The incompressibility of infinite nuclear matter (K infinity) is a parameter in the description of the nuclear equation of state that governs the energy cost associated with density oscillations near the saturation density. The most direct experimental method for studying this property of infinite nuclear matter is to probe the isoscalar giant monopole resonance (ISGMR) in finite nuclei. This paper explores the use of 6Li as a probe to study the ISGMR in several stable nuclei: 58Ni, 90Zr, 116Sn, and 208Pb, as complementary to using inelastic scattering of alpha particles, which has been used to great effect over the last several decades. Elastic and inelastic scattering data for these targets were collected with 343-MeV 6Li beams. In all nuclei studied in this paper, the ISGMR strength distributions extracted from multipole decomposition analyses of the inelastic scattering spectra agree very well with the previously measured ISGMR responses from alpha-particle scattering, establishing the feasibility of employing 6Li inelastic scattering in investigations of the ISGMR.

The emission of α particles has been analyzed using a 14N projectile beam on 59Co, 93Nb, and 197Au targets at an incident energy of 250 MeV, in the angular range from 8° to 40°. The estimated α particles from the break-up channel and the pre-equilibrium mode were compared with the experimentally measured inclusive double differential cross sections at various angles at 250 MeV beam energy. The present results indicate that at such a high incident energy, a significant contribution to the α-particle emission comes from direct reactions, which are dominant at forward angles. At larger emission angles, non-equilibrium and evaporation processes increase and compete with direct reactions.

Angular distributions of the elastic and inelastic deuteron-nucleus scattering off Mg-24, Si-28, Ni-58, Zr-90, Sn-116, and Pb-208 have been measured at a beam energy of 98 MeV/nucleon, with the goal of constraining the deuteron optical potential in this kinematical regime and to extract the reduced transition probabilities for the ground-state transitions to low-lying excited states of these nuclei. Two potential models were used in the analysis of the measured (d,d) and (d,d ') data within the optical model and the distorted-wave Born approximation: the phenomenological optical model potential associated with the collective model of nuclear scattering, and the semimicroscopic double-folding model of the deuteron-nucleus potential based on a realistic density-dependent M3Y interaction. The deuteron optical potential and inelastic (d,d ') scattering form factors were calculated using these two potential models, allowing for a direct comparison between the potential models as well as the validation of the deduced E lambda transition rates.

Quasi-elastic (QEL) scattering measurements have been performed using a 28Si projectile off a 90Zr target at energies around the Coulomb barrier. A Bayesian analysis within the framework of coupled channels (CC) calculations is performed in a large parameter space of quadrupole and hexadecapole deformations (β2 and β4) of 28Si. Our results unambiguously show that 28Si is an oblate shaped nucleus with β2=-0.38±0.01 which is in excellent agreement with results from electromagnetic probes. The sign and magnitude of quadrupole deformation along with a precise value of hexadecapole deformation (β4=+0.03±0.01) of 28Si have been determined for the first time using QEL scattering. A remarkable agreement is obtained between the experimental and calculated β4 values of 28Si based on Skyrme-Hartree-Fock method. The present results demonstrate the strong sensitivity of the quasi-elastic scattering to the sign and magnitude to the ground state deformation parameters, thus affirming its suitability to be used for rare exotic nuclei using low intensity RIBs.

Elastic scattering angular distributions have been measured for $$^{7}$$ Li+ $$^{92,100}$$ Mo systems in the bombarding energy range of 0.85 to almost two times the Coulomb barrier. The measured elastic scattering angular distributions are fitted using optical model to investigate energy dependence of the real and imaginary strength parameters with phenomenological Woods-Saxon and double folding S $${\tilde{a}}$$ o Paulo potentials. Both interaction potential models simulate similar patterns to energy dependence sustaining the same consequence of breakup threshold anomaly. The results of Continuum Discretized Coupled Channels (CDCC) Calculations with inclusion of the breakup coupling of the projectile compares experimental elastic scattering angular distribution better for the $$^{7}$$ Li+ $$^{92,100}$$ Mo systems rather than excluding breakup coupling. A systematic behaviour of total reaction cross section on target and projectile dependency has been investigated by including a wide range of target mass and tightly to weakly bound projectiles. A comparative study on obtained breakup and reaction cross sections has also been carried out for $$^{7}$$ Li+ $$^{92,100}$$ Mo systems.

