Nuclear Theory·nucl-th

Tuesday·October 31, 2017

17 papers—4 primary·13 cross-listed

01
Two-Proton Radioactivity with 2p halo in light mass nuclei A $=$ 18 $-$ 34
G. Saxena · M. Kumawat · M. Kaushik · S. K. Jain · Mamta Aggarwal
Two-proton radioactivity with 2p halo is reported theoretically in light mass nuclei A $=$ 18-34. We predict $^{19}$ Mg, $^{22}$ Si, $^{26}$ S, $^{30}$ Ar and $^{34}$ Ca as promising candidates of ground state 2p-radioactivity with S $_{2 p}$ $<$ 0 and S $_{p}$ $>$ 0. Observation of extended tail of spatial charge density distribution, larger charge radius and study of proton single particle states, Fermi energy and the wave functions indicate 2p halo like structure which supports direct 2p emission. The Coulomb and centrifugal barriers in experimentally identified 2p unbound $^{22}$ Si show a quasi-bound state that ensures enough life time for such experimental probes. Our predictions are in good accord with experimental and other theoretical data available so far.
nucl-thnucl-exPLB(2017)·42 citations
02
Modification of the masses of the lightest neutral mesons in a hadronic medium under an external magnetic field
R. M. Aguirre🇦🇷
The effective masses of the neutral mesons in a hadronic medium and under an external magnetic field are evaluated as functions of the baryonic density and the field intensity. For this purpose the meson polarization is evaluated in the one loop approximation using a Quantum Hadrodynamics model which includes pions, sigma, omega, and rho mesons. The propagators of the baryons include the full effect of the coupling to the magnetic field through their charges and their anomalous magnetic moments. Within the range of magnetic intensities considered here $1 0^{17}$ G $< B < 1 0^{19}$ G, the dependence on B is moderate for the pion and the longitudinal component of the omega meson, and negligible for the remaining mesons.
nucl-thhep-phPRD(2017)·20 citations
03
Extrapolation of scattering data to the negative-energy region II
L. D. Blokhintsev · A. S. Kadyrov · A. M. Mukhamedzhanov · D. A. Savin
A problem of analytical continuation of scattering data to the negative-energy region to obtain information about bound states is discussed within an exactly solvable potential model. This work is continuation of the previous one by the same authors [L. D. Blokhintsev et al., Phys. Rev. C 95, 044618 (2017)]. The goal of this paper is to determine the most effective way of analytic continuation for different systems. The $d + α$ and $α +^{12}$ C systems are considered and, for comparison, an effective-range function approach and a recently suggested $Δ$ -method [O. L. Ram\'ırez Suárez and J.-M. Sparenberg, Phys. Rev. C 96, 034601 (2017)] are applied. We conclude that the $Δ$ -method is more effective for heavier systems with large values of the Coulomb parameter, whereas for light systems with small values of the Coulomb parameter the effective-range function method might be preferable.
nucl-thPRC(2018)·23 citations
04
Influence of fusion dynamics on fission observables: A multi-dimensional analysis
C. Schmitt🇫🇷 · K. Mazurek🇵🇱 · P.N. Nadtochy🇷🇺
An attempt to unfold the respective influence of the fusion and fission stages on typical fission observables, and namely the neutron pre-scission multiplicity, is proposed. A four-dimensional dynamical stochastic Langevin model is used to calculate the decay by fission of excited compound nuclei produced in a wide set of heavy-ion collisions. The comparison of the results from such a calculation and experimental data is discussed, guided by predictions of the dynamical deterministic HICOL code for the compound-nucleus formation time. While the dependence of the latter on the entrance-channel properties can straigthforwardly explain some observations, a complex interplay between the various parameters of the reaction can occur in other cases. A multi-dimensional analysis of the respective role of these parameters, including entrance-channel asymmetry, bombarding energy, compound-nucleus fissility, angular momentum and excitation energy, is proposed. It is shown that, depending on the size of the system, apparent unconsistencies may be deduced when projecting onto specific ordering parameters. The work suggests the possibility of delicate compensation effects in governing the measured fission observables, thereby highlighting the necessity of a multi-dimensional discussion.
