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Peter Christiansen

Publications and source records attributed to Peter Christiansen.

At least 19 recordsLinked to original sources

The 10th AI City Challenge

The 10th AI City Challenge, held with ECCV 2026, marks a decade of community benchmarking for intelligent transportation, smart cities, and physical AI. Since its 2017 start with vehicle detection, classification, and tracking, the challenge has grown into a broad benchmark suite for multi-camera perception, multimodal reasoning, synthetic-to-real learning, generative forecasting, and privacy-preserving evaluation. The 2026 edition continued this growth with 325 registered teams, up from 245 in 2025, and participation from 26 countries and regions, up from 15. Its six primary tracks cover multi-camera 3D perception, transportation safety captioning and VQA, traffic anomaly reasoning, text-based person anomaly search, generative traffic video forecasting, and cross-city object detection. Track 3 further includes two out-of-domain leaderboards, submitted as Tracks 7 and 8, for fisheye traffic-violation understanding and pedestrian situated-intent VQA. This paper summarizes the challenge setup, datasets, evaluation protocols, leaderboard results, and workshop papers. Across tracks, successful systems combine foundation models with geometric grounding, retrieval or reranking, synthetic-data design, domain adaptation, and controlled inference.

cs.CV

$\Lambda$(1520) as a probe of resonance-driven deuteron formation at the LHC

Light nuclei such as deuterons are produced abundantly in high-energy proton-proton and nuclear collisions despite their tiny binding energies. Their production mechanism remains unresolved, as both nucleon coalescence and statistical thermal models reproduce inclusive LHC yields. We propose a direct invariant-mass observable that discriminates between these scenarios using the long-lived $\Lambda(1520) \to {\rm pK}$ resonance. If decay protons coalesce into deuterons, the produced nuclei remain correlated with the kaon, allowing the resonance peak to be reconstructed experimentally through proxy masses, $M_{\rm (d/2)K}$, formed from kaons and half the deuteron four-momentum. Using Thermal-FIST and PYTHIA with a deuteron coalescence afterburner, we show that a $M_{\rm (d/2)K}$ peak emerges only in the coalescence scenario. This observable provides a direct experimental probe of resonance-fed deuteron production and of late-stage coalescence dynamics in high-energy collisions.

hep-ex

Confronting the production mechanisms of nuclei with deuteron and proton-triggered balance functions

In ultra high-energy collisions, nuclei with very low binding energies are not expected to survive the dense and hot final state environment. The traditional view has therefore been that nuclei form via coalescence after the hot environment has dissipated. However, statistical thermal models, where hadrons are produced from a fireball at thermal equilibrium, can describe the relative abundances of light nuclei in pp and heavy-ion collisions at the LHC equally well. In this paper we investigate if balance functions triggered by protons and deuterons can be used to distinguish between the two production mechanisms. The coalescence model is investigated using PYTHIA, while the statistical thermal model is examined using the Thermal FIST package. We find that for both models the same simple relation between proton and deuteron triggered balance functions is applicable. However, there is a striking difference between the two models when the transverse momentum of trigger particles is varied. This dependence offers a promising observable to discriminate between the two production scenarios that goes beyond nuclei production. Furthermore, we find that deuteron-meson balance functions vanish identically for both models due to baryon number conservation and isospin symmetry.

hep-ph

Simplifying Strangeness Fluctuations through Balance Functions in Proton-Proton Collisions

Recent measurements of event-by-event fluctuations of multistrange baryons and kaons in proton-proton collisions by ALICE have been proposed as sensitive probes to distinguish between thermal and string-based hadronization mechanisms. We demonstrate that two key observables -- the normalized net-$\Xi$ second-order cumulant and the net-$K$--net-$\Xi$ Pearson correlation coefficient -- can be re-expressed in terms of balance function integrals, thereby revealing their underlying microscopic content, and relating them to balance functions previously measured by ALICE. This allows us to show that both observables probe the same physics and primarily measure the impact of strangeness conservation on hadronization. We compare both sets of ALICE data with two contrasting models, PYTHIA and Thermal-FIST. Importantly, while Thermal-FIST can reproduce the magnitude of fluctuation observables, it fails to describe the shape of the measured balance functions. Our findings highlight the importance of balance functions as precision tools for testing hadronization models in small collision systems and propose a robust baseline for future studies exploring hadronization dynamics in QCD matter.

