Dr Daniel Watts

EPSRC Advanced Research Fellow

The University of Edinburgh

JCMB - The King's Buildings Room 8209       

Mayfield Road

Edinburgh

 EH9 3JZ

 UK

 +44 131 650 5286 dwatts1@ph.ed.ac.uk  

Some Recent Publications

Incoherent pion photoproduction on 12C [pdf[

Dependence (g,pd)  on  linear polarisation[ pdf[

3-nucleon mechanisms in photoreactions [pdf[

Photoproduction of eta-mesic Helium3 [pdf]

Magnetic moment of the D+ [pdf[

Neutron electric form factor measurement [pdf]

For a full list follow the link

Physics research

I am a nuclear physicist and carry out experiments using the latest generation of intense continuous electron beam facilities in Germany, Sweden and the USA to study nuclear and hadron structure. Links to the home pages of the collaborations are shown below:

Below are outlines of the physics driving the  experimental proposals I have developed at these facilities

Precision measurement of the nuclear matter form factor  -  This experiment will use the Crystal Ball detector to measure the coherent photoproduction of neutral pion mesons. The reaction will allow  the spatial distribution of both protons and neutrons in the nucleus to be determined with high accuracy (~0.1fm). This will allow investigation of the possible existence and nature of the neutron skin on heavy nuclei. The dimensions (and even  the existence!) of this neutron skin are not at all well established and its measurement will have important implications for nuclear physics, neutron star physics and even to the attainable accuracy of some tests of the standard model of particle physics!

Determination of the magnetic moment of the first excited state of the proton - The first excited state of the proton is called the D⁺. Because it only lives for a very short time (<10^-23s) it has previously not been possible to get an accurate determination of its magnetic moment - a fundamental quantity which tells us about the dynamics of the D⁺ constituents. However the short lifetime of the particle means it has a large energy width and there is a small probability that the particle can decay to itself at a lower mass with the emission of a high energy photon (gamma) . We create a very large sample of D⁺  particles from a proton target with a high energy photon beam and then use the Crystal Ball detector to measure the radiative decay gamma from the self-decay of the particle. This will allow us to determine the magnetic moment of the particle with good accuracy for the first time. 

The nature of three-body forces - The possible existence of three-body forces has been postulated for centuries (Galileo discussed their possible existence for gravitational forces in the 17th Century!). Three-body forces only exist when three bodies are present and are not reducible to sequential two-body forces. In very recent years there is growing evidence for the crucial role three-body forces play in developing a more fundamental understanding of nuclear physics. We have measured a large sample of disintegrations of Helium 3 nuclei using the intense high energy electron beam at Jefferson Laboratory in the USA. From comparison of this data with a new generation of Faddeev calculations of the process we will get new insights into the dynamics of nucleons in the nucleus, in particular the nature of three-body forces. Collaboration members can access the proposal here [postscript]

Towards an ambiguity free determination of the excitation spectrum of the nucleon - The nucleon (proton or neutron) is a composite object comprised of quarks and gluons. The nuclei of the atoms around us predominantly contain nucleons in their lowest energy state.  However nucleons involved in energetic reactions can become excited to higher energy states and the properties and distribution of these states gives information on the dynamics of the constituents of the nucleon.  Presently, this spectrum is not well established because these excited states are so short lived they are broad in energy and overlap, resulting in the unfavourable situation where even a monoenergetic incident photon could excite many different excited states. We produce excited nucleons using intense polarised energy tagged photon beams incident on spin polarised nucleon targets and measure the subsequent decay of the excited states to a nucleon and meson(s). I lead the  development of a nucleon polarimeter which will give new observables with which to disentangle the excitation spectrum. The device will make possible a determination the intrinsic spin direction of the recoiling nucleons, a development which is an absolute necessity if we are to acquire sufficient experimental information to achieve an "ambiguity-free" determination of the nucleon excitation spectrum.

Teaching

Teaching responsibilities include the Junior honours Nuclear Physics Course, workshop supervisor for the P1A course, laboratory supervisor for P1B and a tutor for the QUILS course.

 Follow the link below for information relating to the Nuclear Physics course.

For slides of my lectures at the UK Nuclear Physics summer school in Chester 2005 follow the link below

For Edinburgh Nuclear Physics group seminar schedule follow the link below

SUPA Quarks and hadron spectroscopy lecture 3 & 4 (PDF for student download)

Edinburgh recoil polarimeter

We are presently building a recoil nucleon polarimeter for use in meson photoproduction reactions with the Crystal Ball at MAMI. The project home page can be accessed by following the link below.

 Some recent conference talks and contributions

Invited talk at PREX workshop on neutron skins, Jefferson Lab, Newport News, USA (2008)      [pdf (talk)]

Invited talk at Gordon conference on photonuclear reactions, Tilton NH, USA(2008)      [pdf (talk)]

Invited talk at Meson 2008 International workshop on meson production, properties and interaction, Krakow (2008)      [pdf (talk)]

Invited talk at Carnegie conference on Nuclear Physics at the extremes, University of West of Scotland (2008)      [pdf (talk)]

Invited talk at conference on Electromagnetic interactions of nucleons and nuclei, Milos, Greece (2007)      [pdf (talk)]

Invited talk at Conference on electromagnetic interactions of the Delta resonance, ECT Trento (2007)      [pdf (talk)]

Invited talk at the International conference on the physics of excited baryons  (NSTAR), Florida State University (2005). [pdf (proceedings)] [pdf (talk)]

Invited talk at Institute of Physics workshop on the future use of Germanium detectors (2005)  [pdf ]

Invited talk at 24th International conference on calorimetry in high energy physics, Perugia, Italy (2004)     [pdf (proceedings)]

Slides from talk at CLAS collaboration meeting, Jefferson Lab, USA (2005) [pdf]

Invited talk at UK IOP nuclear physics conference, Edinburgh (2004) WattsJLabPrexWorkshop.pdf [pdf]

Research colloquium at  York, UK (2004) [pdf]

Contribution to the proceedings of the Fifth conference on photoinduced two hadron  emission, Lund, Sweden (2001)[Postscript]

Invited talk given to Joint Nuclear and Particle Physics IOP Congress in Salford, UK (1999)[Postscript]

Contribution to proceedings of the Fourth Workshop on Electromagnetically Induced Two-Nucleon Emission at Granada, Spain (1999) [Postscript] [HTML]