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For damage estimation of structural material in the accelerator facility, displacement per atom (DPA) is widely employed as an index of the damage calculated based on the displacement cross section obtained with the calculation model. Although the DPA is employed as the standard, the experimental data of displacement cross section are scarce for a proton in the energy region above 20 MeV. Among the calculation models, the difference exists about 8 times so that experimental data of the displacement cross section is crucial to validate the model. To obtain the displacement cross section, we conducted the experiment in J-PARC. As a preliminary result, the displacement cross section of copper was successfully obtained for 3-GeV proton. The present results showed that the widely utilized the Norgertt-Robinson-Torrens (NRT) model overestimates the cross section as suggested by the previous experiment for protons with lower energy.

For damage estimation of structural material in the accelerator facility, displacement per atom (DPA) is widely employed as an index of the damage calculated based on the displacement cross section obtained with the calculation model. Although the DPA is employed as the standard, the experimental data of displacement cross section are scarce for a proton in the energy region above 20 MeV. Among the calculation models, the difference exists about 8 times so that experimental data of the displacement cross section is crucial to validate the model. To obtain the displacement cross section, we conducted the experiment in J-PARC. As a preliminary result, the displacement cross section of copper was successfully obtained for 3-GeV proton. The present results showed that the widely utilized the Norgertt-Robinson-Torrens (NRT) model overestimates the cross section as suggested by the previous experiment for protons with lower energy.

Muon beam monitoring is indispensable for indirectly monitoring accelerator-produced neutrino beams in real time. Though Si photodiodes and ionization chambers have been successfully used as muon monitors at the T2K experiment, sensors that are more radiation tolerant are desired for future operation. We have investigated the electron-multiplier tube (EMT) as a new sensor for muon monitoring. Secondary electrons produced by the passage of muons at dynodes are multiplied in the tube and produce signal. Two prototype detectors were installed at the T2K muon monitor location, and various EMT properties were studied based on in situ data taken with the T2K muon beam. The signal size is as expected based on calculation, and the EMTs show a sufficiently fast time response for bunch-by-bunch beam monitoring. The spill-by-spill intensity resolution is 0.4%, better than the required value (1%). Signal linearity within $\pm$1% is achieved at proton beam powers up to 460 kW (with +250 kA focusing horn operation). A gradual signal decrease was observed during the initial exposure, due to the stabilization of dynode materials, before the response became stable within $\pm$1%. This work demonstrates that EMTs are a good candidate for future muon monitoring at T2K, and may also have other more general applications., 23 pages, 20 figures, 6 tables

A magnetic horn system to be operated at a pulsed current of 320 kA and to survive high-power proton beam operation at 750 kW was developed for the T2K experiment. The first set of T2K magnetic horns was operated for over 12 million pulses during the four years of operation from 2010 to 2013, under a maximum beam power of 230 kW, and $6.63\times10^{20}$ protons were exposed to the production target. No significant damage was observed throughout this period. This successful operation of the T2K magnetic horns led to the discovery of the $\nu_{\mu}\rightarrow\nu_e$ oscillation phenomenon in 2013 by the T2K experiment. In this paper, details of the design, construction, and operation experience of the T2K magnetic horns are described., Comment: 22 pages, 40 figures, also submitted to Nuclear Instrument and Methods in Physics Research, A

In a series of previous papers the present authors and collaborators have shown strong evidence for existence of the long-sought sigma-particle by analyzing the pi pi-scattering and pi pi-production processes, applying, respectively, the IA method and the VMW method. In this paper we examine the relation between the scattering amplitude T and the production amplitude F from the viewpoint of the unitarity and the final state interaction (FSI) theorem by using a simple field theoretical model. As a result it is shown that the amplitudes in the physical state representation are directly represented through the Breit-Wigner amplitudes of the relevant resonances, and the respective forms of T and F coincide with those in the IA and VMW methods, justifying our methods of analyses.

In a previous work, we have reanalyzed the I=0 S-wave \pi\pi-scattering phase-shift through a new method of Interfering Breit-Wigner amplitudes, and have shown the existence of a light scalar, \sigma particle, accompanied by a negative "repulsive core"-type background phase-shift, whose origin may have some correspondence to a ``compensating'' \pi\pi contact interaction. In this work we make further analysis on the phase shift under KKbar threshold from the same standpoint, to determine precise values of \sigma mass and width, so far as present experimental data are concerned.

