B meson proper time measurements with the LHCb experiment: impact on physics parameters and calibration methods

The LHCb (Large Hadron Collider beauty) experiment is one of the four experiments at the LHC, and is specifically dedicated to explore the B-meson dynamics. To this end, LHCb will exploit the large beauty production cross section, expected to be about 500 µb at 14 TeV p-p collisions. Differently from the B-factory case, the hadronization of the b-quarks at LHC will generate all the possible B-hadrons, remarkably the Bs and Bc mesons, where the present experimental knowledge is still rather poor. The number of b/b_bar pairs produced at the LHCb interaction point will be of the order of 10^12 per year, allowing for the search of extremely rare decays, with branching fractions at the level of 10^-9. In order to reduce the acquisition rate to a sustainable level (order of 2 kHz), maintaining at the same time a high efficiency on the signals of interest, LHCb is provided with an efficient and flexible trigger system. LHCb, by means of its vertex detector, will be able to reconstruct the proper time of decays with a great accuracy (~ 40 fs) and therefore it is well suitable to study minutely CP violation for the very fast oscillating Bs mesons. Moreover the features of the LHCb detector are also suitable to study the charm and tau decays, which also other another great opportunity to find out New Physics. For my Ph.D thesis, I developed a new procedure (called the FITPull method) to monitor and check the measurement of the B decay proper time and its error. The procedure is based on the use of the kinematical constraints between the track parameters of the particles involved in the B decays, without relying on Monte Carlo information. The method can be calibrated on the decay mode J/psi->>µµ, which will be exploited by LHCb as a general monitor channel for the charged tracks calibration, with the aim of identifying and eventually recovering imperfect measurements of the track parameters. I applied the FITPull method to two different reference channels: B --> h+h- and Bs -> Ds pi, evaluating its performance in correcting track measurement errors. I have also contributed to the implementation of a software tool, the GlobalFitter , that is used to compute the FITPull distributions of the input track parameters. The thesis is organized in 4 chapters. In Chapter 1 the LHCb experiment, its sub-detectors and trigger system are described. Chapter 2 introduces the theoretical framework of the B-meson mixing and CP violation in the Standard Model, with some details of the relevant measurements that LHCb will perform. In Chapter 3 the FITPull method is described, and finally Chapter 4 gathers the results of some studies on Monte Carlo simulated data, by investigating the impact of the calibration method on the physical quantities which are mostly affected by the precision of the B proper time measurement

CMB Polarization: Scientific Case and Data Analysis Issues

We review the science case for studying CMB polarization. We then discuss the main issues related to the analysis of forth-coming polarized CMB data, such as those expected from balloon-borne (e.g. BOOMERanG) and satellite (e.g. Planck) experiments.Comment: 6 pages, 4 figures. To appear in "Astrophysical Polarized Background" Workshop Proceedings, eds. S. Cecchini, S. Cortiglioni, R. Sault and C. Sbarra, AIP, in pres

The FIT-pull Method: an experimental tool to monitor the track measurements and the B proper time.

In this note we describe a statistical tool, the \textit{FIT-pull method}, that can test the reliability of the measurements of the tracks and the vertices on real and Monte-Carlo data without knowledge of the truth information. The basic mathematical formalism is derived from the Lagrange Multipliers method and briefly described. Several tests are performed to prove its validity in different situations. %KDifferent useful examples are discussed. In particular, by using Monte-Carlo simulation, we demonstrate that the method can be applied to check if the measured tracks or vertices have biases or incorrect covariance matrices. For correct input measurements we obtain pull distributions with a normal Gaussian statistical form. In this case the B proper time value and its error, which is a function of the track and vertex measurements, are correctly calculated. However, in the case of incorrect measurements, for example due to a systematic error or to a scale factor of the covariance matrix, the pull distributions studied deviate from normal Gaussians and the B proper time measurement can be affected. In principle the method can, if necessary, be used to recover information from corrupted measurements. Its potential in this capacity is demonstrated for the particular case of the decay channel $B^0_d \to \pi^+ \pi^-$ with the reconstructed Monte-Carlo data produced in 2004

Magnetic resonance and ultrasound contrast imaging of polymer-shelled microbubbles loaded with iron oxide nanoparticles

Dual-mode contrast agents (CAs) have great potential for improving diagnostics. However, the effectiveness of CAs is strictly related to both the solution adopted to merge the two agents into a single probe unit, and the ratio between the two agents. In this study, two dual-mode CAs for simultaneous magnetic resonance imaging (MRI) and ultrasound imaging (UI) were assessed. For this purpose, different densities of superparamagnetic iron oxide nanoparticles (SPIONs) were anchored to the external surface of polymer-shelled microbubbles (MBs) or were physically entrapped into the shell. In vitro static and dynamic experiments were carried out with a limited concentration of modified MBs (106 bubbles ml 121) by avoiding destruction during UI (performed at a peak pressure lower than 320 kPa) and by using a lowfield MRI system (with a magnetic flux density equal to 0.25 T). Under these conditions, different imaging techniques, set-up parameters and SPION densities were used to achieve satisfactory detection of the CAs by using both UI and MRI. However, when the SPION density was increased, the MRI contrast improved, whereas the UI contrast worsened due to the reduced elasticity of the MB shell. For both UI and MRI, MBs with externally anchored SPIONs provided better performance than MBs with SPIONs entrapped into the shell. In particular, a SPION density of 29% with respect to the mass of the MBs was successfully tested

