Tag Archives: Evento scientifico

Photocathode technology in accelerator science is an exciting and growing field of research and development. Prior to the first implementation of a photocathode in the RF gun operated at Los Alamos National Laboratory in 1985, thermionic cathodes were typically used in electron guns. Switching from the thermionic cathode to a laser driven photocathode offered a monumental improvement in the overall beam quality. With the advent of the photoinjector, the emittance reduced by over a factor of 10, compared with a thermionic injector. Photocathode research is increasingly important to meet the demands of modern accelerators. In linear accelerator driven 4th generation Free Electron Lasers, the final beam quality is set by the linac and ultimately by its photoinjector and photocathode. Therefore, to deliver cutting-edge beam characteristics, linac based sources have stringent requirements particularly with respect to the photocathode used in the photoinjector. Understanding how surface properties of materials influence photocathode properties such as Quantum Efficiency (QE) and intrinsic emittance is critical for such sources. Metal cathode R&D at Daresbury Laboratory (DL) is driven by our on-site accelerators VELA (Versatile Electron Linear Accelerator) and CLARA (Compact Linear Accelerator for Research and Applications); the Free Electron Laser test facility at DL. Metals offer the advantage of a fast response time which enables the generation of short electron pulses. Additionally, they are robust to conditions within the gun cavity. In this work, the effect of different preparation procedures on the surface composition, work function and QE was investigated for a range of metal photocathode …

Aim of the workshop: Strongly-interacting matter at extreme conditions of temperature and density is a major subject of research in both theoretical and experimental communities. Experiments with ultra-relativistic nuclei at RHIC and LHC create matter at extremely high temperatures, where quark-gluon plasma is formed and studied, reproducing in laboratory conditions which were realized  in the Early Universe. According to the Big Bang Theory this state of matter existed in the Universe roughly between 20 pico-s and 20 micro-s after the BigBang. At a very high density, a cold quark-gluon plasma as well as other exotic phases (quarkyonic, colour superconducting) might exist in the core of neutron stars, outside the reach of current experiments. The analysis of strongly-coupled systems requires non-perturbative methods such as lattice QCD or functional renormalization group. These studies have provided information of the phases and thermodynamics of QCD at equilibrium. On the other hand, the state of matter produced in ultra-relativistic heavy-ion collisions reaches equilibrium only for a very short time. It is a major challenge of contemporary studies to develop theoretical and phenomenological tools which link the experimental observations with the predictions of the fundamental theory at equilibrium. The aim of this 3-day meeting is to convene experts to stimulate an informal discussion on hot QCD and related topics. We plan to have only three talks each day, and plenty of time to discuss some of the open issues in heavy-ion theory and measurements. The equation of state of nuclear matter and its relation with the …

I will discuss the ongoing experiments (CASPEr and GNOME) searching for ultralight galactic dark matter using magnetic-resonance techniques. I will also discuss testing fundamental symmetries of Nature using spectroscopic techniques, including the search for new particles and forces, measuring parity violation in atomic and molecular systems, and testing the permutation-symmetry postulate and the spin-statistics connection in atomic transitions.

Aim of the workshop: The Spring Institute will gather theorists and experimentalists, working mostly in the Rome area in the field of collider physics. In an informal environment, we shall investigate a few selected topics on possible tests of the Standard Model and its extensions after the discovery of the Higgs boson. In particular, we will discuss of recent progresses in effective field theories, of the trilinear Higgs self-coupling, as well as of the hunting for heavy resonances at the LHC, from both experimental and theoretical viewpoints.  

Quarks and neutrinos are known to change flavors, but what about the charged leptons? The proposed Mu2e experiment at Fermilab will offer a sensitivity to charged-lepton flavor violating processes four orders of magnitude better than anything to have come before it. This extraordinary improvement in sensitivity will give Mu2e significant discovery potential over a wide range of new physics models. Moreover, Mu2e probes for this new physics in a manner complementary to the rest of the world’s HEP physics program at effective mass scales approaching 10,000 TeV. The physics motivations, design sensitivity, and status of the Mu2e experiment will be presented.

