Spontaneous Flavor and Parity Breaking with Wilson Fermions

We discuss the phase diagram of Wilson fermions in the $m_0$--$g^2$ plane for two-flavor QCD. We argue that, as originally suggested by Aoki, there is a phase in which flavor and parity are spontaneously broken. Recent numerical results on the spectrum of the overlap Hamiltonian have been interpreted as evidence against Aoki's conjecture. We show that they are in fact consistent with the presence of a flavor-parity broken ``Aoki phase''. We also show how, as the continuum limit is approached, one can study the lattice theory using the continuum chiral Lagrangian supplemented by additional terms proportional to powers of the lattice spacing. We find that there are two possible phase structures at non-zero lattice spacing: (1) there is an Aoki phase of width $\Delta m_0 \sim a^3$ with two massless Goldstone pions; (2) there is no symmetry breaking, and all three pions have an equal non-vanishing mass of order $a$. Present numerical evidence suggests that the former option is realized for Wilson fermions. Our analysis then predicts the form of the pion masses and the flavor-parity breaking condensate within the Aoki phase. Our analysis also applies for non-perturbatively improved Wilson fermions.Comment: 22 pages, LaTeX, 5 figures (added several references and a comment

Tau polarization effects in the CNGS tau-neutrino appearance experiments

We studied tau polarization effects on the decay distributions of tau produced in the CNGS tau-neutrino appearance experiments. We show that energy and angular distributions for the decay products in the laboratory frame are significantly affected by the tau polarization. Rather strong azimuthal asymmetry about the tau momentum axis is predicted, which may have observable consequences in experiments even with small statistics.Comment: 5 pages, 6 eps figures, espcrc2.sty; Proceedings of the 4th International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region (NuInt05), September 26-29, 2005, Okayama, Japa

Nucleon-nucleon interactions via Lattice QCD: Methodology --HAL QCD approach to extract hadronic interactions in lattice QCD--

We review the potential method in lattice QCD, which has recently been proposed to extract nucleon-nucleon interactions via numerical simulations. We focus on the methodology of this approach by emphasizing the strategy of the potential method, the theoretical foundation behind it, and special numerical techniques. We compare the potential method with the standard finite volume method in lattice QCD, in order to make pros and cons of the approach clear. We also present several numerical results for the nucleon-nucleon potentials.Comment: 12 pages, 10 figure

Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04-012502.2

We obtained near-infrared spectroscopy of the z=5.74 QSO, SDSSp J104433.04-012 502.2 with the Infrared Camera and Spectrograph of the Subaru telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr for the current Lambda-dominated cosmology. We found a similar strength of the Fe II (3000-3500 A) emission lines in SDSSp J104433.04-012502.2 as in low redshift QSOs. This is the highest redshift detection of iron. We subtracted a power-law continuum from the spectrum and fitted model Fe II emission and Balmer continuum. The rest equivalent width of Fe II (3000-3500 A) is ~30 A which is similar to those of low redshift QSOs measured by the same manner. The chemical enrichment models that assume the life time of the progenitor of SNe Ia is longer than 1 Gyr predict that weaker Fe II emission than low red shift. However, none of the observed high redshift (z > 3) QSOs show a systematic dec rease of Fe II emission compared with low redshift QSOs. This may due to a shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood. Another reason of strong Fe II emission at z=5.74 may be longer cosmological age due to smaller Omega_M.Comment: 5 pages, 3 figure