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HEP Seminars & Vivas

28 Feb 2024

UCL HEP Seminars 2020

: Jens Weingarten (Dortmund)

A Second Life - ATLAS Pixel Detectors in Medical Physics

The field of medical physics has been growing steadily over the past decades, with more and more hospitals using more and more complex machinery in diagnosis and treatment of patients. Reacting to the increased demand for well-trained medical physics experts, TU Dortmund university offers a medical physics study programme since 2011. Close collaborations with hospitals and dedicated centers for radiotherapy and proton therapy open up a great many possibility for the resident HEP detector physicists to find new applications for our well-known technologies. Coming from the development of silicon pixel detectors for the ATLAS tracking detector, we started looking into applications where those detectors could be useful. These range from beam monitoring for machine QA for proton therapy, via small-field dosimetry to proton radiography and proton CT. In the talk I will report on some of our activities, as well as some future developments.


: Juan Miguel Carceller (UCL)

Ultra-High Energy Cosmic Rays with the Pierre Auger Observatory

Even though cosmic rays were discovered more than one hundred years ago, there are still many questions unanswered about them. Some of them reach energies that are macroscopic (above 10^18 eV or .16 J). What are they? What is their origin? How are they accelerated to such energies? To answer these questions the Pierre Auger Observatory was built. It comprises more than 1600 surface detector that measure the arrival time and signal left by secondary particles of air showers, initiated when of these cosmic rays collides with a molecule of air in the atmosphere. The array of surface detector is overlooked by fluorescence telescopes that measure the fluorescence light emitted. I will introduce cosmic rays, the air showers that they produce and how the Pierre Auger Observatory measures them. A few recent results on composition and hadronic interactions will be shown, and some of my contributions to these topics.


: Thorben Quast (RWTH)

The CMS High Granularity Calorimeter upgrade for HL-LHC

The CMS collaboration is preparing to build replacement endcap calorimeters for the HL-LHC era. The new calorimeter endcap will be a highly-granular sampling calorimeter (HGCAL) featuring unprecedented transverse and longitudinal readout segmentation for both its electromagnetic and hadronic compartments. The granularity together with a foreseen timing precision on the order of a few tens of picoseconds will allow for measuring the fine structure of showers, will enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The regions exposed to higher-radiation levels will use silicon as active detector material. The lower-radiation environment will be instrumented with scintillator tiles with on-tile SiPM readout. In addition to the hardware aspects, the reconstruction of signals, both online for triggering and offline, represents a challenging task - one where modern machine learning approaches are well applicable. In this talk, the reasoning and ideas behind the HGCAL, the proof-of-concept of its design in test beam experiments, and the challenges ahead will be presented.


: Sarah Malik (UCL)

Quantum computing for simulating high energy collisions

The simulation of high energy collisions at experiments like the Large Hadron Collider (LHC) relies on the performance of full event generators and their accuracy and speed in modeling the complexity of multi-particle final states. The rapid improvement of quantum devices presents an exciting opportunity to construct dedicated algorithms to exploit the potential quantum computers can provide. I will present general and extendable quantum computing algorithms to calculate two key stages of an LHC collision; the hard interaction via helicity amplitudes and the subsequent parton shower process. These algorithms fully utilise the quantum nature of the calculations and the machine's ability to remain in a quantum state throughout the computation. It is a first step towards a quantum computing algorithm to describe the full collision event at the LHC.

: Julieta Gruszko (UNC)

Shedding ‘Nu’ Light on the Nature of Matter: NuDot and the Search for Majorana Neutrinos

Why is the universe dominated by matter, and not antimatter? Neutrinos, with their changing flavors and tiny masses, could provide an answer. If the neutrino is its own antiparticle, it would reveal the origin of the neutrino’s mass, demonstrate that lepton number is not a conserved symmetry of nature, and provide a path to leptogenesis in the early universe. To discover whether this is the case, we must search for neutrinoless double-beta decay. As the upcoming ton-scale generation of experiments is built, it is key that research and development (R&D) efforts continue to explore how to extend experimental sensitivities to 1029 years and beyond. These next-next-generation experiments could make a discovery, if neutrinoless double-beta decay is not found at the ton-scale, or offer insight into the mechanism behind lepton number violation, if it is. NuDot is a proof-of-concept liquid scintillator experiment that will explore new techniques for isotope loading and background rejection in future detectors. I’ll discuss the progress we’ve already made in demonstrating how previously-ignored Cherenkov light signals can help us distinguish signal from background, and the technologies we’re developing with an eye towards the coming generations of experiments.