Mathematical modelling of axonal cortex contractility

The axonal cortex is composed of a regular structure of F-actin and spectrin able to contract thanks to myosin II motors. Such an active tension is of fundamental importance in controlling the physiological shape of axons. Recent experiments show that axons modulate the contraction of the cortex when subject to mechanical deformations, exhibiting a non-trivial coupling between the hoop and the axial active tension. However, the underlying mechanisms are still poorly understood. In this paper, we propose a continuum model of the axon based on the active strain theory. By using the Coleman–Noll procedure, we shed light on the coupling between the hoop and the axial active strain through the Mandel stress tensor. We propose a qualitative analysis of the system under the simplifying assumption of incompressibility, showing the existence of a stable equilibrium solution. In particular, our results show that the axon regulates the active contraction to maintain a homeostatic stress state. Finally, we propose numerical simulations of the model, using a more suitable compressible constitutive law. The results are compared with experimental data, showing an excellent quantitative agreement

Sudden death after valve-in-valve procedure due to delayed coronary obstruction. A case report

Background: Valve-in-valve transcatheter aortic valve implantation for degenerated aortic bioprostheses is an effective option for patients at high risk for redo surgery, even if it may be burdened by complications more common in specific settings, such as, coronary artery obstruction. Case presentation: We present the case of a Caucasic 84-year-old woman with degeneration of a previously implanted aortic Mitroflow bioprosthesis. She underwent a valve-in-valve transcatheter aortic valve implantation with a CoreValve® bioprosthesis. End-procedure coronary angiography demonstrated maintained perfusion of both coronary arteries. However, few hours later, she experienced sudden cardiac death. An autopsy showed that Mitroflow prosthesis leaflets were higher than the left main coronary ostium, and no other possible cause for the sudden death. Fatality was thus ascribed to left main coronary ostium obstruction due to apposition of the Mitroflow leaflet pushed upward by the late expansion of CoreValve®. Conclusions: Coronary artery obstruction is a frequently fatal complication which usually presents just after valve implantation, but, as reported in our case, it may also have a delayed presentation. Accurate patient's selection and intraoperative preventive measures can reduce this eventuality

Affine equation of state from quintessence and k-essence fields

We explore the possibility that a scalar field with appropriate Lagrangian can mimic a perfect fluid with an affine barotropic equation of state. The latter can be thought of as a generic cosmological dark component evolving as an effective cosmological constant plus a generalized dark matter. As such, it can be used as a simple, phenomenological model for either dark energy or unified dark matter. Furthermore, it can approximate (up to first order in the energy density) any barotropic dark fluid with arbitrary equation of state. We find that two kinds of Lagrangian for the scalar field can reproduce the desired behaviour: a quintessence-like with a hyperbolic potential, or a purely kinetic k-essence one. We discuss the behaviour of these two classes of models from the point of view of the cosmological background, and we give some hints on their possible clustering properties.Comment: 9 pages, 6 figures. Minor updates, accepted by CQ

Urgent cesarean delivery following a spontaneous coronary artery dissection

Objective: Rare disease Background: Spontaneous coronary artery dissection is the most common etiology of pregnancy-associated myocardial infarction. It is characterized by high rates of maternal morbidity and mortality and may cause fetal complications and death as well. Case Report: A 44-year-old female (G2P1) suffered from pregnancy-related spontaneous coronary artery dissection with dissection of distal left anterior descending coronary artery. The patient was hemodynamically stable and did not required revascularization, but signs of fetal distress were detected and thus an urgent cesarean delivery was performed. This emergency procedure was undertaken in the catheterization laboratory (Cath-Lab) right after coronary angiography, thanks to a multidisciplinary team. Health conditions of the newborn were good. The patient instead suffered from a recurrence of spontaneous coronary artery dissection 6 days later, complicated by left ventricular apical thrombus and epistenocardial pericarditis. The dissection self-healed in 1 month. Conclusions: Careful evaluation of pregnancy-related spontaneous coronary artery dissection is needed to assess and manage both maternal and fetal complications. Under specific circumstances, a cesarean delivery may be required and be even performed in the Cath-Lab after coronary catheterization

Resilience framework for seaport infrastructure: theory and application

The efficient movement of goods is crucial to the economic growth of communities. This makes the existence of seaports essential for the marine transportation system. Due to their natural location, ports are continuously threatened by natural hazards such as wind action, which necessitates a continuous monitoring and assessment for their performance. The work presented here aims at assessing the resilience of ports against natural disasters. This is done by identifying the performance and the recovery rate of such infrastructure during the period following the event. The research commenced with gathering information about the port’s main components that are influenced by natural hazards. The collected data has been compiled in the form of indicators, which have been filtered and grouped under four dimensions in the proposed “PORT framework”. Each of the indicator has been allocated a measure to enable its quantitative evaluation. The aggregation of the indicators’ values allows identifying the port resilience