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Astroparticle Physics

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In the last ~30 years the fields of high energy astrophysics and particle physics have grown a solid partnership based on complementary science goals, detection technologies, system engineering
and analysis techniques. The resulting science is now commonly known as astroparticle physics. The NEWS  project builds on this rich diversity of scientific cultures and hosts champions at different stages of their maturity.

Fermi LAT

The collaboration between particle physicists and astrophysicists has proven particularly productive in bringing together excellence of high performing particle detectors and a strong culture to support long term space operations, in order to maximize the mission return on a multitude of science goals.  Launched in 2008, the Fermi mission has revolutionized the field of high­energy astroparticle physics with accurate and high­statistics observations of photons in the 100 MeV ­ 1 TeV range from a multitude of sources never before observed in the sky. Thanks to this success NASA has decided to extend the mission beyond the nominal 5­year phase. The LAT is performing extraordinarily well and is continuing to study the violent, gamma-­ray side of the Universe with unprecedented detail. Science prospects for the upcoming years were recently boosted by a new event analysis package, released in June 2015 and dubbed Pass 8, which significantly improves the LAT performance. Together with the absence of consumables and very stable operations, this offers improved science discovery potential in four major themes: multi­wavelength and multi­messenger studies, dark matter searches, particle and time domain astrophysics. NEWS aims at specific advances in all these areas of Fermi science through well identified science targets. We will consolidate and disseminate the most accurate knowledge of the gamma­ray sky with the fourth iteration of the LAT gamma­ray source catalog (4FGL). This is the primary science output of the Fermi observatory and encodes precious information for studying the highest energy emissions in different source classes and after particle propagation and interactions across the Universe. Construction of the 4FGL will use the most advanced knowledge of the telescope instrumental response and of multiwavelength catalogs. Starting from this accurate description of the sky, we will be able to set stringent limits on excess gamma­ray emission from putative Dark Matter sources in the sky, therefore constraining the phase space for potential particle candidates to explain the missing mass in the Universe. The LAT is expected to either discover or exclude a conventional WIMP with thermal relic annihilation cross section up to masses of ~400 GeV within 2023 (15 years of observations), relying on the Pass 8 improved sensitivity and synergies with upcoming optical surveys that will discover many more dwarfs spheroidal systems. We will document the intrinsically dynamic nature of the gamma­ray sky by capturing transient emissions and connecting them to detections from a multi­messenger network of observatories sensitive to other types of radiation, like neutrinos or Gravitational Waves. The LAT is the only gamma­ray observatory that can search for variability from the scale of ms, typical of GRBs, Solar Flares and Terrestrial Gamma­Ray Flashes, to the scale of days, typical of AGNs, and of years, that characterizes complex long­period binary systems. Finally, we propose to work on a virtualized computational model to preserve the ability to store and analyse Fermi heritage data for years to come and independently of changes to operating systems and underlying hardware. This project will leverage on the long existing experience with public data servers and analysis tools that the Fermi Collaboration and the Fermi Science Support Center maintain.

Useful Links

The Fermi Large Area Telescope web site at Stanford

Fermi Gamma-ray Space Telescope web site at Nasa Goddard Space Flight Center


X-ray polarimetry

After about a decade of intensive technological developments, Xray polarimeters based on Gas Pixel Detectors (GPD) have reached full maturity for application in astrophysical observations from space. The GPD couples an amplifying Gas Electron Multiplier (GEM) to a high density, 50 micron pitch,pixelated readout CMOS ASIC, and samples the photoelectron track inside the gas for each incoming event on the detector plane, thus significantly improving the efficiency of the measurement with respect to traditional, selective diffraction Bragg crystals. Additionally, the GPD intrinsically features excellent imaging and spectroscopic performance, therefore offering direct access to the traditional Xray observables and adding for the first time the new dimension of polarization. A new genera-tion of dedicated X-ray space telescopes based on this technology i s emerging. They will measure with high accuracy the polarization of X rays captured by the detector in the 110 keV regime. Besides providing images with arcsecond resolution, these instruments will measure the angle and the degree of polarization of X rays from the parent sources, thus probing the curvature of space in the vicinity of black holes and neutron stars, verifying quantum electrodynamics in regions of extreme magnetic fields and opening a new discovery window on exotic phenomena like existence of axionlike particles. Two missions concepts, XIPE and IXPE rely on the GPD and have been selected in 2015 by the ESA and NASA space agencies for upcoming mission opportunities, and technical designs of the telescopes are being laid out. This shows the high technology readiness for space operations of X-ray polarimetry (between 5 and 6 on the standard ISO scale), and confirms the large interest in the science community for a first ever
survey of X-ray polarization from a significant number of sources. While polarization is in fact expected from many nonthermal sources in the sky, only a single, pioneering measurement of the bright Crab nebula was performed with standard imaging techniques coupled to selective polarimetric filters, which operate at very low sensitivity and resolution.

Useful Links

January 3, 2017, NASA Selects Mission to StudyBlack Holes, Cosmic X-ray Mysteries Press Release

IXPE, Imaging X-Ray Polarimetry Explorer Mission at Nasa

Cosmic Microwave Background (CMB) polarization measurements

This intriguing fundamental research field is now taking advantage of the technological advancements of the Transition Edge Sensors (TES) bolometers and microcalorimeters. After WMAP and PLANCK CMB missions, the next goal is the search for the Bmode
polarization features. Bmodes give unique access to the primordial Universe physics at the inflation epoch, i.e. within few seconds after the big bang and to the physics at energy scales of 1E16 GeV. NEWS researchers are giving leading contributions to the development of bolometer and SQUID frontend electronics for the stratospheric balloon borne mission called Large Scale Polarization Explorer (LSPE), scheduled to fly over the arctic in the winter 2017/2018.
LSPE will measure the ratio of scalar to tensor components of the CMB polarization at the level of 1 % – 3% at large angular scales (i.e. low multipoles), with with 1.3° FWHM angular resolution. LSPE will face the difficult work to extract the Bmode signal within a huge foreground. Therefore, in the next future a bigger and coordinate effort for a wide investigation of the overall CMB parameters is needed. This will require longer exposures and very large number of detectors. Two proposals are currently under discussion within the community: a medium-large size satellite mission, CORE++ , and the medium-small mission LiteBIRD in combination with the large ground telescope array called “Stage 4”. Both proposals need huge arrays of polarization sensitive and multiband bolometers. The basic technology developments are at the first study phase in Europe while in the USA and Japan there are research institutes in advanced phase, thanks also to the step by step strategy of testing the detectors in ground and balloon telescopes. CALTECH is one of the most
advanced centers for the study of very sensitive antenna coupled mm-wave bolometers that are very well suited for the next space, balloon and ground observations.