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1.
V.P. Mikhailyuk 《The European Physical Journal A - Hadrons and Nuclei》2000,9(4):473-477
The differential cross-section for elastic scattering of deuterons at 700 MeV, 6Li and 6He at 2.07 GeV nuclei on 12C nucleus is calculated under the assumption of two-cluster (for deuterons and 6Li) and three-cluster (for 6He) structure of incident particle. For 6Li-12C and 6He-12C elastic scattering it is shown that there are quantitative distinctions in the behaviour of the observables calculated in
the above approaches.
Received: 13 October 1999 / Accepted: 3 January 2001 相似文献
2.
N. Ikeda F. Nakamura K. Mizuuchi T. Sugimitsu S. Teruyama T. Okamoto H. Fujita S. Morinobu 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):491-502
The 16O(13C,12C)17O reaction at 50 MeV has been investigated using the kinematical coincidence method. Polarization tensors t
20 and t
40 of 12C[2+
1] for the quantization axis taken along the direction of propagation have been measured by analyzing the energy spectrum of
12C[2+
1], modulated by the effect of γ ray emission. The deduced t
40 values significantly deviate from zero, contrary to the prediction of the distorted-wave Born approximation theory based
on one-step p shell neutron stripping without spin-dependent interactions. The phenomenological spin–orbit interaction necessary
to reproduce the magnitude of measured t
40 is found to be much larger than the folding model prediction. It is shown that the experimental polarization tensors as well
as the cross sections can be reproduced by introducing multi-step processes involving excitations in 12C and 13C without introducing spin-dependent interactions.
Received: 2 August 1999 / Revised version: 3 February 2000 相似文献
3.
T. Nakamura 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):33-37
We present the recent experimental results on the 6He structure studied by the 6Li(t, 3He)6He reaction at 336 MeV. Above the conspicuous peaks for ground and first excited states for 6He, we have observed a broad structures at E
x∼ 5 MeV, and E
x∼ 15 MeV. The angular distribution of this structure exhibits the dominance of a ΔL = 1 transition, indicating the existence of intruder dipole states at low excitation energies in 6He. A slight admixture of positive-parity states in this structure has been indicated as well.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
4.
V. Baru J. Haidenbauer C. Hanhart J.A. Niskanen 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):437-446
We present a new parameterization of the trinucleon wave function. As a novel feature a separable parameterization for the
complete wave function is given. In this way any calculation that considers two-body currents only is largely simplified.
To demonstrate this we calculate the π3He scattering length in chiral-perturbation theory. We find reasonable agreement with experimental values inferred from data
on level shifts in pionic 3He bound states. The relevance of the π-triton system for an alternative determination of the πN scattering lengths is discussed.
Received: 12 August 2002 / Accepted: 25 November 2002 / Published online: 25 February 2003
RID="a"
ID="a"e-mail: c.hanhart@fz.juelich.de
Communicated by V. Vento 相似文献
5.
Low energy single nucleon transfer reactions are proposed as a tool to investigate the structure of nuclei far off stability.
Experimental concepts and conditions are discussed, in particular high resolution γ-ray spectroscopy after single nucleon
pickup reactions. Nuclear structure is described by Skyrme Hartree-Fock calculations including pairing. As representative
examples, binding energies, radii and wave functions for Mg and Sn isotopes are calculated. In the neutron deficient Mg isotopes
a proton skin is found. At the neutron driplines the Mg and Sn isotopes develop extended neutron skins. The nuclear structure
results are used in DWBA and EFR-DWBA transfer calculations. Single nucleon transfer reactions of 32,36Mg and exotic Sn beams on targets ranging from 2H to 24Mg in inverse kinematics are explored. The one-nucleon transfer cross sections decrease strongly for high-Z targets. An impact
parameter analysis shows that the transfer process is selective on the tails of the wave functions. The largest cross sections
are obtained for 2H and 9Be targets at incident energies of E
lab
= 2-5 MeV/u. The energy-momentum dependence is closely related to the special properties of wave functions of weakly bound
states. Two-neutron (p,t) stripping reactions are studied for a 6He projectile. A strong competition of sequential and direct processes is found at low energies.
Received: 1 October 1997 / Revised version: 25 November 1997 相似文献
6.
N. Ikeda F. Nakamura Y. Inotani K. Koga M. Koga S. Koto T. Sugimitsu H. Fujita S. Morinobu 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):213-220
The 16O(11B,12C)15N reaction at 41.25 MeV has been investigated using the kinematical coincidence method. Polarization tensors t20 and t40 of 12C[2+
1] for the quantization axis taken along the direction of propagation have been measured at center-of-mass angles (Θc.m.) between 48° and 62° by analyzing the energy spectrum of 12C[2+
1] modulated by the effect of γ-ray emission. The cross-sections of the transfer reactions leading to the 12C[g.s.]+15N[g.s.], 12C[2+
1]+15N[g.s.] and 12C[g.s.]+15N[3/2-
1] final states have also been measured in the range 48°≤Θc.m.≤ 120°. The polarization tensor terms of 12C[2+
1] largely deviating from zero have been observed, contrary to the prediction by the distorted-wave Born approximation (DWBA).
