Reggeon Field Theory for Large Pomeron Loops

We analyze the range of applicability of the high energy Reggeon Field Theory $H_{RFT}$ derived in [1]. We show that this theory is valid as long as at any intermediate value of rapidity $\eta$ throughout the evolution at least one of the colliding objects is dilute. Importantly, at some values of $\eta$ the dilute object could be the projectile, while at others it could be the target, so that $H_{RFT}$ does not reduce to either $H_{JIMWLK}$ or $H_{KLWMIJ}$. When both objects are dense, corrections to the evolution not accounted for in [1] become important. The same limitation applies to other approaches to high energy evolution available today, such as for example [3] and [4]. We also show that, in its regime of applicability $H_{RFT}$ can be simplified. We derive the simpler version of $H_{RFT}$ and in the large $N_c$ limit rewrite it in terms of the Reggeon creation and annihilation operators. The resulting $H_{RFT}$ is explicitly self dual and provides the generalization of the Pomeron calculus developed in [4] by including higher Reggeons in the evolution. It is applicable for description of `large' Pomeron loops, namely Reggeon graphs where all the splittings occur close in rapidity to one dilute object (projectile), while all the merging close to the other one (target). Additionally we derive, in the same regime expressions for single and double inclusive gluon production (where the gluons are not separated by a large rapidity interval) in terms of the Reggeon degrees of freedom.Comment: 38 pages, 4 figure

KLWMIJ Reggeon Field Theory beyond the large NcN_c limit

We extend the analysis of KLWMIJ evolution in terms of QCD Reggeon fields beyond leading order in the $1/N_c$ expansion. We show that there is only one type of corrections to the leading order Hamiltonian discussed in \cite{last}. These are terms linear in original Reggeons and quadratic in conjugate Reggeon operators. All of these have the interpretation as vertices of the "`merging"' type $2\rightarrow 1$, where two Reggeons merge into one. Importantly, the triple Pomeron merging vertex does not emerge from the KLWMIJ Hamiltonian. We show that, although in the range of applicability of the KLWMIJ Hamiltonian these merging terms are subleading in $N_c$, in the dense-dense regime they all become of the same (leading) order in $N_c$. In this regime vertices involving higher Reggeons are enhanced by inverse powers of the coupling constant.Comment: 25 page

Diffractive Dijet Production in Deep Inelastic Scattering and Photon-Hadron Collisions in the Color Glass Condensate

We study exclusive dijet production in coherent diffractive processes in deep inelastic scattering and real (and virtual) photon-hadron ($\gamma^{(*)}$-h) collisions in the Color Glass Condensate formalism at leading order. We show that the diffractive dijet cross section is sensitive to the color-dipole orientation in the transverse plane, and is a good probe of possible correlations between the $q\bar{q}$-dipole transverse separation vector \r and the dipole impact parameter \b. We also investigate the diffractive dijet azimuthal angle correlations and $t$-distributions in $\gamma^{(*)}$-h collisions and show that they are sensitive to gluon saturation effects in the small-$x$ region. In particular, we show that the $t$-distribution of diffractive dijet photo-production off a proton target exhibits a dip-type structure in the saturation region. This effect is similar to diffractive vector meson production. Besides, at variance with the inclusive case, the effect of saturation leads to stronger azimuthal correlations between the jets.Comment: 15 pages, 10 figures; v2: a clarifying Appendix added, 3 new plots added, references added. The version to appear in PL

Soft photon and two hard jets forward production in proton-nucleus collisions

We calculate the cross section for production of a soft photon and two hard jets in the forward rapidity region in proton-nucleus collisions at high energies. The calculation is performed within the hybrid formalism. The hardness of the final particles is defined with respect to the saturation scale of the nucleus. We consider both the correlation limit of small momentum imbalance and the dilute target limit where the momentum imbalance is of the order of the hardness of the jets. The results depend on the first two transverse-momentum-dependent (TMD) gluon distributions of the nucleus.Comment: 39 pages, 4 figure

Bose enhancement and the ridge

We point out that Bose enhancement in a hadronic wave function generically leads to correlations between produced particles. We show explicitly, by calculating the projectile density matrix in the Color Glass Condensate approach to high-energy hadronic collisions, that the Bose enhancement of gluons in the projectile leads to azimuthal collimation of long range rapidity correlations of the produced particles, the so-called ridge correlations.Comment: 5 pages, 1 figure; v2: 6 pages, 1 figure, discussions enlarged and technical details added, figure changed, final versio