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EPJ A - Hadrons and Nuclei
Journal Prestige (SJR): 1.116  Citation Impact (citeScore): 2 Number of Followers: 0  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1434-6001 - ISSN (Online) 1434-601X Published by Springer-Verlag  [2467 journals]
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- NLOAccess: automated online computations for collider physics
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Abstract: Abstract We present NLOAccess, an online platform acting as a virtual access to automated perturbative computations of physical observables related to collider physics within collinear factorisation. We discuss the design of the project and illustrate how, with few steps and without any need of pre-code or code compilation, a user can generate events and calculate cross sections related for instance to quarkonium production and/or heavy-ion collisions at leading and next-to-leading order in \(\alpha _s\) using MadGraph5_aMC@NLO or HELAC-Onia. Finally, we report about the obtained results in terms of number of users and runs, and we illustrate the future plans of the project.
PubDate: 2023-03-16
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- In-beam $$\gamma $$ -ray spectroscopy of $$^{94}$$ Ag
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Abstract: Abstract A recoil-beta-tagging experiment has been performed to study the excited \(T=0\) and \(T=1\) states in the odd–odd \(N=Z\) nucleus \(^{94}\) Ag, populated via the \(^{40}\) Ca( \(^{58}\) Ni,1p3n) \(^{94}\) Ag reaction. The experiment was conducted using the MARA recoil separator and JUROGAM3 array at the Accelerator Laboratory of the University of Jyväskylä. Through correlating fast, high-energy beta decays at the MARA focal plane with prompt \(\gamma \) rays emitted at the reaction target, a number of transitions between excited states in \(^{94}\) Ag have been identified. The timing characteristics of these transitions confirm that they fall within decay sequences that feed the short-lived \(T=1\) ground state of \(^{94}\) Ag. The transitions are proposed to proceed within and between the sets of states with \(T=0\) and \(T=1\) . Possible correspondence between some of these transitions from analog states in \(^{94}\) Pd has been discussed, and shell-model calculations including multipole and monopole electromagnetic effects have been presented, in order to enable predictions of the decay patterns between the \(T=0\) and \(T=1\) states and to allow a theoretical set of Coulomb energy differences to be calculated for the \(A = 94\) \(T=1\) analog states.
PubDate: 2023-03-15
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- Impact of nuclear shape fluctuations in high-energy heavy ion collisions
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Abstract: Abstract The shape of atomic nuclei is often interpreted to possess a quadrupole deformation that fluctuates around some average profile. We investigate the impact of nuclear shape fluctuations on the initial state geometry in heavy ion collisions, particularly its eccentricity \(\varepsilon _2\) and inverse size \(d_{\perp }\) , which can be related to the elliptic and radial flow in the final state. The fluctuation in overall quadrupole deformation enhances the variances and modifies the skewness and kurtosis of the \(\varepsilon _2\) and \(d_{\perp }\) in a controllable manner. The fluctuation in triaxiality reduces the difference between prolate and oblate shape for any observable, whose values, in the large fluctuation limit, approach those obtained in collisions of rigid triaxial nuclei. The method to disentangle the mean and variance of the quadrupole deformation is discussed.
PubDate: 2023-03-15
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- Resonances in low-energy nuclear processes and nuclear astrophysics and
asymptotic normalization coefficients: a review-
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Abstract: Abstract This paper is continuation of the previous review [Mukhamedzhanov and Blokhintsev, Eur. Phys. J. A 58, 29 (2022)] in which the ANC of a bound state was addressed. However, the ANC is important characteristics not only of bound states but also resonances. In this paper, the role of the ANCs in resonance processes is addressed. Among various topics considered here are Gamow–Siegert resonance wave functions for charged particles and their normalization, relationship between ANCs and resonance widths. Significant part is devoted to the R-matrix approach for resonance processes. The resonance wave functions, internal and external and their projections on the two-body channel are given. Important ingredients of the R-matrix method for resonance states are also discussed. Elastic resonance scatterings are analyzed and extended for subthreshold resonances. It is shown how the notion of the subthreshold resonance works in practical analysis. To this end, the \(^{13}\textrm{C}(\alpha ,\,n)^{16}\textrm{O}\) reaction, which is considered to be the main neutron supply to build up heavy elements from iron-peak seed nuclei in AGB stars, is analyzed. Important part of the review is analysis of the relationship between resonance width and ANC of mirror resonance and bound states using the Pinkston–Satchler equation and the Wronskian method. Practical examples are given. Among important parts of the theoretical research is the theory of transfer reactions populating resonance states. Comparative analysis of prior and post-form DWBA amplitudes shows that the prior form is preferable over the post form due to faster convergence over \(r_{nA}\) . Calculations of the stripping to resonance reaction \({}^{16}\textrm{O}(d,\,p){}^{17}\textrm{O}(1d_{3/2})\) performed using the prior form of the CDCC method. A special attention is given to resonance astrophysical processes. Useful equations for internal and external radiative widths are given. Radiative capture through subthreshold resonance is considered. In particular, radiative capture reactions \({}^{11}\textrm{C}(p,\gamma ){}^{12}\textrm{N}\,\) and \(\,{}^{15}\textrm{N}(p,\gamma ){}^{16}\textrm{O}\,\) and the role of the ANC is addressed in detail.
