Search

SHiP (Search for Hidden Particles) is a proposed beam dump experiment, aiming at searching for new long-lived particles by using the 400 GeV/c proton beam available from the CERN SPS accelerator. In addition, the physics program includes high statistics studies of neutrino physics and the search for light dark matter scattering. The latter tasks are assigned to a Scattering Neutrino Detector, where nuclear emulsions are used as high resolutions trackers. My Ph.D. project is dedicated to the evaluation of the physics performance of this detector, through a full simulation of neutrino interactions. In order to develop and test reconstruction algorithms, I have analysed the data from a proton beam performed at the SPS in 2018 and an electron beam with electrons, performed at DESY in 2019. The acquired experience will be essential for the analysis of SHiP and other large future projects at CERN involving emulsions.

A precise measurement of the luminosity delivered by LHC to the experiments such as ATLAS and CMS is important for a variety of reasons. Online, the luminosity measurement provides real-time feed- back on the LHC performance and operation and is crucial to optimize the experiments operations such as setting and adjustement of trigger prescale factors. Offline, the uncertainty on the luminosity is a relevant source of systematics in all cross-section measurements and for potential observations of new physics: in particular for precision measurements it proves to be a dominant effect. During the whole LHC running period many steps forward have been made in the comprehension of the uncertainties related to luminosity monitoring and calibration, which led to an unprecedented accuracy at hadron colliders. In this presentation, the main luminosity monitors of both ATLAS and CMS are described, together with the method adopted for their absolute calibration. The main systematic uncertainties affecting the luminosity measurement and the final precision obtained by ATLAS and CMS will be presented. Finally perspectives on the luminosity measurement at HL-LHC will be discussed.

This thesis is the result of an internship conducted in 2016 at CERN. The activity was carried out at the laboratories of the TOTEM experiment and, in particular, on CMS joint project equipment, called CMS-TOTEM Precision Proton Spectrometer (CT-PPS). The collaboration envisages reconstructing the quadruple-pulse of protons that survive collisions within LHC, to study Central Exclusive Production (CEP) processes. The accelerator magnetic fields deviate from the beam orbit the protons that lost a small fraction of their initial pulse in the collisions. Protons interacting by inelastic scattering ("central diffraction") are then detected by CT-PPS with detectors at a distance of ~ 220m from both sides of the interaction point, to reconstruct their trajectories. The process described is by means of a multiple exchange of gluons or photons, with quantum numbers exchanged equivalent to those of the vacuum. CT-PPS is active during LHC high-luminosity runs, so the working conditions of the detectors result hard. In fact, the measured protons flux at the detector stations is ~ 10^15 cm^-2 for an integrated luminosity of 100 fb^-1. For this reason, solid state detectors capable to offer "radiation hardness" have been developed. High luminosity runs are also characterized by the marked presence of the "pile-up" phenomenon, that is the occurrence of more than one proton-proton interaction during the same bunch-crossing (expected ~ 30-50). However tracking detectors, due to their distance from the interaction point, cannot separate the various primary vertices and reconstruct only central diffraction events. For this reason, protons time of flight detectors were realized ("4D-Reconstruction"). The difference between the arrival time of the particles at the detectors is proportional to the z-coordinate of their primary vertex. The first prototypes made for CT-PPS are diamond detectors with a timing resolution of less than 100 ps. The new "boards", still under test, show a double layer of diamonds and a resolution of the order of 50 ps. Recently, the collaboration has also developed silicon sensors (UFSD), which seem to have a better timing resolution than that achieved by the other detectors described. Time of Flight detectors require a reference timing system characterized by maximum precision and stability, namely a clock signal characterized by a jitter of less than 5 ps. The work presented in this thesis deals with the analysis I have made on TOTEM's clock distribution system. Particular attention has been given to the study of the measurement parameters of a Vector Network Analyzer (VNA), a tool needed to obtain the phase delay of the clock along a cable. This work was accompanied by the creation of an XML configuration file for the remote control of the VNA and of a C++ script for data analysis. Thanks to the studies made, it was possible to acquire and analyze phase delay of a periodic signal along coaxial cables and short optical fibres. In conclusion, the working point of a MachZender Modulator was studied.

