Partikeldagarna 2024

21 Oct 2024, 08:25 → 22 Oct 2024, 18:00 Europe/Stockholm

Humanistiska Teatern, Engelska Parken. Uppsala

Carlos Pérez de los Heros (Department of Physics and Astronomy)

Partikeldagarna is the annual meeting of the Particle- and Astroparticle Physics section of the Swedish Physical Society (Svenska 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. Please follow the menu on the left for further information.

Note that participation in Partikeldagarna is restricted to members of the Swedish Physical Society (master students are exempted from this restriction). Further information on membership can be found here.

Organizing committee:

C. Pérez de los Heros (UU, chair), S. Choubey (KTH), G. Ferretti (CTH), C. Finley (SU), R. González Suárez (UU),  D. Silvermyr (LU), M. Sjödahl (LU), J. Sjölin (SU)

Secretariat: A. Gallén, A. Pontén (UU)

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Monday, 21 October

08:40 Registration

Session 01

1 Welcome and Introduction

Speaker: Carlos Perez de los Heros (Uppsala University)

2 Leptonic decays of pions and kaons in lattice QCD+QED

Precision calculations within the Standard Model offer the possibility to indirectly search for the existence of new physics. In the flavour physics sector there are emerging tensions that must be further scrutinised, e.g. for determinations of the light-quark Cabibbo-Kobayashi-Maskawa matrix elements through various hadron decays. These decays require good control of the non-perturbative low-energy dynamics of QCD, where methods such as lattice and effective field theory are essential. In this talk I will present recent results for precision determinations of leptonic decays of pions and kaons including also effects from QED, current bottlenecks and possible solutions.

Speaker: Dr Nils Hermansson-Truedsson (University of Edinburgh)

Partikeldagarna24_NHT.pdf

3 Orbifold stability of asymptotic GUTs

In the realm of higher-dimensional grand unified theories (GUTs), the technique of orbifolding has emerged as a powerful tool to achieve spontaneous symmetry breaking by geometrical means. We use this tool to analyze the most general 5D GUT models based on the gauge groups SU(N), Sp(2N) and SO(N). We find a new physical consistency requirement, which these models have to satisfy in order to be phenomenologically viable, and which we call orbifold stability. Using the criteria of orbifold stability, as well as requiring the presence of fixed points for gauge and Yukawa couplings, we can discard all unrealistic scenarios, only to find two feasible models:

• one model based on the SU(6) gauge group, which leads to the Standard Model at low energies
• one model based on the SU(8) gauge group, giving rise to Pati-Salam theory below the compactification scale

Speaker: Anca Preda (Department of Physics, Lund University)

Partikeldagarna_Anca_Preda.pdf

4 Recasting Feynman rules with chirality flow

Since some 70 years, the default method of calculating scattering amplitudes is to use Feynman diagrams. In this talk, I will explore how standard Feynman rules can be significantly simplified by breaking up the Lorentz structure of spin and momentum into smaller objects, the left and right spinors. Adapting the method of color flow from the strong force, I show how amplitudes corresponding to Feynman diagrams can be written down in a transparent and intuitive manner. This simplifies the computation of Feynman diagrams significantly, and puts spin physics in a new light. In this talk, I will review the formalism, and present results from an implementation in MadGraph5_aMC@NLO.

Speaker: Malin Sjodahl (Lund University)

Partikeldagarna2410MalinSjodahl.pdf

10:30 Cofee break

Session 02

5 High-energy cosmic neutrinos in particle physics and astrophysics: present and future

Speaker: Mauricio Bustamante (NBI)

2024-10-21-Bustamante-Partikeldagarna-2024.pdf

6 The IceCube Neutrino Observatory and future extensions

The IceCube Neutrino Observatory, located at the South Pole is the world's largest optical neutrino telescope instrumenting a total of 1 km$^3$ of glacial ice with more than 5000 sensors. After more than a decade of data taking, IceCube has revealed the high-energy astrophysical neutrino flux, identified sources of high-energy neutrinos, probed beyond the standard model and fundamental neutrino physics and contributed to low-energy and supernova science. In addition, the IceCube Upgrade to be completed in the 2025/26 season will deploy about 700 new sensors in a dense detector infill aimed at improving detector calibration, lowering the energy threshold for a subset of the detector and acting as a testbed for newly developed sensors. IceCube-Gen2, an envisioned large-scale extension of IceCube, will increase the instrumented volume by a factor of 8. In this talk, I will give an overview of the latest results from IceCube, summarize the research fields of the Uppsala and Stockholm groups and demonstrate the Swedish hardware contributions.

