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    Production of pions, kaons, and protons as a function of the relative transverse activity classifier in pp collisions at s \sqrt{s} = 13 TeV

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    Springer
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    International audienceThe production of π±^{±}, K±^{±}, and (p‾)p \left(\overline{\textrm{p}}\right)\textrm{p} is measured in pp collisions at s \sqrt{s} = 13 TeV in different topological regions of the events. Particle transverse momentum (pT_{T}) spectra are measured in the “toward”, “transverse”, and “away” angular regions defined with respect to the direction of the leading particle in the event. While the toward and away regions contain the fragmentation products of the near-side and away-side jets, respectively, the transverse region is dominated by particles from the Underlying Event (UE). The relative transverse activity classifier, RT_{T} = NT_{T}/〈NT_{T}〉, is used to group events according to their UE activity, where NT_{T} is the measured charged-particle multiplicity per event in the transverse region and 〈NT_{T}〉 is the mean value over all the analysed events. The first measurements of identified particle pT_{T} spectra as a function of RT_{T} in the three topological regions are reported. It is found that the yield of high transverse momentum particles relative to the RT_{T}-integrated measurement decreases with increasing RT_{T} in both the toward and the away regions, indicating that the softer UE dominates particle production as RT_{T} increases and validating that RT_{T} can be used to control the magnitude of the UE. Conversely, the spectral shapes in the transverse region harden significantly with increasing RT_{T}. This hardening follows a mass ordering, being more significant for heavier particles. Finally, it is observed that the pT_{T}-differential particle ratios \left(\textrm{p}+\overline{\textrm{p}}\right)/\left({\uppi}^{+}+{\uppi}^{-}\right) and (K+^{+} + K−^{−})/(π+^{+} + π−^{−}) in the low UE limit (RT_{T} → 0) approach expectations from Monte Carlo generators such as PYTHIA 8 with Monash 2013 tune and EPOS LHC, where the jet-fragmentation models have been tuned to reproduce e+^{+}e−^{−} results.[graphic not available: see fulltext

    Energy dependence of coherent photonuclear production of J/ψ mesons in ultra-peripheral Pb-Pb collisions at sNN \sqrt{{\textrm{s}}_{\textrm{NN}}} = 5.02 TeV

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    International audienceThe cross section for coherent photonuclear production of J/ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of sNN \sqrt{{\textrm{s}}_{\textrm{NN}}} = 5.02 TeV. Cross sections are presented in five different J/ψ rapidity ranges within |y| < 4, with the J/ψ reconstructed via its dilepton decay channels. In some events the J/ψ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17 < WγPb,n_{γ Pb,n} < 920 GeV, where WγPb,n_{γ Pb,n} is the centre-of-mass energy per nucleon of the γPb system. This range corresponds to a Bjorken-x interval spanning about three orders of magnitude: 1.1 × 10−5^{−5} < x < 3.3 × 10−2^{−2}. In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies.[graphic not available: see fulltext

