Performance of large area CsI-RICH prototypes for ALICE at LHC

We present the performances of large area CsI-RICH prototypes obtained in single particle events. The differential quantum efficiency of the photocathodes has been deduced from Cherenkov rings by means of two different procedures: a direct measurement with a thin NaF radiator and a Monte Carlo based estimation for a C$_6$F$_{14}$ radiator. A factor of merit of 45 cm$^{-1}$ has been found for the typical detector configuration. Two angle reconstruction algorithms have been used and the different errors affecting the Cherenkov angle resolution have been estimated combining the analytical treatment and the Monte Carlo simulation. Also the dependence on radiator thickness, Cherenkov ring radius, chamber voltage and particle incidence angle has been studied

Final tests of the CsI-based ring imaging detector for the ALICE experiment

We report on the final tests performed on a CsI-based RICH detector equipped with 2 C$_6$F$_{14}$ radiator trays and 4 photocathodes, each of 64$\times$38 cm$^2$ area. The overall performance of the detector is described, using different gas mixtures, in view of optimizing the photoelectron yield and the pad occupancy. Test results under magnetic field up to 0.9 T, photocathode homogeneity and stability are presented

A pattern recognition method for the RICH-based HMPID detector in ALICE

A pattern recognition method developed for the High Momentum Particle IDentification (HMPID) detector in the ALICE experiment at CERN is presented. The algorithm is based on the Hough transform with a mapping of the pad coordinate space directly to the Cherenkov angle parameter space. Cherenkov angle reconstruction has been studied as a function of different particle densities in the photodetector using real data taken in the ALICE tests at the CERN SPS: a satisfactory resolution can be achieved even in events where the occupancy reaches more than 12, which is the situation we may be confronted with in central Pb-Pb interactions at LHC. (9 refs)

A large area CsI RICH Detector in ALICE at LHC

A 1m2 CsI RICH prototype has been successfully tested in a hadron beam at CERN SPS. The prototype, fully equipped with 15k electronic channels, has been used to identify particles coming from pi-Be interactions. Track reconstruction has been performed by using a telescope consisting of four gas pad chambers. A detailed description of the detector will be presented and results from the test will be discussed.List of figuresFigure 1 Expected proton and antiproton yields including jet quenching mechanism in central Pb-Pb collisions at LHC.Figure 2 Schematic view of the HMPID CsI-RICHFigure 3 Experimental layout used at the SPS/H4 test beamFigure 4 Distributions of the mean number, per ring, of pad hits (Npad), electrons (Ntot) and Cherenkov photoelectrons (Nres) as a function of the single-electron mean pulse heightFigure 5 Mean single-electron pulse height as a function of high voltage measured at the centre of each of the four photocathodesFigure 6 Evaluation of the uniformity of the chamber gain for the photocathode PC32Figure 7 Azimuthal distribution of the photon pad hits in the Cherenkov fiducial zone (HV=2050 V)Figure 8 Photon angle (a) and track Cherenkov angle (b) distributions for beam events at the SPSFigure 9 Track density on the HMPID cathode plane in real 350 GeV/c pi--Be eventsFigure 10 Three dimensional display of an SPS 350 GeV/c pi--Be event. Eleven tracks are reconstructed in the telescope by requiring one hit on each pad chamber to reconstruct a track</UL

High-resolution coherency functionals for improving the velocity analysis of ground-penetrating radar data

We aim at verifying whether the use of high-resolution coherency functionals could improve the signal-to-noise ratio (S/N) of Ground-Penetrating Radar data by introducing a variable and precisely picked velocity field in the migration process. After carrying out tests on synthetic data to schematically simulate the problem, assessing the types of functionals most suitable for GPR data analysis, we estimated a varying velocity field relative to a real dataset. This dataset was acquired in an archaeological area where an excavation after a GPR survey made it possible to define the position, type, and composition of the detected targets. Two functionals, the Complex Matched Coherency Measure and the Complex Matched Analysis, turned out to be effective in computing coherency maps characterized by high-resolution and strong noise rejection, where velocity picking can be done with high precision. By using the 2D velocity field thus obtained, migration algorithms performed better than in the case of constant or 1D velocity field, with satisfactory collapsing of the diffracted events and moving of the reflected energy in the correct position. The varying velocity field was estimated on different lines and used to migrate all the GPR profiles composing the survey covering the entire archaeological area. The time slices built with the migrated profiles resulted in a higher S/N than those obtained from non-migrated or migrated at constant velocity GPR profiles. The improvements are inherent to the resolution, continuity, and energy content of linear reflective areas. On the basis of our experience, we can state that the use of high-resolution coherency functionals leads to migrated GPR profiles with a high-grade of hyperbolas focusing. These profiles favor better imaging of the targets of interest, thereby allowing for a more reliable interpretation

