Seminar Information

Information

Seminars are held on Fridays at the seminar room 2-10-04 of building #2 of the faculty of science. (Access)
*Until the restriction to help prevent the spread of COVID-19 is lifted, seminars will be held on Zoom meeting.

Each seminar is normally arranged with two separate parts:
the first (morning) part is for a review, introductory or lecture-style talk,
and the second (after-lunch) part is for the main subject in a usual seminar style.

 Next Seminar

Schedule

April

• April 16, 2021
• Speaker: Afternoon(13:30~) Abstract Shih-Yen Tseng (Tokyo Univ.) Title Minimal gauged U(1)$$_{L_\mu - L_\tau}$$ model, leptogenesis, and the sign of cosmological baryon asymmetry The minimal gauged U(1)$$_{L_\mu - L_\tau}$$ model is a simple extension to the Standard Model and has a strong predictive power in the neutrino sector. In particular, the mass spectrum and couplings of the right-handed neutrinos are determined by the neutrino oscillation parameters and the neutrino Dirac Yukawa couplings, and the baryon asymmetry of the Universe can be generated through the decays of right-handed neutrinos. In this talk, I will connect the minimal gauged U(1)$$_{L_\mu - L_\tau}$$ model to the non-thermal leptogenesis scenario, where the U(1)$$_{L_\mu - L_\tau}$$-breaking field plays the role of the inflaton and the right-handed neutrinos are generated from the inflaton decays. An interesting implication to the resulting baryon asymmetry will also be discussed. [1] K. Asai, K. Hamaguchi, N. Nagata, Shih-Yen Tseng, [arXiv:2005.01039[hep-ph]] [2] K. Asai, K. Hamaguchi, N. Nagata, [arXiv:1705.00419[hep-ph]] [3] T. Araki, J. Heeck, J. Kubo, [arXiv:1203.4951[hep-ph]] [4] P.H. Frampton, S.L. Glashow, T. Yanagida, [arXiv:hep-ph/0208157[hep-ph]]

• April 23, 2021
• Speaker: Afternoon(13:30~) Abstract Shigeki Sugimoto (Kyoto Univ.) Title Anomaly of fermions with spacetime dependent mass In this talk, we discuss perturbative anomaly of fermions with spacetime dependent mass. We show that the anomaly can be written by the Chern character of a superconnection introduced by Quillen in 1985 and discuss its applications to systems with interfaces and spacetime boundaries.

May

• May 7, 2021
• Speaker: Afternoon(13:30~) Abstract Mayumi Aoki (Kanazawa Univ.) Title A hybrid seesaw model and hierarchical neutrino flavor structures based on A4 symmetry In this talk, I will discuss a hybrid seesaw model based on A4 flavor symmetry. In this model, tree-level and one-loop seesaw mechanisms predict different flavor structures in the neutrino mass matrix and generate a notable hierarchy among them. The A4 symmetry is spontaneously broken to the Z2 symmetry. A predicted dark matter will also be discussed.

• May 14, 2021
• Speaker: Afternoon(13:30~) E-Print Hikaru Uchida (Hokkaido Univ.) Title Higgs Parity and Grand Unification [1] L. J. Hall, K. Harigaya, [arXiv:1803.08119[hep-ph]] [2] L. J. Hall, K. Harigaya, [arXiv:1905.12722[hep-ph]] [3] Y. Hamada, M. Ibe, Y. Muramatsu, K. Oda, N. Yokozaki, [arXiv:2001.05235[hep-ph]]

• May 21, 2021
• Speaker: Afternoon(13:30~) Abstract Kenzo Ishikawa (Hokkaido Univ.) Title Is the cross section sufficient for the scattering? The cross section describes scattering process completely in classical physics, and is used as a standard quantity in quantum mechanics also. We ask if the scattering probability is expressed by the cross section alone. Studying the probability with a scalar product of the normalized initial and final states, we give the answer. [1] K. Ishikawa, K. Nishiwaki, K. Oda, [arXiv:2102.12032[hep-th]] [2] K. Ishikawa, K. Nishiwaki, K. Oda, [PTEP,2020,103B04] [3] K. Ishikawa, K. Oda, [PTEP,2018,123B01] [4] R. Ushioda et al, [PTEP,2020,043C01] [5] K. Ishikawa et al, [PTEP,2019,033B02] [6] K. Ishikawa, Y. Tobita, [arXiv:2104.02927[hep-ph]] [7] “Is the cross section sufficient for the scattering?” K. Ishikawa et al, [8] “Isospin anomaly in fai -> K K and psi’ ->DD” K. Ishikawa et al, [9] “レクチャー量子力学　I,II　（裳華房）　石川健三”

