Neutral pion and hard photon production in heavy ion collisions around 100-MeV/nucleon

Badala, A. ; Barbera, R. ; Palmeri, A. ; et al.
INFN-BE-96-03, 1996.
Inspire Record 426825 DOI 10.17182/hepdata.10016

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17 data tables

Axis error includes +- 0.0/0.0 contribution (?////The source and the value of the systematic errors is not considered).

Axis error includes +- 0.0/0.0 contribution (?////The source and the value of the systematic errors is not considered).

Axis error includes +- 0.0/0.0 contribution (?////The source and the value of the systematic errors is not considered).

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Deep-subthreshold eta and pi0 production probing pion dynamics in the reaction Ar + Ca at 180-A-MeV.

Martinez, G. ; Charbonnier, Y. ; Aphecetche, L. ; et al.
Phys.Rev.Lett. 83 (1999) 1538-1541, 1999.
Inspire Record 508818 DOI 10.17182/hepdata.19447

We report on a measurement of subthreshold η and π0 mesons in the reaction Ar+Ca at 180A MeV. We find that the ratio of the η to π0 meson-production cross section is more than a factor of 20 smaller than the one expected from threshold-energy scaling of meson production. In addition, the multiplicity of high mt π0 increases faster with the centrality of the reaction than the multiplicity of the bulk of π0 mesons. This behavior is explained by the rescattering of π mesons in nuclear matter at the origin of most energetic particles.

2 data tables

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Pion reabsorption in heavy ion collisions interpreted in terms of the Delta capture process

Holzmann, R. ; Schubert, A. ; Hlavac, S. ; et al.
Phys.Lett.B 366 (1996) 63-68, 1996.
Inspire Record 402497 DOI 10.17182/hepdata.41988

We have measured energy-differential cross sections for π 0 production in 36 Ar+ 197 Au collisions at 95 MeV/u. From an analysis of spectral features due to pion final-state interactions we have estimated the cross section of the capture process Δ + N → N + N in the center-of-mass energy range s ≃2.05−2.25 GeV . Within the frame of BUU calculations, our results support the extension of the detailed-balance principle to broad-width resonances.

1 data table

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Multistep production of eta and hard pi0 mesons in subthreshold Au Au collisions.

Wolf, A.R. ; Appenheimer, M. ; Averbeck, R. ; et al.
Phys.Rev.Lett. 80 (1998) 5281-5284, 1998.
Inspire Record 471975 DOI 10.17182/hepdata.41989

The neutral π0 and η mesons are studied in 197Au−197Au collisions at an incident energy of 800AMeV, substantially below the threshold for η production in N−N collisions. While the gross π0 multiplicity increases almost linearly with the number of participant nucleons, the multiplicities of η and hard π0 mesons show a stronger than linear dependence. The nonlinearity is governed by the average transverse-mass excess 〈mt〉−(s−2mN) of the mesons and is insensitive to their final-state interaction in the nuclear medium.

4 data tables

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Inclusive pi0 production in C C and C Cu interactions at a momentum of 4.5-GeV/c per nucleon. (In Russian)

Abraamian, Kh.U. ; Galoian, A.S. ; Izyurov, V.M. ; et al.
Phys.Atom.Nucl. 60 (1997) 1843-1847, 1997.
Inspire Record 429267 DOI 10.17182/hepdata.17172

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1 data table

Cumulative number COL=(M(N)*E(PI0)-1/2*M(PI0)**2)/E(N)*M(N) - E(N)*E(PI0) -- M(N)**2 + P(N)*P(PI0)*COS(THETA(PI0).


Mass dependence of pi0 production in heavy ion collisions at 1-A/GeV

Schwalb, O. ; Pfeiffer, M. ; Berg, F.-D. ; et al.
Phys.Lett.B 321 (1994) 20-25, 1994.
Inspire Record 376130 DOI 10.17182/hepdata.28781

The production of neutral pions has been studied in the reactions 40 Ar + nat Ca , 86 Kr + nat Zr and 197 Au + 197 Au at 1 A GeV. For high energy pions emitted from the heavier systems a steeper than linear rise of the pion multiplicity with the centrality of the reaction is observed, indicating a pion production process other than binary nucleon-nucleon collisions. At low transverse momenta an enhancement of the π 0 -multiplicity increasing with the mass of the collision system is found. Systematic discrepancies between the experimental results and recent BUU, QMD and Cascade calculations are discussed.

