Nuclear Theory·nucl-th

Friday·May 21, 2021

9 papers—4 primary·5 cross-listed

01
Elliptic flow splittings in the Polyakov-looped Nambu-Jona Lasinio transport model
Wen-Hao Zhou🇨🇳 · He Liu🇨🇳 · Feng Li🇨🇳 · Yi-Feng Sun🇮🇹 · Jun Xu🇨🇳 · Che Ming Ko🇺🇸
To incorporate the effect of gluons on the evolution dynamics of the quark matter produced in relativistic heavy-ion collisions, we extend the 3-flavor Nambu-Jona-Lasinio (NJL) transport model to include the contribution from the Polyakov loops. Imbedding the resulting pNJL partonic transport model in an extended multiphase transport (extended AMPT) model, we then study the elliptic flow splittings between particles and their antiparticles in relativistic heavy-ion collisions at RHIC-BES energies. We find that a weak quark vector interaction in the partonic phase is able to describe the elliptic flow splitting between protons and antiprotons in heavy-ion collisions at $s_{N N} = 7.7$ to 39 GeV. Knowledge on the quark vector interaction is useful for understanding the equation of state of quark matter at large baryon chemical potentials and thus the location of the critical point in the QCD phase diagram.
nucl-thhep-exnucl-exPRC(2021)·9 citations
02
$Λ (1405)$ mediated triangle singularity in the $K^{-} d \to p Σ^{-}$ reaction
Albert Feijoo🇪🇸 · Raquel Molina🇪🇸 · Lian Rong Dai🇨🇳 · Eulogio Oset🇪🇸
We study for the first time the $p Σ^{-} \to K^{-} d$ and $K^{-} d \to p Σ^{-}$ reactions close to threshold and show that they are driven by a triangle mechanism, with the $Λ (1405)$ , a proton and a neutron as intermediate states, which develops a triangle singularity close to the $K ˉ d$ threshold. We find that a mechanism involving virtual pion exchange and the $K^{-} p \to π^{+} Σ^{-}$ amplitude dominates over another one involving kaon exchange and the $K^{-} p \to K^{-} p$ amplitude. Moreover, of the two $Λ (1405)$ states, the one with higher mass around $1420$ MeV, gives the largest contribution to the process. We show that the cross section, well within measurable range, is very sensitive to different models that, while reproducing $K ˉ N$ observables above threshold, provide different extrapolations of the $K ˉ N$ amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the $K ˉ N$ amplitudes below threshold and to more accurate predictions of the $Λ (1405)$ state of lower mass.
nucl-thEPJC(2022)·6 citations
03
Parity Partner Bands in $^{163}$ Lu: A novel approach for describing the negative parity states from a triaxial super-deformed band
R. Poenaru · A. A. Raduta
The wobbling spectrum of $^{163}$ Lu is described through a novel approach, starting from a triaxial rotor model within a semi-classical picture, and obtaining a new set of equations for all four rotational bands that have wobbling character. Redefining the band structure in the present model is done by adopting the concepts of Signature Partner Bands and Parity Partner Bands. Indeed, describing a wobbling spectrum in an even-odd nucleus through signature and parity quantum numbers is an inedited interpretation of the triaxial super-deformed bands.
nucl-thIJMPE(2021)·0 citations
04
Considering non-locality in the optical potentials within eikonal models
Chloë Hebborn🇺🇸 · Filomena M. Nunes🇺🇸
Background: For its simplicity, the eikonal method is the tool of choice to analyze nuclear reactions at high energies ( $E > 100$ MeV/nucleon), including knockout reactions. However, so far, the effective interactions used in this method are assumed to be fully local. Purpose: Given the recent studies on non-local optical potentials, in this work we assess whether non-locality in the optical potentials is expected to impact reactions at high energies and then explore different avenues for extending the eikonal method to include non-local interactions. Method: We compare angular distributions obtained for non-local interactions (using the exact R-matrix approach for elastic scattering and the adiabatic distorted wave approximation for transfer) with those obtained using their local-equivalent interactions. Results: Our results show that transfer observables are significantly impacted by non-locality in the high-energy regime. Because knockout reactions are dominated by stripping (transfer to inelastic channels), non-locality is expected to have a large effect on knockout observables too. Three approaches are explored for extending the eikonal method to non-local interactions, including an iterative method and a perturbation theory. Conclusions: None of the derived extensions of the eikonal model provide a good description of elastic scattering. This work suggests that non-locality removes the formal simplicity associated with the eikonal model.
