Asia-Pacific Workshop on Particle Physics and Cosmology 2021

2 Aug 2021, 00:30 → 6 Aug 2021, 23:00 Asia/Seoul

Online

Koichi Hamaguchi (Tokyo University) , Seong Chan Park (Yonsei University)

Asia-Pacific Workshop on Particle Physics and Cosmology 2021 (Aug 2-6, 2021)

 

Welcome to the “Asia-Pacific Workshop on Particle Physics and Cosmology 2021”, to take place online on August 2-6, 2021. The workshop will bring together researchers working in the fields of theoretical particle physics and cosmology to discuss the latest results and to exchange ideas.

The workshop will feature several invited pedagogical review talks covering topics of recent interest, as well as contributed presentations from early-career scientists. Online conferencing tools (Zoom breakout rooms, Slack workspace, and gather town) will be provided to facilitate discussion and promote communication amongst the participants.

All talks will take place between 10:00 to 17:00 GMT+9.

Registration is free of charge and open to all.

 

Topics to be discussed include:

• Collider

• Flavor

• Dark Matter

• Neutrinos

• Cosmology

• Multi-messengers (cosmic rays, gravitational waves,...)

• BSM theory/formal/lattice/others

 

Review talk speakers include:

• Kyu Jung Bae (Kyungpook National University): Review on BSM

• Celine Boehm (The University of Sydney): Dark Matter Cosmology

• Kazunori Hanagaki (KEK):  LHC/HL-LHC

• Kai Schmitz (CERN): Gravitational Wave

• Kei Yamamoto (Hiroshima University): Flavor physics theory

 

 

Abstract submission deadline: July 5, 2021

Registration deadline: July 30, 2021

 

 

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Monday, 2 August

09:45 → 10:00 Opening talk

10:00 → 11:00 Review talks: Dark matter review

Convener: Yong Tang (University of Chinese Academy of Sciences)

10:00 Dark Matter Cosmology

dark matter particles are the most likely explanation to the formation of large-scale-structures in the universe. I’ll review the body of evidence and the progress in the field

Speaker: Celine Boehm (University of Sydney)

11:00 → 11:30 Discussion / Coffee Break

11:30 → 12:30 Dark matter 1

Convener: Hyun Min Lee (CAU - Chung-Ang University (KR))

11:30 Early kinetic decoupling and Higgs invisible decay in simple dark matter models

We revisit the Higgs-invisible decay branching ratio in Higgs-portal dark matter models. If the mass of the dark matter is slightly below the half of the mass of the Higgs boson, then pairs of the DM particles annihilate into the SM particles efficiently thanks to the Higgs resonance. The DM-Higgs coupling is required to be small to obtain the right amount of the dark matter relic abundance. As a result, the DM-nucleon scattering is highly suppressed and can explain the current null result of the dark matter signal at the direct detection experiments such as the XENON1T experiment. Another consequence of the tiny coupling is that the kinetic decoupling of dark matter from the thermal plasma in the early Universe may happen earlier. This implies that the standard calculation of the relic abundance may not be justified. We reevaluate the DM relic abundance with the evolution of the DM temperature. We show that the DM-Higgs coupling was underestimated in the literatures. Therefore, the Higgs invisible decay branching ratio is larger than previously expected, and the future collider experiments, such as the ILC experiment, can probe larger parameter space.

Speaker: Tomohiro Abe (Tokyo University of Science)

TomohiroAbe_Asia-Pacific_Workshop_on_Particle_Physics_and_Cosmology_2021.pdf

11:45 Does existence of dark matter imply grand unification?

A pseudo-Nambu-Goldstone boson (pNGB) is an attractive dark matter candidate escaping naturally the severe direct ditection constraint. In the previous work, we discussed pNGB dark matter from gauged U(1){B-L} model. In this work, we will consider the further UV completion of the pNGB dark matter model via embedding to a SO(10) grand unified theory. The grand unification determines the some free parameters in the gauged U(1){B-L} model such as U(1){B-L} gauge coupling, the kinetic mixing and U(1){B-L} breaking scale. For these parameters, we will discuss whether the pNGB can realize the current dark matter relic consistent with the observations. This talk is based on the collaboration with Takashi Toma, Koji Tsumura and Naoki Yamatsu, arXiv:2104.13523 [hep-ph].

Speaker: Yoshihiko Abe (Kyoto Univ.)

Asia-Pacific-Workshop-2021-YA.pdf

12:00 Flux-mediated Dark Matter

We propose a new mechanism to communicate between fermion dark matter and the Standard Model (SM) only through the four-form flux. The four-form couplings are responsible for the relaxation of the Higgs mass to the correct value and the initial displacement of the reheating pseudo-scalar field from the minimum. We show that the simultaneous presence of the pseudo-scalar coupling to fermion dark matter and the flux-induced Higgs mixing gives rise to unsuppressed annihilations of dark matter into the SM particles at present, whereas the direct detection bounds from XENON1T can be avoided. We suggest exploring the interesting bulk parameter space of the model for which dark matter annihilates dominantly into a pair of singlet-like scalars with similar mass as for dark matter.

Speaker: Ji-Seon Song (Chung-Ang University)

Asia Pacific Workshop 2021_Jiseon Song.pdf

12:15 Chiral Composite Asymmetric Dark Matter

The asymmetric dark matter (ADM) scenario solves the baryon-dark matter coincidence problem when the dark matter (DM) mass is of O(1)GeV. Composite ADM models based on QCD-like strong dynamics are particularly motivated since the strong dynamics naturally provides the DM mass of O(1) GeV and the large annihilation cross-section simultaneously. In those models, the sub- GeV dark photon often plays an essential role in transferring the excessive entropy in the dark sector into the visible sector, i.e., the Standard Model sector. This paper constructs a chiral composite ADM model where the U(1)D gauge symmetry is embedded into the chiral flavor symmetry. Due to the dynamical breaking of the chiral flavor symmetry, the model naturally provides the masses of the dark photon and the dark pions in the sub-GeV range, both of which play crucial roles for a successful ADM model.

Speaker: Keiichi Watanabe (ICRR)

Asia-Pacific Workshop.pdf

12:30 → 14:00 Discussion / Lunch Break

14:00 → 15:00 Dark matter 1

Convener: Chuan-Ren Chen (National Taiwan Normal University)

14:00 The domain of thermal dark matter candidates

I will consider the possible parameter space of thermal dark matter candidates, starting from the assumption that the dark matter particle is fundamental and was in thermal equilibrium in a hidden sector with a temperature T', which may differ from that of the Standard Model temperature, T. The candidates lie in a region in the T'/T vs. m_{dm} plane, which is bounded by both theoretical and observational constraints. The former includes limits on dark matter candidates that decoupled when relativistic (the relativistic floor) and from those that decoupled when non-relativistic with the largest annihilation cross section allowed by unitarity (the unitarity wall), while the latter concerns big bang nucleosynthesis (N_{eff} ceiling) and free-streaming. I will present a few simplified dark matter scenarios, demonstrating concretely how each fits into the domain. (Based on arXiv 2105.01263)

Speaker: Rupert Coy (ULB)

CoyThermalDMTalk.pdf

14:30 Freezing In with Lepton Flavored Fermions

Dark, chiral fermions carrying lepton flavor quantum numbers are natural candidates for freeze-in. Small couplings with the Standard Model fermions of the order of lepton Yukawas are ‘automatic’ in the limit of Minimal Flavor Violation. In the absence of total lepton number violating interactions, particles with certain representations under the flavor group remain absolutely stable. For masses in the GeV-TeV range, the simplest model with three flavors, leads to signals at future direct detection experiments like DARWIN. Interestingly, freeze-in with a smaller flavor group such as SU (2) is already being probed by XENON1T.

