Barbaro-Galtieri, Angela

Matison, Maxine

Rittenberg, Alan

Shively, Frank T.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitleSEARCH FOR A CHARGED MESON IN THE MASS REGION OF 960 MeVPermalinkhttps://escholarship.org/uc/item/0v84b9v1AuthorsBarbaro-Galtieri, AngelaMatison, MaxineRittenberg, Alanet al.Publication Date1967-12-15eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaUCRL-17914 fa' :L ~ ~ J \",' ,,::,~~ University of California Ernest O. Radiation Lawrence Laboratory SEARCH FOR A CHARGED MESON IN THE MASS REGION OF 960 Me V RESEl' UWREN RAOtATtON L~~ USRAR'{ Angela Barbaro-Galtieri, Maxine Matis on, Alan Rittenberg, and Frank T. Shively Decem.ber 15, 1967 TWO-WEEK LOAN COpy This is a Ubrar!l Circulating Copy which ma!l be borrowed for two weeks. For a personal retention cOP!l, call Tech. Info. Diuision, Ext. 5545 OUGU~FNiE~ ________ --------------------~ Berkeley, California DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warr,anty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. ,I "' ... ../ -. Co) ._< 'c. To be submitted to Physical Review Letters UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory Ber keley, California AEC Contract No. W-7405-eng-48 UCRL-17914 Preprint SEARCH FOR A CHARGED MESON IN THE MASS REGION OF 960 Me V . Angela Barbaro-Galtieri, Maxine Matison, 'Alan Rittenberg, and Frank T. Shively December 15, 1967 l' '1" i i' ,. \ I ! , i. • -1- UCRL-17914 '. '. ..' . . . * SEARCH FOR A CHARGED MESON IN THE MASS REGION OF 960 Me V Angela Barbaro-Galtieri,"Maxine Matison, Alan Rittenberg, and Frank T. Shively t Lawrence Radiation Laboratory University of Ca~ifornia' Berkeley, California December 15, 1967 Evidence has been reported in the past few years for a neutral and a charged meson state in the 960-MeV region. The existence of a neutral meson state (,,') with M ; 958 ± 1 MeV and r :.< 4 MeV was established by several hydrogen bubble chamber experiments. 1 In the reaction K- p - A 11' , the ,,' was found to decay strongly into 1T1TTJ and electromagnetically into 1T1Ty, from which decays its quantum numbers were determined to be IJPG:: 00';"+. Kienzle et al. 2 have reported evidence for a charged meson (0) with a mass of 963 ± 5 MeV and r < 4 MeV in the reaction 1T- p - p(MM) -, with 0 decayi~g into one or three charged particles + possible neutrals. 3 Allison et al. report evidence for the reaction K-p _~±1TOO+ with 0+-1T+1T+1T- at 6.0 GeV/c incident momentum. 4 The coincidence of the mas s and width of the 0 and 11' leads to two possible interpretations: (a) 0 and,,' are the same particle; in this case not only the. isospin, but also the other ,':1 quantum numbers of the ,,' are questioned; (b) [, and 11' are two different particles; this int.erpretation has led to theoretical discussions on mass degene;racy, 5 to, ,a possible assignment of the [, to a 3 PO 6 configuration in the quark-antiquark rn.odel for rn.eson states, and to the conjecture that 6 might be the 0++ daughter trajectory of the p · .,' -2- UCRL-17914 , .' 7 meson. "We report here an experiment which rules out possibility (a) and sets some upper limits on the cross section for production of the o in K-n,- Ao with subsequent decay of the 0 into various states. In this experiment the 72-inch bu~ble chamber, filled with deuterium, was exposed to a K-beamat momenta 2.11 and 2.65 GeV/c. ',' The reaction studied was K-d~ AX- (p ), s (1 ) .. "where X is a negative meson decaying' into two to five pions or pions plus a y; the spectator proton, (p ), was measurable in 30% of the " : S _ events. Excluding the spectator proton from the number of prongs, ,these events were found in the topologies of a V and 1 prong (13000 ! measured events) and of a V and 3 prongs (5000 measured events). The events were measured on Franckenstein and spiral-reader measuring machines, and our standard programs (PKG, DST-EXAM, SUMX) were used for the analysis. 