• May 28, 2021
• Speaker: Afternoon(13:30~) Abstract Kensuke Akita (IBS-CTPU) Title Precise Cosmic Neutrino Capture In this talk, we discuss cosmic neutrino capture experiments on tritium including sub-leading cosmological effects, such as the neutrino spectral distortions from their decoupling and neutrino clustering on our Galaxy and nearby galaxies. In particular, we first calculate the number density of the cosmic neutrino background, including such cosmological effects. After that, we precisely formulate the capture rates of cosmic neutrinos. [1] K. Akita, M. Yamaguchi, [arXiv:2005.07047[hep-ph]] [2] K. Akita, S. Hurwitz, M. Yamaguchi, [arXiv:2010.04454[hep-ph]]

June

• June 4, 2021
• Speaker: Afternoon(13:30~) Abstract Maki Takeuchi (Kobe Univ.) Title Zero-mode counting formula and zeros in orbifold compactifications We thoroughly analyze the number of independent zero modes and their zero points on the toroidal orbifold T2/ZN (N = 2, 3, 4, 6) with magnetic flux background, inspired by the Atiyah-Singer index theorem. We succeed in finding a zero mode counting formula by computing the number of zero modes and winding number, separately. Further, we confirm the formula without magnetic flux directly by deriving it from a trace formula as the index theorem. [1] M. Sakamoto, M. Takeuchi,Y. Tatsuta, [Phys. Rev. D 102 (2020) 025008] [2] M. Sakamoto, M. Takeuchi,Y. Tatsuta, [Phys. Rev. D 103 (2021) 025009]

• June 11, 2021
• Speaker: Afternoon(13:30~) Abstract Kaigo Hirao (Tokyo Univ.) Title Leptonic CP and flavor violations in SUSY SU(5) GUT with right-handed neutrinos We study leptonic CP and flavor violations in supersymmetric (SUSY) SU(5) grand unified theory (GUT) with right handed neutrinos, paying attention to the renormalization group effects on the slepton mass matrices due to the neutrino and GUT Yukawa interactions. In particular, we study in detail the impacts of the so-called Casas- Ibarra parameters on CP and flavor violating observables. The renormalization group effects induce CP and flavor violating elements of the SUSY breaking scalar mass squared matrices, which may result in sizable leptonic CP and flavor violating signals. Assuming seesaw formula for the active neutrino masses, the renormalization group effects have been often thought to be negligible as the right-handed neutrino masses become small. With the most general form of the neutrino Yukawa matrix, i.e., taking into account the Casas-Ibarra parameters, however, this is not the case. We found that the maximal possible sizes of signals of leptonic CP and flavor violating processes are found to be insensitive to the mass scale of the right-handed neutrinos and that they are as large as (or larger than) the present experimental bounds irrespective of the right-handed neutrino masses.

• June 18, 2021
• Speaker: Afternoon(13:30~) Abstract Arindam Das (Hokkaido Univ.) Title Probing the minimal U(1)X model at future electron-positron collider via the fermion pair production channel The general U(1)$$_X$$ extension of the Standard Model (SM) is a well motivated scenario which has a plenty of new physics options. Such a model is anomaly free which requires to add three generations of the SM singlet right-handed neutrinos (RHNs) which naturally generates the light neutrino masses by the seesaw mechanism.This offers interesting phenomenological aspects in the model. In addition to that the model is equipped with a beyond the SM (BSM) neutral gauge boson, $$Z'$$ which interacts with the SM and BSM particles showing a variety of new physics driven signatures. After the anomaly cancellation the U(1)$$_X$$ charge of the particles are expressed in terms of the SM Higgs doublet and the SM Higgs singlet which allows us to study the interaction of the fermions with the $$Z'$$.In this paper we investigate the pair production mechanism of the different charged through the photon, $$Z$$ and $$Z'$$ boson exchange processes at the electron-positron ($$e^-e^+$$).The angular distributions, forward-backward (A$$_{FB}$$), left-right (A$$_{LR}$$) and left-right forward-backward (A$$_{LR,FB}$$)asymmetries of the different charged fermion pair productions show substantial deviation from the SM results. [1] A. Das, P. S. Bhupal Dev, Y. Hosotani, S. Mandal, [arXiv:2104.10902[hep-ph]]