Speaker: Shiuli Chatterjee (Indian Institute of Science)

14:45 Effects of New Heavy Fermions on Complex Scalar Dark Matter Phenomenology in Gauged Two Higgs Doublet Model

We study the inclusion of new heavy fermions on complex scalar dark matter (DM) phenomenology within gauged two Higgs doublet model (G2HDM). We find that for DM mass above 1 TeV, heavy quarks coannihilations into the Standard Model (SM) quarks and gluons dominate the thermally-averaged cross section relevant for the relic abundance of complex scalar DM. We demonstrate that the effects of QCD Sommerfeld correction as well as QCD bound state formation in determining the DM relic density are negligible. We show that the allowed parameter space is significantly constrained by the current PLANCK relic density data as well as XENON1T limit appropriate for DM direct search.

Speaker: Bayu Dirgantara (Suranaree University of Technology)

15:00 → 15:15 Dark matter 2

Convener: Chuan-Ren Chen (National Taiwan Normal University)

15:00 Thermal Real Scalar Triplet Dark Matter

Real scalar triplet dark matter, which is known to be an attractive candidate for a thermal WIMP, is comprehensively studied paying particular attention to the Sommerfeld effect on the dark matter annihilation caused by the weak interaction and the other interaction between the dark matter and the Higgs boson. We find a parameter region that includes the so-called 'WIMP-Miracle' one is still surviving, i.e. it respects all constraints imposed by dark matter searches at collider experiments, underground experiments (direct detection) and astrophysical observations (indirect detection). The region is also found to be efficiently searched for by various near future experiments. In particular, the XENONnT experiment will cover almost the entire parameter region.

Speaker: Yu Watanabe (University of Tokyo)

15:15 → 15:45 Discussion / Coffee Break

15:45 → 16:15 Dark matter 2

Convener: Koichi Hamaguchi (Tokyo University)

15:45 The search for leptophilic WIMP at colliders

We consider the renormalizable leptophilic WIMP models with the scalar mediators which have lepton numbers. We perform a comprehensive analysis for such a WIMP scenario for two distinct cases with SU(2) doublet or singlet mediators considering all the relevant theoretical, cosmological and experimental constraint at present. We show that mono-photon search at near-future lepton collider experiment can play a significant role to probe the yet unexplored parameter region. Furthermore, we discuss the capability of explaining the muon g-2 anomaly by combined model scenario including both the doublet and singlet mediators.

Speaker: Taisuke Katayose (Osaka University)

asian_pacific_Katayose.pdf

16:00 Simplified Dark matter Models in GAMBIT

GUM is a recent addition to the GAMBIT framework that auto-generates the necessary code to run global scans of BSM models. By reducing the time to setup global scans, GUM removes one of the barriers to studying many models simultaneously. In this work I demonstrate an application of this to multiple simplified dark matter models at once. I will discuss scans that include a range of observables from dark matter and collider searches to form a combined likelihood. This work has the potential to produce the most up-to-date constraints on some of the less studied models.

Speaker: Christopher Chang (University of Queensland)

Asia-Pacific Workshop on Particle Physics and Cosmology 2021(2).pptx

16:15 → 17:00 Dark matter 3

Convener: Koichi Hamaguchi (Tokyo University)

16:15 Reshuffled SIMP Dark Matter

In this talk, we reanalyze the multi-component strongly interacting massive particle (mSIMP) scenario using an effective operator approach. As in the single SIMP case, the total relic abundance of mSIMP dark matter (DM) depends on the coupling strengths of 3 → 2 processes achieved by a five-point effective operator. Interestingly, we find that in the dark sector there is an unavoidable 2 → 2 process induced by the corresponding five-point interaction, which would reshuffle the mass densities of SIMP DM after the chemical freeze-out. We name this DM scenario as reshuffled SIMP (rSIMP). Given this observation, we then numerically solve the coupled Boltzmann equations including the 3 → 2 and 2 → 2 processes to get the correct yields of rSIMP DM. It turns out that the masses of rSIMP DM must be nearly degenerate for them to contribute sizable abundances. On the other hand, we also introduce effective operators to bridge the dark sector and visible sector via a vector portal. Since the signal strength of detecting DM is proportional to the individual densities, obtaining the right amount of SIMP DM particles is crucial in the rSIMP scenario. The cosmological and theoretical constraints for rSIMP models are discussed as well.

Speaker: Shu-Yu Ho (KIAS)

rSIMP_Asia_SYH.pdf

16:30 Searching for dark photons as dark matter

The dark photon is a massive hypothetical particle that interacts with the Standard Model by kinetically mixing with the visible photon. For small values of the mixing parameter, dark photons can evade cosmological bounds and be a viable dark matter candidate. Due to the similarities with the electromagnetic signals generated by axions, several bounds on dark photons are simply reinterpretations of results from axion haloscopes. However, the dark photon has a property that the axion does not: an intrinsic polarisation. Due to the rotation of the Earth, accurately accounting for this polarisation is nontrivial, and highly experiment-dependent. However, if one does account for the rotation of the Earth, sensitivity to dark photons can be improved by over an order of magnitude. I will detail some of the strategies for searching for dark photon dark matter and provide some guidelines for optimising those searches given the unknown polarisation state of the dark photon around the Earth.

Speaker: Ciaran O'Hare (University of Sydney)

darkphoton.pdf

16:45 Cosmic-Neutrino-Boosted Dark Matter (νBDM)

A novel mechanism of boosting dark matter by cosmic neutrinos is proposed. The new mechanism is so significant that the arriving flux of dark matter in the mass window 1 keV ≲ m_{DM} ≲ 1 MeV on Earth can be enhanced by two to four orders of magnitude compared to one only by cosmic electrons. Thereby we firstly derive conservative but still stringent bounds and future sensitivity limits for such cosmic-neutrino-boosted dark matter (νBDM) from advanced underground experiments such as Borexino, PandaX, XENON1T, and JUNO.

Speaker: Yongsoo Jho (Yonsei University)

210802_APWPPC2021_slides_YSJ.pdf

19:00 → 21:00 Welcome reception

Gather-town

Tuesday, 3 August

10:00 → 11:00 Review talks: BSM review

Convener: Seong Chan Park (Yonsei University)

10:00 Review on BSM

I will give a brief review on BSM physics.