2017 Annual General Meeting reviewing the activities supported by the MUSE project. MUSE is a EU funded project under the Horizon 2020 Research and Innovation program, Grant Agreement 690835. It coordinates the activities of about 70 researchers from various European research institutes (INFN, University College London, University of Liverpool, Helmholtz-Centrum Dresden-Rossendorf, Fermilab) and industries (PRISMA, CAEN, AdvanSid) for the participation to the experiments at the Muon Campus of the Fermi National Laboratory (FNAL), in USA. The meeting will be held at the Frascati National Laboratory of INFN.

High-precision measurements of flavour-changing processes are sensitive to the virtual effects of particles at energies beyond the reach of current colliders; thus, any New-Physics addressing the hierarchy problem of the electroweak scale must have a non trivial structure in flavour space to avoid all the stringent flavour constraints. In fact, although no new heavy particles have been identified in the high-energy frontier yet, there are tantalizing tensions with the SM in B-meson decays measured at the LHCb and B factories. The first type of anomalies appear in observables of the FCNC rare b→s ll decays, like in the angular distributions of B→K*μ μ, or in the ratio RK = Γ(B→K μ μ) / Γ(B→K e e) . These are currently in 4σ tension with the SM, putatively corresponding to the tree-level exchange of a neutral particle with mass Λ ~ 10 TeV selectively coupling to muons. The second type of anomalies appear in the CC b→ c τ ν transitions which have been measured through the ratios RD(*) = Γ(B→D(*) τ ν)/ Γ(B→D(*) l ν), where l is the muon or the electron. The average of the measurements is enhanced with respect to the SM and it would correspond to the tree-level exchange of a charged particle with mass Λ ~ 1 TeV and coupled selectively to τ leptons. In this talk I will review these decays, discussing the extent up to which the SM predictions are understood and the type of new physics one would need to explain the …

The lecture is devoted to a quantum mechanical consideration of the transmission of positrons of a kinetic energy of 1 MeV through very short (11, 9) single-wall chiral carbon nanotubes. The nanotube lengths are between 50 and 320 nm. The transmission process is determined by the rainbow effects. The interaction potential of a positron and the nanotube is deduced from the Molière’s interaction potential of the positron and a nanotube atom using the continuum approximation. The time-dependent Schrödinger equation is solved numerically, and the spatial and angular distributions of transmitted positrons are calculated. The initial positron beam is assumed to be an ensemble of non-interacting Gaussian wave packets. The spatial and angular distributions are generated using a computer simulation method. The examination is focused on the spatial and angular primary rainbows. It begins with an analysis of the corresponding classical rainbows, and continues with a detailed investigation of the amplitudes and phases of the wave functions of transmitted positrons. These analyses enable one to identify the principal and supernumerary primary rainbows appearing in the spatial and angular distributions. They also result in a detailed explanation of the way of their generation, which includes the effects of wrinkling of each wave packet during its deflection from the nanotube wall, and of its concentration just before a virtual barrier lying close to the corresponding classical rainbow. The wrinkling of the wave packets occurs due to their internal focusing. In addition, the wave packets wrinkle in a mutually coordinated way.

Recent theoretical developments highlight a set of shared principles underpinning macroscopic quantum coherence in high temperature superconducting (HTSC) materials and the emergence of long-range order and macroscopic quantum coherence phenomena such as photosynthesis in biological structures. Preliminary investigations suggest that the emergence of functionality and structure in these systems is driven by dissipative processes, which lead to fractal assembly and a fractal network of charges (with associated quantum potentials) at the molecular scale. At critical levels of charge density and fractal dimension, a percolation threshold is reached where individual quantum potentials merge to form an infinitely interconnected `charged-induced’ macroscopic quantum potential (MQP), which can be viewed as a macroscopic path integral. The process by which a MQP acts as a structuring force (in competition with environmental perturbation) dictating the emergence of structure and function in biological and inorganic systems will be described within the context of a new set of macroscopic quantum mechanics processes. Specific issues to be highlighted include the emergence of different phases (coherent electron pairs, Charge Density Waves and Spin Density Waves) observed in complex HTSC materials. The macroscopic quantum processes that underpin these different phenomena will be compared and contrasted with standard quantum mechanics to highlight the extent of commonality (and key differences) between the two quantum systems. Within the context of these new theoretical developments we consider a new experimental approach to the development of inorganic structures and macroscopic coherent systems, analogous to those emerging through biological processes. It is anticipated that this work will …