2011年度のセミナー

 Date/Place 12 Mar. (Mon.) 15:30〜 / H711 Yasuhiro Yamamoto (KEK) Structure of dimension-six derivative interactions in pseudo Nambu-Goldstone N Higgs doublet models(slides) We derive the general structure of dimension-six derivative interactions in the N Higgs doublet models, where Higgs fields arise as pseudo Nambu-Goldstone modes of a strongly interacting sector. We show that there are several relations among the dimension-six operators, and therefore the number of independent operators decreases compared with models on which only SU(2)_L x U(1)_Y invariance is imposed. As an explicit example, we derive scattering amplitudes of longitudinal gauge bosons and Higgs bosons at high energy on models involving two Higgs doublets, and compare them with the amplitudes in the case of one Higgs doublet.

 Date/Place 21 Feb. (Tue.) 15:30〜 / H711 Sinya Aoki (Tsukuba U) Hadron interaction in lattice QCD(slides) Progress on the potential method, recently proposed to investigate hadron interactions in lattice QCD, is introduced. The strategy to extract the potential in lattice QCD is explained in detail. The method is applied to extract $NN$ potentials, hyperon potentials and the meson-baryon potentials. A theoretical investigation is made to understand the origin of the repulsive core using the operator product expansion. Some recent extensions of the method are also discussed.

 Date/Place 7 Feb. (Tue.) 15:30〜 / H711 Hiroshi Itoyama (Osaka City U) D-term Dynamical Supersymmetry Breaking(slides) Under a few mild assumptions, N=1 supersymmetry in four dimensions is shown to be spontaneously broken in a self-consistent Hartree-Fock approximation of BCS/NJL type to one-loop off-shell, in the gauge theory specified by the gauge kinetic function and the superpotential of adjoint chiral superfields, in particular, that possesses N=2 extended supersymmetry spontaneously broken to N=1 at tree level. The N=2 gauginos receive mixed Majorana-Dirac masses and are split. We derive an explicit form of the gap equation, showing the existence of a nontrivial solution.

 Date/Place 1 Feb. (Wed.) 15:30〜 / H711 Shin-ya Kanemura (Toyama U) Seesaw with loop-Induced Dirac mass term and dark matter from $U(1)_{B-L}$ gauge symmetry breaking(slides) TeV scale models for neutrino masses, dark matter and/or the baryon asymmetry of the Universe can strongly related to physics of extended Higgs sectors. First of all, I present a short review for extended Higgs sectors and the relation to new physics beyond the standard model. Then, I present a new model, where spontaneous symmetry breaking of $U(1)_{B-L}$ at the TeV scale explains the stability of dark matter, and provides the common origin for the Dirac mass of dark matter as well as the Majorana mass of right-handed neutrinos at the tree level. They generate the one-loop induced Dirac mass of neutrinos, and consequaently the masses of neutrinos are generated at the two-loop level via the type-I seesaw mechanism.

 Date/Place 31 Jan. (Tue.) 15:30〜 / H711 Satoshi Mishima (INFN Roma) Analysis of the recent LHCb Evidence for Charming CP Violation The LHCb collaboration has recently reported evidence for direct CP violation in the difference between the CP asymmetries of the D^0 -> \pi^+ \pi^- and D^0 -> K^+ K^- decays. We analyze these CP asymmetries in the Standard Model using isospin symmetry and coupled-channel unitarity for final-state rescattering effects.

 Date/Place 24 Jan. (Tue.) 15:30〜 / H711 Kazuhiro Sakai (YITP, Kyoto U) Seiberg-Witten theories and topological string amplitudes for local 1/2 K3 (slides) The SU(2) Seiberg-Witten theories in four/five/six dimensions are realized by compactifying the string theory on Calabi-Yau threefolds with a del Pezzo four-cycle. The low-energy effective action and the BPS partition function of the gauge theories are essentially given by the topological string amplitudes for the Calabi-Yau threefolds. We develop a method of constructing these topological string amplitudes along the lines of the direct integration of the holomorphic anomaly equation, making full use of the Seiberg-Witten curve. This method enables us to study amplitudes for non-toric Calabi-Yau threefolds beyond the reach of conventional techniques. In this talk, I will explain the method and discuss the properties of the amplitudes.