Recently we have shown an evidence for existence of \sigma-particle in the previous works; where the \pi\pi S-wave phase shift is reanalyzed, by introducing a repulsive background suggested by the chiral symmetry, and by applying a new method of Interfering Breit-Wigner Amplitudes. In this work we also show, reanalyzing the K\pi S-wave phase shift from a similar standpoint, an evidence for existence of \kappa(900), possibly to be a member of \sigma-nonet.

The Tokai-to-Kamioka (T2K) neutrino experiment measures neutrino oscillations by using an almost pure muon neutrino beam produced at the J-PARC accelerator facility. The T2K muon monitor was installed to measure the direction and stability of the muon beam which is produced together with the muon neutrino beam. The systematic error in the muon beam direction measurement was estimated, using data and MC simulation, to be 0.28 mrad. During beam operation, the proton beam has been controlled using measurements from the muon monitor and the direction of the neutrino beam has been tuned to within 0.3 mrad with respect to the designed beam-axis. In order to understand the muon beam properties,measurement of the absolute muon yield at the muon monitor was conducted with an emulsion detector. The number of muon tracks was measured to be $(4.06\pm0.05)\times10^4$ cm$^{-2}$ normalized with $4\times10^{11}$ protons on target with 250 kA horn operation. The result is in agreement with the prediction which is corrected based on hadron production data.

The first results of the K2K(KEK to Kamioka) long-baseline neutrino oscillation experiment are presented in this talk. In 1999 7.2x10^18 protons on target were delivered to the experiment. During this period of running there were 3 events fully contained in the Super-Kamiokande inner detector fiducial area which occurred during the beam spill timing window. In the case of no oscillations the expected number of events during this period was 12.3+1.7-1.9. The near detectors located at KEK also have begun detailed measurements of neutrino interactions in water at around 1 GeV., Comment: 5 pages, 5 figures, Talk at the 7th Conference On Intersections Between Particle And Nuclear Physics (CIPANP2000), 25-28 May 2000, Quebec, Canada

The relation between scattering and production amplitudes are investigated, using a simple field theoretical model, from the general viewpoint of unitarity and the applicability of final state interaction(FSI-) theorem. The IA-method and VMW-method, which are applied to our phenomenological analyses suggesting the \sigma-existence, are obtained as the physical state representations of scattering and production amplitudes, respectively. Moreover, the VMW-method is shown to be an effective method to obtain the resonance properties from general production processes, while the conventional analyses based on the ``universality'' of \pi\pi-scattering amplitude are powerless for this purpose., Comment: Talk at HADRON'97, the 7th int. conf. on hadron spectroscopy, BNL, August 1997. 4 pages with no figure

Re-analyzing [1,2] the old phase shift data of I=0, ππ(I=1/2,Kπ) scattering, we show an evidence for existence of the σ-particle(κ-particle) with a comparatively light mass, which has been missing for a long time: In the analysis we have applied a new method of interfering Breit-Wigner amplitudes, which makes the scattering amplitude parametrized in terms of only physical quantities, mass and width of resonant particles, in conformity with unitarity. We have introduced phenomenologically a background phase shift δBG of repulsive core type. The χ2-fits of the both ππ- and Kπ-phase shifts are improved greatly with the δBG over the conventional fits without it.

A S-wave ππ resonance below 1 GeV/c2, sigma has been observed in analyses of the phase shift data of ππ scatterings. It is important to observe it in production processes. A huge events of π0π0 below 1 GeV/c2 is seen in the central production of the GAMS experiment. Its mass spectrum is well described by the variant mass and width method (VMW) including f0(980), f2(1270) and a S-wave resonance which might be assigned to be a sigma. We report here that the angular distributions of the π0π0 system are also described with the S-wave resonance interfering with f0(980) and the tail of f2(1270) by VMW. The same method is applied to the π+π− data of J/ψ→ωππ decay, and is shown that not only π+π− mass spectrum but also its cos θπ distributions are described well.