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Proton-proton elastic scattering at high energy is a process with simple kinematics but surprisingly complex dynamics. Measurements of these processes at particle colliders require dedicated detectors and unusual measurement conditions. In the article, I describe the physics of elastic processes and the experimental method in the context of the measurement performed by the ATLAS Collaboration at the LHC accelerator. I present the key elements of the data analysis and discuss the consequences of the obtained results for our understanding of the strong interactions. -- Rozpraszanie elastyczne proton-proton przy wysokich energiach jest procesem o prostej kinematyce, lecz zaskakuj\k{a}co z\l{}o\.zonej dynamice. Pomiary tych proces\'ow na zderzaczach cz\k{a}stek wymagaj\k{a} dedykowanych detektor\'ow oraz nietypowych warunk\'ow pomiarowych. W artykule opisuj\k{e} fizyk\k{e} proces\'ow elastycznych oraz metod\k{e} eksperymentaln\k{a} w kontek\'scie pomiaru wykonanego w ramach Wsp\'o\l{}pracy ATLAS na akceleratorze LHC. Przedstawiam kluczowe elementy analizy danych, a tak\.ze omawiam konsekwencje uzyskanego wyniku dla naszego zrozumienia oddzia\l{}ywa\'n silnych., Comment: 11 pages, 10 figures, in Polish

IFJ PAN PPSS Alumni Conference is organized by the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN). It is addressed to: participants of previous editions of Particle Physics Summer Student Programme, attendees of current PPSS edition and students interested in cooperation with IFJ PAN. Second IFJ PAN Particle Physics Summer Student Alumni Conference was held on 14-15 July 2023, with topic focused on, but not restricted to, high energy physics., Comment: 39 pages

Diffractive phenomena constitute a large fraction of interactions occurring in pp collisions at LHC. Because of the non-perturbative nature, their present understanding is still relatively poor and uncertain. One of the methods to study these processes is forward proton tagging. I will discuss the mechanism of diffractive processes, recent results, and potential implications. The proton tagging method can also be used for measurements of photon-induced processes, in particular, the photon-photon interactions. I will present the physics behind these processes, the experimental status and the lessons we can learn for the strong interactions and for the electroweak sector., Comment: Presented at DIS2023: XXX International Workshop on Deep-Inelastic Scattering and Related Subjects, Michigan State University, USA, 27-31 March 2023

IFJ PAN PPSS Alumni Conference is organized by the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN). It is addressed to: participants of previous editions of Particle Physics Summer Student Programme, attendees of current PPSS edition and students interested in cooperation with IFJ PAN. First IFJ PAN Particle Physics Summer Student Alumni Conference was held on 9-10 July 2022, with topic focused on, but not restricted to, high energy physics., Comment: 72 pages, Proceedings of the IFJ PAN Particle Physics Summer Student Alumni Conference 2022

The ATLAS detector at the LHC is equipped with dedicated systems designed for the detection of forward protons produced in diffractive and photon-induced processes. These detectors significantly extend the ATLAS physics reach. Recent measurements performed using these forward proton detectors: elastic proton-proton scattering, exclusive charged pion-pair production, and two-photon production of lepton pairs are presented., Comment: 6 pages, 4 figures

A possible use of forward proton tagging detectors at the LHC in the context of heavy ion interactions is discussed. It is shown that signals registered in such detectors are sensitive to the geometry of the collision. A method of the impact parameter and the collision asymmetry reconstruction on the event-by-event basis is proposed and its performance is studied with Monte Carlo simulations., Comment: 12 pages, 13 figures

The forward proton detectors, already existing at the LHC, are considered in the context of heavy ion collisions. It is shown that such detectors have the potential to measure nuclear debris originating from spectator nucleons. The geometric acceptance for different nuclei is studied, and how it is affected by the motion of the nucleons in the nucleus and by the experimental conditions. A possibility of reconstructing the impact parameter of the collision from the measurement of the nuclear fragments is discussed., Comment: Talk presented at XXV Cracow EPIPHANY Conference on Advances in Heavy Ion Physics, 8-11 January 2019

The use of precise time-of-flight (ToF) detectors for measurements of diffractive and electromagnetic processes in proton-proton collisions is discussed. The performance of background rejection exploiting the ToF measurements of the forward protons is derived. The influence of additional timing measurements delivered by the central detectors is presented and the possible gain is studied., Comment: 7 pages, 6 figures