A probabilistic full waveform inversion of surface waves

Over the past decades, surface wave methods have been routinely employed to retrieve the physical characteristics of the first tens of meters of the subsurface, particularly the shear wave velocity profiles. Traditional methods rely on the application of the multichannel analysis of surface waves to invert the fundamental and higher modes of Rayleigh waves. However, the limitations affecting this approach, such as the 1D model assumption and the high degree of subjectivity when extracting the dispersion curve, motivate us to apply the elastic full-waveform inversion, which, despite its higher computational cost, enables leveraging the complete information embedded in the recorded seismograms. Standard approaches solve the full-waveform inversion using gradient-based algorithms minimizing an error function, commonly measuring the misfit between observed and predicted waveforms. However, these deterministic approaches lack proper uncertainty quantification and are susceptible to get trapped in some local minima of the error function. An alternative lies in a probabilistic framework, but, in this case, we need to deal with the huge computational effort characterizing the Bayesian approach when applied to non-linear problems associated with expensive forward modelling and large model spaces. In this work, we present a gradient-based Markov chain Monte Carlo full-waveform inversion where we accelerate the sampling of the posterior distribution by compressing data and model spaces through the discrete cosine transform. Additionally, a proposal is defined as a local, Gaussian approximation of the target density, constructed using the local Hessian and gradient information of the log posterior. We first validate our method through a synthetic test where the velocity model features lateral and vertical velocity variations. Then we invert a real dataset from the InterPACIFIC project. The obtained results prove the efficiency of our proposed algorithm, which demonstrates to be robust against cycle-skipping issues and able to provide reasonable uncertainty evaluations with an affordable computational cost

SH-wave seismic reflection at a landslide (Patigno, NW Italy) integrated with P-wave

The aim of this paper is to present the acquisition and processing up to the depth migrated section of an SH-wave reflection seismic profile. This experience is conducted on a deep-seated gravitational slope deformation located in the Northern Apennines in Italy. The SH-wave depth-migrated image in the investigated area provides a detailed description of the small reactivation slip surfaces delineating minor landslides at shallow depths, which are responsible for the major damages observed. These results are integrated with a recently acquired P-wave seismic reflection profile investigating the same slope and delineating the highly deformed layer at depth, liable for the deep-seated gravitational slope deformation. The combined use of P-waves and SH-waves allows to gain a deeper knowledge of the landslide internal setting that is necessary to mitigate the risk associated with the mass movement

Antioxidant capacity and athletic condition of endurance horses undergoing nutraceutical supplementation

Endurance is an equestrian discipline that primarily relies on aerobic metabolism. Intense aerobic exercise produces reactive oxygen species due to an imbalance between oxidant and antioxidant substances, known as oxidative stress, which may reduce athletic performance. This study evaluated the effects of a feed supplement containing natural antioxidants and omega-3 fatty acids on the blood antioxidant activity and the athletic condition of endurance horses undergoing an exercise test. Twelve Arabian endurance horses were randomly assigned to treatment or control groups. At T0, blood lactate, whole blood and red blood cells (RBC) antioxidant capacity were assessed. The horses performed an exercise test with heart rate monitoring. After 30 min, blood lactate, antioxidant capacity and serum creatine kinase (CK) were measured. The treatment group received the dietary supplement for 21 days, while controls maintained their diet. Then, the protocol was repeated (T1). Variables were compared within and between groups through two-way ANOVA and post-hoc tests. Significant time*group effects were observed for serum CK (p = 0.026), RBC antioxidant capacity at rest (p = 0.034) and post-exercise (p = 0.019). At T1, in treatment group, CK was lower than controls (p = 0.006), while RBC antioxidant capacity increased at rest (p = 0.037) and after exercise (p = 0.006) compared to T0. The dietary supplement showed efficacy in enhancing RBC antioxidant capacity, and it could be beneficial for horses engaged in intense aerobic exercise