Anti-charmed pentaquark from B decays

We explore the possibility of observing the anti-charmed pentaquark state from the $\Theta_c \bar{n} \pi^+$ decay of $B$ meson produced at $B$-factory experiments. We first show that the observed branching ratio of the $B^+$ to $\Lambda^-_c p \pi^+$, as well as its open histograms, can be remarkably well explained by assuming that the decay proceeds first through the $\pi^+ \bar{D}^0$ (or $\bar{D}^{*0}$) decay, whose branching ratios are known, and then through the subsequent decay of the virtual $\bar{D}^0$ or $\bar{D}^{*0}$ mesons to $\Lambda_c^- p$, whose strength are calculated using previously fit hadronic parameters. We then note that the $\Theta_c$ can be similarly produced when the virtual $\bar{D}^0$ or $\bar{D}^{*0}$ decay into an anti-nucleon and a $\Theta_c$. Combining the present theoretical estimates for the ratio $g_{D N \Lambda_c} / g_{D N \Theta_c} \sim 13$ and $g_{D^* N \Theta_c} \sim {1/3} g_{D N \Theta_c}$, we find that the anti-charmed pentaquark $\Theta_c$, which was predicted to be bound by several model calculations, can be produced via $B^+ \to \Theta_c \bar{n} \pi^+$, and be observed from the $B$-factory experiments through the weak decay of $\Theta_c \to p K^+ \pi^- \pi^-$.Comment: 4 pages, 4 figures, Revised version to be published in Physical Review Letter

Recent Reform in Korean Legal Education

Following many years of attempts to fundamentally change the legal education scheme in Korea, a graduate-level law school system was finally introduced in 2009. This comprehensive yet controversial educational reform has brought about tremendous changes to legal education as well as to many aspects of the Korean legal system. Such legal education reform that is currently ongoing will shape the future of the Korean legal system. Along this line, this article portrays detailed features of the recent reform in Korean legal education and illustrates salient changes that were brought about as a result of the reform. Further, this article proposes a way forward as follows. Concerted efforts among all the stakeholders should be made to form a more solid consensus on the specific mission of a law school, while improving the quality of education should be the focal interest above all. In doing so, legal professions should collaborate with law schools for better education. The government should not only be a strict regulator but also a passionate supporter of the new system. Whether or not this reform has succeeded is too early to tell and remains an open question. The virtues we need now are hope for a better legal education system, diligence in the reform efforts, and patience before challenges.This article was funded by the Seoul National University Law Foundation in 2013

Pure Economic Loss: A Korean Perspective

In general, pure economic loss is understood as economic loss without antecedent harm to plaintiff person or property. Traditionally, pure economic loss was only a topic of interest in the limited number of countries such as Germany, England or the United States. Recently, pure economic loss began to be discussed intensively in the context of the harmonization of tort law, particularly in Europe. Finding out some common principles and rules regarding pure economic loss has been the most essential goal of this discussion. It may be difficult to come up with a single, clear-cut solution on this complicated issue. However, it is important to note that almost all the jurisdictions are concerned about the possible indefinite expansion of liability and chilling effect on the economic activity in a substantially similar manner. This explains various attempts to limit the liability for pure economic loss to a reasonable degree regardless of a jurisdiction. It may take different forms from nation to nation, yet substances are fundamentally similar. Korea is no exception to this. In principle, pure economic loss is recoverable under the open-ended tort liability regime under Korean tort law. Since the notion of pure economic loss has generally been used as a conceptual tool to deny or limit its recoverability in the jurisdictions where there is no comprehensive tort liability regime, this notion was hardly known in Korea. However, Korean judiciary also shares the same concern that imposing excessive liability on economic loss in a densely intertwined society may lead to excessively cautious society, curbing the scope of economic activity for fear of liability. Therefore, Korean judiciary has also been striving to limit the liability by using other conceptual tools such as unlawfulness, causation or damage

Tortious Liability of Internet Service Providers for Defamation: A Korean Perspective

