Ground State Masses Research Articles

On a first order transition in QCD with up, down and strange quarks

We consider the quark-mass dependence of the baryon octet and decuplet ground state masses. It is predicted that QCD dynamics implies a first order transition when increasing the strange quark mass from its chiral limit towards its physical value. Our claim relies on a global fit to the available QCD lattice data on such baryon masses. Quantitative results based on an application of the chiral SU(3) Lagrangian at N^3LO are discussed. We predict an anomalous sector of QCD where stable baryonic matter would be composed of varLambda or bar{varLambda } particles rather than nucleons and anti-nucleons.

Analysis of the Pc(4312), Pc(4440), Pc(4457) and related hidden-charm pentaquark states with QCD sum rules

In this paper, we restudy the ground state mass spectrum of the diquark–diquark–antiquark-type [Formula: see text] pentaquark states with the QCD sum rules by carrying out the operator product expansion up to the vacuum condensates of dimension 13 in a consistent way. The predicted masses support assigning the [Formula: see text] to be the hidden-charm pentaquark state with [Formula: see text], assigning the [Formula: see text] to be the hidden-charm pentaquark state with [Formula: see text], [Formula: see text] or [Formula: see text], assigning the [Formula: see text] to be the hidden-charm pentaquark state with [Formula: see text] or [Formula: see text].

Alpha-decay chains of Z=122 superheavy nuclei using cubic plus proximity potential with improved transfer matrix method

The alpha decay chain properties of Z = 122 isotope in the mass range 298£ A £ 350, even-even nuclei, are studied using a fission-like model with an effective combination of the cubic plus proximity potential in the pre and post-scission regions, wherein the decay rates are calculated using improved transfer matrix method, and the results are in good agreement with other phenomenological formulae such as Universal decay law, Viola-Seaborg, Royer, etc. The nuclear ground-state masses are taken from WS4 mass model. The next minimum in the half-life curves of the decay chain obtained at N=186,178 & 164 suggest the shell closure at N=184, 176 & 162 which coincides well with the predictions of two-centre shell model approach. This study also unveils that the isotopes 298-300, 302, 304-306, 308-310, 312,314122 show 7a, 5a, 4a, 3a, 2a and 1a decay chain, respectively. All the other isotopes from A = 316 to 350 may undergo spontaneous fission since the obtained SF half -lives are comparatively less. The predictions in the present study may have an impact in the experimental synthesis and detection of the new isotopes in near future.

Triply heavy baryons in the constituent quark model * * Supported by China Postdoctoral Science Foundation (2019M650617), National Natural Science Foundation of China (11535005, 11775118), and by Spanish Ministerio de Economía, Industria y Competitividad under contractsno. FPA2017-86380-P and FPA2016-77177-C2-2-P. P.G.O. acknowledges the financial support from Spanish MINECO's Juan de la Cierva-Incorporación programme, Grant Agreement No. IJCI-2016-28525.

The constituent quark model is used to compute the ground and excited state masses of QQQbaryons containing either c or bquarks. The quark model parameters previously used to describe the properties of charmonium and bottomonium states were used in this analysis. The non-relativistic three-body bound state problem is solved by means of the Gaussian expansion method which provides sufficient accuracy and simplifies the subsequent evaluation of the matrix elements. Several low-lying states with quantum numbers and are reported. We compare the results with those obtained by the other theoretical formalisms. There is a general agreement for the mass of the ground state in each sector of triply heavy baryons. However, the situation is more puzzling for the excited states, and appropriate comments about the most relevant features of our comparison are given.

Deuteronlike Heavy Dibaryons from Lattice Quantum Chromodynamics.