8 If the spectator proton was not visible or was too short to be measured, it was assigned a momentum equal to zero, with appropriate errors in the x, y, and z components, and fitted as if it were measured. 9 For the following analysis, only events having a proton momentum P < 280 MeV /c were used. sp _ If the Ttl were isospin 1, the cross section fo'r K n-ATt I would be twice' as large as that for K-p-ATtIO , and the latter cross section 10 we know at both momenta from our hydrogen data. We proceed to test the isospin-i hypothesis under varying assumptions. (a) We assume, for the moment, that the charged Ttl would appear only in the reactions .: -I I f r i ~ l I I' I ~' , •• 1 o '~J • ('1 -3-, , . - .' - + ,. '. '. ' K n -A'IT 'IT 11' MM, K-n -A1I'- MM , UCRL-17914 (2) (3) where MM consisfs of at least two neutrals. This would be the case if . - - 0 - 0 the only decay modes of '1'\' were 11' 11' '1'\ and 'IT 11' y. Figure 1a shows a plot of the invariant mass squared of the negative system recoiling against the A for these reactions for momentum transfer to the A, A2~0.7 (GeV/c)2. ,Using the effective path, length of this experiment for Reactions (2) and (3); we expect a total of 378 ± 32 events above back-ground in the interval 960 ± 45 MeV. 11 We find no enhancement of statistical significance, and, drawing a smopth background, we conclude 12 -that N 1- < 42 events, or the cross section for K n-A"I -(all A) is , "1 a < 25 JJ.b against an expected 220± 18 !Job. (b) Figure 1b shows the situation if we make the additional as-sumption that the branching ratio for TIl - - 'IT -'ITo '11 is the same as for Ttl ° - 'IT-n + '1'\; from our H2 data, this ratio is found to be 0.42 ± 0.03, independent of any isospin assignment for the' '1'\1. In order to reduce the background under a possible n - 'ITo "1 enhancement, for Reaction (2) we impose the condition that at least one 'IT + n - combination satisfies M (n + n -)~ MTt; for Reaction (3) the '1'\ is neutral and we require that MM ~ Mfl + Mm-0' With these conditions, appropriately adjusted to take errQrs into account, we obtain the plot of Fig. 1 b. The expected 12 number of events is now 158 ± 18, and we find Nfll < 21 events, or the cross section for K-n -Afll - (all A, fl' - - fl'IT-'lT°) is a < 12 JJ.b against 13 an expected 92 ± 11 JJ.b. (c) We have shown thus far that there is no evidence for a charged fll decaying into 11' -11'°11. n - 'ITO y, or any mode involving two or -4- UCRL-17914 more neutrals •. To definitely ·settle the question of the isospin of the ,,', we now investigate all the other possible modes. which would be included in the following reactions: K- n - A1T-1TO (or, V), ,.'