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Partikeldagarna 2026
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A-salen (L317) (Lund University, Physics Department)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund
Description
Partikeldagarna 2026 will be held at Lund University September 17-18, 2026. The meeting is organised by a local organising committee and the board of the Particle and Astroparticle Physics Section of the Swedish Physical Society (Fysikersamfundet).
The aim of the meeting is to have a status report and a professional discussion on current particle and astroparticle physics research in Sweden. Partikeldagarna 2026 will follow the same structure as previous years, with a mix of talks given by individual researchers presenting their work, group reports and summaries from funding agencies and international organisations where Sweden is represented.
The meeting starts on Thursday at 9:00 (registration from 8:45) and ends on Friday at 17:00. The social dinner is on Thursday evening. There is an excursion to ESS on Friday afternoon. (The 39 persons who registered for the ESS visit, received additional information regarding the visit on September 11.)
Information regarding the budget/payments, registration fee and conference dinner fees are given in the registration form.
As in previous years, participation to Partikeldagarna is restricted to members of the Swedish Physical Society. Membership can be obtained through the payment of an annual fee. Master students are exempted from this restriction. Further information can be found here.
Partikeldagarna feature two invited speakers covering hot topics in particle and astroparticle physics: Gino Isidori (Zurich) with "The discovery potential of FCC-ee" and Foteini Oikonomou (NTNU) with "Multimessenger diagnostics of hadronic acceleration from PeV to EeV".
To fit all contributed abstracts, we have allocated 15-minute slots for all contributed talks, with 12 minutes for the presentation and 3 minutes for discussion each. The two invited talks have 45-minute slots and we suggest 40 minutes for the presentation itself and 5 minutes for discussion for each.
Registration deadline: August 26, 2026
Abstract submission deadline: August 26, 2026
Venue: Lund University, Physics Department, A-salen (see address and link to google maps below)
Local Organizing Committee (LU):
Hannah Herde, Malin Sjödahl, Johan Rathsman, Valentina Santoro, David Silvermyr
Swedish Physical Society Board and Organizing Committee:
C. Pérez de los Heros (UU, Chair), R. González Suárez (UU), H. Herde (LU), A. Obertacke (SU), T. Ohlsson (KTH), M. Sjödahl (LU), J. Sjölin (SU), J. Sobczyk (CTH)
Participants
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Registration Lobby
Lobby
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Session 1 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
1
ALPHA status and resonator development at Stockholm University.
The search for post-inflation axion dark matter has pushed towards axion masses corresponding to frequencies above 10 GHz (40 µeV). As traditional haloscopes are limited by the loss of interaction volume at high frequencies, this has required the development of new techniques. A plasma haloscope employs wire metamaterials where the inter-wire spacing controls the resonant frequency.
The Axion Longitudinal Plasma Haloscope (ALPHA) collaboration aims to use this concept to search the post-inflation axion starting in 2028. Pending the delivery of the magnet, these plasma haloscopes will be used to search for dark photons in 2026. However, tuning these resonators often requires multiple rotational axes making them mechanically complex. At Stockholm University, we have led the development of spiral-based and ring-nested designs for plasma haloscopes utilizing a single rotational axis. These resonator designs will be used for ALPHA and the first resonant dark photon search in Sweden. In this talk, I will discuss status of the ALPHA experiment and the current and future R&D at Stockholm University with regard to plasma haloscope resonator design.Speaker: Jacob Lindahl (Stockholm University) -
2
ALPHA Data analysis and statistical inference
Axions have become increasingly important candidates in searches for dark matter, due to their ability to also resolve the strong CP problem. One of the primary types of axion detectors is the haloscope, using the conversion of axions into photons in a magnetic field. The Axion Longitudinal Plasma Haloscope (ALPHA) experiment aims to search for axions with masses above 40 µeV, a range favored by recent theoretical developments but where traditional haloscopes have limited sensitivity. ALPHA is on track to perform the first phase of its axion search in 2028, and over the next few months, it will also be used to search for another dark matter candidate particle, the dark photon. Our group at Stockholm University leads the development of the analysis framework and novel statistical inference methods for ALPHA, which will be discussed in this talk.
