Nuclear physics

Nuclear physics

The experimentation with antiprotons at the Low Energy Antiproton Ring (L.E.A.R.) of the CERN begins in the within of the International Collaboration PS179 using a Streamer Chamber filled up with neon or helium in order to visualize the traces of electrically charged particles involved in the collision of an antiproton (p) with the nucleus of the filling gas. This detector of the dimensions of 90x70x18 cm3 was placed in a magnetic field of 0.5 tesla in order to measure the momentum of charged particles through their curvature and to identify their nature. The kinetic energies of the p projectile have been 180MeV, 49 Mev, 20 Mev according to the performances of decelerator L.E.A.R. in the course of the years. Below these energies the Glauber (Nobel prize 2005) approsimation is no more valid.
Beyond that for the various nuclear reactions to these energies, the interaction of the antiproton with the nuclei of the gas target has been studied also after its capture at “rest”. This was obtained by inserting suitable layers of material across the line of the p beam before the detector.
The first phase of the researches at L.E.A.R. terminated in 1985 and the decelerator was modified in order to obtain energies of antiprotons still lower, until to 5.3 MeV; in the successive phase, the Prof. Lodi Rizzini realized with a new and original method the measure of the collision cross section (probability) of the annihilation of antiprotons on helium nuclei at 1 MeV, by far at that time the one at the lowest p energy. This first measure will open the road to the attempts to obtain the same information in the antiproton interaction with other nuclei, starting from hydrogen, (i.e. proton p). Inside the PS201 collaboration OBELIX this goal has been achieved, at least partially, with the amazing discovery that the annihilation cross section of antiprotons of approximately 1 MeV kinetic energy has the same value obtained for the nucleus of hydrogen also for deuterium and He4.
This unexpected result has been otherwise confirmed, in the case of deuterium, by the study of the related antiprotonic atom in the fundamental state. Also the CERN Courier of July/August 2000 haThe experimentation with antiprotons at the Low Energy Antiproton Ring (L.E.A.R.) of the CERN begins in the within of the International Collaboration PS179 using a Streamer Chamber filled up with neon or helium in order to visualize the traces of electrically charged particles involved in the collision of an antiproton p with the nucleus of the filling gas. This detector of the dimensions of 90x70x18 cm3 was placed in a magnetic field of 0.5 tesla in order to measure the momentum of charged particles through their curvature and to identify their nature. The kinetic energies of the p projectile have been 180MeV, 49 Mev, 20 Mev according to the performances of decelerator L.E.A.R. in the course of the years. Below these energies the Glauber (Nobel prize 2005) approsimation is no more valid.
Beyond that for the various nuclear reactions to these energies, the interaction of the antiproton with the nuclei of the gas target has been studied also after its capture at “rest”. This was obtained by inserting suitable layers of material across the line of the p beam before the detector.
The first phase of the researches at L.E.A.R. terminated in 1985 and the decelerator was modified in order to obtain energies of antiprotons still lower, until to 5.3 MeV; in the successive phase, the Prof. Lodi Rizzini realized with a new and original method the measure of the collision cross section (probability) of the annihilation of antiprotons on helium nuclei at 1 MeV, by far at that time the one at the lowest p energy. This first measure will open the road to the attempts to obtain the same information in the antiproton interaction with other nuclei, starting from hydrogen, (i.e. proton p). Inside the PS201 collaboration OBELIX this goal has been achieved, at least partially, with the amazing discovery that the annihilation cross section of antiprotons of approximately 1 MeV kinetic energy has the same value obtained for the nucleus of hydrogen also for deuterium and He4.
This unexpected result has been otherwise confirmed, in the case of deuterium, by the Antiproton-light nuclei annihilation cross section (PS201)study of the related antiprotonic atom in the fundamental state. Also the CERN Courier of July/August 2000 has dealt with this situation “amazing” and antithetical to a “geometric” vision of the size of different nuclei.

This observation has led also to “interpretative” articles among which we like to signal

  • A. Bianconi et al.,
    Limits on the low-energy antinucleon-nucleus annihilations from the Heisenberg principle
    Europhysics Letters 54, 443 (2001)

The Brescia group proposed therefore to the ASACUSA Collaboration to complete and to extend to the lowest possible energies the study of the antiproton annihilation on nuclei. This scientific program became a part of the one of the Collaboration after the approval of the SPSC Committee of the CERN in June 2005. The related data-taking will start from 2006 at 5 MeV energies The data-taking at energies of 1 KeV and lower is foreseen starting from 2007.

  • E. Lodi Rizzini et al.,
    Antiproton-Nucleus annhilation at very low energies down to
    capture
    to be printed by American Institute of Physics (2005)
    ASACUSA Collaboration CERN-SPSC 2005-002; SPSC-97-19

    Spectroscopy and Collisions Using Ultra Slow Antiprotons.

In fig. the proposed experimental setup.

disegno dell'apparato di Brescia per la Collaborazione Asacusa

 

 

 

 

 

 

 

 

 

 

 

ASACUSA Collaboration List
  • Austria
    M. Carnelli, H. Fuhrman, J. Marton, E. Widmann, J. Zmeskal
    Stefan Meyer Institut für subatomare Physik, Boltzmanngasse 3, 1090 Vienna, Austria
  • Denmark
    H. Knudsen, P. Kristiansen, U. I. Uggerhoj
    Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark
    S.P. Møller
    Institute for Storage Ring Facilities (ISA), University of Aarhus, DK-8000 Aarhus C, Denmark
    H.H. Andersen
    Niels Bohr Institute, Blegdamsvej 17, DK-2100 København Ø, Denmark
  • Germany
    T. Ichioka
    MPI für Kernphysik (MPI-K), Heidelberg, Saupfercheckweg 1, 69117 Heidelberg, Germany
  • Hungary
    D. Barna, D. Horváth, P. Zalán
    Research Institute for Particle and Nuclear Physics, H-1525 Budapest, Hungary
    B. Juhász, K. Tökési
    Institute of Nuclear Research (ATOMKI), H-4001 Debrecen, Hungary
  • Italy
    M. Corradini, M. Leali, E. Lodi Rizzini, L. Venturelli, N. Zurlo
    Dipartimento di Chimica e Fisica per l’Ingegneria e per i Materiali, Università di Brescia, 25123 Brescia, Italy
  • Japan
    A.J. Dax, J. Eades , R.S. Hayano, T. Ishikawa, K. Gomikawa, N. Ono, W. Pirkl, T. Yamazaki
    Department of Physics, University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
    K. Komaki, Y. Nagata, H.A. Torii, Y. Yamazaki
    Institute of Physics, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan
    and Atomic Physics Laboratory, RIKEN, Wako 351-01, Japan
    Y. Kanai, N. Kuroda, A. Mohri, N. Oshima, M. Shibata, V. Varentsov, M. Wada
    Atomic Physics Laboratory, RIKEN, Wako 351-01, Japan
  • Switzerland
    M. Hori
    CERN, H-1211 Genève 23, Switzerland
  • United Kingdom
    M. Charlton
    Department of Physics, University of Wales Swansea, Singleton Park, Swansea, SA2 8PP, UK
    R. McCullough
    Dept. of Pure and Applied Physics, Queen’s University Belfast University Road, Belfast BT7 1NN, UK

Meanwhile the Brescia Group partecipated in the nuclear physics program of the DUBTO experiment at JINR Phasotron (Dubna, Russia), using beams of positive and negative pions and a streamer chamber equipped with CCD telecameras. The analysis of the events collected on He4 is in progress but unfurtunately a serious fire accident out in the accelerator whose running is in doubt.
This will involve the temporary suspension of PAINUC program.

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