The high-energy limit of 2 $\to$ 2 QCD scattering amplitudes has a rich history and recently there has been much renewed interest in the perturbative regime. In this talk, I review the salient features of this limit and present an overview of recent results. At Leading Logarithmic (LL) accuracy the partonic amplitude is governed by Regge poles in the complex angular momentum plane. Beyond LL,...
The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is used to precisely, $\sigma_P^{\rm syst}/P\sim0.5\%$, measure the absolute (vertical) polarization of the proton beams at the Relativistic Heavy Ion Collider (RHIC). At HJET, the recoil protons from the beam Coulomb-nuclear interference scattering ($0.0013<-t<0.018\,\rm{GeV}^2$) off the jet target are detected in the vertically...
The anomalous excess of small-kT photons radiated along with multi-hadron production, is challenging the physics community over four decades, but no solution has been proposed so far. We argue that the problem is rooted in the comparison with an incorrect model, usually called โbremsstrahlung modelโ.
The Low theorem, proven only for diffractive photon radiation, relates it to the elastic...
Soft hadronic collisions with multiple production of (anti)quarks accompanied with soft photon radiation are described in terms of higher Fock states of the colliding hadrons, which contain a photon component as well. The Fock state distribution functions are shaped with the Quark-Gluon String Model. Photon radiation by quarks is described within the color-dipole phenomenology. The results of...
The production of jets at hadron provides stringent tests of perturbative QCD. We present the latest measurements using proton-proton collision data collected by the ATLAS experiment at $\sqrt{s}=13$ TeV. We will discuss the measurement of new event-shape jet observables defined in terms of reference geometries with cylindrical and circular symmetries using the energy movers distance. The...
Central diffractive event topologies at the LHC energies can be identified by two different approaches. First, the forward scattered protons can be measured in Roman pots. Second, a veto on hadronic activity away from midrapidity can be imposed to define a double gap topology. Such a double gap trigger has been implemented by the ALICE collaboration in Run 1 and Run 2 of the LHC. The analysis...
I will introduce the physics scope and state-of-the-art technology of GRANIITTI [[github.com/mieskolainen/graniitti][1]], a fully multithreaded C++17 language-driven Monte Carlo event generator designed especially for the central exclusive glueball searches and studies at the LHC and beyond. The extendable set of processes span currently from $\gamma\gamma$-EW and Durham QCD to...
Coherent photoproduction of heavy quarkonia on nuclear targets is studied within the QCD color dipole formalism including several main phenomena:
-i) The higher-twist nuclear shadowing related to the $Q\bar Q$ Fock state of the photon;
-ii) The correlation between impact parameter of a collision $\vec b$ and dipole orientation $\vec r$;
-iii) The leading-twist gluon shadowing corresponding...
We discuss the current status of the ongoing project on
searches for the QCD instantons at hadron colliders
in events with large rapidity gaps. These gaps in rapidity
are formed by either Pomeron or photon exchanges or a combination
of the two. We computed for the first time the relevant
differential cross-sections for a complete set of instanton production
in single diffraction and...
We turn high energy elastic scattering of hadrons into an initial value problem using an evolution equation based on the Regge Field Theory, which has a form of the complex nonlinear reaction-diffusion equation, with time being played by the logarithm of energy. The initial conditions are provided by the data-driven models for the real and imaginary parts of the amplitude. Numerical...
We study the rapidity dependence of the central exclusive production cross sections of C-even mesons in pA and AA collisions, where A is a heavy ion. We observe qualitatively different behaviour of the contributions arising from photon-Odderon and PomeronโPomeron fusion mechanisms. This can be used to extract the Odderon signal from C-evenโ mesons exclusively produced in the forward region....
The Real Extended Bialas-Bzdak (ReBB) model is shown here to describe, in the $0.37 \le -t \le 1.2$ GeV$^2$ region, the proton-proton elastic differential cross section data published by the TOTEM Collaboration at LHC at $\sqrt{s} = 8 $ TeV center of mass energy. In this kinematic range, corresponding to the diffractive minimum-maximum region, a model-dependent Odderon signal higher than 18...
We analyze, model-independently, the scaling properties of the differential cross-section of elastic proton-proton cross-sections, including new TOTEM data published in 2022 at sqrt(s) = 8 TeV. We show that outside the signal region for Odderon exchange, the scaling function of elastic proton-proton data at 8, 7, 2.76 TeV and that of elastic proton-antiproton scattering data at 1.96 TeV are...
he differential cross section of proton-proton elastic scattering ๐๐/๐๐ก, as a function of the magnitude of the four-momentum transfer squared |๐ก|, evolves in a consistent way with ๐ โ at LHC energies, all the curves being translated in the (|๐ก|, ๐๐/๐๐ก) plane for different center-of-mass energies. This means that the cross sections vary according to a scaling law in center-of-mass energy ๐ โ and...
The pp elastic cross section at 1.96 TeV, obtained from a data-driven extrapolation of the cross sections measured by TOTEM at 2.76, 7, 8, and 13 TeV, have been compared with the D0 ppbar elastic cross section at 1.96 TeV in the region of the diffractive minimum and the second maximum of the pp cross section [1]. The two 1.96 TeV data sets have been found disagree at the 3.4ฯ level and thus...
