Invisible Mass Research Articles

Investigation of scintillation properties of a CsI(Tl) crystal at low temperature for dark matter search

The Korea invisible mass search (KIMS) experiment used CsI(Tl) crystals coupled with photomultiplier tubes (PMTs) to detect signals from weakly interacting massive particles (WIMPs) at room temperature. It is expected that combining CsI(Tl) crystals with silicon photomultipliers (SiPMs) will enhance the detection performance. However, SiPMs must operate at low temperatures to reduce the dark count rate. In this study, we examined the temperature dependence of CsI(Tl) crystal properties, including light yield, α/β ratio, decay time, and pulse shape discrimination, before integrating it with a SiPM. The CsI(Tl) crystal was placed in a low-temperature chamber with a radiation source, and scintillation photons were detected by a PMT positioned outside the chamber. The response of CsI(Tl) to α-particles and γ-rays was examined across temperatures ranging from 10 K to 300 K.

MATERIALITY OF THE GRAVITATIONAL FIELD AND THE PROCESS OF DEVELOPMENT OF MACROSCALE GRAVITATIONAL COLLAPSE

The materiality of the gravitational field is taken into account on the basis of the law of universal gravitation, accepted as an exact law describing the pairwise interactions of massive bodies. Unlike Brillouin and Lucas, who were the first to carry out such an account and obtain a negative value of the field mass, the field mass in our work has the same sign as the mass itself. Replacing the "mass-gravitational field" representation with "mass-field mass" distinguishes gravity from other interactions, leads to an increase in mass in such interactions, indicates the existence of a double effect of gravity and allows its physical modeling. In particular, it has been shown that, despite the small value of the relative mass gain in pair interactions, during the formation of clusters of stars with a large number of bodies, the relative mass gain increases nonlinearly. Under certain conditions, this increase becomes infinite, symbolizing the onset of a macroscale gravitational collapse, resulting in the formation of supermassive black holes. Attention is focused on the fact that the final mass of a supermassive black hole (invisible mass) can be tens and hundreds of times greater than the initial mass of the cluster (visible mass). Moreover, half of the black hole's mass is outside the gravitational radius of the black hole, forming a massive invisible halo. According to the authors, a macroscale collapse based on taking into account the materiality of the gravitational field can be considered as one of the effective mechanisms for the formation of invisible (dark) matter in the Universe.

Experimental Discovery of the Particle Properties of Gravity and Gravitons by Theoretical Investigation of the Bent Point of Space Time

As, it is known having more challenged on the wave or particle nature of light, from the theory of Newton to proof of its being wave by Huygens and also Young’s Double-slit experiment, more important ,Maxwell equations, all showed the nature of being wave of the light till Heinrich Hertz discovered photoelectric phenomenon and after that Einstein talked about the mathematic and quantum characteristics of this phenomenon, his explanations about this phenomenon showed failure of the characteristic of being wave of light in photoelectric explanation so double wave- particle characteristic failed in the scientific society .We all know that many of mass and energy fundamental systems have the same double characteristic of the light. The Photoelectric is the action of light and matter interactions that can prove the double light- particle nature because of inability of being wave principals of the light. Another one of the nature fundamental forces which many believed on its double wave- particle nature is gravity. In this essay we try to interpret the inability of wave nature of gravity in explanation of dark matter and we will see how the concept of invisible masses of the matter is the only action of the graviton interaction and proof of existence of constituent packs of gravity energy i.e. gravitons. Discovering this innovation is wonderful.

Demystifying freeze-in dark matter at the LHC

Freeze-in mechanism provides robust dark matter production in the early universe. Due to its feeble interactions, freeze-in dark matter leaves signals at colliders which are often involved with long lived particle decays and consequent displaced vertices (DV). In this paper, we develop a method to read off mass spectrum of particles being involved in the DV events at the LHC. We demonstrate that our method neatly works under a limited statistics, detector resolution and smearing effects. The signature of DV at the LHC can come from either highly suppressed phase-space or a feeble coupling of particle decay processes. By measuring invisible particle mass spectrum, one can discriminate these two cases and thus extract information of dominant freeze-in processes in the early universe at the LHC.

