New results on $\phi$(1020) production from the NA61/SHINE experiment at CERN SPS

TL;DR

This paper reports the first measurements of $\,phi$(1020) meson production in intermediate-size Ar+Sc collisions at CERN SPS, revealing discrepancies with existing models and providing new insights into strangeness production in heavy-ion collisions.

Contribution

It presents the first experimental results on $\,phi$(1020) production in Ar+Sc collisions at CERN SPS, including detailed spectra and particle ratios, and compares them with other collision systems and models.

Findings

$\,phi$(1020) yields increase with energy and system size.

Existing microscopic models fail to accurately describe the measurements.

Strangeness production shows signs of enhancement in intermediate systems.

Abstract

NA61/SHINE is a multipurpose, fixed-target hadron spectrometer at the CERN SPS. Its research program includes studies of strong interactions as well as reference measurements for neutrino and cosmic-ray physics. A significant advantage of NA61/SHINE over collider experiments is its extended coverage of phase space available for particle production. This includes the entire projectile hemisphere of the collision, with no low-pT cut-off. The energy and system-size dependence of strangeness production plays an essential role in studies of the transition from confined to deconfined matter. With its zero net strangeness and its valence structure composed predominantly of s and $\bar{s}$ valence quarks, the $\phi$(1020) meson will not be sensitive to strangeness-related effects in a purely hadronic scenario, but will behave like a doubly strange particle in a partonic system. This contribution presents the first-ever results on $\phi$(1020) meson production in intermediate-size systems at the CERN SPS, that is, central Ar+Sc collisions at $\sqrt{s_\text{NN}}$ = 8.8, 11.9, and 16.8 GeV. The presented results include double-differential rapidity-transverse momentum (y-pT) distributions, transverse mass (mT) spectra at midrapidity, pT-integrated rapidity spectra, mean multiplicities (4$\pi$ yields), and particle ratios. These are compared to data on Pb+Pb and p+p collisions. A discussion of open and hidden strangeness production enhancement is included. Finally, a comparison with three microscopic models is shown, demonstrating their overall failure in describing these new measurements.