Identificación de las diferentes poblaciones migradoras y sedentarias de Paloma Torcaz en Europa y Norte de África determinadas por métodos genéticos

Biologijos katedraGamtos tyrimų centrasGamtos tyrimų centro Ekologijos institutas, [email protected] Didžiojo universiteta

Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at sNN=5.02 TeV

The measurement of the deuteron and anti-deuteron production in the rapidity range −1 < y < 0 as a function of transverse momentum and event multiplicity in p–Pb collisions at √sNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of- flight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number

Particle production as a function of charged-particle flattenicity in pp collisions at s\sqrt{s} = 13 TeV

International audienceThis paper reports the first measurement of the transverse momentum ($p_{\mathrm{T}}$) spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at $\sqrt{s}=13$ TeV. Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, $2.8<\eta<5.1$ and $-3.7<\eta<-1.7$. According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases towards larger $p_{\mathrm{T}}$ due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to $p_{\mathrm{T}}=20$ GeV/$c$. The event selection requires at least one charged particle produced in the pseudorapidity interval $|\eta|<1$. The measured $p_{\mathrm{T}}$ distributions, average $p_{\mathrm{T}}$, kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using PYTHIA 8 based on color strings and EPOS LHC. The modification of the $p_{\mathrm{T}}$-spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate $p_{\mathrm{T}}$ ($2<p_{\mathrm{T}}<8$ GeV/$c$), and approaches the vicinity of unity at higher $p_{\mathrm{T}}$. The results are qualitatively described by PYTHIA, and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator

Measurement of Λ3H{}_{\Lambda}^{3}\mathrm{H} production in Pb-Pb collisions at sNN\sqrt{s_{\mathrm{NN}}} = 5.02 TeV

International audienceThe first measurement of $_{\Lambda}^{3}\mathrm{H}$ and $^3_ {\overline{\Lambda}}\overline{\mathrm{H}}$ differential production with respect to transverse momentum and centrality in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$~TeV is presented. The $_{\Lambda}^{3}\mathrm{H}$ has been reconstructed via its two-charged-body decay channel, i.e., $_{\Lambda}^{3}\mathrm{H} \rightarrow {}^{3}\mathrm{He} + \pi^{-}$. A Blast-Wave model fit of the $p_{\rm T}$-differential spectra of all nuclear species measured by the ALICE collaboration suggests that the $_{\Lambda}^{3}\mathrm{H}$ kinetic freeze-out surface is consistent with that of other nuclei. The ratio between the integrated yields of $_{\Lambda}^{3}\mathrm{H}$ and $^3\mathrm{He}$ is compared to predictions from the statistical hadronisation model and the coalescence model, with the latter being favoured by the presented measurements

Measurement of the production cross section of prompt Ξ0c baryons in p–Pb collisions at √sNN = 5.02 TeV

The transverse momentum (pT) differential production cross section of the promptly-produced charm-strange baryon Ξ0c (and its charge conjugate Ξ0c¯¯¯¯¯¯) is measured at midrapidity via its hadronic decay into π+Ξ− in p−Pb collisions at a centre-of-mass energy per nucleon−nucleon collision sNN−−−√ = 5.02 TeV with the ALICE detector at the LHC. The Ξ0c nuclear modification factor (RpPb), calculated from the cross sections in pp and p−Pb collisions, is presented and compared with the RpPb of Λ+c baryons. The ratios between the pT-differential production cross section of Ξ0c baryons and those of D0 mesons and Λ+c baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt Ξ0c baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p−Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model in which hadronisation is implemented via quark coalescence. The pT-integrated cross section of prompt Ξ0c-baryon production at midrapidity extrapolated down to pT = 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p−Pb collisions at midrapidity

J/ψ\psi-hadron correlations at midrapidity in pp collisions at s\sqrt{s} = 13 TeV

International audienceWe report on the measurement of inclusive, non-prompt, and prompt J/$\psi$-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 $p_{\rm T} < 40~\text{GeV}/c$ for the J/$\psi$ and $0.15 < p_{\rm T} < 10$ GeV/$c$ and $|\eta|<0.9$ for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of $L_{\text{int}} = 34~\text{nb}^{-1}$ and $L_{\text{int}} = 6.9~\text{pb}^{-1}$, 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 $9~\text{GeV}$ in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of $L_{\text{int}} = 0.9~\text{pb}^{-1}$ and $L_{\text{int}} = 8.4~\text{pb}^{-1}$, respectively. The results are presented as associated hadron yields per J/$\psi$ trigger as a function of the azimuthal angle difference between the associated hadrons and J/$\psi$ mesons. The integrated near-side and away-side correlated yields are also extracted as a function of the J/$\psi$ transverse momentum. The measurements are discussed in comparison to PYTHIA calculations

