0000000000242001
AUTHOR
S. Janssen
showing 15 related works from this author
Double pi(0) photoproduction off the proton at threshold
2003
The reaction $\gamma p \to \pi^0 \pi^0 p$ has been measured using the TAPS BaF$_2$ calorimeter at the tagged photon facility of the Mainz Microtron accelerator. Chiral perturbation theory (ChPT) predicts that close to threshold this channel is significantly enhanced compared to double pion final states with charged pions. In contrast to other reaction channels, the lower order tree terms are strongly suppressed in 2$\pi^0$ photoproduction. The consequence is the dominance of pion loops in the 2$\pi^0$ channel close to threshold - a result that opens new prospects for the test of ChPT and in particular its inherent loop terms. The present measurement is the first which is sensitive enough fo…
New results on the Roper resonance and the P_{11} partial wave
2008
Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the $P_{11}$ partial wave are studied in a combined analysis of pion- and photo-induced reactions. We find the Roper pole at $\{(1371\pm7)-i(92\pm10)\}$ MeV and an elasticity of $0.61\pm 0.03$. The largest decay coupling is found for the $N\sigma$ ($\sigma=(\pi\pi)$-$S$-wave). The analysis is based on new data on $\gamma p\to p\pi^0\pi^0$ for photons in the energy range from the two-pion threshold to 820 MeV from TAPS at Mainz and from 0.4 to 1.3 GeV from Crystal Barrel at Bonn and includes further data from other experiments. The partial wave analysis excludes the p…
In-medium modifications of the pi pi interaction in photon-induced reactions
2002
Differential cross sections of the reactions $(\gamma,\pi^\circ\pi^\circ)$ and $(\gamma,\pi^\circ\pi^++\pi^\circ\pi^-)$ have been measured for several nuclei ($^1$H,$^{12}$C, and $^{\rm nat}$Pb) at an incident-photon energy of $E_{\gamma}$=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the $\pi\pi$ invariant-mass distribution is found in the $\pi^\circ\pi^\circ$ channel. This dependence is not observed in the $\pi^\circ\pi^{+/-}$ channel and is consistent with an in-medium modification of the $\pi\pi$ interaction in the $I$=$J$=0 channel. The data are compared to $\pi$-induced measurements and to calculations within …
The Reactionγp→π0γ′pand the Magnetic Dipole Moment of theΔ+(1232)Resonance
2002
The reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\gamma}}^{\ensuremath{'}}p$ has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between $\sqrt{s}=1221--1331\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}$. The cross section's differential in angle and energy have been determined for the photon ${\ensuremath{\gamma}}^{\ensuremath{'}}$ in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the ${\ensuremath{\Delta}}^{+}(1232)$ resonance and, for the first time, a value of ${\ensuremath{\mu}}_{{\ensuremath{\Delta}}^{+}}=\mathbf{[}{2.7}_{\ensu…
"Table 6" of "In-medium modifications of the pi pi interaction in photon-induced reactions."
2005
Differential cross section for PI0PI+/- production with a Lead target. Errors are statistical only.
"Table 2" of "In-medium modifications of the pi pi interaction in photon-induced reactions."
2005
Differential cross section for PI0PI0 production with a Carbon target. Errors are statistical only.
"Table 1" of "In-medium modifications of the pi pi interaction in photon-induced reactions."
2005
Differential cross section for PI0PI0 production with a proton target. Errors are statistical only. Note that the data given in this table are sightly different (newer) than the data points presented in the paper.
"Table 4" of "In-medium modifications of the pi pi interaction in photon-induced reactions."
2005
Differential cross section for PI0PI+ production with a proton target. Errors are statistical only. Note that the data given in this table are sightly different (newer) than the data points presented in the paper.
CCDC 248541: Experimental Crystal Structure Determination
2004
Related Article: C.Boskovic, A.Sieber, G.Chaboussant, H.U.Gudel, J.Ensling, W.Wernsdorfer, A.Neels, G.Labat, H.Stoeckli-Evans, S.Janssen|2004|Inorg.Chem.|43|5053|doi:10.1021/ic049600f
CCDC 248544: Experimental Crystal Structure Determination
2004
Related Article: C.Boskovic, A.Sieber, G.Chaboussant, H.U.Gudel, J.Ensling, W.Wernsdorfer, A.Neels, G.Labat, H.Stoeckli-Evans, S.Janssen|2004|Inorg.Chem.|43|5053|doi:10.1021/ic049600f
"Table 3" of "In-medium modifications of the pi pi interaction in photon-induced reactions."
2005
Differential cross section for PI0PI0 production with a Lead target. Errors are statistical only.
"Table 1" of "Double pi0 photoproduction off the proton at threshold."
2004
Total cross section measurement. Statistical errors only.
"Table 5" of "In-medium modifications of the pi pi interaction in photon-induced reactions."
2005
Differential cross section for PI0PI+/- production with a Carbon target. Errors are statistical only.
CCDC 248542: Experimental Crystal Structure Determination
2004
Related Article: C.Boskovic, A.Sieber, G.Chaboussant, H.U.Gudel, J.Ensling, W.Wernsdorfer, A.Neels, G.Labat, H.Stoeckli-Evans, S.Janssen|2004|Inorg.Chem.|43|5053|doi:10.1021/ic049600f
CCDC 248543: Experimental Crystal Structure Determination
2004
Related Article: C.Boskovic, A.Sieber, G.Chaboussant, H.U.Gudel, J.Ensling, W.Wernsdorfer, A.Neels, G.Labat, H.Stoeckli-Evans, S.Janssen|2004|Inorg.Chem.|43|5053|doi:10.1021/ic049600f