We present the full description of a measurement of the branching ratios for the beta-decay of 38Ca. This decay includes five allowed 0+ --> 1+ branches and a superallowed 0+ --> 0+ one. With our new result for the latter, we determine its ft value to be 3062.3(68) s, a result whose precision (0.2%) is comparable to the precision of the thirteen well known 0+ --> 0+ transitions used up till now for the determination of Vud, the up-down quark-mixing element of the CKM matrix. The 38Ca superallowed transition thus becomes the first addition to this set of transitions in nearly a decade and the first for which a precise mirror comparison is possible, thus enabling an improved test of the isospin-symmetry-breaking corrections required for the extraction of Vud.
We have measured the beta-decay branching ratio for the transition from 21Na to the first excited state of 21Ne. A recently published test of the standard model, which was based on a measurement of the beta-nu correlation in the decay of 21Na, depended on this branching ratio. However, until now only relatively imprecise (and, in some cases, contradictory) values existed for it. Our new result, 4.74(4)%, reduces but does not remove the reported discrepancy with the standard model.
The absolute branching ratio of the beta-delayed gamma-ray emission of N18 was measured, providing absolute normalization of the previous work by Olness et al. [J.W. Olness et al., Nuc. Phys. A373, 13 (1982)] who measured the relative branching ratios for the individual gamma-rays. We find the total absolute branching ratio for beta-delayed gamma emission of N18 to be 76.7 +/- 7.2(stat) +/- 5.8(norm)%. A combination of other results suggests a value consistent with our result, but smaller than that calculated by Millener as quoted in Olness et al.
While the 12C(a,g)16O reaction plays a central role in nuclear astrophysics, the cross section at energies relevant to hydrostatic helium burning is too small to be directly measured in the laboratory. The beta-delayed alpha spectrum of 16N can be used to constrain the extrapolation of the E1 component of the S-factor; however, with this approach the resulting S-factor becomes strongly correlated with the assumed beta-alpha branching ratio. We have remeasured the beta-alpha branching ratio by implanting 16N ions in a segmented Si detector and counting the number of beta-alpha decays relative t…
Beta-decay branching ratios of 62Ga have been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyvaskyla. 62Ga is one of the heavier Tz = 0, 0+ -> 0+ beta-emitting nuclides used to determine the vector coupling constant of the weak interaction and the Vud quark-mixing matrix element. For part of the experimental studies presented here, the JYFLTRAP facility has been employed to prepare isotopically pure beams of 62Ga. The branching ratio obtained, BR= 99.893(24)%, for the super-allowed branch is in agreement with previous measurements and allows to determine t…
In an experiment performed at the ISOLDE facility of CERN, the super-allowed beta-decay branching ratio of 10C was determined with a high-precision single-crystal germanium detector. In order to evaluate the contribution of the pile-up of two 511 keV gamma quanta to one of the gamma-ray peaks of interest at 1021.7 keV, data were not only taken with 10C, but also with a 19Ne beam. The final result for the super-allowed decay branch is 1.4638(50)%, in agreement with the average from literature.
Precise beta-branching-ratio measurements are required in order to determine ft-values as a part of our program to test the Electroweak Standard Model via unitarity of the Cabibbo-Kobayashi-Moskawa matrix. For the measurements to be useful in this test, their precision must be close to 0.1 %. In a branching-ratio measurement, we position the radioactive sample between a thin plastic scintillator used to detect beta-particles, and a HPGe detector for gamma-rays. Both beta singles and beta-gamma coincidences are recorded. Although the branching ratio depends most strongly on the HPGe detector ef…
We used the 8$π$ $γ$-ray spectrometer at the TRIUMF-ISAC radiocative ion beam facility to obtain high-precision branching ratios for $^{19}$Ne $β^+$ decay to excited states in $^{19}$F. Together with other previous work, our measurements determine the superallowed $1/2^+ \to 1/2^+$ beta branch to the ground state in $^{19}$F to be 99.9878(7)\%, which is three times more precise than known previously. The implications of these measurements for testing a variety of weak interaction symmetries are discussed briefly.