Speaker: Kyu Jung Bae (Kyungpook National University)

11:00 → 11:30 Discussion / Coffee Break

11:30 → 12:30 BSM

Convener: Natsumi Nagata (University of Tokyo)

11:30 New physics explanations of $a_\mu$ in light of the FNAL muon $g−2$ measurement

The Fermilab Muon $g−2$ experiment reported the results of its Run-1 measurement of the anomalous magnetic moment $a^{FNAL}_\mu$, which is in full agreement with the previous BNL measurement and pushes the world average deviation $\Delta a^{2021}_\mu$ from the Standard Model to a significance of $4.2\sigma$. In this talk I will present an extensive survey of its impact on beyond the Standard Model physics, based on the work in Ref. [1]. In this work we used state-of-the-art calculations and a sophisticated set of tools to make predictions for $a_\mu$, dark matter and LHC searches. We examined a wide range of simple models with up to three new fields, that represent some of the few ways that large $\Delta a_\mu$ can be explained. The results show that the new measurement excludes a large number of models and provides crucial constraints on others. Generally, these models provide viable explanations of the $a_\mu$ result only by using rather small masses and/or large couplings with chirality flip enhancements, which can lead to conflicts with limits from LHC and dark matter experiments. I will present results for a range of models including scalar leptoquarks and simple models constructed to explain dark matter and g-2 simultaneously. [1] Athron P, Balázs C, Jacob D H, Kotlarski W, Stöckinger D and Stöckinger-Kim H 2021 (Preprint 2104.03691)

Speaker: Douglas Jacob (Monash University)

Douglas Jacob Asia-Pacific Workshop Presentation.pdf

12:00 Aligned Higgs couplings originated from the twisted custodial symmetry at high energies

We study the scenario of the two Higgs doublet model, where the Higgs potential respects the twisted custodial symmetry at high energy scale. In this scenario, experimental data for the Higgs boson couplings and those for the electroweak precision observables can be explained even when the masses of the extra Higgs bosons are near the electroweak scale. We also discuss the predictions on the mass spectrum of the additional Higgs bosons and also those on the coupling constants of the standard-model-like Higgs boson, which make it possible to test this scenario at the current and future collider experiments. This talk is based on JHEP 02 (2021) 046 [arXiv:2009.04330].

Speaker: Masashi Aiko (Osaka University)

Asia-Pacific_Aiko.pdf

12:15 R-symmetric flipped SU(5)

We construct a supersymmetric flipped SU(5) grand unified model that possesses an R symmetry. This R symmetry forbids dangerous non-renormalizable operators suppressed by a cut-off scale up to sufficiently large mass dimensions so that the SU(5)-breaking Higgs field develops a vacuum expectation value of the order of the unification scale along the F- and D-flat directions, with the help of the supersymmetry-breaking effect. The mass terms of the Higgs fields are also forbidden by the R symmetry, with which the doublet-triplet splitting problem is solved with the missing partner mechanism. The masses of right-handed neutrinos are generated by non-renormalizable operators, which then yield a light neutrino mass spectrum and mixing through the seesaw mechanism that are consistent with neutrino oscillation data. This model predicts one of the color-triplet Higgs multiplets to lie at an intermediate scale, and its mass is found to be constrained by proton decay experiments to be ≳5×1011 GeV. If it is ≲1012 GeV, future proton decay experiments at Hyper-Kamiokande can test our model in the p→π0μ+ and p→K0μ+ decay modes, in contrast to ordinary grand unified models where p→π0e+ or p→K+ν¯ is the dominant decay mode. This characteristic prediction for the proton decay branches enables us to distinguish our model from other scenarios. (If it is possible, I would like to have a talk on 3-5 August. Thank you very much.)

Speaker: Shihwen Hor (University of Tokyo)

AsiaPacific_2021_Hor.pdf

12:30 → 14:00 Discussion / Lunch Break

14:00 → 14:30 Neutrinos

Convener: Yvonne Wong (The University of New South Wales)

14:00 Sum Rules for Neutrino Parameters

Sum rules in the lepton sector provide an extremely valuable tool to classify flavour models in terms of relations between neutrino masses and mixing parameters testable in a plethora of experiments. In this talk we present our recent work on this.

Speaker: Martin Spinrath (NTHU)

Spinrath_Sum_Rules.pdf

14:15 Precise Capture Rates of Cosmic Neutrinos and Their Implications on Cosmology

We explore the potential of measurements of cosmological effects, such as neutrino spectral distortions from the neutrino decoupling and neutrino clustering in our Galaxy, via cosmic neutrino capture on tritium. We compute the precise capture rates of each neutrino species including such cosmological effects to probe them. These precise estimates of capture rates are also important in that the would-be deviation of the estimated capture rate could suggest new neutrino physics and/or a non-standard evolution of the universe.

Speaker: Kensuke Akita (IBS-CTPU)

Akita_Asia_Pasific_Workshop2021.pdf

14:30 → 15:15 BSM and the early universe

Convener: Yvonne Wong (The University of New South Wales)

14:30 Electroweak axion string and superconductivity

We study the axion strings with the electroweak gauge flux in the DFSZ axion model and show that these strings, called the electroweak axion strings, can exhibit superconductivity without fermionic zero modes. We construct three types of electroweak axion string solutions. Among them, the string with W-flux can be lightest in some parameter space, which leads to a stable superconducting cosmic string. We also show that a large electric current can flow along the string due to the Peccei-Quinn scale much higher than the electroweak scale. This large current induces a net attractive force between the axion strings with the same topological charge, which opens a novel possibility that the axion strings form Y-junctions in the early universe.

Speaker: Yu Hamada (KEK)

APW_hamada.pdf

15:00 Affleck-Dine Leptogenesis from Higgs Inflation

We investigate the possibility of simultaneously explaining inflation, the neutrino masses and the baryon asymmetry through extending the Standard Model by a triplet Higgs. The neutrino masses are generated by the vacuum expectation value of the triplet Higgs, while a combination of the triplet and doublet Higgs' plays the role of the inflaton. Additionally, the dynamics of the triplet, and its inherent lepton number violating interactions, lead to the generation of a lepton asymmetry during inflation. The resultant baryon asymmetry, inflationary predictions and neutrino masses are consistent with current observational and experimental results.

Speaker: Chengcheng Han (Sun Yat-sen University)

AP.pdf

15:15 → 15:45 Discussion / Coffee Break

15:45 → 17:00 BSM and the early universe

Convener: Jong-Chul Park (Chungnam National University)

15:45 Spontaneous Leptogenesis in Higgs Inflation

We propose a scenario of spontaneous leptogenesis in Higgs inflation with help from two additional operators: the Weinberg operator (Dim 5) and the derivative coupling of the Higgs field and the current of lepton number (Dim 6). The former is responsible for lepton number violation and the latter induces chemical potential for lepton number. The period of rapidly changing Higgs field, naturally realized in Higgs inflation during the reheating, allows large enhancement in the produced asymmetry in lepton number, which is eventually converted into baryon asymmetry of the universe. This scenario is compatible with high reheating temperature of Higgs inflation model.

Speaker: Sung Mook Lee (Yonsei University)

AP210803_SMLee.pdf

16:00 Filling the Gap : (Perturbative) Reheating in Higgs-R2 Inflation

Recent findings on the Higgs-R2 inflationary scenario have significantly increased. Here we focus on the deep-R2 parameter region of the model and report its reheating behavior, comparing with other parameter regions and discuss its phenomenological consequences.