• June 25, 2021
• Speaker: Afternoon(13:00~) Abstract Takehiko Asaka (Nigata Univ.) Title The nuMSM -- the origins of neutrino masses, dark matter, and baryon asymmetry of the Universe The Standard Model extended by three right-handed neutrinos can potentially explain the origins of neutrino masses, dark matter, and baryon asymmetry of the Universe at the same time. The typical mass range of the right-handed neutrinos are within the reach of experiments and the direct (and indirect) tests of the model are possible. We explain this simple framework, called the nuMSM, and its recent developments. [1] T. Asaka, S. Blanchet, M. Shaposhnikov, [arXiv:hep-ph/0503065] [2] T. Asaka, M. Shaposhnikov, [arXiv:hep-ph/0505013] [3] T. Asaka, S. Eijima, H. Ishida, [arXiv:1606.06686 [hep-ph]] [4] T. Asaka, H. Okui, [arXiv:2012.13527 [hep-ph]]

July

• July 2, 2021
• M2 Journal club Speaker: Morning(10:30~) Koki Hoshiya (Hokkaido Univ.) Title Majorana neutrino masses deduced by D-brane instanton effects
M2 Journal club Speaker: Afternoon(13:00~) Kaito Nasu (Hokkaido Univ.) Title String phenomenology with $$T^{2n}$$ compactification

• July 9, 2021
• Speaker: Afternoon(13:30~) Abstract Shinya Kanemura (Osaka Univ.) Title Higgs as a Probe of New Physics Although a Higgs boson was discovered, the nature of the Higgs boson, the structure of the Higgs sector, the dynamics of the electroweak symmetry breaking are still unknown. They are expected to be deeply connected to the physics beyond the standard model. In addition, these properties of the Higgs sector will be thoroughly measured by current and future collider experiments such as HL-LHC and ILC, and by various flavor experiments and also by gravitational wave experiments. Therefore the Higgs physics is regarded as an important probe of new physics. In this talk, I would like to discuss various aspects of non-minimal Higgs sectors and their relationship with scenarios of new physics. In addition, we would discuss how the Higgs sector will be explored by future experiments.

• July 16, 2021
• M2 Journal club Speaker: Morning(10:30~) Akihiro Jo (Hokkaido Univ.) Title Introduction to the swampland program
M2 Journal club Speaker: Afternoon(13:00~) Yo Toda (Hokkaido Univ.) Title Extra components solutions to the Hubble tension with BBN

• July 30, 2021
• M2 Journal club Speaker: Morning(10:30~) Yuya Ogawa (Hokkaido Univ.) Title μ-term induced by D-brane instanton effect

September

• September 3, 2021
• Speaker: Afternoon(15:00~) Abstract Yutaka Sakamura (KEK) Title Time evolution of spacetime in 6D SUGRA on $$S^{2}$$ The time evolution of the background spacetime is investigated in the context of 6D SUGRA compactified on the sphere. We focus on solutions that are isotropic and homogeneous in 3D space and spherically symmetric in the compact 2D space, and are connected to the 4D FLRW universe at late times. By introducing the potential for the dilaton field, the compact space will be stabilized with a finite size. As an initial condition,we assume that the radiation is dominated in the whole 5D space. By numerical calculations, we check that the 3D space continue to expand while the radius of the sphere settles down to a finite value after the oscillation around the stabilized value. We find that the oscillation lasts for a long time after the transition from the 5D space to the 3D is completed.

October

• October 1, 2021
• M2 Journal club Speaker: Morning(10:30~) Ryota Sato (Hokkaido Univ.) Title String Compactification

• October 8, 2021
• Speaker: Afternoon(13:30~) Abstract Kei Yagyu (Osaka Univ.) Title Dark sector as origin of tiny lepton masses and new sources of $$(g-2)_{\mu}$$ We propose a mechanism where charged lepton masses are generated at loop levels such that their smallness can naturally be explained by O(1) Yukawa couplings. This scenario can also explain the muon g-2 anomaly which has been more serious by the first result by FNAL. As an important consequence, the muon Yukawa coupling can significantly deviate from its SM prediction, and it will be tested at the High-Luminosity LHC and/or ILC. My presentation is based on the paper Phys. Rev. D.103.L111302 (arXiv: 2104. 00890 [hep-ph]). [1] C. Chiang, K. Yagyu, Phys. Rev. D.103.L111302 [arXiv:2104.00890 [hep-ph]]

