186 research outputs found
Charm as a domain wall fermion in quenched lattice QCD
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
GeV. We calculate masses of heavy-light (charmed) and
heavy-heavy (charmonium) mesons with spin-parity and ,
leptonic decay constants of the charmed pseudoscalar mesons ( and ),
and the - mixing parameter. The charm quark mass is found to be
GeV. The mass splittings in
charmed-meson parity partners and are
degenerate within statistical errors, in accord with experiment, and they
satisfy a relation , also consistent with
experiment. A C-odd axial vector charmonium state, \chi_{c1}m_{h_{c}} = 3533(11)_{\rm stat.}\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 and mesons are found to be
MeV and
,
where the first error is statistical, the second a systematic due to chiral
extrapolation and the third error combination of other known systematics. The
- mixing bag parameter, which enters the
transition amplitude, is found to be .Comment: 49 pages, 15 figure
Continuum Limit of from 2+1 Flavor Domain Wall QCD
We determine the neutral kaon mixing matrix element 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 . Adding
all sources of error in quadrature we obtain , with an overall combined error of 3.6%.Comment: 65 page
Localization and chiral symmetry in 2+1 flavor domain wall QCD
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 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 GeV.Comment: 59 Pages, 23 figures, 1 MPG linke
Deconfinement transition and string tensions in SU(4) Yang-Mills Theory
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 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() deconfinement transition would explain some features of the SU(3)
and QCD transitions, we confirm older results on a coarser, , lattice.
We see a clear two-phase coexistence signal, characteristic of a first-order
transition, at on a lattice, on which we also
compute a latent heat of . Computing
Polyakov loop correlation functions we calculate the string tension at finite
temperature in the confined phase between fundamental charges, ,
between diquark charges, , and between adjoint charges . We
find that , and our result for the adjoint string
tension 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
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 spectrum by using two distinct
interpolating operators at on a
lattice. The mass estimates extracted from the two operators are consistent
with each other. The observed large mass splitting between this state,
, 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
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
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
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
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 ) 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
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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