OPT-IN:Longitudinal Spin Transfer to Λ Hyperons in Semi-Inclusive Deep Inelastic Scattering with CLAS12

[Mikhail Osipenko]

First of all I acknowledge the enormous amount of work performed by the authors.

General comment: the manuscript is overloaded with phenomenological discussions. It does not seem to be an experimental paper, and may be criticized by journal referees for the reasons irrelevant to CLAS Collaboration.

Eq.2 – omit \mu index everywhere, it is common practice that in the product of 4-vectors running indices are omitted, otherwise you need to write also the sums over mu.

Eq.2f – this is not definition of Feynman x_F, P*q=Eh*nu-vec{ph}*vec{q}, as far as I remember x_F=2*p_long^CM/W. As you can see it has no “Eh*nu” term. Perhaps you meant: 
x_F=2*vec{ph}*vec{q}/W*|vec{q}|,
then you need to remove mu indices, add vector sign (both in numerator and denominator) and add CM superscript, since the quantity is not invariant.

Line 76 - “Transverse momentum and polarization dependent observables in SIDIS often manifest in asymmetries between the cross sections produced from opposite initial lepton probe helicity and target nucleon spin configurations.” - perhaps it is better to remove “transverse momentum” here. I understand what you mean, but put in this way it is not clear.

Line.86 - “preserved in the cross section of” – better use “in angular distribution of”

line.177 - “along the Λ momentum.”, but just few lines before you defined “quantization axis L′ in the Λ rest frame.” - how do you define the direction of Lambda momentum in the Lambda rest frame shown in Fig.1? Is P_lambda not =0 by definition in this plot?

Line.304 – you applied a cut z<1, but this is not completely equivalent to the missing mass cut. Have you checked your missing mass distribution? Are K+ and K+* all excluded in these data?

Table.II – not sure so many significant digits are justified here, and you don’t provide the total.

Fig.9 and 10 – seem to demonstrate that the observable is totally dominated by TF mechanism. First of all don’t use CFR and TFR acronyms – these are Current/Target Fragmentation REGIONs! Being “regions” in kinematics it is very surprising to see them as theoretical contributions (terms of calculation) in every region of the plots. You can use Current/Target Fragmentation mechanisms for example. Second, how could you expect a large current fragmentation contribution at energies that barely enough to produce just one Lambda-antiLambda pair? Is it not that what is extracted from e+e-?

Fig.7 – in the abstract you claim to have “most precise measurement”, but comparison to COMPASS data does not seem to be so clear to make such statements, considering moreover much higher W values of COMPASS, reducing systematic uncertainties of various approximations used in the paper.