ELFT HÍRADÓ

[Zoltan Mate <mate AT namafia.atomki.hu>]

Az MTA Atommagkutató Intézetének nagy előadójában
(Debrecen, Bem tér 18/c. 12. ép. III. em.)
2010. szeptember 21-én, KEDDEN 11:00-kor


                  A. M. Mukhamedzhanov
   (Cyclotron Institute, Texas A&M University, College Station)
   
    Separation of nuclear reactions and spectroscopic factors   


címmel előadást tart.
Az előadás előtt 10:30-tól tea.
Vendégeket szívesen látunk.
             
                                        Máté Zoltán


Kivonat:
The beginning of the 21-st century opens up a new chapter in nuclear 
physics fueled by new generation of the radioactive beam facilities 
allowing us to approach the nuclei away from the valley of stability. It 
should lead to new discoveries in nuclear structure, nuclear reaction
fields and nuclear astrophysics which is closely related to cosmology.  
The important part of the new programs, as it has been for previous fifty 
years, is determination of spectroscopic factors (SFs) from nuclear 
reactions, which play important role in nuclear physics and nuclear 
astrophysics. Since the dawn of nuclear physics  nuclear reactions,  
(d,p), (3He,d), and later on  (e,e'p) and nucleon knockout reactions 
have been the main tool to determine  SFs. 
The phenomenological  SFs  extracted  by  
normalization of the DWBA cross sections  to the experimental data are 
supposed to be used  as  a test of  many-body  theories.  However,  the  
parameterization of the DWBA reaction amplitude in terms  of the SFs is 
based on the drastic approximations. Nowadays ab initio nuclear many-body 
theories  of light nuclei  are available. What should we expect  when  ab 
initio many-body  theory in continuum, at least for light nuclei,  will be 
delivered?    An  exact many-body theory will allow us to calculate 
nuclear reactions based on the adopted NN and many-body nuclear 
potentials. But NN potentials are not observable and there are infinite 
number of the phase-equivalent NN potentials related via finite-range 
unitary transformations.  These unitary transformations are introduced to 
soften the hard-core NN potentials to pave the way for perturbation 
approach in many-body theory.  
       I show that  the asymptotic normalization coefficients, which are 
the amplitudes of the asymptotic tails of the overlap functions are 
invariant under finite-range unitary transformations but SFs are not. The 
main goal of this talk is  to show  that the amplitudes for the (d, p), 
(d, pn) and (e, e'p) reactions determining the asymptotic behavior of the 
exact scattering wave functions in the corresponding channels, in contrast 
to SFs, are invariant under finite-range unitary transformations.  
Moreover, the exact reaction amplitudes are not parameterized in terms of 
the SFs  and, hence,  nuclear reactions in the exact approach cannot 
provide a tool to determine SFs which are not observable. This separation 
of nuclear reaction theory and SFs will require reshaping of the future 
programs of existing and coming up radioactive beam facilities.