Radio-wave detection of ultra-high-energy neutrinos and cosmic rays

Radio waves, perhaps because our terrestrial atmosphere and the cosmos beyond are uniquely transparent to them, or perhaps because they are macroscopic, so the basic instruments of detection (antennas) are easily constructible, arguably occupy a privileged position within the electromagnetic spectrum, and, correspondingly, receive disproportionate attention experimentally. Detection of radio-frequency radiation, at macroscopic wavelengths, has blossomed within the last decade as a competitive method for the measurement of cosmic particles, particularly charged cosmic rays and neutrinos. Cosmic-ray detection via radio emission from extensive air showers has been demonstrated to be a reliable technique that has reached a reconstruction quality of the cosmic-ray parameters competitive with more traditional approaches. Radio detection of neutrinos in dense media seems to be the most promising technique to achieve the gigantic detection volumes required to measure neutrinos at energies beyond the PeV-scale flux established by IceCube. In this article, we review radio detection both of cosmic rays in the atmosphere, as well as neutrinos in dense media

Radio-wave detection of ultra-high-energy neutrinos and cosmic rays

Radio waves, perhaps because our terrestrial atmosphere and the cosmos beyond are uniquely transparent to them, or perhaps because they are macroscopic, so the basic instruments of detection (antennas) are easily constructible, arguably occupy a privileged position within the electromagnetic spectrum, and, correspondingly, receive disproportionate attention experimentally. Detection of radio-frequency radiation, at macroscopic wavelengths, has blossomed within the last decade as a competitive method for the measurement of cosmic particles, particularly charged cosmic rays and neutrinos. Cosmic-ray detection via radio emission from extensive air showers has been demonstrated to be a reliable technique that has reached a reconstruction quality of the cosmic-ray parameters competitive with more traditional approaches. Radio detection of neutrinos in dense media seems to be the most promising technique to achieve the gigantic detection volumes required to measure neutrinos at energies beyond the PeV-scale flux established by IceCube. In this article, we review radio detection both of cosmic rays in the atmosphere, as well as neutrinos in dense media

Constraints on Minute-Scale Transient Astrophysical Neutrino Sources

High-energy neutrino emission has been predicted for several short-lived astrophysical transients including gamma-ray bursts (GRBs), core-collapse supernovae with choked jets, and neutron star mergers. IceCube’s optical and x-ray follow-up program searches for such transient sources by looking for two or more muon neutrino candidates in directional coincidence and arriving within 100 s. The measured rate of neutrino alerts is consistent with the expected rate of chance coincidences of atmospheric background events and no likely electromagnetic counterparts have been identified in Swift follow-up observations. Here, we calculate generic bounds on the neutrino flux of short-lived transient sources. Assuming an E^−2.5 neutrino spectrum, we find that the neutrino flux of rare sources, like long gamma-ray bursts, is constrained to <5% of the detected astrophysical flux and the energy released in neutrinos (100 GeV to 10 PeV) by a median bright GRB-like source is <10^52.5 erg. For a harder E^−2.13 neutrino spectrum up to 30% of the flux could be produced by GRBs and the allowed median source energy is <10^52  erg. A hypothetical population of transient sources has to be more common than 10^−5   Mpc^−3 yr^−1 (5×10^−8   Mpc^−3 yr^−1 for the E^−2.13 spectrum) to account for the complete astrophysical neutrino flux

Radio-frequency probes of Antarctic ice at South Pole

Using hardware developed for the ARA (Askaryan Radio Array) particle astrophysics experiment, we herein report on the amplitude and temporal characteristics of polarized surface radar echo data collected in South Polar ice using radio sounding equipment with 0.5-ns echo-time sampling. We observe strong echoes at 6, 9.6, 13.9, 17, and 19 μs following vertical pulse emission from the surface, corresponding to reflectors in the upper half of the ice sheet. The synchronicity of those echoes for all broadcast azimuthal polarizations affirms the lack of observable birefringence over the upper half of the ice sheet. Of the five strongest echoes, three exhibit an evident amplitude correlation with the local surface ice flow direction, qualitatively consistent with measurements in East Antarctica. Combined with other radio echo sounding data, we conclude that observed birefringent asymmetries at South Pole are generated entirely in the lower half of the ice sheet. By contrast, birefringent asymmetries are observed at shallow depths in East Antarctica.The authors particularly thank Chris Allen and John Paden (University of Kansas), John Ralston (University of Kansas), Rebecca Boon (Pennsylvania State University), Joe MacGregor (University of Texas), and Kenny Matsuoka (Norwegian Polar Institute) for very helpful discussions, as well as our colleagues on the RICE and ANITA experiments. We also thank Andy Bricker of Lawrence High School (Lawrence, KS) for his assistance working with Lawrence High School students who performed essential antenna calibrations. This work was supported by the National Science Foundation’s Office of Polar Programs (grant OPP-0826747) and QuarkNet programs. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation

Search for transient optical counterparts to high-energy IceCube neutrinos with Pan-STARRS1

