Measurement of the tensor ( A yy ) and vector ( A y ) analyzing powers in the fragmentation of a 9-GeV/ c deuteron on hy
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EMENTARY PARTICLES AND FIELDS Experiment
Ayy ) and Vector (A Ay ) Analyzing Powers Measurement of the Tensor (A in the Fragmentation of a 9-GeV/c Deuteron on Hydrogen and Carbon Nuclei at High Proton Transverse Momenta L. S. Azhgirey, S. V. Afanasiev, Yu. T. Borzounov, L. B. Golovanov, V. N. Zhmyrov, L. S. Zolin, V. I. Ivanov, А. Yu. Isupov, V. I. Kolesnikov, V. P. Ladygin* , A. G. Litvinenko, S. G. Reznikov, P. А. Rukoyatkin, А. Yu. Semenov, I. A. Semenova, and A. N. Khrenov Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia Received February 16, 2007; in final form, June 20, 2007
Abstract—Data on the tensor and vector analyzing powers (Ayy and Ay , respectively) in the fragmentation of a 9-GeV/c deuteron on hydrogen and carbon nuclei at high proton transverse momenta are presented. These data are compared with the results of relevant calculations performed within light-front dynamics by using various deuteron wave functions. The best description of the data is attained with the relativistic deuteron wave function derived within field-theory light-front dynamics. PACS numbers: 21.45.+v, 24.70.+s, 25.45.-z, 25.10.+s DOI: 10.1134/S1063778808020063
1. INTRODUCTION The spin structure of the deuteron has been investigated over the last decades by using both electromagnetic and hadron probes. The main goal of those investigations at intermediate and high energies was to deduce information about the high-momentum component of the nucleon distribution in order to study manifestations of relativistic effects and nonnucleon degrees of freedom. Among nuclei, the deuteron stands out because it is the simplest loosely bound system of two nucleons, which are in the 3 S1 and 3 D1 states. The properties of the deuteron, such as the binding energy, the root-mean-square radius, and the electric and magnetic quadrupole moments, have been adequately studied in experiments, and the results are fairly well reproduced by nonrelativistic calculations based on one-boson-exchange nucleon–nucleon potentials. The nonrelativistic deuteron wave function ¨ obtained by solving the Schrodinger equation depends only on the relative momentum of the nucleons, q: Ψ = Ψ(q). Two components of the nonrelativistic deuteron wave function, which represent the S- and D-wave states, are dominant at, respectively, long and short distances between the nucleons. As the energy of the deuteron and its nucleons increases, relativistic effects become ever more important. Since a relativistic boost depends on inter*
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actions (in standard instantaneous-form dynamics), the problem associated with the impossibility of separating the motion of the center of inertia of a bound system from the relative motion of its constituents obviously arises at relativistic energies. The relativistic wave function proves to be dependent both on relative momenta of nucleons, q, and on the total momentum p characterizing the motion of the center of inertia—that is, we have Ψ = Ψ(q, p). Thus, the relativistic wave function is a function
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