186 research outputs found

    Charm as a domain wall fermion in quenched lattice QCD

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    We report a study describing the charm quark by a domain-wall fermion (DWF) in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of a−1∼3a^{-1} \sim 3 GeV. We calculate masses of heavy-light (charmed) and heavy-heavy (charmonium) mesons with spin-parity JP=0∓J^P = 0^\mp and 1∓1^\mp, leptonic decay constants of the charmed pseudoscalar mesons (DD and DsD_s), and the D0D^0-D0ˉ\bar{D^0} mixing parameter. The charm quark mass is found to be mcMSˉ(mc)=1.24(1)(18)m^{\bar{\rm MS}}_{c}(m_{c})=1.24(1)(18) GeV. The mass splittings in charmed-meson parity partners Δq,J=0\Delta_{q,J=0} and Δq,J=1\Delta_{q, J=1} are degenerate within statistical errors, in accord with experiment, and they satisfy a relation Δq=ud,J>Δq=s,J\Delta_{q=ud, J} > \Delta_{q=s, J}, also consistent with experiment. A C-odd axial vector charmonium state, hc),lies22(11)MeVabovetheh_c), lies 22(11) MeV above the \chi_{c1}meson,or meson, or m_{h_{c}} = 3533(11)_{\rm stat.}MeVusingtheexperimental MeV using the experimental \chi_{c1}) mass. However, in this regard, we emphasize significant discrepancies in the calculation of hyperfine splittings on the lattice. The leptonic decay constants of DD and DsD_s mesons are found to be fD=232(7)stat.(−0+6)chiral(11)syst.f_D=232(7)_{\rm stat.}(^{+6}_{-0})_{\rm chiral}(11)_{\rm syst.} MeV and fDs/fD=1.05(2)stat.(−2+0)chiral(2)syst.f_{D_s}/f_{D} = 1.05(2)_{\rm stat.}(^{+0}_{-2})_{\rm chiral}(2)_{\rm syst.}, where the first error is statistical, the second a systematic due to chiral extrapolation and the third error combination of other known systematics. The D0D^0-D0ˉ\bar{D^0} mixing bag parameter, which enters the ΔC=2\Delta C = 2 transition amplitude, is found to be BD(2GeV)=0.845(24)stat.(−6+24)chiral(105)syst.B_D(2{GeV})=0.845(24)_{\rm stat.}(^{+24}_{-6})_{\rm chiral}(105)_{\rm syst.}.Comment: 49 pages, 15 figure

    Continuum Limit of BKB_K from 2+1 Flavor Domain Wall QCD

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    We determine the neutral kaon mixing matrix element BKB_K in the continuum limit with 2+1 flavors of domain wall fermions, using the Iwasaki gauge action at two different lattice spacings. These lattice fermions have near exact chiral symmetry and therefore avoid artificial lattice operator mixing. We introduce a significant improvement to the conventional NPR method in which the bare matrix elements are renormalized non-perturbatively in the RI-MOM scheme and are then converted into the MSbar scheme using continuum perturbation theory. In addition to RI-MOM, we introduce and implement four non-exceptional intermediate momentum schemes that suppress infrared non-perturbative uncertainties in the renormalization procedure. We compute the conversion factors relating the matrix elements in this family of RI-SMOM schemes and MSbar at one-loop order. Comparison of the results obtained using these different intermediate schemes allows for a more reliable estimate of the unknown higher-order contributions and hence for a correspondingly more robust estimate of the systematic error. We also apply a recently proposed approach in which twisted boundary conditions are used to control the Symanzik expansion for off-shell vertex functions leading to a better control of the renormalization in the continuum limit. We control chiral extrapolation errors by considering both the NLO SU(2) chiral effective theory, and an analytic mass expansion. We obtain B_K^{\msbar}(3 GeV) = 0.529(5)_{stat}(15)_\chi(2)_{FV}(11)_{NPR}. This corresponds to B^K=0.749(7)stat(21)χ(3)FV(15)NPR\hat{B}_K = 0.749(7)_{stat}(21)_\chi(3)_{FV}(15)_{NPR}. Adding all sources of error in quadrature we obtain B^K=0.749(27)combined\hat{B}_K = 0.749(27)_{combined}, with an overall combined error of 3.6%.Comment: 65 page

    Localization and chiral symmetry in 2+1 flavor domain wall QCD

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    We present results for the dependence of the residual mass of domain wall fermions (DWF) on the size of the fifth dimension and its relation to the density and localization properties of low-lying eigenvectors of the corresponding hermitian Wilson Dirac operator relevant to simulations of 2+1 flavor domain wall QCD. Using the DBW2 and Iwasaki gauge actions, we generate ensembles of configurations with a 163×3216^3\times 32 space-time volume and an extent of 8 in the fifth dimension for the sea quarks. We demonstrate the existence of a regime where the degree of locality, the size of chiral symmetry breaking and the rate of topology change can be acceptable for inverse lattice spacings a−1≥1.6a^{-1} \ge 1.6 GeV.Comment: 59 Pages, 23 figures, 1 MPG linke

