Chung, Suh Urk

Dahl, Orin I

Hardy, Lyndon M

Hess, Richard I

Kirz, Janos

Miller, Donald H

English

eScholarship - University of California

Lawrence Berkeley National LaboratoryLBL PublicationsTitleFurther Evidence for a Kp Resonance Near 1400 MeVPermalinkhttps://escholarship.org/uc/item/7xd1c359AuthorsHardy, Lyndon MChung, Suh UrkDahl, Orin Iet al.Publication Date1965-02-01Copyright InformationThis work is made available under the terms of a Creative Commons Attribution License, available at https://creativecommons.org/licenses/by/4.0/eScholarship.org Powered by the California Digital LibraryUniversity of Californiar 0 UCRl..-11898 Rev. University of California Ernest 0. Radiation lawrence Laboratory FURTHER EVIDENCE FOR A Krr RESONANCE NEAR 1400 MeV TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Division, Ext. 5545 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 warranty, 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. ~~ Submitted to Physical Review Letters ... UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory Berkeley, California AEC Contract No. W -7405 -eng -48 UCRL-11898 Rev. ·FURTHER EVIDENCE' FOR A Krr RESONANCE NEAR 1400 MeV Lyndon M. Hardy, Suh Urk Chung, Orin I. Dahl, Richard I. Hess, Janos Kirz, and Donald H. Miller February 15, 1965 UCRL-11898 Rev. Further Evidence for a. Krr Resonance Near 1400. MeV* . Lyndon M. Hardy, Suh Urk Chung, Orin I. Da:q.l. · Richard I. Hess, Janos Kirz, and Donald H. Miller Department of Physics and Lawrence Radiation Laboratory University of California, Berkeley, California :February 15, 1965 The recent discovery of the 0- hyperon 1 has provided a firm basis . for the assumption .that strong interactions are dominated by some higher symmetry such as SU(3), so that particle states with the same spin..,parity. will comprise the elements of unitary multiplets. 2 • 3 During the past year, compelling evidence has been presented for the existence of an S = 0, I= 1, JPG = 2+- meson (A2) with mass M z 1.310 MeV. 4 - 6 Consequently, we may:: anticipate the existence of {at least) an octet of Jp = 2+ mesons which, m SU{3), will satisfy an approximate mass formula of the type 2 . ' . . p . The only other established J = 2+ meson is the f 0{S = 0; I= 0} with -9 ' M ~ 1260 MeV. 7, · I£ we consider the f0 as a member of the Jp = 2+ octet, Eq. {1} implies the existence of a state with M(S = ± 1.; I= 1/2) af:'.f275 MeV; thus far no Krr state has been reported at this mass. However, in a study of K- + p- K0 + rr- + p at 3.5 BeV/c, Haque et al. 10 have found clear evidence for a K1T state with M = 1400 ± 10 MeV and r- 160 MeV. A spin analysis indicates that Jp = 2+ is favored by two standard deviations over Jp = 1-; no determination of I-spin was po~sible. In the present Letter we report the observation of this state in 1T- + p interactions and discuss ad-ditional evidence £.or the IJP assignment. In an investigation of rr -p interactions at 3. 9 and 4.2 BeY/ c, we have used the final states summarized in Table I to search for decay of S = +1 · -2- UCRL-11898 Rev. I . bosons in the mass interval 1.0 to 1.5 BeY. The Krr effective-mass distri-butions are shown in Fig. 1. For an I = 1/2.:::K~c {K 0 rr 0 jK+rr~~~ is 1/2; since neutral K 0 decays lead to unanalyzable events, any K*(I = 1/2) peak in A rr°K 0 will be suppressed about 6 relative to A rr-K+. Consequently, we have grouped together only the two most favorable channels, A rr-K+ .and ~0 tr-K+. These final states are especially suited for study of K*• s since the M(Yrr) distri-butions show little enhancement due to formation of negatively charged y*• s. 11 Where production through exchange of I = 1/2 systems is allowed, we observe strong peaks corresponding to K*(890). In addition, the M(n-K+). distribution shows a marked enhancement centered around 1430 MeV. An ac-cumulation of 68 events occurs in an interval (1350 to 1510 MeV} where 32 to 36 were expected; the probability that this represents a statistical fluctuation is less then 10- 5 . 