43rd Johns Hopkins Workshop

Kavli IPMU, Kashiwa, Japan

Kavli IPMU, Kashiwa, Japan

Kashiwa, Japan

The JHU workshops meet annually, and rotate among participating universities. Kavli IPMU will be hosting the workshop for the first time this year. The purpose of each workshop is to discuss outstanding issues in particle theory, ranging from mathematical physics to cosmology.

The theme this year focuses on the intersection of particle physics with the universe across varied fronts: from observational cosmology and astronomy to new theoretical paradigms and ‘swamplands’, and from gigantic underground particle detectors to table-top dark matter experiments.

Dates: June 3rd - 7th, 2019

Venue: Lecture Hall, Kavli IPMU, Kashiwa, Japan

Invited speakers:
Shin'ichiro Ando (U. Amsterdam)
JiJi Fan (Brown U.)
Kensuke Homma (Hiroshima U.)
Masahiro Ibe (ICRR)
Miho N. Ishigaki (Tohoku U.)
Ayuki Kamada (IBS)
Kohei Kamada (RESCEU, U. Tokyo)
David Kaplan (Johns Hopkins U.)
Ying-ying Li (Hong Kong U. of Science & Technology)
Kai Martens (Kavli IPMU)
Kazunori Nakayama (U. Tokyo)
Mihoko M. Nojiri (KEK)
Toshifumi Noumi (Kobe U.)
Serguey Petcov (SISSA)
Josh Rudermann (NYU)
Masahiro Takada (Kavli IPMU)
Neal Weiner (NYU)
Spencer Chang (U. Oregon/NTU)


Local organizers:
Shigeki Matsumoto (Kavli IPMU)
Tom Melia (Kavli IPMU)
Hitoshi Murayama (UC Berkeley/Kavli IPMU)
Satoshi Shirai (Kavli IPMU)

Organizing committee members:
◾L. Brink (Chalmers)
◾D. Seminara (Florence)
◾S. De Curtis (Florence)
◾G. Ferretti (Chalmers)
◾P. Forgacs (KFKI/RMKI)
◾M. Redi (Florence)
◾A. Hebecker (Heidelberg)
◾D. Kaplan (Johns Hopkins)
◾J. Kaplan (Johns Hopkins)
◾S. Katz (Budapest)
◾S. Kovesi-Domokos (Johns Hopkins)
◾B. Nilsson (Chalmers)
◾G. Cynolter (Budapest)
◾T. Plehn (Heidelberg)
◾C. Wetterich (Heidelberg)


Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU),
the University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba 277-8583, Japan


  • Amit Chakraborty
  • Ayuki Kamada
  • Bivudutta Mishra
  • David Kaplan
  • Enrico D. Schiappacasse
  • Francesca Borzumati
  • Fuminobu Takahashi
  • Hai-Bo Yu
  • Hajime Fukuda
  • Hitoshi Murayama
  • Ipsita Saha
  • JiJi Fan
  • Kai Martens
  • Kazunori Nakayama
  • Keisuke Inomata
  • Keita Kanno
  • Kensuke Homma
  • Kohei Kamada
  • Masahiro Ibe
  • Masahiro Takada
  • Megumi Endo
  • Michihisa Takeuchi
  • Miho Ishigaki
  • Misao Sasaki
  • Morimitsu Tanimoto
  • Peter Cox
  • Rodrigo Alonso
  • Satoshi Shirai
  • Serguey Petcov
  • Shao-Feng Ge
  • Shi Pi
  • Shigeki Matsumoto
  • Shin'ichiro Ando
  • Shingo Kazama
  • Spencer Chang
  • Sung Hak Lim
  • Taisuke Katayose
  • Takahiro Terada
  • Tobias Binder
  • Tom Melia
  • Toshifumi Noumi
  • Yingying Li
  • Yong Tang
    • 13:20 15:00
      • 13:20
        Opening 10m
      • 13:30
        Migdal Effect in Dark Matter Direct Detection Experiments and Its Applications 45m

        The elastic scattering of an atomic nucleus plays a central role in dark matter direct detection experiments. In those experiments, it is usually assumed that the atomic electrons around the nucleus of the target material immediately follow the motion of the recoil nucleus. In reality, however, it takes some time for the electrons to catch up, which results in ionization and excitation of the atoms. Those processes are called the Migdal effects. In this talk, I explain how to treat the Migdal effects in the dark matter direct detection experiments. I also explain that the Migdal effects can enhance the detectability of rather light dark matter in the GeV mass range. We also discuss a good candidates of the dark matter models with a mass in the GeV range.

