725 research outputs found
Performance of the Electromagnetic Pixel Calorimeter Prototype EPICAL-2
The first evaluation of an ultra-high granularity digital electromagnetic
calorimeter prototype using 1.0-5.8 GeV/c electrons is presented. The
pixel detector consists of 24 layers of ALPIDE CMOS MAPS
sensors, with a pitch of around 30~m, and has a depth of almost 20
radiation lengths of tungsten absorber. Ultra-thin cables allow for a very
compact design. The properties that are critical for physics studies are
measured: electromagnetic shower response, energy resolution and linearity. The
stochastic energy resolution is comparable with the state-of-the art resolution
for a Si-W calorimeter, with data described well by a simulation model using
GEANT and Allpix. The performance achieved makes this technology a good
candidate for use in the ALICE FoCal upgrade, and in general demonstrates the
strong potential for future applications in high-energy physics.Comment: 30 pages, 19 figures, submitted to JINS
Performance of the electromagnetic and hadronic prototype segments of the ALICE Forward Calorimeter
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 and a hadronic
copper-scintillating-fiber calorimeter (FoCal-H) of about 5.
The data were taken between 2021 and 2023 at the CERN PS and SPS beam lines
with hadron (electron) beams up to energies of 350 (300) GeV. Regarding
FoCal-E, we report a comprehensive analysis of its response to minimum ionizing
particles across all pad layers. The longitudinal shower profile of
electromagnetic showers is measured with a layer-wise segmentation of 1.
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.Comment: 55 pages (without acronyms), 45 captioned figure
Public Sector Reform and Governance for Adaptation: Implications of New Public Management for Adaptive Capacity in Mexico and Norway
Although many governments are assuming the responsibility of initiating adaptation policy in relation to climate change, the compatibility of “governance-for-adaptation” with the current paradigms of public administration has generally been overlooked. Over the last several decades, countries around the globe have embraced variants of the philosophy of administration broadly called “New Public Management” (NPM) in an effort to improve administrative efficiencies and the provision of public services. Using evidence from a case study of reforms in the building sector in Norway, and a case study of water and flood risk management in central Mexico, we analyze the implications of the adoption of the tenets of NPM for adaptive capacity. Our cases illustrate that some of the key attributes associated with governance for adaptation—namely, technical and financial capacities; institutional memory, learning and knowledge; and participation and accountability—have been eroded by NPM reforms. Despite improvements in specific operational tasks of the public sector in each case, we show that the success of NPM reforms presumes the existence of core elements of governance that have often been found lacking, including solid institutional frameworks and accountability. Our analysis illustrates the importance of considering both longer-term adaptive capacities and short-term efficiency goals in public sector administration reform
Performance of the electromagnetic pixel calorimeter prototype Epical-2
The first evaluation of an ultra-high granularity digital electromagnetic calorimeter prototype using 1.0-5.8 GeV/c electrons is presented. The 25 × 106 pixel detector consists of 24 layers of ALPIDE CMOS MAPS sensors, with a pitch of around 30 μm, and has a depth of almost 20 radiation lengths of tungsten absorber. Ultra-thin cables allow for a very compact design. The properties that are critical for physics studies are measured: electromagnetic shower response, energy resolution and linearity. The stochastic energy resolution is comparable with the state-of-the art resolution for a Si-W calorimeter, with data described well by a simulation model using Geant4 and Allpix2. The performance achieved makes this technology a good candidate for use in the ALICE FoCal upgrade, and in general demonstrates the strong potential for future applications in high-energy physics
Characterizing the initial conditions of heavy-ion collisions at the LHC with mean transverse momentum and anisotropic flow correlations
Correlations between mean transverse momentum and anisotropic flow coefficients or are measured as a function of centrality in Pb–Pb and Xe–Xe collisions at sqrt(sNN) = 5.02 TeV and 5.44 TeV, respectively, with ALICE. In addition, the recently proposed higher-order correlation between [pt], v2, and v3 is measured for the first time, which shows an anticorrelation for the presented centrality ranges. These measurements are compared with hydrodynamic calculations using IP-Glasma and TRENTO initial-state shapes, the former based on the Color Glass Condensate effective theory with gluon saturation, and the latter a parameterized model with nucleons as the relevant degrees of freedom. The data are better described by the IP-Glasma rather than the TRENTO based calculations. In particular, Trajectum and JETSCAPE predictions, both based on the TRENTO initial state model but with different parameter settings, fail to describe the measurements. As the correlations between [pt] and vn are mainly driven by the correlations of the size and the shape of the system in the initial state, these new studies pave a novel way to characterize the initial state and help pin down the uncertainty of the extracted properties of the quark–gluon plasma recreated in relativistic heavy-ion collisions
General balance functions of identified charged hadron pairs of (pi,K,p) in Pb-Pb collisions at 2.76 TeV
First measurements of balance functions (BFs) of all combinations of identified charged hadron ( π , K, p)
pairs in Pb–Pb collisions at √sNN = 2.76 TeV recorded by the ALICE detector are presented. The BF
measurements are carried out as two-dimensional differential correlators versus the relative rapidity
(delta-y) and azimuthal angle (delta-φ) of hadron pairs, and studied as a function of collision centrality. The delta-φ
dependence of BFs is expected to be sensitive to the light quark diffusivity in the quark–gluon plasma.
