Observing cosmic-ray extensive air showers with a silicon imaging detector.

Extensive air showers induced from high-energy cosmic rays provide a window into understanding the most energetic phenomena in the universe. We present a new method for observing these showers using the silicon imaging detector Subaru Hyper Suprime-Cam (HSC). This method has the advantage of being able to measure individual secondary particles. When paired with a surface detector array, silicon imaging detectors like Subaru HSC will be useful for studying the properties of extensive air showers in detail. The following report outlines the first results of observing extensive air showers with Subaru HSC. The potential for reconstructing the incident direction of primary cosmic rays is demonstrated and possible interdisciplinary applications are discussed.

Thermal Dark Matter from Freeze-Out of Inverse Decays.

We propose a new thermal dark matter candidate whose abundance is determined by the freeze-out of inverse decays. The relic abundance depends parametrically only on a decay width, while matching the observed value requires that the coupling determining the width-and the width itself-should be exponentially small. The dark matter is therefore very weakly coupled to the standard model, evading conventional searches. This inverse decay dark matter can be discovered by searching for the long-lived particle that decays into the dark matter at future planned experiments.

Resonant Self-Interacting Dark Matter from Dark QCD.

We present new models utilizing QCD-like dark sectors to resolve small-scale structure problems. These models of resonant self-interacting dark matter in a dark sector with QCD are based on analogies to the meson spectra in standard model QCD. We introduce a simple model that realizes resonant self-interaction (analogous to the ϕ-K-K system) and thermal freeze-out, in which dark mesons are made of two light quarks. We also consider asymmetric dark matter composed of heavy and light dark quarks to realize a resonant self-interaction (analogous to the ϒ(4S)-B-B system) and discuss the experimental probes of both setups. Finally, we comment on the possible resonant self-interactions already built into SIMP and ELDER mechanisms while using lattice results to determine feasibility.

Affleck-Dine Leptogenesis from Higgs Inflation.

We find that the triplet Higgs of the type-II seesaw mechanism can simultaneously generate the neutrino masses and observed baryon asymmetry while playing a role in inflation. We survey the allowed parameter space and determine that this is possible for triplet masses as low as a TeV, with a preference for a small vacuum expectation value for the triplet v_{Δ}<10 keV. This requires that the triplet Higgs must decay dominantly into the leptonic channel. Additionally, this model will be probed at the future 100 TeV collider, upcoming lepton flavor violation experiments such as Mu3e, and neutrinoless double beta decay experiments. Thus, this simple framework provides a unified solution to the three major unknowns of modern physics-inflation, the neutrino masses, and the observed baryon asymmetry-while simultaneously providing unique phenomenological predictions that will be probed terrestrially at upcoming experiments.

Some Exact Results in QCD-like Theories.

I propose a controlled approximation to QCD-like theories with massless quarks by employing supersymmetric QCD perturbed by anomaly-mediated supersymmetry breaking. They have identical massless particle contents. Thanks to the ultraviolet insensitivity of anomaly mediation, dynamics can be worked out exactly when m≪Λ, where m is the size of supersymmetry breaking and Λ the dynamical scale of the gauge theory. I demonstrate that chiral symmetry is dynamically broken for N_{f}≤3/2N_{c} while the theories lead to nontrivial infrared fixed points for larger number of flavors. While there may be a phase transition as m is increased beyond Λ, qualitative agreements with expectations in QCD are encouraging and suggest that two limits mâ‰ªΛ and mâ‰«Λ may be in the same universality class.

Demonstration of Confinement and Chiral Symmetry Breaking in SO(N_{c}) Gauge Theories.

We demonstrate that SO(N_{c}) gauge theories with matter fields in the vector representation confine due to monopole condensation and break the SU(N_{F}) chiral symmetry to SO(N_{F}) via the quark bilinear. Our results are obtained by perturbing the N=1 supersymmetric theory with anomaly-mediated supersymmetry breaking.

Testing the Seesaw Mechanism and Leptogenesis with Gravitational Waves.

We present the possibility that the seesaw mechanism with thermal leptogenesis can be tested using the stochastic gravitational background. Achieving neutrino masses consistent with atmospheric and solar neutrino data, while avoiding nonperturbative couplings, requires right handed neutrinos lighter than the typical scale of grand unification. This scale separation suggests a symmetry protecting the right-handed neutrinos from getting a mass. Thermal leptogenesis would then require that such a symmetry be broken below the reheating temperature. We enumerate all such possible symmetries consistent with these minimal assumptions and their corresponding defects, finding that in many cases, gravitational waves from the network of cosmic strings should be detectable. Estimating the predicted gravitational wave background, we find that future space-borne missions could probe the entire range relevant for thermal leptogenesis.

