Boltzmann-Uehling-Uhlenbech calculation of total reaction cross-section and fragmentation cross-section

, and have been calculated via the BUU model with soft EOS and 0.8 times of . The density distribution without any adjustable parameters which comes from the RMF model has been introduced into the BUU calculation to replace the normally used one-parameter square-type distribution. The calculated results can reproduce the experimental data well for both halo- and stable-nuclei-induced reactions. Here or is calculated as the difference between of halo nucleus and core nucleus, by assuming . It indicates that this assumption works very well at high energy in the BUU calculation. More experimental measurements are necessary to test the validity of this assumption at intermediate energy.Received: 12 June 2003, Revised: 29 September 2003, Published online: 27 April 2004PACS: 24.10.-i Nuclear reaction models and methods - 25.60.Dz Interaction and reaction cross-sections - 25.60.Gc Breakup and momentum distributions - 27.20. + n      

Study of drip line nuclei through two-step fragmentation

We have studied the structure of light neutron-rich nuclei around N = 16 by employing the in-beam -ray spectroscopy technique using the fragmentation of secondary beams of ^25,26Ne, ^27,28Na and ^29,30Mg isotopes. This secondary-beam cocktail was obtained by the fragmentation of a ³⁶S beam at 77.5 MeV by the SISSI/GANIL facility. By a second-step fragmentation, we have measured -ray-residue coincidences in ^17-20C and ^23,24O and described the obtained levels in the framework of the shell model.Received: 31 October 2002, Published online: 24 February 2004PACS: 23.20.Lv transitions and level energies - 21.60.Cs Shell model - 27.20. + n - 27.30. + t      

Evidence for an isomer in 76 Ni

In the experiment performed at the LISE2000 spectrometer at GANIL neutron-rich nickel isotopes were studied by microsecond isomer spectroscopy. Evidence for an isomer in ⁷⁶Ni is found, consistently with the shell model prediction of an 8 ⁺ state of structure.Received: 24 October 2002, Published online: 17 February 2004PACS: 23.20.Lv transitions and level energies - 27.50. + e      

Hadrons with charmed quarks in matter

We investigate the decay width of excited charmonium states at finite nuclear density with simultaneous modification of both D- and -mesons in nuclear matter. The strongest effect is found for the -meson. The medium modification can be detected by dilepton spectroscopy as substantial broadening and anomalous absorption.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.25.Gv Decays of , , and other quarkonia - 14.40.Lb Charmed mesons - 14.65.Dw Charmed quarks - 24.85. + p Quarks, gluons, and QCD in nuclei and nuclear processes     

Delayed crossing in the \pi h_{9/2} 1/2-[541] band of 173 Lu

High-spin states in the odd-proton nucleus ¹⁷³Lu have been populated in a ¹⁷⁰Er(⁷Li,4n) reaction and the emitted -radiation was detected with the GASP array. The favoured and unfavoured sequences of the band have been considerably extended. The favoured sequence does not show any indication of a band crossing up to a rotational frequency of 0.45 MeV. This is the largest crossing frequency ever observed for 1/2^- [541] bands of odd-proton nuclei with and . Previous Cranked Shell Model (CSM) calculations underestimate the crossing frequency by 100 keV.Received: 19 May 2003, Published online: 11 November 2003PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.70. + q      

Energy dependence of the Λ/Σproduction cross-section ratio in p-p interactions

The production of the - and -hyperons has been measured via the reaction at the internal COSY-11 facility in the excess energy range between 14 and 60 MeV. The transition of the cross-section ratio from about 28 at MeV to the high-energy level of about 2.5 is covered by the data showing a strong decrease of the ratio between 10 and 20 MeV excess energy. Effects from the final-state interactions in the p- channel seem to be much smaller than in the p- channel. Estimates of the effective range parameters are given for the and the systems.PACS: 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy GeV) - 13.75.Ev Hyperon-nucleon interactions - 13.85.Lg Total cross-sections - 25.40.Ep Inelastic proton scattering     

First structure information on the exotic 149 La from the $\beta^-$-decay of 149 Ba

