1,884 research outputs found
Revisiting the as a hadronic molecule and its strong decays
Recently, the Belle collaboration measured the ratios of the branching
fractions of the newly observed excited state. They did not
observe significant signals for the decay, and reported an upper limit for the ratio of the three
body decay to the two body decay mode of . In
this work, we revisit the newly observed from the molecular
perspective where this resonance appears to be a dynamically generated state
with spin-parity from the coupled channels interactions of the and in -wave and in -wave. With
the model parameters for the -wave interaction, we show that the ratio of
these decay fractions reported recently by the Belle collaboration can be
easily accommodated.Comment: Published version. Published in Eur.\ Phys.\ J.\ C {\bf 80}, 361
(2020
Improving Conversational Passage Re-ranking with View Ensemble
This paper presents ConvRerank, a conversational passage re-ranker that
employs a newly developed pseudo-labeling approach. Our proposed view-ensemble
method enhances the quality of pseudo-labeled data, thus improving the
fine-tuning of ConvRerank. Our experimental evaluation on benchmark datasets
shows that combining ConvRerank with a conversational dense retriever in a
cascaded manner achieves a good balance between effectiveness and efficiency.
Compared to baseline methods, our cascaded pipeline demonstrates lower latency
and higher top-ranking effectiveness. Furthermore, the in-depth analysis
confirms the potential of our approach to improving the effectiveness of
conversational search.Comment: SIGIR 202
Nature of in and decays
We investigate the decays of and
based on the picture where the resonance is strongly coupled to the
channel. In addition to the decay mechanism where the
resonance is formed from the pair hadronization with the
short-distance interaction, we have also considered the
rescattering diagrams in the long-distance scale, where and are
formed from and separately. Because of the difference of the mass
thresholds of charged and neutral channels, and the rather narrow
width of the resonance, at the mass, the loop functions of
and are much different. Taking this
difference into account, the ratio of can be naturally
obtained. Based on this result, we also evaluate the decay widths of . It is expected that future experimental measurements of
these decays can be used to elucidate the nature of the resonance.Comment: 7 pages, 5 figure
The role of and in the reactions of
We have studied the mass distribution of the process from the threshold to about 4250 MeV, by considering the
contribution of the with a narrow width, together with the
state. Our results show that the cusp structure at the
threshold is tied to the molecular nature of the state.Comment: 5 pages, 3 figures, contribution to the 18th International Conference
on Hadron Spectroscopy and Structure (HADRON 2019
Radiative decays of the neutral and
We study the radiative decays (), with the assumption that the
and couple strongly to and channel, respectively. By considering the contributions of intermediate
charmed mesons triangle loops within an effective Lagrangian approach, it is
shown that the calculated partial widths of
are about a few hundreds keVs, while the obtained partial widths are about tens of keVs. The predicted partial widths of
are less than 1 keV, which mainly due to
the very small phase space. For , the
calculated partial widths are usually smaller than 1 keV. For the
process, the obtained partial widths can
reach up to the order of 10 keV. Furthermore, the dependence of these ratios
between different decay modes on the masses of or are
also investigated, which may be a good quantity for the experiments. It is
hoped that these calculations here could be tested by future experiments.Comment: 9 pages, 6 figures. Accepted by Physical Review
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