We present a new measurement of the branching ratio for the decay of $^{14}$O to the ground state of $^{14}$N. The experimental result, $λ_0/λ_{\rm total} = (4.934 \pm 0.040\kern 1pt{\rm (stat.)} \pm 0.061\kern 1pt{\rm (syst.)}) \times 10^{-3}$, is significantly smaller than previous determinations of this quantity. The new measurement allows an improved determination of the partial halflife for the superallowed $0^+ \rightarrow 0^+$ Fermi decay to the $^{14}$N first excited state, which impacts the determination of the $V_{ud}$ element of the CKM matrix. With the new measurement in place, the…
This paper is addressed to the analysis of the set of observables of the bound-state beta-decay, which can be used for the experimental investigation of contributions of i) interactions beyond the Standard Model (SM) and of ii) the left-handed polarisation state of antineutrinos. For this aim we calculate the branching ratio, probabilities and angular distributions of probabilities of hydrogen in the hyperfine states and of the proton-electron pair in different spinorial states, induced by left-handed and right-handed hadronic and leptonic currents. The branching ratio of the bound-state beta-…
The beta+ decay of very neutron deficient 43Cr has been studied by means of an imaging time projection chamber which allowed recording tracks of charged particles. Events of beta-delayed emission of one-, two-, and three protons were clearly identified. The absolute branching ratios for these channels were determined to be 81(4)%, 7.1(4)%, and 0.08(3)%, respectively. The 43Cr is thus established as the second case in which the beta-3p decay occurs. Although the feeding to the proton-bound states in 43V is expected to be negligible, the large branching ratio of 12(4)% for decays without proton …
In the Standard Model of electroweak interactions and in the tree--approximation we calculate the rate and branching ratio of the neutron radiative beta decay with one-real photon emission by taking into account the contributions of the weak magnetism and proton recoil to order 1/m_p of the large proton mass m_p expansion. We find that the obtained contributions of the weak magnetism and proton recoil increase the rate and branching ratio of the neutron radiative beta decay by about 0.70%. This is large compared with the contribution of the weak magnetism and proton recoil of about 0.16% to th…
Measurements of the beta-neutrino correlation coefficient (a$_{βν}$) in nuclear beta decay, together with the Fierz interference term (b$_F$), provide a robust test for the existence of exotic interactions beyond the Standard Model of Particle Physics. The extraction of these quantities from the recoil ion spectra in $β$-decay requires accurate knowledge, decay branching ratios, and high-precision calculations of higher order nuclear effects. Here, we report on a new measurement of the $^{23}$Ne $β$-decay branching ratio, which allows a reanalysis of existing high-precision measurements. Toget…
The branching ratio between the beta- and beta+/electron capture decay of 74As has been measured in different host materials such as Ta, Al, Ge and mylar. No significant dependence of the branching ratio on the host material has been observed. The half-life of 74As has also been measured in metallic Ta and in semiconductor Ge, no difference has been found and the results are in agreement with the literature value. The obtained results provide an upper limit for the possible host material dependence of the decay rate in 74As.
