We study mutual dissociation of heavy nuclei in peripheral collisions at ultrarelativistic energies. Earlier this process was proposed for beam luminosity monitoring via simultaneous registration of forward and backward neutrons in zero degree calorimeters at the Relativistic Heavy Ion Collider ͑RHIC͒ at Brookhaven National Laboratory. Electromagnetic dissociation of heavy ions is considered in the framework of the Weizsäcker-Williams method and simulated by the RELDIS code. Photoneutron cross sections measured in different experiments and calculated by the GNASH code are used as input for the calculations of dissociation cross sections. The difference in results obtained with different inputs provides a realistic estimation for the systematic uncertainty of the luminosity monitoring method. Contributions to simultaneous neutron emission due to grazing nuclear interactions is calculated within the abrasion model. A good description of the CERN SPS experimental data on Au and Pb dissociation gives confidence in the predictive power of the model for AuAu and PbPb collisions at the RHIC and the Large Hadron Collider at CERN.
We study the simultaneous dissociation of heavy ultrarelativistic nuclei followed by the forward-backward neutron emission in peripheral collisions at colliders. The main contribution to this particular heavy-ion dissociation process, which can be used as a beam luminosity monitor, is expected to be due to the electromagnetic interaction. The Weizsäcker-Williams method is extended to the case of simultaneous excitation of collision partners which is simulated by the RELDIS code. A contribution to the dissociation cross section due to grazing nuclear interactions is estimated within the abrasion model and found to be relatively small.
A finite temperature extension of the interacting boson model is developed and applied to the calculation of the collective partition function of transitional even-even Sm isotopes. The effective boson number decreases with increasing temperature, leading to a natural damping of collectivity. Positive and negative parity contributions to the boson partition function are computed and compared to rotational and vibrational enhancement factors commonly used in the generalized superftuid model.
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