." - . - + -K n -.A1T 1T 1T , K-n -A1T - 1T + 1T -1T0 (or y) • (4) ( 5) (6) These modes might be· ~llowed electromagnetically for the ,,·,"'I,.;e.ven:though the:c.orr:.spond.ing modes fOTTl I ° are absent in the H2 data. Figure 2 shows the ?1T, 31T, 41T, n p, n w, and'n-"massdistri-.' '2 butions. ,The shaded histograms refer to low,..6 ~vents , '[ 62 ~O. 7 (GeV jc)2]; the unshaded histograms contain all the events, which we will use l:'lter to set upper limits for production of the o. The Curves on the latter distributions represent fits obtained with the program MURTLEBERT,'14 which takes into account all th~ possible resonant states present in any of the mass combinationS~ The dashed lines drawn on the shaded histograms represent the background esti-mated from the adjacent, bins. Each plot also shows the width which the 111 would have, taken according to our resolution in the different final states. The six low-62 plots .show no statistically significant en-hancement in the 960-MeV region. ~y the analysis of Figs. 1 and 2 it is clear that there is no evi-dence at all for production of the 111 -, which should appear in the distri-butions with a total of N = 378 ±32 events above backg-round. Since even the possibility of decays other than nn" and nny for a charged 111 is ex-cluded, we conclude that the isospin of the 111 is definitely I = O. ! t I t 1 /' \ .. ".; . J ~, -5- UCRL-17914 We now 'turn to the 6. There is no evidence in our data for pro-duction of any mesonresonance'in the 960-MeV region for the reaction K-n - AX,-. With the isospin of the ,,' established. we may take the upper limits for, a signal in this region as being those for production of the o. Table I summarizes these limits for the nine processes con-, ' ' 2 . sidered in this paper, for all events and for low A • We wish to thank the 72-inch bubble chamber crew, our scanning and measuring group, and the spiral reader programmers in addition to the other physicists associated with the early part of this experiment • • We are especially grateful to Dr. Frank Solmitz for discussions in many phases of the analysis. Finally, we gratefully acknowledge the con-tinued support and encouragement of Professor Luis W.' Alvarez • / -6- UCRL-17914 Footnotes and References' *Work done under auspices of the U. S. Atomic Energy Commission. , t Present address: Facultes de S~iences, Institute 'de Physique Nuc1eaire, Paris 5, France. _ 1. A complete list of references can be founei in A. H. Rosenfeld, N. Barash-Schrnidt, A. Barbaro-Galtieri, W. J. Podolsky, L. R. 'Price, P. S6ding, C. G. Wohl, .••• r • M. Roos, and W. J. Willis, UCRL-8030, Sept. 1967 (unpublished)., ' . . Z.·W. Kienzle, B. C. Maglic!, B. Levrat, F. Lefebvres, D. Freystag, ~nd H. R. Blieden, Phys. Letters 19, 438 (1965). 3. ' Evidence for a positively charged 6 has been reported in another missing-mass spectrometer experiment in the reaction pp - d6 + by J. Oostens, P. Chavanon, M. Crozon, and J. Tocqueville, Phys. Letters ZZ, 708 (1966). However, the same experiment was repeated at the same incident energy and. '+ • the evidence for the 6 has now disappeared; see M. Banner, J. Cheze, J. L. Hamel,G. Marel, J~ Teiger, J. Zsembery, P~ Chavanon,. M. Crozon, and L. K. Rangan, Phys. Letters Z5B, 569 (1967).' 4. W. W. M. Allison, A. Cruz, W. Schrankel, M. M. Hague, S; K. Tuli, P. J. Finney, C. M. Fisher, J.' D. Gordon, R. M. Turnbull, R. Erskine, K. Sisterson, K. Paler, P. Chaudhuri, A. Eskreys, and S. J. Goldsack, Phys. Letters Z5B, 619 (1967). ... : , .. .. ' .. ' :; ,',. '.' ~. f' " 'it' i " i r F ,; i-, I~ '1 -7- UCRL-17914 5. S. F •. Tuan and Tai Tsan Wu, Phys. Rev. Letters i~ 349 (1967) • • These authors suggest that the '11 ahd:'the & might be members of a new pseudoscalar' octet along with an as -yet-undetected * K atM~ 960 MeV. In this case the main decay modes for the o should be p1T and 31T. 6. ". R. H. Dalitz, in Proceedings of the XIII International COz:lJerence on ..... High-Energy Physics