# Dark Matter WGセミナー

セミナー

## Axion-like particles from core-collapse supernovae

2022年1月17日11:00 - 12:00

Axion-like particles (ALPs) are a class of hypothetical pseudoscalar particles which feebly interact with ordinary matter. The hot plasma of stars and core-collapse supernovae is a possible laboratory to explore physics beyond the standard model including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. We recently calculated the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics consistently. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as g_{a gamma} ~ 10^{-9} GeV^{-1} and the ALP mass is 40-400 MeV. In this talk, I will briefly review stellar and supernova constraints on ALPs and then discuss our recent results.

イベント公式言語: 英語

セミナー

## The FASER experiment

2021年12月15日17:00 - 18:00

FASER, the ForwArd Search ExpeRiment, is an experiment dedicated to searching for light, extremely weakly-interacting particles at the LHC. Such particles may be produced in the LHC’s high-energy collisions and then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. FASER, also includes a sub-detector, FASER$\nu$, designed to detect neutrino’s produced in the LHC collisions and to study their properties. This seminar will describe the physics motivations, detector design, expected performance of FASER, and current status, as well as the physics prospects.

イベント公式言語: 英語

セミナー

## Distinctive signals of boosted dark matter from semi-annihilations

2021年10月20日10:00 - 11:30

The recent dark matter direct detection experiments impose the stringent upper bound on the elastic scattering cross section with nucleons. This implies that the cross section is suppressed by small dark matter velocity. However such dark matter can be probed if it is boosted by some mechanism. In this talk, we show that the specific semi-annihilation channel where two dark matter particles annihilate into a pair of anti-dark matter and neutrino indicates signals distinctive from the other semi-annihilation and standard dark matter annihilation processes. Since the boosted dark matter produced by this semi-annihilation is regarded as a high energy neutrino, the total flux of the dark matter and the accompanying neutrino yields double peaks at the energy close to the dark matter mass. Both of the particles can be detectable at large volume neutrino detectors.

イベント公式言語: 英語

セミナー

## Precise WIMP Dark Matter Abundance and Standard Model Thermodynamics

2021年6月24日16:30 - 17:30

We are now living in the era of precision cosmology. The relic abundance of dark matter (DM) is now observationally well-determined, and its error is smaller than O(1)%. This means that the same or much higher precision is required when we make theoretical predictions. Weakly Interacting Massive Particle (WIMP) has long been the leading candidate for DM because of its beautiful mechanism to predict the observed relic abundance. WIMP is in the same thermal bath as the Standard Model particles in the beginning. At a certain point when the temperature of the Universe is smaller than the DM mass, it decouples to fix its number density. The yield of the DM is determined by its annihilation cross-section to the Standard Model sector. It seems that there is no ambiguity in the calculation of this process at first: the cross-section is purely theoretical and all the remainings are described in the Standard Model physics. However, the source of the uncertainty does remain in the Standard Model sector. The dilution of the number density of DM particle depends on the expansion rate of the Universe, which is determined by the Standard Model particles. The effective degree of freedom (d.o.f) of the relativistic species controls this factor. We have to deal with the non-equilibrium dynamics to precisely describe the time-evolution of the d.o.f, in which we need numerical approaches. In this talk, he introduced his work to update these calculations. By implementing the latest findings in the non-equilibrium dynamics in i) the neutrino decoupling, ii) the QCD phase transition, iii) the electroweak phase transition, and iv) the perturbative calculations, they found that the final d.o.f is smaller than the previous estimate in more than 1%. This is larger than the level of precision in observations. It is also important that the uncertainty is quantified by them. Another good news is that he makes the calculated d.o.f with its error publically available. With these updates, we now correctly know the points to probe DM!

イベント公式言語: 英語

セミナー

## Emulation for lensing and clustering observables of the cosmological large-scale structure

2021年5月12日10:00 - 11:00

Recent developments in observational technologies open exciting opportunities to map out the detailed structure of the universe. Remarkably, the unique combination of imaging and spectroscopic galaxy surveys is now becoming well established as a standard analysis methodology for precision cosmology. While the former can access directly the underlying clustering of mass dominated by dark matter projected on the sky through the weak gravitational lensing effect, the latter provides us with the three dimensional map of the structure traced by galaxies. One can mitigate the galaxy-bias uncertainty, which has been the major obstacle for cosmology based on galaxy surveys, by jointly analyzing these effects. We still need, however, a robust and versatile theoretical and statistical framework to interpret these datasets. The Dark Quest project, launched in 2015, is a structure formation simulation campaign precisely for this purpose. We have developed an emulation tool, dubbed as Dark Emulator, based on a large database of simulated dark matter halos in virtual universes with different cosmologies efficiently sampled in six-dimensional parameter space. Dark Emulator employs a simple machine-learning architecture with Gaussian process at its core. It makes predictions of various statistical measures of dark matter halos, both lensing and clustering observables, for a given cosmological parameters in a few seconds on laptop computers without running a new simulation. This AI-aided tool, once supplemented with recipes for the halo-galaxy connection, is therefore applicable to real-data analyses as the theoretical template, which typically requires hundreds of thousands of function calls in the course of parameter inference. I will introduce this project and report the status of its application to Subaru HSC data. We are looking forward to seeing you online.

