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An advanced prototype of a digital pixel calorimeter, EPICAL-2, has been constructed using ALPIDE MAPS sensors. It has been successfully tested with cosmic muons and with test beams at DESY and the CERN SPS. We will report on recent updates of performance results, with good linearity and resolution. Comparisons to detailed MC simulations are made and show good understanding of the technology. The spatial precision of event-by-event measurements of the showers allows unprecedented studies of the shower shape. The detector features two-shower separation capabilities at extremely small distances. We will also discuss the limitations of the currently used sensor technology and perspectives for future development of digital calorimetry.

Transverse mass spectra of pions and protons measured in central collisions of heavy ions at the SPS and at RHIC are compared to a hydrodynamic parameterization. While the chemical temperature needed at RHIC is significantly higher compared to SPS, the spectra may be described using kinetic freeze-out parameters which are similar for both beam energies. At RHIC either the temperature or the flow velocity is higher, but the data provide no unambiguous proof for much stronger transverse flow. The contribution of such hydrodynamic emission at high transverse momenta is investigated in detail. It is shown that hydrodynamics may be relevant up to relatively high transverse momenta. The importance of the velocity profile used in this context is highlighted.

Stem cells support tissue maintenance by balancing self-renewal and differentiation. In mice, it is believed that a homogeneous stem cell population of single spermatogonia supports spermatogenesis, and that differentiation, which is accompanied by the formation of connected cells (cysts) of increasing length, is linear and nonreversible. We evaluated this model with the use of lineage analysis and live imaging, and found that this putative stem cell population is not homogeneous. Instead, the stem cell pool that supports steady-state spermatogenesis is contained within a subpopulation of single spermatogonia. We also found that cysts are not committed to differentiation and appear to recover stem cell potential by fragmentation, and that the fate of individual spermatogonial populations was markedly altered during regeneration after damage. Thus, there are multiple and reversible paths from stem cells to differentiation, and these may also occur in other systems.

Abstract The invariant differential cross section of inclusive $$\\omega (782)$$ ω ( 782 ) meson production at midrapidity ( $$|y|<0.5$$ | y | < 0.5 ) in pp collisions at $$\\sqrt{s}=7\\,\\hbox {TeV}$$ s = 7 TeV was measured with the ALICE detector at the LHC over a transverse momentum range of $$2< p_{\\mathrm {T}}< 17\\,\\hbox {GeV}/c$$ 2 < p T < 17 GeV / c . The $$\\omega $$ ω meson was reconstructed via its $$\\omega \\rightarrow \\pi ^+\\pi ^-\\pi ^0$$ ω → π + π - π 0 decay channel. The measured $$\\omega $$ ω production cross section is compared to various calculations: PYTHIA 8.2  Monash 2013 describes the data, while PYTHIA 8.2 Tune 4C overestimates the data by about 50%. A recent NLO calculation, which includes a model describing the fragmentation of the whole vector-meson nonet, describes the data within uncertainties below $$6\\,\\hbox {GeV}/c$$ 6 GeV / c , while it overestimates the data by up to 50% for higher $$p_{\\mathrm {T}}$$ p T . The $$\\omega /\\pi ^0$$ ω / π 0 ratio is in agreement with previous measurements at lower collision energies and the PYTHIA calculations. In addition, the measurement is compatible with transverse mass scaling within the measured $$p_{\\mathrm {T}}$$ p T  range and the ratio is constant with $$C^{\\omega /\\pi ^{0}}= 0.67 \\pm 0.03 \\text {~(stat)~} \\pm 0.04 \\text {~(sys)~}$$ C ω / π 0 = 0.67 ± 0.03 (stat) ± 0.04 (sys) above a transverse momentum of $$2.5\\,\\hbox {GeV}/c$$ 2.5 GeV / c .