Beta-delayed neutron emission and $β$-delayed fission ($β$df) probabilities were calculated for heavy, neutron-rich nuclei using the Los Alamos coupled Quasi-Particle Random Phase Approximation plus Hauser-Feshbach (QRPA+HF) approach. In this model, the compound nucleus is initially populated by $β$-decay and is followed through subsequent statistical decays taking into account competition between neutrons, $γ$-rays and fission. The primary output of these calculations includes branching ratios along with neutron and $γ$-ray spectra. We find a relatively large region of heavy nuclides where th…
The neutron-rich $^{11}$Li halo nucleus is unique among nuclei with known separation energies by its ability to emit a proton and a neutron in a $β$ decay process. The branching ratio towards this rare decay mode is evaluated within a three-body model for the initial bound state and with Coulomb three-body final scattering states. The branching ratio should be comprised between two extreme cases, i.e.\ a lower bound $6 \times 10^{-12}$ obtained with a pure Coulomb wave and an upper bound $5 \times 10^{-10}$ obtained with a plane wave. A simple model with modified Coulomb waves provides plausib…
We argue that conclusions of [PRL 123, 082501 (2019)] are incorrect. The authors present the direct observation of beta-delayed proton emission in the beta decay of 11Be. From the determined branching ratio for this process and from the energy spectrum of emitted protons the existence of a so far unobserved narrow resonance in 11Be was deduced. The given beta strength for the transition to this state is however wrong. In addition, we show that the combination of peak position and branching ratio is in strong disagreement with models considered by the authors. Furthermore, we identify several d…
We report the first branching-ratio measurement of the superallowed 0+-to-0+ beta transition from 38Ca. The result, 0.7728(16), leads to an ft value of 3062.3(68)s with a relative precision of +/-0.2%. This makes possible a high-precision comparison of the ft values for the mirror superallowed transitions, 38Ca-to-38mK and 38mK-to-38Ar, which sensitively tests the isospin symmetry-breaking corrections required to extract Vud, the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, from superallowed beta decay. The result supports the corrections currently used, and poin…
Two experiments, (1) a measurement of the superallowed $0^{+} \rightarrow 0^{+}$ branching ratio in $^{10}$C, and (2) a measurement of (or limit on) non-analogue $0^{+} \rightarrow 0^{+}$ branches in $^{38m}$K, $^{46}$V, $^{50}$Mn and $^{54}$Co, are described. The implications these experiments have on the test of the conservation of the weak vector current (CVC) and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix are surveyed.
The results by A.S. Barabash [Phys. Rev. {\bf C 81}, 035501 (2010)] are shown to be incomplete. Tellurium data sets were reanalyzed using the best practices of ENSDF evaluations. Present analysis indicates much higher value for the 2$ν$-mode half-life time in $^{128}$Te and the corresponding ratio of $^{128,130}$Te half-lives. These values imply the $T^{2 ν}_{1/2}$ $\sim$ $\frac{1}{E^{8}}$ $ββ$-decay transition energy trend that is consistent with the two-nucleon mechanism of $ββ$(2$ν$)-decay.
Beta-delayed-neutron ($β$n) spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The $β$n branching ratios and energy spectra for $^{135,136}$Sb and $^{140}$I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having $β$n branching ratios that impact the r-process abundance pattern around the A~130 peak. For $^{135,136}$Sb and $^{140}$I, $β$n branching ratios of 14.6(11)%, 17.6(28)%, and 7.6(28)% were determined, respectively. The $β$…
We present the results of a National Science Foundation (NSF) Project Scoping Workshop, the purpose of which was to assess the current status of calculations for the nuclear matrix elements governing neutrinoless double-beta decay and determine if more work on them is required. After reviewing important recent progress in the application of effective field theory, lattice quantum chromodynamics, and ab initio nuclear-structure theory to double-beta decay, we discuss the state of the art in nuclear-physics uncertainty quantification and then construct a road map for work in all these areas to f…
The beta decay of tritium in the form of molecular TT is the basis of sensitive experiments to measure neutrino mass. The final-state electronic, vibrational, and rotational excitations modify the beta spectrum significantly, and are obtained from theory. We report measurements of the branching ratios to specific ionization states for the isotopolog HT. Two earlier, concordant measurements gave branching ratios of HT to the bound HHe$^+$ ion of 89.5% and 93.2%, in sharp disagreement with the theoretical prediction of 55-57%, raising concerns about the theory's reliability in neutrino mass expe…
It is demonstrated that remarks and criticism in work [1] (arXiv:1005.2436 nucl-th) have resulted from inattentive reading of work [2] (Phys. Rev.C 81, 035501 (2010)) or just some misunderstanding and do not influence conclusions of work [2].
