Poster Presentations

Board No. 1
Okuma, Akira (Nagoya University)
Title: The Cherenkov Telescope Array (very tentative)
I will show the latest status of the Cherenkov Telescope Array project and its fundamental physics targets.

Board No. 2
Jin, Hong-Bo (NAOC (China))
Title: Cosmic ray $e^{+} e^{-}$ spectrum excess and peak feature observed by the DAMPE experiment from dark matter
The Chinese satellite Wukong, also known as the DArk Matter Particle Explorer (DAMPE) experiment, has released its observation data of the cosmic ray (CR) electrons and positrons, which shows an excess in the energy spectrum up to TeV energy, and possibly a peak-like structure at 1.4 TeV. We investigate the scenario that the source of the excess come from the annihilation or decay of dark matter. We consider the W$^+$W$^-$ channel and direct $e^+e^-$ channel (model A), and the double $\tau^+\tau^-$ channel and direct $e^+e^-$ channel (model B). We find that the annihilation or decay of dark matter in the galactic halo can give excellent fits to the broad excess. However, the annihilation cross section is of the order of $10^{-23} \cm^3 s^{-1}$, larger than required for obtaining the correct relic abundance. We then study whether the narrow peak at 1.4 TeV could be explained by a nearby subhalo, which thanks to the smaller distance, could supply $e^+e^-$ within a narrow energy range. We find that in order to produce a peak width less than the DAMPE energy bin width (0.2 TeV), the source must be located within $r< 0.6 \kpc$. Our global fit models do not produce the peak-like feature, instead at 1.4 TeV the spectrum show either a slope or a cliff-like feature. However, if less than optimal fit is allowed, the peak-like feature could be generated. Furthermore, an excellent fit with peak could be obtained with model B if the background is rescaled. If the dark matter decay and annihilation rates are determined using the broad excess, the required subhalo mass could be $\sim10^{5} \Msun$ for decay model with lifetime $7.3\times 10^{25}$ s, or $\sim10^{4.5} \Msun$ for annihilation model with cross-section $10^{-23} \cm^3 \mathrm{s}^{-1}$, and a shallower density profile slope $\alpha=1.2$, or $\sim10^{2.5} \Msun $ for a steep profile with $\alpha=1.7$. The detail of the talk is found in arXiv 1712.00362.

Board No. 3
Zhang, Wei-Hong (ITP (China))
Title: Origins of sharp cosmic-ray electron structures and the DAMPE excess
Nearby sources may contribute to cosmic-ray electron (CRE) structures at high energies. Recently, the first DAMPE results on the CRE flux hinted at a narrow excess at energy 1.4 TeV. We show that in general a spectral structure with a narrow width appears in two scenarios: I) "Spectrum broadening" for the continuous sources with a δ -function-like injection spectrum. In this scenario, a finite width can develop after propagation through the Galaxy, which can reveal the distance of the source. Well-motivated sources include mini-spikes and subhalos formed by dark matter (DM) particles \chi_ s which annihilate directly into e+e- pairs. II) "Phase-space shrinking" for burst-like sources with a power-law-like injection spectrum. The spectrum after propagation can shrink at a cooling-related cutoff energy and form a sharp spectral peak. The peak can be more prominent due to the energy-dependent diff usion. In this scenario, the width of the excess constrains both the power index and the distance of the source. Possible such sources are pulsar wind nebulae (PWNe) and supernova remnants (SNRs). We analysis the DAMPE excess and find that the continuous DM sources should be fairly close within 0.3 kpc, and the annihilation cross sections are close to the thermal value. For the burst-like source, the narrow width of the excess suggests that the injection spectrum must be hard with power index signifi cantly less than two, the distance is within ~(3 - 4) kpc, and the age of the source is 0.16 Myr. In both scenarios, large anisotropies in the CRE flux are predicted. We identify possible candidates of mini-spike and PWN sources in the current Fermi-LAT 3FGL and ATNF catalog, respectively. The diff use γ-rays from these sources can be well below the Galactic diffuse γ-ray backgrounds and less constrained by the Ferm-LAT data, if they are located at the low Galactic latitude regions.

