Particle Physics Group



Particle Physics Seminars Spring 2007

Seminars 2003     Seminars Spring 2004     Seminars Autumn 2004
Seminars 2005     Seminars Spring 2006     Seminars Autumn 2006    

Location: Moseley Lecture Theatre

Usual time: Wednesdays 2-3pm



Wed 7 Feb.     Robin Marshall (Manchester) Schuster Colloquium
14:30 Bragg The Inversion of Heat Capacity: A Solution to a 100 year old Problem.
Wed 14 Feb     Paul Newman (Birmingham) Experiment
14:00 Moseley Deep Inelastic Scattering: The Structure of Nothing
Wed 21 Feb     Neil Spooner (Sheffield) Experiment
14:00 Moseley WIMP Dark Matter Searches
Wed 28 Feb     Andrzej Jerzy Buras (TU Munich) Theory
14:00 Moseley FCNC Processes in the Littlest Higgs Model with T-Parity
Mon 5 Mar.     Konstantinos Dimopoulos (Lancaster) Astroparticle
13:30 Bragg Generating the Curvature Perturbation with a Vector Field
Wed 7 Mar.     Lucio Piccirillo (Manchester) Schuster Colloquium
14:30 Bragg Detecting primordial gravitational waves through the study of 3K Cosmic Background Radiation
Wed 14 Mar 2007     Chris Damerell (RAL) Experiment
14:00 Moseley Vertex detectors and the linear collider
Tues 20 Mar 2007     Tomislav Prokopec ( Utrecht University) Theory
16:00 Moseley Decoherence of cosmological perturbations
Wed 21 Mar 2007     Chris Hays (Oxford) Experiment
14:00 Moseley New W Mass Results
Tues 24 April     Gustavo Branco (Lisbon, CFTP & IST) Theory
16:00 Bragg Leptogenesis, Invariants and Low Energy Observables
Wed 25 Apr     Stephen Watts (Manchester) Experiment
14:00 Moseley Data Visualisation in Particle Physics
Mon 30 April     Mark Hindmarsh (Sussex) Astroparticle
13:30 Bragg Cosmic Strings and the Cosmic Microwave Background
Wed 9 May     Malin Sjodahl (Manchester) Theory
14:00 Moseley Soft gluons in Higgs plus two jet production
Wed 16 May     Steve Koonin (BP) Schuster Colloquium
14:30 Moseley A Physicist's view of the World Energy Situation
Thurs 17 May     Todd Adams (Florida State) Experiment
14:00 Niels Bohr Searches for Long-lived Particles at D0
Tues 29 May     Joannis Papavassiliou (Valencia) Theory
13:30 Niels Bohr On Dynamical Gluon Mass Generation
Wed 30 May     Nick Dorey (Cambridge) Theory
14:00 Moseley Integrability in Four-Dimensional Gauge Theory
Tue 19 June     Asoke K Nandi (Liverpool) Experiment
14:00 Niels Bohr Clustering and Classification
Fri 22 June.     Savas Dimopoulos (Stanford) Schuster Colloquium
14:30 Zochonis Th.A (B.5) Particle Physics circa 2010
Mon 25 June.     Stephen West (Oxford) Astroparticle
13:30 Bragg Non-Perturbative Flat Direction Decay
Fri 29 June.     Qaisar Shafi (Bartol Research Institute) Theory
14:00 Moseley Warped Extra Dimension


7 Feb   Robin Marshall :
The heat capacity of a substance can be expressed as a Fredholm integral equation of the first kind, with the Einstein function as kernel, multiplied on the lattice and intra-molecular vibration spectrum. An analytic solution for the inverse transformation, converting a heat capacity spectrum as a function of temperature, into a vibration spectrum, has proved intractable over the last 100 years. An method for the inverse transformation will be presented here. Examples will be shown for alkali halides, ice and a number of polyatomic carbides, such a Ti2Si3C, and interpreted in terms of the vibration modes. Comparisons will be made with spectra obtained by Raman and inelastic neutron scattering.

