Mean life of the neutral pion

Dardel, G. Von; Dekkers, D.; Mermod, R.; Putten, J. D. van; Vivargent, M.; Weber, G.; Winter, K.

doi:10.1016/0031-9163(63)90584-5

Cited by 55 publications

(4 citation statements)

References 11 publications

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“…8,9 Then the relation between /^v and f K V is fixed as iT+(7r+)*--[l/(6)^% 0 +l/^Z" 0 7r 0 ]. Thus, from (12) and predict z=0.15 and Y(K 2 0 -* 2Y) = 8X10 3 sec" 1 , assuming (10) and (11). Corresponding to (15) we have r (S-->»+TT-) = (gV.W^Tr)9.6 X10 8 sec-1 so that if (g 2 2 0 nx 0 /47r)«6 the 2T->n+7r~ may be explained by this model.…”

mentioning

confidence: 81%

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Violation of|ΔI|=12Rule in theKπ3
Ôneda
¹
,
Hori
²

1963
Phys. Rev.
14
0
1
0
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The experimental value of the branching ratio T(K 2° -^x + +7r~+7r°)/r(i£ + ->7r + +7r~+7r 0 ) obtained by Alexander et al. differs from the prediction of the A/ = J rule by 30%. We assume that the major part of the violation of the A/ = \ rule in K v $ decay comes from the chain of processes K° -> r\ -» 7r + +7r~-j-7r°, as pointed out by Bouchiat et al. With this assumption, we get a relation between the coupling constant / 2 iey/47r and the width T(V -»7r + +7r~+7r°). We use the experimental value of the branching ratio r(?? -> neutrals)/r (rj -> 7r + -{-7r~-f-7r 0 ) ~ 3.0 to infer the unknown branching ratio r(r)°-*2y)/r(r}°->Tr + -\-7r~-\-Tr°) and the theory of unitary symmetry to deduce the value of the width T(Y)° -> 27) from the experimental decay rate of ir° -> 2y. Further, if only pion and 77-meson pole terms are responsible for the mass difference m(Ki°) -m(K 2°) , we can also derive the value of the coupling constant /W 0 /^. These two coupling constants / 2 xV/4T and j^x V/4TT are illustrated as a function of the deviation x from the Al = J rule. Under the same assumption we obtain a result that r (K 2° -• > 2y) is comparable to r (K 2° -> 7r + +7r~+7r°) or is negligibly small according as /KV and /KV are of the same sign or not. If the deviation x = 30% is really correct, the decay rate of 2~->?7-f-7r~ can be explained with g 2 2°nK 0 /4:ir 2 7 ) = 8X10 3 sec" 1 and the decay rate 2T -» n+ir~ can be fitted with g 2 2°»W4"7r~6. Precise experiments are desired on the decay K 2° -> 2y as well as on the decay K 2 Q -» 71-++7r--r-7r°.I F the I Al I = 1/2 rule were valid, the rate of K 2° -»7r++7r~+7r 0 decay can be related to that of K+-7r + +7r°+7r 0 decay.

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confidence: 81%

“…In Fig. 1 the variations of the values / 2 x°7T 0 and f 2 K°v° with x are shown by using, at the moment, the value of T(r] 0 -»7r + +7r~+7r°) given by (11).…”

Section: K°-mentioning

confidence: 99%

Violation of|ΔI|=12Rule in theKπ3
Ôneda
¹
,
Hori
²

1963
Phys. Rev.
14
0
1
0
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“…The mean lifetime is ca 10 −16 s, making a direct determination difficult. There was no real need to do this work, as a previous direct determination by von Dardel et al (1963) was sufficiently accurate for theoretical purposes. Estimates from an indirect approach in which the width of the π 0 is measured, and so the lifetime inferred, were also available.…”

Section: Measurement Of the Lifetime Of The Neutral Pionmentioning

confidence: 99%

James Watson Cronin. 29 September 1931 — 25 August 2016

Watson

2018

Biogr. Mems Fell. R. Soc.

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James (Jim) Cronin had two outstanding careers. The first, in particle physics, included the discovery of CP violation for which he and Val Fitch were awarded the Nobel Prize in 1980. During the second, in cosmic rays, he played a major role in raising the profile of that field, particularly through his leadership in the creation of the Pierre Auger Observatory, the largest cosmic-ray detector ever constructed. He will be remembered for his incisive mind, his modest style, his internationalism and his encouragement of young scientists, as well as for his brilliance as an experimental physicist and data analyst.

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“…A new lifetime 16 sec has been subsequently obtained. 13 In the "black box" picture where we used K 2 = a/m 2 to obtain the old n° lifetime we p must use 2a/m 2 to obtain the new one. Furthermore, if in our comparison of the ir° and 77 coupling strengths we use SU(3) coefficients, 14 we find the ratio of effective strengths (7r° -2y):(rf -2y):(?7 0 -ir-ny) to be 3:1:9/4.…”

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confidence: 99%

Decay Modes of the 960-MeVηππResonance

Brown

Faier

1964

Phys. Rev. Lett.