12 The low-momentum-transfer events, tl.2y< 1 {BeV/c}2 , are shown separately in Fig. 1a. Almost aU K*{890) events are preserved by . * this selection criterion, as would be expected for production through K or .K exchange. It is apparent that most events contributing to the KiT enhancement at 1430 MeV correspond to a similar :tl.2 y distribution. Since the background I outside these regions is almost uniform in tl.2 Y' this provides independent evidence for the hypothesis that the peak represents the decay of a new S = +1 state. The assignment I = 1/2, for K*{1430) is strongly suggested by the lack of corresponding enhancements in other final states. A n°K 0 /A rr-K+ is 2/3; 13 for all events with tl.2 y. < 1 . ~ For an I= 3/2 K~C, {BeV/c)2 in the mass interval 1430 ± 80 MeV, the experimental ratio is 3/18. For production of such a state through K or K* exchange, -~+ rr-K 0 /I- 0 rr-K+ is 27/1; 13 we observe 5/15. -3- UCRL.;..11898 Rev. ·, In principle, the spin may be deduced from decay angular correlations. ,,,i. These are most conveniently studied in the Krr center of qo.ai,ss. In this frame l .• "': we choose a coordinate system,. with the z -axis along the direction of the incident pion momentum, .E.o, and the. y-axis alo~g the production: normal, :r.; the relative momentum of the final K1T system for.£.= {p, e, <j>). Correlations for. the lowest Jp states are given in Table II; 14 the data are plotted in Fig. 2 for events in both K* peaks with 1:::.2 y < 1 {BeV I c)2 . The angular correlations for K*(890) are similar to those reported by Smith et al., for 2:: 0 1T-K+ at lower momenta, 15 where approximately equal production occurs through K * . (scalar) and K (vector) exchange. Although in strong disagreement with Jp = o+, or with any simple >:C K {vector) -exchange mechanism for production of a higher spin state, the ob-served correlations for K*{1430) are consistent with those expected for decay of either a Jp = 1- or ~+ state produced primarily through K exchange. Since the alignmentof K*(1430) may be modified by absorptive effects and {or) contributions from exchange of higher spin objects, we have fitted the cose distributions to g 1 =a.+ b cos2 e and g2 =a+ b cos4 e {the data require no 2 I . cos 0 term in g 2). Within the limited statistics, acceptable fits to both are possible; the ratio of likelihood functions is L{g2 )l.ii(g_1) = 4.6. In conclusion, the existence of an unstable S = +1, I= 112 meson with M- 1430±20 MeV and full width r = 100:1:20 MeV appeai..S reasonably estab-lished from a study of the K1T effective-mass distributions observed in 1T-p interactions at 3. 9 to 4.2 BeV I c. Within statistics, the mass and width of this state are consistent with the values reported by H<!que~:et;al~O Although h · JP 2+ · 1· h 1 · £ d JP 1- · d d t t e ass1gnment · = 1s s 1g t y pre erre '· = prov1 es an a equa e fit to the present data. If we assume that the then when considered as members of an octet, f0 ·represents a unitary singlet, >'.c the K {1430) and A 2 states -4- UCRL-11898 Rev. imply an S = 0, I= 0 state at M- 1470 MeV; soine shift to hi&ther mass may ;:.~~ result from mixing with the f0:: 2 We are indebted to Werner Koellner for his extensive support in the· reduction of the data, as well a~ to Edward Hoedemaker for supervision of. the scanning and measuring efforts. The film was exposed in a beam designed collaboratively between the Goldhaber-Trilling and Alvarez groups. We thank especially Drs. John A. Kadyk, George H. Trilling, and Joseph J. Murray for their numerous contributions. It is a pleasure to acknowledge the support and encouragement of Professor Luis Alvarez throughout.!the course of this. experiment. .~~· c -5- UCRL-11898 Rev. .FOOTNOTES AND REFERENCES *work supported by the U. S. Atomic Energy Commission, 1. V. E.· Barnes et al. {Brookhaven-Syracuse Collaboration), Phys. Rev. Letters g, 204 (1964). 2. M. Gell-Mann, California Institute of Technology Synchrotron Laboratory Report GTSL-20, .1961 and Phys. Rev. 125, 1067 {1962). 3. Y. Ne'emen, Nuclear Phys. 26, 222 {1961). 