Limit on Br(b→sg)Br(b\to s g) in Two Higgs Doublet Models

Using the recent CLEO measurement of $Br(b\to s \gamma)$, we find that the branching ratio of $b\to s g$ cannot be larger than $10\%$ in two Higgs doublet models. The small experimental value of $Br(b\to e\bar{\nu}X)$ can no longer be explained by charged Higgs boson effects.Comment: 11 pages + 3 Figures (not included), ReVTeX, NTUTH-94-16 and NHCU-HEP-94-1

Generative Adversarial Positive-Unlabelled Learning

In this work, we consider the task of classifying binary positive-unlabeled (PU) data. The existing discriminative learning based PU models attempt to seek an optimal reweighting strategy for U data, so that a decent decision boundary can be found. However, given limited P data, the conventional PU models tend to suffer from overfitting when adapted to very flexible deep neural networks. In contrast, we are the first to innovate a totally new paradigm to attack the binary PU task, from perspective of generative learning by leveraging the powerful generative adversarial networks (GAN). Our generative positive-unlabeled (GenPU) framework incorporates an array of discriminators and generators that are endowed with different roles in simultaneously producing positive and negative realistic samples. We provide theoretical analysis to justify that, at equilibrium, GenPU is capable of recovering both positive and negative data distributions. Moreover, we show GenPU is generalizable and closely related to the semi-supervised classification. Given rather limited P data, experiments on both synthetic and real-world dataset demonstrate the effectiveness of our proposed framework. With infinite realistic and diverse sample streams generated from GenPU, a very flexible classifier can then be trained using deep neural networks.Comment: 8 page

Tunneling between helical Majorana modes and helical Luttinger liquids

We propose and study the charge transport through single and double quantum point contacts setup between helical Majorana modes and an interacting helical Luttinger liquid. We show that the differential conductance decreases for stronger repulsive interactions and that the point contacts become insulating above a critical interaction strength. For a single point contact, the differential conductance as a function of bias voltage shows a series of peaks due to Andreev reflection of electrons in the Majorana modes. In the case of two point contacts, interference phenomena make the structure of the individual resonance peaks less universal and show modulations with different separation distance between the contacts. For small separation distance the overall features remain similar to the case of a single point contact.Comment: v.2: 14 pages, 11 figures; adding one figure, an appendix, and some minor change

Nano Cost Nano Patterned Template for Surface Enhanced Raman Scattering (SERS) for IN-VITRO and IN-VIVO Applications

Raman scattering is a well-known technique for detecting and identifying complex molecular level samples. The weak Raman signals are enormously enhanced in the presence of a nano-patterned metallic surface next to the specimens. This dissertation describes a technique to fabricate a novel, low cost, high sensitive, disposable, and reproducible metallic nanostructure on a transparent substrate for Surface Enhanced Raman Scattering (SERS). Raman signals can be obtained from the specimen surface of opaque specimens. Most importantly, the metallic nanostructure can be bonded on the end of a probe / a needle, and the other end is coupled to a distant spectrometer. This opens up the Raman spectroscopy for a use in a clinical environment with the patient simply sitting or lying near a spectrometer. This SERS system, one of molecular level early diagnosis technologies, can be divided into four parts: SERS nanostructure substrates, reflection Raman signal (in vitro), transmission (in vivo) Raman signal, and a probe / a needle with a gradient-index (GRIN) lens in an articulated arm system. In this work, the aluminum metal was employed as not only a base substrate for a sputtered Au nanostructure (conventional view) but also a sacrificial layer for the Au nanostructure on a transparent substrate (transmission view). The enhanced Raman Signal from reflection and transparent SERS substrates depended on aluminum etching methods, Au deposition angles, and Au deposition thicknesses. Rhodamine 6G solutions on both sides of the SERS substrates were used to analyze and characterize. Moreover, preliminary Raman Spectra from R6G and chicken specimen were obtained through a remote SERS probe head and an articulated arm system. The diameter of the invasive probe head was shrunk to 0.5 mm. The implication is that this system can be applied in medical applications