iten
Home » Evento

Tag Archives: Evento scientifico

The shape of (new) physics in the B decay anomalies

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 ...

Scopri di più »

The Precision Proton Spectrometer at the LHC

The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) is an approved project to add tracking and timing information at approximately ±210~m from the interaction point around the CMS detector. It is designed to operate at high luminosity with up to 50 interactions per 25~ns bunch crossing to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive processes. During 2016, CT-PPS took data in normal high-luminosity proton-proton LHC collisions. In the coming years, high radiation doses and large multiple-vertex interactions will represent difficult challenges that resemble those of the high-luminosity LHC program. A coordinated effort of detector upgrades with the goal of reaching the physics goals while mitigating the degradation effects is under way. The ongoing program, including the status and the planned upgrade projects for the tracking and timing detectors are discussed.

Scopri di più »

The QCD axion, precisely

The QCD axion is probably the most robust solution to the strong CP problem and a natural dark matter candidate. While its properties, such as the mass and the couplings, are mostly determined by non-perturbative QCD effects I will present recent computations demonstrating that they can be reliably extracted with percent accuracy, which is important for the theory interpretation of experimental results. I will also discuss some recent lattice QCD results highlighting a departure from the usual instanton estimates and potentially changing the prediction for the axion relic abundance substantially. In this seminar I will discuss what changes to analysis strategy and detector setup will be necessary to definitively discover or exclude the experimentally-elusive pure-higgsino thermal relic at the FCC, thus closing the window on neutralino dark matter.

Scopri di più »

Workshop on Axion Physics and Experiments

Well motivated extensions of the Standard Model of particle physics predict the existence of light particles such as axions or axion-like particles (ALPS). These particles may constitute the long sought dark matter, solve the strong-CP problem and explain astrophysical anomalies. Contrary to the WIMPs (weakly interacting massive particles), WISPs (weakly interacting slim particles) are hardly observable at large colliders and new experiments involving a wide range of different technologies are needed. Present experiments aim at observing WISPs as a dark matter constituent, as radiation emitted from astronomical objects, or as radiation produced in the laboratory. In all the cases present and future experiments push the technology needed for detection and production of these particles to the state of the art or beyond. During the workshop we will review the status of ongoing and foreseen experiments, discuss of possible new physics at low energy scale that can be probed in such experiments and examine present and future developments of related key technologies.  

Scopri di più »

Enhancement of Superconductivity by Shape Resonances in Nanostructured Materials

Ultrathin superconductors of different materials are becoming a powerful platform to find mechanisms for enhancement of superconductivity, exploiting shape resonances in different superconducting properties. Since 2004, the observation of shape resonances in superconducting nanofilms of Pb and first evidences of shape resonances in the superconducting critical temperature in metallic nanowires of Sn and Al [1–2] clearly established the importance of the interplay between quantum size effects, leading to multiple bands, and superconductivity, when the lateral dimensions of the system are reduced to the order of the interparticle distance or the pair correlation length. Moreover, superconductivity in iron-based, magnesium diborides, and other high-Tc superconductors has a strong multi-band and multi-gap character [3,4]. Recent experiments support the possibility for a BCS-BEC crossover induced by the proximity of the chemical potential to the band edge of one of the bands, with evidences for Lifshitz transitions associated with changes in the Fermi surface topology [5, 6]. Here we present the simplest theoretical model which accounts for superconducting shape resonances and the BCS-BEC crossover in a multi-band / multi-gap superconductor, considering tunable interactions and nanostructured geometries. When the gap is of the order of the local chemical potential, superconductivity is in the crossover regime of the BCS-BEC crossover and the Fermi surface of the small band is completely smeared by the gap opening. In this situation, small and large Cooper pairs coexist in the total condensate, which is the optimal condition for high-Tc or even for room temperature superconductivity [7,8]. As a realizable example of ...

Scopri di più »

QCD precision calculations for Higgs and vector boson production at the LHC

We study the effect of QCD radiative corrections to the production of Higgs and W/Z bosons in hadron collisions. We consider the next-to-next-to-leading order (NNLO) QCD corrections at fully-differential level and discuss the resummation of the logarithmically-enhanced QCD contributions at small transverse-momentum. We show selected numerical results at the LHC.

Scopri di più »

Closing the window for compressed Dark Sectors at hadron colliders.

