Nuclear Theory·nucl-th

Tuesday·November 19, 2019

14 papers—8 primary·6 cross-listed

01
[Submitted on 15 Nov 2019]
Lepton-Proton Two-Photon Exchange in Chiral Perturbation Theory
Pulak Talukdar🇮🇳 · Vanamali C. Shastry🇮🇳 · Udit Raha🇮🇳 · Fred Myhrer🇺🇸
We use heavy baryon chiral perturbation theory to evaluate the two-photon exchange corrections to the low-energy elastic lepton-proton scattering at next-to-leading order accuracy, i.e., $O (α, M^{- 1})$ , including a non-zero lepton mass. We consider the elastic proton intermediate state in the two-photon exchange together in the soft photon approximation. The infrared singular contributions are projected out using dimensional regularization. The resulting infrared singularity-free two-photon exchange contribution is in good numerical agreement with existing predictions based on standard diagrammatic soft photon approximation evaluations.
Comments:
16 pages, 5 figures. Text slightly revised, results the same. Accepted for publication by Phys.Rev.D
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1911.06843 [pdf]
PRD(2020)·22 citations
02
[Submitted on 16 Nov 2019]
Isospin Dependence in Fission Fragment Yields
S. Garg · B. Maheshwari · D. Choudhury · A. K. Jain
In the present paper, we explore the idea of isospin conservation in new situations and contexts based on the directions provided by our earlier works. We present the results of our calculations for the relative yields of neutron-rich fission fragments emitted in fast neutron-induced fission, 238U (n, fission) reaction by using the concept of the conservation of isospin and compare with the experimental data. Our results successfully reproduced the gross features of partition wise fission fragments distribution of 238U (n, fission). This confirms that in all kinds of fission, isospin remains pure in neutron-rich systems even at high excitations. Thus, isospin can be proven as an important quantum number for the prediction of fission fragment distribution.
Comments:
2 pages, 2 figures, DAE-BRNS Symposium on Nuclear Physics, December 23-27, 2019, Lucknow University, Lucknow-226007
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1911.06977 [pdf]
DAE Symp.Nucl.Phys.(2019)·0 citations
03
[Submitted on 17 Nov 2019]
$Ξ^{-} t$ quasibound state instead of $ΛΛ nn$ bound state
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸
We study the coupled $ΛΛ nn - Ξ^{-} p nn$ system to check whether the inclusion of channel coupling is able to bind the $ΛΛ nn$ system. We use a separable potential three-body model of the coupled $ΛΛ nn - Ξ^{-} p nn$ system as well as a variational four-body calculation with realistic interactions. Our results exclude the possibility of a $ΛΛ nn$ bound state by a large margin. However, we have found a $Ξ^{-} t$ quasibound state above the $ΛΛ nn$ threshold.
Comments:
16 pages. To be published in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1911.07194 [pdf]
CPC(2020)·4 citations
04
[Submitted on 14 Nov 2019]
The d*(2380) and its family of pion assisted dibaryons
Avraham Gal🇮🇱
The status of $N Δ$ and $ΔΔ$ dibaryons introduced by Dyson and Xuong in 1964 is briefly reviewed with focus on the d*(2380), tentatively assigned as a $ΔΔ$ dibaryon resonance. It is argued that the apparently small value of width, $Γ_{d^{*}}$ $\approx$ 70 MeV, favors hadronic structure for the d*(2380) dibaryon rather than a six-quark structure.
Comments:
updated version of talks given at MESON 2018, Kraków [1], and at QNP 2018, Tsukuba [2]. arXiv admin note: substantial text overlap with arXiv:1803.08788
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1911.07284 [pdf]
0 citations
05
[Submitted on 17 Nov 2019]
Analysis of the Multi-component Relativistic Boltzmann Equation for Electron Scattering in Big Bang Nucleosynthesis
Nishanth Sasankan · Atul Kedia · Motohiko Kusakabe · Grant J Mathews
Big-bang nucleosynthesis (BBN) is valuable as a means to constrain the physics of the early universe and it is the only probe of the radiation-dominated epoch. A fundamental assumption in BBN is that the nuclear velocity distributions obey Maxwell-Boltzmann (MB) statistics as they do in stars. Specifically, the BBN epoch is characterized by a dilute baryon plasma for which the velocity distribution of nuclei is mainly determined by the dominant Coulomb elastic scattering with mildly relativistic electrons. One must therefore deduce the momentum distribution for reacting nuclei from the multi-component relativistic Boltzmann equation. However, the full multi-component relativistic Boltzmann equation has only recently been analyzed and its solution has only been worked out in special cases. Moreover, a variety of schemes have been proposed that introduce non-thermal components into the BBN environment which can alter the thermal distribution of reacting nuclei. Here, we construct the relativistic Boltzmann equation in the context of BBN. We also derive a Langevin model and perform relativistic Monte-Carlo simulations which clarify the baryon distribution during BBN and can be used to analyze any relaxation from a non-thermal injection. We show by these analyses that the thermalization process leads to a nuclear distribution function that remains very close to MB statistics even during the most relativistic environment relevant to BBN. Hence, the predictions of standard BBN remain unchanged.
