596 research outputs found

    Measurement of the production of (anti)nuclei in p‚ÄďPb collisions at sNN=8.16TeV

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    Measurements of (anti)proton, (anti)deuteron, and (anti)3He production in the rapidity range ‚ąí1<y<0 as a function of the transverse momentum and event multiplicity in p‚ÄďPb collisions at a center-of-mass energy per nucleon‚Äďnucleon pair sNN=8.16TeV are presented. The coalescence parameters B2 and B3, measured as a function of the transverse momentum per nucleon and of the mean charged-particle multiplicity density, confirm a smooth evolution from low to high multiplicity across different collision systems and energies. The ratios between (anti)deuteron and (anti)3He yields and those of (anti)protons are also reported as a function of the mean charged-particle multiplicity density. A comparison with the predictions of the statistical hadronization and coalescence models for different collision systems and center-of-mass energies favors the coalescence description for the deuteron-to-proton yield ratio with respect to the canonical statistical model

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

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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, ‚ąÜRaxis_{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 ‚ąÜRaxis_{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

    Measurements of Groomed-Jet Substructure of Charm Jets Tagged by <math display="inline"><mrow><msup><mrow><mi mathvariant="italic">D</mi></mrow><mrow><mn>0</mn></mrow></msup></mrow></math> Mesons in Proton-Proton Collisions at <math display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext>‚ÄČ</mtext><mtext>‚ÄČ</mtext><mi>TeV</mi></mrow></math>

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    International audienceUnderstanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed D0 meson. The measurement is made in proton-proton collisions at s=13‚ÄČ‚ÄČTeV, in the low jet transverse-momentum interval of 15‚ȧpTjet ch&lt;30‚ÄČ‚ÄČGeV/c where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions

    Measurement of inclusive and leading subjet fragmentation in pp and Pb‚ÄďPb collisions at sNN \sqrt{s_{\textrm{NN}}} = 5.02 TeV