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Register a new userMeasurement and application of electron stripping of ultrarelativistic $^{208}textrm{Pb}^{81+}$
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New measurements of the stripping cross-section for ultrarelativistic hydrogen-like lead ions passing through aluminium and silicon have been performed at the Advanced Wakefield experiment at CERN. Agreement with existing measurements and theory has been obtained. Improvements in terms of electron beam quality and ion beam diagnostic capability, as well as further applications of such an electron beam, are discussed.
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We present and discuss numerical predictions for the neutron density distribution of $^{208}$Pb using various non-relativistic and relativistic mean-field models for the nuclear structure. Our results are compared with the very recent pion photoproduction data from Mainz. The parity-violating asymmetry parameter for elastic electron scattering at the kinematics of the PREX experiment at JLab and the neutron skin thickness are compared with the available data. We consider also the dependence between the neutron skin and the parameters of the expansion of the symmetry energy.
Crystals with small thickness along the beam exhibit top performance for steering particle beams through planar channeling. For such crystals, the effect of nuclear dechanneling plays an important role because it affects their efficiency. We addressed the problem through experimental work carried out with 400 GeV/c protons at fixed-target facilities of CERN-SPS. The dependence of efficiency vs. curvature radius has been investigated and compared favourably to the results of modeling. A realistic estimate of the performance of a crystal designed for LHC energy including nuclear dechanneling has been achieved.
We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.
In ultraperipheral collisions (UPC) of nuclei the impact of Lorentz-contracted electromagnetic fields of collision partners leads to their excitations. In case of heavy nuclei the emission of neutrons is a main deexcitation channel and forward neutrons emitted in UPC were detected at the Relativistic Heavy-Ion Collider (RHIC) and at the Large Hadron Collider (LHC) by means of Zero Degree Calorimeters. However, the excitation of low-lying discrete nuclear states is also possible in UPC below the neutron separation energy. In this work by means of the Weizsacker-Williams method the data on nuclear resonance fluorescence (NRF) induced by real photons in 208 Pb are used to model the excitations of discrete levels in colliding nuclei. Due to Lorentz boosts one can expect that deexcitation photons with energies up to 40 GeV and 300 GeV are emitted in very forward direction, respectively, at the LHC and at the Future Circular Collider (FCC-hh). Energy, rapidity and angular distributions of such photons are calculated in the laboratory system, which can be used for monitoring of collider luminosity or triggering particle production in UPC.
The ATLAS detector at the LHC is capable of efficiently separating photons and neutral hadrons based on their shower shapes over a wide range in eta, phi, ET, either in addition to or instead of isolation cuts. This provides ATLAS with a unique strength for direct photon and gamma-jet physics as well as access to the unique capability to measure non-isolated photons from fragmentation or from the medium. We present a first look at the ATLAS direct photon measurement capabilities in Pb+Pb and, for reference, p+p collisions at sqrt(sNN)=5.5 TeV over the region |eta|<2.4.
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