Comments:
8 pages, 2 figures. This paper supersedes arXiv:1810.05976
Subjects:
Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
arXiv:
1911.07334 [pdf]
PRD(2020)·11 citations
06
[Submitted on 18 Nov 2019]
Vector-boson condensates, spin-triplet superfluidity of paired neutral and charged fermions, and $3 P_{2}$ pairing of nucleons
D. N. Voskresensky🇷🇺
After reminding of properties of the condensate of the complex scalar field in the external uniform magnetic field $H$ focus is made on the study of phases of the complex neutral vector boson fields coupled with magnetic field by the Zeeman coupling and phases of the charged vector boson fields. These systems may behave as nonmagnetic and ferromagnetic superfluids and ordinary and ferromagnetic superconductors. Response of the ferromagnetic superfluid and superconducting systems occupying half of space on the external uniform static magnetic field $H$ is thoroughly studied. Then the spin-triplet pairing of neutral fermions at conserved spin is considered. Novel phases are found. In external magnetic field the phase with zero mean spin proves to be unstable to the formation of a phase with a non-zero spin. For $H > H_{cr2}$ the spin-triplet pairing and ferromagnetic superfluidity continue to exist above the "old" phase transition critical temperature $T_{cr}$ . For a certain parameter choice ferromagnetic superfluid phases are formed already for $H = 0$ , characterized by an own magnetic field $h$ . Formation of domains is discussed. Next, spin-triplet pairing of charged fermions is studied. Novel phases are found with a ferromagnetic superconductivity. Then, the 3P $_{2}$ $nn$ pairing in neutron star matter is studied. Also a 3P $_{2}$ $pp$ pairing is considered. Numerical estimates are performed in the BCS weak coupling limit and beyond it for the $3 P_{2}$ $nn$ and $pp$ pairings, as well as for the 3S $_{1}$ $n p$ pairing.
Comments:
34 pages, some misprints are corrected
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1911.07502 [pdf]
PRD(2020)·6 citations
07
[Submitted on 18 Nov 2019]
Hydrodynamics from free-streaming to thermalization and back again
Chandrodoy Chattopadhyay🇺🇸 · Ulrich W. Heinz (Ohio State University)🇺🇸
We study the evolution of the Knudsen and Reynolds numbers in (0+1)-dimensionally expanding fluids with Bjorken symmetry for systems whose microscopic mean free path rises more quickly with time than usually assumed. This allows us to explore within a simple 1-dimensional model the transition from initially thermalizing to ultimately decoupling dynamics. In all cases studied the dynamics is found to be controlled by hydrodynamic attractors for both the Knudsen and Reynolds numbers whose trajectories undergo characteristic changes as the dynamics changes from thermalizing to decoupling.
Comments:
7 pages, 6 figures. Added Fig. 6 and associated discussion. This version accepted for publication in Physics Letters B
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1911.07765 [pdf]
PLB(2020)·49 citations
08
[Submitted on 18 Nov 2019]
Elastic transfer and parity dependence of the nucleus-nucleus optical potential
Nguyen Tri Toan Phuc · R. S. Mackintosh · Nguyen Hoang Phuc · Dao T. Khoa
Background: A recent coupled reaction channel (CRC) study shows that the enhanced oscillation of the elastic $^{16}$ O+ $^{12}$ C cross section at backward angles is due mainly to the elastic $α$ transfer or the core exchange. Such a process gives rise to a parity-dependent term in the total elastic $S$ -matrix, an indication of the parity dependence of the $^{16}$ O+ $^{12}$ C optical potential (OP). Purpose: To explicitly determine the core exchange potential (CEP) induced by the symmetric exchange of the two $^{12}$ C cores in the elastic $^{16}$ O+ $^{12}$ C scattering at $E_{lab} = 132$ and 300 MeV, and explore its parity dependence. Method: $S$ -matrix generated by CRC description of the elastic $^{16}$ O+ $^{12}$ C scattering is used as the input for the inversion calculation to obtain the effective local OP that contains both the Wigner and Majorana terms. Results: The high-precision inversion results show a strong contribution by the complex Majorana term in the total OP of the $^{16}$ O+ $^{12}$ C system, and thus provide for the first time a direct estimation of the parity-dependent CEP. Conclusions: The elastic $α$ transfer or exchange of the two $^{12}$ C cores in the $^{16}$ O+ $^{12}$ C system gives rise to a complex parity dependence of the total OP. This should be a general feature of the OP for the light heavy-ion systems that contain two identical cores.
