Search

Abstract Kaon physics is at a turning point – while the rare-kaon experiments NA62 and KOTO are in full swing, the end of their lifetime is approaching and the future experimental landscape needs to be defined. With HIKE, KOTO-II and LHCb-Phase-II on the table and under scrutiny, it is a very good moment in time to take stock and contemplate about the opportunities these experiments and theoretical developments provide for particle physics in the coming decade and beyond. This paper provides a compact summary of talks and discussions from the Kaons@CERN 2023 workshop, held in September 2023 at CERN.

Abstract We investigate the possibility of indirectly constraining the $$B^{+}\rightarrow K^{+}\tau ^+\tau ^-$$ B + → K + τ + τ - decay rate using precise data on the $$B^{+}\rightarrow K^{+}\mu ^+\mu ^-$$ B + → K + μ + μ - dimuon spectrum. To this end, we estimate the distortion of the spectrum induced by the $$B^{+}\rightarrow K^{+}\tau ^+\tau ^-\rightarrow K^{+} \mu ^+\mu ^-$$ B + → K + τ + τ - → K + μ + μ - re-scattering process, and propose a method to simultaneously constrain this (non-standard) contribution and the long-distance effects associated to hadronic intermediate states. The latter are constrained using the analytic properties of the amplitude combined with data and perturbative calculations. Finally, we estimate the sensitivity expected at the LHCb experiment with present and future datasets. We find that constraints on the branching fraction of $$O(10^{-3})$$ O ( 10 - 3 ) , competitive with current direct bounds, can be achieved with the current dataset, while bounds of $$O(10^{-4})$$ O ( 10 - 4 ) could be obtained with the LHCb upgrade-II luminosity.

Abstract We perform a likelihood analysis of the minimal anomaly-mediated supersymmetry-breaking (mAMSB) model using constraints from cosmology and accelerator experiments. We find that either a wino-like or a Higgsino-like neutralino LSP, $$\tilde{\chi }^0_{1}$$ χ ~ 1 0 , may provide the cold dark matter (DM), both with similar likelihoods. The upper limit on the DM density from Planck and other experiments enforces $$m_{\tilde{\chi }^0_{1}} \lesssim 3 \,\, \mathrm {TeV}$$ m χ ~ 1 0 ≲ 3 TeV after the inclusion of Sommerfeld enhancement in its annihilations. If most of the cold DM density is provided by the $$\tilde{\chi }^0_{1}$$ χ ~ 1 0 , the measured value of the Higgs mass favours a limited range of $$\tan \beta \sim 5$$ tan β ∼ 5 (and also for $$\tan \beta \sim 45$$ tan β ∼ 45 if $$\mu > 0$$ μ > 0 ) but the scalar mass $$m_0$$ m 0 is poorly constrained. In the wino-LSP case, $$m_{3/2}$$ m 3 / 2 is constrained to about $$900\,\, \mathrm {TeV}$$ 900 TeV and $$m_{\tilde{\chi }^0_{1}}$$ m χ ~ 1 0 to $$2.9\pm 0.1\,\, \mathrm {TeV}$$ 2.9 ± 0.1 TeV , whereas in the Higgsino-LSP case $$m_{3/2}$$ m 3 / 2 has just a lower limit $$\gtrsim 650\,\, \mathrm {TeV}$$ ≳ 650 TeV ( $$\gtrsim 480\,\, \mathrm {TeV}$$ ≳ 480 TeV ) and $$m_{\tilde{\chi }^0_{1}}$$ m χ ~ 1 0 is constrained to $$1.12 ~(1.13) \pm 0.02\,\, \mathrm {TeV}$$ 1.12 ( 1.13 ) ± 0.02 TeV in the $$\mu >0$$ μ > 0 ( $$\mu 0$$ μ > 0 .