Speaker: Andrew Meyer -
3
Particle Reconstruction in a Future Muon Collider
The Large Hadron Collider (LHC) has driven major discoveries in particle physics, but further exploration of the energy frontier calls for the next generation of machines. A multi-TeV muon collider (MuC) has been proposed as a potential next step, but its implementation hinges on solving major reconstruction concerns. Muon decay produces an overwhelming flux of background noise in the form of beam-induced background (BIB); particle identification and tracking algorithms tuned for the relatively clean LHC environment fall short under BIB conditions and must be adapted accordingly. This work investigates particle reconstruction performance for the MAIA detector concept under MuC conditions using jet energy resolution and transverse momentum studies. A neutron gun validation study identified PFOs marked as false multi-TeV neutrons producing significant energy contamination in reconstructed clusters, pointing to major issues in the handling of neutral hadronic jets in the presence of BIB. These findings motivate a closer look at how neutral hadronic energy is clustered and separated from background, with possible improvements drawing on density-based clustering approaches such as CLUE3D, developed for CMS's High Granularity Calorimeter.
Speaker: Sarah Douglass (Northeastern University (US)) -
4
ECal Timing Studies for LHCb's Upgrade II
The aim of the Upgrade II of the LHCb detector is to operate during Run 5 of the CERN Large Hadron Collider (LHC) at a luminosity of 1·1034 cm−2s−1 to collect a data set of 300 f b−1. The increase in particle densities requires a substantial modification of the present Electromagnetic Calorimeter (ECal). The modules of the new calorimeter, the PicoCal, must feature radiation-hard technologies and timing capabilities down to tens of picoseconds. Spaghetti calorimeter (SpaCal) and Shashlik technologies will be used for the upgrade. Moreover, an enhancement is planned already during the LS3 of the LHC, to cope with ageing effects of the present
modules.
Achieving picosecond-level time resolution requires optimization of all calorimeter components. Protypes of SpaCal have been tested on beam at DESY and SPS with electrons between 1 − 100 GeV, studying the contribution to the time resolution of the cables, shaping circuits and readout electronics. Time resoulution at tens of picoseconds have been achieved at high energies.
This contribution will describe the upgraded modules of the LHCb ECal, and the preliminary results of characterization at test beam.Speaker: Andreas Pettersson (Lund University) -
5
Testing for the new Inner Tracker system for ATLAS
The High Luminosity-Large Hadron Collider (HL-LHC) introduces a large increase in luminosity making it necessary to build new detectors that can handle the resulting increase in radiation damage. The most exposed parts will be those closest to the collision point. ATLAS is therefore upgrading their Inner Tracker (ITk) system; the first point of detection. ITk is composed of multiple silicon detector modules.
During production, the collaboration is preforming quality tests, including extensive electrical testing under different thermal conditions in a specialized set-up (Coldbox). In our cleanroom at Lund, we are testing Endcap strip modules received from both DESY and Prague. For this activity, the team has constructed a well-versed protocol. As a result of the testing, multiple modules have been passed and are ready to be installed.
Beyond this, Lund is also investigating modules showing odd behavior(s), that are considered fixable by forms of treatment such as UV-exposure or deionisation.
Collaborators: Solveig Englund and Kacper Opas
Speakers: Ellen Anna Brandt Sahlberg (Lund University (SE)), Vanshika Anand -
6
The FINESSE beamline at ESS
The FINESSE beamline is a proposed particle-physics instrument at the European Spallation Source (ESS) in Lund. It is designed to utilise the high cold-neutron brightness, pulsed time structure and long flight path available at ESS to address open questions in particle physics, including baryon number violation, new sources of CP violation and the nature of dark matter.
The primary strength of FINESSE is its ability to accommodate two complementary classes of particle-physics experiments within a single facility. In its high-flux configuration, an intense neutron beam is transported through a long, magnetically controlled region for neutron oscillation searches. A dedicated annihilation detector, combining charged-particle tracking, calorimetry and cosmic-ray rejection, is designed to identify the multipion signature produced if an antineutron annihilates in a target foil. Detector prototypes, readout systems and reconstruction methods are actively being developed within the collaboration. By exchanging a short section of neutron guide inside the ESS bunker, FINESSE can also operate in a low-background configuration ideal for precision measurements of neutron decay, hadronic parity violation and the neutron electric dipole moment.
The beamline would establish a major new programme at the interface of Swedish particle, nuclear and neutron physics. In this presentation, I will describe its scientific use cases and the current status of the beamline and detector development.
