Anita-lite Physical Review Letter P. Gorham UH

1. A N I T A Anita-lite Physical Review LetterP. GorhamUH

2. Pictures

3. Comments I • We thought your general technique of making this paper about ANITA but with data & limit from Anita-lite was a good idea. • in the intro perhaps de-emphasize the lack of GZK cutoff a little ? We say this because the end of that paragraph may not age well if Auger comes out with a cutoff (probably will) this summer. • You say ice has neglible absorption but we lose a good fraction of events in ice that we would see if it were truly negligible. • The sentence/idea "...leads to the strongest current limit..." which is buried on the first column of page 2, could probably be moved or copied to the abstract. • A couple more sentences in the analysis section about how background is removed or how 50% efficiency was measured would be nice. The part about "analyzed in a variety of ways" was little vague. • acknowlegments, don't forget the NSF. They are touchy about that!

4. Comments II • 1. I'd recommend that we stay with the same units throughout the paper - not flip between eV, GeV, EeV and ZeV. It is hard to keep track and remember things easily when units are switching around. Probably go with GeV in text and figures and avoid EeV, ZeV usage. • 2. Figure 3 should be improved since it is the main argument that average noise is thermal. At first glance, it is not easy to say what the message is, since there is a peak in the distribution. The wings near +-150 deg from the sun are the evidence for baseline behavior of 600K, right? Is there a way to put an expectation curve on that histogram which explicitly indicates the baseline temp? • I guess Fig 3 is used to establish the frequency dependence is expected from the sun+galaxy to verify the peak interpretation of Fig 3, but maybe this real estate can be used for additional discussion of the science results. • 3. I wonder if Fig 1 is necessary - it is a nice picture, but color pictures cost a lot of money in PRL, and it takes up quite a bit of space. I doubt that anyone will question that we indeed flew a prototype mission.

5. Comments II cont. • 4. Fig 5. x-axis, E_nu, rather than just energy (of nu or shower?), Change units in caption. Explain the band of GZK nu comes from a representative survey of GZK models, and we probably should explicitly state that the band does not indicate extreme version of the modeling. Finally, the caption should indicate that the ANITA-lite limit does not include systematic errors, and a few sentences should be devoted to what we are plotting for the experimental limits (2.3 events/ energy decade or whatever definition. David Saltzberg wrote up a nice draft of what a standard paper should include, and I recall that when David gave this talk to the experts at the Nobel Symposium, there was general agreement that David's proposal was better than the current situation of every group doing their own thing in reporting limits. We should think about implementing some or most of those suggestions if paper limitations permit. • Text: • 1. Second paragraph: delete "boosted to GZK energies" - it sounds like jargon and not really necessary. • I'd also think about adding a (4)- the highest energy cosmics are primarily protons. If He or Fe, the fluxes at ANITA energies are reduced (and this is the explicit assumption of the models represented in Fig 5). While this is not a departure from standard model physics, neither is (3) and like (3) is incompatible with usual ideas of cosmic ray generation.

6. Comments II cont. • delete "with certainty" - sounds defensive and unnecessarychange "cosmogenic neutrino background " to cosmogenic neutrino flux and leave the word background to triggered events from non-GZK neutrinos. It is less confusing to the reader. • "the flight was successful" - clarify "flight" - you mean the operation of the anita-lite payload, not the successful launch and flight of the balloon, which was stated previously. • Same paragraph: ...data is of sufficient quality to allow for investigation of any candidate neutrino-induced events... -> and a search for neutrino-induced events was performed. • Finally, we may want to mention that we would not be able to unambiguously determine a signal was located in the ice since anita-lite had no zenith resolution, so I would be more comfortable with the idea that the absence of signal can be used to exclude fluxes, but not vice versa. • negligible absorption -> modest absorption (it is certainly not negligible since it controls the depth distribution of neutrino events) • 1/20 -> 1/16 or change to a less specific number, "fewer than 10%". No need to promise something we may not do. If we promise 32 and eventually fly 40, well so much the better.