The -decay of ¹⁴⁹Ba to ¹⁴⁹La has been investigated by means of - and X-ray spectroscopy, and a partial level scheme of ¹⁴⁹La has been constructed for the first time. It includes thirteen -rays and ten excited states. The exotic ¹⁴⁹La is the heaviest lanthanum for which spectroscopic information is now available. We have applied the shell correction approach with the axially deformed Woods-Saxon potential in order to calculate the deformation energy for the ¹⁴⁹La ground state. The deformed ground state was found at 0.23, 0 and 0.12.Received: 18 July 2003, Revised: 12 January 2004, Published online: 26 May 2004PACS: 27.60. + j - 29.30.Kv X- and -ray spectroscopy     

\alpha-decay spectroscopy of light odd-odd Bi isotopes - I: 188,190Bi nuclei

Detailed fine-structure -decay studies of ^188,190Bi were performed using the complete-fusion reactions of ^50,52Cr ions with a ¹⁴²Nd target at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of recoil- , recoil- - /X-ray and excitation function measurements. Improved data on the -decay of ^188,190Bi were obtained and a number of new low-lying excited states in the daughters ^184,186Tl were observed. An intruder, presumably 10^- state was identified in ¹⁸⁴Tl, extending the systematics of such states in the odd-odd Tl nuclei beyond the neutron mid-shell at N = 104. Some technical aspects of experiment at recoil separators are also discussed.Received: 14 March 2003, Revised: 1 May 2003, Published online: 2 September 2003PACS: 23.60.+e decay - 27.70.+q - 27.80.+w C.D. OLeary: Present address: Department of Physics, University of York, York, UK.M.J. Taylor: Present address: Department of Physics and Astronomy, Rutgers Univesity, NJ, USA.L. Weissman: Present address: NSCL, Michigan State University, East Lansing, MI 48824-1321 USA.K. Heyde: Present address: EP-ISOLDE, CERN, CH-1211, Geneva 23, Switzerland.     

Experimental signals of \sigma-mesons in nuclei and chiral symmetry

The interaction in the scalar isoscalar channel is studied as a function of the baryonic density in the framework of a chiral unitary approach which successfully reproduces vacuum - phase shifts. We present some results on the -meson pole, which is generated dynamically in our model, in nuclear matter. Finally, we analyze the ( ) reaction on nucleons and nuclei in the kinematical region where the scalar isoscalar scattering amplitude is influenced by the low mass of the in nuclei, and thus, presents a large enhancement close to the position of its pole. Indeed, we find, that the final-state interaction of the pions modified by the nuclear medium produces a large shift of strength of the two-pion invariant-mass distribution in the ( ) channel consistent with recent experimental data.Received: 30 September 2002, Published online: 22 October 2003PACS: 14.40.-n Properties of specific particles: Mesons - 25.20.-x Photonuclear reactions - 21.65. + f Nuclear matter     

Spectroscopic quadrupole moments of high-spin isomers in 193 Pb

The quadrupole interaction of high-spin isomers in ¹⁹³Pb implanted into solid Hg cooled at a temperature T = 170 K has been investigated by the time-differential perturbed -ray angular-distribution method. Spectroscopic quadrupole moment values of eb and 0.45(4) eb have been deduced for the 21/2^- and 33/2 ⁺ three-neutron states, respectively. A much higher value eb has been determined for the 29/2^- isomer, the band head of a magnetic rotational band.Received: 4 November 2002, Published online: 2 March 2004PACS: 21.10.Ky Electromagnetic moments - 27.80. + w      

S = -1 meson-baryon scattering in coupled-channel unitarized Chiral Perturbation Theory

The s-wave meson-baryon scattering amplitude is analyzed for the strangeness S = -1 and isospin I = 0 sector in a Bethe-Salpeter coupled-channel formalism incorporating Chiral Symmetry. Four two-body channels have been considered: , , , . The needed two-particle irreducible matrix amplitude is taken from lowest-order Chiral Perturbation Theory in a relativistic formalism. Off-shell behaviour is parameterized in terms of low-energy constants, which outnumber those assumed in previous works and provide a better fit to the data. The position of the complex poles in the second Riemann sheet of the scattering amplitude determines masses and widths of the and resonances which compare well with accepted numbers.Received: 30 September 2002, Published online: 22 October 2003PACS: 11.10.St Bound and unstable states; Bethe-Salpeter equations - 11.30.Rd Chiral symmetries - 11.80.Et Partial-wave analysis - 13.75.Lb Meson-meson interactionsE. Ruiz Arriola: Spokesperson     

