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HEP Seminars

22 Mar 2019

UCL HEP Seminars 2019

05-04-2019 : Preema Rennee Pais (EPFL)

LHCb upgrade



29-03-2019 : Zara Grout (UCL)

Four-lepton invariant mass spectrum in 13 TeV proton-proton collisions with the ATLAS detector



22-03-2019 : TBC




15-03-2019 : Sebastian Trojanowski (Sheffield)

Looking forward to new physics with FASER: ForwArd Search ExpeRiment at the LHC

One of the most rapidly developing areas of research in particle physics nowadays is to look for new, light, extremely weakly-interacting particles that could have avoided detection in previous years due to the lack of luminosity. These, so-called intensity frontier searches, have also broad cosmological connections to e.g. dark matter, as well as can help to unravel the mystery of neutrino masses. In this talk, we will summarize the current status of this field with a particular emphasis on a newly proposed experiment to search for such particles produced in the far-forward region of the LHC, namely FASER, the ForwArd Search ExpeRiment. FASER has been proposed as a relatively cheap detector to supplement traditional experimental programmes searching for heavy new physics particles in the high-pT region and, therefore, to increase the whole BSM physics potential of the LHC. On top of potentially far-reaching implications to BSM particle physics and cosmology, the newly proposed detector can also be used to measure high-energy SM neutrino cross sections.


08-03-2019 : Patrick Dunne (Imperial)

Latest neutrino oscillation results from the T2K experiment

T2K is a long baseline neutrino experiment situated in Japan. We fire beams of muon neutrinos and antineutrinos 295km across the country then observe them using the 50 kTon Super Kamiokande detector. By studying how many of these neutrinos have oscillated into different flavours and whether the oscillations occur differently for antineutrinos we have sensitivity to CP violation in the neutrino sector, the neutrino mass hierarchy and the mixing angles between the neutrino flavours. I will present the latest results from the T2K collaboration including limits on the CP violating parameter \delta_{CP}.


01-03-2019 : Louie Corpe (UCL)

Hacking the ATLAS detector: looking for exotic long-lived particles using displaced jets

Long-lived particles (LLPs) are nothing new: semi-stable particles abound in the SM. There’s no reason why they wouldn’t occur in extensions to the SM too. The lifetime of exotic LLPs in BSM models is typically unconstrained, and since collider detectors are usually designed assuming that the action happens near the beam crossing, LLPs that decay far from the beamline could easily have been missed by standard searches. To look for them, we therefore need to ‘hack’ our detectors to do something they were not designed to do: search for decays deeper in the detector volume. This talk describes one such search for pairs of neutral, long-lived particles decaying in the ATLAS calorimeter, leading to the formation of narrow, trackless displaced jets.


22-02-2019 : Fredrik Bjorkeroth (Frascati)

Flavourful axion phenomenology (and impact on Mu3e/Mu2e)

Traditional axion (or ALP) models assume the axion does not distinguish between fermion generations, i.e. it is flavour-universal. This is not the case in flavoured axion models, where the symmetry that dictates fermion mass structures is (or generates) a Peccei-Quinn symmetry. Such models predict flavour-violating axion-fermion couplings which, in highly constrained flavour models, can be fixed by mass and mixing data. I will discuss the phenomenology of flavoured axions, in particular contributions to heavy meson decays and lepton flavour violating processes.


15-02-2019 : Agni Bethani (Manchester)

Double Higgs production in ATLAS

In the post-Higgs discovery era, studying the Higgs properties and understanding the Higgs mechanism is crucial. The next major milestone in understanding the Higgs mechanism is measuring the tirlinear self-coupling (λΗΗΗ) via Higgs boson pair- production (HH). This would be, arguably, the most important result at the LHC since the Higgs discovery. The HH cross-section is predicted to be very small in the Standard Model (SM) however it can be enhanced in case new physics is present. In the seminar I will discuss the current status of HH searches in ATLAS along with some estimations of what we can achieve in the future.


08-02-2019 : Nicola McConkey (Manchester)

SBND - a state of the art Liquid Argon TPC for Neutrino Physics

The field of neutrino physics is now moving towards the era of precision physics in order to test the 3-neutrino paradigm, neutrino mass hierarchy and CP asymmetry in the lepton sector. The next generation of neutrino detectors, currently under development and construction, will have sensitivity to the fundamental parameters which describe these phenomena. Liquid argon is an excellent detector medium, with good scintillation and charge transport properties. Coupled with the three dimensional position reconstruction possible with a time projection chamber, it makes for a powerful particle detector which has become one of the detectors of choice for rare event physics, especially in neutrino detection. This rapidly developing field has many technical challenges as the desired detector volume increases to the multi-kiloton scale. I will discuss the Short Baseline Neutrino (SBN) programme, with a focus on the detector technology used, current status and future prospects for the Short Baseline Near Detector (SBND).


01-02-2019 : Celeste Carruth (Berkley)

Testing CPT Symmetry with Antihydrogen at ALPHA

One of the biggest unsolved questions in physics is the absence of any large amount of antimatter in the universe. Charge-Parity-Time Symmetry requires that energy convert to equal quantities of matter and antimatter, so at the creation of the universe, the large amount of energy present should have produced equal amounts of matter and antimatter. If an antimatter galaxy existed in the observable universe, we would expect to see radiation coming from particles annihilating in the interstellar space between the matter and antimatter galaxy, but no such signature has yet been discovered. The ALPHA collaboration at CERN combines cold plasmas of antiprotons and positrons to make and trap antihydrogen, and then performs precision measurements on the trapped antimatter. I'll discuss our method for trapping antihydrogen and our recent results of the hyperfine transition and the 1S-2S and 1S-2P spectroscopies.


25-01-2019 : NO SEMINAR

18-01-2019 : Tessa Baker (QMUL)

The Gravitational Landscape for the LSST Era

The Large Synoptic Survey Telescope (LSST), due for first light later this year, spearheads the next generation of cutting-edge astronomical survey facilities. One of its key science goals is to settle questions surrounding dark energy or possible corrections to General Relativity, which are posited to resolve outstanding problems of the standard cosmological model. In this talk I’ll explain how we plan to use LSST to test of the landscape of extended gravity theories. In particular, I’ll focus on the new wave of parameterised techniques developed as the smartest way to probe the landscape of gravity/dark energy models in the current literature. I’ll also discuss some exciting theoretical developments, sparked by recent gravitational wave detections, that offer powerful insights on this model space.


11-01-2019 : Jennifer Ngadiuba (CERN)

Deep Learning on FPGAs for L1 trigger and data acquisition for particle physics

Machine learning methods are becoming ubiquitous across particle physics. However, the exploration of such techniques in low-latency environments like Level-1 (L1) trigger systems has only just begun. In this talk, I will present a new software, based on High Level Synthesis, to generically port several kinds of network models (BDTs, DNNs, CNNs) into FPGA firmware. The task of tagging high-pT jets as H->bb candidates using jet substructure is considered here as benchmark physics use case. The resource usage and latency are mapped out versus types of machine learning algorithms and their hyper-parameters. A set of general practices to efficiently design low-latency machine-learning algorithms on FPGAs will be discussed.