| 1. |
- Arguedas Cuendis, S., et al.
(författare)
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First results on the search for chameleons with the KWISP detector at CAST
- 2019
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Ingår i: Physics of the Dark Universe. - : Elsevier. - 2212-6864. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- We report on a first measurement with a sensitive opto-mechanical force sensor designed for the direct detection of coupling of real chameleons to matter. These dark energy candidates could be produced in the Sun and stream unimpeded to Earth. The KWISP detector installed on the CAST axion search experiment at CERN looks for tiny displacements of a thin membrane caused by the mechanical effect of solar chameleons. The displacements are detected by a Michelson interferometer with a homodyne readout scheme. The sensor benefits from the focusing action of the ABRIXAS X-ray telescope installed at CAST, which increases the chameleon flux on the membrane. A mechanical chopper placed between the telescope output and the detector modulates the incoming chameleon stream. We present the results of the solar chameleon measurements taken at CAST in July 2017, setting an upper bound on the force acting on the membrane of 80pN at 95% confidence level. The detector is sensitive for direct coupling to matter 104≤βm≤108, where the coupling to photons is locally bound to βγ≤1011.
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| 2. |
- Adiels, L., et al.
(författare)
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Investigations on baryonium and other rare pmacrp annihilation modes using high resolution pi0 spectrometers (PS 182)
- 1985
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Ingår i: Antiproton 1984. Proceedings of the VII European Symposium on Antiproton Interactions. - : Institution of Electrical Engineers (IEE). ; , s. 297-304
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Konferensbidrag (refereegranskat)abstract
- In the search for heavy, narrow exotic states such as baryonium or glueballs, carried out so far, various methods of high- and low-energy production, low-energy formation, and e+e- reactions were used. In particular, a search for baryonium states below threshold (mxlsimmppmacr) has shown some evidence [Richter et al., 1983, Brando et al., 1984] for a few states. However, the results of these measurements suffer from poor statistics. Among the possible methods which can be applied in the baryonium bound state research at LEAR, the authors consider the study of the reaction ppmacrrarrX+pi0 as the most promising. They have performed an experiment to study this reaction by means of an experimental set-up especially tailored for measuring monoenergetic pi0,s, allowing for both angular distribution measurements and high-resolution spectroscopy. They report on the preliminary results from our actual measurements of the inclusive pi0 and eta spectra following the antiproton annihilation at rest.
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| 3. |
- Adiels, Lars, et al.
(författare)
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A π0 and η spectrometer of lead glass and BGO for momenta up to 1 GeV/c
- 1986
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 244:3, s. 380-390
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Tidskriftsartikel (refereegranskat)abstract
- A spectrometer consisting of two sets of bismuth germanium oxide (BGO) crystals and a lead-glass array has been used to measure the [pi]0 and [eta] momentum spectra produced from proton-antiproton annihilations at rest. We describe the test of the BGO sets in electron beams of energies from 50 to 450 MeV. We discuss the method of construction and calibration of the lead-glass array, as well as procedures to extract the energy and position resolutions for detected photons. A momentum resolution ([sigma]) for [pi]0’s and [eta]’s of 4% and 3%, respectively has been achieved at momenta below 1 GeV/c.
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| 4. |
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| 5. |
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| 6. |
- Adiels, L., et al.
(författare)
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Pi0 and eta spectra from proton-antiproton annihilations at rest
- 1984
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Ingår i: Zeitschrift für Physik. C, Particles and fields. - 0170-9739. ; 21:4, s. 315-319
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Tidskriftsartikel (refereegranskat)abstract
- The low-energy part of the Ï€0 spectrum associated with Mathematical expression annihilation at rest was measured in order to search for bound baryonium-like states. The upper limit for reaching such states via the emission of monochromatic Ï€0’s was found to be 8% per annihilation in the mass region of 1650 MeV. The low-energy part of the η spectrum from Mathematical expression annihilations at rest was also observed.
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| 7. |
- Adiels, L., et al.
(författare)
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Search for narrow exotic states in annihilations on 4He
- 1984
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 138:1-3, s. 235-240
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Tidskriftsartikel (refereegranskat)abstract
- After having found evidence for narrow exotic states in p annihilation, the production of such states on a nuclear target was studied with similar techniques. The γ spectrum associated with annihilation on 4He at rest was measured. The spectrum shows two peaks, at energies of 161.9 and 203.0 MeV, corresponding to intermediate narrow states of masses which seem to be related to states found in p annihilations. The confidence is better than 4 σ.
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| 8. |
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| 9. |
- Baum, Sebastian, et al.
(författare)
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Detecting solar chameleons through radiation pressure
- 2014
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 739, s. 167-173
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Tidskriftsartikel (refereegranskat)abstract
- Light scalar fields can drive the accelerated expansion of the universe. Hence, they are obvious dark energy candidates. To make such models compatible with tests of General Relativity in the solar system and "fifth force" searches on Earth, one needs to screen them. One possibility is the so-called "chameleon" mechanism, which renders an effective mass depending on the local matter density. If chameleon particles exist, they can be produced in the sun and detected on Earthexploiting the equivalent of a radiation pressure. Since their effective mass scales with the local matter density, chameleons can be reflected by a dense medium if their effective mass becomes greater than their total energy. Thus, under appropriate conditions, a flux of solar chameleons may be sensed by detecting the total instantaneous momentum transferred to a suitable opto-mechanical force/pressure sensor. We calculate the solar chameleon spectrum and the reach in the chameleon parameter space of an experiment using the preliminary results from a force/pressure sensor, currently under development at INFN Trieste, to be mounted in the focal plane of one of the X-Ray telescopes of the CAST experiment at CERN. We show, that such an experiment signifies a pioneering effort probing uncharted chameleon parameter space.
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| 10. |
- Blüm, P., et al.
(författare)
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A modular NaI(Tl) detector for 20-1000 MeV photons
- 1983
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Ingår i: Nuclear Instruments and Methods in Physics Research. - : Elsevier BV. - 0167-5087. ; 213:2-3, s. 251-259
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Tidskriftsartikel (refereegranskat)abstract
- A detector consisting of 54 NaI (Tl) modules is described. The detector has been optimized for the detection of 20-1000 MeV photons. An energy resolution (fwhm) of 5.5% at 130 MeV could be attained, and the stability has been better than 1% over several months.
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