ABSTRACT
Evidence is reported for the existence of a parity doublet of Delta resonances with total angular momentum J=3/2 from photoproduction of the ppi;{0}eta final state. The two parity partners Delta(1920)P33 and Delta(1940)D33 make significant contributions to the reaction. Cascades of resonances into Delta(1232)eta, N(1535)pi, and Na0(980) are clearly observed.
ABSTRACT
Single pi(0) photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of approximately 98% of 4pi. Differential cross sections dsigma/dOmega have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gammap-->N(*)(Delta(*))-->ppi(0). A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15.
ABSTRACT
Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel.
ABSTRACT
Accurate treatment planning for therapeutic beams of negative pions requires knowledge of the multiple scattering of pions in biologically relevant materials. Complete spatial and angular scattering distributions have been measured for pions in scatterers of carbon, water and calcium. Measurements were made for targets varying in thickness from 0.5 to 21 g cm-2 and for pions with ranges of approximately 12 and 20 g cm-2. An array of scintillators, multiwire drift and multiwire proportional chambers was used to record the scattering of individual particles. These data are compared with the results of Molière scattering theory. The implications for pion treatment planning are discussed.
Subject(s)
Elementary Particles , Radiotherapy/methods , Humans , Mathematics , Radiotherapy/instrumentation , Scattering, RadiationABSTRACT
The present paper demonstrates that neutron-photon pairs from radiative capture of stopped pions on chemically bound protons can be used to measure the range of negative pions within phantoms or a patient. Experimental results are given for a polyethylene and a water target of realistic size as well as for a Rando phantom. Monte-Carlo calculations were carried out in order to study the influence of various sizes of treatment volumes, detector geometries and neutron scattering within the targets upon the accuracy of the pion range determination. The results reveal clearly that a pion range monitor for the control of therapy plans and for actual patient irradiations can be designed according to the proposed principle. The absorbed dose required for a measurement is of the order of 0.1 Gy for a single pion beam if one aims at an accuracy of range determination of a few millimeters.
Subject(s)
Radiotherapy, High-Energy/instrumentation , Elementary ParticlesABSTRACT
A technique suitable for mapping pi+/- stopping density distributions in patients or phantoms is described. As a position sensitive detector a multiwire proportional chamber with a slit or a hole collimator in front was applied. Results using a water and a Rando phantom are presented for various momenta and momentum band widths of the pi+/- beam. To our knowledge the two-dimensional visualization of a pi- stopping density distribution was realized for the first time.