The half-life, 3.8755(12) s, and superallowed branching ratio, 0.5315(12), for ^{22}Mg beta-decay have been measured with high precision. The latter depended on gamma-ray intensities being measured with an HPGe detector calibrated for relative efficiencies to an unprecedented 0.15%. Previous precise measurements of 0^+ to 0^+ transitions have been restricted to the nine that populate stable daughter nuclei. No more such cases exist, and any improvement in a critical CKM unitarity test must depend on precise measurements of more exotic nuclei. With this branching-ratio measurement, we show thos…
A new technique has been developed at TRIUMF's TITAN facility to perform in-trap decay spectroscopy. The aim of this technique is to eventually measure weak electron capture branching ratios (ECBRs) and by this to consequently determine GT matrix elements of $ββ$ decaying nuclei. These branching ratios provide important input to the theoretical description of these decays. The feasibility and power of the technique is demonstrated by measuring the ECBR of $^{124}$Cs.
The half-life of 10C has been measured to be 19.310(4)s, a result with 0.02% precision, which is a factor of three improvement over the best previous result. Since 10C is the lightest superallowed 0+ --> 0+ beta emitter, its ft value has the greatest weight in setting an upper limit on the possible presence of scalar currents.
A recent Penning-trap measurement of the masses of 46V and 46Ti leads to a Qec value that disagrees significantly with the previously accepted value, and destroys overall consistency among the nine most precisely characterized T=1 superallowed beta emitters. This raises the possibility of a systematic discrepancy between Penning-trap measurements and the reaction-based measurements upon which the Qec values depended in the past. We carefully re-analyze (n,gamma) and (p,gamma) reaction measurements in the 24 \leq A \leq 28 mass region, and compare the results to very precise Penning-trap measur…
The beta decay of molecular tritium currently provides the highest sensitivity in laboratory-based neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino-mass experiments agree with spectroscopic data. Moreover, when neutrino-mass experiments performed in the 1980s with gaseous tritium are re-evaluated using these modern calculations, the extracted neutrino mass-squared values are co…
The standard model predicts that, in addition to a proton, an electron, and an antineutrino, a continuous spectrum of photons is emitted in the $β$ decay of the free neutron. We report on the RDK II experiment which measured the photon spectrum using two different detector arrays. An annular array of bismuth germanium oxide scintillators detected photons from 14 to 782~keV. The spectral shape was consistent with theory, and we determined a branching ratio of 0.00335 $\pm$ 0.00005 [stat] $\pm$ 0.00015 [syst]. A second detector array of large area avalanche photodiodes directly detected photons …
A new critical survey is presented of all half-life, decay-energy and branching-ratio measurements related to 20 superallowed 0+ --> 0+ beta decays. Included are 222 individual measurements of comparable precision obtained from 177 published references. Compared with our last review in 2008, we have added results from 24 new publications and eliminated 9 references, the results from which having been superseded by much more precise modern data. We obtain world-average ft-values for each of the eighteen transitions that have a complete set of data, then apply radiative and isospin-symmetry-brea…
The half-life of 46V has been measured to be 422.66(6) ms, which is a factor of two more precise than the best previous measurement. Our result is also consistent with the previous measurements, with no repeat of the disagreement recently encountered with Q_{EC} values measured for the same transition. The Ft value for the 46V superallowed transition, incorporating all world data, is determined to be 3074.1(26) s, a result consistent with the average Ft value of 3072.08(79) s established from the 13 best-known superallowed transitions.
