D. Del Re

This document a outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For s-channel, spin-0 and spin-1 mediations are discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented.

This Report summarizes the results of the activities in 2012 and the first half of 2013 of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. This report follows the first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) and the second working group report Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002). After the discovery of a Higgs boson at the LHC in mid-2012 this report focuses on refined prediction of Standard Model (SM) Higgs phenomenology around the experimentally observed value of 125-126 GeV, refined predictions for heavy SM-like Higgs bosons as well as predictions in the Minimal Supersymmetric Standard Model and first steps to go beyond these models. The other main focus is on the extraction of the characteristics and properties of the newly discovered particle such as couplings to SM particles, spin and CP-quantum numbers etc.

Attention supports the allocation of resources to relevant locations and objects in a scene. Under most conditions, several stimuli compete for neural representation. Attention biases neural representation toward the response associated with the attended object [1Reynolds J.H. Chelazzi L. Desimone R. Competitive mechanisms subserve attention in macaque areas V2 and V4.J. Neurosci. 1999; 19: 1736-1753Crossref PubMed Google Scholar, 2Beck D.M. Kastner S. Top-down and bottom-up mechanisms in biasing competition in the human brain.Vision Res. 2009; 49: 1154-1165Crossref PubMed Scopus (311) Google Scholar]. Therefore, an attended stimulus enjoys a neural response that resembles the response to that stimulus in isolation. Factors that determine and generate attentional bias have been researched, ranging from endogenously controlled processes to exogenous capture of attention [1Reynolds J.H. Chelazzi L. Desimone R. Competitive mechanisms subserve attention in macaque areas V2 and V4.J. Neurosci. 1999; 19: 1736-1753Crossref PubMed Google Scholar, 2Beck D.M. Kastner S. Top-down and bottom-up mechanisms in biasing competition in the human brain.Vision Res. 2009; 49: 1154-1165Crossref PubMed Scopus (311) Google Scholar, 3Landau A.N. Esterman M. Robertson L.C. Bentin S. Prinzmetal W. Different effects of voluntary and involuntary attention on EEG activity in the gamma band.J. Neurosci. 2007; 27: 11986-11990Crossref PubMed Scopus (68) Google Scholar, 4Buschman T.J. Miller E.K. Serial, covert shifts of attention during visual search are reflected by the frontal eye fields and correlated with population oscillations.Neuron. 2009; 63: 386-396Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar]. Recent studies investigate the temporal structure governing attention. When participants monitor a single location, visual-target detection depends on the phase of an ∼8-Hz brain rhythm [5Busch N.A. Dubois J. VanRullen R. The phase of ongoing EEG oscillations predicts visual perception.J. Neurosci. 2009; 29: 7869-7876Crossref PubMed Scopus (746) Google Scholar, 6VanRullen R. Perceptual cycles.Trends Cogn. Sci. 2016; 20: 723-735Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar]. When two locations are monitored, performance fluctuates at 4 Hz for each location [7Landau A.N. Fries P. Attention samples stimuli rhythmically.Curr. Biol. 2012; 22: 1000-1004Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar, 8Fiebelkorn I.C. Saalmann Y.B. Kastner S. Rhythmic sampling within and between objects despite sustained attention at a cued location.Curr. Biol. 2013; 23: 2553-2558Abstract Full Text Full Text PDF PubMed Scopus (230) Google Scholar]. The hypothesis is that 4-Hz sampling for two locations may reflect a common sampler that operates at 8 Hz globally, which is divided between relevant locations [5Busch N.A. Dubois J. VanRullen R. The phase of ongoing EEG oscillations predicts visual perception.J. Neurosci. 2009; 29: 7869-7876Crossref PubMed Scopus (746) Google Scholar, 6VanRullen R. Perceptual cycles.Trends Cogn. Sci. 2016; 20: 723-735Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar, 7Landau A.N. Fries P. Attention samples stimuli rhythmically.Curr. Biol. 2012; 22: 1000-1004Abstract Full Text Full Text PDF PubMed Scopus (344) Google Scholar, 9Mathewson K.E. Gratton G. Fabiani M. Beck D.M. Ro T. To see or not to see: prestimulus alpha phase predicts visual awareness.J. Neurosci. 2009; 29: 2725-2732Crossref PubMed Scopus (687) Google Scholar]. The present study targets two properties of this phenomenon, called rhythmic-attentional sampling: first, sampling is typically described for selection over different locations. We examined whether rhythmic sampling is limited to selection over space or whether it extends to feature-based attention. Second, we examined whether sampling at 4 Hz results from the division of an 8-Hz rhythm over two objects. We found that two overlapping objects defined by features are sampled at ∼4 Hz per object. In addition, performance on a single object fluctuated at 8 Hz. Rhythmic sampling of features did not result from temporal structure in eye movements.