Speaker: Jakob Beise (Uppsala University)

IceCube talk.pdf

7 The Radio Neutrino Observatory in Greenland, a path towards IceCube-Gen2

Cosmic neutrinos are the perfect messenger particles. They can propagate vast distances uninterrupted, making it possible to probe the most violent phenomena in the universe, but they are also notoriously difficult to detect. The Radio Neutrino Observatory, currently under construction in Greenland, will, once completed, be the first experiment large enough to tap into the predicted neutrino flux models at EeV energies and serve as a testbed for the order-of-magnitude larger IceCube-Gen2 Radio observatory. Using the Askaryan effect from neutrino-induced particle cascades, 35 autonomously operating radio stations will monitor several cubic kilometers of ice for neutrino interactions for many years into the future. I will present the current status of the experiment and introduce its design and science goals. I will highlight the Swedish contributions of an autonomous power system, deep-learning-based triggers to increase neutrino detection rates, and the development of a new DAQ system to run advanced trigger algorithms in real-time.

Speaker: Nils Heyer (Uppsala University)

Partikeldagarna_RNOG.pdf

Partikeldagarna_RNOG.pptx

8 Neutrinos from heavy quark decay in astrophysical sources and energy dependent flavour ratios

The origin of the high-energy diffuse neutrino flux observed in neutrino telescopes is not known. Most models for astrophysical neutrino generation assume that neutrinos come from decays of pions and kaons produced when accelerated protons collide with ambient photons in the source. I will demonstrate that, similarly to atmospheric neutrinos, if there is a significant amount of hadronic matter in the source, hadrons with heavy quarks may be produced. These are very shortlived and therefore less subject to energy loss than pions, and the resulting neutrinos will have a harder spectrum. In addition, neutrinos from charmed mesons, which dominate, have a different flavor composition than neutrinos from pions. Therefore, apart from the spectral shape, a possible signal of this additional production mechanism would be found in the relative flavor content of the neutrino flux detected at Earth. I will demonstrate how this leads to a non-trivial energy dependence in the flavor compositions and will discuss the possible sensitivity of neutrino observatories. In our recent paper (arXiv:2309.09139) we explored this in the context of two examples of astrophysical sources where charm production may be effective: slow-jet supernovae and magnetar-driven supernovae.

Speaker: Rikard Enberg (Uppsala University)

Astro nu Partikeldagarna 2024.pdf

9 Astroparticle physics with polarised X-rays

Our understanding of compact celestial sources, such as pulsars and mass-accreting neutron stars/black holes, stems from studying high-energy source emission using instruments designed for imaging, spectroscopy, and timing. Recently, instruments have been developed which can measure the linear polarisation of the emission. This allows the nature of the emission and source geometry to be studied in a systematically new way, thereby breaking current observational degeneracies.

In the hard X-ray band (>10 keV), measurements can be conducted at the top of the atmosphere using Tonne-scale telescopes suspended under enormous helium-filled balloons. The astroparticle physics group at KTH has been working on X-ray polarimetry for ~20 years. The latest mission, XL-Calibur, was launched from the Esrange Space Centre in northern Sweden in July 2024. XL-Calibur is the most sensitive hard X-ray polarimeter mission flown to date. The Crab pulsar and black-hole binary Cyg X-1 were observed during the week long flight to northern Canada. The design of the mission will be reviewed and the outcome of the flight presented.

Speaker: Mark Pearce (KTH)

partikeldagarna2024_MP.pdf

12:30 Lunch

Session 03

10 Theoretical upper bounds on detector's response to DM-$e^-$ interactions in direct searches for sub-GeV dark matter

Despite tremendous efforts to detect dark matter (DM), so far, no direct-detection experiment has provided any widely-accepted positive results. Thus, it seems reasonable to redirect the focus of experimental searches to regions of DM masses outside the extensively probed GeV-TeV range which corresponds to the well-known WIMP paradigm. This motivates the prioritization of searches for sub-GeV dark particles.

