Current and future kaon experiments

Rare Kaon Decays: Progress and Prospects

A brief review of current results on rare kaon decays, particularly the charged and neutral K-> pi nu nubar channels, is presented along with prospects for future measurements.

Rare Kaon and Pion Decays

Recent results on rare kaon and pion decays are reviewed and prospects for future experiments are discussed

Rare Kaon Decays with NA48/2 and NA62 at CERN

The Kaon physics program at CERN will be shortly presented, addressing the most recent results from the NA48/2 and NA62 experiments at the CERN SPS and future prospects.

Kaons: Review and Outlook

This article presents a review of recent results and an outlook of kaon physics. After enjoying a renaissance, the discipline is now becoming and endangered species. Action will be needed to keep kaon physics at the heart of future FPCP meetings.

Rare Kaon Decays

Recent results in and future prospects for the study of rare kaon decays are reviewed.

Rare Kaon Decays - a review of results

Recent results and future prospects of rare kaon-decay experiments at KEK, BNL, CERN and FNAL are reviewed. Topics include lepton flavor violation, T-violating transverse muon polarization in K+{mu3}, exotic decays, K0 -> pi0 ell+ ell-, and K -> pi nu nubar.

Precision Kaon and Hadron Physics with KLOE

We describe the KLOE detector at DAFNE, and its physics program. The impact of our results on flavor and hadron physics to date, as well as an outlook for further improvement in the near future, are discussed.

Probing lepton flavour (universality) violation at NA62 and future kaon experiments

Recent results from the LHC's first run have revealed intriguing departures from lepton flavour universality in the semi-leptonic decays of $B$-mesons. We discuss the complementary role that rare kaon decays can provide in testing new physics explanations of these flavour anomalies. In the framework of minimal flavour violation, we relate the chiral low-energy constants involved in $K\toπ\ell\ell'$ and $K\to\ell\ell'$ ($\ell = μ\mbox{ or } e$) with the new physics Wilson coefficients of the $b\to s$ effective Hamiltonian. We comment on the determination of these low-energy constants at NA62 an…

New physics limits from kaon decays

Searches for lepton flavour violation and lepton number violation in kaon decays by the NA62 and NA48/2 experiments at CERN are presented. A new measurement of the ratio of charged kaon leptonic decay rates $R_K=Γ(K_{e2})/Γ(K_{\mu2})$ to sub-percent relative precision is discussed. An improved upper limit on the lepton number violating $K^\pm\rightarrowπ^\mpμ^\pmμ^\pm$ decay rate is also reported. The future 10% precision measurement of the branching ratio of the ultra-rare kaon decay $K^+\rightarrowπ^+ν\barν$ with the NA62 experiment is finally reviewed.

Recent NA48 results on rare kaon decays

Recent NA48 results from detailed studies of $K_{L,S}\to π^+ π^- e^+ e^-$ and $K_S\toπ^0 γγ$ decay modes are presented. The results are based on the data collected with the NA48 detector at the CERN SPS during the 1998-199 9 and 2000 data taking periods, respectively. Prospects for future results on charged kaon decays are briefly described.

Recent Results from KTeV

Recent results are presented for (1) the charge asymmetry in semielectronic kaon decay; (2) the charge radius of the neutral kaon; (3) the decay Klong -> pi0 pi0 e+e-; (4) constraints on rho(CKM) from kaon decays; (5) lepton flavor violation. A few words about future kaon physics work at Fermilab are included.

Charged Higgs Mass Limits from the Charged Kaon and Tau to Kaon Branching Fractions

From an analysis of the current world averages of the charged kaon and tau to kaon branching fractions, we derive, within the framework of type II Higgs doublets models such as the Minimal Supersymmetric Extension of the Standard Model, $\tanβ/m_H < 0.21$ GeV$^{-1}$ at a 90% confidence limit.

Rare Kaon Decays

The current status of rare kaon decay experiments is reviewed. New limits in the search for Lepton Flavor Violation are discussed, as are new measurements of the CKM matrix.

