The 125 GeV boson: A composite scalar?

Doff, A.; Luna, Emerson Gustavo de Souza; Natale, A. A.

doi:10.1103/physrevd.88.055008

Cited by 14 publications

(43 citation statements)

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“…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.…”

Section: Introductionmentioning

confidence: 99%

“…However this result comes out from the homogeneous BSE. The non-homogeneous BSE also includes a normalization condition, as discussed in [27,30,31], that is obeyed by equation (5) but when applied to equation (6) (5) exists, because it would be the only one obeying the BSE normalization condition. This also means that if ⩾ N 6 f QCD may have a chiral broken phase whose selfenergy is given by equation (6).…”

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confidence: 99%

“…up to → ∞ p 2 , this is why we will consider n f = 6). To obtain the extreme field theoretical limit on the pion DA, we shall also work with a simple interpolating expression that roughly reflects the full behavior of the 'hardest' quark self-energy (or BSE solution) discussed in the previous paragraphs, namely [31,35] Note that the μ factor introduced into the logarithm denominator leads to the right infrared2 ). 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.…”

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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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Section: Introductionmentioning

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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“…[40][41][42]53] we discussed the possibility of obtaining a light composite TC scalar boson, and this result is a direct consequence of extreme walking (or quasi-conformal) technicolor theories, where the asymptotic self-energy behavior is described by Eq. (1).…”

Section: Discussionmentioning

confidence: 99%

“…[54,55] we discuss a mechanism for the dynamical mass generation, including the mass generation for the t quark, in the case of grand unified theories that incorporate quarks and techniquarks. We expect that a similar mechanism to the one described in [54,55] can be developed and incorporated in the present model. In Sect.…”

Section: Discussionmentioning

confidence: 99%

The extreme walking behavior in a 331-TC model

Doff

2016

Eur. Phys. J. C

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It is quite possible that the technicolor problems are related to the poorly known self-energy expression, or the way chiral symmetry breaking (CSB) is realized in nonabelian gauge theories. Actually, the only known laboratory to test the CSB mechanism is QCD. The TC dynamics may be quite different from the QCD, this fact has led to the walking TC proposal making the new strong interaction almost conformal and changing appreciably its dynamical behavior. There are different ways to obtain extreme walking (or quasiconformal) technicolor theories, in this paper we propose a scheme to obtain this behavior based on an extension of the electroweak sector of the standard model, in the context of so-called 331-TC model.

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Light composite scalar boson from a see-saw mechanism in two-scale TC models

Doff

Natale

2015

Physics Letters B

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We consider the possibility of a light composite scalar boson arising from mass mixing between a relatively light and heavy scalar singlets in a see-saw mechanism expected to occur in two-scale Technicolor (TC) models. A light composite scalar boson can be generated when the TC theory features two technifermions species in different representations, R 1 and R 2 , under a single technicolor gauge group, with characteristic scales Λ 1 and Λ 2 . We determine the final composite scalar fields, Φ 1 and Φ 2 , effective theory using the effective potential for composite operators approach. To generate a light composite scalar it is enough to have a walking (or quasi-conformal) behavior just for one of the technifermions representations.The nature of the electroweak symmetry breaking is one of the most important problems in particle physics, and the 125 GeV new resonance discovered at the LHC [1] has many of the characteristics expected for the Standard Model (SM) Higgs boson. If this particle is a composite or an elementary scalar boson is still an open question. Many models have considered the possibility of a light composite Higgs based on effective Higgs potentials as reviewed in Ref.[2]. The reason for the existence of the different models (or different potentials) for a composite Higgs, is a consequence of our poor knowledge of the strongly interacting theories, that is reflected in the many choices of parameters in the effective potentials. On the other hand the composite scalar boson mass can be calculated based on the dynamics of the theory [3], and this approach, although more complex, is more restrictive than the analysis of potential coefficients in

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The 125 GeV boson: A composite scalar?

Cited by 14 publications

References 56 publications

Limit on the pion distribution amplitude

Limit on the pion distribution amplitude

The extreme walking behavior in a 331-TC model

Light composite scalar boson from a see-saw mechanism in two-scale TC models

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