Nuclear Theory·nucl-th

Wednesday·September 28, 2016

7 papers—6 primary·1 cross-listed

01
The adjoint neutron transport equation and the statistical approach for its solution
Paolo Saracco · Sandra Dulla · Piero Ravetto
The adjoint equation was introduced in the early days of neutron transport and its solution, the neutron importance, has ben used for several applications in neutronics. The work presents at first a critical review of the adjoint neutron transport equation. Afterwards, the adjont model is constructed for a reference physical situation, for which an analytical approach is viable, i.e. an infinite homogeneous scattering medium. This problem leads to an equation that is the adjoint of the slowing-down equation that is well-known in nuclear reactor physics. A general closed-form analytical solution to such adjoint equation is obtained by a procedure that can be used also to derive the classical Placzek functions. This solution constitutes a benchmark for any statistical or numerical approach to the adjoint equation. A sampling technique to evaluate the adjoint flux for the transport equation is then proposed and physically interpreted as a transport model for pseudo-particles. This can be done by introducing appropriate kernels describing the transfer of the pseudo-particles in phase space. This technique allows estimating the importance function by a standard Monte Carlo approach. The sampling scheme is validated by comparison with the analytical results previously obtained.
nucl-thEur.Phys.J.Plus(2016)·0 citations
02
The Lambda(1405) state in a chiral unitary approach with off-shell corrections to dimensional regularized loop functions
Fang-Yong Dong🇨🇳 · Bao-Xi Sun🇨🇳 · Jing-Long Pang🇨🇳
The Bethe-Salpeter equation is solved in the framework of unitary coupled-channel approximation by using the pseudoscalar meson-baryon octet interaction. The loop function of the intermediate meson and baryon is deduced in a dimensional regularization scheme, where the relativistic kinetic effect and off-shell corrections are taken into account. According to the experimental data at the $K^{-} p$ threshold, the subtraction constants in the loop function are determined. The squared amplitude is suppressed strongly and only one $Λ (1405)$ state is generated dynamically in the strangeness $S = - 1$ and isospin $I = 0$ sector.
nucl-thhep-phCPC(2017)·13 citations
03
Particle production and chemical freezeout from the hybrid UrQMD approach at NICA energies
Abdel Nasser Tawfik (Egyptian Ctr. Theor. Phys., Cairo and WLCAPP, Cairo)🇪🇬 · Loutfy I. Abou-Salem🇪🇬 · Asmaa G. Shalaby🇪🇬 · Mahmoud Hanafy (Benha U)🇪🇬 · Alexander Sorin (JINR, Dubna and Moscow Phys. Eng. Inst.)🇷🇺 · Oleg Rogachevsky🇷🇺 · Werner Scheinast (JINR, Dubna)🇷🇺
The energy dependence of various particle ratios is calculated within the Ultra-Relativistic Quantum Molecular Dynamics approach and compared with the hadron resonance gas (HRG) model and measurements from various experiments, including RHIC-BES, SPS and AGS. It is found that the UrQMD particle ratios agree well with the experimental results at the RHIC-BES energies. Thus, we have utilized UrQMD in simulating particle ratios at other beam energies down to 3 GeV, which will be accessed at NICA and FAIR future facilities. We observe that the particle ratios for crossover and first-order phase transition, implemented in the hybrid UrQMD v3.4, are nearly indistinguishable, especially at low energies (at large baryon chemical potentials or high density).
nucl-thhep-exhep-phEPJA(2016)·16 citations
04
Nuclear Effects in the Deuteron and Global PDF Fits
S.I. Alekhin🇷🇺 · S.A. Kulagin🇷🇺 · R. Petti🇺🇸
We present a detailed study of nuclear corrections in the deuteron (D) from an analysis of data from charged-lepton deep-inelastic scattering (DIS) off proton and D, as well as from dimuon pair production in pp and pD collisions and $W^{\pm}$ and the $Z$ boson production at pp (p $p ˉ$ ) colliders. In particular, we discuss the determination of the off-shell function describing the modification of parton distributions (PDF) in bound nucleons in the context of global PDF fits. Our results are consistent with the ones obtained earlier from the study of the ratios of DIS structure functions $F_{2}^{A} / F_{2}^{D}$ in nuclei with $A \geq 4$ , confirming the universality of the off-shell function. We also discuss the sensitivity to various models of the deuteron wave function and the impact of nuclear corrections on the determination of the $d$ quark distribution.
