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At least 829 records · Page 46
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DOE OSTI2026

Pathfinding quantum simulations of neutrinoless double- β decay

We present results from co-designed quantum simulations of the neutrinoless double- β decay of a simple nucleus in 1+1D quantum chromodynamics using IonQ’s Forte-generation trapped-ion quantum computers. Electrons, neutrinos, and up and down quarks are distributed across two lattice sites and mapped to 32 qubits, with an additional 4 qubits used for flag-based error mitigation. A four-fermion interaction is used to implement weak interactions, and lepton-number violation is induced by a neutrino Majorana mass. Quantum circuits that prepare the initial nucleus and time evolve with the Hamiltonian containing the strong and weak interactions are executed on IonQ Forte Enterprise. Enabled by tuned model parameters, lepton-number violation is observed in real time, providing a clear signal of neutrinoless double- β decay. This was made possible by co-designing the simulation to maximally utilize the all-to-all connectivity and native gate-set available on IonQ’s quantum computers. Quantum circuit compilation techniques and co-designed error-mitigation methods, informed from executing benchmarking circuits with up to 2,356 two-qubit gates, enabled observables to be extracted with high precision. We discuss the potential of future quantum simulations to provide yocto-second resolution of the reaction pathways in these, and other, nuclear processes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Using Prompt Neutron Decay Constant Measurements to Obtain Additional Kinetics Information

Prompt neutron decay constant measurements are typically used to infer the prompt neutron lifetime in a chain-reacting system, but these measurements include much more information about the kinetics of the system. This work focuses specifically on the Rossi-α method of measuring the prompt neutron decay constant. The Rossi-α system of equations consists of five unknown parameters. With five unknowns and three equations, the system of equations solved by the Rossi-α measurement is under-determined. It has been postulated that a well posed problem can be formulated using independent measurement configurations on a single system. The external source strength, the effective delayed neutron fractions, and Diven’s parameter do not typically change for different configurations of a single experiment. If good detector geometry is chosen, the detector efficiency does not change for multiple measurements of a single experiment using Rossi-α measurements. By making these assumptions, there are only two unique variables. This knowledge can be used to solve for most of the unique parameters using two independent, unique Rossi-α measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Kinetics of the luminescence decay of Fe{sup 2+} impurity centres in polycrystalline ZnSe upon excitation by an electron beam

The kinetics of the decay of the luminescence of Fe{sup 2+} ions is measured at nitrogen temperature in polycrystalline ZnSe excited by a short pulse of accelerated electrons. The time dependence of the luminescence intensity differs from the exponential one, observed upon excitation of luminescence by a short light pulse. The obtained nonexponential dependence is theoretically described. The explanation is based on the quenching effect of the excited state of the Fe{sup 2+} ion by free electrons of the volume charge of the current of accelerated electrons in the sample (Auger effect). It was shown that the relaxation of the volume charge after the electron-accelerating voltage is removed makes a significant contribution to the decay kinetics of the impurity luminescence. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

nEXO: neutrinoless double beta decay search beyond 10 28 year half-life sensitivity

The nEXO neutrinoless double beta (0νββ) decay experiment is designed to use a time projection chamber and 5000 kg of isotopically enriched liquid xenon to search for the decay in 136 Xe. Progress in the detector design, paired with higher fidelity in its simulation and an advanced data analysis, based on the one used for the final results of EXO-200, produce a sensitivity prediction that exceeds the half-life of 10 28 years. Specifically, improvements have been made in the understanding of production of scintillation photons and charge as well as of their transport and reconstruction in the detector. The more detailed knowledge of the detector construction has been paired with more assays for trace radioactivity in different materials. In particular, the use of custom electroformed copper is now incorporated in the design, leading to a substantial reduction in backgrounds from the intrinsic radioactivity of detector materials. Furthermore, a number of assumptions from previous sensitivity projections have gained further support from interim work validating the nEXO experiment concept. Together these improvements and updates suggest that the nEXO experiment will reach a half-life sensitivity of 1.35 × 10 28 yr at 90% confidence level in 10 years of data taking, covering the parameter space associated with the inverted neutrino mass ordering, along with a significant portion of the parameter space for the normal ordering scenario, for almost all nuclear matrix elements. Furthermore, the effects of backgrounds deviating from the nominal values used for the projections are also illustrated, concluding that the nEXO design is robust against a number of imperfections of the model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Search for the rare decay $ B^0\to J/ \psi\phi$*

