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HEP Seminars

20 Oct 2019

UCL HEP Seminars 2019

01-11-2019 : Sarah Heim (DESY)

Higgs differential cross section measurements in the H->ZZ*->4l decay channel with the ATLAS detector.

One of the most promising approaches for probing Higgs boson production and decays are differential cross sections. Measuring the Higgs boson transverse momentum and other distributions can shed lights on the couplings of different Standard Model particles to the Higgs boson. I will discuss fiducial and differential cross section measurements in the H->ZZ*->4l decay channel, often called the golden channel, and highlight the important role of lepton reconstruction and identification. Furthermore I will discuss a number of interpretations and give an outlook for Higgs differential cross section measurements at the High-Luminosity LHC.

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25-10-2019 : 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.

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18-10-2019 : Ralf Kaiser (Glasgow)

Cosmic Ray Muography

Muons are fundamental, charged particles that form part of our naturally-occurring background radiation. They are produced in particle showers in the upper atmosphere from the impact of cosmic rays. These muons are incident at sea-level at a rate of about one per square centimetre per minute and with average energies of about 3 GeV - approximately four orders of magnitude more than typical X-rays. Muons are highly penetrating and can traverse hundreds of metres of rock, which has opened up the possibility to use them for challenging imaging applications. Muography is an established technique in volcanology, it has been used to find a cavity in the pyramid of Khufu in Egypt and over the last years a wide variety of applications have been explored – ranging from cargo screening to nuclear waste characterisation and carbon storage monitoring. Lynkeos Technology is a spin-out company from the University of Glasgow, founded in 2016 following a 7-year, £4.8M research programme funded by the NDA. The Lynkeos Muon Imaging System is the worldwide first, CE-marked muon imaging system for the characterization of nuclear waste containers. It has been successfully deployed on the Sellafield site in October 2018. This talk will give an overview of muography applications worldwide and present the activities of Lynkeos Technology in detail, with a focus on the characterization of nuclear waste containers.

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14-10-2019 : Nivedita Ghosh (IACS Kolkata)

Associated $Z^\prime$ production in the flavorful $U(1)$ scenario for $R_{K^{(*)}}$

The flavorful $Z^\prime$ model with its couplings restricted to the left-handed second generation leptons and third generation quarks can potentially resolve the observed anomalies in $R_K$ and $R_{K^*}$. After examining the current limits on this model from various low-energy processes, we probe this scenario at 14 TeV high-luminosity run of the LHC using two complementary channels: one governed by the coupling of $Z'$ to $b$-quarks and the other to muons. We also discuss the implications of the latest LHC high mass resonance searches in the dimuon channel on the model parameter space of our interest.

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20-09-2019 : Yanhui Ma (UCL)

Observation of H-->bb decays and VH production with the ATLAS detector

A search for the decay of the Standard Model Higgs boson into a bb pair when produced in association with a W or Z boson is performed with the ATLAS detector. The analysis of 13 TeV data collected by ATLAS during Run 2 of the LHC in 2015, 2016 and 2017 leads to a significance of 4.9σ – alone almost sufficient to claim observation. This result was combined with those from a similar analysis of Run 1 data and from other searches by ATLAS for the H→bb decay mode, namely where the Higgs boson is produced in association with a top quark pair or via a process known as vector boson fusion (VBF). The significance achieved by this combination is 5.4σ.

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13-09-2019 : Evan Grohs (Berkeley)

Neutrino dynamics in big bang nucleosynthesis

The laboratory of the early universe provides a setting for testing Beyond Standard Model (BSM) physics in the particle and cosmological sectors. Any BSM physics in operation at early times may produce slight deviations in the primordial element abundances and cosmic microwave background observables predicted within the standard cosmology. The identification and characterization of such BSM signatures require a precise numerical treatment of the neutrino energy and flavor wave functions when the neutrinos decouple from the electromagnetic plasma. This weak decoupling process occurs during Big Bang Nucleosynthesis (BBN) and we employ Quantum Kinetic Equations (QKEs) to follow the out-of-equilibrium neutrino evolution. I will give an overview on the role neutrinos play in BBN, as well as give an introduction to the full QKE problem with neutrino oscillations and collisions. A QKE treatment of early-universe neutrino physics will greatly assist observers and theorists as the next-generation-cosmological experiments come on line in the near future.

