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Register a new userMeasurement of the $gamma nrightarrow K^0Sigma^0$ differential cross section over the $K^*$ threshold
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The differential cross section for the quasi-free photoproduction reaction $gamma nrightarrow K^0Sigma^0$ was measured at BGOOD at ELSA from threshold to a center-of-mass energy of SI{2400}{MeV}. A peak is observed at SI{2050}{MeV} where the cross section rises by approximately a factor of four. The available statistics prevent an accurate description of this structure, however it appears consistent with models describing a resonance driven by the constructive interference of dynamically generated vector meson-baryon states, where an equivalent model predicted the $P_C$ states observed at LHCb. If proven correct, this could indicate parallels between the strange and charmed quark sectors.
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This work measured $dsigma/dOmega$ for neutral kaon photoproduction reactions from threshold up to a c.m. energy of 1855MeV, focussing specifically on the $gamma prightarrow K^0Sigma^+$, $gamma nrightarrow K^0Lambda$, and $gamma nrightarrow K^0 Sigma^0$ reactions. Our results for $gamma nrightarrow K^0 Sigma^0$ are the first-ever measurements for that reaction. These data will provide insight into the properties of $N^*$ resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the $pi N$ channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.
The $gamma + p rightarrow K^0 + Sigma^+$ photoproduction reaction is investigated in the energy region from threshold to $E_gamma = 2250$,MeV. The differential cross section exhibits increasing forward-peaking with energy, but only up to the $K^*$ threshold. Beyond, it suddenly returns to a flat distribution with the forward cross section dropping by a factor of four. In the total cross section a pronounced structure is observed between the $K^*Lambda$ and $K^*Sigma$ thresholds. It is speculated whether this signals the turnover of the reaction mechanism from t-channel exchange below the $K^*$ production threshold to an s-channel mechanism associated with the formation of a dynamically generated $K^*$-hyperon intermediate state.
The process $e^+e^-to K^+K^-pi^0$ is studied with the SND detector at the VEPP-2000 $e^+e^-$ collider. Basing on data with an integrated luminosity of 26.4~pb$^{-1}$ we measure the $e^+e^-to K^+K^-pi^0$ cross section in the center-of-mass energy range from 1.28 up to 2 GeV. The measured mass spectrum of the $Kpi$ system indicates that the dominant mechanism of this reaction is the transition through the $K^{ast}(892)K$ intermediate state. The cross section for the $phipi^0$ intermediate state is measured separately. The SND results are consistent with previous measurements in the BABAR experiment and have comparable accuracy. We study the effect of the interference between the $phipi^0$ and $K^ast K$ amplitudes. It is found that the interference gives sizable contribution to the measured $e^+e^- to phi pi^0to K^+K^-pi^0$ cross section below 1.7 GeV.
$K^+Lambda(1405)$ photoproduction has been studied at the BGOOD experiment via the all neutral decay, $Lambda(1405)rightarrowSigma^0pi^0$. BGOODs unique experimental setup allows both the cross section and $Lambda(1405)$ invariant mass distribution (line shape) to be measured over a broad $K^+$ polar angle range, extending to extreme forward $K^+$ angles unattainable at previous experiments. The line shape was determined to be in agreement with the previous results of CLAS and ANKE, and appear consistent with two poles derived in $chi$PT based models. %with hints of a double peak structure which may have been observed in the ANKE results At forward $K^+$ angles the relative strength of the peaks appear to change, however more statistics are required for a firm conclusion. Evidence is provided for the role of a triangle singularity driven by the $N^*(2030)$ resonance, which appears to significantly contribute to $K^+Lambda(1405)$ photoproduction. This is observed in both the angular distributions and the integrated cross section which was determined with unprecedented energy resolution.
We present measurements of the differential cross section and Lambda recoil polarization for the gamma p to K+ Lambda reaction made using the CLAS detector at Jefferson Lab. These measurements cover the center-of-mass energy range from 1.62 to 2.84 GeV and a wide range of center-of-mass K+ production angles. Independent analyses were performed using the K+ p pi- and K+ p (missing pi -) final-state topologies; results from these analyses were found to exhibit good agreement. These differential cross section measurements show excellent agreement with previous CLAS and LEPS results and offer increased precision and a 300 MeV increase in energy coverage. The recoil polarization data agree well with previous results and offer a large increase in precision and a 500 MeV extension in energy range. The increased center-of-mass energy range that these data represent will allow for independent study of non-resonant K+ Lambda photoproduction mechanisms at all production angles.
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