Kaon Physics

The most recent progress and future prospects in kaon physics are reviewed. Main results are the first observation of the rare decays KS->pi0ee and KS->pi0mumu by NA48, new K+->pinunu event observed by E949 and new precision measurements of K0->pienu decays by KTeV, KLOE and NA48 made in an effort to resolve the slight deviation from the unitarity in the CKM matrix, involving the |Vus| coupling.

用于K介子CKM数据的自然复平面：框架、现状与未来

Natural complex plane for kaon CKM data: framework, status and future

该研究提出K介子CKM数据的自然复平面框架，避免B物理输入及参数不确定性导致的误差膨胀，分析当前四个允许区域现状，指出未来数据将排除部分区域以验证CKM范式或发现新物理。

Eperimental Results on Radiative Kaon Decays

This paper reviews the current status of experimental measurements of radiative kaon decays. Several experiments at BNL, CERN and FNAL have recently or will soon complete data collection; as a result, several new results are available.

Rare Kaon Decays

The current status of the study of rare kaon decays is reviewed. Future prospects are discussed.

Rare Kaon Decays

Rare kaon decays via Flavor Changing Neutral Currents are discussed in the context of the CKM unitarity triangle with a particular interest in the rare kaon decays K^+ --> pi^+ nu nubar and K^0_L --> pi^0 nu nubar. New results and the status of these experiments are reported.

Plans for Kaon Physics at BNL

I give an overview of current plans for kaon physics at BNL. The program is centered on the rare decay modes K+ --> pi+ nu nubar and KL --> pi0 nu nubar.

Prospects for kaon physics at LHCb

Despite not being designed for it, the LHCb experiment has given world-leading contributions in kaon and hyperon physics. In this contribution I review the prospects for kaon physics at LHCb exploiting the already acquired data and the current and future Upgrade scenarios.

Rare and Forbidden Kaon Decays at the AGS

An overview of the Rare Kaon Decay program at the AGS is presented, with particular emphasis on the three major experiments currently running and analyzing data. A brief review of earlier kaon decay experiments and of recent improvements in AGS performance is provided. This review concludes with a discussion of proposed and developing experiments planned to run in the year 2000 and beyond (AGS2000).

未来实验中超越标准模型的介子物理前景

Beyond the Standard Model prospects for kaon physics at future experiments

本文研究了稀有K介子衰变在探索新物理中的作用，分析了CERN未来HIKE计划及KOTO-II实验的预测，指出黄金通道与 $K_L\toπ^0 \ell\bar\ell$ 衰变对短距离物理具有强约束力。

Recent results from Kaon Physics

A short review of recent results and future prospects in kaon physics is presented. Recent measurements performed at the NA48, NA62, KLOE and KTeV experiments on CP and Lepton Flavour violation and rare decays will be summarised, together with measurements of CKM elements and Chiral Perturbation Theory tests.

Kaon Physics at BNL

The rare kaon decay program at BNL is summarized. A brief review of recent results is provided along with a discussion of prospects for the future of this program. The primary focus is the two golden modes: k+->pnn and kl->pnn. The first step in an ambitious plan to precisely measure both branching ratios has been successfully completed with the observation of two k+->pnn events by E787. The E949 experiment is poised to reach an order of magnitude further in sensitivity and to observe ~10 Standard Model events.

Searches for new physics with high-intensity kaon beams

The availability of high-intensity kaon beams at the J-PARC Hadron Experimental Facility and the CERN SPS North Area, together with the abundant forward production of kaons at the LHC, 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 $K\toπν\barν$ can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. Building on the success of the current generation of fixed-target experiments, initiatives are taking shape in b…

Latest Results on Kaon Physics from the NA48 Experiment

The NA48 experiment, conceived primarily to look for direct CP violation in neutral kaon decays, has recently published the so far most precise determination of the epsilon'/epsilon parameter. After reviewing shortly this result, we report on the 2001 data-taking, which concluded the epsilon' program by collecting a substantial amount of data with different beam intensity conditions. We also present new precision measurements of the K0 and eta masses and of the K-short lifetime, that provide consistency checks of our analysis. Finally, the prospects for the future experimental program are disc…

Kaon Rare Decays

Recent results and future prospects in the rare kaon-decay experiments at KEK, BNL, CERN and FNAL are reviewed. Emphasis is placed on the quark flavor dynamics in the flavor-changing neutral current processes. Experimental and data-analysis techniques developed in the rare decay experiments are discussed.

