16866620
Analysis of charmonium production at fixed-target experiments in the NRQCD approach
We present an analysis of the existing data on charmonium hadro-production based on non-relativistic QCD (NRQCD) calculations at the next-to-leading order (NLO). All the data on J/psi and psi' production in fixed-target experiments and on pp collisions at low energy are included. We find that the amount of color octet contribution needed to describe the data is about 1/10 of that found at the Tevatron.
22317714
2D and 3D thin pixel technologies for the Layer0 of the SuperB Silicon Vertex Tracker
The high luminosity asymmetric e+e− collider SuperB, recently approved by the Italian Government, is designed to deliver a luminosity greater than 1036cm−2s−1 with moderate beam currents and a reduced center of mass boost with respect to earlier B-Factories. An improved vertex resolution is required for precise time-dependent measurements and the SuperB Silicon Vertex Tracker will be equipped with an innermost layer of small radius (about 1.5 cm), resolution of 10 µm in both coordinates, low material budget (&#60; 1% X0), and able to withstand a hit background rate of several tens of MHz/cm2. The ambitious goal of designing a thin pixel device matching these stringent requirements is being pursued with specific R&D programs on different technologies: CMOS MAPS, pixel sensors in vertical integration technology and hybrid pixels with small pitch and reduced material budget. The latest results on the characterization of the various pixel devices realized for the SuperB Layer0 will be presented.
109210110
Advances in the development of pixel detector for the SuperB Silicon Vertex Tracker
The latest advances in the design and characterization of several pixel sensors developed to satisfy the very demanding requirements of the innermost layer of the SuperB Silicon Vertex Tracker will be presented in this paper. The SuperB machine is an electron positron collider operating at the ϒ(4S)ϒ(4S) peak to be built in the very near future by the Cabibbo Lab consortium. A pixel detector based on extremely thin, radiation hard devices able to cope with rate in the tens of MHz/cm^2 range will be the optimal solution for the upgrade of the inner layer of the SuperB tracking system. At present several options with different levels of maturity are being investigated to understand advantages and potential issues of the different technologies: thin hybrid pixels, Deep N-Well CMOS MAPS, INMAPS CMOS MAPS featuring a quadruple well and high resistivity substrates and CMOS MAPS realized with Vertical Integration technology. The newest results from beam test, the outcomes of the radiation damage studies and the laboratory characterization of the latest prototypes will be reported.
111127502
The front-end chip of the SuperB SVT detector
Abstract The asymmetric e + e − collider SuperB is designed to deliver a high luminosity, greater than 10 36 cm − 2 s − 1 , with moderate beam currents and a reduced center of mass boost with respect to earlier B-Factories. The innermost detector is the Silicon Vertex Tracker which is made of 5 layers of double sided silicon strip sensors plus a layer 0, that can be equipped with short striplets detectors in a first phase of the experiment. In order to achieve an overall track reconstruction efficiency above 98% it is crucial to optimize both analog and digital readout circuits. The readout architecture being developed for the front-end chips will be able to cope with the very high rates expected in the first layer. The digital readout will be optimized to be fully efficient for hit rates up to 2 MHz/strip, including large margins on the maximum expected background rates, but can potentially accommodate higher rates with a proper tuning of the buffer depth. The readout is based on a triggered architecture where each of the 128 strip channel is provided with a dedicated digital buffer. Each buffer collects the digitized charge information by means of a 4-bit TOT, storing it in conjunction with the related time stamp. The depth of buffers was dimensioned considering the expected trigger latency and hit rate including suitable safety margins. Every buffer is connected to a highly parallelized circuit handling the trigger logic, rejecting expired data in the buffers and channeling the parallel stream of triggered hits to the common output of the chip. The presented architecture has been modeled by HDL language and investigated with a Monte Carlo hit generator emulating the analog front-end behavior. The simulations showed that even applying the highest stressing conditions, about 2 MHz per strip, the efficiency of the digital readout remained above 99.8%.
120117699
Latest results of the R&D on CMOS MAPS for the Layer0 of the SuperB SVT
Physics and high background conditions set very challenging requirements on readout speed, material budget and resolution for the innermost layer of the SuperB Silicon Vertex Tracker operated at the full luminosity. Monolithic Active Pixel Sensors (MAPS) are very appealing in this application since the thin sensitive region allows grinding the substrate to tens of microns. Deep N-Well MAPS, developed in the ST 130 nm CMOS technology, achieved in-pixel sparsification and fast time stamping. Further improvements are being explored with an intense R&D program, including both vertical integration and 2D MAPS with the INMAPS quadruple well. We present the results of the characterization with IR laser, radioactive sources and beam of several chips produced with the 3D (Chartered/Tezzaron) process. We have also studied prototypes exploiting the features of the quadruple well and the high resistivity epitaxial layer of the INMAPS 180 nm process. Promising results from an irradiation campaign with neutrons on small matrices and other test-structures, as well as the response of the sensors to high energy charged tracks are presented.
118564891
On a Purely Geometric Approach to the Dirac Matter Field and Its Quantum Properties
We consider the most general axial torsion completion of gravity with electrodynamics for $\frac{1}{2}$-spin spinors in an 8-dimensional representation of the Dirac matter field: this theory will allow to define antimatter as matter with all quantum numbers reversed, where also the sign of the mass beside that of the charge is inverted: we shall see that matter and antimatter solutions of the Dirac field equations coincide with the known ones with respect to all observables, that despite the inversion of the sign of the mass term only positive-mass states are present and only positive-energy densities are given; the present and the common approach will be compared, and some experimental implications will be discussed.
119247598
From the Torsion Tensor for Spinors to the Weak Forces for Leptons
We consider a geometric approach to field theory in which torsion is present beside gravity and also electrodynamics for the matter field equations, and we develop the consequences of the torsion-spin coupling for the spinor fields; we show that these interactions have the structure of the weak interactions acting among leptons: we discuss the implications for the standard model of fundamental interactions of elementary fields in the perspective of the foundations of unification in theoretical physics.
15801853
On the Principle of Equivalence
We consider the Principle of Equivalence along with Weyl theorem to discuss the interpretation of gravity as a geometric effect; we study what are the restrictions on the connections that must be required for this geometrization to occur in the most general case.
118548429
A TORSIONAL MODEL OF LEPTONS
Quite recently it was shown that torsion induces interactions among leptons that are identical to the weak interactions of leptons of the Weinberg Standard Model, if it is in terms of leptonic bound states that the bosonic sector is built; here we obtain the partially conserved axial currents showing that they are the same of the Standard Model, if the composite mediators have specific mass relationships: we show that their masses are indeed the measured ones, if reasonable approximations are taken.
118477044
A Discussion on Dirac Field Theory, No-Go Theorems and Renormalizability
We study Dirac field equations coupled to electrodynamics with metric and torsion fields: we discuss how special spinorial solutions are incompatible with torsion; eventually these results will be used to sketch a discussion on the problem of renormalizability of point-like particles.