The production of ${}^{26}\mathrm{Al}$ in massive stars is sensitive to the ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ cross section. Recent experimental data suggest the currently recommended cross sections are underestimated by a factor of $\sim 40$. We present here differential cross sections for the ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ reaction measured in the energy range $E_{\mathrm{c}.\mathrm{m}.}=1.7–2.5\mathrm{MeV}$. Concurrent measurements of Rutherford scattering provide absolute normalizations that are independent of variations in target properties. Angular distributions are measured for both $p_0$ and $p_1$ permitting the determination of total cross sections. The results show no significant deviation from the statistical model calculations upon which the recommended rates are based. We therefore retain the previous recommendation without the increase in cross section and resulting stellar reaction rates by a factor of 40, impacting the ${}^{26}\mathrm{Al}$ yield from massive stars by more than a factor of 3.

${}^{26}\mathrm{Al}$ is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ reaction has been identified by a sensitivity study as being one of the most important reactions for the production of ${}^{26}\mathrm{Al}$ in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ in this sensitivity study. Current experimental data suggest a reaction rate a factor of $\sim 40$ higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range $E_{\mathrm{c}.\mathrm{m}.}=1.28–3.15\mathrm{MeV}$ at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of ${}^{26}\mathrm{Al}$, due to this reaction, are determined.

We demonstrate an efficient high-precision optical spectroscopy technique for single trapped ions with nonclosed transitions. In a double-shelving technique, the absorption of a single photon is first amplified to several phonons of a normal motional mode shared with a cotrapped cooling ion of a different species, before being further amplified to thousands of fluorescence photons emitted by the cooling ion using the standard electron shelving technique. We employ this extension of the photon recoil spectroscopy technique to perform the first high precision absolute frequency measurement of the ${}^2{D}_{3/2}\to {}^2{P}_{1/2}$ transition in calcium, resulting in a transition frequency of $f=346000234867(96)\mathrm{kHz}$. Furthermore, we determine the isotope shift of this transition and the ${}^2{S}_{1/2}\to {}^2{P}_{1/2}$ transition for ${}^{42}{\mathrm{Ca}}^{+}$, ${}^{44}{\mathrm{Ca}}^{+}$, and ${}^{48}{\mathrm{Ca}}^{+}$ ions relative to ${}^{40}{\mathrm{Ca}}^{+}$ with an accuracy below 100 kHz. Improved field and mass shift constants of these transitions as well as changes in mean square nuclear charge radii are extracted from this high resolution data.

Finding conditions that support synchronization is a fertile and active area of research with applications across multiple disciplines. Here we present and analyze a scheme for synchronizing chaotic dynamical systems by transiently uncoupling them. Specifically, systems coupled only in a fraction of their state space may synchronize even if fully coupled they do not. While for many standard systems coupling strengths need to be bounded to ensure synchrony, transient uncoupling removes this bound and thus enables synchronization in an infinite range of effective coupling strengths. The presented coupling scheme therefore opens up the possibility to induce synchrony in (biological or technical) systems whose parameters are fixed and cannot be modified continuously.

We present a model to understand quantitatively the role of symmetry breaking in assembly of macromolecular aggregates in general, and the protein shells of viruses in particular. A simple dodecahedral lattice model with a quadrupolar order parameter allows us to demonstrate how symmetry breaking may reduce the probability of assembly errors and, consequently, enhance assembly efficiency. We show that the ground state is characterized by large-scale cooperative zero-energy modes. In analogy with other models, this suggests a general physical principle: the tendency of biological molecules to generate symmetric structures competes with the tendency to break symmetry in order to achieve specific functional goals.

By studying a system of Brownian particles that interact among themselves only through a local velocity-alignment force that does not affect their speed, we show that self-propulsion is not a necessary feature for the flocking transition to take place as long as underdamped particle dynamics can be guaranteed. Moreover, the system transits from stationary phases close to thermal equilibrium, with no net flux of particles, to far-from-equilibrium ones exhibiting collective motion, phase coexistence, long-range order, and giant number fluctuations, features typically associated with ordered phases of models where self-propelled particles with overdamped dynamics are considered.

We implement the conformal bootstrap program for three dimensional conformal field theories with $\mathcal{N}=2$ supersymmetry and find universal constraints on the spectrum of operator dimensions in these theories. By studying the bounds on the dimension of the first scalar appearing in the operator product expansion of a chiral and an antichiral primary, we find a kink at the expected location of the critical three dimensional $\mathcal{N}=2$ Wess-Zumino model, which can be thought of as a supersymmetric analog of the critical Ising model. Focusing on this kink, we determine, to high accuracy, the low-lying spectrum of operator dimensions of the theory, as well as the stress-tensor two-point function. We find that the latter is in an excellent agreement with an exact computation.

The first observation of the $B_s^0\to {\eta }^{\prime }{\eta }^{\prime }$ decay is reported. The study is based on a sample of proton-proton collisions corresponding to $3.0{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the LHCb detector. The significance of the signal is 6.4 standard deviations. The branching fraction is measured to be $[3.31\pm 0.64(\text{stat})\pm 0.28(\text{syst})\pm 0.12(\text{norm})]\times {10}^{-5}$, where the third uncertainty comes from the $B^{\pm }\to {\eta }^{\prime }{K}^{\pm }$ branching fraction that is used as a normalization. In addition, the charge asymmetries of $B^{\pm }\to {\eta }^{\prime }{K}^{\pm }$ and $B^{\pm }\to \varphi K^{\pm }$, which are control channels, are measured to be $(-0.2\pm 1.3)\%$ and $(+1.7\pm 1.3)\%$, respectively. All results are consistent with theoretical expectations.

Raman-assisted hopping may be used to realize the anyon Hubbard model in one-dimensional optical lattices. We propose a feasible scenario that significantly improves the proposal of T. Keilmann et al. [Nat. Commun. 2, 361 (2011)], allowing as well for an exact realization of the two-body hard-core constraint, and for controllable effective interactions without the need of Feshbach resonances. We show that the combination of anyonic statistics and two-body hard-core constraint leads to a rich ground-state physics, including Mott insulators with attractive interactions, pair superfluids, dimer phases, and multicritical points. Moreover, the anyonic statistics results in a novel two-component superfluid of holon and doublon dimers, characterized by a large but finite compressibility and a multipeaked momentum distribution, which may be easily revealed experimentally.

We perform phase-space tomography of semiconductor laser dynamics by simultaneous experimental determination of optical intensity, frequency, and population inversion with high temporal resolution. We apply this technique to a laser with delayed feedback, serving as prominent example for high-dimensional chaotic dynamics and as model system for fundamental investigations of complex systems. Our approach allows us to explore so far unidentified trajectories in phase space and identify the underlying physical mechanism.

We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.

The first self-consistent hybrid particle-in-cell (PIC) simulation of intense proton beam transport and energy deposition in solid-density matter is presented. Both the individual proton slowing-down and the collective beam-plasma interaction effects are taken into account with a new dynamic proton stopping power module that has been added to a hybrid PIC code. In this module, the target local stopping power can be updated at each time step based on its thermodynamic state. For intense proton beams, the reduction of target stopping power from the cold condition due to continuous proton heating eventually leads to broadening of the particle range and energy deposition far beyond the Bragg peak. For tightly focused beams, large magnetic field growth in collective interactions results in self-focusing of the beam and much stronger localized heating of the target.

The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a $\sim 3\mathrm{ns}$ duration neutron pulse with ${10}^4\mathrm{n}/\mathrm{MeV}/\mathrm{sr}/\mathrm{shot}$ at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a “high-foot” laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium hohlraums provide a higher albedo and thus an increased drive equivalent to an additional 25 TW laser power at the peak of the drive compared to standard gold hohlraums leading to higher implosion velocity. Additionally, we observe an improved hot-spot shape closer to round which indicates enhanced drive from the waist. In contrast to findings in the National Ignition Campaign, now all of our highest performing experiments have been done in uranium hohlraums and achieved total yields approaching ${10}^{16}$ neutrons where more than 50% of the yield was due to additional heating of alpha particles stopping in the DT fuel.

We present few-femtosecond shadowgraphic snapshots taken during the nonlinear evolution of the plasma wave in a laser wakefield accelerator with transverse synchronized few-cycle probe pulses. These snapshots can be directly associated with the electron density distribution within the plasma wave and give quantitative information about its size and shape. Our results show that self-injection of electrons into the first plasma-wave period is induced by a lengthening of the first plasma period. Three-dimensional particle-in-cell simulations support our observations.

We carry out density-matrix-renormalization group (DMRG) calculations for the problem of one doped hole in a two-leg $t\text{−}J$ ladder. Recent studies have concluded that exotic “Mott” physics—arising from the projection onto the space of no double-occupied sites—is manifest in this model system, leading to charge localization and a new mechanism for charge modulation. In contrast, we show that there is no localization and that the charge-density modulation arises when the minimum in the quasiparticle dispersion moves away from $\pi$. Although singular changes in the quasiparticle dispersion do occur as a function of model parameters, all of the DMRG results can be qualitatively understood from a noninteracting “band-structure” perspective.