Finite-Size Dark Matter and its Effect on Small-Scale Structure.

If dark matter has a finite size that is larger than its Compton wavelength, the corresponding self-interaction cross section decreases with the velocity. We investigate the implications of this puffy dark matter for addressing the small-scale problems of the Λ cold dark matter model and show that the way the nonrelativistic cross section varies with the velocity is largely independent of the dark matter internal structure. Even in the presence of a light particle mediating self-interactions, we find that the finite-size effect may dominate the velocity dependence. We present an explicit example in the context of a QCD-like theory and discuss possible ways to differentiate puffy dark matter from the usual light-mediator scenarios. Particularly relevant for this are low-threshold direct-detection experiments and indirect signatures associated with the internal structure of dark matter.

Velocity Dependence from Resonant Self-Interacting Dark Matter.

The dark matter density distribution in small-scale astrophysical objects may indicate that dark matter is self-interacting, while observations from clusters of galaxies suggest that the corresponding cross section depends on the velocity. Using a model-independent approach, we show that resonant self-interacting dark matter can naturally explain such a behavior. In contrast to what is often assumed, this does not require a light mediator. We present explicit realizations of this mechanism and discuss the corresponding astrophysical constraints.

Model for Thermal Relic Dark Matter of Strongly Interacting Massive Particles.

A recent proposal is that dark matter could be a thermal relic of 3→2 scatterings in a strongly coupled hidden sector. We present explicit classes of strongly coupled gauge theories that admit this behavior. These are QCD-like theories of dynamical chiral symmetry breaking, where the pions play the role of dark matter. The number-changing 3→2 process, which sets the dark matter relic abundance, arises from the Wess-Zumino-Witten term. The theories give an explicit relationship between the 3→2 annihilation rate and the 2→2 self-scattering rate, which alters predictions for structure formation. This is a simple calculable realization of the strongly interacting massive-particle mechanism.

Noncommuting momenta of topological solitons.

We show that momentum operators of a topological soliton may not commute among themselves when the soliton is associated with the second cohomology H2 of the target space. The commutation relation is proportional to the winding number, taking a constant value within each topological sector. The noncommutativity makes it impossible to specify the momentum of a topological soliton, and induces a Magnus force.

Natural Higgs mass in supersymmetry from nondecoupling effects.

The Higgs mass implies fine-tuning for minimal theories of weak-scale supersymmetry (SUSY). Nondecoupling effects can boost the Higgs mass when new states interact with the Higgs boson, but new sources of SUSY breaking that accompany such extensions threaten naturalness. We show that two singlets with a Dirac mass can increase the Higgs mass while maintaining naturalness in the presence of large SUSY breaking in the singlet sector. We explore the modified Higgs phenomenology of this scenario, which we call the "Dirac next-to-minimal supersymmetric standard model."

Massive Nambu-Goldstone bosons.

Nicolis and Piazza have recently pointed out the existence of Nambu-Goldstone-like excitations in relativistic systems at finite density, whose gap is exactly determined by the chemical potential and the symmetry algebra. We show that the phenomenon is much more general than anticipated and demonstrate the presence of such modes in a number of systems from (anti)ferromagnets in a magnetic field to superfluid phases of quantum chromodynamics. Furthermore, we prove a counting rule for these massive Nambu-Goldstone bosons and construct a low-energy effective Lagrangian that captures their dynamics.

Redundancies in Nambu-Goldstone bosons.

We propose a simple criterion to identify when Nambu-Goldstone bosons for different symmetries are redundant. It solves an old mystery why crystals have phonons for spontaneously broken translations but no gapless excitations for equally spontaneously broken rotations. Similarly for a superfluid, the Nambu-Goldstone boson for spontaneously broken Galilean symmetry is redundant with phonons. The most nontrivial example is Tkachenko mode for a vortex lattice in a superfluid, where phonons are redundant to the Tkachenko mode which is identified as the Boboliubov mode.

Unified description of Nambu-Goldstone bosons without Lorentz invariance.

Using the effective Lagrangian approach, we clarify general issues about Nambu-Goldstone bosons without Lorentz invariance. We show how to count their number and study their dispersion relations. Their number is less than the number of broken generators when some of them form canonically conjugate pairs. The pairing occurs when the generators have a nonzero expectation value of their commutator. For non-semi-simple algebras, central extensions are possible. The underlying geometry of the coset space in general is partially symplectic.