: Chris Young (CERN)

Testing lepton flavour universality


: Susanne Westhoff (Heidelberg)

Co-scattering dark matter at the LHC

In this talk I will show how to search for feebly coupled dark matter at the LHC. If dark matter freezes out through co-annihilation or co-scattering in the early universe, the observed relic abundance predicts a clear signature at colliders: soft displaced objects. I will present a strategy to search for soft displaced leptons at the LHC during Runs 2+3.


: Anna Sfyrla (Geneva)


The FASER experiment is a new small and inexpensive experiment that will be placed 480 meters downstream of the ATLAS experiment at the CERN LHC. The experiment will shed light on currently unexplored phenomena, having the potential to make a revolutionary discovery. FASER is designed to capture decays of exotic particles, produced in the very forward region, out of the ATLAS detector acceptance. FASERnu, a newly proposed FASER sub-detector, is designed to detect collider neutrinos for the first time and study their properties. This talk will present the physics prospects, the detector design, and the construction progress of FASER. The experiment is expected to be installed in 2020 and to take data during the LHC Run-3, starting in 2021.


: Stefan Schoernert (TUM)


The Large Enriched Germanium Experiment for Neutrinoless Double-Beta Decay


: Robert Thorne (UCL)

Inferring the effective fraction of the population already infected with Covid-19 by comparing rates in different regions of the same country

I use a very simple deterministic model for the spread of Covid-19 in a large population. Using this to compare the relative decay of the number of deaths per day between different regions in Italy, Spain and England, each applying in principle the same social distancing procedures across the whole country, I obtain an estimate of the total fraction of the population which has already become infected. In the most heavily affected regions, Lombardy, Madrid and London, this fraction is higher than expected, i.e. ~ 0.3. This result can then be converted to a determination of the infection fatality rate ifr, which appears to be ifr ~ 0.0025-0.005, and even smaller in London, somewhat lower than usually assumed. Alternatively, this can also be interpreted as a effectively larger fraction of the population than simple counting would suggest if there is a variation in susceptibility to infection with a variance of up to a value of about 2. The implications are very similar for either interpretation or for a combination of effects.


: Matthias Becker (Dortmund)

The Neutrino Portal To Dark Matter

If Dark Matter is an electroweak gauge singlet, it cannot interact with the standard model via these interactions, thereby requiring the existence of so-called portal couplings. The three renormalizable portal couplings are the Higgs portal, the vector portal, and the neutrino portal. In this talk, we investigate the neutrino portal to Dark Matter and inspect the viable production mechanisms and different constraints on the resulting parameter space.


: Ioannis Katsioulas (Birmingham)

Search for Light dark matter with Spherical Proportional Counters



No seminar

: IOP Practice TALKS

IoP Practice talks


: Kirsty Duffy (FNAL)

Latest neutrino cross-section results from MicroBooNE

MicroBooNE, the Micro Booster Neutrino Experiment at Fermilab, is an 85-ton active mass liquid argon time projection chamber (LArTPC) located in the Booster Neutrino Beam at Fermilab. The LArTPC technology with 3mm wire spacing enables high-precision imaging of neutrino interactions, which leads to high-efficiency, low-threshold measurements with full angular coverage. As the largest liquid argon detector worldwide taking neutrino beam data, MicroBooNE provides a unique opportunity to investigate neutrino interactions in neutrino-argon scattering at O(1 GeV) energies. These measurements are of broad interest to neutrino physicists because of their application to Fermilab's Short Baseline Neutrino program and the Deep Underground Neutrino Experiment (which will both rely on LArTPC technology), as well as the possibility for new insights into A-dependent effects in neutrino scattering on heavier targets such as argon. In this seminar I will present the most recent cross-section results from MicroBooNE, including measurements of inclusive charged-current neutrino scattering, neutral pion production, and low-energy protons. Many of the results I will show represent the first measurements of these interactions on argon nuclei, as well as an exciting demonstration of the potential of LArTPC detector technology to improve our current understanding of neutrino scattering physics.


