arXiv subjects

C. Gaulard

Publications and source records attributed to C. Gaulard.

10 recordsLinked to original sources

arXiv2025

Data sorting modes of phoswich detector array

The different data-sorting modes of the phoswich detector array PARIS used for detecting high-energy (4$-$10 MeV) $\gamma$ rays are investigated. The characteristics including time resolution, energy resolution and detection efficiency under various modes are studied. The present study shows that PARIS has capabilities of rejecting escape and pileup events when used for decay spectroscopy. Notably, the methods presented in this work refer specifically to the $\beta$-decay experiment of $^{80g+m}$Ga conducted with three PARIS clusters comprising 27 phoswich detectors, rather than to a general report on the PARIS array or its overall performance for in-beam spectroscopy. Compared with the 2"$\times$2"$\times$2" LaBr$_3$(Ce) detector (Ciema{\l}a et al., 2009), even in individual mode, PARIS provides significant suppression of single- and double-escape peaks and reduces background via vetoing function of the outer-volume NaI(Tl) crystals. In contrast to the common approach of adding back the energies in LaBr$_3$(Ce) and NaI(Tl) to increase the detection efficiency of the full-energy peak, using NaI(Tl) as a veto shield provides a superior trade-off for applications where spectral purity is essential. Employing add-back analysis within each cluster of nine phoswiches or between all phoswiches could enhance full-energy peak efficiency and further suppress escape peaks and background. Applying a multiplicity condition provides a further suppression but simultaneously lowers the statistics of full-energy peaks.

physics.ins-det↗

arXiv2025

$\beta$-delayed spectroscopy of $^{80}$Ge$_{48}$ and competition between Gamow-Teller and first-forbidden transitions in $^{80g+m}$Ga$_{49}$ $\beta$ decay

The $\beta$-delayed spectroscopy of $^{80}$Ge has been studied using sources of ground and low-lying isomeric states of $^{80}$Ga. A hybrid $\gamma$-ray spectrometer was used, composed of high-purity germanium (HPGe) detectors for low-energy $\gamma$-ray detection, phoswich detectors from the PARIS array for high-energy $\gamma$ rays and a plastic detector for $\beta$ tagging. The new decay level schemes are presented, with 13 and 14 states $\beta$ populated by $^{80g}$Ga and $^{80m}$Ga, respectively, being reported for the first time. We quantitatively compare summed intensities of first-forbidden and previously reported Gamow-Teller $\beta$ transitions [R. Li et al., \href{https://doi.org/10.1103/PhysRevC.111.034303}{Phys. Rev. C 111, 034303 (2025)}]. The upper-limit fractions of first-forbidden transitions contributing to the decays of $^{80g}$Ga and $^{80m}$Ga are (48.0 $\pm$ 2.7)$\%$ and (47.9 $\pm$ 3.3)$\%$ of the observed total $\beta$ transition intensities of (78.2 $\pm$ 2.5)$\%$ and (82.2 $\pm$ 3.7)$\%$, respectively. Notably, the half-lives decrease in accordance with the upper limits of (48.0 $\pm$ 6.0)$\%$ [3.67(20) s $\rightarrow$ 1.91(3) s] and (47.9 $\pm$ 7.2)$\%$ [3.01(19) s $\rightarrow$ 1.57(1) s] for $^{80g}$Ga and $^{80m}$Ga, respectively, when including first-forbidden transitions, in contrast to those by Gamow-Teller transitions only.

nucl-ex↗

arXiv2024

Simultaneous impacts of nuclear shell structure and collectivity on $\beta$ decay: Evidence from $^{80}$Ga$_{49}$

The Gamow-Teller strength distribution covering the entire $\beta$-decay window, up to 10.312(4) MeV, of $^{80g+m}$Ga was measured for the first time in photo fission of UC$_x$ induced by a 50 MeV electron beam. The new data show significant enhancement in the high-energy region with a jump structure. Simultaneously, the $\gamma$ deexciting behavior of $\beta$-populated states presents a competition between deexcitation to 2$_1^+$ [$\beta_2$ = 0.155(9)] and to 2$_2^+$ [$\beta_2$ = 0.053$_{0.009}^{0.008}$)] in $^{80}$Ge. To understand these data, we performed a realistic shell-model calculation and systematic analysis of log $\it{ft}$ ratios between precursors' $\beta$ decay to 2$_2^+$ and to 2$_1^+$ of Ga isotopes. We conclude that these phenomena evidence simultaneous impacts of nuclear shell structure and collectivity on $\it{B}$(GT) distribution and therefore the half-life of the precursor.

