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The path to the “ideal” brain PET imager: The race is on, the role for TOF PET
No full textWith the efforts under way to improve spatial resolution of the revolutionary Explorer family of imagers, the acute need to develop dedicated imagers for breast, prostate, heart, etc. may slowly disappear, except for some specialized cases in treatment guidance and monitoring, for example in proton therapy. It is in fact happening already. Part of the reason is the high cost of the dedicated systems but also an intriguing emerging opportunity that long axial length PET scanners can be equipped with magnifying inserts that can locally boost the resolution, as per the so-called virtual pinhole concept by Yuan-Chuan Tai from WashU, also called Zoom-in PET. However, the exception are the brain imaging scanners. The special geometry of the optimal helmet type designs for imaging of the brain still gives the
opportunity to the brain PET imager developers to compete for the “best” system. We all want to produce good quality dynamic molecular PET brain images at low injected radiation doses (and... low cost). Several designs are being proposed as well as being built at this time in many places around the world. These designs mostly fall in two categories: 1) the mini-Explorer cylindrical type or 2) the compact helmet type, both with large angular brain coverage assuring high sensitivity. Due to the compact sizes of the helmet-type systems, in order to substantially benefit from the improved TOF performance, one needs to achieve better than 100 ps FWHM timing performance. In fact, 50 ps FWHM would be a very nice goal. Several groups are working on such concepts. In this race, any new ideas from the expert instrumentation community (not only the medical one) are highly encouraged, as a great impact is expected on brain imaging once such high-performance but also dissemination-ready (i.e., robust and economical) designs are developed. Ideally, the brain imagers of the next generation will have high sensitivity and high spatial resolution approaching the predicted physical limit (due to positron range plus non-collinearity of the two emitted annihilation photons), limited to about 1 mm FWHM. Interestingly, there is a known connection between spatial resolution and sensitivity in detecting small lesions or structures, through the Partial Volume Effect (PVE). The adversarial effect of poor resolution on the detection of small structures is the blurring of the signal with the background. Inversely, if there is not enough statistics (detected/recorded events) per reconstruction voxel, even the best spatial resolution will not bring the tomographic uptake signal above the noisy background
Precision measurement of cosmic-ray nuclei with the alpha magnetic spectrometer on the International Space Station
No full textThe measurement of the nuclei component in cosmic rays (CR) provides a detailed knowledge of the origin and propagation of cosmic rays. AMS02 is a magnetic spectrometer designed to perform precision measurment of the composition and energy spectrum of cosmic rays from GeV to TeV. Using its large acceptance and long exposure time, AMS-02 is able to measure the fluxes of CR species at least up to iron, studying also the detailed variation of their spectral index as a function of the rigidity. AMS-02 was installed onboard the International Space
Station on May 19, 2011 and has been continuously taking data since then. In 8 years of operations, it collected over 135 billion of cosmic-ray triggers, both primary and
secondary. Primary cosmic rays, such as H, He, C, N and O, are mainly produced and accelerated by supernova explosions, while secondary cosmic rays, such as Li, Be
and B are produced through collisions of heavier nuclei with the interstellar medium. In this contribution, the published results regarding the nuclear component of CR
from hydrogen to oxygen, for rigidity interval between 2 GV and 3.3 TV, have been presented. The contribution will also show the preliminary measurement of the temporal evolution of carbon and oxygen fluxes, during the period between May 2011 and May 2018. This measurerement can provide important information about the propagation of CR inside the heliosphere
Search for four-top-quark production in the single-lepton and opposite-sign dilepton final states in proton-proton collisions at √s = 13 TeV with the ATLAS detector
No full textRecent published results on a search for four-top-quark production, tttt, are presented, based on a dataset collected at √s = 13 TeV with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb−1. The single-lepton and opposite-sign dilepton final states are analysed. The search exploits the high multiplicity of jets/b-tagged jets and the large total sum of jet transverse momenta, which characterise signal events and provide a good discrimination against the tt+jets dominant background, which is estimated through a data-driven method. No significant excess above the Standard Model expectation is observed
Precision anomalous triple gauge coupling measurements at hadron colliders
