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Have we found conclusive evidence for dark matter through direct detection experiments?

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Chinese Physics C 2014年第4期38卷 32-37页

作者：杨俊 Department of Physics Shanghai Jiao Tong University

A WIMP-model-independent method is used to examine the existing evidence for low mass dark matter. Using XENON100＇s recent result of 224.6 live days × 34 kg exposure and PICASSO＇s result that was published in 2012, we have obtained constraints on the couplings │an│ 〈 0.4 and │ap│ 〈 0.3, corresponding to spin-dependent cross-sections of σ〈2.5×10^-38 cm2 and σp〈1.4×10^-38cm2 for a WIMP mass of 10 GeV/c2. It is shown that the spin-independent isospin-violating dark matter model also fails to reconcile the recent result from XENON100 with the positive results from DAMA, CoGeNT and CDMS-Ⅱ.

关键词： dark matter spin-dependent IVDM XENOONIO0 direct detection

Greater than 200 Gb/s Transmission Using direct-detection Optical OFDM Superchannel

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ZTE Communications 2012年第1期10卷 10-17页

作者： Itsuro Morita Hidenori Takahashi Takehiro Tsuritani KDDI R&D Laboratories Inc.

In this paper, we propose directdetection optical orthogonal frequency division multiplexing superchannel （DDOOFDMS） and optical multiband receiving method （OMBR） to support a greater than 200 Gb/s data rate and longer distance for direct-detection systems. For the new OMBR, we discuss the optimum carriertosideband power ratio （CSPR） in the cases of backtoback and post transmission. We derive the analytical form for CSPR and theoretically verify it. A low overhead training method for estimating I/Q imbalance is also introduced in order to improve performance and maintain high system throughput. The experiment results show that these proposals enable an unprecedented data rate of 214 Gb/s （190 Gb/s without overhead） per wavelength over an unprecedented distance of 720 km SSMF in greater than 100 Gb/s DDOFDM systems.

关键词： orthogonal frequency division multiplexing （OFDM） direct detection multiband transmission

Minimizing FWM Impact in DWDM ROF DP-DQPSK System for Optical

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Computers, Materials & Continua 2023年第4期75卷 1033-1050页

作者： Esra Ehsan Razali Ngah Nurul Ashikin Binti Daud Wireless Communication Centre School of Electrical EngineeringUniversiti Teknologi Malaysia Johor BahruMalaysia

The demonstration of a higher data rate transmission system was amajor aspect to be considered by researchers in recent years. The most relevantaspect to be studied and analyzed is the need for a reliable system to handlenonlinear impairments and reduce them. Therefore, this paper examines theinfluence of Four-Wave Mixing (FWM) impairment on the proposed highdata rate Dual polarization–Differential Quadrature phase shift keying (DPDQPSK)system using the Optisystem software. In the beginning, the impactof varied input power on the proposed system’s performance was evaluated interms of QF and BER metrics. More power is used to improve system performance.However, increasing power would raise theFWMeffects. Accordingly,a−10dBminput power and the proposed system are used to reduce the impactof FWM. Additionally, a hybrid amplification method is proposed to enhancesystem performance by utilizing the major amplification methods of erbiumdopedfiber amplifier (EDFA): semiconductor optical amplifier (SOA) andRadio optical amplifier (ROA). The evaluation demonstrates that the OAEDFAoutperformed the other two key amplification techniques of (EDFASOA)and (EDFA-ROA) in improving Quality factor (QF) and Bit error rate(BER) system results for all distances up to 720 km. Consequently, the methodcontributes to minimizing the impact of FWM. In the future, other forms ofnonlinearity will be investigated and studied to quantify their impact on theproposed system.