The physics objectives of SuperB, an asymmetric electron-positron collider with a luminosity above 10^36/cm^2/s are described, together with the conceptual design of a novel low emittance design that achieves this performance with wallplug power comparable to that of the current B Factories, and an upgraded detector capable of doing the physics in the SuperB environment.

Discovering a Higgs boson at the LHC will address a major outstanding issue in particle physics but will also raise many new questions. A concerted effort to determine the couplings of this new state to other Standard Model fields will be of critical importance. Precise knowledge of these couplings can serve as a powerful probe of new physics, and will be needed in attempts to accommodate such a new boson within specific models. In this paper, we present a method for constraining these couplings in a model-independent way, focusing primarily on an exclusive analysis of the gamma gamma final state. We demonstrate the discriminating power of fully exclusive analyses, and discuss ways in which information can be shared between experimentalists and theorists in order to facilitate collaboration in the task of establishing the true origins of any new physics discovered at the LHC.

We report on the response of microchannel plates (MCPs) to single relativistic particles and to electromagnetic showers. Particle detection by means of secondary emission of electrons at the MCP surface has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Several prototypes of photodetectors with the amplification stage based on MCPs were exposed to cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The time resolution and the efficiency of the MCPs are measured as a function of the particle multiplicity, and the results used to model the response to high-energy showers.

The CMS electromagnetic calorimeter (ECAL) is made of about 75000 scintillating lead tungstate crystals arranged in a barrel and two endcaps. The scintillation light is read out by avalanche photodiodes in the barrel and vacuum phototriodes in the endcaps, at which point the scintillation pulse is amplified and sampled at 40 MHz by the on-detector electronics. The fast signal from the crystal scintillation enables energy as well as time measurements from the data collected in proton-proton collisions with high energy electrons and photons. The stability of the time measurement required to maintain the energy resolution is on the order of 1 ns. The single-channel time resolution of ECAL measured at beam tests for high energy showers is better than 100 ps. The time resolution achieved with the data collected in proton-proton collisions at the LHC is presented. The time precision achieved is used in important physics measurements and also allows the study of subtle calorimetric effects, such as the time response of different crystals belonging to the same electromagnetic shower. In addition, we present prospects for the high luminosity phase of the LHC, where we expect an average of 140 concurrent interactions per bunch crossing (pile-up). It is currently being studied how precision time could be exploited for pileup mitigation and for the assignment of the collision vertex for photons. In this respect, a detailed understanding of the time performance and of the limiting factors in time resolution will be important.

This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as $3~\mathrm{ab}^{-1}$ of data taken at a centre-of-mass energy of $14~\mathrm{TeV}$, and of a possible future upgrade, the High Energy (HE) LHC, defined as $15~\mathrm{ab}^{-1}$ of data at a centre-of-mass energy of $27~\mathrm{TeV}$. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials, this report contains results on dark matter and dark sectors, long lived particles, leptoquarks, sterile neutrinos, axion-like particles, heavy scalars, vector-like quarks, and more. Particular attention is placed, especially in the study of the HL-LHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HL-LHC, on top of allowing to extend the present LHC mass and coupling reach by $20-50\%$ on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HL-LHC, the reach in most observables will generally more than double at the HE-LHC, which may represent a good candidate future facility for a final test of TeV-scale new physics.

Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated.

Our ability to detect targets in the environment fluctuates in time. When individuals focus attention on a single location, the ongoing temporal structure of performance fluctuates at 8 Hz. When task demands require the distribution of attention over two objects defined by their location, color or motion direction, ongoing performance fluctuates at 4 Hz per object. This suggests that distributing attention entails the division of the sampling process found for focused attention. It is unknown, however, at what stage of the processing hierarchy this sampling occurs, and whether attentional sampling depends on awareness. Here, we show that unaware selection between the two eyes leads to rhythmic sampling. We presented a display with a single central object to both eyes and manipulated the presentation of a reset event (i.e., cue) and a detection target to either both eyes (binocular) or separately to the different eyes (monocular). We assume that presenting a cue to one eye biases the selection process to content presented in that eye. Although participants were unaware of this manipulation, target detection fluctuated at 8 Hz under the binocular condition, and at 4 Hz when the right (and dominant) eye was cued. These results are consistent with recent findings reporting that competition between receptive fields leads to attentional sampling and demonstrate that this competition does not rely on aware processes. Furthermore, attentional sampling occurs at an early site of competition among monocular channels, before they are fused in the primary visual cortex.

