Narrow Results

We briefly review some recent Cold Dark Matter (CDM) models. Our main focus are charge symmetric models of WIMPs which are not the standard SUSY LSP's (Lightest Supersymmetric Partners). We indicate which experiments are most sensitive to certain aspects of the models. In particular, we discuss the manifestations of the new models in neutrino telescopes and other setups. We also discuss some direct detection experiments and comment on measuring the direction of recoil ions — which is correlated with the direction of the incoming WIMP. This could yield daily variations providing along with the annual modulation signatures for CDM.

We briefly review the constraints on the search for low mass WIMPs (<15 GeV) and the various experimental methods. These experiments depend on the response of detectors to low energy signals (less than 15 keV equivalent energy). We then describe recent fits to the data and attempt to determine L_eff, the energy response at low energy. We find that the use of a liquid Xenon two-phase detector that employs the S₂ data near threshold is the most sensitive current study of the low mass region. We rely on some talks at Dark Matter 2010.

The Micromegas detectors have been gaining importance as reliable options in their implementation to Time Projection Chambers (TPCs) in experiments searching for Rare Events mainly due to their demonstrated good performance regarding low background levels, energy and time resolution, gain and stability of operation. In the present paper, we will briefly review the latest developments carried out within the T-REX project of detector R&D, and the performance achieved in the context of several experiments: the CAST solar axion search experiment, the NEXT experiment of double beta decay and the MIMAC dark matter directional search.

Weakly Interacting Massive Particles (WIMPs) may constitute most of the matter in the Universe. There are intriguing results from DAMA/LIBRA, CoGeNT and CRESST-II, and more recently CDMS-Si suggesting a relatively light dark matter candidate of mass <10 GeV/c². At the same time, experiments using heavy nuclear targets such as CDMS-Ge and XENON detectors suggest that there is no DM candidates with M_W>15 GeV/c². We review the existing experiments and the problems associated with light mass WIMP detection. We find that all six experiments considered (DAMA, CoGeNT, CRESST, CDMS-Si, CDMS-Ge, XENON) are consistent if one assumes that the mass of WIMP is lower than expected: 3.4<M_W<6.8 GeV/c². This is followed by a discussion of the properties of "new" detectors, which may enable more reliable detection of low mass WIMPs.

In this review the current status of several searches for particle dark matter with the Fermi Large Area Telescope instrument is presented. In particular, the current limits on the weakly interacting massive particles, obtained from the analyses of gamma-ray and cosmic ray electron/positron data, will be illustrated.

Weakly Interacting Massive Particles (WIMPs) can constitute a large fraction of the dark matter (DM) in the universe. The importance of coherent scattering and detection of annual modulation effect (AME), diurnal modulation effect (DME) and direction sensitive AME was documented. In particular, DAMA/NaI and DAMA/LIBRA have released data collected during 14 annual cycles, which support in model independent way, the presence of DM particles in the galactic halo. There is a clear evidence of AME signature in DAMA data. Recently, positive hints have also been reported by CoGeNT on AME signature in Ge, while CREST-II and CDMS-Si have published some events in excess of estimated background; these events are compatible with WIMP-like candidates. If these results would be analyzed all together in some WIMP scenario, one could derive: M_DM < 10 GeV/c².

Current generation of detectors is far from being optimal or in some cases even reliable when M_DM approaches 5 GeV/c². We propose a detector, which can detect the direction of incoming WIMPs. This paper focus on a particular implementation of the new class of nano-explosive DM detectors. The local heating ignites an explosion, which release chemical energy stored in such a nano-grain. Use of two component nano-explosive permits to amplify the bolometric effect due to WIMP-candidates. The energy available becomes 100,000-fold larger than the energy initially deposited by DM candidate. This leads to a sonic-boom, which can be detected remotely. This new class of nano-explosive detectors may be especially important in detection of WIMPs with very low mass, say M_DM = O(5 GeV/c²). We describe a configuration, which leads to explosive-triode, and permits detection of the direction of incoming WIMPs.

