arXiv subjects

Praveen C. Srivastava

Publications and source records attributed to Praveen C. Srivastava.

At least 37 records · Page 2Linked to original sources

arXiv2024

Investigation of entanglement in $N = Z$ nuclei within no-core shell model

In this work, we explore the entanglement structure of two $N = Z$ nuclei, $^{20}$Ne and $^{22}$Na using single-orbital entanglement entropy within the No-Core Shell Model (NCSM) framework for two realistic interactions, INOY and N$^3$LO. We begin with the determination of the optimal frequencies based on the variation of ground-state (g.s.) binding energy with NCSM parameters, $N_{max}$ and $\hbar Ω$, followed by an analysis of the total single-orbital entanglement entropy, $S_{tot}$, for the g.s. of $^{20}$Ne and $^{22}$Na. Our results show that $S_{tot}$ increases with $N_{max}$ and decreases with $\hbar Ω$ after reaching a maximum. We use $S_{tot}$ to guide the selection of an additional set of optimal frequencies that can enhance electromagnetic transition strengths. We also calculate the low-energy spectra and $S_{tot}$ for four low-lying states of $^{20}$Ne and six low-lying states of $^{22}$Na. Finally, we calculate a few $E2$ and one $M1$ transition strengths, finding that N$^3$LO provides better results for $B(E2; 5^+_1 \to 3^+_1$) and INOY performs well for the $B(M1; 0_1^+ \to 1_1^+)$ transition in the $^{22}$Na nucleus while considering the first set of optimal frequencies. We also observe that the second set of optimal frequencies enhances electromagnetic transition strengths, particularly for the states with large and comparable $S_{tot}$. Also, for both nuclei, the $S_{tot}$ for INOY and N$^3$LO are close while considering the second set of optimal frequencies, suggesting that the calculated $S_{tot}$ are more dependent on $\hbar Ω$ than the interactions employed for the same model space defined by the $N_{max}$ parameter.

nucl-th↗

arXiv2024

Study of $β^+$/EC-decay properties of $sd$ shell nuclei using nuclear shell model

Our study employs the nuclear shell model to systematically compute the half-lives of $β$ -decay for nuclei in the mass range of $A = 18-39$, encompassing the majority of $sd$ shell nuclei. This analysis utilizes the USDB and SDNN Hamiltonians. The theoretical outcomes contain calculations of various parameters such as $Q$ -values, half-lives, excitation energy, log$ft$ values, and branching ratios. We explore these results with axial-vector coupling constant for weak interactions, denoted as $g_A$$(= 1.27)$, and $κ$ value $(= 6289)$. We perform calculations of Gamow Teller matrix elements for 116 decay processes to calculate the quenching factor; we found a quenching factor of $q = 0.794\pm0.05 $ for the USDB interaction and $q = 0.815\pm0.04 $ for the SDNN interaction. We have also calculated superallowed transitions $0^+ \rightarrow 0^+$ for seven nuclei. Further, we have also included the electron capture phase space factor for the required nuclei to calculate the half-lives. This inclusion leads to small contribution in results, particularly for nuclei where electron capture (EC) plays a significant role. The overall results are in agreement with the experimental data.

nucl-th↗

arXiv2024

Higher forbidden unique $β^-$ decay transitions and shell-model interpretation

In the present work, we have predicted the half-lives for the $β^{-}$ decay for higher forbidden unique transitions in the mass range of nuclei from A = 40-138. For these transitions, the experimental data for half-lives are not available except for a few cases. The calculations for half-lives are performed within the framework of the nuclear shell model (SM). We have used the effective interactions sdpf-mu, gxpf1a, gwbxg, G-matrix, snet, sn100pn, and jj56pnb to perform the SM calculations in different mass regions. A comprehensive discussion has been made between the SM-predicted half-lives and the scaled half-lives from proton-neutron quasiparticle random-phase approximation (pnQRPA). The results of the present study will be useful to plan new experiments to measure half-lives for these higher forbidden unique $β^{-}$ transitions.

nucl-th↗

arXiv2024

Shell-model study for allowed and forbidden $β^-$ decay properties in the mass region "south" of $^{208}$Pb

The large-scale shell-model calculations have been performed for the neutron-rich nuclei in the south region of $^{208}$Pb in the nuclear chart. The $β$-decay properties, such as the $\log ft$, average shape factor values, half-lives, and partial decay rates are calculated for these neutron-rich nuclei using recent effective interaction for the $^{208}$Pb region. These calculations have been performed without truncation in a particular model space for nuclei $N\leq 126$; additionally, particle-hole excitations are included in the case of core-breaking nuclei ($Z\leq 82, N>126$). An extensive comparison with the experimental data has been made, and spin parities of several states have been proposed.

