Charged-particle multiplicity dependence of charm-baryon-to-meson ratio in high-energy proton-proton collisions

Yu Chen,Min He

doi:10.1016/j.physletb.2021.136144

Yu Chen, Min He

Open Access

https://doi.org/10.1016/j.physletb.2021.136144

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Abstract

We propose that the charged-particle multiplicity dependence of the charm-baryon-to-meson ratio observed in high-energy pp collisions can be explained by canonical treatment of quantum charges in the statistical hadronization model (SHM). Taking the full particle listings of PDG complemented by additional charm-baryon states from relativistic quark model predictions, we evaluate the canonical partition function and the charm-hadron chemical factors that measure the canonical suppression arising from the requirement of strict conservation of quantum charges. We demonstrate that, while charm number conservation induces common suppression on the production of both charm-baryons and -mesons, baryon (strangeness) number conservation causes further suppression on charm-baryons (charm-strange mesons) relative to nonstrange charm-mesons, thereby resulting in a decreasing Λc/D0 (Ds/D0) ratio toward smaller multiplicity events. The charm-hadron thermal densities thus computed are then used as pertinent weights to perform charm-quark fragmentation simulations yielding pT-dependent Λc/D0 and Ds/D0 ratios at varying multiplicities in fair agreement with ALICE measurements.

Highlights

IntroductionFactorization provides an approach to compute the production of heavy-flavor (HF) hadrons in high-energy hadronic collisions within the framework of perturbative QCD
Factorization provides an approach to compute the production of heavy-flavor (HF) hadrons in high-energy hadronic collisions within the framework of perturbative QCD. This approach involves the convolution of the parton distribution functions (PDFs) of the colliding hadrons, the hardscattering cross sections at the partonic level and the fragmentation functions (FFs)
While the PDFs are considered to be universal and usually taken from global fits of various sets of empirical data [1], and the partonic cross sections are calculated as perturbative series in powers of the strongcoupling constant, the FFs modelling the nonperturbative hadronization processes represent a major source of theoretical uncertainty

Summary

Introduction

Factorization provides an approach to compute the production of heavy-flavor (HF) hadrons in high-energy hadronic collisions within the framework of perturbative QCD. String fragmentation invoking color reconnection mechanisms accountes for multi-parton interactions in high-energy pp collisions and turns out to enhance the baryon production in both strange and charm sector [10] Another way of determining the fragmentation fractions of a heavy quark hadronizing into various kinds of HF hadrons is given by their thermal weights at a hadronization “temperature” TH in the statistical hadronization model (SHM) [11, 12], given that relative chemical equilibrium among them may be reached in the quark-rich environment such as high-energy pp collisions. Using computed thermal densities of each charm-hadron as pertinent weights, we conduct a simulation of the charm quark fragmentation within the FONLL scheme [28, 29] and compute the transverse momentum (pT ) dependent Λc/D0 and Ds/D0 at different dNch/dη

Canonical partition function

Evaluation of the canonical partition function

Selective canonical suppression

System-size dependence of charm-hadron production

Fragmenation and Decay Simulation

Summary