28 Feb   Andrzej Jerzy Buras
After a short introduction in the field of FCNC processes I will briefly describe the Littlest Higgs Model with T parity. The interactions of the mirror fermions in this model with the standard quarks and leptons bring new sources of flavour and CP violation. I will present the implications of these interactions on FCNC processes both in the quark and lepton sectors.

5 March   Konstantinos Dimopoulos
Cosmic Inflation is the most compelling solution to many of the problems of Hot Big Bang Cosmology. One of the major successes of inflation is that it can explain the origin of the curvature perturbations in the Universe, through particle production of light fields. These curvature perturbations are responsible for the formation of the observed Large Scale Structure in the Universe (distiribution of galactic cluster and superclusters) as well as the observed CMB primordial anisotropies. Traditionally, inflation produces the curvature perturbation by the gravitational amplification of quantum fluctuations of light scalar fields to superhorizon classical perturbations. In contrast, I investigate the possibility that the observed curvature perturbation is due to a massive vector field. To avoid generating a large scale anisotropy the vector field is assumed to become important only after inflation when it may dominate the Universe and imprint its perturbation spectrum before its decay, as in the curvaton scenario. After inflation the vector field engages into oscillations, during which it behaves as isotropic pressureless matter. Hence, large scale anisotropy can be avoided, when the vector field dominates the Universe.

7 March  Lucio Piccirillo:
The 3K Cosmic Background Radiation is a fantastic tool to study the origin and evolution of the universe. The study of CMB spatial anisotropy provides information used to infer many parameters, for example the density and geometry of the universe. With recent advances in technology, cosmologists now plan to measure the polarisation of the CMB. Scalar and tensor perturbations generated by primordial gravitational waves could be detected through their imprints in the CMB B-modes polarisation. The challenges of the new generations of instruments to measure these B-modes will be discussed.

14 March  Chris Damerell:
I review the physics needs, technical requirements, and current status of R&D for vertex detectors, which will offer unprecedented capability for tagging of heavy flavour jets (b and c) including sign-selection of the quark charge (b vs bbar, c vs cbar) which is needed for a broad range of ILC physics.

20 March   Tomislav Prokopec:
The problem of decoherence of cosmological perturbations has been with us for a couple of decades, and it is still an open problem. Namely, cosmological perturbations are generated during inflation in a pure quantum state which exhibits strong quantum coherence when viewed in the field amplitude basis. I shall present a mechanism by which cosmological perturbations efficiently decohere during inflation: when inflation is realised by two light scalar fields, the field that corresponds to the isocurvature mode (that does not couple directly to gravitational potentials), efficiently decoheres the adiabatic perturbation, which couples directly to primordial gravitational potentials. The decohered potentials are then accurately described as a classical stochastic state, which is usually assumed without proof.

25 April   Stephen Watts
Visualisation of data in particle physics currently involves event displays, histograms, line graphs and scatterplots. Since 1975 there has been an explosion of techniques for data visualisation driven by highly interactive computer systems and ideas from statistical graphics. This field has been driven by demands for data mining of large databases and genomics. Two key areas are direct manipulation of visual data and new methods for visualising high-dimensional data. The first area has seen the use of linked views, brushing and pruning. The second area has seen the introduction of methods such as parallel coordinates and the grand tour. In this talk, these ideas are applied to particle physics data to evaluate their ability to reduce data analysis time and improve pattern recognition. In particular, parallel coordinates will be used to analyse a sample of K-short Monte Carlo events. It will be shown that this graphical technique significantly reduces the time taken to determine the key variables for event selection.

The talk will also give a brief review of some data mining techniques and show how visualisation can help one to understand the effectiveness (or not) of some of these methods.

The talk will describe some publicly available software tools that include many of the new statistical graphics techniques and conclude that no single tool includes all the most powerful new techniques and argue that urgent work is required to integrate these ideas into data analysis tools for particle physics.