4·. G. Goldhaber, J. L. Brown, S. Goldhaber, J. A~ Kf-dyk, B. C. Shen, and G. H. Trilling, Phys. Rev. Letters 12, 336 (1964). - .f. 5. S. · U; Chung, 0. I. Dahl, L. M. Hardy, R. I. Hess, G. R. Kalbfleisch, J, K.irz, D .. H. Miller, and G. A. Smith, Phys. Rev. Letters 12, 621 (1964). 6. Aachen-Berlin-Birmingham-Bonn-Hamburg-London-Munchen Collaboration, Phys. Letters 10, 226 (1964}. 7. W. Selove, V. Hagopian, H. Brody, A. Baker, and E. Leb'oy, Phys. Rev. Letters 2_, 272 .(1962}. 8. Y. Y. Lee,: B. P. Roe, D. Sinclair, and J. C. Vander Velde, Phys. Rev. Letters g, 342 (1964). 9. N. Gelfand, G. Lutjens, M. Nussbaum, J. Steinberger, H. 0. Cohn, W. M. Bugg, and G. T. Condo; Phys. Rev. Letters g, 567 (1964). 10. Haque et al., British Collaboration Group {Univ. of Birmingham; Univ. of Glasgow; Imperial College, London; Uni.v. of Oxford; and Rutherford High Energy Laboratory), Rutherford High Energy Laboratory preprint RPP/H/3,. to be published. -6- UCRL-11898 Rev .. 11. L. M. Hardy, S. U. Chung, 0. I. Dahl, R. I. Hess, J.1 Kirz, and D. H. Miller, Lawrence Radiation Laboratory Report i"t{CRL-11442, July 1964, presented at the International Conference qn High Energy 1 Physics, Dubna, USSR, 1964. 12. No account has been taken of the number of histograms examined or number of intervals in which a fluctuation might occur; the proper technique for doing this has been much debated. We believe it more important at this point to determine whether similar enhancements are · produced in other experiments where they might be flXpected. ¥-13. These ratios indude the detection efficiencies for the final states involved. 14. K. Gottfried and J. D. Jackson, Nuovo Cimento E• 309 { 1964) and Phys. Letters ~~ 144 (1964). have pointed out that these correlations may be significantly modified by absorptive effects in the initial and final states. Because of limited experimental data, we neglect these effects. 15. G. A. Smith, J. Schwartz, D. H. Miller, G. R. Kalbfleisch, R. W. Huff, 0. I. Dahl, and G. Alexander, Phys. Rev. Letters~~ 138 {1963). -7- UCRL-11898 Rev. Table I. Events used in the present analysis. Combined data at 3. 9 and 4.2 BeV /c. Number of Final state fitted events ~+rr-K0 78 1::: rr+K 0 146 ~;-TTOKt 95 !: 0 rr -K+ 160 . Atr°K 0 61 Atr_Kt 191 Table II. j Jp o+ 1 2+ 2sa -8- UCRL-11898 Rev. Expected correlations for the final Krr system of spin-parity Jp; cosO = Po. p, and cos a. = n . p, where these 'vecto~s are defined · in the text. }~i K(scalar) exchange r * . K {vector) exchange 1 1 2 cos e 2 sin a. . 2 ( sin e ita cos2<j>) . 2 I 2 (cos e -1 3) 3/8 sin 4a. -1/3 sin 2a.+1/9 sin2ecos 2e(1ta cos2<j>) 4 . 4 cos e sln a. "f., (·~t,~ a Jp =: 2+ with.sufficient coherent s wave to produce a ze1p·~ at cose = 0. ,:\ ~; :1,:,,_:. Fig. 1. Fig. 2. -9- UCRL-11898 Rev. FIGURE LEGENDS Ef£ecti ve -mass distributions for K'TI' systems from Y1rK .. ,> .. final states. Decay angular correlations for events with b..2 < 1 y {BeV / c)2. The M{'TI'_K+) interval 1430±60 MeV is shown in a, c, and e; the interval 890 :I: 80 MeV in b, d, and£. Because of limited statistics, all distributions are folded; <P is the Treiman- Yang angle, cos a. ::: n . p, and cose = p . p, where these quantities 0 are defined in the text. > Q) ~ 0 '\t .... Q) a. (/) .._. c: Q) > w 75 58} 5 1000 A.,.- K+ l;o.,.-K+ -10- UCRL-11898 Rev. 5 351 events 2 !;!! /::,. ~ < 1.0 ( BeV/ c) O 1---l----+----+__I_L--+...L.L.--+_L.I--+-L-l-+-l 10 5 MeV 0 1--'-~f-----+----+--+::;;:---.--+---L--+---l Dl;-.,.°K+ E:Jl;-.,.+KO 15 241 events 1400 1000 1400 1800 M K.,. (MeV) MUB-5094 Fig. 1 1/) +-c: Q) > w -11- UCRL-11898 Rev. OL---~--~~--~~~~--~_.--~--~~--~~--~ 0 30 60 90 0.2 0.6 1.0 0.2 0.6 1.0 ¢ {deg) Cos a Cos 8 MU B-5093 Fig. 2 This report was prepared as an account of Government sponsored work. Neither the United States, nor the Com-mission, 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 pro~ides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. 

Further Evidence for a Kp Resonance Near 1400 MeV

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Further Evidence for a Kp Resonance Near 1400 MeV

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