Pion in the holographic model with 5D Yang-Mills fields

Abstract

We study pion in the holographic model of Hirn and Sanz which contains two Yang-Mills fields defined in the background of the sliced AdS space. The infrared boundary conditions imposed on these fields generate the spontaneous breaking of the chiral symmetry down to its vector subgroup. Within the framework of this model, we get an analytic expression for the pion form factor and a compact result for its radius. We also extend the holographic model to include Chern-Simons term which is required to reproduce the appropriate axial anomaly of QCD. As a result, we calculate the anomalous form factor of the pion and predict its Q 2 -slope for the kinematics when one of the photons is almost on-shell. We also observe that the anomalous form factor with one real and one virtual photon is given by the same analytic expression as the electromagnetic form factor of a charged pion. One of the advantages of the present model is that it does not require an infrared boundary counterterm to correctly reproduce the anomaly of QCD.

Pseudoscalar mass spectrum in a soft-wall model of AdS/QCD

“…We are particularly intrigued by this problem because the pseudoscalar representation used in refs. [6,12] appears to be incompatible with the representations used in [5,13,8,14]. Both are in the exponential form…”

Pion-Photon Transition Form Factor and Pion Distribution Amplitude in QCD: Facing the Enigmatic Behavior of the BaBar Data

“…Should the anomalous behavior of the π 0 BaBar data be confirmed by independent measurements, e.g., by the Belle experiment, then the BaBar effect will amount to crossing the Rubicon and the enigma will become a real challenge for QCD based on collinear factorization. Moreover, one would not be able to take recourse for an explanation to holographic models based on the AdS/QCD correspondence [29,30,40], because these are incompatible with the π 0 BaBar data at high Q 2 .…”

“…[28]. [17], whereas the dotted and the double-dotted-dashed lines denote two independent predictions derived from AdS/QCD in [29] and [30], respectively. The experimental data are taken from various experiments, referenced in the text.…”

“…The calculation of the π 0 , η, and η ′ TFFs has been carried out within holographic approaches of AdS/QCD, e.g., [29], [30], and [38]. In Fig.…”

What does Holographic QCD predict for anomalous (g− 2)μ?

“…For different HQCD models, they were worked out in a series of papers [12][13][14]. The relevant anomalous 3-point function AVV is obtained from the 5D Chern-Simons action (6), which contains the following trilinear term…”