Speaker: Linus Persson (Lund University)
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1
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Coffee break Lobby
Lobby
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Session 2 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
7
ALICE overview
Overview of ALICE group activities in Lund.
Speaker: Alice Ohlson (Lund University (SE)) -
8
Probing path-length dependent jet modification with Event-Shape Engineering
In heavy-ion collisions, where the quark–gluon plasma (QGP) can be created and studied experimentally, we investigate the modification of jets as they propagate through the medium. In particular, we study path-length-dependent effects through the jet yield relative to the event plane and through event-shape engineering. Furthermore, jet–hadron correlations are used to probe medium-induced modifications of the jet structure through the resulting correlation functions.
Speaker: Joachim Hansen (Lund University (SE)) -
9
Searching for delayed jets from long-lived particles with the ATLAS detector
Many beyond-the-standard-model theories allow for new particles with long lifetimes. These long-lived particles will decay away from the primary interaction point, and many searches for these displaced decays have been performed by both ATLAS and CMS. However, spatial displacement is not the only signature of long-lived particles, since sufficiently massive ones also incur a time delay. Timing information from the ATLAS calorimeter systems can be used to measure these delays, supplementing sensitivity for long-lived particle scenarios in a detector region where spatial granularity drops and displaced searches are less efficient. This talk will introduce a search targeting R-parity violating neutralinos and a heavy Higgs signal decaying to delayed jets, and discuss the unconventional background sources that are present in this experimental signature. One background source will be highlighted in particular: collisions between "satellite" bunches, which are bunches of protons in RF buckets outside of the nominal bucket.
Speaker: Renske Wierda (KTH Royal Institute of Technology (SE)) -
10
Establishing Center-of-Mass Energy Dependence for Primordial Transverse Momentum in PYTHIA
The quarks and gluons inside a proton are expected to have an intrinsic momentum proportional to $\Lambda_{QCD}$ due to Fermi motion. In Monte Carlo event generators, primordial $k_T$ acts as an effective parameter that absorbs a broader range of unresolved physics, such as soft emissions below the parton shower cut-off. We present the evolution of the primordial $k_T$ width as a function of the hard scattering scale ($Q$) and the center of mass energy ($\sqrt{s}$) extracted by systematically tuning it to Drell-Yan dilepton production data. We demonstrate the need for a new parametrization for primordial $k_T$ and take steps towards a new global and more principled tune for PYTHIA 8.
Speaker: Ioannis Polychronakos (Lund University) -
11
Luminosity Measurement with the ATLAS High-Granularity Timing Detector at HL-LHC
The HL-LHC era will offer a rich physics program for the ATLAS experiment, alongside a significant challenge for detector performance given the increased pile-up levels of up to 140–200 simultaneous interactions per bunch crossing. The physics program requires a luminosity measurement precision of 1%, which ATLAS will meet using multiple complementary luminosity detectors spanning the full range of beam conditions, from the low-pileup van-der-Meer calibration regime to high-luminosity physics running. A key contributor to this effort is the High-Granularity Timing Detector (HGTD), built on novel Low-Gain Avalanche Detector (LGAD) silicon technology to achieve high timing resolution on tracks. In addition to supporting the Inner Tracker in the forward region and mitigating pile-up, HGTD will also provide luminosity measurement. This contribution presents an overview of ATLAS luminosity determination at the HL-LHC, along with recent developments and the current project status of HGTD as a luminosity detector.
Speaker: Magdalena Vande Voorde (KTH Royal Institute of Technology (SE)) -
12
Low Energy nuSTORM at ESS
The Low Energy nuSTORM (Neutrinos from STored Muons) facility at ESS focuses on the detailed measurement of neutrino-nucleus cross-section within the neutrino energy range relevant to ESSnuSB, a proposed neutrino long-baseline experiment at ESS, Lund, Sweden, which aims to measure the leptonic CP-violating phase, $\delta_{CP}$.
nuSTORM was introduced in 1980 and uses neutrinos from muons stored in a racetrack-shaped ring. The precisely controlled stored muon intensities in the ring make it possible to measure absolute cross-section with high precision, explore the potential existence of sterile neutrinos, and test technologies critical to the progress towards a Muon Collider.
