[Sbs] The Delta-q proposal (PR12-14-008) was DEFERRED at PAC42, we will come back.

[Xiaodong Jiang]

Dear Hall A and SBS Collaborators,

  As you've heard already, our SBS+BB SIDIS Delta-q proposal (PR12-14-008)
has been DEFERRED at PAC42.

  From the closeout and PAC42 feedbacks we understand that:  we did not
succeed in convincing the PAC that the Hall A pol 3He with SBS+BB option has
a "Significantly Higher Impact" than the already approved "high-impact"
CLAS12 NH3+ND3 experiment (E12-09-007), although we've presented to the
Committee a detailed bin-by-bin comparison showing that we are at least
three to four times better off in determining neutron SIDIS asymmetry than
CLAS12.

We will resubmit this proposal again to the next PAC, with the following
improvements in mind:

1. Clearly show the bin-by-bin comparison of CLAS12 neutron asymmetry
(deuteron - proton) vs the Hall A 3He case, under the same kinematic cuts.

2. Emphasis that Hall A SBS+BB combination can measure spin-dependent SIDIS
cross sections, and show the projected precision of measuring SIDIS
multiplicities as well as the double-spin asymmetries. Expected precisions
on \pi+ - \pi- flavor non-singlet asymmetries vs z.

3. Make a convincing case that our higher-Q2 coverage in Hall A would help
to better understand the behavior SIDIS asymmetries and multiplicities, and
reduce interpretation systematics.

4. Expand the physics impact discussion to cover more TMD physics for
valence quarks at high-x and high-Q2, with single-spin asymmetries A_UL
sin(2\phi_h) etc, and double-spin asymmetries. Layout the impacts to
Transversity measurement in separating Longitudinal/Transverse SSA, and
better understanding of higher-twist terms.

5. A more complete impact study from NLO QCD global fit, to illustrate the
power of precision neutron (3He) data

6.  The urgency to produce SIDIS asymmetry data on neutron, to pin down a
possible non-zero dbar polarization, given the expected release of RHIC STAR
and PHENIX's W asymmetry data.

Thank you very much for your supports,


Xiaodong

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 Xiaodong Jiang
 P25 group, MS H846,                     Tel. 505 606 0437
 Los Alamos National Laboratory
 Los Alamos, NM 87545
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