INFN Kids is a science education project of the Italian National Institute for Nuclear Physics addressed to young people of Primary and Middle schools age. The initiative aims at raising children’s curiosity towards science with a focus on Physics, inspiring them with science by illustrating the different research fields that INFN is pursuing, the development in technologies along with the applications in everyday life and presenting people who animate science. It gathers technicians and researchers of thirteen units and National labs in the design and realization of multimedia products, laboratory-based activities, comics, science demos and exhibits. The activities are conducted online and in person in schools, science festivals and at INFN’s sites. The adopted methodologies and the didactic tools (lectures, interactive lessons, hands-on sessions, science games) involve children in the direct exploration of natural phenomena. Given the manifold plan of activities the recipients of the project are also teachers and families, and this allowed to expand and use different formats to meet the audience’s requests. We here present an overview of the ongoing initiatives to share our experiences and we illustrate in particular the comics centered on the characters Leo and Alice that drive children in the investigation of the micro and macro world, and the laboratory-based activities designed to introduce kids some fundamental concepts related to matter and its inner structure.

Italy was the first European country affected by COVID-19. Thanks to governmental containment measures (9 March 2020), the spread of COVID-19 was limited. However, in this context, accurate data assessment is crucial and mortality is a more reliable indicator of the virus spread compared to the count of positive cases. This study aimed to retrospectively evaluate the impact of the pandemic in different areas of Italy using the time series analysis of official deaths and excess COVID-19 deaths.Mortality data (23 February-30 April 2022) by Istituto Nazionale di Statistica (ISTAT) were analyzed, including four waves of COVID-19. Previous mortality data (January 2015-November 2019) were used to estimate a Poisson regression model of the pre-pandemic mortality pattern and derive the excess COVID-19 deaths as the difference between the actual deaths number and the extrapolation of the previous mortality pattern to the pandemic period, separately for Northern, Central, and Southern Italy, to compare the impact of mortality across time periods and geographical areas.Estimated excess compared with official COVID-19 mortality shows that, during the first wave, there was an underestimation of deaths. COVID-19 mortality rate almost doubled the official rate in the North (1.60‰ vs. 0.86‰) and nearly tripled it in the South (0.22‰ vs. 0.08‰). In late 2020-early 2021, official and estimated mortality curves are closer, displaying just a small gap at the start of the second wave. During the fourth wave (end of 2021-early 2022), Northern and Central Italy show reasonable agreement; the South presents a large relative underestimation of deaths (+90% increase), with a large increase in its excess deaths national quota, 9% in the first wave to 42% in the fourth.The results provide a measure of the COVID-19 excess deaths and an unbiased estimate of Italian mortality rates. In the first wave, the gap between official COVID-19 and excess mortality was particularly high and lockdown measures may have reduced the spread of the infection. In the fourth wave, the gap for the South increases again, probably because the healthcare system may not have coped with the prolonged pressure of the pandemic, or for a decreased compliance with the official paper-based mortality surveillance system that could be overcome in the future by digitalizing the process.

Abstract Brookshire (2022) claims that previous analyses of periodicity in detection performance after a reset event suffer from extreme false-positive rates. Here we show that this conclusion is based on an incorrect implemention of a null-hypothesis of aperiodicity, and that a correct implementation confirms low false-positive rates. Furthermore, we clarify that the previously used method of shuffling-in-time, and thereby shuffling-in-phase, cleanly implements the null hypothesis of no temporal structure after the reset, and thereby of no phase locking to the reset. Moving from a corresponding phase-locking spectrum to an inference on the periodicity of the underlying process can be accomplished by parameterizing the spectrum. This can separate periodic from non-periodic components, and quantify the strength of periodicity.

Ensuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.

Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce)is one of the most widely used Cerium-doped Lutetium based scintillation crystals. Initially developed for medical detectors it rapidly became attractive for High Energy Particle Physics (HEP) applications, especially in the frame of high luminosity particle colliders. In this paper, a comprehensive and systematic study of LYSO:Ce ($[Lu_{(1-x)}Y_x]_2SiO_5$:$Ce$) crystals is presented. It involves for the first time a large number of crystal samples (180) of the same size from a dozen of producers.The study consists of a comparative characterization of LYSO:Ce crystal products available on the market by mechanical, optical and scintillation measurements and aims specifically, to investigate key parameters of timing applications for HEP.

The BABAR detector has operated nearly 200 Resistive Plate Chambers (RPCs), constructed as part of an upgrade of the forward endcap muon detector, for the past two years.The RPCs experience widely different background and luminosity-driven singles rates (0.01-10 Hz/cm 2 ) depending on position within the endcap.Some regions have integrated over 0.3 C/cm 2 .RPC efficiency measured with cosmic rays is high and stable.The average efficiency measured with beam is also high.However, a few of the highest rate RPCs have suffered efficiency losses of 5-15%.Although constructed with improved techniques and minimal use of linseed oil, many of the RPCs, which are operated in streamer mode, have shown increased dark currents and noise rates that are correlated with the direction of the gas flow and the integrated current.Studies of the above aging effects are presented and correlated with detector operating conditions.

The performance of electromagnetic calorimeter modules made of proton-irradiated PbWO4 crystals has been studied in beam tests. The modules, similar to those used in the Endcaps of the CMS electromagnetic calorimeter (ECAL), were formed from 5×5 matrices of PbWO4 crystals, which had previously been exposed to 24 GeV protons up to integrated fluences between 2.1× 1013 and 1.3× 1014 cm−2. These correspond to the predicted charged-hadron fluences in the ECAL Endcaps at pseudorapidity η = 2.6 after about 500 fb−1 and 3000 fb−1 respectively, corresponding to the end of the LHC and High Luminosity LHC operation periods. The irradiated crystals have a lower light transmission for wavelengths corresponding to the scintillation light, and a correspondingly reduced light output. A comparison with four crystals irradiated in situ in CMS showed no significant rate dependence of hadron-induced damage. A degradation of the energy resolution and a non-linear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The latter is interpreted, through comparison with simulation, as a side-effect of the degradation in light transmission. The experimental results obtained can be used to estimate the long term performance of the CMS ECAL.

The muon and neutral hadron detector (instrumented flux return or IFR) in the forward endcap of the BaBar detector at SLAC was upgraded by the installation of a new generation of resistive plate chambers (RPCs) and by increasing the absorber. The chamber replacement was made necessary by the rapid aging and efficiency loss of the original BaBar RPCs. Based on our experience with those original RPCs and 24 RPCs with thinner linseed oil treatments, improvements in the design, construction, and testing of the new generation RPCs were implemented and are described in detail.

We search for $B$ meson decays into two-body combinations of $\ensuremath{\eta},{\ensuremath{\eta}}^{\ensuremath{'}},\ensuremath{\omega}$, and $\ensuremath{\phi}$ mesons from $89\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at SLAC. We find the branching fraction $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\omega})=({4.0}_{\ensuremath{-}1.2}^{+1.3}\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ with a significance of $4.3\ensuremath{\sigma}$. For the other decay modes we set the following 90% confidence level upper limits on the branching fractions, in units of ${10}^{\ensuremath{-}6}$: $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\eta})<2.8$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\eta}}^{\ensuremath{'}})<4.6$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\eta}}^{\ensuremath{'}})<10$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\omega})<2.8$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\phi})<1.0$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\phi})<4.5$, and $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi})<1.5$.

The CMS Electromagnetic Calorimeter (ECAL) is made of about 75 000 lead tungstate crystals. The 61 200 crystals of the barrel part are read by Avalanche Photodiodes (APD) with internal amplification of the signal. Since the gain strongly depends on the bias voltage, the APDs require a very stable power supply system. To preserve the high energy resolution of the calorimeter, a stability of the bias voltage of the order of 10-4 is required over several months, a typical interval between absolute calibrations of the full read-out chain with physics events. This paper describes the high voltage power supply system developed for CMS ECAL and its performances as measured in laboratory tests and during test-beam operations of several modules of the calorimeter.

Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with heavy absorber plates, and read out by wavelength-shifting (WLS) fibers is being studied as a calorimeter option for detectors at the upgraded High-Luminosity LHC (HL-LHC) collider at CERN. A prototype has been exposed to electron beams of different energies at the INFN Frascati (Italy) Beam Test Facility. This paper presents results from the studies performed on the prototype, such as signal amplitudes, light yield and energy resolution.

At the high luminosity LHC (HL-LHC) about 200 concurrent interactions are expected, with a spread between the interaction vertices of few centimeters in the beam direction and 200 ps in the collision time. A time of flight resolution of the order of 30 ps would be able to reduce neutral particles pile-up contamination at the calorimeter level of about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates have been used in PMT configuration as fast charged particles detector (resolution of better than 20 ps have been achieved with commercial devices), however they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more then 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This open the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology.

The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. The central portion of the detector, the Barrel Timing Layer (BTL), will be instrumented with LYSO:Ce crystals and Silicon Photomultipliers (SiPMs) providing a time resolution of about 30 ps at the beginning of operation, and degrading to 50-60 ps at the end of the detector lifetime as a result of radiation damage. In this work, we present the results obtained using a 120 GeV proton beam at the Fermilab Test Beam Facility to measure the time resolution of unirradiated sensors. A proof-of-concept of the sensor layout proposed for the barrel region of the MTD, consisting of elongated crystal bars with dimensions of about 3 x 3 x 57 mm$^3$ and with double-ended SiPM readout, is demonstrated. This design provides a robust time measurement independent of the impact point of the MIP along the crystal bar. We tested LYSO:Ce bars of different thickness (2, 3, 4 mm) with a geometry close to the reference design and coupled to SiPMs manufactured by Hamamatsu and Fondazione Bruno Kessler. The various aspects influencing the timing performance such as the crystal thickness, properties of the SiPMs (e.g. photon detection efficiency), and impact angle of the MIP are studied. A time resolution of about 28 ps is measured for MIPs crossing a 3 mm thick crystal bar, corresponding to an MPV energy deposition of 2.6 MeV, and of 22 ps for the 4.2 MeV MPV energy deposition expected in the BTL, matching the detector performance target for unirradiated devices.

We have measured the time-dependent decay rate for the process B-->J/psiK(*0) (892) in a sample of about 88x10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In this sample we study flavor-tagged events in which one neutral B meson is reconstructed in the J/psiK(*0) or J/psi(-)K(*0) final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for J/psiK(*0) and J/psi(-)K(*0), find them to be consistent with the standard model expectations, and set upper limits at 90% confidence level (C.L.) on the decay amplitude ratios |A((-)B(0)-->J/psiK(*0))|/|A(B0-->J/psiK(*0))|<0.26 and |A(B0-->J/psi(-)K(*0))|/|A((-)B(0)-->J/psi(-)K(*0))|<0.32. For a single ratio of wrong-flavor to favored amplitudes for B0 and (-)B(0) combined, we obtain an upper limit of 0.25 at 90% C.L.

An experimental optical synchroniser for packet switched networks is presented; the system can recover time misalignments up to 105.6 ns exploiting switchable delay lines at node-input and wavelength dispersion in a high dispersion fibre at node output, with is 200 ps resolution.

The BaBar detector is currently operating nearly 200 Resistive Plate Chambers (RPCs), constructed as part of an upgrade of the forward endcap muon detector in 2002. Although the average RPC efficiency remains high, numerous changes in the RPC performance (increased currents and rates) have been observed. A few of the highest rate RPCs have suffered efficiency losses of more than 15%. Several types of efficiency loss have been observed. Tests with humidified gas have shown that some of the lost efficiency is recoverable. However, efficiency losses in the highest rate regions have not yet improved with humid gases.

I-MCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of micro-channel plates (MCP) for single ionizing particles and fast timing of showers in high rate environments. Results from tests with electrons with energies up to 50 GeV of MCP devices with different characteristics are presented. In particular detection efficiency and time resolution are measured for a range of MCP prototypes: different MCP channel diameter and layers configuration are studied. Devices operated in I-MCP configuration, where the particle detection proceed through direct ionization of the MCP layers, are studied in comparison with the more usual PMT-MCP configuration. The results show efficiencies up to 70% for single charge particle detection for I-MCP devices with a time resolution of about 40 ps. The efficiency raise to 100% in response to high energy electromagnetic showers.