LEnuSTORM utilizes the ESS linear accelerator and much of the infrastructure of the ESSnuSB long-baseline experiment. It will receive compressed proton beam pulses from the ESSnuSB accumulator, requiring only one of the four sub-pulses per main pulse, and a single target with a horn. The compressed proton pulse will generate a short pulse of charged pions emerging from the horn. These pions will be transferred to and injected into the muon storage ring, where they will decay and produce the muon beam.
Previous nuSTORM designs are designed for higher beam energies in the GeV range, whereas the LEnuSTORM, which relies on the ESS, aims to perform cross-section measurements in the low-energy region of 0.2- 0.6 GeV where cross-section data is currently missing. In this work, I will present the general concept and optimization of the nuSTORM, as well as the latest design of the LEnuSTORM facility.
Speaker: Ting Wing CHOI
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7
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Conference lunch at Stamstället Stamstället
Stamstället
Sölvegatan 21Common lunch
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Session 3 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
13
Towards global interpretation of the LHC data
A simultaneous determination of the proton parton distribution functions (PDFs) together with the strong coupling constant, the top quark15
pole mass, and, for the first time, the effective weak mixing angle, is presented. The analysis is performed
at next-to-next-to-leading order (NNLO) in QCD, based on inclusive DIS measurements at HERA and precise measurements of jet, electroweak boson,
and top quark-antiquark pair production in proton-proton collisions at the LHC. Non-relativistic QCD effects in top quark-antiquark pair production are considered, calculated at NLO in NRQCD, and combined with NLL soft-gluon resummation. Simultaneously with PDFs and Standard Model parameters, two relevant top-quark SM effective-field-theory operators are constrained. Precision of obtained SM parameters is compatitive with
the state-of-the art individual extractions and accounts for the correlations among those parameters and PDFs. This work paves the way for future global interpretation of the LHC data.Speaker: Katerina Lipka (Deutsches Elektronen-Synchrotron (DE)) -
14
Updates from the Light Dark Matter eXperiment
The Light Dark Matter eXperiment (LDMX) is a proposed fixed-target, missing-momentum experiment to be installed at the recently commissioned LESA beamline at the SLAC LCLS-II, that will deliver an $8\,\mathrm{GeV}$ electron-beam starting in summer 2027. The primary goal of LDMX is to search for dark matter in the MeV - GeV mass range, but its science potential includes sensitivity to a broader range of new physics phenomena as well as new measurements of background processes. This talk will present an overview of recent milestones and the current status of LDMX, with a particular focus on the Swedish contributions at Lund University.
Speaker: Ruth Poettgen (Lund University (SE)) -
15
Testing of LDMX's HGCROC-based readout electronics
The Light Dark Matter eXperiment (LDMX) aims to discover dark matter particle candidates produced with electron collisions on a thin, fixed target. To observe such cases via a missing momentum search, the detector consists of tracker modules before and after the target, an electromagnetic calorimeter (ECal), and a hadronic calorimeter (HCal). The HCal consists of alternating layers of absorber and scintillator bars, where signal photons in the scintillator bars are collected by counter-motherboards (CMBs) and sent onwards to the main readout electronics boards. Lund is responsible for producing all the HCal's readout boards, featuring the H2GCROC chip developed by the CMS collaboration as the front end. Over the past year, the Lund team characterised 10 prototype boards mounted with H2GCROCs by the CERN Electronics Workshop. The Lund team developed a standardised testing procedure using internal charge injections, focusing on checking the pedestal alignment and pulse sampling by the analogue-to-digital converter (ADC), as well as time-over-threshold (TOT) and time-of-arrival (TOA) measurements. An "outlier"-scan was developed to identify and characterise samples deviating from the expected pulse structure. In the future, a study will be conducted on the interplay between the HGCROC-board, CMB, and scintillator bars by flashing LEDs into these bars to produce a controlled external signal.
Speaker: Verena Hehl (Lund University) -
16
Modeling electronic final states in liquid xenon for light dark matter detection
Liquid xenon is an important target material for the direct detection of light dark matter (DM) via electron recoils. Consequently, accurate modeling of the DM-electron interaction in this medium is crucial. In particular, a proper description of the electron final states plays a key role in modeling the electronic response of the detector. We present our ongoing work following a novel approach in which the final states are described as linear combinations of positive-energy eigenstates of the Schrödinger equation, combined with a DFT modeling of the liquid xenon phase. These states replace the single positive-energy eigenstate approximation commonly adopted when liquid xenon targets are treated as collections of non-interacting atoms. Our approach therefore represents a step towards a more realistic description of liquid xenon as an interacting many-body system.
