Dark matter searches in the 2020s - At the crossroads of the WIMP

Asia/Tokyo
The University of Tokyo, Kashiwa Campus

The University of Tokyo, Kashiwa Campus

Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba, Japan
Description

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Testing the hypothesis of particle dark matter is one of the key questions in Physics today. While no conclusive experimental evidence has been found so far, a new generation of experiments promise a big leap forward in the next decade. Future indirect, direct and collider experiments will be conjointly in reach to probe the largest part of the parameter space of weakly interacting massive particles (WIMPs), the long-standing canonical dark matter candidates. By this, a confirmation or manifest rejection of the WIMP hypothesis is in reach during the next 10 years.

The goal of this symposium is to stimulate exchange between these various next-generation WIMP searches. Therefore, it brings together Japanese and international researchers from all relevant experimental and theoretical fields. The latter include up-to-date particle and interaction models, astrophysical constraints, and the status of next-generation instruments. Additionally, we aim at a special focus on the neutrino floor background for future direct searches, and searches for DM signatures in charged astroparticles. By this, the symposium helps to foster collaborations and to explore the complementarity of the different search strategies.

Main Topics:

• Dark matter theory
• Collider experiments for dark matter searches
• Dark matter direct detection experiments
• Dark matter indirect detection experiments
• Astrophysical constraints on dark matter distributions

We encourage especially young researchers and students to attend the symposium.

Venue:

6F Conference Hall, Kashiwa research complex, Kashiwa Campus, The University of Tokyo

Confirmed Invited Speakers (as of October 3, 2019):

• Andrea Albert (LANL)
• Yoichi Asaoka (Waseda)
• Cristiano Galbiati (Princeton)
• Graciela Gelmini (UCLA)
• Nagisa Hiroshima (Riken)
• Moritz Hütten (MPP)
• Fabio Iocco (Imp. Coll. London/U. Napoli)
• Rubén López-Coto (INFN Padova, *remote talk)
• Shigeki Matsumoto (Kavli IPMU)
• Takeo Moroi (U. Tokyo)
• Tatsuhiro Naka (Toho)
• Ciaran O'Hare (University of Sydney)
• Yutaka Ohira (U. Tokyo)
• Priscilla Pani (DESY)
• Paolo Salucci (SISSA)
• Kate Scholberg (Duke, *remote talk)
• Satoshi Shirai (Kavli IPMU)
• Masahiro Teshima (ICRR/MPP)
• Koji Terashi (U. Tokyo/CERN)
• Masaki Yamashita (ICRR)
• Gabrijela Zaharijas (U. Nova Gorica)

This symposium is supported in part by:

• MEXT Grant-in-Aid for Scientific Research on Innovative Areas:
16K21730 for Shoji Asai (PI, main hosts),
19H05802 for Shigetaka Moriyama (co-PI, main hosts),
18H05542 for Masahiro Ibe (PI),
18H04359 for Kohei Hayashi (Publicly),
• Grant-in-Aid for Scientific Research (S):
17H06131 for Masahiro Teshima (PI, main hosts),
• Grant-in-Aid for Scientific Research (B):
17H02878 for Shigeki Matsumoto (co-PI),
• and the grant for ICRR’s Fiscal Year 2019 Inter-University Research Program (PI: Moritz Hütten)

Participants
• Akira Okumura
• Andrea Albert
• Asahi Kojima
• Cesar Calderon
• Ciaran O'Hare
• Cristiano Galbiati
• Daiki Hashimoto
• Daniel Kerszberg
• David Paneque
• Diana Werner
• Dylan van Arneman
• Fabio Iocco
• Francesca Borzumati
• Gabrijela Zaharijas
• Galina Shchelkanova
• Graciela Gelmini
• Haochen Yan
• Harm van Leijen
• Hidetoshi Kubo
• Hideyuki Fuke
• Hideyuki Oide
• Hiroshi Ogawa
• Hyuga Abe
• Ipsita Saha
• Joe Sato
• Junichi Tanaka
• Junji Hisano
• Junping Tian
• Kai Martens
• Kate Scholberg
• Katsuaki Kasahara
• Katsuki Hiraide
• Kaz Kohri
• Kazuki Kato
• Kazutaka Aoyama
• Kazuyoshi Kobayashi
• Keisuke Yanagi
• Kenkichi Miyabayashi
• Kentaro Miuchi
• Kohei Hayashi
• Kohei Yorita
• Koichi Hamaguchi
• Koji Ishidoshiro
• Koji Noda
• Koji Terashi
• Kosuke Ozaki
• Kyoshi Nishijima
• Marcel Strzys
• Masahiko Saito
• Masahiro Ibe
• Masahiro Kawasaki
• Masahiro Teshima
• Masaki Yamashita
• Masao Mori
• Masato Kimura
• Midori Sugahara
• Mihoko Nojiri
• Mitsunari Takahashi
• Moritz Hütten
• Motohide Kokubun
• Nagisa Hiroshima
• Osamu Seto
• Oscar Macias
• Paolo Salucci
• Pengwei Xie
• Priscilla Pani
• Rina Yamazaki
• Ryoko Shiraga
• Ryosuke Nomura
• satoko osone
• Satoshi Shirai
• Sergei Blinnikov
• Shigeki Matsumoto
• Shigetaka Moriyama
• Shih-Wen Hor
• Shih-Yen Tseng
• Shingo Kazama
• Shohei Yanagita
• Shoji Asai
• Shoji Torii
• Shunichi Horigome
• shunsuke sakurai
• Takahiro Sudoh
• Takanori Yoshikoshi
• Takao Fukui
• Takayuki Saito
• Takeo Higuchi
• Takeo Moroi
• Tatsuhiro Naka
• Tatsuo Yoshida
• Tobias Binder
• Toru Tanimori
• Toshiaki Kaji
• Toshio Namba
• Toyokazu Sekiguchi
• Wentao Luo
• Yamaguchi Yohei
• Yana Zhezher
• Yoichi Asaoka
• Yoichiro Suzuki
• Yoshiaki Sofue
• Yoshiki Ohtani
• Yoshitaka Itow
• Yoshiyuki Inoue
• Yuki Iwamura
• Yukiho Kobayashi
• Yuta Nakamura
• Yutaka Ohira
• Zang Jiaqi
• Monday, 11 November
• 10:00 12:30
Registration
• 12:30 12:45
Opening remarks

