10,887 research outputs found
Revisiting B\to\pi K, \pi K^{\ast} and \rho K decays: CP violations and implication for New Physics
Combining the up-to-date experimental information on and decays, we revisit the decay rates and CP asymmetries of
these decays within the framework of QCD factorization. Using an infrared
finite gluon propagator of Cornwall prescription, we find that the time-like
annihilation amplitude could contribute a large strong phase, while the
space-like hard spectator scattering amplitude is real. Numerically, we find
that all the branching ratios and most of the direct CP violations, except
, agree with the current experimental data
with an effective gluon mass . Taking the unmatched
difference in direct CP violations between and
decays as a hint of new physics, we perform a
model-independent analysis of new physics contributions with a set of
(q=u,d) operators. Detail
analyses of the relative impacts of the operators are presented in five cases.
Fitting the twelve decay modes, parameter spaces are found generally with
nontrivial weak phases. Our results may indicate that both strong phase from
annihilation amplitude and new weak phase from new physics are needed to
resolve the puzzle. To further test the new physics hypothesis, the
mixing-induced CP violations in and are
discussed and good agreements with the recent experimental data are found.Comment: Version published in JHE
Family Non-universal Z^\prime effects on \bar{B}_q-B_q$ mixing, B\to X_s \mu^+\mu^- and B_s\to \mu^+\mu^- Decays
Motivated by the large discrepancy of CP-violating phase in
mixing between the experimental data and the Standard Model prediction, we
pursue possible solutions within a family non-universal model.
Within such a specific model, we find that both the mixing
anomaly and the well-known " puzzle" could be moderated simultaneously
with a nontrivial new weak phase, (S1) or
(S2). With the stringently constrained coupling
, we then study the effects on the rare and decays, which are also induced by the same
transition. The observables of , at both high and
low regions, are found to be able to put strong constraints on the
coupling, . It is also shown
that the combined constraints from mixing, and
do not allow a large contribution to the
pure leptonic decay.Comment: 29 pages, 10 figs and 6 tables. References and discussions added. To
appear in JHE
, decays in a family non-universal model
Motivated by the observed forward-backward asymmetry in decay, we perform a detailed analysis of this decay mode within a family
non-universal model. With the related coupling
constrained by mixing, , and
decays, we look for further constraint on the
couplings from and get
numerically . Moreover, we find that the
relations, and
, with a small negative , are
crucial to moderate the discrepancy for
between the SM prediction and the experimental data. Numerically, comparing
with the SM prediction, we find that could be enhanced about 80%
and 50% by contribution at most in scenarios S1 and S2,
corresponding to the two fitted results of by UTfit collaboration,
respectively. However, the results are still about lower than the
experimental measurement.Comment: 20 pages, 3 figures. To appear in JHE
An Effective Deployment of Contrastive Learning in Multi-label Text Classification
The effectiveness of contrastive learning technology in natural language
processing tasks is yet to be explored and analyzed. How to construct positive
and negative samples correctly and reasonably is the core challenge of
contrastive learning. It is even harder to discover contrastive objects in
multi-label text classification tasks. There are very few contrastive losses
proposed previously. In this paper, we investigate the problem from a different
angle by proposing five novel contrastive losses for multi-label text
classification tasks. These are Strict Contrastive Loss (SCL), Intra-label
Contrastive Loss (ICL), Jaccard Similarity Contrastive Loss (JSCL), Jaccard
Similarity Probability Contrastive Loss (JSPCL), and Stepwise Label Contrastive
Loss (SLCL). We explore the effectiveness of contrastive learning for
multi-label text classification tasks by the employment of these novel losses
and provide a set of baseline models for deploying contrastive learning
techniques on specific tasks. We further perform an interpretable analysis of
our approach to show how different components of contrastive learning losses
play their roles. The experimental results show that our proposed contrastive
losses can bring improvement to multi-label text classification tasks. Our work
also explores how contrastive learning should be adapted for multi-label text
classification tasks.Comment: Accepted by ACL-Findings 2023, 13 page
Spam Review Detection with Graph Convolutional Networks
Customers make a lot of reviews on online shopping websites every day, e.g.,
Amazon and Taobao. Reviews affect the buying decisions of customers, meanwhile,
attract lots of spammers aiming at misleading buyers. Xianyu, the largest
second-hand goods app in China, suffering from spam reviews. The anti-spam
system of Xianyu faces two major challenges: scalability of the data and
adversarial actions taken by spammers. In this paper, we present our technical
solutions to address these challenges. We propose a large-scale anti-spam
method based on graph convolutional networks (GCN) for detecting spam
advertisements at Xianyu, named GCN-based Anti-Spam (GAS) model. In this model,
a heterogeneous graph and a homogeneous graph are integrated to capture the
local context and global context of a comment. Offline experiments show that
the proposed method is superior to our baseline model in which the information
of reviews, features of users and items being reviewed are utilized.
Furthermore, we deploy our system to process million-scale data daily at
Xianyu. The online performance also demonstrates the effectiveness of the
proposed method.Comment: Accepted at CIKM 201
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