Differential cross sections and spin density matrix elements for the reaction gamma p -> p omega

High-statistics differential cross sections and spin density matrix elements for the reaction gamma p -> p omega have been measured using the CLAS at Jefferson Lab for center-of-mass (CM) energies from threshold up to 2.84 GeV. Results are reported in 112 10-MeV wide CM energy bins, each subdivided into cos(theta_CM) bins of width 0.1. These are the most precise and extensive omega photoproduction measurements to date. A number of prominent structures are clearly present in the data. Many of these have not previously been observed due to limited statistics in earlier measurements

Beam-Recoil Polarization Transfer in the Nucleon Resonance Region in the Exclusive e⃗p→e′K+Λ⃗\vec{e}p \to e'K^+\vec{\Lambda} and e⃗p→e′K+Σ⃗0\vec{e}p \to e'K^+\vec{\Sigma}^0 Reactions at CLAS

Beam-recoil transferred polarizations for the exclusive $\vec{e}p \to e'K^+ \vec{\Lambda},\vec{\Sigma}^0$ reactions have been measured using the CLAS spectrometer at Jefferson Laboratory. New measurements have been completed at beam energies of 4.261 and 5.754 GeV that span a range of momentum transfer $Q^2$ from 0.7 to 5.4 GeV$^2$, invariant energy $W$ from 1.6 to 2.6 GeV, and the full center-of-mass angular range of the $K^+$ meson. These new data add to the existing CLAS $K^+\Lambda$ measurements at 2.567 GeV, and provide the first-ever data for the $K^+\Sigma^0$ channel in electroproduction. Comparisons of the data with several theoretical models are used to study the sensitivity to s-channel resonance contributions and the underlying reaction mechanism. Interpretations within two semi-classical partonic models are made to probe the underlying reaction mechanism and the $s\bar{s}$ quark-pair creation dynamics.Comment: 48 pages, 22 figure

The extraction of ϕ−N\phi-N total cross section from d(γ,pK+K−)nd(\gamma,pK^{+}K^{-})n

We report on the first measurement of the differential cross section of $\phi$-meson photoproduction for the $d(\gamma,pK^{+}K^{-})n$ exclusive reaction channel. The experiment was performed using a \textcolor{black}{tagged-photon} beam and the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. A combined analysis using data from the $d(\gamma,pK^{+}K^{-})n$ channel and those from a previous publication on coherent $\phi$ production on the deuteron has been carried out to extract the $\phi-N$ total cross section, $\sigma_{\phi N}$. The extracted $\phi-N$ total cross section favors a value above 20 mb. This value is larger than the value extracted using vector-meson dominance models for $\phi$ photoproduction on the proton.Comment: 7 pages 4 figure

Limits on active to sterile neutrino oscillations from disappearance searches in the MINOS, Daya Bay, and bugey-3 experiments

Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin^2 2θμe are set over 6 orders of magnitude in the sterile mass-squared splitting Δm^2 41. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Δm^2 41 < 0.8 eV^2 at 95% CLs

Beam-Recoil Polarization Transfer in the Nucleon Resonance Region in the Exclusive vec-ep ---> e-prime K+ vec-Lambda and vec-ep ---> e-prime K+ vec-Sigma0 Reactions at CLAS

Beam-recoil transferred polarizations for the exclusive (e) over right arrow p -> e' K(+)(Lambda) over right arrow, (Sigma) over right arrow (0) reactions have been measured using the Continuous Electron Beam Accelerator Facility's large acceptance spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. New measurements have been completed at beam energies of 4.261 and 5.754 GeV that span a range of momentum transfer Q(2) from 0.7 to 5.4 GeV(2), invariant energy W from 1.6 to 2.6 GeV, and the full center-of-mass angular range of the K(+) meson. These new data add to the existing CLAS K(+)Lambda measurements at 2.567 GeV, and provide the first-ever data for the K(+) Sigma(0) channel in electroproduction. Comparisons of the data with several theoretical models are used to study the sensitivity to s-channel resonance contributions and the underlying reaction mechanism. Interpretations within two semiclassical partonic models are made to probe the underlying reaction mechanism and the s (s) over bar quark-pair creation dynamics

Limits on Active to Sterile Neutrino Oscillations from Disappearance Searches in the MINOS, Daya Bay, and Bugey-3 Experiments.

Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin^{2}2θ_{μe} are set over 6 orders of magnitude in the sterile mass-squared splitting Δm_{41}^{2}. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Δm_{41}^{2}&lt;0.8  eV^{2} at 95%  CL_{s}

Photoproduction of pi(+)pi(-) meson pairs on the proton

The cross section for photoproduction of pion pairs from hydrogen has been calculated from the cut-off static theory, assuming the energy is sufficiently low that one of the mesons is produced in an S state, the other in a P state. It is shown that the cross section for this process can be expressed exactly in terms of the P-wave scattering phase shifts, provided the S-wave meson-nucleon interactions and the meson-meson interaction can be neglected. The theoretical predictions obtained here are in general agreement with preliminary experimental results

Partial wave analysis of the reaction gamma p ---> p omega and the search for nucleon resonances

An event-based partial wave analysis (PWA) of the reaction gamma p -> p omega has been performed on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world's first high-precision spin-density matrix element measurements, available to the event-based PWA through the decay distribution of omega ->pi(+)pi(-)pi(0). The data confirm the dominance of the t-channel pi(0) exchange amplitude in the forward direction. The dominant resonance contributions are consistent with the previously identified states F(15)(1680) and D(13)(1700) near threshold, as well as the G(17)(2190) at higher energies. Suggestive evidence for the presence of a J(P)=5/2(+) state around 2 GeV, a "missing" state, has also been found. Evidence for other states is inconclusive

Differential cross sections for the reactions γp→pη and γp→pη′

High-statistics differential cross sections for the reactions γp→pη and γp→pη′ have been measured using the CEBAF large acceptance spectrometer (CLAS) at Jefferson Lab for center-of-mass energies from near threshold up to 2.84 GeV. The η′ results are the most precise to date and provide the largest energy and angular coverage. The η measurements extend the energy range of the world’s large-angle results by approximately 300 MeV. These new data, in particular the η′ measurements, are likely to help constrain the analyses being performed to search for new baryon resonance states