The one-step DWBA calculation also fails in describing the transfer reaction cross-sections. It is shown that the coupled
channel model calculation including excitations and reorientations in 11B and 12C satisfactorily reproduces both the tensor terms and the cross-sections of the transfer reactions. The multi-step processes
passing through the excited states of 11B are found to significantly contribute to the reaction.
Received: 3 July 2000 / Accepted: 15 September 2000 相似文献
7.
M. Ito Y. Sakuragi Y. Hirabayashi 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):373-383
The nuclear reaction dynamics leading to the formation of recently discovered resonance in the mutual-02
+ channel of the 12C+12C inelastic scattering around E
c.m.≃ 32 MeV is studied in terms of the dynamic polarization potential (DPP) induced by the channel coupling among various excited states in 12C. The microscopic 3α cluster-model wave functions are used to generate the 12C−12C diagonal and coupling potentials in the double-folding model. It is found that DPP for the 02
++ 02
+ channel is an unusually strong attractive potential which even exceeds the zeroth-order folding-model potential of this channel
around the nuclear surface region and that the strong coupling between the 02
+ and 22
+ states is predominantly responsible for the unusual DPP in this channel. The effective potential, the sum of the original
folding-model potential and the attractive DPP, is found to generates resonance states in the same energy region as that of
the resonance states generated by the original folding-model potential but the former states are found to be higher-nodal
states having four additional radial nodes. Similar but more moderate property of DPP is also found in the entrance (elastic)
channel. These results suggest that the reaction dynamics of generating the resonance in the 12C(02
+) +12C(02
+) channel may rather differ from that of the simple crossing of the zeroth-order molecular band generated by the potentials
in the entrance and exit channels suggested by the standard band-crossing model.
Received: 17 December 1998 / Revised version: 1 March 1999 相似文献
8.
9.
V. P. Ladygin L. S. Azhgirey S. V. Afanasiev V. V. Arkhipov V. K. Bondarev G. Filipov A. Yu. Isupov V. I. Ivanov A. A. Kartamyshev V. A. Kashirin A. N. Khrenov V. I. Kolesnikov V. A. Kuznetsov N. B. Ladygina A. G. Litvinenko S. G. Reznikov P. A. Rukoyatkin A. Yu. Semenov I. A. Semenova G. D. Stoletov V. N. Zhmyrov L. S. Zolin 《The European Physical Journal A - Hadrons and Nuclei》2000,8(3):409-416
The tensor Ayy and vector Ay analyzing powers in the inelastic scattering of deuterons with a momentum of 4.5 GeV/c on beryllium at an angle of 80 mr in the vicinity of baryonic resonances excitation have been measured. The Ayy data being in good agreement with the previous results obtained at a zero angle demonstrate an approximate t scaling up to - 0.9 (GeV/c)2. The results of the experiment are compared with the predictions of the multiple-scattering and -meson exchange models.
Received: 20 April 2000 / Accepted: 29 May 2000 相似文献
10.
V.Yu. Grishina L.A. Kondratyuk E.L. Bratkovskaya M. Büscher W. Cassing 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):277-285
We investigate the reactions πN↦a
0
N and pp↦da
0
+ near threshold and at medium energies. An effective Lagragian approach and the Regge pole model are applied to analyze different
contributions to the cross-section of the reaction πN↦a
0
N. These results are used to calculate the differential and total cross-sections of the reaction pp↦da
0
+ within the framework of the two-step model in which two nucleons produce an a0-meson via π-meson exchange and fuse to a deuteron. The necessity of new measurements on a0 production and branching fractions (of its decay to the K
and πη channels) is emphasized for clarifying the a0 structure. Detailed predictions for the reaction pp→da
0
+ are presented for the energy regime of the proton synchrotron COSY-Jülich.
Received: 4 August 2000 / Accepted: 17 September 2000 相似文献
11.