• October 15, 2021
• Speaker: Afternoon(13:30~) Abstract Eung Jin Chun (KIAS) Title Neutrino oscillations in dark matter Considering superlight scalar dark matter interacting with neutrinos, we analyze the dispersion relations of neutrinos distinguishing the types of neutrinos (Weyl, Majorana and Dirac), and show how the CP violating effect induced by asymmetric distribution of dark matter. Remarkably, the neutrino oscillations can occur (even for the Weyl neutrinos) due to the medium effect, and discuss observational restrictions of such a mechanism. [1] K. Y. Choi, E. J. Chun, J. Kim, [arXiv:1909.10478 [hep-ph]] [2] K. Y. Choi, E. J. Chun, J. Kim, [arXiv:2012.09474 [hep-ph]]

• October 22, 2021
• Speaker: Afternoon(13:30~) Abstract Natsumi Nagata (Tokyo Univ.) Title Toward Direct Detection of Axions In this talk, I will discuss two topics regarding the direct detection of axions produced by stellar objects. In the first part, I am going to describe, “supernovascope”, namely, a proposal for using axion helioscope to detect axions from nearby supernovae. In the second part, I will show that there was an incorrect treatment in the previous calculations of the inverse Primakoff scattering rate of axions. After fixing it, we obtain a scattering cross section that is smaller by about an order of magnitude than the previous ones. I will discuss its implications for the solar/supernova axion detection. [1] S. F. Ge, K. Hamaguchi, K. Ichimura, K. Ishidoshiro, Y. Kanazawa, Y. Kishimoto, N. Nagata, J. Zheng, JCAP 11, 059 (2020) [arXiv:2008.03924 [hep-ph]] [2] T. Abe, K. Hamaguchi, N. Nagata, Phys. Lett. B 815, 136174 (2021) [arXiv:2012.02508 [hep-ph]]

• October 29, 2021
• Speaker: Afternoon(13:30~) Abstract Hiroto Shibuya (Kanazawa Univ.) Title Possibility of multi-step electroweak phase transition in the two Higgs doublet models 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. The parameter search shows the multi-step EWPT prefers the scalar potential with the approximate Z2 symmetry and a mass hierarchy between the neutral CP-odd and CP-even extra scalar bosons mA < mH. By contrast, the multi-step EWPT whose first step is strongly first order favors a mass hierarchy mA > mH. 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. [1] M. Aoki, K. Komatsu, H. Shibuya, [arXiv:2106.03439 [hep-ph]]

November

• November 5, 2021
• Rehearsal of Journal Club Speaker: Morning(10:30~) Ryota Sato (Hokkaido Univ.) Title T-duality of closed strings
Seminar Speaker: Afternoon(13:30~) Kaoru Hagiwara (Iwate Univ.) Title Toponium production at the LHC We study reported deviations between observations and theoretical predictions associated with the production of a pair of di-leptonically decaying top quarks at the LHC, and we examine the possibility that they reflect a signal of toponium formation. We investigate the production by gluon fusion of a color-singlet spin-0 toponium $$\eta_t$$ bound state of a top and anti-top quark, that then decays di-leptonically ($$gg \rightarrow \eta_t \rightarrow \bar{\ell}\ell b \bar{b} \nu \bar{\nu}$$). We find strong correlations favoring the production of di-lepton systems featuring a small angular separation in azimuth and a small invariant mass. Although toponium production only contributes to 0.8% of the total top-quark pair-production cross section at the 13 TeV LHC, there is a possibility that it can account for observed excesses in the narrow edges of phase space. We propose a method to discover toponium formation by ‘reconstructing’ both its top and anti-top quark constituents in the di-lepton channel. [1] Benjamin Fuks, Kaoru Hagiwara, Kai Ma, Ya-Juan Zheng, Phys. Rev. D 104, 034023 (2021) [arXiv:2102.11281 [hep-ph]]

• November 12, 2021
• Speaker: Afternoon(14:00~) Abstract Kento Asai (Saitama Univ.) Title 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.

