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.
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.
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.
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%.
109274131
The EDRO Board Connected to the Associative Memory: a “Baby” FastTracKer Processor for the ATLAS Experiment
Abstract The FastTracKer (FTK), a hardware dedicated processor, performs fast and precise online full track reconstruction at the ATLAS experiment, within an average latency of few dozens of microseconds. Before production of the ﬁnal system for tracking in high-occupancy conditions with the best of available technology, we plan to use existing prototypes of the FTK hardware to exercise its functions in the ATLAS environment. We describe the “baby FTK”, consisting of a few hardware elements implementing the ﬁrst stages of the system, and discuss our plans to grow the system into a full-functionality FTK “vertical slice” covering a small projective wedge of the detector. We report on the performances and structure of the “baby FTK”, including the pixel/strip hit clustering (clustering mezzanine), hit organization and distribution (EDRO) and the Associative Memory pattern recognition function. We describe brieﬂy also the possible future evolution including the addition of the Track Fitter.
120546156
A radiation tolerant phototube power supply for the electromagnetic calorimeter of the HERA-B experiment
Abstract The design of the phototube power supply for the HERA- B Electromagnetic Calorimeter is presented. A choice of the solution on the basis of the Cockcroft–Walton voltage multiplier is validated. Schematics developed are discussed. A special section describes the behaviour of the crucial components under irradiation since radiation tolerance becomes one of the most important items in the severe HERA- B radiation environment. Finally, performance achieved is presented.
119165266
The most general ELKO matter in torsional f(R)‐theories
We study f(R)-gravity with torsion in presence of the most general ELKO matter, checking the consistency of the conservation laws with the matter field equations; we discuss some mathematical features of the field equations in connection with a cosmological application.
119118411
The Einstein-Yang-Mills equations from Bianchi identities
We suggest a novel extension to the Kaluza–Klein scheme that allows us to obtain consistently all SU(n) Einstein–Yang–Mills theories. This construction is based on allowing the five-dimensional spacetime to carry some nonvanishing torsion; however, the four-dimensional spacetime remains intrinsically torsion-free.
15234170
Spontaneous breaking of conformal invariance in theories of conformally coupled matter and Weyl gravity
We study the theory of Weyl conformal gravity with matter degrees of freedom in a conformally invariant interaction. Specifically, we consider a triplet of scalar fields and SO(3) non-Abelian gauge fields, i.e. the Georgi–Glashow model conformally coupled to Weyl gravity. We show that the equations of motion admit solutions spontaneously breaking the conformal symmetry and the gauge symmetry, providing a mechanism for supplying a scale in the theory. The vacuum solution corresponds to anti-de Sitter spacetime, while localized soliton solutions correspond to magnetic monopoles in asymptotically anti-de Sitter spacetime. This mechanism strengthens the reasons for considering conformally invariant matter-gravity theory, which has shown promising indications concerning the problem of missing matter in galactic rotation curves.
55190310
Conformal Gravity with Dirac Matter
Recently, we have constructed the conformal gravity with metric and torsion, finding the gravitational field equations that give the conservation laws and trace condition; in the present paper we apply this theory to the case of the Dirac matter field: we shall see that in this case the trace condition becomes trivial, but further constraints arise, which will impose severe limitations on the dynamics of such a system.
118526683
A square-torsion modification of Einstein-Cartan theory
In the present paper a theory of gravity is considered in which not only curvature but also torsion is explicitly present in the Lagrangian, both with their own coupling constant. In particular, the couplings to Dirac fields and spin fluids are discussed: in the case of Dirac fields, it is discusses how the Dirac self-interactions depend on the coupling constant as a parameter that may even make these non-linearitiesmanifest at subatomic scales, showing different applications according to the value of the parameter assigned; in the case of spin fluids, FLRW cosmological models arising from the proposed theory are discussed.