Nuclear Theory·nucl-th

Wednesday·March 10, 2021

11 papers—4 primary·7 cross-listed

01
A proposed solution for the lifetime puzzle of the 229mTh+ isomer
F. F. Karpeshin (D. I. Mendeleyev Institute for Metrology, Saint-Petersburg, Russia)🇷🇺 · M. B. Trzhaskovskaya (National Research Center Kurchatov Institute - Petersburg Nuclear Physics Institute, Russia)🇷🇺
With the example of the 229Th nucleus, which is the most likely candidate for the creation frequency standard of a future, the dynamics of the interplay and the relationship of various resonance conversion mechanisms is analyzed. As a result, a solution is proposed for the so-called thorium puzzle, which consisted of a contradiction between the experimental and theoretical lifetimes of Th+ ions. First, the solution demonstrates the dependence of the lifetime of the nuclear isomer on the ambient conditions. Second, it demonstrates the leveling role of the fragmentation of the single-electron levels, which makes the resonance amplification of the electron-nuclear interaction more likely. Both of these trends lead to a probable decrease of the theoretical lifetime towards agreement with experiment.
nucl-thNPA(2021)·4 citations
02
Classification of resonances and pairing effects on $N A$ -scattering within the HFB framework
K. Mizuyama · H. Cong Quang · T. Dieu Thuy · T. V. Nhan Hao
We analyze the properties of the scattering solutions obtained as the pole of the S- and K-matrix with the help of the Jost function framework and the Strum-Liouville theory within the Hartree-Fock-Bogoliubov(HFB) framework, and clarify the scattering solutions which can be defined as the physical state. We found that there are three types of the resonances; "{\it shape resonance}", "{\it particle-type}" and "{\it hole-type quasiparticle resonances}", and another two types of solutions are given as the independent S-matrix and K-matrix poles. The shape resonance is formed by the Hartree-Fock(HF) mean field potential, is not affected by the pairing correlation so much. The particle-type and hole-type quasiparticle resonances originate from the particle and hole states by the configuration mixing effect by pairing. All of resonance are represented by the S-matrix pole which has the corresponding K-matrix pole. Two other types of solutions are given by the independent S-matrix and K-matrix poles. These poles are formed by the HF mean field potential. The effect of pairing for the independent S-matrix pole is small, but the one for the independent K-matrix pole has the remarkable effect. The independent K-matrix pole destroys the quasiparticle resonance as it approaches to the resonance by the pairing effect. The wave function of all resonances have the characteristic structure of the metastable property. However, the metastable structure of the wave function of the quasiparticle resonance can be broken by the independent standing wave solution or the Fano effect.
nucl-thPRC(2021)·6 citations
03
Gross features of the spectrum of the 36Ar nucleus
Gábor Riczu · József Cseh
Samples of the spectrum of the 36Ar nucleus are known in different energy windows. In addition to the ground state region (GS), the superdeformed (SD) state is observed, too, and there is a good candidate for the hyperdeformed (HD) one, as well. They are populated in different reactions. We intend to describe the gross features of the spectra of different energies, deformations and reactions in a unified way. We apply the multiconfigurational dynamical symmetry (MUSY). The SU(3) quantum numbers of the shape isomers from previous studies pave the way for this description. The MUSY reproduces the gross features of the spectra to a reasonable approximation. The energy spectrum of the three valleys (GS, SD, HD) indicates that the multiconfigurational symmetry is valid to a good approximation, and different cluster configurations coexist in the shape isomers.
nucl-thIJMPE(2021)·3 citations
04
Determine the neutron skin type by relativistic isobaric collisions
Hao-jie Xu🇨🇳 · Hanlin Li🇨🇳 · Xiaobao Wang🇨🇳 · Caiwan Shen🇨🇳 · Fuqiang Wang🇨🇳
The effects of neutron skin on the multiplicity ( $N_{ch}$ ) and eccentricity( $ϵ_{2}$ ) in relativistic $_{44}^{96}$ Ru+ $_{44}^{96}$ Ru and $_{40}^{96}$ Zr+ $_{40}^{96}$ Zr collisions at $s_{_{NN}} = 200$ GeV are investigated with the Trento model. It is found that the Ru+Ru/Zr+Zr ratios of the $N_{ch}$ distributions and $ϵ_{2}$ in mid-central collisions are exquisitely sensitive to the neutron skin type (skin vs.~halo). The state-of-the-art calculations by energy density functional theory (DFT) favor the halo-type neutron skin and can soon be confronted by experimental data. It is demonstrated that the halo-type density can serve as a good surrogate for the DFT density, and thus can be efficiently employed to probe nuclear deformities by using elliptic flow data in central collisions. We provide hereby a proof-of-principle venue to simultaneously determine the neutron skin type, thickness, and nuclear deformity.