Board No. 4
LEE, Chun-Hao (National Tsing Hua University)
Title: Dark Matter Direct Detections
There are many dark matter direct detection experiments around the world. Several experiments, like CDMS-Si, DAMA and CoGeNT, provided potential signals, while most of the other experiments, such as LUX, XENON1T, PandaX-II and so on, provided null results. The negative results from the null experiments have, however, excluded the signal regions from CDMS-Si, DAMA and CoGeNT. The conflicts between the results of CDMS-Si and that of other null experiments could only be resolved by proposing some dark matter models in which several mechanisms, such as isospin violation, exothermic dark matter and light mediator, are considered. Dark matter models with single mechanism had been ruled out by the experimental data which were released after the proposals of those models. Therefore, we studied models with new combinations of these mechanisms to see if they could survived under the new constraints from the latest experimental data. These new models are Elastic DM with Light mediator and Isospin Violation, Exothermic Dark Matter with Isospin Violation, Isospin-conserving Exothermic Dark Matter with Light Mediator and Isospin-violating Exothermic Dark Matter with light mediator.

Board No. 5
Kuo, Jui-Lin (National Tsing Hua University)
Title: Is Fuzzy Dark Matter in tension with Lyman-alpha forest?
Recently some studies suggested that Fuzzy Dark Matter (FDM) might be in tension Lyman-alpha forest data. However, the limit on the mass of FDM was obtained by cold dark matter (CDM) simulations with FDM initial condition without considering the quantum pressure (QP) of FDM which could have generated non-trivial effects in large scales structures. We investigate the QP effects in cosmological simulations systematically, and find that QP leads to further suppression of the matter power spectrum on small scales. Furthermore, we estimate the flux power spectrum of Lyman-alpha forest, and compare it with data from BOSS and XQ-100 to set the lower bound on the FDM particle mass to 10^{-23} eV. We also carefully estimate the uncertainty in the calculation of flux power spectrum due to the temperature of the hydrogen gas. We conclude that unless the effect of QP and the uncertainties of the temperature of the hydrogen gas are properly taken into account, one cannot exclude the FDM of mass larger than 10^{-22} eV at statistically significant levels.

Board No. 6
Leason, Elizabeth (University of Edinburgh)
Title: Dark matter searches with LUX electron recoil data
Direct detection experiments, such as the Large Underground Xenon (LUX) experiment, aim to detect dark matter particles in the Milky Way as they pass through the detector. LUX is a dual phase xenon time project chamber, primarily designed to search for nuclear recoil events from WIMP-nucleus interactions. The detector is also sensitive to electron recoil signals that can be used to search for alternative dark matter models. Here non-WIMP dark matter searches are carried out using LUX electron recoil data taken from April to September 2013.

Board No. 7
Jho, Yongsoo (Yonsei University)
Title: Search for New Physics with High Multiplicity from Ultra-High-Energy Cosmic rays and Neutrinos
We explore the detectability of generic new physics process with high-multiplicity from Ultra-High energy (UHE) neutrinos (above 100 PeV) with the nucleon in the Earth atmosphere. The current sensitivity from the large area air-shower ground detector arrays (Pierre-Auger and TA) are still above various astrophysical models of Cosmic Rays and GZK neutrino flux with large uncertainties. We consider the criterions for the trigger about neutrino-induced new physics air-showers and heavy-nuclei-like features for proton-induced new physics air-showers. We discuss the current bounds on O(10) TeV scale new physics and also the future prospects.

