Wigner Institute for Particle and Nuclear Physics

Budapest, Hungary

Wigner Institute for Particle and Nuclear Physics

Budapest, Hungary
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Aghai-Khozani H.,Max Planck Institute of Quantum Optics | Aghai-Khozani H.,CERN | Barna D.,Wigner Institute for Particle and Nuclear Physics | Barna D.,University of Tokyo | And 21 more authors.
Hyperfine Interactions | Year: 2014

The study of the antiproton (Formula presented.) annihilation cross section on nuclei at low energies (eV-MeV region) has implications for fundamental cosmology as well as for nuclear physics. Concerning the former, different models try to explain the matter/antimatter asymmetry in the universe assuming the existence of the so-called “islands” where antinucleon-nucleon annihilations occur in the border region (Cohen et al. Astrophys. J. 495, 539–549, 1998), while, from the nuclear physics point of view, the annihilation process is a valuable tool to evaluate the neutron/proton ratio in order to probe the external region of the nucleus (Gupta et al. Nucl. Phys. B 70(3), 414–424, 1974). The existing data of antinucleon-nucleon (or -nucleus) annihilation cross-sections are mainly confined to energies above ≈1 MeV, while the cross section measured at LEAR in the 80’s-90’s (mostly with light targets Agnello et al. Phys. Lett. B 256, 349–353, 1991; Bertin et al. Phys. Lett. B 369, 77–85, 1996; Bertin et al. Phys. Lett. B 414, 220–228, 1997; Zenoni et al. Phys. Lett. B 461, 405–412, 1999; Bianconi et al. Phys. Lett. B 481, 194–198, 2000; Bianconi et al. Phys. Lett. B 492, 254–258, 2000) showed an unexpected behaviour for energies below 1 MeV (Bianconi et al. Phys. Lett. B 483, 353–359, 2000; Bianconi et al. Phys. Rev. C 62, 014611-7, 2000; Batty et al. Nucl. Phys. A 689, 721–740, 2001). The results showed a saturation with the atomic mass number against the A2/3 trend which is observed for higher energies (being A the target mass number). The ASACUSA collaboration at CERN recently measured antiproton annihilation cross section on different kinds of nuclei with a (Formula presented.) kinetic energy of 5.3 MeV (Bianconi et al. Phys. Lett. B 704, 461–466, 2011; Corradini et al. Nucl. Instr. Methods A 711, 12–20, 2013). Such results proved compatibility with the black-disk model with the Coulomb correction. But till now experimental difficulties prevented the investigation at energies below ≈1 MeV. In 2012, the 100 keV region has been investigated for the first time (Aghai-Khozani et al. Eur. Phys. J. Plus 127, 125–128, 2012). We present here the first preliminary results of this experiment. © 2014, Springer International Publishing Switzerland.


Aghai-Khozani H.,Max Planck Institute of Quantum Optics | Aghai-Khozani H.,CERN | Barna D.,Wigner Institute for Particle and Nuclear Physics | Barna D.,University of Tokyo | And 20 more authors.
EPJ Web of Conferences | Year: 2014

Investigating the antiproton cross section on nuclei at low energies (1 eV - 1 MeV) is of great interest for fundamental cosmology and nuclear physics as well. The process is of great relevance for the models which try to explain the matter/antimatter asymmetry in the universe assuming the existence of the so-called "island" where antinucleon-nucleon annihilations occur in the border region [1]. For the nuclear physics point of view, the annihilation process is considered a useful tool to evaluate the neutron/proton ratio probing the external region of the nucleus. Moreover, the cross section measured at LEAR in the 80s-90s showed an unexpected behaviour for energies below 1 MeV. The results showed a saturation with the atomic mass number against the A 2/3 trend which is known for higher energies. The ASACUSA collaboration at CERN measured 5.3 MeV antiproton annihilation cross section on different nuclei whose results demonstrated to be consistent with the black-disk model with the Coulomb correction [2]. So far, experimental limits prevented the data acquisition for energies below 1 MeV. In 2012 the 100 keV region has been investigated for the first time [3]. We present here the results of the experiment. © Owned by the authors, published by EDP Sciences, 2013.


Todoroki K.,University of Tokyo | Hori M.,University of Tokyo | Hori M.,Max Planck Institute of Quantum Optics | Aghai-Khozani H.,Max Planck Institute of Quantum Optics | And 21 more authors.
EPJ Web of Conferences | Year: 2014

The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration of CERN is currently attempting to measure the antiproton-nucleus in-flight annihilation cross sections on thin target foils of C, Pd, and Pt at 130 keV of kinetic energy. The low-energy antiprotons were supplied by the Antiproton Decelerator (AD) and a radio-frequency quadrupole decelerator. For this measurement, a beam profile monitor based on secondary electron emission was developed. Data from this monitor was used to ensure that antiprotons were precisely tuned to the position of an 80-mm-diameter experimental target, by measuring the spatial profile of 200-ns-long beam pulses containing 10 5 - 106 antiprotons with an active area of 40 mm × 40 mm and a spatial resolution of 4 mm. By using this monitor, we succeeded in finely tuning antiproton beams on the target, and observed some annihilation events originating from the target. © Owned by the authors, published by EDP Sciences, 2013.

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