Here, transverse momentum (pT) spectra of pions, kaons, and protons up to pT = 20GeV/c have been measured in Pb-Pb collisions at √sNN = 2.76TeV using the ALICE detector for six different centrality ...classes covering 0%–80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at pT ≈ 3GeV/c in central Pb-Pb collisions that decreases for more peripheral collisions. For pT > 10GeV/c, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10%–20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For pT < 10GeV/c, the data provide important constraints for models aimed at describing the transition from soft to hard physics.
The inclusive transverse momentum (pT) distributions of primary charged particles are measured in the pseudo-rapidity range |η|<0.8 as a function of event centrality in Pb–Pb collisions at ...sNN=2.76 TeV with ALICE at the LHC. The data are presented in the pT range 0.15<pT<50 GeV/c for nine centrality intervals from 70–80% to 0–5%. The results in Pb–Pb are presented in terms of the nuclear modification factor RAA using a pp reference spectrum measured at the same collision energy. We observe that the suppression of high-pT particles strongly depends on event centrality. The yield is most suppressed in central collisions (0–5%) with RAA≈0.13 at pT=6–7 GeV/c. Above pT=7 GeV/c, there is a significant rise in the nuclear modification factor, which reaches RAA≈0.4 for pT>30 GeV/c. In peripheral collisions (70–80%), only moderate suppression (RAA=0.6–0.7) and a weak pT dependence is observed. The measured nuclear modification factors are compared to other measurements and model calculations.
Summary of the long term data taking, related to one of the proposed next generation ground-based gravitational detector’s location is presented here. Results of seismic and infrasound noise, ...electromagnetic attenuation and cosmic muon radiation measurements are reported in the underground Matra Gravitational and Geophysical Laboratory near Gyöngyösoroszi, Hungary. The collected seismic data of more than two years is evaluated from the point of view of the Einstein Telescope, a proposed third generation underground gravitational wave observatory. Applying our results for the site selection will significantly improve the signal to noise ratio of the multi-messenger astrophysics era, especially at the low frequency regime.
We present a study of the inclusive charged-particle transverse momentum (
p
T
) spectra as a function of charged-particle multiplicity density at mid-pseudorapidity,
d
N
ch
/
d
η
, in pp collisions ...at
s
=
5.02
and 13 TeV covering the kinematic range
|
η
|
<
0.8
and
0.15
<
p
T
<
20
GeV/
c
. The results are presented for events with at least one charged particle in
|
η
|
<
1
(INEL
>
0
). The
p
T
spectra are reported for two multiplicity estimators covering different pseudorapidity regions. The
p
T
spectra normalized to that for INEL
>
0
show little energy dependence. Moreover, the high-
p
T
yields of charged particles increase faster than the charged-particle multiplicity density. The average
p
T
as a function of multiplicity and transverse spherocity is reported for pp collisions at
s
=
13
TeV. For low- (high-) spherocity events, corresponding to jet-like (isotropic) events, the average
p
T
is higher (smaller) than that measured in INEL
>
0
pp collisions. Within uncertainties, the functional form of
⟨
p
T
⟩
(
N
ch
)
is not affected by the spherocity selection. While EPOS LHC gives a good description of many features of data, PYTHIA overestimates the average
p
T
in jet-like events.
The production cross section of prompt Λc+ charm baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a center-of-mass ...energy per nucleon pair of sNN=5.02TeV. The Λc+ and Λ¯c- baryons were reconstructed in the hadronic decay channels Λc+→pK-π+ and Λc+→pKS0 and respective charge conjugates. The measured differential cross sections as a function of transverse momentum (pT) and the pT-integrated Λc+ production cross section in pp and in p-Pb collisions are presented. The Λc+ nuclear modification factor (RpPb), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the RpPb of D mesons. The Λc+/D0 ratio is also presented and compared with the light-flavor baryon-to-meson ratios p/π and Λ/KS0, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.
The polarization of the Λ and ¯Λ hyperons along the beam (z) direction, Pz, has been measured in Pb-Pb collisions at √sNN=5.02 TeV recorded with ALICE at the Large Hadron Collider (LHC). The main ...contribution to Pz comes from elliptic flow-induced vorticity and can be characterized by the second Fourier sine coefficient Pz,s2=⟨Pzsin(2φ−2Ψ2)⟩, where φ is the hyperon azimuthal emission angle and Ψ2 is the elliptic flow plane angle. We report the measurement of Pz,s2 for different collision centralities and in the 30%–50% centrality interval as a function of the hyperon transverse momentum and rapidity. The Pz,s2 is positive similarly as measured by the STAR Collaboration in Au-Au collisions at √sNN=200 GeV, with somewhat smaller amplitude in the semicentral collisions. This is the first experimental evidence of a nonzero hyperon Pz in Pb-Pb collisions at the LHC. The comparison of the measured Pz,s2 with the hydrodynamic model calculations shows sensitivity to the competing contributions from thermal and the recently found shear-induced vorticity, as well as to whether the polarization is acquired at the quark-gluon plasma or the hadronic phase.
General properties of hadron production are investigated in proton-proton collisions at LHC energies. We are interested in the characteristics of hadron production outside the identified jet cones. ...We improve earlier definitions and introduce surrounding rings/belts around the cone of identified jets. In this way even multiple jet events can be studied in details. We define the underlying event as collected hadrons from outside jet cones and outside surrounding belts, and investigate the features of these hadrons. We use a PYLHIA generated data sample of proton-proton collisions at √s = 7 TeV. This data sample is analysed by our new method and the widely applied CDF method. Angular correlations and momentum distributions have been studied and the obtained results are compared and discussed.
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