1. Modeling the refractive index profile n(z) of polar ice for ultra-high energy neutrino experiments
- Author
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Ali, S., Allison, P., Archambault, S., Beatty, J. J., Besson, D. Z., Bishop, A., Chen, P., Chen, Y. C., Clark, B. A., Clay, W., Connolly, A., Couberly, K., Cremonesi, L., Cummings, A., Dasgupta, P., Debolt, R., de Kockere, S., de Vries, K. D., Deaconu, C., DuVernois, M. A., Flaherty, J., Friedman, E., Gaior, R., Giri, P., Hanson, J., Harty, N., Hoffman, K. D., Huang, J. J., Huang, M. -H., Hughes, K., Ishihara, A., Karle, A., Kelley, J. L., Kim, K. -C., Kim, M. -C., Kravchenko, I., Krebs, R., Kuo, C. Y., Kurusu, K., Latif, U. A., Liu, C. H, Liu, T. C., Luszczak, W., Mase, K., Muzio, M. S., Nam, J., Nichol, R. J., Novikov, A., Nozdrina, A., Oberla, E., Pan, Y., Pfendner, C., Punsuebsay, N., Roth, J., Salcedo-Gomez, A., Seckel, D., Seikh, M. F. H., Shaio, Y. -S., Smith, D., Toscano, S., Torres, J., Touart, J., van Eijndhoven, N., Vieregg, A., Wang, M. -Z., Wang, S. -H., Wissel, S. A., Xie, C., Yoshida, S., and Young, R.
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We have developed an in-situ index of refraction profile n(z) for cold polar ice, using the transit times of radio signals broadcast from an englacial transmitter to 2-5 km distant radio-frequency receivers, deployed at depths up to 200 m. For propagation through a non-uniform medium, Maxwell's equations generally admit two ray propagation solutions from a given transmitter, corresponding to a direct path (D) and a refracted or reflected path (R); the measured D vs. R timing differences (dt(D,R)) are determined by the refractive index profile. We constrain n(z) near South Pole, where the Askaryan Radio Array (ARA) neutrino observatory is located, by simulating D and R ray paths via ray tracing and comparing simulations to measured dt(D,R) values. Using previous ice density data as a proxy for n(z), we demonstrate that our data strongly favors a glaciologically-motivated three-phase densification model rather than a single exponential scale height model. Effective volume simulations for a detector of ARA station antenna depths yield a 14\% increase in neutrino sensitivity over a range of $10^{17} - 10^{21}$ eV using the three-phase model compared to a single exponential.
- Published
- 2024