Double pi(0) photoproduction off the proton at threshold

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…

An Isotensor Dibaryon in the $pp \to pp\pi^+\pi^-$ Reaction?

Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have been carried out at WASA@COSY by means of $pd$ collisions at $T_p$ = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region $T_p = 1.08 - 1.36$ GeV, which is the region of $N^*(1440)$ and $\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P) = 2(1^+)$ produced associatedly with a pion is able to overcome these deficiencies.

Double pion photoproduction off nuclei - Are there effects beyond final-state interaction?

Photoproduction of $\pi^{0}\pi^{0}$ and $\pi^{0}\pi^{\pm}$ pairs from nuclei has been measured over a wide mass range ($^2$H, $^{7}$Li, $^{12}$C, $^{40}$Ca, and $^{\rm nat}$Pb) for photon energies from threshold to 600 MeV. The experiments were performed at the MAMI accelerator in Mainz, using the Glasgow photon tagging spectrometer and a 4$\pi$ electromagnetic calorimeter consisting of the Crystal Ball and TAPS detectors. A shift of the pion-pion invariant mass spectra for heavy nuclei to small invariant masses has been observed for $\pi^0$ pairs but also for the mixed-charge pairs. The precise results allow for the first time a model-independent analysis of the influence of pion final-sta…

Neutron Skin ofPb208from Coherent Pion Photoproduction

Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.)  fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.)  fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.)  fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic p…

Feasibility study for the measurement of πN transition distribution amplitudes at P¯ANDA in p¯p→J/ψπ0

The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is show…

Search for Mesic He with the WASA-at-COSY facility in the And Reactions

We report on the experimental search for the bound state of an η meson and He3 nucleus performed using the WASA-at-COSY detector setup. In order to search for the η-mesic nucleus decay, the pd→3He2γ and pd→3He6γ channels have been analysed. These reactions manifest the direct decay of the η meson bound in a He3 nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to a $^{3}$He-η nucleus width Γ above 20 MeV and binding energy Bs between 0 and 15 MeV. However, the determined cross sections are consistent with…

Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy

We present new data for angular distributions and on the cross section ratio of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.

Search for the $��$ mesic $^3$He in the $pd\rightarrow d p ��^{0}$ reaction with the WASA-at-COSY facility

The excitation function for the $pd\rightarrow$ $d p ��^{0}$ reaction has been measured by WASA-at-COSY experiment with the aim of searching for $^{3}\hspace{-0.03cm}\mbox{He}$-$��$ mesic nuclei. The measurement in the vicinity of $��$ meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the $��$-mesic Helium decays via the formation of an intermediate N$^{*}$(1535) resonance. No direct signal of the $��$-mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the $pd\rightarrow$ $(^{3}\hspace{-0.03c…

Spin dependence of {\eta} meson production in proton-proton collisions close to threshold

Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high degree of the polarized proton beam of COSY, the reaction pp{\to} pp{\eta} has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the precision improved by more than one order of magnitude with respect to previous results allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q = 15 MeV signaling s wave production with no evidence for higher partial waves. At Q = 72 MeV the data reveals strong interference of P s and P p partial waves …

Study of doubly strange systems using stored antiprotons

Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PANDA experiment at FAIR. For the first time, high resolution gamma-spectroscopy of doubly strange Lambda Lambda-hypernuclei will be performed, thus complementing measurements of ground state decays of Lambda Lambda-hypernuclei at J-PARC or possible …

In-medium modifications of the pi pi interaction in photon-induced reactions

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 …

Diagnostik von Pleuraergüssen bei intensivpflichtigen Patienten: Sonographie und Radiologie im Vergleich

Die Sonographie hat als unbelastende und leicht durchzufuhrende Untersuchungsmethode ihren festen Platz auch auf der Intensivstation. Hier konnen u. a. Pleuraergusse beim liegenden Patienten mit hoher Sensitivitat nachgewiesen werden [1–5] und zusatzlich, wie wir zeigen konnten, sicher volumetriert werden [2].

Dialyseassoziierte Amyloidosteopathie - Radiologische Aspekte

Amongst the complications of dialysis, amyloid osteopathy is getting increasingly significant. It is due to deposition of beta 2-microglobulin. To determine the incidence and time of development of this complication, the skeletal radiographs of 185 patients undergoing dialysis, some for up to ten years, were analysed retrospectively. In about 10% of patients, the presence of beta 2-microglobulin osteopathy may be expected. The radiological features, sites of predilection and differential diagnosis of amyloid osteopathy and of other skeletal changes due to dialysis are discussed.

Incoherent neutral pion photoproduction on 12C.