Speaker: Theresa Magdalena Backes -
17
Experimental measurement of thermal shock light yield
Several extensions of the standard model posit the existence of slow moving, heavy particles. Among these, nuclearites and Q-balls are expected to generate black body radiation from plasma through thermal shock upon interacting with matter, making them potentially detectable by experiments like the Icecube Neutrino Observatory. The current estimate for the light yield of this process is only based on simple thermodynamic assumptions. This talk presents an update on the effort to experimentally measure the light yield of plasma in ice by inducing thermal shock by high-powered laser light.
Speaker: Michael Hrywniak (Stockholm University) -
18
Vertex reconstruction with the HIBEAM TPC
The HIBEAM/NNBAR programme at the European Spallation Source will search for neutrons converting to antineutrons. An important observable is the reconstructed vertex arising from charged particles produced by an antineutron annihilating on a thin target foil and which pass through a time projection chamber. We present a comparison of four methods for vertex coordinate reconstruction: two machine learning (ML)-based methods and two non-ML methods, where one of each is tailored for this study.
Speaker: Alexander Burgman (Department of Physics, Stockholm University) -
19
Continuous calibration of ATLAS flavour-tagging classifiers via optimal transport
Algorithms to identify jets from b-hadrons (b-jets) are widely in use in ATLAS and are crucial for measurements and searches targeting processes with top quarks or Higgs bosons in the final state, for instance, b-tagging played a central role in the observation of the Higgs boson decay into bottom quarks. These b-tagging algorithms are trained on simulation, therefore, their performance in data has to be checked and corrections for simulations have to be derived. Traditionally, operating points using intervals of fixed b-tagging efficiencies are defined such that calibrations can be performed in these intervals. However, this limits the flexibility in the application of the algorithms in analyses. This work introduces a continuous calibration of the ATLAS GN2 flavour-tagging algorithm using optimal transport maps. The simulated flavour-tagging classifier outputs (probabilities for b-, c-, tau-, and light-flavour jets) are transformed to match the observed data distributions, minimizing alterations to the simulation while achieving closure with data. The calibration is derived as a function of the jet transverse momentum and pseudorapidity using high-purity samples of b-jets from top-antitop events in ATLAS Run 3 data, employing neural solvers to approximate the optimal transport maps. This approach provides a fully continuous, three dimensional calibration of flavour probabilities, removing the need for discrete operating points and opening new possibilities for high-dimensional corrections in ATLAS analyses, therefore enhancing the precision of measurements and the sensitivity of searches for new physics.
Speaker: Alessandro Montella (Stockholm University (SE)) -
20
Update on the X->SH->bbyy ATLAS analysis
Driven by the need to address the shortcomings of the Standard Model (SM), such as the origin of dark matter or the mystery of baryogenesis, different Beyond the Standard Model (BSM) theories have been proposed. Many such models, for example two-Higgs-doublet models (2HDMs) and supersymmetric (SUSY) models such as the Next–to–Minimal SUSY model (NMSSM), introduce extended Higgs sectors containing additional scalar bosons. In this presentation, an ATLAS search for the resonant production of a heavy new, Higgs-like scalar, X, decaying into the Higgs boson H, and another lighter scalar, S, is presented. The final state studied contains two b-quarks and two photons, where one channel is represented by S→bb, H→γγ and the other by S→γγ, H→bb. The former has previously been studied by ATLAS and CMS, and several moderate excesses have been observed. The latter channel has only been studied by CMS, with one slight excess observed. In this talk the latest ATLAS result obtained in the S→bb, H→γγ channel with partial Run-3 data are presented, as well as the work towards i) updating this channel with full Run-3 data, which will more than triple the dataset size, and ii) introducing the new S→γγ, H→bb channel.
Speaker: Julia Salwén (Stockholm University (SE))
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13
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Coffee break Lobby
Lobby
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Session 4 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
21
Exploring phase transitions and gravitational waves in the conformal two-Higgs-doublet model (C2HDM).
The mechanism behind the observed baryon asymmetry in the Universe remains an open problem that motivates the search for physics beyond the Standard Model. Indeed, within the Standard Model, the smooth crossover electroweak phase transition does not provide the required departure from thermal equilibrium, nor is there a sufficient amount of CP-violation.
