arXiv subjects

Shahid Hussain

Publications and source records attributed to Shahid Hussain.

22 records · Page 2Linked to original sources

arXiv2004

Comparative study of radio pulses from simulated hadron-, electron-, and neutrino-initiated showers in ice in the GeV-PeV range

High energy particle showers produce coherent Cherenkov radio emission in dense, radio-transparent media such as cold ice. Using PYTHIA and GEANT simulation tools, we make a comparative study among electromagnetic (EM) and hadronic showers initiated by single particles and neutrino showers initiated by multiple particles produced at the neutrino-nucleon event vertex. We include all the physics processes and do a complete 3-D simulation up to 100 TeV for all showers and to 1 PeV for electron and neutrino induced showers. We calculate the radio pulses for energies between 100 GeV and 1 PeV and find hadron showers, and consequently neutrino showers, are not as efficient below 1 PeV at producing radio pulses as the electromagnetic showers. The agreement improves as energy increases, however, and by a PeV and above the difference disappears. By looking at the 3-D structure of the showers in time, we show that the hadronic showers are not as compact as the EM showers and hence the radiation is not as coherent as EM shower emission at the same frequency. We show that the ratio of emitted pulse strength to shower tracklength is a function only of a single, coherence parameter, independent of species and energy of initiating particle.

hep-ph↗

arXiv2004

Simulation of the radio signal from ultrahigh energy neutrino-initiated showers

PeV neutrinos produce particle showers when they interact with the atomic nuclei in ice. We briefly describe characteristics of these showers and the radio Cherenkov signal produced by the showers. We study pulses from electromagnetic (em), hadronic, and combined em-hadronic showers and propose extrapolations to EeV energies.

hep-ph↗

arXiv2004

Constraining low scale gravity with ultrahigh energy neutrinos

We show that LSG model predictions of event ratios are clearly distinguished from those of the SM. This is true in all models of ultrahigh energy (UHE) neutrino sources, in both $ν_e:ν_μ:ν_τ = 1:1:1$ and $ν_e:ν_μ:ν_τ = 1:2:0$ scenarios for the flux incident on earth. In particular the ratios of upward $μ$ events to upward shower events and the ratios of up events to down events are different by a factor of 2 to an order of magnitude in the comparisons between SM and LSG. $ν_τ$ rates are low but show high sensitivity to SM vs LSG interaction physics.

hep-ph↗

arXiv2003

Energy and Angular Distribution of Upward UHE Neutrinos and Signals of Low Scale Gravity: Role of Tau Decay

We present extensive results and analysis of energy and angular distributions of diffuse UHE $ν_{e}$, $ν_μ$, and $ν_τ$ fluxes propagated through earth, with and without augmentation of the standard model interactions by low scale gravity. With propagated fluxes in hand we estimate event rates in a $1km^{3}$ detector in ice with characteristics of ICECUBE. We determine that, at 0.5PeV energy threshold, there is a significant difference in the ratios of down shower events to upward muon events between the standard model and the low scale gravity cases with 1TeV and 2TeV mass scales. The same is true for energy threshold at 5PeV. Though the difference is large in all flux models, statistical significance of this difference depends on the flux models, especially at 5PeV and above. Both flavor assumptions, $ν_{e}$, $ν_μ$, $ν_τ::1$, 2, 0 and $% ν_{e}$, $ν_μ$, $ν_τ::1$, 1, 1, and all flux models show large differences. Though rates of tagged events are low, we find that $ν_τ$ regeneration by $τ$ decay may play an important role in disclosing deviations from standard model predictions at energies in the neighborhood of 1 PeV for 1TeV-scale gravity, for example. We emphasize those analyses whose sensitivity to new physics is independent of the flux model assumed.

hep-ph↗