nucl-th↗

arXiv2024

Systematic shell-model study of structure and isomeric states in $^{204-213}$Bi isotopes

In this work, we have performed systematic shell-model calculations for Bi isotopes with $A=$ 204-213 using KHH7B and KHM3Y effective interactions. We have reported yrast and non-yrast shell-model states corresponding to the available experimental data. From the comparison with the experimental data, we could assign spin and parity of several unconfirmed states. We have also calculated electromagnetic properties and compared them with the available experimental data and predicted where experimental data are not available. This study also includes a detailed discussion of multiple isomeric states based on computed shell-model configurations and their respective half-lives.

nucl-th↗

arXiv2024

Shell-model study of $\log ft$ values for $^{139,140,141}$Ba $\rightarrow$ $^{139,140,141}$La transitions

In the present work, beta-decay properties such as $\log ft$ values and half-lives have been systematically studied corresponding to Ba isotopes using large-scale shell-model calculations. An extensive comparison of beta decay results corresponding to $^{141}$Ba$\rightarrow$ $^{141}$La using shell-model calculations is made with the recently available experimental data. In addition, we have also calculated the nuclear and beta decay properties corresponding to $^{139}$Ba$\rightarrow$ $^{139}$La and $^{140}$Ba$\rightarrow$ $^{140}$La transitions. The model-space considered here is $Z=50-82$ and $N=82-126$ with $^{132}$Sn core, and the interaction employed here is jj56pnb interaction. The beta decay results using shell-model calculations for all the mentioned isotopes are compared with the available experimental data. This is the first theoretical interpretation corresponding to recent experimental data.

nucl-th↗

arXiv2024

Systematic shell-model study for structure and isomeric states in $^{200-210}$Po isotopes

We report systematic large-scale shell-model calculation for Po isotopes with $A=$ 200 to 210. We have performed calculations using KHH7B interaction in the model space $Z$ = 58-114 and $N$ = 100-164 around doubly-magic $^{208}$Pb. We allow valence neutrons to occupy in the $1f_{5/2}$, $2p_{3/2}$, $2p_{1/2}$, and $0i_{13/2}$ orbitals, while two valence protons beyond $Z=82$ are occupied in $0h_{9/2}$, $1f_{7/2}$ and $0i_{13/2}$ orbitals. The calculated energies and electromagnetic properties are compared with the available experimental data and predicted where experimental data are not available. We have also reported shell-model results for different isomeric states of these nuclei.

nucl-th↗

arXiv2024

Systematic shell-model study of $^{99-129}$Cd isotopes and isomers in neutron-rich $^{127-131}$In isotopes

Systematic shell-model calculations are presented for odd-mass Cd isotopes with $N=51-81$ utilizing a combination of a $G$-matrix interaction and a semiempirical one. The excited energy spectra and electromagnetic transition probabilities are compared with the recently available experimental data. We have found that the observed quadrupole moments in the $11/2^-_1$ states that linearly change with the neutron number are well accounted for by the dominance of prolate shapes throughout the Cd isotope chain. We have also described the properties of several isomeric states in neutron-rich $^{127-131}$In isotopes that were recently observed in Jyväskylä.

nucl-th↗

arXiv2023

Large-scale shell-model study of two-neutrino double-beta decay of $^{82}$Se, $^{94}$Zr, $^{108}$Cd, $^{124}$Sn, $^{128}$Te, $^{130}$Te, $^{136}$Xe, and $^{150}$Nd

Large-scale shell-model calculations have been performed for the study of two neutrino double-beta ($2νββ$) decay in $^{82}$Se, $^{94}$Zr, $^{108}$Cd, $^{124}$Sn, $^{128}$Te, $^{130}$Te, $^{136}$Xe, and $^{150}$Nd. We have employed JUN45 interaction to calculate the nuclear matrix element (NME) for $2νββ$ decay in $^{82}$Se. In the case of $^{94}$Zr, the glekpn effective interaction is used. For $^{108}$Cd, we have used a realistic effective interaction derived through the G-matrix approach. In the case of $^{124}$Sn, $^{128,130}$Te and $^{136}$Xe, the sn100pn effective interaction is employed. For $^{150}$Nd, we have used KHHE effective interaction based on holes in a $^{208}$Pb core. We have extracted the half-lives of these nuclei for the $2νββ$ decay with the help of calculated NME. Our results are consistent with the available experimental half-lives. The variation of cumulative $2νββ$ NME with respect to the excitation energy of the intermediate $1^+$ states is also shown, and in all cases, it is ensured that their values are almost saturated. In the present work we have calculated more intermediate $1^+$ states as much as possible in comparison to results available in the literature.