Study on sub-terahertz-band wireless system with fiber-optic speed

In the age of connectivity in which we live the ability to access information and data is expected. The Internet revolutionised nearly every aspect of our lives. Everything from travel, to shopping, staying informed, connected to loved ones and even finding new love, has all been uploaded and is performed online. The ingenious innovations behind these programs, apps and devices that keep us in constant contact, the smartphones and tablets, would never have been possible without first a network infrastructure for them to tap into. Communications networks allow anyone with the right device to connect to the invisible mass of data criss-crossing the planet. With the advent of 5G this network is set to get a massive upgrade which means faster transmission and reception of our online activities. This advance demonstrates the near constant improvement of communications networks since their advent. However, we are headed for a fork in the road where certain limitations will force us to choose whether the future is wired or wireless. Professor Minoru Fujishima, an expert in semiconductor electronics, is investigating the terahertz communication technology using silicon integrated circuit technology that supports mass production.

Dark Matter in the Central Region of NGC 3256

We investigated the central mass distribution of the luminous infrared galaxy NGC 3256 at a distance of 35 Mpc by using CO(1-0) observations of the Atacama Large Millimeter and sub-millimeter Array (ALMA) and near-IR data of the Two Micron Sky Survey (2MASS). We found that there is a huge amount of invisible dynamical mass ($4.84 \times 10^{10} M_{\odot}$) in the central region of the galaxy. The invisible mass is likely caused by some dark matter, which might have a cuspy dark matter profile. We note that this dark matter is difficult to explain with the conventional Modified Newtonian Dynamics (MOND) model, which is only applicable at a low acceleration regime, whereas the acceleration at the central region of the galaxy is relatively strong. Therefore, this discovery might pose a challenge to the conventional MOND models.

The Discrepancy between Einstein Mass and Dynamical Mass for SIS and Power-law Mass Models

Abstract We investigate the discrepancy between the two-dimensional projected lensing mass and the dynamical mass for an ensemble of 97 strong gravitational lensing systems discovered by the Sloan Lens ACS Survey, the BOSS Emission-Line Lens Survey (BELLS), and the BELLS for GALaxy-Lyα EmitteR sYstems Survey. We fit the lensing data to obtain the Einstein mass and use the velocity dispersion of the lensing galaxies provided by the Sloan Digital Sky Survey to get the projected dynamical mass within the Einstein radius by assuming the power-law mass approximation. The discrepancy is found to be obvious and quantified by Bayesian analysis. For the singular isothermal sphere mass model, we obtain that the Einstein mass is 20.7% more than the dynamical mass, and the discrepancy increases with the redshift of the lensing galaxies. For the more general power-law mass model, the discrepancy still exists within a 1σ credible region. We suspect the main reason for this discrepancy is mass contamination, including all invisible masses along the line of sight. In addition, the measurement errors and the approximation of the mass models could also contribute to the discrepancy.

On the mass of the Galactic star cluster NGC 4337

Only a small number of galactic open clusters survives for longer than few hundred million years. Longer lifetimes are routinely explained in term of larger initial masses, particularly quiet orbits, and off-plane birth-places. We derive in this work the actual mass of NGC 4337, one of the few open clusters in the Milky Way inner disk that managed to survive for about 1.5 Gyr. We derive its mass in two different ways. First, we exploit an unpublished photometric data set in the UBVI passbands to estimate -using star counts- the cluster luminosity profile, and luminosity and mass function, and hence its actual mass both from the luminosity profile and from the mass function.This data-set is also used to infer crucial cluster parameters, as the cluster half-mass radius and distance. Second, we make use of a large survey of cluster star radial velocities to derive dynamical estimates for the cluster mass. Under the assumption of virial equilibrium and neglecting the external gravitational field leads to values for the mass significantly larger than those obtained by mean of observed density distribution or with the mass function but still marginally compatible with the inferred values of the invisible mass in form of both low mass stars or remnants of high mass stars in the cluster. Finally, we derive the cluster initial mass by computing the mass loss experienced by the cluster during its lifetime, and adopting the various estimates of the actual mass.

Disputed dark-matter result gets put to the test

Despite nearly two decades of scrutiny, nobody has yet explained away—or confirmed—DAMA’s claim of detecting the elusive matter.

Search for solar axions with CsI(Tl) crystal detectors

The results of a search for solar axions from the Korea Invisible Mass Search (KIMS) experiment at the Yangyang Underground Laboratory are presented. Low-energy electron-recoil events would be produced by conversion of solar axions into electrons via the axio-electric effect in CsI(Tl) crystals. Using data from an exposure of 34,596 $\rm kg \cdot days$, we set a 90 \% confidence level upper limit on the axion-electron coupling, $g_{ae}$, of $1.39 \times 10^{-11}$ for an axion mass less than 1 keV/$\rm c^2$. This limit is lower than the indirect solar neutrino bound, and fully excludes QCD axions heavier than 0.48 eV/$\rm c^2$ and 140.9 eV/$\rm c^2$ for the DFSZ and KSVZ models respectively.