• November 19, 2021
• Speaker: Afternoon(13:30~) Abstract Kai Murai (Tokyo Univ.) Title Big Bang Nucleosynthesis constraints on sterile neutrino and lepton asymmetry of the Universe We consider the cosmological effects of sterile neutrinos with the masses of 150–450 MeV. The decay of sterile neutrinos changes the thermal history of the Universe and affects the energy density of radiation at recombination and the big bang nucleosynthesis (BBN) results. We derive severe constraints on the parameters of sterile neutrinos from the primordial abundances of helium-4 and deuterium. We also find that in a particular model the constraints can be considerably relaxed by assuming a large lepton asymmetry in the active neutrinos. In this case, the consistent parameters result in Neff ≃ 3.2–3.4 and can alleviate the Hubble tension. [1] Graciela B. Gelmini, Masahiro Kawasaki, Alexander Kusenko, Kai Murai, Volodymyr Takhistov, JCAP09(2020)051 [arXiv:2005.06721 [hep-ph]]

• November 26, 2021
• Rehearsal of Journal Club Speaker: Morning(10:30~) Yuji Takai (Hokkaido Univ.) Title Semi-Riemannian manifold and number of time-directions
Seminar Speaker: Afternoon(13:30~) Kentarou Mawatari (Iwate Univ.) Title Recent progress in simulation of collider physics I report recent progress in simulation of collider physics, especially in the FeynRules/MadGraph framework. [1] S. Frixione, B. Fuks, V. Hirschi, K. Mawatari, H. Shao, P. Sunder, M. Zaro, JHEP 1912 (2019) 008 [arXiv:1907.04898 [hep-ph]] [2] SK. Hagiwara, J. Kanzaki, K. Mawatari, Eur.Phys.J.C 80 (2020) 584 [arXiv:2003.03003 [hep-ph]]

December

• December 3, 2021
• Rehearsal of Journal Club Speaker: Morning(10:30~) Shohei Takada (Hokkaido Univ.) Title Three-generation models from superstring theory
Seminar Speaker: Afternoon(14:00~) Jun'ya Kume (Tokyo Univ.,RESCEU and Tokyo Univ.) Title Phenomenology of chiral gravitational anomaly; Gravitational Leptogenesis and Chiral Gravitational Effect Chiral gravitational anomaly, which exists within the standard model and general relativity, predicts non-trivial interplay between fermions and gravitational waves. In this talk, I introduce two phenomena in the early universe that are the consequence of this anomaly. The first one is so-called "Gravitational Leptogenesis" where primordial lepton asymmetry, which might be the origin of the observed baryon asymmetry, is produced in models of inflation generating helical primordial gravitational waves. I show the difficulties in the minimal model of GL and briefly discuss the extended models where the gauge fields are involved. The other one is "Chiral Gravitational Effect"(CGE), which takes place in the primordial plasma with chiral asymmetry. Note that such an asymmetry can be generated in well-motivated scenarios like GUT baryogenesis, axion inflation. I present how CGE modifies the dynamics of primordial gravitational waves propagating in the chiral plasma. [1] K. Kamada, J. Kume, Y. Yamada and J. Yokoyama, JCAP 01 (2020) 016 [arXiv:1911.02657 [hep-ph]] [2] K. Kamada, J. Kume and Y. Yamada, JCAP 10 (2020) 030 [arXiv:2007.08029 [hep-ph]] [3] K. Kamada, J. Kume and Y. Yamada, JHEP 05 (2021) 292 [arXiv:2104.00583 [hep-ph]]

• December 10, 2021
• Speaker: Afternoon(13:30~) Abstract Hisakazu Minakata (Tokyo Metropolitan Univ.) Title Sterile neutrino, non-unitarity etc. what is next? Sterile neutrinoが見つかったといわれてもう２０年になります。 追試にあたる実験もいろいろ行われましたが、なお決着せず、現在に至っています。最近も少し動きがありました。 この現状を短く紹介するとともに、もう少し広い視野でこれを捉え、ないし関連の現象を混合行列のユニタリー性の破れとして議論するアプローチについてお話します。文献上ではformalismでもまだ統一見解がないように見え、まだまだ未開の分野です。破れの原因が高いあるいは低いスケールにあるのか、標準模型の位相と破れの物理の位相の相関などについてなどについて紹介します。 [1] Chee Sheng Fong, Hisakazu Minakata, Hiroshi Nunokawa, [arXiv:1609.08623 [hep-ph]] [2] Chee Sheng Fong, Hisakazu Minakata, Hiroshi Nunokawa, [arXiv:1712.02798 [hep-ph]] [3] Ivan Martinez-Soler, Hisakazu Minakata, [arXiv:1806.10152 [hep-ph]] [4] Ivan Martinez-Soler, Hisakazu Minakata, [arXiv:1908.04855 [hep-ph]]

