Results of a search for cold flows of dark matter axions

Theoretical arguments predict that the distribution of cold dark matter in spiral galaxies has peaks in velocity space associated with nonthermalized flows of dark matter particles. We searched for the corresponding peaks in the spectrum of microwave photons from axion to photon conversion in a cavity detector for dark matter axions. We found none and place limits on the density of any local flow of axions as a function of the flow velocity dispersion over the axion mass range 1.98 to 2.17 microeV.     

Dynamical interactions of dark energy and dark matter:Yang-Mills condensate and QCD axions

We analyze a model of cold axion dark matter weakly coupled with a dark gluon condensate,reproducing dark energy.We first review how to recover the dark energy behavior using the functional renormalization group approach,and ground our study in the properties of the effective Lagrangian,to be determined non-perturbatively.Then,within the context of G_(SM)×SU(2)_D×U(1)_(P Q),we consider Yang-Mills condensate(YMC)interactions with QCD axions.We predict a transfer of dark energy density into dark matter density,that can be tested in the next generation of experiments dedicated to dark energy measurements.We obtain new bounds on the interactions between the Yang-Mills condensate and axion dark matter from Planck data:the new physics interaction scale related to the axion/gluon condensate mixing is constrained to be higher than the 10~6GeV energy scale.     

Conversion of dark matter axions to photons in magnetospheres of neutron stars

We propose a new method to detect observational appearance of dark matter axions. The method utilizes radio observations of neutron stars. It is based on the conversion of axions to photons in strong magnetic fields of neutron stars (the Primakoff effect). If the conversion occurs, the radio spectrum of the object has a very distinctive feature—a narrow spike at the frequency corresponding to the rest mass of the axion. For example, if the coupling constant of the photon-axion interaction is M = 10¹⁰ GeV, the density of dark matter axions is ρ = 10⁻²⁴ g cm⁻³ and the axion mass is 5 μeV; then the flux from a strongly magnetized (10¹⁴ G) neutron star at the distance 300 pc from the Sun is expected to be about few tenths of millijansky at a frequency of about 1200 MHz in a bandwidth of about 3 MHz. Close-by X-ray dim isolated neutron stars are proposed as good candidates to look for such radio emission. The article is published in the original.     

暗物质的直接实验探测

暗物质研究是21世纪粒子物理、天体物理和宇宙学最重要的前沿科学课题之一.暗物质被天文学中的引力效应所观察到,但对它的存在和认识仍旧是个谜.文章主要论述了对弱作用大质量暗物质粒子(WIMP)直接探测的基本原理、各种直接探测技术、当前的实验进展和发展方向.最后给出了最近的实验物理结果.     

Status of dark matter detection

The detection of dark matter has made great progresses in recent years. We give a brief review on the status and progress in dark matter detection, including the progresses in direct detection, collider detection at LHC and focus on the indirect detection. The results from PAMELA, ATIC, Fermi-LAT and relevant studies on these results are introduced. Then we give the progress on indirect detection of gamma rays from Fermi-LAT and ground based Cerenkov telescopes. Finally the detection of neutrinos and constraints on the nature of dark matter are reviewed briefly.     

暗物质的直接实验探测

暗物质研究是21世纪粒子物理、天体物理和宇宙学最重要的前沿科学课题之一.暗物质被天文学中的引力效应所观察到,但对它的存在和认识仍旧是个谜.文章主要论述了对弱作用大质量暗物质粒子（WIMP）直接探测的基本原理、各种直接探测技术、当前的实验进展和发展方向.最后给出了最近的实验物理结果.     

Direct detection of WIMP dark matter

The question of the nature of dark matter in the universe is perhaps the greatest problem facing cosmology and particle physics at present. New observations of the cosmic microwave background radiation and distant supernovae show that more that 90% of the mass in the universe is in the form of some unknown matter. Many lines of evidence from cosmology and particle physics suggest that the best candidate for this dark matter is a weakly interacting massive particle, or WIMP. Such particles are predicted by supersymmetry, a theory extending the Standard Model of particle physics, and many experiments around the world are now trying to directly detect these WIMPs. This article reviews the reasons for believing WIMPs to be the dark matter, and considers the challenges involved in detecting their rare low-energy interactions with normal matter. Current experimental searches are reviewed with regard to the claimed detection of WIMPs by the DAMA group. These experiments are just beginning to reach the sensitivity needed to detect, or rule out, supersymmetric WIMPs, and higher sensitivity future experiments are also discussed.     

直接探测暗物质和中国暗物质实验

The nature of dark matter in our universe is one of the most challenging problems in science today. A most probable class of dark matter is the weakly interacting massive particles (WIMPs), which exhibit a wide range of features. Current experiments searching for dark matter aim for direct detection via the elastic scattering off ordinary matter in terrestrial detectors. This paper will present the main methods, status and roadmap for the direct detection of dark matter. The world's deepest laboratory, China Jinping underground laboratory and its extension, will also be described. Finally, we will give a detailed introduction to the research history, detection technologies, current results, and future prospects of China dark matter experiment (CDEX).     