PubDate: 2023-03-13
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- Faster spectral density calculation using energy moments
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Abstract: Abstract Accurate predictions of inclusive scattering cross sections in the linear response regime require efficient and controllable methods to calculate the spectral density in a strongly-correlated many-body system. In this work we reformulate the recently proposed Gaussian Integral Transform technique in terms of Fourier moments of the system Hamiltonian which can be computed efficiently on a quantum computer. One of the main advantages of this framework is that it allows for an important reduction of the computational cost by exploiting previous knowledge about the energy moments of the spectral density. For a simple model of medium mass nucleus like \(^{40}\) Ca and target energy resolution of 1 MeV we find an expected speed-up of \(\approx 125\) times for the calculation of the giant dipole response and of \(\approx 50\) times for the simulation of quasi-elastic electron scattering at typical momentum transfers.
PubDate: 2023-03-09
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- Statistical (n, $$\gamma $$ ) cross section model comparison for
short-lived nuclei-
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Abstract: Abstract Neutron-capture cross sections of neutron-rich nuclei are calculated using a Hauser–Feshbach model when direct experimental cross sections cannot be obtained. A number of codes to perform these calculations exist, and each makes different assumptions about the underlying nuclear physics. We investigated the systematic uncertainty associated with the choice of Hauser-Feshbach code used to calculate the neutron-capture cross section of a short-lived nucleus. The neutron-capture cross section for \(^{73}\hbox {Zn}\) (n, \(\gamma \) ) \(^{74}\hbox {Zn}\) was calculated using three Hauser-Feshbach statistical model codes: TALYS, CoH, and EMPIRE. The calculation was first performed without any changes to the default settings in each code. Then an experimentally obtained nuclear level density (NLD) and \(\gamma \) -ray strength function ( \(\gamma \hbox {SF}\) ) were included. Finally, the nuclear structure information was made consistent across the codes. The neutron-capture cross sections obtained from the three codes are in good agreement after including the experimentally obtained NLD and \(\gamma \hbox {SF}\) , accounting for differences in the underlying nuclear reaction models, and enforcing consistent approximations for unknown nuclear data. It is possible to use consistent inputs and nuclear physics to reduce the differences in the calculated neutron-capture cross section from different Hauser-Feshbach codes. However, ensuring the treatment of the input of experimental data and other nuclear physics are similar across multiple codes requires a careful investigation. For this reason, more complete documentation of the inputs and physics chosen is important.
PubDate: 2023-03-09
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- Kaon spectrum revisited: bound states of high energy and spin
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Abstract: Abstract The European Organization for Nuclear Research (CERN) has recently approved a world-unique QCD facility in which an updated version of the external M2 beam line of the CERN SPS in conjunction with a universal spectrometer of the COMPASS experiment is used. One of its main goals is to use highly intense and energetic kaon beams to map out the complete spectrum of excited kaons with an unprecedented precision; having a broad impact not only on low-energy QCD phenomenology, but also on many high-energy particle processes where excited kaons appear, such as the study of CP violation in heavy-meson decays studied at LHCb and Belle II. In support of the experimental effort, the kaon spectrum is computed herein using a constituent quark model which has been successfully applied to a wide range of hadronic observables, from light to heavy quark sectors, and thus the model parameters are completely constrained. The model’s prediction can be used as a template against which to compare the already collected data and future experimental findings, in order to distinguish between conventional and exotic kaon states. We also compare our results with those available in the literature in order to provide some general statements, common to all calculations.