nucl-thnucl-exPLB(2021)·92 citations
05
Transverse charge density and the radius of the proton
Alexander V. Gramolin🇺🇸 · Rebecca L. Russell🇺🇸
A puzzling discrepancy exists between the values of the proton charge radius obtained using different experimental techniques: elastic electron-proton scattering and spectroscopy of electronic and muonic hydrogen. The proton radius is defined through the slope of the electric form factor, $G_{E} (Q^{2})$ , at zero four-momentum transfer, which is inaccessible in scattering experiments. We propose a novel method for extracting the proton radius from scattering data over a broad $Q^{2}$ range rather than attempting to directly determine the slope of $G_{E}$ at $Q^{2} = 0$ . This method relates the radius of the proton to its transverse charge density, which is the two-dimensional Fourier transform of the Dirac form factor, $F_{1} (Q^{2})$ . We apply our method to reanalyze the extensive data obtained by the A1 Collaboration [J. C. Bernauer et al., Phys. Rev. Lett. 105, 242001 (2010)] and extract a radius value, $r_{E} = 0.889 (5)_{stat} (5)_{syst} (4)_{model} fm$ , that is consistent with the original result. We also provide new parametrizations for the Dirac and Pauli form factors and the transverse charge and magnetization densities of the proton. Our reanalysis shows that the proton radius discrepancy cannot be explained by issues with fitting and extrapolating the A1 data to $Q^{2} = 0$ .
↳ nucl-exhep-exhep-phnucl-thPRD(2022)·18 citations
06
Particle yields in pp interactions at $s = 17.3$ GeV interpreted in the statistical hadronization model
T. Matulewicz🇵🇱 · K. Piasecki🇵🇱
The unified set of yields of particles produced in proton-proton collisions at $s$ = 17.3 GeV (laboratory beam momentum 158 GeV/c) is evaluated, combining the experimental results of the NA49 and NA61/SHINE collaborations at the CERN SPS. With the statistical hadronization code Thermal-Fist we confirm the unacceptably high value of $χ^{2}$ , both in the canonical and grand canonical - strangeness canonical approach, and the common volume for all the hadrons. The use of the energy-dependent width of the Breit-Wigner parametrization for the mass distributions of unstable particles improves the quality of the description of particle yields only slightly. We confirm the observation that exclusion of the $ϕ$ meson yield makes the fit result acceptable. The complete experimental data set of particle yields can be reasonably fitted if the canonical volumes of hadrons without and with open strangeness are allowed to vary independently. The canonical volume of strangeness was found larger than that for non-strange hadrons, which is compatible with the femtoscopy measurements of p+p system at $s =$ 27.4 MeV and 900 MeV. The model with the best-fit parameters allows to predict the yields of several not yet measured particles emitted from p+p at $s$ = 17.3 GeV.
↳ hep-phnucl-thJ.Phys.G(2021)·6 citations
07
Experimental study of intruder components in light neutron-rich nuclei via single-nucleon transfer reaction
Wei Liu · Jian-Ling Lou · Yan-Lin Ye · Dan-Yang Pang
With the development of radioactive beam facilities, studies concerning the shell evolution of unstable nuclei have recently gained prominence. Intruder components, particularly s-wave intrusion, in the low-lying states of light neutron-rich nuclei near N=8 are of importance in the study of shell evolution. The use of single-nucleon transfer reactions in inverse kinematics has been a sensitive tool that can be used to quantitatively investigate the single-particle orbital component of selectively populated states. The spin-parity, spectroscopic factor (or single-particle strength), and effective single-particle energy can all be extracted from such reactions. These observables are often useful to explain the nature of shell evolution, and to constrain, check, and test the parameters used in nuclear structure models. In this article, the experimental studies of the intruder components in low-lying states of neutron-rich nuclei of He, Li, Be, B, and C isotopes using various single-nucleon transfer reactions are reviewed. The focus is laid on the precise determination of the intruder s-wave strength in low-lying states.
