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1.
Production of strange and charm particles by hadron-proton collisions is analyzed in terms of a fire-ball (FB) model assuming the multiplicity of secondaries of a given massm, to be proportional to the FB mass: n(m)M
*, the FB kinematics being determined by the Feynman-Yang scaling, as in the case of production. It is found that (m)1/m
2 and that, using this property together with the scaling, no-free-parameter fits to currently available data of strange and charm particles frompp and p collisions are satisfactory, as well as for the photoproduction of charm mesonD and charm hyperon
c
. 相似文献
2.
Hard form factors for meson-baryon strong couplings as derived from deep inelastic lepton scattering
W. -Y. P. Hwang J. Speth G. E. Brown 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(3):383-389
As stimulated by earlier attempts for obtaining theNN andN form factors from the deep inelastic lepton scattering data, we extend the analysis by taking into account effects of additional mesons including, , ,K, andK
*, with the coupling constants fixed by the lowenergy nucleon-nucleon and hyperon-nucleon scattering data. Contrary to an earlier claim that the NN andN form factor must be very soft (e.g., with the cutoff mass less than 500 MeV in the monopole form), we find, for example, that with all form factors parametrized in the dipole form, a universal cutoff mass of 1150 MeV in the/N sector and 1400 MeV in the/ sector yields predictions in excellent agreement with recently published neutrino data on the momentum fractions carried by thes, , and¯d quarks, as well as consistent with the sea-to-valence ratio extracted from the CDHS data and the Femilab E615 experiment. Similar results can also be obtained by using exponential cutoffs for all couplings, or by using monopole forms for some vertices while retaining dipole forms for the rest. The success of the mesonexchange picture in generating the strangeness content in a proton suggests an alternative understanding of the origin of sea quarks in the proton.We wish to thank G. Garvey, K. Holinde, L.-C. Liu, M. B. Johnson, M. Strikman, A. W. Thomas and Jochen Wambach for helpful conversations. W-Y. P. Hwang wishes to acknowledge the Alexander von Humboldt Foundation for a fellowship to visit Jülich for conducting research. His research works was also supported in part by the National Science Council of the Republic of China. The work of G. E. Brown is supported in part by a Humboldt award, in part by NATO Grant RG85/0093, and in part by the U.S. Department of Energy. 相似文献
3.
A. Scherdin A. Schäfer W. Greiner G. Soff P. J. Mohr 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(3):273-277
The emission of high-energy-rays in the deexcitation of hot40Ca and39K nuclei formed in heavy-ion fusion reactions at excitation energyE
x 90 MeV has been studied. The high energy-rays were measured in coincidence with evaporation residues or light charged particles. The spectrum from the self-conjugated compound nucleus40Ca shows an appreciable yield suppression in the Giant Dipole Resonance (GDR) energy region with respect to the39K, due to isospin selection rules in the dipole-decay. The spectral line shapes of the spectra are well reproduced by using a statistical code which treats explicitly the isospin quantum number in evaluating level densities and transmission coefficients. The GDR parameters determined from the present coincidence measurements are in good agreement with the systematic in theA 40 mass region at lower bombarding energy based on the analysis of inclusive spectra.We thank M. Caldogno for technical support in the development of evaporation residues detectors. We acknowledge the participation of M. Anghinolfi, P. Corvisiero, M. Taiuti and A. Zucchiatti in the early stages of this work. Thanks are due to M. Kicinska-Habior for providing the isospin-dependent code. Discussions with B. Fornal are also gratefully acknowledged. 相似文献
4.
We report the first measurement of the total charge-loss cross section tot=em+nuc and partial cross sections (for Z=1, 2, ..., 9) of 11.4 A GeV197Au nuclei in various targets. The large Coulomb barrier for Au reduces the electromagnetic contribution em in a Pb target to only 18% of nuc, compared with 70% for 14.5 A GeV28Si and 120% for 200 A GeV32S. With em taken to be Z
T
1.8
, nuc can be fitted with nuc=(A
P
1/3
+A
T
1/3
–b)2, with b=0.83 and =59 mb, essentially the same as found at energies of 1 to 2 A GeV. Electromagnetic partial cross sections for Z=1 exceed 40 mb in the Pb, Sn, Cu, and Fe targets and are substantial for larger values ofZ in the heavier targets.We are indebted to D. Beavis and the staff of the Alternating Gradient Synchrotron at Brookhaven National Laboratory for producing the beam of 11.4 A GeV Au ions, to D. Snowden-Ifft for his efforts in developing the automated scanning system, and to S. Hirzebruch for a useful discussion. This work was supported in part by the Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics, of the Department of Energy under contract No. DEAC03-76SF00098. 相似文献
5.