A search for the rare decay $ B^0\to J/ \psi\phi$ is performed using $ pp$ collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb -1 . No significant signal of the decay is observed and an upper limit of $ 1.1 \times 10^{-7}$ at 90% confidence level is set on the branching fraction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

The nylon balloon for xenon loaded liquid scintillator in KamLAND-Zen 800 neutrinoless double-beta decay search experiment

The KamLAND-Zen 800 experiment is searching for the neutrinoless double-beta decay of 136 Xe by using 136 Xe-loaded liquid scintillator. The liquid scintillator is enclosed inside a balloon made of thin, transparent, low-radioactivity film that we call Inner Balloon (IB). The IB, apart from guaranteeing the liquid containment, also allows to minimize the background from cosmogenic muon-spallation products and 8B solar neutrinos. Indeed these events could contribute to the total counts in the region of interest around the Q-value of the double-beta decay of 136 Xe. In this paper, we present an overview of the IB and describe the various steps of its commissioning minimizing the radioactive contaminations, from the material selection, to the fabrication of the balloon and its installation inside the KamLAND detector. Finally, we show the impact of the IB on the KamLAND background as measured by the KamLAND detector itself.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Observation of the decays 𝐵 + → Σ 𝑐 ⁢(2455) ++ $\bar{Ξ}^-_c$ and 𝐵 0 → Σ 𝑐 ⁢(2455) 0⁢ $\bar{Ξ}^0_𝑐$

We report the first observation of the two-body baryonic decays 𝐵 + → Σ 𝑐 ⁢(2455) ++ $\bar{Ξ}^-_c$ and 𝐵 0 → Σ 𝑐 ⁢(2455) 0⁢ $\bar{Ξ}^0_𝑐$ with significances of 7.3⁢𝜎 and 6.2⁢𝜎, respectively, including statistical and systematic uncertainties. The branching fractions are measured to be ℬ⁡(𝐵 + → Σ 𝑐 ⁢(2455) ++ $\bar{Ξ}^-_c$) = (5.74 ± 1.11 ± 0.4⁢2$^{+2.47}_{−1.53}$) ×10 −4 and ℬ⁡(𝐵 0 → Σ 𝑐 ⁢(2455) 0⁢ $\bar{Ξ}^0_𝑐$) = (4.83 ± 1.12 ± 0.3⁢7$^{+0.72}_{−0.60}$) ×10 −4 . The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the absolute branching fractions of $\bar{Ξ}^-_c$ or $\bar{Ξ}^0_𝑐$ decays. The data samples used for this analysis have integrated luminosities of 711 fb −1 and 365 fb −1 , and were collected at the ϒ⁡(4⁢𝑆) resonance by the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy 𝑒 + ⁢𝑒 − colliders, respectively.

branching fraction↗
DOE OSTI2025

$Ξ$ 𝑐 → $Ξ$ form factors from lattice QCD with domain-wall quarks: A new piece in the puzzle of $Ξ^0_𝑐$ decay rates

We present a lattice quantum chromodynamics (QCD) determination of the vector and axial-vector form factors that describe the charm-baryon semileptonic decays Ξ 𝑐 → Ξ⁢ℓ + ⁢𝜈 ℓ . The calculation uses a domain-wall action for the up, down, and strange quarks, and an anisotropic clover action for the charm quark. We use four ensembles of gauge-field configurations generated by the RBC and UKQCD collaborations, with lattice spacings between 0.111 and 0.073 fm and pion masses ranging from 420 to 230 MeV. We present Standard Model predictions for the decay rates and branching fractions of Ξ$^0_𝑐$ → Ξ$^−_𝑐$⁢ℓ + ⁢𝜈 ℓ and Ξ$^+_𝑐$ → Ξ$^0_𝑐$⁢ℓ + ⁢𝜈 ℓ for ℓ =𝑒, 𝜇. In particular, we obtain Γ⁡(Ξ$^0_𝑐$ → Ξ − ⁢𝑒 + ⁢𝜈 𝑒 )/|𝑉 𝑐⁢𝑠 | 2 = 0.2515⁢(73) ps −1 and ℬ⁡(Ξ$^0_𝑐$ → Ξ − ⁢𝑒 +⁢ 𝜈 𝑒 ) = 3.58⁢(12)%. These values are higher than those predicted by a previous lattice calculation and substantially higher than the experimentally measured values, but consistent with expectations from approximate 𝑆⁢𝑈⁡(3) flavor symmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for 𝑃 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 and 𝑃 𝑐$\overline{𝑐}$𝑠 (4338) 0 in ϒ(1𝑆,2𝑆) Inclusive Decays at Belle