Future high rate hadron colliders are expected to have hundreds of concurrent proton-proton interactions in the same bunch crossing, deteriorating the energy resolution and identification capabilities of calorimeters. The possibility to distinguish neutral particles coming from different interaction vertices is being pursued as a tool to reduce pile-up contamination in calorimeters, and restore optimal performance. A time of flight resolution of the order of 20 ps will be able to reduce neutral particles pile-up contamination at the calorimeter level by about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates (MCP) can be used in PMT configuration as fast charged particles detector (resolution of better then 30 ps can be achieved with commercial devices). However they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more than 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This opens the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology. Preliminary results on the radiation hardness of the i-MCP configuration will be also presented.

Abstract The mortality data can be used as an alternative source to monitor the status of Covid-19. We have studied a dataset including deaths up to the fourth week of April. There is a large excess, more pronounced at the beginning of the pandemic, showing a difference in age and gender compared to the Covid-19-confirmed cases. The study indicates that mortality information can be used to provide a less biased time profile of the pandemic.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with absorber plates made of tungsten, and read out by wavelength-shifting fibres has been tested with high-energy electron beams at the CERN SPS H4 beam line, as well as with lower-energy beams at the INFN Frascati Beam Test Facility in Italy. Energy resolution studies revealed a low stochastic term (<10%/E). This result, combined with high radiation hardness of the material used, marks this sampling calorimeter as a good candidate for the detectors׳ forward regions during the high luminosity phase of LHC.

Experimental results are interpreted in terms of a simple lumped-element model that is also used to reproduce the hysteresis phenomenon with discrete components. The hysteresis is related to a three-dimensional (3-D) nonuniformity in the current distribution. Such hysteresis can lead to an erroneous evaluation of latchup parameters, such as the holding current density.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The CMS electromagnetic calorimeter (ECAL) comprises 75848 scintillating lead tungstate crystals. 61200 crystals are contained in the ECAL Barrel section and are read out by avalanche photodiode (APD) with internal gain of about 50. This gain is achieved with a high voltage (HV) of about 400 Volts. The gain stability requirement implies a supply voltage stable to within 0.01%. We describe our experience with the installed Barrel HV power supply system, which has been used for data taking since 2008.

The High-Luminosity phase of the Large Hadron Collider at CERN (HL-LHC) poses stringent requirements on calorimeter performance in terms of resolution, pileup resilience and radiation hardness. A tungsten-CeF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sampling calorimeter is a possible option for the upgrade of current detectors. A prototype, read out with different types of wavelength-shifting fibers, has been built and exposed to high energy electrons, representative for the particle energy spectrum at HL-LHC, at the CERN SPS H4 beam line. This paper shows the performance of the prototype, mainly focussing on energy resolution and uniformity. A detailed simulation has been also developed in order to compare with data and to extrapolate to different configurations to be tested in future beam tests. Additional studies on the calorimeter and the R&D projects ongoing on the various components of the experimental setup will be also discussed.

The use of an InGaAs/InGaAs tensile-strained-barrier MQW active layer is an interesting approach to achieve polarization-insensitive semiconductor optical amplifiers (SOAs) at the 1.55 /spl mu/m wavelength. This work reports on the design and experimental results obtained on MQW structures grown by LP-MOCVD and characterized for their optical and structural quality. SOA devices made from these layers show a dichroism below 1 dB with signal fiber-to-fiber gains up to 20 dB, confirming the good optical and electrical quality of the structure.

LHC has worked beautifully and collected more than 100 fb−1 at 13 TeV. Thanks to this enormous statistics of p-p collisions, LHC experiments have been able to explore several different new physics scenarios. We present the most recent results of the ATLAS, CMS, and LHCb experiments on the so-called Exotics searches for physics beyond the Standard Model.

A surface characterization technique based on the Internal Second-Harmonic Generation (SHG) in optoelectronic devices has been used to study the mirror degradation of 1.55 μm semiconductor optical amplifiers (SOAs) exposed to an antireflection coating deposition technique and 980 nm pump lasers suffering from mirror oxidation during life-tests. In both cases, an overall increase in SH emission was observed, as a consequence of mechanical stress enhancement and defects formation due to oxidation phenomena occurring at the interface between semiconductor and coating film. In the case of pump lasers, an oscillating, periodic trend superimposed to the general increasing one was also observed and interpreted as the periodic relaxation of compressive strain in the active layer due to vacancies formation in the near-mirror semiconductor layer.