We report the first lattice quantum chromodynamics (QCD) study of deuteronlike (np-like) dibaryons with heavy quark flavors. These include particles with the following dibaryon structures and valence quark contents: Σ_{c}Ξ_{cc}(uucucc), Ω_{c}Ω_{cc}(sscscc), Σ_{b}Ξ_{bb}(uububb), Ω_{b}Ω_{bb}(ssbsbb), and Ω_{ccb}Ω_{cbb}(ccbcbb), and with spin (J) parity (P), J^{P}≡1^{+}. Using a state-of-the art lattice QCD calculation, after controlling relevant systematic errors, we unambiguously find that the ground state masses of dibaryons Ω_{c}Ω_{cc}(sscscc), Ω_{b}Ω_{bb}(ssbsbb), and Ω_{ccb}Ω_{cbb}(ccbcbb) are below their respective two-baryon thresholds, suggesting the presence of bound states that are stable under strong and electromagnetic interactions. We also predict their masses precisely. For dibaryons Σ_{c}Ξ_{cc}(uucucc), and Σ_{b}Ξ_{bb}(uububb), we could not reach to a definitive conclusion about the presence of any bound state due to large systematics associated with these states. We also find that the binding of these dibaryons becomes stronger as they become heavier in mass. This study also opens up the possibility of the existence of many other exotic nuclei, which can be formed through the fusion of heavy baryons, similar to the formation of nuclei of elements in the periodic table.

Ground-state mass in short lattices by controlling overconfidence and bias in Bayesian fits

We investigate the seemingly ill-defined problem of extracting a ground-state mass from a lattice simulation where the extent of the lattice is not long enough to project out the ground-state properly. We regulate the problem using a Bayesian method. We show that controlling meta-parameters (overconfidence) can allow the data to overcome the input priors (bias). We can write the method as a black-box technique which allows extraction of a ground-state mass, even on a relatively short lattice.

Nuclear Structure Investigation of Some Ni-Isotopes Using Skyrme-Hartree-Fock Method

The nuclear ground-state structure of some Nickel (58-66Ni) isotopes has been investigated within the framework of the mean field approach using the self-consist Hartree-Fock calculations (HF) including the effective interactions of Skyrme. The Skyrme parameterizations SKM, SKM*, SI, SIII, SKO, SKE, SLY4, SKxs15, SKxs20 and SKxs25 have been utilized with HF method to study the nuclear ground state charge, mass, neutron and proton densities with the corresponding root mean square radii, charge form factors, binding energies and neutron skin thickness. The deduced results led to specifying one set or more of Skyrme parameterizations that used to achieve the best agreement with the available experimental data.

High-resolution, accurate multiple-reflection time-of-flight mass spectrometry for short-lived, exotic nuclei of a few events in their ground and low-lying isomeric states

Mass measurements of fission and projectile fragments, produced via $^{238}$U and $^{124}$Xe primary beams, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with a mass resolving powers (FWHM) up to 410,000 and an uncertainty of $6\cdot 10^{-8}$. The nuclides were produced and separated in-flight with the fragment separator FRS at 300 to 1000 MeV/u and thermalized in a cryogenic stopping cell. The data-analysis procedure was developed to determine with highest accuracy the mass values and the corresponding uncertainties for the most challenging conditions: down to a few events in a spectrum and overlapping distributions, characterized only by a broader common peak shape. With this procedure, the resolution of low-lying isomers is increased by a factor of up to three compared to standard data analysis. The ground-state masses of 31 short-lived nuclides of 15 different elements with half-lives down to 17.9~ms and count rates as low as 11 events per nuclide were determined. This is the first direct mass measurement for seven nuclides. The excitation energies and the isomer-to-ground state ratios of six isomeric states with excitation energies down to about 280~keV were measured. For nuclides with known mass values, the average relative deviation from the literature values is $(2.9 \pm 6.2) \cdot 10^{-8}$. The measured two-neutron separation energies and their slopes near and at the N=126 and Z=82 shell closures indicate a strong element-dependent binding energy of the first neutron above the closed proton shell Z=82. The experimental results deviate strongly from the theoretical predictions, especially for N=126 and N=127.

Isospin influence on the decay of compound nuclei formed in 78,82Kr + 40Ca and 78,86Kr + 40,48Ca reactions

Isospin influence on the decay of hot and rotating compound systems 118,122Ba⁎ and 118,134Ba⁎ formed in 78,82Kr + 40Ca and 78,86Kr + 40,48Ca reactions at incident energies 5.5 and 10 MeV/A, respectively, has been studied using the dynamical cluster-decay model. Binding energies used in the model have been calculated using semi-empirical mass formula of Davidson et al., where the bulk and asymmetry constants have been adjusted to reproduce the ground state mass excess for all the nuclei which have been added to AME2003 and mass table in Möller et al. 1995 to build AME2016 and FRDM2012 data. The theoretical mass excess is considered only for those cases where experimental mass excess was not available. The shell corrections have been calculated with shell closures at 2, 8, 14, 28, 50, 82, 126, 184 for both protons and neutrons and 258 for neutron only. The influence of isospin and incident energies have been seen on the following: mass and charge distribution of the fragments, de-excitation/evaporation, binary decay/fission processes of the compound system, odd-even staggering, isotopic composition, angular momentum distribution of preformation probabilities and decay cross-sections for evaporation and fission like events. The calculated cross-sections for evaporation and fission like events have been compared with experiments and the role of angular momentum on decay/fission processes have been discussed.

Investigation of the Static Nuclear Properties of Some Cr-Isotopes Using Skyrme-Hartree-Fock Method

The self-consistent Hartree-Fock (HF) calculations with several Skyrme parameterizations; SKM, SKM*, SLY4, SKxs25, MSK7, SKO, SKxta, and SKxtb have been used to investigate some static nuclear ground-state properties of some Chromium (50-54Cr) isotopes. The nuclear ground state charge, mass, neutron and proton densities with the corresponding root mean square radii, the charge form factors, the total binding energies and the neutron skin thickness can be calculated. The calculations are performed using NuShellX@MSU code, where the deduced results led to specifying one set or more of Skyrme parameterizations that used to achieve the best agreement with the available experimental data.

New program for measuring masses of silver isotopes near the N = 82 shell closure with MLLTRAP at ALTO

The ISOL facility ALTO, located at Orsay in France, provides stable ion beams from a 15 MV Tandem accelerator and neutron-rich radioactive ion beams (RIB) from the interaction of a γ-flux induced by a 50 MeV 10 μA electron beam in a uranium carbide target. A magnetic dipole mass separator and a resonance ionization laser ion source allow to select the ions of interest. New setups are under preparation to extend the fundamental properties measured at ALTO of ground and excited states of exotic nuclei. For example, high-precision mass measurements for an accurate determination of the nuclear binding energy. To perform these measurements two devices will be hosted at ALTO: a radio frequency quadrupole to cool and bunch (RFQCB) the continuous radioactive beam and the double Penning trap mass spectrometer MLLTRAP, commissioned off-line at the Maier-Leibnitz Laboratory (MLL) in Garching, Germany. The unique production mechanism using photo-fission at the ALTO facility allows for mass measurements in a neutron rich area of nuclides of major interest around 132Sn with less isobaric contamination than using proton drivers. In this context, we plan to measure neutron-rich silver isotopes (Z = 47, A > 121) to explore the possible weakening of the shell gap for Z < 50 and its impact on the A = 130 r- process nucleosynthesis. The ground-state light silver masses (A < 121), known with a precision below 20 keV, will be used for the on-line commissioning of MLLTRAP and to characterize the performance of the detection system. The status and timeline of the novel setup is presented.

Linear instability and nondegeneracy of ground state for combined power-type nonlinear scalar field equations with the Sobolev critical exponent and large frequency parameter

AbstractWe consider combined power-type nonlinear scalar field equations with the Sobolev critical exponent. In [3], it was shown that if the frequency parameter is sufficiently small, then the positive ground state is nondegenerate and linearly unstable, together with an application to a study of global dynamics for nonlinear Schrödinger equations. In this paper, we prove the nondegeneracy and linear instability of the ground state frequency for sufficiently large frequency parameters. Moreover, we show that the derivative of the mass of ground state with respect to the frequency is negative.

Exploring the production of new superheavy nuclei with proton and α -particle evaporation channels

Existing experimental facilities limit the possibilities for discovery of new nuclides to those synthesized with cross sections above 100 fb, but the perspectives for future high current accelerators could lower this limit by two orders of magnitude. Therefore, in the present work excitation functions for fusion-$xn$ evaporation reaction channels induced not only by $^{48}Ca$ but also by heavier projectiles (usually leading to smaller cross sections) on actinide targets were calculated in the framework of the fusion-by-diffusion (FBD) model. For the first time, in this approach, channels in which a proton ($pxn$) or alpha particle ($\alpha$$xn$) is evaporated have been included in the first step of the deexcitation cascade. To calculate the synthesis cross sections entry data such as fission barriers, ground-state masses, deformations and shell effects of the superheavy nuclei calculated in a consistent way within the Warsaw macroscopic-microscopic model were used. The only adjustable parameter of the FBD model is the injection point distance $s_{inj}$ and the value determined in our previous analysis of experimental cross sections for the synthesis of superheavy nuclei of Z=114-118 has been used. Excitation functions for the synthesis of selected (cross section above a few fb) new superheavies in the range of atomic numbers 112-120 are presented. Observation of 21 new heaviest isotopes is predicted. A realistic discussion of the FBD model uncertainties is presented for the first time.

Hyperons in thermal QCD: A lattice view

The hadron resonance gas (HRG) is a widely used description of matter under extreme conditions, e.g. in the context of heavy-ion phenomenology. Commonly used implementations of the HRG employ vacuum hadron masses throughout the hadronic phase and hence do not include possible in-medium effects. Here we investigate this issue, using nonperturbative lattice simulations employing the FASTSUM anisotropic Nf=2+1 ensembles. We study the fate of octet and decuplet baryons as the temperature increases, focussing in particular on the positive- and negative-parity groundstates. While the positive-parity groundstate masses are indeed seen to be temperature independent, within the error, a strong temperature dependence is observed in the negative-parity channels. We give a simple parametrisation of this and formulate an in-medium HRG, which is particularly effective for hyperons. Parity doubling is seen to emerge in the deconfined phase at the level of correlators, with a noticeable effect of the heavier s quark. Channel dependence of this transition is analysed.

Hot fusion of fission fragments for the synthesis of doubly magic nucleus $${}_{126}^{310} X^{184}$$ 126 310 X 184

The suitable fission fragments have been predicted to synthesize a doubly magic superheavy element $${}_{126}^{310} X^{184}$$ in the fusion of the fission fragments. This has been done within the framework of fragmentation theory which states that the fragment combinations at/near the minima of various η-regions of the fragmentation potentials are more probable to produce a cool compound nucleus than the combinations away from it. The fragmentation potentials have been calculated for the hot and cold optimized orientations. The binding energies/mass excess used in the fragmentation potentials have been calculated by using the semi-empirical mass formula of Davidson et al. and the bulk and asymmetry constants of it have been readjusted to reproduce the ground state mass excess of AME2016 and FRDM (2012) data. The suitability of the fission fragments at and around various minima of the fragmentation potentials is tested further by comparing the formation yields and the fission barriers.

Lattice QCD study of doubly charmed strange baryons

We present the energy spectra of the low lying doubly-charmed baryons using lattice quantum chromodynamics. We precisely predict the ground state mass of the charmed-strange Omega(cc) (1/2+) baryon to be 3712(11)(12) MeV which could well be the next doubly-charmed baryon to be discovered at the LHCb experiment at CERN. We also predict masses of other doubly-charmed strange baryons with quantum numbers 3/2+, 1/2-, and 3/2-.

First Observation of ^{20}B and ^{21}B.

The most neutron-rich boron isotopes ^{20}B and ^{21}B have been observed for the first time following proton removal from ^{22}N and ^{22}C at energies around 230 MeV/nucleon. Both nuclei were found to exist as resonances which were detected through their decay into ^{19}B and one or two neutrons. Two-proton removal from ^{22}N populated a prominent resonancelike structure in ^{20}B at around 2.5MeV above the one-neutron decay threshold, which is interpreted as arising from the closely spaced 1^{-},2^{-} ground-state doublet predicted by the shell model. In the case of proton removal from ^{22}C, the ^{19}B plus one- and two-neutron channels were consistent with the population of a resonance in ^{21}B 2.47±0.19 MeV above the two-neutron decay threshold, which is found to exhibit direct two-neutron decay. The ground-state mass excesses determined for ^{20,21}B are found to be in agreement with mass surface extrapolations derived within the latest atomic-mass evaluations.

Ground-state and stability properties of [formula omitted] isotopes based on semi-microscopic calculations

In this study, we present theoretical predictions on the stability properties of the yet unknown Og118276−293,295−308 isotopes using the Skyrme-SLy4 nucleon–nucleon interaction and the deformed Woods–Saxon single-particle potential in a semi-microscopic approach. The ground-state masses, binding energy, deformations and fission barriers are calculated from the total energy surfaces produced in a multidimensional deformation space using the dynamical differential evolution optimization method. Besides, the Q-values of the different decay modes and the nucleon separation energies for each isotope, and its α-decay (Tα) and spontaneous fission half-lives are also calculated. Our study revealed the Og290−296 elements to be the most bound Oganesson isotopes, among which 302,304,306Og elements are predicted to be spherical nuclei, and 299,300,301,303,305Og elements are shown to be almost spherical. The predicted ground-state and decay properties successfully reproduced the available data of the solely known Oganesson isotope 294Og. In addition to the principle α-decay modes, we studied the rival decay modes that challenge the stability of nuclei in the superheavy regions, namely the electron capture β+ decays and the spontaneous fission. An overall oscillating increasing behavior of Tα with the mass number is obtained, which obviously reverses the hesitating decreasing behavior of Qα and follows increasing trend of the corresponding change in the neutron-skin thickness after α-decays. The Og291,294−296,299−302 isotopes are expected to have relatively long half-lives, Tα≈ 1–45 ms, while 295Og is found to have the longest half-life between the considered nuclei. The Og291−300 isotopes exhibited relatively high fission barriers and small branching ratios for their spontaneous fission modes.

Consequences of broken axial symmetry in heavy nuclei—an overview of the situation in the valley of stability

An overview on the various effects of axial symmetry breaking is presented for medium heavy and heavy nuclei covering the mass number range 70 < A < 240. The discussion includes various observations for nuclei: level densities, spectroscopic features as energies and transition rates, ground state masses and finally the splitting of giant dipole resonances. Quadrupole moments and rates can be derived from models of triaxial rigid rotation or cranking for a given triaxiality parameters γ, but microscopic considerations are needed to predict these for each nucleus investigated. Respective predictions were adopted from recently made Hartree–Fock–Bogolyubov (HFB) calculations extended to arbitrary triaxiality by a generator coordinate method. In accord to these, various observations as reported in this overview demonstrate the importance of allowing a breaking of axial symmetry for heavy nuclei already in the valley of stability. Considering this breaking as indicated from the HFB approach surprisingly many experimental data are well described globally without the need for local fit parameters. In addition to these comparisons it will be shown that it is advantageous to consider cγ = cos(3γ) an indicator of axiality for heavy nuclei independent of their quadrupole moment.

Precise Predictions of Charmed-Bottom Hadrons from Lattice QCD.

We report the ground state masses of hadrons containing at least one charm and one bottom quark using lattice quantum chromodynamics. These include mesons with spin (J) and parity (P), (J^{P}): 0^{-}, 1^{-}, 1^{+}, and 0^{+} and the spin 1/2 and 3/2 baryons. Among these hadrons, only the ground state of 0^{-} is known experimentally, and therefore our predictions provide important information for the experimental discovery of all other hadrons with these quark contents.