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19-08-2019 : Jon Butterworth (UCL)

Highlights from EPS HEP 2019

I gave the highlights talk for this year's EPS meeting in Ghent and will repeat it for anyone in the group who is around and interested.

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22-07-2019 : Alfredo Galindo-Ubarri (Oak Ridge National Laboratory) - 4pm Harry Massey Lecture Theatre

Neutrino Physics Opportunities at ORNL

The Physics Division at ORNL is exploring key opportunities for neutrino physics and supporting the formation of an experimental program at the intersection of particle, nuclear, and astrophysics. The Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) of ORNL are two very powerful neutrino sources that open new physics opportunities. Two new experiments, PROSPECT and COHERENT, make use of these unique capabilities and enable us to broaden the understanding of neutrino properties. PROSPECT consists of segmented 6Li-loaded liquid scintillator antineutrino detectors designed to probe short-baseline neutrino oscillations and precisely measure the reactor antineutrino spectrum. The COHERENT collaboration aims to measure CEvNS (Coherent Elastic Neutrino-Nucleus Scattering) at the SNS. The CEvNS process is cleanly predicted in the Standard Model and its measurement provides a Standard Model test. I will present a novel neutrino experiment which consists of a differential measurement of coherent-elastic neutrino-nucleus scattering using isotopically enriched Ge detectors. I will review some of the current activities taking place at ORNL including the development of ultrasensitive analytical techniques to detect trace elements of interest for neutrinoless double beta decay experiments and will present recent results.

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18-07-2019 : Alex Keshavarzi (Fermilab)

The Muon g-2: theory and experiment

The study of the muon g-2 stands as an enduring and stringent test of the Standard Model (SM), where the current 3.5 standard deviations (or higher) discrepancy between the theoretical prediction and the experimental measurement could be an indication of new physics beyond the SM. The precision of the SM prediction is limited by hadronic contributions and, therefore, the Muon g-2 Theory Initiative are working hard to improve the SM evaluation in time for the next experimental result. In tandem, the Muon g−2 experiment at Fermilab is set to measure the muon anomaly with a four-fold improvement in the uncertainty with respect to previous experiment, with an aim to determine whether the g−2 discrepancy is well established. The experiment recently completed its first physics run and a summer programme of essential upgrades, before continuing on with its experimental programme. The Run-1 data alone are expected to yield a statistical uncertainty of 350 ppb and the publication of the first result is expected in late-2019. In this talk, I will discuss the advances in both the theoretical and experimental determinations of the muon magnetic anomaly, placing focus on my own evaluations of the hadronic vacuum polarisation contributions to the Muon g-2 and my current contributions to the Muon g-2 experiment at Fermilab.

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07-06-2019 : Fabon Dzogang (ASOS)

TBC

TBC

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31-05-2019 : Erika Catano-Mur (William and Mary)

Recent results and outlook for the NOvA neutrino experiment

NOvA is a long-baseline neutrino oscillation experiment, which consists of two finely-segmented liquid-scintillator detectors operating 14 mrad off-axis from Fermilab’s NuMI muon neutrino beam. With an 810 km baseline, the measurements of muon neutrino disappearance and electron neutrino appearance allow the determination of neutrino oscillation unknowns, namely the mass hierarchy, the octant of the largest neutrino mixing angle, and the CP violating phase. In this talk, I will present the latest results of the NOvA oscillation analyses from four years of data taking, and discuss the experiment’s projected sensitivity to determine the mass hierarchy and to discover CP violation in the neutrino sector in future analyses with increased exposure.

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24-05-2019 : Peter Wijeratne (UCL)

From the Higgs to Huntington's: methods for learning from data

With the advent of datasets of unprecedented size and dimensionality in both physics and medicine, there is high demand for new methodologies that can extract hidden or obscured information. This is particularly important in ill-posed problems - such as the reconstruction of particles from detector interactions - and in problems with non-informative priors, which occur frequently in biological processes. In this talk I will give a high level view of the types of computational methods used to tackle these problems at the UCL Centre for Medical Image Computing, with a particular focus on Bayesian methods and unsupervised machine learning. I will also discuss how my previous research on ATLAS led to my current research in computational modelling of Huntington's disease, a devastating neurological condition that computational methods are shining new light on.

