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Using the solenoidal magnetic detector PLUTO, we have measured the total cross section for e÷e -annihilation into hadrons. Results are presented for center of mass energies between 3.6 and 4.8 GeV, and in the regions of the J/~0(3.1) and ~ (3.7) resonances. We also present results for the 2 prong cross section in the energy range 3.6 to 4.8 GeV.We present measurements of the total cross section for e+e -annihilatign into hadrons at CMS energies between 3.6 and 4.8 GeV, and in the regions of the J/if(3.1) and tk(3.7) resonances. We also present the cross section for the process e+e--~ 2 prongs + unseen neutrals at CMS energies between 3.6 and 4.8 GeV. Data were taken with the magnetic detector PLUTO at the e+e -storage ring DORIS.The total cross section for hadron production through one photon amaihilation (or the ratio R = (Oe+e-_}hadrons)/(Oe+e-__}/~+t~-)) provides fundamental reformation on the structure of hadrons. For example in the quark parton model the quantity R is directly related to the number of charged partons, provided that the CMS energy is large enough. In particular 1 Now at Tate Institute, Bombay, India. 2 On leave from CERN, Geneva, Switzerland. Recently data on R have been published for the CMS energy range 3.84.6 GeV [1]. The data show not only that R is large but also that there is at least one resonacne and most probably more in this energy region. The strong threshold effect seen in the data around 4.0 GeV is widely assumed to be due to the onset of charmed particle production [2].With the present generation of e+e -experiments the accuracy with which the absolute value of R can be measured is limited by systematic errors. The authors of ref.[ 1 ] quote systematic errors of the order of 15% i.e. of the order of one unit in R at the energies in question. In view of the importance of R we consider it essential that the measurements be repeated by a detector with a different trigger system and high detection efficiency (hence a different systematic error). For the present experiment we estimate the systematic 395

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