https://indico.icrr.u-tokyo.ac.jp/event/259/attachments/1124/1426/Information.pdf

• 12:30
Opening remarks 15m
Speaker: Prof. Masahiro Teshima
• 12:45 14:15
DM theory
Convener: Dr Masahiro Ibe (ICRR)
• 12:45
Overview on thermal DM models with emphasis on Electroweak charges 30m

Dark matter (DM) problem is now one of the most important problems in many fields of physics. DM mass is, however, currently predicted to be in a range between 10^–55 g and 10^40 g; uncertainty of a hundred orders of magnitude. A certain diversity of research is thus required to solve the DM problem and many DM candidates are now being proposed and discussed. Among various candidates, TeV-scale thermal DM candidates now attract attention as they are predicted by new physics models intensively discussed after the Higgs discovery at LHC and they also have a certain reason why current DM search experiments/observations do not detect their signals. I will summarize above interesting discussions of the TeV scale thermal DM candidates in this talk.

Speaker: Prof. Shigeki Matsumoto (Kavli IPMU)
• 13:15
Higgsino Dark Matter 30m

I will discuss phenomenology of Higgsino dark matter. First, I will briefly overview theoretical issues related to Higgsino dark matter. Then, I will summarize present status and future prospects of Higgsino dark matter search using colliers and direct detection experiments.

Speaker: Prof. Takeo Moroi
• 13:45
Wino theory and future prospects 30m

Wino is one of the most attractive candidates of the dark matter.
The Wino is a natural prediction of SUSY models and provides very rich signatures in collider, direct and indirect search for the dark matter.
I will talk about the current experimental and theoretical status of the Wino dark matter and the future prospects.

Speaker: Satoshi Shirai
• 14:15 14:45
Coffee break
• 14:45 16:15
DM Direct Detection
Convener: Prof. Shigetaka Moriyama (ICRR)
• 14:45
DM searches with LXe 30m

Direct dark matter searches have been conducted for more than 30 years in the underground laboratories to look for signals via dark matter-nucleus elastic scattering of its target materials. Weakly interacting massive particles as dark matter candidates arise naturally in various theories, such as Supersymmetry, Extra Dimensions. WIMPs interact through the weak interaction and can efficiently transfer kinetic energy by the scattering from atomic nuclei, the WIMP model can be tested by searching for nuclear recoils in a sensitive, low-radioactivity detector. This review talk will focus on a liquid xenon base detectors among those searches which include current bounds and future prospects.

Speaker: Prof. Masaki Yamashita (ICRR, The University of Tokyo)
• 15:15
DM searches with LAr 30m

Experimenters from four different argon dark matter searches have joined their forces in the the “Global Argon Dark Matter Collaboration” to carry out a unified program for dark matter direct detection.
The next step at the scale of a few tens of tonnes is the DarkSide-20k experiment, a 20-tonne fiducial volume dual-phase TPC to be operated at LNGS with an underground argon fill, designed to collect an exposure of 100 tonne×years, completely free of neutron-induced nuclear recoil background and all electron recoil background. DarkSide-20k is set to start operating by 2023 and will have sensitivity to WIMP-nucleon spin-independent cross sections of 7.4×10−48 cm2 for WIMPs of 1 TeV/c2 mass, to be achieved during a 10 year run with an exposure of 200 tonne×years. DarkSide-20k will explore the WIMP-nucleon cross-section down to the edge of the ’neutrino floor’, where coherent neutrino-nucleus scattering from environmental neutrinos induce nuclear recoils in the detector.
A second step in the program is the construction and operation of Argo, a detector with a fiducial mass of a few hundred tonnes, capable of collecting an exposure of several thousands of tonne×years, completely free of all backgrounds on top of CNNS, slated for a 2030 start.

