| 1. |
- Ahdida, C., et al.
(författare)
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Track reconstruction and matching between emulsion and silicon pixel detectors for the SHiP-charm experiment
- 2022
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Ingår i: Journal of Instrumentation. - : IOP Publishing. - 1748-0221. ; 17:3
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Tidskriftsartikel (refereegranskat)abstract
- In July 2018 an optimization run for the proposed charm cross section measurement for SHiP was performed at the CERN SPS. A heavy, moving target instrumented with nuclear emulsion films followed by a silicon pixel tracker was installed in front of the Goliath magnet at the H4 proton beam-line. Behind the magnet, scintillating-fibre, drift-tube and RPC detectors were placed. The purpose of this run was to validate the measurement's feasibility, to develop the required analysis tools and fine-tune the detector layout. In this paper, we present the track reconstruction in the pixel tracker and the track matching with the moving emulsion detector. The pixel detector performed as expected and it is shown that, after proper alignment, a vertex matching rate of 87% is achieved.
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| 2. |
- Ahdida, C., et al.
(författare)
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The SHiP experiment at the proposed CERN SPS Beam Dump Facility
- 2022
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Ingår i: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 82:5
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Tidskriftsartikel (refereegranskat)abstract
- The Search for Hidden Particles (SHiP) Collaboration has proposed a general-purpose experimental facility operating in beam-dump mode at the CERN SPS accelerator to search for light, feebly interacting particles. In the baseline configuration, the SHiP experiment incorporates two complementary detectors. The upstream detector is designed for recoil signatures of light dark matter (LDM) scattering and for neutrino physics, in particular with tau neutrinos. It consists of a spectrometer magnet housing a layered detector system with high-density LDM/neutrino target plates, emulsion-film technology and electronic high-precision tracking. The total detector target mass amounts to about eight tonnes. The downstream detector system aims at measuring visible decays of feebly interacting particles to both fully reconstructed final states and to partially reconstructed final states with neutrinos, in a nearly background-free environment. The detector consists of a 50m\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm { \,m}$$\end{document} long decay volume under vacuum followed by a spectrometer and particle identification system with a rectangular acceptance of 5 m in width and 10 m in height. Using the high-intensity beam of 400GeV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\,\mathrm {GeV}$$\end{document} protons, the experiment aims at profiting from the 4x1019\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4\times 10<^>{19}$$\end{document} protons per year that are currently unexploited at the SPS, over a period of 5-10 years. This allows probing dark photons, dark scalars and pseudo-scalars, and heavy neutral leptons with GeV-scale masses in the direct searches at sensitivities that largely exceed those of existing and projected experiments. The sensitivity to light dark matter through scattering reaches well below the dark matter relic density limits in the range from a few MeV/c2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm {\,MeV\!/}c<^>2}$$\end{document} up to 100 MeV-scale masses, and it will be possible to study tau neutrino interactions with unprecedented statistics. This paper describes the SHiP experiment baseline setup and the detector systems, together with performance results from prototypes in test beams, as it was prepared for the 2020 Update of the European Strategy for Particle Physics. The expected detector performance from simulation is summarised at the end.
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| 3. |
- Ahdida, C., et al.
(författare)
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Sensitivity of the SHiP experiment to dark photons decaying to a pair of charged particles
- 2021
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Ingår i: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 81:5
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Tidskriftsartikel (refereegranskat)abstract
- Dark photons are hypothetical massive vector particles that could mix with ordinary photons. The simplest theoretical model is fully characterised by only two parameters: the mass of the dark photon m(gamma)D and its mixing parameter with the photon, epsilon. The sensitivity of the SHiP detector is reviewed for dark photons in the mass range between 0.002 and 10 GeV. Different productionmechanisms are simulated, with the dark photons decaying to pairs of visible fermions, including both leptons and quarks. Exclusion contours are presented and compared with those of past experiments. The SHiP detector is expected to have a unique sensitivity for m. D ranging between 0.8 and 3.3(-0.5)(+0.2) GeV, and epsilon(2) ranging between 10(-11) and 10(-17).
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| 4. |
- Ahdida, C., et al.