While the BF azimuthal widths of all pairs substantially decrease from peripheral to central collisions, the
longitudinal widths exhibit mixed behaviors: BFs of π π and cross-species pairs narrow significantly in
more central collisions, whereas those of KK and pp are found to be independent of collision centrality.
This dichotomy is qualitatively consistent with the presence of strong radial flow effects and the existence
of two stages of quark production in relativistic heavy-ion collisions. Finally, the first measurements of
the collision centrality evolution of BF integrals are presented, with the observation that charge balancing
fractions are nearly independent of collision centrality in Pb–Pb collisions. Overall, the results presented
provide new and challenging constraints for theoretical models of hadron production and transport in
relativistic heavy-ion collisions
Measurement of the non-prompt D-meson fraction as a function of multiplicity in proton-proton collisions at = 13 TeV
The fractions of non-prompt (i.e. originating from beauty-hadron decays) D0
and D+ mesons with respect to the inclusive yield are measured as a function of the
charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of √s =
13 TeV with the ALICE detector at the LHC. The results are reported in intervals of
transverse momentum (pT) and integrated in the range 1 < pT < 24 GeV/c. The fraction
of non-prompt D0 and D+ mesons is found to increase slightly as a function of pT in
all the measured multiplicity intervals, while no significant dependence on the charged-
particle multiplicity is observed. In order to investigate the production and hadronisation
mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well
as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour
glass condensate including three-pomeron fusion
Hypertriton Production in p-Pb Collisions at √sNN = 5.02 TeV
The study of nuclei and antinuclei production has proven to be a powerful
tool to investigate the formation mechanism of loosely bound states in
high-energy hadronic collisions. The first measurement of the production of
in p-Pb collisions at = 5.02
TeV is presented in this Letter. Its production yield measured in the rapidity
interval -1 < y < 0 for the 40% highest multiplicity p-Pb collisions is . The measurement is compared with the expectations of statistical
hadronisation and coalescence models, which describe the nucleosynthesis in
hadronic collisions. These two models predict very different yields of the
hypertriton in small collision systems such as p-Pb and therefore the
measurement of is crucial to distinguish between them.
The precision of this measurement leads to the exclusion with a significance
larger than 6 of some configurations of the statistical hadronisation,
thus constraining the production mechanism of loosely bound states
K∗(892)0 and φ(1020) production in p-Pb collisions at √s NN = 8.16 TeV
The production of K*(892)(0) and phi(1020) resonances has been measured in p-Pb collisions at root s(NN) = 8.16 TeV using the ALICE detector. Resonances are reconstructed via their hadronic decay channels in the rapidity interval -0.5 8 GeV/c), the R-pPb values of all hadrons are consistent with unity within uncertainties. The R-pPb of K*(892)(0) and phi(1020) at root s(NN) = 8.16 and 5.02 TeV show no significant energy dependence
Measurement of the Lifetime and Λ Separation Energy of _{Λ}^{3}H
The most precise measurements to date of the _{Λ}^{3}H lifetime τ and Λ separation energy B_{Λ} are obtained using the data sample of Pb-Pb collisions at sqrt[s_{NN}]=5.02 TeV collected by ALICE at the LHC. The _{Λ}^{3}H is reconstructed via its charged two-body mesonic decay channel (_{Λ}^{3}H→^{3}He+π^{-} and the charge-conjugate process). The measured values τ=[253±11(stat)±6(syst)] ps and B_{Λ}=[102±63(stat)±67(syst)] keV are compatible with predictions from effective field theories and confirm that the _{Λ}^{3}H structure is consistent with a weakly bound system
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