The study of shell-type supernova remnants is a key science focus for the VERITAS TeV telescope array. Supernova remnants (SNRs) are widely considered to be the strongest candidate for the source of ...cosmic rays below the knee around 10^15 eV. This presentation will highlight new VERITAS results including new measurements of the spectra of Cas A and IC 443 and observations of the "Forbidden Velocity Wing" FVW 190.2+1.1. These results and their implications for the nature of the cosmic rays - hadronic or electronic - accelerated in the remnants will be discussed.
The high-energy universe has revealed that energetic particles are ubiquitous in the cosmos and play a vital role in the cultivation of cosmic environments on all scales. Though they play a key role ...in cultivating the cosmological environment and/or enabling our studies of it, there is still much we do not know about AGNs and GRBs, particularly the avenue in which and through which they supply radiation and energetic particles, namely their jets. This White Paper is the second of a two-part series highlighting the most well-known high-energy cosmic accelerators and contributions that MeV gamma-ray astronomy will bring to understanding their energetic particle phenomena. The focus of this white paper is active galactic nuclei and gamma-ray bursts.
The study of supernova remnants and pulsar wind nebulae was one of the Key Science Projects for the first two years of VERITAS observations. VERITAS is an array of four imaging Cherenkov telescopes ...located at the Whipple Observatory in southern Arizona. Supernova remnants are widely considered to be the strongest candidate for the source of cosmic rays below the knee at around 10^15 eV. Pulsar wind nebulae are synchrotron nebulae powered by the spin-down of energetic young pulsars, and comprise one of the most populous very-high-energy gamma-ray source classes. This poster will summarize the results of this observation program.
The CTA (Cherenkov Telescope Array) is the next generation ground-based experiment for very high-energy (VHE) gamma-ray observations. It will integrate several tens of imaging atmospheric Cherenkov ...telescopes (IACTs) with different apertures into a single astronomical instrument. The US part of the CTA collaboration has proposed and is developing a novel IACT design with a Schwarzschild-Couder (SC) aplanatic two mirror optical system. In comparison with the traditional single mirror Davies-Cotton IACT the SC telescope, by design, can accommodate a wide field-of-view, with significantly improved imaging resolution. In addition, the reduced plate scale of an SC telescope makes it compatible with highly integrated cameras assembled from silicon photo multipliers. In this submission we report on the status of the development of the SC optical system, which is part of the effort to construct a full-scale prototype telescope of this type at the Fred Lawrence Whipple Observatory in southern Arizona.
Experiment E158 at the Stanford Linear Accelerator Center (SLAC) will make the first measurement of parity violation in Moller scattering. The left-right cross-section asymmetry in the elastic ...scattering of a 45-GeV polarized electron beam with unpolarized electrons in a liquid hydrogen target will be measured to an accuracy of better than 10/sup -8/, with the expected Standard Model asymmetry being approximately 10/sup -7/. Because helicity-correlated (left-right) charge and position asymmetries in the electron beam can give rise to systematic errors in the measurement, great care must be given to beam monitoring and control. We have developed beam current monitors that measure the charge per pulse at the 3 /spl times/ 10/sup -5/ level and RF cavity beam position monitors that measure the position per pulse to 1 /spl mu/m, which should allow precisions of 1 ppb and 1 nm for the final integrated charge and position asymmetries, respectively. In addition, since most helicity-correlated systematics in the electron beam can be traced back to the laser that drives the photoemission from the GaAs source cathode, we first use careful control of laser beam polarization, point-to-point imaging, and other techniques to minimize systematics. We also provide the capability of modulating in a helicity-correlated way the laser beam's intensity and position as it strikes the photocathode, allowing the implementation of active feedbacks to ensure that the average charge and position asymmetries integrate close to zero over the course of the experiment. We present this system of precision beam monitoring and control and report on its performance during a recent commissioning run, T-437 at SLAC, which demonstrated charge and position asymmetry precisions of 12 ppb and 2 nm, respectively.
The first gravitational-wave (GW) observations will greatly benefit from the detection of coincident electromagnetic counterparts. Electromagnetic follow-ups will nevertheless be challenging for GWs ...with poorly reconstructed directions. GW source localization can be inefficient (i) if only two GW observatories are in operation; (ii) if the detectors' sensitivities are highly non-uniform; (iii) for events near the detectors' horizon distance. For these events, follow-up observations will need to cover 100-1000 square degrees of the sky over a limited period of time, reducing the list of suitable telescopes. We demonstrate that the Cherenkov Telescope Array will be capable of following up GW event candidates over the required large sky area with sufficient sensitivity to detect short gamma-ray bursts, which are thought to originate from compact binary mergers, out to the horizon distance of advanced LIGO/Virgo. CTA can therefore be invaluable starting with the first multimessenger detections, even with poorly reconstructed GW source directions. This scenario also provides a further scientific incentive for GW observatories to further decrease the delay of their event reconstruction.
We discuss the potential for the detection of dark matter and the characterization of its particle nature via the observation of dark matter subhalos. Specifically, we discuss the search for dark ...matter Galactic subhalos in the gamma-ray band with the Large Area Telescope on-board the Fermi gamma-ray Space Telescope, and the future generation of imaging atmospheric Cherenkov telescopes, best represented by the planned Cherenkov Telescope Array.
The Cherenkov Telescope Array (CTA) observatory will be one of the largest ground-based very high-energy gamma-ray observatories. The On-Site Analysis will be the first CTA scientific analysis of ...data acquired from the array of telescopes, in both northern and southern sites. The On-Site Analysis will have two pipelines: the Level-A pipeline (also known as Real-Time Analysis, RTA) and the level-B one. The RTA performs data quality monitoring and must be able to issue automated alerts on variable and transient astrophysical sources within 30 seconds from the last acquired Cherenkov event that contributes to the alert, with a sensitivity not worse than the one achieved by the final pipeline by more than a factor of 3. The Level-B Analysis has a better sensitivity (not be worse than the final one by a factor of 2) and the results should be available within 10 hours from the acquisition of the data: for this reason this analysis could be performed at the end of an observation or next morning. The latency (in particular for the RTA) and the sensitivity requirements are challenging because of the large data rate, a few GByte/s. The remote connection to the CTA candidate site with a rather limited network bandwidth makes the issue of the exported data size extremely critical and prevents any kind of processing in real-time of the data outside the site of the telescopes. For these reasons the analysis will be performed on-site with infrastructures co-located with the telescopes, with limited electrical power availability and with a reduced possibility of human intervention. This means, for example, that the on-site hardware infrastructure should have low-power consumption. A substantial effort towards the optimization of high-throughput computing service is envisioned to provide hardware and software solutions with high-throughput, low-power consumption at a low-cost.
Parity-violating electron scattering has developed over the last 25 years into a tool to study both the structure of electroweak interactions and the structure of nucleons. This thesis reports work ...on two parity-violation experiments, the Hall A Proton Parity Experiment (HAPPEX) and SLAC E-158. HAPPEX (Jefferson Laboratory, 1998–1999) measured the parity-violating asymmetry in elastic e-p scattering at Q2 = 0.477 GeV2. This asymmetry is sensitive to the proton's strange elastic form factors. An asymmetry of ALR = −15.05 ± 0.98(stat) ± 0.56(syst) ppm was measured. This asymmetry measurement allowed HAPPEX to set new constraints on the strange elastic form factors of the proton: special characters omitted where GEs and GMs are the strange electric and magnetic form factors of the proton, respectively. The first error is the quadrature sum of the experimental errors and the second error is due to uncertainty in electromagnetic form factors. This result is consistent with the absence of a contribution from strange quarks. This thesis reports an analysis of the 1999 data set. SLAC E-158 is a measurement of the parity-violating asymmetry in Møller scattering. A 45-GeV longitudinally polarized electron beam is scattered off unpolarized electrons in a liquid hydrogen target at Q2 = 0.025 GeV2. The asymmetry in this process is proportional to (1/4 - sin2 W), where W is the weak mixing angle. This measurement tests electroweak theory at the one-loop level and probes for new physics, including additional gauge bosons and electron compositeness. Within the Standard Model, the raw asymmetry is expected to be approximately 0.1 ppm. E-158 had engineering runs in 2000 and 2001 and its first physics runs in 2002. Data from the physics runs are currently being analyzed. One class of systematic error to which both of these experiments are sensitive is an asymmetry in the rate of scattered electrons due to helicity-correlated asymmetries in properties of the electron beam. This thesis describes work done in preparation for each experiment to understand and suppress those asymmetries. Results on beam asymmetries from the 1999 HAPPEX run and the 2000 E-158 engineering run are presented.
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