We discuss the process of colour-singlet parton-parton scattering, which in hadron-hadron collision can lead to production of jet events, where a rapidity gap between the jets is present. The dynamics of the process is calculated within LL BFKL approximation. Using Pythia MC generator, hadronic shapes of jet-gap-jet events are studied, in particular the distributions of the rapidity gap size resulting from the jet formation processes. Using Pythia's modelling of multiple parton interactions, the rescattering effects are simulated. It is shown how these effects influence the gap size distributions. The kinematic dependence of the gap survival probability is discussed., Comment: 5 pages, 5 figures, presented at: EDS Blois 2017, Prague, Czech Republic, June 26-30, 2017

We discuss an application of dynamical multi-parton interaction model, tuned to measurements of underlying event topology, for a description of destroying rapidity gaps in the jet-gap-jet processes at the LHC. We concentrate on the dynamical origin of the mechanism of destroying the rapidity gap. The cross section for jet-gap-jet is calculated within LL BFKL approximation. We discuss the topology of final states without and with the MPI effects. We discuss some examples of selected kinematical situations (fixed jet rapidities and transverse momenta) as distributions averaged over the dynamics of the jet-gap-jet scattering. The color-singlet ladder exchange amplitude for the partonic subprocess is implemented into the \textsc{Pythia 8} generator, which is then used for hadronisation and for the simulation of the MPI effects. Several differential distributions are shown and discussed. We present the ratio of cross section calculated with and without MPI effects as a function of rapidity gap in between the jets., Comment: 18 pages, 10 figures

The calculations of the double parton scattering cross sections are discussed. It is shown that the commonly used factorised formula is valid only in the limit of low cross sections. The applicability of this approximation is studied with a more general approach based on the Poisson distribution averaged over the impact parameter space., Comment: 4 pages, 3 figures

The two-photon production of photon pairs, i.e. the $\gamma\gamma\to\gamma\gamma$ process, is studied. Different production modes regarding the elastic or inelastic coupling of the intermediate-state photons to the protons are considered. The semi-exclusive measurement, where one intact proton is registered by a dedicated forward proton detector, is discussed. As an example, the signal and background simulations are performed for the $\gamma\gamma\to\gamma\gamma$ process mediated by the hypothetical 750 GeV resonance.

The forward proton detectors, already existing at the LHC, are considered in the context of heavy ion collisions. It is shown that such detectors have the potential to measure nuclear debris originating from spectator nucleons. The geometric acceptance for different nuclei is studied, and how it is affected by the motion of the nucleons in the nucleus and by the experimental conditions. A possibility of extending the acceptance region is discussed., Comment: 10 pages, 8 figures

This study focuses on hard diffractive events produced in proton-proton collision at LHC exhibiting one intact proton in the final state which can be tagged by forward detectors. We report prospective results on the W boson charge asymmetry measured for such events, which allow to constrain the quark diffractive density functions in the Pomeron., Comment: 17 pages, 8 figures, Submitted to JHEP

We show that the double diffractive electroweak vector boson production in the $pp$ collisions at the LHC is an ideal probe of QCD based mechanisms of diffraction. Assuming the resolved Pomeron model with flavor symmetric parton distributions, the $W$ production asymmetry in rapidity equals exactly zero. In other approaches, like the soft color interaction model, in which soft gluon exchanges are responsible for diffraction, the asymmetry is non-zero and equal to that in the inclusive $W$ production. In the same way, the ratio of the $W$ to $Z$ boson production is independent of rapidity in the models with resolved Pomeron in contrast to the predictions of the soft color interaction model., Comment: 9 pages, 6 figures (submitted to Phys. Rev. D)

The paper describes the transport of the elastically and diffractively scattered protons in the proton-proton interactions at the LHC for the high beta* runs. A parametrisation of the attered proton transport through the LHC magnetic lattice is presented. The accuracy of the unfolding of the kinematic variables of the scattered protons is discussed., Comment: 12 pages, 15 figures

Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hern\'andez, Ivanov, Dechambre exclusive model. We then study the uncertainties. We compare their predictions to the CDF measurement and discuss the possibility of constraining the exclusive Higgs production at the LHC with early measurements of exclusive jets. We show that the present theoretical uncertainties can be reduced with such data by a factor of 5.

The implementation of exclusive diffractive production of Higgs boson and dijets in the FPMC (Forward Physics Monte Carlo) framework is presented following the models by Khoze, Martin, Ryskin and Cudell, Dechambre, Hernandez and Ivanov. The predictions of the models are compared to the CDF measurement of exclusive jets and the uncertainties on the Higgs boson and jet production cross sections at the LHC are discussed., Comment: Proceedings of the DIS 2010 workshop, Florence, Italy