Session 1

Introduction & Lecture #1

Session Chair: Ben McAllister

10 minutes

Introduction

Irene (zoom), Ben and Markus

40 minutes + questions

Dark Matter Rates for Direct Detection Events and Capture in Stars with Effective Field Theories

I will concentrate on candidates around the ElectroWeak scale who can interact with nucleons.

I will make a brief overview with examples on how to recast a complete UV model in terms of EFT operators.

I will make a full derivation of the rate of events in Direct Detection and of the Capture Rate in Stars like the Sun.

I will talk of the inputs coming from Particle, AstroParticle and Nuclear Physics, their uncertainties, and how they affect the results.

If time allows, I will make a brief digression about Capture rates in Compact Stars with matter in degenerate state.

Giorgio Busoni

15:00-15:15

Afternoon Tea

Peninsula Room

Session 2

Lecture #2 & ECR Science Presentations

Session Chair: Markus Mosbech

40 minutes + questions

An introduction to dark matter direct detection methods
One avenue in the search for dark matter are earth-based detectors in which scientists aim to observe the interaction of dark matter particles with baryonic matter. Over the past decades, direct detection experiments have developed methods to be sensitive to dark matter interactions, which are expected to be rare and of low energy. In this talk I will give an overview of different experimental methods employed by past and present experiments and look the challenges the field needs to address in the future.

Theresa Fruth

10 mins + questions

ORGAN: Phase 1, and Future Plans
The ORGAN (Oscillating Resonant Group AxioN) experiment (in Perth, Australia) is a
microwave cavity axion haloscope that aims to search the majority of the mass range predicted by the SMASH model (50 to 200 micro–electron volts). Our initial phase 1a scan sets an upper limit on the coupling of axions to two photons, sufficient to exclude the well-motivated axion-like particle cogenesis model for dark matter over the mass range of 63.2 to 67.1 micro–electron volts with 95% confidence interval.

Aaron Quiskamp

10 mins + questions

Modelling Josephson Junctions photon counters for axion haloscopes
Current biased Josephson junctions have been proposed as a microwave single photon counter to beat the standard quantum limit in axion haloscope experiments. Many attempts have been made in the past to model such devices, however only semi-classical or unjustified phenomenological models have been proposed for modelling its dissipation. Here we present a quantum dissipative model to reproduce key observed behaviours of the device. We discuss the difficulties in applying standard techniques to this problem as well as the phenomenological solution which succeeds in some useful regimes.

Graeme Flower

10 mins + questions

Merging clusters as a testbed for self-interacting dark matter
Self-interacting dark matter (SIDM) has been proposed as a means to alleviate tensions on small scales between observations and simulations. A possible avenue for constraining the interaction cross-section is to study the major mergers of galaxy clusters. These mergers are defined by three components: galaxies, which act as collisionless test particles, gas, which is dissociated from the galaxies through ram pressure stripping, and DM. If the DM is collisionless, as it is in the cold DM (CDM) paradigm, it should remain coincident with the galaxies. However, if the DM is able to interact, it can be offset from the galaxies due to drag from the DM self-interactions. In my current project, I compare the offsets between the galaxies and DM in hydrodynamical simulations of clusters run with both CDM and SIDM physics. My first results show that, as expected, these offsets indeed increase with SIDM cross-section.

Ellen Sirks

10 mins + questions

AMPM: Microlensing of Asteroid-mass Primordial Black Holes

Primordial black holes (PBH) are a class of black holes produces from the cosmological interactions in the very early universe. PBHs are physically analog to stellar black holes, yet are millions of years older and may act as progenitors to supermassive black holes, gravitational wave mergers, as well as provide a neat solution to compact Dark Matter theories.

A Milky Way galactic halo population of PBHs are detectable on Earth using small scale gravitational lensing, or ‘microlensing’. Several decades of microlensing research have gone into constraining the potential range of PBHs and their contribution to halo DM. Yet, a single remaining mass range between 10^-15 - 10^-10 M_sun remains open to investigation. The mass constraint gap — termed the asteroid-mass range— can now be investigated with high cadence DECam imaging towards the LMC. This research has searched light curves from over 300,000 LMC stars across 5 contiguous nights for very fast microlensing signals from low-mass PBHs. The PBH survey results will produce novel and stringent density limits on compact object Dark matter, and are summarised in this talk.

Renee Key

17:00

Close

17:00 - 19:00

Sundowner & Networking Session: Canapes! - Limeburners Bar and Terrace (adjacent to Peninsula Room)

6:30-9:00

Breakfast

Waterfront Restaurant

Session 1

Science Communication Workshop (Part 1)

Phil Dooley

10:30-11:00

Morning Tea

Peninsula Room

Session 2

Science Communication Workshop (Part 2)

Phil Dooley

13:00-14:00

Lunch

Peninsula Room

Session 3

ECR Science Presentations

Session Chair: Ben McAllister

10 mins + questions

Background Characterisation of an Ultra-pure NaI test Crystal for SABRE South
The Sodium Iodide with Active Background Rejection (SABRE) experiment is a dark matter detector that aims to provide a model independent test of the annual modulation results of the DAMA/LIBRA collaboration, attributed to dark matter in the form of WIMPs (Weakly Interacting Massive Particles). SABRE will consist of dual detectors in the Northern and Southern hemispheres, individually called the SABRE North and SABRE South experiments. One of the main goals of SABRE is to use ultra-pure NaI crystal detector material, with minimal radio-contaminants, which will rival that of DAMA/LIBRA. This talk reports on characterisation results of an ultra-pure crystal called NaI-035, produced by the commercial company, RMD based in Boston, USA. This 3.7 kg crystal has been produced using AstroGrade powder from Merck, which is some of the purest starting powder commercially available.

In April 2022, the crystal was sent to the Laboratori Nazionali del Gran Sasso underground laboratory in Italy, for characterisation and radioactivity counting. This talk will present preliminary results of the crystal measurements, with a focus on determining 238U and 232Th contamination present in the crystal through identification of 214Bi – 214Po, and 212Bi – 212Po coincidences, that occur as daughter decays.

Ferdos Dastgiri

10 mins + questions

Prototype Particle ID for the SABRE South Active Veto
The SABRE South direct detection experiment aims to test a purported dark matter annual modulation signal from the DAMA experiments — a measurement with 12.9 σ significance that remains incompatible with null results from other direct detection experiments. Whilst the target mass of the SABRE South detector consists of an array of ultra-pure NaI crystals, the surrounding active veto sub-detector will reject background processes and increase sensitivity to a dark matter (DM) signal. Important for vetoing key intrinsic and extrinsic backgrounds, such as 40K electron capture decays and external modulating backgrounds that may mimic a DM signal, the liquid scintillator veto is instrumented with 18 Hamamatsu 20 cm R5912 oilproof PMTs in a configuration designed to optimise veto efficiency and provide background identification and position reconstruction.
To achieve this optimal veto efficiency each PMT must be well understood, such that their performance and position in the veto system can be optimised. Being a novel sub-detector for NaI(Tl) experiments of this kind, specific focus is placed on characterising properties that help leverage the veto’s key purposes — background veto and reconstruction, thus placing different requirements on the veto PMT system compared to other PMT systems in SABRE South. Optimal particle identification and position reconstruction is desirable, allowing for the disentanglement of the various detected backgrounds that may mimic a DM signal. The important characteristics to understand for achieving these aims include single photo-electron response and gain for optimal background veto, alongside transit time/transit time spread and linearity
for effective position reconstruction and particle identification.

This talk will present the results and methods from the characterisation of some of these properties, their impact on veto performance and the experiment’s sensitivity, alongside a discussion of particle ID techniques to be extended to the veto.

Lachlan Milligan

10 mins + questions

Boosted dark matter detection within the dark photon framework
We investigate the inelastic boosted dark matter model (IBDM) in the dark photon framework. We calculate the primary DM - electron/nucleon scattering cross section, and the secondary DM decay rate. We expect to assess the sensitivity of the SABRE experiments to the dark matter parameters.

Xuangong Wang

10 mins + questions

What can go wrong in experimental physics: power outages and disappearing samples
In experimental physics, things often don't work out the way we plan. In my talk I will speak about challenges of experimental physics, from lost samples through accidents in the chemistry lab to facilities shutting down due to thunderstorms.

