Chiral symmetry breaking in QCD-like gauge theories with a confining propagator and dynamical gauge boson mass generation

Doff, A.; Machado, F. A.; Natale, A. A.

doi:10.1016/j.aop.2011.11.005

Cited by 30 publications

(80 citation statements)

References 50 publications

(136 reference statements)

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“…In this simulation the quark condensate qq is drastically reduced (≈40%) by removing very low momentum gluons. This last result is consistent with the CSB mechanism obtained in the confinement model of [6], as shown in [8], where most of the CSB is due to gluons with a momentum smaller than a few hundred MeV. Finally, continuum arguments also claim that confinement is necessary and sufficient for CSB [22].…”

Section: Chiral Symmetry Breaking As a Consequence Of Confinementsupporting

confidence: 88%

How may confinement affect technicolour?

2012

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Confinement has been introduced into the quark gap equation, as proposed by Cornwall, as a possible solution to the problem of chiral symmetry breaking in quantum chromodynamics with dynamically massive gluons. We argue that the same mechanism can be applied for technicolour with dynamically massive technigluons. Within this approach both theories develop a hard selfenergy dynamic, resulting from an effective four-fermion interaction, which does not lead to the known technicolour phenomenological problems. We outline a quite general type of technicolour model within this proposal that may naturally explain the masses of different fermion generations. Contents

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Section: Chiral Symmetry Breaking As a Consequence Of Confinementsupporting

confidence: 88%

How may confinement affect technicolour?

2012

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“…It has been argued that equation (6) may be a realistic wave function in a scenario where the chiral symmetry breaking is associated to confinement and the gluons have a dynamically generated mass [31,34,35]. This solution also appears when using an improved renormalization group approach in QCD, associated to a finite quark condensate [36], and it minimizes the vacuum energy as long as > n 5 f [37].…”

mentioning

confidence: 99%

“…which is an infrared finite coupling determined in QCD where gluons have an effective dynamical mass m g [38] and is consistent with the models of [31,34,35]. Λ QCD is the QCD characteristic scale.…”

mentioning

confidence: 99%

“…Furthermore, this is just one possible ansatz for the full behavior of the self-energy and other possible interpolations between the IR and ultraviolet (UV) behaviors are possible, but as long as Σ p ( ) 2 shows the logarithmic UV behavior our final result will not change. The coupling constant g 2 is calculated at the chiral symmetry breaking scale μ, and given by which is an infrared finite coupling determined in QCD where gluons have an effective dynamical mass m g [38] and is consistent with the models of [31,34,35]. Λ QCD is the QCD characteristic scale.…”

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confidence: 99%

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Limit on the pion distribution amplitude

Luna¹,

Natale²

2014

J. Phys. G: Nucl. Part. Phys.

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The pion distribution amplitude (DA) can be related to the fundamental QCD Greenʼs functions as a function of the quark self-energy and the quark-pion vertex, which in turn are associated with the pion wave function through the Bethe-Salpeter equation. Considering the extreme hard asymptotic behavior in momentum space allowed for a pseudoscalar wave function, which is limited by its normalization condition, we compute the pion DA and its second moment. From the resulting amplitude, representing the field theoretical upper limit on the DA behavior, we calculate the photon-pion transition form factor πγγ F Q ( ) * 2 . The resulting upper limit on the pion transition form factor is compared with existing data published by CLEO, BaBar and Belle Collaborations.Keywords: non-perturbative QCD, pion distribution amplitude, hadron physics (Some figures may appear in colour only in the online journal)A few years ago new data were published [1,2] for the γ γ π → * 0 process, where one of the photons is far off mass shell (large Q 2 ) and the other one is near mass shell ( ≈ Q 0 2 ). These measurements of the photon-pion transition form factor πγγ F Q ( ) * 2 , taken in the single-taggede e e e 0 reaction, were performed in a wide range of momentum transfer squared (4-40) GeV 2 ). At sufficiently high Q 2 it is expected that the standard factorization approach can be applied [3][4][5] (for a review, see [6]). The amplitude for this process at high virtuality has the form As a consequence of these experiments there were many theoretical papers speculating why the data should (or not) obey the BL limit [9][10][11][12][13][14][15][16][17][18][19]. The first attempt to explain the BaBar result can be found in [20]. Among these there were proposals claiming that the pion distribution amplitude should be modified [9][10][11]16], leading to a broader or flatter distribution in the place of the asymptotic form φas [21]. A flat DA would be consistent with the BaBar data, although a field theoretical support for such possibility is still missing. Some papers claim that other transition form factors of heavier mesons are compatible among themselves and with the saturation required by factorization theorems obtained from pQCD [13,22]. However, for heavier mesons than the pion the DA may be more peaked away from the end points [12]. A common statement in all papers is the need for more data to settle this problem.Meanwhile, the pion transition form factor is the most sensitive physical quantity to observe a non-perturbative contribution to the DA. Other quantities, for instance, like the pion form factor, may already contain a hard scattering amplitude at leading order with a soft behavior, due to the effect of extra coupling constants or gluon propagators [23]. This means that they do not lead to such a simple integral over a DA as the one shown by equation (1). As claimed in [24], we may assume that at present there is no definite conclusion on which is the asymptotic form of the pion DA, and it is possible that in the futur...

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“…(15) even in this case. It should be remembered that chiral symmetry breaking, or the dynamical generation of quark masses, in the presence of dynamically generated gluon masses is still a motive of debate [52,53], possibly being associated to the confinement mechanism [52], demanding a non-perturbative anomalous dimension calculation. However in the sequence we will just assume that we can use Eq.…”

Section: Analyticity and Anomalous Dimensionmentioning

confidence: 99%

QCD fixed points: Banks–Zaks scenario or dynamical gluon mass generation?

Gómez

Natale

2017

Int. J. Mod. Phys. A

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Fixed points in QCD can appear when the number of quark flavors (N f ) is increased above a certain critical value as proposed by Banks and Zaks (BZ). There is also the possibility that QCD possess an effective charge indicating an infrared frozen coupling constant. In particular, an infrared frozen coupling associated to dynamical gluon mass generation (DGM) does lead to a fixed point even for a small number of quarks. We compare the BZ and DGM mechanisms, their β functions and fixed points, and within the approximations of this work, which rely basically on extrapolations of the dynamical gluon masses at large N f , we verify that between N f = 8 and N f = 12 both cases exhibit fixed points at similar coupling constant values (g * ). We argue that the states of minimum vacuum energy, as a function of the coupling constant up to g * and for several N f values, are related to the dynamical gluon mass generation mechanism.

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Chiral symmetry breaking in QCD-like gauge theories with a confining propagator and dynamical gauge boson mass generation

Cited by 30 publications

References 50 publications

How may confinement affect technicolour?

How may confinement affect technicolour?

Limit on the pion distribution amplitude

QCD fixed points: Banks–Zaks scenario or dynamical gluon mass generation?

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