hep-ph

Soft QCD Physics at the LHC: highlights and opportunities

The Large Hadron Collider (LHC) at CERN in Switzerland became operational in 2009 and has since then produced a plethora of results for proton-proton (pp) collisions. This short review covers results that relates to soft QCD focusing on non-diffractive physics at mid-rapidity. Most of the presented results comes from transverse momentum ($p_{\rm T}$) spectra and related/derived observables such as multiplicity, $\langle p_{\rm T} \rangle$ and ratios, but also the observed ``ridge'' and the questions of quark-gluon plasma in pp collisions will be discussed. The goal of the review is on one hand to introduce the topics and provide references for scientists joining the LHC program while at the same time highlighting what we consider the most interesting results and open questions to inspire novel measurements.

hep-ex

Going against the flow: Revealing the QCD degrees of freedom in hadronic collisions

In collisions between heavy nuclei, such as those at the Large Hadron Collider (LHC) at CERN, hydrodynamic models have successfully related measured azimuthal momentum anisotropies to the transverse shape of the collision region. For an elliptically shaped interaction area, the hydrodynamic pressure gradient is greater along the minor axis, resulting in increased particle momentum in that direction - a phenomenon known as positive elliptic flow. In this paper, we demonstrate that in smaller systems, such as proton-proton and peripheral ion-ion collisions, microscopic models for final state interactions, can produce anisotropies where the elliptic flow is negative - that is, the momentum is largest along the major axis, contrary to hydrodynamic predictions. We present results from two distinct microscopic models: one based on repulsion between string-like fields and another based on effective kinetic theory. Negative elliptic flow is a solid prediction of the string interaction model while in the model based on kinetic theory it is linked to a finite interaction range. Consequently, an experimental determination of the sign of elliptic flow, will provide novel insights into the degrees of freedom governing strong nuclear interactions in high-energy collisions and the way in which they interact.

hep-ph

QCD challenges from pp to AA collisions -- 4th edition

This paper is a write-up of the ideas that were presented, developed and discussed at the fourth International Workshop on QCD Challenges from pp to AA, which took place in February 2023 in Padua, Italy. The goal of the workshop was to focus on some of the open questions in the field of high-energy heavy-ion physics and to stimulate the formulation of concrete suggestions for making progresses on both the experimental and theoretical sides. The paper gives a brief introduction to each topic and then summarizes the primary results.

hep-ex

Perfect QCD -- a new Universal approach to soft QCD

The ideas presented in this proceeding aims to be a first step towards a description of hadronic collisions where all soft processes are fundamentally strongly coupled and the same Universal strongly coupled physics drives both initial and final-state interactions. As it is not currently possible to derive such a picture from first principles, instead, an attempt to generalize the perfect liquid observation to a ``perfect QCD'' guiding principle is presented, focusing on implications for particle production in small systems. The first steps towards a microscopic model is taken by arguing that ``perfect QCD'' suggests that the screening in the initial state is so large that multi-parton interactions are of little or no importance. Instead, a target and projectile remnant is coherently excited and particle production is mainly driven by radiation in a qualitative similar manner as $e^+e^- \rightarrow q\bar{q}$. Finally, some of the possible implications of this ``excited remnant model'' are presented. It is argued that the time ordering of soft and hard physics can explain the absence of jet quenching in small systems and that the coherence scale of the projectile and target provides insights into what small systems will exhibit flow.