nucl-th↗

arXiv2023

Prediction of the neutron drip line in oxygen isotopes using quantum computation

In the noisy intermediate-scale quantum era, variational algorithms have become a standard approach to solving quantum many-body problems. Here, we present variational quantum eigensolver (VQE) results of selected oxygen isotopes within the shell model description. The aim of the present work is to locate the neutron drip line of the oxygen chain using unitary coupled cluster (UCC) type ansatze with different microscopic interactions (DJ16, JISP16, and N3LO), in addition to a phenomenological USDB interaction. While initially infeasible to execute on contemporary quantum hardware, the size of the problem is reduced significantly using qubit tapering techniques in conjunction with custom circuit design and optimization. The optimal values of ansatz parameters from classical simulation are taken for the DJ16 interaction, and the tapered circuits are run on IonQ's Aria, a trapped-ion quantum computer. After applying gate error mitigation for three isotopes, we reproduced exact ground state energies within a few percent error. The post-processed results from hardware also clearly show $^{24}$O as the drip line nucleus of the oxygen chain. Future improvements in quantum hardware could make it possible to locate drip lines of heavier nuclei.

nucl-th↗

arXiv2023

Shell-model study for $^{204-210}$Tl isotopes and core excitations across the $Z = 82$ and $N = 126$ shell gaps

In the present work, the $^{204-210}$Tl isotopes have been investigated by performing large-scale shell-model calculations, including configurations allowing both neutron and proton core excitations across the $Z$ = 82 and $N$ = 126 shell gaps. Inspired by the recent high-spin experimental data, the structure of Tl isotopes has been studied for a considerably large model space. The KHHE interaction has been used for $^{204-206}$Tl isotopes, KHH7B interaction for $^{204-210}$Tl isotopes, and additionally KHM3Y interaction has been used for $^{208}$Tl isotope. The core excitation has been performed using the KHH7B and KHM3Y interactions. The level spectra of $^{204-210}$Tl isotopes are comprehensively described and explained by multi-nucleon couplings of single-particle-hole orbitals within the valence space and by core excitations across $^{208}$Pb core. The well-known isomeric states are analyzed in terms of the shell model configurations.

nucl-th↗

arXiv2023

Shell-model study of $β^+$/EC-decay half-lives for $Z = 21-30$ nuclei

In the present work, we have reported $β^+$/EC-decay half-lives for $Z = 21 -30$ nuclei using large-scale shell-model. %and N $\leq$ A recent study shows that some proton-rich nuclei in this region belong to the island of inversion. We have performed calculations for these nuclei using KB3G effective interaction, while for Ni, Cu, and Zn nuclei we have used JUN45 effective interaction in the $f_{5/2}pg_{9/2}$ model space. The calculated quenching factors for $fp$ and $f_{5/2}pg_{9/2}$ space using KB3G and JUN45 effective interactions are also reported. Shell-model results of $β$-decay half-lives, excitation energies, log$ft$ values, and branching fractions are discussed and compared with the available experimental data. We have obtained a reasonable agreement with the available data.

nucl-th↗

arXiv2023

Systematic shell-model study of $^{98-130}$Cd isotopes and $8^+$ isomeric states

We present systematic shell-model studies of even-even $^{98-130}$Cd isotopes using a realistic effective shell-model interaction derived from the G-matrix approach with an inert core $^{88}$Sr. Our calculated low-lying excited energy spectra and electromagnetic properties are compared with the experimental data. On the basis of recently available experimental data, we predict spins and parities corresponding to unconfirmed states. We also discuss the properties of $8^+$ isomeric states in $^{98-104,130}$Cd isotopes.

nucl-th↗

arXiv2023

Study of S, Cl and Ar isotopes with $N \geq Z$ using microscopic effective $sd$-shell interactions

In the present work, newly developed microscopic effective $sd$-valence shell interactions such as chiral next-to-next-to-next-to-leading order (N3LO), $J$-matrix inverse scattering potential (JISP16), Daejeon16 (DJ16), and monopole-modified DJ16 (DJ16A) are employed to study the nuclear structural properties of sulphur, chlorine, and argon isotopes with $N \geq Z$. These interactions are derived using the \textit{ab initio} no-core shell-model and the OLS unitary transformation method. We calculate energy spectra and electromagnetic properties to test the predictive strength of the effective interactions for these heavier $sd$-shell nuclei. For a complete systematic study, we compare the microscopic results with the phenomenological USDB results and experimental data. By looking at the excitation energies of these nuclei, the DJ16A interaction is found to be {the} most suitable for these $sd$-shell nuclei among all microscopic interactions. The electric quadrupole transition strength and excitation energy of the first $2^+$ state data of even-even sulphur isotopes indicate the presence of the $N=20$ shell closure. Quadrupole moment predictions are also made using these interactions where experimental data are unknown. Magnetic moments are in excellent agreement with the experimental values. The root-mean-square deviations are also calculated to provide an idea of how accurate the interactions are.

