研究者業績
基本情報
- 所属
- 千葉大学 大学院理学研究院物理学研究部門素粒子宇宙物理学講座 准教授名古屋大学 素粒子宇宙起源研究所 客員研究員
- 学位
- 博士（理学）(2015年3月 東京大学)
- 連絡先
- kitahara
chiba-u.jp - ORCID ID
https://orcid.org/0000-0002-4847-9511- J-GLOBAL ID
- 201701005824905218
- researchmap会員ID
- B000270613
- 外部リンク
経歴
8-
2024年2月 - 現在
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2023年8月 - 現在
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2023年6月 - 2024年2月
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2018年10月 - 2023年5月
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2022年4月 - 2023年3月
学歴
4-
2012年4月 - 2015年3月
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2010年4月 - 2012年3月
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2006年4月 - 2010年3月
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2003年4月 - 2006年3月
委員歴
3-
2024年12月 - 現在
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2023年5月 - 現在
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2021年10月 - 2024年1月
受賞
4-
2022年3月
論文
53-
Physical Review D 110(7) 2024年10月11日 査読有りThe measurements of the lepton flavor universality (LFU) in B(B¯→D(*)lν¯) indicate a significant deviation from the standard model prediction at a 3–4σ level, revealing a violation of the LFU (RD(*) anomaly). It is known that the RD(*) anomaly can be easily accommodated by an SU(2)L-singlet vector leptoquark (LQ) coupled primarily to third-generation fermions, whose existence is further motivated by a partial gauge unification. In general, such a LQ naturally leads to additional CP-violating phases in the LQ interactions. In this paper, we point out that the current RD(*) anomaly prefers the CP-violating interaction although B(B¯→D(*)lν¯) are CP-conserving observables. The CP-violating LQ predicts a substantial size of the bottom-quark electric dipole moment (EDM), the chromo-EDM, and also the tau-lepton EDM. Eventually at low energy, the nucleon and electron EDMs are radiatively induced. Therefore, we conclude that the RD(*) anomaly with the SU(2)L-singlet vector LQ provides unique predictions: neutron and proton EDMs with opposite signs and a magnitude of O(10−27) e cm, and suppressed electron EDM. Furthermore, we show that a similar EDM pattern is predicted in an SU(2)L-doublet scalar LQ scenario that can accommodate the RD(*) anomaly as well. These EDM signals could serve as crucial indicators in future experiments. Published by the American Physical Society 2024
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Physical Review D 110(7) 2024年10月9日 査読有りRecently, several new experimental results of the test of lepton flavor universality (LFU) in B→D(*) semileptonic decays were announced: the first result of RD from the LHCb run 1 data, the first results of RD and RD* from the LHCb run 2 data, and the first result of RD* from the Belle II collaboration. Including these new data, a global analysis still prefers the violation of the LFU between the tau and light leptons. A new world average of the data from the , LHCb, Belle, and Belle II collaborations is RD=0.342±0.026 and RD*=0.287±0.012. Including this new data, we update a circumstance of the b→cτν¯ measurements and their implications for new physics (NP). Incorporating recent developments for the B→D(*) form factors in the Standard Model, we observe a 4.4σ deviation from the Standard Model prediction. Our updates also include model-independent NP formulas for the related observables and the global fittings of parameters for leptoquark scenarios as well as single NP operator scenarios. Furthermore, we show future potential to indirectly distinguish different NP scenarios with the use of the precise measurements of the polarization observables in B→D(*)τν¯ at the Belle II and the high-pT flavored-tail searches at the LHC. We also discuss an impact on the LFU violation in ϒ→l+l−. Published by the American Physical Society 2024
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Journal of High Energy Physics 2024(2) 2024年2月26日 査読有りAbstract In this paper, we scrutinize a radiatively generated QCD θ parameter at the two-loop level based on both full analytical loop functions with the Fock-Schwinger gauge method and the effective field theory approach, using simplified models. We observe that the radiatively generated θ parameters at the low energy scale precisely match between them. It provides validity to perturbative loop calculations of the QCD θ parameter with the Fock-Schwinger gauge method. Furthermore, it is also shown that the ordinary Fujikawa method for the radiative θ parameter by using $$ \overline{\theta} $$ = −arg det $$ {\mathcal{M } }_q^{\textrm{loop } } $$ does not cover all contributions in the simplified models. But, we also find that when there is a scale hierarchy in CP-violating sector, evaluation of the Fujikawa method is numerically sufficient. As an application, we calculate the radiative θ parameter at the two-loop level in a slightly extended Nelson-Barr model, where the spontaneous CP violation occurs to solve the strong CP problem. It is found a part of the radiative θ parameters cannot be described by the Fujikawa method.