M. Liang H. Ohm B. De Sutter-Pommé K. Sistemich 《Zeitschrift für Physik A Hadrons and Nuclei》1995,351(1):13-18
The half-lives of seven levels in105Mo have been determined with high precision at the fission-product separator Josef. The-- triple coincidence method with plastic and BaF2 scintillators was used for a determination of the time between the
q feeding of a level of interest and its depopulation. A value of
q
=0.38 (1) for the deformation parameter has been deduced from the half-lives of the first and second excited states. The results of Particle-Rotor model-calculations with the Nilsson parameters=0.084 and=0.28 support the assignment of the Nilsson orbital [532] 5/2– to the ground state of105Mo.The authors acknowledge with pleasure fruitful discussions with Profs. W.R. Phillips, I. Ragnarsson and O.W.B. Schult. 相似文献
6.
The130Te(,n)133Xe,130Te(,p)133I,130Te(,pn)132I and130Te(, n)129Te excitation functions for alpha particle energies between 14.7 and 36.5 MeV are presented. Excitation functions for the last three reactions are measured for the first time and more consistent results for (, n) are obtained. The isomeric ratios for the ( n), (, pn) and (, n) reactions were deduced. Calculations based on different theoretical models of equilibrium and preequilibrium decay are compared with the experimental results and discussed. Acceptable presentation of the energy behavior of the measured isomeric ratios was obtained when higher angular momentum depletion for preequilibrium emitted particles was included. The absolute values of the isomeric ratios however remain overestimated.We want to express our gratitude to Prof. Ts. Vylov and Dr. V. Brudanin (Dubna) who supplied us with measurement equipment, to Dr. Chr. Necheva for taking part in the experiments, to the U-200 cyclotron staff and to the direction of the Laboratory of Nuclear Reactions (JINR) for making the irradiation possible and to Dr. E. Dobreva (Sofia) for fruitful discussion of the experimental method. We wish to express our gratitude also to Prof. M. Uhl and the NEA data bank for making the computer code STAPRE available to us and to Prof. J. Ernst (Bonn) for fruitful discussions. This project has been completed with the financial support of the Committee for Science at the Council of Ministers under contract No. 644. 相似文献
7.
S. Hofmann V. Ninov F. P. Heßberger P. Armbruster H. Folger G. Münzenberg H. J. Schött A. G. Popeko A. V. Yeremin A. N. Andreyev S. Saro R. Janik M. Leino 《Zeitschrift für Physik A Hadrons and Nuclei》1995,350(4):281-282
In an experiment carried out to identify element 110, we have observed an-decay chain, that can be unambiguously assigned to269110. In a scries of preexperiments the excitation functions of the fusion reactions50Ti +208Pb258104* and58Fe +208Pb266108* were measured with high precision in order to get the optimum projectile energies for the production of these heavy elements. The cross-section maxima of the 1n evaporation channels were observed at excitation energies of 15.6 MeV and 13.4 MeV, respectively. These data result in an optimum excitation energy of 12.3 MeV of the compound nucleus for the production of269110 in the reaction62Ni +208Pb269110 + 1n. In irradiations at the corresponding beam energy of 311 MeV we have observed a decay chain of 4 subsequent a decays. This can be assigned to the isotope with the mass number 269 of the element 110 on the basis of delayed - coincidences. The accurately measured decay data of the daughter isotopes of the elements 108 to 102, obtained in the previous experiments, were used. The isotope269110 decays with a hair-life of (270
-120
+1300
) s by emission of (11.132±0.020) MeV alpha particles. The production cross-section is (3.3
-2.7
+6.2
) pb. 相似文献
8.
