共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Benlliure P. Armbruster M. Bernas C. Böckstiegel S. Czajkowski C. Donzaud H. Geissel A. Heinz C. Kozhuharov P. Dessagne G. Münzenberg M. Pfützner C. Stéphan K.-H. Schmidt K. Sümmerer W. Schwab L. Tassan-Got B. Voss 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):193-198
Projectile fragmentation of 238U in a lead target was investigated at a bombarding energy of 750 A MeV. Isotopic production cross sections of about 250 different projectile fragments in the element range Z= 30–53 were measured with the FRagment Separator (FRS). The magnetic selection and the kinematical analysis of the measured
isotopes allowed to disentangle fission and fragmentation residues. The mass loss of these residues indicates a violent collision
where a large amount of energy is dissipated. The position of the fragmentation corridor defined by the measured residues
was used to determine an effective proton-evaporation barrier.
Received: 3 October 1997 / Revised version: 27 February 1998 相似文献
2.
L.V. Fil'kov V.L. Kashevarov E.S. Konobeevski M.V. Mordovskoy S.I. Potashev V.A. Simonov V.M. Skorkin S.V. Zuev 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):369-374
The analysis of new experimental data, obtained at the Proton Linear Accelerator of INR, with the aim to search for supernarrow
dibaryons in the pd↦ppX
1 and pd↦pdX
2 reactions is presented. Narrow peaks with an experimental width of 5 MeV at masses of 1904±2, 1926±2, and 1942±2 MeV have
been observed in missing mass M
pX1 spectra. In the missing mass M
X1 spectra, the peaks at M
X1 = 966±2, 986±2, and 1003±2 MeV have been found. The analysis of the data obtained leads to the conclusion that the observed
peaks in M
pX1 spectra are most likely supernarrow dibaryons, the decay of which into two nucleons is forbidden by the Pauli exclusion principle.
An alternative interpretation of the spectra by assuming a decay of the supernarrow dibaryons in “exotic baryon states” with
masses M
X1 is discussed.
Received: 22 October 2001 / Accepted: 15 November 2001 相似文献
3.
Zhi Yong He Gen Ming Jin Zu Yu Li Li Min Duan Guang Xi Dai Bao Guo Zhang He Yu Wu Wan Xin Wen Yu Jin Qi Qing Zheng Luo Su Fang Wang 《The European Physical Journal A - Hadrons and Nuclei》1998,1(1):61-64
Emission orders of light charged particles and Li fragments from highly excited fissioning nuclei in the reaction of 40Ar+197Au at E
beam
/A=25 MeV have been studied by measuring difference velocity distributions of two correlated particles at small relative angles
in coincidence with two fission fragments. By comparing the data with three-body trajectory calculations, we found that high
velocity deuterons are emitted prior to high velocity Li fragments but low velocity deuterons are emitted after low velocity
Li fragments. On the other hand, no preferential emission was observed among light particles, such as protons and deuterons.
Furthermore, the emission orders are found to depend only weakly on the mass asymmetry of fission fragments.
Received: 3 June 1997 / Revised version: 23 July 1997 相似文献
4.
C. Signorini M. Mazzocco G.F. Prete F. Soramel L. Stroe A. Andrighetto I.J. Thompson A. Vitturi A. Brondi M. Cinausero D. Fabris E. Fioretto N. Gelli J.Y. Guo G. La Rana Z.H. Liu F. Lucarelli R. Moro G. Nebbia M. Trotta E. Vardaci G. Viesti 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):249-253
Large cross-section reaction channels were measured in the systems 6Li( 7Li) + 208Pb with high statistical accuracy at 5(3) energies around the Coulomb barrier from 29 to 39 MeV. These channels were assigned
(mainly) to the breakup of 6Li, very loosely bound, into α + d and to the breakup of 5Li, produced by n-transfer to the target, into α + p and to similar processes with 7Li beam. The cross-sections with 6Li, S
α = 1.475 MeV, are systematically larger than the 7Li ones. This reflects, most likely, the higher binding energy of 7Li, S
α = 2.468 MeV. Theoretical predictions for the 6Li + 208Pb system which include for 6Li breakup to continuum states within a continuum discretized coupled-channels approach (CDCC) and resonant breakup plus n-transfer
with DWBA reproduce the angular distribution shapes but still underestimate the cross-sections by a factor ∼ 3.
Received: 15 January 2001 / Accepted: 3 March 2001 相似文献
5.
S. Sodaye K. Sudarshan B.S. Tomar A. Goswami S. Mukherjee K. Mahata 《The European Physical Journal A - Hadrons and Nuclei》2002,14(3):371-376
Kinetic-energy spectra and angular distribution of projectile-like fragments have been measured in the reaction of 84 MeV
12C on 169Tm, using the surface barrier silicon-based ΔE-E telescopes. The fragments close to the projectile show typical spectra of quasi-elastic transfer reactions, which were found
to be in agreement with the calculations based on the direct surface transfer reaction model. A significant cross-section
of fast alpha-particles was found at forward angles, reminiscent of incomplete fusion reactions, which could be explained
in terms of the direct surface transfer reaction model after taking into account the level density of continuum states in
the heavy reaction product. The results have been explained in terms of the continuous evolution of the reaction mechanism
as a function of the mass transfer.