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Physical Review D 108(11) 2023年12月26日 査読有り
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Physical Review D 108(11) 2023年12月11日 査読有り
MISC
14-
International Journal of Modern Physics A 39(26n27) 2024年8月24日 査読有りIn this paper, we present the current situation of the determinations of the first-row CKM components and show the Cabibbo angle anomaly corresponding to a deficit in the first-row CKM unitarity condition at the [Formula: see text] level. In this contribution, we show two new physics interpretations: heavy vector-like quark models and a MeV scale sterile neutrino scenario. The super tau-charm facility will directly probe the other CKM unitarity conditions related to [Formula: see text].
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Journal of Physics: Conference Series 2446(1) 012009-012009 2023年2月1日 査読有りAbstract Based on recent developments in the lattice simulations and calculations of the radiative corrections to the charged-current interactions, the uncertainties for each component in the CKM matrix have been sophisticated. It is known that the first-row CKM unitarity is violated at about 3σ level, implying a 3σ level deviation from the standard model prediction. This new deviation is called Cabibbo-Angle Anomaly (CAA). These CKM components are mainly extracted from kaon, pion, and the superallowed beta decays. In this contribution, we point out that a MeV scale sterile neutrino can economically explain the CAA. We consistently investigate the sterile neutrino contributions to the kaon, pion, superallowed beta decays, and also the Fermi coupling constant.
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2022年10月19日Recently, the LHCb collaboration announced a preliminary result of the test of lepton flavor universality (LFU) in $B\to D^{(\ast)}$ semi-leptonic decays: $R_{D}^{\rm LHCb2022} = 0.441 \pm 0.089$ and $R_{D^{\ast } }^{\rm LHCb2022} = 0.281 \pm 0.030$ based on the LHC Run\,1 data. This is the first result of $R_{D}$ for the LHCb experiment, and its precision is comparable to the other $B$-factory data. Interestingly, those data prefer the violation of the LFU again. Including this new result, we update a circumstance of the $b \to c \tau \bar\nu$ measurements and their implications for new physics. A new wold average of the data by the BaBar, Belle, and LHCb collaborations is $R_{D} = 0.358 \pm 0.028$ and $R_{D^{\ast } } = 0.285 \pm 0.013$. Incorporating several recent developments of determinations of the $B \to D^{(\ast)}$ form factors in the Standard Model (SM), we observe a $4.1 \sigma$ deviation from the SM predictions. The general new physics formulae and the global fittings of the new physics parameters are also updated. Furthermore, precise measurements of the polarization observables in the $B\to D^{(\ast)}$ semi-leptonic decays at the Belle~II experiment, and the high-$p_{\rm T}$ flavored-tail searches at the LHC experiment will be able to indirectly distinguish different new physics models. We also discuss the LFU violation in $\Upsilon \to l^+ l^-$.
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2022年9月27日This is the Snowmass2021 Energy Frontier (EF) Beyond the Standard Model (BSM) report. It combines the EF topical group reports of EF08 (Model-specific explorations), EF09 (More general explorations), and EF10 (Dark Matter at Colliders). The report includes a general introduction to BSM motivations and the comparative prospects for proposed future experiments for a broad range of potential BSM models and signatures, including compositeness, SUSY, leptoquarks, more general new bosons and fermions, long-lived particles, dark matter, charged-lepton flavor violation, and anomaly detection.