PubDate: 2023-03-07
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- Bethe–Salpeter kernel and properties of strange-quark mesons
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Abstract: Abstract Focusing on the continuum meson bound-state problem, a novel method is used to calculate closed-form Bethe–Salpeter kernels that are symmetry consistent with any reasonable gluon-quark vertex, \(\varGamma _\nu \) , and therewith deliver a Poincaré-invariant treatment of the spectrum and decay constants of the ground- and first-excited states of u, d, s mesons. The predictions include masses of as-yet unseen states and many unmeasured decay constants. The analysis reveals that a realistic, unified description of meson properties (including level orderings and mass splittings) requires a sound expression of emergent hadron mass in bound-state kernels; alternatively, that such properties may reveal much about the emergence of mass in the standard model.
PubDate: 2023-03-04
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- To study the strange particles production at RHIC energies
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Abstract: Abstract The minimum bias differential yield is reported for \(K^{0}_{S}\) , \(\Lambda ,\bar{\Lambda }\) , \(\Xi ^{-},\bar{\Xi ^{+}}\) , \(\Omega ^{-},\bar{\Omega ^{+}}\) and \(\phi \) strange hadrons, obtained from \(Au-Au\) collisions at RHIC energies of \(\sqrt{s_{NN}} = 11.5,19.6,27 \; \mathrm{{and}} \; 39 \; \mathrm{{GeV}}\) as a function of \(p_{T}\) in kinematic range of \(0< p_{T} < 5\; GeV\) and pseudorapidity region of \( \eta < 0.5\) using PYTHIA8 and HIJING2 event generators. The PYTHIA8 is tuned to different Colour Reconnection (CR) modes, and results are compared with STAR data at RHIC. PYTHIA8 predictions agree with STAR data at low \(p_{T}\) values, while underestimate at high \(p_T\) values.The observed deviations in CR0 are due to multiparton interactions, the deviations in CR1 are due to QCD effects. At low \(p_T\) , the non-pQCD effects are dominant, while at high \(p_T\) , the pQCD effects are dominant. The deviations in CR2 mode is due to the minimization of strings followed by different colour combinations, and the deviations in case of CR3 mode is connected with strings as viewed diagonally in extended bags. HIJING2 predictions explain the STAR data very well over the entire \(p_T\) region.
PubDate: 2023-02-28
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- Three- $$\alpha $$ configurations of the second $$J^\pi =2^+$$ state in
$$^{12}$$ C-
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Abstract: Abstract We investigate geometric configurations of \(\alpha \) ( \(^4\) He nucleus) clusters in the second \(J^\pi =2^+\) state of \(^{12}\) C, which has been discussed as a rotational band member of the second \(0^+\) state, the Hoyle state. The ground and excited \(0^+\) and \(2^+\) states are described by a three- \(\alpha \) cluster model. The three-body Schrödinger equation with orthogonality conditions is accurately solved by the stochastic variational method with correlated Gaussian basis functions. To analyse the structure of these resonant states in a convenient form, we introduce a confining potential. The two-body density distributions together with the spectroscopic information clarify the structure of these states. We find that main configurations of both the second \(0^+\) and \(2^+\) states are acute-angled triangle shapes originating from the \(^8\) Be( \(0^+\) ) \(+\alpha \) configuration. However, the \(^{8}\textrm{Be}+\alpha \) components in the second \(2^+\) state become approximately 2/3 because the \(^8\) Be subsystem is hard to excite, indicating that the state is not an ideal rigid rotational band member of the Hoyle state.
PubDate: 2023-02-25
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- Neutron capture cross section of $$^{83}$$ Kr
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Abstract: Abstract The neutron capture cross section of \(^{83}\) Kr has been measured via the time-of-flight technique between 25 meV and 500 keV. The experiment used the DANCE array at the Los Alamos National Laboratory. Maxwellian Averaged Cross Sections have been derived for a range of stellar temperatures and are found to be in good agreement with previous data. The impact of the new cross sections on stellar nucleosynthesis has been investigated.
PubDate: 2023-02-24
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- High-precision Penning-trap mass spectrometry for neutrino physics
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Abstract: Abstract After several decades of a dramatic development Penning-trap mass spectrometry now demonstrates unprecedented precision and sensitivity in measurements of the masses of a broad range of nuclides for various aspects of fundamental physics. This article reviews one facet of such mass measurements—a contribution of Penning-trap mass spectrometry to experiments on studies of neutrinos. These studies encompass the determination of the neutrino mass, the search for sterile and relic neutrinos and the search for neutrinoless double electron capture in order to determine the type of neutrinos as well as to check the conservation law of the total lepton number.
PubDate: 2023-02-24
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- Mirror beta decays
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Abstract: Abstract Beta decays of mirror nuclei differ in Q-value, but will otherwise proceed with transitions of similar strength. The current status is reviewed: Fermi transitions are all very similar, whereas Gamow–Teller transitions can differ in strength by more than a factor two. Several effects that can contribute to the asymmetries are discussed, the largest effect appears to be due to binding-energy differences between the mirror systems. Recommendations are given for future experimental investigations.