 Date/Place 17 Jan. (Tue.) 15:30〜 / H711 Kenzo Ishikawa (Hokkaido U) ニュートリノの干渉・回折 [Neutrino Diffraction: Theory and Implications](slides) パイ中間子やミュー崩壊で生成されるニュートリノは 崩壊点から数１００メートル離れた地点にある測定器で観測される。 この親粒子の崩壊からニュートリノの測定までの量子力学的な過程の振幅は、両地点間の長い距離、小さな質量、相対論的な不変性、原子核との反応による測定、等のニュートリノに固有な複数の性質を反映し極めて広い空間領域で干渉・回折効果を示す。 この効果は、平面波を使う通常の計算では求められないものであり、波束による振幅で計算される。計算結果は、実験におけるニュートリノフラックス、分岐比、エネルギー分布、角度分布等のニュートリノの物理量の測定値が有意な大きさの影響を受けることを示す。また、距離やエネルギーへの依存性は、ニュートリノの質量の絶対値に依存する普遍的な形をしている。このため、干渉・回折効果より、ニュートリノの質量の絶対値が決まる可能性が出てくる。これらの理論並びに、過去のニュートリノ高エネルギー実験との比較、将来の検証の見通し等を述べる。 Neutrino produced in pion or muon decays are detected at positions of a few hundred meters away from source positions and whole processes are described by quantum mechanical wave function. Neutrino process has several unique features such as long distance between the source and observation positions, small mass,relativistic invariance, interaction with nucleus, and others. Transition -detection amplitude of the neutrino reveals an interference effect in a form of a diffraction and detection probability shows a long-distance diffraction behavior that depends upon the absolute neutrino mass. The diffraction component is added to the neutrino flux and affects various physical quantities of neutrino. Comparisons with previous neutrino experiments and a test for a confirmation of the neutrino diffraction will be discussed.

 Date/Place 10 Jan. (Tue.) 15:30〜 / H711 Tatsu Takeuchi (Virginia Tech.) Some curious consequences of the minimal length uncertainty relation(ppt file) In theories of quantum gravity, it is expected that spacetime distances smaller than the Planck length would not be resolvable. In quantum mechanical language, gravitational effects are expected to deform the uncertainty relation between position and momentum from the canonical Heisenberg form to Δx ≥ (ℏ/2)(1/Δp + βΔp), which would imply that Δx is bounded from below by Δxmin = ℏ√β. Indeed, this "minimal length uncertainty relation" has been shown to hold in perturbative string theory, which is the top candidate theory of quantum gravity. Canonical non-relativistic quantum mechanics, on the other hand, is completely oblivious of the existence of this minimal length, even though we expect it to be the infrared limit of quantum gravity (or string theory, if it is indeed the theory of everything). One way to incorporate the "minimal length" into non-relativistic quantum mechanics is to deform the commutation relation between position and momentum to [x,p]=iℏ(1+βp2). In this talk, I will discuss the consequences of this deformation on the eigenstates and eigenvalues of the harmonic oscillator hamiltonian, and present several curious puzzles that have been uncovered.

 Date @ Place (part 1) 10 Jan. (Tue.) 10:30〜12:00 @ E216/ (part 2) 10 Jan. (Tue.) 13:30〜15:00 @ H711 Tatsu Takeuchi (Virginia Tech.) [Informal Lecture] Introduction to the Analysis of Precision Electroweak Measurements (ppt file) In this talk, I will discuss how to analyze the data from precision electroweak measurements for information on yet undiscovered particles and interactions. In particular, I will explain in detail how to perform the STU-parameter analysis, and how to calculate the values of the STU-parameters for several representative models. Limitations of the method and how to overcome them will also be discussed.

