[Alert_collaboration] LOI using ALERT: Partonic Structure of the bound alpha

[Whitney R. Armstrong]

Hello Everyone,

I would like to submit a LOI to the CLAS collaboration and coming PAC 
for an experiment that will explore the partonic structure of the bound 
alpha particle in nuclei. Please see the title and abstract below. The 
idea is to extend the Nuclear GPD proposal to alpha knockout in isocalar 
and isovector nuclear targets and study the (A,N-Z) dependence of the 
structure of the bound alpha through DVCS/DVMP. Then we can compare the 
bound and free alpha's charge and gluon radii.

Any feedback would be appreciated. I'll send around a full LOI/proposal
in the next week or so.

Cheers,
Whit


Title: Partonic Structure of the bound $\alpha$ 

Abstract:

We propose to study the partonic structure of a bound $\alpha$ particle 
by measuring the Beam Spin Asymmetry (BSA) through $\alpha$ knockout 
reactions in coherent Deeply Virtual Compton Scattering (DVCS) and the 
differential cross-section of the Deeply Virtual Meson Production (DVMP) 
of the $\phi$. The transverse charge and gluon distributions of a bound 
$\alpha$ will be extracted from a set of isoscalar alpha-conjugate 
($^{12}$C, $^{16}$O, $^{20}$Ne) and heavier isovector ($^{40}_{18}$Ar, 
$^{84}_{36}$Kr) nuclear targets. The ALERT detector will detect the 
alpha-knockout and CLAS12 will detect the scattered electron and the 
produced photon or $\phi$ meson. This proposal builds on he physics of 
the recently approved ALERT run-group, specifically, ``The Partonic 
Structure of Light Nuclei'' experiment which will measure the transverse 
quark and gluon distributions of $^4$He. The nuclear medium effects on 
the partonic structure of the alpha will be made apparent by taking 
EMC-like ratios of the extracted BSAs, Compton form factors (CFFs), 
meson production cross sections, and transverse charge and gluon 
distributions.  These results will answer key questions: Does the gluon 
radius of the $\alpha$ change in larger nuclei? Does the corresponding 
quark (charge) radius behave similarly?  Is there an observed 
enhancement in isovector targets?