²⁰⁸Pb Radius Experiment PREX

maintained by Robert Michaels rom@jlab.org last updated 21-Mar-2008

This file: hallaweb.jlab.org/parity/prex

The Lead Radius Experiment ("PREX"), experiment number E06002, uses the parity violating weak neutral interaction to probe the neutron distribution in a heavy nucleus, namely ²⁰⁸Pb, thus measuring the RMS neutron radius to 1% accuracy, which has an important impact on nuclear theory. The experiment is being performed by the HAPPEX collaboration which has recently completed experiments E99115 & E00114 -- i.e. HAPPEX II and HAPPEX Helium.

Spokespersons: Krishna Kumar (U. Mass), Paul Souder (Syracuse), Robert Michaels (JLab), Guido Urciuoli (INFN).

Jan '08 test run has been completed.

Test the lead/diamond target at high current. 100 uA achieved !
Test the new PREX detector. worked well
Commission a new Compton Integrating method.
Test new cavity BPM/BCM electronics at very low current (10 to 50 nA)
Luminosity monitor beam-noise and electronic noise tests
Test the Hall A and C beam interaction.

Information related to the Jan '08 test run:

Run Plan
Target info for the run.
Docs: Conduct of Operations ; ESAD ; RSAD
Compton Integrating DAQ.
two PPT slides summarizing the goals.
KK's pictures

PROPOSAL and UPDATES (talks are further down)

2005 Proposal Update (Postscript), and Same, PDF.
2002 Proposal Update
Original Proposal (Dec 1999).

RELATED PHYSICS INFO

Paper on Parity Violating Neutron Densities published in Phys. Rev. C63, 025501 (2001). Cited 61 times according to SPIRES (Nov 2005).
1-Page Experiment Summary for the Public Postscript or PDF
EINN 2005 Poster about PREX (powerpoint).
References from C. Horowitz (needs to be updated).
The Trento 2000 Workshop on Parity Violation.

STATUS and PLANS

An index of Meeting Talks from recent meetings.
Here are recent (Dec 5, 2007) diagrams of the 18-bit ADC and the somewhat older schematic from Fernando Barbosa.
Paul Souder provided a task list (PDF) necessary to perform the experiment. The tentative schedule is Feb 2009 !
We will test our lead target again in Jan 2007.
- Target info for the run.
- Here are Design Drawings from J. Miller . And here are assembly pics (updated jan 14, 2008).
- We have tested our Pb target. See diagram of target and writeup about test (postscript) and same, PDF
- Polarimetry is crucial.
  - In 2003 JLab held a Polarimetry Workshop
  - There is an idea to use atomic hydrogen polarimetry.
  - Here is a draft of plans to upgrade the Compton polarimeter.
- In Nov 2005 we had a 2 day run to test all aspects of the experiment at ~850 MeV. Results were explained in the 2005 propsal update (see talks, below).

TALKS including seminars and PAC Defenses

Here are some talks about PREX at workshops, etc.
Here is an Index of Meeting Talks from recent collaboration meetings.

SLIDES

Here are some old transparencies .

208Pb Radius Experiment PREX

²⁰⁸Pb Radius Experiment PREX