Speaker: Prof. Cristiano Galbiati (Princeton University)
• 15:45
Particle and halo model uncertainties in direct dark matter detection 30m

After briefly reviewing the WIMP status as dark matter (DM) candidate, I will mention how the impact of the neutrino floor on the direct detection (DD) reach depends on the type of WIMP-nucleus interaction and mass, and then how a DD signal would translate into properties of the DM local velocity distribution, allowing to compare different DD data sets through these predictions (in a “halo-independent” analysis complementary to the usual halo-dependent method).

Speaker: Prof. Graciela Gelmini (UCLA)
• 16:15 16:30
Coffee break
• 16:30 18:00
Focused Session: Neutrino Floor
Convener: Dr Kentaro Miuchi (Kobe University)
• 16:30
The Neutrino Floor 30m Remote talk

Remote talk

WIMP detectors in the 2020's will approach the sensitivity at which
scatters of natural neutrinos will create a background sufficient to
obscure the WIMP recoil signal. This is the so-called "Neutrino
Floor". This talk will discuss the nature of the neutrino floor and
the motivations to get to it, and to potentially go beyond it.

Speaker: Prof. Kate Scholberg (Duke University)
• 17:00
Breaking through the neutrino floor 30m

I will explain why the neutrino floor exists from a statistical perspective and then discuss what kind of information we need from an experimental search to be able to subtract the neutrino background.

Speaker: Dr Ciaran O'Hare
• 17:30
Discussion of experimental approach to go beyond the neutrino floor in the WIMP search 30m

In the standard methodology for the WIMP search detect recoiled nuclei due to elastic scattering with that, the neutrino should become background to be not able to avoid. If not detect significant signals or just few events detected before neutrino floor, more reliable search to confirm those are the signals due to WIMP or new information to distinguish the WIMP signals from neutrino backgrounds will be required. For example, one of the promising information in current studies is to use “direction” or signals attributed to that. In this talk, I will report current experimental approach about direction sensitive search, and discuss about the issues to go beyond neutrino floor.

Speaker: Dr Tatsuhiro Naka (Toho University )
• Tuesday, 12 November
• 10:00 11:00
DM Collider
Convener: Prof. Shoji Asai (University of Tokyo/CERN)
• 10:00
Current status of Dark matter searches at LHC 30m

This talk aims to provide an overview of the theoretical framework, the search strategies and the current status of the results of Dark Matter searches at the LHC. The focus will be restricted to mediator-based Dark Matter models (non-SUSY). Experimental analyses and results will be presented on a selection of the models, using up to 150 ifb of $\sqrt{s} = 13$ TeV $pp$ collision data collected by the ATLAS and CMS experiments at the LHC.

Speaker: Dr Priscilla Pani (DESY)
• 10:30
SUSY Dark matter Search at LHC and future colliders 30m

The existence of dark matter (DM) is a cornerstone of extensive search programs at colliders. The ATLAS and CMS experiments at the LHC have performed a wide range of searches for DM particles predicted in SUSY, in particular for the lightest neutralino in R-parity conserving scenarios. The event topology and final states containing the neutralino DMs depend on the mass eigenstates of the gauginos and their compositions. In this talk, I will present the current status of neutralino DM searches at the LHC, putting some emphasis on DMs with Wino and Higgsino components. Prospects for the Wino/Higgsino DM searches at future colliders are also discussed.

Speaker: Dr Koji Terashi (University of Tokyo, ICEPP)
• 11:00 11:30
Coffee break
• 11:30 12:00
DM Collider
Convener: Prof. Shoji Asai (University of Tokyo/CERN)
• 11:30
Disappearing track searches at LHC and future colliders 30m

The neutral wino and the lightest neutral higgsino are dark-matter candidates. If those are the lightest SUSY particles, the lightest chargino can be long-lived and can travel macroscopic distances then decay in detectors. In such scenarios, dark matter particles can be searched for using a "disappearing track" signature. Such searches have been done at the LHC giving lower limits on their masses. Much higher sensitivities are expected in future analyses at the LHC and at future colliders. With an optimal detector layout at the Future Circular Collider, the sensitivity can cover the entire mass range compatible to the thermal relic abundance.

Speaker: Prof. Ryu Sawada (U. Tokyo)
• 12:00 12:30
Poster short presentations
Convener: Dr Kohei Hayashi (ICRR)
• 12:00
The GAPS experiment: sensitive survey of cosmic-ray antinuclei to search dark matter 1m

The General Antiparticle Spectrometer (GAPS) is an international balloon-borne project for indirect dark matter (DM) searches that investigates low-energy antinuclei in cosmic-ray, especially undiscovered antideuterons. Cosmic-ray antideuterons can be produced by self-annihilation or decay of WIMP DM. The flux of DM-originated antideuterons can be orders of magnitude higher than that of the secondary (or background) component. Therefore, antideuterons are considered to be a background-free probe to search for DM. GAPS uses a unique concept to identify antinuclei by applying the physics of exotic atom creation and decay. The GAPS instrument is composed of lithium-drifted silicon (Si(Li)) detectors surrounded by a double-layered plastic scintillation-counter time-of-flight system. An incoming antinucleus forms an exotic atom in the Si(Li) detectors. Through the deexcitation and nuclear annihilation processes of the exotic atom, characteristic X-rays and charged particles are emitted. By detecting and tracking those X-rays and particles, GAPS has strong particle identification, resulting in a high sensitivity for rare antinuclei. The first GAPS flight is scheduled for late 2021. We are currently developing all different subsystems, such as the Si(Li) tracker, time-of-flight system, cooling system, and detailed simulation code of the instrument. We will report the scientific motivation, detection concept, and development status of GAPS.