nucl-thPRC(2018)·12 citations
05
Neutron-star radius constraints from GW170817 and future detections
Andreas Bauswein🇩🇪 · Oliver Just🇯🇵 · Hans-Thomas Janka🇩🇪 · Nikolaos Stergioulas🇬🇷
We introduce a new, powerful method to constrain properties of neutron stars (NSs). We show that the total mass of GW170817 provides a reliable constraint on the stellar radius if the merger did not result in a prompt collapse as suggested by the interpretation of associated electromagnetic emission. The radius R_1.6 of nonrotating NSs with a mass of 1.6 M_sun can be constrained to be larger than 10.68_{-0.04}^{+0.15} km, and the radius R_max of the nonrotating maximum mass configuration must be larger than 9.60_{-0.03}^{+0.14} km. We point out that detections of future events will further improve these constraints. Moreover, we show that a future event with a signature of a prompt collapse of the merger remnant will establish even stronger constraints on the NS radius from above and the maximum mass M_max of NSs from above. These constraints are particularly robust because they only require a measurement of the chirp mass and a distinction between prompt and delayed collapse of the merger remnant, which may be inferred from the electromagnetic signal or even from the presence/absence of a ringdown gravitational-wave (GW) signal. This prospect strengthens the case of our novel method of constraining NS properties, which is directly applicable to future GW events with accompanying electromagnetic counterpart observations. We emphasize that this procedure is a new way of constraining NS radii from GW detections independent of existing efforts to infer radius information from the late inspiral phase or postmerger oscillations, and it does not require particularly loud GW events.
↳ astro-ph.HEnucl-thApJL(2017)·628 citations
06
Compton Scattering of Gamma-Ray Vortex with Laguerre Gaussian Wave Function
Tomoyuki Maruyama🇯🇵 · Takehito Hayakawa🇯🇵 · Toshitaka Kajino🇨🇳
In this work, we report calculation for Compton scattering of a gamma-ray vortex with Laguerre Gaussian wave function on an electron in the framework of the relativistic quantum mechanics. We have found the following unexpected feature. The momentum of scattered photon distributes outside of the reaction plane determined by the incident photon and the scattered electron, and hence the energy of the scattered photon also distributes. This novel result indicates that one can identify a gamma-ray vortex by measuring coincidentally the scattered angles of the electron and photon.
↳ hep-phnucl-thphysics.atom-phphysics.opticsSci.Rep.(2019)·22 citations
07
Kaon quark distribution functions in the chiral constituent quark model
Akira Watanabe🇨🇳 · Takahiro Sawada🇺🇸 · Chung Wen Kao🇹🇼
We investigate the valence $u$ and $s ˉ$ quark distribution functions of the $K^{+}$ meson, $v^{K (u)} (x, Q^{2})$ and $v^{K (s ˉ)} (x, Q^{2})$ , in the framework of the chiral constituent quark model. We judiciously choose the bare distributions at the initial scale to generate the dressed distributions at the higher scale, considering the meson cloud effects and the QCD evolution, which agree with the phenomenologically satisfactory valence quark distribution of the pion and the experimental data of the ratio $v^{K (u)} (x, Q^{2}) / v^{π (u)} (x, Q^{2})$ . We show how the meson cloud effects affect the bare distribution functions in detail. We find that a smaller $S U (3)$ flavor symmetry breaking effect is observed, compared with results of the preceding studies based on other approaches.
↳ hep-phnucl-thPRD(2018)·36 citations
08
First Monte Carlo global analysis of nucleon transversity with lattice QCD constraints
Huey-Wen Lin🇺🇸 · W. Melnitchouk🇺🇸 · Alexei Prokudin🇺🇸 · N. Sato🇺🇸 · H. Shows III🇺🇸
We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a new Monte Carlo method based on nested sampling and constraints on the isovector tensor charge $g_{T}$ from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with $g_{T}$ values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses which found significantly smaller $g_{T}$ values. The contributions to the nucleon tensor charge from $u$ and $d$ quarks are found to be $δ u = 0.3 (2)$ and $δ d = - 0.7 (2)$ at a scale $Q^{2} = 2$ GeV $^{2}$ .
↳ hep-phhep-exhep-latnucl-thPRL(2018)·129 citations
09
Large- $N_{c}$ operator analysis of hyperon-nucleon interactions in SU(3) chiral effective field theory
Xuyang Liu🇨🇳 · Viroj Limkaisang🇹🇭 · Daris Samart🇹🇭 · Yupeng Yan🇹🇭
We study octet-octet baryon ( $J^{P} = \frac{1}{2}^{+}$ ) contact interactions in SU(3) chiral effective field theory by using large- $N_{c}$ operator analysis. Applying the $1/ N_{c}$ expansion of the Hartee Hamiltonian, we find 15 operators in the octet-octet baryon potential where 4 operators for leading order (LO) and 11 for and net-to-next-to-leading order (NNLO). The large- $N_{c}$ operator analysis of octet-octet baryon matrix elements reduces the number of free parameters from 15 to 6 at LO of the $1/ N_{c}$ expansion. The application of large- $N_{c}$ sum rules to the Jülich model of hyperon-nucleon (YN) interactions at the LO of the chiral expansion reduces the model parameters to 3 from 5 at the LO of $1/ N_{c}$ expansion. We find that the values of LECs fitted to YN scattering data in Ref. \cite{Li:2016paq} in the relativistic covariant ChEFT (EG) approach is more consistent with the predictions of large- $N_{c}$ than in the heavy baryon (HB) formalism approach.
