School of Physics & Astronomy

Dr. Koji Nakamura (KEK, Japan) ● Monday, May 19, 2:00 PM ● Kelvin Building, Room 312 (PPE Seminar)

Development of high time and spatial resolution tracking detectors for future collider experiments

Abstract
Particle detectors at future lepton or hadron colliders will require covering a huge area tracker with fine spatial resolution of O(10)um. A timing capability of O(10)ps in addition should improve the tracking reconstruction, particle identification of charged particles and mass measurement of newly discovered particles. Capacitive-coupled Low-Gain Avalanche Diode (AC-LGAD) is a semiconductor tracking detector with precise timing resolution and spatial resolution developed by KEK and Tsukuba group collaborating with Hamamatsu Photonics K.K. (HPK). A 100um x 100um pitch pixel type sensor and 80um pitch with 10mm length strip type sensor with 20-50um active thickness have been successfully developed with fully uniform gain across sensor active area and these detectors achieved 20ps timing resolution at the high energy hadron test beam. In this presentation we will present about recent status of the development of AC-LGAD detector and possibility of improvement fortiming resolution and radiation tolerance as well as the journey to the installation of the detectors for collider experiment.

Biography
Dr. Koji Nakamura received a Ph.D. from the University of Tsukuba in 2009 for research on the observation and measurement of singly produced top quarks at the Tevatron CDF experiment. From 2009 to 2012, Dr. Koji Nakamura worked as a postdoctoral researcher at the University of Tokyo, contributing to physics analyses in the ATLAS experiment, including the observation of the Higgs boson decaying into tau pairs (tau Yukawa coupling) and the measurement of the top Yukawa coupling via the ttH production process. Since 2012, Dr. Koji Nakamura has been an assistant professor at the High Energy Accelerator Research Organization (KEK), where they have been involved in the R&D and production of the ATLAS Inner Tracking Detector upgrade. Their current research also focuses on developing future semiconductor tracking detectors with precise timing capabilities.

https://indico.global/event/14594/ 

‡ Prof. Simon Horsley (Uni. of Exeter) ● Wednesday, April 30, 11:00 AM ● Kelvin Building, Room 312 

 The Physics of Time-Varying Materials

The refractive index of a material is usually just a number.  But imagine if it could be changed in time:  mirrors could be turned on and off, or an object could change its appearance at the flick of a switch.  Change the refractive index very quickly - on a timescale comparable to the period of the optical wave - and new effects become evident.  There are the temporal analogues of refraction and reflection, which allow us to amplify, or time reverse any waveform.    Recent experiments have proved able to modulate material properties such as the refractive index by a large amount (~1), over a short time.  This has forced physicists to think about the solution to wave equations in time dependent media, without resorting to perturbation theory, as was done in the past.  In this talk I will review some approaches to the theory of wave propagation in time-varying materials, highlighting novel effects such as amplification and the generation of negative frequencies, as well as complications that arise due to the finite memory of the material to the past behaviour of the field.

Dr Elise Wright Knutsen (Uni. of Olso, Norway) ● Wednesday, March 19, 2:00 PM ● Kelvin Building, Room 312 

First detection of visible-wavelength aurora on Mars

Mars is known to host a variety of auroral processes despite the planet’s tenuous atmosphere and lack of a global magnetic field. All aurora detections reported to date have been observed at ultraviolet wavelengths. This presentation will describe the discovery of visible-wavelength aurora at Mars, originating from the green atomic oxygen line at 557.7 nm. We used space weather simulations to estimate the arrival time of the solar storm at Mars, and observed with the SuperCam and Mastcam-Z instruments on the Mars 2020 Perseverance rover. The emission was observed three days after the eruption of a coronal mass ejection, suggesting particles accelerated by this event induced the aurora. This detection represents the first observation of aurora from any planetary surface other than Earth, the first detection of visible-wavelength aurora at Mars, and demonstrates that auroral forecasting at Mars is possible. During events with higher particle precipitation, or under less dusty atmospheric conditions, aurorae will be visible to future astronauts.

Prof. Dr. Reinhold Walser (TU Darmstadt Germany) ● Wednesday, 19 February, 2:00 PM ● Kelvin Building, Room 312

Technical optics with quantum matter-waves

Atoms are the ultimate quantum sensors for electro-magnetic fields and gravi­tational forces. By a feat of nature, atoms occur with bosonic or fermionic attributes, but where produced otherwise identically without any “manufacturing tolerance”.

