abstract

I need to cover more than these 43 years! Staszek’s achievements started before my time, that means before 1981. Some of these early steps were essential and hopefully his projects will continue to exist in the future. My aim is to collect the pivotal points of a lifetime research. Selection of these points was inevitable, moreover, some of them, which could be covered in an oral presentation, are not suitable for the printed version.

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We present the history and current status of the YFS Monte Carlo approach to precision theory for accelerator physics experiments. Key contributions of Professor Stanisław Jadach are highlighted.

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Theory and high-energy physics connected with present and future colliders need progress in precision low-energy studies. In particular, at the FCC-ee collider, a better knowledge of input parameters by roughly one order of magnitude is required for many quantities, starting with \(\alpha _{\rm QED},\alpha _\mathrm {s}\), \(m_W\), \(m_Z, m_H\), \(m_t\). We focus on \(\alpha _{\rm QED}(M_Z^2)\) where analysis indicates that the uncertainty determination for this parameter should be roughly five times better than the presently determined value. In turn, better knowledge of the low-energy non-perturbative hadronic contribution to \(\alpha _{\rm QED}\) from \(\Delta \alpha _\mathrm {had}\) with the five light quarks is required. In this context, we mention recent low-energy tensions concerning pion production processes which contribute to \(e^+e^- \rightarrow \gamma ^* \rightarrow {\rm hadrons}\), so \(\Delta \alpha _\mathrm {had}\). We also discuss another important high–low energy connection: the influence of lepton flavor violating intensity frontier processes with CP heavy neutrino effects on the non-standard processes at high-energy colliders.

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Comparisons of higher-order predictions within the Standard Model of Particle Physics (SM) to data are central to high-energy collider experiments like the Large Hardon Collider (LHC). Processes with multiple kinematic scales, such as multi-jet and prompt photon production, provide a unique possibility for probing Quantum Chromodynamics (QCD). These processes directly test perturbative QCD and can be used to extract fundamental parameters like the strong coupling constant and to search for BSM physics. Recent developments enabled lifting three-jet, photon\(\,+\,\)two-jet, photon-pair\(\,+\,\)jet, and three-photon cross sections to QCD’s next-to-next-to-leading order (NNLO). This contribution presents phenomenological results at NNLO QCD for the three-jet and photon plus two-jet production.

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The most complete high-energy evolution of Wilson line operators is described by the set of equations called Balitsky–JIMWLK evolution equations. It is known from the studies of the linear — the BFKL — evolution equation that the leading corrections come from the kinematically-enhanced double colinear logarithms. A method for resuming such logarithmic corrections to all orders for the Balitsky–Kovchegov equation is known under the name of kinematical constraint. In this work, we discuss the progress in implementing these corrections into the Langevin formulation of the JIMWLK equation. In particular, we introduce a set of correlation functions which are nonlocal in the rapidity variable. They appear in the construction of the kinematical constraint, however, their behavior with rapidity has not been investigated numerically so far. We derive their large-\(N\) evolution equations, solve them numerically, and comment on their implications for the implementation of the full kinematical constraint.

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The unprecedented precision of experimental measurements at the Large Hadron Collider (LHC) and the increased statistics that will be reached in the High-Luminosity phase of the LHC (HL-LHC) are pushing the phenomenology community to a new precision frontier, in which new challenges present themselves and new questions arise. Key ingredients of theoretical predictions at hadron colliders are the Parton Distribution Functions (PDFs) of the proton. This contribution highlights some of the new developments in the determination of PDFs from a global set of experimental data, from approximate N\(^3\)LO PDFs and the inclusion of theory uncertainties in PDF fits, to the realisation of the non-trivial interplay between parton densities at large-\(x\) and possible signals of new physics in high-energy tails of the distributions, which highlights the synergy between high-energy and low-energy experimental programs.

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The GENEVA method provides a means to combine resummed and fixed order calculations at the state-of-the-art accuracy with a parton shower program. GENEVA NNLO+PS generators have now been constructed for a range of colour-singlet production processes, using several different choices of resolution variable. I will review the GENEVA framework and then describe several recent advances, such as the use of jet veto resummation at NNLL\('\) accuracy and the ongoing extension to processes including jets in the final state.