This thesis describes the innovative applications to the monitoring in harsh environment, represented by the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC), of the Fibre Bragg Grating (FBG) technology, which, although invented almost 40 years ago, is currently undergoing an explosion in variant manufacturing technologies and applications. The environment inside a large particle physic experiment like the CMS poses several challenges of monitoring spatially varying quantities in an aggressive environment, with high radiation, high magnetic field, tight electromagnetic compatibility (EMC) requirements, where particle detection priorities require monitoring sensors to have very low mass and associated service volume as well as excellent EMC compliance, conditions that can be very well satisfied by FBG-based sensors inscribed on optical fibres. The particular application described here is the monitoring of strain and temperature variation along the beryllium central beam pipe, a vacuum chamber which carries the counter-rotating proton beams in the Large Hadron Collider (LHC) to collisions within the CMS experiment.

The SHiP experiment (Search for Hidden Particles) is a beam dump experiment proposed at the CERN SPS with the submission of a Technical Proposal in April 2015. SHiP aims at the observation of long lived particles very weakly coupled with ordinary matter. These particles are mostly produced in the decay of charmed hadrons whose production is therefore enhanced through the definition of the characteristics of both the beam and the proton target. This makes the SHiP experiment a Standard Model neutrino factory too, in particular of tau neutrinos produced by the Ds decay chain. My studies have mainly focused on the design of the neutrino detector and on the evaluation of its performances. The Neutrino Detector is placed in a magnetic field and it exploits the Emulsion Cloud Chamber Technology with the micrometric position resolution needed to disentangle the tau lepton decay vertex from the neutrino interaction vertex. This peculiarity, together with the high electron identification efficiency, makes this detector also suitable to search for sub-GeV Dark Matter (produced in the decay of the dark photon) through its scattering with the electrons in the emulsion target. The main unit of the Neutrino Detector is the brick (lead plates interleaved with emulsion films) followed downstream by a Compact Emulsion Spectrometer (CES, 3 emulsion films interleaved with light material) needed to measure the charge and momentum of hadrons produced in neutrino interactions and short lived particles decays. A Muon Magnetic Spectrometer is placed immediately downstream to measure the charge and the momentum of muons produced in charged current muon neutrino interactions or in tau to muon decays. In this thesis the signal and background yield for all the different neutrino flavours are presented: more than twenty thousand nutau and nutau-bar charged current interactions are expected in five years of data taking. This unprecedented statistics of tau neutrinos will allow to measure the structure functions F4 and F5 entering the neutrino-nucleon cross section. The SHiP performances in the measurement of the tau neutrino anomalous magnetic moment are also reported with the estimation of the background yield for this searches. A preliminary estimate of the background events expected for LDM searches is also shown. Detailed studies will be performed with more general assumptions on the dark photon and the dark matter masses. Thanks to the large flux of electron and muon neutrinos interacting in the neutrino target, the measurement of the strange quark content of the nucleon has also been studied. The second to last chapter of the thesis is devoted to the description of the optimisation studies which are on going in view of the production of a Comprehensive Design Report to hand in to the CERN SPS Committee by the end of 2018. In this optimised version of the SHiP detector, the Neutrino Detector is roughly 20 m closer to the proton target, with a resulting increment in the incoming neutrino flux. However, being closer to the proton target has also generated the need for a complete redesign of the detector layout to fit the muon free region. A study of muon background rates on the Neutrino Detector and on the downstream Muon Magnetic Spectrometer is also reported. The last chapter describes the Test Beam activities conducted at CERN to study the performances of both the Compact Emulsion Spectrometer and of the gaseous electronic detectors (GEM) which complement the Neutrino Detector. The data analysis was carried out in the Napoli Emulsion Laboratory. The test beam for the CES has led us to discard the option of using the Rohacell as a light material interleaved to the emulsion films. The test beam with the GEM-emulsion coupled detector has shown a rapid degradation of the GEM performances in terms of position resolution when dealing with inclined tracks also in absence of magnetic field. The degradation is enhanced when the polarisation of the magnetic field contributes to the avalanche displacement. In case of a compensating magnetic field, the position resolution shows the same behaviour as in absence of field, except for a phase-shift of 15 degrees corresponding to the Lorentz angle of the generated electron avalanche.