Review of dark matter direct detection experiments

Matter, as we know it, makes up less than 5% of the Universe. Various astrophysical observations have confirmed that one quarter of the Universe and most of the matter content in the Universe is made up of dark matter. The nature of dark matter is yet to be discovered and is one of the biggest questions in physics. Particle physics combined with astrophysical measurements of the abundance gives rise to a dark matter candidate called weakly interacting massive particle (WIMP). The low density of WIMPs in the galaxies and the extremely weak nature of the interaction with ordinary matter make detection of the WIMP an extraordinarily challenging task, with abundant fakes from various radioactive and cosmogenic backgrounds with much stronger electromagnetic interaction. The extremely weak nature of the WIMP interaction dictates detectors that have extremely low naturally occurring radioactive background, a large active volume (mass) of sensitive detector material to maximize statistics, a highly efficient detector-based rejection mechanism for the dominant electromagnetic background and sophisticated analysis techniques to reject any residual background. This paper reviews currently available major technologies being pursued by various collaborations, with special emphasis on the cryogenic Ge detector technology used by the Cryogenic Dark Matter Search Collaboration (CDMS).     

Direct detection searches for WIMP dark matter

A very active hunt is underway to discover the composition of dark matter in the universe. A large effort is devoted to the direct detection of dark matter through interactions with detectors in the laboratory. In this paper, we give an overview of the dark matter problem, discuss some of the design considerations taken in direct detection experiments, and describe some of the current efforts to discover Weakly Interacting Massive Particles (WIMPs), a well-motivated class of candidates for dark matter.     

Direct detection constraints on superheavy dark matter

The dark matter in the Universe might be composed of superheavy particles (mass greater, similar 10(10) GeV). These particles can be detected via nuclear recoils produced in elastic scatterings from nuclei. We estimate the observable rate of strongly interacting supermassive particles (simpzillas) in direct dark matter search experiments. The simpzilla energy loss in Earth and in the experimental shields is taken into account. The most natural scenarios for simpzillas are ruled out based on recent EDELWEISS and CDMS results. The dark matter can be composed of superheavy particles only if these interact weakly with normal matter or if their mass is above 10(15) GeV.     

Sensitivity for detection of decay of dark matter particle using ICAL at INO

We report on the simulation studies addressing the possibility of dark matter particle (DMP) decaying into μ⁺μ^? channel. While not much is known about the properties of dark matter particles except through their gravitational effect, it has been recently conjectured that the so-called ‘anomalous Kolar events’ observed some decades ago may be due to the decay of unstable dark matter particles. The aim of this study is to see if this conjecture can be verified at the proposed iron calorimeter (ICAL) detector at INO. We study the possible decay to μ^± mode which may be seen in this detector with some modifications. For the purposes of simulation, we assume that the channel saturates the decay width for the mass ranging from 1 to 50 GeV/c². The aim is not only to investigate the decay signatures, but also, more generally, to establish lower bounds on the lifetime of DMP even if no such decay takes place.     

Experiments aiming at direct detection of dark matter

We present a review of existing and planned dark matter direct detection experiments. The emphasis is on principle limitations for this detection technique and resulting consequences for future projects. We argue that the near future experiments, CDMS and HDMS, will give such stringent limits on WIMP–nucleon elastic cross sections that the next round of experiments will have to be either massive direction–sensitive detectors or massive ton–scale detectors with almost zero background. Candidate experiments with these requirements are shortly introduced like the newly announced GENIUS proposal. We also shortly discuss the implications of WIMP search results for accelerator experiments and vice versa. Received: 16 April 1998     

Stochastic Resonance for a SQUID with Dichotomous Resistance

We investigate the response to the ac current for a superconducting quantum interference device （SQUID） with a dichotomous resistance. It is shown that, for some suitably selected parameters＇ values, stochastic resonance appears for the amplitude of the stationary average voltage of the SQUID versus the correlation time of the dichotomous noise. Our result can provide some useful insights for the investigation of the response of the SQUID （especially for the ones with the nano junctions） to the temporal-periodic signal （including the input ac current, the irradiation microwave, the detected temporal-periodic signal, and the added ac voltage）.     

Realistic predictions for the detection of supersymmetric dark matter

We present new predictions for the detection of supersymmetric dark matter via its annihilation in the Sun and elastic scattering off heavy nuclei in the laboratory. Our predictions include many effects found in realistic models such as non-degenerate left- and right-squark masses, unequal supersymmetric Higgs v.e.v.s and photino/higgsino/zino mixing in the lightest supersymmetric particle (LSP). Hadronic matrix elements are estimated using either the naive quark model or the EMC measurement of the spin-dependent proton structure function and perturbative QCD. Nuclear matrix elements are calculated using the shell-model and the small effects of quark vector current operators are discussed. Previous predictions for the elastic LSP-proton scattering cross section, and hence for high energy solar neutrinos from LSP annihilations, are reduced by the EMC estimate and by unequal squark masses, but may be increased by unequal Higgs v.e.v.s. Previous predictions for elastic photino scattering off nuclei with unpaired neutrons are greatly enhanced by the EMC estimate. As a result, preferences for the nuclei to be used in laboratory experiments to detect supersymmetric dark matter may be greatly altered.     

Split-SUSY dark matter in light of direct detection limits

We examine the present and future XENON limits on the neutralino dark matter in split supersymmetry (split-SUSY). Through a scan over the parameter space under the current constraints from collider experiments and the WMAP measurement of the dark matter relic density, we find that in the allowed parameter space a large part has been excluded by the present XENON100 limits and a further largish part can be covered by the future exposure (6000 kg day). In case of unobservation of dark matter with such an exposure in the future, the lightest neutralino will remain bino-like and its annihilation is mainly through exchanging the SM-like Higgs boson in order to get the required relic density.