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The proposed future lepton collider experiments will reach an unprecedented level of precision for electroweak pseudo-observables. To ensure the success of these experiments, the corresponding theoretical uncertainty must be at least of the same order if not lower. One dominant source of uncertainty is due to the treatment of photon radiation and the potentially large logarithms which need to be resummed. In this work, we present the Yennie–Frautschi–Suura theorem and its implementation in the Sherpa Monte-Carlo framework. In particular, we focus on the automated inclusion of next-to-leading order electroweak corrections.

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The consistent combination of Next-to-Leading-Order (NLO) perturbative QCD with the logarithmic resummation provided by parton shower algorithms (‘NLO matching’) is an indispensable tool for LHC phenomenology. Two methods for achieving this have been widely adopted: Mc@Nlo and Powheg. We summarise a third method, KrkNLO, its implementation in Herwig 7, and compare the results it produces with comparable results from Mc@Nlo.

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The role of soft gluons in inclusive collinear parton densities as well as in Transverse Momentum Dependent (TMD) parton densities is discussed. Applying the Parton Branching (PB) method, the so-called non-perturbative Sudakov form factor could be identified with the integration range of \(z \to 1\), which is neglected in collinear parton shower approaches. The importance of soft gluons could be shown by investigating the transverse momentum spectrum of Drell–Yan lepton pairs, leading to a width of the intrinsic-\(k_{\mathrm {T}}\) distribution which is independent of \(\sqrt {s}\), in contrast to what is observed in parton shower approaches. The reason for this behavior is traced back to the non-perturbative Sudakov form factor. The role of soft gluons for observable hadron spectra is discussed and shown to be negligible.

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We discuss the diffractive bremsstrahlung of a single photon in the \(pp \to pp \gamma \) reaction at LHC energies and at forward photon rapidities. We compare the results for our standard approach, based on QFT and the tensor-Pomeron model, with two versions of soft-photon approximations, SPA1 and SPA2, where the radiative amplitudes contain only the leading terms proportional to \(\omega ^{-1}\) (the inverse of the photon energy). SPA1, which does not have the correct energy-momentum relations, performs surprisingly well in the kinematic range considered, namely at very forward photon rapidities and \(0.02 \lt \xi _{1,2} \lt 0.1\), the relative energy loss of the protons, corresponding to small values of the photon transverse momentum. Azimuthal correlations between outgoing particles are presented. We discuss also the role of the \(p p \to p p \pi ^0\) background for single-photon production. We discuss also the possibility of a measurement of the \(pp \to pp \gamma \gamma \) reaction. Our predictions can be verified by ATLAS-LHCf combined experiments.

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As is well known, computing multi-leg QCD scattering amplitudes using the standard elementary three- and four-particle vertices is cumbersome even at tree level, due to a number of diagrams growing dramatically with each external state. Over the last two decades, the problem was addressed in essentially two ways. The first approach uses the on-shell methods that try to eliminate fields as degrees of freedom whatsoever. The second approach is to construct a new field theory that contains new degrees of freedom that are more efficient in computing scattering amplitudes. One such example is the MHV action, which is based on the light-cone Yang–Mills action and where the new fields interact via multi-leg vertices related to the maximally-helicity-violating amplitudes. We discuss a further extension of such a theory, called the \(Z\)-field theory, which is obtained via the field transformation based on Wilson lines. Classically, it contains no triple couplings at all and thus is very efficient in computing tree amplitudes.

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We recently derived a new action for gluodynamics by canonically transforming the Yang–Mills action on light cone. The transformation eliminated triple gluons vertices and replaced the gauge fields with Wilson lines. This greatly reduced the number of diagrams required to compute tree-level amplitudes. However, at the quantum level, the action turned out to be incomplete. We present two ways, based on a one-loop effective action approach, to systematically develop quantum correction to our action. The first method retains Yang–Mills vertices in the loop, while the second method explicitly incorporates the interaction vertices of our action into the loop. We demonstrate that both approaches are equivalent, although the former appears to be more efficient for computing higher-multiplicity one-loop amplitudes.

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We discuss far-forward production of charm mesons and neutrinos from their semileptonic decays in proton–proton collisions at the LHC energies. We include the gluon–gluon fusion \(gg \to c\bar {c}\), the intrinsic charm (IC) \(gc \to gc\) as well as the recombination \(gq \to Dc\) partonic mechanisms. We present energy distributions for forward electron, muon, and tau neutrinos to be measured at the LHC by the FASER\(\nu \) experiment. For all kinds of neutrinos, the IC and the recombination dominate over the standard charm production contribution for neutrino energies \(E_{\nu } \gt 300\) GeV. For electron and muon neutrinos, both mechanisms lead to a similar production rates and their separation seems rather impossible. On the other hand, for \(\nu _{\tau } + {\bar \nu }_{\tau }\) neutrino flux, the recombination is reduced making the measurement of the IC contribution very attractive.

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Recent physics results from the ATLAS experiment, covering both high-precision measurements and exciting observations, are presented. These results involve the production of vector bosons, multi-jets, and top quarks. Building on top of measuring production cross sections, these results also offer determination of the Standard Model parameters, confrontation of state-of-art predictions, as well as constraints of new physics models in a model-independent way.

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Run 2 of the LHC has produced a lot of physics results from the electroweak sector of the Standard Model. We briefly overview CMS results that relate to measurements of triple and quartic gauge couplings: diboson, vector-boson fusion, vector-boson scattering, and triboson production. We present the most recent results and activities in the field and discuss the prospects for Run 3 and beyond.

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The LHCb Collaboration has successfully recorded heavy-flavour decays during the first two runs of the LHC high-energy proton–proton collider between 2011 and 2018. A selection of recent precision measurements in beauty decays is presented. The detector has now been largely rebuilt for the first upgrade, to handle a higher collision rate and for a more efficient selection of collisions containing beauty and charm decays. Ideas for a second upgrade are under development.

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The Belle II detector started taking data in 2019, with the goal of extending the physics reach of its predecessor, Belle, which collected about 1 ab\(^{-1}\) of integrated luminosity of \(e^+e^-\) collisions at a center-of-mass energy corresponding (or near) to the mass of the \({\mit \Upsilon }(4S)\) resonance. In this contribution, we present results based on (part of) the Run 1 data set of Belle II, corresponding to 424 fb\(^{-1}\), in some cases combined with the full Belle data set. The results include measurements related to quantities of the CKM Unitarity Triangle, searches for the rare decay \(B^+ \to K^+ \nu \bar {\nu }\), for Lepton Flavor Universality violating phenomena, and for Dark Sector particles.

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I discuss the thermodynamics-based derivation of the formula for the entanglement entropy of a system of gluons. The derivation is based on an approach where saturation and the Unruh effect were used to obtain and discuss the entropy of gluons. The formula agrees, in the high-energy limit, up to a numerical factor, with more recent results, where arguments based on the density matrix and bipartition of the proton were used to obtain the formula. I also discuss the relation of entropy as obtained in BFKL in DLL approximation and with the application of the BK equation.

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Anomalous contributions to the electric and magnetic dipole moments of the \(\tau \) lepton from new physics scenarios have brought renewed interest in the development of new CP-violating signatures in the \(\tau \)-pair production at Belle II energies, and also at higher energies of the LHC and the Future Circular Collider. We discuss the effects of spin correlations, including transverse degrees of freedom, in the \(\tau \)-pair production and decay. The effects of the dipole moments are introduced on top of precision simulations of \(e^-e^+ \to \tau ^-\tau ^+\), \(q\bar {q} \to \tau ^-\tau ^+\), and \(\gamma \gamma \to \tau ^-\tau ^+\) processes, involving many-body final states and radiative corrections, in particular, electroweak box contributions of \(WW\) and \(ZZ\) exchanges. Extensions of the Standard Model amplitudes and the reweighting algorithms are implemented into the KKMC Monte Carlo, which is used to simulate \(\tau \)-pair production in \(e^-e^+\) collisions, and the TauSpinner program, which is used to reweight events with \(\tau \) pair produced in \(pp\) collisions.

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In this note, we will discuss some of the latest high-precision measurements performed by the Compact Muon Solenoid (CMS) experiment in the \(B\)-physics sector of high energy physics.

