Strange fireball as an explanation of the muon excess in Auger data

Abstract

We argue that ultrahigh energy cosmic ray collisions in the Earth's atmosphere can probe the strange quark density of the nucleon. These collisions have center-of-mass energies 10 4.6 A GeV, where A ≥ 14 is the nuclear baryon number. We hypothesize the formation of a deconfined thermal fireball which undergoes a sudden hadronization. At production the fireball has a very high matter density and consists of gluons and two flavors of light quarks (u, d). Because the fireball is formed in the baryon-rich projectile fragmentation region, the high baryochemical potential damps the production of uū and dd pairs, resulting in gluon fragmentation mainly into ss. The strange quarks then become much more abundant and upon hadronization the relative density of strange hadrons is significantly enhanced over that resulting from a hadron gas. Assuming the momentum distribution functions can be approximated by Fermi-Dirac and Bose-Einstein statistics, we estimate a kaon-to-pion ratio of about 3 and expect a similar (total) baryon-to-pion ratio. We show that, if this were the case, the excess of strange hadrons would suppress the fraction of energy which is transferred to decaying π 0 's by about 20%, yielding a ∼ 40% enhancement of the muon content in atmospheric cascades, in agreement with recent data reported by the Pierre Auger Collaboration.

Open Questions in Cosmic-Ray Research at Ultrahigh Energies

“…This would put more energy into the hadronic channel compared to the electromagnetic channel, thus producing more muons. A similar effect could be achieved by the production of a fireball consisting of deconfined quarks and gluons (Anchordoqui et al, 2017).…”

Probing QCD approach to thermal equilibrium with ultrahigh energy cosmic rays

“…Very recently we presented a model that can accommodate all these anomalies [4]. The model builds up on an old idea, which allows formation of a deconfined quark matter (fireball) state in central collisions of ultrarelativistic cosmic rays with air nuclei [10].…”

“…As recently demonstrated by the Pierre Auger Collaboration [2], it is possible to test particle physics well above 100 TeV in the UHECR-air nucleon center-of-mass energy, using hybrid UHECR air showers, even with a mixed primary composition. Moreover, the column energydensity in UHECR-air collisions is an order of magnitude greater than in Pb-Pb collisions at the LHC, suggesting the potential for new hadronic physics from gluon saturation and possibility of exploring quark-gluon plasma as well as quark matter formation by heavy nuclear primaries at far higher energies than available in accelerators [3,4].…”

Can strangelets solve the muon puzzle?

“…The comparison of observed and simulated densities of E µ > 10 GeV muons in air showers induced by E ∼ 10 17 eV primaries, based on the Moscow State University Extensive Air Shower (EAS-MSU) data [5], demonstrate that the muon excess is absent and that the fit never requires primaries heavier than iron. To explain the muon excess, several new models have been proposed, exploring new physics [6][7][8] or new forms of matter, namely strange quark matter (SQM) [9]. In this paper we adopt a purely phenomenological approach to develop an SQM scheme.…”