Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried bybaryons,, in hadronic collisions. The results are obtained in proton-proton () collisions atat the LHC, withbaryons and charged (track-based) jets reconstructed in the transverse momentum intervals ofand, respectively. Thedistribution is compared to a measurement of-tagged charged jets incollisions as well as to 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation.
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© 2024 CERN, for the ALICE Collaboration 2024 CERN Free, publicly-accessible full text available April 1, 2025 -
A search for the nonresonant production of Higgs boson pairs in thechannel is performed usingof proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The analysis strategy is optimized to probe anomalous values of the Higgs boson self-coupling modifierand of the quartic() coupling modifier. No significant excess above the expected background from Standard Model processes is observed. An observed (expected) upper limitis set at 95% confidence-level on the Higgs boson pair production cross section normalized to its Standard Model prediction. The coupling modifiers are constrained to an observed (expected) 95% confidence interval of() and(), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The results are also interpreted in the context of effective field theories via constraints on anomalous Higgs boson couplings and Higgs boson pair production cross sections assuming different kinematic benchmark scenarios.
© 2024 CERN, for the ATLAS Collaboration 2024 CERN Free, publicly-accessible full text available August 1, 2025 -
The production of thecharmonium state was measured with ALICE in Pb-Pb collisions at, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (). The measurement of the ratio of the inclusive production cross sections of theandresonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region. The results are compared with the corresponding measurements incollisions, by forming the double ratio. It is found that in Pb-Pb collisions theis suppressed by a factor ofwith respect to the. Thenuclear modification factorwas also obtained as a function of both centrality and. The results show that theresonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up towith respect to. Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and ofwith higher-results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC.
© 2024 CERN, for the ALICE Collaboration 2024 CERN -
A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 andof proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweakchannel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is, with a total uncertainty of 0.33 GeV.
© 2024 CERN, for the CMS and ATLASs Collaboration 2024 CERN Free, publicly-accessible full text available June 1, 2025 -
A bstract A combination of searches for new heavy spin-1 resonances decaying into different pairings of
W ,Z , or Higgs bosons, as well as directly into leptons or quarks, is presented. The data sample used corresponds to 139 fb− 1of proton-proton collisions at = 13 TeV collected during 2015–2018 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting quark pairs ($$ \sqrt{s} $$ qq ,bb , , and$$ t\overline{t} $$ tb ) or third-generation leptons (τν andττ ) are included in this kind of combination for the first time. A simplified model predicting a spin-1 heavy vector-boson triplet is used. Cross-section limits are set at the 95% confidence level and are compared with predictions for the benchmark model. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The complementarity of the various analyses increases the sensitivity to new physics, and the resulting constraints are stronger than those from any individual analysis considered. The data exclude a heavy vector-boson triplet with mass below 5.8 TeV in a weakly coupled scenario, below 4.4 TeV in a strongly coupled scenario, and up to 1.5 TeV in the case of production via vector-boson fusion.Free, publicly-accessible full text available April 1, 2025 -
A bstract The fractions of non-prompt (i.e. originating from beauty-hadron decays) D0and D+mesons with respect to the inclusive yield are measured as a function of the charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of
= 13 TeV with the ALICE detector at the LHC. The results are reported in intervals of transverse momentum ($$ \sqrt{s} $$ p T) and integrated in the range 1< p T< 24 GeV/c . The fraction of non-prompt D0and D+mesons is found to increase slightly as a function ofp Tin all the measured multiplicity intervals, while no significant dependence on the charged-particle multiplicity is observed. In order to investigate the production and hadronisation mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour glass condensate including three-pomeron fusion.