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2022年9月21日The wealth of experimental data collected at laboratory experiments suggests that there is some scale separation between the Standard Model (SM) and phenomena beyond the SM (BSM). New phenomena can manifest itself as small corrections to SM predictions, or as signals in processes where the SM predictions vanish or are exceedingly small. This makes precise calculations of the SM expectations essential, in order to maximize the sensitivity of current and forthcoming experiments to BSM physics. This topical group report highlights some past and forthcoming theory developments critical for maximizing the sensitivity of the experimental program to understanding Nature at the shortest distances.
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2022年3月15日The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.
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2022年3月14日Once all the sleptons as well as the Bino are observed at the ILC, the Bino contribution to the muon anomalous magnetic dipole moment (muon $g-2$) in supersymmetric (SUSY) models can be reconstructed. Motivated by the recently confirmed muon $g-2$ anomaly, we examine the reconstruction accuracy at the ILC with $\sqrt{s}$ = 500 GeV. For this purpose, measurements of stau parameters are important. We quantitatively study the determination of the mass and mixing parameters of the staus at the ILC. Furthermore, we discuss the implication of the stau study to the reconstruction of the SUSY contribution to muon $g-2$. At the benchmark point of our choice, it is found that the uncertainty can be $\sim 8\%$ with the stau study at the ILC.
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2022年3月13日In this contribution to the Snowmass 2021 process we review theoretical developments in the Standard Model Effective Field Theory (SMEFT) with a focus on effects at the dimension-8 level and beyond. We review the theoretical advances that led to the complete construction of the operator bases for the dimension-8 and dimension-9 SMEFT Lagrangians. We discuss the possibility of obtaining all-orders results in the $1/\Lambda$ expansion for certain SMEFT observables, and briefly present the on-shell approach to constructing SMEFT amplitudes. Finally we present several new phenomenological effects that first arise at dimension-8 and discuss the impact of these terms on experimental analyses.
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Proceedings of XIV International Conference on Heavy Quarks and Leptons — PoS(HQL2018) 2018年 査読有り
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2017年5月15日 査読有りRecent calculations have pointed to a 2.8 $\sigma$ tension between data on $\epsilon^{\prime}_K / \epsilon_K$ and the standard-model (SM) prediction. Several new physics (NP) models can explain this discrepancy, and such NP models are likely to predict deviations of $\mathcal{B}(K\to \pi \nu \overline{\nu})$ from the SM predictions, which can be probed precisely in the near future by NA62 and KOTO experiments. We present correlations between $\epsilon^{\prime}_K / \epsilon_K$ and $\mathcal{B}(K\to \pi \nu \overline{\nu})$ in two types of NP scenarios: a box dominated scenario and a $Z$-penguin dominated one. It is shown that different correlations are predicted and the future precision measurements of $K \to \pi \nu \overline{\nu}$ can distinguish both scenarios.
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Proceedings of 38th International Conference on High Energy Physics — PoS(ICHEP2016) 2017年2月 査読有り
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Journal of Physics: Conference Series 800 012019 2017年 査読有り
書籍等出版物
3講演・口頭発表等
91担当経験のある科目(授業)
8共同研究・競争的資金等の研究課題
4-
日本学術振興会 科学研究費助成事業 2024年7月 - 2026年3月
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日本学術振興会 科学研究費助成事業 若手研究 2019年4月 - 2023年3月
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Pursuit of CP-violating physics beyond the Standard Model through precision flavor physics (decline)National Natural Science Foundation of China National Natural Science Fund
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The Lady Davis Foundation
学術貢献活動
6-
企画立案・運営等University of Santiago de Compostela 2023年9月
社会貢献活動
2メディア報道
9-
KIT, Elementary Particle and Astroparticle Physics Center (KCETA) News 2024年1月 インターネットメディア