Nagoya University · Physics and Astronomy
Professor Teppei Kitahara's research lab specializes in beyond-the-Standard-Model (BSM) physics, with a strong focus on flavor physics, CP violation, and the interplay between precision flavor observables and new physics. The lab investigates anomalies in kaon decays—such as the ε′/ε discrepancy and the KOTO signal—using effective field theory, renormalization group methods, and lattice QCD inputs to probe new physics scenarios. They also explore dark matter models mediated by light bosons, including protophobic 16.7 MeV vector bosons, and examine connections between flavor anomalies and dark sector phenomenology. Their work emphasizes model-independent constraints and the development of analytic tools for precision calculations in quantum field theory.
Figures are computed from collected data and may differ slightly.
Recent progress in the determination of hadronic matrix elements has revealed a tension between the measured value of ε_{K}^{'}/ε_{K}, which quantifies direct CP violation in K→ππ decays, and the standard-model prediction. The well-understood indirect CP violation encoded in the quantity ε_{K} typically precludes large new-physics contributions to ε_{K}^{'}/ε_{K} and challenges such an explanation of the discrepancy. We show that it is possible to cure the ε_{K}^{'}/ε_{K} anomaly in the minimal
New physics contributions to the Z penguin are revisited in the light of the recently-reported discrepancy of the direct CP violation in K→ππ. Interference effects between the standard model and new physics contributions to ΔS=2 observables are taken into account. Although the effects are overlooked in the literature, they make experimental bounds significantly severer. It is shown that the new physics contributions must be tuned to enhance B(KL→π0νν¯), if the discrepancy of the direct CP violat
The KOTO experiment recently reported four candidate events in the signal region of K_{L}→π^{0}νν[over ¯] search, where the standard model only expects 0.10±0.02 events. If confirmed, this requires physics beyond the standard model to enhance the signal. We examine various new physics interpretations of the result including these: (1) heavy new physics boosting the standard model signal, (2) reinterpretation of "νν[over ¯]" as a new light long-lived particle, or (3) reinterpretation of the whole
The standard analytic solution of the renormalization group (RG) evolution for the ΔS = 1 Wilson coefficients involves several singularities, which complicate analytic solutions. In this paper we derive a singularity-free solution of the next-to-leading order (NLO) RG equations, which greatly facilitates the calculation of ϵ ′ , the measure of direct CP violation in K → ππ decays. Using our new RG evolution and the latest lattice results for the hadronic matrix elements, we calculate the ratio ϵ
The observation of a protophobic 16.7 MeV vector boson has been reported by a $^{8}\mathrm{Be}$ nuclear transition experiment. Such a new particle could mediate between the Standard Model and a dark sector, which includes the dark matter. In this paper, we show some simple models of the dark matter which satisfy the thermal relic abundance under the current experimental bounds from the direct and the indirect detections. In a model, it is found that an appropriate self-scattering cross section t
Abstract Recently, the CMS collaboration has reported a di-tau excess with a local significance of 2.6–3.1 $$\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>σ</mml:mi> </mml:math> where the invariant mass is $$m_{\tau \tau } =95$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>m</mml:mi> <mml:mrow> <mml:mi>τ</mml:mi> <mml:mi>τ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>95</mml:mn> </mml:mrow> </mml:math> –100 G
We study the possibility to determine the supersymmetric (SUSY) contribution to the muon anomalous magnetic dipole moment by using ILC measurements of the properties of superparticles. Assuming that the contribution is as large as the current discrepancy between the result of the Brookhaven E821 experiment and the standard-model prediction, we discuss how and how accurately the SUSY contribution can be reconstructed. We will show that, in a sample point, the reconstruction can be performed with
The ATLAS and CMS collaborations discovered a new boson particle. If the new boson is the Higgs boson, the diphoton signal strength is 1.5 - 1.8 times larger than the Standard Model (SM) prediction, while the WW and ZZ signal strengths are in agreement with the SM one. In the Minimal Supersymmetric Standard Model (MSSM), overall consistency can be achieved by a light stau and the large left-right mixing of staus. However, a light stau and large left-right mixing of staus may suffer from vacuum i
Recently the ATLAS experiment has reported 3.0 σ excess in an on-Z signal region in searches for supersymmetric particles. We find that the next-to-minimal supersymmetric standard model can explain this excess by the production of gluinos which mainly decay via $$ \tilde{g}\to g{\tilde{\chi}}_{2,3}^0\to gZ{\tilde{\chi}}_1^0 $$ where $$ {\tilde{\chi}}_{2,3}^0 $$ and $$ {\tilde{\chi}}_1^0 $$ are the Higgsino and the singlino-like neutralinos, respectively. We show that the observed dark matter den
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