On Signatures of a Possible New Physics Resonance in Atmospheric Air Showers Using a Parameterized Model

TL;DR

The paper develops a parameterized atmospheric air-shower model to investigate signatures of a hypothetical new physics resonance. It implements a mixed, fluctuation-aware shower scheme and tunes it against Conex with EPOS/SIBYLL to reproduce key observables such as $X_ ext{max}$ and its width. It then introduces resonances at 100 GeV and 1 TeV with varying widths and three decay channels, showing channel-dependent impacts on $X_ ext{max}$ and revealing potential 2D signatures in the first two shower moments, including threshold-related structures. The results indicate that resonance effects depend strongly on width and decay mode and can persist over about a decade in $\log_{10} E/\mathrm{eV}$, offering guidance for future analyses and more realistic simulations.

Abstract

We present a parameterized model of atmospheric particle showers initiated by cosmic rays. Few physics shower parameters are tuned in a comparison to the Conex generator. Resulting shower properties are studied, with a comment on the cases where multiple shower maxima develop. Finally, we implement simple models of new physics resonance of masses of 100 GeV and 1 TeV and examine their effects on the shower profile, depth and maximum variation in dependence of the decay channel of the hypothetical resonance. It is shown that a new resonance effects can appear at the energy threshold and can persist for about a decade in $\log_{10} E/\mathrm{eV}$. Various assumed decay modes of the hypothetical resonance have different effects on the direction and shape of the modified average shower depth as function of the energy, with possible implications for current or future measurements. It is shown that, within the presented model, the visibility of the resonance in modified shower depth strongly depends on the resonance width. A significant modification at 10\% width gradually diminishes towards the percent-level width. We propose that looking at the 2D distributions of the two first individual shower moments can also reveal signatures of new physics.

Figures (16)

• Figure 1: The probability density function used to share energies of the parent particle between the produced hadrons. The vertical line indicates the average energy per one pion, here on the example of $N=10$ and the parent hadron energy fraction to be shared by the charged pions of 5 TeV.
• Figure 2: Two visualizations of a simple parameterized atmospheric air shower, once splitting particles every half-interaction or radiation lengths (top), or following a random choice from the exponential probability distributions (bottom). The showers are initiated by a 100 GeV and 500 GeV electrons, respectively. Total particles multiplicities are indicated in the legend. Shower transverse profile is only indicative, see text. Colors in legend correspond to colors of particle tracks in the shower.
• Figure 3: Three visualizations of a simple parameterized atmospheric air shower, once splitting particles every half-interaction or radiation lengths (top), or following a random choice from the exponential probability distributions (middle and bottom). The showers are initiated by a 1.5 TeV protons with the middle shower exhibiting a double peak structure. Total particles multiplicities are indicated in the legend and differ for each splitting model. Shower transverse profile is only indicative, see text. Colors in legend correspond to colors of particle tracks in the shower.
• Figure 4: Top left: A visualization of a simple parameterized atmospheric air shower initiated by a 50 TeV proton, with stable muons assumed, and particles multiplicities indicated in legend. Only the EM and hadronic component is propagated, with neutrinos from pion decays also shown. Neutrons are not taken into account. Shower transverse profile is only indicative, see text. Top right: Longitudinal shower development in terms of the number of charged particles as function of the atmospheric depth. A fit based on the Gaisser-Hillas profile is shown. Similar is shown in the bottom row for an electromagnetic shower initiated by an electron of the same initial energy.
• Figure 5: Mean (top) and standard deviation (bottom) of the atmospheric shower maxima as function of $\log_{10} E / \mathrm{eV}$ for the private simulation (blue) and the Conex generator used with the EPOS hadronization model (red). Also shown (dashed) are the predictions from the simple logarithmic models as in MATTHEWS2005387 for both EM and hadronic showers, the latter also with an additional constant shift of 100 $\mathrm{g/cm}^2$ leading to a better agreement.