Speaker: Dhong Yeon Cheong (Yonsei University)

AP_DY_Cheong.pdf

16:15 Subcritical hybrid inflation in generalized superconformal model

We study a generalized superconformal model that gives rise to a subcritical regime of D-term hybrid inflation. Formulating the model in a Jordan frame, the effective potential of the subcritical regime is derived in the Einstein frame. It turns out the inflaton-waterfall field dynamics leads to various types of inflaton potential. Consequently the tensor-to-scalar ratio is found to range from 10^{−4} (10^{−3}) to 0.1 for get 60 (50) e-folds before the end of inflation.

Speaker: Yoshihiro Gunji (Kanazawa University)

APW_Gunji.pdf

16:30 Hubble Selection of the Weak Scale: possibility from QCD quantum phase transition

During inflation, a scalar field undergoes a quantum diffusion following the de-Sitter temperature. Aided by the greater Hubble rate at higher potential, the quantum diffusion can make the global distribution of the field climb up the potential. If the potential exhibits a criticality at the maximum point, the field distribution can be sharply located near there. We show a possibility from QCD phase transition that it can have a critical point near the weak scale, so that the ``Hubble selection" may account for the Higgs hierarchy problem.

Speaker: TaeHun Kim (Seoul National University)

TaeHun_Kim_upload.pdf

Wednesday, 4 August

10:00 → 11:00 Review talks: LHC review

Convener: Chuan-Ren Chen (National Taiwan Normal University)

10:00 Towards LHC Run3 and HL-LHC

The basics of the LHC experiment and prospects for HL-LHC will be discussed.

Speaker: Hanagaki Kazunori (KEK)

APworkshop_210804.pdf

11:00 → 11:30 Discussion / Coffee Break

11:30 → 12:30 Collider phenomenology

Convener: Cheng-Wei Chiang (National Taiwan University / National Center for Theoretical Sciences)

11:30 The anomalous Zbb couplings at the LHC and ep colliders

The bottom quark forward-backward asymmetry ($A_{FB}^b$) data at LEP exhibits a long-standing discrepancy with the standard model prediction. We propose a novel method to probe the $Zb\bar{b}$ interactions through $gg\to Zh$ production at the LHC, which is sensitive to the axial-vector component of the $Zb\bar{b}$ couplings. We demonstrate that the $Zh$ data collected at the 13 TeV LHC can already resolve the apparent degeneracy of the anomalous $Zb\bar{b}$ couplings implied by the LEP precision electroweak measurements, with a strong dependence on the observed distribution of the $Z$ boson transverse momentum. We also show the potential of the HL-LHC to either verify or exclude the anomalous $Zb\bar{b}$ couplings observed at LEP through measuring the $Zh$ production rate at the HL-LHC, and this conclusion is not sensitive to possible new physics contribution induced by top quark or Higgs boson anomalous couplings in the loop.

Speaker: Bin Yan (LANL)

Zbb_BY.pdf

12:00 electron proton collider for the quartic coupling between a Higgs boson pair and a vector boson pair

The measurement of the quartic coupling between a Higgs boson pair and a vector boson pair is expected to be achieved from vector-boson fusion (VBF) production of a Higgs boson pair at the LHC. However, this process involves another unmeasured parameter, the trilinear Higgs self-coupling. Since the LHC cannot avoid the gluon fusion pollution, which becomes severe for anomalous Higgs trilinear coupling, an electron-proton collider is more appropriate for the comprehensive measurement. In this regard, we study the VBF production of a Higgs boson pair in the bbbb final state at the LHeC and FCC-he. Performing detailed analysis using the simulated dataset, we devise the search strategy specialized at the LHeC and FCC-he and give a prediction for the sensitivity to both couplings. We find that the two electron-proton colliders have high potential.

Speaker: Jeonghyeon Song (Konkuk University)

12:15 Probing doubly charged scalar bosons from the doublet at the HL-LHC

In the SM, it is assumed that there is only one kind of scalar field, the isodoublet with Y=1/2. On the other hand, many models beyond the SM include extensions of the scalar potential, and some of them predict the charged scalar states. One of interesting candidates is the doubly charged scalar bosons from the isodoublet with Y=3/2. However, phenomenology of them had not been fully investigated. We have investigated how to probe them at the future HL-LHC, and we have found that it would be possible to observe the signal of the doubly charged scalars by using appropriate kinematical cuts unless their mass is too large. In this talk, I will introduce the results of our analyses. This talk is based on K. Enomoto, S. Kanemura, K. Katayama, arXiv:2102.12950[hep-ph].

Speaker: Kazuki Enomoto (Osaka University)

Enomoto_Asia-Pasific.pdf

12:30 → 14:00 Discussion / Lunch Break

14:00 → 15:15 Collider phenomenology

Convener: Mayumi Aoki (Kanazawa University)

14:00 Investigating New Physics Models with Signature of Same-Sign Diboson+\slashed{E}_{T}

We investigate the prospect of searching for new physics via the novel signature of same-sign diboson + \slashed{E}_{T} at current and future LHC. We study three new physics models: (i) natural SUSY models, (ii) type-III seesaw model and (iii) type-II seesaw/Georgi-Machacek model. In the first two class of models, this signature arises due to the presence of a singly-charged particle which has lifetime long enough to escape detection, while in the third model this signature originates resonantly from a doubly-charged particle produced along with two forward jets that, most likely, would escape detection. We analyze in great detail the discovery prospects of the signal in these three classes of models in the current as well as the upcoming runs of the LHC (such as HL-LHC and HE-LHC) by showing a distinction among these scenarios.

Speaker: Dibyashree Sengupta (National Taiwan University)

AP_ssdb.pdf

14:15 The 2-Higgs Doublet Model facing dipole moments and colliders

We analyze CP-violating effects in both electric dipole moment (EDM) measurements and future analyses at the Large Hadron Collider (LHC) assuming a two-Higgs-doublet model (2HDM) with “soft” CP violation. Our analysis of EDMs and current LHC constraints shows that, in the case of Type II and Type III 2HDMs, an O(0.1) CP-violating phase in the Yukawa interaction between H1 (the 125 GeV Higgs boson) and fermions is still allowed. For these scenarios, we study CP-violating effects in the neutron EDM and tt¯H1 production at the LHC. Our analysis shows that such an O(0.1) CP-violating phase can be easily confirmed or excluded by future neutron EDM tests, with LHC data providing a complementary cross-check.

Speaker: Adil Jueid (Konkuk University)

14:30 New physics searches at the ILC positron and electron beam dumps

We study capability of the ILC beam dump experiment to search for new physics, comparing the performance of the electron and positron beam dumps. The dark photon, axion-like particles, and light scalar bosons are considered as new physics scenarios, where all the important production mechanisms are included: electron-positron pair-annihilation, Primakoff process, and bremsstrahlung productions. We find that the ILC beam dump experiment has higher sensitivity than past beam dump experiments, with the positron beam dump having slightly better performance for new physics particles which are produced by the electron-positron pair-annihilation.

Speaker: Kento Asai (Saitama University)

Asia-Pacific-Workshop_Asai.pdf

14:45 Leptophilic gauge bosons at ILC beam dump experiment

We study the prospects of searching for leptophilic gauge bosons (LGBs) associated with a new U(1) gauge symmetries at ILC beam dump experiment. When the LGBs are light and weakly interacting, we show a significant number of signals can occur at ILC beam dump experiment and we can cover the parameter region which has not been explored yet. .

