20 research outputs found

    Elliptic anisotropy measurement of the f0_0(980) hadron in proton-lead collisions and evidence for its quark-antiquark composition

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    International audienceDespite the f0_0(980) hadron having been discovered half a century ago, the question about its quark content has not been settled: it might be an ordinary quark-antiquark (qqňČ\mathrm{q\bar{q}}) meson, a tetraquark (qqňČqqňČ\mathrm{q\bar{q}q\bar{q}}) exotic state, a kaon-antikaon (KKňČ\mathrm{K\bar{K}}) molecule, or a quark-antiquark-gluon (qqňČg\mathrm{q\bar{q}g}) hybrid. This paper reports strong evidence that the f0_0(980) state is an ordinary qqňČ\mathrm{q\bar{q}} meson, inferred from the scaling of elliptic anisotropies (v2v_2) with the number of constituent quarks (nqn_\mathrm{q}), as empirically established using conventional hadrons in relativistic heavy ion collisions. The f0_0(980) state is reconstructed via its dominant decay channel f0_0(980) ‚Üí\toŌÄ+ŌÄ‚ąí\pi^+\pi^-, in proton-lead collisions recorded by the CMS experiment at the LHC, and its v2v_2 is measured as a function of transverse momentum (pTp_\mathrm{T}). It is found that the nqn_q = 2 (qqňČ\mathrm{q\bar{q}} state) hypothesis is favored over nqn_q = 4 (qqňČqqňČ\mathrm{q\bar{q}q\bar{q}} or KKňČ\mathrm{K\bar{K}} states) by 7.7, 6.3, or 3.1 standard deviations in the pTp_\mathrm{T}<\lt 10, 8, or 6 GeV/cc ranges, respectively, and over nqn_\mathrm{q} = 3 (qqňČg\mathrm{q\bar{q}g} hybrid state) by 3.5 standard deviations in the pTp_\mathrm{T}<\lt 8 GeV/cc range. This result represents the first determination of the quark content of the f0_0(980) state, made possible by using a novel approach, and paves the way for similar studies of other exotic hadron candidates

    Search for new Higgs bosons via same-sign top quark pair production in association with a jet in proton-proton collisions at s= \sqrt{s}= 13 TeV