From prl@aps.org Tue May 4 14:58:35 2004 Date: Wed, 21 Apr 2004 19:15:14 UT From: Physical Review Letters To: doug@triumf.ca Subject: Your_manuscript LQ9460 Anisimovsky Re: LQ9460 Further study of the decay $K sup +$$-> pi sup +$$nu$$nu$ by V.V. Anisimovsky, A.V. Artamonov, B. Bassalleck, et al. Dr. D.A. Bryman TRIUMF 4004 Wesbrook Mall Vancouver B.C., CANADA V6T 2A3 Dear Doug, The above manuscript has been reviewed by our referees. While we cannot make a definite commitment, we will probably accept your paper for publication, provided you make changes which we judge to be in accordance with the enclosed comments (or other satisfactory responses are given). Please accompany your resubmittal by a summary of the changes made, and a brief response to all recommendations and criticisms. Yours sincerely, /Robert/ Robert Garisto Senior Assistant Editor Physical Review Letters Email: prl@aps.org Fax: 631-591-4141 http://prl.aps.org/ ---------------------------------------------------------------------- Editorial Note: Referee B wrote the following note to me, which I think is useful to communicate with you: "I have a concern which I have not mentioned in my report because I feel the editors should make the judgement on the issue. In the guidelines to PRL referees it states that 'The journal does not accept marginal extensions ....' This paper describes what is clearly an extension to the previous work - it is new data with an improved detector and a different beam configuration - however it has not significantly changed the conclusions and is in effect a verification of things the group have previously done. In view of the fact that it is an important decay mode, I think that it was good to look again. I think that for scientific correctness the group are bound to publish whatever they observe and not just in the case that they are lucky and see a lot of events. However, in the strict interpretation of your guidelines, this is an incremental increase in scientific knowledge of which the group have published in PRL before (refs [2,3,4]). It's your call." We are happy to accept this paper for publication in PRL (provided the referee comments below are addressed), but for future papers, the considerations above might play a more dominant role. The other issue is the title, which is not as descriptive as it could be. How about something like, "Improved measurement of the K^+-> pi^+ nu nubar branching ratio" ? R.G. ---------------------------------------------------------------------- Report of Referee A -- LQ9460/Anisimovsky ---------------------------------------------------------------------- This paper reports the first results from BNL E949 on the very rare decay K+ -> pi+ nu nubar. The branching ratio of this decay mode measures, with small theoretical uncertainty, the quantity |V_td|, the magnitude of one of the elements of the CKM matrix. This measurement is part of the larger program, involving many experiments, of overconstraining the CKM matrix to determine its consistency and its ability to account for a wide range of phenomena, including CP violation. This program of measurements is one of the central thrusts of experimental particle physics today. Because of the high importance of this measurement to fundamental issues in particle physics, I believe this result is of broad interest. I will, however, say the authors have NOT provided much of an introduction to the topic for the nonspecialist reader. They have reduced the whole story to a single opening sentence: "Measurement of the rare decay K+ -> pi+ nu nubar provides a stringent test of the standard model which predicts B(K+ -> pi+ nu nubar) = (0.77+-0.11)X10**(-10)." Succinct to be sure. My understanding of PRL guidelines is that there should be an introduction that is appropriate for a nonspecialist. In the spirit of providing that, I would suggest the authors expand upon that first sentence, to put this measurement in a fuller context, particularly vis-a-vis on-going complementary measurements at the B-factories at SLAC and KEK. E949 is a follow-on to E787, with some upgrades. It has the potential of improving by large factors over the previous experiment, although that now seems unlikely owing to DOE decisions that may limit E949's opportunity to take data to fully exploit its potential. Independent of that unfortunate situation, the result presented in this paper is an important one and it significantly advances the state of the measurement of K+ -> pi+ nu nubar. As such, it definitely deserves to be published in Physical Review Letters. The paper is clearly written and I believe the result is valid. The group is well-advanced in understanding the backgrounds and subtle analysis issues associated with this measurement. The experiment is a tour de force and it is gratifying to see, after so many years of effort, a signficant sample of signal events emerging. One hopes more data can be taken to turn this measurement into the stringent test it is capable of being. In summary, this paper meets the PRL criterial of importance, validity, and broad interest. It should be published in PRL for sure. It meets these criteria in its present form, but a somewhat expanded introduction would make the value of this very substantial piece of work more apparent to the nonspecialist. ---------------------------------------------------------------------- Report of Referee B -- LQ9460/Anisimovsky ---------------------------------------------------------------------- The paper describes a new measurement of the branching ratio of charged kaons into a pion and two neutrinos. This is a very interesting decay theoretically as it provides information on various CKM matrix elements which could indicate or constrain the existence of new physics. I recommend that, after revision along the lines indicated below, the paper be published in PRL. The paper is generally well written. The introduction is a little terse for the general readership of PRL, however I understand that space is limited and references are immediately given to places where more detailled information can be found. The diagrams and tables are used well to present the result. From the information given in the paper, the analysis looks comprehensive and scientifically sound. There is a problem in the presentation of the method in the paragraph which begins 'As a test of the method, ...' and in the first half of the following paragraph which begins 'An acceptance function ...'. I strongly recommend that these two paragraphs are rewritten to be more accesible to a general readership. I know that this (or a similar) method is described in refs [2,3,4], however in a paper in this journal, I think that it is important that the main experimental method be clearly described in in-situ text in the article. To try to aid the authors in understanding what is wrong with the paragraphs I indicate some of the things I (and a colleage) could not understand, however if this explaination is difficult to understand apologies, but I expect you will be able to improve the paragraphs: 1. We did not know what the 'rejection function' is ? Which variables is it a function of (I guess there are two functions one depending on each of the independent cut variables.) What does the value of the fuction represent ? Is it the same thing as the efficiency (of either the cut on its own, or of the cut combined with any cuts in all of the rest of the analysis). 2. The first sentence is way too long. Suggest that the second part which explains (I think) that the procedure is done for each of the three backgrounds is separated. 3. We could not understand the constants c fitting to five bins of rejection. Presumably this means that the data was divided into five exclusive parts somehow and that the ratio of observed to predicted numbers should be the same in each case. 4. In the paragraph starting 'As a test of the method' the quantity 'ratios of the observed to predicted numbers of events in the 2/3 sample' is described. Is this the same as s_i/b_i as described in the next paragraph ? If so, it may be simpler for the reader to define it earlier. 5. We could not understand the second sentence of the paragraph which starts 'An acceptance function ...'. Try understanding the first clause first: 'An event characterisation function consiting of a set of discrete bins s_i/b_i' - how can a function consist of discrete bins ? - is it a function of the values in the bins or something? - is the bin 'i' or 's_i/b_i' 6. In the definition of W_i further down the paragraph, is 'i' now the index of the bin in which the event resides, or just the event number (1,2,3)