Commissioning of the tracking system in the ATLAS detector

ATLAS is one of the four experiments that will analyze the p-p collisions at LHC. It consists of several subsystems: the Inner Detector is devoted to the measurement of the charged particle tracks in the interaction point region and the Pixel Detector is its innermost component. Both have been commissioned by using cosmic rays collected by the ATLAS detector in 2009. In the first part of the thesis, the spatial resolution of the Pixel Detector is studied and optimized. When a charged particle traverses the Pixel Detector, charges released in the sensors are collected by segmented electrodes, the pixels. The charge of each pixel is read out by the Time-over-Threshold technique and adjacent pixels are grouped into clusters. Cluster position can be computed by considering its geometrical center, but spatial resolution can be optimized if using charge information to improve position determination. In the second part of the thesis, the Inner Detector resolution in all track parameters has been studied by splitting each cosmic ray track into two halves. Since both halves stem from the same particle, they should be described by the same parameters. At the same time, the two tracks are fitted independently and can be compared to study the resolution of the tracking system. Resolution been studied as a function of track direction and distance from the beam axis. The multiple scattering contribution and several systematic effects due to residual misalignments have been evaluated

Ricerca di particelle supersimmetriche nell'ambito dell'esperimento ATLAS

The first part of the thesis reports a phenomenological study of the supersymmetric models known as “MSUGRA”. Particular emphasis is given to the “Focus Point” choice of the parameters that characterizes the MSUGRA models. The Focus Point model features a description of the Dark Matter density in the Universe that is compatible with the WMAP experimental data. Furthermore this model can be easily studied using ATLAS data, starting from the very few years of data taking. My original contribution to this study has been the calculation of the invariant mass distribution of the leptons that characterize a particular decay of neutralinos. The invariant mass distribution has been studied as a function of the neutralino mass. In the final part of the thesis, simulated data have been used to study the possibility of neutralino decay discovery with the ATLAS detector. The background relevance has been analyzed, as well as the precision that can be achieved in the neutralino mass measurement. As a conclusion the limits that can be imposed on the MSUGRA parameters have been determined as a function of the neutralino mass

Testing a phantom eye under various signal-to-noise ratio conditions using eleven different OCT devices

We compared eleven OCT devices in their ability to quantify retinal layer thicknesses under different signal-strength conditions, using a commercially available phantom eye. We analyzed a medium-intensity 50 µm layer in an identical manner for all devices, using the provided log-scale images and a reconstructed linear-scale tissue reflectivity metric. Thickness measurements were highly comparable when the data were analyzed in an identical manner. With optimal signal strength, the thickness of the 50 µm layer was overestimated by a mean of 4.3 µm in the log-scale images and of 2.7 µm in the linear-scale images

Cataract and optic disk drusen in a patient with glycogenosis and di George syndrome: clinical and molecular report

Background We report the ophthalmic findings of a patient with type Ia glycogen storage disease (GSD Ia), DiGeorge syndrome (DGS), cataract and optic nerve head drusen (ONHD). Case presentation A 26-year-old white woman, born at term by natural delivery presented with a post-natal diagnosis of GSD Ia. Genetic testing by array-comparative genomic hybridization (CGH) for DGS was required because of her low levels of serum calcium. The patient has been followed from birth, attending the day-hospital every six months at the San Paolo Hospital, Milan, outpatient clinic for metabolic diseases and previously at another eye center. During the last day-hospital visit, a complete eye examination showed ONHD and cataract in both eyes. Next Generation Sequencing (NGS) was subsequently done to check for any association between the eye problems and metabolic aspects. Conclusions This is the first description of ocular changes in a patient with GSD Ia and DGS. Mutations explaining GSD Ia and DGS were found but no specific causative mutation for cataract and ONHD. The metabolic etiology of her lens changes is known, whereas the pathogenesis of ONHD is not clear. Although the presence of cataract and ONHD could be a coincidence; the case reported could suggest that hypocalcemia due to DGS could be the common biochemical pathway

Commissioning of the tracking system in the ATLAS detector

ATLAS is one of the four experiments that will analyze the p-p collisions at LHC. It consists of several subsystems: the Inner Detector is devoted to the measurement of the charged particle tracks in the interaction point region and the Pixel Detector is its innermost component. Both have been commissioned by using cosmic rays collected by the ATLAS detector in 2009. In the first part of the thesis, the spatial resolution of the Pixel Detector is studied and optimized. When a charged particle traverses the Pixel Detector, charges released in the sensors are collected by segmented electrodes, the pixels. The charge of each pixel is read out by the Time-over-Threshold technique and adjacent pixels are grouped into clusters. Cluster position can be computed by considering its geometrical center, but spatial resolution can be optimized if using charge information to improve position determination. In the second part of the thesis, the Inner Detector resolution in all track parameters has been studied by splitting each cosmic ray track into two halves. Since both halves stem from the same particle, they should be described by the same parameters. At the same time, the two tracks are fitted independently and can be compared to study the resolution of the tracking system. Resolution been studied as a function of track direction and distance from the beam axis. The multiple scattering contribution and several systematic effects due to residual misalignments have been evaluated

Experimental results of crystal-assisted slow extraction at the SPS

The possibility of extracting highly energetic particles from the Super Proton Synchrotron (SPS) by means of silicon bent crystals has been explored since the 1990's. The channelling effect of a bent crystal can be used to strongly deflect primary protons and eject them from the synchrotron. Many studies and experiments have been carried out to investigate crystal channelling effects. The extraction of 120 and 270 GeV proton beams has already been demonstrated in the SPS with dedicated experiments located in the ring. Presently in the SPS, the UA9 experiment is performing studies to evaluate the possibility to use bent silicon crystals to steer particle beams in high energy accelerators. Recent studies on the feasibility of extraction from the SPS have been made using the UA9 infrastructure with a longer-term view of using crystals to help mitigate slow extraction induced activation of the SPS. In this paper, the possibility to eject particles into the extraction channel in LSS2 using the bent crystals already installed in the SPS is presented. Details of the concept, simulations and measurements carried out with beam are presented, before the outlook for the future is discussed.Comment: 4 pages, 7 figures, submitted to to International Particle Accelerator Conference (IPAC) 2017 in Copenhagen, Denmar

Solitary Fibrous Tumor of the Lower Leg: A Rare and Difficult Diagnosis

Solitary fibrous tumor (SFT) is a rare neoplasm that commonly originates in the pleura. Extrapleural locations are rare and for this reason sometimes difficult to diagnose. Malignant forms with local recurrence or distant metastases have been reported, also as a consequence of inappropriate treatment. In this article, we report the case of an SFT of the lower leg in a 37-year-old man. Leg SFT is a rare occurrence, and differential diagnosis may be difficult because they can mimic a variety of benign and malignant mesenchymal tumors; immunohistochemical analysis for CD34, CD99, vimentin, and Bcl-2 is necessary. Misdiagnosis carries a significant risk of inadequate removal with subsequent increased risk of recurrence and distant metastases

Healthcare Associated Infections. educational intervention by "Adult Learning" in an Italian teaching hospital

An educational intervention for HAI prevention based on a combination of training, motivation and subsequent application in the current clinical practice in an Italian teaching hospital