Using data samples of 102 million ϒ⁡(1⁢𝑆) events and 158 million ϒ⁡(2⁢𝑆) events collected by the Belle detector at the KEKB asymmetric-energy 𝑒+⁢𝑒− collider, we search for [𝑢⁢𝑑⁢𝑠⁢𝑐$\overline{𝑐}$ ] pentaquark states decaying to 𝐽/𝜓⁢Λ. Using the first observations of ϒ⁡(1⁢𝑆,2⁢𝑆) inclusive decays to 𝐽/𝜓⁢Λ, we find evidence of the 𝑃 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 state with a local significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the 𝑃 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 to be (4471.7±4.8±0.6) MeV/𝑐 2 and (22 ±13 ±3) MeV, respectively. The branching fractions for 𝑃 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 production are measured to be ℬ⁡[ϒ⁡(1⁢𝑆)→𝑃 𝑐$\overline{𝑐}$𝑠 ⁢(4459)0/ $\overline{𝑃}$ 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 +anything]=(3.5±2.0±0.2)×10 −6 and ℬ⁡[ϒ⁡(2⁢𝑆)→𝑃 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 /$\overline{𝑃}$ 𝑐$\overline{𝑐}$𝑠 ⁢(4459) 0 +anything]=(2.9±1.7±0.4)×10 −6 . The inclusive branching fractions of ϒ⁡(1⁢𝑆,2⁢𝑆) →𝐽/𝜓⁢Λ/$\overline{Λ}$ are measured to be ℬ⁡[ϒ⁡(1⁢𝑆) →𝐽/𝜓⁢Λ/$\overline{Λ}$ +anything] =(36.9 ±5.3 ±2.4) ×10 −6 and ℬ⁡[ϒ⁡(2⁢𝑆) →𝐽/𝜓⁢Λ/$\overline{Λ}$ +anything] =(22.3 ±5.7 ±3.1) ×10 −6 . We measure the visible cross section 𝜎⁡(𝑒+⁢𝑒−→𝐽/𝜓⁢Λ/ $\overline{Λ}$ +anything)=(90±14±6) fb for the continuum production at √𝑠 =10.52 GeV. In all cases, the first uncertainties are statistical and the second are systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Superallowed 0 + → 0 + nuclear β decays: 2020 critical survey, with implications for V ud and CKM unitarity

A new critical survey of all half-life, decay-energy and branching-ratio measurements related to 23 superallowed 0 + → 0 + β decays is presented. Included are 222 individual measurements of comparable precision obtained from 174 published references. Compared with our last survey in 2015, we have added results from 28 new publications and eliminated an approximately equal number whose results have been superseded by much more precise modern data. We obtain world-average ft values for each of the 21 transitions that have a complete set of data, then apply radiative and isospin-symmetry-breaking corrections to extract “corrected” Ft values. Fifteen of these Ft values now have a precision of 0.3% or better and all take the same value within statistics, as expected from conservation of the vector current. Their average, Ft¯, when combined with the muon lifetime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa matrix, V ud = 0.97373 ± 0.00031. This is lower than our 2015 result by one standard deviation and its uncertainty is increased by 50%. This is a consequence, not of any shifts in the experimental data, but of new calculations for the radiative corrections. The lower V ud value now leads to greater tension in the top-row test of unitarity in the CKM matrix. Updates in experimental data have independently led to a factor-of-two tighter limit being set on the possible existence of a scalar interaction. In conclusion, the new limit on Fierz interference is b F ≤ 0.0033 at the 90% confidence level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Ab initio benchmarks of neutrinoless double- β decay in light nuclei with a chiral Hamiltonian

