Nuclear Instruments and Methods in Physics Research A 494 (2002) 68–74 Analysis of errors and estimation of accuracy in the experiment on precise mass measurement of J=c; c 0 mesons and t-lepton on the VEPP-4M collider V.E. Blinov, A.V. Bogomyagkov*, V.A. Kiselev, S.A. Nikitin, I.Ya. Protopopov, K.Yu. Todyshev, G.M. Tumaikin Budker Institute of Nuclear Physics, Acad. Lavrentiev prospect 11, 630090 Novosibirsk, Russia Abstract The goal of this work is an evaluation of utmost precision and analysis of any possible errors and corrections in planned experiment of new mass measurement of J=c and c 0 mesons on VEPP-4M collider with absolute energy calibration by the spin precession frequency measurements. r 2002 Published by Elsevier Science B.V. PACS: 13.65; 29.20 Keywords: Energy calibration; Depolarization technique; Electron positron collisions; Accelerator cyclic 1. Introduction More than 25 years ago, a method of precise particle energy calibration based on spin preces- sion frequency measurements was proposed at BINP [1,2]. Since that time, this method of narrow resonance mass measurements on colliding elec- tron–positron beams has been providing the high- est accuracy [3–7]. The first experiments planned to be accomplished on VEPP-4M collider with detector KEDR will be high-accuracy mass measurements of J=c and c 0 mesons and t-lepton. The first mass measurements of mesons have been done on VEPP-4 with detector OLYA in 1980 [2]. None of the other facilities repeated these experi- ments until the present time. Only in 1993, the mass of J=c meson has been measured on anti- proton beam with a higher accuracy, with usage of our mass measurements of c 0 meson as a reference point [8]. At the present time we have a possibility to repeat those measurements with a higher accuracy. We believe that this experiment will be an important step for t-lepton mass measurement. Questions about accuracy, first of all, come from the existence of the beam energy distribution. During scanning of the resonance, by changing energy of the storage ring, one receives a resonance curve that characterized the number of events registered by the detector with respect to the energy. The width of this curve is equal to the energy spread in the center of the mass reference system. As one can see, the problem of accuracy is *Corresponding author. E-mail address: a.v.bogomyagkov@inp.nsk.su (A.V. Bogomyagkov). 0168-9002/02/$ - see front matter r 2002 Published by Elsevier Science B.V. PII:S0168-9002(02)01447-X