[G8b_run] Two-Pion Analysis: Response to Ken's Comments

[Volker Crede]

Hi Ken,

here are our responses to your comments. Thanks again for looking into this.

Best wishes

       Chuck & Volker

========================================================================

Chapter 1.
p1 It would be useful to label the topologies for reference later.   Okay.

p6 What proportion of events have more than one photon and not analyzed.   Chuck is still working on adding this information to the analysis note.

p7 Eloss - would be good to use an example plot.   What example plot do you have in mind? Well, we can think of something.

p20 Top Timing - I find this confusing. "Once again" - where was it previously used?   "Once again" does not add any information here, so we will take it out.

Fig 1.16 Would be useful to see contours.   Honestly, we have not seen much improvement over the current picture by using contours. We will keep looking into this and perhaps update this picture later.

Fig 1.17 Why 5% c.l. And in text --- removes "much of the background" how much is "much"?   We consider our mass distributions pretty much background-free. I talked to Marco Battaglieri about this and they also assumed background-free distributions in their two-pion analysis. I have attached two pictures showing this, one for the missing-proton mass and one for the missing-pion mass. The 4-vecs used are not kinematically fitted otherwise we would observe spikes for the missing particles. The black solid line is the distribution with all cuts used in the analysis, but without a CL cut for the event. Background is visible, but is almost negligible under the missing-mass peak. The blue line represents the distribution with an additional CL cut of 5%. We loose very little signal, but the background is essentially cut out. The CL cut of 5% is a compromise. Usually a 10% cut is used, but since our background is so small, I think we can afford 5% to retain more good statistics. I will describe this better in the analysis draft.


Chapter 2.
p27 bottom. "Thusly" should be "thus".   Okay.

Eq 2.4 some terms not defined.   Okay, will add more definitions.

Fig 2.2 is not needed.   Since Chuck put quite some effort into this for his dissertation, we prefer to leave it in ;-)

Eq 2.9, 2.10 They should, in general, have different I_0 - eg I_0_para, I_0_perp, or some reference made to how they were normalized. No mention of phi_0 in these eqns.   Well, the discussion at this point is quite general and the equations are meant for the ideal case of having no acceptance effects. I will add a reference/comment as to how we normalized the distributions in the analysis. I agree that the definition of beta is missing since we continue to talk about phi-distributions.

2.4 p34 The vertical offsets result from a systematic error in the scaling of the data.   I agree and for this reason, we have used the offsets as a source of the systematic error to account for the normalization issues. The asymmetric distribution for Topology 3 (missing proton) in Fig. 2.8 remains strange, though. Since this topology also has other problems, we simply decided not to use it for our final results.

2.5 p35. Remind us which topologies are which (worth re-writing them here again).   Okay.

Fig 2.9 "hinting" in the caption is too vague a word.   Okay, we will use "showing" or a similar word.

The different vertical offsets means that the data were not scaled correctly when making asymmetries.   This is correct, but there are also statistical effects. The size of the offset is correlated to the statistics for the corresponding distributions. We do not expect an offset of exactly zero. Nevertheless, the effect on the observables is almost negligible.

I don't understand the thing about the detector acceptance dropping out for topology 0, but not topology 5. The diagram with all the X and Ys with arrows doesn't help me!   When we form the asymmetry for one particular topology, the acceptance in principle drops out (as we all know). We have done this individually for each of our four topologies to extract the observables and then averaged over our results. This we have called Topology 0. For Topology 5, we have first added all the phi distributions for all the different topologies, then formed the asymmetry, and then extracted the observables. Since the topologies have all slightly different acceptances, these effects do not cancel out. A comparison of Topologies 0 and 5 gives us a feeling for how big these acceptance effects are. We will think of a better way to make this point clear.

p42 2.7.2 Where does it say how the PARA and PERP histograms were normalized?   I guess nowhere at this point; it needs to be added of course. Thanks for pointing this out.

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