[b1_ana] Inclusive paper by Arenhoevel

[O. A. Rondon]

Hi b1 fans,

Arenhoevel's paper on inclusive polarized deuteron electrodisintegration
has, to me, a much clearer description of the processes we are trying
to study in our proposal, than either H-J-M, Edelmann et al., or
Frankfurt and Strikman.
http://dx.doi.org/10.1103/PhysRevC.43.1022

In particular, it has a definition of the tensor target asymmetry that
seems to make much more sense for solid targets, than trying to repeat
what HERMES did with their gas target, which we just cannot duplicate.

Although Arenhoevel's analysis is focused on electrodisintegration (x ~
2), of course it can be extended to any region of x. Obviously, as x
gets lower, the nuclear response becomes nucleonic response, and finally
partonic, and only special mechanisms, like shadowing, can preserve any
connection to two nucleon coherent processes, which are related to spin
1. But this must depend on the coherence length, as all theorist say,
and I can't believe there is any b1 <> 0 at x > ~ 0.3.

So I think that we should stick to Arenhoevel's approach, and consider
measuring a version of his A_zz = A^T_d, eq. (26), especially
considering that in addition to the usual T20 and L20 deuteron form
factors, there are the F^{2,-1}_{LT} and F^{2,-2}_{TT} factors which
aren't zero only because of the D-state, see discussion at the end of p.
1027. In fact, these form factors would be what would be measured above
x ~ 0.1, not b1, which is a DIS quantity, associated with partonic DF's,
like Kumano says.

It's also very illuminating that, per eq. (30), what Jaffe calls b1 may
just be F^{2,-1}_{LT}, since it can be extracted directly by the
difference between para and perp cross sections, as we proposed last
time. Only that this form factor may not be ~ 1E-3 or smaller, like
b1 is expected to be, but something more accessible. Of course, this
would be a measurement somewhere between 0.5 < x < 1.5. In fact, the
paper discusses the regions near threshold, quasifree and Delta.

One more thing is that Arenhoevel is very clear in his definitions of
what his angles are, etc. And A^T_d does not involve the likely
unattainable P_zz <0, just P_zz>0 for opposite P_z, and the unpolarized
sigma.

It may be kind of late to switch to this approach for this PAC, but we
could try formulating the proposal in terms of measuring the tensor
asymmetry, to extract useful quantities, that no one has measured before
and that should illuminate our understanding of the deuteron much more
effectively than trying to make connections to physics beyond the
experimental possibilities.

Cheers,

Oscar