All existing "positive" results on two neutrino double beta decay in different nuclei were analyzed. Using the procedure recommended by the Particle Data Group, weighted average values for half-lives of $^{48}$Ca, $^{76}$Ge, $^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{100}$Mo - $^{100}$Ru ($0^+_1$), $^{116}$Cd, $^{130}$Te, $^{150}$Nd, $^{150}$Nd - $^{150}$Sm($0^+_1$) and $^{238}$U were obtained. Existing geochemical data were analyzed and recommended values for half-lives of $^{128}$Te, $^{130}$Te and $^{130}$Ba are proposed. Given the measured half-life values, nuclear matrix elements were calculate…
A significant decay branch of 8B to the ground state of 8Be would extend the solar neutrino spectrum to higher energies than anticipated in the standard solar models. These high-energy neutrinos would affect current neutrino oscillation results and also would be a background to measurements of the hep process. We have measured the delayed alpha particles from the decay of 8B, with the goal of observing the two 46-keV alpha particles arising from the ground-state decay. The 8B was produced using an in-flight radioactive beam technique. It was implanted in a silicon PIN-diode detector that was c…
Measurements of neutron beta decay observables required to determine $|V_{ud}|$ are reaching the 0.1% accuracy. In this paper we review the calculation of the decay rate of this process, discuss its relevant uncertainties, and obtain an expression that is precise at the $10^{-4}$ level. Our analysis clearly shows the necessity of measurements of $λ$, the ratio of axial/vector couplings. The current situation in neutron beta decay is that one cannot yet quote a single consistent value for $|V_{ud}|$ from it. We also discuss the region of parameter space in the $|V_{ud}|$--$λ$ plane where new ph…
Although well studied, the neutron still offers a unique laboratory for precise tests of Standard Model (SM) predictions. Neutron decay is free of nuclear structure corrections present in nuclear beta decays, and, with a $10^8$ times larger branching ratio than the theoretically cleaner pion beta decay, it is more readily accessible to experimental study than the latter. Measurements at sufficient precision of the neutron lifetime, and of correlations in free neutron beta decay, offer several stringent tests of the SM, including the weak quark couplings (quark-lepton universality), and certain…
A new and independent determination of the Gamow-Teller branching ratio in the beta-decay of 21Na is reported. The value obtained of 5.13 +- 0.43 % is in agreement with the currently adopted value and the most recent measurement. In contrast to previous experiments, the present method was based on the counting of the parent 21Na ions and the resulting 351 keV gamma-rays without coincident beta-particle detection.
Beta decay is a well-established and efficient probe of nuclear structure and provides important information also for halo nuclei. Detailed decay studies of near-dripline nuclei are challenging, but are now feasible due to the technical progress during the last decades in isotope production as well as detection capabilities. The halo structure can change the dynamics of the decay process, most noticably when decays proceed directly to continuum states as seems to be the case in beta-delayed deuteron emission, a process only observed until now for the halo nuclei $^6$He and $^{11}$Li. The prono…
We have measured the half-life of the superallowed 0+ -to- 0+ beta+ emitter 26Si to be 2245.3(7) ms. We used pure sources of 26Si and employed a high-efficiency gas counter, which was sensitive to positrons from both this nuclide and its daughter 26mAl. The data were analyzed as a linked parent-daughter decay. To contribute meaningfully to any test of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, the ft value of a superallowed transition must be determined to a precision of 0.1% or better. With a precision of 0.03% the present result is more than sufficient to be compatable with…
A complete survey is presented of all half-life and branching-ratio measurements related to the isospin T = 1/2 mirror beta transitions ranging from 3He to 83Mo. No measurements are ignored, although some are rejected for cause. Using the decay energies obtained in the 2003 Mass Evaluation experimental ft values are then determined for the transitions up to 45V. For the first time also all associated theoretical corrections needed to convert these results into "corrected" Ft values, similar to the superallowed 0+ -> 0+ pure Fermi beta transitions, were calculated. Precisions of the resulting v…
Limits on parameters describing physics beyond the Standard Model are presented. The most general Lorentz invariant effective Hamiltonian at the quark-lepton level involving vector, scalar and tensor operators has been used. The fits have been done using the most precise and up to date experimental data for correlation coefficients measured in free neutron beta decay as well as the Fierz term measured in superallowed Fermi decays.
