Parity of the Neutral Pion

Plano, R.J.; Prodell, A.; Samios, N.; Schwartz, M.; Steinberger, J.

doi:10.1103/physrevlett.3.525

Cited by 40 publications

(20 citation statements)

References 6 publications

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“…Interestingly enough, double-virtual effects have never been measured, and are relevant for predicting the hadronic light-by-light contribution to the anomalous magnetic moment of the muon [23,24]. On the other hand, the angular distribution associated to the lepton planes (ϕ ≡ ϕl l;l 0 l 0 ) is a CP-sensitive observable and was indeed the first experimental evidence for the parity of the π 0 [12,25]. Since no significant amount of CP violation is expected in these processes within the standard model, any signal of this would be very interesting.…”

Section: Introductionmentioning

confidence: 99%

Radiative corrections to double-Dalitz decays revisited

2018

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In this study, we revisit and complete the full next-to-leading order corrections to pseudoscalar doubleDalitz decays within the soft-photon approximation. Comparing to the previous study, we find small differences, which are nevertheless relevant for extracting information about the pseudoscalar transition form factors. Concerning the latter, these processes could offer the opportunity to test them-for the first time-in their double-virtual regime.

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Section: Introductionmentioning

confidence: 99%

Radiative corrections to double-Dalitz decays revisited

2018

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“…The first experimental observation of a double Dalitz decay was published in 1962 [6,7]. A total of 206 examples of the decay π 0 → e + e − e + e − were observed by Samios in a sample of some 800,000 bubble chamber photographs.…”

Section: Introductionmentioning

confidence: 99%

Radiative corrections to double Dalitz decays: Effects on invariant mass distributions and angular correlations

et al. 2003

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We review the theory of meson decays to two lepton pairs, including the cases of identical as well as non-identical leptons, as well as CP-conserving and CP-violating couplings. A complete lowestorder calculation of QED radiative corrections to these decays is discussed, and comparisons of predicted rates and kinematic distributions between tree-level and one-loop-corrected calculations are presented for both π 0 and K 0 decays. PACS numbers: 12.15.Lk, 13.20.Cz, 13.20.Eb, 13.40.Gp, 13.40.Hq I. BACKGROUNDMeson decays to two photons should exhibit interesting correlations between the photon polarizations [1]. Although existing particle detectors cannot measure photon polarizations directly, it has long been known that the polarization correlations can be measured indirectly by studying angular correlations in the related double Dalitz decays [2] in which both photons undergo internal conversion to a lepton pair. More recently, it has been pointed out [3] that a detailed study of these correlations can be used to determine the relative amount of two possible meson-γγ couplings (one CP-conserving and one CP-violating for mesons that are CP eigenstates) that can contribute to this process.Dalitz and double Dalitz decays are also of interest because they can be exploited to perform a measurement of the electromagnetic form factor of the decaying mesonthat is, how the meson couples to one real and one virtual photon (Dalitz decay) or two virtual photons (double Dalitz) depends on the q 2 values of the photon(s). An accurate knowledge of this form factor is essential, for example, to calculate the so-called long-distance contribution to the rare decay K L → µ + µ − . The short-distance contribution to this process, mediated by loops involving heavy quarks and massive vector bosons, is sensitive to the CKM matrix element V td , but this contribution cannot be extracted from the accurate experimental measurement of the partial width unless the long-distance amplitude is precisely known.The tree-level rates for several double Dalitz processes have been published in various forms [2,3,4,5]. The first experimental observation of a double Dalitz decay was published in 1962 [6,7]. A total of 206 examples of the decay π 0 → e + e − e + e − were observed by Samios in a sample of some 800,000 bubble chamber photographs. Based on the observed angular correlations, Samios was * E-mail: tonyb@cuhep.colorado.edu † Current address: Department of Physics, 104 Davey Lab, Pennsylvania State University, University Park, PA 16802-6300. able to exclude the possibility that the π 0 was a scalar particle (with a CP-conserving decay) at the 3.3σ confidence level. His measurement of the branching ratio for that process remains the only one published to date.Experimental observations of the much rarer kaon double Dalitz decays began to appear in the 1990's. Several measurements have been made of the decay K L → e + e − e + e − [8,9,10,11,12,13,14], the most recent of which are based on several hundred observed events. The still rarer doub...

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“…In another example, Dick's work on the single conversion in π 0 decays was extended by N. N. Kroll and W. Wada to the double-Dalitz process π 0 → e + e − e + e − (Kroll & Wada 1955). Their analysis was used by Plano et al (1959) to establish that the parity of the π 0 was odd, the same as that of the charged pions.…”

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Richard Henry Dalitz. 28 February 1925 — 13 January 2006

Aitchison¹,

Smith²

2016

Biogr. Mems Fell. R. Soc.

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Richard (Dick) Henry Dalitz was a theoretical physicist whose principal contributions were intimately connected to some of the major breakthroughs of the twentieth century in particle and nuclear physics. His formulation of the ‘τ–θ’ puzzle led to the discovery that parity is not a symmetry of nature—the first of the assumed space-time symmetries to fail. He pioneered the theoretical study of hypernuclei, of strange baryon resonances, and of baryon spectroscopy in the quark model (at a time when many considered it ‘naive’), to all of which he made lasting contributions. The ‘Dalitz plot’ and ‘Dalitz pairs’ are part of the vocabulary of particle physics. Throughout his career he remained in close touch with many experimentalists, and he had an encyclopaedic knowledge of the data. Many of his papers were stimulated by experimental results and were concerned with their analysis and interpretation, work that often required the forging of new phenomenological tools; many also indicated what new experiments needed to be done. As a consequence, he was a theorist exceptionally valued by experimentalists. He created and ran a strong particle theory group at Oxford, which attracted many talented students and researchers, and which has continued to thrive.

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Parity of the Neutral Pion

Cited by 40 publications

References 6 publications

Radiative corrections to double-Dalitz decays revisited

Radiative corrections to double-Dalitz decays revisited

Radiative corrections to double Dalitz decays: Effects on invariant mass distributions and angular correlations

Richard Henry Dalitz. 28 February 1925 — 13 January 2006

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