Dark Matter (DM) is currently one of the most challenging goal in the LHC programme: if DM exists it can be pair-produced in proton-proton collisions. Since its weakly-interacting nature, final signatures with high missing momentum and Standard Model (SM) particles are employed in these searches. This thesis presents results on signatures involving bottom quarks in final states, described in models where DM production occurs via massive spin-0 mediators (scalar or pseudoscalar) with a coupling to SM particles proportional to their masses. These collider searches provide an interesting complementarity to DM direct and indirect detection experiments, covering the parameter space with low DM masses. The results shown in the thesis are obtained on the data collected by the ATLAS experiment in 2015 and 2016.

Una recente analisi sui dati del decadimento del mesone B+ raccolti dall'esperimento LHCb al Large Hadron Collider del CERN sembra escludere che la particella ritenuta responsabile della fase di super espansione dell'universo nei primi istanti dopo il Big Bang, nota come inflazione, possa essere il 'fratello minore' del bosone di Higgs

The neutrino is the most elusive particle that we know and for many years physicists doubted that neutrinos might never be revealed. Today we know and we reveal neutrinos produced by different astrophysical objects and by interactions of cosmic rays (natural neutrinos) or produced by nuclear reactors and as secondary particles in accelerators (artificial neutrinos). This paper focus on naturally occurring neutrinos, the disclosure of which requires enormous experimental apparatus in underground laboratories, under water or under the ice of the South Pole. They have allowed huge advances in understanding of neutrino properties with the discovery of the oscillation mechanism. And at the same time they opened new frontiers for the study of astrophysics of the processes that produce energy inside the Sun; on the mechanisms leading to stellar gravitational collapses; on astrophysical objects that produce cosmic rays up to extreme energies., The review is written in Italian. Accepted by the "Giornale di Fisica"

Sterile neutrino, in addition to providing neutrino mass generation, depending on its mass scale, may have many important cosmological implications. eV sterile neutrinos may explain the dark radiation problem (i.e. additional relativistic density quantified by the effective number of neutrino species) and the experimental data of short baseline experiments, a KeV sterile neutrino may be a warm dark matter candidate and furthermore sterile neutrinos may also provide baryogenesis through leptogenesis. The main way of obtaining a significant abundance of sterile neutrinos is through their mixing and oscillations with the active neutrinos. Active-sterile neutrino oscillations may have considerable effects in the early universe. One or more than one sterile neutrino may exist avoiding the cosmological constraints only by suppressing the thermalization of sterile neutrinos in the early universe and/or by considering non-standard cosmological theories. Two different mechanisms to suppress the sterile neutrinos thermalization and their eventual large production have been studied. In particular, the existence of neutrino asymmetries or the introduction of secret interactions among sterile neutrinos. The existence of sterile neutrinos not fully thermalized with the active species in the early universe in principle is compatible with Big-Bang Nucleosynthesis data. It is also compatible with cosmological measurements of the Cosmic Microwave Background and Large-Scale Structures, if the neutrino masses do not exceed 1 eV. However, the scenarios of secret self-interactions studied so far are not suffcient to reconcile sterile neutrinos with cosmology. The new picture, that we will introduce consists in assuming the same secret interactions with a light pseudoscalar as the source of sterile neutrino production by oscillations (when they involve active species) and, in addition, along with the self-interactions we will also consider interactions between sterile neutrino and pseudoscalar particle in the sterile sector.

