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A bstract Based on an integrated luminosity of 1.61 fb − 1 e + e − collision data collected with the KLOE detector at DAΦNE, the Frascati ϕ -factory, a search for the P - and CP -violating decay η → π + π − has been performed. Radiative ϕ → ηγ decay is exploited to access the η mesons. No signal is observed in the π + π − invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ℬ( η → π + π − ) < 4 . 9 × 10 − 6 , which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ℬ( η → π + π − ) < 4 . 4 × 10 − 6 at 90% confidence level.

The Data Acquisition System (DAQ) and the Front-End electronics for an array of Kinetic Inductance Detectors (KIDs) are described. KIDs are superconductive detectors, in which electrons are organized in Cooper pairs. Any incident radiation could break a pair generating a couple of quasi-particles that increase the inductance of the detector. The DAQ system we developed is a hardware software co-design, based on state machines and on a microprocessor embedded into an FPGA. A commercial DAC ADC board is used to interface the FPGA to the array of KIDs. The DAQ system generates a Stimulus signal suitable for an array of up to 128 KIDs. Such signal is up-mixed with a 3 GHz carrier wave and it then excites the KIDs array. The read-out signal from the detector is down-mixed with respect to the 3 GHz sine wave and recovered Stimulus is read back by the ADC device. The microprocessor stores read out data via a PCI express bus (PCIe) into an external disk. It also computes the Fast Fourier Transform of the acquired read out signal: this allows extrapolating which KID interacted and the energy of the impinging radiation. Simulations and tests have been performed successfully and experimental results are presented.

A general purpose FPGA based DAQ module has been developed based on a Virtex-4 FPGA. It is able to acquire up to 1024 different channels distributed over 10 slave cards. The module has an optical interface a RS-232 a USB and a Gigabit Interface. The KLOE-2 experiment is going to use it to collect data from the Inner tracker and the QCALT. An embedded processor (power pc 604) is present on the FPGA and a telnet server has been developed and installed. A new general purpose data taking system has been based on this module to acquire the Inner Tracker. The system is at the moment working at LNF (Laboratori Nazionali di Frascati).

A bstract We report a search for the lepton-flavor-violating decays τ ± → ℓ ± α ( ℓ = e , μ ), where α is an undetected spin-0 particle, such as an axion-like particle using 736 × 10 6 tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energy e + e − collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at 95% confidence level: ( τ ± → e ± α ) < (0.4–6.4) × 10 − 4 and ( τ ± → μ ± α ) < (0.2–3.5) × 10 − 4 at 95% confidence level for an α mass in the range 0.0 ≤ m α ≤ 1.6 GeV/ c 2 .

Investigation at a φ -factory can shed light on several debated issues in particle physics. We discuss: (i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, (ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled-kaon states, (iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and η / η ′ mesons, (iv) the contribution to understand the nature of light scalar mesons, and (v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the e + e − physics in the continuum with the measurements of (multi)hadronic cross sections and the study of γ γ processes.

A bstract We present a search for the lepton-flavor-violating decays B s 0 → ℓ ∓ τ ± , where ℓ = e, μ , using the full data sample of 121 fb − 1 collected at the Υ(5 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. We use B s 0 B ¯ s 0 events in which one B s 0 meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for B s 0 → ℓ ∓ τ ± decays and set upper limits on their branching fractions at 90% confidence level as B ( B s 0 → e ∓ τ ± ) < 14 × 10 − 4 and B ( B s 0 → μ ∓ τ ± ) < 7 . 3 × 10 − 4 . Our result represents the first upper limit on the B s 0 → e ∓ τ ± decay rate.

We present measurements ofB → K^(*)(892)γdecays using365 \\rm fb⁻¹of data collected from 2019 to 2022 by the Belle II experiment at the SuperKEKB asymmetric-energye⁺e⁻collider. The data sample contains(387 ± 6) × 10⁶Υ(4S)events. We measure branching fractions ( 𝓑 ) andC\\!{P}{}{a}symmetries ( 𝓐_(C\\!P) ) for bothB⁰→ K^(*0)γandB⁺→ K^(*+)γdecays. The difference inC\\!{P}{}{a}symmetries ( Δ𝓐_(C\\!P) ) and the isospin asymmetry ( Δ₀₊ ) between these neutral and charged channels are also measured. We obtain the following branching fractions andC\\!{P}{}{a}symmetries:𝓑 (B⁰ → K^(*0)γ) = (4.14 ± 0.10 ± 0.11 ) × 10⁻⁵ ,𝓑 (B⁺ → K^(*+)γ) = (4.04 ± 0.13 ^(+0.13)_(-0.15) )× 10⁻⁵ ,𝓐_(C\\!P) (B⁰ → K^(*0)γ) = (-3.3 ± 2.3 ± 0.4 )% , and𝓐_(C\\!P) (B⁺ → K^(*+)γ) = (-0.7 ± 2.9 ± 0.5 )% . The measured difference inC\\!{P}{}{a}symmetries isΔ𝓐_(C\\!P) = (+2.6 ± 3.8 ± 0.6 )% , and the measured isospin asymmetry isΔ₀₊ = (+4.8 ± 2.0 ± 1.8 )% . The first uncertainties listed are statistical and the second are systematic. These results are consistent with world-average values and theory predictions.

We present the results of a search for the charged-lepton-flavor violating decays B ⁰→ K ^(*0) τ ^(±) ℓ ^(∓) , where ℓ ^(∓)is either an electron or a muon. The results are based on 365 fb ⁻¹and 711 fb ⁻¹datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic B-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed B meson. We find no evidence for B ⁰→ K ^(*0) τ ^(±) ℓ ^(∓)decays and set upper limits on the branching fractions in the range of (2.9–6.4)×10 ⁻⁵at 90% confidence level. 19 pages, 4 figures

A bstract We present the results of a search for the charged-lepton-flavor violating decays B 0 → K *0 τ ± ℓ ∓ , where ℓ ∓ is either an electron or a muon. The results are based on 365 fb − 1 and 711 fb − 1 datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic B -tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed B meson. We find no evidence for B 0 → K *0 τ ± ℓ ∓ decays and set upper limits on the branching fractions in the range of (2.9–6.4)×10 − 5 at 90% confidence level.

A bstract We measure the cross section of e + e − → η c J/ψ at the Υ( nS )( n = 1–5) on-resonance and 10.52 GeV off-resonance energy points using the full data sample collected by the Belle detector with an integrated luminosity of 955 fb − 1 . We also search for double charmonium production in e + e − → η c J/ψ via initial state radiation near the η c J/ψ threshold. No evident signal of the double charmonium state is found, but evidence for the e + e − → η c J/ψ process is found with a statistical significance greater than 3 . 3 σ near the η c J/ψ threshold. The average cross section near the threshold is measured and upper limits of cross sections are set for other regions.