Using faces representing exaggerated emotional expressions, recent behaviour and eye-tracking studies have suggested a dominant role of individual facial features in transmitting diagnostic cues for ...decoding facial expressions. Considering that in everyday life we frequently view low-intensity expressive faces in which local facial cues are more ambiguous, we probably need to combine expressive cues from more than one facial feature to reliably decode naturalistic facial affects. In this study we applied a morphing technique to systematically vary intensities of six basic facial expressions of emotion, and employed a self-paced expression categorization task to measure participants' categorization performance and associated gaze patterns. The analysis of pooled data from all expressions showed that increasing expression intensity would improve categorization accuracy, shorten reaction time and reduce number of fixations directed at faces. The proportion of fixations and viewing time directed at internal facial features (eyes, nose and mouth region), however, was not affected by varying levels of intensity. Further comparison between individual facial expressions revealed that although proportional gaze allocation at individual facial features was quantitatively modulated by the viewed expressions, the overall gaze distribution in face viewing was qualitatively similar across different facial expressions and different intensities. It seems that we adopt a holistic viewing strategy to extract expressive cues from all internal facial features in processing of naturalistic facial expressions.
Tremendous progress has been made experimentally in the hadron spectrum containing heavy quarks in the last two decades. It is surprising that many resonant structures are around thresholds of a pair ...of heavy hadrons. There should be a threshold cusp at any S-wave threshold. By constructing a nonrelativistic effective field theory with open channels, we discuss the generalities of threshold behavior, and offer an explanation of the abundance of near-threshold peaks in the heavy quarkonium regime. We show that the threshold cusp can show up as a peak only for channels with attractive interaction, and the width of the cusp is inversely proportional to the reduced mass relevant for the threshold. We argue that there should be threshold structures at any threshold of a pair of heavy-quark and heavy-antiquark hadrons, which have attractive interaction at threshold, in the invariant mass distribution of a heavy quarkonium and light hadrons that couple to that open-flavor hadron pair. The structure becomes more pronounced if there is a near-threshold pole. Predictions of the possible pairs are also given for the ground state heavy hadrons. Precisely measuring the threshold structures will play an important role in revealing the heavy-hadron interactions, and thus understanding the puzzling hidden-charm and hidden-bottom structures.
We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the
b
b
b
¯
b
¯
bound state, where
b
stands for the bottom quark, in a nonrelativistic ...effective field theory framework with one-gluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state
b
b
b
¯
b
¯
tetraquark mass is predicted to be
(
18.72
±
0.02
)
GeV. Mass inequality relations among the lowest
Q
Q
Q
¯
Q
¯
states, where
Q
∈
{
c
,
b
}
, and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state
Q
Q
Q
¯
Q
¯
. The possible decays of the lowest
b
b
b
¯
b
¯
are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV.
The spectrum of hadrons is the manifestation of color confinement of quantum chromodynamics. Hadronic resonances correspond to poles of the S-matrix. Since 2003, lots of new hadron resonant ...structures were discovered in the mass regions from light mesons to hadrons containing a pair of a heavy quark and an antiquark. Many of them are candidates of exotic hadrons, and they are usually observed as peaks in invariant mass distributions. However, the S-matrix also has kinematical singularities due to the on-shellness of intermediate particles for a process, such as two-body thresholds and triangle singularities (TSs), and they can produce peaks as well. On the one hand, such singularities may be misidentified as resonances; on the other hand, they can be used as tools for precision measurements. In this paper, we review the threshold cusps and various triangle singularities in hadronic reactions, paying attention to their manifestations in phenomena related to exotic hadron candidates.
Physical states are characterised uniquely by their pole positions and the corresponding residues. Accordingly, in those parameters also the nature of the states should be encoded. For bound states ...(poles on the real
s
-axis below the lowest threshold on the physical sheet) there is an established criterion formulated originally by Weinberg in the 1960s, which allows one to estimate the amount of compact and molecular components in a given state. We demonstrate in this paper that this criterion can be straightforwardly extended to shallow virtual states (poles on the real
s
-axis below the lowest threshold on the unphysical sheet) which should be classified as molecular. We argue that predominantly non-molecular or compact states exist either as bound states or as resonances (poles on the unphysical sheet off the real energy axis) but not as virtual states. We also discuss the limitations of the mentioned classification scheme.
Revisiting the nature of the Pc pentaquarks Du, Meng-Lin; Baru, Vadim; Guo, Feng-Kun ...
The journal of high energy physics,
27/8, Letnik:
2021, Številka:
8
Journal Article
Recenzirano
Odprti dostop
A
bstract
The nature of the three narrow hidden-charm pentaquark
P
c
states, i.e.,
P
c
(4312),
P
c
(4440) and
P
c
(4457), is under intense discussion since their discovery from the updated analysis ...of the process
Λ
b
0
→
J
/
ψ
pK
−
by LHCb. In this work we extend our previous coupled-channel approach Phys. Rev. Lett.