In order to identify the sources of the observed diffuse high-energy neutrino flux, it is crucial to discover their electromagnetic counterparts. To increase the sensitivity of detecting counterparts of transient or variable sources by telescopes with a limited field of view, IceCube began releasing alerts for single high-energy (Eν >  60 TeV) neutrino detections with sky localisation regions of order 1° radius in 2016. We used Pan-STARRS1 to follow-up five of these alerts during 2016–2017 to search for any optical transients that may be related to the neutrinos. Typically 10–20 faint (miP1 ≲ 22.5 mag) extragalactic transients are found within the Pan-STARRS1 footprints and are generally consistent with being unrelated field supernovae (SNe) and AGN. We looked for unusual properties of the detected transients, such as temporal coincidence of explosion epoch with the IceCube timestamp, or other peculiar light curve and physical properties. We found only one transient that had properties worthy of a specific follow-up. In the Pan-STARRS1 imaging for IceCube-160427A (probability to be of astrophysical origin of ∼50%), we found a SN PS16cgx, located at 10.0′ from the nominal IceCube direction. Spectroscopic observations of PS16cgx showed that it was an H-poor SN at redshift z = 0.2895 ± 0.0001. The spectra and light curve resemble some high-energy Type Ic SNe, raising the possibility of a jet driven SN with an explosion epoch temporally coincident with the neutrino detection. However, distinguishing Type Ia and Type Ic SNe at this redshift is notoriously difficult. Based on all available data we conclude that the transient is more likely to be a Type Ia with relatively weak Si II absorption and a fairly normal rest-frame r-band light curve. If, as predicted, there is no high-energy neutrino emission from Type Ia SNe, then PS16cgx must be a random coincidence, and unrelated to the IceCube-160427A. We find no other plausible optical transient for any of the five IceCube events observed down to a 5σ limiting magnitude of miP1 ≈ 22 mag, between 1 day and 25 days after detection

Precision measurements of the timelike electromagnetic form factors of pion, kaon, and proton

Using 20.7 pb(-1) of e(+)e(-) annihilation data taken at root s = 3.671 GeV with the CLEO-c detector, precision measurements of the electromagnetic form factors of the charged pion, charged kaon, and proton have been made for timelike momentum transfer of vertical bar Q(2 vertical bar)=13.48 GeV2 by the reaction e(+)e(-)-> h(+)h(-). The measurements are the first ever with identified pions and kaons of vertical bar Q (2)vertical bar > 4 GeV2, with the results F-pi(13.48 GeV2) = 0.075 +/- 0.008(stat)+/- 0.005(syst) and F-K(13.48 GeV2) = 0.063 +/- 0.004(stat)+/- 0.001(syst). The result for the proton, assuming G(E)(p)=G(M)(p), is G(M)(p)(13.48 GeV2) = 0.014 +/- 0.002(stat)+/- 0.001(syst), which is in agreement with earlier results

Measurement of the νμ energy spectrum with IceCube-79

This work is licensed under a Creative Commons Attribution 4.0 International License.IceCube is a neutrino observatory deployed in the glacial ice at the geographic South Pole. The νμ energy unfolding described in this paper is based on data taken with IceCube in its 79-string configuration. A sample of muon neutrino charged-current interactions with a purity of 99.5% was selected by means of a multivariate classification process based on machine learning. The subsequent unfolding was performed using the software truee. The resulting spectrum covers an Eν-range of more than four orders of magnitude from 125 GeV to 3.2 PeV. Compared to the Honda atmospheric neutrino flux model, the energy spectrum shows an excess of more than 1.9σ in four adjacent bins for neutrino energies Eν≥177.8TeV. The obtained spectrum is fully compatible with previous measurements of the atmospheric neutrino flux and recent IceCube measurements of a flux of high-energy astrophysical neutrinos

Observation of the h(c)((1)P1) state of charmonium

The h(c)(P-1(1)) state of charmonium has been observed in the reaction psi(2S)->pi(0)h(c)->(gamma gamma)(gamma eta(c)) using 3.08x10(6) psi(2S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the eta(c) are not identified, and for exclusive reactions, in which eta(c) decays are reconstructed in seven hadronic decay channels. We find M(h(c))=3524.4 +/- 0.6 +/- 0.4 MeV which corresponds to a hyperfine splitting Delta M-hf(1P)equivalent to -M(P-1(1))=+1.0 +/- 0.6 +/- 0.4 MeV, and B(psi(2S)->pi(0)h(c))xB(h(c)->gamma eta(c))=(4.0 +/- 0.8 +/- 0.7)x10(-4)

Search for rare and forbidden decays D+-> h(+/-)e(-/+)e(+)

Using 0.8x10(6) D+D- pairs collected with the CLEO-c detector at the psi(3770) resonance, we have searched for flavor-changing neutral current and lepton-number-violating decays of D+ mesons to final states with dielectrons. We find no indication of either, obtaining 90% confidence level upper limits of B(D+->pi(+)e(+)e(-))pi(-)e(+)e(+)) K(+)e(+)e(-)) K(-)e(+)e(+))< 4.5x10(-6)

Experimental limits on weak annihilation contributions to b -> ul nu decays

We present the first experimental limits on high-q(2) contributions to charmless semileptonic B decays of the form expected from the weak annihilation (WA) decay mechanism. Such contributions could bias determinations of vertical bar V(ub)vertical bar from inclusive measurements of B -> X(u)l nu. Using a wide range of models based on available theoretical input we set a limit of Gamma(WA)/Gamma(b -> u)< 7.4% (90% confidence level) on the WA fraction, and assess the impact on previous inclusive determinations of vertical bar V(ub)vertical bar