La rilevazione di sorgenti radioattive disperse illecitamente nell'ambiente è di interesse in molte situazioni, ad esempio per l'emersione di "sorgenti orfane" in alcune tipologie di insediamenti, quali acciaierie, fonderie, depositi di rottame metallico, inceneritori dove il materiale lavorato può includere parti radiogene, ovvero discariche in cui si sia smaltito materiale/rifiuto radioattivo. In questo lavoro si presenta un sistema di teleoperazione aptico per un veicolo aereo senza equipaggio (UAV, o più comunemente drone) per la localizzazione e l'identificazione di sorgenti radioattive situate in ambienti esterni non strutturati. Il UAV è equipaggiato con un rivelatore di raggi gamma a semiconduttore al Tellurio di Cadmio Zincato (CdZnTe). Rispetto ad un volo automatico, inserire un essere umano nel circuito di controllo del UAV, permette di concentrarsi su aree maggiormente candidate ad un potenziale inquinamento. Tuttavia, il pilotaggio via radio di veicoli aerei è complesso a causa della mancanza di consapevolezza della situazione da parte dell'operatore. E' infatti fondamentale fornire all'operatore oltre al feedback visivo diretto anche fonti di informazioni aggiuntive, sfruttando segnali acquisititi da sensori di bordo. In questo lavoro il sistema a feedback di forza viene utilizzato come canale sensoristico supplementare per guidare l'esplorazione dell'ambiente. In particolare, viene presentato un algoritmo di "rendering aptico" che fornisce una delimitazione della zona di interesse attorno alla posizione della sorgente di radiazioni rilevata. L'approccio proposto per la teleoperazione aptica è nuovo rispetto ai precedenti studi in cui il feedback aptico è stato soprattutto sfruttato per evitare collisioni dell'UAV stesso.

Individuato presso i laboratori del CERN il bosone di Higgs., Il Colle di Galileo, Vol 2, No 1 (2013)

The NA62 experiment at CERN is intended to measure, with 10% relative error, the Branching Ratio of the K decay $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ which is expected to occur only in about 8 out $10^{11}$ kaon decays. The measurement strategy is to detect the decaying kaon and its product $\pi^{+}$ and to reject all the background channels, which are up to ten orders of magnitude more abundant than the signal, using both kinematical constraints and particle identification systems as veto. The exceptionally low signal yield makes it necessary to prevent also background which is not due to kaon decays, but is rather connected to the interaction of the intense hadron beam with the residual material enconuntered along the decay volume including the beam spectrometer itself: in order to reduce to an acceptable level this last background we designed the Charged Anti Counter (CHANTI). CHANTI is designed to be a compact, efficient and fast response detector to be operated in vacuum and is made up assembling FNAL-NICADD scintillator bars and fast wavelength shifter fibers. It is read out via silicon photomultipliers coupled to fast electronics. It is composed by 6 stations with x-y views and tracking capability; we already constructed 90% of the bars needed, and we characterized more than 50% of them. Finally, the first station was fully assembled and it was tested in the NA62 framework during a testbeam in November 2012. The data collected allowed us to estimate the time resolution of the station, which is a crucial parameter of every veto system. A first MonteCarlo estimation of the amount of the potentially dangerous inelastic interactions was performed showing that it could be a primary source of background, also taking into account the rejection factor ensured by the CHANTI and the other detectors. It is thus indispensable to plan a strategy towards a data-driven estimation of this backgrund source.

Time correlated events due to cosmic muons from extensive air showers have been detected by means of telescope pairs of the EEE (Extreme Energy Events) Project array. The coincidence rate, properly normalized for detector acceptance, efficiency and altitude location, has been extracted as a function of the relative distance between the telescopes. The results have been also compared with additional measurements carried out by small scintillator detectors at various distances. The European Physical Journal Plus The European Physical Journal Plus Look Inside Other actions Export citation Register for Journal Updates About This Journal Reprints and Permissions Add to Papers Share Share this content on Facebook Share this content on Twitter Share this content on LinkedIn

Nel giorno in cui il Large Hadron Collider (LHC) viene spento per essere reso più potente, il satellite della NASA Fermi conferma che il fratelli maggiori dell’acceleratore del Cern, si trovano nell’universo, giganteschi LHC cosmici.

In this thesis a triple GEM prototype has been characterised by using a 9 KeV X-Ray source. This type of technology will be also used by the TOTEM experiment for the realisation of the T2 detector, placed at about 14 m from the IP, with a pseudorapidity acceptance in the range 5.3

ATLAS is the largest detector at the LHC, the most powerful particle accelerator in the world. ATLAS is a multi-purpose detector, designed to throw light on fundamental questions such as the origin of mass and the nature of the Universe's dark matter.

CMS is the heaviest detector at the LHC, the most powerful particle accelerator in the world, which started up in 2008. A multi-purpose detector, CMS is composed of several systems built around a powerful superconducting magnet.

