Nuclear Theory·nucl-th

Monday·September 10, 2018

10 papers—4 primary·6 cross-listed

01
Splitting of single-particle levels in clusters potentials
A.H. Santana-Valdés · R. Bijker
In analogy with the Nilsson model, we calculate the splitting of spherical single-particle levels in a deformed field, but for cluster potentials. We study applications to alpha-cluster nuclei with two, three and four alpha particles, in which the deformation corresponds to the relative distance between the alpha particles. The splitting of the single-particle levels is studied for the cases of a dumbbell, equilateral triangle and a regular tetrahedron. The observed patterns may be used to gain insight into how the single-particle levels evolve with deformation.
nucl-thnucl-exJ.Phys.Conf.Ser.(2018)·1 citation
02
Excitation spectra of exotic nuclei in a self-consistent phonon-coupling model
N. Lyutorovich · V. Tselyaev · J. Speth · P.-G. Reinhard
We explore giant resonance spectra and low-lying dipole strength in the Ni and Sn chains from proton rich to very neutron rich isotopes, relevant in astrophysical reaction chains. For the theoretical description we employ the random-phase approximation (RPA) plus many-body effects through a phonon coupling model with optimized selection of phonons. The nuclear force is based on the Skyrme-Hartree-Fock energy functional carried consistently through all steps of modelling. The main effect of phonon coupling is a broadening of the spectral distributions (collisional width). This broadening is particularly dramatic for low-lying dipole strength in very neutron rich nuclei delivering there a qualitative change of the spectra.
nucl-thPRC(2018)·12 citations
03
Nascent fragment shell effects on the nuclear fission processes in semiclassical periodic orbit theory
Ken-ichiro Arita · Takatoshi Ichikawa · Kenichi Matsuyanagi
Making use of the semiclassical periodic orbit theory (POT), we propose, for the first time, a method to exclusively evaluate the shell effects associated with each of the nascent fragments (prefragments) generated by the neck formation in nuclear fission processes. In spite of the strong indication of such shell effects in asymmetric fragment mass distributions, they could not have been accessed by any previous theoretical approach since most of the single-particle wave functions are delocalized. In the POT, we have found that the prefragment shell effects can be naturally and unambiguously identified as the ontributions of the classical periodic orbits localized in each of the prefragments. For a numerical test, simple cavity potential models are employed with the shape described by the three-quadratic-surface shape parametrization. Deformed shell energies are studied with the trace formula for degenerate orbits in a runcated spherical cavity which was recently derived [K. Arita, Phys. Rev. C 98, 064310 (2018)]. In this simple model, it is shown that the prefragment shell effect dominates the total shell energy shortly after the neck formation, and the magicity of the heavier prefragment plays a significant role in establishing the fission saddle with asymmetric shape which leads to an asymmetric scission.
nucl-thPRC(2018)·8 citations
04
Interplaying mechanisms behind single inclusive jet suppression in heavy-ion collisions
Yayun He (CCNU, LBNL)🇨🇳 · Shanshan Cao (WSU)🇺🇸 · Wei Chen (CCNU)🇨🇳 · Tan Luo (CCNU)🇨🇳 · Long-Gang Pang (UCB, LBNL)🇺🇸 · Xin-Nian Wang (CCNU, LBNL, UCB)🇨🇳
The suppression factor for single inclusive jets in Pb+Pb collisions at the Large Hadron Collider (LHC) has a weak dependence on the transverse momentum $p_{T}$ and remains almost the same at two colliding energies, $s = 2.76$ and 5.02 TeV, though the central rapidity density of bulk hadrons increases by about 20\%. This phenomenon is investigated within the Linear Boltzmann Transport (LBT) model, which includes elastic and inelastic processes based on perturbative QCD for both jet shower and recoil medium partons as they propagate through a quark-gluon plasma (QGP). With the dynamic evolution of the QGP given by the 3+1D CLVisc hydrodynamic model with event-by-event fully fluctuating initial conditions, single inclusive jet suppression in Pb+Pb collisions from LBT agrees well with experimental data. The weak $s$ and $p_{T}$ -dependence of the jet suppression factor at LHC are found to result directly from the $s$ -dependence of the initial jet $p_{T}$ spectra and slow $p_{T}$ -dependence of the jet energy loss. Contributions from jet-induced medium response, influence of radial expansion, both of which depend on jet-cone size, and jet flavor composition all conjoin to give a slow $p_{T}$ -dependence of jet energy loss and the single jet suppression factor $R_{AA}$ , their dependence on $s$ and jet-cone size. Single inclusive jet suppression at $s = 200$ GeV is also predicted that actually decreases slightly with $p_{T}$ in the $p_{T} < 50$ GeV/ $c$ range because of the steeper initial jet spectra though the $p_{T}$ -dependence of the jet energy loss is weaker than that at LHC.
nucl-thhep-phPRC(2019)·133 citations
05
Addressing the Majorana vs. Dirac Question with Neutrino Decays
A. Baha Balantekin🇺🇸 · André de Gouvêa🇺🇸 · Boris Kayser🇺🇸
