青木秀夫, 東大理学系・産総研
[理論センター・構造物性研究センター共催セミナー] 超伝導の最近の進展
4号館1F セミナーホール 最近でも様々に発展している超伝導をoverviewする。先ず物質としては、高温超伝導銅酸化物は、最近高圧下でゼロ抵抗として観測されたようにTcは150Kを超えるが、相図については未だに混沌としている。鉄系超伝導は様々なファミリーがあり、100K程度のTcをもつ単原子層も報告されており、多彩な相図が議論されている。軽元素系超伝導体では、硫化水素において最近超高圧下でTcが200Kを超えたが、従来型超伝導とされる。
最近でも様々に発展している超伝導をoverviewする。先ず物質としては、高温超伝導銅酸化物は、最近高圧下でゼロ抵抗として観測されたようにTcは150Kを超えるが、相図については未だに混沌としている。鉄系超伝導は様々なファミリーがあり、100K程度のTcをもつ単原子層も報告されており、多彩な相図が議論されている。軽元素系超伝導体では、硫化水素において最近超高圧下でTcが200Kを超えたが、従来型超伝導とされる。
グラフェンでも超伝導が観測されている。非平衡（レーザー照射下）では10 ps程度では室温超伝導も報告されている。
理論としては、電子間多体相互作用による非従来型超伝導という描像はおおむね確立しているが、電子相関をより正しく扱う方法論の開発もふくめて、進展が続いている。トポロジカル超伝導、ボソン交換機構を超えた機構、非平衡超伝導機構などのエキゾチックな超伝導についても触れる。
Roberto Franceschini, CERN
What is X(750)? and what to do with that?
Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
In this talk I will review the experimental results about hints of significant deviation from SM predictions in the diphoton mass spectrum. I will also discuss the interpretation of this putative signal in relation to other searches for new phenomena carried out at the LHC. After this phenomenological characterization, I will motivate how new strong interactions at the TeV scale are a leading candidate to explain the putative signal and I will discuss a few examples of Goldstone bosons and related degrees of freedom that can account for the putative signal. Furthermore I will discuss key observations to be carried out in the future to test the nature of the theory behind the putative signal, *e.g.* the CP parity of the new states and their pair production.
Vladimir Gudkov, University of South Carolina
Time-Reversal Invariance Violation in Neutron Nuclei Interactions
Meeting room 1, Kenkyu honkan 1F
Time Reversal Invariance Violating (TRIV) effects in neutron transmission through a nuclei target are discussed. We explore the possibility to search TRI violation using two important advantages of neutron nuclei interactions: the possibility of the enhancement of TRIV observables by many orders of magnitude, and the relatively large number of the nuclear targets, which provides the assurance of avoiding possible “accidental” cancelations of TRIV effects due to unknown structural factors related to the strong interactions. The absence of final state interactions for the set of specific observables makes these neutron experiments complementary to electric dipole moment (EDM) measurements. The comparison of expected results in neutron scattering at new high flux Spallation Neutron Sources with the existing limits on neutron, nuclear and atomic electric dipole moments (EDMs) shows that TRIV observables in neutron scattering can essentially improve the current limits on the TRIV interactions.
Masatoshi Yamada, Kanazawa University
Non-perturbatively renormalizable quantum gravity and hierarchy problem
Meeting room 1, Kenkyu honkan 1F
We discuss the possibility of the non-perturbatively renormalizable quantum gravity which is called asymptotically safe gravity. The functional renormalization group method is used to analyze the system. I first review the basic ideas of the asymptotically safe gravity and the functional renormalization group. After that, we consider the asymptotic safety scenarios of the scalar-gravity system and the Higgs-Yukawa one coupled to quantum gravity. It is shown that the fermionic fluctuation makes the scalar mass and non-minimal coupling irrelevant. With this in mind, we discuss the hierarchy problem and the possibility of large non-minimal coupling.
Yuki Yokokura, RIKEN
Thermodynamic entropy as a Noether invariant (in Japanese)
Seminar room, Kenkyu honkan 3F We study a classical many-particle system with an external control represented by a time-dependent extensive parameter in a Lagrangian. We show that thermodynamic entropy of the system is uniquely characterized as the Noether invariant associated with a symmetry for an infinitesimal non-uniform time translation $t\to t+\eta\hbar \beta$, where $\eta$ is a small parameter, $\hbar$ is the Planck constant, $\beta$ is the inverse temperature that depends on the energy and control parameter, and trajectories in the phase space are restricted to those consistent with quasi-static processes in thermodynamics.
