We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudorapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the fluctuations at the LHC are smaller compared to the measurements at the BNL Relativistic Heavy Ion Collider, and as such, closer to what has been theoretically predicted for the formation of a quark-gluon plasma.

The second $J^{\pi }=2^{+}$ state of ${}^{12}\mathrm{C}$, predicted over 50 years ago as an excitation of the Hoyle state, has been unambiguously identified using the ${}^{12}\mathrm{C}(\gamma ,{\alpha }_0){}^8\mathrm{Be}$ reaction. The alpha particles produced by the photodisintegration of ${}^{12}\mathrm{C}$ were detected using an optical time projection chamber. Data were collected at beam energies between 9.1 and 10.7 MeV using the intense nearly monoenergetic gamma-ray beams at the $\mathrm{HI}\gamma \mathrm{S}$ facility. The measured angular distributions determine the cross section and the $E1\mathrm{\text{−}}E2$ relative phases as a function of energy leading to an unambiguous identification of the second $2^{+}$ state in ${}^{12}\mathrm{C}$ at 10.03(11) MeV, with a total width of 800(130) keV and a ground state gamma-decay width of 60(10) meV; $B(E2:2_2^{+}\to 0_1^{+})=0.73(13)e^2{\mathrm{fm}}^4$ [or 0.45(8) W.u.]. The Hoyle state and its rotational $2^{+}$ state that are more extended than the ground state of ${}^{12}\mathrm{C}$ presents a challenge and constraints for models attempting to reveal the nature of three alpha-particle states in ${}^{12}\mathrm{C}$. Specifically, it challenges the ab initio lattice effective field theory calculations that predict similar rms radii for the ground state and the Hoyle state.

We present the first experimental realization of the quantum illumination protocol proposed by Lloyd [Science 321, 1463 (2008)] and S. Tan et al. [Phys. Rev. Lett. 101, 253601 (2008)], achieved in a simple feasible experimental scheme based on photon-number correlations. A main achievement of our result is the demonstration of a strong robustness of the quantum protocol to noise and losses that challenges some widespread wisdom about quantum technologies.

A tabletop device uses 1.4 J to drive the symmetric collapse of a 1.8 mm radius vapor bubble in water at 22 bar. Single shot streak imaging reveals a stagnation plasma of 28 micron radius at over 12 000 K and an unprecedented pressure of 3.2 Mbar. Compared to sonoluminescence, the most commonly studied cavitation mechanism, this event is greater by factors of 30–40 in size, 1 000 000 in energy, and 100 in stagnation pressure. This regime of high energy density has previously been accessible only in massive facilities with very low repetition rates.

We report the generation of MeV x rays using an undulator and accelerator that are both driven by the same 100-terawatt laser system. The laser pulse driving the accelerator and the scattering laser pulse are independently optimized to generate a high energy electron beam ($>200\mathrm{MeV}$) and maximize the output x-ray brightness. The total x-ray photon number was measured to be $\sim 1\times {10}^7$, the source size was $5\mu \mathrm{m}$, and the beam divergence angle was $\sim 10\mathrm{mrad}$. The x-ray photon energy, peaked at 1 MeV (reaching up to 4 MeV), exceeds the thresholds of fundamental nuclear processes (e.g., pair production and photodisintegration).

A hitherto unexplained feature of electromagnetic simulations of ion temperature gradient turbulence is the apparent failure of the transport levels to saturate for certain parameters; this effect, termed here nonzonal transition, has been referred to as the high-$\beta$ runaway. The resulting large heat fluxes are shown to be a consequence of reduced zonal flow activity, brought on by magnetic field perturbations shorting out flux surfaces.

