T. Emura

A separation method of 0ν- and 2ν-events in double beta decay experiments with DCBA

Abstract A detector called Drift Chamber Beta-ray Analyzer (DCBA) will provide momentum information of each β-ray in double beta decay. The DCBA is expected to have good capabilities for particle identification, detection efficiency, background elimination and decay-source integration. Under the assumption of mass mechanism dominance in neutrinoless double beta decay, a simulation study shows that a combination method using both sum and single-energy distributions of double beta decay events can separate 0 ν - and 2 ν -events down to 0.05 eV of the effective neutrino mass with the help of a calculated nuclear matrix element, even though the DCBA has relatively poor energy resolution.

THE LARGE-ACCEPTANCE SPECTROMETER TAGX FOR PHOTOREACTION STUDIES AT THE 1.3-GEV TOKYO ELECTRON SYNCHROTRON

Abstract The study of photoreactions on light nuclei with the TAGX spectrometer started in 1987 using the 20% duty-cycle tagged-photon beam at the 1.3-GeV Tokyo electron synchrotron. TAGX is comprised of a π-sr magnetic spectrometer for detection of charged pions, kaons, and protons and a 0.85-sr time-of-flight spectrometer for neutrons. It has served in the past eight years as a unique medium-energy-resolution multi-particle spectrometer for coincidence experiments to detect such final states as pn, pp, π + π − , ppn, pp − , and pn π + π − : some of which were kinematically-complete measurements of three-particle and four-particle final states. Details of the detector components, their performance, data acquisition, event reconstruction analyses, and detector-acceptance calculations are described together with the results of experience acquired in those experiments. A TAGX improvement in the momentum resolution required for charged particle measurements in the 1-GeV photon energy region is also reported.

Observation of a dip-bump structure in differential cross section for pp → nn in the 700–760 MeV/c momentum range

Abstract Based on a sample of about 3500 events, we have measured the total and differential cross sections of p p → n n in the 700–760 MeV/c incident momentum region. It is found that σCE = 10.7 ± 0.2 mb at the average momentum of 730 MeV/c. The differential angular distribution is characterised by a sharp peak and a dip in the forward direction followed by a secondary maximum. The position of the dip corresponds to |t| ≈ mπ2. These results are compared with the predictions of the model of Bryan-Phillips. On the other hand, this dip-bump structure can be well understood on a simple picture involving a π exchange and a constant background (for |t| ≲ 3 mπ2).

Determination of the QCD scale parameter ΛMS with QCD cascade on the basis of the next-to-leading logarithmic approximation

Abstract The relative production ratio of 3-jet events to the total number of hadronic events was studied in e+e− annihilations at centre-of-mass energies between 54 and 61.4 GeV. The QCD scale parameter has been determined to be Λ MS =254 −47 +55 ±56 MeV on the basis of a QCD cascade with the next-to-leading logarithmic approximation.

Measurement of the differential cross sections ofe+e−→γγ ande+e−→γγγ at\(\sqrt s = 55,56,56.5\) and 57 GeV and search for unstable photino pair production

AbstractDifferential cross sections fore+e−→γγ have been measured at center-of-mass energies of 55, 56, 56.5 and 57 GeV. The results are in good agreement with those predicted by QED. Possible deviations from QED are studied in terms of contact interactions, and the limits on compositeness scales are obtained. Using events with a gramma pair in the final state, a search is made for the pair production of unstable photons,

Measurement of the Differential Cross-sections of

e^ + e^ - \to \tilde \gamma \tilde \gamma

and

. No candidate events were found and a new limit on the photino mass is obtained.

e^+ e^- \to \gamma \gamma \gamma

Abstract We have developed the baseline design for a straw drift tube tracking system for the Solenoidal Detector Collaboration (SDC) detector. The system was designed to operate in the high-rate environment of a high luminosity hadron collider. We present an overview of the tracking system and the requirements it was expected to fulfill. We describe the construction and properties of the straw drift tubes. We discuss the design of the carbon-fiber foam-laminate shell, which supported the wire tension and held the straws in alignment. We also present descriptions of the designs of the front-end and digitization electronics as well as the electronics associated with the level 1 track trigger.