No abstract

Inelastic scattering of 800-MeV protons from 40 Ca, 116 Sn, and 208 Pb shows a broad giant resonance at an excitation energy of 110/'A 1 ' 3 MeV. The angular distributions are consistent only with scalar-isoscalar I =3 transfer. The excitation energy and width of this high-energy octupole giant resonance are in reasonable accord with theory. However, its energy-weighted sum-rule strength (~20%) is only about one half that predicted by randomphase-approximation calculations.

No abstract

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The spin rotation parameter Q has been measured for/>-40 Ca elastic scattering at 497 MeV for 0.01^-t ^ 0.15 (GeV/c) 2 with use of the new high-resolution spectrometer focalplane polarimeter. In conjunction with analyzing power and differential cross section, this measurement uniquely determines the elastic scattering amplitudes up to an arbitrary phase. A parameter-free analysis within the Glauber diffractive approximation with use of N-N phase-shift solutions is presented.PACS numbers: 25.40. Rb, 24.70,+s Up to the present time, />-nucleus elastic scattering experiments at intermediate energies 1 " 3 have been limited to the measurement of three observables; o T , the total cross section (which constrains the scattering amplitude at £ = 0 only), (do/dt) unpoi > the unpolarized differential cross section, and A y , the analyzing power, with very few measurements of the spin rotation parameters. 4 (do/dt)unpoi and A y do not uniquely determine the scattering amplitude F(t) at finite t. For spin-0 targets, another observable is required. The scattering operator for this system can be written as F(t)=f(t)+g(t)G-n f (1) where a is the proton spin operator and n = (k i xkyO/lkfXky | defines the scattering plane, k^ and k f being the incident and scattered projectile momenta, respectively. (Note that some authors include an additional factor of i in the spin-orbit amplitude thereby changing the decomposition of real and imaginary parts.) To obtain a third independent observable, and thus to make it possi-1811 ble to extract the scattering amplitude uniquely, requires a double scattering experiment. We have chosen to measure a particular spin rotation Q as suggested by Glauber and Osland. 5 This observable measures the total spin rotation angle /3 in the plane of scattering through the relation 5 Q^sin/VU-P 2 ] 172 ,where P is the induced polarization. It can also be shown that Q is defined in terms of the Wolf enstein spin rotation observables 6 bywhere £ lab is the laboratory scattering angle. Similarly, because of the symmetries of the system Q=A'sin0 lab -jR'cos# lab .Noticeable in Eq.(3) is that this expression for Q depends only on analyzing the s (transverse horizontal) component of the scattered-proton polarization. Similarly, Q in Eq. (4) depends only on the I (longitudinal) component of the polarization.