arXiv subjects

Dawson Huth

Publications and source records attributed to Dawson Huth.

5 recordsLinked to original sources

arXiv2025

The Correspondence Between Leaky-Box and Diffusion Models of Cosmic-Ray Propagation

The leaky-box model and the attendant concept of path-length distribution of cosmic rays were invented in the mid-1960's. Even though versatile computational packages such as GALPROP and DRAGON with the diffusion approach are now available for analyzing cosmic ray data, the concepts of the leaky-box and path-length distribution continue to be adopted extensively. We show here mathematically that there is a close correspondence between the two approaches: The path-length or resident-time of the leaky-box models are similar to 'impulse response functions' of complex dynamical systems and are intuitively transparent. The results provided by the leaky-box model are valid when used judiciously.

astro-ph.HE↗

arXiv2023

Mapping the AMS-02 and CALET Data onto the Source Spectra and Residence Times of Galactic Cosmic Rays

The recent measurements of the spectral intensities of cosmic-ray nuclei have suggested that the ratio of Boron to Carbon nuclei, $R(E)$, comprises two components, $R_1(E)$ which carries all of the energy dependence and the other $R_A$, a constant independent of energy per nucleon. This finding supports the earlier theoretical expectations and results of gamma-ray astronomy that one of these components is attributable to spallation in a cocoon like region surrounding the sources and the other in the general interstellar medium before cosmic rays leak away from the Galaxy. A new model-independent way of analyzing cosmic-ray spectra is presented here to shed light on the recent findings: Imposing the single constraint that the source function of B nuclei is minimal we use a cascade of rate equations to map point-by-point the observed cosmic ray spectra of p, B, C, O and Fe on to their source spectra and the two life-times of cosmic rays $\tau_G$ in the Galaxy and $\tau_S$ in the cocoons surrounding the sources. The model independent results show that the appropriate choice is $\tau_S(E)$ is responsible for $R_1(E)$ and the source spectra are power laws with indices of $\sim-2.7$.

astro-ph.HE↗

arXiv2023

A Minimal Model for Understanding Secondary Cosmic Rays

We take a phenomenological approach in a minimal model to understand the spectral intensity of secondary cosmic-ray particles like positrons, antiprotons, Lithium, Beryllium and Boron. Our analysis shows that cosmic rays at $\sim$ GeV energies pass through a significant amount of matter in regions surrounding the sources. This grammage decreases with increasing cosmic-ray energy and becomes negligible beyond $\sim 100$ GeV. During the subsequent propagation in the interstellar medium cosmic rays of all energies up to $\sim 10^5$ GeV/$n$ pass through about 1-2 g cm$^{-2}$ of matter before leaking into the intergalactic medium. It is in the interstellar medium that the bulk of the positrons and antiprotons are generated. Also cosmic-ray nuclei like C, N, and O at all energies generate additional amounts of Li, Be and B nuclei with a spectrum similar to those of C, O etc. The implications of these findings of the minimal model to the observations of gamma rays and also the importance of spatial and temporal discreteness of cosmic-ray sources for modeling cosmic-ray propagation are briefly pointed out.

astro-ph.HE↗

arXiv2021

A New Torsion Balance for the Search of Long-range Interactions Coupling to Baryon and Lepton Numbers

We have developed a torsion balance with a sensitivity about ten times better than those of previously operating balances for the study of long range forces coupling to baryon and lepton number. We present here the details of the design and expected characteristics of this balance. Operation of this balance for a year will also result in improved bounds on long range interactions of dark matter violating Einstein's equivalence principle.

gr-qc↗

arXiv2019

Test of Einstein's Equivalence Principle by Galactic Dark Matter

We report here the results of operation of a torsion balance with a period of $\sim 1.27 \times 10^4$ s. The analysis of data collected over a period of $\sim$115 days shows that the difference in the accelerations towards the Galactic Center of test bodies made of aluminum and quartz was $(0.61 \pm 1.27) \times 10^{-15} \, \mathrm{ m \, s}^{-2}$. This sets a bound on the violation of the equivalence principle by forces exerted by Galactic dark matter which is expressed by the Eötvös parameter $η_{DM} = (1.32 \pm 2.68) \times 10^{-5}$, a significant improvement upon earlier bounds.

gr-qc↗