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This report summarizes measurements of the Higgs boson properties performed with the CMS experiment at the CERN LHC. The measurements presented here are based on data from \(pp\) collisions at the center-of-mass energy of 7, 8, and 13 TeV collected up to the year 2018 and corresponding to integrated luminosity of 5, 20, and 138 fb\(^{-1}\), respectively. These results represent most up-to-date knowledge on the Higgs boson properties. All presented measurements agree with predictions of the Standard Model of particle physics within their uncertainties.

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With the full Run 2 \(pp\) collision dataset collected at 13 TeV with the ATLAS detector, very precise measurements of Higgs-boson properties and its interactions can be performed, shedding light on the electroweak symmetry breaking mechanism. This contribution presents the latest measurements of the Higgs-boson properties by the ATLAS experiment in various decay channels, including differential, fiducial, and simplified template cross sections, mass, width, as well as their combination and interpretations. Specific scenarios of physics beyond the Standard Model are tested, as well as a generic extension in the framework of the Standard Model Effective Field Theory.

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The present document focuses on the sensitivity studies to observe massive long-lived particles predicted by the Hidden Valley models. The study is based on a data sample of \(e^+e^-\) collisions at \(\sqrt {s}=350\) GeV and \(\sqrt {s}=3\) TeV, simulated with the CLIC_ILD detector, and corresponding to an integrated luminosity of 1 ab\(^{-1}\) and 3 ab\(^{-1}\), respectively. The upper limits on the production cross section for the long-lived particle lifetimes from 1 to 300 ps, masses between 25 and 50 GeV/\(c^2\), and a parent Higgs mass of 126 GeV/\(c^2\) are discussed, together with sensitivities to the production cross section.

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We briefly introduce H-COUP_3.0, which we developed for evaluating higher-order corrections to any Higgs boson decays in various extended Higgs sectors. Focusing on two Higgs doublet models (2HDMs), we then discuss how the non-decoupling effects of the additional Higgs bosons are significant in Higgs boson decays.

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This paper outlines results from the measurement of the anomalous magnetic dipole moment of the \(\tau \) lepton (\(a_{\tau }\)) using \(\gamma \gamma \rightarrow \tau ^{+}\tau ^{-}\) events from ultra-peripheral Pb+Pb collisions recorded by CMS in 2015 and by ATLAS in 2018 at the LHC. The first and most stringent experimental constraints on \(a_{\tau }\) were established by the DELPHI Collaboration in 2004, during their investigations of the ditau production in the \(e^{+}e^{-} \rightarrow e^{+}e^{-}\tau ^{+}\tau ^{-}\) process. Relativistic heavy-ion beams at the LHC are accompanied by a substantial flux of equivalent photons, which lead to photon-induced processes. This paper describes two analyses of the photon-induced production of tau pairs and constraints on the tau lepton’s anomalous magnetic dipole moment analysing ultra-peripheral Pb+Pb collisions.

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Electroweak Precision Measurements are stringent tests of the Standard Model and sensitive probes to new physics. Accurate studies of the \(Z\)-boson couplings to the first-generation quarks could reveal potential discrepancies between the fundamental theory and experimental data. Future lepton colliders offering high statistics of \(Z\) bosons would be an excellent tool to perform such a measurement based on a comparison of radiative and non-radiative hadronic decays of the \(Z\) boson. Due to the difference in quark charge, the relative contribution of the events with final-state radiation (FSR) directly reflects the ratio of up- and down-type quark decays. Such an analysis requires a proper distinction between photons coming from different sources, including initial-state radiation (ISR), FSR, parton showers, and hadronisation. In our paper, we will show how to extract the values of the \(Z\) couplings to quarks and present preliminary results of the analysis for ILC.

