On the observation of an antiproton star in emulsion exposed at the bevatron

Chamberlain, O.; Chupp, Warren W.; Goldhaber, G.; Segrè, E.; Wiegand, C.; Amaldi, E.; Baroni, G.; Castagnoli, C.; Franzinetti, C.; Manfredini, A.

doi:10.1007/bf02745430

Cited by 34 publications

(22 citation statements)

References 10 publications

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“…The data from KEK are approximately reproduced when accounting for the internal momentum distribution of the deuteron which provides a natural explanation for the large enhancement of the/5 cross section in d+A as compared to p+A. 25.40.-h Antiproton production at energies of a few GeV/u is the most extreme subthreshold production process and has been observed in proton-nucleus collisions some time ago [1][2][3]. In the last years the problem was taken up again at KEK [4] and GSI [5] with new detector setups.…”

mentioning

confidence: 90%

Antiproton production inp+A andd+A reactions at subthreshold energies

Cassing

Lykasov

Teis

1994

Z. Physik A - Hadrons and Nuclei

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The production of antiprotons in proton-nucleus and deuteron-nucleus collisions is analyzed with respect to onestep nucleon-nucleon (NN ---+ NNp/5) and secondary Anucleon (AN ~ NNN/5) production channels within a phase-space model incorporating the selfenergies of the baryons. It is found that contrary to nucleus-nucleus collisions the A induced reaction channels are of minor importance except at very low bombarding energies. The data from KEK are approximately reproduced when accounting for the internal momentum distribution of the deuteron which provides a natural explanation for the large enhancement of the/5 cross section in d+A as compared to p+A. 25.40.-h Antiproton production at energies of a few GeV/u is the most extreme subthreshold production process and has been observed in proton-nucleus collisions some time ago [1][2][3]. In the last years the problem was taken up again at KEK [4] and GSI [5] with new detector setups. Various descriptions for these data have been proposed (cf. PACS:[6] and refs. therein), most of them based on the assumption of kinetic and chemical equilibrium.First fully relativistic transport calculations for antiproton production including/~ annihilation as well as the change of the quasi-particle properties in the medium have been reported in [7]. There it was found that according to the reduced nucleon mass in the medium the threshold for /5-production is shifted to lower energy and the antiproton cross section prior to annihilation becomes dramatically enhanced as compared to a relativistic cascade calculation where no in-medium effects are incorporated. In fact, Teis et al. [6] have shown recently (within the relativistic BUU approach) that the t5 yields for p + A and A + A can be well reproduced simultaneously when employing proper selfenergies for the baryons in the dense medium.It is the aim of the present note to investigate the question, whether the KEK data on/5 production [4] -which show a dramatic enhancement for the deuteron projectile at the same bombarding energy per nucleon -can be understood within the same scheme as well. Since the RBUU transport approach is not well suited for modelling the proSupported by BMFT, GSI Darmstadt and Forschungszentrum J/ilich perties of a weakly bound deuteron, we use a phase-space approach [8,9] which allows for a proper incorporation of the deuteron momentum distribution.The phase-space model adopted is described in more detail in [9,10]. Its ingredients are as follows: apart from the elementary differential cross section E,jda@/dak~ the inclusive t5 cross section for p+ A reactions is determined by the momentum distribution p(p) describing the available momentum components in a nucleus as well as by pd(k) in case of d + A reactions. We use a Ganssian fit to the experimental momentum distribution for 12C from [11] and use pd(k) for the deuteron from the Paris NN-potential [12]. Whereas the latter two distributions are known sufficiently well, the t5 production cross section in the medium is still a matter of debate. Here we ado...

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confidence: 90%

Antiproton production inp+A andd+A reactions at subthreshold energies

Cassing

Lykasov

Teis

1994

Z. Physik A - Hadrons and Nuclei

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“…With a threshold at 5.6 GeV, antiproton production in nucleus-nucleus collisions at energies of a few GeV/nucleon is clearly the most extreme subthreshold process in particle production. The first observation of subthreshold antiproton production in proton-nucleus collisions dates back to the 1950s [10] and 1960s [11,12]. The experiments at the BEVALAC [8] and the JINR [9] in the 1980s provided the first evidence of subthreshold antiproton production in nucleus-nucleus collisions.…”

Section: Introductionmentioning

confidence: 99%

“…Deltas are also propagated according to Eqs. (9) and (10) with their self-energies taken to be similar to the nucleon self-energies.…”

Section: Introductionmentioning

confidence: 99%

Subthreshold antiproton production in nucleus-nucleus collisions

Xia

1994

Phys. Rev. C

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Antiproton production in nucleus-nucleus collisions at energies below the threshold for its production from the nucleon-nucleon interaction in free space is studied in the relativistic Vlasov-UehlingUhlenbeck model. The antiproton self-energies in the medium are obtained in the mean-field approximation &om the G-parity transformation of the nucleon self-energies. Due to the decrease of antiproton mass in the medium as a result of the attractive scalar mean field, there is an enhanced production of primordial antiprotons which are, however, mostly annihilated by nucleons as they propagate through the matter. The calculated final antiproton momentum spectrum is seen to agree reasonably with the experimental data.PACS number(s): 25.75.+r, 24.10.Jv

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“…Antiproton production at energies of a few GeV/u is the most extreme subthreshold production process and has been observed in proton-nucleus collisions already more than 20 years ago [5][6][7]. Experiments at the JINR [8] and at the BEVALAC [9,10] have provided, furthermore, first measurements of subthreshold antiproton production in nucleus-nucleus collisions.…”

Section: Introductionmentioning

confidence: 99%

Analysis of subthreshold antiproton production inp-nucleus and nucleus-nucleus collisions in the relativistic Boltzmann-Uehling-Uhlenbeck approach

et al. 1994

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We calculate the subthreshold production of antiprotons in the Lorentzcovariant RBUU approach employing a weighted testparticle method to treat the antiproton propagation and absorption nonperturbatively. We find that the antiproton differential cross sections are highly sensitive to the baryon and antiproton selfenergies in the dense baryonic environment. Adopting the baryon scalar and vector selfenergies from the empirical optical potential for proton-nucleus elastic scattering and from Dirac-Brueckner calculations at higher density ρ > ρ 0 we examine the differential antiproton spectra as a function of the antiproton selfenergy. A detailed comparison with the available experimental data for p-nucleus and nucleus-nucleus reactions shows that the antiproton feels a moderately attractive mean-field at normal nuclear matter density ρ 0 which is in line with a dispersive potential extracted from the free annihilation cross section. † Supported by BMFT, GSI Darmstadt and KFA Jülich.

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On the observation of an antiproton star in emulsion exposed at the bevatron

Cited by 34 publications

References 10 publications

Antiproton production inp+A andd+A reactions at subthreshold energies

Antiproton production inp+A andd+A reactions at subthreshold energies

Subthreshold antiproton production in nucleus-nucleus collisions

Analysis of subthreshold antiproton production inp-nucleus and nucleus-nucleus collisions in the relativistic Boltzmann-Uehling-Uhlenbeck approach

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