Precision tests of first-row unitarity of the Cabibbo–Kobayashi–Maskawa matrix currently display two intriguing tensions, both at the 3σ level. First, combining determinations of Vud from ...superallowed β decays with Vus from kaon decays suggests a deficit in the unitarity relation. At the same time, a tension of similar significance has emerged between Kℓ2 and Kℓ3 decays. In this Letter, we point out that a measurement of the Kμ3/Kμ2 branching fraction at the level of 0.2% would have considerable impact on clarifying the experimental situation in the kaon sector, especially in view of tensions in the global fit to kaon data as well as the fact that the Kμ2 channel is currently dominated by a single experiment. Such a measurement, as possible for example at NA62, would further provide important constraints on physics beyond the Standard Model, most notably on the role of right-handed vector currents.
Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the ...availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.
Abstract
The availability of high intensity kaon beams at the CERN SPS North Area gives rise to unique possibilities for sensitive tests of the Standard Model in the quark flavor sector. Precise ...measurements of the branching ratios for the flavor-changing neutral current decays
K
→
π
ν
ν
−
can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. Building on the success of the NA62 experiment, plans are taking shape at CERN for a comprehensive program that will include experimental phases to measure the branching ratio for
K
+
→
π
+
ν
ν
−
to ∼5% and to
K
L
→
π
0
ν
ν
−
to ∼20% precision. These planned experiments would also carry out lepton flavor universality tests, lepton number and flavor conservation tests, and perform other precision measurements in the kaon sector, as well as searches for exotic particles in kaon decays. We overview the physics goals, detector requirements, and project status for the next generation of kaon physics experiments at CERN.
Precise measurements of the branching ratios for the flavor-changing neutral current decays K→πνν¯ can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. It is ...important to measure both decay modes, K+→π+νν¯ and KL→π0νν¯, since different new physics models affect the rates for each channel differently. The NA62 experiment at the CERN SPS will measure the BR for the charged channel to better than 20%. The BR for the neutral channel has never been measured. We are designing the KLEVER experiment to measure BR( KL→π0νν¯) to ∼20% using a high-energy neutral beam at the CERN SPS. The boost from the high-energy beam facilitates the rejection of background channels such as KL → π0π0 by detection of the additional photons in the final state. On the other hand, the layout poses particular challenges for the design of the small-angle vetoes, which must reject photons from KL decays escaping through the beam exit amid an intense background from soft photons and neutrons in the beam. We present findings from our design studies, with an emphasis on the challenges faced and the potential sensitivity for the measurement of BR(KL→π0νν¯).
Progress in experimental high-energy physics has been closely tied to developments of high-performance calorimeters. Since their invention, crystal calorimeters have consistently achieved the best ...resolution for measurements of the energies of electromagnetic (e.m.) particles (electrons and photons). Recently, we experimentally demonstrated the possibility of significantly accelerating the e.m. shower development inside lead tungstate (PWO) crystal when the incident beam is aligned with the crystal axes within some tenths of a degree. Here, we present the innovative photodetection system, based on Silicon PhotoMultipliers, implemented for the direct measurement of the scintillation light enhancement in case of beam aligned to the main crystal axes, along with its characterization performed with cosmic rays at the Insulab laboratory (Insubria University, Como). In 2021 we performed a test at H2 beam line of CERN SPS with a hundred-GeV electron beam with two PWO samples (1 and 2 X0 thick) directly coupled with SiPMs. Since the angular acceptance of the crystal strong field depends weakly on particle energy, while instead the decreasing of the shower length remains pronounced at very high-energy, a crystal calorimeter based on oriented crystals would feature a consistent compactness enhancement while rivaling the current state of the art in terms of resolution in the range of interest of present and future forward detectors, beam dumps for light dark matter search and source-pointing space-borne γ-ray telescopes.
Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the ...availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. Here, we summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.
The Physics of DAΦNE and KLOE Franzini, Paolo; Moulson, Matthew
Annual review of nuclear and particle science,
01/2006, Letnik:
56, Številka:
1
Journal Article
Recenzirano
Odprti dostop
▪ Abstract DAΦNE, the Frascati φ factory, has been in operation since 1999. At the center of the physics program is the KLOE experiment, a multipurpose detector with optimizations for tagged and ...interferometry-based measurements of the neutral kaon system. KLOE has been taking data since 2000 and has helped to explore a wide array of topics in kaon and hadronic physics, including a comprehensive set of measurements to determine the CKM matrix element Formula: see text, and a measurement of the Formula: see text cross section for the determination of the hadronic contribution to the muon anomaly. In addition, the DEAR experiment has measured the X-ray spectrum of kaonic hydrogen, and the FINUDA experiment has conducted its first studies in hypernuclear spectroscopy and a search for Formula: see text-nuclear bound states. We review the design, construction, and operation of the DAΦNE facility, with an emphasis on the physics program of the KLOE experiment.
Precise measurements of the branching ratios for the flavor-changing neutral current decays \(K\to\pi\nu\bar{\nu}\) can provide unique constraints on CKM unitarity and, potentially, evidence for new ...physics. It is important to measure both decay modes, \(K^+\to\pi^+\nu\bar{\nu}\) and \(K_L\to\pi^0\nu\bar{\nu}\), since different new physics models affect the rates for each channel differently. The NA62 experiment at the CERN SPS will measure the BR for the charged channel to better than 20%. The BR for the neutral channel has never been measured. We are designing the KLEVER experiment to measure BR(\(K_L\to\pi^0\nu\bar{\nu}\)) to \(\sim\)20% using a high-energy neutral beam at the CERN SPS. The boost from the high-energy beam facilitates the rejection of background channels such as \(K_L\to\pi^0\pi^0\) by detection of the additional photons in the final state. On the other hand, the layout poses particular challenges for the design of the small-angle vetoes, which must reject photons from \(K_L\) decays escaping through the beam exit amid an intense background from soft photons and neutrons in the beam. We present findings from our design studies, with an emphasis on the challenges faced and the potential sensitivity for the measurement of BR(\(K_L\to\pi^0\nu\bar{\nu}\)).
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