Utilizing a quark model characterized by parameters that effectively replicate the masses of ground state hadrons, we illustrate that <math><mo>(</mo><mi>u</mi><mi>s</mi><mo>)</mo></math> or <math><mo>(</mo><mi>d</mi><mi>s</mi><mo>)</mo></math> diquarks exhibit greater compactness in comparison to <math><mo>(</mo><mi>u</mi><mi>d</mi><mo>)</mo></math> diquarks. Concretely, the binding energy of the <math><mo>(</mo><mi>u</mi><mi>s</mi><mo>)</mo></math> diquark - defined as the diquark's mass minus the combined masses of its individual quarks - is found to be stronger than that of the <math><mo>(</mo><mi>u</mi><mi>d</mi><mo>)</mo></math> diquark. This heightened attraction present in <math><mo>(</mo><mi>u</mi><mi>s</mi><mo>)</mo></math> diquarks could lead to enhanced production of <math><msub><mrow><mi>Ξ</mi></mrow><mrow><mi>c</mi></mrow></msub><mo>/</mo><mi>D</mi></math> particles in high-energy pp or ultrarelativistic heavy-ion collisions.

South Korea

Hyeongock Yun

Sungsik Noh

Sanghoon Lim

Germany

Taesoo Song

Juhee Hong

Aaron Park

Su Houng Lee

Benjamin Dönigus

Diquarks and the production of charmed baryons

We estimate the feeddown contributions from decays of unstable <math><mi>A</mi><mo>=</mo><mn>4</mn></math> and <math><mi>A</mi><mo>=</mo><mn>5</mn></math> nuclei to the final yields of protons, deuterons, tritons, $^{3}$He, and $^{4}$He produced in relativistic heavy-ion collisions at <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>&gt;</mo><mn>2.4</mn></math> GeV, using the statistical model. The feeddown contribution effects do not exceed 5% at LHC and top RHIC energies due to the large penalty factors involved, but are substantial at intermediate collision energies. We observe large feeddown contributions for tritons, $^{3}$He, and $^{4}$He at <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>≲</mo><mn>10</mn></math> GeV, where they may account for as much as 70% of the final yield at the lower end of the collision energies considered. Sizable (&gt;10%) effects for deuteron yields are observed at <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>≲</mo><mn>4</mn></math> GeV. The results suggest that the excited nuclei feeddown cannot be neglected in the ongoing and future analysis of light nuclei production at intermediate collision energies, including HADES and CBM experiments at FAIR, NICA at JINR, RHIC beam energy scan and fixed-target programmes, and NA61/SHINE at CERN. We further show that the freeze-out curve in the T-<math><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></math> plane itself is affected significantly by the light nuclei at high baryochemical potential.

United States

Volodymyr Vovchenko

Behruz Kardan

Manuel Lorenz

Horst Stoecker

Feeddown contributions from unstable nuclei in relativistic heavy-ion collisions

The system-size dependence of hadrochemistry at vanishing baryon density is considered within the canonical statistical model (CSM) with local exact conservation of three conserved charges, allowing for a possibility of strangeness undersaturation, i.e., <math><mrow><msub><mi>γ</mi><mi>S</mi></msub><mo>≤</mo><mn>1</mn></mrow></math>. Exact baryon number conservation is found to be even more important than that of strangeness in the canonical suppression picture at the CERN Large Hadron Collider, in contrast to intermediate and low collision energies. The model is applied to <math><mrow><mi>p</mi><mtext>−</mtext><mi>p</mi></mrow></math>, <math><mi>p</mi></math>-Pb, and Pb-Pb data of the ALICE Collaboration. A chemical equilibrium CSM with a fixed <math><mrow><msub><mi>T</mi><mi>ch</mi></msub><mo>=</mo><mn>155</mn></mrow></math> MeV describes the trends seen in most yield ratios. However, this “vanilla” version of CSM predicts an enhancement of the <math><mrow><mi>ϕ</mi><mo>/</mo><mi>π</mi></mrow></math> ratio at smaller multiplicities, in stark contrast to the suppression seen in the data. The data are described with a 15% relative accuracy level whence a multiplicity dependence of both the temperature and the strangeness saturation parameter <math><mrow><msub><mi>γ</mi><mi>S</mi></msub><mo>≤</mo><mn>1</mn></mrow></math> is accepted. Both the canonical suppression and the strangeness undersaturation effects are small at <math><mrow><mi>d</mi><msub><mi>N</mi><mi>ch</mi></msub><mo>/</mo><mi>d</mi><mi>η</mi><mo>≳</mo><mn>100</mn></mrow></math>, but they do improve substantially the description of hadron yields in <math><mrow><mi>p</mi><mtext>−</mtext><mi>p</mi></mrow></math> collisions, in particular the <math><mi>Ω</mi></math> yields. A possibility to constrain the rapidity correlation volume using net-proton fluctuation measurements is pointed out.

Canonical statistical model analysis of <math><mrow><mi>p</mi><mtext>−</mtext><mi>p</mi></mrow></math>, <math><mi>p</mi></math>-Pb, and Pb-Pb collisions at energies available at the CERN Large Hadron Collider

We show that the recently observed suppression of the yield ratio of deuteron to proton and of helium-3 to proton in p+p collisions compared to those in p+Pb or Pb+Pb collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) can be explained if light nuclei are produced from the coalescence of nucleons at the kinetic freeze-out of these collisions. This suppression is attributed to the non-negligible sizes of deuteron and helium-3 compared to the size of the nucleon emission source in collisions of small systems, which reduces the overlap of their internal wave functions with those of nucleons. The same model is also used to study the production of triton and hypertriton in heavy-ion collisions at the LHC. Compared to helium-3 in events of low charged particle multiplicity, the triton is less suppressed due to its smaller size and the hypertriton is even more suppressed as a result of its much larger size.

Kai-Jia Sun

Che Ming Ko

Suppression of light nuclei production in collisions of small systems at the Large Hadron Collider

The statistical model with exact conservation of baryon number, electric charge, and strangeness – the Canonical Statistical Model (CSM) – is used to analyze the dependence of yields of light nuclei at midrapidity on charged pion multiplicity at the LHC. The CSM calculations are performed assuming baryon-symmetric matter, using the recently developed Thermal-FIST package. The light nuclei-to-proton yield ratios show a monotonic increase with charged pion multiplicity, with a saturation at the corresponding grand-canonical values in the high-multiplicity limit, in good qualitative agreement with the experimental data measured by the ALICE collaboration in pp and Pb–Pb collisions at different centralities and energies. Comparison with experimental data at low multiplicities shows that exact conservation of charges across more than one unit of rapidity and/or a chemical freeze-out temperature which decreases with the charged pion multiplicity improves agreement with the data.

Multiplicity dependence of light nuclei production at LHC energies in the canonical statistical model