New limits on β+EC and ECEC processes in 74Se have been obtained using a 600 cm3 HPGe detector and an external source consisting of 1600 g of a natural selenium powder. For different β+EC and ECEC transitions (to the ground and excited states) obtained limits are on the level ∼(0.2−4.8)×1019 yr at 90\% C.L. In particular, for the potentially resonant transition into the 1204.2 keV excited state of 74Ge a lower half-life limit of 1.1×1019 yr at 90\% C.L. has been obtained. Possibility to increase the sensitivity of such measurements is discussed.
Gamma-ray production cross section excitation functions have been measured for 30, 42, 54 and 66 MeV proton beams accelerated onto targets of astrophysical interest, natC, C + O (Mylar), natMg, natSi and 56Fe, at the Sector Separated Cyclotron (SSC) of iThemba LABS (near Cape Town, South Africa). The AFRODITE array equipped with 8 Compton suppressed HPGe clover detectors was used to record γ-ray data. For known, intense γ-ray lines the previously reported experimental data measured up to Ep≃25 MeV at the Washington and Orsay tandem accelerators were extended to higher proton energies. Our experimental data for the last 3 targets are reported here and discussed with respect to previous data and the Murphy \textit{et al.} compilation [ApJS 183, 142 (2009)], as well as to predictions of the nuclear reaction code TALYS. The overall agreement between theory and experiment obtained in first-approach calculations using default input parameters of TALYS has been appreciably improved by using modified optical model potential (OMP), deformation, and level density parameters. The OMP parameters have been extracted from theoretical fits to available experimental elastic/inelastic nucleon scattering angular distribution data by means of the coupled-channels reaction code OPTMAN. Experimental data for several new γ-ray lines are also reported and discussed. The astrophysical implications of our results are emphasised.
We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential number correlation functions, R2(Δη,Δφ), and transverse momentum correlation functions, P2(Δη,Δφ) of charged particles produced in \PbPb\ collisions at the LHC centre-of-mass energy sNN= 2.76 TeV with the UrQMD, AMPT and EPOS models. Model predictions for R2 and P2 correlation functions are presented for inclusive charged hadrons (h±) in selected transverse momentum ranges and with full azimuthal coverage in the pseudorapidity range ∣η∣<1.0. We compare these predictions for the strength, shape, and particularly the width of the correlation functions with recent measurements of these observables by the ALICE collaboration. Our analysis indicate that comparative studies of R2 and P2 correlation functions provide valuable insight towards the understanding of particle production in Pb--Pb collisions. We find, in particular, that these models have quantitatively different predictions for these three observables but none reproduce the measured correlation functions reported by the ALICE collaboration. Accounting for quantum number conservation in models, particularly charge conservation, is mandatory to reproduce the detailed measurements of number and transverse momentum correlation functions.
The aim of this work is to develop the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) theory based on the point-coupling density functionals and extend it to provide a unified description for all even-even nuclei in the nuclear chart by overcoming all possible challenges. The nuclear superfluidity is considered via Bogoliubov transformation. Densities and potentials are expanded in terms of Legendre polynomials to include the axial deformation degrees of freedom. Sophisticated relativistic Hartree-Bogoliubov equations in coordinate space are solved in the DiracWoods-Saxon basis to consider the continuum effects. Numerical checks are performed from light nuclei to heavy nuclei. The techniques to construct the DRHBc mass table for even-even nuclei are explored. The DRHBc theory is extended to study heavier nuclei beyond magnesium isotopes. Taking Nd isotopes as examples, the experimental binding energies, two-neutron separation energies, quadrupole deformations, and charge radii are reproduced rather well. The deformation and continuum play essential roles in the description of nuclear masses and prediction of drip-line nuclei. By examining the single-particle levels in the canonical basis and their contributions to the total density, the thickness of the neutron skin, the particles number in continuum, and the Coulomb barrier, the exotic structures including the neutron skin and the proton radioactivity are predicted.
