M. Ueda

Bio: M. Ueda is an academic researcher from Osaka University. The author has contributed to research in topics: Photomultiplier & Photocathode. The author has an hindex of 4, co-authored 7 publications receiving 44 citations.

Modularized NaI(Tl) detectors in a half barrel configuration

Abstract: We have constructed a modularized array of NaI(Tl) detectors in a half barrel configuration that is about 75 cm long with an inner radius of 25 cm. 96 NaI modules are surrounded by a layer of 48 modules of scintillating glass which have similar dimensions to the NaI modules. Each NaI crystal was shaped as a trapezoidal pyramid and encapsulated in a 1 mm thick aluminium container with dimensions of (43 × 94) × (110 × 94) × 377 mm3. The construction and performance are described along with the gain calibration and monitoring, the beam position sensitivity, the scattering between modules, etc. The fwhm energy resolution of a 5 × 5 array of NaI modules varied from 6.5% for incident electrons at 100 MeV to 3.6% at 1000 MeV

Search for narrow states by detection of monochromatic gamma rays in p ̄p annihilation at rest

Abstract: We measured inclusive ..gamma..-ray spectra from p-barp annihilation at rest to search for narrow ..gamma.. lines associated with the production of baryonia. The measurement was done with statistics several times as high as those of earlier experiments by using modularized NaI(Tl) detectors. We have not observed any narrow states, i.e., baryonium candidates, with statistical significance higher than 4sigma. The 4sigma upper limits for the yield of p-barp..--> gamma..B times the decay branching ratio of B into N/sub ch/-prong states is (1.2--0.2) x 10/sup -3/ at ..gamma..-ray energy of 80--938 MeV for the sum over N/sub ch/, (0.3--0.1) x 10/sup -3/ for each of N/sub ch/ = 0 and greater than or equal to6, and (0.8--0.1) x 10/sup -3/ for each of N/sub ch/ = 2 and 4. At 2 to 3sigma levels, however, we have seen nine narrow ..gamma..-ray peaks with individual yields between 10/sup -4/ and 10/sup -3/ for various charge multiplicities.

Antiproton-proton annihilation at rest into two-body final states

Abstract: We report measurements of branching ratios for production of a series of two meson final states in $$\bar p$$ p annihilations at rest in liquid hydrogen. We find: $$\begin{gathered} BR(\bar pp \to \pi ^ + \pi ^ - ) = (3.07 \pm 0.13) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to K^ + K^ - ) = (0.99 \pm 0.05) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \pi ^0 ) = (6.93 \pm 0.43) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \eta ) = (2.12 \pm 0.12) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \omega ) = (5.73 \pm 0.47) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \eta ') = (1.23 \pm 0.13) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \eta ) = (1.64 \pm 0.10) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \omega ) = (1.51 \pm 0.12) \cdot 10^{ - 2} \hfill \\ BR(\bar pp \to \eta \eta ') = (2.16 \pm 0.25) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \omega \omega ) = (3.32 \pm 0.34) \cdot 10^{ - 2} \hfill \\ BR(\bar pp \to \omega \eta ') = (0.78 \pm 0.08) \cdot 10^{ - 2} \hfill \\ \end{gathered}$$ These are the first measurements of the channels ηη′ and ωη′ and in almost all the other channels are more precise than previous results. We also obtain, in a more precise fashion, the following ratios of branching ratios:K + K −/π+π−=0.323±0.013, π0η′/π0η=0.548±0.056, ηη′/ηη=0.31±0.15, ωη′/ωη=0.515±0.040, π0η/π0π0=0.303±0.010, ηη/π0π0=0.232±0.011 and π0ω/ηω=0.377±0.12. The measurements are made for different η and η′ decays, and we thus obtain Γη→3π 0/Γη→γγ=0.841±0.034, and $$\Gamma _{\eta ' \to \gamma \gamma } /\Gamma _{\eta ' \to \pi ^0 \pi ^0 \eta } = 0.091 \pm 0.009$$ .