Here, we report ab initio benchmark calculations of nuclear matrix elements (NMEs) for neutrinoless double-β (0νββ) decays in light nuclei with mass numbers ranging from A = 6 to A = 22. We use the transition operator derived from light-Majorana neutrino exchange and evaluate the NME with three different methods: two variants of in-medium similarity renormalization group (IMSRG) and importance-truncated no-core shell model (IT-NCSM). The same two plus three nucleon interaction from chiral effective field theory is employed, and both isospin-conserving (ΔT = 0) and isospin-changing (ΔT = 2) transitions are studied. We compare our resulting ground-state energies and NMEs to those of recent ab initio no-core shell model and coupled-cluster calculations, also with the same inputs. We show that the NMEs of ΔT = 0 transitions are in good agreement among all calculations, at the level of 10%. For ΔT = 2, relative deviations are more significant in some nuclei. The comparison with the exact IT-NCSM result allows us to analyze these cases in detail, and indicates the next steps toward improving the IMSRG-based approaches. The present study clearly demonstrates the power of consistent cross checks that are made possible by ab initio methodology. This capability is crucial for providing meaningful many-body uncertainties in the NMEs for the 0νββ decays in heavier candidate nuclei, where quasiexact benchmarks are not available.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Proton decays in 16 Ne and 18 Mg and isospin-symmetry breaking in carbon isotopes and isotones

We report that proton-rich nuclei possess unique properties in the nuclear chart. Due to the presence of both continuum coupling and Coulomb interaction, phenomena such as halos, Thomas-Ehrman shift, and proton emissions can occur. Relevant experimental data are difficult to obtain, so that theoretical calculations are needed to understand nuclei at drip lines and to guide experimentalists. In particular, the 16 Ne and 18 Mg isotopes are supposed to be one-proton and/or two-proton emitting nuclei, but associated experimental data are either incomplete or even unavailable. Consequently, we performed Gamow shell model calculations of carbon isotones bearing A = 15 - 18 . Isospin-symmetry breaking occurring in carbon isotones and isotopes is also discussed. It is hereby shown that the mixed effects of continuum coupling and Coulomb interaction at drip lines generate complex patterns in isospin multiplets. Added to that, it is possible to determine the one-proton and two-proton widths of 16 Ne and 18 Mg . Obtained decay patterns are in agreement with those obtained in previous experimental and theoretical works. Moreover, to our knowledge, this is the first theoretical calculation of binding energy and partial decay widths of 18 Mg in a configuration interaction picture.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Application of an efficient generator-coordinate subspace-selection algorithm to neutrinoless double- β decay

The generator coordinate method begins with the variational construction of a set of nonorthogonal mean-field states that span a subspace of the full many-body Hilbert space. These states are then often projected onto states with good quantum numbers to restore symmetries, leading to a set with members that can be similar to one another, and it is sometimes possible to reduce this set without greatly affecting results. Here, we propose a greedy algorithm that we call the energy-transition-orthogonality procedure (ENTROP) to select subsets of important states. As applied here, the approach selects on the basis of diagonal energy, orthogonality, and contribution to the matrix element that governs neutrinoless double-β decay. We present both shell-model and preliminary ab initio calculations of this matrix element for the decay of 76Ge, with quadrupole deformation parameters and the isoscalar pairing strength as generator coordinates. ENTROP converges quickly, reducing significantly the number of basis states needed for an accurate calculation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Ab initio calculation of the β-decay spectrum of 6 He

Here, we calculate the β spectrum in the decay of 6 He using quantum Monte Carlo methods with nuclear interactions derived from chiral effective field theory and consistent weak vector and axial currents. We work at second order in the multipole expansion, retaining terms suppressed by O(q 2 /m$^{2}_{π}$), where q denotes low-energy scales such as the reaction’s Q value or the electron energy, and m π is the pion mass. We go beyond the impulse approximation by including the effects of two-body vector and axial currents. We estimate the theoretical error on the spectrum by using four potential models in the Norfolk family of local two- and three-nucleon interactions, which have different cutoffs, fit two-nucleon data up to different energies, and use different observables to determine the couplings in the three-body force. We find the theoretical uncertainty on the β spectrum, normalized by the total rate, to be well below the permille level, and to receive contributions of comparable size from first- and second-order corrections in the multipole expansion. We consider corrections to the β decay spectrum induced by beyond-standard-model charged-current interactions in the standard model effective field theory, with and without sterile neutrinos, and discuss the sensitivity of the next generation of experiments to these interactions.