nucl-thhep-exhep-phPoS(2016)·4 citations
05
Mass spectra and Regge trajectories of $Λ_{c}^{+}$ , $Σ_{c}^{0}$ , $Ξ_{c}^{0}$ and $Ω_{c}^{0}$ Baryons
Zalak Shah🇮🇳 · Kaushal Thakkar · Ajay Kumar Rai🇮🇳 · P. C. Vinodkumar🇮🇳
We calculate the mass spectra of the singly charmed baryons ( $Λ_{c}^{+}$ , $Σ_{c}^{0}$ , $Ξ_{c}^{0}$ and $Ω_{c}^{0}$ ) using Hypercentral constituent quark model(hCQM). The hyper color coloumb plus linear potential is used to calculate the masses of positive(upto $J^{p} = \frac{7}{2}^{+}$ ) and negative parity(upto $J^{p} = \frac{9}{2}^{-}$ ) excited states. The spin-spin, spin-orbital and tensor interaction terms are also incorporated for mass spectra. We have compared our results with other theoretical predictions and Lattice QCD for each baryons. Moreover, the known experimental results are also reasonably closed to our predicted masses. By using the radial and orbital excitation, we construct Regge trajectories for the baryons in (n, $M^{2}$ ) plane and find their slopes and intercepts. The other properties like, magnetic moments, radiative transitions and radiative decay widths of these baryons are also calculated successfully.
nucl-thhep-phCPC(2016)·114 citations
06
Charge and Matter Form Factors of Two-Neutron Halo Nuclei in Halo Effective Field Theory at Next-to-leading-order
Jared Vanasse🇺🇸
Using halo effective field theory (EFT), an expansion in $R_{cor e} / R_{ha l o}$ , where $R_{cor e}$ is the radius of the core and $R_{ha l o}$ the radius of the halo nucleus, we calculate the charge and neutron form factors of the two-neutron halo nuclei $^{11}$ Li, $^{14}$ Be, and $^{22}$ C to next-to-leading-order (NLO) by treating them as an effective three-body system. From the form factors we extract the point charge and point matter radii, inter-neutron distance, and neutron opening angle. Agreement is found with existing experimental extractions. Results are given for the point charge and point matter radii for arbitrary neutron core scattering effective range, $ρ_{c n}$ , that can be used for predictions once $ρ_{c n}$ is measured. Estimates for $ρ_{c n}$ are also used to make NLO predictions. Finally, our point charge radii are compared to other halo-EFT predictions, and setting the core mass equal to the neutron mass our point charge radius is found to agree with an analytical prediction in the unitary limit.
nucl-thPRC(2017)·14 citations
07
Chiral study of the $a_{0} (980)$ resonance and $π η$ scattering phase shifts in light of a recent lattice simulation
Zhi-Hui Guo🇩🇪 · Liuming Liu🇩🇪 · Ulf-G. Meißner🇩🇪 · J. A. Oller🇪🇸 · A. Rusetsky🇩🇪
We investigate the $a_{0} (980)$ resonance within chiral effective field theory through a three-coupled-channel analysis, namely $π η$ , $K K ˉ$ and $π η^{'}$ . A global fit to recent lattice finite-volume energy levels from $π η$ scattering and relevant experimental data on a $π η$ event distribution and the $γ γ \to π η$ cross section is performed. Both the leading and next-to-leading-order analyses lead to similar and successful descriptions of the finite-volume energy levels and the experimental data. However, these two different analyses yield different $π η$ scattering phase shifts for the physical masses for the $π, K, η$ and $η^{'}$ mesons. The inelasticities, the pole positions in the complex energy plane and their residues are calculated both for unphysical and physical meson masses.
↳ hep-phhep-exhep-latnucl-thPRD(2017)·68 citations

Affiliations

first authorsco-authorsvia INSPIRE

The adjoint neutron transport equation and the statistical approach for its solution

The Lambda(1405) state in a chiral unitary approach with off-shell corrections to dimensional regularized loop functions

Particle production and chemical freezeout from the hybrid UrQMD approach at NICA energies

Nuclear Effects in the Deuteron and Global PDF Fits

Mass spectra and Regge trajectories of Λc+​, Σc0​, Ξc0​ and Ωc0​ Baryons

Charge and Matter Form Factors of Two-Neutron Halo Nuclei in Halo Effective Field Theory at Next-to-leading-order

Chiral study of the a0​(980) resonance and πη scattering phase shifts in light of a recent lattice simulation

Affiliations

Mass spectra and Regge trajectories of $Λ_{c}^{+}$ , $Σ_{c}^{0}$ , $Ξ_{c}^{0}$ and $Ω_{c}^{0}$ Baryons

Chiral study of the $a_{0} (980)$ resonance and $π η$ scattering phase shifts in light of a recent lattice simulation