Abstract
A Forward Calorimeter (FoCal) has been proposed as part of the ALICE upgrades for data
taking from 2029 onwards. The FoCal will feature a sampling electromagnetic calorimeter segmented
into ...110 towers supplemented by a hadron calorimeter. The electromagnetic calorimeter will be
composed of 20 passive layers of tungsten absorber interleaved with 18 active layers of
low-granularity silicon pad sensors and two layers of high-granularity pixel detectors. Each pad
layer will be read out by 110 silicon pad sensors of 72 channels, amounting to a total of 1980
sensors.
This paper describes, from front-end to back-end, the electronics developed to instrument a tower
prototype composed of 18 silicon pad sensors as well as a design proposal for the full-detector
readout system.
This paper addresses the optimization of paths generated using randomized algorithms. We shall present an iterative algorithm to optimize raw paths. However, unlike local post-processing optimizers, ...our method aims at a more global optimization of the initial path, if possible, performing a drastic topological update, but instead of re-planning in the whole robot configuration space (
C
), it uses the initial path to limit the search within an optimal subset of
C
. Should a better solution be found, the subspace is further reduced. A lazy A
∗ search is used to efficiently search the graph representing the optimal subspace connectivity. The algorithm is designed to achieve a satisfactory and general optimization, while remaining computationally attractive. This paper also exposes some of the issues associated with shortcuts-like post-processing algorithms, namely, the problem of local shortcuts and their effect on the final solution. In order to assess the performance of this iterative re-planning algorithm, it is compared to the well established random shortcuts technique. Extensive experimental results are provided, these include different optimization criteria, a variety of robotic systems and environments, and different statistical measures.
► An Iterative Local Re-planning algorithm for post-optimizing randomized paths. ► The algorithm is computationally competitive with local methods but less sensitive to initial solutions. ► A lazy collision checking A
∗ graph search algorithm. ► A generic path optimization technique, with respect to the cost function or robot type.
The ALICE experiment at the LHC is equipped with an electromagnetic calorimeter (EMCal) designed to enhance its capabilities for jet, photon and electron measurement. In addition, the EMCal enables ...triggering on jets and photons with a centrality dependent energy threshold. After its commissioning in 2010, the EMCal Level 1 (L1) trigger was officially approved for physics data taking in 2011. After describing the L1 hardware and trigger algorithms, the commissioning and the first year of running experience, both in proton and heavy ion beams, are reviewed. Additionally, the upgrades to the original L1 trigger design are detailed.
A dedicated front-end electronics has been developed for the trigger chambers of the ALICE muon spectrometer under construction at the future LHC at CERN. This trigger detector is based on RPCs ...(Resistive Plate Chambers) working in streamer mode. The number of electronics channels (about 21000) and the fact that RPC signals have specific characteristics have led to the design of an 8 channel front-end ASIC using a new discrimination technique. The principle of the ASIC is described and the radiation hardness is discussed. Special emphasis is put on production characteristics of about 4000 ASICs.
Abstract We present the performance of a full-length prototype of the ALICE Forward Calorimeter (FoCal). The detector is composed of a silicon-tungsten electromagnetic sampling calorimeter with ...longitudinal and transverse segmentation (FoCal-E) of about 20 X 0 and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) of about 5 λ int . The data were taken in various test beam campaigns between 2021 and 2023 at the CERN PS and SPS beam lines with hadron beams up to energies of 350 GeV, and electron beams up to 300 GeV. Regarding FoCal-E, we report a comprehensive analysis of its response to minimum ionizing particles across all pad layers, employing various operational modes including different pre-amplifier and bias voltage settings. The longitudinal shower profile of electromagnetic showers is measured with a layer-wise segmentation of 1 X 0 . As a projection to the performance of the final detector in electromagnetic showers, we demonstrate linearity in the full energy range, and show that the energy resolution fulfills the requirements for the physics needs. Additionally, the performance to separate two-showers events was studied by quantifying the transverse shower width. Regarding FoCal-H, we report a detailed analysis of the response to hadron beams between 60 and 350 GeV. The results are compared to simulations obtained with a Geant4 model of the test beam setup, which in particular for FoCal-E are in good agreement with the data. The energy resolution of FoCal-E was found to be lower than 3% at energies larger than 100 GeV. The response of FoCal-H to hadron beams was found to be linear, albeit with a significant intercept that is about factor 2 larger than in simulations. Its resolution, which is non-Gaussian and generally larger than in simulations, was quantified using the FWHM, and decreases from about 16% at 100 GeV to about 11% at 350 GeV. The discrepancy to simulations, which is particularly evident at low hadron energies, needs to be further investigated.
