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Resta-Lopez, J. (2013). Nonlinear protection of beam delivery systems for multi-TeV linear colliders. J. Instrum., 8, P11010–19pp.
Abstract: The post-linac energy collimation system of future e(+)e(-) multi-TeV linear colliders is designed to fulfil an essential function of protection of the Beam Delivery System (BDS) against miss-steered or errant beams likely generated by failure modes in the main linac. For the case of the Compact Linear Collider (CLIC), the energy collimators are required to withstand the impact of a full bunch train in case of failure. This condition makes the design of the energy collimation system especially challenging, if we take into account the need to dispose of an unprecedented transverse beam energy density per beam of the order of GJ/mm(2), when assuming the nominal CLIC beam parameters at 3 TeV centre-of-mass energy, which translates into an extremely high damage potential of uncontrolled beams. This leads to research activities involving new collimator materials and novel collimation techniques. The increase of the transverse spot size at the collimators using nonlinear magnets is a potential solution to guarantee the survival of the collimators. In this paper we present an alternative nonlinear optics based on a multipole magnet pair for energy collimation. In order to preserve an acceptable luminosity performance, we carefully study the general conditions for self-cancellation of optical aberrations between two multipoles. This nonlinear optics scheme is adapted to the requirements of the post-linac energy collimation system for the CLIC BDS, and its performance is investigated by means of beam tracking simulations. Although applied to the CLIC case, this nonlinear protection system could be adapted to other future colliders.
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Marco-Hernandez, R. (2011). Development of a beam test telescope based on the Alibava readout system. J. Instrum., 6, C01002–7pp.
Abstract: A telescope for a beam test have been developed as a result of a collaboration among the University of Liverpool, Centro Nacional de Microelectronica (CNM) of Barcelona and Instituto de Fisica Corpuscular (IFIC) of Valencia. This system is intended to carry out both analogue charge collection and spatial resolution measurements with different types of microstrip or pixel silicon detectors in a beam test environment. The telescope has four XY measurement as well as trigger planes (XYT board) and it can accommodate up to twelve devices under test (DUT board). The DUT board uses two Beetle ASICs for the readout of chilled silicon detectors. The board could operate in a self-triggering mode. The board features a temperature sensor and it can be mounted on a rotary stage. A peltier element is used for cooling the DUT. Each XYT board measures the track space points using two silicon strip detectors connected to two Beetle ASICs. It can also trigger on the particle tracks in the beam test. The board includes a CPLD which allows for the synchronization of the trigger signal to a common clock frequency, delaying and implementing coincidence with other XYT boards. An Alibava mother board is used to read out and to control each XYT/DUT board from a common trigger signal and a common clock signal. The Alibava board has a TDC on board to have a time stamp of each trigger. The data collected by each Alibava board is sent to a master card by means of a local data/address bus following a custom digital protocol. The master board distributes the trigger, clock and reset signals. It also merges the data streams from up to sixteen Alibava boards. The board has also a test channel for testing in a standard mode a XYT or DUT board. This board is implemented with a Xilinx development board and a custom patch board. The master board is connected with the DAQ software via 100M Ethernet. Track based alignment software has also been developed for the data obtained with the DAQ software.
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Mendez, V., Amoros, G., Garcia, F., & Salt, J. (2010). Emergent algorithms for replica location and selection in data grid. Futur. Gener. Comp. Syst., 26(7), 934–946.
Abstract: Grid infrastructures for e-Science projects are growing in magnitude terms. Improvements in data Grid replication algorithms may be critical in many of these infrastructures. This paper shows a decentralized replica optimization service, providing a general Emergent Artificial Intelligence (EAI) algorithm for the problem definition. Our aim is to set up a theoretical framework for emergent heuristics in Grid environments. Further, we describe two EAI approaches, the Particle Swarm Optimization PSO-Grid Multiswarm Federation and the Ant Colony Optimization ACO-Grid Asynchronous Colonies Optimization replica optimization algorithms, with some examples. We also present extended results with best performance and scalability features for PSO-Grid Multiswarrn Federation.
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Rodriguez-Alvarez, M. J., Sanchez, F., Soriano, A., Iborra, A., & Mora, C. (2011). Exploiting symmetries for weight matrix design in CT imaging. Math. Comput. Model., 54(7-8), 1655–1664.
Abstract: In this paper we propose several methods of constructing the system matrix (SM) of a Computed Tomography (CT) scanner with two objectives: (1) to construct SMs in the shortest possible time and store them in an ordinary PC without losing quality, (2) to analyze the possible applications of the proposed method to 3D, taking into account SMs' sizes, computing time and reconstructed image quality. In order to build the SM, we propose two new field of view (FOV) pixellation schemes, based on a polar coordinate system (polar grid) by taking advantage of the polar rotation symmetries of CT devices. Comparisons between the SMs proposed are performed using two phantom and a real CT-simulator images. Global error, contrast, noise and homogeneity of the reconstructed images are discussed.
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Panotopoulos, G. (2011). A dynamical dark energy model with a given luminosity distance. Gen. Relativ. Gravit., 43(11), 3191–3199.
Abstract: It is assumed that the current cosmic acceleration is driven by a scalar field, the Lagrangian of which is a function of the kinetic term only, and that the luminosity distance is a given function of the red-shift. Upon comparison with baryon acoustic oscillations and cosmic microwave background data the parameters of the models are determined, and then the time evolution of the scalar field is determined by the dynamics using the cosmological equations. We find that the solution is very different than the corresponding solution when the non-relativistic matter is ignored, and that the universe enters the acceleration era at larger red-shift compared to the standard I > CDM model.