Charm fragmentation fractions and cc‾{\rm c\overline{c}} cross section in p−-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}}=5.02 TeV

International audienceThe total charm-quark production cross section per unit of rapidity $\mathrm{d}\sigma({\rm c\overline{c}})/\mathrm{d}y$, and the fragmentation fractions of charm quarks to different charm-hadron species $f(\mathrm{c}\rightarrow {\rm h_{c}})$, are measured for the first time in p$-$Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV at midrapidity ($-0.96<y<0.04$ in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measurements of prompt production of ground-state charm-hadron species: $\mathrm{D}^{0}$, $\mathrm{D}^{+}$, $\mathrm{D}_\mathrm{s}^{+}$, and $\mathrm{J/\psi}$ mesons, and $\Lambda_\mathrm{c}^{+}$ and $\Xi_{\rm c}^{0}$ baryons. The resulting cross section is $\mathrm{d}\sigma({\rm c\overline{c}})/\mathrm{d}y =219.6 \pm 6.3\;(\mathrm{stat.}) {\;}_{-11.8}^{+10.5}\;(\mathrm{syst.}) {\;}_{-2.9}^{+7.6}\;(\mathrm{extr.})\pm 5.4\;(\mathrm{BR})\pm 4.6\;(\mathrm{lumi.}) \pm 19.5\;(\text{rapidity shape})+15.0\;(\Omega_{\rm c}^{0})$ mb, which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at $\sqrt{s} = 5.02$ and $13$ TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p$-$Pb collisions compared with $\mathrm{e^{+}e^{-}}$ and $\mathrm{e^{-}p}$ collisions. The $p_\mathrm{T}$-integrated nuclear modification factor of charm quarks, $R_\mathrm{pPb}({\rm c\overline{c}})= 0.91 \pm 0.04\;{\rm (stat.)}{}^{+0.08}_{-0.09}\;{\rm (syst.)}{}^{+0.04}_{-0.03}\;{\rm (extr.)}{}\pm 0.03\;{\rm (lumi.)}$, is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions

Measurement of the inclusive isolated-photon production cross section in pp collisions at s\sqrt{s} = 13 TeV

International audienceThe production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at centre-of-momentum energy of $\sqrt{s}=13$ TeV collected during the LHC Run 2 data-taking period. The measurement is performed by combining the measurements of the electromagnetic calorimeter EMCal and the central tracking detectors ITS and TPC, covering a pseudorapidity range of $|\eta^{\gamma}|<0.67$ and a transverse momentum range of $7<p_{\rm T}^{\gamma}<200$ GeV/$c$. The result extends to lower $p_{\rm T}^{\gamma}$ and $x_{\rm T}^{\gamma} = 2p_{\rm T}^{\gamma}/\sqrt{s}$ ranges, the lowest $x_{\rm T}^{\gamma}$ of any isolated photon measurements to date, extending significantly those measured by the ATLAS and CMS experiments towards lower $p_{\rm T}^{\gamma}$ at the same collision energy with a small overlap between the measurements. The measurement is compared with next-to-leading order perturbative QCD calculations and the results from the ATLAS and CMS experiments as well as with measurements at other collision energies. The measurement and theory prediction are in agreement with each other within the experimental and theoretical uncertainties

Exploring nuclear structure with multiparticle azimuthal correlations at the LHC

International audienceUnderstanding nuclear structure provides essential insights into the properties of atomic nuclei. In this paper, details of the nuclear structure of $^{\rm 129}$Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in Xe$-$Xe collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.44$ TeV with the ALICE detector at the LHC. The results are compared with those from Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV for a baseline, given that the $^{\rm 208}$Pb nucleus is not deformed. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with different values of nuclear parameters, the one using a nuclear diffuseness parameter of $a_0=0.492$ and a nuclear quadrupole deformation parameter of $\beta_2=0.207$ provides a better description of the presented flow measurements. These studies represent an important step towards a thorough exploration of the imaging power of nuclear collisions at ultrarelativistic energy and the search for the imprint of nuclear structure on various flow observables in heavy-ion collisions at the LHC. The findings demonstrate the potential of nuclear structure studies at the TeV energy scale and highlight that the LHC experiments can complement existing low-energy experiments on nuclear structure studies