Spatial Drift Dynamics of Shovelnose Sturgeon and Pallid Sturgeon Prelarvae in the Transition Zone of Ft. Peck Reservoir

Habitats in reservoir headwaters may cause high mortality of sturgeon prelarvae. Short inter-reservoir reaches export drifting prelarvae from hatch locations into reservoirs. However, flooded vegetation could entrain prelarvae. We used 2 day post hatch (dph) shovelnose sturgeon (Scaphirhynchus platorynchus) and 1-dph pallid sturgeon (Scaphirhynchus albus) to determine the spatial dynamics of drifting prelarvae.We released 220,000 2-dph shovelnose sturgeon 4 km upstream of Ft. Peck Reservoir and 135,000 1-dph pallid sturgeon 2.5 km upstream of the reservoir the following day. We recaptured shovelnose sturgeon prelarvae with nets deployed along three transects of the transition zone and within the headwaters of the reservoir.We sampled 5148.2 m3 of water and recaptured 323 prelarval shovelnose sturgeon for a recapture rate of 0.14 percent. Fifty-nine percent of recaptured prelarvae were recaptured from the thalweg, 12 percent from the flooded vegetation-main channel interface, 9 percent from the channel border, and 19 percent from the zero-velocity area of Ft. Peck Reservoir. We recaptured pallid sturgeon prelarvae with nets deployed along one transect of the transition zone and within the headwaters of the reservoir. We sampled 6608.5 m3 of water and recaptured 397 pallid sturgeon prelarvae for a recapture rate of 0.29 percent. Twenty one percent of prelarvae were recaptured within the thalweg, 0.25 percent were recaptured along the channel margins, and 79 percent from the zero-velocity area of Ft. Peck Reservoir. Although recapture rates were low, the majority of prelarvae were captured in the thalweg and transported to the headwaters of Ft. Peck Reservoir. The drift dynamics observed in this study provide a springboard for further research

Zero mode quantization of multi-Skyrmions

A zero mode quantization of the minimal energy SU(2) Skyrmions for nucleon numbers four to nine and seventeen is described. This involves quantizing the rotational and isorotational modes of the configurations. For nucleon numbers four, six and eight the ground states obtained are in agreement with the observed nuclear states of Helium, Lithium and Beryllium. However, for nucleon numbers five, seven, nine and seventeen the spins obtained conflict with the observed isodoublet nuclear states.Comment: 37 pages, LaTeX, 4 figures. More careful treatment of double covers, reference adde

Electroweak Baryogenesis and Standard Model CP Violation

We analyze the mechanism of electroweak baryogenesis proposed by Farrar and Shaposhnikov in which the phase of the CKM mixing matrix is the only source of $CP$ violation. This mechanism is based on a phase separation of baryons via the scattering of quasiparticles by the wall of an expanding bubble produced at the electroweak phase transition. In agreement with the recent work of Gavela, Hern\'andez, Orloff and P\`ene, we conclude that QCD damping effects reduce the asymmetry produced to a negligible amount. We interpret the damping as quantum decoherence. We compute the asymmetry analytically. Our analysis reflects the observation that only a thin, outer layer of the bubble contributes to the coherent scattering of the quasiparticles. The generality of our arguments rules out any mechanism of electroweak baryogenesis that does not make use of a new source of $CP$ violation.Comment: 36 pages, in LaTeX, one LaTeX figure included, 5 others available upon request, SLAC-PUB-647

Measurement of J/Psi and Psi(2S) Polarization in ppbar Collisions at sqrt(s) = 1.8 TeV

We have measured the polarization of J/Psi and Psi(2S) mesons produced in p\bar{p} collisions at \sqrt{s} = 1.8 TeV, using data collected at CDF during 1992-95. The polarization of promptly produced J/Psi [Psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4[5.5] < P_T < 20 GeV/c and |y| < 0.6. For P_T \gessim 12 GeV/c we do not observe significant polarization in the prompt component.Comment: Revised version, accepted for publication in Physical Review Letter