In this paper, we investigate the hydrodynamic collectivity in high-multiplicity events of proton-proton collisions at s= 13 TeV, using iEBE-VISHNU hybrid model with three different initial conditions, namely, HIJING, super-MC and TRENTo. With properly tuned parameters, hydrodynamic simulations with each initial model give reasonable descriptions of the measured two-particle correlations, including the integrated and pT-differential flow for all charged and identified hadrons. However, the hydrodynamic simulations fail to describe the negative value of the four-particle cumulant c2v{4} as measured in experiments. Further investigations show that the non-linear response between the elliptic flow v2 and the initial eccentricity ε2 becomes significant in the small p-p systems. This leads to a large deviation from linear eccentricity scaling and generates additional flow fluctuations, which results in a positive c2v{4} even with a negative c2ε{4} from the initial state. We also presented the first hydrodynamic calculations of multi-particle mixed harmonic azimuthal correlations in p-p collisions, such as normalized asymmetric cumulant nacn{3}, normalized Symmetric-Cumulant, nsc2,3{4} and nsc2,4{4}. Although many qualitative features are reproduced by the hydrodynamic simulations with chosen parameters, the measured negative nsc2,3{4} cannot be reproduced. The failure of the description of negative c2{4} and nsc2,3{4} triggers the question on whether hydrodynamics with a fundamentally new initial state model could solve this puzzle, or hydrodynamics itself might not be the appreciated mechanism of the observed collectivity in p-p collisions at the LHC.
A recent experimental breakthrough identified the last bound neutron-rich nuclei in fluorine and neon isotopes. Based on this finding, we perform a theoretical study of Z=9,10,11,12 isotopes in the relativistic mean field (RMF) model. The mean field parameters are assumed from the PK1 parameterization, and the pairing correlation is described by the particle number conservation BCS (FBCS) method recently formulated in the RMF model. We show that the FBCS approach plays an essential role in reproducing experimental results of fluorine and neon isotopes. Furthermore, we predict 39Na and 40Mg to be the last bound neutron-rich nuclei in sodium and magnesium isotopes.
The transverse momentum spectra of different types of particles produced in central and peripheral gold-gold (Au-Au) and (inelastic) proton-proton (pp) collisions at the Relativistic Heavy Ion Collider (RHIC), as well as in central and peripheral lead-lead (Pb-Pb) and pp collisions at the Large Hadron Collider (LHC) are analyzed by the standard distribution in terms of multi-component. The obtained results from the standard distribution give an approximate agreement with the measured experimental data by the STAR, PHENIX and ALICE Collaborations. The methodical behavior of the effective (kinetic freeze-out) temperature, transverse flow velocity and kinetic freeze-out volume with the mass dependence for different particles is obtained, which observes the early kinetic freeze-out of heavier particles as compared to the lighter particles. The parameters for emissions of different particles are observed to be different, which reveals a direct signature of the mass dependent differential kinetic freeze-out. It is also observed that the peripheral nucleus-nucleus (AA) and pp collisions at the same center-of-mass energy per nucleon pair are close in terms of the extracted parameters.
Transverse spherocity, an event shape observable, has a very unique capability to separate the events based on their geometrical shape, i.e. jetty and isotropic. In this work, we use transverse spherocity for the first time in heavy-ion collisions using A Multi-Phase Transport Model (AMPT). We obtain the transverse momentum spectra, integrated yield, mean transverse momentum and azimuthal anisotropy for identified particles in Xe-Xe collisions at sNN=5.44 TeV and Pb-Pb collisions at sNN=5.02 TeV. The indication of collectivity in heavy-ion collisions can be clearly seen while comparing the transverse momentum spectra from jetty and isotropic events. The elliptic flow as a function of transverse spherocity shows that the isotropic events have nearly zero elliptic flow and the elliptic flow is mostly dominated by the jetty events. This study will pave a way to focus on jetty events in heavy-ion collisions in order to investigate jet medium modification and jet hadro-chemistry in a sophisticated manner.
↳ hep-phhep-exnucl-exnucl-th7 citations
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.