Nuclear Theory·nucl-th

Tuesday·December 6, 2016

15 papers—11 primary·4 cross-listed

01
Resolving the $R_{AA}$ to $v_{n}$ puzzle
Jacquelyn Noronha-Hostler🇺🇸
After 10 years of struggling to simultaneously describe the nuclear modification factor $R_{AA}$ and flow harmonics $v_{n}$ 's at high $p_{T}$ , now theoretical models are able to reproduce experimental data well. The necessary theoretical developments such as event-by-event fluctuations, choice of initial conditions, and the scalar product method to calculate flow harmonics at high $p_{T}$ are reviewed. Additionally, a discussion of new proposed experimental observables known as Soft Hard Event Engineering (SHEE) that are sensitive to the path length dependence of the energy loss is included.
nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2017)·4 citations
02
Sum rule study for Double Gamow-Teller states
H. Sagawa · T. Uesaka
We study the sum rules of double Gamow-Teller (DGT) excitations through double spin-isospin operator $(σ t_{-})^{2}$ . In general, $2^{+}$ states in the granddaughter nuclei have dominant transition strength in DGT excitations and $0^{+}$ states are weak, except in $T = 1$ mother nuclei in which $0^{+}$ strength is competitive with 2 $^{+}$ strength. The isospin selection of DGT is also discussed among 5 possible isospin states in granddaughter nuclei. A possibility to extract the unit cross section for the DGT transition strength is pointed out in the $(σ t_{-})^{2}$ excitation of double isobaric analog state (DIAS) in $T = 1$ nuclei.
nucl-thPRC(2016)·25 citations
03
The nuclear contacts and short range correlations in nuclei
R. Weiss · R. Cruz-Torres · N. Barnea · E. Piasetzky · O. Hen
Atomic nuclei are complex strongly interacting systems and their exact theoretical description is a long-standing challenge. An approximate description of nuclei can be achieved by separating its short and long range structure. This separation of scales stands at the heart of the nuclear shell model and effective field theories that describe the long-range structure of the nucleus using a mean- field approximation. We present here an effective description of the complementary short-range structure using contact terms and stylized two-body asymptotic wave functions. The possibility to extract the nuclear contacts from experimental data is presented. Regions in the two-body momentum distribution dominated by high-momentum, close-proximity, nucleon pairs are identified and compared to experimental data. The amount of short-range correlated (SRC) nucleon pairs is determined and compared to measurements. Non-combinatorial isospin symmetry for SRC pairs is identified. The obtained one-body momentum distributions indicate dominance of SRC pairs above the nuclear Fermi-momentum.
nucl-thcond-mat.quant-gasnucl-exPLB(2018)·99 citations
04
Gauge symmetry breaking in the adiabatic self-consistent collective coordinate method
Koichi Sato
We study gauge symmetry breaking by adiabatic approximation in the adiabatic self-consistent collective coordinate (ASCC) method. In the previous study, we found that the gauge symmetry of the equation of collective submanifold is (partially) broken by its decomposition into the three moving-frame equations depending on the order of $p$ . In this study, we discuss the gauge symmetry breaking by the truncation of the adiabatic expansion. A particular emphasis is placed on the symmetry under the gauge transformations which are not point transformations. We also discuss a possible version of the ASCC method including the higher-order operators which can keep the gauge symmetry.
nucl-thPTEP(2017)·2 citations
05
Short range correlations - The important role of few-body dynamics in many-body systems
Ronen Weiss · Ehoud Pazy · Nir Barnea
For many-body systems with short range interaction a series of relations were derived connecting many properties of the system to the dynamics of a closely packed few-body subsystems. Some of these relations were experimentally verified in ultra cold atomic gases. Here we shall review the implications of these developments on our understanding of nuclear one and two-body momentum distributions, and on the electron scattering Coulomb sum rule.
nucl-thFew Body Syst.(2017)·15 citations
06
Quarkonium wave functions on the light front
Yang Li🇺🇸
We study heavy quarkonium within the light-front Hamiltonian formalism. Our effective Hamiltonian is based on the holographic QCD confining potential and the one-gluon exchange interaction with a running coupling. The obtained spectra are compared with experimental measurements. We present a set of light-front wave functions, which exhibit rich structure and are consistent with the nonrelativistic picture. Finally, we use the wave functions to compute the charge and mass radii.
nucl-thhep-phFew Body Syst.(2017)·9 citations
07
Asymmetry dependence of Gogny based optical potential
G. Blanchon🇫🇷 · M. Dupuis🇫🇷 · R. N. Bernard🇫🇷 · H. F. Arellano🇨🇱
An analysis of neutron and proton scattering off $^{40, 48}$ Ca has been carried out. Real and imaginary potentials have been generated using the Nuclear Structure Method (NSM) for scattering with the Gogny D1S nucleon-nucleon effective interaction. Observables are well described by NSM for neutron and proton elastic scattering off $^{40}$ Ca and for neutron scattering off $^{48}$ Ca. For proton scattering off $^{48}$ Ca, NSM yields a lack of absorption. This discrepancy is attributed to double-charge-exchange contribution and coupling to Gamow- Teller mode which are not included in the present version of NSM. A recipe based on a Perey-Buck fit of NSM imaginary potential and Lane model is proposed to overcome this issue in an approximate way.
nucl-thEPJA(2017)·10 citations
08
Interpretation of the Neutrino-Nucleus Cross Section
Omar Benhar🇮🇹
I discuss the near-degeneracy between models of neutrino-nucleus interactions based on diverse assumptions, and analyze a specific example illustrating how the different reaction mechanisms taken into account, as well as the approximations associated with their implementation, may conspire to make the prediction of two models look similar. I argue that the relevant reaction mechanisms may be unambiguously identified exploiting the availability of electron-nucleus scattering data other than inclusive cross sections, providing detailed information on the nuclear spectral function.