Compressed dark sectors, with invisible decay products, are notoriously hard to probe at hadron colliders, particularly in the region of masses that are most relevant for thermal relics. Current search strategies rely mainly on hard radiation off the initial state. If the compressed sector contains an electrically-charged state, it is also possible to search for charged tracks that ‘disappear’ within the collider volume. A well-motivated example of a framework that contains such particles is the Minimal Supersymmetric Standard Model in the pure higgsino or wino limits. The current hadron-collider search strategy has no sensitivity to the upper range of pure higgsino masses that are consistent with the thermal relic density, even at a future circular collider (FCC) at 100~TeV centre-of-mass – the proper lifetime of its charged component, at around 10 picoseconds, is too short to be detected. In this seminar I will discuss what changes to analysis strategy and detector setup will be necessary to definitively discover or exclude the experimentally-elusive pure-higgsino thermal relic at the FCC, thus closing the window on neutralino dark matter.

Scopri di più »

The TwinMic spectromicroscopy beamline at Elettra: recent achievements and future perspective

Characterisation and exploiting properties of complex materials with high spatial resolution requires the deployment of multidisciplinary techniques and expertise. Soft X-ray microscopy, combining imaging and spectroscopy at sub-micron scales, has already been recognised as a powerful technique proving both morphological and chemical information. The TwinMic microscopy station [1] operated in the 400-2200 eV energy range at the Elettra synchrotron has been attracting different scientific community, from Life Sciences to Cultural Heritage and Material Science, thanks to its complementary imaging capabilities (brightfield and phase contrast) with spatial resolution down to sub 20nm with special CDI methods, combined with low energy X-ray Fluorescence (XRF) [2, 3] and X-ray absorption microspectroscopy. Unique feature is that the developed low energy XRF system enables monitoring light elements down to B. The presentation will use selected representative results to illustrate the recent achievements in the fields of neuroscience [4], nanotoxicology [5], clinical medicine [6,7], environmental science [8] and electrochemistry [9]. The progress in implementation of novel TwinMic imaging modalities for pushing the lateral resolution has recently been demonstrated by ptychography experiments with biological samples [10, 11]. Finally the first results of an on-going low energy XRF system development will be presented and discussed [12].

Scopri di più »

SISSI-BIO: THE CHEMICAL AND LIFE SCIENCES BRANCH OF THE IR BEAMLINE AT ELETTRA – SINCROTRONE TRIESTE

SISSI (Synchrotron Infrared Source for Spectroscopy and Imaging) is the infrared beamline at Elettra Sincrotrone Trieste. It extracts the IR and visible components of synchrotron emission for performing spectroscopy, microspectroscopy and imaging at the two SISSI branches: SISSI-Mat (IOM-CNR, Sapienza) and SISSI-Bio (Elettra). The applications cover a wide range of research fields, including surface and material science, high-pressure experiments, geology, cultural heritage, biochemistry, cellular biology, etc. The present talk aims to provide an overview of the actual beamline status, focusing on the equipment and potentialities of SISSI-Bio branchline. Selected examples of both user and in-house research activities at SISSI-Bio will be presented, covering fields of science such as in-situ cell sorting according to cell-cycle phases by FTIR microscopy and X-ray radiation damage probed by non-damaging IR beams. An overview of the planned upgrades of SISSI will be also provided, in order to explore potential synergisms with LNF, encompassing both technical developments and scientific topics. LISA VACCARI1 AND GIOVANNI BIRARDA1 1) Elettra Sincrotrone Trieste, SS 14 Km 143.5 34149 Trieste, ITALY

Scopri di più »

X-ray computed tomography using synchrotron sources and advanced lab setups for comprehensive microstructural properties of materials and biomaterials

Imaging techniques based on the use of hard X-rays play an important role in several research fields and industrial applications. Many topics in medicine, biology, material science, geosciences and cultural heritage studies can be afforded thanks to the high potential and large applicability of X-ray imaging. In the last twenty years a great interest has been devoted to the development of X-ray computed microtomography (micro-CT) techniques, both employing microfocus and synchrotron radiation sources. These techniques allows to produce 3D or 4D (dynamic micro-CT) images of the internal structure of objects at the micron- and submicron- scale. Investigations performed directly in the 3D domain overcome the limitations of stereological methods usually applied to microscopy-based analyses and a non-destructive method is more suitable for further complementary analyses and for precious or unique samples (fossils and archeological finds, in-vivo imaging, etc …). An intriguing challenge is to extract directly from 3D and 4D images quantitative parameters related to the physical properties of the studied materials. However, accurate image processing, analysis and visualization methods for an effective assessment of these parameters are still an open issue especially in the case of 4D micro-CT experiments. In this talk, several scientific applications of advanced hard X-ray imaging techniques will be presented trying to critically expose advantages, limitations and open problems in the different fields.

Scopri di più »