Speaker: Takuya Wada on behalf of the GAPS collaboration (Aoyama Gakuin University)
• 12:03
Scalar dark matter interacting through an extra U (1) gauge interaction 1m

We propose models of a thermal relic DM with the present annihilation cross-section being very suppressed. This property can be realized in an extra U(1) gauge interacting complex scalar DM. We consider scalar dark matter in U(1)B−L,U(1)(B−L)3 and U(1)Lμ−Lτ extended models and identify viable parameter regions. We also discuss various implication to future DM detection experiments, the DM interpretation of the gamma ray excess in the globular cluster 47 Tucanae, the muon anomalous magnetic moment, the Hubble Tension and others.

Speaker: Osamu Seto (Hokkaido University)
• 12:06
Constraint on the nature of annihilating dark matter with Low Surface Brightness Galaxies 1m

In the context of the high energy astrophysics, the nature of dark matter annihilation expected to emit gamma rays have been probed utilizing observed gamma-ray flux in a direction of a high matter-density region. Recently, some studies have been performed with nearby dwarf galaxies or the Galactic center and then the cross section for dark matter annihilation have been constrained.
In our study, we focus on Low Surface Brightness Galaxies (LSBGs) cataloged by the observation data of Hyper Suprime-Cam (HSC). LSBGs can be used as novel tracers of dark matter annihilation signals because of being more massive than dwarf spheroids and having less astronomical contaminations due to relatively quiescent states of those, which can perform robuster research for dark matter annihilation signals.
We model the gamma-ray flux from LSBGs using the 8 HSC-LSBGs measured each redshift, and compering with observed gamma-ray flux by Fermi Large Area Telescope, provide the upper limit of the cross section for dark matter annihilation.
Moreover, we prospect the future constraint with soon-to-be-detected LSBGs by future observation. In our poster presentation, we report our method and results, and also discuss the prospects for the future constraint.

Speaker: Daiki Hashimoto (Nagoya University)
• 12:09
J-factor estimation of Draco, Sculptor and Ursa Minor dSphs with the member/foreground mixture model 1m

Dwarf spheroidal galaxies (dSphs) are promising targets for indirect detection experiments since they contain a large amount of dark matter (DM). For the precise calculation of the amount of annihilation signal flux from dSph, we must know the DM mass density distribution of target dSphs, estimated from the observation of the stellar motion.
In the DM profile estimation, the major uncertainty of DM profile comes from the foreground contamination of the Milky Way stars in front of dSph. In the conventional analyses, the contaminated stars are partially removed based on their membership probability estimated by a clustering technique called EM algorithm. However, even if we use this technique, some contaminated stars still remain in the data set, which leads to the incorrect sensitivity of indirect detection experiments.
In this work, we adopt a new method to deal with the contamination effect based on the mixture model of the dSph member and foreground stars.
Using this method, we estimate the DM density profile of Draco, Sculptor, and Ursa Minor, the top three DM rich dSphs, with reliable errorbars properly including the uncertainty of the contamination effect.

Speaker: Shunichi Horigome (Kavli IPMU)
• 12:12
Probing heavy dark matter decays with multi-messenger astrophysical data 1m

We set conservative constraints on decaying dark matter particles with masses spanning a very wide range ($10^4-10^{16}$ GeV). For this we use multimessenger observations of cosmic-ray (CR) protons/antiprotons, electrons/positrons, neutrinos/antineutrinos and gamma rays. Focusing on decays into the $b\bar{b}$ channel, we simulate the spectra of dark matter yields by using the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equations and the Pythia package. We then propagate the CRs of dark matter origin till Earth by using the state-of-the-art numerical frameworks CRPropa, GALPROP and HelMod for the solution of the CR transport equation in the extragalactic, Galactic region and the heliosphere, respectively. Conservative limits are obtained by requiring that the predicted dark matter spectra at Earth be less than the observed CR spectra. Overall, we exclude dark matter lifetimes of $10^{28}$ s or shorter for all the masses investigated in this work. The most stringent constraints reach $10^{30}$ s for very heavy dark matter particles with masses in the range $10^{11}−10^{14}$ GeV.

Speaker: Dr Oscar Macias
• 12:15
Galaxy collisions and the missing satellite problem in the cold dark matter model 1m

Cold dark matter (CDM) cosmology is the standard paradigm of structure formation in the universe. However, it has several unsolved severe problems. The missing satellites problem refers to the overabundance of theoretically predicted CDM subhalos compared to observed satellite galaxies in the Local Group. The most popular interpretation is that the small dark matter halos have extremely inefficient star-forming history. In this study, we investigate the possible existence of the stellar deficient CDM halos using large scale numerical simulations for galaxy collisions between a CDM subhalo and a dwarf galaxy in the Local Group.

