under flow. Therefore, APP may facilitate an early step in thrombus formation when A╬▓ peptides accumulate in cerebral vessel walls or atherosclerotic plaques
    corecore