    Production of Pb-203 from target manufacturing to chemical separation Tl/Pb

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    HAL CCSD
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    International audienceLead-212 (t1/2 = 10.6 h) and lead-203 (t1/2 = 51.9 h), can be used as a theranostic pair of isotopes for theranostic applications in nuclear medicine. 212Pb can be obtained from ageing 232Th and is used for alpha targeted therapy [1] whereas 203Pb can be produced by proton or deuteron irradiation of a thallium target and allows for single photon emission computed tomography (SPECT) thanks to its 279.2 keV (80.9%) photons. Current production of 203Pb uses natTl bombarded by a proton beam. In this work, we consider alternative production routes using enriched 205Tl and a deuteron beam in order to limit the level of 201Pb (t1/2 = 9.33h) impurities and to avoid the production of 200Pb (t1/2 = 21.5h). Starting from cross section measurements, we have defined optimal production parameters and yields. In parallel, we have developed a manufacturing process of the target by electroplating as well as a separation chemical process using a Pb resin from Triskem. This scheme will allow us to produce 203Pb in the near future.The electrodeposition technique is used to prepare enriched Tl target for both cross section measurements and mass production. A pulse reverse potential is used to reduce Tl+ to Tl on gold substrate. The temperature and pH of the solution are fixed respectively at 20°C and 8. The solution contains EDTA as complexing agent, hydrazine to prevent Tl+ from oxidation to Tl3+ and Brig-35 as surfactant. For the study of 203Pb production cross sections and its impurities, thin deposits of 205Tl (thicknesses ranging from 10 µm and 15 µm) with a circular shape (4 cm2) were made. Experiments were done with a deuteron beam whose energy is ranging from 22 MeV and 34 MeV. For the future routine production, a large deposit of enriched Tl is needed (14 cm2 area) to reduce the heat deposition density. To this end, we are using our rabbit system that accommodate a 15° tilted angle target. A 40 µm thick was successfully obtained with a smooth deposit and good adhesion on gold backing. In parallel, we have studied the chemical separation of Pb/Tl using 203Pb and 202Tl (t1/2 = 12.31 d) obtained by irradiation of thin deposits of natTl (20 µm) with an intensity of 50 nA deuteron beam during 1 h beam. Large Tl targets were dissolved in 1 mol/L of hot nitric acid (70°C) and tracers were added to be able to follow the different species. The solution was first filtered to recover the precipitate of thallium nitrate, which is formed at ambient temperature. The solution was then poured in the column containing the Pb resin previously conditioned with 1 mol/L of HNO3. Tl was recovered by further eluting with 1 mol/L of nitric acid. For the elution of Pb, we studied two methods: the first one corresponds to elution with 0.001 mol/L of nitric acid and the second one with ammonium acetate 1M at pH 7. The recovery of Pb is 83% and 88% respectively with less than 1% of the presence of the impurities of Tl in the solution containing Pb. Our results shows that future routine production of 203Pb using enriched thallium target and deuteron beam is feasible and that the direct elution of 203Pb with ammonium acetate 1M at pH 7 seems very promising.[1]E. Delpassand, I. Tworowska, R. Esfandiari, J. Torgue, J. D. Hurt, and R. Nunez, “Phase I dose-escalation study of AlphaMedix for targeted-alpha-emitter therapy of PRRT-naive neuroendocrine patients.,” JCO, vol. 39, no. 15_suppl, pp. 4117–4117, May 2021, doi: 10.1200/JCO.2021.39.15_suppl.4117

    Monitoring of data-MC discrepancies with MCH-cluster maps

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    HAL CCSD
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    National audienc

    First measurement of the Λ\Lambda-Ξ\Xi interaction in proton-proton collisions at the LHC

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    HAL CCSD
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    International audienceThe first experimental information on the strong interaction between Λ\Lambda and Ξ−\Xi^- strange baryons is presented in this Letter. The correlation function of Λ−Ξ−\Lambda-\Xi^- and Λ‾−Ξ‾+\overline{\Lambda}-\overline{\Xi}^{+} pairs produced in high-multiplicity proton-proton (pp) collisions at s\sqrt{s} = 13 TeV at the LHC is measured as a function of the relative momentum of the pair. The femtoscopy method is used to calculate the correlation function, which is then compared with theoretical expectations obtained using a meson exchange model, chiral effective field theory, and Lattice QCD calculations close to the physical point. Data support predictions of small scattering parameters while discarding versions with large ones, thus suggesting a weak Λ−Ξ−\Lambda-\Xi^{-} interaction. The limited statistical significance of the data does not yet allow one to constrain the effects of coupled channels like Σ−Ξ\Sigma-\Xi and N−Ω-\Omega

    System-size dependence of the charged-particle pseudorapidity density at <math altimg="si1.svg"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>5.02</mn><mspace width="0.2em"/><mtext>TeV</mtext></math> for pp, pPb, and PbPb collisions

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    HAL CCSD
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    International audienceWe present the first systematic comparison of the charged-particle pseudorapidity densities for three widely different collision systems, pp, pPb, and PbPb, at the top energy of the Large Hadron Collider (sNN=5.02TeV) measured over a wide pseudorapidity range (−3.5&lt;η&lt;5), the widest possible among the four experiments at that facility. The systematic uncertainties are minimised since the measurements are recorded by the same experimental apparatus (ALICE). The distributions for pPb and PbPb collisions are determined as a function of the centrality of the collisions, while results from pp collisions are reported for inelastic events with at least one charged particle at midrapidity. The charged-particle pseudorapidity densities are, under simple and robust assumptions, transformed to charged-particle rapidity densities. This allows for the calculation and the presentation of the evolution of the width of the rapidity distributions and of a lower bound on the Bjorken energy density, as a function of the number of participants in all three collision systems. We find a decreasing width of the particle production, and roughly a smooth ten fold increase in the energy density, as the system size grows, which is consistent with a gradually higher dense phase of matter

