Observations on the radiative corrections to pion<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>decay

Passera, M.; Philippides, Kostas; Sirlin, A.

doi:10.1103/physrevd.84.094030

Cited by 12 publications

(9 citation statements)

References 21 publications

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“…PIONEER also aims to improve the precision for the branching ratio of pion beta decay π + → π 0 e + ν(γ) [175]. Pion beta decay, while providing the theoretically cleanest determination of the CKM matrix element V ud , is currently not competitive: V ud = 0.9739 (28) exp (1) th , where the experimental uncertainty comes almost entirely from the π + → π 0 e + ν(γ) branching ratio [175] (the pion lifetime contributes δV ud = 0.0001), and the theory uncertainty has been reduced from (δV ud ) th = 0.0005 [176][177][178] to (δV ud ) th = 0.0001 via a lattice QCD calculation of the radiative corrections [179]. As pointed out in Ref.…”

Section: Future Prospects a Pion And Kaon Experimentsmentioning

confidence: 99%

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

Bryman,

Cirigliano,

Crivellin

et al. 2021

Preprint

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We present an overview of searches for 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 modelindependent fit to modified W couplings to leptons and four-fermion operators. We also discuss new physics in the context of simplified models and review Standard Model extensions with focus on those that can explain a possible deviation from unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

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Section: Future Prospects a Pion And Kaon Experimentsmentioning

confidence: 99%

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

Bryman,

Cirigliano,

Crivellin

et al. 2021

Preprint

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“…Finally, up to leading order in ∆ 2 /(m + + m 0 ) 2 2.8 × 10 −4 , the function f ( , ∆) has the value of f ( , ∆) 0.94104. The overall uncertainty of the rate in (19) is dominated by two comparable contributions, one from the ∆ 5 factor, and the other from the δ π radiative/loop corrections, each uncertainty contribution being in the range of 0.05-0.1% of the full rate [37,73,77,78]. Thus, the pion beta decay rate provides a direct means to determine the CKM matrix element |V ud |.…”

Section: General Considerations: Quark-lepton Universalitymentioning

confidence: 99%

Experimental study of rare charged pion decays

Počanić

Frlež

Schaaf

2014

J. Phys. G: Nucl. Part. Phys.

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The combination of simple dynamics, small number of available decay channels, and extremely well controlled radiative and loop corrections, make charged pion decays a sensitive means for testing the underlying symmetries and the universality of weak fermion couplings, as well as for improving our understanding of pion structure and chiral dynamics. This paper reviews the current state of experimental study of the allowed rare decays of charged pions: (a) leptonic, π + → e + ν e , or π e2 , (b) radiative, π + → e + ν e γ, or π e2γ , and π + → e + ν e e + e − , or π e2ee , and (c) semileptonic, π + → π 0 e + ν, or π e3 . Taken together, the combined data set presents an internally consistent picture that also agrees well with standard model predictions. The internal consistency is illustrated well by the π e2 branching ratio of (R π e/µ ) PIBETA = (1.2366±0.0064)×10 −4 extracted in this work from the PIBETA measurement of the π e3 decay and the current best value for the CKM matrix element V ud . However, even after the great progress of the recent decades, experimental precision is lagging far behind that of the theoretical description for all above processes. We review the implications of the present state of knowledge and prospects for further improvement in the near term.

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“…Pion beta decay, π + → π 0 e + ν(γ), provides the theoretically cleanest determination of the CKM matrix element V ud . With current input one obtains V ud = 0.9739 (28) exp (1) th , where the experimental uncertainty comes almost entirely from the π + → π 0 e + ν(γ) branching ratio (BRPB) [16] (the pion lifetime contributes δV ud = 0.0001), and the theory uncertainty has been reduced from (δV ud ) th = 0.0005 [19][20][21] to (δV ud ) th = 0.0001 via a lattice QCD calculation of the radiative corrections [22]. The current precision of 0.3% on V ud makes π + → π 0 e + ν(γ) not presently relevant for the CKM unitarity tests because super-allowed nuclear beta decays provide a nominal precision of 0.03%.…”

Section: Introductionmentioning

confidence: 99%

An LGAD-Based Full Active Target for the PIONEER Experiment

Mazza

2021

Instruments

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PIONEER is a next-generation experiment to measure the charged pion branching ratios to electrons vs. muons Re/μ=Γπ+→e+ν(γ)Γπ+→μ+ν(γ) and pion beta decay (Pib) π+→π0eν. The pion to muon decay (π→μ→e) has four orders of magnitude higher probability than the pion to electron decay (π→eν). To achieve the necessary branching-ratio precision it is crucial to suppress the π→μ→e energy spectrum that overlaps with the low energy tail of π→eν. A high granularity active target (ATAR) is being designed to suppress the muon decay background sufficiently so that this tail can be directly measured. In addition, ATAR will provide detailed 4D tracking information to separate the energy deposits of the pion decay products in both position and time. This will suppress other significant systematic uncertainties (pulse pile-up, decay in flight of slow pions) to <0.01%, allowing the overall uncertainty in to be reduced to O (0.01%). The chosen technology for the ATAR is Low Gain Avalanche Detector (LGAD). These are thin silicon detectors (down to 50 μm in thickness or less) with moderate internal signal amplification and great time resolution. To achieve a 100% active region several emerging technologies are being evaluated, such as AC-LGADs and TI-LGADs. A dynamic range from MiP (positron) to several MeV (pion/muon) of deposited charge is expected, the detection and separation of close-by hits in such a wide dynamic range will be a main challenge. Furthermore, the compactness and the requirement of low inactive material of the ATAR present challenges for the readout system, forcing the amplifier chip and digitizer to be positioned away from the active region.

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Observations on the radiative corrections to pionβdecay

Cited by 12 publications

References 21 publications

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

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

Experimental study of rare charged pion decays

An LGAD-Based Full Active Target for the PIONEER Experiment

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