7. Comments II cont. • Rather than put in a bunch of antenna specs - can you put in a reference page to this general information? If not, then it is OK to leave in. • "factor of two improvement" over what? In rejection of events from thermal fluctuation? Is this worth mentioning since the trigger thresholds were set very high due to local noise. • "This channel was excluded from the analysis" -> Perhaps it is useful to note here that in practice, this problem has <20% (in Jiwoos analysi anyway)impact on the sensitivity because the threshold were so high. • I am not sure if the reader will agree that we are approaching the most optimistic GZK fluxes, and it is not really necessary to say. Rather it would be more useful to provide a table with expected number of events for the upper band, rather than a vague idea that we are approaching something. • A couple of general comments: • 1. Lets include E-2 limits in a table with the GZK flux number as well • 2. No discussion of energy resolution? Maybe leave it for the longer paper, but I just wanted to check.

8. Comments III • 1. ref for TIGER • 2. better ref for Weiler ref [5] - it must be published or choose one that is • 3. While Fig 3 is nice to show that the time averaged ambient noise of antarctica is thermal, it may be better to use the PRL real estate for a discussion for the absence of transient manmade (nonpayload) and physics backgrounds. For example, we do not see background from atmospheric cascades or transmitter stations (although perhaps there was a hint of VLF, at one point in Peds analysis) This certainly is critical info to those who have been in the audiences when I give talks. • 4. What is "usable ice sheet"? The phrase needs explanation. Why is some ice not usable? • 5. Livetimes of 40% are VERY LOW and people may wonder how this value was calculated and its error. We explained why it was small, but not how it was calculated.

9. Comments IV • 1) you say that the coherent radio cherenkov signal is distinctive in its broadband characteristics - is this really true? I thought all cherenkov radiation was, in principle, broadband, provided (1/beta*n(w))<1. • 2) "Antarctic ice does not produce significant depolarization" is probably true, but I'm not aware of data that demonstrate that circular birefringence is not present in ice (maybe this is just a known property of cold ice, in general); of course, in the RICE mc, we also assume no such effects... • 3) I'd encourage you to replace fig. 1 or fig. 2 with a figure of the effective volume. Given that, theorist X can take her/his model of flux from some random neutrino-producing process, and then convolute that flux model with your Veff(Energy) to yield a predicted number of events.

10. Comments V • on second page there is conflict in flight dates (top of the page and the lower third) • on second page, I think you're quoting antenna beam halfwidths while you say you're giving FWHM • on second page, column two, you give ~30 mV rms; raw rms is ~35 mV, while notch filtered one is ~25 mV • third page, system temp. You quote 600 K, but that doesn't correspond to any of the possible rms values; 35 mV -> 1400 K, 25 mV -> 700 K, 30 mV -> 1000 K. • statement that 3rd trigger channel and RF channel 3 are one and the same is wrong. 3rd trigger channel mixes rf channels 3 and 4. • 12 dB on RF channel 3 is based on ground calibration guestimate. We (I guess, Jiwoo and I) should press a bit harder to establish that fact for the duration of the flight • page 4, of 130k triggers, we have 113k waveforms, and most of those were on USB drives, not xfered by TDRSS. • intrinsic cherenkov pulse actually used for analysis is based on theoretical expectations, not accelerator measurements

11. Model independent limits • Paraphrase of L. A. Anchordoqui et al. PRD 66, 103002 (2002) • Same method we have used since 1996, initial DUMAND SPS results

12. Model independent limits, cont.

13. Model Independent limits, cont. • This quantifies the use of dF/d(lnE) as the dependent variable, along with the predominant use of the exposure*cross section evaluated at a series of single logarithmic interval bin centers

14. Saltzberg’s Nobel proposal • Quote aperture (volumetric or areal) for each neutrino species • 1:1:1 mix seems reasonable standard model • Specify which cross sections are used • OK, which ones? • Specify livetime • OK, (including explanation why 40%) • Give expected background number of events during livetime • Currently 0 as far as we know • Quote aperture for 0.75 & 1.25 times cross section used • No, too much detail • Quote aperture for variation in inelasticity • No, too much detail • Number of events observed if any (vs. threshold if many) • none