Resummation, Evolution, Factorization 2025

Session

Thursday

16 Oct 2025, 08:45

Sala Consiglio (Physics Department, Milan University)

25. The CGC/TMD correspondence: TMD factorisation and evolution at small x

Edmond Iancu (Institut de Physique Théorique de Saclay)

16/10/2025, 08:45

We discuss TMD factorisation at high energy (or small $x$), as emerging from the Color Glass Condensate (CGC) effective theory. We first present exemples of high-energy processes for which TMD factorisation was shown to hold at leading order in CGC perturbation theory. This includes back-to-back di-jet production in electron-nucleus ($eA$) and proton-nucleus ($pA$) collisions, single inclusive...

38. Diffractive jets and evolution of DTMDs in coordinate and momentum space

DIONYSIS TRIANTAFYLLOPOULOS (ECT*, Trento)

16/10/2025, 09:10

We consider diffractive production of two or three jets in high energy photon-nucleus collisions. We show that the leading twist contribution for two hard jets is sensitive to gluon saturation and is determined by large three-parton configurations with size $R \sim 1/Q_s$, with $Q_s$ the nuclear saturation momentum. The corresponding cross section can be written in a factorized form and in...

40. Transverse momentum dependent factorisation in the target fragmentation region at small x

Paul Caucal (SUBATECH, Nantes Université, IN2P3/CNRS)

16/10/2025, 09:35

In this talk, based on [1], I will discuss the differential cross-section for single-inclusive jet/hadron production with transverse momentum $P_\perp$ in Deep Inelastic Scattering (DIS) at small Bjorken $x_{\rm Bj}$, mediated by a virtual photon with virtuality $Q^2$. Unlike most studies at small $x$, which focus on particle production in the current fragmentation region, this study...

42. From JIMWLK to CSS

Michael Lublinsky (BGU)

16/10/2025, 10:30

We demonstrate how the low x evolution (JIMWLK Hamiltonian) can be adapted to derive an evolution equation for TMDs. The latter are traditionally described using the CSS equation.Our work establishes
a connection between the two formalisms.

32. Reggeon exchange off the lightcone

Andrea Simonelli (Istituto Nazionale di Fisica Nucleare)

16/10/2025, 10:55

The relationship between Regge theory and the formalism of Collins-Soper-Sterman is explored by considering the off lightcone effects induced in color octet exchange in $2\to2$ forward scattering. An attempt to unify the language of rapidity divergences and high-energy asymptotic behavior is presented, with insights on the extensions of $k_T$-factorization beyond leading-log accuracy and the...

6. Higher-twist corrections to exclusive vector meson production at high energies

Michael Fucilla

16/10/2025, 11:20

We present a framework that combines the higher-twist formalism for exclusive processes in the $s$-channel with the semi-classical effective theory describing small-$x$ dynamics in the $t$-channel. This framework is applied to the exclusive production of a transversely polarized light vector meson—a process that starts at next-to-leading power and for which standard collinear factorization...

33. Conformal Small-$x$ Evolution at the QCD Wilson–Fisher Point

Giovanni Antonio Chirilli (University of Salento)

16/10/2025, 11:45

We develop a conformal formulation of small-$x$ QCD at the Wilson--Fisher point $d=4-2\epsilon_\ast$. In $d=4$ the LO BK kernel is M\"obius invariant, and at the critical coupling the BK/BFKL evolution \emph{remains} conformal through NLO (with the appropriate composite/conformal dipole), yielding power-law eigenfunctions, an explicitly organized $b_0$ dependence, and a shifted Pomeron...

44. Small-x resummation of photon impact factors and virtual photon scattering at high energies

Dimitri Colferai (Istituto Nazionale di Fisica Nucleare)

16/10/2025, 13:40

I present the renormalization group improved collinear resummation of the
photon-gluon impact factors. We construct the resummed cross section for
virtual photon-photon (𝛾∗𝛾∗) scattering
which incorporates the impact factors and BFKL gluon Green’s function up
to the next-to-leading logarithmic accuracy in energy. The impact factors
include important kinematical effects which
are...

7. On the interplay between the BFKL resummation and high-energy factorization in Mueller-Navelet dijet production

Alexey Chernyshev (BLTP JINR)

16/10/2025, 14:05

We study the interplay between the high-energy resummation based on the BFKL equation [1] and initial state radiation effects, taken into account within the framework of the high-energy factorization [2-4] in the production of Mueller-Navelet dijets [5] at hadron colliders. We use the solution of the NLO BFKL equation built out of eigenfunctions perturbatively constructed up to NLO [6] to...

51. Small-x resummation for muon colliders

Marco Bonvini (Istituto Nazionale di Fisica Nucleare)

16/10/2025, 14:30

In the context of an ongoing project, I will motivate the interest for the inclusion of small-x resummation in the computation of the parton distributions in a muon, relevant for the description of scattering processes at a future muon collider. To achieve this task, some technical developments have been made, that I will briefly review.

26. Understanding the collinearly-improved high-energy evolution

Maxim Nefedov (Ben Gurion University)

We study the consequences of collinear resummation in the kernel of JIMWLK equation, proposed in hep-ph/2308.15545 in the linear regime, which is relevant for several observables in high-energy hadronic collisions, such as Mueller-Navelet dijet production. We show that DGLAP evolution of the projectile is indeed correctly reproduced by the resummed kernel and discuss the role of...