 Date/Place 20 Dec. (Tue.) 15:30〜 / H711 Yu Nakayama (IPMU, Tokyo Univ.) Scale vs Conformal Invariance(ppt file) Is scale invariance equivalent to conformal invariance? I'm going to review the recent developments of the subject from field theory perspectives (connection with a-theorem, or the generalization to its chiral (1+1) dimensional theory) as well as from a holographic approach.

 Date/Place 6 Dec. (Tue.) 15:30〜 / H711 Yuki Yokokura (Kyoto Univ.) Formulation of Spacetime Thermodynamics(pdf file) Black holes can be equilibrium with the surrounding thermal bath by Hawking radiation. In the paper of Gibbons and Hawking, black hole’s entropy S = A/4 is derived from the free energy for the canonical system of a black hole, by using WKB approximation in Euclidean field theory. Then the finite statistical entropy results from a single classical black hole configuration. This may indicate that a solution of the Einstein equation corresponds to a thermodynamic state. Jacobson considered a part of any spacetime as a thermodynamic system, and showed the Einstein equation can be regarded as the equation of state for spacetime. However, his derivation is unnatural in many ways. After reviewing various definitions of entropy and black hole thermodynamics, I will review Jacobson’s discussion and point out the unnaturalness. Then I will talk about my interpretation and approach.

 Date/Place 29 Nov. (Tue.) 15:30〜 / H711 Sanefumi Moriyama (Nagoya Univ.) Summing Up All Genus Free Energy of ABJM Matrix Model(powerpoint file) Using the localization technique, the partition function of the ABJM theory, which describes parallel M2 branes, is reduced to a matrix model. We have found that, aside from the worldsheet instanton effect, the all-genus contribution of the matrix model is summed up to the Airy function. I would like to discuss the derivation, the result and the implication.

 Date/Place 22 Nov. (Tue.) 16:30〜 / H711 Masaharu Tanabashi (Nagoya Univ.) Higgs(less) confronts LHC(powerpoint file) The SM Higgs boson has escaped from its discovery at LEP and Tevatron. Also, we have not yet discovered the SM Higgs in the present data of LHC experiments. If we don't have a Higgs boson, wheat happens then? In this seminar, after a brief review on the recent status of the SM Higgs hunting in the LHC data, I plan to discuss Higgsless possibilities. I explicitly show the model can be consistent with the present data of precision EW and flavor measurements.

 Date/Place 15 Nov. (Tue.) 15:30〜 / H711 Koichi Hamaguchi (Tokyo Univ.) Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters(pdf file) We study the muon anomalous magnetic moment (muon g-2) and the Higgs boson mass in a simple extension of the minimal supersymmetric (SUSY) Standard Model with extra vector-like matters, in the frameworks of gauge mediated SUSY breaking (GMSB) models and gravity mediation (mSUGRA) models. It is shown that the deviation of the muon g-2 and a relatively heavy Higgs boson can be simultaneously explained in large tan-beta region. (i) In GMSB models, the Higgs mass can be more than 135 GeV (130 GeV) in the region where muon g-2 is consistent with the experimental value at the 2 sigma (1 sigma) level, while maintaining the perturbative coupling unification. (ii) In the case of mSUGRA models with universal soft masses, the Higgs mass can be as large as about 130 GeV when muon g-2 is consistent with the experimental value at the 2 sigma level. In both cases, the Higgs mass can be above 140 GeV if the g-2 constraint is not imposed.