Thus, from fundamental questions on the universality of free fall, to multi-component condensed matter phases (BEC, BCS), to entangled NOON vortex states in Bose-Hubbard rings, to quantum technological application of precision matter-wave interferometry, all subfields of many-body quantum physics can be addressed. In this presentation, we will give an overview of some of the topics that were instigated by the German QUANTUS collaboration: classical ray tracing with magnetic on atom-chips, thermal optics with cold gases (cooling, thermalization), coherent mean-field optics (delta-kick collimation, Bragg beam-splitting, vortex creation with OAM) and quantum optics in the Bose-Hubbard rings (maybe more, most likely less….).

References:

1. "Efficient multipole representation for matter-wave optics“, J. Teske, R. Walser, AVS Quantum Sci. 6, 014406 (2024)
2. "Quantum simulators by design: Many-body physics in reconfigurable arrays of tunnel-coupled traps“, M. R. Sturm, M. Schlosser, R. Walser and G. Birkl, Rev. A., 95, 063625 (2017)
3. "Space-borne Bose–Einstein condensation for precision interferometry”, Becker et al., Nature 562, 391–395 (2018)

Prof. Marialuisa Aliotta (Uni. of Edinburgh) ● Wednesday, 05 February, 2:00 PM ● Kelvin Building, Room 312

Underground studies of nuclear reactions in stars

Nuclear reactions in stars govern the synthesis of elements and the evolution of the universe, yet many of these processes remain poorly understood. Underground facilities such as LUNA (Laboratory for Underground Nuclear Astrophysics) offer a unique environment to study these reactions with unprecedented precision, free from cosmic ray interference. In this talk, I will present key findings from LUNA experiments and their impact on our understanding of stellar evolution. I will also discuss plans to investigate nucleosynthesis in first stars and address other unresolved puzzles in astrophysics.

Prof. Dino Jaroszynski (Strathclyde) ● Wednesday, 06 November, 2:00 PM ● Boyd Orr Building, Room 407

Plasma photonics and particle acceleration using high power lasers

Plasma is the fourth state of matter and forms more than 99.9% of observable matter in the universe. It is a fascinating medium because it is quasi-neutral, and can support currents and electric and magnetic fields. Here we will discuss how high power lasers can exert forces on plasma to manipulate and fashion it into ultra-compact accelerators, radiation sources and unique structured dielectric media for controlling light.  We will examine how the “ponderomotive” force of an intense and ultra-short duration laser pulse displaces electrons to set up a space charge electrostatic field while more massive ions are not displaced and remain quasi-static. Displaced electrons oscillate locally to form a wake behind the laser pulse, much in the same way as a boat displaces water to create a wake. The plasma density wake has an ultra-high electrostatic field associated with displaced electrons, which can be several hundreds of gigavolts per meter. This is one thousand to ten thousand times higher than the accelerating fields in a conventional accelerator. The ultra-compact laser wakefield accelerator can also be used as a radiation source. In this talk we will discuss progress that has been in developing laser wakefield accelerators and their unique properties. As with conventional accelerators they have numerous applications. We will discuss our most recent results applying the laser wakefield accelerator, including demonstration of an ultra-compact coherent radiation source, application of the particle beams in radio-therapy and using these devices to create medical radio-isotopes for therapy and imaging. We will also show how they can be used as test facilities for particle physics detectors.

In the last part of the talk we will focus on how intercepting intense laser beams can be used to create robust time dependent plasma dielectric structures in 1D, 2D and 3D. These layered, rod like or crystalline structures can be fashioned into robust optical components for manipulating light with light, using plasma as the intermediate medium. Because of their time dependent they open up a fourth dimension and can act as a time boundary, in contrast to the usual space boundaries that we are used to in optics. We will discuss fascinating new results where we have observed birefringence and amplification of light using these time dependent media.

Prof. Deepak Kar (Uni. of Witwatersrand, Johannesburg, South Africa) ● Wednesday, 30 October, 2:00 PM ● Boyd Orr Building, Room 407

A new paradigm in dark matter searches in the colliders

The existence and nature of dark matter (DM) is one of the biggest challenges in physics. Confirmed by myriad astrophysical observations, no sign DM has been observed in direct or indirect detection experiments. Historically searches for DM in colliders have focused on Weakly Interacting Massive Particles, or so called WIMPs. The usual signature is a Standard Model particle on one side, balanced by the WIMP candidate, which being invisible, results in an imbalance of energy-momentum in the detector, termed as missing transverse momentum. No evidence for WIMPs has been seen despite extensive search programs in previous and current colliders. That necessitates a paradigm shift in ways we search for DM in colliders. Strongly interacting dark sector models have gained popularity, as they have extensive phenomenology and novel, albeit challenging experimental signatures. For the last few years, the author has been involved in such explorations, not only publishing the first semi-visible jets search result from ATLAS, but also involved in studies in model building and designing sensitive observables. In this talk, he will pedagogically introduce the models, show the current experimental results, and discuss the ongoing work in this area.