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In this paper, we argue that the only way to improve systematic precision of \(W\)-boson mass and weak-mixing angle measurements at the LHC is to replace proton beams with isoscalar-ion beams. This results in a significant simplification of relations between \(W\)- and \(Z\)-boson production processes, with the latter serving as a precision “standard candle”. However, with the presently operating LHC ion injectors, partonic luminosity for ion–ion collisions is significantly lower than the one for proton–proton collisions. Therefore, statistical precision of the above measurements is lower for the former case. The proposed way out to improve the partonic luminosity in the ion–ion mode is to transversely cool the beams. The Gamma Factory project can achieve this goal with the use of laser cooling. This will allow to improve the precision of experimental determination of the above parameters to \(\delta M_W \lt 5\) MeV and \(\delta \sin ^2\theta _\mathrm {W} \lt 10^{-4}\). The proposed calcium beams are also optimal for exclusive Higgs-boson production in multiperipheral \(\gamma \gamma \) collisions and studies of \(H\to b\bar {b}\) decays in a clean environment.

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The electron–Proton/Ion Collider Experiment (ePIC) Collaboration was formed to design, build, and operate the Electron–Ion Collider (EIC) project detector. Measurements to be performed with ePIC aim to address some of the most profound questions in Quantum Chromodynamics (QCD) related to the emergence of nuclear properties by precisely imaging gluons and quarks inside protons and nuclei. This paper presents an overview of the current configuration of the ePIC detector and its physics program.

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Properties of proton trajectories along the High Luminosity LHC beam-line in the vicinity of ATLAS, ALICE, and LHCb interaction points are discussed. Based on this, possible locations of forward proton detectors in the vicinity of these experiments were identified. Finally, studies of geometric and mass acceptances were performed.

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The CMS detector at the LHC has implemented a two-stage trigger system in order to cope with a huge event rate given by the accelerator. In the article, the Level-1 Muon Trigger is presented, providing insights into its essential components with an emphasis on the Overlap Muon Track Finder (OMTF) reponsible for Level-1 muon reconstruction in the detector pseudorapidity region of \(0.83\lt |\eta |\lt 1.24\). The OMTF algorithm as well as its performance are discussed and a recent development is described.

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The experimental data-based alignment procedure of the Absolute Luminosity for ATLAS (ALFA) detectors is discussed. The procedure is heavily based on the symmetry properties of the elastic proton–proton scattering. The detectors operate in the vicinity of the LHC beams during dedicated running periods. Each time they are moved towards data-taking position, their alignment must be determined independently for each insertion into the accelerator beam pipe.

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The ATLAS Forward Proton (AFP) detectors open new possibilities to expand the reach of the ATLAS Experiment physics and to probe unique physics processes by measuring intact protons produced in diffractive or photon-induced processes. The AFP system uses Roman pots located approximately 210 meters from the ATLAS interaction point on both outgoing beams. These devices enable measurements in the vicinity of the LHC beam. Each AFP station contains a tracking detector, consisting of four planes of silicon pixel sensors. The present study focuses on the alignment of the AFP detector, a critical process to ensure the highest accuracy in proton measurements. Local alignment, the first step in this process, concentrates on accurately determining the relative positions of the pixel planes. Subsequently, global alignment is dedicated to determining the overall position of the AFP detector relative to the beam.

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The ATLAS heavy-ion physics program includes the study of ultra-peripheral collisions (UPC). This gives rise to various photon-induced interactions at high energies. In order to extend the ATLAS UPC physics program, higher efficiencies at very low particle transverse momenta are required, but no suitable Level 1 trigger exists in the ATLAS detector to record such events. To provide such capabilities, the ATLAS Level 1 Transition Radiation Tracker cosmics trigger, known as the TRT FastOR, is adapted for use in a recent heavy-ion collision run. These proceedings present the achieved performance of the TRT FastOR trigger in the September–October 2023 Pb+Pb run, with data recorded at \(\sqrt {s_{NN}} = 5.36\) TeV.

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This paper provides a cross-check of a novel method for measuring quark- and gluon-jet properties at the Large Hadron Collider (LHC). The method relies on data of dijet events collected at two different centre-of-mass energies of LHC operation. By combining these two datasets each with a different abundance of gluon jets, the jet properties categorized into quark and gluon distributions are obtained on a statistical basis. The cross-check of derived quark and gluon distributions is performed against “truth” distributions obtained by matching jet to parton using the minimal difference in rapidity-azimuth distance \(\Delta R(\mathrm {jet}, \mathrm {parton})\).

