arXiv subjects

Igor Vaiman

Publications and source records attributed to Igor Vaiman.

3 recordsLinked to original sources

arXiv2026

Enabling fundamental understanding of Nature with novel binning methods for 2D histograms

Context. Visualization of 2D distributions is an essential task, commonly done with a 2D histogram. The histogram is built by subdividing the sample space into regions and color-coding the number of samples in each region. Aims. We aim to solve long-standing problems with common 2D histogram methods: lack of thematic, visual, and conceptual unity with underlying data, and general stagnation in the field. Methods. We develop a new method for plotting 2D histograms with arbitrary bin shapes, including aperiodic tilings and geographic maps. We apply the method to several common plot types from the literature. Results. We find our method performs best across all tasks, solving the problems and propelling the scientific progress forward.

astro-ph.IM↗

arXiv2026

Updated Air-Shower $X_{\rm max}$ Moment Parametrizations for UHECR Composition with Latest Hadronic Interaction Models

The mass composition of ultra-high-energy cosmic rays (UHECRs) is commonly inferred from the first two moments of the depth of shower maximum, $X_{\rm max}$, measured by fluorescence and hybrid detectors. Such analyses require fast and accurate mappings between the moments of $X_{\rm max}$ and those of the logarithmic mass, $\ln A$, based on realistic air-shower simulations. In this work we provide updated parametrizations of the $X_{\rm max}$ moments and distributions for air showers initiated by nuclei from proton to iron, simulated with CONEX for three state-of-the-art hadronic interaction models: Epos LHC-R, Sibyll 2.3e, and QGSJet-III-01. We parametrize the mean depth $\langle X_{\rm max}\rangle$ and the variance $\sigma^2(X_{\rm max})$ as functions of energy and mass. For the variance we compare a second-order polynomial model with an exponential model. In addition, we model the full $X_{\rm max}$ distributions with a three-parameter generalized Gumbel function. The Gumbel parameters are fitted using an unbinned likelihood and are validated by comparing the implied mean and variance with the raw CONEX samples and with the moment parametrizations. Across the full energy range considered, residuals between the parametrizations (or the Gumbel representation) and the simulations are at the level of a few g cm$^{-2}$ for the mean and a few (g cm$^{-2}$)$^2$ for the variance, making these parametrizations suitable for precision UHECR composition studies and forward-folding analyses of $X_{\rm max}$ distributions.

astro-ph.HE↗

arXiv2021

The primary proton spectrum of the hadronic PeVatron candidate HAWC J1825-134

The $\gamma$-ray spectrum of the source HAWC J1825-134 measured with the High Altitude Water Cherenkov (HAWC) observatory extends beyond 200 TeV without any evidence for a steepening or cutoff. There are some indications that the $\gamma$-rays detected with HAWC were produced by cosmic ray protons or nuclei colliding with the ambient gas. Assuming primary protons, we inquire which shape of the primary proton spectrum is compatible with the HAWC measurements. We find that the primary proton spectrum with the power-law shape of $\gamma_{p}$=2.2 and the cutoff energy $E_{c-p} > 500$ TeV describes the data well. However, much harder spectra with $\gamma_{p}$ down to 1.3 and $E_{c-p}$ as low as 200 TeV also do not contradict the HAWC measurements. The former option might be realized if the accelerator is inside or very near to the $\gamma$-ray production zone. The latter option is viable for the case of a cosmic ray source which effectively confines low-energy ($E_{p} < 10$ TeV) accelerated protons. Using publicly-available data of the Fermi-LAT space $\gamma$-ray telescope, we derive upper limits on the intensity of the HAWC J1825-134 source in the 1 GeV -- 1 TeV energy range. We show that the account of these upper limits drastically changes the interpretation: only hard ($\gamma_{p} < 1.7$) spectra describe the combined HAWC and Fermi-LAT datasets well.

astro-ph.HE↗