Response_PRL Date: Tue, 20 Feb 2007 14:03:31 UT From: Physical Review Letters To: vlk@lav01.sinp.msu.ru Subject: Your_manuscript LZ10772 Adams Parts/Attachments: 1 Shown 179 lines Text 2 OK 88 KB Application ---------------------------------------- Re: LZ10772 Confirmation of a $\pi_1^0$ exotic meson in the $ \eta \pi^0$ system by G.S. Adams, T. Adams, Z. Bar-Yam, J.M. Bishop, et al. Dr. V.L. Korotkikh Moscow State University Institute of Nuclear Physics Leninskie Gory Moscow 119992, RUSSIA Dear Dr. Korotkikh, The above manuscript has been reviewed by our referees. A critique drawn from the reports is enclosed. On this basis, we judge that while the work probably warrants publication in some form, it does not meet the special criteria of importance and broad interest required for Physical Review Letters. The paper, with revision as appropriate, might be suitable for publication in Physical Review D. If you submit the paper to Physical Review, the editors of that journal will make the decision on publication of the paper, and may seek further review; however, our complete file will be available. If you submit this manuscript or a revision of it to Physical Review D, be sure to respond to all referee comments and cite the code number assigned to the paper to facilitate transfer of the records. Yours sincerely, Jerome Malenfant Senior Assistant Editor Physical Review Letters Email: prl@ridge.aps.org Fax: 631-591-4141 http://prl.aps.org/ ---------------------------------------------------------------------- Report of Referee A -- LZ10772/Adams ---------------------------------------------------------------------- The manuscript reports the analysis of data on the charge exchange reaction pi- proton to neutron plus eta pi0. The authors claim confirmation of an exotic meson in the title. This would be an important finding and the results should be published. I do not believe however the paper merits publication in PRL. The status of the exotic state is highly controversial. Based on the data of E852, two papers have been published. Ref [12] reported results in a similar reaction which are claimed to be confirmed here; Ref [19] studied the same reaction as presented here (using a different eta decay mode which by itself does not warrant a new PRL). The two papers come to opposite conclusions what regards the existence of an exotic resonance. A third paper would be acceptable if it would clarify the situation. This goal is however not reached. The mass of the exotic meson in this paper is close to that in [19], the width shows a ~2 sigma difference, hence nearly compatibility. Statistically, the exotic mesons observed here and in ref [12] are more distinct. The authors claim however to confirm their own paper [12]. The reason is of course that they like the interpretation of [12] and not that given in [19]. However, the difference (in chi^2) to [19] is smaller than that to [12]. Hence the conclusions are not well founded. In reading [12] and [19], ref [19] gives much more detailed information. Of course, the latter paper is a full publication but it is reassuring to see non-exotic mesons like a0 and a2 to be reproduced well in [19]; the studies of leakage is presented in a detailed way. The reader would certainly like to compare amplitudes and assumptions which go into the two different analyses and to understand the roots of the different claims. A few specific requests for a manuscript for PR D: 1st page: [13] is superior to [14], and mass and width should be quoted from [13]. [15] was withdrawn at a conference if I remember correctly. [17] is GAMS and not VES. VES reported pi eta in 198x, the paper is not quoted. With respect to ref [19] it is said, "the authors chose not to claim...". Would the authors of this paper like a statement: "the authors chose to claim"? Last full sentence: are interactions outside of the target a problem? 2nd page: The mass cut selects well measured eta and rejects eta with larger errors. Do 'good' eta select a special kinematics? Or is at least the eta width well reproduced by the MC simulation? (Fig. 1) 4th page: A comment is needed concerning the measured eta mass. If the wrong mass is due to a momentum measurement error, mass errors will be large in the 1400 MeV region. 6th page: A value of about 70% is expected ... (why? give ref.) Is that ratio independent of the mass? 7th page: The fit is done to the average of eight solutions. If I am malicious, may I choose the smallest amplitude in each mass bin, and can I say, that is an allowed solution? Does the error cover all these extremes? Or is there a false argument of mine? Then, it should be stated that such a treatment is not allowed. Some solutions show significant a0(980) production in the P+ wave. Does this indicate a significant leakage problem? Was there an attempt to introduce an a2(1600) or an non-resonant eta-pi background amplitudes due to t channel exchange in the D+ wave? 8th page: Is the leakage assumed to be fully coherent? 9th page: The number given in the first two lines are not from ref [19]. Concerning the discussion, the papers T.~Burns, F.~E.~Close and J.~J.~Dudek, %``Pentaquark implications for exotic mesons,'' Phys.\ Rev.\ D {\bf 71} (2005) 014017 and S.~F.~Tuan, T.~Ferbel and R.~H.~Dalitz, %``COMMENTS ON EVIDENCE FOR A 1-+ EXOTIC MESON,'' Phys.\ Lett.\ B {\bf 213} (1988) 537. should be consulted. Summarizing: The existence or not of exotic resonances is still controversial at pre sent. The results of this paper add to the confusion of the reader. Are there two close-by exotic resonances, both coupling to eta pi, one in addition to rho pi, the other one to Pomeron pi? Does the paper confirm [19] or [12] or is incompatible with both? The reader gains the impression that the analyses are not well enough advanced to lead to definite conclusions. This impression should be avoided. The pro's and con's should be exchanged in public but not in PRL. The discussion requires a certain length, the paper Adams et al can be made a useful contribution if more analysis details are given. Such a paper will exceed the PRL length limit. ---------------------------------------------------------------------- Report of Referee B -- LZ10772/Adams ---------------------------------------------------------------------- Paper LZ10772 provides strong evidence for spin exotic meson(s) near 1400 MeV/ c2 by analyzing a reaction channel complementary to other investigations. The exotic meson field is very active and will continue to be active with upcoming experiments. The results presented herein will contribute to the field, by shaping future experiments and theoretical investigations. The paper is clear and well written, although could be improved with minor revision. It would be beneficial to readers outside of the subtopic to include more discussion as to the role that exotic mesons play in QCD tests. The abstract should have a sentence or two added noting the how the measurement connects to QCD. The first paragraph of the text could also be improved with a sentence or two discussing more clearly why exotic mesons test QCD. ---------------------------------------------------------------------- Report of Referee C -- LZ10772/Adams ---------------------------------------------------------------------- Please see the enclosed PDF attachment. Attachments: LZ10772rptC.pdf - Report of Referee C [89.7kb] Please see the following forms: http://forms.aps.org/author/prorprl.pdf Physical Review or Physical Review Letters? [ Part 2, Application/PDF 117KB. ] [ Not Shown. Use the "V" command to view or save this part. ]