11,857 research outputs found
: A Promising Detectable Tetraquark
We propose to investigate a particle with four different flavors, , which is a promising detectable tetraquark state. Its threshold,
5773 MeV, is 270 MeV higher than the threshold of and
, leading to a large mass region to be stable. If the
lowest-lying \bsud state exists below threshold, it can be definitely observed
via the weak decay mode , with the expectation of hundreds
of events in the current LHCb data sample but rejecting backgrounds due to its
long lifetime. This can be a benchmark of the existence of which is a
partner of under the flavor symmetry. If no signal is
observed in this mode, it constrain the mass of the ground tetraquark state to
be larger than the threshold. In the case above threshold, it can be detected
via the strong decay mode . The state has
similar features.Comment: 5 pages, 2 figures and 2 table
Fiscal, Monetary, and Reserve Requirement Policy in an Endogenous Growth with Financial Market Imperfections
A simple endogenous growth model is developed in a framework where informational imperfections in financial markets give rise to adverse selection as well as costly state verification problems and the government needs to intervene financial markets to monetize its deficits. In the model, adverse selection problem raises credit rationing and financial intermediaries arise endogenously due to costly state verification. Inflation is shown to influence the amount of credit rationing and economic growth. We then examine the effects of government fiscal and monetary policies on equilibrium inflation, the amount of credit rationing, and thus economic growth. Results show that multiple equilibria arise when the share of government deficits is relatively large. We also illustrate how the use of reserve requirement policy can eliminate high inflation equilibrium and enable the government to reduce the inflation rate. In sum, it is found that Tobin effect hold when there is no reserve requirement or it is not binding. However, if the reserve requirement is set too high, such a policy will raise the equilibrium inflation rate and reduce economic growth, leading to a violation of Tobin effect.
Quantum phase transition in a three-level atom-molecule system
We adopt a three-level bosonic model to investigate the quantum phase
transition in an ultracold atom-molecule conversion system which includes one
atomic mode and two molecular modes. Through thoroughly exploring the
properties of energy level structure, fidelity, and adiabatical geometric
phase, we confirm that the system exists a second-order phase transition from
an atommolecule mixture phase to a pure molecule phase. We give the explicit
expression of the critical point and obtain two scaling laws to characterize
this transition. In particular we find that both the critical exponents and the
behaviors of ground-state geometric phase change obviously in contrast to a
similar two-level model. Our analytical calculations show that the ground-state
geometric phase jumps from zero to ?pi/3 at the critical point. This
discontinuous behavior has been checked by numerical simulations and it can be
used to identify the phase transition in the system.Comment: 8 pages,8 figure
Masses of Scalar and Axial-Vector B Mesons Revisited
The SU(3) quark model encounters a great challenge in describing even-parity
mesons. Specifically, the quark model has difficulties in
understanding the light scalar mesons below 1 GeV, scalar and axial-vector
charmed mesons and charmonium-like state . A common wisdom for
the resolution of these difficulties lies on the coupled channel effects which
will distort the quark model calculations. In this work, we focus on the near
mass degeneracy of scalar charmed mesons, and , and its
implications. Within the framework of heavy meson chiral perturbation theory,
we show that near degeneracy can be qualitatively understood as a consequence
of self-energy effects due to strong coupled channels. Quantitatively, the
closeness of and masses can be implemented by adjusting
two relevant strong couplings and the renormalization scale appearing in the
loop diagram. Then this in turn implies the mass similarity of and
mesons. The interaction with the Goldstone boson is
crucial for understanding the phenomenon of near degeneracy. Based on heavy
quark symmetry in conjunction with corrections from QCD and effects, we
obtain the masses of and mesons, for example,
,
with being
corrections. We find that the predicted mass difference of 48 MeV
between and is larger than that of MeV
inferred from the relativistic quark models, whereas the difference of 15 MeV
between the central values of and is much smaller than
the quark model expectation of MeV.Comment: 21 pages, 1 figure, to appear in Eur. Phys. J. (2017). arXiv admin
note: text overlap with arXiv:1404.377
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