UCL HEP Seminars 2012
14/12/2012 : Prof. Jeff Forshaw, Manchester
The breakdown of collinear factorization in QCD
Collinear factorization underpins the calculation of many particle physics cross sections, through the use of parton distribution and fragmentation functions. All of the principal Monte Carlo event generators exploit it in their design. In this talk I will explain that in general the factorization does not hold in hadron-hadron collisions and shed light on the mechanism of the breakdown in the language of perturbation theory.
07/12/2012 : Dr. Stephen West, RHUL
Models of Dark Matter
I will outline some alternatives to the standard neutralino dark matter scenario. In particular, I will review asymmetric dark matter and the production of dark matter via ``freeze-in". I will present the possible ways in which we can search for these candidates in dedicated dark matter search experiments and at colliders.
30/11/2012 : Dr. Chamkaur Ghag, UCL
Direct Dark Matter detection
Discovery of the nature of dark matter is internationally recognized as one of the greatest contemporary challenges in science, fundamental to our understanding of the Universe. The most compelling candidates for dark matter are Weakly Interacting Massive Particles (WIMPs) that arise naturally in several models of physics beyond the Standard Model. Although no definitive signal has yet been discovered, the worldwide race towards direct detection has been dramatically accelerated by the progress and evolution of liquid xenon (LXe) time projection chambers (TPCs). The XENON phased programme operates LXeTPCs at Gran Sasso, Italy, and has released results from analysis of 225 days of WIMP search data from the XENON100 detector - presently the most sensitive instrument in the worldwide hunt for WIMPs. XENON100 finds no evidence of signal above expected background and constrains scalar WIMP-nucleon interactions above 2x10-45 cm2 at 55 GeV/c2 WIMP mass (90% C.L.) - over an order of magnitude more stringent than any competing experiment. This result seriously challenges interpretation of the DAMA, CoGeNT or CRESST-II observations as being due to scalar WIMP-nucleon interactions.
23/11/2012 : Prof. David Evans, Birmingham
Probing the Quark-Gluon Plasma - recent results from ALICE at the LHC
ALICE is a general purpose heavy-ion experiment aimed at studying QCD at extreme energy densities and the properties of the deconfined state of matter, known as a quark-gluon plasma. A selection of the latest results will be presents, together with the first results from proton-lead collisions.
26/10/2012 : Dr. Simon Jolly
Proton Accelerators for Cancer Therapy
Proton beam therapy (PBT) is a more sophisticated form of radiotherapy for the treatment of cancer. Due to the Bragg Peak, protons can deliver the necessary dose to the tumour site much more precisely than the 6-18 MeV photons used in conventional radiotherapy. This is particularly valuable for tumours in the head and neck and central nervous system and for treating children, whose growing organs need to be protected from excessive dose. Until now proton therapy was only available from the Clatterbridge Centre for Oncology on the Wirral, and then only for eye treatments using 62 MeV protons. Two new sites are planned for the UK to deliver large-scale proton therapy treatment for the first time: at the Christie Hospital in Manchester and at UCL Hospital. I will describe the reasons for using protons over photons and the accelerator technologies used to deliver 70-250 MeV protons for the full range of treatment we will offer at UCLH. I will also cover some of the issues in selecting the right accelerator technology in my role as the accelerator lead for the new UCLH PBT facility and as an advisor to the Christie programme.
19/10/2012 : Prof. Kael Hanson, Brussels
Particle astrophysics at 90° south : reports from the IceCube Neutrino Observatory
The IceCube Neutrino Observatory is a kilometer-scale cosmic ray muon and neutrino telescope deployed in the deep ice at the South Pole. It detects the Cherenkov radiation emitted by charged particles in transit through the transparent glacial medium by means of a huge array of photomultiplier tubes, each of which independently registers the intensity and arrival time of the radiated photons. The resulting ensemble of hits is processed by event reconstruction algorithms which determine the energy, direction, and type of particle underlying the event. Under construction since 2003, the so-called IC86 array was finally completed December 2010 with the installation of the 86th deep ice string and the full detector was commissioned and placed in operation in May 2011. This talk outlines the science goals of the facility and highlights the results to date that have been released by the IceCube collaboration: searches for high-energy and ultrahigh-energy cosmic neutrinos and lower-energy neutrinos from dark matter; measurements of the cosmic ray anisotropy; detection of neutrino oscillations at high energies. Planned extensions to IceCube are additionally described. Finally, the Askaryan Radio Array (ARA) is introduced. It is an array of radio antennas located next to the current IceCube array which is expected to eventually cover an area of over 100 square kilometers and which targets the detection of the GZK neutrino flux at extreme high-energies which should result from the observed absorption of cosmic rays at these energies.