Changes in physical function after palliative surgery for metastatic spinal tumor: association of the revised Tokuhashi score with neurologic recovery.

STUDY DESIGN: A retrospective study of patients undergoing palliative surgery for metastatic spinal tumors. OBJECTIVE: To investigate short-term functional recovery and duration of improvement after palliative surgery, to correlate these outcomes with the revised Tokuhashi score, and to examine the relationship between function and neurologic deterioration. SUMMARY OF BACKGROUND DATA: The revised Tokuhashi score is a scoring system used to predict life expectancy for patients with metastatic spinal tumors. The relationship between the revised Tokuhashi score and physical functional improvement after palliative surgery has not been examined previously. METHODS: The clinical charts of 86 patients were reviewed. The Eastern Cooperative Oncology Group Performance Status (ECOG-PS) was used to assess physical function. Each score was documented before surgery and at every month after surgery. The duration of ECOG-PS improvement, defined as the period between surgery and deterioration to the preoperative ECOG-PS grade, was correlated with the revised Tokuhashi score. RESULTS: The ECOG-PS grade improved in 44 (51.1%) patients at 1 month postoperative. When ECOG-PS improvement was found after surgery, it persisted above the preoperative level for an average of 9.3 months. At 1 month postoperative, patients scoring 0 to 8 on the total revised Tokuhashi score had significantly lower ECOG-PS improvement (26 of 55 patients) when compared to patients with higher scores (18 of 27 patients, P < 0.05). In 44 patients with ECOG-PS improvement, the existence of major internal organ metastases significantly shortened the duration of improvement (P < 0.05). CONCLUSION: Palliative surgery benefited half of the patients with metastatic spinal tumor, with a greater probability of benefit found in persons with a higher total revised Tokuhashi score (score 9-15) and/or primary cancers with longer survival times.

Gauge mediation simplified.

Gauge mediation of supersymmetry breaking is drastically simplified using generic superpotentials without U(1)R symmetry by allowing metastable vacua.

Simultaneous monitoring method of polycyclic aromatic hydrocarbons and persistent organic pollutants in the atmosphere using activated carbon fiber filter paper.

In order to simultaneously monitor the concentrations of PAHs and POPs in the atmosphere, an activated carbon fiber filter paper (ACFP) was used as the adsorbing material in this study. The pressurized liquid extraction method (PLE method) was used to extract PAHs and POPs collected on the ACFP. Toluene was an effective solvent to extract them from ACFP using the PLE method, but some of PAHs, such as benzo(a)pyrene, benzo(g,h,i)perylene, dibenzo(a,h)anthracene and indeno(1,2,3-cd)pyrene, were hardly extracted. These PAHs were adsorbed on the particulate matter in the atmosphere. In general, these forms of particulate matter could be collected using a quartz fiber paper (QFP); these PAHs were efficiently extracted from the QFP using the PLE method with toluene. In this study, the collecting method of the PAHs was modified by using QFP overlapped in front of the ACFP. Atmospheric monitoring of PAHs and POPs in Niigata area was performed using this method, and most of the target compounds were detected. However, some of the POPs, such as aldrin, endrin, mirex, could not be detected. The POPs, such as hexachlorobenzene, alpha-hexachlorocyclohexane and chlordanes, and most of the PAHs were detected from all of the samples collected throughout the monitoring period. It was confirmed that these methods were effective to simultaneously monitor the concentrations of the PAHs and POPs in the atmosphere.

How can we test the neutrino mass seesaw mechanism experimentally?

The seesaw mechanism for the small neutrino mass has been a popular paradigm, yet it has been believed that there is no way to test it experimentally. We present a conceivable outcome from future experiments that would convince us of the seesaw mechanism. It would involve data from the CERN Large Hadron Collider, International Linear Collider, cosmology, underground, and low-energy flavor experiments to establish the case.

Electroweak baryogenesis from late neutrino masses.

Electroweak baryogenesis, given a first-order phase transition, does not work in the standard model because the quark Yukawa matrices are too hierarchical. On the other hand, the neutrino mass matrix is apparently not hierarchical. In models with neutrino mass generation at low scales, the neutrino Yukawa couplings lead to large CP violation in the reflection probability of heavy leptons by the expanding Higgs bubble wall, and can generate the observed baryon asymmetry of the universe. The mechanism predicts new vectorlike leptons below the TeV scale and sizable mu --> e processes.