关键词： direct detection DQPSK bit error rate quality factor Dense wavelength division multiplexing(DWDM)

Cryo-ET bridges the gap between cell biology and structural biophysics

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Chinese Physics B 2018年第6期27卷 62-71页

作者：程小芳王睿沈庆涛 iHuman Institute Shanghai Tech University Laboratory for Marine Biology and Biotechnology Qingdao National Laboratory for Marine Science and Technology School of Life Science and Technology Shanghai Tech University

Cryo-electron tomography（cryo-ET） is a cutting-edge technology providing three-dimensional in situ ultra-structural information of macromolecular machineries, organelles, and eukaryotic cells in their native environment at an unprecedented level of detail. Cryo-ET enables the direct observation of dynamic macromolecular architectures of bio-samples in their naturally occurring physiological state, without any harmful artifacts introduced by heavy metal staining, dehydration, and chemical fixation, which occur in traditional transmission electron microscopy. Over decades, cryo-ET has been providing insights into numerous aspects of cellular biology by revealing the pristinely preserved ultra-structures of different cellular components comprising the crowded and complex environment of the cell, thus, bridging the gap between cellular biology and structural biophysics. In this paper, we review the fundamentals of this technique, its recent advances in optics, detection devices, and computational algorithms. The enhancement of our understanding of structural cellular biology by combining these improvements, when integrated with other methods, such as cryo-focused ion beam milling,correlative light and electron microscopy, is discussed via a few examples from research groups worldwide. We also believe that cryo-ET applications in cell biology continue to provide fundamental insights into the field, revolutionizing structural biology itself.

关键词： sub-tomogram averaging segmentation direct detection phase plate

Theoretical and numerical analyses for PDM-IM signals using Stokes vector receivers

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Science China(Information Sciences) 2020年第10期63卷 194-202页

作者： Jiahao HUO Xian ZHOU Chao SHANG Wei HUANGFU Jinhui YUAN Huansheng NING Keping LONG Changyuan YU Alan Pak Tao LAU Chao LU Beijing Engineering and Technology Research Center for Convergence Networks and Ubiquitous Services University of Science and Technology Beijing Department of Electronic and Information Engineering The Hong Kong Polytechnic University Key Laboratory of Luminescence and Optical Information Ministry of EducationInstitute of Optical InformationSchool of ScienceBeijing Jiaotong University Department of Electrical Engineering The Hong Kong Polytechnic University

Different from current coherent-detection-based long-haul transmission systems, inter-and intradatacenter transmissions require a simpler transmitter and receiver. A promising way to significantly meet the demands of datacenter transmission is polarization division multiplexing intensity modulation with direct detection(PDM-IM-DD) using a Stokes vector receiver(SVR). However, for different SVR architectures,the corresponding demultiplexing matrix is required to recover the Stokes vectors from the detected signals,which are combined with an arbitrary state of polarization(SOP), will change the effect of noise dynamically and significantly influence the system performance. In this study, PDM-IM signals using four SVRs,i.e., a 90? optical hybrid with 2 balanced photodetectors(BPDs) and 2 photodetectors(PDs), a 90? optical hybrid with 4 PDs, a Stokes analyzer and a 3×3 coupler with 4 PDs, are studied theoretically and numerically. Theoretical system models using the four SVRs are developed, and the noise power variations are analyzed quantitatively based on these models. Moreover, the performance of the systems is also investigated for 224 Gbit/s polarization division multiplexing pulse amplitude modulation 4 level with direct detection(PDM-PAM4-DD) transmission in a simulation. The simulation results show that the bit error rate(BER)performance of the systems is consistent with the theoretical noise power variation curves. The theoretical analysis scheme is helpful for the practical design of SVR-based systems.

关键词： short-reach optical communications PAM4 polarization division multiplexing Stokes vector direct detection

Experimental search for dark matter in China

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Frontiers of physics 2020年第4期15卷 121-131页

作者： Li Zhao Jianglai Liu School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Tsung Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 200240China

The nature of dark matter is one of the greatest mysteries in modern physics and astronomy.A wide variety of experiments have been carried out worldwide to search for the evidence of particle dark matter.Chinese physicists started experimental search for dark matter about ten years ago,and have produced results with high scientific impact.In this paper,we present an overview of the dark matter program in China,and discuss recent results and future directions.

