Jefferson Lab Weekly Briefs
February 4, 2009
In Hall A, experiments E06-010, Measurement of Single Target-Spin Asymmetry in Semi-Inclusive Pion-Electroproduction on a Transversely Polarized 3He Target, and E07-013, Target Normal Single-Spin Asymmetry in Inclusive DIS n(e,e') with a polarized 3He Target, have continued to take production data with a high reliability. E06-010 is on schedule; E07-013, running parasitically, will obtain a poorer accuracy than projected due to the late availability of the BigBite gas Cerenkov detector. Both experiments will stop running on Thursday, one day early, to start the transition to Experiment E06-014, Precision Measurements of the Neutron d2: Towards the Electric and Magnetic Color Polarizabilities.
The accelerator continued to perform well, with a continued low trip rate. Six hours were spent on Jan. 27 for beam studies (parallel tuning and measuring the quality factors of cavities and some injector work). Some maintenance was done on an Arc4 box supply and a trim magnet rack.
Free-Electron Laser (FEL)
The FEL was operated this week for measurements necessary for three Joint Technology Office funded projects: low-energy injection, off-axis injection and short Rayleigh-range lasing. The match to the wiggler was sufficiently good that FEL staff successfully lased at 2.8 microns with only 5 MeV of injection energy.
In investigating the deep inelastic structure functions of a nucleus like Fe, it is traditional to correct for the small neutron excess before comparison with deuterium data, which defines an EMC effect. However, the additional neutrons have another, hitherto neglected effect; namely, they generate an isovector mean vector field which modifies the bound structure functions of all the nucleons in the target, as observed in a recent Theory Center article (arXiv:0901.3559). This effect unambiguously shifts momentum from the u-quarks to the d-quarks, which represents a new correction for the NuTeV experiment, which when combined with the smaller charge symmetry violation term, eliminates any disagreement with the Standard Model. Alternatively, given the Standard Model couplings, the NuTeV measurement may be interpreted as providing strong support for an explanation of the EMC effect in terms of the modification of the structure of the bound nucleon by the nuclear mean fields.
JLab's Safety Numbers
30 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
Feb. 4: JLab Colloquium and Public Lecture; CC auditorium, 4 p.m.
Environment, Safety, Health & Quality
The JLab Quality Assurance Plan invokes a graded approach for the application of its associated procedures. The Graded Approach Procedure describes how JLab implements this concept. A graded approach uses a disciplined approach to determine the levels of analysis, management controls, documentation and necessary actions commensurate with an activity's potential to:
The graded approach concept is used to place the most emphasis on and allocate proper resources to those items and/or processes that may have the greatest effect upon personnel, environment, safety, health, cost, data, equipment, performance, quality and schedule. This procedure applies to all Jefferson Lab activities, including construction, operations, maintenance and research, as well as the procurement of equipment for these activities. It does not allow internal or external requirements to be ignored or waived, but does allow for the degree of controls, verification and documentation to be varied in meeting requirements based on ESH&Q and programmatic risks.
Additionally, a worker fell from a ladder while conducting overhead maintenance this past Monday. There were no injuries; an initial fact-finding meeting was held, with the objective of finalizing Lessons Learned and any CATS items by Feb. 9.
JLab Mourns Loss of Physicist, Poet, Activist Mike Finn
JLab Colloquium and Public Lecture
JLab Meeting Rooms Locked After Core Business Hours for Property Protection