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We discuss diffractive photon production of vector mesons in holographic QCD. At large

Diffractive scattering at high energy is dominated by pomeron exchange, an effective object corresponding to the highest Regge trajectory. The slowly rising cross sections are described by the soft Pomeron with a small intercept (0.08) and vacuum quantum numbers. Reggeon exchanges have even smaller intercepts and are therefore subleading. Reggeon theory for hadron-hadron scattering with large rapidity intervals provide an effective explanation for the transverse growth of the cross sections

The soft Pomeron kinematics suggests an altogether nonperturbative approach. Through duality arguments, Veneziano suggested long ago that the soft Pomeron is a closed string exchange

In the past decade there have been several attempts at describing the soft pomeron using holographic QCD

Our approach is different from calculating the entire diffractive process in the holographic setup through the use of boundary currents and graviton exchange as in, e.g.,

The organization of the paper is as follows: In Sec.

In this section we briefly review the setup for dipole-dipole scattering using an effective string theory. For that we follow

Dipole-Dipole scattering.

Following standard arguments as in

In flat

In a valence quark picture an incoming meson is considered as a dipole made of a

Note that in flat

The description of the light-cone photon wave function in terms of a

We note that in

The vector meson wave function on the light cone will be sought by analogy with the photon wave function given above. Specifically we write

The partial diffractive cross sections for the production of longitudinal and transverse vector mesons are given by

The intrinsic light-cone distributions in the vector mesons are inherently nonperturbative. Our holographic setup for the description of the

With this in mind, consider an

In the presence of

We now suggest that the holographic wave function

For a massive spin-1 meson with the helicity content and quark mass analogous to the

The substitution

The size of the light-cone wave function is empirically constrained by the electromagnetic decay width

More specifically, the longitudinal wave function gives, for the right-hand side in

For a consistency check, the same rules apply to the transverse component of the current

Substituting the value of

Ratio

To carry out the numerical analysis, we can partially eliminate the model dependence in the transition amplitudes

With the exception of

Holographic parameters along with the model prediction for

In terms of

In Fig.

Differential cross section for

Total cross section for

In Figs.

Total cross section for

Differential cross section for

Differential cross section for

Differential cross section for

In Fig.

Differential cross section for

Differential cross section for

Finally, we note that the general result

In QCD the diffractive photoproduction of vector mesons on protons at large

The soft Pomeron parameters used in this work were previously constrained by the DIS data

This work was supported by the U.S. Department of Energy under Contract No. DE-FG-88ER40388. H. Y. R. and C. H. L. were partially supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP and MOE) (Grants No. 2015R1A2A2A01004238, No. 2016R1A5A1013277 and No. 2018R1D1A1B07048599).