Comments:
22 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1911.07770 [pdf]
PRC(2019)·8 citations
09
[Submitted on 15 Nov 2019] (cross-list from hep-ph)
Calculating the angle between jet axes
Pedro Cal🇳🇱 · Duff Neill🇺🇸 · Felix Ringer🇺🇸 · Wouter J. Waalewijn🇳🇱
We study the angle between i) the standard jet axis, ii) the axis of a jet which has been groomed using soft drop, with reduced sensitivity to soft radiation, iii) the jet axis obtained with the winner-take-all recombination scheme, which is insensitive to soft radiation at leading power. We calculate the distributions for these angles at next-to-leading logarithmic accuracy, including non-global logarithms. The angle between the standard and groomed jet axis directly probes soft wide-angle radiation, leading to a novel factorization formula. This angle is also very sensitive to nonperturbative physics, which is directly connected to nonperturbative contribution to the rapidity anomalous dimension for transverse momentum distributions. Comparing our predictions to Pythia we find good agreement, and we foresee applications to jet substructure in proton-proton and heavy ion collisions.
Comments:
39 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1911.06840 [pdf]
JHEP(2020)·42 citations
10
[Submitted on 16 Nov 2019] (cross-list from gr-qc)
Studying strong phase transitions in neutron stars with gravitational waves
Katerina Chatziioannou🇺🇸 · Sophia Han🇺🇸
The composition of neutron stars at the extreme densities reached in their cores is currently unknown. Besides nuclear matter of normal neutrons and protons, the cores of neutron stars might harbor exotic matter such as deconfined quarks. In this paper we study strong hadron-quark phase transitions in the context of gravitational wave observations of inspiraling neutron stars. We consider upcoming detections of neutron star coalescences and model the neutron star equations of state with phase transitions through the Constant-Speed-of-Sound parametrization. We use the fact that neutron star binaries with one or more hadron-quark hybrid stars can exhibit qualitatively different tidal properties than binaries with hadronic stars of the same mass, and hierarchically model the masses and tidal properties of simulated populations of binary neutron star inspiral signals. We explore the parameter space of phase transitions and discuss under which conditions future observations of binary neutron star inspirals can identify this effect and constrain its properties, in particular the threshold density at which the transition happens and the strength of the transition. We find that if the detected population of binary neutron stars contains both hadronic and hybrid stars, the onset mass and strength of a sufficiently strong phase transition can be constrained with 50-100 detections. If the detected neutron stars are exclusively hadronic or hybrid, then it is possible to place lower or upper limits on the transition density and strength.
Comments:
21 pages, 13 figures, 3 tables; accepted for publication in PRD, discussion on softer quark matter added, typos corrected
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1911.07091 [pdf]
PRD(2020)·105 citations
11
[Submitted on 16 Nov 2019] (cross-list from hep-ph)
QGP droplet formation in small asymmetric collision systems
Thomas A. Trainor🇺🇸
The journal Nature recently published a letter titled "Creating small circular, elliptical, and triangular droplets of quark-gluon plasma" [1]. The basis for that claim is a combination of measured Fourier amplitudes $v_{2}$ and $v_{3}$ from collision systems $p$ -Au, $d$ -Au and $h$ -Au (helion $h$ is the nucleus of atom $^{3}$ He), Glauber Monte Carlo estimates of initial-state transverse collision geometries for those systems and hydro Monte Carlo descriptions of the $v_{n}$ data. Correspondence between hydro $v_{n}$ trends and data trends is interpreted as confirmation of "collectivity" occurring in the small collision systems, further interpreted to indicate QGP formation. QGP formation in small systems runs counter to pre-RHIC theoretical assumptions that QGP formation should require large collision systems (e.g. central A-A collisions). There is currently available a broad context of experimental data from $p$ - $p$ , A-A and $p$ -Pb collisions at the RHIC and LHC against which the validity of the Nature letter claims may be evaluated. This talk provides a summary of such results and their implications. [1] Nature Phys. 15, no. 3, 214 (2019).}
Comments:
6 pages, 6 figures, Proceedings of XLIX International Symposium on Multiparticle Dynamics (ISMD 2019)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1911.07094 [pdf]
EPJ Web Conf.(2020)·1 citation
12
[Submitted on 17 Nov 2019] (cross-list from astro-ph.HE)
Properties of binary components and remnant in GW170817 using equations of state in finite temperature field theory models
