Evidence for formation of a narrow pKshort resonance with mass near 1533 MeV in neutrino interactions

A narrow baryon resonance is observed in invariant mass of the pKshort system formed in neutrino and antineutrino collisions with nuclei. The mass of the resonance is estimated as (1533+-5)MeV. The observed width is less than 20 MeV, and is compatible with being entirely due to experimental resolution. The statistical significance of the signal is near 6.7 standard deviations. As the position of the observed resonance does not match the mass of any known \Sigma^{*+} state, we believe that it arises from neutrino production of the \Theta^+ pentaquark baryon. The analysis is based on the data obtained in past neutrino experiments with big bubble chambers: WA21, WA25, WA59, E180 and E632.Comment: Institute of Theoretical and Experimental Physics, B.Cheremyshkinskya 25, Moscow 117259, Russi

Antikaon angular distributions in the reaction γd→K−Θ+p→K−K+np{\gamma}d \to K^-{\Theta}^+p \to K^-K^+np near the threshold and the parity of the Θ+{\Theta}^+ pentaquark

Within spectator model we study the reaction ${\gamma}d \to K^-{\Theta}^+p \to K^-K^+np$ in the threshold energy region. We present the predictions for the exclusive and inclusive antikaon angular distributions in the laboratory system for this reaction calculated for two possible parity states of the ${\Theta}^+$ resonance at 1.5 and 1.75 GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the sampled phase space where contribution from the main background sources associated with the ${\phi}(1020)$, ${\Lambda}(1520)$ production as well as with the $K^-p$--rescattering in the final state, is expected to be dominant. We show that under chosen kinematics these distributions are sensitive to the ${\Theta}^+$ parity and, therefore, can be used as a filter for the determination of its parity.Comment: 18 pages, 8 figures; will be published in Phys.Atom.Nucl_4_200

SARS-CoV-2 antibodies protect against reinfection for at least 6 months in a multicentre seroepidemiological workplace cohort.

Identifying the potential for SARS-CoV-2 reinfection is crucial for understanding possible long-term epidemic dynamics. We analysed longitudinal PCR and serological testing data from a prospective cohort of 4,411 United States employees in 4 states between April 2020 and February 2021. We conducted a multivariable logistic regression investigating the association between baseline serological status and subsequent PCR test result in order to calculate an odds ratio for reinfection. We estimated an odds ratio for reinfection ranging from 0.14 (95% CI: 0.019 to 0.63) to 0.28 (95% CI: 0.05 to 1.1), implying that the presence of SARS-CoV-2 antibodies at baseline is associated with around 72% to 86% reduced odds of a subsequent PCR positive test based on our point estimates. This suggests that primary infection with SARS-CoV-2 provides protection against reinfection in the majority of individuals, at least over a 6-month time period. We also highlight 2 major sources of bias and uncertainty to be considered when estimating the relative risk of reinfection, confounders and the choice of baseline time point, and show how to account for both in reinfection analysis