Speaker: Atsuya Niki (University of Tokyo)

asia_pacific_workshop.pptx

15:00 Search for new light vector boson using J/Ψ at BESIII and Belle II

We investigate various search strategies for light vector boson X in O(10) MeV mass range using J/Ψ associated channels at BESIII and Belle II: (i) J/Ψ → ηcX with 1010J/Ψs at BESIII, (ii) J/Ψ(ηc + X) + ℓℓ¯ production at Belle II, and (iii) J/Ψ + X with the displaced vertex in X → e+e− decay are analyzed and the future sensitivities at Belle II with 50 ab−1 luminosity are comprehensively studied. By requiring the displaced vertex to be within the beam pipe, the third method results in nearly background-free analysis, and the vector boson-electron coupling and the vector boson mass can be probed in the unprecedented range, 10−4 ≤ |εe| ≤ 10−3 and 9 MeV ≤ mX ≤ 100MeV with 50 ab−1 at Belle II. This covers the favored signal region of 8Be* anomaly recently reported by Atomki experiment with mX ≃ 17 MeV.

Speaker: Kayoung Ban (Yonsei University)

2021_APWPPC_KBan.pdf

15:15 → 15:45 Discussion / Coffee Break

15:45 → 17:00 Late-time cosmology

Convener: Yvonne Wong (The University of New South Wales)

15:45 Neutrino lifetime constraint from neutrino-majoron decay

Neutrino decay interaction with scalar majorons naturally arises from Standard Model extensions to model neutrino mass generation. The interaction if present during the CMB epoch has the potential to disrupt neutrino free streaming and hence the CMB anisotropy spectra. This has been previously studied as a cosmological constraint on neutrino lifetime. In this work, we model the decay interaction with the full collisional Boltzmann hierarchy. The result shows the lifetime constraint from neutrino decay can be relaxed by several orders of magnitude.

Speaker: Joe Zhiyu Chen (The University of New South Wales)

AP_Presentation_Chen.pdf

16:00 Easing the sigma8-tension with nu-DM interactions

The sigma8-tension of Planck data with weak lensing and redshift surveys is one of the main problems with the LambdaCDM model of cosmology. We show that the tension can be alleviated by introducing an interaction between dark matter and neutrinos. We model the interaction using a linear Boltzmann treatment, introducing a novel implementation that for the first time uses the full massive neutrino hierarchy. We also provide upper limits on the interaction cross-section between neutrinos and dark matter.

Speaker: Markus Mosbech (The University of Sydney)

Markus Mosbech Asia-Pacific Workshop.pdf

16:15 Analysing CMB Lensing with Minkowski functionals

Minkowski functionals are set of descriptors used to describe the morphological structures of a field. CMB weak lensing, a powerful probe which imprinting projective information of matter distribution in the universe all the way back to the last scattering surface. With Minkowski functionals, one can reveal much more statistical features in the CMB lensing observations and eventually tighter the constrain of cosmological parameters. In this talk, I will introduce the Minkowski functionals method, and discuss it application to CMB lensing analyzes in both numerical and analytical aspects.

Speaker: Yuqi KANG (University of New South Wealth)

16:30 Optimising the Search for Features in the Primordial Power Spectrum

Features in the CMB data have been discussed for a long time without striking evidence for or against them. Could the analysis of the data be the reason for this lack of evidence? Is there beyond LCDM physics hiding in the Planck CMB data? Applying a popular machine learning algorithm known as Bayesian Optimisation to Planck CMB can help us to find features in the data. Looking at modulations to the primordial power spectrum, I will compare the results of this novel approach to the current analysis. Further, I will talk about the future of features in the power spectrum.

Speaker: Julius Wons (The University of New South Wales)

Optimizing the Search for Features in the Primordial.pdf

16:45 Breakdown in FLRW: fact or fiction?

I will motivate why H0 tension may be indicative of a breakdown in the cosmological principle.

Speaker: Eoin Ó Colgáin (Sogang University)

Thursday, 5 August

10:00 → 11:00 Review talks: Flavour review

Convener: Natsumi Nagata (University of Tokyo)

10:00 Flavor physics theory (Tentative)

Speaker: Kei Yamamoto (Hiroshima University)

KeiYamamoto_APW21.pdf

11:00 → 11:30 Discussion / Coffee Break

11:30 → 12:15 Flavour

Convener: Cheng-Wei Chiang (National Taiwan University / National Center for Theoretical Sciences)

11:30 Symplectic modular symmetry in heterotic string vacua: flavor, CP, and R-symmetries

We examine a common origin of four-dimensional flavor, CP, and $U(1)_R$ symmetries in the context of heterotic string theory with standard embedding. We find that flavor and $U(1)_R$ symmetries are unified into the $Sp(2h+2, \mathbb{R})$ modular symmetries of Calabi-Yau threefolds with $h$ being the number of moduli fields. Together with the $\mathbb{Z}_2^{\rm CP}$ CP symmetry, they are enhanced into $GSp(2h+2, \mathbb{R})\simeq Sp(2h+2, \mathbb{R})$\rtimes $\mathbb{Z}_2^{\rm CP}$ generalized symplectic modular symmetry. We exemplify the $S_3, S_4, T^\prime, S_9$ non-Abelian flavor symmetries on explicit toroidal orbifolds with and without resolutions and $\mathbb{Z}_2,S_4$ flavor symmetries on three-parameter examples of Calabi-Yau threefolds. Thus, non-trivial flavor symmetries appear in not only the exact orbifold limit but also a certain class of Calabi-Yau threefolds. These flavor symmetries are further enlarged to non-Abelian discrete groups by the CP symmetry.

Speaker: Hajime Otsuka (KEK)

otsuka.pdf

11:45 Modular flavor symmetry of three-generation modes in magnetized orbifold models

The origin of the flavor structure of three-generational quarks and leptons is one of the most significant mysteries. Modular flavor symmetry induced from the modular symmetry on a torus or some orbifolds is an attractive candidate of the origin of the flavor structure. In this talk, I will show that the modular flavor symmetry of three-generation modes on a torus orbifold with background magnetic flux can be identified by the magnetic flux.

Speaker: Hikaru Uchida (Hokkaido University)

Asia-Pacific Workshop_Hikaru Uchida (1).pdf

12:00 Quark-hadron duality for neutral meson mixings in the 't Hooft model

We study local quark-hadron duality and its violation for the $D^0-\bar{D}^0$, $B^0_d-\bar{B}^0_d$ and $B^0_s-\bar{B}^0_s$ mixings in the 't Hooft model, offering a laboratory to test QCD based on two-dimensional spacetime in the large-$N_c$ limit. With the 't Hooft equation being numerically solved, the width difference is calculated as an exclusive sum over two-body decays. The obtained rate is compared to inclusive one that arises from four-quark operators to check the validity of the heavy quark expansion (HQE). In view of the observation in four-dimension that the HQE prediction for the width difference in the $D^0-\bar{D}^0$ mixing is four orders of magnitude smaller than the experimental data while the measurement for the $B^0_s-\bar{B}^0_s$ mixing is in agreement with the HQE, in this work we investigate duality violation in the presence of the GIM mechanism. We show that the order of magnitude of the width difference in the $D^0-\bar{D}^0$ mixing is enhanced in the exclusive analysis relative to the inclusive counterpart, when the 4D-like phase space function is used for the inclusive analysis. By contrast, it is shown that for the $B^0_d-\bar{B}^0_d$ and $B^0_s-\bar{B}^0_s$ mixings analyzed by the most color-allowed topology, not large yet non-negligible corrections to the inclusive result emerge, which are not inconsistent with what is currently indicated in four-dimensions.

