[Paper Review] Strangelets at Chacaltaya

M. Rybczyński, Z. Włodarczyk+1 more|arXiv (Cornell University)|Sep 14, 2000

Asian Geopolitics and Ethnography3 citations

TL;DR

This paper proposes that strangelets—hypothetical stable lumps of strange quark matter—could be detected in cosmic ray data from Chacaltaya due to their deep atmospheric penetration. Using a quark-level interaction model, the authors simulate strangelet propagation through the atmosphere, showing that only initial strangelets with mass number $ A_0 \gtrsim 7A_{\text{crit}} $ ($ A_{\text{crit}} \sim 300-400 $) survive to detection, yielding a predicted flux of $ 7 \cdot 10^{-6} $ m$^{-2}$ h$^{-1}$ sr$^{-1}$ above 10 GeV, consistent with experimental upper limits and astrophysical constraints.

ABSTRACT

We discuss the possible imprints of strangelets (i.e., lumps of Strange Quark Matter) in Chacaltaya experimental data using model of propagation of such objects through the atmosphere developed by us recently.

Motivation & Objective

• To investigate the feasibility of detecting strangelets—stable lumps of strange quark matter—in cosmic ray experiments at high-altitude Chacaltaya.
• To model the propagation of strangelets through the Earth's atmosphere, accounting for sequential nuclear interactions and mass reduction via neutron evaporation.
• To assess the detectability of strangelets using passive nuclear track detectors and extensive air shower (EAS) data, particularly in relation to anomalous events like Centauros and aligned families.
• To compare predicted strangelet fluxes and mass spectra with experimental upper limits and cosmic abundance patterns to validate the model.
• To explore the implications of strangelets for explaining exotic cosmic ray phenomena such as long-delayed neutrons and high-multiplicity muon bundles.

Proposed method

• Employed a quark-level interaction model where each quark in the target nucleus interacts with one quark in the strangelet, reducing its mass number by $ A_t $ per collision.
• Simulated atmospheric propagation using modified SHOWERSIM software, tracking the decrease in strangelet mass number $ A(h) $ with depth $ h $ until reaching $ A_{\text{crit}} \sim 300-400 $, below which decay occurs.
• Assumed a primary power-law spectrum $ F(E) \sim E^{-2.7} $ for cosmic rays, including protons, iron, and strangelets, with energies above 1000 TeV.
• Calculated the detection efficiency for strangelets at Chacaltaya as a function of initial mass number $ A_0 $, showing that only $ A_0 \gtrsim 7A_{\text{crit}} $ yield detectable signals.
• Predicted EAS hadron and muon multiplicity distributions for primary strangelets with $ A_0 = 400 $, comparing them with proton and iron-induced showers.
• Estimated the expected flux of strangelets at Chacaltaya and compared it with experimental upper limits (e.g., Price [20]) and astrophysical constraints (Big Bang and dark matter models).

Experimental results

Research questions

• RQ1 Can strangelets with $ A > A_{\text{crit}} \sim 300-400 $ survive atmospheric penetration to be detectable at Chacaltaya?
• RQ2 What initial mass $ A_0 $ is required for strangelets to reach Chacaltaya with $ A > A_{\text{crit}} $, and what is the resulting detectable flux?
• RQ3 How do the multiplicity distributions of hadrons and muons in EAS initiated by strangelets compare with those from protons and iron nuclei?
• RQ4 Can the model explain anomalous cosmic ray events such as Centauros, aligned families, and long-delayed neutrons?
• RQ5 Is the predicted mass spectrum of strangelets ($ A_0^{-7.5} $) consistent with the observed abundance of elements in the Universe?

Key findings

• Strangelets with initial mass number $ A_0 \gtrsim 7A_{\text{crit}} $ ($ A_{\text{crit}} \sim 300-400 $) are required to survive atmospheric penetration and be detectable at Chacaltaya.
• The predicted flux of strangelets at Chacaltaya is $ 7 \cdot 10^{-6} $ m$^{-2}$ h$^{-1}$ sr$^{-1}$ for energies above 10 GeV per particle, consistent with experimental upper limits.
• The detection efficiency for strangelets with $ A > A_{\text{crit}} $ increases significantly for $ A_0 \gtrsim 1600 $, with full detection expected for $ A_0 \gtrsim 7A_{\text{crit}} $.
• EAS initiated by strangelets with $ A_0 = 400 $ produce distinct hadron and muon multiplicity distributions, differing from those of protons and iron nuclei, providing a detectable signature.
• The model successfully explains the slow attenuation and multiple maxima in some exotic air showers, as well as the extreme imbalance in hadronic and gamma-ray components seen in Centauro events.
• The predicted mass spectrum of strangelets, $ N(A_0) \propto A_0^{-7.5} $, matches the observed abundance pattern of normal nuclei in the Universe, lending credibility to the model.