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Nehme, A.

doi:10.1103/physrevd.69.094012

Cited by 10 publications

(6 citation statements)

References 17 publications

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“…Regarding our model Lagrangian, the new couplings, the primed ones in (9), must not dominate over the N c dependence of the unprimed ones. This means that in their leading contributions they scale at most as the unprimed couplings, c i ∼ 1/N c , see (5) . Attributing this counting to the c i suffices to warrant that one can use the reparametrization freedom (9), in particular to obtain κ′ 1 = ḡ′ 9 = ḡ′ 10 = 0.…”

Section: Survey Of the Model Lagrangian II A Multiquark Picturementioning

confidence: 99%

“…This means that in their leading contributions they scale at most as the unprimed couplings, c i ∼ 1=N c , see (5). Attributing this counting to the c i suffices to warrant that one can use the reparametrization freedom (9), in particular to obtain κ 0 1 ¼ḡ 0 9 ¼ḡ 0 10 ¼ 0.…”

Section: A Multiquark Picturementioning

confidence: 99%

“…A detailed quantitative analysis however requires isospin breaking corrections to be taken into account in a series of low energy phenomena, such as the description of mass splittings of mesons and Dashen's theorem [3]; sum rules for quark condensates [2,4]; kaon decays [5]; π − π [6,7] and π − K scattering [8,9] in relation to mesonic atoms; [10,11], ρ and τ decays involving ηðη 0 Þ mesons [12]; and a 0 − f 0 mixing [13] in the scalar meson sector.…”

Section: Introductionmentioning

confidence: 99%

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π0−η−η′mixing in a generalized multiquark interaction scheme

2016

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We investigate the isospin symmetry breaking effects within a recently derived Nambu-Jona-Lasinio related model by fitting the measured pseudoscalar meson masses and weak decay couplings f π , f K . Our model contains the next to leading order terms in the 1=N c expansion of the effective multiquark Lagrangian, including the ones that break the chiral symmetry explicitly. We show the important phenomenological role of these interactions: (1) They lead to an accurate fit of the low-lying pseudoscalar nonet characteristics. (2) They account for a very good agreement of the current quark masses with the present PDG values. (3) They reduce by 40% the ratio ϵ=ϵ 0 of the π 0 − η and π 0 − η 0 mixing angles, as compared to the case that contemplates explicit breaking only in the leading order, bringing it in consonance with the quoted values in the literature. The conventional NJL-type models fail in the joint description of these parameters.

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Section: Survey Of the Model Lagrangian II A Multiquark Picturementioning

confidence: 99%

Section: A Multiquark Picturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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π0−η−η′mixing in a generalized multiquark interaction scheme

2016

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“…It is not yet clear if the most recent NNLO calculations support the energy dependence of the now precisely measured form factors. Isospin breaking effects may have to be taken into account as suggested in some preliminary work [33,34]. However, we can compare NA48/2 results with previous experimental results in terms of slopes and relative form factors using the absolute f s value of each experiment as a normalization factor and propagating errors as uncorrelated in absence of any published correlation information.…”

Section: S-and P-wave Form Factorsmentioning

confidence: 99%

Precise tests of low energy QCD from $\mbox {$\mathrm {K}_{\mathrm {e}4}$}$ decay properties

Batley¹,

Kalmus²,

Lazzeroni³

et al. 2010

Eur. Phys. J. C

126

214

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We report results from the analysis of the K ± → π + π − e ± ν (K e4 ) decay by the NA48/2 collaboration at the CERN SPS, based on the total statistics of 1.13 million decays collected in [2003][2004]. The hadronic form factors in the S-and P-wave and their variation with energy are obtained. The phase difference between the S-and P-wave states of the ππ system is accurately measured and allows a precise determination of a 0 0 and a 2 0 , the I = 0 and I = 2 S-wave ππ scattering lengths: a 0 0 = 0.2220 ± 0.0128 stat ± 0.0050 syst ± 0.0037 th , a 2 0 = −0.0432 ± 0.0086 stat ± 0.0034 syst ± 0.0028 th . Combination of this result with the other NA48/2 measurement obtained in the study of K ± → π 0 π 0 π ± decays brings an improved determination of a 0 0 and the first precise experimental measurement of a 2 0 , providing a stringent test of Chiral Perturbation Theory predictions and lattice QCD calculations. Using constraints based on analyticity and chiral symmetry, even more precise values are obtained: a 0 0 = 0.2196 ± 0.0028 stat ± 0.0020 syst and a 2 0 = −0.0444 ± 0.0007 stat ± 0.0005 syst ± 0.0008 ChPT .

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“…In the present work, we will use the method proposed in Ref. [11] to split analytically the isospin limit and isospin breaking part in form factors, allowing a first evaluation of isospin breaking effects in charged K ℓ4 decays.…”

Section: Introductionmentioning

confidence: 99%

Size of isospin breaking in charged $K_{\ell 4}$ decay

Nehme

2005

Eur. Phys. J. C

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We evaluate the size of isospin breaking corrections to form factors f and g of the K ℓ4 decay process K + → π + π − ℓ + ν ℓ which is actually measured by the extended NA48 setup at CERN. We found that, keeping apart the effect of Coulomb interaction, isospin breaking does not affect modules. This is due to the cancelation between corrections of electromagnetic origin and those generated by the difference between up and down quark masses. On the other hand, electromagnetism affects considerably phases if the infrared divergence is dropped out using a minimal subtraction scheme.Consequently, the greatest care must be taken in the extraction of ππ phase shifts from experiment.

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Splitting strong and electromagnetic interactions inKl4decays

Cited by 10 publications

References 17 publications

π0−η−η′mixing in a generalized multiquark interaction scheme

π0−η−η′mixing in a generalized multiquark interaction scheme

Precise tests of low energy QCD from $\mbox {$\mathrm {K}_{\mathrm {e}4}$}$ decay properties

Size of isospin breaking in charged $K_{\ell 4}$ decay

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