12/10/2012 : Dr. Tamsin Edwards, Bristol
Predicting future changes in climate and sea level
How can we predict the future of our planet? I will give an overview of modelling and assessment of uncertainty for future climate change and sea level, focusing on the world-leading UK Climate Projections 2009 and our recent research on Antarctica.
05/10/2012 : Dr. Kumiko Kotera
From the magnetized Universe to neutrinos: a life of an ultrahigh energy cosmic ray
The origin of ultrahigh energy cosmic rays (UHECRs, particles arriving on the Earth with energy 10^17- 10^21 eV) is still a mystery. I will review the experimental and theoretical efforts that are being deployed by the community to solve this long-standing enigma, including the recent results from the Auger Observatory. I will describe in particular the interactions experienced by UHECRs while propagating from their sources to us, in the cosmic magnetic fields and the various intergalactic backgrounds. These interactions, that induce deflections and multi-messenger production (neutrinos, gamma-rays and gravitational waves) could reveal crucial information about the path taken by these particles, and help us track down their progenitors. I will also focus on one candidate source that has been little discussed in the literature: young rotation-powered pulsars. The production of UHECRs in these objects could give a picture that is surprisingly consistent with the latest data measured with the Auger Observatory.
29/06/2012 : Prof. Mark Lancaster & Dr. Dave Waters
History of the Tevatron & The Mass of the W Boson
CDF, with significant involvement of the UCL group, have published a W mass measurement with greater precision that all previous measurements combined. We'll take a look at the history of the Tevatron project and particularly the latest ground-breaking W mass measurement. This is an important legacy of the Tevatron as all eyes are now focused on the LHC ...
14/06/2012 : Prof. Kam-Biu Luk, University of California at Berkeley and Lawrence Berkeley National Laboratory
Latest results of the Daya Bay Reactor Antineutrino Experiment
The goal of the Daya Bay Reactor Antineutrino Experiment is to determine the neutrino-mixing angle, &theta13, with a precision better than 0.01 in sin2(&theta13). The value of sin2(&theta13) is measured by comparing the observed electron-antineutrino rates and energy spectra with functionally identical detectors located at various baselines from the reactors. This kind of relative measurement using a near-far configuration significantly reduces the systematic errors. Daya Bay began data taking near the end of 2011 and reported the observation of a non-zero value for &theta13 recently. In this seminar, an overview of the experiment and the latest results from Daya Bay will be presented.
01/06/2012 : Basil Hiley, Birkbeck College and Rob Flack, UCL
Weak measurement: a new type of quantum measurement and its experimental implications
We will discuss the notion of a ‘weak measurement’, originally introduced by Aharonov et al and carefully analyzed by Duck et al. This technique opens up new experimental possibilities for exploring quantum phenomena. It has already been used to measure the spin Hall effect of light and to measure photon ‘trajectories’ in a two slit interference set up, traditionally deemed to be impossible without destroying the interference effects. We will discuss the theoretical basis for the experimental technique and propose new experiments to explore foundational issues, throwing new light on the Bohm interpretation.
18/05/2012 : Dr. Frank Deppisch, UCL
Lepton Flavour and Number Violation in Left-Right Symmetrical Models
We discuss lepton flavour and number violating processes induced in the production and decay of heavy right-handed neutrinos at the Large Hadron Collider. Such particles appear in Left-Right symmetrical extensions of the Standard Model as the "messengers"' of neutrino mass and may have masses of order TeV, potentially accessible at the LHC. We determine the expected sensitivity on the right-handed neutrino mixing matrix, as well as on the right-handed gauge boson and heavy neutrino masses, and compare the results with low-energy probes such as searches for mu-e conversion in nuclei and neutrinoless double beta decay.
11/05/2012 : Prof. Max Klein, Liverpool
The LHeC Project at CERNAn overview is given on the physics, detector and accelerator designs of the Large Hadron electron Collider. The LHeC is a new electron- proton/ion collider, which, operating at TeV energy and using the intense LHC p/A beams, is designed to open a new chapter of deep inelastic lepton-hadron physics.
04/05/2012 : Dr. Marumi Kado, LAL
Higgs searches at the LHC
This talk will give an overview of the searches for the Higgs boson with the ATLAS and CMS detectors at the LHC with the full 2011 dataset, corresponding to an integrated luminosity of nearly 5 fb-1. Both experiments have explored the Higgs boson mass hypotheses range from 110 GeV up to 600 GeV. Most of this range is now excluded at a high confidence level. However, at its low end, for Higgs boson mass hypotheses close to 125 GeV, both experiments observe an excess of events above the background expectation. More data are required to determine the origin of this excess. These results will be reviewed and the short to medium term prospects will be briefly discussed.