Received: 13 March 2002 / Accepted: 3 May 2002 相似文献
6.
R.I. Badran D.J. Parker I.M. Naqib 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):317-325
Excitation functions for the production of eight radioactive products of the reactions of 7Li on 56Fe have been measured up to E(7
Li) = 89 MeV. Recoil range distributions for these products, together with inclusive proton, deuteron, triton and alpha spectra,
have been measured at energies of 50 and 68 MeV. The α, t and d spectra show characteristic “break-up” components at forward
angles, while the recoil distributions show evidence of complete fusion and incomplete-fusion process 56Fe( 7Li,α) 59Co * . A parallel study on 55Mn shows some evidences of the ( 7Li,t) incomplete-fusion process, but the cross-section for this process is significantly less than for the triton fusion process.
The recoil distributions can be reproduced on the assumption that essentially all the observed break-up fragments are in fact
associated with incomplete fusion, but uncertainties in normalisation leave open the possibility of a significant contribution
of pure break-up. A diffraction model of the ( 7Li,α) transfer process reproduces the observed break-up α spectra with some success.
Received: 29 March 2001 / Accepted: 12 November 2001 相似文献
7.
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
8.
E. Vardaci G. La Rana A. Brondi R. Moro A. Principe D. Fabris G. Nebbia G. Viesti M. Cinausero E. Fioretto G. Prete F. Lucarelli E.M. Fiore L. Fiore V. Paticchio P.F. Bortignon 《The European Physical Journal A - Hadrons and Nuclei》1998,2(1):55-60
The α-particle emission from the 28Si+170Er fusion-evaporation reaction at 165 and 185 MeV has been measured and compared with published data relative to the pre-scission
emission in the same reaction. The spectra in the two channels exhibit nearly the same shape in the low energy region, whereas
in the high energy region the spectrum for the fusion-evaporation case features a larger apparent temperature. The interpretation
of the difference in shape between the two decay channels is based on statistical model calculations which account for the
effects due to the different length of the decay chain. Statistical model calculations with standard parameters describe well
the gross features of the alpha particle spectra in the fusion-evaporation channel and the proton spectra in the pre-scission
channel. On the contrary, the model predictions seem to overestimate by ≃2 MeV the emission barrier for the alpha particles
in the pre-fission channel. This effect is ascribed to the larger elongation of the nucleus during the fission process. An
average axis ratio b/a∼ 2 for the emitter is suggested.
Received 29 April 1997 / Revised version 10 September 1997 相似文献
9.
10.
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
11.
D. Pierroutsakou A. Boiano A. De Rosa M. Di Pietro G. Inglima M. La Commara Ruhan Ming B. Martin R. Mordente A. Ordine F. Rizzo V. Roca M. Romoli M. Sandoli F. Soramel L. Stroe M. Trotta E. Vardaci 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):71-76
The 32S + 100Mo and 36S + 96Mo fusionlike reactions were studied at incident energy of E
lab = 298 MeV and 320 MeV, respectively, with the aim of probing the influence of the entrance channel charge asymmetry on the
dipole γ-ray emission. The excitation energy and spin distribution of the compound nucleus created in these reactions were
identical, the only difference being associated with the unequal charge asymmetry of the two entrance channels. High-energy
γ-rays were detected in an array of 9 seven-pack BaF2 clusters. Coincidence with fusionlike residues detected in four PPAC ensured the selection of central reaction events. By
studying the differential γ-ray multiplicity associated with the two reactions it was shown that the dipole strength excited
in the compound nucleus increases with the entrance channel charge asymmetry. From the linearized spectra, the increase of
the GDR γ-ray intensity was found to be ∼ 25% for the more charge asymmetric system. The results are discussed and compared
with those of previous data obtained at different incident energies.
Received: 21 October 2002 / Accepted: 23 December 2002 / Published online: 1 April 2003 相似文献
12.
V. Kleber P. Achenbach J. Ahrens R. Beck V. Hejny J.D. Kellie M. Kotulla B. Krusche V. Kuhr R. Leukel V. Metag R. Novotny V. Olmos de León R.O. Owens F. Rambo A. Schmidt M. Schumacher U. Siodlaczek H. Ströher J. Weiß F. Wissmann M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):1-4
The photoproduction of two neutral pions from the deuteron has been studied for incident photon energies from 200 MeV to
820 MeV with the TAPS spectrometer at MAMI (Mainz Microtron). The total cross-section was determined and used to deduce the
cross-section from the neutron. Due to the good statistical quality of the data Dalitz plots for the three particles in the
exit channel (π0π0
N) could be constructed. The invariant mass distributions derived from them are presented in this paper. They indicate that
the important reaction mechanism in the second resonance region is a sequential decay pattern involving the population of
the Δ(1232)-resonance as an intermediate state.