M. Hirsch K. Muto T. Oda H. V. Klapdor-Kleingrothaus 《Zeitschrift für Physik A Hadrons and Nuclei》1994,347(3):151-160
Nuclear matrix elements for double positron emisson (
+
+), positron emission/electron capture (
+/ EC) and double electron capture (EC/EC) in the 2 decay mode and for
+
+ and
+/EC decay in the 0 mode are calculated for the experimentally most promising isotopes58Ni,78Kr,96Ru,106Cd,124Xe,130Ba and136Ce within pn-QRPA. We point out that the matrix element for the 2
+/EC decay differs from the 2
+
+ matrix element, an effect not considered previously. For the neutrino accompanied decays our calculation predicts for the
+/EC and the EC/EC mode half lives which are shorter typically by 4–7 orders of magnitude than those for the double positron emission. However, even for the best candidates typical values for 2
+/EC (2 EC/EC) are still in the range of 1022 ((some) 1021) years. For 0 decay we have calculated all matrix elements relevant for both, the mass mechanism and the right-handed currents for the first time complete. A detailed discussion of the differences between the 0
++, the 0
+/EC and 0
–
– decay is given.This work is supported in part by a Grant-in-Aid for Scientific Research (05243204) from the Ministry of Education, Science and Culture. One of us (M.H.) would like to thank the Japanese Ministry of Education, Science and Culture (Monbusho) for financial support. He also acknowledges valuable discussions with S.S. 相似文献
9.
H. Keller V. Borrel D. Guillemaud-Mueller A. C. Mueller F. Pougheon O. Sorlin P. Baumann F. Didierjean A. Huck A. Knipper G. Walter R. Anne D. Bazin M. Lewitowicz M. G. Saint-Laurent G. Marguier 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(1):67-68
Beta-coincident-rays were measured from implanted44V and42Sc nuclei. These were selected after58Ni+nickel reactions by means of the LISE3 spectrometer at GANIL. The production of the isomeric states was identified by detecting their typical-delayed-ray cascades. From the intensities of the detected-lines the ratio between isomer and ground-state production of44V follows to be 1 to 3.0(4).on leave of absence from GSI Darmstadt. 相似文献
10.
M. Schramm H. Grawe J. Heese H. Kluge K. H. Maier R. Schubart R. Broda J. Grebosz W. Krolas A. Maj J. Blomqvist 《Zeitschrift für Physik A Hadrons and Nuclei》1993,344(4):363-367
208Pb has been excited with inelastic heavy ion scattering of 350 MeV64Ni and 420 MeV82Se on a thick208Pb target. With - coincidence measurements 2 new decays of the 10+ isomer, namely a 34.5 keVE2-transition to 8
2
+
and a 857.7 keVE3 transition to 7– have been found and the wavefunctions of the participating levels deduced. An observed gamma cascade of 295.3, 348.0, 865.4 and 340.2 keV on top of the 10+ isomer is assigned to the particle-hole states with the highest spins 14– 6744.1 keV13– 6448.9 keV12+ 6100.9 keV11+ 5235.6 keV10+ 4895.4 keV.This work has been supported in part through the agreement on scientific cooperation between Poland and Germany. 相似文献
11.
G. Perrin H. Dabrowski G. Duhamel-Chrétien D. Lebrun P. de Saintignon R. Bougault D. Durand A. Genoux-Lubain C. Le Brun J. F. Lecolley M. Louvel 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(2):199-202
Low energy
+ and
– production cross sections have been measured in16O at 65 MeV/u and84Kr at 60 MeV/u induced reactions on7Li,12C,27Al,108Ag and197Au. The results are compared with a previous measurement obtained with16O at 93 MeV/u. Large deviations are observed between light and heavy ion data. At variance with16O, the ratios
–/
+ are independent of the target in the Krypton case. A change in the regime of the projectile-target mass scaling of cross-sections is observed with the heaviest projectile.Experiments performed at GANIL facility, F-14032 Caen, France 相似文献
12.
