Nuclear Theory·nucl-th

Wednesday·September 27, 2017

13 papers—6 primary·7 cross-listed

01
Sub-leading correction of two-gluon rapidity correlations of strong colour field
Ye-Yin Zhao🇨🇳 · Ming-Mei Xu🇨🇳 · Heng-Ying Zhang🇨🇳 · Yuan-Fang Wu🇨🇳
In the framework of Color Glass Condensate (CGC) effective field theory (EFT), we calculate two-gluon rapidity correlations in the leading and sub-leading orders of $p_{⊥} / Q_{s}$ . In the leading order, both short- and long-range rapidity correlations are enhanced. In contrast, the contribution of sub-leading order is mainly short range quantum correlations. It is much smaller than that of the leading one, but is not negligible. Transverse momentum dependence of rapidity correlation shows that the leading order is sensitive to the saturation momentum of two incident particles, but the sub-leading one is not.
nucl-thhep-ph4 citations
02
The interplay of short-range correlations and nuclear symmetry energy in hard photon productions from heavy-ion reactions at Fermi energies
Gao-Chan Yong · Bao-An Li
Within an isospin- and momentum-dependent transport model for nuclear reactions at intermediate energies, we investigate the interplay of the nucleon-nucleon short-range correlations (SRC) and nuclear symmetry energy $E_{sy m} (ρ)$ on hard photon spectra in collisions of several Ca isotopes on $^{112}$ Sn and $^{124}$ Sn targets at a beam energy of 45 MeV/nucleon. It is found that over the whole spectra of hard photons studied, effects of the SRC overwhelm those due to the $E_{sy m} (ρ)$ . The energetic photons come mostly from the high-momentum tails (HMT) of single-nucleon momentum distributions in the target and projectile. Within the neutron-proton dominance model of SRC based on the consideration that the tensor force acts mostly in the isosinglet and spin-triplet nucleon-nucleon interaction channel, there are equal numbers of neutrons and protons, thus a zero isospin-asymmetry in the HMTs. Therefore, experimental measurements of the energetic photons from heavy-ion collisions at Fermi energies have the great potential to help us better understand the nature of SRC without any appreciable influence by the uncertain $E_{sy m} (ρ)$ . These measurements will be complementary to but also have some advantages over the ongoing and planned experiments using hadronic messengers from reactions induced by high-energy electrons or protons. Since the underlying physics of SRC and $E_{sy m} (ρ)$ are closely correlated, a better understanding of the SRC will in turn help constrain the nuclear symmetry energy more precisely in a broad density range.
nucl-thnucl-exPRC(2017)·43 citations
03
Proton pairing in neutron stars from chiral effective field theory
Yeunhwan Lim · Jeremy W. Holt
We study the $^{1} S_{0}$ proton pairing gap in beta-equilibrated neutron star matter within the framework of chiral effective field theory. We focus on the role of three-body forces, which strongly modify the effective proton-proton spin-singlet interaction in dense matter. We find that three-body forces generically reduce both the size of the pairing gap and the maximum density at which proton pairing may occur. The pairing gap is computed within BCS theory, and model uncertainties are estimated by varying the nuclear potential and the choice of single-particle spectrum in the gap equation. We find that a second-order perturbative treatment of the single-particle spectrum suppresses the proton $^{1} S_{0}$ pairing gap relative to the use of a free spectrum. We estimate the critical temperature for the onset of proton superconductivity to be $T_{c} = (3.7 - 6.0) \times 1 0^{9}$ K, which is consistent with previous theoretical results in the literature and marginally within the range deduced from a recent Bayesian analysis of neutron star cooling observations.
nucl-thPRC(2021)·19 citations
04
Mixed Phase within the Multi-polytrope Approach to High Mass Twins
David Alvarez-Castillo🇩🇪 · David Blaschke🇷🇺 · Stefan Typel🇩🇪
We present a multi-polytrope approach to describe high-mass twins fulfilling chiral effective field theory estimations of the neutron star equation state and test it against the appearance of mixed phases at the hadron-quark interface. In addition, we discuss astrophysical applications of this method and expected future measurements that shall further constrain neutron star matter and the understanding of the QCD phase diagram.
nucl-thastro-ph.HEhep-phAstron.Nachr.(2017)·7 citations
05
Effects of retarded electrical fields on observables sensitive to the high-density behavior of nuclear symmetry energy in heavy-ion collisions at intermediate energies
Gao-Feng Wei🇨🇳 · Bao-An Li🇺🇸 · Gao-Chan Yong🇨🇳 · Li Ou🇨🇳 · Xin-Wei Cao🇨🇳 · Xu-Yang Liu🇨🇳