A simple kinematic analysis shows that DM-induced detector's response should be maximal when the mass of the target particle inside the detector is as close as possible to the mass of the incident dark particle. Hence, for sub-GeV DM, theoretical studies of direct searches should focus on interactions of the dark particles with electrons rather than nuclei.

The detector's response can be described in terms of the so-called generalized susceptibilities, which extend the notion of the dielectric function to describe the detector's material response induced by a general class of DM-$e^-$ interactions. The susceptibilities must satisfy certain mathematical constraints, known as the Kramers-Kronig relations. Using these constraints, it is possible to derive material-independent theoretical upper bounds on the detector's response.

Properties of known materials can be investigated in order to identify those that are closest to saturating these upper bounds, providing suitable candidates for being used in future detectors of sub-GeV DM.

This talk will focus on the derivation of the theoretical upper bounds and compare them to the properties of some materials widely used in direct searches for DM.

Speaker: Michał Iglicki (Chalmers University of Technology)

iglicki_partikeldagarna2024.pdf

11 Hunting for dark photon trident and beyond

We discuss a novel decay process for dark matter searches known as the dark photon-photon trident, where a dark photon can interact with Standard Model particles through kinetic mixing with the visible photon, producing three-photon final states. Indirect searches for this process are categorized into two scenarios. Firstly, dark photons can be produced by dark matter annihilation in celestial objects and dwarf galaxies. Secondly, the dark photon can itself constitute dark matter, which decays into photons falling into the energy range of X-ray observations. We give constraints on dark matter-Standard Model interactions and the dark photon parameter space based on these search strategies. Additionally, we present results for the decay of heavier dark photon dark matter beyond the dark photon trident scenario, along with a discussion of previous searches for dark matter decay.

Speaker: Thong Nguyen (Stockholm University)

Uppsala2024.pdf

12 Update from the Light Dark Matter eXperiment

The Light Dark Matter eXperiment (LDMX) is a fixed-target missing-energy and missing-momentum experiment searching for sub-GeV dark matter, planned to be constructed at SLAC's LCLS-II accelerator. The Lund group is involved in design and construction of LDMX's hadronic calorimeter, in the trigger-scintillator system, simulation studies, offline-software development, and test beam activities. This talk will give an overview of recent activities on the Swedish side of the LDMX collaboration.

Speaker: Hannah Herde (Lund University)

HEH-SE-in-LDMX-Partikeldagarna2024.pdf

13 Noise and shower shapes in the LDMX prototype hadronic calorimiter

The Light Dark Matter eXperiment (LDMX) is a proposed fixed target missing energy and momentum experiment with the purpose of searching for light dark matter in the ranges of MeV to low GeV masses. The experiment utilises a steel-scintilator hadronic calorimiter (HCal) for event veto, a prototype of which was tested at CERN in the spring of 2022. The data taken during the 2022 test run has undergone extensive analysis with the goal to quantitatively verify the HCal's performance and search for potential issues in the data pipeline. Results of noise measurements, as well as an analysis of pulse shapes and minimally ionizing particle (MIP) detection efficiency are presented.

Speakers: Axel Helgstrand (Lund University), Gréta Gajdán (Lund University)

Noise and shower characteristics in the LDMX hadronic calorimeter prototype - slides.pdf

14 On the Dark Matter Origin of a LDMX Signal

The search for a particle candidate explaining the origin of dark matter is one of the central goals in modern astro-particle physics. New fixed target experiments show great potential for probing this new physics, particularly in the sub-GeV dark matter paradigm. In the event that a dark matter signal is seen at such an experiment, it is crucial to make an independent validation to confirm detection. In this presentation, we explore the possibility of using a direct detection (DD) experiment to validate a hypothetical dark matter signal seen at the Light Dark Matter eXperiment (LDMX). We propose a four-step analysis strategy, which we have implemented with Monte Carlo simulations. First we simulate a hypothetical LDMX detection signal (as an excess in final state electron energy and transverse momentum distributions). Secondly, a hypothetical semiconductor based DD signal is simulated with increasing exposure. The third step is to extract a posterior distribution for the considered dark matter model parameters by performing Bayesian parameter estimation on the DD signal. In the last step, the parameter posterior is incorporated as a predicted electron recoil energy and transverse momentum for LDMX, which is then compared to the recorded LDMX result by utilizing a chi-square hypothesis test. We present the results of this comparison in terms of a threshold exposure that a DD experiment has to operate with to assert whether the predicted and recorded signals can be statistically dependent. This result varies from 0.007 kg-year for a DM mass of mχ=4 MeV to 1.45 kg-year for mχ=25 MeV, which is soon to be within reach.