        Speaker: Masahiro Ibe
      • 14:15
        Baryon Asymmetry, Chiral Asymmetry, and the Magnetic Fields in the Universe 45m

        I will talk about the nontrivial relationship among the baryon, the chiral asymmetry and the magnetic fields in the Universe. They are related through the chiral anomaly in the Standard Model, and hence the hypermagnetic fields can produce the baryon and the chiral asymmetry of the Universe and vice versa. This opens new possibilities of nontrivial phenomena in the early Universe. I will also discuss some of their observational signatures.

        Speaker: Kohei Kamada
    • 15:00 15:30
      Break 30m
    • 15:30 16:15
      • 15:30
        Dark matter in split supersymmetry: thermal wino dark matter and beyond 45m

        (Mini) split supersymmetry explains the observed Higgs mass and evades stringent constraints, while keeps good features of TeV-scale supersymmetry other than the little hierarchy problem. A compelling dark matter candidate in split supersymmetric scenarios is thermal wino dark matter whose mass is around 3 TeV. Even if wino is lighter and its thermal relic is a sub-dominant component of dark matter, non-thermal production of wino, e.g., late-time decay of gravitino, can account for the rest of dark matter. It is also possible that the rest of dark matter consists of hidden baryon whose asymmetry is produced by thermal leptogenesis at the same time as asymmetry of visible baryon. Such composite asymmetric dark matter scenarios require some entropy transfer mechanism below the composite scale. A tiny kinetic mixing term between a dark photon and the visible photon is a promising example. Split supersymmetry plays an important role to explain the origin of such a tiny kinetic mixing by realizing grand unifications in the dark and the visible sectors. We see a broad spectrum of dark matter candidates and phenomenology in split supersymmetry.

        Speaker: Ayuki Kamada
    • 10:30 11:15
      • 10:30
        Understanding halo substructure for indirect dark matter searches 45m

        It is believed that the dark matter structures were formed hierarchically through mergers and accretions of smaller structures. This means that larger dark matter halos host many smaller subhalos. Cosmological N-body simulations have been performed to probe properties of the subhalos. However, because of finite computational resources, it is not possible to resolve the subhalos all the way down to their mass spectrum (which might be on the order of the Earth mass). Here I propose analytic models of dark matter subhalos, which combine extended Press-Schechter formalism that describes the subhalo accretion history with tidal stripping processes after the accretion. I show that the models provide extremely good fits to the subhalo mass functions found in numerical simulations of various scales. I then apply the models to indirect searches for particle dark matter through self-annihilation. First, I will compute the annihilation “boost" factor due to the subhalos, i.e., overall enhancement of the annihilation rate in the host halo. Second I will predict the number of dwarf galaxies that might be discovered with future surveys such as LSST. Third, I will provide new estimates of dark matter annihilation rates in known dwarf galaxies. Lastly, I will discuss implications for Fermi unassociated sources from the Gaia searches for possibly associated dwarf galaxies.

        Speaker: Shin'ichiro Ando
    • 11:15 11:30
      Break 15m
    • 11:30 12:15
    • 12:15 13:30
      Lunch 1h 15m
    • 13:30 15:00
      • 13:30
        Direct Detection of Dark Matter and XENONnT 45m

        A brief review of the context of and general approaches to the direct
        detection of dark matter will be given. We will then focus on the
        XENONnT detector which is currently being built at LNGS in Italy and
        Japanese know-how we contribute to it. Looking at the future we will close
        by asking what will come after XENONnT.

        Speaker: Kai Martens
      • 14:15
        Latest Results from the XENON1T Dark Matter Project 15m

        The most recent results from XENON1T, the world largest direct dark matter search experiment, will be presented. XENON1T is a dual-phase xenon Time Projection Chamber (TPC) using 248 low radioactivity PMTs to detect scintillation signals in a 2-ton active liquid xenon target. Since November 2016, the XENON1T detector is continuously taking data, with a background rate of more than one order of magnitude lower than any current generation dark matter search experiment. This talk will summarize the dark matter search results of XENON1T using 278.8 days of data collected between November 2016 and February 2018.

        Speaker: Shingo Kazama
      • 14:30
        Effects of an early matter dominated era on gravitational waves induced by scalar perturbations 15m

        We revisit the effects of an early matter dominated era on gravitational waves induced by scalar perturbations. We carefully take into account the evolution of the gravitational potential, source of the gravitational waves, around the transition from an early matter dominated era to the radiation dominated era. As a result, we find that the induced gravitational waves can be suppressed or enhanced depending on the timescales of the transition. This talk will be based on our papers, arXiv:1904.12878, 1904.12879.