↳ hep-phnucl-thPLB(2019)·6 citations
10
Color dipole predictions for the exclusive vector meson photoproduction in $pp / pP b / P b P b$ collisions at Run 2 LHC energies
V. P. Goncalves🇧🇷 · M.V.T. Machado🇧🇷 · B. D. Moreira🇧🇷 · F. S. Navarra🇧🇷 · G. Sampaio dos Santos🇧🇷
In this paper we present a comprehensive analysis of exclusive vector meson photoproduction in $pp$ , $pP b$ and $P b P b$ collisions at Run 2 LHC energies using the Color Dipole formalism. The rapidity distributions and total cross sections for the $ρ$ , $ϕ$ , $J /Ψ$ , $Ψ (2 S)$ and $Υ$ production are estimated considering the more recent phenomenological models for the dipole - proton scattering amplitude, which are based on the Color Glass Condensate formalism and are able to describe the inclusive and exclusive $e p$ HERA data. Moreover, we also discuss the impact of the modelling of the vector meson wave functions on the predictions. The current theoretical uncertainty in the Color Dipole predictions is estimated and a comparison with the experimental results is performed.
↳ hep-phhep-exnucl-exnucl-thPRD(2017)·93 citations
11
Nucleon structure functions in the truncated moments approach
D. Strozik-Kotlorz🇷🇺 · S.V. Mikhailov🇷🇺 · O.V. Teryaev🇷🇺 · A. Kotlorz🇵🇱
We demonstrate advantages of the truncated Mellin moments (TMM) approach in the analysis of DIS data. We present a novel method for determination of the Bjorken sum rule (BSR) from restricted in $x$ variable experimental data. We show how to incorporate different uncertainties for each kinematic bin. We apply our analysis to recent COMPASS data.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2017)·3 citations
12
Nuclear pasta in hot dense matter and its implications for neutrino scattering
Alessandro Roggero🇺🇸 · Jérôme Margueron🇺🇸 · Luke F. Roberts🇺🇸 · Sanjay Reddy🇺🇸
We find that the abundance of large clusters of nucleons in neutron-rich matter at sub-nuclear density is greatly reduced by finite temperature effects when matter is close to beta-equilibrium. Large nuclei and exotic non-spherical nuclear configurations called pasta, favored in the vicinity of the transition to uniform matter at $T = 0$ , dissolve at relatively low temperature. For matter close to beta-equilibrium we find that the pasta melting temperature is $T_{m}^{β} ≃ 4 \pm 1$ ~MeV for realistic equations of state. The mechanism for pasta dissolution is discussed, and in general $T_{m}^{β}$ is shown to be sensitive to the proton fraction. We find that coherent neutrino scattering from nuclei and pasta makes a modest contribution to the opacity under the conditions encountered in supernovae and neutron star mergers. Implications for neutrino signals from galactic supernovae are briefly discussed.
↳ astro-ph.HEnucl-thPRC(2018)·23 citations
13
Deep crustal heating by neutrinos from the surface of accreting neutron stars
F. J. Fattoyev · Edward F. Brown · Andrew Cumming · Alex Deibel · C. J. Horowitz · Bao-An Li · Zidu Lin
We present a new mechanism for deep crustal heating in accreting neutron stars. Charged pions ( $π^{+}$ ) are produced in nuclear collisions on the neutron star surface during active accretion and upon decay they provide a flux of neutrinos into the neutron star crust. For massive and/or compact neutron stars, neutrinos deposit $\approx 1 - 2 MeV$ of heat per accreted nucleon into the inner crust. The strength of neutrino heating is comparable to the previously known sources of deep crustal heating, such as from pycnonuclear fusion reactions, and is relevant for studies of cooling neutron stars. We model the thermal evolution of a transient neutron star in a low-mass X-ray binary, and in the particular case of the neutron star MXB~1659-29 we show that additional deep crustal heating requires a higher thermal conductivity for the neutron star inner crust. A better knowledge of pion production cross sections near threshold would improve the accuracy of our predictions.