Speaker: Andreas Lund (KTH)

Andreas_presentation_LDMXval.pdf

15:00 Coffee break

Session 04

15 Experimental Efforts to Search for Dark Matter Axions at Stockholm University

The axion is a hypothetical particle emerging from the Peccei-Quinn mechanism, which was proposed to solve the strong CP problem in quantum chromodynamics. With a mass below the electron-volt range, axions interact feebly with Standard Model particles, making them a strong candidate for dark matter. One of the most sensitive methods for dark matter axion detection is the cavity haloscope. This approach utilizes a microwave cavity in a strong magnetic field, where axions can convert into photons when the cavity’s resonant frequency matches the axion mass. At Stockholm University, we are part of the ALPHA collaboration, working to develop a tunable wire metamaterial cavity to enhance sensitivity to high-mass axions. This talk will present our plans to design a cavity tuning system and build a weak microwave photon detection system.

Speaker: Junu Jeong (Stockholm University)

Partikeldagarna2024_JUNU.pdf

Partikeldagarna2024_JUNU.pptx

16 Resonant or asymmetric: The status of sub-GeV dark matter

Sub-GeV dark matter (DM) has been gaining significant interest in recent years, since it can account for the thermal relic abundance while evading nuclear recoil direct detection constraints. However, sub-GeV DM is still subject to a number of constraints from laboratory experiments, and from astrophysical and cosmological observations. In this work, we compare these observations with the predictions of two sub-GeV DM models (Dirac fermion and scalar DM) within frequentist and Bayesian global analyses using the Global And Modular BSM Inference Tool (GAMBIT). We infer the regions in parameter space preferred by current data, and compare with projections of near-future experiments; providing a status update to sub-GeV DM.

Speaker: Taylor Gray (Chalmers University of Technology)

TaylorGray_Partikeldagarna_pdfformat.pdf

17 A study of jet-medium interactions in small systems using a "brick"-like medium model

The present work addresses the puzzle related to the observation of collective flow in collisions of small systems and the apparently contradictory absence of jet quenching in those cases. This study has been done using the JEWEL event generator with a "brick"-like medium made up of a collection of gluons at a certain temperature and density in a given ellipsoidal region of space. This simplified medium allows us to study the number and characteristics of jet-medium interactions necessary to create signs of jet quenching and collective flow without relying on specific models for medium evolution.

To do that, we generate pairs of jets in the center of the medium and, as they evolve, count the number of jet-medium interactions. What we have found is that the observables do not depend only on the number of interactions but on how much energy and momentum are transferred at each interactions. However, our results so far indicate that more interactions (and thus more energy/momentum) are required to create a visible R$_{\text{AA}}$ signal than for a v$_2$ signal. This in turn could explain how small systems can show signs of collectivity but not jet quenching.

Speaker: Chiara Le Roux (Lund University)

partikledaggarna-final2.pdf

partikledaggarna-final.pdf

18 CP symmetry tests of baryon weak decays with LHCb and BESIII

There exists an imbalance between matter and antimatter in the Universe. Charge parity violating (CP) mechanisms are necessary to generate such an asymmetry.
CP violation has only been observed in weak decays of mesons. Baryon weak decays offer unique and complementary ways of testing the validity of the Standard Model. Notably, spin polarization can significantly enhance the sensitivity of CP-violating precision tests. The two particle physics experiments LHCb and BESIII can be used for such tests. The LHCb experiment at CERN, a single-arm spectrometer optimized for the study of beauty and charm-flavoured hadrons, is the only experiment to observe CP-violation in charmed hadron decays.
The BESIII experiment at the electron-positron collider BEPCII in Beijing, operational since 2008, has collected the world's largest data samples of J/Psi and Psi(2S). Recent observations of hyperon polarisation at BESIII open new avenues for probing CP violation, by enabling simultaneous detection of spin-correlated hyperon and anti-hyperon weak decays. In this presentation, a brief overview of the two experiments will be provided, the physics case for baryon CP violation and prospects for the future.

