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Search Results: 1 - 10 of 189851 matches for " G. Ranucci "
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Results and perspectives of the solar neutrino experiment Borexino
G. Ranucci,Borexino Collaboration
Physics , 2008,
Abstract: Borexino is a massive, calorimetric, liquid scintillator detector aimed at the detection of low energy sub-MeV solar neutrinos, installed at the Gran Sasso Laboratory. After several years of construction, data taking started in May 2007, providing immediately incontrovertible evidence of the unprecedented radiopurity of the target mass, at the level required to ensure the successful detection of 7Be solar neutrinos, which was then announced in the 2007 summer. In this talk first the main technical characteristics of the detector will be highlighted, with special emphasis on the exceptional purity challenges successfully faced by the Collaboration, and afterwards the physics outputs reached so far will be carefully reported and illustrated, together with the perspectives for the future measurements that will complete the broad program of the experiment.
Precision measurements of timing characteristics of the 8" ETL9351 series photomultiplier
O. Ju. Smirnov,P. Lombardi,G. Ranucci
Physics , 2004,
Abstract: During the test measurements of the PMTs to be used in the future Borexino experiment, the data from 2200 PMT were accumulated. The unique timing characteristics of the apparatus used and the large statistics acquired, permit resololution of the fine structure of the ETL9351 PMT time response. A method to obtain the probability density function of the single photoelectron counting from the experimental data is proposed and applied to derive the PMT average characteristics. For the first time, an analytical model of the single photoelectron PMT time response is proposed, describing all the features of the single photoelectron time arrival. The origin of the small amplitude pulses is explained.
Neutrino Oscillations
G. Bellini,L. Ludhova,G. Ranucci,F. L. Villante
Advances in High Energy Physics , 2014, DOI: 10.1155/2014/191960
Abstract: In the last decades, a very important breakthrough has been brought about in the elementary particle physics by the discovery of the phenomenon of the neutrino oscillations, which has shown neutrino properties beyond the Standard Model. But a full understanding of the various aspects of the neutrino oscillations is far to be achieved. In this paper the theoretical background of the neutrino oscillation phenomenon is described, referring in particular to the paradigmatic models. Then the various techniques and detectors which studied neutrinos from different sources are discussed, starting from the pioneering ones up to the detectors still in operation and to those in preparation. The physics results are finally presented adopting the same research path which has been crossed by this long saga. The problems not yet fixed in this field are discussed, together with the perspectives of their solutions in the near future. 1. Introduction Neutrino studies brought us to some of the most relevant breakthroughs in particle physics of last decades. In spite of that, the neutrino properties are still far to be completely understood. The discovery of the oscillation phenomenon produced quite a revolution in the Standard Model of elementary particles, especially through the direct evidence of a nonzero neutrino mass. The first idea of neutrino oscillations was considered by Pontecorvo in 1957 [1–3], before any experimental indication of this phenomenon. After several-decades-lasting saga of experimental and theoretical research, many questions are still open around the interpretation of this phenomenon and on the correlated aspects, on the oscillation parameters, on the neutrino masses, on the mass hierarchy, on CP violation in the leptonic sector, and on a possible existence of a fourth, sterile neutrino. The generally accepted MSW model [4–6] to interpret solar neutrino oscillations is presently validated for the oscillation in vacuum and in matter, but not yet in the vacuum-matter transition region. The shape of this transition could be influenced in a relevant way, as suggested by various theories going beyond the Standard Model as, for example, the nonstandard neutrino interactions and a possible existence of a very light sterile neutrino. For this reason, the transition region deserves further and refined experimental studies. Checks on the neutrino oscillations are under way through several experiments in data-taking phase, while few others are in preparation or even construction. These projects exploit various approaches, for example, neutrino-flavor
The measurements of 2200 ETL9351 type photomultipliers for the Borexino experiment with the photomultiplier testing facility at LNGS
A. Ianni,P. Lombardi,G. Ranucci,O. Smirnov
Physics , 2004, DOI: 10.1016/j.nima.2004.07.249
Abstract: The results of tests of more than 2200 ETL9351 type PMTs for the Borexino detector with the PMT test facility are presented. The PMTs characteristics relevant for the proper detector operation and modeling are discussed in detail.
The photomultiplier tube testing facility for the Borexino experiment at LNGS
A. Brigatti,A. Ianni,P. Lombardi,G. Ranucci,O. Smirnov
Physics , 2004, DOI: 10.1016/j.nima.2004.07.248
Abstract: A facility to test the photomultiplier tubes (PMTs) for the solar neutrino detector Borexino was built at the Gran Sasso laboratory. Using the facility 2200 PMTs with optimal characteristics were selected from the 2350 delivered from the manufacturer. The details of the hardware used are presented.
