Shell model yrast states in the many-particle nucleus 72 157 Hf85

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 h_9/2 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 configurationf_7/2h_9/2i_13/2.     

Two-proton multiplets in theN=82 nucleus 62 144 Sm82 from in-beamγ-measurements

In a high sensitivity (,2n) in-beam study of ₆₂ ¹⁴⁴ Sm₈₂, with the Kölner Würfel OSIRIS -detector array including a Compton polarimeter, we have identified the complete two-proton multiplets d ₅ ^2/–2 , d ₅ ^2/–1 g ₇ ^2/–1 , g ₇ ^2/–2 , h_11/2d ₅ ^2/–1 and the 9^– to 4^– members of the h_11·/2g ₇ ^2/–1 multiplet.Work partially supported by CICYT (Spain).     

Shell model high-spin states in 67 151 Ho84

In an in-beam study of ₆₇ ¹⁵¹ Ho₈₄ we have established its high-spin states up to 10 MeV and have suggested spin assignments up to (49/2) at 6.2 MeV. The main decay-cascade proceeds through the yrast states of the h³ _11/2f² _7/2 and h³ _11/2f_7/2h_9/2 5-particle configurations, which are predicted with good accuracy in parameter-free shell-model calculations. States with one proton in d_3/2, or involving i_13/2 or f_7/2×3^– excitations were also identified.     

The proton g9/2 isomer in theN=50 nucleus87Rb and M2 transition rates in85,87Rb

Low-lying states of theN=50 nucleus⁸⁷Rb have been investigated in the (, ') reaction measuring- and delayed-rf-coincidences. A half-life ofT _1/2=6(1) ns was obtained for the level at 1578.1 keV. This experimental result confirms the 9/2⁺ assignment and the proton 1g_9/2 single-particle character of this state. Experimental M2 transition strengths in^85,87Rb are compared with predictions of the shell model and the particle-core coupling model.This work was partly supported by the Bulgarian National Research Foundation.     

The structure of28Si above 10 MeV excitation energy I: gamma-decay modes and radiative widths of levels

The systematics of-decay modes and radiative widths of highly excited states in²⁸Si has been extended by taking-ray spectra on 60 resonances of the²⁷Al(p,) reaction in the range 1097 keVE _p 4492 keV (12643 keVE _x 15915 keV) and on the²⁴Mg(,) resonances atE =3355, 3431, 4003 keV (E _x =12860, 12925, 13 415 keV). The-decay modes of levels in the sub-resonance region (E _x =10–12.5 MeV) were studied with both the²⁷ A1(p, ) reaction and the²⁷ A1(d, n) reaction at E_d=4,5,6 MeV. Information on radiative widths of levels was obtained by measuring the resonance strengthsS =(2I+1) _p / for 52 resonances of the²⁷Al(p, ) reaction with an emphasis on prospective T=1 states.     

Non-collective oblate states in121Te

Two new neutron-deficient isotopes,²¹³Pa and²¹⁴Pa were produced in complete fusion reactions of⁵¹V-ions with¹⁷⁰Er targets at (5.2–5.6) AMeV. The assignment was based on delayed evaporation residue - - time and position coincidences. The- decay energies of^213,214Pa were measured to be E=(8236±20) keV and E=(8116±20) keV, respectively. The half-lives of^213,214Pa were determined to be T_1/2=(5.3 _–1.6 ^+4.0 ms and T_1/2=(17 ±3) ms, respectively.This article was processed by the author using the LAT_EX style filecljour2 from Springer-Verlag.     

Observation of isomeric states in197Bi

The high spin states of¹¹⁹Te, populated in¹¹⁰Pd(¹³C,4n) and¹¹⁰Pd(¹²C,3n) reactions, have been studied through -ray spectroscopy. The level scheme has been established upto a spin of 55/2. Three-quasiparticle states, based on g² _7/2h_11/2 and g_7/2d_5/2h_11/2 configurations, have been identified. The 35/2 and 39/2 states are suggested to be the fully aligned states constituted by five valence h_11/2 ³, g_7/2, d_5/2 quasiparticles.     

Analysis of the 33-133-133-1final state in photon-photon collisions

The reactione ⁺ e ^- e ⁺ e ^{- 00}e ⁺ e ^- 6 has been analysed using the full data sample taken with the Crystal Ball detector at the DORIS II storage ring at DESY. The ⁰⁰ invariant mass spectrum is dominated by the ', for which we determine the radiative width (') to be (4.5±0.3±0.5)keV. Near 1.9 GeV/c² we observe a second enhancement in the ⁰⁰ mass distribution. Assuming that these events are created by the production and subsequent decay of a wide resonanceX(1900), we have investigated the decay modes, the invariant mass distributions of the ⁰ and ⁰⁰ subsystems and the angular distributions of the final state mesons. We find that the data is best described byJ ^PC=2. For thisJ ^P assignment the resonance parameters are (X) BR(X)=(0.95±0.27±0.20) keV _tot (X)=(221±92±44)MeV, andM(X)=(1881±32±40) MeV/c².Deceased     

Fixed exciton number level density for a finite potential well

We present a calculation of the nuclear level density _ph(E) for a fixed number of particlesp and holesh, taking into account the energy dependence of the singleparticle level densityg(). We demonstrate the significant effects of the finite depth of the potential well (continuum effect) and the finite surface thickness of the nucleus on the value of _ph(E).Communicated by: X. Campi     

Experimental evidence for the box anomaly inη/η′ decays and the electric charge of quarks

Motivated by nearly unanimous claim that the observed mass spectrum ^+- is not that expected from pure ⁰ dominance, we reanalyze all the published data on / ^+- decays. We find non-resonant contributions. In order to evaluate precisely the magnitude of these terms, we also refit the e⁺e^{- +-} data to get reliably the ⁰ parameters and decay amplitude. We show that identifying the non-resonant contribution with the box anomaly predicted by QCD and chiral theories, one achieves a consistent picture. Several checks are performed which show the consistency of our fitted parameters. From four measurements, we determinef ₁,f ₈ and _PS on purely experimental grounds, and we find them in the expected range. Presently available data allow for two solutions, one is consistent with QCD, the other favours integral charge quark models. We show that presently available data do not allow to choose among these two solutions. We discuss the interrelation of uncertainties in e⁺e^{- +-} physics with our two solutions.     

