Nuclear Theory·nucl-th

Friday·December 11, 2015

11 papers—7 primary·4 cross-listed

01
Probing short-range nucleon-nucleon interactions with an Electron-Ion Collider
Gerald A. Miller🇺🇸 · Matthew D. Sievert🇺🇸 · Raju Venugopalan🇩🇪
We derive the cross-section for exclusive vector meson production in high energy deeply inelastic scattering off a deuteron target that disintegrates into a proton and a neutron carrying large relative momentum in the final state. This cross-section can be expressed in terms of a novel gluon Transition Generalized Parton Distribution (T-GPD); the hard scale in the final state makes the T-GPD sensitive to the short distance nucleon-nucleon interaction. We perform a toy model computation of this process in a perturbative framework and discuss the time scales that allow the separation of initial and final state dynamics in the T-GPD. We outline the more general computation based on the factorization suggested by the toy computation: in particular, we discuss the relative role of "point-like" and "geometric" Fock configurations that control the parton dynamics of short range nucleon-nucleon scattering. With the aid of exclusive $J /Ψ$ production data at HERA, as well as elastic nucleon-nucleon cross-sections, we estimate rates for exclusive deuteron photo-disintegration at a future Electron-Ion Collider (EIC). Our results, obtained using conservative estimates of EIC integrated luminosities, suggest that center-of-mass energies $s_{N N} \sim 12$ GeV $^{2}$ of the neutron-proton subsystem can be accessed. We argue that the high energies of the EIC can address outstanding dynamical questions regarding the short-range quark-gluon structure of nuclear forces by providing clean gluon probes of such "knockout" exclusive reactions in light and heavy nuclei.
nucl-thhep-phnucl-exPRC(2016)·11 citations
02
Describing the heavy-ion above-barrier fusion using the bare potentials resulting from Migdal and M3Y double-folding approaches
Igor Gontchar (Omsk State Transport University) · Maria Chushnyakova (Omsk State Technical University, Tomsk Polytechnic University)
Systematic calculations of the Coulomb barrier parameters for collisions of spherical nuclei are performed within the framework of the double folding approach. The value of the parameter $B_{Z} = Z_{P} Z_{T} / (A_{P}^{1/3} + (A_{P}^{1/3})$ (which estimates the Coulomb barrier height) varies in these calculations from 10 MeV up to 150 MeV. The nuclear densities came from the Hartree-Fock calculations which reproduce the experimental charge densities with good accuracy. For the nucleon-nucleon effective interaction two analytical approximations known in the literature are used: the M3Y and Migdal forces. The calculations show that Migdal interaction always results in the higher Coulomb barrier. Moreover, as $B_{Z}$ increases the difference between the M3Y and Migdal barrier heights systematically increases as well. As the result, the above barrier fusion cross sections calculated dynamically with the M3Y forces and surface friction are in agreement with the data. The cross sections calculated with the Migdal forces are always below the experimental data even without accounting for the dissipation.
nucl-thJ.Phys.G(2016)·8 citations
03
Two-body dissipation effects on synthesis of superheavy elements
M. Tohyama · S. Umar
To investigate the two-body dissipation effects on the synthesis of superheavy elements, we calculate low-energy collisions of the $N = 50$ isotones ( $^{82}$ Ge, $^{84}$ Se, $^{86}$ Kr and $^{88}$ Sr) on $^{208}$ Pb using the time-dependent density-matrix theory (TDDM). TDDM is an extension of the time-dependent Hartree-Fock (TDHF) theory and can determine the time evolution of one-body and two-body density matrices. Thus TDDM describes both one-body and two-body dissipation of collective energies. It is shown that the two-body dissipation may increase fusion cross sections and enhance the synthesis of superheavy elements.