Abstract The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in pp collisions at $$\\sqrt{s} =5.02\\ \\hbox {TeV}$$ s = 5.02 TeV and p–Pb collisions at $$\\sqrt{s_{\\mathrm{NN}}} = 5.02\\ \\hbox {TeV}$$ s NN = 5.02 TeV with the ALICE detector at the LHC is reported. The $$\\mathrm{D}^{0}$$ D 0 , $$\\mathrm{D}^{+} $$ D + , and $$\\mathrm{D}^{*+} $$ D ∗ + mesons, together with their charge conjugates, were reconstructed at midrapidity in the transverse momentum interval $$3< p_\\mathrm{T} < 24\\ \\hbox {GeV}/c$$ 3 < p T < 24 GeV / c and correlated with charged particles having $$p_\\mathrm{T} > 0.3\\ \\hbox {GeV}/c$$ p T > 0.3 GeV / c and pseudorapidity $$|\\eta | < 0.8$$ | η | < 0.8 . The properties of the correlation peaks appearing in the near- and away-side regions (for $$\\Delta \\varphi \\approx 0$$ Δ φ ≈ 0 and $$\\Delta \\varphi \\approx \\pi $$ Δ φ ≈ π , respectively) were extracted via a fit to the azimuthal correlation functions. The shape of the correlation functions and the near- and away-side peak features are found to be consistent in pp and p–Pb collisions, showing no modifications due to nuclear effects within uncertainties. The results are compared with predictions from Monte Carlo simulations performed with the PYTHIA, POWHEG+PYTHIA, HERWIG, and EPOS 3 event generators.

Abstract The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of $$\\text {(anti-)deuterons}$$ (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at $$\\sqrt{s}=13$$ s = 13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity ( $${\\mathrm {d} N_{ch}/\\mathrm {d} \\eta } \\sim 26$$ d N ch / d η ∼ 26 ) as measured in p–Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p–Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM).

Abstract This paper presents the measurements of $$\\pi ^{\\pm }$$ π± , $$\\mathrm {K}^{\\pm }$$ K± , $$\\text {p}$$ p and $$\\overline{\\mathrm{p}} $$ p¯ transverse momentum ($$p_{\\text {T}}$$ pT ) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at $$\\sqrt{s}\\ =\\ 13\\ \\text {TeV}$$ s=13TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a $$p_{\\text {T}}$$ pT range from 0.1 to 20 $$\\text {GeV}/c$$ GeV/c and are done in the rapidity interval $$|y|<0.5$$ |y|<0.5 . The $$p_{\\text {T}}$$ pT -differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at $$\\sqrt{s}\\ =\\ 7\\ \\text {TeV}$$ s=7TeV , which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the $$p_{\\text {T}}$$ pT -integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems.

Abstract This paper presents the primary charged-particle multiplicity distributions in proton–lead collisions at a centre-of-mass energy per nucleon–nucleon collision of $$\\sqrt{s_{\\textrm{NN}}}~=~5.02$$ s NN = 5.02  TeV. The distributions are reported for non-single diffractive collisions in different pseudorapidity ranges. The measurements are performed using the combined information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE. The multiplicity distributions are parametrised with a double negative binomial distribution function which provides satisfactory descriptions of the distributions for all the studied pseudorapidity intervals. The data are compared to models and analysed quantitatively, evaluating the first four moments (mean, standard deviation, skewness, and kurtosis). The shape evolution of the measured multiplicity distributions is studied in terms of KNO variables and it is found that none of the considered models reproduces the measurements. This paper also reports on the average charged-particle multiplicity, normalised by the average number of participating nucleon pairs, as a function of the collision energy. The multiplicity results are then compared to measurements made in proton–proton and nucleus–nucleus collisions across a wide range of collision energies.

Abstract We report on the measurement of inclusive, non-prompt, and prompt J/ψ-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of 13 TeV. The correlations are studied at midrapidity (|y| < 0.9) in the transverse momentum ranges p T < 40 GeV/c for the J/ψ and 0.15 < p T < 10 GeV/c and |η| < 0.9 for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of L int = 34 nb −1 and L int = 6.9 pb −1, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of E = 4 and 9 GeV in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of L int = 0.9 pb −1 and L int = 8.4 pb −1, respectively. The azimuthally integrated near and away side yields of associated charged hadrons per J/ψ trigger are presented as a function of the J/ψ and associated hadron transverse momentum. The measurements are discussed in comparison to PYTHIA calculations.

Abstract This paper presents a study of the inclusive forward J/ψ yield as a function of forward charged-particle multiplicity in pp collisions at s $$ \\sqrt{s} $$ = 13 TeV using data collected by the ALICE experiment at the CERN LHC. The results are presented in terms of relative J/ψ yields and relative charged-particle multiplicities with respect to these quantities obtained in inelastic collisions having at least one charged particle in the pseudorapidity range |η| < 1. The J/ψ mesons are reconstructed via their decay into μ + μ − pairs in the forward rapidity region (2.5 < y < 4). The relative multiplicity is estimated in the forward pseudorapidity range which overlaps with the J/ψ rapidity region. The results show a steeper-than-linear increase of the J/ψ yields versus the multiplicity. They are compared with previous measurements and theoretical model calculations.