124
, 072001 (2020), in which the
P
c
states are treated as
Σ
c
∗
D
¯
∗
molecules, by including the
Λ
c
D
¯
∗
and
η
c
p
as explicit inelastic channels in addition to the
J/ψp
, as required by unitarity and heavy quark spin symmetry (HQSS), respectively. Since inelastic parameters are very badly constrained by the current data, three calculation schemes are considered: (a) scheme I with pure contact interactions between the elastic, i.e.,
Σ
c
∗
D
¯
∗
, and inelastic channels and without the
Λ
c
D
¯
∗
interactions, (b) scheme II, where the one-pion exchange (OPE) is added to scheme I, and (c) scheme III, where the
Λ
c
D
¯
∗
interactions are included in addition. It is shown that to obtain cutoff independent results, OPE in the multichannel system is to be supplemented with
S
-wave-to-
D
-wave mixing contact terms. As a result, in line with our previous analysis, we demonstrate that the experimental data for the
J/ψp
invariant mass distribution are consistent with the interpretation of the
P
c
(4312) and
P
c
(4440)/
P
c
(4457) as
Λ
c
D
¯
and
Σ
c
D
¯
∗
hadronic molecules, respectively, and that the data show clear evidence for a new narrow state,
P
c
(4380), identified as a
Σ
c
∗
D
¯
molecule, which should exist as a consequence of HQSS. While two statistically equally good solutions are found in scheme I, only one of these solutions with the quantum numbers of the
P
c
(4440) and
P
c
(4457) being
J
P
= 3/2
−
and 1/2
−
, respectively, survives the requirement of regulator independence once the OPE is included. Moreover, we predict the line shapes in the elastic and inelastic channels and demonstrate that those related to the
P
c
(4440) and the
P
c
(4457) in the
Σ
c
∗
D
¯
and
η
c
p
mass distributions from
Λ
b
0
→
Σ
c
∗
D
¯
K
−
and
Λ
b
0
→
η
c
pK
−
will shed light on the quantum numbers of those states, once the data are available. We also investigate possible pentaquark signals in the
Λ
c
D
¯
∗
final states.
Deep‐learning‐based spectral identification received intensive interests benefiting from the availability of large scale spectral databases. However, for the identification of spectroscopic data such ...as Raman, the massive experimental data remained challenging, impeding the application of deep neural networks. Here, we describe a new approach with a transfer‐learning model pretrained on a standard Raman spectral database for the identification of Raman spectra data of organic compounds that are not included in the database and with limited data. Our results show that, with transfer learning, classification accuracy improvement of our convolutional neural network reaches 4.1% and that of our fully connected deep neural network reaches 5.0%. By investigating the influence of the source datasets, we find that our transfer learning method is able to incorporate both relevant and seemingly irrelevant source datasets for pretraining, and the relevant source dataset brings better classification accuracy than that of the seemingly irrelevant source dataset. This study demonstrates that the transfer learning technique has great potential in the effective identification of Raman spectra when the number of Raman data is limited.
An efficient transfer learning method—fine‐tuning which focuses on taking advantages of the weights pretrained on a large‐scale Raman database was evaluated on a multiclass classification task of small‐scale Raman spectra. Both DNN and CNN exhibited significant better performance when applying this method, indicating the external knowledge learned from standard Raman database raised the model's ability to extract features. Further investigation on the influence of the source datasets shows that even seemingly irrelevant source dataset makes progress on this classification task.
The photoproduction of the
J
/
ψ
off the proton is believed to deepen our understanding of various physics issues. On the one hand, it is proposed to provide access to the origin of the proton mass, ...based on the QCD multipole expansion. On the other hand, it can be employed in a study of pentaquark states. The process is usually assumed to proceed through vector-meson dominance, that is the photon couples to a
J
/
ψ
which rescatters with the proton to give the
J
/
ψ
p
final state. In this paper, we provide a compelling hint for and propose measurements necessary to confirm a novel production mechanism via the
Λ
c
D
¯
(
∗
)
intermediate states. In particular, there must be cusp structures at the
Λ
c
D
¯
(
∗
)
thresholds in the energy dependence of the
J
/
ψ
photoproduction cross section. The same mechanism also implies the
J
/
ψ
-nucleon scattering lengths of order 1 mfm. Given this, one expects only a minor contribution of charm quarks to the nucleon mass.
The global epidemic of COVID-19 makes people realize that wearing a mask is one of the most effective ways to protect ourselves from virus infections, which poses serious challenges for the existing ...face recognition system. To tackle the difficulties, a new method for masked face recognition is proposed by integrating a cropping-based approach with the Convolutional Block Attention Module (CBAM). The optimal cropping is explored for each case, while the CBAM module is adopted to focus on the regions around eyes. Two special application scenarios, using faces without mask for training to recognize masked faces, and using masked faces for training to recognize faces without mask, have also been studied. Comprehensive experiments on SMFRD, CISIA-Webface, AR and Extend Yela B datasets show that the proposed approach can significantly improve the performance of masked face recognition compared with other state-of-the-art approaches.
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