Seeking for sterile neutrinos with displaced leptons at the LHC

We study the signal of long-lived sterile neutrino at the LHC produced through the decay of the $W$ boson. It decays into charged lepton and jets. The characteristic signature is a hard prompt lepton and a lepton from the displaced decay of the sterile neutrino, which leads to a bundle of displaced tracks with large transverse impact parameter. Different from other studies, we neither reconstruct the displaced vertex nor place requirement on its invariant mass to maintain sensitivity for low sterile neutrino masses. Instead, we focus on the displaced track from the lepton. A difficulty for low mass sterile neutrino study is that the displaced lepton is usually \textit{non-isolated}. Therefore, leptons from heavy flavor quark is the major source of background. We closely follow a search for displaced electron plus muon search at CMS and study their control regions, which is related to our signal regions, in great detail to develop a robust estimation of the background for our signals. After further optimization on the signal limiting the number of jets, low $H_T$ and large lepton displacement $d_0$ to suppress SM background, we reach an exclusion sensitivity of about $10^{-8}$ ($10^{-5}$) for the mixing angle square at 10 (2) GeV sterile neutrino mass respectively. The strategy we propose can cover the light sterile masses complimentary to beam dump and forward detector experiments.Comment: 22 pages, 6 figures, 1 table; v2: matched to Journal version

The Structure Transfer Machine Theory and Applications

Representation learning is a fundamental but challenging problem, especially when the distribution of data is unknown. We propose a new representation learning method, termed Structure Transfer Machine (STM), which enables feature learning process to converge at the representation expectation in a probabilistic way. We theoretically show that such an expected value of the representation (mean) is achievable if the manifold structure can be transferred from the data space to the feature space. The resulting structure regularization term, named manifold loss, is incorporated into the loss function of the typical deep learning pipeline. The STM architecture is constructed to enforce the learned deep representation to satisfy the intrinsic manifold structure from the data, which results in robust features that suit various application scenarios, such as digit recognition, image classification and object tracking. Compared to state-of-the-art CNN architectures, we achieve the better results on several commonly used benchmarks\footnote{The source code is available. https://github.com/stmstmstm/stm }

Local architectural identities within modernization context in southern China

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1996.Includes bibliographical references (leaves 52-55).In the processing of modernization, local architecture identities are diminishing in Kaiping, my home county in Canton Province, China. This thesis is searching for new architectural features that are based on the local climate, social rules, economic strength and modem technologies. New architecture identities should not be the rearrangement of Chinese architectural motifs. In contrast, they are the continuity of the essence of vernacular architecture and new spirits of modernization. Western modernization in Kaiping brings in the so called "international architecture style." It dominates the county's planning and architectural design. It is no doubt that architectural design reflects the changing times, yet different cultures in different regions and environments are at various presents. Therefore, architecture design should not have only one solution. Vernacular architecture in Kaiping County has its own characteristics such as the narrow alleys, small courtyards and watchtowers. They are not the same as the courtyard houses in Beijing, nor other regions in the world. Consequently, many factors that had influenced the local vernacular architecture have diminished or changed while the economic reform brings new perspectives in politics, social lives and family rules. Bridging the gap between the past and present in Kaiping's regional architecture is not as simple as copying other countries' architecture. The project investigates the past, interprets the present and anticipates the near future of Kaiping County architecture. A 200 meter by 250 meter city block next to a vernacular village two miles from the Old County Town is the test site for this approach. It is a housing development project which focuses on the relationships between rural areas and urban, public and private, community and family and environment and inhabitants. Both a master plan and a prototype house will be emphasized in details to examine relevant issues that evoke new local architecture identities.by Lian Quan Zhen.M.Arch

WIMPs at High Energy Muon Colliders

The Weakly Interacting Massive Particle (WIMP) paradigm is one of the most compelling scenarios for particle dark matter (DM). We show in this paper that a high energy muon collider can make decisive statements about the WIMP DM, and this should serve as one of its main physics driver cases. We demonstrate this by employing the DM as the lightest member of an electroweak (EW) multiplet, which is a simple, yet one of the most challenging WIMP scenarios given its minimal collider signature and high thermal target mass scale of 1 TeV$-$23 TeV. We perform a first study of the reach of high energy muon colliders, focusing on the simple, inclusive and conservative signals with large missing mass, through the mono-photon, VBF di-muon and a novel mono-muon channel. Using these inclusive signals, it is possible to cover the thermal targets of doublet and triplet with a 10 TeV muon collider. Higher energies, 14 TeV$-$75 TeV, would ensure a $5 \sigma$ reach above the thermal targets for the higher EW multiplets. We also estimate the reach of a search for disappearing tracks, demonstrating the potential significant enhancement of the sensitivity.Comment: v1: 33 pages, 16 figures, 3 tables; v2: minor updates, matches PRD published version; v3: doublet disappearing track numerical results corrected, conclusions improves; also matches PRD errat

Electronic Structures of SiC Nanoribbons

Electronic structures of SiC nanoribbons have been studied by spin-polarized density functional calculations. The armchair nanoribbons are nonmagnetic semiconductor, while the zigzag nanoribbons are magnetic metal. The spin polarization in zigzag SiC nanoribbons is originated from the unpaired electrons localized on the ribbon edges. Interestingly, the zigzag nanoribbons narrower than $\sim$4 nm present half-metallic behavior. Without the aid of external field or chemical modification, the metal-free half-metallicity predicted for narrow SiC zigzag nanoribbons opens a facile way for nanomaterial spintronics applications.Comment: 10 pages, 5 figure