hep-ph

Multiplicity fluctuations and correlations in 5.02 TeV p+Pb collisions at zero impact parameter

We present a Bayesian method to reconstruct event-by-event multiplicity fluctuations and rapidity correlations in p+Pb collisions at zero impact parameter from minimum-bias data, without assuming any model of the collision dynamics. We test it on Monte Carlo simulations with the Angantyr model, then apply it to ATLAS data on the distribution of charged multiplicity and transverse energy in p+Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Fluctuations in $b=0$ collisions are quantum fluctuations which originate mostly from the proton wave function, and therefore have the potential to constrain the subnucleonic structure of the proton. The Angantyr model is found to overestimate fluctuations. In addition, we find that as the rapidity increases (towards the Pb-going side), not only the multiplicity density increases, but also its relative event-by-event fluctuation. This counter-intuitive phenomenon is also observed in simulations with Angantyr, and with the QCD dipole model, where its origin can be traced back to the branching process through which gluons are produced.

nucl-th

The ESS neutrino super-beam near detector

The ESS Neutrino Super-Beam (ESSnuSB) is a proposed long-baseline neutrino oscillation experiment, performed with a high-intensity neutrino beam, to be developed as an extension to the European Spallation Source proton linac currently under construction in Lund, Sweden. The neutrinos would be detected with the near and far detectors of the experiment, the former within several hundred meters of the neutrino production point and the latter within several hundred kilometers. The far detector will consist of a megaton-scale water-Cherenkov detector, and the near detector will consist of a kiloton-scale water-Cherenkov detector in combination with a fine-grained tracking detector and an emulsion detector. The purpose of the near detector is to constrain the flux of the neutrino beam as well as to extract the electron-neutrino interaction cross-section in water, which requires high-performance energy reconstruction and particle flavor identification techniques. These measurements are crucial for the neutrino oscillation measurements that will be conducted using the far detector. Year 2021 sees the finalization of the conceptual design of the near detector after a thorough evaluation of the performance of a number of different design options, and a characterization of the neutrino reconstruction and flavor identification performances. In this talk we report on thesestudies.

hep-ex

Probing the Gluon Plasma with Charm Balance Functions

Recent theoretical explanations for how hydrodynamic-like flow can build up quickly in small collision systems (hydrodynamization) has led to a microscopic picture of flow building up in a gluon-dominated phase before chemical equilibrium between quarks and gluons has been attained. The goal of this contribution to Offshell-2021 is to explore consequence of assuming a long-lived gluon-dominated phase, which we shall denote a gluon plasma (GP). As these consequences are naturally enhanced in a large systems, we assume and explore the extreme scenario in which a GP would be created in AA collisions and exist for significant time before the formation of a chemically-equilibrated quark-gluon plasma (QGP). The GP and its formation would be impossible to probe with light-quark hadrons, which are first produced later in this scenario. As charm quarks are produced early in the collision, they can circumvent the limitations of light quarks and we propose charm balance functions as an effective tool to test this idea and constrain the dynamics of the GP.

hep-ph

Towards Inverse Sensor Mapping in Agriculture

In recent years, the drive of the Industry 4.0 initiative has enriched industrial and scientific approaches to build self-driving cars or smart factories. Agricultural applications benefit from both advances, as they are in reality mobile driving factories which process the environment. Therefore, acurate perception of the surrounding is a crucial task as it involves the goods to be processed, in contrast to standard indoor production lines. Environmental processing requires accurate and robust quantification in order to correctly adjust processing parameters and detect hazardous risks during the processing. While today approaches still implement functional elements based on a single particular set of sensors, it may become apparent that a unified representation of the environment compiled from all available information sources would be more versatile, sufficient, and cost effective. The key to this approach is the means of developing a common information language from the data provided. In this paper, we introduce and discuss techniques to build so called inverse sensor models that create a common information language among different, but typically agricultural, information providers. These can be current live sensor data, farm management systems, or long term information generated from previous processing, drones, or satellites. In the context of Industry 4.0, this enables the interoperability of different agricultural systems and allows information transparency.

