Thomas-Ehrman shifts in nuclei around ^{16}O and role of residual nuclear interaction

The asymmetry in the energy spectra between mirror nuclei (the Thomas-Ehrman shifts) around $^{16}$O is investigated from a phenomenological viewpoint. The recent data on proton-rich nuclei indicates that the residual nuclear interaction is reduced for the loosely bound s-orbit by as much as 30%, which originates in the broad radial distribution of the proton single-particle wave function.Comment: to appear in Phys. Lett. B, with 3 eps figure

The bar PANDA focussing-lightguide disc DIRC

bar PANDA will be a fixed target experiment internal to the HESR antiproton storage ring at the future FAIR complex. The ANDA detector requires excellent particle-identification capabilities in order to achieve its scientific potential. Cherenkov counters employing the DIRC principle were chosen as PID detectors for the Target Spectrometer. The proposed Focussing-Lightguide Disc DIRC will cover the forward part of the Target Spectrometer acceptance in the angular range between 5° and 22°. Its design includes a novel approach to mitigate dispersion effects in the solid radiator of a DIRC counter using optical elements. The dispersion correction will enable the Focussing-Lightguide Disc DIRC to provide pion-kaon identification for momenta well above 3.5 GeV/c

The Reaction 7Li(pi+,pi-)7B and its Implications for 7B

The reaction 7Li(pi+,pi-)7B has been measured at incident pion energies of 30-90 MeV. 7Li constitutes the lightest target nucleus, where the pionic charge exchange may proceed as a binary reaction to a discrete final state. Like in the Delta-resonance region the observed cross sections are much smaller than expected from the systematics found for heavier nuclei. In analogy to the neutron halo case of 11Li this cross section suppression is interpreted as evidence for a proton halo in the particle-unstable nucleus 7B.Comment: 4 pages, 4 figure

Search for Exotic Muon Decays

Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN collaboration, can be interpreted as a signal from an exotic muon decay branch mu+ to e+ X. It has been shown that this hypothesis gives an acceptable fit to the KARMEN data if the boson X has a mass of m_X=103.9MeV/c^2, close to the kinematical limit. We have performed a search for the X particle by studying for the first time the very low energy part of the Michel spectrum in mu+ decays. Using a HPGe detector setup at the muE4 beamline at PSI we find branching ratios BR(mu+ to e+ X)<5.7e-4 (90% C.L.) for most of the region 103MeV/c^2<m_X<105MeV/c^2.Comment: 9 page

Search for the Hypothetical pi -> mu x Decay

The KARMEN collaboration has reported the possible observation of a hitherto unknown neutral and weakly interacting particle x, which is produced in the decay pi -> mu + x with a mass m(x) = 33.9 MeV. We have searched for this hypothetical decay branch by studying muons from pion decay in flight with the LEPS spectrometer at the piE3 channel at PSI and find branching ratios BR(pi- to mu- anti-x) < 4e-7 and BR(pi+ to mu+ x) < 7e-8 (95\% C.L.). Together with the limit BR > 2e-8 derived in a recent theoretical paper our result would leave only a narrow region for the existence of x if it is a heavy neutrino.Comment: 10 pages, TeX (uses epsf), 3 Postscript figures uu-encode

Reconstruction methods — P&#8254;ANDA focussing-light guide disc DIRC

The Focussing-Lightguide Disc DIRC will provide crucial Particle Identification (PID) information for the P&#8254;ANDA experiment at FAIR, GSI. This detector presents a challenging environment for reconstruction due to the complexity of the expected hit patterns and the operating conditions of the P&#8254;ANDA experiment. A discussion of possible methods to reconstruct PID from this detector is given here. Reconstruction software is currently under development

Collision damping in the pi 3He -> d'N reaction near the threshold

We present a simple quantum mechanical model exploiting the optical potential approach for the description of collision damping in the reaction pi 3He -> d'N near the threshold, which recently has been measured at TRIUMF. The influence of the open d'N -> NNN channel is taken into account. It leads to a suppression factor of about ten in the d' survival probability. Applications of the method to other reactions are outlined.Comment: RevTeX4, 14 pages, 3 Postscript figures, uses epsfig.sty, to appear in Phys.Rev.

The barrel DIRC of PANDA

Cooled antiproton beams of unprecedented intensities in the momentum range of 1.5-15 GeV/c will be used for the PANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The PANDA detector will investigate antiproton annihilations with beams in the momentum range of 1.5 GeV/c to 15 GeV/c on a fixed target. An almost 4π acceptance double spectrometer is divided in a forward spectrometer and a target spectrometer. The charged particle identification in the latter is performed by ring imaging Cherenkov counters employing the DIRC principle

Photoproduction of eta-mesic 3He

The photoproduction of eta-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma+3He->eta+X has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted up to energies of 745 MeV. A resonance-like structure just above the eta production threshold with an isotropic angular distribution suggests the existence of a resonant quasi-bound state. This is supported by studies of a competing decay channel of such a quasi-bound eta-mesic nucleus into pi^0+p+X. A binding energy of (-4.4+-4.2) MeV and a width of (25.6+-6.1) MeV is deduced for the quasi-bound eta-mesic state in 3He.Comment: v1: 4 pages, 4 figures, submitted to PRL; v2: minor revisions and corrections, new figure added, 4 pages, 5 figs; v3: minor change

The barrel DIRC of PANDA

Cooled antiproton beams of unprecedented intensities in the momentum range of 1.5-15 GeV/c will be used for the PANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The PANDA detector will investigate antiproton annihilations with beams in the momentum range of 1.5 GeV/c to 15 GeV/c on a fixed target. An almost 4π acceptance double spectrometer is divided in a forward spectrometer and a target spectrometer. The charged particle identification in the latter is performed by ring imaging Cherenkov counters employing the DIRC principle