6 ≤ A ≤ 19↗
DOE OSTI2023

Pair production as a probe for the dynamics of nuclear fission and α decay

Electron-positron pairs can be produced via the Schwinger mechanism in the presence of strong electric fields. In particular, the fields involved in α decay and nuclear fission are strong enough to produce them. The energy of the e⁺⁢e⁻ pair is related to the relative distance and velocity of the daughter nuclei. Thus, the energy distribution of the produced pairs can give information about the dynamics of the fission and α-decay processes. A neck model of nuclear fission is used to illustrate how the pairs can be used as a probe of the dynamics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Effects of quasiparticle-vibration coupling on Gamow-Teller strength and 𝛽 decay with the Skyrme proton-neutron finite-amplitude method

We adapt the proton-neutron finite-amplitude method, which in its original form is an efficient implementation of the Skyrme quasiparticle random phase approximation, to include the coupling of quasiparticles to like-particle phonons. The approach allows us to add beyond-quasiparticle random-phase approximation correlations to computations of Gamow-Teller strength and 𝛽-decay rates in deformed nuclei for the first time. We test the approach in several deformed isotopes for which measured strength distributions are available. Furthermore, the additional correlations dramatically improve agreement with the data, and will lead to improved global 𝛽-decay rates.

Beta decay↗
DOE OSTI2020

Direct CP violation and the ΔI=1/2 rule in K→ππ decay from the standard model

We present a lattice QCD calculation of the Δ I = 1 / 2 , K → π π decay amplitude A 0 and ϵ ' , the measure of direct C P violation in K → π π decay, improving our 2015 calculation [1] of these quantities. Both calculations were performed with physical kinematics on a 32 3 × 64 lattice with an inverse lattice spacing of a - 1 = 1.3784 ( 68 ) GeV . However, the current calculation includes nearly 4 times the statistics and numerous technical improvements allowing us to more reliably isolate the π π ground state and more accurately relate the lattice operators to those defined in the standard model. We find Re ( A 0 ) = 2.99 ( 0.32 ) ( 0.59 ) × 10 - 7 GeV and Im ( A 0 ) = - 6.98 ( 0.62 ) ( 1.44 ) × 10 - 11 GeV , where the errors are statistical and systematic, respectively. The former agrees well with the experimental result Re ( A 0 ) = 3.3201 ( 18 ) × 10 - 7 GeV . These results for A 0 can be combined with our earlier lattice calculation of A 2 [2] to obtain Re ( ϵ ' / ϵ ) = 21.7 ( 2.6 ) ( 6.2 ) ( 5.0 ) × 10 - 4 , where the third error represents omitted isospin breaking effects, and Re ( A 0 ) / Re ( A 2 ) = 19.9 ( 2.3 ) ( 4.4 ) . The first agrees well with the experimental result of Re ( ϵ ' / ϵ ) = 16.6 ( 2.3 ) × 10 - 4 . A comparison of the second with the observed ratio Re ( A 0 ) / Re ( A 2 ) = 22.45 ( 6 ) , demonstrates the standard model origin of this “ Δ I = 1 / 2 rule” enhancement.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Lyman-α constraints on cosmic heating from dark matter annihilation and decay

We derive new constraints on models of decaying and annihilating dark matter (DM) by requiring that the energy injected into the intergalactic medium (IGM) not overheat it at late times, when measurements of the Lyman-α forest constrain the IGM temperature. We improve upon previous analyses by using the recently developed DarkHistory code package, which self-consistently takes into account additional photoionization and photoheating processes due to reionization and DM sources. Our constraints are robust to the uncertainties of reionization and competitive with leading limits on sub-GeV DM that decays preferentially to electrons

79 ASTRONOMY AND ASTROPHYSICS↗