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research
The Low Energy
Ï€
 
Ï€
\pi\,\pi
Ï€
Ï€
Amplitude to One and Two Loops
Authors
't Hooft
Adeva
+76Â more
Anderson
B. Moussallam
Baillargeon
Banks
Basdevant
Basdevant
Bernard
Bernard
Bijnens
Bijnens
Bijnens
Chetyrkin
Chew
Colangelo
Coleman
Dominguez
Donoghue
Dyakonov
Dyakonov
Ericson
Estabrooks
Fearing
Floratos
Frishman
Fuchs
Fuchs
Gasser
Gasser
Gasser
Gasser
Gasser
Gasser
Gasser
Gell-Mann
Georgi
Georgi
Glashow
Gupta
Hoogland
Hyams
J. Sterna
Jamin
Knecht
Knecht
Knecht
Knecht
Leutwyler
Leutwyler
Leutwyler
Leutwyler
M. Knecht
Maltman
Manohar
Morgan
Morgan
N.H. Fuchs
Nagels
Nambu
Nambu
Narison
Neufeld
Ochs
Olsson
Pennington
Petersen
Rosselet
Smilga
Stern
Stern
stern
Urech
Vafa
Vafa
Weinberg
Weinberg
Weinberg
Publication date
1 January 1995
Publisher
'Elsevier BV'
Doi
Cite
View
on
arXiv
Abstract
The low-energy
Ï€
Ï€
\pi\pi
ππ
amplitude is computed explicitly to two-loop accuracy in the chiral expansion. It depends only on six independent (combinations of) low-energy constants which are not fixed by chiral symmetry. Four of these constants are determined {\it via} sum rules which are evaluated using
Ï€
Ï€
\pi\pi
ππ
scattering data at higher energies. Dependence of the low-energy phase shifts and of the threshold parameters on the remaining two constants (called
α
\alpha
α
and
β
\beta
β
) are discussed and compared to the existing data from
K
l
4
K_{l4}
K
l
4
​
experiments. Using generalised
χ
\chi
χ
PT, the constants
α
\alpha
α
and
β
\beta
β
are related to fundamental QCD parameters such as the quark condensate
⟨
0
∣
q
ˉ
q
∣
0
⟩
\langle 0|\bar{q}q|0\rangle
⟨
0∣
q
ˉ
​
q
∣0
⟩
and the quark mass ratio
m
s
/
m
^
m_s/\widehat{m}
m
s
​
/
m
. It is shown that forthcoming accurate low-energy
Ï€
Ï€
\pi\pi
ππ
data can be used to provide, for the first time, experimental evidence in favour of or against the existence of a large quark-antiquark condensate in the QCD vacuum.Comment: 61 pages, LaTeX, 10 figures in separate tarred, compressed and uuencoded Postscript fil
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