イベント公式言語: 英語

セミナー

## Mapping the Milky Way by VLBI Astrometry

2021年2月16日13:30 - 15:00

Astrometry is the only way to obtain 6D (position-velocity) phase space information for astronomical objects. The unique capability allows us to examine the past, present, and future of the Milky Way. Firstly, I will introduce history and basics of astrometry. Secondly, I will overview astrometric projects in the world. Thirdly, I will highlight recent astrometric results about the Galactic structure. Lastly, I will introduce astrometric research in Korea as well as future astrometric projects and sciences in 2020s and 30s.

イベント公式言語: 英語

セミナー

## Directional dark matter search and the technologies

2020年12月3日10:00 - 11:00

For identification of the dark matter, various methodologies are required. Especially, the direct detection is one of the most important goals to directly understand itself. Now, there are various technologies for direct detection, but almost all detectors have no direction sensitivity. We can obtain essential information such as dependence of motion between the earth and the dark matter, velocity distribution and background from direction information, therefore that becomes a very important methodology to identify the dark matter for future as long as we consider "particle dark matter". In this seminar, I report about the potential of direction sensitive dark matter search and current experimental effort.

イベント公式言語: 英語

セミナー

## Composite Dark matter and gravitational waves

2020年10月20日10:00 - 11:00

エンリコ・リナルディ (数理創造プログラム 客員研究員 / AI Researcher/Engineer, Arithmer Inc.)

With non-perturbative lattice calculations we investigate the finite-temperature confinement transition of a composite dark matter model. We focus on the regime in which this early-universe transition is first order and would generate a stochastic background of gravitational waves. Future searches for stochastic gravitational waves will provide a new way to discover or constrain composite dark matter, in addition to direct-detection and collider experiments. As a first step to enabling this phenomenology, we determine how heavy the dark fermions need to be in order to produce a first-order stealth dark matter confinement transition.

イベント公式言語: 英語

セミナー

## The Uchuu Simulations: Data Release 1 and Dark Matter Halo Concentrations

2020年10月1日14:00 - 15:00

We introduce the Uchuu suite of large high-resolution cosmological N-body simulations. The largest simulation, named Uchuu, consists of 2.1 trillion dark matter particles in a box of 2.0 Gpc/h. The highest resolution simulation, called Shin-Uchuu, consists of 262 billion particles in a box of 140 Mpc/h. Combining these simulations we can follow the evolution of dark matter haloes (and subhaloes) spanning from dwarf galaxies to massive galaxy cluster hosts. We present basic statistics, dark matter power spectra and halo (subhalo) mass function, to demonstrate the huge dynamic range and superb statistics of the Uchuu simulations. From the analysis of the evolution of the power spectra we conclude that our simulations are accurate enough from the Baryon Acoustic Oscillations up to very small scales. We also provide parameters of a mass-concentration model, which describes the evolution of halo concentrations, that reproduces our simulation data within 5% error for haloes with masses spanning nearly eight orders of magnitude at redshift 0<z<14. We make publicly available various N -body products, as part of Uchuu Data Release 1, on the Skies & Universes site. We also plan to release gravitational lensing maps, mock galaxy, X-ray cluster and active galactic nuclei catalogues in the near future.

イベント公式言語: 英語

セミナー

## DMWG special seminar : “The result of the XENON1T experiment and its implications”

2020年7月22日15:30 - 17:00

イベント公式言語: 日本語

セミナー

## Search for ultralight dark matter with laser interferometric gravitational wave detectors

2020年7月13日10:00 - 11:00

イベント公式言語: 英語

セミナー

## Dark Matter Heating vs. Rotochemical Heating in Old Neutron Stars

2020年6月22日16:00 - 17:00

*Detailed information about the seminar refer to the email

イベント公式言語: 英語

セミナー

## The effect of the early kinetic decoupling in a fermionic dark matter model

2020年6月12日10:00 - 11:00

*Detailed information about the seminar refer to the email

イベント公式言語: 英語

セミナー

## Characterizing the continuous gravitational-wave signal from boson clouds around Galactic isolated black holes

2020年4月27日16:00 - 17:00

Dr. Sylvia Zhu (Postdoctoral Researcher, Deutsches Elektronen-Synchrotron DESY, Germany)

Bosons such as axions or axion-like particles can form enormous clouds around black holes via the superradiance instability. As the bosons annihilate in the presence of the black hole, they produce a long-lived, slowly-evolving continuous gravitational-wave signal that is potentially detectable using the current generation of gravitational-wave interferometers.A non-detection can disfavor the existence of axions in certain mass ranges, although this is highly dependent on the Galactic black hole population. In this talk, I will discuss the expected annihilation signal from the population of isolated stellar-mass black holes in the Galaxy, and the prospects for detecting the signal using standard searches for continuous gravitational waves.

イベント公式言語: 英語

セミナー

## Mining for Dark Matter substructure: Learning from lenses without a likelihood

2020年2月17日14:00 - 15:30

Dr. Johann Brehmer (Postdoctoral Researcher, New York University, USA)

イベント公式言語: 英語

セミナー

## Weak lensing cosmology by Subaru HSC survey

2019年12月12日10:30 - 12:00

Place: IPMU seminar room C

イベント公式言語: 英語

セミナー

## Haloes at the low-mass end in wino dark matter

2019年10月21日13:00 - 15:00

イベント公式言語: 英語

セミナー

## A new lamppost in dark matter searches: Composite Dark Matter

2019年10月1日10:00 - 18:00

エンリコ・リナルディ (数理創造プログラム 研究パートタイマー)

イベント公式言語: 英語