        Speaker: Keisuke Inomata
      • 14:45
        Bouncing Universe from Nothing 15m

        We find a class of solutions for a homogeneous and isotropic universe in which the initially expanding universe stops expanding, experiences contraction, and then expands again (the "bounce"), in the framework of Einstein gravity with a real scalar field without violating the null energy condition nor encountering any singularities. Two essential ingredients for the bouncing universe are the positive spatial curvature and the scalar potential which becomes flatter at large field values. Depending on the initial condition, either the positive curvature or the negative potential stops the cosmic expansion and begins the contraction phase. The flat potential plays a crucial role in triggering the bounce. After the bounce, the flat potential naturally allows the universe to enter the slow-roll inflation regime, thereby making the bouncing universe compatible with observations. If the e-folding of the subsequent inflation is just enough, a positive spatial curvature may be found in the future observations. Our scenario nicely fits with the creation of the universe from nothing, which leads to the homogeneous and isotropic universe with positive curvature. As a variant of the mechanism, we also find solutions representing a cyclic universe.

        Speaker: Takahiro Terada
    • 15:00 15:30
      Break 30m
    • 15:30 16:30
      • 15:30
        Accounting deep learning decision in Jet Classification 45m
        Speaker: Mihoko M. Nojiri
      • 16:15
        The role of future lepton colliders for fermionic Z-portal dark matter 15m

        We discussed about the search for Z-portal dark matter using future lepton colliders
        by analyzing mono-photon channel, and how they are effective compared to LEP experiment or
        direct detection experiments.

        Speaker: Taisuke Katayose
    • 10:30 11:15
      • 10:30
        Halometry from Astrometry 45m
        Speaker: Neal Weiner
    • 11:15 11:30
      Break 15m
    • 11:30 12:15
      • 11:30
        Neutrino Masses and Mixing: Theoretical Aspects 45m

        he phenomenology of 3-neutrino mixing, the present status of our knowledge about the 3-neutrino mixing parameters, including the absolute neutrino mass scale, and of the Dirac and Majorana CP violation in the lepton sector, are summarised. The current theoretical ideas about the origins i) of neutrino masses and of the enormous disparity between their values and the values of the charged lepton and quark masses, and ii) of the pattern of neutrino mixing revealed by the neutrino oscillation experiments, are reviewed, with the non-Abelian discrete symmetry approach considered in somewhat greater detail. The possibilities to test these idea are also briefly discussed.

        Speaker: Serguey Petcov
    • 12:15 12:30
      Group Photo 15m
    • 12:30 13:30
      Lunch 1h
    • 13:30 15:00
      • 13:30
        Perspective to search for dark components in the Universe with coherent photon collisions 45m

        We will discuss possibilities to directly produce sub-eV to keV pseudo Nambu-Goldstone bosons with stimulated photon-photon collider experiments. Especially, we focus on whether we can reach gravitationally weak coupling domains in laboratory experiments so that the probed pNGBs can be natural candidates for dark components in the Universe.

        Speaker: Kensuke Homma
      • 14:15
        An inflationary probe of cosmic Higgs switching 45m

        While the Higgs mass is fixed today, it is possible that the Higgs mass is dynamical and varied with time in the early Universe. In particular, there is an intriguing possibility that if the Higgs field couples to some oscillating scalar (e.g., a modulus) in the early Universe, the Higgs oscillated between symmetry preserving and broken phases. I will discuss one possible cosmological (inflationary) probe of this type of phase oscillation. If the Higgs couples to the inflaton, the phase oscillations could imprint on the primordial spectrum, resulting in novel “k-wavepacket" features. I will explain the origin of the wavepacket feature and briefly discuss a potential observable through measuring fine structures in the CMB temperature spectrum.

        Speaker: JiJi Fan
    • 15:00 15:30
      Break 30m
    • 15:30 16:45
      • 15:30
        Anatomy of the tthh Physics 45m

        I will talk about a comprehensive analysis on the tthh physics at colliders. This channel can be applied to detect Higgs self-couplings and hence probe for the nature of electroweak phase transition. It is also an important channel to search for heavy resonances in neutral naturalness models, e.g. Turtle Twin Higgs model, and constrain the scale of new physics from an EFT perspective.

        Speaker: Ying-ying Li
      • 16:15
        Dark Matter Sommerfeld enhanced annihilation and bound-state decay at finite temperature 15m

        Long-range interactions can lead to the existence of meta-stable bound-state solutions in the spectrum of WIMPs. During the last decade, it has been shown that the formation and subsequent decay of these bound states into SM particles gives a significant effect in the relic density computation, typically allowing for heavier DM masses. In this talk, I present some recent progress made in how to describe the chemical evolution of such systems beyond the Boltzmann framework, including environmental effects like charge screening and Landau damping. The latter two collective phenomena could lead to a melting or disappearance of the bound-state solutions, giving rise to non-trivial corrections in the relic density computation.