    Deconfinement transition and string tensions in SU(4) Yang-Mills Theory

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    We present results from numerical lattice calculations of SU(4) Yang-Mills theory. This work has two goals: to determine the order of the finite temperature deconfinement transition on an Nt=6N_t = 6 lattice and to study the string tensions between static charges in the irreducible representations of SU(4). Motivated by Pisarski and Tytgat's argument that a second-order SU(∞\infty) deconfinement transition would explain some features of the SU(3) and QCD transitions, we confirm older results on a coarser, Nt=4N_t = 4, lattice. We see a clear two-phase coexistence signal, characteristic of a first-order transition, at 8/g2=10.798/g^2 = 10.79 on a 6×2036\times 20^3 lattice, on which we also compute a latent heat of Δϵ≈0.6ϵSB\Delta\epsilon\approx 0.6 \epsilon_{SB}. Computing Polyakov loop correlation functions we calculate the string tension at finite temperature in the confined phase between fundamental charges, σ1\sigma_1, between diquark charges, σ2\sigma_2, and between adjoint charges σ4\sigma_4. We find that 1<σ2/σ1<21 < \sigma_2/\sigma_1 < 2, and our result for the adjoint string tension σ4\sigma_4 is consistent with string breaking.Comment: 10 pages with included figures. For version 2: New calculation and discussion of latent heat added; 2 new figures and 1 new table. Typo in abstract corrected for v3. To appear in Physical Review

    A Lattice Study of the Nucleon Excited States with Domain Wall Fermions

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    We present results of our numerical calculation of the mass spectrum for isospin one-half and spin one-half non-strange baryons, i.e. the ground and excited states of the nucleon, in quenched lattice QCD. We use a new lattice discretization scheme for fermions, domain wall fermions, which possess almost exact chiral symmetry at non-zero lattice spacing. We make a systematic investigation of the negative-parity N∗N^* spectrum by using two distinct interpolating operators at β=6/g2=6.0\beta=6/g^2=6.0 on a 163×32×1616^3 \times 32 \times 16 lattice. The mass estimates extracted from the two operators are consistent with each other. The observed large mass splitting between this state, N∗(1535)N^*(1535), and the positive-parity ground state, the nucleon N(939), is well reproduced by our calculations. We have also calculated the mass of the first positive-parity excited state and found that it is heavier than the negative-parity excited state for the quark masses studied.Comment: 46 pages, REVTeX, 11 figures included, revised version accepted for publication in Phys. Rev.

    Ovarian Metastasis in Patients with Colorectal Carcinoma

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    The records of 159 patients who underwent surgical resection of colorectal cancer were reviewed to assess the incidence of ovarian metastasis and to define the role of oophorectomy. Four of these patients presented with metachronous metastases, and one patient had synchronous ovarian involvement. The incidence of ovarian involvement was higher in younger patients. While most patients with ovarian involvement had the primary tumor located at the rectosigmoid region, a similar distribution of the primary tumor was observed in patients without ovarian metastasis. The histological type and degree of differentiation was similar regardless of whether or not ovarian metastasis was present. Of the patient without ovarian metastasis, 57% presented with nodal metastases and 3.2% with peritoneal dissemination, while all patients with ovarian metastasis had nodal and peritoneal involvement. Our results suggest that histological type and degree of differentiation of the primary tumor do not influence likelihood of ovarian metastasis. However, the exposure of the tumor to the serosal surface and the subsequent peritoneal dissemination may be an important route by which malignant tumor cells reach the ovaries. However, due to the wide lymphatic involvement in patients with ovarian metastasis, the lymphatic route may be important as well. Thus, we consider that oophorectomy should be performed in all postmenopausal women, when the ovaries are macroscopically affected, and in premenopausal patients with Astler-Coller B2 tumors or over.</p

    Validity and Reliability of the Japanese Version of the Rome III Diagnostic Questionnaire for Irritable Bowel Syndrome and Functional Dyspepsia

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    Background/AimsReliable diagnostic instruments for measuring the presence of functional gastrointestinal disorders based on the Rome III criteria have been lacking in Japan. The aims of the present study were to translate and validate the Rome III diagnostic questionnaire which was widely used in Western countries.MethodsThe original version of Rome III diagnostic questionnaire was translated from English into Japanese through 3 independent forward translations, resolution, back translation and reconciliation of the differences. Forty-nine patients with irritable bowel syndrome (IBS), 32 patients with functional dyspepsia (FD) and 56 subjects without any current GI symptoms as controls were recruited from three hospitals located in different regions of Japan and completed the IBS and FD diagnostic modules twice within 14 days. Kappa statistic was used to assess test-retest reliability. The sensitivity and specificity of each diagnostic module for distinguishing IBS or FD patients from controls was tested.ResultsMedian kappa statistics were 0.63 for the translated IBS diagnostic module and 0.68 for the FD module. The sensitivity, specificity, and positive predict value of the IBS module against physician diagnosis was 61.2%, 100%, and 100% and those of the FD module was 53.2%, 98.2%, and 94.4%, respectively. Meanwhile, IBS patients were significantly more likely to report blood in stools compared to controls (18.4% vs 1.8%, P < 0.01).ConclusionsThe IBS and FD diagnostic modules on the Japanese version of the Rome III diagnostic questionnaire are valid and reliable. Further studies are warranted to elucidate the diagnostic utility of the red flag questionnaire

    Coincidence analysis to search for inspiraling compact binaries using TAMA300 and LISM data

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    Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor ∼10−4\sim 10^{-4} compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 /hours (CL =90= 90 %) to the Galactic event rate within 1kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.Comment: 28 pages, 17 figures, Replaced with the version to be published in Physical Review

    Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004

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    We analyze the data of TAMA300 detector to search for gravitational waves from inspiraling compact star binaries with masses of the component stars in the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the years 2000-2004, are used for the event search. We combine the results of different observation runs, and obtained a single upper limit on the rate of the coalescence of compact binaries in our Galaxy of 20 per year at a 90% confidence level. In this upper limit, the effect of various systematic errors such like the uncertainty of the background estimation and the calibration of the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was correcte
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