Th. Frommhold F. Steiper W. Henkel U. Kneissl J. Ahrens R. Beck J. Peise M. Schmitz I. Anthony J. D. Kellie S. J. Hall G. J. Miller 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(3):249-261
The total photofission cross section ,F
for235U and238U has been measured in the energy range 50E
800 MeV at the 855 MeV Mainz Microtron MAMI using energy and time tagged photons (Glasgow Tagger) and a 4 arrangement of position sensitive fragment detectors. Besides the absolute photofission cross section F
, which almost completely exhausts the total photon absorption cross section for these nuclei, fragment mass distributions in this energy domain were determined via time of flight techniques (TOF). The results for the total photofission cross sections ,F
normalized to the atomic numberA for both isotopes coincide, and agree in the-resonance region, within the systematic errors, with the socalledUniversal Curve ,T
/A of the total photon absorption cross section ,T
. At higher energies the cross sections exhibit a smooth behaviour. In particular, it is shown for the first time that there isno resonance-like shape near the D13 resonance (at 710 MeV) as observed for the free proton. This complete suppression of the D13 resonance in complex nuclei is not yet understood on a microscopic level. The fragment mass distributions show a predominantly mass symmetric fission. However, contributions from mass asymmetric fission at some photon energies may give a hint of an increased mass asymmetric fission after the onset of the pion and two pion channels.Excerpt from D26 Supported by the Deutsche Forschungsgemeinschaft, SFB 201 Mainz 相似文献
13.
A new procedure is devised to evaluate the proton form-factor at the ¯pp threshold from experimental data on ¯ppe
+
e
– annihilation at rest. Comparison of the ¯ppe
+
e
– and¯pp
+– processes reveals that annihilation ranges for various channels are ranked in line with quark dynamics.This work has been funded in part by the German Federal Minister for Research and Technology (BMFT) under the contract number 06HD756 相似文献
14.
P. Figuera W. Bohne B. Drescher F. Goldenbaum D. Hilscher U. Jahnke B. Lott L. Pienkowski P. Ziem 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(3):315-320
By using two 4 detector systems for charged particles and neutrons, we measured the evaporated light particles emitted in coincidence with evaporation residues (ER) produced in the reaction32S+58Ni atE(32S) 820 MeV. From the analysis of the light particle multiplicities as a function of the ER velocity, we extracted the maximum excitation energy reached in fusion evaporation reactions for the studied system.Supported by the European Community Programme Human Capital and Mobility 相似文献
15.
S. Michaelsen K. P. Lieb S. J. Robinson 《Zeitschrift für Physik A Hadrons and Nuclei》1991,338(4):371-387
The gamma-ray spectra emitted after thermal neutron capture in highly enriched50V andnatV targets have been studied using in-pile targets at the ILL high flux reactor and pair and germanium detectors. The neutron binding energies in51V and52V were determined to beB
n
(51V)=11051.11(17) keV andB
n
(52V)=7311.22(26) keV. The thermal neutron capture cross-section in50V was measured to be 21
–2
+4
b. From 724 lines attributed to51V, 330 transitions, comprising 90% of the-ray flux, were placed into the level scheme. Fifty-nine primary dipole transitions from the 11/2+ or 13/2+ capture states in51V were established from which the E1 strength distribution was deduced. The energy scaling of these primary transitions was found to follow the E1-giant dipole resonance dominance. Many new levels were established; a number of states proposed in previous (d,p) and (n,) work were confirmed from their primary population and decaying secondary radiations. The density of levels in the high spin (9/2I15/2) region was parametrized with the Fermi gas model. The spin distributions of51V were analyzed and a spin cut-off parameter =2.8 (3) was deduced. — A nearly complete level scheme of52V up to 3.5 MeV excitation and similar results concerning the level density and the primary -ray spectrum were obtained in the51V (n, )52V study.Supported by Deutsches BMFT under contract 06GÖ141 相似文献
16.
K. Okano A. Taniguchi S. Yamada T. Sharshar M. Shibata K. Yamauchi 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(3):243-244
The -decay of150La, the heaviest isotope of lanthanum, has been identified by observing -rays from mass separated activities obtained at KUR-ISOL. From the decay curves of 97.0 and 208.7 keV -rays in150Ce and of Ce-K X-ray, the half-life of150La has been determined as 0.51(3) s. This value is in agreement with theoretical predictions from microscopic theory. 相似文献
17.
