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Constraints on axionlike particles from VERITAS observations of a flaring radio galaxy in the Perseus cluster
No full textAxion-like particles (ALPs) are hypothetical particles that emerge in numerous theoretical extensions to the Standard Model. Their coupling to electromagnetic field implies that ALPs would mix with photons in the presence of external magnetic fields. As ALP phenomenology is governed by the mass and strength of its coupling, there is a subset of this parameter space in which this mixing would be expected to leave an imprint on the spectra of TeV γ-ray sources. In 2017, the VERITAS γ-ray observatory recorded the second day of a dramatic flare of the radio galaxy NGC 1275, embedded at the center of the Perseus galaxy cluster. This serendipitous locale provides a spatially-extended magnetic field of strength O(10 μG) through which escaping photons traverse, making it an excellent target to study ALPs. We analyze the VERITAS data of NGC 1275’s 2017 flare with the gammapy analysis package. Extensive fitting and modeling are performed to ultimately conduct a likelihood analysis used to search for any evidence of a preference for ALPs and to explore the confidence with which constraints can be set. We adopt the CLs method for this study for its conservative approach to setting limits in regimes where the search has limited sensitivity. No evidence for the existence of ALPs is found, and no combination of mass and coupling strength can be excluded at or above 95% confidence level. We provide a map showing the strength of our exclusions in the mass and coupling parameter space. The strongest exclusions are found in the mass range 2×10-7 eV≲ma≲4×10-7 eV and at the coupling strength of gaγ≳3×10-11 GeV-1 up to 80% confidence level, which are consistent with previous studies. We find the CLs to be a trustworthy approach, and advocate for its continued usage in future studies. We note that many of the limitations contributing to the limited sensitivity seen by VERITAS in this study will be improved with next-generation γ-ray instruments, such as the Cherenkov Telescope Array Observatory
How to produce ceramics in the millimeter thickness range at room temperature by the Powder Aerosol Deposition Method (ADM)
No full textThe Aerosol Deposition Method (ADM) is a coating technique that facilitates the direct production of ceramic films from powders at room temperature. A vacuum chamber is employed to spray a powder-carrier gas mixture onto the substrate, where it undergoes a room temperature impact consolidation (RTIC) to form a dense and nanocrystalline ceramic film.During the presentation, exceptionally thick “films” in the thickness range of a few millimeters are showcased, which were produced using the ADM. Film properties are described as outcomes of various characterization methods, and distinctions to conventional aerosol-deposited films are elucidated. Additionally, the presentation will explore the potential of this coating process as a method for additive manufacturing, considering the powder requirements for such thick films
X-ray thermal diffuse scattering as a texture-robust temperature diagnostic for dynamically compressed solids
No full textWe present a model of x-ray thermal diffuse scattering (TDS) from a cubic polycrystal with an arbitrary crystallographic texture, based on the classic approach of Warren [B. E. Warren, Acta Crystallogr. 6, 803 (1953)]. We compare the predictions of our model with femtosecond x-ray diffraction patterns gathered from ambient and dynamically compressed rolled copper foils obtained at the High Energy Density instrument of the European X-Ray Free-Electron Laser facility and find that the texture-aware TDS model yields more accurate results than does the conventional powder model owed to Warren. Nevertheless, we further show: with sufficient angular detector coverage, the TDS signal is largely unchanged by sample orientation and in all cases strongly resembles the signal from a perfectly random powder; shot-to-shot fluctuations in the TDS signal resulting from grain-sampling statistics are at the percent level, in stark contrast to the fluctuations in the Bragg-peak intensities (which are over an order of magnitude greater); and TDS is largely unchanged even following texture evolution caused by compression-induced plastic deformation. We conclude that TDS is robust against texture variation, making it a flexible temperature diagnostic applicable just as well to off-the-shelf commercial foils as to ideal powders
Anomalous lattice relaxation dynamics in optimally doped LaSrCuO
No full textThe atomic lattice plays a critical role in the emergence of high- superconductivity in cuprates. While the dynamics associated with electron-lattice coupling typically unfold on picosecond-to-femtosecond timescales, we present an x-ray photon correlation spectroscopy investigation on an optimally doped La-based cuprate that reveals a strong response of kilosecond-scale lattice relaxation dynamics to the superconducting state. Notably, an anomaly emerges around : upon cooling into the superconducting state, the average atomic relaxation lifetime decreases, i.e., dynamics accelerate. This indicates a significant change in the local disorder-induced strain field dynamics at the superconducting transition, highlighting a remarkable coupling between superconductivity and the lattice on quasistatic timescales
Beam dynamics Optimization for a High-brightness PhotoInjector with various Photocathode Laser Pulse Shapes