Bivalirudin and post-cardiotomy ECMO: a word of caution
Marco Ranucci
Critical Care , 2012, DOI: 10.1186/cc11314
Abstract: In a recent issue of Critical Care [1], we presented a series of 13 patients undergoing post-cardiotomy extracorporeal membrane oxygenation (ECMO) with bivalirudin-based anticoagulation. After this series, we satisfactorily continued this experience, reaching about 20 patients treated. However, we think that a word of caution should be added to our recently published experience.Owing to its pharmacological profile, bivalirudin is rapidly cleaved by proteolytic enzymes, and its half-life is about 25 minutes when the renal function is normal [2]. The use of bivalirudin for cardiopulmonary bypass (CPB) [3] and ECMO [4] is a feasible option. However, it is recommended that, during CPB, blood stagnation in the circuit be avoided because the rapid cleavage of bivalirudin may result in thrombosis. The ECMO circuit is devoid of a reservoir, and therefore blood stagnation is usually not a circuit- related problem. Conversely, under some circumstances, the cardiac chambers may act as a 'natural reservoir', which entails blood stagnation and the risk for spontaneous intracardiac thrombosis. This is particularly true in the case of a very large right or left atrium with insufficient venous drainage or the case of very poor ventricular systolic function with intraventricular blood stagnation.To avoid this condition, we think that maintaining a partial ECMO support, leaving a minimal degree of intracardiac blood flow, may be a reasonable choice. This may be checked by echocardiographic view of heart valve movement or simply by the observation of some degree of pulsatile arterial blood pressure.We think that, in the event of echocardiographic evidence of a 'smoke effect' within one or more cardiac chambers, bivalirudin should be replaced by standard heparin anticoagulation. Intracardiac thrombus formation during ECMO with heparin anticoagulation has been described as well [5], but the pharmacokinetic properties of heparin may limit the risk of thrombus formation due to blood stagn
Which cardiac surgical patients can benefit from placement of a pulmonary artery catheter?
Marco Ranucci
Critical Care , 2006, DOI: 10.1186/cc4833
Abstract: Placement of a pulmonary artery catheter (PAC) is an intraoperative right heart catheterization procedure. It therefore provides clinical information on heart chamber pressures, blood flows and vascular resistances – similar to the information obtained during a catheterization laboratory investigation before the operation. Unsurprisingly, since the inception of the PAC cardiac pathology has been its natural 'battlefield' [1], and cardiac surgery is the natural setting in which is it applied.By definition, the cardiac surgical patient always has underlying cardiac pathology; such pathology can affect intracardiac pressures and/or myocardial ability to sustain adequate cardiac output. As a consequence of the underlying pathology and/or use of specific drugs, the patient can exhibit changes in systemic and pulmonary resistive state. Moreover, the cardiac surgery itself may result in sudden changes in systolic and diastolic right or left ventricular function, and cardiopulmonary bypass (CPB) may induce release of vasoactive mediators that change flow resistances at the level of the systemic or pulmonary circulation. Finally, the common intraoperative and postoperative use of drugs that act potently on myocardial contractility, and that induce systemic or pulmonary vasodilatation or vasoconstriction permits control of the patient's haemodynamic profile both during and after the operation.In spite of this, and for several reasons, PACs are not routinely used in all cardiac surgical institutions or in all cardiac surgical patients. The present review addresses the present situation regarding use of PACs in cardiac surgery, and defines those categories of cardiac surgical patients that may truly benefit from PAC placement.In 1997 a consensus conference PACs [2] was convened to address the issue of PAC use in different clinical scenarios. In the setting of cardiac surgery it was agreed that clinical management with PACs does not improve outcome in low-risk cardiac surgical p
Luis VERDESOTO CUSTODE (coord.). La Región Andina y Espa a: hacia una reformulación de sus relaciones . Ecuador: Flacso, 2012. 208 pp. ISBN: 978-997-8673-40-9.
América Latina Hoy , 2012,
Binomial and ratio-of-Poisson-means frequentist confidence intervals applied to the error evaluation of cut efficiencies
Gioacchino Ranucci
Physics , 2009,
Abstract: The evaluation of the error to be attributed to cut efficiencies is a common question in the practice of experimental particle physics. Specifically, the need to evaluate the efficiency of the cuts for background removal, when they are tested in a signal-free-background-only energy window, originates a statistical problem which finds its natural framework in the ample family of solutions for two classical, and closely related, questions, i.e. the determination of confidence intervals for the parameter of a binomial proportion and for the ratio of Poisson means. In this paper the problem is first addressed from the traditional perspective, and afterwards naturally evolved towards the introduction of non standard confidence intervals both for the binomial and Poisson cases; in particular, special emphasis is given to the intervals obtained through the application of the likelihood ratio ordering to the traditional Neyman prescription for the confidence limits determination. Due to their attractiveness in term of reduced length and of coverage properties, the new intervals are well suited as interesting alternative to the standard Clopper-Pearson PDG intervals.
On the significance of the excesses in the ATLAS diphoton and four lepton decay channels
Gioacchino Ranucci
Physics , 2012,
Abstract: This note describes an assessment of the statistical significance of the recently released ATLAS data regarding the Higgs search in the decay channels especially suited for the low mass region, in particular the diphoton and four lepton decay channels. Besides providing the significance evaluation of the considered channels, alone or combined, in the low mass range from 110 to 146 GeV, some details of the profile likelihood procedure employed for the calculations are described, too. Special emphasis is given to the look elsewhere effect, which arises when the search of a new signal is carried out over a broad mass range, therefore specifying separately local and global significances. When combined together, the global p-value of the localized excesses detected in the two channels is found equal to either 0.033 or 0.013, corresponding, respectively, to a significance of 1.8 sigma and 2.2 sigma depending upon the assumption of mutual independence or dependence of the amplitudes of the expected signal in each channel. Among the other obtained results, the local and global significances of the two channels individually taken are computed in good agreement with those reported by the Collaboration, while only a minor discrepancy is found for their combined local significance. Finally, some considerations are illustrated related to the low statistics four lepton decay channel, showing that a search strategy different from the profile likelihood method, e.g. scan statistics, can result in a substantially different significance, enhanced to a 3.3 sigma global effect.
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