nLab Belle experiment

Idea

The Belle experiment is an experiment with focus on the physics of B-mesons (similar to the LHCb experiment, see also the BaBar experiment).

After the discovery of the Higgs field at the two major other detectors of LHC, these B-meson experiments currently stand out as seeing hints for physics beyond the standard model of particle physics with considerable statistical significance: the flavour anomalies (see Adamczyk 19)

Related concepts

• related experiments

  • LHCb

  • BaBar experiment

• observations

  • flavour anomaly

  • V_cb puzzle

  • pentaquark

  • XYZ particle

• precision experiment

References

General

• Belle homepage

• Belle II homepage

• C. Z. Yuan (for the Belle II Collaboration), The Belle II Experiment at the SuperKEKB (arXiv:1208.3813)

• Belle collaboration, Physics Achievements from the Belle Experiment (arXiv:1212.5342)

• S.I. Eidelman, A.V. Nefediev, P.N. Pakhlov, V.I. Zhukova, Superfactory of bottomed hadrons Belle II (arXiv:2012.05147)

See also

• Wikipedia, Belle experiment

• Wikipedia, Belle II experiment

More on Belle II:

• Belle II Executive Summary [arXiv:2203.10203]

• Snowmass White Paper: Belle II physics reach and plans for the next decade and beyond [arXiv:2207.06307]

  Belle II is an experiment operating at the intensity frontier.

On flavour anomalies

flavour anomalies:

• Belle collaboration, Measurement of the $\tau$ lepton polarization and $R(D^\ast)$ in the decay $\bar B \to D^\ast \tau^- \bar \nu_\tau$ with one-prong hadronic τ decays at Belle (arXiv:1709.00129)

• Karol Adamczyk, Semitauonic B decays at Belle/Belle II, Proceedings of the 10th International Workshop on the CKM Unitarity Triangle (CKM 2018), Heidelberg, Germany, September 17-21, 2018 (arXiv:1901.06380)

• Belle collaboration, Measurement of the $D^{\ast -}$ polarization in the decay $B^0 \to D^{\ast -} \tau^+ \nu_\tau$ (arXiv:1903.03102)

• Giacomo Caria on behalf of the Belle collaboration, Measurement of $R(D)$ and $R(D^\ast)$ with a semileptonic tag at Belle, Moriond, EW 22/03/2019 (pdf)

• Belle Collaboration, Test of lepton flavor universality in $B \to K^\ast \ell^+ \ell^-$ decays at Belle (arXiv:1904.02440)

• Belle collaboration, Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^\ast)$ with a semileptonic tagging method, Phys. Rev. Lett. 124, 161803 (2020)

  (arXiv:1910.05864, doi:10.1103/PhysRevLett.124.161803)

Outlook for Belle II to confirm the flavour anomalies, if they are real:

• Tobias Huber, Tobias Hurth, Jack Jenkins, Enrico Lunghi, Qin Qin, K.Keri Vos, Phenomenology of inclusive $\bar B \to X_s \ell^+ \ell^-$ for the Belle II era (arXiv:2007.04191)

With $[$ … $]$ Belle II, we are at the brink of a new era in quark flavour physics $[...]$ we present a phenomenological study of the potential for Belle II to reveal possible new physics in the inclusive decay channel.

(p. 15:) We see that anomalies in the exclusive sector can be confirmed at the 5σ level by inclusive measurements if the true values of $C_{9,10}^{\mu NP}$ are at the current best-fit point of the exclusive fits

(p. 16:) After including $B_s \to \mu^+ \mu_-$, the reach in the $[C_9^{\mu NP}, C_{10}^{\mu NP}]$ plane improves considerably. Exclusive anomalies could be confirmed at the 6σ level.

(p. 20:) Should the true value of $C_9^{NP}$ and $C_{10}^{NP}$ be at the current best-fit points of the global fits, an analysis of inclusive $\bar B_ \to X_s \ell^+ \ell^-$ at Belle II with $50 ab^{-1}$ of data will exclude the SM point $C_9^{NP} = C_{10}^{NP} = 0$ at the level of $\sim 5$σ. This again underlines the necessity of a full angular analysis of $\bar B_ \to X_s \ell^+ \ell^-$ at Belle II.