A search for nuclear-bound states of the 77 meson has been carried out. Targets of lithium, carbon, oxygen, and aluminum were placed in a /r"^ beam at 800 MeV/c. A predicted T] bound state in ^^O* {Ex « 540 MeV) with a width of « 9 MeV was not observed. A bound state of a size j of the predicted cross section would have been seen in this experiment at a confidence level of 3CT {P> 0.9987).PACS numbers: 25.80.-e, 21.90.+f, 27.20.+n This Letter describes a search for a novel nuclear excitation involving the creation of a bound r] meson in the nuclear medium. The concept is similar in spirit to a number of ideas which have recently been vigorously pursued. Some familiar examples are A hypernuclear states, Z hypernuclear states, antiprotonic nuclear states, and various dibaryon resonances. In each case an attractive particle-nucleus potential is required together with some mechanism to inhibit the decay process, such as strangeness conservation in the case of the A.Several suggestions of the existence of bound states of the 7] meson in a wide range of nuclei have recently been published. ^"^ The suggestions of this novel nuclear excitation are based on bound-state formation through the attractive N-T] channel of the TV* (1535), where A^*(1535) is the {KN) resonance with (/,/'') = (T, y") and mass 1535 MeV/c^. This resonance dominates 77 production near threshold. Bhalerao and Liu'* have shown, by a coupled-channels analysis, that the lowenergy rfN interaction is attractive with a scattering length of 0.28 + 0.202/ fm. The attractive interaction is a consequence of the threshold being below the A^*(1535) resonance.Liu and his collaborators have examined the consequences of this attractive interaction in the formation of a bound-77 state as a function of mass number. Their study indicates that nuclear bound states could exist for mass numbers larger than A^\Q. At low mass numbers, only 5-state bound r/'s are predicted. At larger mass numbers, p and d states could become bound. Both binding energies and widths increase with A. The optimum case, in their analysis, is \^0, formed from the in^.p) reaction on *^0 at a momentum near 740 MeV/c. ^ At an angle near 15°, the momentum transfer is favorable for the transition involving the conversion of a p-shell neutron to an ^-shell ry. For higher mass numbers, the increase in predicted width would make this excitation more difficult to see over the continuum {K^,p) background which is present.An experiment to test these predictions was devised with the positive pion beam available at the low-energy separated beam I at the Brookhaven alternating-gradient synchrotron (AGS), and the Moby Dick spectrometer. The experimental arrangement is virtually identical with that used for the production and measurement of hypernuclei, and it has been described in detail in a number of publications (see Milner et al.^ and related references). The only differences involve the selection of pions, rather

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We demonstrate that the binding energies ǫ η and widths Γ η of η-mesic nuclei depend strongly on subthreshold η-nucleon interaction. This strong dependence is made evident from comparing three different η-nucleus optical potentials: (1) a microscopic optical potential taking into account the full effects of off-shell ηN interaction; (2) a factorization approximation to the microscopic optical potential where a downward energy shift parameter is introduced to approximate the subthreshold ηN interaction; and (3) an optical potential using on-shell ηN scattering length as the interaction input. Our analysis indicates that the in-medium ηN interaction for bound-state formation is about 30 MeV below the free-space ηN threshold, which causes a substantial reduction of the attractive force between the η and nucleon with respect to that implied by the scattering length. Consequently, the scattering-length approach overpredicts the ǫ η and caution must be exercised when these latter predictions are used as guide in searching for η-nucleus bound states. We also show that final-state-interaction analysis cannot provide an unequivocal determination of the existence of η-nucleus bound state. More direct mea-surements are, therefore, necessary.

Fuzely and Liu Reply: Tomoda's Comment l addresses two issues: (a) effects of the interchange of the electrons, and (b) effects of the recoil related to the nuclear vector current. Our reply and comments are as follows.With the inclusion of the interchange of electrons, the quantity X that defines A^ in our Letter 2 becomes * 4 C" ,-i, P 2 (ki-k 2 In a similar way, the quantity (ki -k^)'VK/v/vCp) will replace V N N in A" of Ref. 2. Further, we have