Trapped positrons observed by PAMELA experiment

Mikhailov, V. V.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, É. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; Consiglio, L.; Santis, C. De; Simone, N. De; Felice, V. Di; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobsky, S. A.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A. A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Мерге, М.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Papini, P.; Palma, F.; Panico, B.; Pearce, Mark; Picozza, P.; Ricci, M.; Ricciarini, S.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Спиллантини, П.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasiliev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

doi:10.1088/1742-6596/675/3/032003

“…The reason is magnetic deflection: while a neutral particle travels along a straight path and has only one chance to cross a detector, a charged particle may be deflected by the magnetic field and cross more than once a given surface. This effect is evident for the trapped protons and electrons in the Earth magnetosphere (an effect known since decades, and measured with unprecedented precision by AMS-01 [37,38] and PAMELA [39][40][41]), and should work similarly over wide regions if the magnetic field intensity is smaller. Thus, the measured flux of charged particle is enhanced by any sort of trapping, whereas the flux of neutral particles is independent of magnetic fields.…”

Section: Cosmic Neutronsmentioning

confidence: 99%

Neutron astronomy

Casadei¹

2017

Preprint

0

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Neutrons travel along straight lines in free space, but only survive for a distance which depends on their energy. Thus, detecting neutrons in space in principle provides directional and distance information. Apart from secondary neutrons produced by cosmic-ray interactions in the Earth atmosphere, which are the dominant background, direct neutron emission is caused by solar flares, with clear time correlation with X-rays, which can be measured from few tens MeV up to few GeV. There is no detectable astrophysical source up to the PeV scale, when neutrons coming from supernova remnants may reach the Earth before decaying. In addition, ultra high energy neutrons are the most plausible explanation for the measured anisotropy of cosmic-ray showers produced in the atmosphere above 10 18 eV. From the GeV to the PeV scale, the expected neutron flux is very low and not too different from the antiproton flux, as the same cosmic-ray collisions with the interstellar medium which can produce antiprotons can also produce neutrons and antineutrons. This background flux of cosmic-ray neutrons is very low and has not yet been detected. Measuring the neutron energy spectrum in space is a very effective way of searching for decays of exotic particles. For example, dark matter could consist of Weakly Interacting Massive Particles (WIMPs), which may annihilate into final states with particle and antiparticle pairs. Consequently, a number of indirect WIMP searches are being carried on, focusing on positron and antiproton spectra. However, no experiment is presently foreseen to look for "bumps" in the neutron energy spectrum, which is virtually background free. Here we consider the implications of a measurement of the neutron energy spectrum in astronomy and astrophysics and list the interesting energy regions in the search for WIMPs.

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Calculations of positron scattering from atomic oxygen

Mori,

Scarlett,

Bray

et al. 2023

Eur. Phys. J. D

2

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The single-center convergent close coupling (CCC) method has been applied to positron scattering from the oxygen atom. Cross sections have been calculated for total, elastic, momentum transfer, total ionization, inelastic, and excitation scattering processes from threshold to 5000 eV. Due to their relevance in transport studies, we also present stopping power and mean excitation energy results. Low-energy studies have been conducted to calculate scattering length, the hidden Ramsauer–Townsend minimum, and the energy of the positron virtual state. CCC-scaled complex optical potential calculations are utilized to calculate positronium-formation, direct ionization, and values between the positronium-formation and ionization thresholds. Good agreement is generally observed at high energies with past theory, electron-atomic oxygen experiment, and halved electron/positron O$$_2$$ 2 experiment. Large discrepancies, however, have been found between current and previous calculations for positronium-formation cross section and for low-energy elastic scattering cross section. Graphic Abstract

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Calculations of positron scattering from small molecules

Mori,

Bray,

Fursa

2024

Eur. Phys. J. D

0

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Recently, convergent close-coupling calculations have been completed for positron scattering from the carbon and oxygen atomic targets. These, together with previously completed calculations for atomic hydrogen, are utilized to perform positron scattering calculations for molecular hydrogen ($$\hbox {H}_2$$ H 2 ), molecular oxygen ($$\hbox {O}_2$$ O 2 ), diatomic carbon ($$\hbox {C}_2$$ C 2 ), carbon monoxide (CO), carbon dioxide ($$\hbox {CO}_2$$ CO 2 ), ozone ($$\hbox {O}_3$$ O 3 ), water ($$\hbox {H}_2\hbox {O}$$ H 2 O ), and methane ($$\hbox {CH}_4$$ CH 4 ) through a modified independent atom approach. For these molecules, positronium-formation, direct ionization, electron-loss, elastic, total electronic excitation, total inelastic, and total cross sections are obtained for energies between 0.1 and 5000 eV. There is, in general, good agreement between the current results and past experiments for most transitions, particularly at high energies where this approach is expected to be most accurate. Graphic Abstract

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Trapped positrons observed by PAMELA experiment

Cited by 3 publications

References 6 publications

Neutron astronomy

Neutron astronomy

Calculations of positron scattering from atomic oxygen

Calculations of positron scattering from small molecules

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