6 data tables

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RESULTS OF AN EXTRAPOLATION TO THE FULL SOLID ANGLE TAKING THE EXPERIMENTALTEMPERATURES INTO ACCOUNT.

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Production of eta mesons in 200-A/GeV S + S and S + Au reactions

The WA80 collaboration Albrecht, R. ; Antonenko, V. ; Awes, T.C. ; et al.
Phys.Lett.B 361 (1995) 14-20, 1995.
Inspire Record 397305 DOI 10.17182/hepdata.41686

Minimum Bias production cross sections of $\eta$ mesons have been measured in 200AGeV S+Au and S+S collisions at the CERN SPS by reconstructing the $\eta\rightarrow\gamma\gamma$ decay. The measurements have been made over the rapidity range $2.1 \leq y \leq 2.9$ using the leadglass spectrometer of WA80. Within the statistical and systematical uncertainties the spectral shapes of $\pi~0$ and $\eta$ mesons yields are identical when their invariant differential cross section is plotted as a function of the transverse mass. The relative normalization of the $\eta$ to $\pi~0$ transverse mass spectra is found to be $0.53 \pm 0.07$ for S+Au and $0.43 \pm 0.15$ for S+S reactions. Extrapolation to full phase space leads to an integrated cross section ratio of $\eta$ to $\pi~0$ mesons of $0.15 \pm 0.02 {\rm (stat.)} \pm 0.02 {\rm (syst.)}$, and $0.12 \pm 0.03 {\rm (stat.)} \pm 0.02 {\rm (syst.)}$ for S+Au and S+S collisions, respectively.

6 data tables

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Subthreshold pi0 production in the reactions Mg-24 (alpha, pi0) X at 43-MeV/A and Mg-24 (O-16, pi0) X at 24-MeV/A and 33-MeV/A

Waters, M. ; Machner, H. ; Gotta, D. ; et al.
Nucl.Phys.A 564 (1993) 595-608, 1993.
Inspire Record 365059 DOI 10.17182/hepdata.16594

The subthreshold production of neutral pions was studied in the reactions 24 Mg(α,π 0 )X at 43 MeV·. A and 24 Mg( 16 O,π 0 )X at 24 and 33 MeV·. A . The energies and emission angles of the two coincident photons from the π 0 -decay were measured with a lead glass shower detector. The cross sections of 3.5 and 6.6 nb from the 16 O-induced reactions are compatible with other experiments in this energy region. For the α-induced reaction a production cross section of 1.3 nb was found. Here, only 22 MeV above the absolute threshold, the pion emission from an excited Δ -nucleon hole state is strongly suppressed. The differential cross sections at very backward angles are by an order of magnitude bigger than the yields at 90° pointing to a strong absorption of the produced pions by the larger target nucleus.

1 data table

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Single photon and neutral meson production from WA80

The WA80 collaboration Santo, R. ; Albrecht, R. ; Awes, T.C. ; et al.
Nucl.Phys.A 566 (1994) 61C-68C, 1994.
Inspire Record 36273 DOI 10.17182/hepdata.9268

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2 data tables

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Investigation of pion absorption in heavy ion induced subthreshold pi0 production

Mayer, R.S. ; Henning, W. ; Holzmann, R. ; et al.
Phys.Rev.Lett. 70 (1993) 904-907, 1993.
Inspire Record 339110 DOI 10.17182/hepdata.42032

We present results from an experimental study of reabsorption effects in subthreshold π0 production in the reaction Xe129+197Au at 44 MeV/nucleon. Within the picture of pion generation in nucleon-nucleon scattering we deduce, from our data and from a comparison with the systematics of production cross sections available for lighter reaction systems, information on the π0 absorption length in nuclear matter. For the π0 kinetic-energy range ≃5–100 MeV the energy-averaged λabs and its momentum dependence are obtained, and compared with optical-model calculations.

3 data tables

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