The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring beta-delayed neutron-emission probabilities. The detector was designed to work in conjunction with a beta-decay implantation station, so that beta decays and beta-delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring beta-delayed neutron emission branchings for neutron-rich r-process nuclei produced …
Total absorption spectroscopy was used to investigate the beta-decay intensity to states above the neutron separation energy followed by gamma-ray emission in 87,88Br and 94Rb. Accurate results were obtained thanks to a careful control of systematic errors. An unexpectedly large gamma intensity was observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The gamma branching as a function of excitation energy was compared to Hauser-Feshbach model calculations. For 87Br and 88Br the gamma branching reaches 57% and…
The results of a study of the beta decays of three proton-rich nuclei with $T_z=\text{-}2$, namely $^{48}$Fe, $^{52}$Ni and $^{56}$Zn, produced in an experiment carried out at GANIL, are reported. In all three cases we have extracted the half-lives and the total $β$-delayed proton emission branching ratios. We have measured the individual $β$-delayed protons and $β$-delayed $γ$ rays and the branching ratios of the corresponding levels. Decay schemes have been determined for the three nuclei, and new energy levels are identified in the daughter nuclei. Competition between $β$-delayed protons an…
Beta delayed neutron emission of $N=84$ $^{132}$Cd
University of Tennessee（田纳西大学）；Obsidian Research（黑曜石研究公司）；University of Notre Dame（圣母大学）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；University of York（约克大学）；INFN, Sezione di Milano（意大利国家核物理研究所米兰分部）；CERN（欧洲核子研究中心）；“Horia Hulubei” National Institute of Physics and Nuclear Engineering（霍里亚·胡卢贝伊国家物理与核工程研究所）；Institute for Nuclear Research and Nuclear Energy, BAS（保加利亚科学院核研究与核能研究所）；K.U. Leuven（荷语鲁汶大学）；Universidad Complutense de Madrid（马德里康普顿斯大学）
Penning trap measurements using mixed beams of 100Mo - 100Ru and 76Ge - 76Se have been utilized to determine the double-beta decay Q-values of 100Mo and 76Ge with uncertainties less than 200 eV. The value for 76Ge, 2039.04(16) keV is in agreement with the published SMILETRAP value. The new value for 100Mo, 3034.40(17) keV is 30 times more precise than the previous literature value, sufficient for the ongoing neutrinoless double-beta decay searches in 100Mo. Moreover, the precise Q-value is used to calculate the phase-space integrals and the experimental nuclear matrix element of double-beta de…
We have observed beta-delayed proton emission from the neutron-rich nucleus 11Be by analysing a sample collected at the ISOLDE facility at CERN with accelerator mass spectrometry (AMS). With a branching ratio of (8.4 +- 0.6) 10^{-6} the strength of this decay mode, as measured by the B(GT)-value, is unexpectedly high. The result is discussed within a simple single-particle model and could be interpreted as a quasi-free decay of the 11Be halo neutron into a single-proton state.
In anticipation of results from current and future double-beta decay studies, we report a measurement resulting in a 82Se double-beta decay Q-value of 2997.9(3) keV, an order of magnitude more precise than the currently accepted value. We also present preliminary results of a calculation of the 82Se neutrinoless double-beta decay nuclear matrix element that corrects in part for the small size of the shell model single-particle space. The results of this work are important for designing next generation double-beta decay experiments and for the theoretical interpretations of their observations.