We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The C-12(gamma,pi(0))C-12(4.4 MeV)* reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form fa…

Measurement of the $pn \to pp\pi^0\pi^-$ Reaction in Search for the Recently Observed Resonance Structure in $d\pi^0\pi^0$ and $d\pi^+\pi^-$ systems

Exclusive measurements of the quasi-free $pn \to pp\pi^0\pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $\sqrt s$ = (2.35 - 2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. No ABC effect, {\it i.e.} low-mass enhancement is found in the $\pi^0\pi^-$-invariant mass spectrum -- in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative s-wave. At the upper end of the covered energy region $t$-channel processes for Roper, $\Delta(1600)$ and $\Delta…

Search for the $\eta$ mesic $^3$He in the $pd\rightarrow d p \pi^{0}$ reaction with the WASA-at-COSY facility

The excitation function for the $pd\rightarrow$ $d p \pi^{0}$ reaction has been measured by WASA-at-COSY experiment with the aim of searching for $^{3}\hspace{-0.03cm}\mbox{He}$-$\eta$ mesic nuclei. The measurement in the vicinity of $\eta$ meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the $\eta$-mesic Helium decays via the formation of an intermediate N$^{*}$(1535) resonance. No direct signal of the $\eta$-mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the $pd\rightarrow$ $(^{3}\hspa…

Transparency ratio in γA→η′A′ and the in-medium η′ width

Abstract The photoproduction of η ′ -mesons off different nuclei has been measured with the CBELSA/TAPS detector system for incident photon energies between 1500–2200 MeV. The transparency ratio has been deduced and compared to theoretical calculations describing the propagation of η ′ -mesons in nuclei. The comparison indicates a width of the η ′ -meson of the order of Γ = 15 – 25 MeV at ρ = ρ 0 for an average momentum p η ′ = 1050 MeV / c , at which the η ′ -meson is produced in the nuclear rest frame. The inelastic η ′ N cross section is estimated to be 3–10 mb. Parameterizing the photoproduction cross section of η ′ -mesons by σ ( A ) = σ 0 A α , a value of α = 0.84 ± 0.03 has been dedu…

Gadolinium-DTPA (Magnevist®) als Kontrastmittel für die Galaktographie

Charge Symmetry Breaking in dd->4He{\pi}0 with WASA-at-COSY

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd->4He{\pi}0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of p=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to sigma(tot) = (118 +- 18(stat) +- 13…

Diagnostik von Pleuraergüssen und Atelektasen: Sonographie und Radiologie im Vergleich

In a prospective study it was shown that chest ultrasonography is superior to conventional x-ray diagnosis of recumbent patients in diagnosing pleural effusion and lung atelectasis. In 110 supine radiographs we found a sensitivity of 47% and a specificity of 71% for right pleural effusions and a sensitivity of 55% and a specificity of 93% for left pleural effusions in comparison to 110 sonographic examinations. The results of supine radiographs in detection of atelectasis were less efficient: sensitivity for the right side: 7%; sensitivity for the left side: 13.5%. Hence, the knowledge of chest ultrasonographic diagnosis can improve the interpretation of supine radiographs.

The Reactionγp→π0γ′pand the Magnetic Dipole Moment of theΔ+(1232)Resonance

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…

On the Production of an Isotensor Dibaryon in the $pp \to pp\pi^+\pi^-$ Reaction

Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p = 1.08 - 1.36$ GeV ($\sqrt s$ = 2.35 - 2.46 GeV), which includes the regions of $N^*(1440)$ and $\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with experimental differential cross sections and underpredict substantially the measured total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P) = 2(1^+)$ produced associatedly…

Direct Observation of aρDecay of theD13(1520)Baryon Resonance

The reaction {gamma}p{yields}{pi}{sup +}{pi}{sup 0}n has been measured at MAMI for photon energies up to 820MeV. Invariant mass spectra of the particles in the final state ({pi}{sup +}n) , ({pi}{sup 0}n) , ({pi}{sup +}{pi}{sup 0}) have been determined for several bins of incident photon energy. Differences in {pi}{sup +}{pi}{sup 0} and simultaneously measured {pi}{sup 0}{pi}{sup 0} invariant mass distributions are assigned to a {rho} branch of the D{sub 13}(1520) nucleon resonance.

"Table 6" of "In-medium modifications of the pi pi interaction in photon-induced reactions."

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."

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."

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."

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.

"Table 3" of "In-medium modifications of the pi pi interaction in photon-induced reactions."

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."

Total cross section measurement. Statistical errors only.

"Table 5" of "In-medium modifications of the pi pi interaction in photon-induced reactions."

Differential cross section for PI0PI+/- production with a Carbon target. Errors are statistical only.