7,187 research outputs found
Understanding the newly observed heavy pentaquark candidates
We find that several thresholds can contribute to the enhancements of the
newly observed heavy pentaquark candidates and via
the anomalous triangle singularity (ATS) transitions in the specific kinematics
of . Apart from the observed two peaks we find that
another peaks around 4.5 GeV can also be produced by the ATS. We also show that
the can be produced at leading order in decay.
This process is different from the triangle diagram and its threshold
enhancement only appears as CUSP effects if there is no pole structure or the
ATS involved. The threshold interaction associated with the presence of the ATS
turns out to be a general phenomenon and plays a crucial role in the
understanding of candidates for exotic states.Comment: 9 pages, 6 figures, 4 tables; published version in PL
Photoproduction of hidden charm pentaquark states and
We propose to study the pentaquark candidates of and
in photoproduction and look for further experimental
evidence for their nature. Since the photoproduction process does not satisfy
the so-called "anomalous triangle singularity" condition their presence in
photoproduction would conclude that they should be genuine states and
provide further evidence for their existence.Comment: Accepted by Phys.Rev.
Probing the nature of and in the isospin violating process
The isospin violation process is studied
assuming that is a hadronic molecule. In
association with the production of the , which is treated as a hadronic molecule, this process can help us distinguish their
molecular natures from other scenarios, since the incomplete cancellation
between the charged and neutral--meson loops, which are prominent in the
molecular picture only, produces a peak in the cross section at the threshold and a very
prominent peak in the invariant mass spectrum in between the thresholds; the latter being much narrower than the
corresponding one in the isospin conserving channel, i.e. . The partial width of is about of that of . The cross section of
at the threshold is
about which is much larger than that produced by the
nearby resonances. These features are the direct consequences of the assumed
nature of these two states which might be accessible at the high-statistics
experiments such as BESIII and LHCb.Comment: 11 pages, 4 figure
Further understanding of the non- decays of
We provide details of the study of non- decays into
, where and denote light vector meson and pseudoscalar meson,
respectively. We find that the electromagnetic (EM) interaction plays little
role in these processes, while the strong interaction dominates. The strong
interaction can be separated into two parts, i.e. the short-distance part
probing the wave function at origin and the long-distance part reflecting the
soft gluon exchanged dynamics. The long-distance part is thus described by the
intermediate charmed meson loops. We show that the transition of can be related to such that the parameters in our model
can be constrained by comparing the different parts in to
those in . Our quantitative results confirm the findings of
[Zhang {\it et al.}, Phys. Rev. Lett. 102, 172001 (2009)] that the
OZI-rule-evading long-distance strong interaction via the IML plays an
important role in decays, and could be a key towards a full
understanding of the mysterious non- decay mechanism.Comment: 11 pages, 4 figures, version to appear in Phys. Rev.
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