We estimate the conventional astrophysical emission from dwarf spheroidal satellite galaxies (dSphs) of the Milky Way, focusing on millisecond pulsars (MSPs), and evaluate the potential for confusion ...with dark matter (DM) annihilation signatures at GeV energies. In low-density stellar environments, such as dSphs, the abundance of MSPs is expected to be proportional to stellar mass. Accordingly, we construct the \(\gamma\)-ray luminosity function of MSPs in the Milky Way disk, where \(>90\) individual MSPs have been detected with the \(\textit{Fermi}\) Large Area Telescope (LAT), and scale this luminosity function to the stellar masses of 30 dSphs to estimate the cumulative emission from their MSP populations. We predict that MSPs within the highest stellar mass dSphs, Fornax and Sculptor, produce a \(\gamma\)-ray flux \(>500\)~MeV of \(\sim10^{-11}\)~ph~cm\(^{-2}\)~s\(^{-1}\), which is a factor \(\sim10\) below the current LAT sensitivity at high Galactic latitudes. The MSP emission in ultra-faint dSphs, including targets with the largest J-factors, is typically several orders of magnitude lower, suggesting that these targets will remain clean targets for indirect DM searches in the foreseeable future. For a DM particle of mass 25~GeV annihilating to \(b\) quarks at the thermal relic cross section (consistent with DM interpretations of the Galactic Center excess), we find that the expected \(\gamma\)-ray emission due to DM exceeds that of MSPs in all of the target dSphs. Using the same Milky Way MSP population model, we also estimate the Galactic foreground MSP coincidence probability along the same sightlines to the dSphs.
J.Phys.Conf.Ser.60:101-106,2007 Neutrino astronomy was initiated primarily to search for TeV to PeV neutrinos
from Active Galactic Nuclei, and the optical Cherenkov technique is well suited
for this ...energy range. Interest has grown recently in detecting EeV neutrinos,
particularly the ``cosmogenic'' neutrinos produced during propagation of
ultra-high-energy cosmic rays (UHECR) through the microwave background
radiation. These neutrinos could be a powerful tool both to resolve the mystery
of the UHECR sources and to test fundamental physics at the $\sim$100 TeV
scale. The optical technique is not cost effective at these energies and newer
techniques such as radio and acoustic detection are necessary. Accelerator
experiments have confirmed the production of both types of signals from
high-energy showers in various media, and quantitative measurements have
confirmed theoretical descriptions of the signal strength, frequency content
and pulse shape. While radio experiments have set the strongest limits so far,
the acoustic method could contribute with an entirely independent signal
production and detection mechanism and may be more effective at the highest
energies. Efforts are underway to develop the acoustic method in various media
around the world, with arrays operating in ocean water at the Bahamas, the UK,
and the Mediterranean Sea; detectors prepared for deployment in the South Pole
ice in the next year; and ideas for future acoustic detectors in salt domes and
on Antarctica's Ross Ice Shelf. Regardless of which method is individually most
sensitive, the best configuration may be to co-deploy arrays to combine the
techniques and seek coincident detection of individual neutrino events.
Astrophysical neutrinos are excellent probes of astroparticle physics and high-energy physics. With energies far beyond solar, supernovae, atmospheric, and accelerator neutrinos, high-energy and ...ultra-high-energy neutrinos probe fundamental physics from the TeV scale to the EeV scale and beyond. They are sensitive to physics both within and beyond the Standard Model through their production mechanisms and in their propagation over cosmological distances. They carry unique information about their extreme non-thermal sources by giving insight into regions that are opaque to electromagnetic radiation. This white paper describes the opportunities astrophysical neutrino observations offer for astrophysics and high-energy physics, today and in coming years.
The excess of positrons in cosmic rays above \(\sim\)10 GeV has been a puzzle since it was discovered. Possible interpretations of the excess have been suggested, including acceleration in a local ...supernova remnant or annihilation of dark matter particles. To discriminate between these scenarios, the positron fraction must be measured at higher energies. One technique to perform this measurement is using the Earth-Moon spectrometer: observing the deflection of positron and electron moon shadows by the Earth's magnetic field. The measurement has been attempted by previous imaging atmospheric Cherenkov telescopes without success. The Cherenkov Telescope Array (CTA) will have unprecedented sensitivity and background rejection that could make this measurement successful for the first time. In addition, the possibility of using silicon photomultipliers in some of the CTA telescopes could greatly increase the feasibility of making observations near the moon. Estimates of the capabilities of CTA to measure the positron fraction using simulated observations of the moon shadow will be presented.