nucl-thPRC(2021)·3 citations
05
Measurements of $^{160}$ Dy( $p, γ$ ) at energies relevant for astrophysical $γ$ process
Hao Cheng🇨🇳 · Bao-Hua Sun🇨🇳 · Li-Hua Zhu🇨🇳 · Motohiko Kusakabe🇨🇳 · Yun Zheng🇨🇳 · Liu-Chun He · Toshitaka Kajino🇨🇳 · Zhong-Ming Niu🇨🇳 · Tian-Xiao Li🇨🇳 · Cong-Bo Li · Dong-Xi Wang🇨🇳 · Meng Wang🇨🇳 and 11 other authors
Rare information on photodisintegration reactions of nuclei with mass numbers $A \approx 160$ at astrophysical conditions impedes our understanding of the origin of $p$ -nuclei. Experimental determination of the key ( $p, γ$ ) cross sections has been playing an important role to verify nuclear reaction models and to provide rates of relevant ( $γ, p$ ) reactions in $γ$ -process. In this paper we report the first cross section measurements of $^{160}$ Dy( $p, γ$ ) $^{161}$ Ho and $^{161}$ Dy( $p, n$ ) $^{161}$ Ho in the beam energy range of 3.4 - 7.0 MeV, partially covering the Gamow window. Such determinations are possible by using two targets with various isotopic fractions. The cross section data can put a strong constraint on the nuclear level densities and gamma strength functions for $A \approx$ 160 in the Hauser-Feshbach statistical model. Furthermore, we find the best parameters for TALYS that reproduce the A $\sim$ 160 data available, $^{160}$ Dy( $p, γ$ ) $^{161}$ Ho and $^{162}$ Er( $p, γ$ ) $^{163}$ Tm, and recommend the constrained $^{161}$ Ho( $γ, p$ ) $^{160}$ Dy reaction rates over a wide temperature range for $γ$ -process network calculations. Although the determined $^{161}$ Ho( $γ$ , p) stellar reaction rates at the temperature of 1 to 2 GK can differ by up to one order of magnitude from the NON-SMOKER predictions, it has a minor effect on the yields of $^{160}$ Dy and accordingly the $p$ -nuclei, $^{156, 158}$ Dy. A sensitivity study confirms that the cross section of $^{160}$ Dy( $p$ , $γ$ ) $^{161}$ Ho is measured precisely enough to predict yields of $p$ -nuclei in the $γ$ -process.
↳ nucl-exastro-ph.SRnucl-thApJ(2021)·8 citations
06
Jet quenching from heavy to light ion collisions
B.G. Zakharov🇷🇺
We perform an analysis of jet quenching in heavy and light ion collisions for scenarios without and with quark-gluon plasma formation in $pp$ collisions. We find that the results for these scenarios are very similar, and both of them are in reasonable agreement with data for heavy ion collisions. However, their results become differ significantly for light nuclei. Using the parameters fitted to heavy ion data on the nuclear modification factor $R_{AA}$ , we make predictions for 0.2 and 7 TeV O+O collisions that can be verified by future experiments at RHIC and the LHC.
↳ hep-phnucl-thJHEP(2021)·41 citations
07
Interpolating 't Hooft model between instant and front forms
Bailing Ma🇺🇸 · Chueng-Ryong Ji🇺🇸
The 't Hooft model, i.e. the two-dimensional quantum chromodynamics in the limit of infinite number of colors, is interpolated by an angle parameter $δ$ between $δ = 0$ for the instant form dynamics (IFD) and $δ = π /4$ for the light-front dynamics (LFD). With this parameter $δ$ , we formulate the interpolating mass gap equation which takes into account the non-trivial vacuum effect on the bare fermion mass to find the dressed fermion mass. Our interpolating mass gap solutions link the IFD and LFD results with the $δ$ parameter. We find the interpolation angle independent characteristic energy function which satisfies the energy-momentum dispersion relation of the dressed fermion, identifying the renormalized fermion