Background study of NaI(Tl) crystals for the KIMS-NaI experiment

The DAMA experiment has reported an annual-modulation signal in an array of low-background NaI(Tl) scintillating crystals that may be caused by WIMP-nucleon interactions. However, to date there has been no direct confirmation of this result that uses the same taget nuclides. The Korea Invisible Mass Search (KIMS) collaboration has been engaged in an extensive R&D program to grow ultra-low background NaI(Tl) crystals for use as a direct test of the DAMA result using same nuclide targets. Six crystals were grown from different powders in order to understand mechanisms of internal background contaminations and to reduce their effects. Studies of internal backgrounds in these crystals were performed with the ultimate goal of reducing internal background contamination levels to 1 dru at 2 keV.

Understanding internal backgrounds in NaI(Tl) crystals toward a 200 kg array for the KIMS-NaI experiment

The Korea Invisible Mass Search (KIMS) collaboration has developed low-background NaI(Tl) crystals that are suitable for the direct detection of WIMP dark matter. Building on experience accumulated during the KIMS-CsI programs, the KIMS-NaI experiment will consist of a 200 kg NaI(Tl) crystal array surrounded by layers of shielding structures and will be operated at the Yangyang underground laboratory. The goal is to provide an unambiguous test of the DAMA/LIBRA annual modulation signature. Measurements of six prototype crystals show progress in the reduction of internal contamination from radioisotopes. Based on our understanding of these measurements, we expect to achieve a background level in the final detector configuration that is less than 1 count/day/keV/kg for recoil energies around 2 keV. The annual modulation sensitivity for the KIMS-NaI experiment shows that an unambiguous 7 $$\sigma $$ test of the DAMA/LIBRA signature would be possible with a 600 kg year exposure with this system.

Atom & cosmos: Split galaxy offers dark matter clues: Division of stars, invisible mass hints at self‐interacting particles

Atom & cosmos: Split galaxy offers dark matter clues: Division of stars, invisible mass hints at self‐interacting particles

Precession of Fast S0 Stars in the Vicinity of Supermassive Black Hole in the Galactic Center

We elaborate the model of the influence of the diffuse dark matter, invisible stars or stellar mass black holes on the motion of the observed fast moving S0 stars [1–4] around the supermassive black hole SgrA* in the Galactic center with a mass MBH = 4·106▪. We will call all this invisible mass as a dark matter. The additional mass perturbs the elliptical orbits of the S0 mass resulting in the so called Newtonian precession of the elliptical orbits. The major aim of our research is the fitting of the published dates on the observed orbital positions of the S0 stars by the theoretically modeling orbit with a power-law profile of the additional (dark matter) mass. Nowadays the observational data provide only the upper limit on the additional mass. In the nearest years the observations of the S0 stars may provide the real weighing of the dark matter inside the orbits of these S0 stars in the Galactic center. This method is a very perspective for the elucidation of the formation and evolution of the dark matter in the Galactic nucleus.

Search for low-mass dark matter with CsI(Tl) crystal detectors

We present a search for low-mass ($\leq 20 GeV/c^{2}$) weakly interacting massive particles(WIMPs), strong candidates of dark matter particles,using the low-background CsI(Tl) detector array of the Korea Invisible Mass Search (KIMS) experiment. With a total data exposure of 24,324.3kg$\cdot$days,we search for WIMP interaction signals produced by nuclei recoiling from WIMP-nuclear elastic scattering with visible energies between 2 and 4keV. The observed energy distribution of candidate events is consistent with null signals, and upper limits of the WIMP-proton spin-independent interaction are set with a 90% confidence level. The observed limit rejects most of the low mass region of parameter space favored by the DAMA annual modulation signal.

The comparison of oncologic and clinical outcomes of laparoscopic liver resection for hepatocellular carcinoma.