nucl-th↗

arXiv2023

Quasideuterons in Light Nuclei

The role of pairing correlations for nucleon pairs with isospin $T=1$ and $T=0$ is investigated for nuclei in the mass region $12 \leq A \leq 42$. For that purpose the two-nucleon densities resulting from nuclear shell-model calculations in one and two major shells are analyzed. Significant effects on the resulting energies are observed due to the formation of $T=0$ pairs. The formation of quasi-deuterons is maximal for symmetric nuclei with $N=Z$. The formation of $T=0$ pairs is less sensitive to the density of single-particle states close to the Fermi energy than the $T=1$ pairing and is relevant also for excitations across shell-closures. This robustness also explains why $T=0$ pairing does not lead to such a clear evidence in comparing energies of neighbored nuclei as the "odd-even mass staggering" due to the formation of $T=1$ pairing.

nucl-th↗

arXiv2023

Nuclear structure properties of Si and P isotopes with the microscopic effective interactions

In the present work, we have reported comprehensive study of the $sd$-shell nuclei Si and P with neutron number varying from $N = 9$ to $N = 20$ using the microscopic effective valence shell interactions, namely, N3LO, JISP16 and DJ16A. These effective $sd$-shell interactions are developed using the \textit{ab initio} no-core shell model wave functions and the Okubo-Lee-Suzuki transformation method. For comparison, we have also performed shell model calculations with the empirical USDB interaction. Energy spectra and electromagnetic properties of these isotopic chains have been studied. Theoretically calculated shell model results are compared with the available experimental data, to check the predictive strength of these microscopic interactions. It is found that the binding energies of the ground states are better reproduced with the DJ16A interaction as compared to other microscopic interactions and a proton subshell closure at $Z=14$ is obtained in Si. Spin-tensor decomposition of two-body interaction is presented to understand the contributions from central, vector and tensor components into these interactions. Spectroscopic strengths of $^{23}$Al($d$,$n$)$^{24}$Si are examined for the newly performed experiment at NSCL.

nucl-th↗

arXiv2023

Study of structure and radii for $^{20-31}$Na isotopes using microscopic interactions

In this work, Na isotopes with mass varying from $A=$ 20 to 31 have been studied using DJ16A, JISP16 and N3LO microscopic effective interactions in the $sd$-shell. These effective interactions are derived for $sd$-shell using no-core shell model wavefunctions and a unitary transformation method. We have also performed calculation with IMSRG effective interactions targeted for a particular nucleus. The studies include a detailed analysis of ground state binding energy, low-lying spectra, and electromagnetic properties such as reduced electric quadrupole transition strengths, quadrupole and magnetic dipole moments of the Na chain. The results obtained from these microscopic effective interactions were compared with the experimental data as well as with the results of phenomenological interaction USDB. The charge radii of Na isotopes are evaluated using shell model harmonic oscillator wave functions. In addition to charge radii, matter radii and neutron skin thickness in the Na chain are discussed with a focus on neutron-deficient Na isotopes.

nucl-th↗

arXiv2023

Ab-initio no-core shell model study of $^{18-24}$Ne isotopes

We report \textit{ab initio} no-core shell model (NCSM) study of $^{18-24}$Ne isotopes for energy spectra, electromagnetic properties, and point-proton radii using three realistic $NN$ interactions. We have used inside nonlocal outside Yukawa (INOY), charge-dependent Bonn 2000 (CDB2K) and the chiral next-to-next-to-next-to-leading order (N$^3$LO) interactions. We are able to reach basis size up to $N_{max}$ = 6 for $^{18}$Ne and $N_{max}$ = 4 for the $^{19-24}$Ne isotopes with m-scheme dimensions up to 1.0 $\times$ $10^9$ in case of $^{24}$Ne. We observed better results for INOY interaction in terms of the binding energies of ground state (g.s.), and overall all three interactions provide good agreement with the experimental low-energy spectra. Our results for reduced $M1$ transition strengths and magnetic moments are close to the experimental values. We found that for long-range observables such as the $E2$ transition strengths, the electric quadrupole moments, and the point-proton radii ($r_p$), we need higher $N_{max}$ calculations to obtain results comparable to the experimental data. We have observed almost 6 \% increment in the converged $r_p$ as we increase the model space from $N_{max}$ = 4 to $N_{max}$ = 6.

nucl-th↗