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

Kai-Jia Sun,Che Ming Ko,Benjamin Dönigus

doi:10.1016/j.physletb.2019.03.033

Kai-Jia Sun, Che Ming Ko + Show 1 more

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https://doi.org/10.1016/j.physletb.2019.03.033

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Abstract

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.

Highlights

Besides the production of the quark-gluon plasma (QGP) [1,2,3], relativistic heavy-ion collisions have led to the production of anti-nuclei [4,5,6,7] and the discovery of anti-hypernuclei [8, 9]
In recent measurements by the ALICE Collaboration at the Large Hadron Collider (LHC), the yield ratios d/p and 3He/p from p+p, p+Pb and Pb+Pb collisions at center-of-mass energies ranging from 900 GeV to 7 TeV have been measured, and they are found to decrease monotonically with decreasing charged particle multiplicity in the collisions [7, 37
Based on the coalescence model in full phase space, we have studied the dependence of deuteron, heilium-3, and triton production in nuclear collisions at energies available from the LHC on the charged particle multiplicity of the collisions

Summary

INTRODUCTION

Besides the production of the quark-gluon plasma (QGP) [1,2,3], relativistic heavy-ion collisions have led to the production of anti-nuclei [4,5,6,7] and the discovery of anti-hypernuclei [8, 9]. The resulting ratios of light nuclei to proton in these collisions are, too small compared with the experimental data unless the canonical correlation volume for exact charge conservations is taken to span three units of rapidity, instead of the usual one unit of rapidity for collisions with large particle multiplicity, or using a higher chemical freezeout temperature of 170 MeV than the usual value of 155 MeV for collisions of large systems. In this Letter, we use a more realistic coalescence model to study the system size or charged particle multiplicity dependence of the d/p and 3He/p ratios by taking into account the finite size of deuteron and 3He through their internal wave functions Our results on these yield ratios are found in good agreement with available experimental data. We have mTK ≫ 1/σ2, and the yield ratio d/p is approximately given by

Nd Np

Our prediction

CONCLUSIONS

We have further found that the production of triton is