Pentaquark searches at FOCUS

We find no evidence for high-energy photoproduction of pentaquarks at 1540 MeV/$c^2$, 1862 MeV/$c^2$, or 3099 MeV/$c^2$ using decay modes $pK_S^0$, $\Xi^-\pi^-$, and $D^{(*)-}p$, respectively.Comment: Proceedings from talk at 2004 DPF Meeting at University of California, Riversid

On the SigmaN cusp in the pp -> pK+Lambda reaction

Measurements of the $pp \to pK^+\Lambda$ reaction at $T_p$ = 2.28 GeV have been carried out at COSY-TOF. In addition to the $\Lambda p$ FSI and $N^*$ resonance excitation effects a pronounced narrow structure is observed in the Dalitz plot and in its projection on the $p\Lambda$-invariant mass. The structure appears at the $pp \to$N$K^+\Sigma$ threshold and is interpreted as $\Sigma$N cusp effect. The observed width of 20 MeV/$c^2$ is substantially broader than anticipated from previous inclusive measurements. Angular distributions of this cusp structure are shown to be dissimilar to those in the residual $pK^+\Lambda$ channel, but similar to those observed in the $pK^+\Sigma^0$ channel

Investigating the Unexpected Behavior for the Release Kinetics of Brilliant Blue Encapsulated into Calcium Alginate Beads

This work is focused on investigating the unexpected behavior for the release kinetics of brilliant blue (BB) encapsulated into calcium alginate beads. By increasing the alginate concentration from 1-3% (w/v), the release of BB over time was found to follow two different behaviors. For the first two hours, the order was 1% > 2% > 3%, after which it was as follow: 1% > 3% > 2%. The unanticipated increase in BB release using 3% (w/v) alginate beads after two hours over that of 2% (w/v) alginate was examined by the swelling and bursting tests. The results were showing clear evidences by data and image the unusual behavior of 3% (w/v) alginate beads at two hours of swelling. This unexpected behavior for the 3% (w/v) alginate beads might be due to the higher osmotic pressure inside the beads. Overall, 2% (w/v) calcium alginate beads were considered to be the optimum formulation showing an excellent carrier for targeting drugs to the intestine, where the swelling of the beads were 60 % in the acidic medium, it was 5000 % in the alkaline medium

Phenomenology of pp->pp eta reaction close to threshold

The recent high statistics measurement of the pp -> pp eta reaction at an excess energy Q=15.5 MeV has been analysed by means of partial wave decomposition of the cross section. Guided by the dominance of the final state 1S0 pp interaction (FSI), we keep only terms involving the FSI enhancement factor. The measured p-p and p-eta effective mass spectra can be well reproduced by lifting the standard on-shell approximation in the enhancement factor and by allowing for a linear energy dependence in the leading 3P0->1S0,s partial wave amplitude. Higher partial waves seem to play only a marginal role

Production of Lambda and Sigma^0 hyperons in proton-proton collisions

This paper reports results on simultaneous measurements of the reaction channels pp -> pK+\Lambda and pp -> pK+\Sigma^0 at excess energies of 204, 239, and 284 MeV (\Lambda) and 127, 162, and 207 MeV (\Sigma^0). Total and differential cross sections are given for both reactions. It is concluded from the measured total cross sections that the high energy limit of the cross section ratio is almost reached at an excess energy of only about 200 MeV. From the differential distributions observed in the overall CMS as well as in the Jackson and helicity frames, a significant contribution of interfering nucleon resonances to the \Lambda production mechanism is concluded while resonant \Sigma^0-production seems to be of lesser importance and takes place only through specific partial waves of the entrance channel. The data also indicate that kaon exchange plays a minor role in the case of \Lambda- but an important role for \Sigma^0-production. Thus the peculiar energy dependence of the \Lambda-to-\Sigma^0 cross section ratio appears in a new light as its explanation requires more than mere differences between the p\Lambda and the p\Sigma^0 final state interaction. The data provide a benchmark for theoretical models already available or yet to come.Comment: 18 pages, 10 figures; accepted by The European Physical Journal A (EPJ A

Salivary PCR detection of Helicobacter pylori DNA in Egyptian patients with dyspepsia