Collective enhancement in nuclear level density (CELD) and its fadeout has been studied experimentally using neutron and high energy gamma-ray spectra earlier. Attempts to probe CELD with alpha-particle spectra were made for compound nucleus (CN) Hf-178 in the excitation energy 54-124 MeV, but no signature of CELD was found. The possible reason behind this nonobservance has been discussed in a few subsequent reports. In our previous study, evidence of CELD was found using neutron spectra and enhancement faded away near 25 MeV of excitation energy. This implies that the effect of CELD on alpha particles, if any, would be found at excitation lower than 25 MeV. With the aim to observe CELD and its fadeout with alpha-particle spectra, two reactions C-12 + Sn-116, Tb-159, forming CN in different mass region (A approximate to 128 and A approximate to 171) were studied. Evaporation alpha-particle spectra were measured for these reactions in singles as well as in coincidence with neutrons. Experimental data were compared with statistical model calculations and inverse level density parameter (k) were obtained from alpha-particle spectra. As a function of CN excitation energy, the k value showed peak like structure for the reaction C-12 + 159Tb which indicates fadeout of CELD. No such evidence was found for the reaction C-12 + Sn-116. Collective enhancement factor for daughter nuclei populated in C-12 + Tb-159 reaction was extracted. Critical energy of the fadeout was found to be similar to that of mass A approximate to 188 region.

β decay of proton-rich nuclei plays an important role in exploring isospin mixing. The β decay of ^{26}P at the proton drip line is studied using double-sided silicon strip detectors operating in conjunction with high-purity germanium detectors. The T=2 isobaric analog state (IAS) at 13 055 keV and two new high-lying states at 13 380 and 11 912 keV in ^{26}Si are unambiguously identified through β-delayed two-proton emission (β2p). Angular correlations of two protons emitted from ^{26}Si excited states populated by ^{26}P β decay are measured, which suggests that the two protons are emitted mainly sequentially. We report the first observation of a strongly isospin-mixed doublet that deexcites mainly via two-proton decay. The isospin mixing matrix element between the ^{26}Si IAS and the nearby 13 380-keV state is determined to be 130(21) keV, and this result represents the strongest mixing, highest excitation energy, and largest level spacing of a doublet ever observed in β-decay experiments.

Group B Streptococcus (GBS) is a common intestinal colonizer during the neonatal period, but also may cause late-onset sepsis or meningitis in up to 0.5% of otherwise healthy colonized infants after day 3 of life. Transmission routes and risk factors of this late-onset form of invasive GBS disease (iGBS) are not fully understood. Cases of iGBS with recurrence (n=25) and those occurring in parallel in twins/triplets (n=32) from the UK and Ireland (national surveillance study 2014/15) and from Germany and Switzerland (retrospective case collection) were analyzed to unravel shared (in affected multiples) or fixed (in recurrent disease) risk factors for GBS disease. The risk of iGBS among infants from multiple births was high (17%), if one infant had already developed GBS disease. The interval of onset of iGBS between siblings was 4.5 days and in recurrent cases 12.5 days. Disturbances of the individual microbiome, including persistence of infectious foci are suggested e.g. by high usage of perinatal antibiotics in mothers of affected multiples, and by the association of an increased risk of recurrence with a short term of antibiotics [aOR 4.2 (1.3-14.2), P=0.02]. Identical GBS serotypes in both recurrent infections and concurrently infected multiples might indicate a failed microbiome integration of GBS strains that are generally regarded as commensals in healthy infants. The dynamics of recurrent GBS infections or concurrent infections in multiples suggest individual patterns of exposure and fluctuations in host immunity, causing failure of natural niche occupation.

Background. The true frequency of hospital outbreaks of invasive group B streptococcal (iGBS; Streptococcus agalactiae) disease in infants is unknown. We used whole genome sequencing (WGS) of iGBS isolates collected during a period of enhanced surveillance of infant iGBS disease in the UK and Ireland to determine the number of clustered cases. Methods. Potentially linked iGBS cases from infants with early (<7 days of life) or late-onset (7-89 days) disease were identified from WGS data (HiSeq 2500 platform, Illumina) from clinical sterile site isolates collected between 04/2014 and 04/2015. We assessed time and place of cases to determine a single-nucleotide polymorphism (SNP) difference threshold for clustered cases. Case details were augmented through linkage to national hospital admission data and hospital record review by local microbiologists. Results. Analysis of sequences indicated a cutoff of <= 5 SNP differences to define iGBS clusters. Among 410 infant iGBS isolates, we identified 7 clusters (4 genetically identical pairs with 0 SNP differences, 1 pair with 3 SNP differences, 1 cluster of 4 cases with <= 1 SNP differences) of which 4 clusters were uncovered for the first time. The clusters comprised 16 cases, of which 15 were late-onset (of 192 late-onset cases with sequenced isolates) and 1 an early-onset index case. Serial intervals between cases ranged from 0 to 59 (median 12) days. Conclusions. Approximately 1 in 12 late-onset infant iGBS cases were part of a hospital cluster. Over half of the clusters were previously undetected, emphasizing the importance of routine submission of iGBS isolates to reference laboratories for cluster identification and genomic confirmation.

The beta-delayed two-proton (beta 2p) decay of S-27 was studied using a state-of-the-art silicon array and Clover-type HPGe detectors. An energy peak at 6372(15) keV with a branching ratio of 2.4(5)% in the decay-energy spectrum was identified as a two-proton transition via the isobaric-analog state in P-27 to the ground state of Al-25 in the beta decay of S-27. Two-proton angular correlations were measured by the silicon array to study the mechanism of two-proton emission. Based on experimental results and Monte Carlo simulations, it was found that the main mechanism for the emission of beta 2p by S-27 is of sequential nature.

Two resonant states above the He-6 +t threshold in Li-9 have been observed using a Li-9 beam bombarding a Pb-208 target at the incident energy of 32.7 MeV/nucleon. An angular correlation analysis and the continuum discretized coupled channels (CDCC) method have been applied to identify the spin-parities of observed resonant states. The obtained results from the present methods of calculations indicate the first resonant state at 9.8 MeV with a spin-parity of 3/2(-). The second resonant state at 12.8 MeV with limited statistics might suggest the spin-parity of 7/2(-), which needs to be further investigated. The monopole matrix element of the 3/2(-) state is extracted as 8.1(8) fm(2) with a multipole decomposition analysis based on a distorted wave Born approximation (DWBA) calculation. These results give the first experimental evidence supporting the theoretical prediction of the generator coordinate method (GCM) and disclose the feature of clustering structure involving two neutron-rich clusters in the neutron-rich nucleus Li-9.

A detailed beta-decay spectroscopic study of Al-22 was performed at the Radioactive Ion Beam Line in Lanzhou. With the beta-gamma-particle coincidence measurement by a high-resolution DSSD particle detection array and a high efficiency gamma-ray detection array, total eight excited states in Mg-22 fed by Gamow-Teller transitions was newly identified. The one-proton, two-proton, and a decays of the IAS at 14046(5) keV in Mg-22, which were partly observed in different experiments before, were identified simultaneously in the present work, providing accurate spectroscopic information about its decay. A more complete beta-decay scheme of Al-22 was constructed and compared to the shell-model calculations with the USD-type Hamiltonians, USDC and USDB.

Large amounts of high quality biophysical data are needed to improve current biological effects models but such data are lacking and difficult to obtain. The present study aimed to more efficiently measure the spatial distribution of relative biological effectiveness (RBE) of charged particle beams using a novel high-accuracy and high-throughput experimental platform. Clonogenic survival was selected as the biological endpoint for two lung cancer cell lines, H460 and H1437, irradiated with protons, carbon, and helium ions. Ion-specific multi-step microplate holders were fabricated such that each column of a 96-well microplate is spatially situated at a different location along a particle beam path. Dose, dose-averaged linear energy transfer (LETd), and dose-mean lineal energy (yd) were calculated using an experimentally validated Geant4-based Monte Carlo system. Cells were irradiated at the Heidelberg Ion Beam Therapy Center (HIT). The experimental results showed that the clonogenic survival curves of all tested ions were yd-dependent. Both helium and carbon ions achieved maximum RBEs within specific yd ranges before biological efficacy declined, indicating an overkill effect. For protons, no overkill was observed, but RBE increased distal to the Bragg peak. Measured RBE profiles strongly depend on the physical characteristics such as yd and are ion specific.

The beta decay of P-26 was used to populate the astrophysically important E-x = 5929.4(8) keV, J(pi) = 3(+) state of Si-26. Both beta-delayed protons at 418(8) keV and gamma rays at 1742(2) keV emitted from this state were measured simultaneously for the first time, and the corresponding absolute intensities have been estimated as 11.1(12)% and 0.59(44)%, respectively. The half-life of P-26 has been determined to be 43.6(3) ms, which is in good agreement with previous experimental results. Besides, shell-model calculations with weakly bound effects were performed to investigate the decay properties of other resonant states and a spin-parity of 4(+) rather than 0(+) is favored for the E-x = 5945.9(40) keV state. Combining the experimental results and theoretical calculations, the Al-25(p, gamma) Si-26 reaction rate in explosive hydrogen burning environments was calculated. The new determined total reaction rate is consistent with previous studies at T > 0.2 GK.

The mass of P-27 is expected to impact the X-ray burst (XRB) model predictions of burst light curves and the composition of the burst ashes, but large uncertainties and inconsistencies still exist in the reported P-27 masses. We have used the beta-decay spectroscopy of S-27 to determine the most precise mass excess of P-27 to date to be -659(9) keV, which is 63 keV (2.3 sigma) higher and a factor of 3 more precise than the value recommended in the 2016 Atomic Mass Evaluation. Based on the new P-27 mass, the Si-26(p, gamma)P-27 reaction rate and its uncertainty were recalculated using Monte Carlo techniques. We also estimated the previously unknown mass excess of S-27 to be 17678(77) keV, based on the measured beta-delayed two-proton energy and the Coulomb displacement energy relations. The impact of these well-constrained masses and reaction rates on the modeling of the explosive astrophysical scenarios has been investigated by post-processing XRB and hydrodynamic nova models. Compared to the model calculations based on the masses and rates from databases, the abundance of A = 26 in the burst ashes is increased by a factor of 2.4, while no substantial change was found in the XRB energy generation rate or the light curve. Our calculation also suggests that S-27 is not a significant waiting point in the rapid proton capture process, and the change of the Si-26(p, gamma)P-27 reaction rate is not sufficiently large to affect the conclusion previously drawn on the nova contribution to the synthesis of galactic Al-26. (C) 2020 The Author. Published by Elsevier B.V.

Complete fusion (CF) cross section measurement for the weakly bound Be- 9 projectile interacting with the intermediate mass target Y-89 has been extended to energies greater than the fusion barrier, by implementing off-line characteristic gamma-ray detection techniques. The available experimental data for the Be-9 + Y-89 reaction system were compared with the theoretical predictions, using the PLATYPUS code that is based on a classical dynamical model. By introducing the breakup probability that deduced in the literature from the fitting of the experimental data, the model managed to reproduce the CF cross sections of Be-9 beam with targets of different atomic mass. Through the study, it is revealed that the extended CF excitation function for the Be-9 + Y-89 system is consistent with the systematical behavior that the prompt-breakup probability at above-barrier energies is roughly independent of the target in the reactions induced by the same weakly bound projectiles.