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The discovery of a new meson of mass about 960 MeV has been recently announced by two independent groups. 1 ' 2 The method of production (K" +p-~A+X°) shows that it must have isospin T = 0 or 1. The only well-established decay mode is^° -7r + +7r" + r7, which includes about half of the identified X° events, almost all of the remaining events consisting of decays of the type X°~all neutrals. Within the available statistics, the number of neutral decays is consistent with X° -7T° + 7T° + 77 being the companion mode to H^H'T). The absence of measurable decay into two, three, or four pions, together with the observation that five-pion decays almost always include three pions having total charge zero and effective mass corresponding to the 7? meson, leads to the conjecture that spin-par ity-G-parity assignment is either 0" + or 1 ++ , with 0" + being favored by the low rate of Assuming that X° has TJ PG = 00" + and that it decays mainly via the strong interactions, we show that the dominance of the TTTTT] mode implies that the principal mechanism iswhere a is an isosinglet neutral scalar meson. 5 We estimate the decay width for this process using an extension of the Coleman-Glashow notion of a unitary-symmetric scalar-meson coupling of universal strength. 6 We also obtain the branching ratios into subsidiary decay modes, including the electromagnetic modes. An interesting point is implied by this work: If the "A invariance" of Bronzan and Low 7 is relevant to decay processes, then X° must have A= -1.Disregarding for the moment the a meson, the allowed strong decays are into the modes mrr], 47r, and 6?r; we shall assume the last to be negligible. A conservative estimate of the four-pion partial decay width is r^o(47r)< 1 keV. This is based on the lowest possible angular-momentum configuration, that corresponding to two neutral di-pions having the quantum numbers of the p° meson. This rate is negligible compared with other partial rates discussed below. A straightforward calculation of X° -ir + + TT~ + 77, assuming a structureless vertex with effective coupling G'X°TT + iT~ri, gives the result 1^(7^-7?) = 2G' 2 keV,where G' is expected to be of order unity.The calculation of the rate for process (1) is exactly analogous to the calculation of 7j-~CT+7r° given in reference 5, except for omission of the factor a = 1/137 in the present case. The results areo o X 0 ' cp(w) = (w 2 -m r f) 1/2 (m x0 2 +m 2 -4^2-2ra__ 0 a>) : 7] ^ % X* 1/2 x (m^2 +rw^2-2w^)-1/2 , ^m^{ w^^m v'^2 )/2m^ (3) (4) (5) (6) (7) (8)and \x is the mass of the charged pion. The quantity g is the a7r + 7r~ coupling and is related to the mass m 0 and the width T 0 of the a meson by £-2 = r (327rm 2 )/3(m 2 -4/i 2 ) 1/2 .With m a = 400 MeV and T a = 100 MeV, one obtains (^2/4rrm a 2 ) = 0.93. The rate for X° -ir° + ir° + 77 is given by one half of the expression (3) with JLL 0 , the neutral pion mass, substituted everywhere for /i. As a first approach, we may consider equating the coupling constant at the X°TJ(J vertex (which we have denoted by gG) with ...

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Mean life of the neutral pion

Cited by 55 publications

References 11 publications

Violation of|ΔI|=12Rule in theKπ3
Ôneda
¹
,
Hori
²

1963
Phys. Rev.
14
0
1
0
View full text Add to dashboard Cite

Violation of|ΔI|=12Rule in theKπ3
Ôneda
¹
,
Hori
²

1963
Phys. Rev.
14
0
1
0
View full text Add to dashboard Cite

James Watson Cronin. 29 September 1931 — 25 August 2016

Decay Modes of the 960-MeVηππResonance

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Mean life of the neutral pion

Cited by 55 publications

References 11 publications

Violation of|ΔI|=12Rule in theKπ3Ôneda1, Hori2 1963Phys. Rev.14010View full textAdd to dashboardCite

Violation of|ΔI|=12Rule in theKπ3Ôneda1, Hori2 1963Phys. Rev.14010View full textAdd to dashboardCite

James Watson Cronin. 29 September 1931 — 25 August 2016

Decay Modes of the 960-MeVηππResonance

Contact Info

Product

Resources

About

Violation of|ΔI|=12Rule in theKπ3
Ôneda
¹
,
Hori
²

1963
Phys. Rev.
14
0
1
0
View full text Add to dashboard Cite

Violation of|ΔI|=12Rule in theKπ3
Ôneda
¹
,
Hori
²

1963
Phys. Rev.
14
0
1
0
View full text Add to dashboard Cite