 Date 8 Nov. (Tue.) [No seminar due to Camp] - - -

 Date/Place 1 Nov. (Tue.) 15:30〜 / H711 Andrey Tayduganov (LAL/LPT U. Pari) Determining the photon polarization of the $b\to s\gamma$ using the $B\to K_1(1270)\gamma\to(K\pi\pi)\gamma$ decay (pdf file) Recently the radiative $B$ decay to the strange axial-vector mesons, $B\to K_1(1270) \gamma$, has been observed with rather large rate. This process is particularly interesting as the subsequent $K_1$ decay into its three body final state allows to determine the polarization of the gamma, which is mostly left- (right-)handed for $\overline{B} (B)$ in the SM while various new physics models predict additional right- (left-)handed components. A new method is proposed to determine the polarization, exploiting the full Dalitz plot distribution, which seems to reduce strongly the statistical errors. In order to obtain a theoretical prediction for this polarization measurement, it is necessary to understand the hadronic $K_1 \to K \pi \pi$ decay channel and its uncertainties. The strong decays of the $K_1$ mesons, namely the partial wave amplitudes as well as their relative phases, are revisited in the framework of the $^3P_0$ quark-pair-creation model. Then, the result on the sensitivity of the $B\to K_1(1270) \gamma$ process to the photon polarization is presented.

 Date 25 Oct. (Tue.) 15:30〜 H711 Kohsaku Tobioka (IPMU) Degenerate BSM at the LHC(pdf file) The LHC experiment is eager to find dark matter candidatetes and new particles predicted by various new physics (BSM) models. However, any signal has not been discovered yet with 1fb^{-1} data. One possibility to hide the signal events is to have a degenerate spectrum. Since small ETmiss and soft jets are mostly produced for the spectrum, it is very difficult to find the signal and the search strategy is unestablished. In my talk, I discuss the effectiveness of the kinematical cut on MT2 in searching for the degenerate new physics models. The Minimal Universal Extra Dimension model(MUED) is taken as an example of the degenera model, and it is shown that its discovery potential is significantly improved by the MT2 cut.

 Date 18 Oct. (Tue.) 15:30〜 H711 Yoshinobu Kuramashi (Tsukuba Univ.) 1+1+1 flavor QCD+QED simulation at the physical point (pdf file) 電磁相互作用およびアップクォークとダウンクォークの質量差を取り入れた1+1+1フレーバー格子QCDシミュレーションの試みをアルゴリズム的側面も含めて紹介する。

 date 11 Oct. (Tue.) 15:30〜 H711 Mihoko N. Nojiri (KEK) Beyond the Standard Model at LHC (pdf file) New physics search at LHC and resent reserches (MUED, spin-dependency in jet distributions).

 date 4 Oct. (Tue.) 15:30〜 H711 Kazuo Hosomichi (YITP) SUSY Gauge Theories on Squashed Three-Spheres(pdf file) We study Euclidean 3D N=2 supersymmetric gauge theories on squashed three-spheres preserving isometries SU(2) x U(1) or U(1) x U(1). We show that, when a suitable background U(1) gauge field is turned on, these squashed spheres support charged Killing spinors and therefore N=2 supersymmetric gauge theories. We present the Lagrangian and supersymmetry rules for general gauge theories. The partition functions are computed using localization principle, and are expressed as integrals over Coulomb branch. For the squashed sphere with U(1) x U(1) isometry, its measure and integrand are identified with the building blocks of structure constants in Liouville or Toda conformal field theories with b different from 1.

 date 27 Sep. (Tue.) 15:30〜 H711 Hiroshi Suzuki (Riken) Numerical simulation of the N=(2,2) Landau-Ginzburg model(pdf file) The two-dimensional N=(2,2) Wess-Zumino (WZ) model with a cubic superpotential is numerically studied with a momentum-cutoff regularization that preserves supersymmetry. A numerical algorithm based on the Nicolai map is employed and the resulting configurations have no autocorrelation. This system is believed to flow to an N=(2,2) superconformal field theory (SCFT) in the infrared (IR). From a finite-size scaling of the susceptibility of the scalar field in the WZ model, we measure the scaling dimension of a (would-be) chiral primary field. We also measure the central charge in the IR region from a correlation function between conserved supercurrents. These results are consistent with the conjectured emergence of a SCFT, and at the same time demonstrate that numerical studies can be complementary to analytical investigations for this two-dimensional supersymmetric field theory.