Speaker: Hiroyuki Umeeda (Academia Sinica)

Umeeda_Asia_Pacific2021.pdf

12:15 → 12:30 Formal

Convener: Cheng-Wei Chiang (National Taiwan University / National Center for Theoretical Sciences)

12:15 New effect in wave-packet scatterings of quantum fields

We find a new contribution in wave-packet scatterings, which has been overlooked in the standard formulation of S-matrix. As a concrete example, we consider a two-to-two scattering of light scalars 's' by another intermediate heavy scalar 'Phi', in the Gaussian wave-packet formalism: ss → Phi → ss. This contribution can be interpreted as an “in-time-boundary effect” of s for the corresponding Phi → ss decay, proposed by Ishikawa et al., with a newly found modification that would cure the previously observed ultraviolet divergence. If time permits, we show that such an effect can be understood as a Stokes phenomenon in an integral over complex energy plane.

Speaker: Kenji Nishiwaki (Shiv Nadar University)

Kenji_AsiaPacificWorkshop_5thAug2021.pdf

12:30 → 14:00 Discussion / Lunch Break

14:00 → 14:30 Collider phenomenology

Convener: Mayumi Aoki (Kanazawa University)

14:00 Exploring long-lived particles and its properties at colliders

Long-lived particles appear in many new physics models. Especially, the particle with decay length below 1 m can generate various displaced signatures at the colliders and such events are expected to have low background. There are huge opportunities in this lifetime parameter. In this context, we study not only the experimental reach of the LLP searches at colliders (LHC, HL-LHC, Belle II) but also how to reconstruct the event with displaced vertex and missing energy which can provide the understanding for the underlying new physics.

Speaker: Dong Woo Kang (KIAS)

APWPPPC_DWK.pdf

14:15 Time-delayed electrons from neutral currents at the LHC

We investigate long-lived particles (LLPs) produced in pair from neutral currents and decaying into a displaced electron plus two jets at the LHC, utilizing the proposed minimum ionizing particle timing detector at CMS. We study two benchmark models: the R-parity-violating supersymmetry with the lightest neutralinos and two different $U(1)$ extensions of the standard model with heavy neutral leptons (HNLs). The light neutralinos are produced from the standard model $Z$-boson decays via small Higgsino components, and the HNLs arise from decays of a heavy gauge boson, $Z'$. By simulating the signal processes at the HL-LHC with center-of-mass energy $\sqrt{s}=14$ TeV and integrated luminosity of 3 ab$^{-1}$, our analyses indicate that the search strategy based on a timing trigger and the final state kinematics has the potential to probe the parameter space that is complementary to other traditional LLP search strategies such as those based on the displaced vertex.

Speaker: Zeren Simon Wang (National Tsing Hua University (TW))

nc_timing (1).pdf

14:30 → 15:15 EWPT

Convener: Mayumi Aoki (Kanazawa University)

14:30 Electroweak phase transition triggered by fermion sector

To realize first-order electroweak phase transition, it is necessary to generate a barrier in the thermal Higgs potential, which is usually triggered by scalar degree of freedom. We instead investigate phase transition patterns in pure fermion extensions of the standard model, and find that additional fermions with mass hierarchy and mixing could develop such barrier and realize strongly first-order phase transition in such models. In the Higgs potential with polynomial parametrization, the barrier can be generated in the following two patterns: (I) positive quadratic term, negative cubic term and positive quartic term or (II) positive quadratic term, negative quartic term and positive higher dimensional term, such as dimensional 6 operator. The parameter region with first-order phase transition in this model could be tested by precision measurement of hhh coupling.

Speaker: Katsuya Hashino (Center for High Energy Physics, Peking University)

Asia-Pacific_Katsuya.pdf

14:45 Possibility of a multistep electroweak phase transition in two Higgs doublet models

In this talk, we discuss whether a multi-step electroweak phase transition (EWPT) occurs in two Higgs doublet models (2HDMs). The EWPT is related to interesting phenomena such as baryogenesis and a gravitational wave from it. We examine parameter regions in CP-conserving 2HDMs and find certain areas where the multi-step EWPTs occur. In addition, we compute the Higgs trilinear coupling in the parameter region where the multi-step EWPTs occur, which can be observed at future colliders. We also discuss a multi-peaked gravitational wave from a multi-step EWPT.

Speaker: Hiroto Shibuya (Kanazawa University)

AsiaPacific2021(Shibuya).pdf

15:00 Probing B+L violation with cosmic magnetic field observation

We numerically investigate the B + L violation process by performing three-dimensional lattice simulations of a unified scenario of first-order phase transitions and the sphaleron generation. The simulation results indicate that the Chern-Simons number changes along with the helical magnetic field production when the sphaleron decay occurs. Based on these numerical results, we then propose a novel method to probe the baryon asymmetry generation of the Universe, which is a general consequence of the electroweak sphaleron process, through the astronomical observation of corresponding helical magnetic fields.

Speaker: Ligong Bian (Chongqing University)

15:15 → 15:45 Discussion / Coffee Break

15:45 → 16:15 EWPT

Convener: Kin-ya Oda (Tokyo Woman's Christian University)

15:45 Electroweak phase transition in the Georgi-Machacek model under constraints of LHC data

The Georgi-Machacek model extends the standard model Higgs sector with one complex and one real isospin triplet scalar fields and preserves the custodial symmetry. Using the HEPfit, a Bayesian MCMC analysis package for particle physics, we scan for allowed parameter space under the constraints of Higgs productions and direct searches from LHC data, as well as various theory bounds. From the obtained parameter samples, we find that the model features only one-step electroweak phase transition at critical temperature of O(10-100) GeV that are sufficiently strong for baryogenesis.

Speaker: Cheng-Tse Sam Huang (National Taiwan University)

ELECTR~1.PDF

16:00 Electroweak phase transition in a complex singlet extension of the Standard Model with degenerate scalars

We study the feasibility of strong first-order electroweak phase transition in a degenerate-scalar scenario of a complex singlet extension of the Standard Model, in which a mass of an additional scalar is nearly degenerate with that of the Higgs boson, 125 GeV. This scenario is known to be free from strong constraints from dark matter direct detection experiments due to cancellations between two scattering amplitudes mediated by two scalars. We point out that one of the conditions for the strong first-order EWPT is incompatible with the suppression mechanism of a dark matter cross-section scattering off the nucleons. Nevertheless, we find that strong first-order EWPT is still possible in the degenerate-scalar scenario.

