Summer Internship Programme 2018

Beam studies for the Compact Linear Collider (CLIC) at CERN

Supervisor: Professor Phil Burrows (philip.burrows@physics.ox.ac.uk)
Duration: 8 weeks, starting date ideally around 25th June

The new CLEAR facility – CERN Linear Electron Accelerator for R&D – has been commissioned and first experiments have been taking place since 2017. The intern will have the opportunity to work on both hardware and simulation studies for setting up and operating the new 220 MeV electron beamline.

Robot for Bus Tape Testing

Supervisors: Professor Tony Weidberg (tony.weidberg@physics.ox.ac.uk)
Duration: 8 weeks

We would like a summer student to work with us on the development of the software for the tape testing robot. While the current software has been used to demonstrate the feasibility of the tape testing robot, there are still developments required to get it ready for production. The current system relies on small fiducials near pad fields to correct for the distortions in the tape and therefore allow the probing on the small pads. We are not sure if we will be able to have local fiducials near all pad fields and we therefore want to develop pattern recognition software to do “pad finding”. We also want to do image analysis on the photos of the pads to validate the quality of the pads. This is important to ensure that we can make reliable wire bonds. These are interesting and important projects which would suit a student with an interest in software. The student could also study the High Voltage Insulation Resistance (HVIR) as we need to test this to 1.5 kV and obtain leakage currents less than 10 nA will be challenging. We have had several summer students in the past and they have all made very significant contributions to the project.

Lepton universality test with W boson decays

Supervisor: Dr Mika Vesterinen (mika.vesterinen@physics.ox.ac.uk)
Duration: 8 weeks

A stringent assertion of the Standard Model of Particle Physics is that the electroweak gauge bosons couple, at the fundamental level, with strengths that are universal across the three (known) leptonic generations. Recent studies of (semi)leptonically decaying beauty mesons hint at possible physics beyond the Standard Model with non-universal leptonic couplings.
Experiments at the LEP-II electron positron collider also revealed an anomalously high decay rate of W bosons to third generation leptons, as compared to the first two generations. Could these anomalies have a common explanation in terms of physics beyond the Standard Model? For more than a decade, the LEP-II result remains to be challenged by other experiments, largely because tau leptons are challenging to reconstruct in current hadron collider experiments with access to W boson production. The LHCb experiment is well suited thanks to its incredibly precise silicon vertex detector which can resolve the subtle signature of the tau lifetime. This project aims to exploit the vast dataset of the LHCb experiment to conclusively test the LEP-II claim.

Measuring the W boson mass with LHCb

Supervisor: Dr Mika Vesterinen (mika.vesterinen@physics.ox.ac.uk) and Professor Chris Hays (chris.hays@physics.ox.ac.uk)
Duration: 8 weeks

One of the most promising approaches to uncover physics beyond the Standard Model is to confront it with ultra-precise tests of key relations between its fundamental parameters. For example the Standard Model asserts a relationship between the masses of the W boson, Higgs boson, and top quark, which results from quantum loop effects. A measured deviation from this prediction could indicate quantum loops involving heavy new particles from beyond the Standard Model. This fundamental test is mostly limited by the precision with which we have been able to directly measure the mass of the W boson, primarily at the Tevatron and LHC hadron colliders. The W boson mass is notoriously challenging to measure since its leptonic decays only provide one reconstructable charged lepton, while the neutrino proceeds undetected. Incredible accuracy is required from our models of how W bosons are produced in hadron collisions. Oxford researchers are leading key measurements of the W boson mass: Professor Chris Hays at the CDF experiment at the Tevatron, where the mass has been measured to a precision of 2 parts in 10,000 and is expected to improve by a factor of two; and Dr. Mika Vesterinen at the LHCb experiment, where a measurement in a completely new kinematic regime promises to reduce systematic uncertainties in the world-average value of the W boson mass. In this study the student will work with Professor Hays and Dr Vesterinen to study how parton distributions and initial-state radiation impact the measurements, as well as methods to constrain their modelling in situ with data.