Zuzana Slavkovska

10 mins + questions

Sensitivity of dark matter-nucleus interactions to nuclear structure
Non-relativistic effective field theory (NREFT) is one approach used for describing the interaction of WIMPs with ordinary matter. Among other factors, these interactions are expected to be affected by the structure of the atomic nuclei in the target. The sensitivity of the nuclear response components of the WIMP-nucleus scattering amplitude is investigated using shell model calculations for isotopes relevant to direct detection experiments: (19)F, (23)Na, (28,29,30)Si, (40)Ar, (127)I, (70,72,73,74,76)Ge and (128,129,130,131,132,134,136)Xe. Resulting integrated nuclear response values are shown to be sensitive to some specifics of the nuclear structure calculations.

Raghda Abdel Khaleq

10 mins + questions

The decay of neutrons has been a puzzle since decades. Neutrons in a beam seem to have longer lifetime than the lifetime of neutrons in a bottle. The experiments to determine the lifetime of neutron has been repeatedly done by many groups and it always show the same characteristics. Moreover, the difference in the lifetimes of neutron in beam and bottle is approximately 8 sec, always. There are proposals that suggest that may be 1% of the time neutron decay into dark matter which goes undetected in the beam method. The hypothesis [1] that neutrons might decay into dark matter, n → χ + φ (where χ is dark matter particle having a mass 937.9 MeV < mχ < 938.7 MeV and φ is very light boson) is explored using neutron stars as a testing ground because neutron stars have abundance of neutrons and if there is such neutron decay channel than we must have dark matter inside neutron star and that can change the properties of neutron star. Based on constraints on properties of neutron stars we can test the hypothesis. It is found that in order to obtain neutron stars with masses at the upper end of those observed, the dark matter must experience a relatively strong self-interaction. Conservation of baryon number and energy then require that the star must undergo some heating, with a decrease in radius, leading to an increase in speed of rotation over a period of days. Since this hypothesis require the dark matter to be significantly more interactive than the neutron-omega interaction we explored the suggestion [2] that neutrons decaying into dark matter through the process, n → χχχ, with χ having a mass one third of that of the neutron. We examine the consequences of such a decay mode for the properties of neutron stars. Unlike an earlier suggested decay mode, in order to satisfy the constraints on neutron star mass and tidal deformability, there is no need for a strong repulsive force between the dark matter particles. This study suggests the possibility of having hot dark matter at the core of the neutron star and examines the possible signal of neutrons decaying in this way inside the neutron star right after its birth. Both the hypothesis agrees that there should be a signal of neutron decay the signal we suggested are neutron star glowing up and change in rotation period of neutron star.

Wasif Husain

10 mins + questions

ttH production at the HL-LHC
The High-Luminosity Large Hadron Collider (HL-LHC) is an upgrade to the current LHC whose pre- dominant objective is to drastically increase the luminosity of the LHC, allowing for more collisions and a more statistically significant dataset to be produced overtime. In particular, one major goal of the HL- LHC upgrade is to attain precise measurements of the Higgs boson properties, as well as to probe physics Beyond the Standard Model of Particle Physics (BSM). The Yukawa coupling of the Higgs boson to the top quark is an important parameter that has not been able to be measured to high levels of precision at the LHC. These couplings can be directly determined by measuring the rate of the process where the Higgs boson is produced in association with a tt ̄ pair (tt ̄H). Additionally tt ̄H events may be able to shed light onto ‘invisible’ Higgs decays, that is decays where the decay products are undetectable, such as H → ν ν ̄ . An excess in the SM expected branching ratio could be explained by many BSM models, including the possibility of the Higgs boson coupling to dark matter particles, known as Higgs portal models. We present an investigation into this tt ̄H process, including the capability for measuring the Higgs boson ‘invisible’ decays with the HL-LHC and ATLAS detector upgrade.

Isabel Carr

15:30-16:00

Afternoon Tea

Peninsula Room

Session 4

Inter-Node Collaboration Activity

Session Chair: Markus Mosbech

17:00

Close

Evening

Social Activity (Laser Tag/Arcade)