No full textSearch for Heavy Neutral Leptons with IceCube DeepCore
No full textThe observation of neutrino oscillations has established that neutrinos have non-zero masses. This phenomenon is not explained by the Standard Model of particle physics, but one viable explanation to this dilemma involves the existence of heavy neutral leptons in the form of right-handed neutrinos. This work presents the first search for heavy neutral leptons with the IceCube Neutrino Observatory. The standard three flavor neutrino model is extended by adding a fourth GeV-scale mass state allowing mixing with the sector through the parameter . The analysis is performed by searching for signatures of heavy neutral leptons that are directly produced via up-scattering of atmospheric 's inside the IceCube detection volume. Three heavy neutral lepton mass values, , of 0.3 GeV, 0.6 GeV, and 1.0 GeV are tested using ten years of data, collected between 2011 and 2021. No significant signal of heavy neutral leptons is observed for any of the tested masses. The resulting constraints for the mixing parameter are ( GeV), ( GeV), and ( GeV) at the 90% confidence level. This analysis serves as proof-of-concept for heavy neutral lepton searches in IceCube. The heavy neutral lepton event generator, developed in this work, and the analysis of the expected signatures lay the fundamental groundwork for future searches thereof
Constraints on axionlike particles from VERITAS observations of a flaring radio galaxy in the Perseus cluster
No full textAxion-like particles (ALPs) are hypothetical particles that emerge in numerous theoretical extensions to the Standard Model. Their coupling to electromagnetic field implies that ALPs would mix with photons in the presence of external magnetic fields. As ALP phenomenology is governed by the mass and strength of its coupling, there is a subset of this parameter space in which this mixing would be expected to leave an imprint on the spectra of TeV γ-ray sources. In 2017, the VERITAS γ-ray observatory recorded the second day of a dramatic flare of the radio galaxy NGC 1275, embedded at the center of the Perseus galaxy cluster. This serendipitous locale provides a spatially-extended magnetic field of strength O(10 μG) through which escaping photons traverse, making it an excellent target to study ALPs. We analyze the VERITAS data of NGC 1275’s 2017 flare with the gammapy analysis package. Extensive fitting and modeling are performed to ultimately conduct a likelihood analysis used to search for any evidence of a preference for ALPs and to explore the confidence with which constraints can be set. We adopt the CLs method for this study for its conservative approach to setting limits in regimes where the search has limited sensitivity. No evidence for the existence of ALPs is found, and no combination of mass and coupling strength can be excluded at or above 95% confidence level. We provide a map showing the strength of our exclusions in the mass and coupling parameter space. The strongest exclusions are found in the mass range 2×10 eV ≲ m ≲ 4 × 10 eV and at the coupling strength of g ≳ 3 × 10-11 GeV up to 80% confidence level, which are consistent with previous studies. We find the CLs to be a trustworthy approach, and advocate for its continued usage in future studies. We note that many of the limitations contributing to the limited sensitivity seen by VERITAS in this study will be improved with next-generation γ-ray instruments, such as the Cherenkov Telescope Array Observatory
HAWC, VERITAS, Fermi-LAT and XMM-Newton follow-up observations of the unidentified ultra-high-energy gamma-ray source LHAASO J2108+5157
No full textWe report observations of the ultra-high-energy gamma-ray source LHAASO J21085157, utilizing VERITAS, HAWC, Fermi-LAT, and XMM-Newton. VERITAS has collected 40 hours of data that we used to set ULs to the emission above 200 GeV. The HAWC data, collected over days, reveal emission between 3 and 146 TeV, with a significance of , favoring an extended source model. The best-fit spectrum measured by HAWC is characterized by a simple power-law with a spectral index of . Fermi-LAT analysis finds a point source with a very soft spectrum in the LHAASO J2108+5157 region, consistent with the 4FGL-DR3 catalog results. The XMM-Newton analysis yields a null detection of the source in the 2 - 7 keV band. The broadband spectrum can be interpreted as a pulsar and a pulsar wind nebula system, where the GeV gamma-ray emission originates from an unidentified pulsar, and the X-ray and TeV emission is attributed to synchrotron radiation and inverse Compton scattering of electrons accelerated within a pulsar wind nebula. In this leptonic scenario, our X-ray upper limit provides a stringent constraint on the magnetic field, which is G
Fine spectrum from crude analytic bootstrap
No full textThe magnetic line defect in the O(N) model gives rise to a non-trivial one-dimensional defect conformal field theory of theoretical and experimental value. This model is considered here in and the full spectrum of defect operators with dimensions close to one, two and three at order ɛ is presented. The spectrum of several classes of operators of dimension close to four and operators of large charge are also discussed. Analytic bootstrap techniques are used extensively, and efficient tools to deal with the unmixing of nearly degenerate operators are developed. Integral identities are also incorporated, and it is shown that they lead to constraints on some three-point function coefficients and anomalous dimensions to order ɛ