cs.RO

What Quark-Gluon Plasma in small systems might tell us about nucleons

The origin of flow-like effects in small systems, such as those produced in ultra-relativistic proton-proton and proton-lead collisions, is still widely debated. In this paper the goal is to look at possible consequences if indeed a mini-Quark-Gluon Plasma is formed in these collisions. It is argued that this could indicate a duality between the QGP phase and the color fields in hadrons. A qualitative dense field picture is presented for this duality and discussed.

hep-ph

FieldSAFE: Dataset for Obstacle Detection in Agriculture

In this paper, we present a novel multi-modal dataset for obstacle detection in agriculture. The dataset comprises approximately 2 hours of raw sensor data from a tractor-mounted sensor system in a grass mowing scenario in Denmark, October 2016. Sensing modalities include stereo camera, thermal camera, web camera, 360-degree camera, lidar, and radar, while precise localization is available from fused IMU and GNSS. Both static and moving obstacles are present including humans, mannequin dolls, rocks, barrels, buildings, vehicles, and vegetation. All obstacles have ground truth object labels and geographic coordinates.

cs.RO

High $p_{\rm T}$ spectra and anisotropy of light and heavy hadrons

Data driven studies of heavy-ion results has played a big role in highlighting interesting features of these complex systems. In this proceeding, a simple QGP-brick interpretation of the $R_{\rm AA}$ and $v_{2}$ at high $p_{\rm T}$ ($p_{\rm T} \approx 10$ GeV/c) is presented. This interpretation draws attention to two fundamental questions: is there an effect of the asymmetric QGP expansion on the $v_{2}$ at high $p_{\rm T}$? is there an energy loss difference between quarks and gluons? Finally, it is discussed how these studies can be extended using Event-Shape Engineering and how they can be applied to compare the energy loss of light and heavy quarks.

hep-ph

The opportunity offered by the ESSnuSB project to exploit the larger leptonic CP violation signal at the second oscillation maximum and the requirements of this project on the ESS accelerator complex

Very intense neutrino beams and large neutrino detectors will be needed to enable the discovery of CP violation in the leptonic sector. The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world's most powerful neutron source. The average power will be 5 MW. Pulsing this linac at higher frequency, at the same instantaneous power, will make it possible to raise the average beam power to 10 MW to produce, in parallel with the spallation neutron production, a high performance neutrino Super Beam of about 0.4 GeV mean neutrino energy. The ESS neutrino Super Beam, ESSnuSB, operated with a 2.0 GeV linac proton beam, together with a large underground Water Cherenkov detector located at 540 km from Lund, close to the second oscillation maximum, will make it possible to discover leptonic CP violation at 5 sigma significance level in 56 percent (65 percent for an upgrade to 2.5 GeV beam energy) of the leptonic Dirac CP-violating phase range after 10 years of data taking. The paper gives an overview of the proposed facility and presents the outstanding physics reach possible for CP violation with ESSnuSB.

physics.ins-det

Event-Shape Engineering and Jet Quenching

Event-Shape Engineering (ESE) is a tool that enables some control of the initial geometry in heavy-ion collisions in a similar way as the centrality enables some control of the number of participants. Utilizing ESE, the path length in and out-of plane can be varied while keeping the medium properties (centrality) fixed. In this proceeding it is argued that this provides additional experimental information about jet quenching. Finally, it is suggested that if ESE studies are done in parallel for light and heavy quarks one can determine, in a model independent way, if the path-length dependence of their quenching differs.

hep-ph

Towards a DSL for Perception-Based Safety Systems

This paper is an extension to an early presented programming language, called a domain specific language. This paper extends the proposed concept with new sensors and behaviours to address real-life situations. The functionality was tested in lab experiments, and an extension to the earlier concepts is proposed.

cs.RO