Ferro-Luzzi, M.

Solmitz, Frank T.

Stevenson, M.Lynn.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitleK--p CHARGE EXCHANGE AT 1.22 GeV/cPermalinkhttps://escholarship.org/uc/item/2t59f131AuthorsFerro-Luzzi, M.Solmitz, Frank T.Stevenson, M.Lynn.Publication Date1962-06-06eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaUniversity of California Ernest 0. Radiation lawrence laboratory 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. Dioision, Ext. 5545 Berkeley, California UCRL-10234 %-~ 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. .. . - I • -~----~ l ~~=---"'- -::.-=·:!... ::....· -·- -- .. - . -- -- -. 1 International Conference on High :Energy PhyslCS 1 CERN, July 1962 _J UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory Berkeley, California Contract No. W -7405-eng-48 K- -p CHARGE EXCHANGE AT 1.22 GeV/c I I I UCRL-10234 Massimiliano Ferro-Luzzi, Frank T. Solmitz, and M. Lynn Stevenson June 6, 1962 -1- UCRL-10234 1962 Conference on High Energy Physics, CERN K- -p CHARGE EXCHANGE AT 1.22 GeVIc* Massimiliano Ferro-Luzzi,t Frank T. Solmitz, and M. Lynn Stevenson Lawrence Radiation Laboratory University of California Berkeley, California June 6, '1962 (To be presented by Arthur H. Rosenfeld) The reaction (l) has been studied at an incident K momentum of l. 22 GeV I c (1895 MeV total c. m. energy), using the Lawrence Radiation Laboratory 72-inch hydrogen bubble chamber and a separated K beam. The angular distribution for the reaction in the center of mass shows a prominent backward peaking of the RO. This behavior had been noticed in earlier experiments at lower K incident momenta, starting at about 760 MeV I c 1 and increasing steadily up to 1.22 GeVIc. Preliminary results at 1.53 GeVIc incident momentum (2025 MeV total c. m. energy) indicate the effect to have disappeared or, at any rate, to have lost its spectacular character. The events appear in the chamber as incident tracks that interact in flight without outgoing charged prongs, accompanied by the two-prong decay of a neutral particle. The measurement of the associated decay products -·· '"work done under the auspices of the U.S. Atomic Energy Commission. tNational Academy of Sciences Fellow. 1Private communication from the Alvarez 15-inch bubble chamber group Berkeley); W. Graziano and S. G. Wojcicki, (to be published in Phys. Rev.). (Lawrence Radiation Laboratory, K- -p Interactions at 1.15 GeVIc -2- UCRL-10234 usually suffices to identify the decaying particle as K> or A. Cases of am-biguous kinematical fit are solved in general by ionization estimates on the positive track; a x2 criterion was imposed on the decay configuration such that only::::: 1 o/o of a pure sample of K~-+ rr + + rr would fail to satisfy it. Figure 1 shows the spectrum for the total mass of the neutrals recoiling against the K>. The separation of reaction 1 from the inelastic charge-exchange events is quite unambiguous. In order to correct for scan-ning biases, a cutoff was applied to the length of the K 0 in. the chamber: the projected length of the K 0 was required to be greater than 5 mm in space before accepting the event. Afterward, a correction was applied to compen-sate for this loss. Figure 2 shows the angular distribution in the center of mass of reaction 1. The values on the ordinate are based on a total K- +p -+ K 0 + n cross section of 2.3 ± 0.1 mb. An expansion in powers of case requires the 6 presence of at least (cos e) . The values of the coefficients giving a satis-factory fit are shown in Table I. The features of the angular distribution for the same reaction at 1.53-GeV/c K- incident momentum (2025-MeV total c.m. energy) are shown in p::. eliminary form in Fig. 3. Here the backward peak appears to be drasti-cally reduced. Further work is in progress. -3- UCRL-10234 Table I. Coefficients of (cos 8)n in the angular distribution for reaction 1. a n . (mb/sr) 0 0.06± 0.01 1 -0.34± 0.05 2 o. 79 ± 0. 17 3 1.95± 0.21 4 -2. 17 ± 0,55 5 -1.99± 0.21 6 2.01 ± 0.44 -4- UCRL-10234 FIGURE CAPTIONS Fig. 1. Mass spectrum of the neutrals in the reaction K- + p-+K? +neutrals at 1.22 GeV/c incident K- momentum (1895 MeV c. m. energy) for 916 events. The peak at the neutron mass corresponds to the events of re-action 1. Fig. 2. Angular distribution in the center of mass of the reaction K- + p-+ K 0 + n ·at 1.22-GeV/c incident K- momentum (1895-MeV c. m. energy). The dashed histogram represents the angular distribution of the events for which the projected length of the R? was greater than 5 mm (500 events). The curve is a fit to the data up to the 6th power of case. Fig. 3. Angular distribution in the center of mass of the reaction K- + p-+ R.O + n at 1.51-GeV/c incident K- momentum (2025-MeV c.m. energy) for 217 events. The data are uncorrected for scanning biases. -5-120 K- + p- K0 + neutrals :a; (.!) Q 0 PI<= 1.22 GeV/c Ec.m.= 1.895 GeV '-Q) 0. (/) ·-c Q) 60 > Q) -0 ~ Q) ..0 E ::s z Mass of the neutrals (GeV) MUB-1106 Fig. I -6-1.0 80 0.9 0.8 K -+p- j(O + a. n 0.7 If) 60 q -c::: PK-= 1.22 GeV/c, Ec.m.= 1.895 GeV ' (J) 0.6 a. > ::::> (J) -- I 0.5 3 0 I 40 I o-.... I ' I (J) I 0.4 If) ..0 I ~ I E I I ::J L z 20 MU·26917 Fig. 2 • en -c: Q) > Q) -0 ~ Q) ..0 E ~ z 30 -7-Pk = 1.51 GeV/c, E c.m.= 2.025 GeV K-+ p -K0 + n +0.5 + 1.0 MU-26918 Fig. 3 

K--p CHARGE EXCHANGE AT 1.22 GeV/c

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