arXiv subjects

Seongbae Yang

Publications and source records attributed to Seongbae Yang.

5 recordsLinked to original sources

arXiv2026

First Measurement of the $K^-$ Escape Cross Section in the ${}^{12}{\rm C}(K^{-},p)$ Reaction

We investigated the $\bar{K}$-nucleus interaction through the simultaneous measurement of the inclusive $^{12}{\rm C}(K^-, p)$ and exclusive $K^-$-escape $^{12}{\rm C}(K^-, p K^-_{esc})$ reactions at $1.8$ GeV/$c$ at J-PARC. The present measurement explicitly focuses on the $K^-$ escape process for the first time, successfully accomplishing a direct experimental determination of the imaginary part of the $K^-$ optical potential. The differential cross section for the $K^-$-escape reaction was determined to be $436 \pm 6\:(\text{stat.}) \pm 44\:(\text{syst.})~\mu\text{b/sr}$. A simultaneous likelihood fit yielded real and imaginary potential strengths of $V_0 = -72\:^{+3}_{-5}\:(\text{stat.})\:^{+0}_{-8}\:(\text{syst.})~\text{MeV}$ and $W_0 = -100\:^{+7}_{-1}\:(\text{stat.})\:^{+0}_{-16}\:(\text{syst.})~\text{MeV}$ at the nuclear center, respectively. The derived $W_0$ is significantly stronger than that predicted by theoretical models based on one-nucleon processes, suggesting possible contribution of multi-nucleon involving processes.

nucl-ex↗

arXiv2025

Cross section Measurements for $^{12}$C$(K^-, K^+\Xi^-)$ and $^{12}$C$(K^-, K^+\Lambda\Lambda)$ Reactions at 1.8 GeV$/c$

We present a measurement of the production of $\Xi^-$ and $\Lambda\Lambda$ in the $^{12}$C$(K^-, K^+)$ reaction at an incident beam momentum of 1.8 GeV/$\mathit{c}$, based on high-statistics data from J-PARC E42. The cross section for the $^{12}$C$(K^-, K^+\Xi^-)$ reaction, compared to the inclusive $^{12}$C$(K^-, K^+)$ reaction cross section, indicates that the $\Xi^-$ escaping probability peaks at 70\% in the energy region of $E_\Xi=$100 to 150 MeV above the $\Xi^-$ emission threshold. A classical approach using eikonal approximation shows that the total cross sections for $\Xi^-$ inelastic scattering ranges between 42 mb and 23 mb in the $\Xi^-$ momentum range from 0.4 to 0.6 GeV/c. Furthermore, based on the relative cross section for the $^{12}$C$(K^-, K^+\Lambda\Lambda)$ reaction, the total cross section for $\Xi^-p\to\Lambda\Lambda$ is estimated in the same approach to vary between 2.2 mb and 1.0 mb in the momentum range of 0.40 to 0.65 GeV/c. Specifically, a cross section of 1.0 mb in the momentum range of 0.5 to 0.6 GeV/c imposes a constraint on the upper bound of the decay width of the $\Xi^-$ particle in infinite nuclear matter, revealing $\Gamma_\Xi< \sim 0.6$ MeV.

nucl-ex↗

arXiv2019

Hyperon production in $Λ_c^+\to K^-pπ^+$ and $Λ_c^+\to K^0_Spπ^0 $

We investigate $S=-1$ hyperon production from the $Λ_c^+\to K^-pπ^+$ and $Λ_c^+\to K^0_Spπ^0$ decays within the effective Lagrangian approach. We consider the $Σ/Λ$ ground states, $Λ(1520)$, $Λ(1670)(J^p=1/2^-)$, $Λ(1890)(J^p=3/2^+)$; $Λ/Σ$-pole contributions from the combined resonances between 1800 MeV and 2100 MeV; and $N/Δ$-pole and $K^\ast$-pole contributions, which include the proton, $Δ(1232)$, and $K(892)$. We calculate the Dalitz plot density $(d^2Γ/dM_{K^-p}dM_{K^-π^+}$) for the $Λ_c^+\to K^-pπ^+$ decay. The calculated result is in good agreement with experimental data from the Belle Collaboration. Using the parameters from the fit, we present the Dalitz plot density for the $Λ_c^+\to K^0_Spπ^0$ decay. In our calculation, a sharp peak-like structure near 1665 MeV is predicted in the $Λ_c^+\to K^-pπ^+$ decay because of the interference effects between the $Λ(1670)$ resonance and $η$-$Λ$ loop channels. We also demonstrate that we can access direct information regarding the weak couplings of $Λ(1670)$ and $Σ(1670)$ from the $Λ_c^+\to K^0_Spπ^0$ decay. Finally, a possible interpretation for the 1665 MeV structure beyond our prediction is briefly discussed.

hep-ph↗

arXiv2014

Observation of the "$K^-pp$"-like structure in the $d(π^+, K^+)$ reaction at 1.69 GeV/$c$

We have observed a "$K^-pp$"-like structure in the $d(π^+,K^+)$ reaction at 1.69 GeV/$c$. In this reaction $Λ(1405)$ hyperon resonance is expected to be produced as a doorway to form the $K^-pp$ through the $Λ^*p\rightarrow K^-pp$ process. However, most of the produced $Λ(1405)$'s would escape from deuteron without secondary reactions. Therefore, coincidence of high-momentum ($>$ 250~MeV/$c$) proton(s) in large emission angles ($39^\circ<θ_{lab.}<122^\circ$) was requested to enhance the signal-to-background ratio. A broad enhancement in the proton coincidence spectra are observed around the missing-mass of 2.27 GeV/$c^2$, which corresponds to the $K^-pp$ binding energy of 95 $^{+18}_{-17}$ (stat.) $^{+30}_{-21}$ (syst.) MeV and the width of 162 $^{+87}_{-45}$ (stat.) $^{+66}_{-78}$ (syst.) MeV.

nucl-ex↗

arXiv2014

Inclusive spectrum of the $d(π^+, K^+)$ reaction at 1.69 GeV/c

We have measured an inclusive missing-mass spectrum of the $d(π^+, K^+)$ reaction at the pion incident momentum of 1.69 GeV/$c$ at the laboratory scattering angles between 2$^\circ$ and 16$^\circ$ with the missing-mass resolution of 2.7 $\pm$ 0.1 MeV/$c^2$ (FWHM) at the missing mass of 2.27 GeV/$c^{2}$. In this Letter, we first try to understand the spectrum as a simple quasi-free picture based on several known elementary cross sections, considering the neutron/proton Fermi motion in deuteron. While gross spectrum structures are well understood in this picture, we have observed two distinct deviations; one peculiar enhancement at 2.13 GeV/$c^2$ is due to the $ΣN$ cusp, and the other notable feature is a shift of a broad bump structure, mainly originating from hyperon resonance productions of $Λ(1405)$ and $Σ(1385)^{+/0}$, by about 22.4 $\pm$ 0.4 (stat.) $^{+2.7}_{-1.7}$ (syst.) MeV/$c^2$ toward the low-mass side, which is calculated in the kinematics of a proton at rest as the target.

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