4,782 research outputs found
QCD and the Chiral Critical Point
As an extension of , consider a theory with ``'' flavors, where the
current quark masses are held in a fixed ratio as the overall scale of the
quark masses is varied. At nonzero temperature and baryon density it is
expected that in the chiral limit the chiral phase transition is of first
order. Increasing the quark mass from zero, the chiral transition becomes more
weakly first order, and can end in a chiral critical point. We show that the
only massless field at the chiral critical point is a sigma meson, with the
universality class that of the Ising model. Present day lattice simulations
indicate that is (relatively) near to the chiral critical point.Comment: 7 pages + 2 figures, BNL-GGP-
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Discriminating active from latent tuberculosis in patients presenting to community clinics.
BACKGROUND: Because of the high global prevalence of latent TB infection (LTBI), a key challenge in endemic settings is distinguishing patients with active TB from patients with overlapping clinical symptoms without active TB but with co-existing LTBI. Current methods are insufficiently accurate. Plasma proteomic fingerprinting can resolve this difficulty by providing a molecular snapshot defining disease state that can be used to develop point-of-care diagnostics. METHODS: Plasma and clinical data were obtained prospectively from patients attending community TB clinics in Peru and from household contacts. Plasma was subjected to high-throughput proteomic profiling by mass spectrometry. Statistical pattern recognition methods were used to define mass spectral patterns that distinguished patients with active TB from symptomatic controls with or without LTBI. RESULTS: 156 patients with active TB and 110 symptomatic controls (patients with respiratory symptoms without active TB) were investigated. Active TB patients were distinguishable from undifferentiated symptomatic controls with accuracy of 87% (sensitivity 84%, specificity 90%), from symptomatic controls with LTBI (accuracy of 87%, sensitivity 89%, specificity 82%) and from symptomatic controls without LTBI (accuracy 90%, sensitivity 90%, specificity 92%). CONCLUSIONS: We show that active TB can be distinguished accurately from LTBI in symptomatic clinic attenders using a plasma proteomic fingerprint. Translation of biomarkers derived from this study into a robust and affordable point-of-care format will have significant implications for recognition and control of active TB in high prevalence settings
One Spin Trace Formalism for
It has been known for some time that there are two methods to calculate with staggered fermions: one is the two spin trace formalism and the other is
the one spin trace formalism. Until now, the two spin trace formalism has been
exclusively used for weak matrix element calculations with staggered fermions.
Here, the one spin trace formalism to calculate with staggered fermions
is explained. It is shown that the one spin trace operators require additional
chiral partner operators in order to keep the continuum chiral behavior. The
renormalization of the one spin trace operators is described and compared with
the two spin trace formalism.Comment: 47 pages, latex, 4 figures are available on reques
Form Factors of Composite Systems by Generalized Wigner-Eckart Theorem for Poincar\'e group
The relativistic approach to electroweak properties of two-particle composite
systems developed previously is generalized here to the case of nonzero spin.
This approach is based on the instant form of relativistic Hamiltonian
dynamics. A special mathematical technique is used for the parametrization of
matrix elements of electroweak current operators in terms of form factors. The
parametrization is a realization of the generalized Wigner--Eckart theorem on
the Poincar\'e group, form factors are corresponding reduced matrix elements
and they have the sense of distributions (generalized functions). The
electroweak current matrix element satisfies the relativistic covariance
conditions and in the case of electromagnetic current it also automatically
satisfies the conservation law.Comment: Submitted to Theor. Math. Phy
SU(3) Decomposition of Two-Body B Decay Amplitudes
We present the complete flavor SU(3) decomposition of decay amplitudes for
decays of the triplet (B^+_u, B^0_d, B^0_s) of B mesons nonleptonically into
two pseudoscalar mesons. This analysis holds for arbitrarily broken SU(3) and
can be used to generate amplitude relations when physical arguments permit one
to neglect or relate any of the reduced amplitudes.Comment: 31 pages, revtex, no figure
Determination of CKM phases through rigid polygons of flavor SU(3) amplitudes
Some new methods for the extraction of CKM phases and using
flavor SU(3) symmetry have been suggested through the construction of rigid
polygons in the complex plane with sides equal to the decay amplitudes of B
mesons into two mesons belonging to the light (charmless) pseudoscalar octet.
These rigid polygons incorporate all the possible amplitude triangles and,
being overdetermined, also serve as consistency checks and in estimating the
rates of some decay modes. The same techniques also lead to numerous useful
amplitude triangles when octet-singlet mixing has been taken into account and
nearly physical are used.Comment: A few detailed explanations added, some rearrangement of sections and
a few minor changes in notation. 19 pages, 1 PostScript figure, uses
psfig.st
Charged Scalar Particles and Leptonic Decay
Charged scalar particles introduced in some extensions of the standard model
can induce leptonic decay at tree level. We find that with some charged
SU(2)-singlet scalar particles, like ones introduced in Zee-type models,
leptonic decay width is always smaller than what is predicted by the standard
model, therefore they may offer a natural solution to decay puzzle. To
be more specific, we examine some Zee-type models in detail to see if at the
same time they are acceptable in particle physics, cosmology and astrophysics.
It is shown that decay data do put some constrains on these models.Comment: ICTP Report No. IC/93/31, 12 pages, Latex, one figure is not
included, it is available upon deman
Resonant behaviour in double charge exchange reaction of \pi^+ mesons on the nuclear photoemulsion
The invariant mass spectra of the and systems produced in the
double charge exchange (DCX) of positively charged pions on photoemulsion are
analysed. A pronounced peak is observed in the invariant mass
spectrum, while the spectrum exhibits a strong Migdal-Watson effect of
the proton-proton final state interaction. These findings are in favor of the
-decoupled pseudoscalar resonance with T=0 called .Comment: 13 pages, 5 figures, revised versio
Chiral effective theory predictions for deuteron form factor ratios at low Q^2
We use chiral effective theory to predict the deuteron form factor ratio
G_C/G_Q as well as ratios of deuteron to nucleon form factors. These ratios are
calculated to next-to-next-to-leading order. At this order the chiral expansion
for the NN isoscalar charge operator (including consistently calculated 1/M
corrections) is a parameter-free prediction of the effective theory. Use of
this operator in conjunction with NLO and NNLO chiral effective theory wave
functions produces results that are consistent with extant experimental data
for Q^2 < 0.35 GeV^2. These wave functions predict a deuteron quadrupole moment
G_Q(Q^2=0)=0.278-0.282 fm^2-with the variation arising from short-distance
contributions to this quantity. The variation is of the same size as the
discrepancy between the theoretical result and the experimental value. This
motivates the renormalization of G_Q via a two-nucleon operator that couples to
quadrupole photons. After that renormalization we obtain a robust prediction
for the shape of G_C/G_Q at Q^2 < 0.3 GeV^2. This allows us to make precise,
model-independent predictions for the values of this ratio that will be
measured at the lower end of the kinematic range explored at BLAST. We also
present results for the ratio G_C/G_M.Comment: 31 pages, 7 figure
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