Excluding Electroweak Baryogenesis in the MSSM

In the context of the MSSM the Light Stop Scenario (LSS) is the only region of parameter space that allows for successful Electroweak Baryogenesis (EWBG). This possibility is very phenomenologically attractive, since it allows for the direct production of light stops and could be tested at the LHC. The ATLAS and CMS experiments have recently supplied tantalizing hints for a Higgs boson with a mass of ~ 125 GeV. This Higgs mass severely restricts the parameter space of the LSS, and we discuss the specific predictions made for EWBG in the MSSM. Combining data from all the available ATLAS and CMS Higgs searches reveals a tension with the predictions of EWBG even at this early stage. This allows us to exclude EWBG in the MSSM at greater than (90) 95% confidence level in the (non-)decoupling limit, by examining correlations between different Higgs decay channels. We also examine the exclusion without the assumption of a ~ 125 GeV Higgs. The Higgs searches are still highly constraining, excluding the entire EWBG parameter space at greater than 90% CL except for a small window of m_h ~ 117 - 119 GeV.Comment: 24 Pages, 4 Figures (v3: fixed typos, minor corrections, added references

Production of Y(1S) Mesons from chib Decays in pp(bar) Collisions at sqrt(s)=1.8 TeV

We have reconstructed the radiative decays $\chi_{b}(1P) \to \Upsilon(1S) \gamma$ and $\chi_{b}(2P) \to \Upsilon(1S) \gamma$ in $p \bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV, and measured the fraction of $\Upsilon(1S)$ mesons that originate from these decays. For $\Upsilon(1S)$ mesons with $p^{\Upsilon}_{T}>8.0$ GeV/$c$, the fractions that come from $\chi_{b}(1P)$ and $\chi_{b}(2P)$ decays are $(27.1\pm6.9(stat)\pm4.4(sys))$ and $(10.5\pm4.4(stat)\pm1.4(sys))$, respectively. We have derived the fraction of directly produced $\Upsilon(1S)$ mesons to be $(50.9\pm8.2(stat)\pm9.0(sys))$.Comment: 13 Pages, 2 figure

Observation of B_c Mesons in p-bar p Collisions at sqrt{s} = 1.8 TeV

We report the observation of bottom-charmed mesons B_c in 1.8 TeV p-bar p collisions using the CDF detector at the Fermilab Tevatron. The B_c mesons were found through their semileptonic decays, B_c -> J/psi lepton X. A fit to the J/psi lepton mass distribution yielded 20.4 +6.2 -5.5 events from B_c mesons. A test of the null hypothesis, i.e. an attempt to fit the data with background alone, was rejected at the level of 4.8 standard deviations. By studying the quality of the fit as a function of the assumed B_c mass, we determined M(B_c) = 6.40 +- 0.39 +- 0.13 GeV/c^2. From the distribution of trilepton intersection points in the plane transverse to the beam direction we measured the B_c lifetime to be tau(B_c) = 0.46 +0.18 -0.16 +- 0.03 ps. We also measured the ratio of production cross section times branching fraction for B_c -> J/psi lepton neutrino relative to that for B+ -> J/psi K to be: 0.132 +0.041 -0.037 (stat) +- 0.031 (syst) +0.032 -0.020 (lifetime)Comment: 79 pages, 28 figures, available at http://www-cdf.fnal.gov/physics/pub98/cdf4438_Bc_prd_V52.ps . Submitted to Physical Review

The Influence of Habitat Structure and Environmental Variability on Habitat Use By Fish in the Vermillion River, South Dakota