We investigate the decay of 87Br, 88Br and 94Rb using total absorption gamma-ray spectroscopy. These important fission products are beta-delayed neutron emitters. Our data show considerable gamma-intensity, so far unobserved in high-resolution gamma-ray spectroscopy, from states at high excitation energy. We also find significant differences with the beta intensity that can be deduced from existing measurements of the beta spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discr…
The s-process in massive stars, producing nuclei up to $A\approx 90$, has a different behaviour at low metallicity if stellar rotation is significant. This enhanced s-process is distinct from the s-process in massive stars around solar metallicity, and details of the nucleosynthesis are poorly known. We investigated nuclear physics uncertainties in the enhanced s-process in metal-poor stars within a Monte-Carlo framework. We applied temperature-dependent uncertainties of reaction rates, distinguishing contributions from the ground state and from excited states. We found that the final abundanc…
The E36 experiment recently conducted at J-PARC by the TREK Collaboration will provide a precise mesurement of the decay ratio $ R_K = Γ(K^+ \rightarrow e^+ν_e) / Γ(K^+ \rightarrow μ^+ν_μ) $ with the aim of testing lepton universality, a basic assumption of the Standard Model (SM). The SM prediction for the decay ratio $R_K$ is highly precise ($δR_K / R_K = 4 \times 10^{-4}$) and any observed deviation from this prediction would clearly indicate the existence of new physics. The E36 experimental apparatus, designed to offer small systematic errors, was installed at the J-PARC K1.1BR kaon beam …
The $β$-decay properties of the neutron-deficient nuclei $^{25}$Si and $^{26}$P have been investigated at the GANIL/LISE3 facility by means of charged-particle and $γ$-ray spectroscopy. The decay schemes obtained and the Gamow-Teller strength distributions are compared to shell-model calculations based on the USD interaction. B(GT) values derived from the absolute measurement of the $β$-decay branching ratios give rise to a quenching factor of the Gamow-Teller strength of 0.6. A precise half-life of 43.7 (6) ms was determined for $^{26}$P, the $β$- (2)p decay mode of which is described.
A sample of $^{47}$Ca produced through isotope harvesting at the National Superconducting Cyclotron Laboratory was used to measure branching ratios of 7.17(5)%, 7.11(5)%, and 75.0(5)% for the 489.2, 807.9, and 1297.1 keV characteristic gamma-rays, respectively. Based on these updated branching ratios, the ground state to ground state $^{47}$Ca to $^{47}$Sc beta decay branching ratio has been indirectly measured as 17.7(5)% and the ground state to 1297.1 keV excited state as 82.2(5)%. These values represent a greatly increased precision for all five branching ratios compared to the currently ac…
In the context of the LENS R&D solar neutrino project, the gamma spectrum of a sample of metallic indium was measured using a single experimental setup of 4 HP-Ge detectors located underground at the Gran Sasso National Laboratories (LNGS), Italy. A gamma line at the energy (497.48 +/- 0.21) keV was found that is not present in the background spectrum and that can be identified as a gamma quantum following the beta decay of In-115 to the first excited state of Sn-115 (9/2+ --> 3/2+). This decay channel of In-115, which is reported here for the first time, has an extremely low Q-value, Q = (2 +…
We present for the first time precise spectroscopic information on the recently discovered decay mode beta-delayed 3p-emission. The detection of the 3p events gives an increased sensitivity to the high energy part of the Gamow-Teller strength distribution from the decay of 31Ar revealing that as much as 30% of the strength resides in the beta-3p decay mode. A simplified description of how the main decay modes evolve as the excitation energy increases in 31Cl is provided.
The deuteron-emission channel in the beta-decay of the halo-nucleus 11Li was measured at the ISAC facility at TRIUMF by implanting post-accelerated 11Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of 11Li with those of the daughter nuclei. This method allowed the energy spectrum of the emitted deuterons to be extracted, free from contributions from other channels, and a precise value for the branching ratio B_d = 1.30(13) x 10-4 to be deduced for E(c.m.) > 200 keV. The results provide the first unambiguous experimental evidence that …
The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. The neutron lifetime recently obtained, 878.5 +/- 0.7stat +/- 0.3sys s, is the most accurate one to date. The new result for the neutron lifetime differs from the world average value by 6.5 standard deviations. The impact of the new result on testing of Standard Model and on data analysis for the primordial nucleosynthesis model is scrutinized.