Constraints on scalar leptoquarks from lepton and kaon physics

We present a comprehensive analysis of low-energy signals of hypothetical scalar leptoquark interactions in lepton and kaon transitions. We derive the most general effective four-fermion Lagrangian induced by tree-level scalar leptoquark exchange and identify the Wilson coefficients predicted by the five possible types of scalar leptoquarks. The current constraints on the leptoquark Yukawa couplings arising from lepton and kaon processes are worked out, including also loop-induced transitions with only leptons (or quarks) as external states. In the presence of scalar leptoquark interactions, w…

On V_ud determination from kaon decays

The pion beta decay pi^+ -> pi^0 e^+ nu proceeds through pure weak vector hadronic currents and, therefore, the theoretical prediction for it is more reliable than for the processes with axial-vector current contribution. For example, recently the pion beta decay has been used for V_ud determination. The main aim of this letter is to point that kaon beta decay K^0 -> K^+(pi^+ pi^0) e^- nu-bar analogously can be used for this purpose.

Determination of Vus at the KLOE experiment: present results and future perspectives

Precise measurements of semileptonic kaon decay rates at KLOE provide the measurement of the CKM mixing matrix element \vus\ and information about lepton universality. Leptonic kaon decays provide an independent measurement of $\abs{\vus}^2/\abs{\vud}^2$, through the ratio $Γ(K\toμν)/Γ(π\toμν)$. These measurements, together with the result of $|\vud|$ from nuclear $β$ transitions, provide the most precise test of CKM unitarity, allowing the universality of lepton and quark weak couplings to be tested. After the completion of the KLOE data taking, the proposal of a new run with an upgraded KLOE…

Experiments with K-Meson Decays

Recent results and future prospects of the particle physics experiments with neutral and charged K-meson (kaon) decays are reviewed. Topics include CP violation, rare decays, leptons in kaon decays, tests of CPT and quantum mechanics, radiative decays, hadrons in kaon decays, basic observables, Vus and CKM unitarity, and exotic searches. Experimental techniques developed for the kaon decay experiments are discussed.

Kaon Decays in the Standard Model

A comprehensive overview of kaon decays is presented. The Standard Model predictions are discussed in detail, covering both the underlying short-distance electroweak dynamics and the important interplay of QCD at long distances. Chiral perturbation theory provides a universal framework for treating leptonic, semileptonic and nonleptonic decays including rare and radiative modes. All allowed decay modes with branching ratios of at least 10^(-11) are analyzed. Some decays with even smaller rates are also included. Decays that are strictly forbidden in the Standard Model are not considered in thi…

K介子衰变对耦合非守恒电流的向量玻色子的限制

Kaon decay constraints on vector bosons coupled to non-conserved currents

通过研究K介子衰变限制轻向量玻色子与非守恒电流的耦合，发现其对轻夸克耦合的约束为10^-5量级，并探讨了17 MeV玻色子假说的测试前景。

New physics in $s\to d$ semileptonic transitions: rare hyperon vs. kaon decays

We investigate the potential of rare hyperon decays to probe the short distance structure in the $s\to dν\barν$ and $s\to d\ell^+\ell^-$ transitions. Hyperon decays into neutrinos ($B_1\to B_2ν\barν$) can be reliably predicted by using form factors determined in baryon chiral perturbation theory. Their decay rates are sensitive to different short-distance operators, as compared to their kaon counterparts, and the corresponding branching fractions are in the range of $10^{-14}\sim10^{-13}$ in the standard model. In the context of the low-energy effective theory, we find that the anticipated BES…

Kaon physics with a high-intensity proton driver

We study opportunities for future high-precision experiments in kaon physics using a high-intensity proton driver, which could be part of the front-end of a muon storage ring complex. We discuss in particular the rare decays $K_L\toπ^0ν\barν$, $K^+\toπ^+ν\barν$, $K_L\toπ^0e^+e^-$, and lepton-flavour violating modes such as $K_L\toμe$ and $K\toπμe$. The outstanding physics potential and long-term interest of these modes is emphasized. We review status and prospects of current and planned experiments for the processes under consideration, and indicate possible improvements and strategies towards…

HIKE: High Intensity Kaon Experiments at the CERN SPS

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 $K\toπν\barν$ 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 $K^+\toπ^+ν\barν$ to ~5% and to $K_L\toπ^0ν\…

Kaon物理：未来发现的基石

Kaon Physics: A Cornerstone for Future Discoveries

本文阐述Kaon物理作为高能物理前沿领域，凭借多TeV能级探索新物理的能力，有望推动全球范围内变革性突破，重塑对宇宙的理解。

Modeling quasielastic interactions of monoenergetic kaon decay-at-rest neutrinos

Monoenergetic muon neutrinos at 236 MeV are readily produced in intense medium-energy proton facilities ($\gtrsim$2-3~GeV) when a positive kaon decays at rest (KDAR; $K^+ \rightarrow μ^+ ν_μ$). These neutrinos provide a unique opportunity to both study the neutrino interaction and probe the nucleus with a monoenergetic weak-interaction-only tool. We present cross section calculations for quasielastic scattering of these 236~MeV neutrinos off $^{12}$C and $^{40}$Ar, paying special attention to low-energy aspects of the scattering process. Our model takes the description of the nucleus in a mean…

Developments in Rare Kaon Decay Physics

We review the current status of the field of rare kaon decays. The study of rare kaon decays has played a key role in the development of the standard model, and the field continues to have significant impact. The two areas of greatest import are the search for physics beyond the standard model and the determination of fundamental standard-model parameters. Due to the exquisite sensitivity of rare kaon decay experiments, searches for new physics can probe very high mass scales. Studies of the k->pnn modes in particular, where the first event has recently been seen, will permit tests of the stan…

Update on $|V_{us}|$ and $|V_{us}/V_{ud}|$ from semileptonic kaon and pion decays

We discuss the recent progress in the study of semileptonic kaon and pion decays, including new experimental results, improved electroweak radiative corrections, form factor calculations and isospin-breaking effects. As a result, we obtain $|V_{us}|=0.22309(40)(39)(3)$ from kaon semileptonic decays and $|V_{us}/V_{ud}|=0.22908(66)(41)(40)(2)(1)$ from the ratio between the kaon and pion semileptonic decay rates. We report an apparent violation of the top-row Cabibbo-Kobayashi-Maskawa matrix unitarity at a $3.2\sim 5.6σ$ level, and a discrepancy at a $2.2σ$ level between the value of $|V_{us}/V_…

Testing Lepton Flavor Universality with Pion, Kaon, Tau, and Beta Decays

We present an overview of searches fo violation of lepton flavor universality with focus on low energy precision probes using pions, kaons, tau leptons, and nuclear beta decays. The current experimental results are reviewed, the theoretical status within the context of the Standard Model is summarized, and future prospects (both experimental and theoretical) are discussed. We review the implications of these measurements for physics beyond the Standard Model by performing a global model-independent fit to modified $W$ couplings to leptons and four-fermion operators. We also discuss new physics…

π介子（K介子）诱发的单举Drell-Yan过程的次领头阶QCD修正

Next-to-next-to-leading order QCD corrections to pion (kaon)-induced exclusive Drell-Yan process

针对未来J-PARC实验的高能π介子和K介子束诱发的单举Drell-Yan过程，在广义部分子分布因子化框架内计算次领头阶QCD修正，发现其修正大且为正，对可靠理论预测及与未来实验对比很关键。

Sterile neutrinos facing kaon physics experiments

We discuss weak kaon decays in a scenario in which the Standard Model is extended by massive sterile fermions. After revisiting the analytical expressions for leptonic and semileptonic decays we derive the expressions for decay rates with two neutrinos in the final state. By using a simple effective model with only one sterile neutrino, compatible with all current experimental bounds and general theoretical constraints, we conduct a thorough numerical analysis which reveals that the impact of the presence of massive sterile neutrinos on kaon weak decays is very small, less than $1\%$ on decay …