S. Shimizu

Apparatus for a search for T-violating muon polarization in stopped-kaon decays

Abstract The detector built at KEK to search for T-violating transverse muon polarization in K + → π 0 μ + ν μ ( K μ 3 ) decay of stopped kaons is described. Sensitivity to the transverse polarization component is obtained from reconstruction of the decay plane by tracking the μ+ through a toroidal spectrometer and detecting the π0 in a segmented CsI(Tl) photon calorimeter. The muon polarization was obtained from the decay positron asymmetry of muons stopped in a polarimeter. The detector included features which minimized systematic errors while maintaining high acceptance.

Forward coherent ϕ-meson photoproduction from deuterons near threshold

Abstract Differential cross sections and decay asymmetries for coherent ϕ -meson photoproduction from deuterons were measured for the first time at forward angles using linearly polarized photons at E γ = 1.5 – 2.4 GeV . This reaction offers a unique way to directly access natural-parity pomeron dynamics and gluon exchange at low energies. The cross sections at zero degrees increase with increasing photon energy. The decay asymmetries demonstrate a complete dominance of natural-parity exchange processes, showing that isovector unnatural-parity π -meson exchange is small. Nevertheless the deduced cross sections of ϕ -mesons from nucleons contributed by isoscalar t -channel exchange processes are not well described by the conventional pomeron model.

Measurement of Γ(Kμ3)/Γ(Ke3) ratio using stopped positive kaons

Abstract The ratio of the K + → π 0 μ + ν ( K μ 3 + ) and K + → π 0 e + ν ( K e 3 + ) decay widths, Γ ( K μ 3 )/ Γ ( K e 3 ), has been measured with stopped positive kaons. K μ 3 + and K e 3 + samples containing 2.4×10 4 and 4.0×10 4 events, respectively, were analyzed. The Γ ( K μ 3 )/ Γ ( K e 3 ) ratio was obtained to be 0.671±0.007(stat.)±0.008(syst.) calculating the detector acceptance by a Monte Carlo simulation. The coefficient of the q 2 dependent term of the f 0 form factor was also determined to be λ 0 =0.019±0.005(stat.)±0.004(syst.) with the assumption of μ – e universality in K l 3 + decay. The agreement of our result with the λ 0 value obtained from K μ 3 + Dalitz plot analyses supports the validity of the μ – e universality.

Uniform mixing of antiferromagnetism and high-temperature superconductivity in electron-doped layers of four-layered Ba(2)Ca(3)Cu(4)O(8)F(2): a new phenomenon in an electron underdoped regime.

We report (63,65)Cu- and (19)F-NMR studies on a four-layered high-temperature superconductor Ba(2)Ca(3)Cu(4)O(8)F(2)((0234F(2.0)) with apical fluorine (F(-1)), an undoped 55 K superconductor with a nominal Cu(2+) valence on average. We reveal that this compound exhibits the antiferromagnetism (AFM) with a Néel temperature T(N)=100 K despite being a T(c)=55 K superconductor. Through a comparison with a related trilayered cuprate Ba(2)Ca(3)Cu(4)O(8)F(2)(0233F(2.0)), it is demonstrated that electrons are transferred from the inner plane (IP) to the outer plane (OP) in 0234F(2.0) and 0223F(2.0), confirming the self-doped high-temperature superconductivity (HTSC) having electron and hole doping in a single compound. Remarkably, uniform mixing of AFM and HTSC takes place in both the electron-doped OPs and the hole-doped IPs in 0234F(2.0).

Test of exotic scalar and tensor interactions in K(e3) decay using stopped positive kaons

The form factors of the decay K+ → π0e+νe (Ke3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 105Ke3 events. The following values of the parameters were obtained: λ+=0.0278±0.0017 (stat.)±0.0015 (syst.), |fS/f+(0)|=0.0040±0.0160 (stat.)±0.0067 (syst.), and |fT/f+(0)|=0.019±0.080 (stat.)±0.038 (syst.). Both scalar fS and tensor fT form factors are consistent with the Standard Model predictions of zero values.

First measurement of the T-violating muon polarization in the decay K+→μ+νγ

Abstract We present the result of the first measurement of the T-violating transverse muon polarization P T in the decay K + → μ + νγ . This polarization is sensitive to new sources of CP-violation in the Higgs sector. Using data accumulated in the period 1996–1998 we have obtained P T =(−0.64±1.85(stat)±0.10(syst))×10 −2 which is consistent with no T-violation in this decay.

New Limit on the T-Violating Transverse Muon Polarization in K^+ ¿ pi^0mu^+nu Decays

A search for T-violating transverse muon polarization (P(T)) in the K+-->pi(0)mu(+)nu decay was performed using kaon decays at rest. A new improved value P(T)=-0.0017+/-0.0023(stat)+/-0.0011(syst) was obtained giving an upper limit |P(T)|<0.0050. The T-violation parameter was determined to be Imxi=-0.0053+/-0.0071(stat)+/-0.0036(syst) giving an upper limit |Imxi|<0.016.

A new limit of T-violating transverse muon polarization in the

A search for T-violating transverse muon polarization (P(T)) in the K+-->pi(0)mu(+)nu decay was performed using kaon decays at rest. A new improved value P(T)=-0.0017+/-0.0023(stat)+/-0.0011(syst) was obtained giving an upper limit |P(T)|<0.0050. The T-violation parameter was determined to be Imxi=-0.0053+/-0.0071(stat)+/-0.0036(syst) giving an upper limit |Imxi|<0.016.

K^{+}\to\pi^{0}\mu^{+} \nu

The radiative decay

decay

K^+ \to \pi^+ \pi^0 \gamma