The paper deals with the thorny issue of tortuous liability of internet service providers from a Korean perspective. The Internet is the most participatory media that widens the scope of free speech, both quantitatively and qualitatively. At the same time, it is difficult to deny that there is a dark side of the Internet as well, such as on-line defamations, invasion of privacy and obscenity. The present paper attempts to establish a modified standard for determining liability of ISPs for defamation. The main argument is that neither complete immunity nor broad liability is desirable. Actual knowledge and obviousness of defamation are two factors that give rise to the duty of care for ISPs. This may add clarity and predictability to the ISP liability standard without causing too much of a chilling effect on the Internet

Probing sterile neutrino in BB (DD) meson decays at Belle II (BESIII)

We present, how a systematic study of $B \to D\ell N$ ($D \to K \ell N$) decays with $\ell=\mu,\tau$, at Belle II (BESIII) can provide unambiguous signature of a heavy neutrino $N$ and/or constrain its mixing with active neutrinos $\nu_\ell$, which is parameterized by $|U_{\ell N}|^2$. Our constraint on $|U_{\mu N}|^2$ that can be achieved from the full Belle II data is comparable with what can be obtained from the much larger data set of the upgraded LHCb. Additionally, our method offers better constraint on $|U_{\mu N}|^2$ for mass of sterile neutrino $m_N < 2$ GeV. We can also probe the Dirac and Majorana nature of $N$ by observing the sequential decay of $N$, including suppression from observation of a displaced vertex as well as helicity flip, for Majorana $N$.Comment: 9 pages, 6 figures. This is a pre-print of an article published in European Physical Journal C. The final authenticated version is available online at https://doi.org/10.1140/epjc/s10052-020-8310-

Optimal Experimental Design for Uncertain Systems Based on Coupled Differential Equations

We consider the optimal experimental design (OED) problem for an uncertain system described by coupled ordinary differential equations (ODEs), whose parameters are not completely known. The primary objective of this work is to develop a general experimental design strategy that is applicable to any ODE-based model in the presence of uncertainty. For this purpose, we focus on non-homogeneous Kuramoto models in this study as a vehicle to develop the OED strategy. A Kuramoto model consists of N interacting oscillators described by coupled ODEs, and they have been widely studied in various domains to investigate the synchronization phenomena in biological and chemical oscillators. Here we assume that the pairwise coupling strengths between the oscillators are non-uniform and unknown. This gives rise to an uncertainty class of possible Kuramoto models, which includes the true unknown model. Given an uncertainty class of Kuramoto models, we focus on the problem of achieving robust synchronization of the uncertain model through external control. Should experimental budget be available for performing experiments to reduce model uncertainty, an important practical question is how the experiments can be prioritized so that one can select the sequence of experiments within the budget that can most effectively reduce the uncertainty. In this paper, we present an OED strategy that quantifies the objective uncertainty of the model via the mean objective cost of uncertainty (MOCU), based on which we identify the optimal experiment that is expected to maximally reduce the MOCU. We demonstrate the importance of quantifying the operational impact of the potential experiments in designing optimal experiments and show that the MOCU-based OED scheme enables us to minimize the cost of robust control of the uncertain Kuramoto model with the fewest experiments compared to other alternatives. The proposed scheme is fairly general and can be applied to any uncertain complex system represented by coupled ODEs

A comprehensive study of vector leptoquark with U(1)B3−L2U(1)_{B_3-L_2} on the BB-meson and Muon g-2 anomalies

Recently reported anomalies in various $B$ meson decays and also in the anomalous magnetic moment of muon $(g-2)_\mu$ motivate us to consider a particular extension of the standard model incorporating new interactions in lepton and quark sectors simultaneously. Our minimal choice would be leptoquark. In particular, we take vector leptoquark ($U_1$) and comprehensively study all related observables including ${(g-2)_{\mu}},\ R_{K^{(*)}},\ R_{D^{(*)}}$,$B \to (K) \ell \ell' $where$\ell\ell'$are various combinations of$\mu$and$\tau$, and also lepton flavor violation in the$\tau$decays. We find that a hybrid scenario with additional$U(1)_{B_3-L_2}$ gauge boson provides a common explanation of all these anomalies.Comment: 16 pages, 3 figure