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Yepes, H. (2012). The ANTARES neutrino detector instrumentation. J. Instrum., 7, C01022–9pp.
Abstract: ANTARES is actually the fully operational and the largest neutrino telescope in the Northern hemisphere. Located in the Mediterranean Sea, it consists of a 3D array of 885 photomultiplier tubes (PMTs) arranged in 12 detection lines (25 storeys each), able to detect the Cherenkov light induced by upgoing relativistic muons produced in the interaction of high energy cosmic neutrinos with the detector surroundings. Among its physics goals, the search for neutrino astrophysical sources and the indirect detection of dark matter particles coming from the sun are of particular interest. To reach these goals, good accuracy in track reconstruction is mandatory, so several calibration systems for timing and positioning have been developed. In this contribution we will present the design of the detector, calibration systems, associated equipment and its performance on track reconstruction.
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Esperante-Pereira, D. (2014). DEPFET active pixel sensors for the vertex detector of the Belle-II experiment. J. Instrum., 9, C03004–11pp.
Abstract: Active pixels sensors based on the DEPFET technology will be used for the innermost vertex detector of the future Belle-II experiment. The increased luminosity of the e(+) e(-) SuperKEKB collider entails challenging detector requirements, namely: low material budget, low power consumption, high precision and efficiency, and a large readout rate. The DEPFET active pixel technology has shown to be a suitable solution for this purpose. A review of the different aspects of the detector design (sensors, readout ASICS and supplementary infrastructure) and the results of the latest thinned sensor prototypes (50 μm) are described.
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Pallis, C. (2014). Linking Starobinsky-type inflation in no-scale supergravity to MSSM. J. Cosmol. Astropart. Phys., 04(4), 024–31pp.
Abstract: A novel realization of the Starobinsky inflationary model within a moderate extension of the Minimal Supersymmetric Standard Model (MSSM) is presented. The proposed superpotential is uniquely determined by applying a continuous R and a Z2 discrete symmetry, whereas the Kahler potential is associated with a no-scale-type SU(54, 1)/ SU(54) x U(1) R X Z2 Kahler manifold. The inflaton is identified with a Higgs-like modulus whose the vacuum expectation value controls the gravitational strength. Thanks to a strong enough coupling (with a parameter CT involved) between the inflaton and the Ricci scalar curvature, inflation can be attained even for subplanckian values of the inflaton with CT >= 76 and the corresponding effective theory being valid up to the Planck scale. The inflationary observables turn out to be in agreement with the current data and the inflaton mass is predicted to be 3 10(3) GeV. At the cost of a relatively small superpotential coupling constant, the model offers also a resolution of the f,t problem of MSSM for CT <= 4500 and gravitino heavier than about 10(4) GeV. Supplementing MSSM by three right-handed neutrinos we show that spontaneously arising couplings between the inflaton and the particle content of MSSM not only ensure a sufficiently low reheating temperature but also support a scenario of non-thermal leptogenesis consistently with the neutrino oscillation parameters.
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Hidalgo-Duque, C., & Llanes-Estrada, F. J. (2015). Soft interactions in jet quenching. Int. J. Mod. Phys. A, 30(13), 1550067–25pp.
Abstract: We study the collisional aspects of jet quenching in a high-energy nuclear collision, especially in the final state pion gas. The jet has a large energy, and acquires momentum transverse to its axis more effectively by multiple soft collisions than by few hard scatterings (as known from analogous systems such as J/psi production at Hera). Such regime of large E and small momentum transfer corresponds to Regge kinematics and is characteristically dominated by the pomeron. From this insight we estimate the jet quenching parameter in the hadron medium (largely a pion gas) at the end of the collision, which is naturally small and increases with temperature in line with the gas density and compare it to the jet quenching parameter obtained within the quark-gluon plasma (QGP) phase in widely known perturbative approximations. The physics in the quark-gluon plasma/liquid phase is less obvious, and here we revisit a couple of simple estimates that suggest indeed that the pomeron-mediated interactions are very relevant and should be included in analysis of the jet quenching parameter. Finally, since the occasional hard collisions produce features characteristic of a Levy flight in the q(perpendicular to)(2) plane perpendicular to the jet axis, we suggest one- and two-particle q perpendicular to correlations as interesting experimental probes sensitive to the nature (softness versus hardness) of the interactions of a jet inside the QGP.
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de Salas, P. F., & Pastor, S. (2016). Relic neutrino decoupling with flavour oscillations revisited. J. Cosmol. Astropart. Phys., 07(7), 051–18pp.
Abstract: We study the decoupling process of neutrinos in the early universe in the presence of three-flavour oscillations. The evolution of the neutrino spectra is found by solving the corresponding momentum-dependent kinetic equations for the neutrino density matrix, including for the first time the proper collision integrals for both diagonal and off-diagonal elements. This improved calculation modifies the evolution of the off-diagonal elements of the neutrino density matrix and changes the deviation from equilibrium of the frozen neutrino spectra. However, it does not vary the contribution of neutrinos to the cosmological energy density in the form of radiation, usually expressed in terms of the effective number of neutrinos, N-eff. We find a value of N-eff = 3.045, in agreement with previous theoretical calculations and consistent with the latest analysis of Planck data. This result does not depend on the ordering of neutrino masses. We also consider the effect of non-standard neutrino-electron interactions (NSI), predicted in many theoretical models where neutrinos acquire mass. For two sets of NSI parameters allowed by present data, we find that Neff can be reduced down to 3.040 or enhanced up to 3.059.
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