(författare)
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The magnet of the scattering and neutrino detector for the SHiP experiment at CERN
- 2020
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 15:01
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Tidskriftsartikel (refereegranskat)abstract
- The Search for Hidden Particles (SHiP) experiment proposal at CERN demands a dedicated dipole magnet for its scattering and neutrino detector. This requires a very large volume to be uniformly magnetized at B > 1.2 T, with constraints regarding the inner instrumented volume as well as the external region, where no massive structures are allowed and only an extremely low stray field is admitted. In this paper we report the main technical challenges and the relevant design options providing a comprehensive design for the magnet of the SHiP Scattering and Neutrino Detector.
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| 5. |
- Ahdida, C., et al.
(författare)
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Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target
- 2020
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:3
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Tidskriftsartikel (refereegranskat)abstract
- The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27 +/- 0.07)x1011protons on target was recorded. This amounts to approximatively 1% of a SHiP spill.
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| 6. |
- Ahdida, C., et al.
(författare)
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Sensitivity of the SHiP experiment to light dark matter
- 2021
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :4
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Tidskriftsartikel (refereegranskat)abstract
- Dark matter is a well-established theoretical addition to the Standard Model supported by many observations in modern astrophysics and cosmology. In this context, the existence of weakly interacting massive particles represents an appealing solution to the observed thermal relic in the Universe. Indeed, a large experimental campaign is ongoing for the detection of such particles in the sub-GeV mass range. Adopting the benchmark scenario for light dark matter particles produced in the decay of a dark photon, with αD = 0.1 and mA′ = 3mχ, we study the potential of the SHiP experiment to detect such elusive particles through its Scattering and Neutrino detector (SND). In its 5-years run, corresponding to 2 · 1020 protons on target from the CERN SPS, we find that SHiP will improve the current limits in the mass range for the dark matter from about 1 MeV to 300 MeV. In particular, we show that SHiP will probe the thermal target for Majorana candidates in most of this mass window and even reach the Pseudo-Dirac thermal relic.
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| 7. |
- Muxlow, T. W. B., et al.
(författare)
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The e-MERGE Survey (e-MERLIN Galaxy Evolution Survey): overview and survey description
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 495:1, s. 1188-1208
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Tidskriftsartikel (refereegranskat)abstract
- We present an overview and description of the e-MERGE Survey (e-MERLIN Galaxy Evolution Survey) Data Release 1 (DR1), a large program of high-resolution 1.5-GHz radio observations of the GOODS-N field comprising similar to 140 h of observations with enhanced-Multi-Element Remotely Linked Interferometer Network (e-MERLIN) and similar to 40 h with the Very Large Array (VLA). We combine the long baselines of e-MERLIN (providing high angular resolution) with the relatively closely packed antennas of the VLA (providing excellent surface brightness sensitivity) to produce a deep 1.5-GHz radio survey with the sensitivity (similar to 1.5 mu Jy beam(-1)), angular resolution (0.2-0.7 arcsec) and field-of-view (similar to 15x15 arcmin(2)) to detect and spatially resolve star-forming galaxies and active galactic nucleus (AGN) at z greater than or similar to 1. The goal of e-MERGE is to provide new constraints on the deep, sub-arcsecond radio sky which will be surveyed by SKA1-mid. In this initial publication, we discuss our data analysis techniques, including steps taken to model in-beam source variability over an similar to 20-yr baseline and the development of newpoint spread function/primary beam models to seamlessly merge e-MERLIN and VLA data in the uv plane. We present early science results, including measurements of the luminosities and/or linear sizes of similar to 500 galaxies selected at 1.5 GHz. In combination with deep Hubble Space Telescope observations, we measure a mean radio-to-optical size ratio of r(e-MERGE)/r(HST) similar to 1.02 +/- 0.03, suggesting that in most high-redshift galaxies, the similar to GHz continuum emission traces the stellar light seen in optical imaging. This is the first in a series of papers that will explore the similar to kpc-scale radio properties of star-forming galaxies and AGN in the GOODS-N field observed by e-MERGE DR1.
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| 8. |
- Gurvits, L. I., et al.