• December 17, 2021
• Seminar Speaker: Morning(10:30~) C.S. Lim (Tokyo Women's Christian Univ.) Title The strong CP problem and higher dimensional gauge theories We discuss a scenario to solve the strong CP problem in the framework of the higher dimensional gauge theory. An axion-like field $$A_y$$ has been built-in as the extra-space component of the higher dimensional gauge field. The coupling of $$A_y$$ with gluons is attributed to the radiatively induced Chern-Simons" (CS) term. The CS term is obtained in two ways: first by a concrete 1-loop calculation and next by use of the Fujikawa's method to deal with the chiral anomaly in 4D space-time. The obtained results are identical, which implies that the radiative correction to the CS term is 1-loop exact" and is also free from UV-divergence. As a novel feature of this scenario, such obtained CS term is no longer linear in the field $$A_y$$ but its periodic function. We argue how such a novel feature of this scenario causes the modification of the ordinary solutions of the strong CP problem based on the axion fields. [1] Yuki Adachi, C.S. Lim, Nobuhito Maru, [arXiv: 2108.07367 [hep-th]]
Rehearsal of Journal Club Speaker: Afternoon(13:30~) Ibuki Yamamoto (Hokkaido Univ.) Title Black Hole’s mechanics and Information Paradox

January

• January 7, 2022
• Master thesis presentation Speaker: Afternoon(13:00~) Kaito Nasu (Hokkaido Univ.) Title Magnetized $$T^4$$ and $$T^2/Z_2$$ Orbifold Models

• January 14, 2022
• Master thesis presentation Speaker: Morning(10:30~) Kouki Hoshiya (Hokkaido Univ.) Title A possibility to get the neutrino masses from String Theory Yuya Ogawa (Hokkaido Univ.) Title Yukawa Texture in magnetized model Yo Toda (Hokkaido Univ.) Title Extra components solutions to the Hubble tension with BBN

• January 21, 2022
• Master thesis presentation Speaker: Morning(10:30~) Akihiro Jo (Hokkaido Univ.) Title The two proposition for “Free Edge condition” of the String

• January 28, 2022
• Master thesis presentation(short) Speaker: Morning(10:30~) Akihiro Jo (Hokkaido Univ.) Title The two proposition for “Free Edge condition” of the String Yo Toda (Hokkaido Univ.) Title Extra components solutions to the Hubble tension with BBN Kouki Hoshiya (Hokkaido Univ.) Title A Possibility to Get the Lepton Masses from String Theory Kaito Nasu (Hokkaido Univ.) Title Magnetized $$T^4$$ and $$T^2/Z_2$$ Orbifold Models Yuya Ogawa (Hokkaido Univ.) Title Yukawa Texture in magnetized model

February

• February 8, 2022
• Seminar Speaker: Afternoon(15:00~) Takahiko Matsubara (Theory Center, Institute for Particle and Nuclear Physics, High Energy Accelerator Research Organization) Title Random Field Statistics and Cosmology

• February 18, 2022
• Seminar Speaker: Afternoon(16:00~) Yuta Orikasa (IEAP,CTU) Title Resonant Leptogenesis in B-L Model with a modular $$S_4$$ symmetry We have investigated the resonant leptogenesis scenario in the minimal B−L extended model with the B−L symmetry breaking at the TeV scale. In the model, the right amount of baryon number asymmetry can be achieved through resonant leptogenesis with right-handed neutrinos and B−L gauge boson at the TeV scale. However the resonant leptogenesis needs fine-tuned two right-handed neutrino masses. In this talk, I will show that a modular $$S_4$$ symmetry naturally realizes the resonant leptogenesis and we can achieve the right amount of baryon number in the model. [1] S.Iso, N.Okada and Y.Orikasa, Phys.Rev.D83(2011)093011 [arXiv:1011.4769 [hep-ph]] [2] N.Okada, Y.Orikasa and T.Yamada, Phys.Rev.D86(2012)076003 [arXiv:1207.1510 [hep-ph]]