: Theresa Fruth (UCL)

Searching for Dark Matter with the LZ experiment

The nature of dark matter remains one of the biggest mysteries of the universe. Extensions to the Standard Model of particle physics provide potential candidates for it. Such dark matter particles can be searched for using direct detection experiments. The LUX-ZEPLIN (LZ) experiment is a next-generation direct detection experiment, which employs a two-phase, liquid xenon time projection chamber. It is currently under construction 4850 feet underground in an old gold mine in South Dakota. In this talk I will give an overview of the experiment and its projected sensitivity reach, as well as the current status of construction and integration.

: Susanne WestHoff (Heidelberg) POSTPONED

Dark matter searches with long-lived particles POSTPONED

In cosmological scenarios beyond thermal freeze-out dark matter interactions with standard-model particles can be tiny. This leads to mediators with a lifetime that is long compared with the scales of particle colliders. In this talk I will discuss two new ideas for collider searches with long-lived mediators: soft displaced objects as signs of compressed dark sectors at the LHC; and displaced vertices from long-lived light scalars at flavor and long-distance experiments. I will show that novel search strategies allow us to explore dark matter interactions ranging over several orders of magnitude.

: Alex Martyniuk (UCL)

Recent results from the LHC

Between 2015 to 2018 (a.k.a. Run 2) the LHC delivered around 160fb^-1 to both of its general purpose detectors: ATLAS and CMS. In this talk I will try to roughly outline what the experiments have done so far with this bounty of data, and where they are headed in the future. (This talk was previously given as the opening talk of the Lake Louise Winter Institute).


: Ilektra Christidi (UCL)

Research Software Development at UCL and the software landscape in HEP

With computing and large amounts of data becoming more and more an everyday reality in all research domains, the world is waking up to what High Energy Physicists knew all along: software is an integral part of research, and as such, it is a necessity to have the infrastructure and people to support its sustainable development. The UCL Research Software Development Group, a centralised service for the whole university research community, and the first group of its kind in the UK, has been here since 2012 to serve exactly this purpose. In the first part of this talk, I'll introduce the scope and work of our group, and will try to identify (with your help!) ways that we can be of service to the UCL HEP researchers. In the second part, I'll present a review of the latest PyHEP workshop, a forum where developments in the use of Python in Particle Physics are presented.

: Katharina Behr (DESY)

The puzzle of dark matter: missing pieces at the LHC?

Unravelling the particle nature of dark matter is one of the key goals of the LHC physics programme. Dark matter cannot be detected directly by the LHC experiments but would manifest itself as missing energy in the detector signature of collision events. Complementary resonance searches targeting new mediator particles between dark and known matter provide an additional approach to explore the interactions of dark matter. To date, no evidence for dark matter or related mediators has been found. Could dark matter interactions be more complex or have otherwise have evaded detection? I will review the diverse programme of dark matter searches on LHC Run 2 data and address strategies to extend our coverage of possible dark matter signatures at the LHC.

: Tevong You (Cambridge)

Where art thou, new physics?

Searching for new fundamental physics beyond the Standard Model, by experimenting, observing and theorising, is a tremendously exciting journey. One of our most reliable guides in this voyage of exploration is the framework of effective field theory. Through this lens, I will survey the landscape of where new physics may be hiding, from electroweak precision observables, diboson, Higgs, and flavour physics to light dark sectors. I conclude with the question of what, if anything, could we ultimately discover at future colliders?

: POSTPONED till 14.02.

Enjoy cake and puppies instead