Shriya Soma · Debades Bandyopadhyay
We investigate gross properties of binary components and remnant in GW170817 using equations of state within the finite temperature field theoretical models. We also adopt finite temperature equations of state in the density dependent hadron field theory for this study. Properties of binary components are studied using zero temperature equations of state. Particularly, we investigate tidal deformabilities and radii of binary components in light of GW170817. An analytical expression relating the radii and the combined tidal deformability is obtained for binary neutron star masses in the range $1.1 M_{⊙} ≲ M ≲ 1.6 M_{⊙}$ . The upper bound on the tidal deformability gives the upper bound on the neutron star radius as 13 km. Next, the role of finite temperature on the remnant in GW170817 is explored. In this case, we investigate the gravitational and baryon mass, radius, Kepler frequency and moment of inertia of the rigidly rotating remnant for different equations of state at fixed entropy per baryon. The remnant radius is enlarged due to thermal effects compared with the zero temperature case. Consequently, it is found that the Kepler frequency is much lower at higher entropy per baryon than that of the case at zero temperature. These findings are consistent with the results found in the literature.
Comments:
LaTex, 17 pages including 7 Figures; title is slightly modified and article is revised
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1911.07332 [pdf]
ApJ(2020)·15 citations
13
[Submitted on 18 Nov 2019] (cross-list from hep-ph)
Excitation functions of related parameters from transverse momentum (mass) spectra in high energy collisions
Li-Li Li🇨🇳 · Fu-Hu Liu🇨🇳 · Muhammad Waqas🇨🇳 · Rasha Al-Yusufi🇨🇳 · Altaf Mujear🇨🇳
Transverse momentum (mass) spectra of positively and negatively charged pions, positively and negatively charged kaons, protons and antiprotons produced at mid-(pseudo)rapidity in various collisions at high energies are analyzed in this work. The experimental data measured in central gold-gold, central lead-lead, and inelastic proton-proton collisions by several international collaborations are studied. The (two-component) standard distribution is used to fit the data and extract the excitation function of effective temperature. Then, the excitation functions of kinetic freeze-out temperature, transverse flow velocity, and initial temperature are obtained. In the considered collisions, the four parameters increase with the increase of collision energy in general, and the kinetic freeze-out temperature appears the trend of saturation at the top Relativistic Heavy Ion Collider and the Large Hadron Collider.
Comments:
20 pages, 6 figures. Advances in High Energy Physics, accepted
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1911.07419 [pdf]
Adv.High Energy Phys.(2020)·15 citations
14
[Submitted on 18 Nov 2019] (cross-list from astro-ph.HE)
Co-production of light and heavy $r$ -process elements via fission deposition
Nicole Vassh · Matthew R. Mumpower · Gail C. McLaughlin · Trevor M. Sprouse · Rebecca Surman
We apply for the first time fission yields determined across the chart of nuclides from the macroscopic-microscopic theory of the Finite Range Liquid Drop Model to simulations of rapid neutron capture ( $r$ -process) nucleosynthesis. With the fission rates and yields derived within the same theoretical framework utilized for other relevant nuclear data, our results represent an important step toward self-consistent applications of macroscopic-microscopic models in $r$ -process calculations. The yields from this model are wide for nuclei with extreme neutron excess. We show that these wide distributions of neutron-rich nuclei, and particularly the asymmetric yields for key species that fission at late times in the $r$ process, can contribute significantly to the abundances of the lighter heavy elements, specifically the light precious metals palladium and silver. Since these asymmetric yields correspondingly also deposit into the lanthanide region, we consider the possible evidence for co-production by comparing our nucleosynthesis results directly with the trends in the elemental ratios of metal-poor stars rich in $r$ -process material. We show that for $r$ -process enhanced stars palladium over europium and silver over europium display mostly flat trends suggestive of co-production and compare to the lanthanum over europium trend which is often used to justify robustness arguments in the lanthanide region. We find that such robustness arguments may be extendable down to palladium and heavier and demonstrate that fission deposition is a mechanism by which such a universality or robustness can be achieved.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1911.07766 [pdf]
ApJ(2020)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE