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Marko Djurić

Publications and source records attributed to Marko Djurić.

13 recordsLinked to original sources
arXiv2016

Soft Pomeron in Holographic QCD

We study the graviton Regge trajectory in Holographic QCD as a model for high energy scattering processes dominated by soft pomeron exchange. This is done by considering spin J fields from the closed string sector that are dual to glueball states of even spin and parity. In particular, we construct a model that governs the analytic continuation of the spin J field equation to the region of real J < 2, which includes the scattering domain of negative Maldelstam variable t. The model leads to approximately linear Regge trajectories and is compatible with the measured values of 1.08 for the intercept and 0.25 GeV$^{-2}$ for the slope of the soft pomeron. The intercept of the secondary pomeron trajectory is in the same region of the subleading trajectories, made of mesons, proposed by Donnachie and Landshoff, and should therefore be taken into account.

hep-ph↗
arXiv2015

Holographic Approach to Deep Inelastic Scattering at Small-x at High Energy

We focus on a holographic approach to DIS at small-x in high energy where scattering is dominated by exchanging a Reggeized Graviton in $AdS_5$. We emphasize the importance of confinement, which corresponds to a deformation of $AdS_5$ geometry in the IR. This approach provides an excellent fit to the combined HERA data at small $x$. We also discuss the connection of Pomeron/Odderon intercepts in the conformal limit with anomalous dimensions in strong coupling.

hep-ph↗
arXiv2015

Strong Coupling Expansion for the Conformal Pomeron/Odderon Trajectories

From the perspective of AdS/CFT the Pomeron is identified with a Reggeized Graviton, while the Odderons correspond to Reggeized anti-symmetric $AdS_5$ Kalb-Ramond tensor-fields. In this paper, we consider the strong coupling expansion of the dimension of the leading twist operators dual to these Regge trajectories, $Δ(j)$, to determine its analytic continuation in $j$ beyond the diffusion limit. In particular, we compute the strong coupling expansion of the intercept to order $λ^{-3}$, where $λ$ is the t'Hooft coupling, for both the Pomeron, which is $C=+1$ crossing-even, and the "Odderons", which are the leading $C=-1$ crossing-odd Regge singularities. We discuss the spectral curves of the class of single-trace operators to which these string modes couple.

hep-th↗
arXiv2014

Towards holographic QCD: AdS/CFT, confinement deformation, and DIS at small-x

We investigate the softwall AdS/CFT model. We specifically looked at the Pomeron, leading Regge contribution to a scattering process and used it to fit deep inelastic scattering data from the HERA collaboration. We find that the model fits the data with much more success than the purely conformal case, and find similar success to previous confinement models.

hep-ph↗
arXiv2013

Vector meson production at low x from gauge/gravity duality

We use gauge/gravity duality to study vector meson (J/Ψ, ρ_0, Ω, Φ) production in electron-proton scattering, in the limit of high center of mass energy at fixed momentum transfer, corresponding to the limit of low Bjorken x, where the process is dominated by pomeron exchange. Our approach considers the pomeron at strong coupling, described by the graviton Regge trajectory in AdS space with a hard-wall to mimic confinement effects. Both the proton and vector mesons are described by simple holographic wave functions in AdS. This model agrees with HERA H1 data with a χ^2 per degree of freedom below one on total cross-sections, and below two on differential cross-sections, confirming the success of previous studies that model low x DIS and DVCS using gauge/gravity duality.

hep-ph↗
arXiv2012

Deeply Virtual Compton Scattering and Higgs Production Using the Pomeron in AdS

In the past decade overwhelming evidence has emerged for a conjectured duality between a wide class of gauge theories in d dimensions and string theories on asymptotically AdS_{d+1} spaces. We apply this duality to scattering processes that occur via Pomeron exchange. First we develop the Pomeron in string theory, as done by Brower, Polchinski, Strassler and Tan, showing that it naturally emerges as the Regge Trajectory of the AdS graviton. Next we apply the AdS Pomeron to the study of Deeply Virtual Compton Scattering (DVCS), and see that our model gives good results when compared to HERA data. We then show how we can extend our results to double Pomeron exchange, and apply it to developing a formalism for the study of double diffractive Higgs production.

hep-ph↗
arXiv2012

Holographic Double Diffractive Production of Higgs and the AdS Graviton/Pomeron

The holographic approach to double diffractive Higgs production is presented for the AdS graviton/Pomeron. The goal is to provide a predictive phenomenology for the strong coupling expansion of QCD. This is the first step to set up the framework for the double diffractive Higgs production in anticipation of experimental observations at the LHC. Comparisons are made with the weak coupling approach based on the BFKL Pomeron models and soft Regge parameterizations.

hep-ph↗
arXiv2012

Small-x Deep Inelastic Scattering via the Pomeron in AdS

We examine the process of Deep Inelastic Scattering (DIS) in the small-x limit, where Pomeron exchange dominates. Using the AdS/CFT correspondence, we study Pomeron exchange in the dual string theory in AdS space, which allows us to study DIS at strong coupling. Two possibilities are examined, a purely conformal model, and a model with a hard-wall cutoff introduced to take into account the effects of confinement. Comparing our calculations with HERA DIS data, we find a very good agreement not only at large $Q^2$ dominated by conformal symmetry, but due to our strong coupling approach which allows us to go beyond traditional pQCD methods, at small $Q^2$ as well, taking into account all available HERA small x data.

hep-ph↗
arXiv2012

Deeply Virtual Compton Scattering from Gauge/Gravity Duality

We use gauge/gravity duality to study deeply virtual Compton scattering (DVCS) in the limit of high center of mass energy at fixed momentum transfer, corresponding to the limit of low Bjorken x, where the process is dominated by the exchange of the pomeron. Using conformal Regge theory we review the form of the amplitude for pomeron exchange, both at strong and weak 't Hooft coupling. At strong coupling, the pomeron is described as the graviton Regge trajectory in AdS space, with a hard wall to mimic confinement effects. This model agrees with HERA data in a large kinematical range. The behavior of the DVCS cross section for very high energies, inside saturation, can be explained by a simple AdS black disk model. In a restricted kinematical window, this model agrees with HERA data as well.

hep-th↗
arXiv2012

Diffractive Higgs Production by AdS Pomeron Fusion

The double diffractive Higgs production at central rapidity is formulated in terms of the fusion of two AdS gravitons/Pomerons first introduced by Brower, Polchinski, Strassler and Tan in elastic scattering. Here we propose a simple self-consistent holographic framework capable of providing phenomenologically compelling estimates of diffractive cross sections at the LHC. As in the traditional weak coupling approach, we anticipate that several phenomenological parameters must be tested and calibrated through factorization for a self-consistent description of other diffractive process such as total cross sections, deep inelastic scattering and heavy quark production in the central region.

hep-ph↗
arXiv2010

String-Gauge Dual Description of Deep Inelastic Scattering at Small-$x$

The AdS/CFT correspondence in principle gives a new approach to deep inelastic scattering as formulated by Polchinski and Strassler. Subsequently Brower, Polchinski, Strassler and Tan (BPST) computed the strong coupling kernel for the vacuum (or Pomeron) contribution to total cross sections. By identifying deep inelastic scattering with virtual photon total cross section, this allows a self consistent description at small-$x$ where the dominant contribution is the vacuum exchange process. Here we formulate this contribution and compare it with HERA small-$x$ DIS scattering data. We find that the BPST kernel along with a very simple local approximation to the proton and current "wave functions" gives a remarkably good fit not only at large $Q^2$ dominated by conformal symmetry but also extends to small $Q^2$, supplemented by a hard-wall cut-off of the AdS in the IR. We suggest that this is a useful phenomenological parametrization with implications for other diffractive processes, such as double diffractive Higgs production.

hep-ph↗
arXiv2009

Odderon in Gauge/String Duality

At high energies, elastic hadronic cross sections, such as $pp, \overline p p, π^{\pm} p$, are dominated by vacuum exchange, which in leading order of the $1/N_c$ expansion has been identified as the BFKL Pomeron or its strong AdS dual the closed string Reggeized graviton \cite{Brower:2006ea}. However the difference of particle anti-particle cross sections are given by a so-called Odderon, carrying C = -1 vacuum quantum numbers identified in weak coupling with odd numbers of exchanged gluons. Here we show that in the dual description the Odderon is the Reggeized Kalb-Ramond field ($B_{μν}$) in the Neveu-Schwartz sector of closed string theory. To first order in strong coupling, the high energy contribution of Odderon is evaluated for ${\cal N} = 4$ Super Yang-Mills by a generalization of the gravity dual analysis for Pomeron in Ref. \cite{Brower:2006ea}. The consequence of confinement on the Odderon are estimated in the confining QCD-like $AdS^5$ hardwall model of Polchinski and Strassler \cite{Polchinski:2001tt}.

hep-th↗