Speaker: Prof. Masao Mori (University of Tsukuba)
• 12:18
Dynamics of the cusp-to-core transformation in the cold dark matter halos 1m

The lambda cold dark matter model is the standard paradigm of structure formation in the universe. However, there is a discrepancy known as the “cusp–core problem” in the mass–density distribution of a dark matter halo (DMH) between theory and observation. We investigate the dynamical response of DMHs to recurrent starbursts on the formation of less massive galaxies to solve this issue. In the early epoch of the galaxy formation, the cycle of expansion and contraction of the interstellar gas driven by the stellar feedbacks leads to a recursive change in the gravitational potential of the gas. The eccentricity of the DMH particles around the centre becomes large by this change. Then, the system expands, and the core scale increases due to the oscillation process. Finally, the DMH then reaches the new quasi-equilibrium state. Our simulation shows that the energy transport by the overtone components contained in the periodic oscillation of the potential change strongly influences the inner slope of the mass–density profile of the DMH. We conclude that the resonance between DMH particles and the density wave excited by the oscillating potential plays a crucial role in understanding the physical mechanism of the cusp–to–core transition of DMHs.

Speaker: Dr Kazuki Kato (University of Tsukuba)
• 12:21
Characterization of new photo-detectors for the future dark matter experiments with liquid xenon 1m

In the last three decades, numerous terrestrial experiments have been built to detect the faint interactions between WIMP dark matter and ordinary matter. Among them, experiments using dual-phase xenon time projection chambers (TPCs) are leading the search especially for high mass WIMPs. In these experiments, photomultipliers (PMTs) are used to detect the prompt primary scintillation and secondary electro-luminescence of ionized electrons. However, PMTs have several important shortcomings: the residual radioactivity levels, cost, bulkiness, and stability at cryogenic conditions. Therefore, several alternative technologies are under consideration toward the future dark matter experiments using ~50 tons of liquid xenon (LXe). One of the such technologies is silicon photomultipliers (SiPMs). SiPM has very low radioactivity, compact geometry, low operation voltages and reasonable photo-detection efficiency for VUV light. However, current SiPM still has ~two order of magnitude higher dark count rate compared with PMT, which significantly increases accidental coincidence background. In order to solve these problems, we are currently developing a new SiPM with the help of Hamamatsu and FBK. In this poster, we will report the current status of the performance measurements of the Hamamatsu VUV4 SiPMs (3mm×3mm), new SiPMs with less dark count and FBK VUV SiPMs (6mm×6mm).

Speaker: Kosuke Ozaki (Nagoya University)
• 12:30 12:40
Group picture Outside on the stairs below the Lecture Hall

Outside on the stairs below the Lecture Hall

• 12:40 13:30
Lunch
• 13:30 15:00
DM Astrophysics
Convener: Dr Kohei Hayashi (ICRR)
• 13:30
Paradigms and Scenarios for the Dark Matter 30m

The deeper we go into the knowledge of the dark component that embeds the stellar component of galaxies, the more we realize the profound interconnection which is present between the two of them. The scaling laws among the structural properties of the dark and luminous matter in disc systems are too complex to be arisen by two inert components that just share the same gravitational field. This brings us to critically focus on the 30 years old paradigm, that, resting on a priori knowledge of the nature of dark matter (DM), has led us to a restricted number of scenarios for dark matter. The galaxies's structural properties show strong indications that the dark and luminous components have interacted in a direct way over the Hubble time. We propose to break the dark matter mystery by taking a step back and start following a new paradigm: the Nature of dark matter can be guessed/derived only from deep analyzing the properties of the dark and luminous mass distribution at galactic scales. As first result in Spirals, the quantity $\rho_{DM}(r,L,R_D) \rho_\star (r,L,R_D)$, the (macroscopic) kernel of a dark-to-luminous interaction, shows specific properties that call for a collisional nature of the dark particle.

Speaker: Prof. Paolo Salucci (SISSA)
• 14:00
The Dark Matter distribution of the Milky Way (its astrophysical uncertainties and effects on determination of physics beyond the standard model) 30m

The distribution of Dark Matter in galaxies is one remarkable output of structure formation in a cosmological context, and an important input for the searches of the nature of Dark Matter. In this talk I will present the results of recent, fully data-driven analysis of the determination of the Dark Matter content and distribution in the Milky Way.
I will also highlight the current uncertainties of empirical (and astrophysical) nature, and how they affect the interpretation of direct and indirect searches, and eventually the searches for the very nature of the Dark Matter.

