Sixth Sydney meeting

26 Jul 2023, 09:00 → 27 Jul 2023, 18:00 Australia/Sydney

G59/G60 (Old Main Building)

The Sydney-based particle physics and cosmology meeting will take place on Wednesday 26 - 27 July 2023. It is organised by the particle physics group at the University of Sydney and the particle physics and cosmology group at UNSW Sydney.

Wednesday 26 July ¶

09:30 → 10:30 Lectures¶

09:30 Direct dark matter detection¶

Speaker: Ciaran O'Hare (Sydney)

DirectDetection.pdf

10:30 → 11:00 Coffee break

11:00 → 12:30 Talks¶

11:00 What a flavour (and CP) symmetry can do for you¶

Symmetries are a very important ingredient of the Standard Model of particle physics. In this talk, we discuss the role that symmetries can play in the flavour sector. We give different examples of possible symmetries and their phenomenological impact, e.g. the prediction of lepton mixing parameters, constraints on and correlation with the size and sign of the baryon asymmetry of the Universe as well as signals of flavour violation in the lepton and quark sector.

Speaker: Claudia Hagedorn (IFIC)

Hagedorn_Sydney2023.pdf

12:00 On dual formulation of axion physics and the θ-vacua¶

Speaker: Otari Sakhelashvili (Sydney University)

12:30 → 14:00 Lunch break

14:00 → 15:30 Talks¶

14:00 Ultralight Dark Matter and g-2¶

If dark matter is ultralight, the number density of dark matter is very high and the techniques of zero-temperature field theory are no longer valid. The dark matter number density modifies the vacuum giving it a non-negligible particle occupation number. For fermionic dark matter, this occupation number can be no larger than one. However, in the case of bosons the occupation number is unbounded. If there is a large occupation number, the Bose enhancement needs to be taken into consideration for any process involving particles which interact with the dark matter. Because the occupation number scales inversely with the dark matter mass, this effect is most prominent for ultralight dark matter. In fact, the Bose enhancement effect from the background is so significant for ultralight dark matter that, if dark matter is a dark photon, the correction to the anomalous magnetic moment is larger than experimental uncertainties for a mixing parameter of order ${10}^{-16}$ and a dark photon mass of order ${10}^{-20}$ eV. Furthermore, the constraint on the mixing parameter scales linearly with the dark photon mass and so new significant constraints can be placed on the dark matter mass all the way up to ${10}^{-14}$ eV. Future experiments measuring $g-2$ will probe even smaller gauge mixing parameters.

Speaker: Jason Evans (Shanghai Jiaotong University/TDLI)

15:00 Miniclusters from axion string simulations¶

The properties of axion miniclusters and of the ensuing voids between them can have very strong implications for the discovery of axions and the dark matter of the Universe. These properties can be strongly affected by the dynamics in the early Universe, such as the axion string network and the non-linear dynamics around the QCD phase transition. In this talk we briefly discuss the phenomenology of miniclusters and their implications to current experiments, in the different approaches used in the literature.

Speaker: Giovanni Pierobon

15:30 → 16:00 Coffee break

16:00 → 17:30 Talks¶

16:00 Galaxy clusters: giant dark matter particle colliders¶

Galaxy clusters are the largest gravitationally bound objects in the Universe. Because of their high density and high local velocity dispersion, they are ideal environments for probing the nature of dark matter. The specific properties of dark matter can have great effects on both clusters as a whole as well as on the galaxies residing in them. For example, if the self-interaction cross-section is non-zero, such effects include (but are not limited to) offsets in merging clusters, rounder cluster haloes, modified gravitational lensing, subhalo evaporation, and the flattening of density profiles. In this talk I will present my work studying some of the effects of self-interacting dark matter on simulated galaxy clusters.

Speaker: Ellen Sirks (The University of Sydney)

16:30 Probing the early universe with stochastic gravitational wave backgrounds¶

Speaker: Ameek Malhotra

Malhotra_CPPC_2023.pdf

17:00 Searching for Features in the Primordial Power Spectrum¶

Speaker: Julius Wons

18:30 → 21:00 Dinner

Thursday 27 July ¶

09:30 → 10:30 Lectures¶

09:30 Direct dark matter detection¶

Speaker: Ciaran O'Hare (Sydney)

10:30 → 11:00 Coffee break

11:00 → 12:00 Talks¶

11:00 Unitarizing scattering amplitudes in theories of compact Extra Dimensions¶

Scattering amplitudes are paramount to understanding the validity of quantum field theories. In this talk I will discuss scattering amplitudes of massive spin-2 particles. I will contrast the unitarity violating scales of theories of massive gravity and compact extra dimensions. I will also demonstrate how scattering amplitudes in extra dimensions can be obtained via the double copy prescription that relates gauge theory and gravity amplitudes.

Speaker: Dipan Sengupta (University of Adelaide)

12:00 → 14:00 Lunch break

14:00 → 15:15 Talks¶

14:00 The Hyper-Kamiokande Experiment¶

Hyper-Kamiokande is a next-generation water Cherenkov detector in Japan whose construction started in early 2020 and is expected to complete in 2027.

The detector has a fiducial volume more than 8 times the size of the currently-running Super-Kamiokande detector for a total of about 188 kton fiducial volume. The full experiment includes an upgraded J-PARC neutrino beam, and a near detector suite with upgraded and new detectors. Hyper-Kamiokande

has an extremely diverse science program and will be able to measure neutrino oscillations with beam and atmospheric neutrinos with unprecedented statistical precision. The large size of the detector will also significantly improve the study of astrophysical neutrinos, like solar or supernova neutrinos, as well as provide contributions to multi-messenger astronomy, dark matter searches and also search for proton decays in a variety of final-state decays.

Speaker: Francesca Di Lodovico (University of London (GB))

15:15 → 15:50 Coffee break

15:50 → 17:30 Talks¶

15:50 The Belle II experiment¶

Speaker: Chia-Ling Hsu (The University of Sydney)

16:20 Search for lepton flavour violation at Belle II with B0 -> tau ell¶

Speaker: Ms Priyanka Cheema (University of Sydney)

sydney_cppc_sixth.pdf

16:40 Towards B to pi tau nu at Belle II with SL tagging¶

Speaker: Andre Hao Yuan Huang

CPPC_Meeting_2023-2.pdf

17:00 Connecting Inflation to Particle Physics with Next Generation CMB and LSS Observations¶

The CMB and the large scale structure of the universe provide powerful probes that constrain models of inflation. It is well-known that the relations between inflationary model parameters and observables depend on the duration of the reheating epoch, which also determines the reheating temperature. While current observations are not sensitive enough to extract any knowledge about these quantities, a detection of tensor modes with next-generation CMB observations would simultaneously constrain the scale of inflation and the reheating temperature within a given class of models, providing the first ever measurement of the reheating temperature. This constraint can be translated into a measurement of the inflaton coupling if the latter is comparable to the electron Yukawa coupling in the Standard Model or smaller, as one may expect if inflation happens in a dark sector. Constraining this microphysical parameter would provide a unique opportunity to shed light on the embedding of a given model of inflation into underlying theories of particle physics. Further improvement can be achieved if data from optical and 21cm surveys are added.

Speaker: Marco Drewes

Sydney CPPC 2023.pdf