A search for J^{PC}=1^{-+} exotic mesons in the pi- pi- pi+ and pi- pi0 pi0 systems

A partial wave analysis (PWA) of the pi-pi-pi+ and pi-pi0pi0 systems produced in the reaction pi- p -> (3pi)-p at 18 GeV/c was carried out using an isobar model assumption. This analysis is based on 3.0M pi-pi0pi0 events and 2.6M pi-pi-pi+ events and shows production of the a2(1320), pi2(1670) and \pi(1800) mesons. An earlier analysis of 250K pi-pi-pi+ events from the same experiment showed possible evidence for a J^{PC}=1^{-+}$ exotic meson with a mass of 1.6 GeV/c^2 decaying into rho pi. In this analysis of a higher statistics sample of the (3pi)- system in two charged modes we find no evidence of an exotic meson.Comment: 4 pages, 5 figures, added comment about the negative reflectivity exotic wave

A Study of the \eta \pi^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson

A partial wave analysis (PWA) of the of the $\eta \pi ^0$ system (where $\eta \to \gamma \gamma$) produced in the charge exchange reaction $\pi ^-p\to \eta \pi ^0n$ at an incident momentum of 18 GeV$/c$ is presented as a function of ${\eta \pi ^0}$ invariant mass, $m_{\eta\pi^0}$, and momentum transfer squared, $t_{\pi^{-}\to\eta\pi}$, from the incident $\pi^-$ to the outgoing ${\eta\pi ^0}$ system. $S$, $P$ and $D$ waves were included in the PWA. The $a_0(980)$ and $a_2(1320)$ states are clearly observed in the overall ${\eta\pi ^0}$ effective mass distribution as well as in the amplitudes associated with $S$ wave and $D$ waves respectively after partial wave decomposition. The observed distributions in moments (averages of spherical harmonics) were compared to the results from the PWA and the two are consistent. The distribution in $t_{\pi^{-}\to\eta\pi}$ for individual $D$ waves associated with natural and unnatural parity exchange in the $t$-channel are consistent with Regge phenomenology. Of particular interest in this study is the $P$ wave since this leads to an exotic $J^{PC}=1^{-+}$ for the $\eta \pi$ system. A $P$ wave is present in the data, however attempts to describe the mass dependence of the amplitude and phase motion with respect to the $D$ wave as a Breit-Wigner resonance are problematic. This has implications regarding the existence of a reported exotic $J^{PC} = 1^{-+}$ meson decaying into $\eta \pi^0$ with a mass near 1.4 GeV$/c^2$.Comment: 19 pages, 29 figures, to appear in Phys. Rev.

Preliminary results from E756 on the Ξ− and Ω− magnetic moments

We have used the spin precession technique to measure the Ξ− and Ω− magnetic moments. The preliminary results are μ(Ξ−)=−0.64±0.02 nuclear magnetons and μ(Ω−)=−2.0±0.2 nuclear magnetons where the error for both measurements is statistical. The polarization of Ξ−’s produced at 2.5 mr by 800 GeV protons on a Be target was 11% while the polarization of Ω−’s was consistent with zero. Polarized Ξ−’s and Ω−’s were produced using spin transfer from a polarized neutral hyperon beam. The Ω− polarization at 325 GeV/c was 6.5%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87375/2/374_1.pd

Polarization and spin transfer of Ω− and Ξ− hyperons at 800 GeV

Fermilab experiment E756 has measured the polarization of W− hyperons produced by 800 GeV protons to be small compared to that of Ξ− hyperons. When produced by a neutral beam containing polarized Λ and Ξ0 hyperons, both the Ω− and the Ξ− have a significant polarization indicating a large spin transfer at high energies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87380/2/80_1.pd

Weak Hyperon Decays: Quark Sea and SU(3) Symmetry Breaking

An explanation of the difference in the values of the apparent $f/d$ ratios for the S- and P- wave amplitudes of nonleptonic hyperon decays is proposed. The argument is formulated in the framework of the standard pole model with $(56,0^{+})$ ground-state and $(70,1^{-})$ excited baryons as intermediate states for the P- and S- waves respectively. Under the assumption that the dominant part of the deviation of $(f/d)_{P-wave}$ from $-1$ is due to large quark sea effects, $SU(3)$ symmetry breaking in energy denominators is shown to lead to a prediction for $(f/d)_{S-wave}$ which is in excellent agreement with experiment. This corroborates our previous unitarity calculations which indicated that the matrix elements $$ of the parity conserving weak Hamiltonian between the ground-state baryons are characterized by $f_{0}/d_{0} \approx -1.6$ or more. A brief discussion of the problem of the relative size of S- and P- wave amplitudes is given. Finally, implications for weak radiative hyperon decays are also discussed.Comment: 26 pages, LATEX, 1647/PH IFJ Krako