We report, for the first time, to our knowledge, the realisation of a HDBR (hybrid distributed Bragg reflector) laser for picosecond optical pulse generation at about 10 GHz repetition rate. 12.7 ps pulses, with 400 MHz locking bandwidth have been obtained.

Semiconductor optical amplifiers (SOAs) are becoming key elements of modern communication systems, particularly in view of optical signal processing. The carrier dynamics in the gain medium can be exploited to implement all-optical wavelength conversion, demultiplexing, clock-recovery and signal regeneration. Furthermore, SOAs can be integrated with waveguides to form compact and polarization-insensitive functional devices. In this contribution we present a very compact Michelson interferometer, obtained by monolithic integration of two SOAs with a passive waveguide section, incorporating turning mirrors. It operates in the 1550 nm window. Based on the cross-phase modulation effect, taking place in the SOAs under optical pumping, we used our device to obtain wavelength conversion to wavelengths either longer or shorter than the pump wavelength.

We present the measurements of the CKM matrix parameters Vub, Vcb and of the B mixing oscillation frequency with the BaBar experiment at the asymmetric B-factory PEPII. Data were collected in the years 2000-2002 and the total available statistics corresponds to 91 fb-1. The Vub, Vcb measurements utilize both inclusive and exclusive semileptonic decays of the $B$ meson. The Delta(md) parameter is measured by using the time evolution of the B, determined from the flight length difference between the two B mesons.

IMCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of microchannel plates (MCP) for fast timing of showers in high rate environments. The usage of MCPs in “ionisation” mode has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The fast time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Results from tests with electrons with energies up to 150 GeV of MCP devices with different characteristics will be presented, in particular detection efficiency and time resolution.

Several extensions of the Standard Model, including Hidden Valley models and few supersymmetric models, predict the existence of long-lived particles decaying far from the interaction point or traveling inside the detector with beta significantly smaller than one.Searches for new longlived particles using 2011 and 2012 LHC data have been carried by ATLAS [1] and CMS [2] experiments at the Large Hadron Collider.The sensitivity of these searches is reviewed.

The Compact Muon Solenoid detector at the CERN LHC is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC.A new timing detector, MTD, will measure minimum ionizing particles with a time resolution of 30-40 ps at a rate of 2.5 Mhit/s per channel at the beginning of the operations.The precision time information from this detector will reduce the effects of the high levels of pileup, bringing new capabilities to the CMS detector.The barrel timing layer will use sensors that are based on LYSO:Ce scintillating crystals coupled to SiPMs with TOFHIR ASICs for the front-end readout.We will present motivations for precision timing at the High-Luminosity LHC and an overview of the MTD barrel design, including ongoing R&D studies targeting enhanced timing performance and radiation tolerance.

Abstract The construction industry faces several challenges every day, which are pushing this sector to start a process of innovation. In this contest, Additive Manufacturing (AM) represents an innovation and digitalization opportunity; on this basis, this work will focus on an assessment of AM as an enabling technology for this industry, especially from a cost perspective. In particular, since there is not yet a suitable cost model for AM in construction, a cost model will be developed to assess whether it is cost effective to use 3D printing in the building industry. The results obtained from the application of the cost model on a case study are very promising as they open up new avenues for considering 3D printing as a valid alternative to traditional construction methods.

The correlation between film composition and refractive index has been investigated for TiZrOx films used as anti-reflective coatings. The films were evaporated by e-gun with an oxygen partial pressure during the deposition process. The refractive index is governed by the total content and distribution of Ti in the film. The source composition evolves with the number of depositions, possibly because of titanium oxide decomposition produced by the electrons. As a consequence, these changes are reflected in the composition of the film. A comparison between two forms of the oxide mixture source, ‘small grains’ and ‘pellet’, indicates better reproducibility for the latter.

We report studies of B {yields} X{sub u}{ell}{nu} decays, based on a sample of 88 million B{bar B} events recorded with the BABAR detector. From both tagged and untagged B{bar B} events we have isolated inclusive charmless decays in kinematic regions for which the dominant background from B {yields} X{sub c}{ell}{nu} is reduced by making requirements on different variables: the electron energy E{sub l}, the momentum transfer q{sup 2}, and the hadronic mass m{sub X}. Using theoretical calculations we extrapolate to the total decay rate to determine the CKM matrix element |V{sub ub}|. In addition, we have measured the branching fraction for exclusive semileptonic decays, such as B {yields} {pi}({rho}, {omega}, {eta}, a{sub 0}){ell}{nu}. A high signal purity is achieved by selecting events in which a decay of the second B meson is either fully or partially reconstructed.