M. Wolf J. Ahrens R. Beck V. Hejny J.D. Kellie M. Kotulla B. Krusche V. Kuhr R. Leukel V. Metag J.C. Nacher R. Novotny V. Olmos de León R.O. Owens F. Rambo A. Schmidt M. Schumacher U. Siodlaczek H. Ströher J. Weiß F. Wissmann 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):5-8
Double neutral pion photoproduction from the proton has been measured at MAMI for photon energies between threshold and 820
MeV. The reaction was identified by an invariant mass and missing mass analysis. From threshold up to 370 MeV the total cross-section
does not exceed 30 nb. For higher energies it shows a smooth rise until it reaches a maximum of about 10 μb at E
γ = 740 MeV. Dalitz plots of m
2(π0π0) versus
m
2(p,π0) for seven bins of incident photon energy have been analysed. For E
γ > 610 MeV, a strong contribution of a sequential decay is observed with the Δ(1232)-resonance as intermediate state. A comparison
to model calculations shows that these sequential decays presumably originate from the D
13(1520) and also the P
11(1440)-resonance.
Received: 6 June 2000 / Accepted: 18 August 2000 相似文献
12.
D. Pierroutsakou M. Di Toro F. Amorini V. Baran A. Boiano A. De Rosa A. D'Onofrio G. Inglima M. La Commara A. Ordine N. Pellegriti F. Rizzo V. Roca M. Romoli M. Sandoli M. Trotta S. Tudisco 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):423-435
We report on the results obtained from the study of the 32S + 64Ni and 32S + 58Ni peripheral reactions at incident energies E
lab = 288 MeV and E
lab = 320 MeV, respectively. High-energy γ-rays were detected in an array of 8 seven-pack BaF2 clusters. Coincidence with complex fragments detected in 12 three-stage telescopes ensured the selection of peripheral reaction
events. All of the relevant reaction parameters were kept constant with the exception of the different initial dipole moment
caused by the different entrance channel charge asymmetry. While for quasi-elastic events no N/Z effect was observed in the differential γ-ray multiplicities of the two reactions, for deep-inelastic events a larger dipole
γ-ray emission occurs during the more N/Z asymmetric reaction. A theoretical interpretation based on a collective Bremsstrahlung analysis of the reaction dynamics
is presented.
Received: 26 September 2002 / Accepted: 13 November 2002 / Published online: 6 March 2003
RID="a"
ID="a"e-mail: pierroutsakou@na.infn.it
RID="b"
ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Padova, Italy.
Communicated by C. Signorini 相似文献
13.
P. Bartsch D. Baumann J. Bermuth K. Bohinc R. Böhm D. Bosnar N. Clawiter S. Derber M. Ding M.O. Distler A. Ebbes I. Ewald J.M. Friedrich J. Friedrich P. Jennewein M. Kahrau M. Kohl A. Kozlov K.W. Krygier M. Kuss A. Liesenfeld H. Merkel P. Merle U. Müller R. Neuhausen T. Pospischil M. Potokar D. Rohe G. Rosner H. Schmieden S. Širca A. Wagner T. Walcher M. Weis S. Wolf 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):209-216
The reaction 12C(e,e'Δ0)11C →12C(e,e'pπ−)11C was investigated at the Mainz Microtron MAMI in a triple coincidence measurement using the three spectrometer setup of the
A1 Collaboration. The good missing mass resolution of σm= 0.27 MeV/c2 allowed to select the events belonging to the ground state of 11C. Cutting on these events the excitation energy spectra of 12CΔ0 show evidence for two peaks of about 4 MeV width (FWHM) at 282 MeV and 296 MeV with a significance of about 4.5 standard
deviations. The peaks are interpreted in a simple weak coupling model as bound Δ0 states in 12CΔ0.
Received: 23 December 1998 相似文献
14.
Yu.E. Penionzhkevich Yu.A. Muzychka S.M. Lukyanov R. Kalpakchieva N.K. Skobelev V.P. Perelygin Z. Dlouhy 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):123-127
The experimentally measured excitation functions for the fission and 4n evaporation channels are presented for the 6He + 209Bi reaction. The secondary 6He beam was produced using the special beam line (Q4DQ-spectrometer) of the U400M accelerator at FLNR, JINR. The comparison
of the obtained experimental data with similar results for the 4He + 209Bi reaction shows that in the case of the 6He + 209Bi reaction a significant enhancement of the cross-section is observed for energies above the barrier. In order to get an
agreement between the experimental data and the theoretical calculations it is necessary to reduce the Coulomb barrier by
15-20% , which corresponds to an increase of the parameter r0 of the nuclear potential up to 1.5-1.6 fm.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
15.
J.G. Messchendorp A. Sibirtsev W. Cassing V. Metag S. Schadmand 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):95-103
Simulations based on a coupled-channel transport model have been performed to analyze the feasibility to study the in-medium
ω mass exploiting the process γ + A→π0γ + X for C, Ca and Nb nuclei. The distortions due to final-state interactions of the π0 and background contributions from the reaction γ + A→π0π0 + X are found to be small in the mass range of interest ( 0.6 < M
π0γ < 0.8 GeV). Furthermore, the effect of the detector resolution on the π0γ mass determination is discussed.