Resistive Plate Chambers operated in streamer mode have been chosen as trigger detectors for the forward dimuon spectrometer of the ALICE experiment. During tests performed at CERN PS, small size ...prototypes with low-resistivity bakelite electrodes and with a strongly quenched gas mixture have shown the required rate capability, tracking and timing properties. Present efforts are devoted to the study of the detector performance after long irradiation periods. In this paper, a summary of the results of aging tests performed at the Gamma Irradiation Facility at CERN will be presented. Detectors show quite stable performance up to about 50mC/cm2, as the requirements for 10years operation program at LHC including a safety factor of 2. Afterwards, we observed an increase of the dark current not associated with an increase of the counting rate. We also report results of chemical analysis carried out by different CERN teams on exhaust gases and electrode surfaces of the detectors after aging.
The measurement of two-particle angular correlations is a powerful tool to study jet quenching in a $p_{\mathrm{T}}$ region inaccessible by direct jet identification. In these measurements ...pseudorapidity ($\Delta\eta$) and azimuthal ($\Delta\varphi$) differences are used to extract the shape of the near-side peak formed by particles associated to a higher $p_{\mathrm{T}}$ trigger particle ($1 < p_{\mathrm{T, trig}} <$ 8 GeV/c). A combined fit of the near-side peak and long-range correlations is applied to the data allowing the extraction of the centrality evolution of the peak shape in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. A significant broadening of the peak in the $\Delta\eta$ direction at low $p_{\mathrm{T}}$ is found from peripheral to central collisions, which vanishes above 4 GeV/c, while in the $\Delta\varphi$ direction the peak is almost independent of centrality. For the 10% most central collisions and $1 < p_{\mathrm{T, assoc}} <$ 2 GeV/c, $1 < p_{\mathrm{T, trig}} <$ 3 GeV/c a novel feature is observed: a depletion develops around the centre of the peak. The results are compared to pp collisions at the same centre of mass energy and to AMPT model simulations. The comparison to the investigated models suggests that the broadening and the development of the depletion is connected to the strength of radial and longitudinal flow.
The production of muons from heavy-flavour hadron decays in p-Pb collisions at $\sqrt{{\textit s}_{\rm NN}}=5.02$ TeV was studied for $2 < p_{\rm T} < 16$ GeV/$c$ with the ALICE detector at the CERN ...LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the center-of-mass system (cms) $2.03<y_{\rm cms}<3.53$ and $-4.46<y_{\rm cms}<-2.96$, respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum ($p_{\rm T}$). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval $2.5<p_{\rm T}<3.5$ GeV/$c$, it is above unity by more than 2$\sigma$. The ratio of the forward-to-backward production cross sections is also measured in the overlapping interval $2.96 < \vert y_{\rm cms} \vert < 3.53$ and is smaller than unity by 3.7$\sigma$ in $2.5<p_{\rm T}<3.5$ GeV/$c$. The data are described by model calculations including cold nuclear matter effects.
In two-particle angular correlation measurements, jets give rise to a near-side peak, formed by particles associated to a higher $p_{\mathrm{T}}$ trigger particle. Measurements of these correlations ...as a function of pseudorapidity ($\Delta\eta$) and azimuthal ($\Delta\varphi$) differences are used to extract the centrality and $p_{\mathrm{T}}$ dependence of the shape of the near-side peak in the $p_{\mathrm{T}}$ range $1 < p_{\mathrm{T}} <$ 8 GeV/c in Pb-Pb and pp collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. A combined fit of the near-side peak and long-range correlations is applied to the data and the peak shape is quantified by the variance of the distributions. While the width of the peak in the $\Delta\varphi$ direction is almost independent of centrality, a significant broadening in the $\Delta\eta$ direction is found from peripheral to central collisions. This feature is prominent for the low $p_{\mathrm{T}}$ region and vanishes above 4 GeV/c. The widths measured in peripheral collisions are equal to those in pp in the $\Delta\varphi$ direction and above 3 GeV/c in the $\Delta\eta$ direction. Furthermore, for the 10\% most central collisions and $1 < p_{\mathrm{T, assoc}} <$ 2 GeV/c, $1 < p_{\mathrm{T, trig}} <$ 3 GeV/c a departure from a Gaussian shape is found: a depletion develops around the centre of the peak. The results are compared to AMPT model simulations as well as other theoretical calculations indicating that the broadening and the development of the depletion is connected to the strength of radial and longitudinal flow.
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