Weakly Interacting Massive Particles (WIMPs) may constitute a large fraction of the matter in the Universe. There are excess events in the data of DAMA/LIBRA, CoGeNT, CRESST-II, and recently CDMS-Si, which could be consistent with WIMP masses of approximately 10 GeV/c². However, for M_DM > 10 GeV/c² null results of the CDMS-Ge, XENON, and LUX detectors may be in tension with the potential detections for certain dark matter scenarios and assuming a certain light response. We propose the use of a new class of biological dark matter (DM) detectors to further examine this light dark matter hypothesis, taking advantage of new signatures with low atomic number targets. Two types of biological DM detectors are discussed here: DNA-based detectors and enzymatic reactions (ER) based detectors. In the case of DNA-based detectors, we discuss a new implementation. In the case of ER detectors, there are four crucial phases of the detection process: (a) change of state due to energy deposited by a particle; (b) amplification due to the release of energy derived from the action of an enzyme on its substrate; (c) sustainable but nonexplosive enzymatic reaction; (d) self-termination due to the denaturation of the enzyme, when the temperature is raised. This paper provides information of how to design as well as optimize these four processes.

After a concise introduction about the dark matter issue and a discussion of the problematics related to its direct detection, the bolometric technique is presented in this context, with a special focus on double-readout devices. The bolometric experiments for the search for dark matter are then described and reviewed. Their present and future roles are discussed, arguing about pros and cons of this technology.

It is discussed how the ideas of entropy and the second law of thermodynamics, conceived long ago during the nineteenth century, underly why cosmological dark matter exists and originated in the first three years of the universe in the form of primordial black holes, a very large number of which have many solar masses including up to the supermassive black holes at the centres of galaxies. Certain upper bounds on dark astrophysical objects with many solar masses based on analysis of the CMB spectrum and published in the literature are criticised. For completeness we discuss WIMPs and axions which are leading particle theory candidates for the constituents of dark matter. The PIMBHs (Primordial Intermediate Mass Black Holes) with many solar masses should be readily detectable in microlensing experiments which search the Magallenic Clouds and measure light curves with durations of from one year up to several years.

The DAMA/NaI experiment (≃100 kg highly radiopure NaI(Tl)) was proposed, designed and realized to effectively investigate in a model-independent way the presence of a Dark Matter particle component in the galactic halo by exploiting the annual modulation signature. With a total exposure of 107731 kg · day, collected over seven annual cycles deep underground at the Gran Sasso National Laboratory of the I.N.F.N., it has pointed out — at 6.3σC.L. — an effect which satisfies all the peculiarities of the signature and neither systematic effects nor side reactions able to mimic the signature were found. Moreover, several (but still few with respect to the possibilities) corollary model dependent quests for the candidate particle have been carried out. In this paper the obtained results are summarized and some perspectives are discussed at some extent.

Dark matter, an invisible substance which constitutes 85% of the matter in the observable universe, is one of the greatest puzzles in physics and astronomy today. Dark matter can be made of a new type of fundamental particle, not yet observed due to its feeble interactions with visible matter. In this talk, we present the first results of PandaX-4T, a 4-ton-scale liquid xenon dark matter observatory, searching for these dark matter particles from deep underground. We will briefly summarize the performance of PandaX-4T, introduces details in the data analysis, and present the latest search results on dark matter-nucleon interactions.

Galaxy clusters, employed by Zwicky to demonstrate the existence of dark matter (DM), pose new stringent tests. First, the possibility is considered that merging clusters demonstrate that DM is self-interacting with cross-section $\sigma ∕m\sim$ 2cm²/gr. In that case, MACHOs, primordial black holes (PBHs) and light axions that build MACHOs are ruled out as cluster DM, while GeV and TeV WIMPs and keV sterile neutrinos are challenged. Next, recent strong lensing and X-ray gas data of the quite relaxed and quite spherical cluster A1835 are analyzed. These lensing data involve a covariance matrix of which the small eigenvalues have to be regularized. This is achieved with a new, general, parameter-free method: binning with respect to a model fit, and accounting for intra-bin fluctuations. This method allows to test the cases of DM with Maxwell–Boltzmann, Bose–Einstein and Fermi–Dirac (FD) distribution, next to Navarro–Frenck–White profiles. Fits to all these profiles are formally rejected at over $5\sigma$, except in the fermionic situation. The interpretation in terms of pseudo-Dirac neutrinos with mass of $1.61_{-0.30}^{+0.19}$eV/$c^2$ is consistent with results on the cluster A1689, with the DM fractions from WMAP, Planck and DES, and with the non-detection of neutrinoless double $\beta$-decay. The predicted mass will be tested in the KATRIN and PTOLEMY experiments.