mass function and the wave function renormalization factor. Using the dressed fermion propagator interpolating between IFD and LFD, we derive the corresponding quark-antiquark bound-state equation in the interpolating formulation. The mass spectra of mesons bearing the feature of the Regge trajectories are found independent of the $δ$ -parameter for the equal mass quark and antiquark bound-states. The Gell-Mann - Oakes - Renner relation for the pionic ground-state in the zero fermion mass limit is confirmed indicating that the spontaneous breaking of the chiral symmetry occurs regardless of the quantization for $0 \leq δ \leq π /4$ . We obtain the corresponding bound-state wave functions and discuss their reference frame dependence. Applying them for the computation of the so-called quasi parton distribution functions, we note a possibility of utilizing not only the reference frame dependence but also the interpolation angle dependence to get an alternative effective approach to the LFD-like results.
↳ hep-phhep-thnucl-thPRD(2021)·21 citations
08
Event topology and constituent-quark scaling of elliptic flow in heavy-ion collisions at the Large Hadron Collider using a multiphase transport model
Neelkamal Mallick🇮🇳 · Sushanta Tripathy🇮🇹 · Raghunath Sahoo🇮🇳
Transverse spherocity is an event shape observable, which separates the events based on their geometrical shapes. In this work, we use transverse spherocity to study the identified light flavor production in heavy-ion collisions using A Multi-Phase Transport (AMPT) model. We obtain the elliptic flow coefficients for pions, kaons and protons in Pb+Pb collisions at $s_{NN} = 5.02$ TeV as a function of transverse spherocity and collision centrality. Also, we study the number of constituent-quark (NCQ) scaling of elliptic flow which interprets the dominance of the quark degrees of freedom at the early stages of the collision. We observe a clear dependence of the elliptic flow for identified particles on transverse spherocity. It is found that the NCQ-scaling is strongly violated in events with low transverse spherocity compared to transverse spherocity-integrated events, confirming the fragmentation-based hadronization mechanism for high-momentum partons involved in the dynamics of jetty-like events.
↳ hep-phhep-exhep-thnucl-ex+1EPJC(2022)·19 citations
09
Impact of inclusive hadron production data on nuclear gluon PDFs
nCTEQ Collaboration: P. Duwentäster🇩🇪 · L. A. Husová🇩🇪 · T. Ježo🇩🇪 · M. Klasen🇩🇪 · K. Kovařík🇩🇪 · A. Kusina🇵🇱 · K. F. Muzakka🇩🇪 · F. I. Olness🇺🇸 · I. Schienbein🇫🇷 · J. Y. Yu🇺🇸
A precise knowledge of nuclear parton distribution functions (nPDFs) is -- among other things -- important for the unambiguous interpretation of hard process data taken in pA and AA collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). The available fixed target data for deep inelastic scattering (DIS) and Drell-Yan (DY) lepton pair production mainly constrain the light quark distributions. It is hence crucial to include more and more collider data in global analyses of nPDFs in order to better pin down the different parton flavors, in particular the gluon distribution at small x. To help constrain the nuclear gluon PDF, we extend the nCTEQ15 analysis by including single inclusive hadron (SIH) production data from RHIC (PHENIX and STAR) and LHC (ALICE). In addition to the DIS, DY and SIH data sets, we will also include LHC W/Z production data. As the SIH calculation is dependent on hadronic fragmentation functions (FFs), we use a variety of FFs available in the literature to properly estimate this source of uncertainty. We study the impact of these data on the PDFs, and compare with both the nCTEQ15 and nCTEQ15WZ sets. The calculations are performed using a new implementation of the nCTEQ code (nCTEQ++) including a modified version of INCNLO which allows faster calculations using pre-computed grids. The extension of the nCTEQ15 analysis to include the SIH data represents an important step toward the next generation of PDFs.
↳ hep-phnucl-thPRD(2021)·50 citations

Affiliations

first authorsco-authorsvia INSPIRE