↳ nucl-exnucl-th20 citations
08
Science Requirements and Detector Concepts for the Electron-Ion Collider: EIC Yellow Report
R. Abdul Khalek🇳🇱 · A. Accardi🇺🇸 · J. Adam🇺🇸 · D. Adamiak🇺🇸 · W. Akers🇺🇸 · M. Albaladejo🇺🇸 · A. Al-bataineh🇸🇦 · M. G. Alexeev🇮🇹 · F. Ameli🇮🇹 · P. Antonioli🇮🇹 · N. Armesto🇪🇸 · W. R. Armstrong🇺🇸 and 403 other authors
This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for further development of concepts for experimental equipment best suited for the science needs, including the importance of two complementary detectors and interaction regions. This report consists of three volumes. Volume I is an executive summary of our findings and developed concepts. In Volume II we describe studies of a wide range of physics measurements and the emerging requirements on detector acceptance and performance. Volume III discusses general-purpose detector concepts and the underlying technologies to meet the physics requirements. These considerations will form the basis for a world-class experimental program that aims to increase our understanding of the fundamental structure of all visible matter
↳ physics.ins-dethep-exhep-phnucl-ex+1NPA(2022)·1634 citations
09
Are the CKM anomalies induced by vector-like quarks? Limits from flavor changing and Standard Model precision tests
Benedetta Belfatto🇮🇹 · Zurab Berezhiani🇮🇹
Recent high precision determinations of $V_{u s}$ and $V_{u d}$ indicate towards anomalies in the first row of the CKM matrix. Namely, determination of $V_{u d}$ from superallowed beta decays and of $V_{u s}$ from kaon decays imply a violation of first row unitarity at about $4 σ$ level. Moreover, there is tension between determinations of $V_{u s}$ obtained from leptonic $K μ 2$ and semileptonic $K ℓ 3$ kaon decays. These discrepancies can be explained if there exist extra vector-like quarks at the TeV scale, which have large enough mixings with the lighter quarks. In particular, extra vector-like weak singlets quarks can be thought as a solution to the CKM unitarity problem and an extra vector-like weak doublet can in principle resolve all tensions. The implications of this kind of mixings are examined against the flavour changing phenomena and SM precision tests. We consider separately the effects of an extra down-type isosinglet, up-type isosinglet and an isodoublet containing extra quarks of both up and down type, and determine available parameter spaces for each case. We find that the experimental constraints on flavor changing phenomena become more stringent with larger masses, so that the extra species should have masses no more than few TeV. Moreover, only one type of extra multiplet cannot entirely explain all the discrepancies, and some their combination is required. We show that these scenarios are testable with future experiments. Namely, if extra vector-like quarks are responsible for CKM anomalies, then at least one of them should be found at scale of few TeV, and anomalous weak isospin violating $Z$ -boson couplings with light quarks should be detected if the experimental precision on $Z$ hadronic decay rate is improved by a factor of $2$ or so.
↳ hep-phhep-exnucl-exnucl-thJHEP(2021)·77 citations
10
Charming Charm, Beautiful Bottom, and Quark-Gluon Plasma in the Large Hadron Collider Era
Santosh K. Das🇮🇳 · Raghunath Sahoo🇮🇳
After a few microseconds of the creation of our Universe through the Big Bang, the primordial matter was believed to be a soup of the fundamental constituents of matter -- quarks and gluons. This is expected to be created in the laboratory by colliding heavy nuclei at ultra-relativistic speeds. A plasma of quarks and gluons, called Quark-Gluon Plasma (QGP) can be created at the energy and luminosity frontiers in the Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory, New York, USA, and the Large Hadron Collider (LHC) at CERN, Geneva, Switzerland. Heavy quarks, namely the charm and bottom quarks, are considered as novel probes to characterize QGP, and hence the produced Quantum Chromodynamics (QCD) matter. Heavy quark transport coefficients play a significant role in understanding the properties of QGP. Experimental measurements of nuclear suppression factor and elliptic flow can constrain the heavy quark transport coefficients, which are key ingredients for phenomenological studies, and they help to disentangle different energy loss mechanisms. We give a general perspective of the heavy quark drag and diffusion coefficients in QGP and discuss their potentials as probes to disentangle different hadronization mechanisms, as well as to probe the initial electromagnetic fields produced in non-central heavy-ion collisions. Experimental perspectives on future measurements are discussed with special emphasis on heavy-flavors as next-generation probes in view of new technological developments.
↳ hep-phhep-exnucl-exnucl-thCurr.Sci.(2021)·3 citations
11
Unusual Features of QCD Low-Energy Modes in IR Phase
Andrei Alexandru🇺🇸 · Ivan Horváth🇺🇸
It was recently proposed that there is a phase in thermal QCD (IR phase) at temperatures well above the chiral crossover, featuring elements of scale invariance in the infrared (IR). Here we study the effective spatial dimensions, $d_{I R}$ , of Dirac low-energy modes in this phase, in the context of pure-glue QCD. Our $d_{I R}$ is based on the scaling of mode support toward thermodynamic limit, and hence is an IR probe. Ordinary extended modes, such as those at high energy, have $d_{I R} = 3$ . We find $d_{I R} < 3$ in the spectral range whose lower edge coincides with $λ_{I R} = 0$ , the singularity of spectral density defining the IR phase, and the upper edge with $λ_{A}$ , the previously identified Anderson-like non-analyticity. Details near $λ_{I R}$ are unexpected in that only exact zero modes are $d_{I R} = 3$ , while a thin spectral layer near zero is $d_{I R} = 2$ , followed by an extended layer of $d_{I R} = 1$ modes. With only integer values appearing, $d_{I R}$ may have topological origin. We find similar structure at $λ_{A}$ , and associate its adjacent thin layer ( $d_{I R} >\approx 2$ ) with Anderson-like criticality. Our analysis reveals the manner in which non-analyticities at $λ_{I R}$ and $λ_{A}$ , originally identified in other quantities, appear in $d_{I R} (λ)$ . This dimension structure may be important for understanding the near-perfect fluidity of the quark-gluon medium seen in accelerator experiments. The role of $λ_{A}$ in previously conjectured decoupling of IR component is explained.
↳ hep-latcond-mat.dis-nnhep-thnucl-thPRL(2021)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE