Summary
The paths of zeros of the low-energy K-π scattering amplitudes\(A^{I_s = \tfrac{3}{2}} \) and\(A^{I_t = 1} \) are examined in a simple K* and ρ dominance model, where it is found that the roles of PCAC zero, K* and ρ Legendre zero, and double-pole-killing zero are played by the same zero-contour in the (s, t, u)-plane, an ellipse for the first amplitude, an ellipse plus the lines=u for the second one. The behaviour of these zero-contours in theu-channel physical region is studied in comparison with the experimental zeros determined from the K+π−→K+π− and K+π0→K0π− scattering results, and it is found that up to the K* mass region the elliptic contour of\(A^{I_s = \tfrac{3}{2}} \) is essentially unaffected by unitarity, whilst the elliptic contour of\(A^{I_t = 1} \) is slightly more sensitive to such constraints. A comparison with the behaviour of the zeros of the corresponding π-π amplitudes\(A_{\pi \pi }^{I_s = 2} \) and\(A_{\pi \pi }^{I_t = 1} \) is also performed.
Riassunto
Si esaminano i percorsi di zero delle ampiezze di scattering a bassa energia\(A^{I_s = \tfrac{3}{2}} \) e\(A^{I_t = 1} \) in un semplice modello di dominanza di K* e ρ, in cui si trova che i ruoli degli zeri di PCAC, di Legendre K* e ρ, e di eliminazione dei poli doppi sono sostenuti dagli stessi contorni di zero nel pianos,t,u: un ellisse per la prima ampiezza e un ellisse più la lineas=u per la seconda. Si studia l’andamento di questi contorni di zero nella regione di interesse fisico del canaleu, a confronto degli zeri sperimentali determinati a partire dai risultati degli scattering K+π−→K+π− e K+π0→K0π− e si trova che fino alla regione della massa del K* il contorno ellittico di\(A^{I_s = \tfrac{3}{2}} \) essenzialmente non risente dell’unitarietà, mentre il contorno ellittico di\(A^{I_t = 1} \) è leggermente più sensibile a queste condizioni. Si fa anche un confronto con l’andamento degli zeri delle ampiezze ππ corrispondenti\(A_{\pi \pi }^{I_s = 2} \) e\(A_{\pi \pi }^{I_t = 1} \).
Реэюме
Иследуются траектории нулей амплитуд\(A^{I_s = \tfrac{3}{2}} \) и\(A^{I_t = 1} \) рассеяния K-π при ниэких знергиях в простой модели с доминантностью K* и ρ, где обнаружено, что роли нуля PCAC, нуля Лежандра для K* и ρ и нуля, подавляюшего двойной полюс, исполняют нулевой контур в (s, t, u)-плоскости, зллипс для первой амплитуды, зллипс плюс линияs=m для второй амплитуды. Поведение зтих нулевых контуров в фиэической области μ-канала сравнивается с зкспериментальными нулями, определенными иэ реэультатов рассеяния K+π−→K+π− и K+π0→K0π−. Получено, что вплоть до массовой области K* зллиптический контур\(A^{I_s = \tfrac{3}{2}} \), по сушеству, не эависит от унитарности, тогда как зллиптический контур для\(A^{I_t = 1} \) является чувствительным к таким ограничениям. Также проводится сравнение поведения нулей соответствуюших π-π амплитуд\(A_{\pi \pi }^{I_s = 2} \) и\(A_{\pi \pi }^{I_t = 1} \).
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Arneodo, A. Zero-contours in low-energy K-π scattering. Nuov Cim A 25, 511–533 (1975). https://doi.org/10.1007/BF02820862
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DOI: https://doi.org/10.1007/BF02820862