Color Transparency and Light-Front Holographic QCD
Abstract
:- High-momentum transfer coherent reactions make point-like color-singlet objects, denoted as point-like configurations (PLCs). This statement was a prediction initially based on perturbative QCD (pQCD). For example, early pQCD calculations [5,6,7,8,9,10] of the pion elastic electromagnetic form factor were interpreted [11] to involve point-like configurations of quarks, meaning that the important regions of integration that contribute to the form factor are those in which the quark and anti-quark are very close together. The idea is that for the system to stay together when hit by a high-momentum virtual photon, the quark and anti-quark must be connected by the exchange of a high-momentum gluon, see Figure 1a. This idea is based on the ideas of perturbative QCD, but the validity of that version of QCD is not a necessary condition. Other strong interaction effects may also lead to the creation of a PLC.
- Small objects have small cross-sections. It has been widely reported that the imaginary part of the forward scattering amplitude, f, of a rapidly moving color singlet object is proportional to the square of the transverse separation b between positive and negative color charges. Two-gluon exchange [12,13,14] provides the lowest-order perturbative contribution to f. The remarkable feature is that, in the limit that b approaches 0, the cross-section vanishes because the color singlet point particles do not exchange colored gluons; concisely, This result is caused by interference between emission by quarks of different colors in coherent processes. Coherence means that one adds amplitudes to obtain the scattering amplitude, which is then squared to obtain the cross-section. The cancellation, known as color cancellation, is the basic ingredient behind QCD factorization proofs and is used elsewhere [15] and not questioned.
- A PLC, once created, will expand as it moves. This is because a PLC is not an eigenstate of the Hamiltonian. The expansion effect is diminished if the PLC moves with sufficiently high momentum.
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Miller, G.A. Color Transparency and Light-Front Holographic QCD. Physics 2022, 4, 590-596. https://doi.org/10.3390/physics4020039
Miller GA. Color Transparency and Light-Front Holographic QCD. Physics. 2022; 4(2):590-596. https://doi.org/10.3390/physics4020039
Chicago/Turabian StyleMiller, Gerald A. 2022. "Color Transparency and Light-Front Holographic QCD" Physics 4, no. 2: 590-596. https://doi.org/10.3390/physics4020039
APA StyleMiller, G. A. (2022). Color Transparency and Light-Front Holographic QCD. Physics, 4(2), 590-596. https://doi.org/10.3390/physics4020039