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We study photon+jet production in proton–proton and proton–lead collisions using the small-\(x\) Improved Transverse Momentum Dependent (ITMD) factorization framework in Ka Tie. The ITMD factorization framework, rooted in the Color Glass Condensate (CGC) theory (and for this particular process essentially identical to it), proves particularly useful at probing particle production at relatively large transverse momenta remaining at the same time sensitive to saturation effects in transverse momentum dependent (TMD) gluon distributions. Our investigation focuses on the azimuthal correlations and few other observables across a spectrum of center-of-mass energies. The comprehensive exploration of these observables leads to a deeper understanding of the underlying dynamics of gluons in the saturation domain.

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The ATLAS experiment at the Large Hadron Collider searches for very rare processes of the beyond Standard Model physics. The greatest challenge in these studies is to extract the extremely rare signals from overwhelming background that arise from the Standard Model processes. The use of the multivariate analysis techniques is crucial in achieving this goal. An example of such a signal would be the production of a charged Higgs boson, predicted, for example, by the Two-Higgs-Doublet Model. This paper presents two analyses: the search for the charged Higgs boson decaying into a \(\tau \) lepton and neutrino, based on 2015–2016 data; and the search for the charged Higgs boson decaying into top and bottom quarks, based on the data from the whole Run 2. The different applications of the multivariate analysis are presented.

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Lepton flavor violating (LFV) \(B\)-meson decays are the unique probes to search for new physics and \(B\) factories provide an ideal setup to look for them. To study one such type of \(B\rightarrow K \tau \ell \) (\(\ell = e,\mu \)) decay, we are using the basic kinematics constraints of the \(B\) factories to search for our signal decay. Initial checks for it are performed on the Belle/Belle II signal and generic Monte Carlo (MC). In these preliminary results, we have found that by using this method, we can significantly suppress the background, while retaining a good reconstruction efficiency for the signal decay.

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The recent discovery of CP violation in \(D^0\) mesons by the LHCb experiment raised theoretical and experimental interest. It is still unclear whether this result is compatible with the Standard-Model predictions and there is a consensus on the need for further measurements to clarify the picture. The LHCb experiment is therefore conducting a wide range of searches for CP violation in the charm sector using multiple observables. Among those, \(y_{\mathrm {CP}}\) is sensitive to CP violation in the mixing of \(D^0\) mesons and is sensitive to physics beyond the Standard Model. By measuring the difference between the effective-decay widths of the \(D^0\) meson and its anti-particle to CP eigenstates, the CP violation in the \(D^0\) meson time evolution can be probed. This communication reports the latest measurements of \(y_{\mathrm {CP}}\) from LHCb as well as prospects for the LHCb Upgrade, which will take data during Runs 3 and 4 of the LHC.

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The basic idea of CP violation and its importance for cosmology, Standard Model, and possible new physics are introduced. Recent (2019) discovery of CP violation in charm in the \(\Delta A_{\mathrm {CP}}\) between \(D^0\rightarrow K^-K^+\) and \(D^0\rightarrow \pi ^+\pi ^-\) decay channels and evidence for direct CP violation in \(D^0\rightarrow \pi ^-\pi ^+\) decays in 2023 are discussed. Motivation and a brief outline for the search of CP violation in the \(D^0\rightarrow V\gamma \), where \(V=\phi ,\rho ^0, \bar {K}^{*0}\) decays are given.

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The ATLAS Collaboration’s 2017 article validated light-by-light scattering, showing photon pair production from strong electromagnetic field interactions during ultraperipheral collisions of heavy ions. The next phase in light-by-light scattering research involves an extension to smaller values of transverse momentum and diphoton invariant mass. An opportunity for scientific advancement will come with new ATLAS measurements with new rapidity acceptance, and with the FoCal detector, developed by the ALICE Collaboration, which will start taking data in 2027. Measurements with FoCal have the potential to measure low-mass meson resonances that evade modern detectors. Both acceptance and resolution of the FoCal detector were taken into account in the calculation presented here.

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Correlations obtained from neutrino oscillation data on mixing parameters may help to validate neutrino mixing schemes. In this context, we explore how correlations of neutrino oscillation parameters affect the \(\rm {TM}_1\) and \(\rm {TM}_2\) mixing scenarios.