No full textWe discuss the measurements of the anomalous triple gauge couplings at Large Hadron Collider focusing on the contribution of the O3W and O3W˜ operators. These deviations were known to be particularly hard to measure due to their suppressed interference with the SM amplitudes in the inclusive processes, leading to approximate flat directions in the space of these Wilson coefficients. The prospects for the measurements of these interactions are discussed, for HL-LHC and HE-LHC, using exclusive variables sensitive to the interference terms and taking carefully into account effects appearing due to NLO QCD corrections
Observation of direct CP violation in D0 meson decays at LHCb
No full textA search for charge-parity (CP) violation in D0 → K−K+ and
D0 → π−π+ decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb−1 collected at a center-of-mass energy of 13 TeV with the
LHCb detector. The flavor of the D0 meson is determined from the charge of the pion in D∗(2010)+ → D0π+ decays or from the charge of the muon in B → D0μ−ν¯μX decays. The difference between the CP asymmetries in D0 → K−K+ and D0 → π−π+ decays is measured to be ΔACP = [−18.2 ± 3.2 (stat.) ± 0.9 (syst.)] × 10−4 for πtagged and ΔACP = [−9±8 (stat.)±5 (syst.)]×10−4 for μ-tagged D0 mesons. The
combination with previous LHCb results leads to ΔACP = (−15.4 ± 2.9) × 10−4, where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than five standard deviations, corresponding to the first observation of CP violation in the decay of charm hadrons
K+ → π+νν¯ measurement at the NA62 experiment
No full textThe high precision of the theoretical prediction and the strong suppression make the ultra-rare kaon decay K+ → π+νν¯ an excellent probe for new physics. The NA62 experiment at CERN SPS aims to measure BR(K+ → π+νν¯) with a 10% precision. NA62 collected data in 2016, 2017 and 2018. The 2016 data has been analyzed and the result published: one candidate signal event was found, showing that the decay-in-flight techinque works. The 2017 sample is currently under analysis and 2.5 ± 0.4 Standard Model signal events are expected, while the background is still under study
Leptoquarks in B-meson anomalies: Simplified models and HL-LHC discovery prospects
No full textI will review simplified models with leptoquarks, which can explain recent anomalies in B-meson physics, and I will indicate the High-Luminosity LHC prospects for testing these theories, with a special focus on the efficient channel of
pair leptoquark production in the tt ¯ plus missing energy final state
Assembly of the SM1 MicroMegas chambers for the muon spectrometer upgrade of the ATLAS experiment at LHC
No full textMicroMegas (MICRO MEsh GAseous Structure) detectors have
been chosen as new precision tracking detectors for the upgrade of the forward muon spectrometer of the ATLAS experiment, composing the New Small Wheel (NSW), for their high efficiency (better than 95%), high spatial resolution and they are able to cope with high particle fluxes. The National Institute of Nuclear Physics (INFN) has been committed to built 32 micromegas chambers for the small sector of the NSW (SM1). The SM1 modules have 2 m2 surface area and they are composed of four gaps, each one made of a catodic plane, a metallic micromesh and an anodic plane with the readout strips to reconstruct the precision coordinate and the second coordinate stereo. The panels construction and the assembly procedure of the SM1 modules are presented
BIS78, a pilot project for Phase-2 ATLAS RPC and beyond
No full textThe architecture of the present trigger system in the ATLAS muon barrel was designed according to a reference luminosity of 1034 cm−2s−1 with a safety factor of 5, with respect to the simulated background rates, now confirmed
by LHC Run 1 data. HL-LHC will provide a luminosity 5 times higher and an order of magnitude higher background. As a result, the performance demand increases, the detector being operated under a much harsher condition than the design scenario. The ATLAS Muon Collaboration approved an appropriate upgrade plan, to guarantee the performance required by the physics program for the 20 years scheduled, consisting in installing a layer of new generation Resistive Plate Chambers (RPC) in the inner barrel, to increase the redundancy, the selectivity, and provide almost full acceptance. The BIS78 project aims to install the first 10% of the system already in LS2, at the edges of the inner barrel even sectors (BIS7 and 8). This is the barrel region with the highest background so it is an excellent pilot project for the Phase-2 full coverage. The BIS78 RPCs represent a new generation of the RPC
detectors, based on a new and advanced FE electronics capable to exploit 10 times smaller signals, correspondingly increasing the rate capability. The gas gap has been halved, along with electrodes thickness and weight reduction, improving by a factor of two the time resolution. The performance of the new detectors and the project status are discussed in this document
The Recoil Directionality Experiment
No full textDirectional sensitivity to nuclear recoils could provide a smoking gun for a possible discovery of dark matter in the form of WIMPs. A hint of directional dependence of the response of a dual-phase liquid argon Time Projection
Chamber 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 in the framework of the DarkSide Collaboration, in order to scrutinize this hint