In this talk, I will present our ongoing work with a model that seeks to address these shortcomings. This is a two-Higgs-doublet model with classical scale invariance (hence conformal at the classical level) and (potential) explicit CP-violation.
We explore the parameter space of the model and restrict ourselves to viable scenarios constrained by collider data. Using dimensional reduction, we construct the effective potential, and explore the phase structure and the phase transitions. For the strongly first-order ones, we also calculate the contribution to the stochastic gravitational wave background, sourced by the energy released in the transition. Such a signal could potentially be observed by future space-based gravitational-wave detectors, and thereby provide insight into the nature of phase transitions in the early Universe.
Speaker: Mårten Bertenstam (Lund University) -
22
Search results for Higgs boson pair production in the $bb\tau\tau$ final state from ATLAS using Run 2 and Run 3 data
ATLAS has recently published a new search for non-resonant $pp\to HH$ production, using Run 3 data from 2022 and 2023, combined with the full Run 2 dataset.
This analysis targets the $b\bar{b}\tau^{+}\tau^{-}$ final state.The observed Higgs boson pair production signal strength is $2.6^{+1.4}_{-1.0}$, which corresponds to an observed significance of 2.6$\sigma$, compared to an expected significance of 1.2$\sigma$ under the standard model (SM) hypothesis.
Also, 95\% confidence intervals for the modifiers $\kappa_\lambda$ of the Higgs self-coupling and $\kappa_{2V}$ of the $HHVV$ coupling ($V=W,Z$) are derived: $\kappa_\lambda \in [-3.14, 1.6] \cup [5.5, 10.1]$ and $\kappa_{2V} \in [-0.2,2.4]$.The analysis is validated through auxiliary measurements of the $ZZ / ZH \to b\bar{b}\tau^{+}\tau^{-}$ processes.
The measured signal strengths are consistent with the SM expectations, with an observed significance of 3.5 $\sigma$, and thereby the first evidence, for $ZH \to b\bar{b}\tau^{+}\tau^{-}$.The backgrounds are modeled using simulation and data-driven estimates.
This talk presents the analysis strategy, the data-driven Fake Factor method used to model multijet backgrounds, as well as the results of the search.Speaker: Philipp Rincke (Uppsala University (SE)) -
23
Overview of fake tau background methods and their use in the type-II seesaw searches
Hadronically decaying tau leptons are reconstructed as narrow jets, and quark or gluon-initiated jets that are misidentified as hadronic taus are a dominant background in searches with hadronic tau final states. Since the misidentification probability depends on the least well-modelled aspects of the simulation (soft fragmentation) and this background can't be taken from Monte Carlo and must be measured in data. The idea of this talk is to give an overview of the data-driven methods used in ATLAS for this purpose (matrix method, fake factors and the universal fake factor method), and then focus on the new, continuous fake factor method and its application within the Type II (and III) seesaw analysis. A common limitation of the standard approaches is that they are binned in a few variables and assume that the control region reproduces the fake composition of the signal region, which is usually the dominant systematic uncertainty. Instead the continuous method estimates the fake factor as a event density ratio (in event) learned from data in a high-dimensional feature space.
Speaker: Lara Calic (Lund University (SE)) -
24
Normalising flows for all-orders QED corrections in lattice quantum field theory
Many low-energy precision tests of hadronic observables in the Standard Model now require the inclusion of isospin-breaking corrections due to light-quark mass differences and electromagnetism (QED). Isospin breaking typically appears for any prediction with better than percent-level precision, such as for the neutron beta decay. Lattice quantum field theory is a first-principles approach to calculate hadronic observables in a systematically improvable fashion. In this talk I will present how normalising flows and machine learning can be used to calculate all-orders electromagnetic corrections in lattice field theory, generally bypassing the complexity in Wick-contraction diagrams needed at fixed order. The new method is applied to lattice scalar QED in two, three, and four spacetime dimensions, yielding estimates with significantly reduced variance with respect to standard methods. A generalisation to theories with fermions is envisaged, paving the way for applications in challenging field theories including lattice QCD.
Speaker: Nils Hermansson Truedsson -
25
5D Unified Theories: from general principles to an SU(6) example
Higher-dimensional gauge theories provide a compelling framework for physics beyond the Standard Model, offering new approaches to gauge unification and ultraviolet (UV) completions. In particular, five dimensional (5D) theories compactified on orbifolds can generate realistic four dimensional (4D) models through boundary conditions, while asymptotically safe dynamics may render them UV complete.
We investigate the theoretical viability of such constructions from several complementary perspectives. We will review the role of orbifold compactification and the conditions required for the resulting setup to remain consistent and stable, as well as the renormalization properties of 5D gauge theories. We then illustrate these general considerations through a concrete 5D SU(6) model. After constructing the theory and its symmetry-breaking structure, we perform a set of consistency checks and examine how the model fits within the broader framework of viable higher-dimensional unified theories.Speaker: Anca Preda (Lund University) -
26
Exploring SU(6) based 5 dimensional Grand Unification Theory
We present the explicit construction of a minimal, stable example of an asymptotic Grand Unified Theory (aGUT). We start by formulating the theory in the high energy regime and performing a series of checks to understand its low energy limit. The model, based on an SU(6) gauge group, and formulated in five spacetime dimensions, is compactified on an $S^{1}/(\mathbb{Z}_{2}\times\mathbb{Z}_{2}')$ orbifold. We show that gauge couplings exhibit the existence of an ultraviolet fixed point, while Yukawa couplings need to be localised on one of the orbifold boundaries to generate the correct fermion masses. Moreover, the scalar sector reduces to a restricted two Higgs doublet model, with additional scalar fields.
Speaker: Alejandro Pierola Cervantes -
27
Renormalisable four-fermion interactions in four dimensions
Four-fermion interactions are important in many areas of particle physics, from effective descriptions of weak interactions and QCD to parametrisations of new physics in frameworks such as SMEFT. In this talk I demonstrate that four-fermion interactions may develop strongly coupled UV fixed points in four dimensional QFTs, becoming non-perturbatively renormalisable, and UV-completing themselves from the bottom up. The idea will be illustrated in a purely fermionic model of the Gross-Neveu type using the toolbox of the large-$N$ expansion.
Speaker: Charlie Cresswell-Hogg -
28
Field Theory for Neutronics
Recent research suggests that neutron fluctuations in combination with feedback effects might have a non-negligible impact on the neutron distribution in nuclear reactors. This phenomenon can be analysed with statistical physics by using methods from quantum field theory. In this presentation, I will give an overview of previous research and our plan for how to improve the theoretical model. Preliminary results might be included, depending on our progress.
Speaker: Jacob Persson (Uppsala universitet)
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21
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Conference dinner
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Session 5 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
29
The discovery potential of FCC-ee
The discovery potential of FCC-ee
Speaker: Gino Isidori (University of Zurich (CH)) -
30
ECFA report
This talk will report on the ECFA activities in 2026.
Speakers: Bernhard Meirose (Lunds Universitet), Rebeca Gonzalez Suarez (Uppsala University (SE)) -
31
ACCU report (file upload only)
ACCU report (slides upload only)
Speaker: Rebeca Gonzalez Suarez (Uppsala University (SE)) - 32
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33
CERN OpenData for teaching and outreach
The CERN OpenData project has made a huge amount of LHC data open to the public for use in education, outreach, and research. This data, and the related analysis tools provided by the experiments, can be used in our teaching to give students of all levels hands-on experience in data analysis and introduce them to modern particle physics methods. In this talk, we will show several examples of OpenData exercises that we have developed for use in our classrooms, and discuss the varied pedagogical goals of the exercises, target student groups, and classroom implementations.
Speakers: Alice Ohlson (Lund University (SE)), Christian Bierlich (Lund University (SE)), Christian Ohm (KTH Royal Institute of Technology (SE)) - 34
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29
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Coffee break Lobby
Lobby
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Session 6 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
35
VR (S. Bertilsson) discussion
with Stefan Bertilsson (VR-NT),
Speakers: Catharina Sahlberg, Stefan Bertilsson -
36
ICHEP 2030 comes to Sweden: the flagship of particle physics in Lund-Malmö
The 45th International Conference on High Energy Physics, the flagship
conference of our field, gathering over a thousand delegates, will be hosted in Lund-Malmö on 17-24 July 2030. For the first time in the 80-year history of the series, ICHEP comes to Sweden and the Nordic region.This talk presents the winning bid and what carried it: a compact, sustainable and deliberately affordable conference model built on the Öresund region's scientific infrastructure, backed by Lund University, the Particle and Astroparticle Section of the Swedish Physical Society, the City of Malmö and Region Skåne. Above all, it opens the conversation within our community that must follow. Hosting ICHEP is a national and Nordic undertaking — from the Local Organizing Committee and its working groups to the programme committees, convenerships and outreach — and a rare opportunity to place Swedish particle and astroparticle physics at the centre of the world stage in the middle of the post-Strategy decade. I will outline the organizational roadmap and invite your opinions, suggestions and expressions of interest. The road to 2030 starts here.