Speaker: Patrik Adlarson (Uppsala University)

Partikeldagarna_Adlarson_LHCb_BESIIII.pdf

19:00 Dinner. Trattoria Brezza, Skolgatan 31.

Tuesday, 22 October

Session 05

19 News from (R)ECFA

Speaker: Arnaud Ferrari (Uppsala University)

ECFA-PD2024.pdf

20 News from IPPOG

Speaker: Christian Ohm (KTH Royal Institute of Technology)

Outreach_and_IPPOG.pdf

21 News from IUPAP (C4 and C11)

Speakers: Riccardo Catena (Chalmers), Roman Pasechnik (Lund University)

catena.pdf

IUPAP_C11-Pasechnik-2024.pdf

22 News from APPEC

Speaker: Alexander Burgman (Department of Physics, Stockholm University)

ABurgman__Partikeldagarna2024__APPEC.pdf

23 News from ACCU

Speaker: Rebeca Gonzalez Suarez (Uppsala University)

ACCU_PartikelDagarna2024.pdf

24 News from the CERN Council and the European Particle Physics Roadmap

Speaker: Richard Brenner (Uppsala University)

CERN_Partikeldagar2024.pdf

10:30 Coffee break

Session 06

25 Beyond the Standard Model physics at the LHC and beyond

Speaker: Sarah Williams (University of Cambridge)

BSM_at_LHCandBeyond-221024-final.pdf

26 Combination of searches for Higgs boson pair production in the ATLAS experiment

Searches for the production of Higgs boson pairs (HH) are of great interest especially for measuring the Higgs boson self-coupling, which is related to the shape of the Higgs potential. While the Standard Model (SM) predicts a very small event rate for this process, modifications of the Higgs boson self-coupling or new couplings introduced in effective field theories (EFTs) can lead to enhancements of the HH cross-section. In this talk, the latest non-resonant HH searches by the ATLAS experiment are reported, with emphasis on the results obtained from their statistical combination with the full LHC Run 2 dataset at 13 TeV. Results are interpreted both in terms of SM sensitivity and as limits on the Higgs boson self-coupling and Wilson coefficients in EFTs.

Speaker: Christina Dimitriadi (KTH Royal Institute of Technology)

Partikeldagarna2024_diHiggs.pdf

27 Beyond simplified models; ATLAS SUSY searches re-interpreted in the pMSSM framework

Many searches for supersymmetric (SUSY) particles have been conducted by the ATLAS experiment using simplified models, but so far, no evidence of physics beyond the Standard Model has been found. In the absence of new physics, exclusion limits on SUSY particle masses are typically derived from the searches. However, these simplified models do not fully cover the whole SUSY parameter space. In the phenomenological minimal supersymmetric standard model (pMSSM) the vast parameter space of SUSY is reduced to 19 parameters by assuming R-parity conservation, minimal flavour violation and the lightest SUSY particle is assumed to be the lightest neutralino.

This talk will present a summary of the ATLAS Run 2 SUSY searches within the context of the pMSSM framework. By scanning the pMSSM parameters the exclusion abilities of ATLAS SUSY searches are shown. The results will be presented in terms of constraints on SUSY particle masses and will be compared to the exclusion limits obtained from simplified models.

Speaker: Ellen Riefel (Stockholm University)

Slides_partikeldagarna_okt2024.pdf

28 ALICE Lund group activities

Overview of ALICE Lund group activities

Speaker: David Silvermyr (Lund University)

p_christiansen_lund_alice.pdf

29 Studying $\Lambda$-Hadron correlations in Pb-Pb collisions using the ALICE detector

Heavy-ion collisions in large-scale particle accelerators, like the LHC, are frequently used to study the theory of Quantum-Chromodynamics (QCD). These collisions result in the creation of a fireball with a very high energy density and pressure, leading to a state of matter known as the Quark-Gluon Plasma (QGP). The extreme conditions achieved in heavy-ion collisions provide a fascinating testing grounds for studying various physical effects in QCD.

The goal of this analysis is to study the production mechanisms for strangeness and baryon number, as well as how these mechanisms affect each other, in Pb-Pb collisions using the ALICE detector. To this end, two-particle correlation functions are constructed that show where particles carrying a conserved charge are most likely to be formed relative to each other. For this analysis specifically, $\Lambda$ - K and $\Lambda$ - p correlations are used to study strangeness- and baryon number production, respectively. These correlation functions are complemented by $\Lambda$ - $\pi$ correlations, which lack both strangeness and baryon number correlations, and act as a baseline.