Received: 5 December 2000 / Accepted: 18 May 2001 相似文献
16.
R. Kalpakchieva H.G. Bohlen W. von Oertzen B. Gebauer M. von Lucke-Petsch T.N. Massey A.N. Ostrowski Th. Stolla M. Wilpert Th. Wilpert 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):451-461
New information has been obtained on excited states of the neutron-rich boron isotopes 14B, 15B and 16B, using the reactions 12C(14C,12N)14B, 13C(14C,12N)15B and 14C(14C,12N)16B at about 24 MeV/A. The mass excess of 16B has been measured for the first time, it is 37.08(6) MeV. This means that 16B is unbound by only 0.04(6) MeV. Furthermore, the nucleus 13B has been investigated with the four reactions 16O(14C,17F), 12C(14C,13N), 12C(13C,12N) and 12C(15N,14O). Choosing different target-projectile combinations, it was possible to populate states with different selectivity. New
states are observed in 13B at excitation energies above the threshold for two-neutron decay.
Received: 27 December 1999 / Revised version: 11 February 2000 相似文献
17.
P. Descouvemont 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):413-419
The 9Be and 9B nuclei are investigated in a microscopic three-cluster model involving α + α +
n (or α + α +
p) configurations. The 8Be (0
+
, 2
+
) +
n and 5He (3/2
-
, 1/2
-
) + α (or mirror) channels are included by taking account of the unstable nature of 8Be and 5He. Spectroscopic properties of 9Be and 9B are analyzed. We show that the 5He + α configurations cannot be neglected to derive accurate results. The 9Be(γ,αα)n photodisintegration cross-section is shown to be mainly determined by 8Be + n channels at low energies, but 5He + α channels become important beyond E
γ≈ 4 MeV.
Received: 7 September 2001 / Accepted: 19 November 2001 相似文献
18.
U. Siodlaczek P. Achenbach J. Ahrens H.-J. Arends R. Beck R. Bilger H. Clement V. Hejny J.D. Kellie M. Kotulla B. Krusche V. Kuhr R. Leukel J.C. McGeorge V. Metag R. Novotny V. Olmos de León F. Rambo M. Schepkin A. Schmidt H. Ströher G.J. Wagner Th. Walcher J. Weiß F. Wissmann M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):309-311
The reaction γd↦π0
X has been measured with TAPS at MAMI in the energy range E
γ = 140-300 MeV. Using the Glasgow tagging spectrometer a photon energy resolution of 0.8 MeV was achieved. The energy excitation
functions of integral and differential total cross-sections show no structures of statistical significance > 2σ. Upper limits
for the production of narrow isoscalar or isovector dibaryons with masses m? 2100 MeV/c2 were deduced. They are in the range 2-5 μb averaged over the 0.8 MeV energy resolution.
Received: 25 October 2000 / Accepted: 24 November 2000 相似文献
19.
Yun Chang Shin Bong Soo Han Myung Ki Cheoun K.S. Kim Il-Tong Cheon 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):269-276
A SU(2) effective Lagrangian is extended to a SU
L(3) ⊗SU
R(3) by including the vector and axial vector meson. With this effective Lagrangian, electromagnetic form factors of charged
pion and kaon are calculated in both time- and space-like regions. The pseudoscalar meson loops are taken into account. Good
agreement with experimental data is obtained for those form factors and charged pseudoscalar meson radii. Decay widths of
ρ→ππ and φ→K
+
K
- are also calculated and shown to agree with experimental data very well.
Received: 20 December 1999 / Accepted: 12 October 2000 相似文献
20.
V. Koptev M. Nekipelov M. Büscher S. Dymov M. Hartmann V. Hejny H.R. Koch N. Lang S. Mikirtichyants H. Ohm A. Petrus Z. Rudy R. Schleichert A. Sibirtsev K. Sistemich H. Ströher K.-H. Watzlawik 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):235-240
Results of a first experiment on (K+p) and (K+d) correlations from proton-carbon (pC) and proton-deuteron (pd) interactions at beam energies above and much below the threshold for elementary kaon production in nucleon-nucleon reactions
( T
NN = 1580 MeV) are discussed. These data, obtained with the ANKE spectrometer at COSY-Jülich, provide first direct evidence
for K+ production via the two-step mechanism and an indication for a cluster mechanism. It is shown that both processes contribute
significantly in pC collisions at 1200 MeV, while they are strongly suppressed at 2300 MeV and also in pd-interactions at 1344 MeV. It is emphasized that the underlying kinematics can be exploited to distinguish between these reaction
mechanisms.
Received: 26 November 2002 / Accepted: 26 March 2003 / Published online: 20 May 2003 相似文献