| 1. |
- Addazi, A., et al.
(författare)
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New high-sensitivity searches for neutrons converting into antineutrons and/or sterile neutrons at the HIBEAM/NNBAR experiment at the European Spallation Source
- 2021
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Ingår i: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 48:7
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Tidskriftsartikel (refereegranskat)abstract
- The violation of baryon number, , is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation () via mixing, neutron–antineutron oscillation via regeneration from a sterile neutron state (), and neutron disappearance (n → n'); the effective process of neutron regeneration () is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics.
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| 2. |
- Badole, S., et al.
(författare)
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High-resolution imaging with the International LOFAR Telescope : Observations of the gravitational lenses MG 0751+2716 and CLASS B1600+434
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Tidskriftsartikel (refereegranskat)abstract
- We present Low-Frequency Array (LOFAR) telescope observations of the radio-loud gravitational lens systems MG 0751+2716 and CLASS B1600+434. These observations produce images at 300 milliarcseconds (mas) resolution at 150 MHz. In the case of MG 0751+2716, lens modelling is used to derive a size estimate of around 2 kpc for the low-frequency source, which is consistent with a previous 27.4 GHz study in the radio continuum with Karl G. Jansky Very Large Array. This consistency implies that the low-frequency radio source is cospatial with the core-jet structure that forms the radio structure at higher frequencies, and no significant lobe emission or further components associated with star formation are detected within the magnified region of the lens. CLASS B1600+434 is a two-image lens where one of the images passes through the edge-on spiral lensing galaxy, and the low radio frequency allows us to derive limits on propagation effects, namely scattering, in the lensing galaxy. The observed flux density ratio of the two lensed images is 1.19 ± 0.04 at an observed frequency of 150 MHz. The widths of the two images give an upper limit of 0.035 kpc m−20∕3 on the integrated scattering column through the galaxy at a distance approximately 1 kpc above its plane, under the assumption that image A is not affected by scattering. This is relatively small compared to limits derived through very long baseline interferometry studies of differential scattering in lens systems. These observations demonstrate that LOFAR is an excellent instrument for studying gravitational lenses. We also report on the inability to calibrate three further lens observations: two from early observations that have less well determined station calibration, and a third observation impacted by phase transfer problems.
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| 3. |
- Schalk, Oliver, et al.
(författare)
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Time-resolved photoelectron spectroscopy of nitrobenzene and its aldehydes
- 2018
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 691, s. 379-387
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Tidskriftsartikel (refereegranskat)abstract
- We report the first femtosecond time-resolved photoelectron spectroscopy study of 2-, 3-and 4-nitrobenzaldehyde (NBA) and nitrobenzene (NBE) in the gas phase upon excitation at 200 nm. In 3- and 4-NBA, the dynamics follow fast intersystem crossing within 1-2 picoseconds. In 2-NBA and NBE, the dynamics are faster (similar to 0.5 ps). 2-NBA undergoes hydrogen transfer similar to solution phase dynamics. NBE either releases NO2 in the excited state or converts internally back to the ground state. We discuss why these channels are suppressed in the other nitrobenzaldehydes.
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