12^{12}C/13^{13}C ratio in planetary nebulae from the IUE archives

We investigated the abundance ratio of $^{12}$C/$^{13}$C in planetary nebulae by examining emission lines arising from \ion{C}{3} 2s2p ^3P_{2,1,0} \to 2s^2 ^1S_0. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object were coadded to achieve improved signal-to-noise. The $^{13}$C hyperfine structure line at 1909.6 \AA was detected in NGC 2440. The $^{12}$C/$^{13}$C ratio was found to be $\sim4.4\pm$1.2. In all other objects, we provide an upper limit for the flux of the 1910 \AA line. For 23 of these sources, a lower limit for the $^{12}$C/$^{13}$C ratio was established. The impact on our current understanding of stellar evolution is discussed. The resulting high signal-to-noise \ion{C}{3} spectrum helps constrain the atomic physics of the line formation process. Some objects have the measured 1907/1909 flux ratio outside the low-electron density theoretical limit for $^{12}$C. A mixture of $^{13}$C with $^{12}$C helps to close the gap somewhat. Nevertheless, some observed 1907/1909 flux ratios still appear too high to conform to the presently predicted limits. It is shown that this limit, as well as the 1910/1909 flux ratio, are predominantly influenced by using the standard partitioning among the collision strengths for the multiplet $^1S_0$--$^3P_J$ according to the statistical weights. A detailed calculation for the fine structure collision strengths between these individual levels would be valuable.Comment: ApJ accepted: 19 pages, 3 Figures, 2 Table

Status and overview of development of the Silicon Pixel Detector for the PHENIX experiment at the BNL RHIC

We have developed a silicon pixel detector to enhance the physics capabilities of the PHENIX experiment. This detector, consisting of two layers of sensors, will be installed around the beam pipe at the collision point and covers a pseudo-rapidity of | \eta | < 1.2 and an azimuth angle of | \phi | ~ 2{\pi}. The detector uses 200 um thick silicon sensors and readout chips developed for the ALICE experiment. In order to meet the PHENIX DAQ readout requirements, it is necessary to read out 4 readout chips in parallel. The physics goals of PHENIX require that radiation thickness of the detector be minimized. To meet these criteria, the detector has been designed and developed. In this paper, we report the current status of the development, especially the development of the low-mass readout bus and the front-end readout electronics.Comment: 9 pages, 8 figures and 1 table in DOCX (Word 2007); PIXEL 2008 workshop proceedings, will be published in the Proceedings Section of JINST(Journal of Instrumentation

Solar interacting protons versus interplanetary protons in the core plus halo model of diffusive shock acceleration and stochastic re-acceleration

With the first observations of solar γ-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the γ-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported back to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the γ-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space

Charge-Transfer Excitations in One-Dimensional Dimerized Mott Insulators

We investigate the optical properties of one-dimensional (1D) dimerized Mott insulators using the 1D dimerized extended Hubbard model. Numerical calculations and a perturbative analysis from the decoupled-dimer limit clarify that there are three relevant classes of charge-transfer (CT) states generated by photoexcitation: interdimer CT unbound states, interdimer CT exciton states, and intradimer CT exciton states. This classification is applied to understanding the optical properties of an organic molecular material, 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which is known for its photoinduced transition from the dimerized spin-singlet phase to the regular paramagnetic phase. We conclude that the lowest photoexcited state of TTTA is the interdimer CT exciton state and the second lowest state is the intradimer CT exciton state.Comment: 6 pages, 6 figures, to be published in J. Phys. Soc. Jp

Vinte anos de integração pesquisa-extensão-agricultor com feijão no Rio Grande do Sul.

bitstream/item/58268/1/7-feijao-Iraja-2011.pd

First observation of the KS->pi0 gamma gamma decay

Using the NA48 detector at the CERN SPS, 31 KS->pi0 gamma gamma candidates with an estimated background of 13.7 +- 3.2 events have been observed. This first observation leads to a branching ratio of BR(KS->pi0 gamma gamma) = (4.9 +- 1.6(stat) +- 0.9(syst)) x 10^-8 in agreement with Chiral Perturbation theory predictions.Comment: 10 pages, 4 figures submitted to Phys. Lett.

Search for CP violation in K0 -> 3 pi0 decays

Using data taken during the year 2000 with the NA48 detector at the CERN SPS, a search for the CP violating decay K_S -> 3 pi0 has been performed. From a fit to the lifetime distribution of about 4.9 million reconstructed K0/K0bar -> 3 pi0 decays, the CP violating amplitude eta_000 = A(K_S -> 3 pi0)/A(K_L -> 3 pi0) has been found to be Re(eta_000) = -0.002 +- 0.011 +- 0.015 and Im(eta_000) = -0.003 +- 0.013 +- 0.017. This corresponds to an upper limit on the branching fraction of Br(K_S -> 3 pi0) < 7.4 x 10^-7 at 90% confidence level. The result is used to improve knowledge of Re(epsilon) and the CPT violating quantity Im(delta) via the Bell-Steinberger relation.Comment: 18 pages, 7 figures, submitted to Phys. Lett.