at Berkeley (University of California Press, 1967; Berkeley), page 213. The quantum numbers for the 0 would be J PG = 0 + - in thi seas e, and 0 - TpT would be the favored decay mode. ,7. D. Freedman, in Symposium on Regge Poles, Argonne National _J;A.boratory, December 1966, page 108. Note that the G parity in this case is positive, whereas it is negative in the quark model; & - 41T would be the main decay mode. 8 •. All ambiguous events were checked on the scanning table in an attempt to resolve the ambiguity. For about 3% of the events it was not possible to distinguish between two' possible fits, and in this case the one with the larger confidence level was accepted. 9. For the events with a four-constraint (4-c) fit, the fitted spectator proton momentum distribution is in agreement with the one ex-p~cted from the impulse approximation, and the mass resolution is not affected by this procedure. However, for the (i-c) fits, the momentum distribution is shifted toward zero, resulting in . a mass resolution of the order of 30 MeV, full width at half maxi-mum, as calculated from the width of the 11 and w peaks. Finally for the (O-c) final states the resolution is ~ 45 MeV (calculated again from the '1 and w peaks, when the (i-c) events are treated as (O-cp. [ f I I t l , ! I' I t ! I r ! I I (: f ! l l I I I f ! r ! ! ~ I -8- VCRL-17914 10. The cross' sections for the reactionK-p _AT\I, for visible A decay, '" . at 2.11 and 2.65 GeV/C are 89:1:8 tJ.b and 57:1:4 f.1b for momentum '2' 2 transfer squared f::l. " ~ 0;5 (GeV /c) . In what follows we take a f::l.2 cutoff at 0.7 (GeV/c}2 in order to take into account the poor ,resolution.for (O-c) fits." 11. The effective path length calculation takes into account the scanning and measuring efficiency, as well as the correction for short A cutoff, the cutoff on the spectator momentum, and the Glauber , correction for the screening of the neutron in the deuterium nucleus. The path lengths are ).., = (1.35:1:0.10) events/I-lb and '(1.21:1: 0.10) events/I-lb at 2.11 and 2.65 GeV / c respectively. For Table I we wj1l use a larger sample of data in Reaction (2). ,12. This and all subsequent limits are determined by calculating the number of events (N3f::l.) above background (Nb), which would re-quire a three -standard-deviation downward fluctuation to produce no signal (N3f::l. = 3 (Nb + N3f::l.) 1/2). These limits are thus at the 990/0 confidence level. 13. A previous similar experiment by H. J. Martin, R. R. Crittenden, , ' and L.S. Schroeder, Phys. Letters 22,' 352 (1966), has reported (5:1: 4) events seen where (19:1: 6) events were expected. At the Heidelberg Conference on Elementary Particles (Sept. 1967) the Amsterdam-Bologna-Paris-Rehovoth-Saclay Collaboration , . (Abstract 131) reported results similar to ours. -( 14. J. Friedman, MUR TLEBER T, Alvarez Programming Group Note P-156, 1966. ( J " I· I \ I I I ! -9- UCRL-17914 .' ... Figure Captions - - + -Fig~ 1 •. Mass-squared distribution of the 11'MM and 11' 11' 11' MM systems in Reactions (2) and (3). Only events with sma.ll rn.omentum trans-fer to the A [6.2 ~O.7 (GeV/c)2] are plotted. (a) Search for 1'\' - _11'- MM and 11'-'iT+11'-MM. (b) search for ,,1 - _11'-11'0". The shaded histograms refer to events with three charged pions. The arrows indicate the position of the ,,1 mass and have bars representing twice the resolution of the mass squared. The ex-pected number of Ttl events (Ne) above background for isospin one is given in each hrstogram •. Fig. 2. Search for