↳ astro-ph.HEnucl-exnucl-thPRC(2018)·11 citations
14
Combined parametrization of the neutron electric form factor and the $γ^{*} N \to Δ (1232)$ quadrupole form factors
G. Ramalho🇧🇷
Models based on $S U (6)$ symmetry breaking and large $N_{c}$ limit provide relations between the pion cloud contributions to the $γ^{*} N \to Δ (1232)$ quadrupole form factors, electric ( $G_{E}$ ) and Coulomb ( $G_{C}$ ), and the neutron electric form factor $G_{E n}$ , suggesting that those form factors are dominated by the same physical processes. Those relations are improved in order to satisfy a fundamental constraint between the electric and Coulomb quadrupole form factors in the long wavelength limit, when the photon three-momentum vanishes (Siegert's theorem). Inspired by those relations, we study alternative parametrizations for the neutron electric form factor. The parameters of the new form are then determined by a combined fit to the $G_{E n}$ and the $γ^{*} N \to Δ (1232)$ quadrupole form factor data. We obtain a very good description of the $G_{E}$ and $G_{C}$ data when we combine the pion cloud contributions with small valence quark contributions to the $γ^{*} N \to Δ (1232)$ quadrupole form factors. The best description of the data is obtained when the second momentum of $G_{E n}$ is $r_{n}^{4} ≃ - 0.4$ fm $^{4}$ . We conclude that the square radii associated with $G_{E}$ and $G_{C}$ , $r_{E}^{2}$ and $r_{C}^{2}$ , respectively, are large, revealing the long extension of the pion cloud. We conclude also that those square radii are related by $r_{E}^{2} - r_{C}^{2} = 0.6 \pm 0.2$ fm $^{2}$ . The last result is mainly the consequence of the pion cloud effects and Siegert's theorem.
↳ hep-phhep-exhep-latnucl-ex+1EPJA(2019)·15 citations
15
$γ γ \to γ γ$ scattering in ultrarelativistic UPC
Antoni Szczurek🇵🇱 · Mariola Klusek-Gawenda🇵🇱
We discuss diphoton semi(exclusive) production in ultraperipheral lead-lead collisions at energy of $s_{N N}$ = 5.5 TeV (LHC) and in proton-proton collisions at $s_{pp}$ = 7 TeV (LHC) and $s_{pp}$ = 100 TeV (FCC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary $γ γ \to γ γ$ subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution. We get relatively high cross sections in heavy ion collisions. This opens a possibility to study the light-by-light (quasi)elastic scattering at the LHC. We find that the cross section for elastic $γ γ$ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to $W_{γ γ} \approx$ 15 - 20 GeV. Our Standard Model predictions are compared to a recent ATLAS experimental result. We present differential distributions for PbPb $\to$ PbPb $γ γ$ and pp $\to$ pp $γ γ$ reaction.
↳ hep-phnucl-thPoS(2017)·1 citation
16
Instantaneous Bethe-Salpeter Look at the Lightest Pseudoscalar Mesons
Wolfgang Lucha🇦🇹 · Franz F. Schoberl🇦🇹
Within our description of Goldstone-type pseudoscalar mesons as almost massless bound states of quark and antiquark by a three-dimensional bound-state equation of Bethe-Salpeter origin, taking into account the pointwise behaviour of the full light-quark propagators enables to characterize the effective interquark interactions more precisely than earlier studies exploiting just specific aspects.
↳ hep-phnucl-thPoS(2018)·0 citations
17
Envelope and phase distribution of a resonance transmission through a complex environment
Dmitry V. Savin
A transmission amplitude is considered for quantum or wave transport mediated by a single resonance coupled to the background of many chaotic states. Such a model provides a useful approach to quantify fluctuations in an established signal induced by a complex environment. Applying random matrix theory to the problem, we derive an exact result for the joint distribution of the transmission intensity (envelope) and the transmission phase at arbitrary coupling to the background with finite absorption. The intensity and phase are distributed within a certain region, revealing essential correlations even at strong absorption. In the latter limit, we obtain a simple asymptotic expression that provides a uniformly good approximation of the exact distribution within its whole support, thus going beyond the Rician distribution often used for such purposes. Exact results are also derived for the marginal distribution of the phase, including its limiting forms at weak and strong absorption.
↳ cond-mat.mes-hallmath-phmath.MPnucl-th+1PRE(2018)·3 citations

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first authorsco-authorsvia INSPIRE