The Majorana versus Dirac nature of neutrinos remains an open question. This is due, in part, to the fact that virtually all the experimentally accessible neutrinos are ultra-relativistic. Noting that Majorana neutrinos can behave quite differently from Dirac ones when they are non-relativistic, we show that, at leading order, the angular distribution of the daughters in the decay of a heavy neutrino into a lighter one and a self-conjugate boson is isotropic in the parent's rest frame if the neutrinos are Majorana, independent of the parent's polarization. If the neutrinos are Dirac fermions, this is, in general, not the case. This result follows from CPT invariance and is independent of the details of the physics responsible for the decay. We explore the feasibility of using these angular distributions -- or, equivalently, the energy distributions of the daughters in the laboratory frame -- in order to address the Majorana versus Dirac nature of neutrinos if a fourth, heavier neutrino mass eigenstate reveals itself in the current or next-generation of high-energy colliders, intense meson facilities, or neutrino beam experiments.
↳ hep-phhep-exnucl-thPLB(2019)·93 citations
06
Conductivities of magnetic quark-gluon plasma at strong coupling
Wei Li🇨🇳 · Shu Lin🇨🇳 · Jiajie Mei🇨🇳
In the presence of a strong magnetic field, the quark gluon plasma is magnetized, leading to anisotropic transport coefficients. In this work, we focus on the effect of magnetization on electric conductivity, ignoring the possible contribution from the axial anomaly. We generalize longitudinal and transverse conductivities to finite frequencies. For transverse conductivity, a separation of contribution from fluid velocity is needed. We study the dependence of the conductivities on the magnetic field and frequency using a holographic magnetic brane model. The longitudinal conductivity scales roughly linearly in the magnetic field, while the transverse conductivity is rather insensitive to the magnetic field. Furthermore, we find the conductivities can be significantly enhanced at large frequency. This can possibly extend the lifetime of the magnetic field, which is a key component of the chiral magnetic effect.
↳ hep-thhep-phnucl-thPRD(2018)·30 citations
07
Total hadronic cross sections at high energies in holographic QCD
Akira Watanabe🇨🇳 · Mei Huang🇨🇳
We present our analysis on high energy hadron-hadron scattering in the framework of the holographic QCD. Combining the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel and gravitational form factors of the involved hadrons which are obtained by using the bottom-up AdS/QCD models in the five-dimensional AdS space, we calculate the total cross sections at high energies. We show that our calculations for the nucleon-nucleon scattering agree with the experimental data including the recent ones taken by the TOTEM collaboration at the LHC. The present framework is applicable to any high energy process, in which the strong interaction can be approximated by the Pomeron exchange. We present the results for the pion-nucleon and pion-pion scattering as examples, which can be obtained without any additional parameter because all the adjustable parameters are fixed via the analysis on the nucleon-nucleon scattering. The resulting total cross section ratios are $σ_{t o t}^{π N} / σ_{t o t}^{N N} = 0.63$ and $σ_{t o t}^{π π} / σ_{t o t}^{N N} = 0.45$ , respectively.
↳ hep-phnucl-thPLB(2019)·19 citations
08
Scattering in a Euclidean formulation of relativistic quantum mechanics
W. N. Polyzou🇺🇸 · Gordon Aiello🇺🇸 · Philip Kopp🇺🇸
A Euclidean formulation of relativistic quantum mechanics is discussed. Representations of the Hilbert space inner product and Poincaré generators are all expressed in terms of Euclidean space-time variables. The formulation does not require analytic continuation and can be used to directly calculate scattering observables. A toy model is used to demonstrate the feasibility of performing scattering calculations using the suggested computational methods.
↳ hep-lathep-thnucl-thPoS(2019)·0 citations
09
Symmetries and Algebraic Methods in Neutrino Physics
A.B. Balantekin🇺🇸
Symmetry properties associated with neutrino propagation with or without a background of other particles, including neutrinos, is reviewed. The utility of symmetries is illustrated with examples chosen from the see-saw mechanism and both matter-enhanced and collective neutrino oscillations. The role of symmetries in neutrino astrophysics is highlighted.
↳ hep-phastro-ph.SRnucl-thJ.Phys.G(2018)·14 citations
10
Scattering with real-time path integrals
W. N. Polyzou🇫🇷 · Ekaterina Nathanson🇫🇷
Sharp-momentum transition matrix elements for scattering from a short-range Gaussian potential are computed using a real-time path integral. The computation is based on a numerical implementation of a new interpretation of the path integral as the expectation of a potential functional with respect to a complex probability distribution on cylinder sets of paths. The method is closely related to a unitary transfer matrix computation.
↳ hep-lathep-thnucl-thSpringer Proc.Phys.(2020)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE