45196843
Determination of the S-wave scattering length in pionic deuterium with a high resolution crystal spectrometer.
The pionic deuterium 3{ital P}{minus}1{ital S} x-ray transition was measured with a quartz crystal spectrometer in combination with a cyclotron trap and charge coupled device detectors. The strong interaction shift and total decay width of the 1{ital S} level are {epsilon}{sub 1{ital S}}(shift)=2.48{plus_minus}0.10 eV (repulsive), {Gamma}{sub 1{ital S}}(width)=1.02{plus_minus}0.21 eV, where the statistical and systematic errors were added linearly. They yield the total pionic deuterium {ital S}-wave scattering length: {ital a}{sub {pi}{sup {minus}}{ital d}}= {minus}0.0264({plus_minus}0.0011)+{ital i}0.0054({plus_minus}0.0011){ital m}{sub {pi}}{sup {minus}1}.
124571333
New R values in 2-GeV - 5-GeV from the BESII at BEPC
We report the preliminary R values for all the 85 energy points scanned in the energy region of 2-5 GeV with the upgraded Beijing Spectrometer (BESII) at Beijing Electron Positron Collider (BEPC). On average, the uncertainties of the R values we measured are 7%. The new R values has a signican t impact on the predicted mass of the Higgs (mH) from the global t to the electroweak data, and will also contribute to the interpretation of the E821 g 2 experiment.
35007541
KARMEN time anomaly: search for a neutral particle of mass 33.9 MeV in pion decay
We have searched for the pion decay pi(+)-->&mgr;+X, where X is a neutral particle of mass 33.905 MeV. This process was suggested by the KARMEN Collaboration to explain an anomaly in their observed time distribution of neutrino induced reactions. Having measured the muon momentum spectrum of charged pions decaying in flight, we find no evidence for this process and place an upper limit on the branching fraction eta</=6.0x10(-10) of such a decay at a 95% confidence level.
120397351
BESIII status and recent results
We report the status of BESIII at BEPCII and recent results from 106M ψ′ and 226M J/ψ samples at BESIII. These results include the confirmation of X (1860) in ψ′→π+π−J/ψ(J/ψ→γpp) from ψ′ sample and J/ψ→γpp from J/ψ samples, and X (1835) in J/ψ→γη′ππ., the suty of a0(980) - f0(980) mixing, as well as the preliminary results on the excited baryon states. The physics potentials, especially that for the baryon physics program at BESIII are also mentioned briefly.
92019819
Kinetic Energy Distribution of $\pi^{-}p$ Atoms in Liquid and Gaseous Hydrogen
123875509
The strong interaction shift and width of the ground state of pionic hydrogen
Abstract The 3p-1s transition in pionic hydrogen was investigated with a high-resolution crystal spectrometer system. From the precisely measured transition energy, together with the (calculated) electromagnetic energy, the strong interaction shift of the 1s state was obtained as ϵ 1s = −7.127 ± 0.028(stat.)± 0.036(syst.) eV (attractive). From the natural line width, measured for the first time, we determine the decaywidth of the 1s state: Γ 1s (decay) = 0.97 ± 0.10(stat.)± 0.05(syst.) eV. With the recently calculated electromagnetic corrections the s-wave scattering lengths of an isospin symmetric strong interaction are deduced. The scattering length for elastic scattering of a negative pion on a proton is a π − p → π − p h = 0.0885±0.00003(stat.)±0.0006(syst.) m π −1 . The scattering lengthe for single charge exchange is found to be a π − p → π 0 n h = −0.136 ± 0.007(stat.) ± 0.003(syst.) m π −1 . The experiment was performed at the Paul Scherrer Institute (PSI) in Switzerland. A focussing crystal spectrometer with an array of bent crystals, the cyclotron trap (a magnetic system designed to increase the particle stop density) and a CCD (charge-coupled device) detector system were employed. The results from the pionic hydrogen experiment — together with those from the pionic deuterium experiment — were used to test the isospin symmetry of the strong interaction. The present data are still consistent with isospin sysmmetry.
7437032
Magnitude Bias of Microlensed Sources toward the Large Magellanic Cloud.
There are lines of evidence suggesting that some of the observed microlensing events in the direction of the Large Magellanic Cloud (LMC) are caused by ordinary star lenses as opposed to dark MACHOs in the Galactic halo. Efficient lensing by ordinary stars generally requires the presence of one or more additional concentrations of stars along the line of sight to the LMC disk. If such a population behind the LMC disk exists, then the source stars (for lensing by LMC disk objects) will be drawn preferentially from the background population and will show systematic differences from LMC field stars. One such difference is that the (lensed) source stars will be farther away than the average LMC field stars, and this should be reflected in their apparent baseline magnitudes. We focus on red clump stars; these should appear in the color-magnitude diagram at a few tenths of a magnitude fainter than the field red clump. Suggestively, one of the two near-clump confirmed events, MACHO-LMC-1, is a few tenths of magnitude fainter than the clump.