We present the measurements of the CKM matrix parameters V{sub ub}, V{sub cb} and of the B mixing oscillation frequency with the BaBar experiment at the asymmetric B-factory PEPII. Data were collected in the years 2000-2002 and the total available statistics corresponds to 91 fb{sup -1}. The V{sub ub}, V{sub cb} measurements utilize both inclusive and exclusive semileptonic decays of the B meson. The {Delta}m{sub d} parameter is measured by using the time evolution of the B, determined from the flight length difference between the two B mesons.

Current optoelectronic devices extensively use dry etching for their fabrication, in particular, reactive ion etching (RIE) is the most used technique. Unfortunately, dry etching induces a damaged layer on the etched surfaces that can negatively influence the electro-optical performance of the devices in terms of specs and reliability. In this work we evaluate the thickness of the surface damaged layer induced by CH4/H2 RIE on InP using a technique based on the comparison of the conductance of the material before and after the RIE. The method can be used to optimise the RIE conditions in order to minimise the extension of the surface damaged layer. To perform the conductance measurements, transmission line model and Hall effect were used. Two different etching conditions have been considered. The first is typical for low etch rate (ER) (DC bias=−315 V), for example, used in grating formation for a DFB laser. The second for high ER (DC bias=−650 V), for example used in mesa etching for several kinds of buried lasers. The experimental results gave damaged thicknesses of 130 and 340 Å, respectively, for low and high ER conditions. This thin layer can be easily removed by annealing and with a very short wet etching to give high performances devices (27th European Conference on Optical Communication ECOC‘01, Amsterdam).

The elements of the CKM matrix enter the expressions for the decay rates and mixing amplitudes of hadrons. In some cases, the theoretical expressions are free of strong interaction effects, for example the CP asymmetry in B {yields} J/{psi} K{sub S}{sup 0}, so that measuring the CP asymmetry directly gives the value of sin 2{beta}, with the error in the result given by the experimental error in the measurement. In most cases, however, the experimentally measured quantities depend on strong interactions physics, and it is absolutely essential to have accurate model-free theoretical calculations to compare with experiment. A number of theoretical tools have been developed over the years which now allow us to compute B decays with great accuracy, sometimes at the level of a few percent or better. These calculations are done using effective theory methods applied to QCD, and do not rely on model assumptions. Inclusive decays can be treated using the operator product expansion (OPE). The total decay rate is given by twice the imaginary part of the forward scattering amplitude, using the optical theorem. In heavy hadron decays, the intermediate states in the forward scattering amplitude can be integrated out, so that the decay rate canmore » be written as an expansion in local operators. The expansion parameter is 1/m{sub B}, the mass of the decaying hadron. OPE techniques have been well-studied in the context of deep-inelastic scattering, where the expansion in powers of 1/Q{sup 2} is called the twist expansion. In inclusive B decays, the leading term in the 1/m{sub B} expansion gives the parton decay rate, and nonperturbative effects enter at higher orders in 1/m{sub B}.« less

Abstract In this work we present a wavelength converter based on a Michelson interferometer. It is obtained by monolithic integration of two-semiconductor optical amplifiers with a passive waveguided X-coupler, incorporating turning mirrors. It operates in the 1.55 μm spectral window and allows the wavelength conversion of data streams up to 10 Gb/s, showing open-eye diagrams and extinction–ratio regeneration capabilities. Comparison of two structures with different active layers and their influence on the polarization sensitivity is also presented.

Deposition rate, thickness unriformity and step coverage of SiO 2 films deposited on Si substrates by pyrolysis of TEOS have been studied as a function of process parameters: temperature, pressure, and gas flow. Oxide films with iformrities of ±1% on 100-mm. wafers and step coverage of 76% on 1 ?m wide and deep trenches have been obtained. The electrical characterization of TEOS-SiO 2 films deposited on single crystal Si shows a charge density of about 1011 cm?2, a surface state density at Si midgap lower than 1010 eV?1 cm?2, a Si/SiO 2 barrier height of 2.6 eV and a breakdown field strength from 7.5 to 9 MV/cm. TEOS-SiO 2 films deposited on POCl 3 doped poly-Si show insulation properties comparable to that of Si O 2 films grown at 1100°C.