decay modes of "1' other .than the known decay 'modes of 'Il'o. (a) X- _~-11'0,: ,(b) iX~-11'-11'+11'-i' (~) X- _1T-1T+1T-1TO~ (d) X- - 1T - p,(e) X-.:. Tj- w. (f) X- - 1T -". The position of the .1'\' is indicated by the arrows, with error bars representing twice the resolution for each plot. The events with small . .. .2 2 momentum transfer to the A [6. ~ O. 7(Ge Vic) ] are shown in the shaded histograms . The solid curves represent fits to each mass plot as explained in the text. The dashed lines represent 2 our estimated background for the low-6. plots. 1. 2. 3. 4. 5. 6. 7. 8. 9. Table I. Cross section limits -for' pr~duction of a negative m-e'~o-n 'at 960- MeV~ N a Reaction - - ab ~ K-n - AX-- _1T-1TO +34±16 '. X -X -1T MM +20 - - + - -:4*{4 X -1T1T1T - -X _ 'TT P + 8±11 - - + + '7 X _ 1T 'TT 'TT 'TT ° - - +11±10 X -'TT" X - - -19:1:9 -'TTW - - + -X - 'TT 'TT 'TT MM - 1 X - ~ 'TT-'TT 0 " + 7 -X - 1 charged +54 -X - 3 charged + 2 All events b ~3t::. 44 64 38 27 34 32 30 13 28 71 49 t::.2 ~0.7 (GeV/c)2 c b u N a (!ib) ab N3t::. ---~ .... - . ~ '-'. ' <26, ' +13 32 < 37 +17 42 <16 ' ,0 24 <1.1 - 1 18 <14 + 5 22., _ <'13 + 9 21 .'.' ...• <12 +,4 19 <5 - 2 10 < 16 - 7 21 - <:42 +30 50 < 20 + 3 30 u c (fJ.b) <19 ~ <25 <10 < 8 < 9 < «) < 8-< 4< < 12 < 29 <1Z (a) Nab = number of events seen above background (those values of Nab having an error were obtained from fitting as discussed i~ the text; the remainder were determined by estimating the background). (b) For the definition of N 3t::., see footnote 12. (c) (j = upper limit for the,cross section, ,as ,obtained by combining the 2.11- and 2.65-GeV/c data, and cor-rected for neutral A decay (there is no significant difference between the values for the two momenta taken separately). ~ e;-' ~ ,~ I -.... 0 . c: () ;x1 ,t"' I ..... -.J ..0 ..... -~ N > CI) <.!) .. <:j" 40 o c5 '" (/) C 20 CI) > w .. (0) K-n ~AX- {X-~ 7I"-MM (750) X-~ 7I"-7I"+7I"-M M (42) Ne= 37St 32 + ~ X-:-. 7I"-7I"+7I"-MM (42) ,( • (b) . K-n - A X'- {X';' -71""':71"0"7" (222) X--'71"-71"01: (41 ) ~X-- 7I"-7I"°"7c (41) Ne =15S.±IS " T 01 ·6 ",.,,_~I I.,/ .... n ... ...,."".~,b .....J j) 0.4 o.S 1.2 M2 (X-) (GeV)2 1.6 2.0 Fig. 1. 0.8 1.2 1.6 2 '.' 2 M (71"-71"0"7) (GeV) XBL3712-a1l1l2 I .... . ~ I g !XI t"' I ... -J -.t) ... ~ ."; .. , ... 'N >. (c) QI (!) v 0 0 5 ....... II) -c. QI. > w (e) 50 -12-1.0 M2 K- n -- A .,,-.,,+.,,-.,,0 ( 114 Ell A2 S 0.7 ~)I (380) + 1.0 1.4 1.82 M2 (.,,-.,,+.,,-.,,0) ((GeV) ] K-n -A .,,-,., (576) m A2 s 07 IGeV)1 (193) • c2 1.4 1.8 M2 (,,-,.,) [(GeV)2] UCRL-17914· (b)K-n -A ".-".+".- (1407) I'll A2 S 0.7 IG:~)1(485) 0.6 (d) (f) 50 011WZi~ 0.6 1.0 1.4 ~ 2l"8 M2 (".- ".+.,,-) (GeV) . K-n -A "'-p (591 ) Ell A2 ~ 0.7 2 IG~~) (205) t K- n -+ A "'-'1(495) Ell A2 S 0.7 (Gce~)I( 183 ) T 1.0 1.4 1.8 M2 ("-'1) [(GeV)2] .ILI'.I-I ••• Fig. 2. .. ~) , This report was prepared as an account of Government sponsored work. Neither the United States, nor the Com~ m1SS10n, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, appa-ratus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any infor-mation, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission" includes any employee or contractor of the Com~ mission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. 

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SEARCH FOR A CHARGED MESON IN THE MASS REGION OF 960 MeV

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SEARCH FOR A CHARGED MESON IN THE MASS REGION OF 960 MeV

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