26570396
Measurement of the inclusive semielectronic D0 branching fraction.
18200063
Masers as Probes of Massive Star Formation in the Nuclear Disk
Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 USAemail: bwhitney@spacescience.orgAbstract.OH(1720 MHz) and methanol masers are now recognized to be excellent probes of theinteractions of supernova remnants with molecular clouds and tracers of massive star formation,respectively. To better understand the nature of star formation activity in the central regionof the Galaxy, we have used these two classes of masers combined with the IRAC and MIPSdata to study prominent sites of ongoing star formation in the nuclear disk. The nuclear diskis characterized by massive GMCs with elevated gas temperatures, compared to their dusttemperatures. We note an association between methanol masers and a class of mid-infrared“green sources”. These highly embedded YSOs show enhanced 4.5µm emission due to excitedmolecular lines.The distribution of methanol masers and supernova remnants suggest a low eﬃciency of starformation (with the exception of Sgr B2), which we believe is due to an enhanced ﬂux of cosmicray electrons impacting molecular clouds in the nuclear disk. We also highlight the importanceof cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.Keywords. Masers, supernova remnants, cosmic rays.
118055903
New Measurements of Rare K0L and pi0 Decays from Fermilab E799
119648296
FastSim: A Fast Simulation for the SuperB Detector
We have developed a parameterized (fast) simulation for detector optimization and physics reach studies of the proposed SuperB Flavor Factory in Italy. Detector components are modeled as thin sections of planes, cylinders, disks or cones. Particle-material interactions are modeled using simplified cross-sections and formulas. Active detectors are modeled using parameterized response functions. Geometry and response parameters are configured using xml files with a custom-designed schema. Reconstruction algorithms adapted from BaBar are used to build tracks and clusters. Multiple sources of background signals can be merged with primary signals. Pattern recognition errors are modeled statistically by randomly misassigning nearby tracking hits. Standard BaBar analysis tuples are used as an event output. Hadronic B meson pair events can be simulated at roughly 10Hz.
34021352
Color-singlet quark-pair transmutation: Helicity amplitudes and partial-wave analysis.
Quark-pair transmutation via two gluons is the lowest-order, color-singlet process. In this paper the helicity amplitudes for this process are evaluated and a partial-wave analysis performed. The amplitudes for these annihilations are infrared divergent and this divergence is removed by giving the gluons a confinement mass. The results are generally dependent on this mass. Many of the features are similar to those of quark-pair annihilation into two gluons. Somewhat surprisingly, there is a large proportion of a ${1}^{+}$ partial wave. Threshold effects are understood in terms of threshold effects in pair annihilation into two gluons. However, there is a ``competition'' effect that depends on the ratio of masses of the initial- and final-quark pairs. For similar masses, singlet production dominates as expected, but for very dissimilar masses, singlet annihilation of the heavier pair competes with triplet production of the lighter pair. Some comments about the possible applications and extensions of this work are made. Obvious applications are to the Okubo-Zweig-Iizuka-rule-suppressed decays of quarkonia. Other applications include development of a quark-pair-creation model that differs from the usual $^{3}\mathrm{P}_{0}$ and $^{3}\mathrm{S}_{1}$ models.
43243436
Production of an isomeric, excited radioactive nuclear beam.
28323397
Very-high-energy light charged-particle production near 0 degrees in heavy-ion collisions, 9 <= E/A <= 40 MeV.
Very energetic light ions (primarily protons and alphas) with energies often approaching the full beam energy have been observed at or near {theta}=0{degree} in heavy-ion collisions, {ital Z}=8 to 28, {ital E}/{ital A}{dot =}9 to 40 MeV/nucleon from Ta and, in selected cases, Cu targets. Analysis of spectral shapes and angular distributions using a standard moving source model requires that the source velocity approaches the beam velocity as {theta}{r arrow}0{degree} and that the spectral slope parameters and apparent source temperatures be increased. Large values for the latter ({ital T}{sub {ital S}}{r arrow}16 MeV), which are typically twice as large as those deduced from complex fragment emission, are often required to fit the alpha particle spectra {theta}=0{degree}. Massive cluster transfer and other quasitransfer mechanisms may provide an alternative model for the generation of the {ital E}{r arrow}{ital E}{sub beam} alpha particles and other light fragments.
19324012
Fragmentation and splitting of Gamow-Teller resonances in Sn(3He,t)Sb charge-exchange reactions, A=112-124.
Fragmentation and splitting of the Gamow-Teller (GT) strength has been observed in a systematic study of the ([sup 3]He,[ital t]) charge-exchange reaction at [ital E]([sup 3]He)=200 MeV over the entire range of stable Sn isotopes. Triton energy spectra were observed with a high-resolution magnetic spectrometer at angles near [theta]=0[degree] where [Delta][ital L]=0 transitions are enhanced. Excitation energies, widths, 0[degree] cross sections, and strengths [ital B](GT) were determined. A theoretically predicted configuration splitting of the main GT component into two components, expected to be dominant near [ital A]=118 at the onset of the filling of the 1[ital h][sub 11/2] neutron orbital, could not be observed. This may be due to the fact that the total widths of the resonances of 5--6 MeV exceed the predicted splitting. A comparison of the 0[degree] cross sections for the transitions to the GT resonances and the isobaric analog states leads to strengths [ital B](GT) for the main Gamow-Teller components of typically 65% of the sum-rule value of 3([ital N][minus][ital Z]). Three to four additional Gamow-Teller fragments were observed in all final nuclei at lower excitation energies. The excellent energy resolution of the experiment made it possible to observe a pronounced fine structure in these low-lyingmore » resonances which is believed to be due to coupling to two-particle--two-hole doorway states. Also seen with all target nuclei was a systematic sequence of strong [ital J][sup [pi]]=1[sup +] states near the ground states in all Sb isotopes ([ital E][sub [ital x]]=0 to 220 keV). In addition, strong [Delta][ital L]=1 resonances were observed in all nuclei at excitation energies of typically 20 MeV. Furthermore, nonresonant background from quasifree charge exchange was observed. An average of [similar to]85% of all excess neutrons seems to contribute to this background in approximate agreement with results from ([ital e],[ital e][prime][ital p]) experiments.« less
23671598
N pi decays of baryons in a relativized model.
We calculate the [ital N][pi] decay amplitudes of baryon resonances in a semirelativistic version of the [sup 3][ital P][sub 0] model of hadron decays. We use relativized wave functions for the baryons and mesons, and include an intuitive modification of the usual [sup 3][ital P][sub 0] model. Our results are in reasonable agreement with the reported amplitudes for [ital all] known nonstrange resonances, and confirm a proposed solution to the mystery of the missing'' states.