Board No. 8
Nilima, Athoy (University of Edinburgh)
Title: Towards Electron-Recoil Background Models for LUX and LZ
Direct detection of dark matter is probably the most exciting and long-awaited missing piece in the puzzling world of particle physics. Being amongst the world's leading direct dark matter search programmes, LUX and its successor, LUX-ZEPLIN (LZ), aim to detect interactions of Weakly Interacting Massive Particles (WIMPs), or other dark matter candidates such as certain classes of axions, using the dual phase xenon time projection chamber technology. This provides high efficiency, low threshold, 3D reconstruction of events, together with the ability to discriminate between interactions that generate nuclear recoils (e.g. WIMPs) from those that generate electron recoils (e.g. axions). In general, nuclear recoil backgrounds are controlled significantly more effectively than electron recoil backgrounds, making searches for signals such as axions more difficult. Consequently, the success of such searches depends critically on the accuracy of the modelling of electron recoil backgrounds. Here we summarise some of the issues and their solutions that are being addressed within the LUX and LZ collaborations.

Board No. 9
Kimura, Masato (Waseda University)
Title: Particle Identification in Double Phase Argon Detector (ANKOK)
The ANKOK project is a dark matter search experiment in Japan using the double phase argon detector which is specialized for the low mass WIMP detection. One of the key elements in this project is electron recoil background rejection using liquid argon ionization and scintillation signals, together with the scintillation pulse shape discrimination. We are proceeding R&D efforts to establish the rejection power, especially under high electric field (> 1 kV/cm). In this poster, field and energy dependence of the detector response based on our measurement is presented.

Board No. 10
Sakurai, Akitada (Tokyo institute of technology)
Title: Relativistic Many-Body Theory of Electric Dipole Moments of Diamagnetic Atoms for Probing New Physics Beyond the Standard Model

Board No. 11
Iguro, Shuhei (Nagoya University)
Title: R(D^\{(*)}) in General Two Higgs Doublet Model
Motivated by recent anomalies in B physics, we completely investigated R(D^((∗))) in G2HDM which can generate flavor violating interactions easily. However flavor constraints like in BR(B_c→τν) <30(10%) is known as stringent, we found 2 scenarios that still can (can not) explain 1σ region of Belle experiment. We also studied implications in LHC and show some significant examining modes. We also summarized compatibility between R(K), P^'_5, muon g-2. This poster is based on Nucl.Phys. B925 (2017) 560-606 and arXiv:1802.01732

Board No. 12
Suzuki, Motoo (ICRR)
Title: Gauged Peccei-Quinn symmetry
The Peccei-Quinn (PQ) solution to the strong CP problem requires an anomalous global U(1) symmetry, the PQ symmetry. The origin of such a convenient global symmetry is quite puzzling from the theoretical point of view in many aspects. In this paper, we propose a simple prescription which provides an origin of the PQ symmetry. There, the global U(1) PQ symmetry is virtually embedded in a gauged U(1) PQ symmetry. Due to its simplicity, this mechanism can be implemented in many conventional models with the PQ symmetry. We also apply this mechanism into SUSY theory.

Board No. 13
Kanzawa, Kayo (Nagoya University)
Title: Development of single phase liquid xenon TPCs for future dark matter search
We develop single phase liquid xenon TPCs aiming for a future large scale dark matter detector. Our goal is to achieve a spherical TPC which collects ionized electrons towards an anode placed at the center of the detector. Using thin wires as anodes, we have observed S2 signals originated from 5.5MeV alphas from 241Am, 662keV gammas from 137Cs and neutrons and gammas from 252Cf. Currently we are investigating the property of S2 in LXe. We also developed a small needle-shaped anode for realization of spherical TPC.

Board No. 14
Matsuo, Yamato (Hiroshima University)
Title: Scalaron in F(R) gravity and Dark Matter
F(R) gravity, extension of the general relativity, gives us a candidate for dark matter (DM) and dark energy (DE). We study a scalar field (scalaron) derived from the F(R) gravity as a DM candidate. We discuss a possible scale of the curvature for the description by scalaron.

Board No. 15
Abe, Tomohiro (Nagoya University)
Title: Effects of CP violation in a singlet-doublet dark matter model
Recent direct detection searches for dark matter give stringent bounds on the dark matter mass and couplings. One way to relax the constraint is to rely on pseudoscalar interactions with fermion dark matter. This interaction term arises from CP violation in the dark sector. In this talk, we will focus on a model which contains a gauge singlet Weyl fermion and an SU(2) doublet Dirac fermion. We discuss the effects of CP violation on the elastic scattering cross section of dark matter with nuclei. We also discuss the correlation between the direct detection and the electron EDM.

