Physics Letters B 305 (1993) 5-8 North-Holland PHYSICS LETTERS B nK correlations in relativistic heavy-ion collisions D.J. Dean and S.E. Koonin W.K. Kellogg Radiation Laboratory, 106-38, California Institute ofTechnology, Pasadena, CA 91125, USA Received 12 February 1993; revised manuscript received 8 March 1993 We show that strong and Coulomb final-state interactions induce correlations between n and K mesons emitted with small relative momenta ( ~< 100 MeV/c) from relativistic heavy-ion collisions. Measurements of these correlations, estimated to have a ( 5-10 ) % effect, might further constrain source parameters and/or nK scattering lengths. Strong-interaction correlations <~ 5% are also estimated for n +n - pairs. The correlations between identical particles (pp, nn, nn, KK) produced with nearly equal momenta have become a standard tool for studying the space-time structure of heavy-ion collisions [ 1-6 ]. However, the few studies of such correlations between non-identical particles have been restricted to light nuclear fragments. In view of the large number of mesons produced in ultrarelativistic heavy-ion collisions, we have been prompted to consider what might be learned from nK correlations. The nK correlation function can be written as /dr~drKf~( rn, Pn)fx( rK, PK) I qb( rn, rK; Pn, PK) I2 c(p., p,<) = , ( 1 ) fdrndrKfn(rn, Pn)fK(rK, PK) where f~/K gives the probability of producing a n(K) with momentum P~/K at position r~/K, and • is the wave- function of the two emitted particles. We assume, for simplicity, an instantaneous source, and also that f is momentum independent and of the normalized gaussian form 1 frt/K(r) -- ( Z ~ )'nT~(7~/K'3/2 exp ( - r2/2a2/K) . (2) We also neglect any subsequent interactions of the emitted mesons with the rest of the system. With these assumptions, it is most convenient to cast eq. ( 1 ) in terms of the center of momentum and relative coordinates of the nK system: rnnr~ + mKrK rnKP~ -- mnPx R= , P=p.+pK, r=r.--rK, q= rn~ + m K m n 31- m K where m~= 139.5 MeV and mK= 493.6 MeV are the n and K masses, respectively, and the reduced mass is given by m= m~mK/(m~+ mr). To simplify our estimates, we have assumed here a small total momentum for the pair; the relative momentum scales as ~ 1/an~K, and is also small. Then eq. ( 1 ) becomes 1 f C(q,P)- (2na~aK) 3 dRdrexp[-(½otR2+½flr2+½7R'r)]l~(r,R;q,P)[ 2, (3) where we have defined 0370-2693/93/$ 06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved. 5