Speaker: Prof. Fabio Iocco (Imperial College / Università di Napoli)
• 14:30
Varieties of DM density profile in Galactic dwarf spheroidal galaxies and the gamma-ray search of the annihilation signature 30m

Dwarf spheroidal galaxies (dSph) are good targets to search for dark matter annihilation signals through gamma-ray observations. Currently, the most strong constraints on the cross-section at mDM<~100GeV are obtained by observing them with Fermi-LAT. The dark matter distribution in dSphs is difficult to model and the errors in the current constraints are dominated by those in the J-factor. In this talk, I explain the general procedure to determine the DM distribution in dSphs and the variation of the resultant models. I also discuss the effect of the DM spatial distribution on the future gamma-ray search of WIMP annihilation signals using ground-based telescopes.

Speaker: Dr Nagisa Hiroshima (Riken)
• 15:00 15:45
Coffee break: Poster session
• 15:45 16:45
Young Scientists session: I
Convener: Dr Kohei Hayashi (ICRR)
• 15:45
Rapid bound-state formation of Dark Matter in the Early Universe 20m

The thermal decoupling description of multi-TeV scale dark matter (DM) and co-annihilating partners is reconsidered. In such a high-mass region, even the electroweak force carriers could act as long-range forces, leading to the existence of meta-stable DM bound states. The formation and subsequent decay of the latter further depletes the relic density on top of the Sommerfeld enhancement, allowing for heavier DM masses. So far, only the on-shell mediator emission (W, Z, H, g, photon or exotic) was considered as the formation process of the bound states. In this talk, I show that bound-state formation via bath particle scattering, i.e. the mediator instead in the t-channel and connected to the SM plasma, can be the dominant conversion process. For a simplified setup we find that bound-state formation via bath particle scattering exceeds the single mediator bound-state formation cross-section by several orders of magnitude at the freeze-out temperature. The implications of these findings are that bound-state effects become more pronounced during chemical decoupling and consequently DM could be heavier than previously expected, eventually informing indirect and collider searches.

Speaker: Dr Tobias Binder
• 16:05
Status and Prospect of PandaX experiment 20m

PandaX is a dark matter search experiment located at China Jin Ping Underground Lab using xenon time projection chamber.
In this talk, I will present the latest result from PandaX-II experiment and the current status of PandaX-4T experiment.

Speaker: Dr Pengwei Xie (Tsung-Dao Lee Institute)
• 16:25
N-body self-consistent stars-halo modelling of the Fornax dwarf galaxy 20m

We present nearly self-consistent stellar-halo models of the dwarf spheroidal Fornax galaxy the satellite of the Milky Way galaxy. Such galaxies are dark matter dominated objects with almost no gas in them so they are excellent objects for N-body modelling that takes into account visible and dark matter(DM) halo components. Three models are self-consistent realizations containing a truncated King or Plummer models bulge (it stands for the stellar component of the galaxy) and the lowered Evans dark halo model. These components are given by the distribution functions which are the functions of $E$ and $L_z$ only. And four models with the King and Plummer visible components are made by the AGAMA code based on the calculation of orbits. To guess the parameters which make the N-body models close to the visible object we use hydrodynamic stellar-dark model of the Fornax galaxy taking into account the velocity anisotropy parameter. The AGAMA models show better agreement of the resulting velocity dispersion profiles with the observed data. We also traced the evolution of all these models and found them rather stable during several typical dynamical times.

Speaker: Mrs Galina Shchelkanova (NRC "Kurchatov institute" - ITEP)
• 16:45 17:00
Coffee break 15m
• 17:00 17:40
Young Scientists session: II
Convener: Dr Kohei Hayashi (ICRR)
• 17:00
SMILE project: all-sky MeV gamma-ray observation and dark matter survey 20m

In the MeV gamma-ray band, the observed Galactic diffuse gamma-rays has the excessive component cannot be explained by the current standard model of the Galaxy. This excess might be gamma-rays due to annihilation of MeV scale WIMP dark matter or evaporations of primordial black holes. The MeV band has the advantage over the GeV band because there is less diffuse gamma-ray background due to no $\pi ^0$ bump.
In 2018 April 7, we carried out the campaign, sub-MeV and MeV gamma-ray imaging loaded-on balloon experiment 2+ (SMILE-2+), in order to demonstrate the imaging performance of the gaseous electron tracking Compton camera (ETCC). Unlike conventional Compton cameras such as COMPTEL, ETCC uniquely reconstructs the directions of gamma-rays and realizes the noiseless gamma-ray observation even in the space environment by the particle identification and Compton kinematical test. This detector has the energy range from $200\,\mathrm{keV}$ to $5\,\mathrm{MeV}$ and the wide field of view ($3\,\mathrm{str}$). We observed the Galactic center for 8 hours and detect it with the significances of $5\,\sigma$ ($511\,\mathrm{keV}$) and $10\,\sigma$ (continuum). The sensitivity of the satellite with ETCC will reach $1\,\mathrm{mCrab}$ ($10^6\,\mathrm{sec}$, $3\,\sigma$) and the HPR of its PSF will be $5\,\mathrm{degree}$.

