Clinical Endoscopic and Histological Characteristics of Helicobacter Pylori Positive and Negative Armenian Children with Recurrent Abdominal Pain and/or Dyspepsia

Recurrent abdominal pain (RAP) and dyspepsia are common complaints in children. These symptoms are often associated with Helicobacter pylori (Hp) infection. The aim of the present study was to prospectively analyze clinical, endoscopic, and histological characteristics of Hp+ and Hp- children with RAP and/or dyspepsia. Patients aged 2-18 years with RAP and/or dyspepsia, referred for an upper endoscopy to Arabkir Medical Center - Institute of Child and Adolescent Health (Arabkir MC-ICAH) from November 2015 to December 2017, were involved in the study. Histology was assessed according to the updated Sydney system. Gastric and duodenal specimens were stained by modified Giemsa staining for Hp infection. One antral biopsy was cultured in Hp selective media. 150 patients were included into the study: 70.7% Hp+, 29.3% Hp-. Nausea and vomiting were significantly more common in Hp+ patients (p<0.05). Gastric nodularity (p=0.02), erosions in the stomach (p=0.056), and duodenal erosions (p=0.019) were more common in Hp+. Chronic active (p=0.027) and non-active gastritis (p=0.002), cumulative findings of metaplasia/dysplasia/atrophy in the stomach (p=0.014) and chronic non-active duodenitis (p=0.016), were significantly more common in Hp+ patients. Hp infection prevalence is high in Armenian children with dyspepsia and/or RAP. Clinical symptoms, endoscopic findings, and histopathological findings were significantly different in Hp+ patients as compared to Hp- patients

Experimental Tests of QCD Scaling Laws at Large Momentum Transfer in Exclusive Light-Meson Photoproduction

We evaluated CLAS Collaboration measurements for the 90◦ meson photoproduction off the nucleon using a tagged photon beam spanning the energy interval s = 3–11 GeV2. The results are compared with the “quark counting rules” predictions

Observation of a narrow structure in p(gamma,K_s)X via interference with phi-meson production

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width sigma=6 MeV in the missing of K_s in the reaction gamma+p = pK_sK_L. The observed structure may be due to the interference between a strange (or anti-strange) baryon resonance in the pK_L system and the phi(K_sK_L) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log likelihood ratio of the resonant signal+background hypothesis and the phi-production based background only hypothesis corresponds to 5.3 sigma.Comment: Accepted for publication in Physical Review C, 9 pages, 11 figures, 1 table added, revise

Differential Cross Sections for Λ (1520) Using Photoproduction at CLAS

The reaction p → K+Λ (1520) using photoproduction data from the CLAS g12 experiment at Jefferson Lab is studied. The decay of Λ(1520) into two exclusive channels, Σπ+π- and Σ-π+, is studied from the detected K+, π+, and π- particles. A good agreement is established for the Λ(1520) differential cross sections with the previous CLAS measurements. The differential cross sections as a function of center-of-mass angle are extended to higher photon energies. Newly added are the differential cross sections as a function of invariant four-momentum transfer t, which is the natural variable to use for a theoretical model based on a Regge-exchange reaction mechanism. No new N* resonances decaying into the K+Λ (1520) final state are found

First Measurement of Ξ− Polarization in Photoproduction

Despite decades of studies of the photoproduction of hyperons, both their production mechanisms and their spectra of excited states are still largely unknown. While the parity-violating weak decay of hyperons offers a means of measuring their polarization, which could help discern their production mechanisms and identify their excitation spectra, no such study has been possible for doubly strange baryons in photoproduction, due to low production cross sections. However, by making use of the reaction γ p → K+K+Ξ−, we have measured, for the first time, the induced polarization, P, and the transferred polarization from circularly polarized real photons, characterized by Cx and Cz, to recoiling Ξ−s. The data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab for photon energies from just over threshold (2.4 GeV) to 5.45 GeV. These first-time measurements are compared, and are shown to broadly agree, with model predictions in which cascade photoproduction proceeds through the decay of intermediate hyperon resonances that are produced via relativistic meson exchange, offering a new step forward in the understanding of the production and polarization of doubly strange baryons

Observation of a Narrow Structure in \u3csup\u3e1\u3c/sup\u3eH(yKSO)X Via Interference with φ-Meson Production

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width σ = 6 MeV in the missing mass of KS in the reaction γ+p → pKSKL. The observed structure may be due to the interference between a strange (or antistrange) baryon resonance in the pKL system and the φ(KSKL) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log-likelihood ratio of the resonant signal + background hypothesis and the φ-production-based background-only hypothesis corresponds to 5.3σ. ©2012 American Physical Societ

Photoproduction of the f₂(1270) Meson Using the CLAS Detector

The quark structure of the f2(1270) meson has, for many years, been assumed to be a pure quark-antiquark (qq⁻) resonance with quantum numbers JPC = 2++. Recently, it was proposed that the f2(1270) is a molecular state made from the attractive interaction of two mesons. Such a state would be expected to decay strongly to final states with charged pions due to the dominant decay → π+π-, whereas decay to two neutral pions would likely be suppressed. Here, we measure for the first time the reaction p -\u3e π0π0p, using the CEBAF Large Acceptance Spectrometer detector at Jefferson Lab for incident beam energies between 3.6 and 5.4 GeV. Differential cross sections, dσ/dt, for f2(1270) photoproduction are extracted with good precision due to low backgrounds and are compared to theoretical calculations