PurposeWe evaluate the operative outcome and oncologic outcome of laparoscopic liver resection for hepatocellular carcinoma (HCC), and compare with open liver resection.MethodsFrom January 2004 to December 2012, clinical data of 70 patients who underwent laparoscopic liver resection for HCC (laparoscopic liver resection group, lapa-group) were collected and analyzed retrospectively. Control group (open liver resection group, open-group) were retrospectively matched, and compared with lapa-group.ResultsLaparoscopic major liver resections were performed in 4 patients. Laparoscopic anatomical resections and nonanatomical resections were performed in 39 patients, and 31 patients, respectively. Mean operative time was shorter in lapa-group (215.5 ± 121.84 minutes vs. 282.30 ± 80.34 minutes, P = 0.001), mean intraoperative transfusion rate and total amount were small in lapa-group (24.28%, 148.57 ± 3,354.98 mL vs. 40.78%, 311.71 ± 477.01 mL). Open conversion occurred in 6 patients (8.57%) because of bleeding, inadequate resection, invisible mass on intraoperative ultrasonography, and tumor rupture. In lapa-group and open-group, 3-year disease-free survival rates were 58.3% ± 0.08%, and 62.6% ± 0.06%, respectively (P = 0.773). In lapa-group and open-group 3-year overall survival rates were 65.3% ± 0.8%, and 65.7% ± 0.6%, respectively (P = 0.610).ConclusionLaparoscopic liver resection for HCC is feasible and safe in a large number of patients, with reasonable operative and oncologic results.

The recent results from KIMS experiment

In this paper, the recent results from KIMS (Korea invisible mass search) experiment are presented. KIMS has searched for WIMPs (Weakly Interactig Massive Particles) scattering off the nucleus by using the CsI(Tℓ) scintillator. The detector is an array of 12 CsI(Tℓ) scintilltors, whose total mass is 103.4 kg. The results reported here used the exposure of 24524.3 kg-days. With pulse shape discrimination (PSD) analysis, we estimated the nuclear recoil (NR) event rate and no meaningful excess of NR events rate were found. From this, we derived the improved cross section limit for WIMP–nucleon interaction.

A NEW TYPE OF COMPACT STELLAR POPULATION: DARK STAR CLUSTERS

Among the most explored directions in the study of dense stellar systems is the investigation of the effects of the retention of supernova remnants, especially that of the massive stellar remnant black holes (BHs), in star clusters. By virtue of their eventual high central concentration, these stellar mass BHs potentially invoke a wide variety of physical phenomena, the most important ones being emission of gravitational waves (GWs), formation of X-ray binaries, and modification of the dynamical evolution of the cluster. Here we propose, for the first time, that rapid removal of stars from the outer parts of a cluster by the strong tidal field in the inner region of our Galaxy can unveil its BH sub-cluster, which appears as a star cluster that is gravitationally bound by an invisible mass. We study the formation and properties of such systems through direct N-body computations and estimate that they can be present in significant numbers in the inner region of the Milky Way. We call such objects "dark star clusters" (DSCs) as they appear dimmer than normal star clusters of similar mass and they comprise a predicted, new class of entities. The finding of DSCs will robustly cross-check BH retention; they will not only constrain the uncertain natal kicks of BHs, thereby the widely debated theoretical models of BH formation, but will also pinpoint star clusters as potential sites for GW emission for forthcoming ground-based detectors such as the Advanced LIGO. Finally, we also discuss the relevance of DSCs for the nature of IRS 13E.

Three-Dimensional Reconstruction of Renovascular-Tumor Anatomy to Facilitate Zero-Ischemia Partial Nephrectomy

Zero-ischemia robotic and laparoscopic partial nephrectomy, a novel concept, eliminates ischemia to the tumor-free normal kidney. Anatomic microdissection of tertiary/higher-order tumor-specific arteries is performed to selectively devascularize only the tumor, maintaining normal perfusion of the remaining kidney. A thorough understanding of renovascular tumor anatomy is essential. Based on 0.5-mm-slice thickness computed tomography scans, we developed a novel three-dimensional (3D) reconstruction technique that fuses three key anatomic aspects: surface-rendered tumor, semitransparent kidney, and extra- and intrarenal arterial anatomy. Four central completely intrarenal hilar masses underwent 3D reconstruction for surgical navigation during zero-ischemia partial nephrectomy. Negative surgical margins were obtained in all four cases, with no intraoperative complications or transfusions. For these challenging laparoscopically invisible masses, 3D image navigation precisely identified tumor-specific arterial branches, thus facilitating zero-ischemia partial nephrectomy without hilar cross clamping.

Radon Environment in the Korea Invisible Mass Search Experiment and Its Measurement

The level of radioactivity from Rn in the air has to be monitored to control systematic effects on the background level at the KIMS (Korea Invisible Mass Search) dark matter search experiment. We designed and constructed a radon detector using a silicon photodiode that collects Po and Po daughter ions electrically and detects their α decays. Results for the detector calibration with a standard radon source, as well as the dependence of the α-particle detection efficiency on the humidity, are presented. The radioactivity of radon at the YangYang underground laboratory is measured and continuously monitored.