Received: 5 June 2000 / Accepted: 4 September 2000 相似文献
13.
S.V. Golovkin A.P. Kozhevnikov V.P. Kubarovsky V.F. Kurshetsov L.G. Landsberg V.V. Molchanov V.A. Mukhin S.V. Petrenko V.A. Senko D.V. Vavilov V.A. Victorov V.Z. Kolganov G.S. Lomkatsi A.F. Nilov V.T. Smolyankin 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):409-416
New data for the diffractive reaction p+N→ [Σ0
K
+] +N at E
p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous
study of this reaction. In the mass spectrum M(Σ0
K
+) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously
large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark
baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P
2
T < 0.01 GeV2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
Received: 28 April 1999 相似文献
14.
L. Vannucci P. Boccaccio A. Bologna R.A. Ricci G. Vannini R. Donà I. Massa J.P. Coffin P. Fintz G. Guillaume F. Jundt F. Rami P. Wagner 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):65-77
Final states indicating the presence in the reaction of three-body fragmentation processes has been observed in 32S+59Co and 32S+63Cu dissipative collisions at 5.6 A · MeV. Besides the already observed sequential binary process, data analysis reveals the
presence of prompt ternary break-up of the composite system. Indications on the system configuration at the scission have
been deduced by analyzing the event shape in the momentum phase space. The decay appears to occur in a collinear configuration,
one of the produced fragments originating from the neck which connects the other two. In spite of the large energy dissipation,
structure effects in the charge partition seem to affect part of events.
Received: 3 July 1998 / Revised version: 15 October 1999 相似文献
15.
K. Jessen M. Bergström P. von Brentano A. Dewald B. Herskind H. Meise C. Schumacher G. Sletten O. Stuck D. Weißhaar I. Wiedenhöver J. Wrzesinski 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):113-114
An in-beam experiment with the reaction 122Sn(27Al,4np) at 127 MeV was performed at the Nordball multi-detector array in Roskilde. It provided evidence for a new high-spin
isomer in 144Sm. This isomer with T
1/2= (2.6 ± 0.5) ns at an excitation energy E
x= 9232 keV seems to belong to a family of isomers of similar configuration in neighbouring N= 82 nuclei.
Received: 16 November 1997 相似文献
16.
M.V. Polyakov A. Sibirtsev K. Tsushima W. Cassing K. Goeke 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):115-118
The possibility for an observation of a narrow penta-quark Z+-baryon in NN reactions is discussed. It is shown that the pp↦nΣ+
K
+ reaction at excess energies around 100 MeV above threshold provides optimal conditions for Z+-baryon detection by an analysis of the nK+ invariant mass spectrum, if the Z+ mass is located around 1.5 GeV involving a rather narrow width.
Received: 24 May 2000 / Accepted: 3 August 2000 相似文献
17.
A. Jokinen J.C. Wang J. Äystö P. Dendooven S. Nummela J. Huikari V. Kolhinen A. Nieminen K. Peräjärvi S. Rinta-Antila 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):9-12
Beta decay of a refractory isotope 118Rh produced in symmetric fission and mass separated by the ion guide technique has been applied for the study of low-lying
excited states of 118Pd. The yrast band in 118Pd has been observed up to a 6+ state and the lowest states of the asymmetric γ-band have been identified. The measured half-life of 118Rh is (300±60)ms. The systematics of the excited states in neutron-rich Pd-isotopes implies the saturation towards an O(6) symmetry at N = 70.
Received: 19 June 2000 / Accepted: 1 August 2000 相似文献
18.
B. Tatischeff J. Yonnet M. Boivin M.P. Comets P. Courtat R. Gacougnolle Y. Le Bornec E. Loireleux M. MacCormick F. Reide N. Willis 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):245-267
The reaction pp → pπ+
X was studied at different incident energies around T
p = 2 GeV. Narrow baryonic structures were observed in the missing mass M
X and in the invariant mass M
pπ{+}. The masses of these structures are 1004, 1044, 1094, 1136, 1173, 1249, 1277, and 1384 MeV (and possibly 1339 MeV). Some
of them were also observed at the same masses in the missing-mass spectra of the dp → ppX reaction although with a weaker
signature. Many checks were performed to make sure that these structures were not produced by experimental artifacts. Several
narrow small-amplitude peaks, were also extracted using already published photonucleon cross-sections. The small widths of
all these results, and the stability of the observed structures, regardless of the experiment, were used to conclude that
they are genuine baryons and not merely the consequence of dynamical rescatterings. These baryons cannot be associated with
classical q3 quark configurations. We associate them with two colored-quark cluster configurations.
Received: 3 July 2002 / Accepted: 30 January 2003 / Published online: 5 June 2003 相似文献
19.
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
20.
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