Within the isospin- and momentum-dependent transport model IBUU11, we examine the relativistic retardation effects of electrical fields on the $π^{-} / π^{+}$ ratio and neutron-proton differential transverse flow in heavy-ion collisions at intermediate energies. Compared to the static Coulomb fields, the retarded electric fields of fast-moving charges are known to be anisotropic and the associated relativistic corrections can be significant. They are found to increase the number of energetic protons in the participant region at the maximum compression by as much as 25\% but that of energetic neutrons by less than 10\% in $^{197}$ Au+ $^{197}$ Au reactions at a beam energy of 400 MeV/nucleon. Consequently, more $π^{+}$ and relatively less $π^{-}$ mesons are produced, leading to an appreciable reduction of the $π^{-} / π^{+}$ ratio compared to calculations with the static Coulomb fields. Also, the neutron-proton differential transverse flow, as another sensitive probe of high-density symmetry energy, is also decreased appreciably due to the stronger retarded electrical fields in directions perpendicular to the velocities of fast-moving charges compared to calculations using the isotropic static electrical fields. Moreover, the retardation effects on these observables are found to be approximately independent of the reaction impact parameter.
nucl-thhep-phPRC(2018)·10 citations
06
Properties of nuclei up to $A = 16$ using local chiral interactions
D. Lonardoni · J. Carlson · S. Gandolfi · J. E. Lynn · K. E. Schmidt · A. Schwenk · X. B. Wang
We report accurate quantum Monte Carlo calculations of nuclei up to $A = 16$ based on local chiral two- and three-nucleon interactions up to next-to-next-to-leading order. We examine the theoretical uncertainties associated with the chiral expansion and the cutoff in the theory, as well as the associated operator choices in the three-nucleon interactions. While in light nuclei the cutoff variation and systematic uncertainties are rather small, in $^{16}$ O these can be significant for large coordinate-space cutoffs. Overall, we show that chiral interactions constructed to reproduce properties of very light systems and nucleon-nucleon scattering give an excellent description of binding energies, charge radii, and form factors for all these nuclei, including open-shell systems in $A = 6$ and 12.
nucl-thPRL(2018)·109 citations
07
Dihadron fragmentation functions in the quark-jet model: Transversely polarized quarks
Hrayr H. Matevosyan🇦🇺 · Aram Kotzinian🇦🇲 · Anthony W. Thomas🇦🇺
Within the most recent extension of the quark-jet hadronization framework, we explore the transverse-polarization-dependent dihadron fragmentation functions (DiFFs) $H_{1}^{∢}$ and $H_{1}^{⊥}$ of a quark into $π^{+} π^{-}$ pairs. Monte Carlo (MC) simulations are employed to model polarized quark hadronization and calculate the corresponding number densities. These, in turn, are used to extract the Fourier cosine moments of the DiFFs $H_{1}^{∢}$ and $H_{1}^{⊥}$ . A notable finding is that there are previously unnoticed apparent discrepancies between the definitions of the so-called interference DiFF (IFF) $H_{1}^{∢}$ , entering the cross sections for two-hadron semi-inclusive electroproduction, and those involved in the production of two pairs of hadrons from back-to-back jets in electron-positron annihilation. This manuscript completes the studies of all four leading twist DiFFs for unpolarized hadron pairs within the quark-jet framework, following our previous work on the helicity-dependent DiFF $G_{1}^{⊥}$ .
↳ hep-phhep-exnucl-thPRD(2018)·23 citations
08
On $^{146}$ Nd, $^{144}$ Sm and other unexplored 2 $β$ decay isotopes
Francesco Nozzoli🇮🇹
$^{146}$ Nd is one of only four (over a total of 35 existing) 2 $β^{-}$ decay isotope candidates whose half-lives currently lack experimental limits. The $α$ activity of the $^{146}$ Sm daughter nuclide allows placement of limits on the 2 $β$ decay using the $^{146}$ Nd/ $^{142}$ Nd abundance ratio ( $T_{1/2}^{β β} \gsim 3 \times 1 0^{9}$ yr) or direct search for $^{146}$ Sm with accelerator mass spectrometers ( $T_{1/2}^{β β} \gsim 4.5 \times 1 0^{19}$ yr). With a similar approach, a modest ( $\sim$ Gyr) first limit on half-lives for the other unexplored $2 β$ unstable isotopes and competitive limits (few $1 0^{13}$ yr) for $^{98}$ Mo and $^{122}$ Sn are also given. Finally, it is shown how the limit $T_{1/2}^{0 ν ϵ β^{+}} \gsim 1 0^{15}$ yr for the unexplored $^{144}$ Sm $0 ν ϵ β^{+}$ decay may be obtained from the data of a GSO crystal scintillator.
↳ nucl-exhep-phnucl-thPRC(2018)·7 citations
09
A meson-baryon molecular interpretation for some $Ω_{c}$ excited baryons
Glòria Montaña🇪🇸 · Albert Feijoo🇪🇸 · Àngels Ramos🇪🇸
We explore the possibility that some of the five narrow $Ω_{c}$ resonances recently observed at LHCb could correspond to pentaquark states, structured as meson-baryon bound states or molecules. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm $+ 1$ , strangeness $- 2$ and isospin 0 sector is built from t-channel vector meson exchange, using effective Lagrangians. The resulting s-wave coupled-channel unitarized amplitudes show the presence of two structures with similar masses and widths to those of the observed $Ω_{c} (3050)^{0}$ and $Ω_{c} (3090)^{0}$ . The identification of these resonances with the meson-baryon bound states found in this work would also imply assigning the values $1/ 2^{-}$ for their spin-parity. An experimental determination of the spin-parity of the $Ω_{c} (3090)^{0}$ would help in disentangling its structure, as the quark-based models predict its spin-parity to be either $3/ 2^{-}$ or $5/ 2^{-}$ .