The results of a numerical and analytical investigation on hybrid steel truss RC beams are described. Hybrid steel truss RC beams are beams where, during the construction phase and the concrete casting (Phase I), the steel truss system only carries the vertical loads. The steel truss of the beams may have different shapes, depending on the technology adopted, the span and the load. In this report, Steel trusses constituted by upper and diagonal bars and a steel plate at the bottom are considered. In construcion phase, the verification against failure due to the safety against instability of the upper steel bars in compression or the diagonal elements is the most important design requirement. In the present study, four different beams are considered, with different steel trusses in Phase I condition. Finite Element modelizations of the beams are made and the failure loads are obtained, taking into account second-order effects due to large displacements. It is shown that the stability of the steel truss strongly depends on the lateral stiffness of the diagonal elements of the truss, as well as on the torsional rigidity of the lower steel plate. Starting from results of the numerical model, some design criteria are illustrated and discusseded.

The LHCb Muon system performance is presented using cosmic ray events collected in 2009. These events allowed to test and optimize the detector configuration before the LHC start. The space and time alignment and the measurement of chamber efficiency, time resolution and cluster size are described in detail. The results are in agreement with the expected detector performance., Comment: Submitted to JINST and accepted

The ATLAS Inner Detector is a charged particle tracking system built on three subdetectors: silicon detectors, Pixel and SCT, are complemented with the Transition Radiation Tracker. They provide high precision measurements with fine granularity. The performance of the track reconstruction and the resolution on track parameters are studied in detail with the first data. This study is essential for all physics analysis and for the understanding of the detector during the commissioning phase. In particular, tracking allows to discriminate charged particles sign and to determine their momentum. Furthermore it allows to reconstruct primary vertices of interactions and to identify, through secondary vertices, particles with an average life long enough to cover a significant path within detector.

The violation of the CP symmetry is one of the still open issues in the physics of fundamental interactions. Moreover, CP violation is important to understand the asymmetry between matter and anti-matter in the universe. LHCb is one of the experiments installed at the Large Hadron Collider (LHC) at CERN, and it is dedicated to precise measurements of CP violation and rare decays in the B hadron sector to test flavour physics in the Standard Model and to point out possible New Physics beyond the Standard Model. One of the key aspects of LHCb is the identification of the B decay products. The capability to distinguish between a pion and a kaon in the final state is fundamental to measure CP violation. This identification is provided by two RICH (Ring Imaging CHerenkov) detectors covering the particle momentum range 1 $\div$ 100 GeV/$c$. Cherenkov photons are detected using Hybrid Photon Detector (HPD). My thesis deals with three topics: characterization and correction of the magnetic distortion effects on the HPD; spatial HPD alignment; preliminary study of the decay channel $B^{\pm} \rightarrow K^{\pm}\pi^{0}$. HPD must operate in the fringe field of the LHCb dipole. Photo-electron trajectories are deviated by the Lorentz force with respect to the nominal ones. This produces a distortion effect of the image on the HPD anode. The distortion, if not corrected, even if it is small, can increase the error on the Cherenkov angle meas urement and can deteriorate the particle identification capability, that is fundamental for the physics programme at LHCb. For this reason it is necessary to study and correct this distortion, implementing an offline procedure to restore the nominal resolution. Measurements of a known light pattern projected onto the HPD matrix has been performed with and without magnetic field to evaluate the effect. An algorithm capable to reconstruct the position of the pattern points and to parametrise the distortion has been implemented. The distortion has been corrected and the obtained residual uncertainty is smaller than the one due to the pixel size. The same measurements have been used both to study magnetic distortion effects and to align the HPD. The projected pattern of light points, can be used to verify if there are misalignments among the HPD. A fit algorithm has been developed to correct misalignments. The obtained resolution is smaller than the one due to the pixel size. Charmless decays are important for the LHCb physics program to study CP violation. The $B^{\pm} \rightarrow K^{\pm}\pi^{0}$ decay is interesting and shows direct CP violation. An asymmetry: $A_{CP}$ = 0.051 $\pm$ 0.025 has been measured by the BaBar, Belle and CLEO experiments. Moreover an asymmetry of $A_{CP}$ = -0.098 $\pm$ 0.013 has been measured by the same experiments for the $B^0 \rightarrow K^{\mp} \pi^{\pm}$ channel. On theoretical grounds one would ex pect that the two asymmetries are about equal. This discrepancy gives rise to the so-called “$K-\pi$ puzzle". In order to understand the origin of this discrepancy both further theoretical developments and more precise experimental measurements are necessary. A preliminary study has been performed to reconstruct the $B^{\pm} \rightarrow K^{\pm}\pi^{0}$ channel decay at LHCb using Monte-Carlo data. A fit algorithm to find the secondary vertex has been developed. A selection using kinematic variables and taking into account the channel topology has been used. Efficiency and purity of the selection have been evaluated.

