The Sheffield HARP group
HARP, otherwise known as PS214, is a hadron production experiment at the CERN PS. It aims to study relatively low energy hadron production both to optimise the construction of the target for a proposed neutrino factory and to aid in understanding of the atmospheric neutrino flux.
Currently, the multiplicity of low energy pions produced in hadron-nucleus interactions is poorly measured, and the transverse momentum distributions of these particles is even less well known. This is particularly the case for heavier nuclei. The predictions of "standard" Monte Carlo programs disagree significantly, largely due to the lack of reliable data which is needed to tune the different models involved. HARP aims to provide reliable data from the interaction of protons, of energy 2 to 30 GeV, with a range of nuclear targets. This should allow targets for the muon collider/neutrino factory to be optimised for the maximum collection of low energy pions, whose decays will provide the required muon beams. The study of particle production in collsions with nitrogen and oxygen (in a second phase of the experiment) will aid in the understanding of the production of neutrinos as a result of cosmic ray interactions in the upper atmosphere.
The HARP detector consists of a Time Projection Chamber (TPC) mounted inside a solenoid, followed by a spectrometer composed of drift chambers on either side of a dipole magnet. For particle identification, this is followed by a Cherenkov counter, time-of-flight system and combined electromagnetic and hadronic calorimeter. This is shown schematically below.
Sheffield, along with other UK groups, was accepted into the newly formed HARP collaboration at the end of February 2000, and UK funding was agreed following the PPESP meeting in March. The time scale of the experiment was quite short, with a technical run taking place in September 2000, followed by a lengthy data taking phase in 2001.
Sheffield has reponsibility for the target supports. Together with RAL and Oxford, we have produced an insertion mechanism which allows targets to be mounted within the Time Projection Chamber using a method which allows rapid changes in target type with precise relocation of the new target. A support cap holds the targets accurately in position, with the minimum of surrounding material. Targets supplied include a number of thin and thick metal cylinders, as well as specialised test and alignment objects.
We are also preparing for analysis of the data which will come from HARP. This will involve Monte Carlo simulation of the hadronic interactions involved, using programs such as MARS and FLUKA. Our aim is to improve the production models within these programs so that they more reliably reproduce the data and so can be used for future target design studies. In addition, we are working on reconstruction of tracks from the hits in the upstream beam chambers.
This PowerPoint presentation contains an amalgamation of HARP status reports delivered at various venues in May and June 2001. The original material was collected by Craig Buttar, Lucie Linssen (CERN) and Chris Booth.
The following Sheffield personnel are involved in HARP:
- Dr. Chris Booth, physicist
- Dr. Paul Hodgson, research associate
- Dr. Lara Howlett, research associate
- Mr. Richard Nicholson, engineer