    Dependence of the fission half-lives of heavy nuclei on the highest proton magic number within a macro-microscopic approach

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    HAL CCSD
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    International audienceThe potential barriers in the cold fission valley were determined within the original generalized liquid drop model, which takes into account the proximity energy, the charge and mass asymmetries, the microscopic shell and pairing corrections, and quasimolecular one- and two-body shapes. Due to microscopic effects and the proximity energy, double-humped fission barriers appear. The calculations were done within four hypotheses for the heaviest proton magic number: 114, 116, 118, and 120. The calculated partial or total fission half-lives of actinides and superheavy nuclei follow roughly the trend of the experimental data, the agreement being better for Z=118

    Measurement of the Lifetime and <math display="inline"><mi mathvariant="normal">Λ</mi></math> Separation Energy of <math display="inline"><mmultiscripts><mrow><mi mathvariant="normal">H</mi></mrow><mprescripts/><mrow><mi mathvariant="normal">Λ</mi></mrow><mn>3</mn></mmultiscripts></math>

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    American Physical Society
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    International audienceThe most precise measurements to date of the HΛ3 lifetime τ and Λ separation energy BΛ are obtained using the data sample of Pb-Pb collisions at sNN=5.02  TeV collected by ALICE at the LHC. The HΛ3 is reconstructed via its charged two-body mesonic decay channel (HΛ3→He3+π- and the charge-conjugate process). The measured values τ=[253±11(stat)±6(syst)]  ps and BΛ=[102±63(stat)±67(syst)]  keV are compatible with predictions from effective field theories and confirm that the HΛ3 structure is consistent with a weakly bound system

    First Measurement of Antideuteron Number Fluctuations at Energies Available at the Large Hadron Collider

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    American Physical Society
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    International audienceThe first measurement of event-by-event antideuteron number fluctuations in high energy heavy-ion collisions is presented. The measurements are carried out at midrapidity (|η|&lt;0.8) as a function of collision centrality in Pb-Pb collisions at sNN=5.02  TeV using the ALICE detector. A significant negative correlation between the produced antiprotons and antideuterons is observed in all collision centralities. The results are compared with a state-of-the-art coalescence calculation. While it describes the ratio of higher order cumulants of the antideuteron multiplicity distribution, it fails to describe quantitatively the magnitude of the correlation between antiproton and antideuteron production. On the other hand, thermal-statistical model calculations describe all the measured observables within uncertainties only for correlation volumes that are different with respect to those describing proton yields and a similar measurement of net-proton number fluctuations

    Measurement of the angle between jet axes in pp collisions at s \sqrt{s} = 5.02 TeV

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    Springer
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    International audienceThis article reports measurements of the angle between differently defined jet axes in pp collisions at s \sqrt{s} = 5.02 TeV carried out by the ALICE Collaboration. Charged particles at midrapidity are clustered into jets with resolution parameters R = 0.2 and 0.4. The jet axis, before and after Soft Drop grooming, is compared to the jet axis from the Winner-Takes-All (WTA) recombination scheme. The angle between these axes, ∆Raxis_{axis}, probes a wide phase space of the jet formation and evolution, ranging from the initial high-momentum-transfer scattering to the hadronization process. The ∆Raxis_{axis} observable is presented for 20 <pTch jet {p}_{\textrm{T}}^{\textrm{ch}\ \textrm{jet}} < 100 GeV/c, and compared to predictions from the PYTHIA 8 and Herwig 7 event generators. The distributions can also be calculated analytically with a leading hadronization correction related to the non-perturbative component of the Collins-Soper-Sterman (CSS) evolution kernel. Comparisons to analytical predictions at next-to-leading-logarithmic accuracy with leading hadronization correction implemented from experimental extractions of the CSS kernel in Drell-Yan measurements are presented. The analytical predictions describe the measured data within 20% in the perturbative regime, with surprising agreement in the non-perturbative regime as well. These results are compatible with the universality of the CSS kernel in the context of jet substructure.[graphic not available: see fulltext

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