PubDate: 2023-02-24
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- Vorticity in isobar collisions of $$^{96}_{44}$$ Ru + $$^{96}_{44}$$ Ru
and $$^{96}_{40}$$ Zr + $$^{96}_{40}$$ Zr at
$$\sqrt{{\textrm{s}}_{\textrm{NN}}}$$ = 200 GeV-
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Abstract: Abstract The kinematic vorticity and thermal vorticity are calculated in isobar collisions of 200 GeV \(^{96}_{44}\) Ru + \(^{96}_{44}\) Ru and \(^{96}_{40}\) Zr + \(^{96}_{40}\) Zr with different deformation parameters within the framework of Ultra-relativistic Quantum Molecular Dynamics model (UrQMD), and a little difference of vorticity between \(^{96}_{44}\) Ru + \(^{96}_{44}\) Ru and \(^{96}_{40}\) Zr + \(^{96}_{40}\) Zr collisions is observed. From the ratios of (Zr-Ru)/Ru of vorticity in different deformation cases, it is found that ratios in deformation cases decrease with the increasing of centrality (i.e. more peripheral) but increase in the case without deformation. And an opposite signal is observed for ratios between nuclear collisions with deformation and without deformation. In addition, the effect of deformation parameter \(\beta _{2}\) is discussed and it is found that the larger \(\beta _{2}\) the deformation of the nuclei has, the higher vorticity the collision system presents in the \(^{96}_{40}\) Zr + \(^{96}_{40}\) Zr collisions. However, it is insensitive in the \(^{96}_{44}\) Ru + \(^{96}_{44}\) Ru collisions.
PubDate: 2023-02-23
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- Neutrino and Antineutrino captures on $$^{18}$$ O within QRPA models
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Abstract: Abstract In this work we have evaluated the neutrino (NS) and antineutrino (AS) scattering cross sections on \(^{18}\) O and the inclusive muon capture rates at low energies within the Quasiparticle Random Phase Approximation (QRPA) and Projected QRPA (PQRPA) models. We present the first study of \(^{18}\) O \((\nu _e,e^-)^{18}\) F and \(^{18}\) O \((\bar{\nu }_e,e^+)^{18}\) N cross sections. These reactions are an important nuclear input for astrophysical calculations such as the CNO cycle. We have employed the weak formalism developed in Krmpotić et al. (Phys Rev C 71:044319, 2005) to analyze neutrino/antineutrino-nucleus scattering. Within this formalism, the nuclear residual interaction is described by \(\delta \) -force previously employed to evaluate single and double beta decays in QRPA models. The adopted parametrization leads to good results for the inclusive muon capture: we reproduce the available experimental data for the rate and the Gamow–Teller strength in \(^{18}\) F. We compared our results for the NS and AS cross sections on \(^{18}\) O with other theoretical evaluations on \(^{16}\) O, since there are no experimental data available for the processes on \(^{18}\) O. We noticed that the cross sections present a similar behavior as a function of the neutrino/antineutrino energy. For NS and AS we observed that the PQRPA procedure yields cross sections smaller than QRPA. We show that the Pauli blocking has an important role in the distribution of the partial contributions and the presence of two neutrons over the closed shell yields to higher NS cross sections than the AS cross sections. For NS and AS, the largest contribution comes from allowed and first-forbidden transitions, respectively.
PubDate: 2023-02-23
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- Composite pulses for population transfer in the interaction of two-level
nuclear systems with X-ray laser pulses-
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Abstract: Abstract Population transfer of two-state nuclei interacting with a train of composite X-ray free electron laser (XFEL) pulses has been investigated theoretically. In this study, we calculate the effective intensity of the XFEL pulse for each nucleus so that the time temporal pulse area of Rabi frequency is equal to \(\pi \) . We show that with increasing the number of composite pulses, even with a significant deviation of the effective intensity of the laser beam from the calculated value, the population is completely transferred from the ground state to the excited state. For numerical study, nuclei with a high lifetime in the excited state, compared to the XFEL laser pulse duration, have been selected so that the effect of spontaneus emission can be neglected. Finally, it has been shown that despite the detuning effects, by increasing the number of XFEL composite pulses as well as the effective intensity of the laser pulse, the population is completely transferred to the excited state.