Search for new physics and constraining Higgs properties with H->bb decays

Supervisor: Professor Cigdem Issever (cigdem.issever@physics.ox.ac.uk)
Duration: 8 weeks

The discovery of the Higgs boson at the LHC gives the possibility to study nature at the highest energy scales with a new particle, a new probe. The project will work MC simulations and possibly ATLAS data and study the potential of searches for new physics and Higgs property measurements with the Higgs boson decaying into a pair of b-quarks. The project may have phenomenology studies which include theoretical models or the development of new analysis strategies or detector performance studies to improve the sensitivity to H->bb decays in our data. Details of the project can be discussed and agreed on based on the interest of the summer student.

Absolute distance interferometry using a frequency comb

Supervisor: Dr Armin Reichold (armin.reichold@physics.ox.ac.uk)
Duration: 8 weeks

Frequency scanning interferometry is a technique for absolute distance measurements. In the incarnation referred to as dynamic FSI, developed at Oxford physics, it relies on the ability to measure the frequency of scanning laser using absorption spectroscopy on molecular excitations of gases such as acetylene or hydrogen cyanide. This technique has already generated a patent and four commercial licenses and is currently implemented as an industrial precision instrument (Absolute Multiline) through the German company Etalon AG.

In 2015 FSI measurements were made by Oxford Professor Armin Reichold at the German national institute of standards (PTB) in Braunschweig in which in addition to multiple gas absorption cells and a precision reference interferometer a state of the art, high precision frequency comb was used to record beat-patterns of the scanning lasers with the comb laser. This data has not yet been analysed and has a high potential to enable new ways for improving the spectroscopic methods used in FSI and hence improve the distance measurement accuracy.

This summer projects purpose will be to analyse the data with extensions of existing MATLAB or Fortran codes in a variety of ways among which could be:

1. Fitting the beat signals of the scanning lasers with the comb to obtain a highly precise frequency axis.
2. Fitting the positions and widths of the peaks in the absorption spectra with Voigt functions instead of the simpler Gaussian functions used so far.
3. Potentially performing the fits from 2. using a total chi-squared method in which errors in both axes can be considered.
4. Comparing the results of the above fits to see how accurately the Gaussian fraction of the width of the peaks can be fit and hence how accurately the pressure of the gas cell can be determined.
5. Comparing the results of the above fits to measure the relative spacing of the gas cell peaks
6. Using these results to improve the distance measurement results.

The project is open ended and the data has not been analysed systematically before. How many of the above points can be dealt with depends on the student and on the data. The data analysis aspects demand good analytical skills and good programming skills with some experience in Java preferred because the majority of existing analysis code is in Java.

Depending on the preferences of the students this project could also be directed towards the hardware aspects of the FSI technique. The full hardware for the above experiments (except for the frequency comb) is now available in Oxford together with a new high speed data acquisition system which can extend the capabilities of the technique significantly. Students with a desire to work more on the hardware side of this technique could participate in this aspect.

Study of permanent magnets for a robust medical LINAC for challenging environments

Supervisor: Dr Suzie Sheehy (suzie.sheehy@physics.ox.ac.uk)
Duration: 8 weeks

A new international collaboration is forming to address the shortfall of radiotherapy LINACs in low to middle-income countries. This important project will contribute to the design of a linear electron accelerator for radiotherapy where all subsystems will be optimised to ensure it is robust, reliable, cost effective and appropriate for use in challenging environments including developing countries. This project aims to design a beam delivery system (magnetic focusing and steering) which uses modern capabilities in permanent magnets to ensure that a high-quality electron beam can be taken from the source to the x-ray generating target with minimal losses. Replacing some or all of the existing electromagnets with permanent magnets should enable a maintenance-free focusing system which requires very little electricity, which has been highlighted as a barrier to providing this technology in ODA countries. The vacation student will work on modelling the LINAC in simulation codes, and working together with the team to consider relevant error studies and implementation questions.