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Nuclear Theory

New submissions

[ total of 12 entries: 1-12 ]
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New submissions for Fri, 17 Nov 17

[1]  arXiv:1711.05888 [pdf, other]
Title: Proxy-SU(3) symmetry in heavy nuclei: Prolate dominance and prolate-oblate shape transition
Comments: 10 pages, 4 tables, to appear in the proceedings of the Workshop on Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects (SDANCA17, Sofia 2017), ed. N. Minkov
Subjects: Nuclear Theory (nucl-th)

Using a new approximate analytic parameter-free proxy-SU(3) scheme, simple predictions for the global feature of prolate dominance and for the locus of the prolate-oblate shape transition have been made and compared with empirical data. Emphasis is placed on the mechanism leading to the breaking of the particle-hole symmetry, which is instrumental in shaping up these predictions. It turns out that this mechanism is based on the SU(3) symmetry and the Pauli principle alone, without reference to any specific Hamiltonian.

[2]  arXiv:1711.05896 [pdf, ps, other]
Title: Nucleon electromagnetic form factors with non-local chiral effective Lagrangian
Authors: Fangcheng He, P. Wang
Comments: 14 pages, 8 figures
Subjects: Nuclear Theory (nucl-th)

The relativistic version of finite-range-regularisation is proposed. The covariant regulator is generated from the nonlocal Lagrangian. This nonlocal interaction is gauge invariant and is applied to study the nucleon electromagnetic form factors at momentum transfer up to 2 GeV$^2$. Both octet and decuplet intermediate states are included in the one loop calculation. Using a dipole regulator with $\Lambda$ around 0.85 GeV, the obtained form factors, electromagnetic radii as well as the ratios of the form factors are all comparable with the experimental data. This successful application of chiral effective Lagrangian to relatively large momentum transfer make it possible to further investigation of hadron quantities at high $Q^2$.

[3]  arXiv:1711.05950 [pdf, other]
Title: Comparison of heavy-ion transport simulations II: Collision integral in a box
Comments: 23 pages, 10 figures. The abstract is changed a little bit due to the limits character number. The complete abstract is in the paper
Subjects: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)

Simulations by transport codes are indispensable to extract valuable physics information from heavy ion collisions. In order to understand the origins of discrepancies between different widely used transport codes, we compare 15 such codes under controlled conditions of a system confined to a box with periodic boundary, initialized with Fermi-Dirac distributions at saturation density and temperatures of either 0 or 5 MeV. In such calculations, one is able to check separately the different ingredients of a transport code. In this second publication of the code evaluation project, we only consider the two-body collision term, i.e. we perform cascade calculations. When the Pauli blocking is artificially suppressed, the collision rates are found to be consistent for most codes (to within $1\%$ or better) with analytical results, or completely controlled results of a basic cascade code after eliminating the correlations within the same pair of colliding particles. In calculations with active Pauli blocking, the blocking probability was found to deviate from the expected reference values. The reason is found in substantial phase-space fluctuations and smearing tied to numerical algorithms and model assumptions in the representation of phase space. This results in the reduction of the blocking probability in most transport codes, so that the simulated system gradually evolves away from the Fermi-Dirac towards a Boltzmann distribution. As a result of this investigation, we are able to make judgements about the most effective strategies in transport simulations for determining the collision probabilities and the Pauli blocking. Investigation in a similar vein of other ingredients in transport calculations, like the mean field propagation or the production of nucleon resonances and mesons, will be discussed in the future publications.

[4]  arXiv:1711.06008 [pdf, ps, other]
Title: A quark coalescence model for polarized vector mesons and baryons
Comments: Revtex 4, 22 pages, no figure
Subjects: Nuclear Theory (nucl-th)

A non-relativistic quark coalescence model is formulated for polarized vector mesons and baryons of spin-1/2 octet and spin-3/2 decuplet. With the spin density matrix, one can compute in a uniform way the polarizations of vector mesons and baryons from those of quarks and antiquarks with explicit momentum dependence. The results are compared to that obtained from kinetic and statistical models for hadrons.

Cross-lists for Fri, 17 Nov 17

[5]  arXiv:1711.05868 (cross-list from hep-lat) [pdf, other]
Title: A complex path around the sign problem
Authors: Paulo F. Bedaque
Comments: Write up of the talk delivered al Lattice 2017
Subjects: High Energy Physics - Lattice (hep-lat); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th); Nuclear Theory (nucl-th)

We review recent attempts at dealing with the sign problem in Monte Carlo calculations by deforming the region of integration in the path integral from real to complex fields. We discuss the theoretical foundations, the algorithmic issues and present some results for low dimensional field theories in both imaginary and real time.

[6]  arXiv:1711.06112 (cross-list from hep-lat) [pdf, other]
Title: $SU(2N_F)$ symmetry of confinement in QCD and its observation at high temperature
Authors: L. Ya. Glozman
Comments: 11 pages, talk presented at 6th International Conference on New Frontiers in Physics, 18.08 - 26.08, 2017, Crete
Subjects: High Energy Physics - Lattice (hep-lat); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); Nuclear Theory (nucl-th)

In this talk we first overview lattice results that have led to the observation of new SU(2)_{CS} and SU(2N_F) symmetries upon artificial truncation of the near-zero modes of the Dirac operator at zero temperature and at high temperature without any truncation. These symmetries are larger than the chiral symmetry of the QCD Lagrangian and contain chiral symmetries SU(N_F)_L \times SU(N_F)_R and U(1)_A as subgroups. In addition to the standard chiral transformations the SU(2)_{CS} and SU(2N_F) transformations mix the right- and left-handed components of the quark fields. It is a symmetry of the confining chromo-electric interaction while the chromo-magnetic interaction manifestly breaks it. Emergence of these symmetries upon truncation of the near-zero modes of the Dirac operator at T=0 means that all effects of the chromo-magnetic interaction are located exclusively in the near-zero modes, while confining chromo-electric interaction is distributed among all modes. Appearance of these symmetries at high T, where the temperature suppresses the near-zero modes, has radical implications because these symmetries are incompatible with the asymptotically free deconfined quarks at increasing temperature. The elementary objects in the high-temperature phase of QCD should be quarks bound by the pure chromo-electric field that is not accompanied by the chromo-magnetic effects.