Complete fusion (CF) cross section measurement for the weakly bound 9Be projectile interacting with the intermediate mass target 89Y has been extended to energies greater than the fusion barrier, by implementing off-line characteristic γ -ray detection techniques. The available experimental data for the 9Be + 89Y reaction system were compared with the theoretical predictions, using the PLATYPUS code that is based on a classical dynamical model. By introducing the breakup probability that deduced in the literature from the fitting of the experimental data, the model managed to reproduce the CF cross sections of 9Be beam with targets of different atomic mass. Through the study, it is revealed that the extended CF excitation function for the 9Be + 89Y system is consistent with the systematical behavior that the prompt-breakup probability at above-barrier energies is roughly independent of the target in the reactions induced by the same weakly bound projectiles.

β decay of ^26P was used to populate the astrophysically important E_x=5929.4(8) keV J^π=3^+ state of ^26Si. Both β-delayed proton at 418(8) keV and gamma ray at 1742(2) keV emitted from this state were measured simultaneously for the first time with corresponding absolute intensities of 11.1(12)% and 0.59(44)%, respectively. Besides, shell model calculations with weakly bound effects were performed to investigate the decay properties of other resonant states and a spin-parity of 4^+ rather than 0^+ was favored for the E_x=5945.9(40) keV state. Combining the experimental results and theoretical calculations, ^25Al(p,γ)^26Si reaction rate in explosive hydrogen burning environments was calculated and compared with previous studies.

G. S. Li ,1 M. L. Liu,1,* D. Patel,1,† Y. D. Fang,1 X. H. Zhou,1 Y. H. Zhang,1 A. Diaz-Torres,2 C. S. Palshetkar,3 J. Lubian,4 N. T. Zhang,1 J. G. Wang,1 B. S. Gao,1 Y. H. Qiang,1 S. Guo,1 Y. Zheng,1 K. L. Wang,1 K. K. Zheng,1 R. Li,1 and S. Mukherjee5 1Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People’s Republic of China 2Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom 3Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai 400005, India 4Instituto de Física, Universidade Federal Fluminense, Avenida Litorânea s/n, Gragoatá, Niterói, Rio de Janeiro 24210-340, Brazil 5Physics Department, Faculty of Science, M. S. University of Baroda, Vadodara 390002, India

Background: beta-decay spectroscopy provides valuable nuclear physics input for accurate modeling of nova and x-ray burst observables and a stringent test for shell-model theories far from the stability line. The decay scheme of S-27 is complicated and far from being understood due to a lack of experimental data prior to this work. Purpose: We aim to experimentally constrain the thermonuclear Si-26(p, gamma)P-27 reaction rate and to probe the possible mirror asymmetry in S-27 and Na-27 decays. Method: The S-27 ions were collected by double-sided silicon strip detectors operating in conjunction with high-purity germanium detectors, so the positrons, protons, and gamma rays emitted in the decay were measured simultaneously. Results: The precise resonance energy and the ratio between gamma and proton partial widths of the key 3/2(+) resonance were obtained, thereby determining the Si-26(p, gamma)P-27 reaction rate based mainly on experimental constraints. The half-life of S-27, the excitation energies, beta-feeding intensities, log ft values, and Gamow-Teller transition strengths for the states of P-27 populated in the beta decay of S-27 were determined. A more complete S-27 P-decay scheme was constructed and compared to the beta decay of mirror nucleus Na-27 and to the shell-model calculations with the universal sd (USD) Hamiltonian taking into account the shift of single-particle energies and the reduction of two-body matrix elements. Conclusions: This work yields a new Si-26(p, gamma)P-27 reaction rate two orders of magnitude lower than the rate recommended in the reaction rate libraries at around 0.1 GK. Experimental evidence for the observation of mirror asymmetries for the Gamow-Teller transitions of S-27 and Na-27 is also provided. The shell-model calculations using a modified USD interaction related to the weakly bound proton 1s(1/2) orbit give a reasonable description of the decay properties of S-27.