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Comparing the fluorination of Pb+ and Po+: insights into p-block relativistic effects for superheavy elements
It is expected that the chemical properties of the heaviest of the superheavy elements (SHEs, = 113 – 118) do not align with what is suggested by their current positions on the periodic table. Specifically, the onset of significant relativistic effects, including increased spin–orbit splitting of the p-orbitals may lead to enhanced stability of low-oxidation states. Notably, it is predicted that flerovium ( = 114) may exhibit pseudo-noble gas behavior from a electron configuration that acts as an ‘inert pair’. Even though it is expected that the – splitting becomes pronounced toward the end of the p-block’s sixth row, there is currently limited experimental evidence to confirm its extent or impact. Here, the production of gas-phase lead ( = 82) and polonium ( = 84) fluoride cations (PbF and PoF ) were compared to elucidate differences in accessible oxidation states. The PoF and PbF species were produced and identified with the FIONA spectrometer at the Lawrence Berkeley National Laboratory 88-Inch Cylctron Facility. Polonium showed notably different fluorination chemistry than lead, producing PoF and PoF as primary products compared to lead’s PbF and PbF . The distribution of PoF products observed offer insights as to the role of spin–orbit splitting for polonium. Similar studies of superheavy elements would elucidate the accessibility of their low-oxidation states as well as to inform chemical predictions for eighth-row elements not yet discovered.
Observation of the Charged-Particle Multiplicity Dependence of 𝜎 𝜓(2𝑆 )/𝜎 𝐽/𝜓 in 𝑝-Pb Collisions at 8.16 TeV
Bound states of charm and anticharm quarks, known as charmonia, have a rich spectroscopic structure that can be used to probe the dynamics of hadron production in high-energy hadron collisions. Here, the cross section ratio of excited (𝜓(2𝑆)) and ground state (𝐽/𝜓) vector mesons is measured as a function of the charged-particle multiplicity in proton-lead (𝑝Pb) collisions at a center-of-mass (CM) energy per nucleon pair of 8.16 TeV. The data corresponding to an integrated luminosity of 175 nb −1 were collected using the CMS detector. The ratio is measured separately for prompt and nonprompt charmonia in the transverse momentum range 6.5 < 𝑝 T < 30 GeV and in four rapidity ranges spanning −2.865 < 𝑦 CM < 1.935. For the first time, a statistically significant multiplicity dependence of the prompt cross section ratio is observed in proton-nucleus collisions. There is no clear rapidity dependence in the ratio. The prompt measurements are compared with a theoretical model which includes interactions with nearby particles during the evolution of the system. These results provide additional constraints on hadronization models of heavy quarks in nuclear collisions.
Local monoclinic polarization rotation promoting a different domain alignment in rhombohedral Pb(Zr,
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Pb 9 Cu ( PO 4 ) 6 ( OH ) 2 : Phonon bands, localized flat-band magnetism, models, and chemical analysis
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Multiparticle correlation studies in p Pb collisions at s N N = 8.16 TeV
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Production of ( anti- ) He 3 and ( anti- ) H 3 in p -Pb collisions at s N N = 5.02 TeV
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Measurement of isolated photon-hadron correlations in s NN = 5.02 TeV p p and p -Pb collisions
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γ -hadron spectra in p + Pb collisions at s N N = 5.02 TeV
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Measurement of the prompt-production cross-section ratio σ ( χ c 2 ) / σ ( χ c 1 ) in p Pb collisions at s N N = 8.16 TeV
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Λ c + production in p p and in p -Pb collisions at s N N = 5.02 TeV
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Incorporating the weak mixing angle dependence to reconcile the neutron skin measurement on Pb 208 by PREX-II
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Contributions from ultraperipheral collisions to the forward rapidity gap distribution in p Pb collisions at the CERN Large Hadron Collider at s N N = 8.16 TeV
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K * ( 892 ) 0 and ϕ ( 1020 ) production in p − Pb collisions at s N N = 8.16 TeV
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Production of η and η ′ mesons in p p and p Pb collisions
The production of η and η ′ mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of 5.02 and 13 TeV and proton-lead collisions are studied at a center-of-mass energy per nucleon of 8.16 TeV . The studies are performed in center-of-mass (c.m.) rapidity regions 2.5 < y c . m . < 3.5 (forward rapidity) and − 4.0 < y c . m . < − 3.0 (backward rapidity) defined relative to the proton beam direction. The η and η ′ production cross sections are measured differentially as a function of transverse momentum for 1.5 < p T < 10 GeV and 3 < p T < 10 GeV , respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for η and η ′ mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of η mesons are also used to calculate η / π 0 cross-section ratios, which show evidence of a deviation from the world average. These studies offer new constraints on mass-dependent nuclear effects in heavy-ion collisions, as well as η and η ′ meson fragmentation. ©2024 CERN, for the LHCb Collaboration 2024 CERN
Measurement of Pb n a t ( ν e , X n ) production with a stopped-pion neutrino source
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Exclusive and dissociative $J/ψ$ photoproduction, and exclusive dimuon production, in p-Pb collisions at $\sqrt{s_{NN}}$ = 8.16 $\mathrm{TeV}$
The ALICE Collaboration reports three measurements in ultraperipheral proton-lead collisions at forward rapidity. The exclusive two-photon process γγ → μ + μ - and the exclusive photoproduction of J/ψ are studied. J/ψ photoproduction with proton dissociation is measured for the first time at a hadron collider. The cross section for the two-photon process of dimuons in the invariant mass range from 1 to 2.5 GeV/c 2 agrees with leading-order quantum electrodynamics calculations. The exclusive and dissociative cross sections for J/ψ photoproductions are measured for photon-proton center-of-mass energies from 27 to 57 GeV. They are in good agreement with HERA results.