A presentation of the largest and the most powerful particle accelerator in the world, the Large Hadron Collider (LHC), which will start up in 2008. Its role, characteristics, technologies, etc. are explained for the general public.

Scintillating fiber detectors are widely used in high energy physics for their excellent characteristics in terms of fast response that makes them ideal for monitoring and triggering in a wide range of intensities. A coarse but fast monitoring/tracking system based on scintillating fibers has been built during the “Laboratorio di Fisica IV” course at the Insubria University dedicated to particle and nuclear physics. The detector consists of two modules placed at a distance of 20 cm; each module contains two layers of 1 mm diameter scintillating fibers organized in a x-y way. Each layer features 128 fibers organized in a doublet ribbon geometry to reduce the dead zones and improve the spatial resolution. The fibers are connected to one multi anode photomultiplier per layer through two different coupling masks and the electronics is based on the VA64TAP2.1 and LS64_2 ASICs (from Gamma - Medica IDEAS) and standard VME boards. This thesis work deals with the construction and the commissioning of the detector and the analysis of the experimental data. The tracker has been characterized at the Beam Test Facility (BTF) of the Frascati INFN National Laboratories (LNF) and has also been used, together with a high precision tracking system based on microstrip silicon detectors, at the CERN H8 SPS beam line to study the channeling and volume reflection effects of a bent silicon crystal.

CMS is the heaviest detector at the LHC, the most powerful particle accelerator in the world, which will start up in 2008. A multi-purpose detector, CMS is composed of several systems built around a powerful superconducting magnet.

Different firms involved in the vanguard project of CERN: the LHC

The OPERA experiment, designed to conclusively prove the existence of Vμ → Vτ oscillations in the atmospheric sector, makes use of a massive lead-nuclear emulsion target to observe the appearance of VτS in the CNGS Vμ beam. The location and analysis of the neutrino interactions in quasi real-time required the development of fast computer-controlled microscopes able to reconstruct particle tracks with sub-micron precision and high efficiency at a speed of ∼ 20cm2/h. This paper describes the performance in particle track reconstruction of the European Scanning System, a novel automatic microscope for the measurement of emulsion films developed for OPERA.

It's the particle accelerator LHC, the biggest ever built by Man. It will help us to understand was happened at the Big Bang. And how was born our universe. It is built in Geneva, and is a huge ring underground. It's proton beams that collide at the speed of light. There, thousands of scientists are working, they hope to find mysterious dimensions and particles, that will revolutionize science." (4 pages and lot of photos)

The ARGO-YBJ detector is an Extensive Air Shower (EAS) array located in Tibet (P.R. China) at 4300 m a.s.l., performing a continuos sky observation by shower reconstruction with an energy threshold of a few hundreds of GeV. To lower this threshold to E~1GeV the detector has been designed to work in scaler mode, i.e. recording the counting rate of each module of the detector at fixed time intervals. At these energies, signals due to local (e.g. solar events) and cosmological (e.g. Gamma Ray Bursts, GRBs) phenomena are expected as a significant enhancement of the counting rate over the background. Results of the search for the GRBs in coincidence with satellite detections are presented.

Yesterday in CERN, a celebration occured to mark the end of one crucial phase of the LHC installation. (1/2 page)

A detailed study of spatial resolution of Atlas pixel sensors prototypes was performed. Charge interpolation was used and allowed for a significant improvement with respect to digital resolution. A simplified algorithm for charge interpolation was developed. Its application to both unirradiated and irradiated sensors is presented and discussed.

With the competences of the physics and the italian industry, the super magnet that will be part of the biggest machine ever built bay Man: the particle accelerator LHC

Cern in Geneva announced in the past days that the installation phases of the lhc (Large Hadron Collider) reached the conclusive phase