nucl-thPRC(2016)·31 citations
04
Impact of nuclear mass uncertainties on the $r$ -process
Dirk Martin · Almudena Arcones · Witold Nazarewicz · Erik Olsen
Nuclear masses play a fundamental role in understanding how the heaviest elements in the Universe are created in the $r$ -process. We predict $r$ -process nucleosynthesis yields using neutron capture and photodissociation rates that are based on nuclear density functional theory. Using six Skyrme energy density functionals based on different optimization protocols, we determine for the first time systematic uncertainty bands -- related to mass modeling -- for $r$ -process abundances in realistic astrophysical scenarios. We find that features of the underlying microphysics make an imprint on abundances especially in the vicinity of neutron shell closures: abundance peaks and troughs are reflected in trends of neutron separation energy. Further advances in nuclear theory and experiments, when linked to observations, will help in the understanding of astrophysical conditions in extreme $r$ -process sites.
nucl-thastro-ph.SRPRL(2016)·114 citations
05
Formation spectra of charmed meson--nucleus systems using an antiproton beam
J. Yamagata-Sekihara🇯🇵 · C. Garcia-Recio🇪🇸 · J. Nieves🇪🇸 · L.L. Salcedo🇪🇸 · L. Tolos🇪🇸
We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson--nucleon interactions and the properties of the charmed mesons in the nuclear medium. The $D ˉ$ mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the $D ˉ N$ pair. Employing an effective model for the $D ˉ N$ and $D N$ interactions and solving the Klein--Gordon equation for $D ˉ$ and $D$ in finite nuclei, we find that the $D^{-}$ - $^{11} B$ system has $1 s$ and $2 p$ mesic nuclear states and that the $D^{0}$ - $^{11} B$ system binds in a $1 s$ state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the $[D^{-}$ - $^{11} B]$ and $[D^{0}$ - $^{11} B]$ mesic nuclei for an antiproton beam on a $^{12} C$ target. Our results suggest that it is possible to observe the $2 p$ $D^{-}$ mesic nuclear state with an appropriate experimental setup.
nucl-thhep-phPLB(2016)·15 citations
06
Calculation of expectation values of operators in the Complex Scaling method
G. Papadimitriou
The complex scaling method (CSM) provides with a way to obtain resonance parameters of particle unstable states by rotating the coordinates and momenta of the original Hamiltonian. It is convenient to use an L $^{2}$ integrable basis to resolve the complex rotated or complex scaled Hamiltonian H $_{θ}$ , with $θ$ being the angle of rotation in the complex energy plane. Within the CSM, resonance and scattering solutions do not exhibit an outgoing or scattering wave asymptotic behavior, but rather have decaying asymptotics. One of the consequences is that, expectation values of operators in a resonance or scattering complex scaled solution are calculated by complex rotating the operators. In this work we are exploring applications of the CSM on calculations of expectation values of quantum mechanical operators by retrieving the Gamow asymptotic character of the decaying state and calculating hence the expectation value using the unrotated operator. The test cases involve a schematic two-body Gaussian model and also applications using realistic interactions.
nucl-thphysics.atom-phFew Body Syst.(2016)·3 citations
07
Nucleon Effective E-Mass in Neutron-Rich Matter from the Migdal-Luttinger Jump
Bao-Jun Cai🇺🇸 · Bao-An Li🇺🇸