        Speaker: Tobias Binder
      • 16:30
        Higgs data does not rule out a sequential fourth generation fermion 15m
        Speaker: Ipsita Saha
    • 10:30 11:15
      • 10:30
        The effects of contamination on the estimation of dark matter annihilation profile of the Milky Way's dwarf spheroidal galaxies 45m

        I will present our collaborative effort to obtain a robust constraint on the expected gamma-ray flux from dark matter annihilation events in the Milky Way's dwarf spheroidal satellite galaxies. We have built a new statistical method to take into account the effects of contaminating foreground stars to the estimate of dark matter profile based on stellar kinematic measurements. The results of testing our method using mock stellar samples and the future prospects with the Prime Focus Spectrograph on the Subaru Telescope will be presented.

        Speaker: Miho N. Ishigaki
    • 11:15 11:30
      Break 15m
    • 11:30 12:15
      • 11:30
        Gravitational particle production and dark matter 45m

        In the purely gravitational dark matter scenario, the dark matter particle does not have any interaction except for gravitational one. We study the gravitational particle production of dark matter particle in such a minimal setup and show that correct amount of dark matter can be produced depending on the inflation model and the dark matter mass. In particular, we carefully evaluate the particle production rate from the transition epoch to the inflaton oscillation epoch in a realistic inflation model and point out that the gravitational particle production is efficient even if dark matter mass is much larger than the Hubble scale during inflation as long as it is smaller than the inflaton mass.

        Speaker: Kazunori Nakayama
    • 12:15 13:30
      Lunch 1h 15m
    • 13:30 15:00
      • 13:30
        Weak Gravity Conjecture and Phenomenological Implications 45m

        The Weak Gravity Conjecture, motivated by string theory and black hole thought experiments, states that gravity is the weakest force. In particular, it claims that there exist theoretical bounds on the charge-to-mass ratio and the axion decay constant in quantum gravity, which provides theoretical constraints on models of inflation and dark matter for example. In this talk, I will first review the Weak Gravity Conjecture and its phenomenological implications. I will then introduce our recent work providing its strong evidence based on unitarity and causality.

        Speaker: Toshifumi Noumi
      • 14:15
        Unitarity Violation of Nonstandard Higgs Couplings 45m

        In this talk, I will discuss the link between nonstandard Higgs coupling and unitarity violation. This motivates a correlated effort at the LHC and future colliders between Higgs coupling measurements, searches for processes that grow at high energy, and new resonances. Calculations of the unitarity violating bounds help to identify the interesting collider channels and give upper bounds on the masses of the new resonances.

        Speaker: Spencer Chang
    • 15:00 15:30
      Break 30m
    • 15:30 16:30
      • 15:30
        Anthropic Bound on Dark Radiation 15m

        I will derive an anthropic bound on dark radiation based on the same argument adopted by S. Weinberg to derive the anthropic bound on the cosmological constant.

        Speaker: Fuminobu Takahashi
      • 15:45
        QCD Axion Stars in Cosmology and Astrophysics 15m

        In this talk I discuss QCD axion stars making emphasis on their stability and astrophysical properties. First, I cover the study of Bose-Einstein condensates of axion dark matter. I explain that these condensates form spatially localized clumps. I analyze both the ground state and higher eigenstates coming from finite angular momentum. I also discuss the possibility of these clumps undergo parametric resonance into electromagnetic waves. Then I move to boson stars comprised of a generic scalar dark matter. I analyze the effect of repulsive and/or attractive terms in the self-interacting potential over star parameters and observational outputs.

        Speaker: Enrico D. Schiappacasse
      • 16:00
        The Dark Matter-Phonon Coupling 15m
        Speaker: Peter Cox
      • 16:15
        Gravitational waves induced by non-Gaussian scalar perturbations 15m

        In this talk I will introduce our recent work on the secondary gravitational waves induced by non-Gaussian scalar perturbations with their connection to the primordial black holes which may be candidates for dark matter, and also discuss the possible detectability of such GWs on LISA-like detectors.

        Speaker: Shi Pi
    • 10:30 11:15
      • 10:30
        Dark Matter Targets with Exponentially Small Couplings 45m
        Speaker: Josh Ruderman
    • 11:15 11:30
      Break 15m
    • 11:30 12:30
      • 11:30
        Classical Firewalls in General Relativity 45m

        We construct spherically symmetric solutions in GR with a thin shell of matter approaching Planckian densities. We show such constructions can replace the interior of charged (and potentially rotating) black holes by replacing the inner Cauchy horizon with a singular surface. We also show a shell can be placed a Planck distance away from the outer horizon of a Schwarzschild (or charged) black hole. Such a surface would appear to have enough degrees of freedom to give the expected entropy of a black hole. We speculate how 'normal' black holes could evolve into this state.

        Speaker: David Kaplan
      • 12:15
        Closing 15m