Speaker: Roman Pasechnik (Lund university) -
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IUPAP Report
C4 IUPAP update
Speaker: Riccardo Catena (Chalmers University of Technology, Göteborg, Sweden) -
38
News from APPEC
APPEC, the AstroParticle Physics European Consortium, is working towards finishing the next decade's European roadmap for astroparticle physics, 2027-2036. This talk will cover recent news from APPEC.
Speaker: Alexander Burgman (Department of Physics, Stockholm University)
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Conference lunch at Stamstället Stamstället
Stamstället
Sölvegatan 21Common lunch
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Session 7 A-salen (L317)
A-salen (L317)
Lund University, Physics Department
Sölvegatan 14, Lund-
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Multimessenger diagnostics of hadronic acceleration from PeV to EeV
The origin of high-energy cosmic rays remains one of the central open questions in astroparticle physics. In recent years, new observations of Galactic cosmic rays and gamma-rays, high-energy neutrinos, and ultra-high-energy cosmic rays have provided important clues about the astrophysical environments that can accelerate hadrons to extreme energies. In this talk, I will review recent progress in the search for cosmic-ray accelerators from PeV to EeV energies. I will discuss the emerging picture of Galactic cosmic-ray sources, including supernova remnants, stellar clusters, and microquasars, as well as the prospects for identifying the main Galactic PeVatrons. I will then turn to high-energy neutrinos and what recent multimessenger observations tell us about their sources. Finally, I will discuss the transition to the ultra-high-energy regime and the latest developments in the search for the sources of ultra-high-energy cosmic rays.
Speaker: Foteini Oikonomou (NTNU) -
40
Search for neutral long-lived particles with IceCube
We present the first-ever search for Long-Lived Particles (LLPs) produced by atmospheric muons with the IceCube neutrino telescope.
Atmospheric muons, disregarded as background in most IceCube analyses, could produce LLPs in the detector volume via an exotic muon–nucleus bremsstrahlung-like scattering, which would travel undetected for some distance before decaying back into Standard Model particles, creating a distinct “dark gap" segment in the otherwise bright muon track. Identifying these rare signatures within the sparse detector geometry is a significant challenge, but provides a probe into new physics scenarios involving feebly interacting particles with long lifetimes.Speaker: Carlos Perez de los Heros -
41
The IceCube Upgrade
The IceCube Neutrino Observatory has completed its first major expansion since construction: five new, densely instrumented strings carrying next-generation optical sensors, deployed at the detector's center in the 2025/2026 Antarctic field season.
The Upgrade lowers IceCube's energy threshold into the few GeV range, enabling improved measurements of atmospheric neutrino oscillation parameters while also reducing ice-optical-property systematics that currently limit several astrophysical analyses.
As part of the calibration effort, Stockholm University and Uppsala University groups deployed steerable in-ice cameras to monitor hole-ice refreezing and constrain the bulk-ice optical model. We report on the Upgrade's design and deployment together with first results from the camera system.
Speaker: Anna Obertacke (Stockholm University) -
42
Constraints on light Z' bosons and the X17 from neutrino decoupling in the early universe
The number of effective relativistic neutrino species Neff is a sensitive probe of new physics if there are new particles that couple to SM particles at the time of the neutrino decoupling, which occurs at a temperature of around MeV, one second after the Big Bang. We calculate how the existence of a light Z' boson with generic vector and axial-vector couplings to electrons and neutrinos affects the predicted value of Neff and compare with the measured value to put bounds on the couplings. We further apply this analysis to the case of our previously studied model for the 17 MeV Z' boson that can potentially explain the ATOMKI anomaly and thereby further tighten the constraints on its parameters.
Speaker: Rikard Enberg
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39
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ESS visit ESS
ESS
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