arXiv subjects

J. K. Ahn

Publications and source records attributed to J. K. Ahn.

149 records · Page 9Linked to original sources

arXiv2005

Diffractive $ϕ$-meson photoproduction on proton near threshold

Photoproduction of $ϕ$-meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to $E_γ$= 2.37 GeV. The differential cross sections at $t = -|t|_{min}$ do not increase smoothly as $E_γ$ increases, but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that $ϕ$-mesons are photo-produced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

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arXiv2005

Measurement of the Xi-p Scattering Cross Sections at Low Energy

In this paper we report cross-section measurements for $Ξ^-p$ elastic and inelastic scatterings at low energy using a scintillating fiber active target. Upper limit on the total cross-section for the elastic scattering was found to be 24 mb at 90% confidence level, and the total cross section for the $Ξ^-p\toΛΛ$ reaction was found to be $4.3^{+6.3}_{-2.7}$ mb. We compare the results with currently competing theoretical estimates.

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arXiv2004

Nonlinear Dynamical Behaviors of the Equilibrium Longitudinal Distribution by Localized Wakes in an Electron Storage Ring

We investigate the effects of a localized constant wake and a localized linear wake on the longitudinal beam distribution in equilibrium. We also examine the effects of the composite wake on the particle distribution when the constant wake and linear wake simultaneously exist in the ring. While moving around the parameter space, the system can show bifurcation phenomena and transition features between periodic states. We study the dynamical states in a beam, using the multi-particle tracking method in a Gaussian approximation. They show good qualitative agreement.

physics.acc-ph↗

arXiv2004

phi photo-production from Li, C, Al, and Cu nuclei at Egamma=1.5 - 2.4 GeV

The photo-production of $ϕ$ mesons from Li, C, Al, and Cu at forward angles has been measured at $E_gamma$=1.5--2.4 GeV. The number of events for incoherent phi photo-production is found to have a target mass number dependence of $A^{0.72\pm 0.07}$ in the kinematical region of $|t|\le 0.6$ ${\rm GeV}^2/c^2$. The total cross section of the $ϕ$-nucleon interaction, $σ_{ϕN}$, has been estimated as $35^{+17}_{-11}$ mb using the $A$-dependence of the $ϕ$ photo-production yield and a Glauber-type multiple scattering theory. This value is much larger than $σ_{ϕN}$ in free space, suggesting that the $ϕ$ properties might change in the nuclear medium.

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arXiv2003

Beam polarization asymmetries for the p(gamma,K+)Lambda and p(gamma,K+)Sigma0 reactions at Egamma=1.5-2.4 GeV

Beam polarization asymmetries for the p(gamma,K+)Lambda and p(gamma,K+)sigma0 reactions are measured for the first time for Egamma=1.5-2.4 GeV and 0.6<cos(theta_cm(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are sofar undiscovered.

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