 date 19 July (Tue.) 13:00〜 H711 Masato Minamituji (YITP) Nonminiamlly coupled hybrid inflation (pdf file) We discuss the hybrid inflation models where the inflaton or the waterfall field is nonminimally coupled to gravity. In the nonminimally coupled inflaton model, we add the $\phi^4$ term to the Jordan frame potential to realizes a flat potential in the Einstein frame. We then discuss the field dynamics and observational predictions from inflation in the large field region and around a local maximum/minimum, as well as in the vacuum region. In the model of the nonminimally coupled waterfall field, we study the conversion process of the isocurvature perturbation to the curvature perturbation during the waterfall phase. For a negative coupling large quantum backreactions suppress the isocurvature mode. On the other hand, for a positive coupling which makes the phase transition milder, the slow-roll inflation is possible also during the waterfall stage. Inflation in this phase could produce curvature perturbations with the slightly red-tilted power spectrum consistent with current observations.

 date 12 July (Tue.) 13:00〜 H711 Natsumi Nagata (Nagoya Univ.) Gluon contribution to dark matter direct detection ( pdf file ) We calculate the nucleon-dark matter elastic scattering cross section at the leading order of the strong coupling constant \alpha_s, which is relevant to the dark matter direct detection experiments. Our approach based on the effective field theory reveals that the interaction of dark matter with gluon as well as quarks yields sizable contribution to the scattering cross section, though the gluon contribution is induced at loop level. In the evaluation of the contribution, we treat separately the loop diagrams whose typical loop momentum scales are the masses of quarks and other heavier particles. Then, we have properly taken into account each contribution and completed formulae for the cross section. As an application of our formulae, we study the direct detection of pure bino and wino dark matter in the supersymmetric model, and the first Kaluza-Klein photon dark matter in the minimal universal extra dimension model. It is found that there is a substantial difference between all of the results and those in the previous works. In the wino dark matter scenario we find the cross section is smaller than the previous results by more than an order of magnitude, while the cross section of the first Kaluza-Klein photon dark matter turns out to be larger by up to a factor of ten.

 date 5 July (Tue) 13:00〜 H711 Takuya Okuda (Tokyo Univ.) Exact results for 't Hooft loops on S^4 and S^1xS^3 (pdf file) We evaluate the path integral of a general N=2 supersymmetric gauge theory on S^4 and S^1xR^3 exactly in the presence of a supersymmetric ’t Hooft loop operator. The result we find – obtained using localization techniques – captures all perturbative quantum corrections as well as non-perturbative effects due to monopoles. Our gauge theory calculations successfully confirm the predictions made for ’t Hooft loops obtained from Liouville/Toda field theory as well as the quantum Hitchin system.

 date 28 June (Tue) 13:30〜 H711 Nodoka Yamanaka (Osaka Univ.) Constraint on R-parity violating MSSM at the one-loop level from P, CP-odd 4-fermion interaction (pdf file) Minimal Supersymmetric Standard Model with R-parity violation (RPVMSSM) contributes to the P, CP-odd electron-nucleon (e-N) interaction. The P, CP-odd e-N interaction is constrained by the 199Hg EDM experimental data. It is then possible to constrain R-parity violating couplings from the 199Hg EDM data. In this talk, we analyze the contribution of the RPVMSSM to the P, CP-odd e-N interaction at the one-loop level to give constraints on RPV interactions.

