401 research outputs found
Comment on the "Coupling Constant and Quark Loop Expansion for Corrections to the Valence Appeoximation" by Lee and Weingarten
Lee and Weingarten have recently criticized our calculation of quarkonium and
glueball scalars as being "incomplete" and "incorrect". Here we explain the
relation of our calculations to full QCD.Comment: 5 pages,2 epsfigs. Submitted to the Comment section of Phys. Rev. D
28th April 199
The s-sbar and K-Kbar nature of f_0(980) in D_s decays
We examine the D_s -> f_0(980) pi amplitude through a constituent quark-meson
model, incorporating heavy quark and chiral symmetries, finding a good
agreement with the recent E791 data analysis of D_s -> 3pi via f_0(980). The
f_0(980) resonance is considered at the moment of production as an s sbar
state, later evolving to a superposition of mainly s sbar and K Kbar. The
analysis is also extended to the more frequent process D_s -> phi pi.Comment: 8 pages, 5 figure
Unquenching the scalar glueball
Computations in the quenched approximation on the lattice predict the
lightest glueball to be a scalar in the 1.5-1.8 GeV region. Here we calculate
the dynamical effect the coupling to two pseudoscalars has on the mass, width
and decay pattern of such a scalar glueball. These hadronic interactions allow
mixing with the scalar nonet, which is largely fixed by the
well-established K_0^*(1430). This non-perturbative mixing means that, if the
pure gluestate has a width to two pseudoscalar channels of ~100 MeV as
predicted on the lattice, the resulting hadron has a width to these channels of
only ~30 MeV with a large eta-eta component. Experimental results need to be
reanalyzed in the light of these predictions to decide if either the f_0(1500)
or an f_0(1710) coincides with this dressed glueball.Comment: 12 pages, LaTex, 3 Postscript figure
Spin correlations and consequences of quantum-mechanical coherence
The difference in the properties of the spin correlation tensor for
factorizable and nonfactorizable two-particle states is analyzed. The
inequalities for linear combinations of the components of this tensor are
obtained for the case of incoherent mixtures of factorizable two-particle spin
states. They include the well known Bell inequalities and can be violated for
coherent superpositions of two-particle spin states. The possibility to verify
the consequences of the quantum-mechanical coherence is discussed using the
angular correlations in the asymmetric (parity violating) decays of the pairs
of spin-1/2 particles (muons, top-quarks or lambda-hyperons), the coherence
arising either from the production dynamics or due to the effect of quantum
statistics.Comment: 11 pages, LaTe
Pion propagation in the linear sigma model at finite temperature
We construct effective one-loop vertices and propagators in the linear sigma
model at finite temperature, satisfying the chiral Ward identities and thus
respecting chiral symmetry, treating the pion momentum, pion mass and
temperature as small compared to the sigma mass. We use these objects to
compute the two-loop pion self-energy. We find that the perturbative behavior
of physical quantities, such as the temperature dependence of the pion mass, is
well defined in this kinematical regime in terms of the parameter
m_pi^2/4pi^2f_pi^2 and show that an expansion in terms of this reproduces the
dispersion curve obtained by means of chiral perturbation theory at leading
order. The temperature dependence of the pion mass is such that the first and
second order corrections in the above parameter have the same sign. We also
study pion damping both in the elastic and inelastic channels to this order and
compute the mean free path and mean collision time for a pion traveling in the
medium before forming a sigma resonance and find a very good agreement with the
result from chiral perturbation theory when using a value for the sigma mass of
600 MeV.Comment: 18 pages, 11 figures, uses RevTeX and epsfig. Expanded conclusions,
added references. To appear in Phys. Rev.
Possible Molecular States of System and Y(4140)
The interpretation of Y(4140) as a molecule is studied
dynamically in the one boson exchange approach, where , and
exchange are included. Ten allowed states with
low spin parity are considered, we find that the , ,
, and configurations are most
tightly bound. We suggest the most favorable quantum numbers are
for Y(4140) as a molecule, however,
and can not be excluded. We propose to search for the
and partners in the and final
states, which is an important test of the molecular hypothesis of Y(4140) and
the reasonability of our model. The molecule is
deeply bound, experimental search in the channel at Tevatron
and LHC is suggested.Comment: 13 pages,2 figure
Identification of Quantitative Trait Loci for Plant Height, Crown Diameter, and Plant Biomass in a Pseudo-F2 Population of Switchgrass
Switchgrass (Panicum virgatum) is a perennial warm-season grass that produces high biomass yield. Identification of mechanisms for genetic regulation of biomass traits has potential to facilitate genetic manipulation of switchgrass for enhancing biomass yield. The objective of this study was to identify quantitative trait loci for biomass-related traits in a pseudo-F2 population of switchgrass derived from an upland cross with a lowland switchgrass cultivar. Plant height (HT), crown diameter (CD), and plant biomass (PB) were assessed in field studies in 2015 and 2016. Plant height was positively correlated with PB in both years but only correlated with CD in 2016. Positive correlations between CD and PB were found in both years. Six quantitative trait loci (QTLs) were detected, including three QTLs on chromosome 2b for HT (2015) or CD (2016), two 2 QTLs on chromosome 2a for CD and PB in 2016, and one QTL on chromosome 5b for CD in 2016. The logarithm of the odds scores for these QTLs ranged from 4.9 to 8.2, and percentage variance explained ranged from 7.1 to 12.9%. One QTL on chromosome 2b appeared to simultaneously control HT in 2015 and CD in 2016. Homologs of candidate genes related to cell wall development and biosynthesis, hormone regulation, and metabolism were identified within the confidence interval of these QTLs. The findings from this study indicate that these QTLs can be important signals for genetic control of switchgrass growth
Analysis of preliminary data on reaction
We perform the analysis of the preliminary data on reaction simultaneously with the data on
scattering and reactions and
. It is found that the meson mass
MeV and .Comment: 8 pages, revtex, 3 ps files of figures, minor change
Large Nc and Chiral Dynamics
We study the dependence on the number of colors of the leading pi pi
scattering amplitude in chiral dynamics. We demonstrate the existence of a
critical number of colors for and above which the low energy pi pi scattering
amplitude computed from the simple sum of the current algebra and vector meson
terms is crossing symmetric and unitary at leading order in a truncated and
regularized 1/Nc expansion. The critical number of colors turns out to be Nc=6
and is insensitive to the explicit breaking of chiral symmetry.
Below this critical value, an additional state is needed to enforce the
unitarity bound; it is a broad one, most likely of "four quark" nature.Comment: RevTeX4, 6 fig., 5 page
Radiative open charm decay of the Y(3940), Z(3930), X(4160) resonances
We determine the radiative decay amplitudes for decay into and , or and of some of the charmonium like
states classified as X,Y,Z resonances, plus some other hidden charm states
which are dynamically generated from the interaction of vector mesons with
charm. The mass distributions as a function of the or
invariant mass show a peculiar behavior as a consequence of
the nature of these states. The experimental search of these
magnitudes can shed light on the nature of these states.Comment: 18 pages, 9 figure
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