AbstractSeveral methods are available for detecting Helicobacter pylori infection: (1) invasive methods based on gastric biopsies, (2) non invasive methods like Urea Breath Test (UBT), serology and stool antigen tests. Importance of salivary PCR in detection of H. pylori is still questionable. To evaluate the role of salivary PCR technique in detecting H. pylori gastric affection in Egyptian patients with dyspepsia and in differentiating between functional dyspepsia and acid-ulcer syndrome. This study included 60 patients with dyspepsia classified into three groups: (Group 1) patients with gastric H. pylori and ulcers or erosions (n=20), (Group 2) patients with gastric H. pylori and no ulcers or erosions and had functional dyspepsia (n=20), (Group 3) patients without H. pylori and had functional dyspepsia (n=20). All underwent upper gastrointestinal endoscopy with biopsies, rapid urease test and salivary samples for H. pylori PCR. Significant difference between the three groups regarding salivary PCR values. No significant difference between Group 1 and Group 2 but both had significant difference with Group 3, significant difference between gastric H. pylori positive patients (n=40) and negative ones (n=20). Salivary PCR test had sensitivity of 85%, specificity of 70% in diagnosing H. pylori. PCR value of 534000Iu/ml had best sensitivity (75%) and specificity (100%) for diagnosing H. pylori, highly significant positive correlation between H. pylori gastric affection and salivary PCR values. No significant difference between patients with acid ulcer syndrome (n=20) and those with functional dyspepsia (n=40) as regard salivary PCR mean values. Salivary PCR test showed sensitivity of 100%, specificity of 50% in differentiating between patients with acid ulcer syndrome and those with functional dyspepsia. PCR value of 440000 Iu/ml had best sensitivity (100%) and specificity (55%) in differentiating acid ulcer syndrome from functional dyspepsia with non significant. H. pylori salivary PCR may be of value in diagnosing H. pylori gastric affection and is strongly correlated with it but it is of limited value in differentiating between acid ulcer syndrome and functional dyspepsia

Systematic study of the pp -> pp omega reaction

A systematic study of the production of omega-mesons in proton-proton-collisions was carried out in a kinematically complete experiment at three excess energies(epsilon= 92, 128, 173MeV). Both protons were detected using the large-acceptance COSY-TOF spectrometer at an external beam line at the Cooler Synchrotron COSY at Forschungszentrum J\"ulich. The total cross section, angular distributions of both omega-mesons and protons were measured and presented in various reference frames such as the overall CMS, helicity and Jackson frame. In addition, the orientation of the omega-spin and invariant mass spectra were determined. We observe omega-production to take place dominantly in Ss and Sp final states at epsilon = 92, 128 MeV and, additionally, in Sd at epsilon= 173 MeV. No obvious indication of resonant omega-production via N^*-resonances was found, as proton angular distributions are almost isotropic and invariant mass spectra are compatible with phase space distributions. A dominant role of ^3P_1 and ^1S_0 initial partial waves for omega-production was concluded from the orientation of the decay plane of the omega-meson. Although the Jackson angle distributions in the omega-p-Jackson frame are anisotropic we argue that this is not an indication of a resonance but rather a kinematical effect reflecting the anisotropy of the omega angular distribution. The helicity angle distribution in the omega-p-helicity frame shows an anisotropy which probably reflects effects of the omega angular momenta in the final state; this observable may be, in addition to the orientation of the omega decay plane, the most sensitive one to judge the validity of theoretical descriptions of the production process.Comment: 17 pages, 16 figures, accepted for publication in EPJ

An analysis of the reaction pp --> pp\eta near threshold

It is shown that most of the available data on the $pp\to pp\eta$ reaction, including the invariant mass distributions in the $pp\to pp\eta$ reaction recently measured at COSY, can be understood in terms of the partial-wave amplitudes involving final $pp$ $S$ and $P$ states and the $\eta$ meson s-wave. This finding, together with the fact that results within a meson--exchange model are especially sensitive to the details of the excitation mechanism of the $S_{11}(1535)$ resonance, demonstrates the possibility of investigating the properties of this resonance in $NN$ collisions. The spin correlation function $C_{xx}$ is shown to disentangle the $S$- and $P$-wave contributions. It is also argued that spin correlations may be used to help constrain the contributions of the amplitudes corresponding to the final $pp$ $^3P_0$Comment: 10 pages, 7 figures, minor revision with one additional figur