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17-05-2019 : Kate Scholberg (Duke)

Coherent elastic neutrino-nucleus scattering

Coherent elastic neutrino-nucleus scattering (CEvNS) is a process in which a neutrino scatters off an entire nucleus at low momentum transfer, and for which the observable signature is a low-energy nuclear recoil. It represents a background for direct dark matter detection experiments, as well as a possible signal for astrophysical neutrinos. Furthermore, because the process is cleanly predicted in the Standard Model, a measurement is sensitive to beyond-the-Standard-Model physics, such as non-standard interactions of neutrinos. The process was first predicted in 1973. It was measured for the first time by the COHERENT collaboration using the high-quality source of pion-decay-at-rest neutrinos from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory and a CsI[Na] scintillator detector. This talk will describe COHERENT's recent measurement of CEvNS, the status and plans of COHERENT's suite of detectors at the SNS, and future physics reach. I will also cover prospects for supernova neutrino detection if time permits.

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10-05-2019 : Monika Wielers (RAL)

HL-LHC and HE-LHC physics prospects

The Large Hadron Collider (LHC) has been successfully delivering proton-proton collision data at a centre of mass energy of 13 TeV. An upgrade is planned to increase the instantaneous luminosity delivered by the LHC by a factor of 5-7 (HL-LHC) for running in 2026 and beyond and there is also another possible future upgrade considered for running at an energy of 27 TeV at the high-energy LHC (HE-LHC). In the last 1.5 years, the LHC experiments prepared a CERN Yellow Report which summarises the physics reach for HL-LHC and HE-LHC and serves as input to the European Strategy this year. This talk shows highlights of the physics reach at the HL-LHC and HE-LHC detailed in the report. The physics prospects are shown for Higgs couplings measurements, di-Higgs boson production sensitivity, Vector Boson Scattering prospects as well as the discovery potential for electroweak SUSY and other exotic benchmark scenarios.

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03-05-2019 : NO SEMINAR

NO SEMINAR

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26-04-2019 : Sudan Paramesvaran (Bristol)

The CMS Trigger: Through the Ages

A trigger represents a fundamental component of hadron collider experiments. The ability to separate signal from background on extremely short time-scales represents a major technological and intellectual challenge. This seminar will seek to explain how the trigger system for the CMS Experiment at the LHC has evolved from the first run (2010 - 2012) through to its first major upgrade in 2016, where a significantly more advanced trigger was deployed. The focus will be on discussing custom electronics, architecture choices, and ultimate performance. With preparations well underway for High Luminosity LHC, the challenges and status of the next major overhaul of the trigger system will be also be described.

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19-04-2019 : EASTER FRIDAY

NO SEMINAR

TBC

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12-04-2019 : Zara Grout (UCL)

A detector-corrected ATLAS measurement of four leptons designed for re-interpretation

This recently published analysis is at the forefront of designing precision measurements using the ATLAS detector which are sensitive to new physics. Traditional ATLAS searches provide maximally sensitive results on specific models with a fast turnaround using highly optimised event selections. I will discuss how these searches can be complemented by detector-corrected measurements which have a long shelf-life and can be used to search for Beyond the Standard Model scenarios by those within and external to the collaboration. In this instance the invariant mass spectrum of four leptons is shown to provide insight into a number of Standard Model processes and BSM scenarios.

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

'The LHCb detector upgrades, and prospects for rare decays and LFU measurements'

The LHCb detector is a single-arm forward spectrometer, designed to study decays of hadrons containing beauty and charm quarks. A major upgrade of the experiment is being performed during the ongoing LHC long shutdown 2. The upgraded detector will operate at an instantaneous luminosity five times higher than in Run 2. It can be read out at the full LHC bunch-crossing frequency of 40 MHz, enabling the use of a flexible software trigger system. The high luminosity LHC could provide peak luminosities of up to $2 \times 10^{34$} cm$^{-2}$ s$^{-1}$ to LHCb, about an order of magnitude above Upgrade I conditions. The collaboration is planning an Upgrade II detector, to be installed during long shutdown 4 of the LHC (2030), which will enhance sensitivity to a wide range of physics signatures. In this talk, I will present an overview of the Upgrade I detectors, and highlight detector design options and recent R&D to meet the challenge of real-time reconstruction in the HL-LHC environment. The talk will conclude with a discussion of the outlook for measurements of rare decays of $b$-hadrons and tests of lepton flavour universality with the upgrade datasets.

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29-03-2019 :

IoP practce talks

TBC

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22-03-2019 : TBC

TBC

TBC

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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.

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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}.

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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.

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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.

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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.

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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).

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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.

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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.

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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.

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