This study was initiated to 1) examine the associations of fish with meso- and microhabitat in the Vermillion River, South Dakota, and 2) quantify fish communities in Vermillion River tributaries. Fish were collected from four mesohabitats (riffles, pools, runs, stream areas with woody debris) in natural and channelized regions of the river during July and August 1991, and May 1992 with an electric seine. Fish collected were categorized as small (\u3c 76 mm) or large (\u3e 75 mm). Density (number/100 m2) and biomass (grams/100 m2) were calculated in each habitat for the entire community (all species combined), and density was also determined for individual species in each habitat. Densities of small fish were highest in riffles and woody habitats, but small fish were most concentrated in riffles during low flow conditions (August) when young-of-the-year fish were recruited to the community. Patterns of habitat use by larqe fish were unaffected by flow and densities of large fish were evenly distributed among woody habitats, riffles, and pools. Densities of both small and large fish were linearly dependent on microhabitat conditions (depth, velocity, substrate) within individual mesohabitats. Biomass patterns closely resembled patterns of habitat use by large fish. Mesohabitats in natural and channelized areas of the river supported similar fish density and biomass, but channelized runs had higher densities than natural runs, and natural pools supported higher fish biomass than channelized pools. Most species were generalized in their habitat use patterns during moderate flow conditions (May and July), but several species (i.e., sand shiner Notropis stramineus, central stoneroller campostoma anomalum, red shiner Cyprinella lutrensis, channel catfish Ictalurus punctatus) constricted their habitat use to one or two habitats during low flow conditions. Tributary fish communities were dominated by fathead minnows Pimephales promelas, brassy minnows Hvbognathus hankinsoni, oranqespotted sunfish L@pomis humilis, and black bullheads Ameiurus melas, but seasonal changes in species composition and abundance were evident and may have been induced through predator-prey interactions. Topeka shiners Notropis tristis, a candidate for federal threatened and endangered status, was locally abundant in some tributary pools. The results of this study emphasize that habitat complexity strongly influences fish distribution and abundance in the Vermillion River, but season, temporal changes in stream flow, and juvenile recruitment affect habitat utilization patterns. Protection of complex habitats and tributary streams is essential for the wellbeing of Vermillion River fishery resource

The Influence of Habitat Structure and Environmental Variability on Habitat Use by Fish in the Vermillion River, South Dakota

This study was initiated to 1) examine the associations of fish with meso- and microhabitat in the Vermillion River, South Dakota, and 2) quantify fish communities in Vermillion River tributaries. Fish were collected from four mesohabitats (riffles, pools, runs, stream areas with woody debris) in natural and channelized regions of the river during July and August 1991, and May 1992 with an electric seine. Fish collected were categorized as small (\u3c76 mm) or large(\u3e 75 mm). Density (number/100 m2) and biomass (grams/100 m2) were calculated in each habitat for the entire community (all species combined), and density was also determined for individual species in each habitat. Densities of small fish were highest in riffles and woody habitats, but small fish were most concentrated in riffles during low flow conditions (August) when younq-of -the- year fish were recruited to the community. Patterns of habitat use by large fish were unaffected by flow and densities of large fish were evenly distributed among woody habitats, riffles, and pools. Densities of both small and larqe fish were linearly dependent on microhabitat conditions (depth, velocity, substrate) within individual mesohabitats. Biomass patterns closely resembled patterns of habitat use by large fish. Mesohabitats in natural and channelized areas of the river supported similar fish density and biomass, but channelized runs had higher densities than natural runs, and natural pools supported higher fish biomass than channelized pools. Most species were generalized in their habitat use patterns during moderate flow conditions (May and July), but several species (i.e., sand shiner Notropis stramineus, central stoneroller campostoma anomalum, red shiner Cyprinella lutrensis, channel catfish Ictalurus punctatus) constricted their habitat use to one or two habitats during low flow conditions. Tributary fish communities were dominated by fathead minnows Pimephales promelas, brassy minnows Hvboqnathus hankinsoni, oranqespotted sunfish Lepomis humilis, and black bullheads Ameiurus melas, but seasonal changes in species composition and abundance were evident and may have been induced through predator-prey interactions. Topeka shiners Notropis tristis, a candidate for federal threatened and endangered status, was locally abundant in some tributary pools. The results of this study emphasize that habitat complexity strongly influences fish distribution and abundance in the Vermillion River, but season, temporal changes in stream flow, and juvenile recruitment affect habitat utilization patterns. Protection of complex habitats and tributary streams is essential for the wellbeing of Vermillion River fishery resource