Dark matter, an invisible substance which constitutes 85% of the matter in the observable universe, is one of the greatest puzzles in physics and astronomy today. Dark matter can be made of a new type of fundamental particle, not yet observed due to its feeble interactions with visible matter. In this talk, we present the first results of PandaX-4T, a 4-ton-scale liquid xenon dark matter observatory, searching for these dark matter particles from deep underground. We will briefly summarize the performance of PandaX-4T, introduces details in the data analysis, and present the latest search results on dark matter-nucleon interactions.

In the framework of the ArDM project, a next-generation one ton liquid argon WIMP detector, we built a 5 litre prototype chamber. This setup is primarily used to develop the appropriate read out for argon VUV scintillation light (128 nm) using wave length shifting dyes. The final aim is a energy threshold of 30 keV corresponding to yield of roughly 2% for detected photo-electrons. Beside light yield studies we investigate purity effects as well as background suppression power from the light pulse shape.

Neutron background for the high-sensitivity dark matter experiments is discussed. Neutron production via spontaneous fission and (α, n) reactions from U and Th, and by cosmic-ray muons is considered.

A CaF₂ scintillator complex system (ELEGANT VI) is developed to search for the axial-vector coupled dark matter (WIMPs) and study the neutrino-less double beta decay of ⁴⁸Ca. Active light guides of pure CaF₂ crystals which are on both sides of the central CaF₂(Eu) crystal act as a 4π active shield, combined with surrounding CsI(Tl) scintillators. The whole system is in operation at the underground laboratory (Oto Cosmo Observatory) located in Nara. In this article recent several improvements and our current status of the investigation are described, especially putting emphasis on the radioactive impurities of CaF₂ crystal and development of flash scaler/trigger system with FPGA (Field Programmable Gate Array) to do a single photon counting and a noise-cut via photon time distribution.

Recent work has indicated that WIMP annihilation in stellar cores has the potential to contribute significantly to a star's total energy production. We report on progress in simulating the effects of WIMP capture and annihilation upon stellar structure and evolution near supermassive black holes, using the new DarkStars code. Preliminary results indicate that low-mass stars are the most influenced by WIMP annihilation, which could have consequences for upcoming observational programs.

The quest to understand the nature dark matter is one of the most relevant ones in Particle Physics nowadays, since it constitutes most of the matter of the Universe and it is still unknown what it is made of. In order to answer to this question, a multi-front attack is needed because our knowledge of its properties is very incomplete. Among the different experimental strategies, neutrino telescopes are very relevant tools. There are several promising sources to look at: the Sun, the Galactic Center, the Earth, dwarf galaxies, galaxy clusters… As an example of the power of neutrino telescopes, we can mention the analysis of the Sun, which offers the best sensitivity for spin dependent WIMP-nucleon scattering and is free of alternative astrophysical interpretations. In this talk I will review the status and prospects of the main present and future neutrino telescopes: ANTARES, IceCube and KM3NeT.

We announce the public release of the 'dark' stellar evolution code DarkStars. The code simultaneously solves the equations of WIMP capture and annihilation in a star with those of stellar evolution assuming approximate hydrostatic equilibrium. DarkStars includes the most extensive WIMP microphysics of any dark evolution code to date. The code employs detailed treatments of the capture process from a range of WIMP velocity distributions, as well as composite WIMP distribution and conductive energy transport schemes based on the WIMP mean-free path in the star. We give a brief description of the input physics and practical usage of the code, as well as examples of its application to dark stars at the Galactic centre.

An active veto detector to complement the ZEPLIN-III two phase Xenon, direct dark matter device is described. The design consists of 52 plastic scintillator segments, individually read out by high efficiency photomultipliers, coupled to a Gd loaded passive polypropylene shield. Experimental work was performed to determine the plastic scintillator characteristics which were used to inform a complete end-to-end Monte Carlo simulation of the expected performance of the new instrument, both operating alone and as an active veto detector for ZEPLIN-III. The veto device will be capable of tagging over 65% of expected coincident nuclear recoil events in the energy range of interest in ZEPLIN-III, and over 14% for gamma ray rejection (gamma and neutron rate is predicted by simulation), while contributing no significant additional background. In addition it will also provide valuable diagnostic capabilities. The inclusion of the veto to ZEPLIN-III will aid to significantly improve the sensitivity to spin independent WIMP-nucleon cross sections ~10^-9 pb.