27/04/2012 : Dr. Tracey Berry, Royal Holloway
Searching for Extra Dimensions at ATLASThe ATLAS experiment at the LHC has been recording data from proton-proton collisions at a centre-of-mass energy of 7 TeV since March 2010. In 2011 it collected an integrated luminosity of over 5 inverse femtobarns. The combination of the large amount of data available and the excellent detector performance has enabled searches for evidence of new physics at this unprecedented energy scale to be performed. In this talk I will give an overview of the ATLAS searches for extra dimensions.
20/04/2012 : Prof. Mark Lancaster, UCL
The Muon: a probe for new physics
The muon whose discovery in 1937 caused a furore at the time is about to have a renaissance. The availability of new high intensity proton sources at PSI, J-PARC and FNAL will allow the muon's decay modes and dipole moments to be probed to an unprecedented precision. Lepton violation measurements can probe physics far beyond the LHC energy scale and elucidate and resolve degeneracy in new physics models potentially exposed by the LHC. In conjunction with measurements of neutrinoless double beta decay and neutrino oscillations, the muon measurements can also shed light on the mechanism that has generated the universe's matter anti-matter asymmetry. In this talk I will discuss the motivation for, and describe, the next generation of muon experiments and particularly the UK involvement in the COMET experiment.
23/03/2012 : Dr. Aidan Robson, Glasgow
Final Higgs results from the Tevatron
I will present Higgs search results from the complete Tevatron dataset, which were shown for the first time two weeks ago, and discuss them in the context of recent LHC results.
09/03/2012 : Dr. Dan Browne, UCL
Putting Bell inequality violation to work
Entanglement and the violation of Bell inequalities are the most striking examples of the incompatibility of quantum physics and the classical world. Quantum experiments can exhibit correlations which would be impossible in any classical world, unless information could travel faster than light. This behaviour is captured by Bell inequalities and other effects. Giving a general introduction to these effects for the non-specialist, I will give examples of the non-classical correlations which can lead to Bell inequality violations and describe how, in my own recent research, Bell inequality violation has been shown to represent something useful - computation.
02/03/2012 : Dr. Boris Kayser, Fermilab
Neutrino Phenomenology, News, and QuestionsWe will explain the quantum mechanics of neutrino oscillation, which is a quintessentially quantum mechanical phenomenon. Then we will summarise what has been learned so far about neutrino oscillation experiments and discuss several experimental surprises. Finally, we will turn to the future, focusing on neutrino questions that will be addressed by the search for neutrinoless double beta decay.
24/02/2012 : Prof. Ben Allanach, Cambridge
LHC versus SUSYWe review what last year's searches mean for supersymmetry, focusing on what they mean in terms of naturalness and fits to indirect data.
17/02/2012 : Dr. Morgan Wascko, Imperial
T2K's First Neutrino Oscillation Result
The discovery of non-zero neutrino mass, via neutrino flavor oscillation, is the only confirmed observation of physics beyond the standard model of particle physics. Neutrino oscillation experiments have so far measured two of three mixing angles. I will describe the T2K experiment, a long baseline accelerator neutrino experiment in Japan searching for the third mixing angle, and present our first neutrino oscillation results.
10/02/2012 : Dr. Sarah Bridle, UCL
Quantifying Dark Energy using Cosmic Lensing
I will describe the great potential and possible limitations of using the bending of light by gravity (gravitational lensing) to constrain the mysterious dark energy which seems to dominate the contents of our Universe. In particular we have to remove the blurring effects of our telescopes and the atmosphere to extreme precision, and account for possibly coherent distortions of galaxy shapes due to processes in galaxy formation. I will discuss these issues in more detail and review some recent progress in tackling them, putting them into the context of the upcoming Dark Energy Survey.
03/02/2012 : Prof. Dmitri Vassiliev, UCL
Is God a geometer or an analyst?The speaker is a specialist in the analysis of partial differential equations (PDEs) and the talk is an analyst's take on theoretical physics. We address the question: why do all the main equations of theoretical physics such as the Maxwell equation, Dirac equation and the linearized Einstein equation of general relativity contain the same physical constant - the speed of light? The accepted point of view is that this is because our world was designed on the basis of geometry, with the speed of light encoded in the concept of Minkowski metric. We suggest an alternative explanation: electromagnetism, fermions and gravity are different solutions of a single nonlinear hyperbolic system.
27/01/2012 : Dr. Chris White, Glasgow
Polarisation Studies in Ht and Wt ProductionThe polarisation of the top quark can be an efficient probe of new physics models. In this seminar, I will focus on the associated production of a single top quark with either a charged Higgs boson or a W boson. Angular and energy observables relating to leptonic decay products of the top will be presented, which carry strong imprints of the top polarisation. These can be used to constrain the parameter space of two Higgs doublet models, as well as reduce backgrounds to either Ht or Wt production. The talk is based on arXiv:1111.0759.