(författare)
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The science case and challenges of spaceborne sub-millimeter interferometry: the study case of TeraHertz Exploration and Zooming-in for Astrophysics (THEZA)
- 2021
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Ingår i: Proceedings of the International Astronautical Congress, IAC. - 0074-1795. ; A7
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Konferensbidrag (refereegranskat)abstract
- Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the super-massive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope (EHT) and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10−20 microrcseconds (0.05−0.1 nanoradian). Angular resolution is proportional to the observing wavelength and inversely proportional to the interferometer baseline length. In the case of Earth-based EHT, the highest angular resolution was achieved by combining the shortest possible wavelength of 1.3 mm with the longest possible baselines, comparable to the Earth’s diameter. For RadioAstron, operational wavelengths were in the range from 92 cm down to 1.3 cm, but the baselines were as long as ∼350,000 km. However, these two highlights of radio astronomy, EHT and RadioAstron do not”saturate” the interest to further increase in angular resolution. Quite opposite: the science case for further increase in angular resolution of astrophysical studies becomes even stronger. A natural and, in fact, the only possible way of moving forward is to enhance mm/sub-mm VLBI by extending baselines to extraterrestrial dimensions, i.e. creating a mm/sub-mm Space VLBI system. The inevitable move toward space-borne mm/sub-mm VLBI is a subject of several concept studies. In this presentation we will focus on one of them called TeraHertz Exploration and Zooming-in for Astrophysics (THEZA), prepared in response to the ESA’s call for its next major science program Voyage 2050 (Gurvits et al. 2021). The THEZA rationale is focused at the physics of spacetime in the vicinity of super-massive black holes as the leading science drive. However, it will also open up a sizable new range of hitherto unreachable parameters of observational radio astrophysics and create a multi-disciplinary scientific facility and offer a high degree of synergy with prospective “single dish” space-borne sub-mm astronomy (e.g., Wiedner et al. 2021) and infrared interferometry (e.g., Linz et al. 2021). As an amalgam of several major trends of modern observational astrophysics, THEZA aims at facilitating a breakthrough in high-resolution high image quality astronomical studies.
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| 9. |
- Nimmo, K., et al.
(författare)
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Milliarcsecond Localization of the Repeating FRB 20201124A
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 927:1
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Tidskriftsartikel (refereegranskat)abstract
- Very long baseline interferometric (VLBI) localizations of repeating fast radio bursts (FRBs) have demonstrated a diversity of local environments: from nearby star-forming regions to globular clusters. Here we report the VLBI localization of FRB 20201124A using an ad hoc array of dishes that also participate in the European VLBI Network (EVN). In our campaign, we detected 18 bursts from FRB 20201124A at two separate epochs. By combining the visibilities from both epochs, we were able to localize FRB 20201124A with a 1 sigma uncertainty of 2.7 mas. We use the relatively large burst sample to investigate astrometric accuracy and find that for greater than or similar to 20 baselines (greater than or similar to 7 dishes) we can robustly reach milliarcsecond precision even using single-burst data sets. Subarcsecond precision is still possible for single bursts, even when only similar to 6 baselines (four dishes) are available. In such cases, the limited uv coverage for individual bursts results in very high side-lobe levels. Thus, in addition to the peak position from the dirty map, we also explore smoothing the structure in the dirty map by fitting Gaussian functions to the fringe pattern in order to constrain individual burst positions, which we find to be more reliable. Our VLBI work places FRB 20201124A 710 +/- 30 mas (1 sigma uncertainty) from the optical center of the host galaxy, consistent with originating from within the recently discovered extended radio structure associated with star formation in the host galaxy. Future high-resolution optical observations, e.g., with Hubble Space Telescope, can determine the proximity of FRB 20201124A's position to nearby knots of star formation.
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| 10. |
- Hewitt, Dante M., et al.
(författare)
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Milliarcsecond localization of the hyperactive repeating FRB 20220912A
- 2024
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 529:2, s. 1814-1826
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Tidskriftsartikel (refereegranskat)abstract
- We present very long-baseline interferometry (VLBI) observations of the hyperactive repeating FRB 20220912A using the European VLBI Network (EVN) outside of regular observing sessions (EVN-Lite). We detected 150 bursts from FRB 20220912A over two observing epochs in 2022 October. Combining the burst data allows us to localize FRB 20220912A to a precision of a few milliarcseconds, corresponding to a transverse scale of less than 10 pc at the distance of the source. This precise localization shows that FRB 20220912A lies closer to the centre of its host galaxy than previously found, although still significantly offset from the host galaxy's nucleus. On arcsecond scales, FRB 20220912A is coincident with a persistent continuum radio source known from archival observations; however, we find no compact persistent emission on milliarcsecond scales. The 5σ upper limit on the presence of such a compact persistent radio source is 120 μJy, corresponding to a luminosity limit of (D/362.4 Mpc)erg s-1 Hz-1. The persistent radio emission is thus likely to be from star formation in the host galaxy. This is in contrast to some other active FRBs, such as FRB 20121102A and FRB 20190520B.
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