275 research outputs found
Coupled-channel model for charmonium levels and an option for X(3872)
The effects of charmed meson loops on the spectrum of charmonium are
considered, with special attention paid to the levels above open-charm
threshold. It is found that the coupling to charmed mesons generates a
structure at the D \bar{D}* threshold in the 1++ partial wave. The implications
for the nature of the X(3872) state are discussed.Comment: 27 pages, 7 EPS figure
Angular distributions in states near threshold
A resonance X(3872), first observed in the decays , has been seen
to decay to . The mass spectrum peaks near
its kinematic upper limit, prompting speculation that the dipion system may be
in a . The decay also has been observed.
The reaction has been studied.
Consequently, angular distributions in decays of
states near threshold are of interest, and results are presented.Comment: 10 pages, no figures. To be submitted to Phys. Rev.
Chiral Lagrangian for strange hadronic matter
A generalized Lagrangian for the description of hadronic matter based on the
linear -model is proposed. Besides the baryon
octet, the spin-0 and spin-1 nonets, a gluon condensate associated with broken
scale invariance is incorporated. The observed values for the vacuum masses of
the baryons and mesons are reproduced. In mean-field approximation, vector and
scalar interactions yield a saturating nuclear equation of state. We discuss
the difficulties and possibilities to construct a chiral invariant baryon-meson
interaction that leads to a realistic equation of state. It is found that a
coupling of the strange condensate to nucleons is needed to describe the
hyperon potentials correctly. The effective baryon masses and the appearance of
an abnormal phase of nearly massless nucleons at high densities are examined. A
nonlinear realization of chiral symmetry is considered, to retain a Yukawa-type
baryon-meson interaction and to establish a connection to the Walecka-model.Comment: Revtex, submitted to Phys. Rev.
Evidence for two-quark content of in exclusive decays
Inspired by a large decay branching ratio (BR) of
measured by Belle recently, we propose that a significant evidence of the
component of in could be
demonstrated in exclusive decays by the observation of in
the final states and . We predict the BRs of to be () while
the unknown wave functions of () are chosen to fit the
observed decays of .Comment: 4 pages, 2 figures, Revtex4, version to appear in PR
Angular momentum coefficients for meson strong decay and unquenched quark models
In most meson strong decay and unquenched (coupled-channel) quark models, the
pair-creation operator is a scalar product of vectors in the spin and spatial
degrees of freedom. While differing in the spatial part, most models have the
same spin part, which creates a qq* pair coupled to spin triplet, with the
spins of the initial quarks as spectators. This is a basic assumption of the
3P0 model, and is well-known to arise also in the flux tube model, starting
from the strong coupling expansion of lattice QCD. In this article the same
structure is shown to emerge in the Cornell model, in the dominant
contributions of a more general microscopic decay model, and in the
pseudoscalar-meson emission model. A solution is obtained for arbitrary matrix
elements in these ``non-flip, triplet'' models, expressed as a weighted sum
over spatial matrix elements. The coefficients in the expansion, which involve
the spin degrees of freedom and the associated angular momentum algebra, are
model-independent. Tables of the angular momentum coefficients are presented
which can be used in future calculations, avoiding tedious Clebsch-Gordan sums.
The symmetry and orthogonality properties of the coefficients are discussed, as
well as their application to transitions involving hybrid mesons and states of
mixed spin. New selection rules are derived, and existing ones generalised. The
coefficients lead to model-independent relations among decay amplitudes and
widths which can be tested in experiment and lattice QCD. They can also be used
to explain how mass shifts in the unquenched quark model do not spoil
successful predictions of the ordinary (quenched) quark model.Comment: 45 pages, 4 figures, 16 table
Structure of the axial-vector meson and the strong coupling constant with the light-cone QCD sum rules
In this article, we take the point of view that the charmed axial-vector
meson is the conventional meson and calculate the
strong coupling constant in the framework of the light-cone
QCD sum rules approach. The numerical values of strong coupling constants
and are very large, and support the
hadronic dressing mechanism. Just like the scalar mesons and
, the scalar meson and axial-vector meson
may have small kernels of the typical
meson size, the strong couplings to the hadronic channels (or the virtual
mesons loops) may result in smaller masses than the conventional
mesons in the constituent quark models, and enrich the pure states
with other components.Comment: 17 pages, 7 figures, revised version. In the first version, I take
the value in numerical calculation, in the
revised version, I take a small value , the
value of the strong coupling constant is also change
Climate related sea-level variations over the past two millennia
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 108 (2011): 11017-11022, doi:10.1073/pnas.1015619108.We present new sea-level reconstructions for the past 2100 years based on salt-marsh
sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal
four phases of persistent sea-level change after correction for glacial isostatic adjustment.
Sea level was stable from at least BC 100 until AD 950. It then increased for 400 years at
a rate of 0.6 mm/yr, followed by a further period of stable, or slightly falling, sea level
that persisted until the late 19th century. Since then, sea level has risen at an average rate
of 2.1 mm/yr, representing the steepest, century-scale increase of the past two millennia.
This rate was initiated between AD 1865 and 1892. Using an extended semi-empirical
modeling approach, we show that these sea-level changes are consistent with global
temperature for at least the past millennium.Research was supported by NSF grants (EAR-0951686) to BPH and JPD. ACK thanks a
NOSAMS internship, UPenn paleontology stipend and grants from GSA and NAMS.
North Carolina sea-level research was funded by NOAA (NA05NOS4781182), USGS
(02ERAG0044) and NSF (EAR-0717364) grants to BPH with S. Culver and R. Corbett
(East Carolina University). JPD (EAR-0309129) and MEM (ATM-0542356)
acknowledge NSF support. MV acknowledges Academy of Finland Project 123113 and
COST Action ES0701
Light hadron, Charmonium(-like) and Bottomonium(-like) states
Hadron physics represents the study of strongly interacting matter in all its
manifestations and the understanding of its properties and interactions. The
interest on this field has been revitalized by the discovery of new light
hadrons, charmonium- and bottomonium-like states. I review the most recent
experimental results from different experiments.Comment: Presented at Lepton-Photon 2011, Mumbai, India; 21 pages, 18 figures;
add more references; some correctio
Studying Kaon-pion S-wave scattering in K-matrix formalism
We generalize our previous work on \pi\pi scattering to K\pi scattering, and
re-analyze the experiment data of K\pi scattering below 1.6 GeV. Without any
free parameter, we explain K\pi I=3/2 S-wave phase shift very well by using
t-channel rho and u-channel K^* meson exchange. With the t-channel and
u-channel meson exchange fixed as the background term, we fit the K\pi I=1/2
S-wave data of the LASS experiment quite well by introducing one or two
s-channel resonances. It is found that there is only one s-channel resonance
between K\pi threshold and 1.6 GeV, i.e., K_0^*(1430) with a mass around
1438~1486 MeV and a width about 346 MeV, while the t-channel rho exchange gives
a pole at (450-480i) MeV for the amplitude.Comment: REVTeX4 file, 11 pages and 3 figure
- …