 date 24 June (Fri.) 12:10〜 H711 Kazunori Hanagaki (Osaka Univ.) ヒッグスやSUSY探索の現状 (pdf file, keynote file) LHC実験の一つATLAS実験における ヒッグス粒子やSUSY事象などの探索の 現状を実験屋の視点からお話しします。

 date 14 June (Tue) 13:00〜 H711 Ryuichiro Kitano (Tohoku univ.) Supertopcolor We consider a supersymmetric QCD with soft supersymmetry breaking terms as the dynamics for the electroweak symmetry breaking. We find various advantages compared to the non-supersymmetric models, such as a natural incorporation of the dynamical top-quark mass generation (the topcolor mechanism), the existence of a boson-pair condensation (the composite Higgs fields) and a large anomalous dimension of the composite operator to cure the flavor-changing-neutral-current and the S-parameter crises of the technicolor theories. The knowledge of the weakly coupled description (the Seiberg duality) enables us to perform perturbative computations in strongly coupled theories. Working in a large flavor theory where perturbative calculations are reliable in the dual description, one can find a stable vacuum with chiral symmetry breaking. The top/bottom quarks and also the Higgsinos obtain masses through a dynamically generated superpotential.

 date 7 June (Tue) 13:00〜 H711 Kaoru Hagiwara (KEK) TBA TBA

 date 24 May (Tue) 13:00〜 H711 Alan Cornell Scaling of the Yukawa couplings, Quark flavour mixings and Higgs self-coupling in the UED model The evolution properties of the Yukawa couplings, quark mixings and Higgs self-coupling are performed for the one-loop renormalisation group equations in the Universal Extra Dimension (UED) model. It is found that the UED model has a substantial effect on the scaling of the fermion masses, including both quark and lepton sectors, however, the radiative effects on the unitarity triangle is not a sensitive test in this model. We also study the one-loop evolution of the Higgs quartic coupling and find that there are certain bounds on the extra dimension due to the singularity and vacuum stability conditions of the Higgs sector.

 date 17 May (Tue) 13:00〜 H711 Takashi Okada (YITP) Wormholes and the Cosmological Constant in the Multiverse We study the problem of the cosmological constant in the context of the multiverse in Lorentzian spacetime. This sort of argument was started from Coleman in 1989, and he argued that the Euclidean wormholes make the multiverse partition function a superposition of various values of the cosmological constant, which has a sharp peak at Λ=0. However, the implication of the Euclidean analysis to our Lorentzian spacetime is unclear. With this motivation, we analyze the quantum state of the multiverse in Lorentzian spacetime, and calculate the density matrix of our universe. Our result predicts vanishing cosmological constant in the far future.

 date 10 May (Tue) 13:00〜 H711 Tohru Eguchi (YITP) Recreational Mathematics; K3 surface and Mathieu group M24 We present some evidence for the existence of a symmetry under Mathieu group M24 in string theory compactified on K3 surface. Situation looks quite analogous to the famous monstrous moonshine relating Monster group and the modujar J function and altogether has the flavor of　 recreational mathematics.

 date 26 April (Tue) 13:00〜 H711 Hideo Kodama (KEK) Axiverse Project Recently, some people pointed out that superlight axions including QCD axions predicted by string theory produce quite rich varieties of cosmophysical (=astrophysical and cosmological) phenomena such as black hole sirens and deformation of cosmological perturbations, which can be used as a probe for the compactification and moduli stabilisation of string theory in our universe. Motivated by this, we recently started a project to pursue this possibility further by exploiting the axiverse both from the cosmophyics side and from the string phenomenology side. In this talk, I overview this Axiverse Project.

 date 19 April (Tue) 13:00〜 H711 Hisaki Hatanaka (Osaka University) Gauge-Higgs Unification in Lifshitz type Gauge Theory We discuss the gauge-Higgs unification in a framework of Lifshitz type gauge theory. We study a higher dimensional gauge theory on $R^{D-1}\times S^{1}$ in which the normal second (first) order derivative terms for scalar (fermion) fields in the action are replaced by higher order derivative ones for the direction of the extra dimension. We provide some mathematical tools to evaluate a one-loop effective potential for the zero mode of the extra component of a higher dimensional gauge field and clarify how the higher order derivative terms affect the standard form of the effective potential. Our results show that they can make the Higgs mass heavier and change its vacuum expectation value drastically. Some extensions of our framework are briefly discussed.