PubDate: 2023-02-23
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- Non-equilibrium cumulants within model A from crossover to first-order
phase transition side-
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Abstract: Abstract We study the non-equilibrium cumulants of the chiral order parameter field ( \(\sigma \) field) in different phase transition scenarios via Langevin dynamics. Cumulants up to fourth-order have been calculated based on the spacetime-dependent \(\sigma \) configurations from the event-by-event numerical simulations. By limiting the cooling of the system in a Hubble-like way, the out-of-equilibrium cumulants illustrate clear memory effects during the evolution. Both the signs and the magnitudes of the high-order cumulants differ from the equilibrium ones below the phase transition temperature. Especially, the dynamical cumulants grow more intensively from the first-order phase transition side than they do from the crossover side. In addition, analysis of the high-order off-equilibrium cumulants on the hypothetical freeze-out lines present non-monotonic curves in the large chemical potential region.
PubDate: 2023-02-21
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- First application of the phase-imaging ion-cyclotron resonance technique
at TRIGA-Trap-
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Abstract: Abstract The phase-imaging ion cyclotron resonance technique (PI-ICR) has been implemented at TRIGA-Trap together with a newly built five-pole cylindrical trap. In PI-ICR the total phase of trapped ions is measured by projecting the ion motion onto a position-sensitive delay-line micro-channel plate detector. The systematic uncertainties have been investigated and first mass measurements on stable Pb isotopes have been performed with PI-ICR. The new technique offers higher mass-resolving power, allows checking for the presence of contaminant ion species, and it proved useful in tuning the harmonicity of the trapping potential as well as in aligning the trap symmetry axis with respect to the magnetic field axis by visualizing the radial ion motion. This is a non-scanning technique where every detected ion contributes equally, therefore it is more sensitive than the previously used time-of-flight ion-cyclotron-resonance (ToF-ICR) technique, which is based on the scanning of the sideband-frequency of trapped ions and recording their time of flight after ejection. It will enable us to carry out high-precision mass measurements in the actinide region with uncertainties on the ppb level.
PubDate: 2023-02-17
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- Nucleosynthesis and observation of the heaviest elements
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Abstract: Abstract The rapid neutron capture or ‘r process’ of nucleosynthesis is believed to be responsible for the production of approximately half the natural abundance of heavy elements found on the periodic table above iron (with proton number \(Z=26\) ) and all of the heavy elements above bismuth ( \(Z=83\) ). In the course of creating the actinides and potentially superheavies, the r process must necessarily synthesize superheavy nuclei (those with extreme proton numbers, neutron numbers or both) far from isotopes accessible in the laboratory. Many questions about this process remain unanswered, such as ‘where in nature may this process occur'’ and ‘what are the heaviest species created by this process'’ In this review, we survey at a high level the nuclear properties relevant for the heaviest elements thought to be created in the r process. We provide a synopsis of the production and destruction mechanisms of these heavy species, in particular the actinides and superheavies, and discuss these heavy elements in relation to the astrophysical r process. We review the observational evidence of actinides found in the Solar system and in metal-poor stars and comment on the prospective of observing heavy-element production in explosive astrophysical events. Finally, we discuss the possibility that future observations and laboratory experiments will provide new information in understanding the production of the heaviest elements.
PubDate: 2023-02-15
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- $$B\rho $$ -defined isochronous mass spectrometry and mass measurements of
$$^{58}$$ Ni fragments-
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Abstract: Abstract A novel isochronous mass spectrometry, termed as \(B\rho \) -defined IMS, has been established at the experimental cooler-storage ring CSRe in Lanzhou. Its potential has been studied through high precision mass measurements of \(^{58}\) Ni projectile fragments. Two time-of-flight detectors were installed in one of the straight sections of CSRe, thus enabling simultaneous measurements of the velocity and the revolution time of each stored short-lived ion. This allows for calculating the magnetic rigidity \(B\rho \) and the orbit length C of each ion. The accurate \(B\rho (C)\) function has been constructed, which is a universal calibration curve used to deduce the masses of the stored nuclides. The sensitivity to single stored ions, fast measurement time, and background-free characteristics of the method are ideally suited to address nuclides with very short lifetimes and smallest production yields. In the limiting case of just a single particle, the achieved mass resolving power allows one to determine its mass-over-charge ratio m/q with a remarkable precision of merely \(\sim 5\) keV. Masses of \(T_z=-3/2\) fp-shell nuclides are re-determined with high accuracy, and the validity of the isospin multiplet mass equation is tested up to the heaviest isospin quartet with \(A=55\) . The new masses are also used to investigate the mirror symmetry of empirical residual proton-neutron interactions.
PubDate: 2023-02-14
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