Speaker: Chikako Idegawa (Ochanomizu university)

Asia Pacific workshop(C.Idegawa).pdf

16:15 → 17:00 Formal

Convener: Kin-ya Oda (Tokyo Woman's Christian University)

16:15 A complete set of Lorentz-invariant wave packets and modified uncertainty relation

We define a set of fully Lorentz-invariant wave packets and show that it spans the corre- sponding one-particle Hilbert subspace, and hence the whole Fock space as well, with a manifestly Lorentz-invariant completeness relation (resolution of identity). The position- momentum uncertainty relation for this Lorentz-invariant wave packet deviates from the ordinary Heisenberg uncertainty principle, and reduces to it in the non-relativistic limit.

Speaker: WADA Juntaro (The University of Tokyo)

ForAPWPPC.key

16:30 Dynamically emergent gravity from hidden local Lorentz symmetry

Gravity can be regarded as a consequence of local Lorentz (LL) symmetry, which is essential in defining a spinor field in curved spacetime. The gravitational action may admit a zero-field limit of the metric and vierbein at a certain ultraviolet cutoff scale such that the action becomes a linear realization of the LL symmetry. Consequently, only three types of term are allowed in the four-dimensional gravitational action at the cutoff scale: a cosmological constant, a linear term of the LL field strength, and spinor kinetic terms, whose coefficients are in general arbitrary functions of LL and diffeomorphism invariants. In particular, all the kinetic terms are prohibited except for spinor fields, and hence the other fields are auxiliary. Their kinetic terms, including those of the LL gauge field and the vierbein, are induced by spinor loops simultaneously with the LL gauge field mass. The LL symmetry is necessarily broken spontaneously and hence is nothing but a hidden local symmetry, from which gravity is emergent.

Speaker: Masatoshi Yamada (Heidelberg University)

Masatoshi Yamada.pdf

19:00 → 21:00 Farewell reception

Gather-town

Friday, 6 August

10:00 → 10:30 Formal

Convener: Ryuichiro Kitano (KEK)

10:00 Missing final state puzzle in monopole-fermion scattering

It has been known that when a charged fermion scatters off a monopole, the fermion in the s-wave component must flip its chirality. Because of this feature, if there are two or more flavors of massless fermions, any superposition of the fermion states cannot be the final state of the s-wave scattering as it is forbidden by conservation of the electric and flavor charges. The unitary evolution of the state vector, on the other hand, requires some interpretation of the final states. We solve this puzzle by finding new particle excitations in the monopole background, where multi-fermion operators exhibit condensation. The particles are described as excitations of closed-string configurations of the condensates.

Speaker: Ryutaro Matsudo (KEK Theory Center)

slide.pdf

10:30 → 11:00 Multimessenger and astrophysics probes of dark matter 1

Convener: Ryuichiro Kitano (KEK)

10:30 Light Dark Matter Scattering in Gravitational Wave Detectors

We present prospects for discovering dark matter scattering in gravitational wave detectors. The focus of this work is on light, particle dark matter with masses below 1 GeV/c2. We investigate how a potential signal compares to typical backgrounds like thermal and quantum noise, first in a simple toy model and then using KAGRA as a realistic example. That shows that for a discovery much lighter and cooler mirrors would be needed. We also give some brief comments on space-based experiments and future atomic interferometers.

Speaker: Chun-Hao Lee (National Tsing Hua University)

CHLee_Asia-Pacific-Workshop.pdf

10:45 Gravitational wave signals of dark matter freeze-out

We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

Speaker: Po-Yen Tseng (Yonsei University)

talk.pdf

11:00 → 11:30 Discussion / Coffee Break

11:30 → 12:00 Multimessenger and astrophysics probes of dark matter 1

Convener: Jong-Chul Park (Chungnam National University)

11:30 Black hole quasinormal modes in GR and beyond

Quasinormal modes (QNMs) of perturbed black holes have recently gained much interest because of their tight relations with the gravitational wave signals emitted during the post-merger phase of a binary black hole coalescence. One of the intriguing features of these modes is that they respect the no-hair theorem, and hence, they can be used to test black hole spacetimes and the underlying gravitational theory. In this talk, I will exhibit three different aspects of how black hole QNMs could be altered in theories beyond Einstein’s general relativity (GR). These aspects are (i) the direct alterations of QNM spectra as compared with those in GR, (ii) the violation of the geometric correspondence between the high-frequency QNMs and the photon geodesics around the black hole, and (iii) the breaking of the isospectrality between the axial and polar gravitational perturbations. Several examples will be provided in each individual case.

Speaker: Che-Yu Chen (Institute of Physics, Academia Sinica)

2021APPPC.pdf

11:45 Mergers as a Probe of Particle Dark Matter

Unusual masses of the black holes being discovered by gravitational wave experiments pose fundamental questions about the origin of these black holes. More interestingly, black holes with masses smaller than the Chandrasekhar limit (~1.4 solar mass)? are essentially impossible to produce through any standard stellar evolution. Black holes of primordial origin, with fine-tuned parameters and with no well-established formation mechanisms, are the most discussed explanation of these objects. In this talk, I will discuss a simple and elegant production channel of sub-Chandrasekhar mass non-primordial black holes. Particle dark matter with no antiparticle counterpart, owing to their interaction with stellar nuclei, can catastrophically accumulate inside compact stars and eventually transmute them to sub-Chandrasekhar mass black holes. Our recent work points out several avenues to test the transmuted origin of low mass black holes, and demonstrates that binary merger rates at high redshift are distinctively different for primordial and transmuted black holes. Measurement of these binary merger rates by the imminent gravitational wave detectors can conclusively determine the origin of low mass black holes.

Speaker: Anupam Ray (Tata Institute of Fundamental Research)

TBH_Asia_Pacific.pdf

12:00 → 12:30 Multimessenger and astrophysics probes of dark matter 2

Convener: Jong-Chul Park (Chungnam National University)

12:00 Cosmological PBHs as Dark Matter

In the early universe, primordial black holes (PBHs) can no longer be described by the simple Schwarzschild metric-- we need a metric which is locally surrounded by the cosmological fluid and asymptotically FLRW. It turns out that the phenomenology of PBHs is very sensitive to the choice of such a metric. In particular, the Thakurta metric stands out as perhaps the most justifiable metric for the radiation-dominated universe. In this description, PBHs have an effective mass proportional to the cosmological scale factor. We demonstrate two very significant effects of this choice of metric for the phenomenology of PBHs as dark matter (DM) candidates. Firstly, the binary abundance bounds which tightly constrain LIGO-size PBHs as DM candidates are entirely evaded. Secondly, these PBHs are significantly hotter and so evaporate very rapidly-- we show that the smallest black hole which actually survives until today is of order 10^21 g, which fully closes the asteroid-mass window for DM candidates, which was previously totally unconstrained.

Speaker: zachary picker (university of sydney)

asia-pacific workshop 2021 (1).pdf

12:15 Low-mass primordial black holes as the dark matter candidate

Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the very early universe, are one of the earliest proposed and viable dark matter (DM) candidates. Recent studies indicate that PBHs can make up a large or even entire fraction of the present day DM density for a wide range of masses. Ultralight PBHs in the mass range of 10^{15} - 10^{17} g, emit particles through Hawking radiation, and can be probed via observations of those emitted particles in various detectors. In this talk, I will discuss how the observations of the 511 keV gamma ray line and continuum gamma-rays set some of the most stringent exclusion limits on the DM fraction of ultralight PBHs. I will also demonstrate how measurements of low-energy photons from the Galactic Center by the imminent telescopes such as AMEGO can probe the DM fraction of PBHs into a completely unexplored mass window.