nucl-th1 citation
09
Ab initio optical potentials and nucleon scattering on medium mass nuclei
A. Idini · C. Barbieri · P. Navrátil
We show the first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials. The potential is derived using self consistent Green's function theory (SCGF) with the saturating chiral interaction NNLO $_{sat}$ . Our calculations are compared to available scattering data and show that it is possible to reproduce low energy scattering observables in medium mass nuclei from first principles.
nucl-thActa Phys.Polon.B(2017)·14 citations
10
Can tetraneutron be a narrow resonance?
K. Fossez🇺🇸 · J. Rotureau🇺🇸 · N. Michel🇺🇸 · M. Płoszajczak🇫🇷
The search for a resonant four-neutron system has been revived thanks to the recent experimental hints reported in Phys. Rev. Lett. \textbf{116}, 052501 (2016). The existence of such a system would deeply impact our understanding of nuclear matter and requires a critical investigation. In this work, we study the existence of a four-neutron resonance in the quasi-stationary formalism using \textit{ab initio} techniques with various two-body chiral interactions. We employ the No-Core Gamow Shell Model and the Density Matrix Renormalization Group method, both supplemented by the use of natural orbitals and a new identification technique for broad resonances. We demonstrate that while the energy of the four-neutron system may be compatible with the experimental value, its width must be larger than the reported upper limit, supporting the interpretation of the experimental observation as a reaction process too short to form a nucleus.
nucl-thPRL(2017)·79 citations
11
Is a Trineutron Resonance Lower in Energy than a Tetraneutron Resonance?
S. Gandolfi · H.-W. Hammer · P. Klos · J. E. Lynn · A. Schwenk
We present quantum Monte Carlo calculations of few-neutron systems confined in external potentials based on local chiral interactions at next-to-next-to-leading order in chiral effective field theory. The energy and radial densities for these systems are calculated in different external Woods-Saxon potentials. We assume that their extrapolation to zero external-potential depth provides a quantitative estimate of three- and four-neutron resonances. The validity of this assumption is demonstrated by benchmarking with an exact diagonalization in the two-body case. We find that the extrapolated trineutron resonance, as well as the energy for shallow well depths, is lower than the tetraneutron resonance energy. This suggests that a three-neutron resonance exists below a four-neutron resonance in nature and is potentially measurable. To confirm that the relative ordering of three- and four-neutron resonances is not an artifact of the external confinement, we test that the odd-even staggering in the helium isotopic chain is reproduced within this approach. Finally, we discuss similarities between our results and ultracold Fermi gases.
nucl-thnucl-exPRL(2017)·80 citations
12
Nucleon spin-averaged forward virtual Compton tensor at large $Q^{2}$
Richard J. Hill🇨🇦 · Gil Paz🇺🇸
The nucleon spin-averaged forward virtual Compton tensor determines important physical quantities such as electromagnetically-induced mass differences of nucleons, and two-photon exchange contributions in hydrogen spectroscopy. It depends on two kinematic variables: $ν$ , the virtual photon energy in the proton rest frame, and $Q^{2}$ , the photon's invariant four-momentum squared. Using the operator product expansion, we calculate the tensor's large- $Q^{2}$ behavior for $ν = 0$ , including for the first time the full spin-2 contribution and correcting a previous result in the literature for the spin-0 contribution. Implications for the proton radius puzzle are discussed.
↳ hep-phnucl-thPRD(2017)·44 citations
13
Spins in Exotic Nuclei: RI-beam Experiments with Polarized Targets
Tomohiro Uesaka
Spin-degrees of freedom play a significant role in exotic nuclei. Scattering with polarized protons has potential as a powerful tool to explore the spin effects in nuclei. This lecture note discusses the background, current status, and future prospects of experimental studies with spin polarized targets and radioactive ion beams.
↳ nucl-exnucl-thEur.Phys.J.Plus(2016)·3 citations
14
Systematic study of symmetric cumulants at $s_{N N}$ = 200 GeV in Au+Au collision using transport approach
Md. Nasim🇺🇸
Measurement of 4-particle symmetric cumulants has been considered to be a good tool to study the correlations between amplitudes of different orders of anisotropic flow harmonics in the heavy-ion collision. These new observables not yet been measured at RHIC. Using A Multi-Phase Transport model, a set of predictions for the centrality dependence of the normalized 4-particle symmetric cumulants in Au+Au collisions at $s_{N N}$ = 200 GeV has been given. In addition, the effects of shear viscosity and hadronic rescattering on the magnitude of symmetric cumulants are discussed using AMPT model at $s_{N N}$ = 200 GeV. It is shown that $sc (2, 3)$ is found to be more sensitive to hadronic rescattering, whereas $sc (2, 4)$ is more sensitive to the shear viscosity. Rapidity dependence of symmetric cumulants is also shown. A relation between symmetric cumulant and event plane correlation is investigated using AMPT model.
↳ nucl-exnucl-thPRC(2017)·16 citations
15
An algebraic model for the pion's valence-quark GPD
N. Chouika🇫🇷 · C. Mezrag🇺🇸 · H. Moutarde🇫🇷 · J. Rodríguez-Quintero🇪🇸
We briefly report on a recent computation, with the help of a fruitful algebraic model, sketching the pion valence dressed-quark generalized parton distribution. Then, preliminary, we introduce on a sensible procedure to get reliable results in both Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and Efremov-Radyushkin-Brodsky-Lepage (ERBL) kinematical regions, grounded on the GPD overlap representation and its parametrization of a Radon transform of the so-called double distribution (DD).
↳ hep-phnucl-thFew Body Syst.(2017)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE