V_us from kaon decays Moulson, Matthew
arXiv (Cornell University),
03/2007
Journal Article
Odprti dostop
Recent measurements of kaon decays contributing to the determination of
|V_us| are summarized, and up-to-date evaluations of |V_us|f+(0) and |V_us| are
presented.
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.
Numerous recent measurements of kaon decays are described, with an emphasis
on results offering constraints on chiral perturbation theory calculations. An
up-to-date estimate of |Vus|f+(0) based on ...semileptonic kaon decay rates is
presented.
The decay \(K^+\to\pi^+\nu\bar{\nu}\) is highly suppressed in the Standard Model (SM), while its rate can be predicted with minimal theoretical uncertainty. The branching ratio (BR) for this decay is ...thus a sensitive probe of the flavor sector of the SM; its measurement, however, is a significant experimental challenge. The primary goal of the NA62 experiment is to measure \({\rm BR}(K^+\to\pi^+\nu\bar{\nu})\) with 10% precision. NA62 took data in pilot runs in 2014 and 2015, reaching the design beam intensity. The status of the experiment and the prospects for the measurement of \({\rm BR}(K^+\to\pi^+\nu\bar{\nu})\) are presented.
NA62, an experiment at the CERN SPS to measure the branching ratio for the decay K+ -> pi+ nu nu-bar with ~10% precision, will observe ~10^13 K+ decays in its fiducial volume, and will thus also be ...able to carry out a rich program to search for forbidden K+ and pi0 decays, including in particular K+ decays that violate the conservation of lepton flavor and/or number. NA62's potential performance in searches for a number of forbidden K+ and pi0 decays is discussed, with initial sensitivity estimates.
Recent measurements of kaon decays contributing to the determination of |V_us| are summarized, and up-to-date evaluations of |V_us|f+(0) and |V_us| are presented.
Numerous recent measurements of kaon decays are described, with an emphasis on results offering constraints on chiral perturbation theory calculations. An up-to-date estimate of |Vus|f+(0) based on ...semileptonic kaon decay rates is presented.
While measuring the ratio R_K = \Gamma(K+e2(\gamma))/\Gamma(K+\mu2(\gamma)), the KLOE Collaboration has studied the radiative process Ke2\gamma. The ratio of the width for the Ke2\gamma decay with a ...positively polarized photon from structure-dependent radiation to the inclusive K\mu2(\gamma) width is found to be 1.484(68) 10-5. The observed radiation spectrum agrees with predictions from chiral perturbation theory and is in contrast with predictions based on the light front quark model. This result reduces the contribution to systematic uncertainties on measurements of R_K. In a separate study, KLOE has measured the ratio of the radiative Ke3\gamma decay width to the inclusive Ke3(\gamma) width to be 924(28) 10-5. The distribution in energy and angle of the radiative photon has been analyzed in an attempt to isolate the signature from interference of the inner-bremsstrahlung and structure-dependent amplitudes.
Ann.Rev.Nucl.Part.Sci.56:207-251,2006 DAFNE, the Frascati phi 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 |Vus|,
and a measurement of the e+e- --> pi+pi- 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
\bar{K}-nuclear bound states. We review the design, construction, and operation
of the DAFNE facility, with an emphasis on the physics program of the KLOE
experiment.
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