Abstract:We discuss some phenomenological applications of an infrared finite gluon propagator characterized by a dynamically generated gluon mass. In particular we compute the effect of the dynamical gluon mass on pp andpp diffractive scattering. We also show how the data on γp photoproduction and hadronic γγ reactions can be derived from the pp andpp forward scattering amplitudes by assuming vector meson dominance and the additive quark model.
I. A QCD-INSPIRED EIKONAL MODEL WITH A GLUON DYNAMICAL MASSNowadays, severa… Show more
“…In this model (henceforth referred to as DGM model) the onset of the dominance of semihard gluons in the interaction of high-energy hadrons is managed by the dynamical gluon mass m g [11] (intrinsically related to an infrared finite gluon propagator, [12]) whose existence is strongly supported by recent QCD lattice simulations [13] as well as by phenomenological results [6,11,14,15,16,17]; for recent reviews on the phenomenology of massive gluons see Ref. [18] and references therein. In the DGM model the infrared coupling constant is also a function of the dynamical gluon mass [11].…”
Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small x behavior of the gluon distribution function at moderate Q2 is directly related to the rise of total hadronic cross-sections. In this model the rise of total cross-sections is driven by gluon–gluon semihard scattering processes, where the behavior of the small x gluon distribution function exhibits the power law xg(x, Q2) = h(Q2)x-∊. Assuming that the Q2 scale is proportional to the dynamical gluon mass one, we show that the values of h(Q2) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales.
“…In this model (henceforth referred to as DGM model) the onset of the dominance of semihard gluons in the interaction of high-energy hadrons is managed by the dynamical gluon mass m g [11] (intrinsically related to an infrared finite gluon propagator, [12]) whose existence is strongly supported by recent QCD lattice simulations [13] as well as by phenomenological results [6,11,14,15,16,17]; for recent reviews on the phenomenology of massive gluons see Ref. [18] and references therein. In the DGM model the infrared coupling constant is also a function of the dynamical gluon mass [11].…”
Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small x behavior of the gluon distribution function at moderate Q2 is directly related to the rise of total hadronic cross-sections. In this model the rise of total cross-sections is driven by gluon–gluon semihard scattering processes, where the behavior of the small x gluon distribution function exhibits the power law xg(x, Q2) = h(Q2)x-∊. Assuming that the Q2 scale is proportional to the dynamical gluon mass one, we show that the values of h(Q2) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales.
“…Chapter 6 gives a value 0.5. We can also compare this result to phenomenological determinations [29,30,31] of α s (q 2 0) 0.7 ± 0.3 coming from studies of infrared-sensitive scattering data. But in the real world to which these data apply, there are three families of light quarks, so we have to modify the FSE estimate.…”
Section: The Proposed Infrared-effective Actionmentioning
A brief summary of d = 3 NAGTs
IntroductionNAGTs in three dimensions have valuable applications in their own right because they are the high-temperature limit of d = 4 NAGTs with infrared slavery (see Chapter 11 for more details). They also lead to important insights into d = 4 NAGTs at zero T , and in many ways, d = 3 QCD is more interesting to study to gain this insight than the far more often-invoked two-dimensional theories. It is not a free-field theory (as is a d = 2 pure-gauge NAGT), and it has many features strongly analogous to those of d = 4 NAGTs that are best understood by applying the pinch technique. In particular, although a d = 3 NAGT cannot be asymptotically free (because it is superrenormalizable, not possessing the usual renormalization group), it is still very much infrared unstable, with even worse singularities than those in d = 4. Although this d = 3 infrared slavery had been strongly suspected before the pinch technique on the basis of conventional Feynman graph calculations, it took the pinch techniqe to settle the issue and demonstrate the existence of infrared slavery in d = 3 NAGTs.Because a d = 3 NAGT is the critical nonperturbative part of the high-temperature behavior of its d = 4 counterpart, infrared slavery prevents the use of perturbation theory (beyond O(g 4 3 )) in understanding all the phenomena of high temperature, including generation of a so-called magnetic mass, which vanishes identically to all orders of perturbation theory. Just as we have already seen at zero temperature, the magnetic mass, found from the PT Schwinger-Dyson equations, cures the otherwise intractable infrared singularities of high-temperature d = 4 gauge theories. We study here only the d = 3 NAGT part of finite-temperature d = 4 NAGTs, In this chapter, we continue to use the notation introduced in Chapter 7. Also in the present chapter, g 3 is the d = 3 NAGT coupling, and g continues to be the d = 4 coupling.
“…Therefore the infrared finiteness of the effective charge can be considered as one of the manifestations of the phenomenon of dynamical gluon mass generation. Phenomenology sensitive to infrared properties of QCD gives: α s (0) ≃ 0.7 ± 0.3 [61][62][63], while the phenomenological evidences for the strong coupling constant freezing in the infrared are much more numerous, as with the models where a static potential is used to compute the hadronic spectra make use of a frozen coupling constant at long distances, for more details see for example the Ref. [64].…”
The exotic J P C =1 −+ resonance π1(1600) is examined in the framework of the Quark Model with Constituent Gluon (QMCG). We report the possibility of interpreting that resonance as q qg meson, with a masse ≃ 1.65 +0.05 −0.04 GeV and a decay width to ρπ ≃ 0.28 +0.14 −0.09 GeV.
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