† Thanks to project CTM2016-77325-C2-1-P and CTM2016-77325-C2-2-P funded by Ministerio de Economía y Competitividad and by the European Regional Development Fund, FEDER.
The first measurements of elliptic flow of π±, K±, $$ \textrm{p}+\overline{\textrm{p}} $$
p
+
p
¯
, $$ {\textrm{K}}_{\textrm{S}}^0 $$
K
S
0
, $$ \Lambda +\overline{\Lambda} $$
Λ
+
Λ
¯
, ϕ, $$ {\Xi}^{-}+{\overline{\Xi}}^{+} $$
Ξ
−
+
Ξ
¯
+
, and $$ {\varOmega}^{-}+{\overline{\varOmega}}^{+} $$
Ω
−
+
Ω
¯
+
using multiparticle cumulants in Pb–Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$
s
NN
= 5.02 TeV are resented. Results obtained with two- (v2{2}) and four-particle cumulants (v2{4}) are shown as a function of transverse momentum, pT, for various collision centrality intervals. Combining the data for both v2{2} and v2{4} also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark–gluon plasma. The characteristic features observed in previous pT-differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low pT and the approximate scaling with the number of constituent quarks at intermediate pT, are similarly present in the four-particle correlations and the combinations of v2{2} and v2{4}. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide pT range.
We present in this work the calibration procedure and a performance study of long scintillator bars used for the time-offlight (TOF) measurement in the HADES experiment. The digital front-end electronics installed at the TOF detector required to develop novel calibration methods. The exceptional performance of the spectrometer for particle identification and pointing accuracy allows one to determine in great detail the response of scintillators to minimum ionizing particles. A substantial position sensitivity of the calibration parameters has been found, in particular for the signal time walk. After including the position dependence, the timing accuracy for minimum ionizing particles was improved from 190 ps to 135 ps for the shortest rods (1475 mm) and to 165 ps for the longest (2356 mm). These results are in accordance with the time degradation length of the scintillator bars, as determined from previous measurements.
The TRISTAN detector. Cosmic ray survey between latitudes 38ºN and 53ºS along the Atlantic Ocean D. García-Castro * on behalf of the TRISTAN Collaboration
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