Speaker: Ranjan Laha (Indian Institute of Science)

Asia-Pacific_workshop_on_particle_physics_and_cosmology_2021.pdf

12:30 → 14:00 Discussion / Lunch Break

14:00 → 14:45 Multimessenger and astrophysics probes of dark matter 1

Convener: Yong Tang (University of Chinese Academy of Sciences)

14:00 Gamma-ray line from electroweakly interactingnon-abelian spin-1 dark matter

We study gamma-ray line signatures from electroweakly interacting non-abelian spin-1 dark matter (DM). In this model, Z_2-odd spin-1 particles including DM candidate have the SU(2)_L triplet-like features, and the Sommerfeld enhancement significantly affects the annihilation processes. The spin-1 DM system has additional partial wave contributions with the higher total spin angular momentum. Consequently, our spin-1 DM predicts the larger annihilation cross sections into 2gamma/Z gamma than those for the SU(2)_L triplet spin-0/spin-1/2 DM. Our spin-1 DM also has a new annihilation mode into a photon and Z_2-even extra heavy vector. The photon energy depends on the mass of DM and the heavy vector, which provides a chance to seek the mass spectrum.We show the current bounds and the prospect sensitivity of the future gamma-ray observation.

Speaker: Motoko Fujiwara (Nagoya University)

Motoko_Fujiwara-Asia_Pacific_Workshop.pdf

14:30 A search for dark matter using sub- PeV γ-rays observed by Tibet ASγ

The discovery of diffuse sub-PeV gamma-rays by the Tibet ASγ collaboration promises to revolutionize our understanding of the high-energy astrophysical universe. It has been shown that this data broadly agrees with prior theoretical expectations. In this talk, We will discuss the impact of this discovery on a well-motivated new physics scenario: PeV-scale decaying dark matter (DM). Considering a wide range of final states in DM decay, a number of DM density profiles, and numerous astrophysical background models, we find that this data provides the most stringent limit on DM lifetime for various Standard Model final states. In particular, we find that the strongest constraints are derived for DM masses in between a few PeV to few tens of PeV. Near future data of these high-energy gamma-rays can be used to discover PeV-scale decaying DM.

Speaker: Tarak Maity (Centre for High Energy Physics, Indian Institute of Science, Bengaluru, Karnataka 560012, India)

APWorkshop-Tarak.pdf

14:45 → 15:30 Multimessenger and astrophysics probes of dark matter 3

Convener: Yong Tang (University of Chinese Academy of Sciences)

14:45 Improved Treatment of Dark Matter Capture in Neutron Stars

The capture of Dark Matter in Neutron Stars has garnered considerable interest in recent years. This interest is driven by the prospect that the energy deposited by dark matter scattering can heat these objects to infra-red temperatures, which may soon be within reach of observations. In order to obtain reliable results from these searches, proper incorporation of the physics of Neutron stars into the capture process is necessary. Key among these are gravitational focusing, relativistic kinematics, Pauli blocking, and multiple scattering. Additionally, we incorporate the internal structure of the Neutron star through the adoption of an equation of state coupled to the Tolman-Oppenheimer-Volkoff equations. In the case of hadronic targets, we must also account for strong interactions of the targets, which induce an effective mass, and that the momentum transfer is sufficiently large that hadrons cannot be treated as pointlike objects. Accounting for these effects allows us to project sensitivities for dark matter-lepton and nucleon cross sections using dimension-6 effective operators. In many cases, limits are potentially stronger than those obtained from direct detection searches.

Speaker: Michael Virgato (The University of Melbourne)

2021_APWPPC_MV.pptx

15:00 Exploring dark sector parameters in light of neutron star temperatures

Neutron star (NS) as the dark matter (DM) probe has gained a broad attention recently, either from heating due to DM annihilation or its stability under the presence of DM. In this work, we investigate spin-$1/2$ fermionic DM $\chi$ charged under the $U(1)_{X}$ in the dark sector. The massive gauge boson $V$ of $U(1)_{X}$ gauge group can be produced in NS via DM annihilation. The produced gauge boson can decay into Standard Model (SM) particles before it exits NS, despite its tiny couplings to SM particles. Thus, we perform a systematic study on $\chi\bar{\chi}\to2V\to4{\rm SM}$ as a new heating mechanism for NS in addition to $\chi\bar{\chi}\to2{\rm SM}$ and kinetic heating from DM-baryon scattering. The self-trapping due to $\chi V$ scattering is also considered. We assume the general framework that both kinetic and mass mixing terms between $V$ and SM gauge bosons are present. This allows both vector and axial-vector couplings between $V$ and SM fermions even for $m_V\ll m_Z$. Notably, the contribution from axial-vector coupling is not negligible when particles scatter relativistically. We point out that the above approaches to DM-induced NS heating are not yet adopted in recent analyses. Detectabilities of the aforementioned effects to the NS surface temperature by the future telescopes are discussed as well.

Speaker: Yen-Hsun Lin (Institute of Physics, Academia Sincia)

asia_pacific.pdf

15:15 Dark Matter Capture in White Dwarfs

We discuss the capture of dark matter in white dwarfs (WD), the most abundant stellar remnants, as complimentary to terrestrial searches. We consider the capture of DM due to interactions with either ion or the degenerate electron component of WDs. For the discussion of the capture rate we account for the stellar structure, the star opacity, realistic nuclear form factors and temperature effects. In the case of ions we use a Maxwell Boltzmann distribution while for the degenerated electrons, we require a formalism that properly incorporates Pauli blocking and a relativistic treatment for electrons. We also discuss the dark matter evaporation rate. The DM interactions can be constrained by comparing the heating rate, due to the presence of DM in the star nucleus, with observatons of cold WDs. We have calculated the capture rate and applied this technique to observed WDs in the Messier 4 (M4) globular cluster.

Speaker: Maura Ramirez-Quezada (University of Tokyo)

15:30 → 16:00 Discussion / Coffee Break

16:00 → 17:00 Review talks: GW review

Convener: Sunghoon Jung (Seoul National University)

16:00 Gravitational Waves from the Early Universe

The field of gravitational-wave astronomy has seen rapid and impressive progress since the first direct detection of gravitational waves in 2015; and yet the exciting journey has just begun. In the coming decades, gravitational waves will continue to expand their role as an indispensable tool for astrophysics and cosmology and advance to a primary probe of fundamental physics in the 21st century. In light of these prospects, this lecture will highlight some of the exciting new physics scenarios that we might be able to discover in the gravitational-wave sky, with a special focus on gravitational waves from the early Universe. Specifically, it will cover gravitational waves from cosmic inflation, first-order phase transitions, and cosmic defects. The lecture will conclude with a brief discussion of the recently announced NANOGrav signal and its possible interpretations in terms of primordial gravitational waves.

Speaker: Kai Schmitz (CERN)

17:00 → 17:15 Closing talk