关键词： dark matter weakly interacting massive particle(WIMP) direct detection indirect de-tection Xenon Germanium

PandaX limits on the light dark matter with a light mediator in the singlet extension of MSSM

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Chinese Physics C 2020年第6期44卷 20-25页

作者：王雯宇吴佳骏熊兆华赵俊 Institute of Theoretical Physics College of Applied ScienceBeijing University of TechnologyBeijing 100124China Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

Using the latest PandaX limits on the light dark matter(DM) with a light mediator, we check their implication on the parameter space of the general singlet extension of MSSM(without Z3 symmetry), which can have a sufficient DM self-interaction to solve the small-scale structure problem. We find that the PandaX limits can tightly constrain the parameter space, depending on the coupling λ between the singlet and doublet Higgs fields. For the singlet extension of MSSM with Z3 symmetry, the so-called NMSSM, we also demonstrate the PandaX constraints on its parameter space, which gives a light DM with the correct relic density but without sufficient self-interaction to solve the small-scale structure problem. We find that in NMSSM, the GeV dark matter with a sub-GeV mediator is tightly constrained.

关键词： dark matter supersymmetry direct detection small structure

Dark matter search at colliders and neutrino floor

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Chinese Physics C 2020年第11期44卷 70-78页

作者：曹庆宏魏安康向仟飞 Department of Physics and State Key Laboratory of Nuclear Physics and Technology Peking UniversityBeijing 100871China Center for High Energy Physics Peking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China

The sensitivity of the direct detection of dark matter(DM)approaches the so-called neutrino floor,below which it is difficult to disentangle the DM candidate from the neutrino background.In this work,we consider the scenario that no DM signals are reported in various DM direct detection experiments and explore whether collider searches could probe DM below the neutrino floor.We adopt several simplified models in which the DM candidate couples to electroweak gauge bosons or leptons in the standard model only through high-dimensional operators.After including the RGE running effect,we investigate the constraints of direct detection,indirect detection,and collider searches.The collider search can probe light DM below the neutrino floor.Particularly,for the effective interaction of χχBμνB^μν,current data from the mono-photon channel at the 13 TeV LHC has already covered the entire parameter space of the neutrino floor.

关键词： dark matter collider direct detection

Results of dark matter search using the full PandaX-Ⅱ exposure

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Chinese Physics C 2020年第12期44卷 184-200页

作者：王秋红阿布都沙拉木·阿布都克力木陈葳谌勋陈云华程晨崔祥仪樊英杰方德清符长波付孟婷耿立升 Karl Giboni 顾琳慧郭绪元韩柯何昶达黄迪黄焱黄彦霖黄周季向东巨永林李帅杰刘华萱刘江来马文博马余刚冒亚军孟月倪恺翔宁金华宁旭阳任祥祥商长松司琳申国防谈安迪王安庆王宏伟王萌王思广王为王秀丽王舟武蒙蒙吴世勇邬维浩夏经铠肖梦姣谢鹏伟燕斌斌杨继军杨勇喻纯旭袁鞠敏袁影曾鑫宁张丹张涛赵力郑其斌周济芳周宁周小朋 INPAC and School of Physics and Astronomy Shanghai Jiao Tong UniversityMOE Key Lab for Particle PhysicsAstrophysics and CosmologyShanghai Key Laboratory for Particle Physics and CosmologyShanghai 200240China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China Shanghai Jiao Tong University Sichuan Research Institute Chengdu 610213China Yalong River Hydropower Development Company Ltd.288 Shuanglin RoadChengdu 610051China School of Physics Sun Yat-Sen UniversityGuangzhou 510275China Tsung-Dao Lee Institute Shanghai 200240China School of Physics Nankai UniversityTianjin 300071China Key Laboratory of Nuclear Physics and Ion-beam Application(MOE) Institute of Modern PhysicsFudan UniversityShanghai 200433China School of Physics Peking UniversityBeijing 100871China School of Physics Beihang UniversityBeijing 100191China International Research Center for Nuclei and Particles in the Cosmos&Beijing Key Laboratory of Advanced Nuclear Materials and Physics Beihang UniversityBeijing 100191China School of Medical Instrument and Food Engineering University of Shanghai for Science and TechnologyShanghai 200093China Department of Physics University of MarylandCollege ParkMaryland 20742USA School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Physics and Key Laboratory of Particle Physics and Particle Irradiation(MOE) Shandong UniversityJinan 250100China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China Center for High Energy Physics Peking UniversityBeijing 100871China

We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified above the expected background.Upper limits are set on the spin-independent dark matter-nucleon interactions.The lowest 90%confidence level exclusion on the spin-independent cross section is 2.2×10−46 cm2 at a WIMP mass of 30 GeV/c2.

关键词： dark matter direct detection liquid xenon