Prevention of intention invention in the affect misattribution procedure

The affect misattribution procedure (AMP) is one of the most promising indirect measures, showing high reliability and large effect sizes. However, the AMP has recently been criticized for being susceptible to explicit influences, in that priming effects tend to be larger and more reliable among participants who report that they intentionally responded to the primes instead of the targets. Consistent with interpretations of these effects in terms of retrospective confabulation, two experiments obtained reliable priming effects when (a) participants lacked meta-cognitive knowledge about their responses to the primes and (b) participants’ attention was directed away from response-eliciting features of the primes. Under either of these conditions, priming effects were unrelated to self-reported intentionality, although self-reported intentionality was positively related to priming effects under control conditions. The findings highlight the contribution of meta-cognitive inferences to retrospective self-reports of intentionality and suggest an effective procedure to rule out explicit influences in the AMP

Partial-wave analysis of the eta pi+ pi- system produced in the reaction pi-p --> eta pi+ pi- n at 18 GeV/c

A partial-wave analysis of 9082 eta pi+ pi- n events produced in the reaction pi- p --> eta pi+ pi- n at 18.3 GeV/c has been carried out using data from experiment 852 at Brookhaven National Laboratory. The data are dominated by J^{PC} = 0^{-+} partial waves consistent with observation of the eta(1295) and the eta(1440). The mass and width of the eta(1295) were determined to be 1282 +- 5 MeV and 66 +- 13 Mev respectively while the eta(1440) was observed with a mass of 1404 +- 6 MeV and width of 80 +- 21 MeV. Other partial waves of importance include the 1++ and the 1+- waves. Results of the partial wave analysis are combined with results of other experiments to estimate f1(1285) branching fractions. These values are considerably different from current values determined without the aid of amplitude analyses.Comment: 22 pages, 8 figure

A partial wave analysis of the π0π0\pi ^0\pi ^0 system produced in π−p\pi ^-p charge exchange collisions

A partial wave analysis of the of the $\pi ^0\pi ^0$ system produced in the charge exchange reaction: $\pi ^-p\to \pi ^0\pi ^0n$ at an incident momentum of $18.3 GeV/c$ is presented as a function of ${\pi ^0\pi ^0}$ invariant mass, $m_{\pi^0\pi^0}$, and momentum transfer squared, $| {t} |$, from the incident $\pi^-$ to the outgoing ${\pi ^0\pi ^0}$ system.Comment: 24 pages total,8 pages text, 14 figures, 1 table. Submitted to Phys Rev

Search for Direct CP Violation in Non-Leptonic Decays of Charged Ξ\Xi and Λ\Lambda Hyperons

A search for direct CP violation in the non-leptonic decays of hyperons has been performed. In comparing the product of the decay parameters, $\alpha_{\Xi}\alpha_{\Lambda}$, in terms of an asymmetry parameter, $A_{\Xi\Lambda}$, between hyperons and anti-hyperons in the charged $\Xi \to \Lambda \pi$ and $\Lambda \to p \pi$ decay sequence, we found no evidence of direct CP violations. The parameter $A_{\Xi\Lambda}$ was measured to be $0.012 \pm 0.014$.Comment: Submitted for publication; RevTex, 13 pages, 4 figure

PERMEABILITY TO RESIDUAL WATER SATURATION IN OIL SATURATED PLUGS

ABSTRACT A series of laboratory experiments have been conducted to determine the permeability of brine close to irreducible water saturations with varying rock types, capillary pressures, saturations and permeabilities. X-ray tomography (CT) was used in one experiment as a quality assurance measure, visualizing the distribution of the flow of S wi phase in the sample. Water-saturated plugs attached to a water-wet ceramic membrane were drained by oil to S wi . Oil was then substituted by water at the inlet keeping both the water-and the oilsaturations in the plug constant. This was done in order to allow for water to flow through the plug and the membrane. A subsurface analogue to this laboratory experiment is a hydrocarbon-filled reservoir that is leaking water through a cap rock or a fault -keeping the hydrocarbons in place. The CT scan images showed that, although the overall flow rate was very low, the injected water moved quickly through the S wi -phase. Only a small fraction of the S wi volume contributed to this flow. The CT experiment also revealed some experimental artefacts such as spontaneous imbibition and gravity effects, which warrants further investigation. The result of the experiments verified that water could flow through different core plugs with varying S wi -phase permeability without forcing the oil through the membrane or changing the water saturation. The residual water permeability was dependent on the water saturation (S wi ) and the core plug permeability. Lowering the absolute permeability does not give a similar reduction in water permeability at S wi . The water permeability at S wi ranged from 0.02 µD to 1 µD. The absolute permeability for the different plugs ranged from approximately