M. Karny J. Kownacki D. Seweryniak A. Atac B. Cederwall C. Fahlander A. Johnson A. Kerek L. -O. Norlin J. Nyberg E. Adamides E. Ideguchi R. Julin S. Juutinen W. Karczmarczyk S. Mitarai M. Piiparinen R. Schubart G. Sletten S. Törmänen A. Virtanen 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(3):179-180
Proton rich nuclei close to
100
Sn have been investigated inbeam using the NORDBALL detector array. A beam of 270 MeV58
Ni was used to bombard a
54
Fe target. Reaction channel separation was achieved with a 4 charged particle multi-detector set-up together with a 1 neutron detector wall placed in the forward direction. Gamma-ray transitions belonging to the
111
I nucleus were identified for the first time. A level scheme constructed from --particle-coincidence analysis is proposed. The level structure is discussed within the framework of the shell model and the systematics of the heavier odd iodine nuclei. 相似文献
18.
T. Brohm H. -G. Clerc U. Gollerthan W. Schwab K. -H. Schmidt R. S. Simon 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(4):495-501
In the fusion reactions90Zr(89Y,p)178Pt and90Zr(89Y,)175Ir the sum energy of all emitted rays as well as the energy of the promptly emitted charged particle were measured. From these data the mass-excess values for the evaporation residues178Pt and175Ir were extracted to be(178Pt)=(–32.4±1.1)MeV/c2 and(175Ir)=(–32.0±1.2) MeV/c2. The method provides absolute mass values for nuclides far from stability which can be produced in fusion reactions as evaporation residues in the 1p or 1 channel. The sources of the experimental uncertainties of the method are discussed, and the potential for considerable improvements is outlined.Dedicated to P. Armbruster on the occasion of his 60th birthday 相似文献
19.
A. F. Saad C. T. Zhang R. Collatz P. Kleinheinz R. Menegazzo R. Broda K. H. Maier H. Grawe M. Schramm R. Schubart M. Lach J. Heese J. Eberth W. Krolas S. Hofmann H. Folger J. Blomqvist 《Zeitschrift für Physik A Hadrons and Nuclei》1995,351(3):247-248
In-beam- andn-measurements have for the first time identified excited states in the
72
157
Hf85 nucleus and have established its yrast levels up to 6.5 MeV and I=(51/2). The results of parameter-free 11-particle recoupling calculations in the framework of the shell model for the configurationsh
11
2/8
f
7
2/3
andh
11
2/8
f
7
2/2
h9/2 are in excellent agreement with the observed levels up to 39/2 at 4.758 MeV. A weakly populated 52 ns 29/2+ yrast isomer at 2.876 MeV is assigned as the three-neutron configurationf7/2h9/2i13/2. 相似文献
20.
L. Campajola A. De Rosa A. D'Onofrio L. Gialanella G. Inglima M. La Commara A. Ordine D. Pierroutsakou V. Roca M. Romano M. Romoli M. Sandoli F. Terrasi G. Cardella A. Di Pietro A. Musumarra M. Papa G. Pappalardo F. Rizzo N. Alamanos F. Auger A. Gillibert A. Incicchitti D. Prosperi G. De Angelis E. Fioretto R. Bernabei 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(4):421-425
-rays are measured in coincidence with the dissipative complex fragments from the35Cl +64Ni reaction at 7.7 A MeV. Theoretical -ray coincidence spectra are determined through a fitting procedure using the contribution of the excited fragment statistical -decay calculated by means of the CASCADE code. Whereas the expected statistical spectra fit very well the data in the energy regionE
=2 to 8 MeV, above this energy another emission mechanism in addition to the statistical decay has to be considered in order to reproduce the experimental spectra. Simulations based on the Vlasov equation suggest that this emission could come from the decay of dipole strength excited in the intermediate dinuclear system.The authors are greatly indebted with A. Boiano, A. Buccheri, M. Cipriano, F. Pagano and R. Rocco for their assistance during the set up of the experimental apparatus. Dr. J. Girard and the technical staff of the CEA/DAPNIA-DPhN are acknowledged for the valuable operation of the accelerator. 相似文献