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Drivers of persistent marine heatwaves in the Mediterranean in recent years
Get PDFThe Mediterranean basin has experienced several marine heatwaves (MHWs) over the last few decades. During MHWs anomalous warm ocean temperatures are present for several days at least and can influence atmospheric circulation and negatively affect ecosystems. There is increased interest in these events as they occurred more frequently and with larger severity, fuelled by global warming trends. Here we examine the strong Mediterranean MHW of 2022, which started in May and lasted for several months. This MHW event rapidly spread through western and central Mediterranean with peak intensity at par with the record-breaking 2003 event. In this communication we focus on the drivers of the prolonged 2022/2023 case which led to its exceptional duration. We find that persistent anticyclonic conditions, that continued through fall and winter, were responsible for the persistence of the 2022/23 MHW. We also discuss recent Mediterranean conditions by analyzing near real-time observational products, and discuss the possible impacts of global warming on MHW characteristics
Developing a data-driven method to constrain the antiproton background in the Mu2e experiment
Get PDFThe Mu2e experiment will search for CLFV neutrinoless coherent muon to electron conversion in the field of an Al nucleus. The expected signal is a 104.97 MeV/c monochromatic e- (CE). CE-like e-’s could also come from p ̄’s annihilating in the Stopping Target (ST). The background induced by p ̄’s is expected to be low but has a large systematic uncertainty. It cannot be suppressed by the time window cut used to reduce the prompt background. However, pp ̄ annihilation in the ST is the only source of events in the Mu2e detector with multiple tracks coming from the ST, simultaneous in time, each with a momentum in the signal window region. We exploited this unique feature and developed algorithms to identify and reconstruct multi-track events. This paper discusses the status and prospects of this data-driven method to constrain the p ̄ background at Mu2e
Mechanical design of the interaction region of the Future Circular Collider e+e− and support structural optimization
Get PDFWe describe the vacuum chamber of the Future Circular Collider e+ e− interaction region, the conceptual design of the bellows and the lightweight structure called Support Tube. We also present a study on the structural optimization of the support structure. The aim is to optimize the structure to reduce the mass, maintaining the stiffness needed. Finite element analysis is used to develop a detailed numerical model considering complex geometries, material properties, and loading conditions. The study seeks to identify design improvements using optimization algorithms, such as Solid Isotropic Material with Penalization, Generative Design and Lattice approach
γ decay of giant resonances to low-lying states
Get PDFWith growing studies on giant resonances, the deep insight about their damping mechanisms draws more and more attentions. Here we provide an alternative way to study the detailed structures of giant resonances apart from the wavelet analysis of the high-resolution strength distribution, including isospin prop- erties and wavefunctions, the latter of which indicates the main damping mechanism of giant resonances. We utilize a fully self-consistent random phase approximation (RPA) + particle vibration coupling (PVC) model to calculate the γ decay width based on Skyrme density functional. We find that the complex configuration, i.e., one-particle one-hole coupled with phonon, has much larger component in the wave- function of GQR than that of GDR, which indicates the main damping mechanisms in these two modes are different
Resonance via (d,p) reactions
Get PDFThe low-lying E1 strength below, around, and partially above the neutron-separation threshold, Sn, is often referred to as Pygmy Dipole Resonance (PDR). At the moment, it is not clear whether the PDR is a collective excita- tion mode and whether it is a general feature of the γ-ray strength function, which needs to be answered to reliably calculate capture rates for nucleosynthesis processes when using statistical Hauser-Feshbach approaches. To further understand the mi- croscopic origin of the PDR and possible cancellation effects between isovector E1 matrix elements, which appear to be strongly model-dependant, an experimental program studying the neutron one-particle-one-hole (1p-1h) structure of the PDR via (d,p) and (d,pγ) reactions was started. Some results of the already published work will be discussed and additional remarks, including future plans, are made
Overview of the experimental quest for the giant pairing vibration
Get PDFThe search for the giant pairing vibration (GPV) has a long standing history since the 1970’s when it was predicted. First experimental measurements focused on (p,t) transfer reactions in the heavy nuclei and did not show convincing evidence. The discovery of a signal compatible with the GPV in the light carbon isotopes has renewed the interest for the GPV. It triggered new theoretical models showing that the GPV in the heavy nuclei might be too wide or too melted to be observed and triggered new experiments with radioactive probes based on (6He,4He) transfer
Overview and performance of the 2023 MUGAST@LISE campaign at GANIL
Get PDFMUGAST is a state-of-the-art silicon array combining trapezoidal and square shaped double-sided silicon strip detectors (DSSD) to four MUST2 tele- scopes. Coupled to a γ-ray spectrometer, the excellent angular coverage and com- pacity of the MUGAST array make it an ideal tool for the study of transfer reactions. It is a first step toward the development of the new generation of silicon arrays us- ing pulse shape analysis (PSA) for particle identification, such as the future GRIT array developed by our collaboration. In recent years, MUGAST has been widely used at GANIL. First with the AGATA γ-ray spectrometer and the VAMOS large acceptance spectrometer for the study of ISOL beams from the SPIRAL1 facility. It is now coupled with twelve EXOGAM clovers and to a new zero degree detection system at the end of the LISE fragmentation beamline
From KATRIN to TRISTAN: Neutrino mass and sterile neutrinos
Get PDFKATRIN (Karlsruhe Tritium Neutrino Experiment) is an experiment built to perform a high-statistics and high-resolution measurement of the endpoint region of the Tritium β spectrum, with the main goal of measuring the neutrino mass. KATRIN holds the world-leading limit on the neutrino mass of 0.8 eV as a result of the joint analysis of the first two measurement campaigns. After KATRIN’s data taking, a new phase with an upgraded detector, called TRISTAN, is planned. This new detector will sustain a higher count rate, allowing a high-statistics measurement of the whole spectrum. The main target is the search for new physics, like sterile neutrinos with mass in the keV-range, which are candidates to be Dark Matter particles
Neutrinoless double beta decay: A brief view of the field
Get PDFForemost among the open questions regarding neutrinos are whether they are their own anti-particles, hence Majorana fermions, and the magnitude of their rest mass, in particular also why they are so much lighter than the charged leptons. The most sensitive probe of the Majorana nature of neutrinos is a remarkable rare nuclear transition, neutrinoless double beta decay (0νββ), in which two electrons and no neutrinos are emitted. Its observation would not only demonstrate that neutrinos are Majorana fermions, but would also establish lepton number violation. A large number of 0νββ-decay experiments, using different candidate isotopes and detection techniques for the two outgoing electrons, are operational or planned to be constructed in deep-underground laboratories. Their extraordinary goal is to observe but a handful of events at the Q-value of the decay, and thus to reduce radioactivity-induced backgrounds to unprecedentedly low levels. Current results limit the 0νββ-decay half-lives to values larger than 1025−26 years, while experiments taking data, under construction or in advanced planning stage aim to probe the 1027−28 years regime. In parallel, new ideas on the possibility to build much larger detectors to explore the half-life regime beyond 1028−29 years are being put forward. Here we give a brief view of the current status of the field, and of future developments including the main experimental challenges