nucl-ex↗

arXiv2015

First Measurement of the $Σ$ Beam Asymmetry in $η^{\prime}$ Photoproduction off the Proton near Threshold

The $Σ$ beam asymmetry in $η^{\prime}$ photoproduction off the proton was measured at the GrAAL polarised photon beam with incoming photon energies of 1.461 and 1.480 GeV. For both energies the asymmetry as a function of the meson production angle shows a clear structure, more pronounced at the lowest one, with a change of sign around 90$^o$. The observed behaviour is compatible with P-wave D-wave (or S-wave F-wave) interference, the closer to threshold the stronger. The results are compared to the existing state-of-the-art calculations that fail to account for the data.

nucl-ex↗

arXiv2014

The magnetic properties of $^{\rm 177}$Hf and $^{\rm 180}$Hf in the strong coupling deformed model

This paper reports NMR measurements of the magnetic dipole moments of two high-K isomers, the 37/2$^-$, 51.4 m, 2740 keV state in $^{\rm 177}$Hf and the 8$^-$, 5.5 h, 1142 keV state in $^{\rm 180}$Hf by the method of on-line nuclear orientation. Also included are results on the angular distributions of gamma transitions in the decay of the $^{\rm 177}$Hf isotope. These yield high precision E2/M1 multipole mixing ratios for transitions in bands built on the 23/2$^+$, 1.1 s, isomer at 1315 keV and on the 9/2$^+$, 0.663 ns, isomer at 321 keV. The new results are discussed in the light of the recently reported finding of systematic dependence of the behavior of the g$_{\rm R}$ parameter upon the quasi-proton and quasi-neutron make up of high-K isomeric states in this region.

nucl-ex↗

arXiv2008

Measurement of beam-recoil observables Ox, Oz and target asymmetry for the reaction gamma p -> K Lambda

The double polarization (beam-recoil) observables Ox and Oz have been measured for the reaction gamma p -> K Lambda from threshold production to Egamma = 1500 MeV. The data were obtained with the linearly polarized beam of the GRAAL facility. Values for the target asymmetry T could also be extracted despite the use of an unpolarized target. Analyses of our results by two isobar models tend to confirm the necessity to include new or poorly known resonances in the 1900 MeV mass region.

nucl-ex↗

arXiv2007

Measurement of eta photoproduction on the proton from threshold to 1500 MeV

Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.

nucl-ex↗

arXiv2005

Accurate mass measurements of $^{26}$Ne, $^{26-30}$Na, $^{29-33}$Mg performed with the {\sc Mistral} spectrometer

The minuteness of the nuclear binding energy requires that mass measurements be highly precise and accurate. Here we report on new measurements $^{29-33}$Mg and $^{26}$Na performed with the {\sc Mistral} mass spectrometer at {\sc Cern}'s {\sc Isolde} facility. Since mass measurements are prone to systematic errors, considerable effort has been devoted to their evaluation and elimination in order to achieve accuracy and not only precision. We have therefore conducted a campaign of measurements for calibration and error evaluation. As a result, we now have a satisfactory description of the {\sc Mistral} calibration laws and error budget. We have applied our new understanding to previous measurements of $^{26}$Ne, $^{26-30}$Na and $^{29,32}$Mg for which re-evaluated values are reported.

nucl-ex↗

arXiv2001

Differential cross section measurement of eta photoproduction on the proton from threshold to 1100 MeV

The differential cross section for the reaction p(gamma, eta p) has been measured from threshold to 1100 MeV photon laboratory energy. For the first time, the region of the S11(1535) resonance is fully covered in a photoproduction experiment and allows a precise extraction of its parameters at the photon point. Above 1000 MeV, S-wave dominance vanishes while a P-wave contribution is observed whose nature will have to be clarified. These high precision data together with the already measured beam asymmetry data will provide stringent constraints on the extraction of new couplings of baryon resonances to the eta meson.

hep-ex↗

arXiv1998

Tensor Analyzing Powers for Quasi-Elastic Electron Scattering from Deuterium

We report on a first measurement of tensor analyzing powers in quasi-elastic electron-deuteron scattering at an average three-momentum transfer of 1.7 fm$^{-1}$. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to 150 MeV/$c$ with a tensor polarized $^2$H target internal to an electron storage ring. The data are well described by a calculation that includes the effects of final-state interaction, meson-exchange and isobar currents, and leading-order relativistic contributions.

nucl-ex↗