30 April   Mark Hindmarsh
I will report on the first field-theoretic calculations of the contribution made by cosmic strings to the temperature power spectrum of the Cosmic Microwave Background, and the results of fitting inflationary models with strings to the CMB data. Intriguing hints are found that strings may be contributing about 10% of the signal.

9 May  Malin Sjodahl
I will talk about soft gluon resummation in the context of qq -> qqH. Not surprisingly, the probability for additional gluon emission depends critically on whether the underlying hard process is a colour octet exchange, as in qq -> qqH via gluon fusion, or a colour singlet exchange, as in qq -> qqH via weak boson fusion). This can be used to experimentally discriminate between these channels of Higgs production at the LHC. Performing the all order soft gluon resummation also allows us to calculate the interference between the two processes.

16 May  Steve Koonin:
The world's demand for energy will grow by some 60% in the next 25 years. Satisfying the demand in an economical and environmentally acceptable manner is one of the most significant challenges facing this society. New technologies will play a central role in meeting this challenge, albeit conditioned by the economic, social and political contexts in which they are developed and deployed. The presentation will focus on the major forces shaping the world's energy future and the technologies required to respond to them

29 May   Joannis Papavassiliou:
At present it is generally accepted that the non-perturbative QCD dynamics lead to the generation of an infrared regulator that may be thought of as an effective gluon mass. The generation of such a mass does no affect the local gauge invariance of the theory, which remains intact. In addition to its theoretical appeal, this description is rather succesfull in low-energy QCD phenomenology, especially in nucleon-nucleon scattering (two-gluon exchange model). In this talk I will present a general introduction to the subject, addressing some of the main conceptual and technical issues. In the non-perturbative framework of the Schwinger-Dyson equations I will study the gluon propagator of pure (quark-less) QCD, focusing on a special type of solutions that are free of the Landau singularity, and reach a finite value in the deep infrared. The strong coupling obtained displays asymptotic freedom in the ultraviolet and freezes at a finite value at low energies, thus giving rise to an infrared fixed point for QCD. Various open questions and possible future directions will be briefly discussed.

30 May   Nick Dorey:
I will introduce the concept of integrability and review its role in recent progress towards an exact solution of N=4 SUSY Yang-Mills in the limit of many colours.

19 June   A K Nandi:
Clustering is the classification of objects into different groups, or more precisely, the partitioning of a data set into subsets (clusters), so that the data in each subset (ideally) share some common trait - often proximity according to some defined distance measure. Data clustering is a common technique for statistical data analysis, which is used in many fields, including machine learning, data mining, pattern recognition, image analysis and bioinformatics. [source: wikipedia on the web].

Statistical classification is a statistical procedure in which individual items are placed into groups based on quantitative information on one or more characteristics inherent in the items (referred to as traits, variables, characters, etc) and based on a training set of previously labeled items. [source: wikipedia]. This has numerous applications in medical imaging, speech recognition, handwriting recognition, document classification, biometric identification, etc.

Effective, informative and efficient visualisation of complex data needs to be closely related to clustering and classification. In my presentation, I shall explore some of the ideas involved and some of the algorithms used. I shall demonstrate their applications on some data and their results. I aim to start from the very basic and plan to take you to some of the most current, advanced ideas.

22 June   Savas Dimopoulos:
We will survey some of the ideas for physics beyond the Standard Model that have been developed in the last quarter century. These are now undergoing significant re-evaluation in view of the cosmological constant problem, and the apparent presence of an enormous number of ground states in string theory. We will also discuss experimental tests of these ideas in the Large Hadron Collider, which will begin in 2008.

25 June   Stephen West:
The cosmological fate of flat directions provides a major ingredient for the history of the early universe. Flat directions can provide mechanisms for generating the baryon asymmetry of the universe and can play an important role in reheating after inflation. We analyze the possibility that the flat direction condensate decays non-perturbatively in a way similar to preheating in models of inflation.

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