\pi\pi correlations in \gamma + A reactions

Preliminary differential cross-sections of the reactions and with A = ¹ H, ¹² C, and ^nat Pb are presented. A significant nuclear-mass dependence of the invariant-mass distribution is found in the channel. The dependence is not observed in the channel. The in-medium observation in the channel is consistent with an in-medium modification of the interaction in the I = J = 0 channel, changing width and pole position of a resonant state.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.60.Le Meson production - 21.65. + f Nuclear matterJ.G. Messchendorp: For the TAPS and A2 Collaborations     

Cluster structure of <Superscript>16</Superscript>O

A folding potential describing the -scattering on ¹⁶O over a broad energy range 25.8-146.0 MeV is constructed on the basis of -like cluster and unclustered-nucleon configurations of ¹⁶O. The resulting potential does not need any renormalization to fit the angular distribution of elastic cross-sections. The effects of the repulsive part of - and -nucleon interactions are investigated. The analysis suggests that both the - repulsive potential and the unclustered nucleonic configuration in the target are important to describe the scattering data over a broad range of incident energies. The root-mean-square radius for the ¹⁶O nucleus is deduced.Received: 5 December 2002, Published online: 9 October 2003PACS: 25.55.Ci Elastic and inelastic scattering - 24.10.Ht Optical and diffraction models - 21.60.Gx Cluster models     

Transport analysis of in-medium hadron effects in pA and AA collisions

The production and decay of vector mesons ( ) in pA and AA reactions is studied with particular emphasis on their in-medium spectral functions. It is explored within transport calculations if hadronic in-medium decays like or might provide complementary information to their dilepton (e ⁺ e ^-) decays. Whereas the signal from the -meson is found to be strongly distorted by pion rescattering, the -meson Dalitz decay to appears promising even for more heavy nuclei in and pA reactions. Furthermore, the influence of nucleon and kaon/antikaon potentials on the yields and spectra in pA collisions is calculated and compared to the recent data from the ANKE Collaboration.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.60.Le Meson production - 13.75.Jz Kaon-baryon interactions - 14.40.Aq , K, and mesons - 25.40.-h Nucleon-induced reactionsW. Cassing: In collaboration with E.L. Bratkovskaya, M. Büscher, Ye.S. Golubeva, V. Grishina, V. Hejny, V. Metag, J. Messchendorp, B. Kamys, L.A. Kondratyuk, P. Kulessa, Z. Rudy, S. Schadmand, A.A. Sibirtsev, H. Ströher     

\alpha-decay spectroscopy of light odd-odd Bi isotopes - II: 186Bi and the new nuclide 184Bi

Alpha-decay of the new nuclide ¹⁸⁴Bi has been studied in the complete-fusion reaction ⁹³Nb(⁹⁴Mo, 3n)¹⁸⁴Bi at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of recoil- , recoil- - analysis and excitation functions measurements. Two -decaying isomeric states in ¹⁸⁴Bi with half-life values of 13(2) ms and 6.6(1.5) ms were identified. The -branching ratio of ¹⁸⁰Tl was deduced for the first time as . Improved data on the fine-structure -decay of ¹⁸⁶Bi were obtained in the ⁹³Nb(⁹⁵Mo, 2n)¹⁸⁶Bi reaction. A similarity of the decay energies and half-life values of ^184,186Bi is pointed out and a possible explanation for this effect is suggested.Received: 14 March 2003, Revised: 29 April 2003, Published online: 2 September 2003PACS: 23.60.+e decay - 27.70.+q - 27.80.+w K. Heyde: Present address: EP-ISOLDE, CERN, CH-1211, Geneva 23, Switzerland.     

Study of thermally excited nuclei through <Emphasis Type="Italic">E</Emphasis>1 and <Emphasis Type="Italic">E</Emphasis>2 decay from collective modes

The nuclear system at the limit of excitation energy and angular momentum is here studied in the case of the superdeformed nucleus ¹⁴³Eu using -spectroscopy techniques. The data are based on a EUROBALL experiment using the reaction ³⁷Cl + ¹¹⁰Pd Eu + 4n. The influence of thermal energy on superdeformed configurations is investigated through the analysis of the quasi-continuum spectra formed by E2 transitions among states of excited rotational bands with energy extending up to 4-5 MeV above the yrast line. In particular, the effective lifetimes of the discrete rotational bands forming ridge structures in - coincidence matrices is measured by a Doppler Shift Attenuation Method. The deduced quadrupole deformation of 10 eb indicates that the nucleus maintains its collectivity with increasing excitation energy, supporting the superdeformed character of the excited nuclear rotation. The obtained number of superdeformed discrete bands forming the ridge structures is found in good agreement with microscopic cranked shell model calculations including the decay-out process into the lower deformation minimum. In addition, the nuclear properties at higher excitation energies are investigated through the E1 -decay of the giant dipole resonance (GDR). It is found that the intensity of the superdeformed yrast and excited bands increases by a factor of approximately 1.6 when a coincidence with a high-energy -ray is required, showing the importance of the E1 cooling in the feeding mechanism of the superdeformed states.Received: 2 December 2002, Published online: 2 March 2004PACS: 21.10.Tg Lifetimes - 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.60. + j      