Isotonic and isobaric dependencies of nuclear charge radii for rare-earth nuclei

Isotonic and isobaric dependencies of nuclear charge radii in the region between Z=54 and Z=70 are obtained from the analysis of isotope shift data r² and muonic and electron scattering data on r². They are compared with the predictions of the droplet model and the Hartree-Fock calculations. The isobaric dependencies of r² have proven to be especially sensitive to the choice of an effective nucleon-nucleon interaction.     

Excitations in208Pb nearE x=5683 keV

A search for the recently proposed two-phonon octupole vibrational (2-POV) 4⁺ or 6⁺ state in²⁰⁸Pb at an excitation energy of 5683 keV has been performed using the²⁰⁷Pb(d,p),²⁰⁸Pb (p,p) and (,) reactions at high energy resolution. No evidence for a two-phonon excitation at this energy is found.This work was supported in part by the DFG under contract nr. II C4-Gr 894/2-1 and by the DFG-Graduiertenkolleg Struktur der Hadronen und Kerne under contract nr. Mu 705/3-1.     

The influence of shape changes on the alpha decay in the191Bi m,g →187Tl→183Au chain

The¹⁹¹Bi^{m,g 187}T1 ¹⁸³Au a-decay chain has been studied using mass — separated sources. The a — branching ratios have been measured. Out of the reduced a — decay widths, it is clear that the s_1/2 — S_1/2 and h_9/2 h_9/2 transitions are not hindered although they involve strong shape changes.     

Spin and parity of isomeric and ground states of the doubly-odd nucleus184Au

Low-spin states in doubly-odd¹⁸⁴Au have been populated in the ⁺/EC decay of¹⁸⁴Hg produced by bombarding¹⁸⁴Sm targets with an 185 MeV⁴⁰Ar beam. Radioactive Hg nuclei were transported by a He jet system. A new level scheme has been established from --t and X--t coincidence measurements. Spin and parity values I=5⁺, I =2⁺ and I=3^– were assigned to the ground state and the two isomeric states of¹⁸⁴Au, respectively. The structure of these states is discussed using B(E1) values.     

An analysis of dibaryon resonance spectra by GSAP,AUTSPAN and SAMPO-80 codes

Narrow dibaryon resonances observed in elastic and inelastic hadron scattering channels atM _NN ^* =1875–2300 MeV/c² are characterized by the relative resolution (FWHM/M _pp ^* ) 10^–3 comparable to that provided by Ge(Li) detectors in the case of gamma-ray spectroscopy. The gamma-ray spectrum analysis codes GSAP, AUTSPAN and SAMPO-80 have been used to analyse the effective mass distributions of dibaryons from the reactions dp (pn) p, dp (pp) n, np pp^–, and pppp studied at the Dubna synchrophasotron. The produced results suggest these codes to be reliable software tools in the new spectroscopic region of interest.On leave fromNuclear Physics Institute, Czechosl. Acad. Sci., 250 68 e near Prague, Czechoslovakia.     

The decay of spin-isospin modes in a semi-infinite slab

The surface response for charge exchange (p, n) and (³He, T) reactions is studied in the-region using the semi-infinite slab model. The contribution to the total response from different decay channels, (NN, N, ), is calculated. These decay channels corresponds to the exclusive channels, (pp, p ⁺, ⁺), measured in recent (p, n) and (³He, T) experiments. The in-medium properties of the-resonance is taken into account by using microscopic calculations of the-width in nuclear matter. From the-width in nuclear matter a non-local imaginary-potential, as well as a local potential, is constructed for the semi-infinite slab model. The results in the semi-infinite slab model gives a qualitative understanding of the exclusive experiments. The exclusive (NN, N, ) channels are more sensitive, than the total response, tog-correlation parameters,-width and the absorption function used at the external vertex. Our calculations suggest low values of theg-correlation parametersg _N andg , (0.3). The results with the-width represented as a non-local or a local-potential are very similar, with only minor differences in the exclusive channels.Supported in part by the Swedish Natural Science Research Council and by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract No. DE-ACO3-76SF00098     

Nuclear and electromagnetic fragmentation of 2.25-TeV197Au nuclei

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.     

Study of theπ + π − γ system centrally produced in the reactionpp→p f (π + π − γ)p s at 300 GeV/c

The reactionppp _f ( ^{+ –} )p _s , where the ^{+ –} system is centrally produced, has been studied at 300 GeV/c. The ^{+ –} mass spectrum shows evidence for a ⁰ decay mode of the (958) andf ₁ (1285). The branching ratio (f ₁(1285) ^{+ +})/(f ₁(1285) ⁰ ) is found to be 5.0±0.7. No evidence is found for a ⁰(770) decay mode of theE/f ₁ (1420) for which an upper limit BR (E/f ₁(1420) ⁰ )<0.08 at=" 95%=" cl=" is=">