Speaker: Mr Yuta Nakamura (Kyoto University)
• 17:20
Dark Matter Heating vs. Rotochemical Heating in Old Neutron Stars 20m

WIMP DMs in the Universe accumulate in neutron stars (NSs) through their interactions with nucleons. It has been known that their annihilation inside the NS core causes late-time heating, with which the surface temperature becomes $T_s \simeq (2-3) \times 10^3$ K for the NS age $t > 10^{6-7}$ years. Thus the measurement of NS surface temperature can be used as a new probe of WIMP DMs. Because of the strong gravity of NSs, DM heating has several advantages compared to the direct detection experiments on the earth.

Despite such advantages, the background on the DM heating is rarely discussed in the particle physics community. In particular, the rotochemical heating, internal heating caused by the out-of-equilibrium beta reactions in a NS, should be considered because it does not assume any exotic physics. In fact, if the rotochemical heating operates in a NS, it may conceal the DM heating effects.

In this work, we reevaluate the significance of the DM heating in NSs, including the effect of the rotochemical heating. We show that the signature of DM heating can still be detected in old ordinary pulsars, and discuss what is necessary to confirm the evidence for the DM heating.

Speaker: Dr Keisuke Yanagi (University of Tokyo)
• 18:30 20:30
Banquet
• Wednesday, 13 November
• 10:00 11:00
DM Indirect Detection
Convener: Prof. Tatsuo Yoshida (Ibaraki University)
• 10:00
High Energy Gamma Ray Instruments for Dark Matter Searches 30m
Speaker: Prof. Masahiro Teshima (ICRR, the University of Tokyo)
• 10:30
TeV dark matter search at the Galactic center with the CTA 30m

High-energy gamma rays are among the most promising tools to constrain or reveal the nature of dark matter (DM), in particular the Weakly Interacting Massive Particles models. The Cherenkov Telescope Array (CTA) is well into its pre-construction phase and will soon probe the high-energy gamma-ray sky in the 20 GeV - 300 TeV energy range. Thanks to its improved energy and angular resolutions as well as significantly larger effective area, the CTA will probe a parameter space of heavier dark matter (above 100 GeV), with unprecedented sensitivity, reaching the DM thermal annihilation rate at the TeV regime.

This talk will summarise the planned DM search strategies with CTA, focusing on the signal of DM in the centre of our Galaxy. As observed with the Fermi LAT at lower energies, this region exhibits complex large-scale gamma-ray emission and the CTA is expected to be the first ground based observatory able to detect it. In this talk we report on the collaboration effort to study the impact of extended astrophysical backgrounds on DM search, based on the astrophysical emission observed with the Fermi LAT at lower energies and to suggest the promising data analysis and observational strategies for the upcoming CTA data.

Speaker: Prof. Gabrijela Zaharijas (University of Nova Gorica)
• 11:00 11:30
Coffee break
• 11:30 12:30
DM Indirect Detection
Convener: Prof. Tatsuo Yoshida (Ibaraki University)
• 11:30
CTA Dark Matter searches in dwarf galaxies, dark halos, and galaxy clusters 30m

The Cherenkov Telescope Array (CTA) represents the next-generation ground-based gamma-ray observatory in the energy range between 30 GeV and 300 TeV. It will open the window to gamma-ray searches for annihilation or decay of heavy (TeV) Weakly Interacting Massive Particles (WIMPs) in astrophysical Dark Matter (DM) budgets with unprecedented sensitivity. In this talk, I will review the current prospects for WIMP searches with CTA in dwarf spheroidal galaxies orbiting our Milky Way, enhanced annihilation in close-by dark halos, and galaxy clusters of the local Universe. I will also outline the current knowledge of the DM targets and foreseen observation strategies, on which the success of the searches crucially depends.

Speaker: Dr Moritz Hütten (Max Planck Institute for Physics)
• 12:00
Current and Future WIMP Searches with Fermi-LAT, HAWC, and SWGO 30m

Evidence suggests ~85% of the mass in the Universe is dark matter (DM). Several promising DM theories predict that it is a fundamental particle. The most famous of which is the Weakly Interacting Massive Particle (WIMP). WIMPs that annihilate at a weak-scale cross section that were in thermal equilibrium in the Universe produce the observed DM abundance today. DM particles are theorized to interact and produce standard model particles, like gamma rays. So far, no definitive gamma-ray signal has been detected, but current experiments have started excluding several thermal WIMP models. I will discuss the current status of DM searches with gamma-ray observatories like the Fermi LAT and HAWC. I will also discuss how both future analysis with current observatories and future observatories like CTA and SWGO will probe thermal WIMP models for masses from 5 GeV to ~100 TeV.

Speaker: Dr Andrea Albert (Los Alamos National Lab)
• 12:30 13:30
Lunch
• 13:30 15:00
Focused Session: Charged particles
Convener: Dr Moritz Hütten (Max Planck Institute for Physics)
• 13:30
Recent Results and Dark Matter Search with CALET on the ISS 30m

The CALorimetric Electron Telescope (CALET), which is currently conducting direct cosmic-ray observations onboard the International Space Station (ISS), uses an all-calorimetric instrument with total vertical thickness of 30 radiation lengths and fine imaging capability. The instrument is optimized for cosmic-ray electron measurements by achieving large proton rejection and excellent energy resolution well into the TeV energy region. In addition, very wide dynamic range of energy measurements and absolute charge identification capability of the instrument enable us to measure proton and nuclei spectra as well as electron and gamma-ray spectra. The CALET mission goals include the investigation of acceleration and propagation of galactic cosmic rays, of possible nearby sources, and of potential signature of dark matter. Since the start of observation in October 2015, smooth and continuous operations have taken place. In this talk, we will give a brief summary of the recent results obtained with CALET and discuss about the dark matter search using the CALET all-electron spectrum.