Board No. 16
Lin, Yu-Xiang (National Taiwan Normal University)
Title: Boosted Higgs-pair production associated with large Missing E_T
The production of Higgs-pair associated with large missing transverse energy is a distinctive collider signature within the Littlest Higgs Model with T-parity. We use jet-substructure techniques in attempt to increase the reconstruction efficiency.

Board No. 17
Nugroho, Chrisna Setyo (National Taiwan Normal University)
Title: Top Quark Rare Decays via Loop-Induced FCNC Interaction in Extended Mirror Fermion Model

Flavor changing neutral current (FCNC) interactions for a top quark $t$ decays into $Vq$ with $V$ represents a neutral gauge boson, and $q$ a up- or charm-quark are studied in the context of an extended mirror fermion model. Whilst current limits on the branching ratios of these processes have been established at order $10^{-4}$ by the Large Hadron Collider (LHC) experiments, Standard Model predictions are at least nine order of magnitudes below. % We show that one can probe for the process $t \to Zc$ for a wide range of parameter space with branching ratios vary from $10^{-6}$ to $10^{-8}$, which may be accessible at the LHC.

Board No. 18
Okawa, Shohei (Nagoya University)
Title: Secluded dark matter with a massive mediator
We study a dark matter (DM) scenario, what is called a secluded DM scenario, in which DM predominantly annihilates into intermediate particles (mediator) decaying into the SM particles later, while DM has only tiny couplings to the SM. We first introduce a simple model of secluded DM and survey the parameter space. Then, we find that if the mass splitting between DM and mediator is small, there is a novel thermal history in which the DM number density evolution exhibits a temporary freeze-out behavior. Besides, it is pointed out that a larger annihilation cross section than the canonical value for the thermal relic DM is required in order to achieve the observed density. Based on these observations, a novel possibility of DM model building is proposed in which DM and mediator are unified in an approximate dark symmetry multiplet. A pionic DM model is introduced to illustrate this idea in a renormalizable field theory framework. The model naturally realizes the degenerate mass spectrum and the large cross section of the DM and the mediator.

Board No. 19
Matsuoka, Kodai (KMI, Nagoya University)
Title: One step model of photoelectron emission for a thin multi-alkali photocathode
The dependence of the quantum efficiency on the incident angle and polarization is an important feature to precisely describe the detector response especially for Cherenkov light, which is naturally 100% polarized. A simplified theoretical model which can fully describe the dependence of the quantum efficiency was developed for a thin multi-alkali (NaKSbCs) photocathode in a visible range. It was proved by a measurement of the dependence, with which the model fitted in precise agreement. Meanwhile the measurement also revealed the complex refractive index of the photocathode of this type reliably for the first time over the whole visible range. The model and the measurement will be presented in this poster.

Board No. 20
Ishiura, Hirohisa (Kobe University)
Title: Characteristics of Micro Pattern Gaseous Detector in negative ion gas for direction-sensitive dark matter search
NEWAGE is the direction-sensitive dark matter search experiment using a gaseous detector μ-TPC, a time projection chamber with micro-pixel chamber(μ-PIC) and GEM, at the Kamioka Observatory in Japan. From the previous research, we find that our detection sensitivity is mainly constrained by alpha-ray backgrounds from U/Th radioactivity contained in the readout device, the μ-PIC[1]. We have two approaches to decrease these backgrounds. The first one is a production of a low-background μ-PIC which has much less radioactivity contamination than the ordinary μ-PIC. We produced low-background μ-PIC and tested detector performances. The second one is the full-fiducial analysis by using the Negative-Ion μ-TPC (NI μ-TPC). We started to develop NI μ-TPC and we need to understand characteristics of Micro Pattern Gaseous Detector (MPGD) for NI μ-TPC in negative ion gas. In this presentation, we present measurement results of MPGD and current status of MPGD simulation study in negative ion gas.
[1] Progress of Theoretical and Experimental Physics (2015) 043F01s