↳ hep-phnucl-thEPJA(2018)·76 citations
10
The Roper resonance: a genuine quark state or a dynamically generated structure?
B. Golli🇸🇮 · H. Osmanović🇧🇦 · S. Širca🇸🇮 · A. Švarc🇭🇷
In view of the recent results of lattice QCD simulation in the P11 partial wave that has found no clear signal for the three-quark Roper state we investigate a different mechanism for the formation of the Roper resonance in a coupled channel approach including the $π N$ , $π Δ$ and $σ N$ channels. We fix the pion-baryon vertices in the underlying quark model while the $s$ -wave sigma-baryon interaction is introduced phenomenologically with the coupling strength, the mass and the width of the $σ$ meson as free parameters. The Laurent-Pietarinen expansion is used to extract the information about the $S$ -matrix pole. The Lippmann-Schwinger equation for the $K$ matrix with a separable kernel is solved to all orders. For sufficiently strong $σ N N$ coupling the kernel becomes singular and a quasi-bound state emerges at around 1.4~GeV, dominated by the $σ N$ component and reflecting itself in a pole of the $S$ -matrix. The alternative mechanism involving a $(1 s)^{2} 2 s$ quark resonant state is added to the model and the interplay of the dynamically generated state and the three-quark resonant state is studied. It turns out that for the mass of the three-quark resonant state above 1.6~GeV the mass of the resonance is determined solely by the dynamically generated state, nonetheless, the inclusion of the three-quark resonant state is imperative to reproduce the experimental width and the modulus of the resonance pole.
↳ hep-phnucl-thPRC(2018)·18 citations
11
Quarkonium-photoproduction prospects at a fixed-target experiment at the LHC (AFTER@LHC)
L. Massacrier🇫🇷 · J.P. Lansberg🇫🇷 · L. Szymanowski🇵🇱 · J. Wagner🇵🇱
We report on the potentialities offered by a fixed-target experiment at the LHC using the proton and ion LHC beams (AFTER@LHC project) regarding the study of J/psi exclusive-photoproduction in pA and AA collisions. The foreseen usage of polarised targets (hydrogen, deuteron, helium) gives access to measurements of the Single-Transverse-Spin Asymmetries of this exclusive process, therefore allowing one to access the helicity-flip Generalised Parton Distribution (GPD) Eg. We detail the expected yields of photoproduced J/psi in proton-hydrogen and lead-hydrogen collisions and discuss the statistical uncertainties on the asymmetry measurement for one year of data taking at the LHC.
↳ nucl-exhep-exnucl-thCERN Proc.(2018)·7 citations
12
Note on X(3872) production at hadron colliders and its molecular structure
Miguel Albaladejo🇪🇸 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Ulf-G. Meißner🇩🇪 · Juan Nieves🇪🇸 · Andreas Nogga🇩🇪 · Zhi Yang🇩🇪
The production of the X(3872) as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103 (2009) 162001, that the production of the X(3872) at high $p_{T}$ implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.
↳ hep-phhep-exnucl-thCPC(2017)·58 citations
13
Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra
J. Nättilä · M. C. Miller · A. W. Steiner · J. J. E. Kajava · V. F. Suleimanov · J. Poutanen
Observations of thermonuclear X-ray bursts from accreting neutron stars (NSs) in low-mass X-ray binary systems can be used to constrain NS masses and radii. Most previous work of this type has set these constraints using Planck function fits as a proxy: both the models and the data are fit with diluted blackbody functions to yield normalizations and temperatures which are then compared against each other. Here, for the first time, we fit atmosphere models of X-ray bursting NSs directly to the observed spectra. We present a hierarchical Bayesian fitting framework that uses state-of-the-art X-ray bursting NS atmosphere models with realistic opacities and relativistic exact Compton scattering kernels as a model for the surface emission. We test our approach against synthetic data, and find that for data that are well-described by our model we can obtain robust radius, mass, distance, and composition measurements. We then apply our technique to Rossi X-ray Timing Explorer observations of five hard-state X-ray bursts from 4U 1702-429. Our joint fit to all five bursts shows that the theoretical atmosphere models describe the data well but there are still some unmodeled features in the spectrum corresponding to a relative error of 1-5% of the energy flux. After marginalizing over this intrinsic scatter, we find that at 68% credibility the circumferential radius of the NS in 4U 1702-429 is R = 12.4+-0.4 km, the gravitational mass is M=1.9+-0.3 Msun, the distance is 5.1 < D/kpc < 6.2, and the hydrogen mass fraction is X < 0.09.
↳ astro-ph.HEnucl-thAstron.Astrophys.(2017)·219 citations

Affiliations

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