Speaker: Joey Staa (Lund university (LU))

12:30 Lunch

Session 07

30 Climate for Change?

Limiting global warming to 1.5ºC — or even something less ambitious — requires enormous changes in practically every sector of society. The question of climate sustainability in research and the academic system has received increasing attention over the past years, not least in the field of high-energy physics. This contribution will highlight some cornerstones of the discussion and recent initiatives, both internationally and in Sweden, sprinkled with some personal reflections. As a particular example, it will showcase GHG emissions related to the construction and operation of the Light Dark Matter eXperiment. It is intended as a starting point to discuss what (more) we could do to reduce the footprint of our research activities and transition to climate-sustainable science.

Speaker: Ruth Pöttgen (Lunds Universitet)

Partikeldagarna2024_RP.pdf

31 When BART Writes Lagrangians: Towards a HEP-LLM (Large Lagrangian Model)

By drawing parallels between linguistic structure and the formulation of Lagrangians — where fields, terms, and symmetry conservation resemble words, sentences, and grammatical structures — we explore the use of transformer architectures, specifically BART, for generating Lagrangians in particle theory. Trained on datasets of approximately 300,000 Lagrangians each, our models demonstrate high accuracy in generating symmetry-conserving Lagrangians containing up to six fields. They demonstrate the ability to recognise important features such as dummy indices, spins, field conjugations and much more. While still in the exploratory phase, it demonstrates the potential of leveraging machine learning for formal theoretical tasks in particle physics and lays the groundwork for developing foundational models in this field.

Speaker: Yong Sheng Koay (Uppsala University)

pd2024_v4.pdf

32 A map of First-Order Electroweak Phase Transitions in the SMEFT

In this talk, we present a map of first-order electroweak phase transitions within the Standard Model Effective Field Theory (SMEFT), using modern dimensionally reduced effective field theory methods with careful attention to scale hierarchies and power-counting techniques. While previous works have focused on a few specific cases, we comprehensively map all possible scenarios, uncovering new mechanisms beyond those previously identified. By also performing a global likelihood scan, we identify parameter regions consistent with experimental and theoretical constraints and a first-order transition.

Speaker: Eliel Camargo-Molina (Uppsala University)

Partikeldagarna2024.pdf

33 Landau Singularities from Whitney Stratifications

I will demonstrate that the complete and non-redundant set of Landau singularities of Feynman integrals may be explicitly obtained from the Whitney stratification of a certain map. As a proof of concept, I leverage recent theoretical and algorithmic advances in their computation in order to determine this set for nontrivial examples of two-loop integrals. Interestingly, different strata of the Whitney stratification describe not only the singularities of a given integral, but also those of integrals obtained from kinematic limits, e.g. by setting some of its masses or momenta to zero.

Speaker: Felix Tellander (University of Oxford)

Landau___Partikeldagarna_2024.pdf

34 Pythia as a sustainable infrastucture of national interest

I will discuss the importance of the Pythia event generator program as a critical infrastructure for any particle physics experiment, and for the LHC experiments in particular. I will describe how the collaboration developing Pythia is organised, and discuss how to ensure that the current level of development and support can be sustained.

Speaker: Leif Lönnblad (Lund University)

Partikeldagarna24.pdf

15:00 Coffee break

Session 08

35 Solar neutrinos from XENONnT and a first look at the ABALONE photosensor

While mainly build for the search for dark matter, the extremely low background and high sensitivity of the latest detector of the XENON collaboration, XENONnT, also allows for the detection of other rare events, such as the interaction of solar neutrinos with the Xenon nuclei. We present the first measurement of $\textbf{C}$oherent $\textbf{E}$lastic $\textbf{N}$eutrino-$\textbf{N}$ucleus $\textbf{S}$cattering (CE$\nu$NS) from neutrinos produced by boron-8 decay in the sun with a statistical significance of 2.7 $\sigma$.
In addition we will have a first look at results from the novel photodetector called ABALONE. A candidate for future dark matter experiments, which we are currently characterising in our lab at Stockholm university.