Near-threshold production of a0(980)-mesons in the reaction \rm {pp \rightarrow d K^ + \bar{K^0}}

Using an effective Lagrangian approach as well as the Quark-Gluon Strings Model, we analyze near-threshold production of a ₀(980)-mesons in the reaction as well as the background of non-resonant -pair production. We argue that the reaction at an energy release MeV is dominated by the intermediate production of the a ₀(980)-resonance. At larger energies the non-resonant -pair production --where the kaons are produced in a relative P-wave-- becomes important. The effects of final-state interactions are evaluated in a unitarized scattering length approach and found to be in the order of a 20% suppression close to threshold. Thus, in present experiments at the Cooler Synchrotron COSY-Jülich for MeV the a ₀ ⁺ signal can reliably be separated from the non-resonant background.Received: 26 February 2004, Published online: 21 September 2004PACS: 25.10. + s Nuclear reactions involving few-nucleon systems - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy GeV)     

Exclusive and semi-inclusive strangeness and charm production in \pi N and NN reactions

Using the Quark-Gluon Strings Model (QGSM) combined with Regge phenomenology we consider the reactions and which are dominated by the contributions of the K ^* and D ^* Regge trajectories, respectively. The spin structure of the amplitudes is described by introducing Reggeized Born terms. It is found that the existing data for the reaction are in reasonable agreement with the model predictions. To describe the absolute values of the cross-sections it is necessary to introduce also suppression factors which can be related to absorption corrections. Furthermore, assuming the SU(4) symmetry to hold for Regge residues and the universality of absorption corrections we calculate the cross-section of the reaction . Employing the latter results from reactions we then estimate the contributions of the pion exchange mechanism to the cross-sections of the reactions and and compare them with the contributions of the K and D exchanges. We find that the NN reactions are dominated not by pion exchange but by K and D exchanges, respectively. Moreover, assuming the SU(4) symmetry to hold approximately for the coupling constants = we analyze also the production of leading -hyperons in the reaction . It is shown that the non-perturbative mechanism should give an essential contribution to the yield for .Received: 30 September 2002, Published online: 22 October 2003PACS: 13.85.Fb Inelastic scattering: two-particle final states - 13.85.Hd Inelastic scattering: many-particle final states - 14.20.Lq Charmed baryons - 14.40.Lb Charmed mesons     

Pseudo-spin band in the odd-odd nucleus 172Lu

High-spin states in the odd-odd nucleus ¹⁷²Lu have been populated in a ¹⁷⁰Er(⁷Li, 5n) reaction and the emitted -radiation was detected with the GASP array. Two sequences of a new identical band have been observed with the transition energies in the favoured and unfavoured sequences being identical within keV at low spins and keV at high spins over the whole observed spin range. Aninterpretation as a pseudo-spin singlet band of configuration is proposed. It represents the best example of a pseudo-spin singlet band in normal deformed nuclei known until now.Received: 19 February 2003, Revised: 27 March 2003, Published online: 12 August 2003PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.70.+q      

Parity non-conservation in proton-proton elastic scattering

The parity-non-conserving longitudinal asymmetry in proton-proton (p p) elastic scattering is calculated in the lab energy range 0-350 MeV using contemporary, realistic strong-interaction potentials combined with a weak-interaction potential comprised of - and -meson exchanges as exemplified by the DDH model. Values for the - and -meson coupling constants, and , are determined from comparison with the measured asymmetries at 13.6 MeV, 45 MeV, and 221 MeV.Received: 30 September 2002, Published online: 22 October 2003PACS: 21.30.-x Nuclear forces - 24.80. + y Nuclear tests of fundamental interactions and symmetries - 25.40.Cm Elastic proton scattering