26550883
Relationship between Gamow-Teller transition probabilities and (p,n) cross sections at small momentum transfers.
Gamow-Teller transition probabilities are extracted for eight nuclei with masses between A = 13 and A = 39 from medium-energy (p,n) reactions via the distorted-wave impulse approximation, and compared with experimental ..beta..-decay and with free-nucleon transition probabilities. These comparisons indicate strongly that the renormalization of the Gamow-Teller operator needed for (p,n) reactions on finite nuclei is different from that needed for ..beta.. decay.
34139540
Shape of the beta spectra in the A=14 system.
56232513
Search for physics beyond the standard model via a polarization-asymmetry correlation experiment on In-107
We report on a new precision measurement of the longitudinal polarization of positrons emitted by polarized 107In nuclei. Preliminary results yield a lower limit of 303 GeV/c2 for the mass of a possible, predominantly right-handed, W gauge boson, if interpreted in the framework of the manifest, left-right symmetric model. In more general left-right symmetric models our result is complementary to those from muon decay experiments and to results from searches for a similar particle in collider experiments. Our data also provide new results on possible tensor contributions to the weak interaction.
35436961
Predicted features of the beta decay of neutron-rich sd-shell nuclei
The Gamow-Teller beta-decay transitions of sd-shell nuclei with five or more excess neutrons are calculated from complete (0d/sub 5/2/, 1s/sub 1/2/, 0d/sub 3/2/)-space shell-model wave functions. These wave functions are obtained from diagonalizations of a model Hamiltonian formulation which reproduces observed energy-level structures throughout the sd shell. The calculations are carried out with both the ''free-nucleon'' normalization for the Gamow-Teller single-nucleon matrix elements and one based on the empirical values obtained for these quantities from a comparison of corresponding theoretical and experimental Gamow-Teller magnitudes near the line of stability. The phase-space factors f which connect the reduced Gamow-Teller strengths to the total half-lives and the individual decay probabilities are calculated both from the energies obtained in the shell-model calculations and, alternatively, from hybrid energy spectra in which available experimental energies are substituted for the corresponding calculated values wherever possible. Comparisons of the beta-decay predictions to existing experimental results are presented and discussed.
120853289
The 52,54Cr(p, n)52,54Mn and 57,58Fe(p, n)57,58Co reactions at Ep = 120 MeV
Abstract Differential cross sections for the (p, n) reaction on 52, 54 Cr and 57, 58 Fe have been measured for angles up to θ lab = 10.5° and 14.6°, respectively, using 120 MeV protons. The observed angular distributions are used to evaluate the location and strength of Gamow-Teller resonances. A shell-model calculation of this strength distribution is presented and compared with the experimental results. The M1 strength for 52 Cr is also calculated and compared with available results from (e, e') and (p, p') experiments. A comparison is made with other If 7 2 nuclei.
41679008
Proton capture to excited states of O 16 : M 1 , E 1 , and Gamow-Teller transitions and shell model calculations
We have measured excitation functions of the ..gamma..-rays resulting from the bombardment of /sup 15/N by polarized and unpolarized protons in the energy range E/sub p/ = 2.5 to 9.5 MeV with emphasis on identifying dipole decays to the first (0/sup +/) and second (3/sup -/) excited states in /sup 16/O. Resonances in ..gamma../sub 12/ are observed at E/sub x/ = 16.21, 16.45, 16.82, 17.12, 18.03, 18.98, 19.90 and 20.41 MeV. The 16.21 and 17.12 MeV resonances in ..gamma../sub 12/ are identified as M1-decays of the 1/sup +/ T = 1 states to the 6.05 MeV 0/sup +/ state in /sup 16/O. The measured ratio of reduced strengths B(m1,..gamma../sub 1/)/(B(M1,..gamma../sub 0/) is 0.48 +- 0.03 for decays from the 16.21 MeV state and 0.55 +- 0.04 for decays from the 17.12 MeV state. The 18.03 MeV resonance is due to a 3/sup -/ T = 1 state in /sup 16/O with a strength Gamma/sup p/Gamma/sub gamma 2//Gamma = (1.96 +- 0.27) eV and the 18.98 MeV resonance is due to the 4/sup -/ T = 1 stretched particle-hole state with a strength of (0.85 +- 0.10) eV. We determine absolute particle and ..gamma.. widths for these states. The M1 ..gamma../submore » 2/-width of the 18.98 MeV state, (7.1 +- 3.1) eV, is in agreement with a shell-model calculation. Resonances in ..gamma../sub 3/ are observed at 16.82 and 17.27 MeV and in ..gamma../sub 4/ at 17.88 MeV. The excitation energies and widths of these levels as well as the strengths of the ..gamma.. transitions suggest T = 1 character for all of the resonances for which capture ..gamma..-rays are observed. Correspondences of our resonances to levels in /sup 16/N are given. We compare ..gamma.. widths, including ground-state M1 decays, and allowed ..beta.. transition rate in A = 16 nuclei with shell model calculations and obtain rough agreement. Additional shell model calculations for M1 and GT (Gamow-Teller) decays in the A-14, 15, 17 and 18 nuclei are presented, which indicate that GT matrix elements are quenched by approx. 20% relative to shell model predictions and also relative to the spin part of the M1 matrix elements.« less
115714674
BaBar results on sin(2beta) and B0 oscillations
28110065
Kaon production from hot and dense matter formed in heavy-ion collisions.
In heavy-ion collisions, kaons can be produced from baryon-baryon, meson-baryon, and meson-meson interactions. Simple meson-exchange models are introduced to study kaon production from these processes in the free space. These models are then extended to determine kaon production in hot, dense nuclear matter by taking into account the decreasing hadron masses as a result of the restoration of chiral symmetry and the condensation of kaons. We find that the cross sections for kaon production from all three processes are enhanced. In particular, the effect of decreasing hadron masses on kaon production from the meson-meson annihilation is most significant. In the hydrochemical model for heavy-ion collisions, we demonstrate that the observed enhancement of kaon yield in high-energy heavy-ion collisions can be explained if the medium effect is included.
8309896
Photonuclear fission from high energy electrons from ultraintense laser-solid interactions
A new regime of laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic, with energies extending well above the threshold for nuclear processes, is studied using a petawatt laser system. In solid target experiments with focused intensities exceeding 10(20) W/cm(2), high energy electron generation, hard bremsstrahlung, and nuclear phenomena have been observed. We report here a quantitative comparison of the high energy electrons and the bremsstrahlung spectrum, as measured by photonuclear reaction yields, including the photoinduced fission of 238U.
1772289
Temporal development of the plasma phase transition.
We present a simple argument to show why a high entropy phase must exhibit an extended pion source lifetime. The plasmas that would be formed under the conditions of the recent heavy ion experiments would emit pions over a time of the order of 10 fm/{ital c} or longer, if the plasma has an entropy density larger than that of a pion gas by an order of magnitude.
19013112
Order of the QCD transition and QCD sum rules.
We propose using the finite-temperature {rho}-meson mass as an order parameter to monitor the QCD transition. This is suggested by the {rho}-meson mass formula that emerges from finite-temperature QCD sum rules in the vector channel, and which encompasses the effects of both quark and gluon condensates. We find that a second-order chiral-restoring transition implies a second-order behavior for the {rho} mass even if the value of the gluon condensate is unaffected by the transition.