Speaker: Torben Flehmke (Stockholm University)

partikeldagarna2024_Torben.pdf

36 The ESSnuSB large water Cherenkov neutrino detector project in Zinkgruvan

The ESSnuSB high intensity neutrino beam will be directed towards a 540 000 m3 water Cherenkov detector situated 1000 underground, near the location of the second neutrino oscillation maximum, in the Zinkgruvan mine 360 km north of the ESS site in Lund in Sweden. The design of the large underground caverns to house the detector will require core-drillings to be made to measure the pressure and strength of the rock at the planned detector location. A presentation will be made of the planned rock engineering design of the neutrino Cherenkov detector caverns and service galleries as well as of the design of the photodetector system, of the water purification system, of the system to mix in Gadolinium and of the detector calibration system, part of which is currently being tested in the Water Cherenkov Test Experiment (WCTE) at CERN, and the use, concurrently with neutrino data collection, of the large detector for muon tomography of wide rock volumes around the mine and the use, after decommissioning of the Cherenkov detector, of the detector caverns for pumped water energy storage. This design work is the object of an infrastructure development (INFRADEV) project UnuDET to be submitted to EU.

Speaker: Tord Ekelöf (Uppsala University)

Tord_Ekelof_Partikeldagarna_22_Oct_2024.pdf

37 Atmospheric neutrino oscillations at the ESSnuSB far detectors

The European Spallation Source neutrino SuperBeam (ESSnuSB) project plans to send high-intensity beams of neutrinos and antineutrinos to study neutrino oscillations over a 360-km-long baseline. The main goal of the project is to measure the leptonic CP phase by studying neutrino oscillations at the second oscillation maximum. In this talk, we discuss the prospects of observing atmospheric neutrinos at the ESSnuSB far detector facility, which consists of two cylindrical Water Cherenkov detectors with a total of 540 kt fiducial mass. The physics prospects that are examined in this work include the determinations of the neutrino mass ordering and the $\theta_{23}$ octant, and also the precisions for the leptonic mixing parameters $\theta_{23}$ and $\Delta m_{31}^2$.

Speaker: Sampsa Vihonen (KTH Royal Institute of Technology)

AtmosphericNeutrinos.pdf

38 Fundamental Particle Physics at ESS

Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach, complementing those available at other facilities. In this talk, I will provide a general overview of the proposed particle physics activities for the ESS, which encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision measurements and searches. In particular I will focus on the projects led by Swedish researchers, The HIBEAM/NNBAR and the ESSnuSB projects.
The HIBEAM/NNBAR initiative will explore baryon number violation (BNV) by searching for neutron oscillations, a breakthrough that could challenge the Standard Model of particle physics. The first phase, HIBEAM, will focus on investigating neutron-antineutron oscillations, sterile neutrons from a potential 'dark sector' of particles, and axion-like particle searches. The second phase, NNBAR, aims to improve sensitivity to neutron-antineutron oscillations by three orders of magnitude compared to previous experiments, making it the most precise test of BNV to date.
The ESSnuSB project will investigate leptonic CP violation, a key factor in explaining the dominance of matter over antimatter in the universe. By leveraging the ESS's high-power linear accelerator, ESSnuSB will measure the CP phase angle $\delta_{CP}$ with unprecedented precision, significantly advancing the study of leptogenesis models. The project will also provide unique opportunities to detect neutrinos from supernovae and search for proton decay, crucial for testing theories of baryon-number non-conservation.
Together, these projects will position the ESS at the forefront of both neutron science and particle physics, enabling groundbreaking discoveries in the understanding of the universe's fundamental forces.
A Consortium for Fundamental Particle Physics at ESS has been created earlier this year with the aim to stimulate and coordinate this program of research.

Speaker: David Milstead (Stockholm University)

2024-pd-ess.pdf

39 The HIBEAM/NNBAR Experiments

The violation of baryon number is an essential ingredient for baryogenesis - the preferential creation of matter over antimatter - needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed.
The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation via mixing, neutron-antineutron oscillation via regeneration from a sterile neutron state and neutron disappearance; the effective process of neutron regeneration is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches, which is a rare opportunity. A conceptual design report, funded by European Union and national funding agency grants, has recently been prepared and is available.

Speaker: Alexander Burgman (Department of Physics, Stockholm University)

ABurgman__Partikeldagarna2024__the_HIBEAM_NNBAR_experiments.pdf