The cumulative emission resulting from hadronic cosmic-ray interactions in star-forming galaxies (SFGs) has been proposed as the dominant contribution to the astrophysical neutrino flux at TeV to PeV ...energies reported by IceCube. The same particle interactions also inevitably create \(\gamma\)-ray emission that could be detectable as a component of the extragalactic \(\gamma\)-ray background (EGB), which is now measured with the Fermi-LAT in the energy range from 0.1 to 820 GeV. New studies of the blazar flux distribution at \(\gamma\)-ray energies above 50 GeV place an upper bound on the residual non-blazar component of the EGB. We show that these results are in strong tension with models that consider SFGs as the dominant source of the diffuse neutrino backgrounds. A characteristic spectral index for parent cosmic rays in starburst galaxies of \(\Gamma_{\rm SB} \simeq 2.3\) for \(dN/dE \propto E^{-\Gamma_{\rm SB}}\) is consistent with the observed scaling relation between \(\gamma\)-ray and IR luminosity for SFGs, the bounds from the non-blazar EGB, and the observed \(\gamma\)-ray spectra of individual starbursts, but underpredicts the IceCube data by approximately an order of magnitude.
The prototype Schwarzschild-Couder Telescope (pSCT) is a candidate for a medium-sized telescope in the Cherenkov Telescope Array. The pSCT is based on a novel dual mirror optics design which reduces ...the plate scale and allows for the use of silicon photomultipliers as photodetectors. The prototype pSCT camera currently has only the central sector instrumented with 25 camera modules (1600 pixels), providing a 2.68\(^{\circ}\) field of view (FoV). The camera electronics are based on custom TARGET (TeV array readout with GSa/s sampling and event trigger) application specific integrated circuits. Field programmable gate arrays sample incoming signals at a gigasample per second. A single backplane provides camera-wide triggers. An upgrade of the pSCT camera is in progress, which will fully populate the focal plane. This will increase the number of pixels to 11,328, the number of backplanes to 9, and the FoV to 8.04\(^{\circ}\). Here we give a detailed description of the pSCT camera, including the basic concept, mechanical design, detectors, electronics, current status and first light.
We present a deep learning, computer vision algorithm constructed for the purposes of identifying and classifying charged particles in camera image sensors. We apply our algorithm to data collected ...by the Distributed Electronic Cosmic-ray Observatory (DECO), a global network of smartphones that monitors camera image sensors for the signatures of cosmic rays and other energetic particles, such as those produced by radioactive decays. The algorithm, whose core component is a convolutional neural network, achieves classification performance comparable to human quality across four distinct DECO event topologies. We apply our model to the entire DECO data set and determine a selection that achieves \(\ge90\%\) purity for all event types. In particular, we estimate a purity of \(95\%\) when applied to cosmic-ray muons. The automated classification is run on the public DECO data set in real time in order to provide classified particle interaction images to users of the app and other interested members of the public.
The total area of silicon in cell phone camera sensors worldwide surpasses that in any experiment to date. Based on semiconductor technology similar to that found in modern astronomical telescopes ...and particle detectors, these sensors can detect ionizing radiation in addition to photons. The Distributed Electronic Cosmic-ray Observatory (DECO) uses the global network of active cell phones in order to detect cosmic rays and other energetic particles such as those produced by radioactive decays. DECO consists of an Android application, database, and public data browser available to citizen scientists around the world (https://wipac.wisc.edu/deco). Candidate cosmic-ray events have been detected on all seven continents and can be categorized by the morphology of their corresponding images. We present the DECO project, a novel particle detector with wide applications in public outreach and education.
Neutrino astronomy was initiated primarily to search for TeV to PeV neutrinos from Active Galactic Nuclei, and the optical Cherenkov technique is well suited for this energy range. Interest has grown ...recently in detecting EeV neutrinos, particularly the ``cosmogenic'' neutrinos produced during propagation of ultra-high-energy cosmic rays (UHECR) through the microwave background radiation. These neutrinos could be a powerful tool both to resolve the mystery of the UHECR sources and to test fundamental physics at the \(\sim\)100 TeV scale. The optical technique is not cost effective at these energies and newer techniques such as radio and acoustic detection are necessary. Accelerator experiments have confirmed the production of both types of signals from high-energy showers in various media, and quantitative measurements have confirmed theoretical descriptions of the signal strength, frequency content and pulse shape. While radio experiments have set the strongest limits so far, the acoustic method could contribute with an entirely independent signal production and detection mechanism and may be more effective at the highest energies. Efforts are underway to develop the acoustic method in various media around the world, with arrays operating in ocean water at the Bahamas, the UK, and the Mediterranean Sea; detectors prepared for deployment in the South Pole ice in the next year; and ideas for future acoustic detectors in salt domes and on Antarctica's Ross Ice Shelf. Regardless of which method is individually most sensitive, the best configuration may be to co-deploy arrays to combine the techniques and seek coincident detection of individual neutrino events.
South Pole ice is predicted to be the best medium for acoustic neutrino detection. Moreover, ice is the only medium in which all three dense-medium detection methods (optical, radio, and acoustic) ...can be used to monitor the same interaction volume. Events detected in coincidence between two methods allow significant background rejection confidence, which is necessary to study rare GZK neutrinos. In 2007 and 2008 the South Pole Acoustic Test Setup (SPATS) was installed as a research and development project associated with the IceCube experiment. The purpose of SPATS is to measure the acoustic ice properties at the South Pole in order to determine the feasibility of a future large hybrid array. The deployment and performance of SPATS are described, as are first results and work in progress on the sound speed, background noise, and attenuation.