[7]  arXiv:1711.06143 (cross-list from hep-ph) [pdf, other]
Title: Double heavy tri-hadron bound state via delocalized $π$ bond
Comments: 5 pages, 7 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)

The number of exotic candidates which are beyond the conventional quark model has grown dramatically during the last decades. Some of them could be viewed as analogues of the deuteron. Similarly, the existence of the triton indicates that bound states formed by three hadrons could also exist. To illustrate this possibility, we study the $DD^*K$ and $BB^*\bar{K}$ systems by using the Born-Oppenheimer Approximation. To leading order, only one-pion exchange potentials are considered, which means that the three constitutes share one virtual pion. That is similar to the role of the delocalized $\pi$ bond for the formation of Benzene in chemistry. After solving the Schr\"odinger equation, we find two three-body $DD^*K$ and $BB^*\bar{K}$ bound states with masses $4317.92_{-4.32}^{+3.66}~\mathrm{MeV}$ and $11013.65_{-8.84}^{+8.49}~\mathrm{MeV}$, respectively. The masses of their $D\bar{D}^*K$ and $B\bar{B}^*\bar{K}$ analogues are $4317.92_{-6.55}^{+6.13}~\mathrm{MeV}$ and $11013.65_{-9.02}^{+8.68}~\mathrm{MeV}$. From the experimental side, the $D\bar{D}^*K$ bound state could be found by analyzing the current world data of the $B\to J/\psi\pi\pi K$ process by focusing on the $J/\psi \pi K$ channel. Its confirmation could also help to understand the formation of kaonic nuclei in nuclear physics.

[8]  arXiv:1711.06181 (cross-list from hep-ph) [pdf, other]
Title: Can one ever prove that neutrinos are Dirac particles?
Comments: 5 pages, 3 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

According to the "Black Box" theorem the experimental confirmation of neutrinoless double beta decay ($0 \nu 2 \beta$) would imply that at least one of the neutrinos is a Majorana particle. However, a null $0 \nu 2 \beta$ signal cannot decide the nature of neutrinos, as it can be suppressed even for Majorana neutrinos. In this letter we argue that if the null $0 \nu 2 \beta$ decay signal is accompanied by a $0 \nu 4 \beta$ quadruple beta decay signal, then at least one neutrino should be a Dirac particle. This argument holds irrespective of the underlying processes leading to such decays.

[9]  arXiv:1711.06244 (cross-list from astro-ph.HE) [pdf, other]
Title: Holographic compact stars meet gravitational wave constraints
Comments: 7 pages, 5 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)

We investigate a simple holographic model for cold and dense deconfined QCD matter consisting of three quark flavors. Varying the single free parameter of the model and utilizing a Chiral Effective Theory equation of state (EoS) for nuclear matter, we find four different types of compact stars: traditional neutron stars, strange quark stars, and two novel solutions we refer to as hybrid stars of the second and third kind (HS2 and HS3, respectively). The HS2s are composed of a nuclear matter core and a crust made of stable strange quark matter, while the HS3s have both a quark mantle and a nuclear crust on top of a nuclear matter core. For all types of stars constructed, we determine not only their mass-radius relations, but also tidal deformabilities, Love numbers, as well as moments of inertia and the mass distribution. We find that there exists a range of parameter values in our model, for which the novel hybrid stars have properties in very good agreement with all existing bounds on the macroscopic properties of compact stars. In particular, the tidal deformabilities of these solutions are smaller than those of ordinary neutron stars of the same mass, implying that they provide an excellent fit to the recent gravitational wave data GW170817 of LIGO and Virgo.

[10]  arXiv:1711.06245 (cross-list from hep-ph) [pdf, ps, other]
Title: Effect of the chromo-electromagnetic field fluctuations on heavy quark propagation at the LHC energies
Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)

We consider the effect of the chromo-electromagnetic field fluctuations in addition to the collisional as well as the radiative energy loss suffered by heavy quarks while propagating through the hot and densed deconfined medium of quarks and gluons created in relativistic heavy ion collisions. The chromo-electromagnetic field fluctuations play an important role as it leads to an energy gain of heavy quarks of all momentum, significantly effective at the lower momentum region. With this, we have computed, for the first time, the nuclear modification factor (R_{AA}) of heavy mesons, viz., D-mesons and B-mesons and compared with the those experimental measurements in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV and \sqrt{s_{NN}} = 5.02 TeV by the CMS and ALICE experiments at the LHC. Our results are found to be in very good agreement with those available data measured by CMS and ALICE experiments.

Replacements for Fri, 17 Nov 17

[11]  arXiv:1708.00177 (replaced) [pdf, ps, other]
Title: Introduction of the one-body correlation operator in the unitary-model-operator approach
Comments: 16 pages, 11 figures, published in PRC
Subjects: Nuclear Theory (nucl-th)
[12]  arXiv:1708.00515 (replaced) [pdf, other]
Title: Bulk Viscosity of Quark-Gluon Plasma in Strong Magnetic Fields
Comments: 13 pages, 4 figures; v2: Eq. (2.2) corrected; v3: a paragraph added at the end of Sec. IV, also a few minor changes
Journal-ref: Phys. Rev. D 96, 094009 (2017)
Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
[ total of 12 entries: 1-12 ]
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