Speaker: Yoichi Asaoka (WISE, Waseda University)
• 14:00
Propagation processes of cosmic rays 30m

In this talk, I'll review recent theoretical studies and observational results about propagation processes of cosmic rays in our galaxy.

Speaker: Yutaka Ohira (The university of Tokyo)
• 14:30
Constraints on cosmic ray propagation and magnetic fields using gamma-ray observations 30m Remote talk

Remote talk

The origin and propagation of cosmic rays is one of the most important questions in astroparticle physics nowadays. To perform Indirect searches of Dark Matter searching for their products in the local cosmic ray spectra, we first need to comprehend what is the background coming from astrophysical sources. We can only model this background by achieving a deep understanding of cosmic ray propagation. Although the transport of these cosmic rays through the galaxy make them lose the information about their origin due to interstellar magnetic fields, we can directly study the properties of their propagation using gamma rays. In this talk, I will give a review of current measurements of magnetic fields and cosmic ray propagation parameters using gamma rays.

Speaker: Dr Rubén López-Coto (INFN Padova)
• 15:00 15:30
Coffee break
• 15:30 16:30
Young Scientists session: III
Convener: Dr Moritz Hütten (Max Planck Institute for Physics)
• 15:30
Improved search for Dark Matter annihilation with a combined analysis of data from Fermi-LAT, HAWC, H.E.S.S., MAGIC and VERITAS: a framework for future DM analyses 20m

The next generation of gamma-ray experiments are expected to improve significantly the current results in the search for Dark Matter (DM). Before these next-generation instruments start operating at their nominal design, one possibility to improve the current results is to combine data from existing experiments. This technique allows to increase energy coverage by combining data from instruments with better sensitivity in different energy ranges and also to maximize the sensitivity by combining individual data sets from all the experiments for which the energy ranges overlap. We will report on such an initiative aiming at combining data from dwarf spheroidal galaxies (dSphs) from the Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS experiments. Being among the most DM dominated objects with negligible expected astrophysical gamma-ray emission, dSphs are ideal targets for DM indirect searches and thus will be also primary targets for the next generation of experiments. Preliminary results of the combination constraining the DM annihilation cross section will be presented spanning a range of DM masses from 10 GeV to 100 TeV. The potential of extending this analysis framework to more experiments as well as to future experiments will also be discussed.

Speaker: Daniel Kerszberg (IFAE-BIST)
• 15:50
Search for dark matter TeV spectral lines around the Galactic Centre with the MAGIC telescopes 20m

In this talk, we will present a status report on the search for dark matter spectral lines around the Galactic centre (GC) with the MAGIC telescope system located on the Canary island of La Palma, Spain. MAGIC is sensitive to gamma rays from 50 GeV to 50 TeV. So far, MAGIC has produced groundbreaking results in the field of indirect DM searches observing a variety of targets, such as the Galactic halo, dwarf spheroidal galaxies and clusters of galaxies. We are now aiming to add the GC region as an observational target to search for line signatures from DM annihilation. MAGIC has observed the GC region for hundreds of hours at high zenith angles, at which the collection area for TeV gamma rays is significantly increased. This allows us to probe promising SUSY models of heavy DM candidates, and to set limits on the DM annihilation cross section competitive to those obtained from observations in the Southern hemisphere. We will also discuss how we exploit the data from a complex sky region to analise for line-like gamma-ray signatures.

Speaker: Mr Tomohiro Inada (ICRR, UTokyo)
• 16:10
Constraining Secluded Dark Matter Scenarios with HAWC 20m

It is possible that DM particles are secluded to their own dark sector, where the interactions are carried by one or several dark mediators. If this dark sector exists, DM particles do not couple directly to the standard model (SM) particles, as in the case of WIMP scenarios. However, indirect DM searches are still possible if we assume that dark mediators are coupled to SM particles through a kinetic mixing parameter. The HAWC Observatory is a wide-field-of-view gamma-ray experiment with a high duty cycle (>95%) and looking for gamma rays with energies between 1 and 100 TeV. So, for secluded DM candidates in the TeV range, the HAWC Observatory is able to explore and constrain the parameter space of dark sector scenarios by searching for gamma-ray signals of dark mediator decays in nearby astrophysical targets. Here, we present preliminary results of these indirect searches using HAWC data.

Speaker: Mr Sergio Hernandez Cadena (Instituto de Física, UNAM)
• 16:30 16:40
Closing Remarks
• 16:30
Closing remarks 10m
Speaker: Prof. Ryu Sawada (U. Tokyo)