[Hallb] Letter of Intent for the polarized EMC effect

Will Brooks brooksw at jlab.org
Mon Dec 14 10:55:36 EST 2009

Dear Mark,

 Thanks for the comments. We never had intended to use a simple shell 
model approach, but as you correctly pointed out, the previous 
evaluation did include objections based on the shell model picture. I 
have revised the text to emphasize that we are planning to use the 
results from the various Quantum Monte Carlo calculations, which are 
known to be quite accurate in this mass range. I will replace the posted 
copy with the revised text.


 - Will

Mark Strikman wrote:
> Dear Will,
> A critique which influenced  evaluation of  the 6 GeV proposal was the 
> issue of polarization of protons in 7Li as well as polarization of 
> neutrons in 7Li. Really now that Jlab has established presence of the 
> significant short-range tensor pn correlations in nuclei we definitely 
> know that there exist significant corrections o the shell model 
> estimates of polarizations.
> When we did our calculations/analysis  with Vadim we were certainly 
> concerned with this point. Hence we used the observation that g_1d << 
> g_1p to demonstrate that though the ratio g_17Li /g_1p is somewhat 
> sensitive to uncertainties in the polarization of proton and neutron 
> in 7Li, these effects do not change the x dependence of the ratio, 
> while the polarized EMC effect does.
> I think it would be important to emphasize that ability  of the 
> experiment to study x dependence of g_1 in a wide range of x allows
> to discriminate between the spin EMC effect and deviation of the 
> nucleon  polarization of nucleons in 7Li from specific nucler models.
> I think it would also nice to add an option of investigating using the 
> same target (e,e'p) reaction with polarized 7Li as a method of
> direct measurement of the spin structure of 7Li.
> Best regards,
> Mark
> On Dec 11, 2009, at 3:47 PM, Will Brooks wrote:
>> Dear CLAS collaborator,
>>  Linked below is a draft letter of intent for CLAS12 that is planned to
>> be submitted to PAC 35 on Monday morning. It describes a measurement of
>> the "polarized EMC effect," that is, the modification of the g1 spin
>> structure function of the proton within the nuclear medium. Your
>> comments are solicited, and you are welcome to join the effort if you
>> are interested.
>> The document builds on the work from the 6 GeV letters of intent (V.
>> Dharmawardane, LOI-06-003; A. Deur and X. Zheng, LOI-06-004) and
>> benefits from an increased level of participation by theory experts (A.
>> W. Thomas, I. Cloet, W. Bentz, V. Guzey). Section 1 is expected to
>> evolve somewhat further over the weekend.
>> Best regards,
>>  - Will
>> http://www.jlab.org/~brooksw/LOI_12.pdf
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