The well-known Migdal-Luttinger theorem states that the jump of the single-nucleon momentum distribution at the Fermi surface is equal to the inverse of the nucleon effective E-mass. Recent experiments studying short-range correlations (SRC) in nuclei using electron-nucleus scatterings at the Jefferson National Laboratory (JLAB) together with model calculations constrained significantly the Migdal-Luttinger jump at saturation density of nuclear matter. We show that the corresponding nucleon effective E-mass is consequently constrained to $M_{0}^{*, E} / M \approx 2.22 \pm 0.35$ in symmetric nuclear matter (SNM) and the E-mass of neutrons is smaller than that of protons in neutron-rich matter. Moreover, the average depletion of the nucleon Fermi sea increases (decreases) approximately linearly with the isospin asymmetry $δ$ according to $κ_{p / n} \approx 0.21 \pm 0.06 \pm (0.19 \pm 0.08) δ$ for protons (neutrons). These results will help improve our knowledge about the space-time non-locality of the single-nucleon potential in neutron-rich nucleonic matter useful in both nuclear physics and astrophysics.
nucl-thastro-ph.SRnucl-exPLB(2016)·9 citations
08
Observational signatures of neutron stars in low-mass X-ray binaries climbing a stability peak
Elena Kantor · Mikhail Gusakov · Andrey Chugunov
In the recent papers by Gusakov, Chugunov, and Kantor (2014) a new scenario describing evolution of rapidly rotating neutron stars in low-mass X-ray binaries was proposed. The scenario accounts for a resonant interaction of normal r modes with superfluid inertial modes at some specific internal stellar temperatures ("resonance temperatures"). This interaction results in an enhanced damping of r mode and appearance of the "stability peaks" in the temperature -- spin frequency plane, which split the r-mode instability window in the vicinity of the resonance temperatures. The scenario suggests that the hot and rapidly rotating NSs spend most of their life climbing up these peaks and, in particular, are observed there at the moment. We analyze in detail possible observational signatures of this suggestion. In particular, we show that these objects may exhibit `anti-glitches' -- sudden frequency jumps on a time scale of hours-months.
↳ astro-ph.SRastro-ph.HEgr-qcnucl-thMNRAS(2016)·14 citations
09
Spectra and elliptic flow of charmed hadrons in HYDJET++ model
G. Eyyubova (SINP, Moscow & Prague, Tech. U.)🇷🇺 · I.P. Lokhtin (SINP, Moscow)🇷🇺 · A.V. Belyaev (SINP, Moscow)🇷🇺 · G. Ponimatkin🇨🇿 · E. Yu. Pronina (SINP, Moscow)🇷🇺
Heavy-flavour quarks are predominantly produced in hard scatterings on a short time-scale and traverse the medium interacting with its constituents, thus they are one of the effective probes of the transport properties of the medium formed in relativistic heavy ion collisions. On the other hand, the thermal production of heavy-flavour quarks in quark-gluon plasma (QGP) is itself of interest. In this report, the production and elliptic flow of the prompt charmed mesons $D^{0}$ , $D^{+}$ , $D^{*+}$ and $J / ψ$ in PbPb collisions at the center-of-mass energy 2.76 TeV per nucleon pair are described in the framework of two-component HYDJET++ model. The model combines thermal and pQCD production mechanisms. The spectra and elliptic flow of charmed mesons are presented, the results are compared with LHC data.
↳ hep-phnucl-thPoS(2015)·0 citations
10
Compositeness of Hadron Resonances and Quasi-Bound States
Tetsuo Hyodo🇯🇵
We discuss the composite nature of hadrons appearing near the s-wave two-hadron threshold. Generalizing the Weinberg's weak-binding relation for stable bound states, we show that the compositeness of near-threshold resonances and quasi-bound states can be determined by observable quantities.
↳ hep-phnucl-thJPS Conf.Proc.(2017)·0 citations
11
Understanding the Nature of $Λ (1405)$ through Regge Physics
Cesar Fernandez-Ramirez🇺🇸 · Igor V. Danilkin🇩🇪 · Vincent Mathieu🇺🇸 · Adam P. Szczepaniak🇺🇸
It appears that there are two resonances with $J^{P} = 1/ 2^{-}$ quantum numbers in the energy region near the $Λ (1405)$ hyperon. The nature of these states is a topic of current debate. To provide further insight we use Regge phenomenology to access how these two resonances fit the established hyperon spectrum. We find that only one of these resonances is compatible with a three-quark state.
↳ hep-phnucl-thPRD(2016)·36 citations

Affiliations

first authorsco-authorsvia INSPIRE