39021023
Strong interaction shift and width of the 1s level in pionic hydrogen.
The 3{ital p}{minus}1{ital s} x-ray line of pionic hydrogen was measured with a reflecting bent crystal spectrometer. The strong interaction energy level shift and the total decay width of the 1{ital s} state, obtained from the transition energy and the linewidth, are {var_epsilon}{sub 1{ital s}}={minus}7.127{plus_minus}0.028(stat){plus_minus}0.036(syst)eV (attractive) and {Gamma}{sub 1{ital s}}=0.97{plus_minus}0.10(stat){plus_minus}0.05(syst)eV. The corresponding hadronic {pi}{ital N} {ital s}-wave scattering lengths for elastic scattering and single charge exchange are {ital a}{sub {pi}{sup {minus}}{ital p}{r_arrow}{pi}{sup {minus}}{ital p}}{sup {ital h}}=0.0885{plus_minus}0.0009{ital m}{sub {pi}}{sup {minus}1} and {ital a}{sub {pi}{sup {minus}}{ital p}{r_arrow}{pi}{sup 0}{ital n}}{sup {ital h}}={minus}0.136{plus_minus}0.010{ital m}{sub {pi}}{sup {minus}1}. {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.
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.
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
63344758
MDT Commissioning Procedures Guidelines for Certifying RFI Chambers
12460113
R-VALUES FROM LOW ENERGY e+e- ANNIHILATION
The QED running coupling constant α(s) and the anomalous magnetic moment of muon aμ are two fundamental quantities for the precision test of the Standard Model (SM). The current uncertainties on α(s) and aμ are dominated by the contribution from the R-values measured about 20 years ago with an averaged uncertainty of 15% in the energy region below 5 GeV. This review article summarizes the recent measurements of R-values in low energy e+e- annihilation. The new experiments aimed at reducing the uncertainties in R-values and performed with the upgraded Beijing Spectrometer (BESII) at Beijing Electron Positron Collider (BEPC) in Beijing and with Cryogenic Magnetic Detector, CMD-2 and SND (Spherical Neutral Detector) at VEEP-2M in Novosibirsk are reviewed and discussed.
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.