We study a classical many-particle system with an external control represented by a time-dependent extensive parameter in a Lagrangian. We show that thermodynamic entropy of the system is uniquely characterized as the Noether invariant associated with a symmetry for an infinitesimal non-uniform time translation $t\to t+\eta\hbar \beta$, where $\eta$ is a small parameter, $\hbar$ is the Planck constant, $\beta$ is the inverse temperature that depends on the energy and control parameter, and trajectories in the phase space are restricted to those consistent with quasi-static processes in thermodynamics.
（References)
・Shin-ichi Sasa,Yuki Yokokura:Phys. Rev. Lett. 116, 140601 (2016)
Sukanta Dutta, SGTB Khalsa College, University of Delhi
Constraints on Anomalous Couplings from Perturbative Unitarity
Meeting Room 3, Kenkyu Honkan 1F
We perform a model independent analysis of the helicity amplitudes at high energy for all the 2 $\to$ 2 scattering processes involving gauge and Higgs bosons in the presence of anomalous $WWV, WWVV, VVH, VVHH$ ($V \equiv Z, gamma$ and $W^\pm$), $HHHH$ and $HHH$ interactions. Further, assuming all anomalous couplings to have arisen only from dimension six operators, we show that the per- turbative unitarity violation can be evaded up to $\sim$ 9 TeV corresponding to the best fit values of $f_{WW}/\Lambda^2$ and $f_{BB}/\Lambda^2$ from the combined analysis of Tevatron and LHC data.
Seng Pei Liew, Univ. of Tokyo, Hongo
Bound-state effects on dark matter phenomenology: from cosmology to the LHC
Meeting room 1, Kenkyu honkan 1F
We consider the case where dark matter is accompanied by an almost mass-degenerate colored particle. The colored particle is typically long-lived and can, in pair, form a QCD bound state which have interesting implications on cosmology and LHC physics. Bound state formation enhances the effective annihilation cross section significantly. For the stop-bino coannihilation scenario, we find that the bino dark matter mass can be as heavy as 2.5 TeV. Meanwhile, at the LHC, a 750 GeV quarkonium can accommodate the recently observed diphoton excesses. We show with explicit model building that other LHC excesses may be accommodated simultaneously in this framework.
Yuji Kato, KMI, Nagoya University
Charmed hadron spectroscopy at Belle and Belle II
Seminar room, Kenkyu honkan 3F
We know that constituent quark model works very well to describe mesons and baryons. However, we do not know “why” it works so well. In order to understand the nature of the constituent quark, the B-factory experiment is a powerful probe. Belle is an asymmetric energy e+e- collider experiment constructed to study the CP-violation in the B-meson decay to prove the Kobayashi-Maskawa theory. Unexpected bonus of the Belle is discoveries of a large number of “new hadrons” which include candidates of exotic states such as X(3872). In this talk, an overview the hadron spectroscopy at Belle and report some details on the recent studies on exotic charmonium and charmed baryons are presented. Finally, the prospect of hadron spectroscopy at the upcoming Belle II experiment is presented.
Hyungjin Kim, KAIST
Diphoton Excess and Electric Dipole Moments
Meeting room 1, Kenkyu honkan 1F
We examine the implication of the recently observed diphoton excess for the electric dipole moments of the neutron and electron. The excess can be due to a spin zero resonance which couples to photons and gluons through the loops of massive vector-like fermions. In this case, the resulting neutron electric dipole moment can be comparable to the present experimental bound if the CP-violating angle alpha in the underlying new physics is of O(10^-1). An electron EDM comparable to the present bound can be achieved through a mixing between the 750 GeV resonance and the Standard Model Higgs boson, if the mixing angle itself for an approximately pseudoscalar resonance, or the mixing angle times the CP-violating angle alpha for an approximately scalar resonance, is of O(10^-3). For the case that the 750 GeV resonance corresponds to a composite pseudo-Nambu-Goldstone boson formed by a QCD-like hypercolor dynamics confining at Lambda_HC, the resulting neutron EDM can be estimated with alpha ~ (750GeV/Lambda_HC)2theta_HC, where theta_HC is the hypercolor vacuum angle.
Masaki Yamada, Tohoku Univ
Thermalization process and DM production in the reheating era
Meeting room3, Kenkyu honkan 1F