We have succeeded in synthesizing single crystals of a new organic radical 3-Cl-4-F-V [3-(3-chloro-4-fluorophenyl)-1,5-diphenylverdazyl]. Through the ab initio molecular orbital calculation and the analysis of the magnetic properties, this compound was confirmed to be the first experimental realization of an $S=1/2$ spin-ladder system with ferromagnetic leg interactions. The field-temperature phase diagram indicated that the ground state is situated very close to the quantum critical point. Furthermore, we found an unexpected field-induced successive phase transition, which possibly originates from the interplay of low dimensionality and frustration.

We investigate the ground states of antiferromagnetic Mn nanochains on Ni(110) by spin-polarized scanning tunneling microscopy in combination with theory. While the ferrimagnetic linear trimer experimentally shows the predicted collinear classical ground state, no magnetic contrast was observed for dimers and tetramers where noncollinear structures were expected based on ab initio theory. This striking observation can be explained by zero-point energy motion for even-numbered chains derived within a classical equation of motion leading to nonclassical ground states. Thus, depending on the parity of the chain length, the system shows a classical or a quantum behavior.

We derive hierarchies of separability criteria that identify the different degrees of entanglement ranging from bipartite to genuine multipartite in mixed quantum states of arbitrary size.

Superconducting qubits probe environmental defects such as nonequilibrium quasiparticles, an important source of decoherence. We show that “hot” nonequilibrium quasiparticles, with energies above the superconducting gap, affect qubits differently from quasiparticles at the gap, implying qubits can probe the dynamic quasiparticle energy distribution. For hot quasiparticles, we predict a non-negligible increase in the qubit excited state probability $P_e$. By injecting hot quasiparticles into a qubit, we experimentally measure an increase of $P_e$ in semiquantitative agreement with the model and rule out the typically assumed thermal distribution.

We study real space condensation in aggregation-fragmentation models where the total mass is not conserved, as in phenomena such as cloud formation and intracellular trafficking. We study the scaling properties of the system with influx and outflux of mass at the boundaries using numerical simulations, supplemented by analytical results in the absence of fragmentation. The system is found to undergo a phase transition to an unusual condensate phase, characterized by strong intermittency and giant fluctuations of the total mass. A related phase transition also occurs for biased movement of large masses, but with some crucial differences which we highlight.

The relaxation of a dissipative system to its equilibrium state often shows a multiexponential pattern with relaxation rates, which are typically considered to be independent of the initial condition. The rates follow from the spectrum of a Hermitian operator obtained by a similarity transformation of the initial Fokker-Planck operator. However, some initial conditions are mapped by this similarity transformation to functions which grow at infinity. These cannot be expanded in terms of the eigenfunctions of a Hermitian operator, and show different relaxation patterns. Considering the exactly solvable examples of Gaussian and generalized Lévy Ornstein-Uhlenbeck processes (OUPs) we show that the relaxation rates belong to the Hermitian spectrum only if the initial condition belongs to the domain of attraction of the stable distribution defining the noise. While for an ordinary OUP initial conditions leading to nonspectral relaxation can be considered exotic, for generalized OUPs driven by Lévy noise, such initial conditions are the rule.

Scalar fields are crucial components in high energy physics and extensions of general relativity. The fact that they are not observed in the Solar System may be due to a mechanism which screens their presence in high dense regions. We show how observations of the ellipticity of galaxy clusters can discriminate between models with and without scalar fields and even between different screening mechanisms. Using current x-ray observations we put novel constraints on the different models.

The 21 cm background from the epoch of reionization is a promising cosmological probe: line-of-sight velocity fluctuations distort redshift, so brightness fluctuations in Fourier space depend upon angle, which linear theory shows can separate cosmological from astrophysical information. Nonlinear fluctuations in ionization, density, and velocity change this, however. The validity and accuracy of the separation scheme are tested here for the first time, by detailed reionization simulations. The scheme works reasonably well early in reionization ($\lesssim 40\%$ ionized), but not late ($\gtrsim 80\%$ ionized).

In supersymmetric models with light Higgsinos (which are motivated by electroweak naturalness arguments), the direct production of Higgsino pairs may be difficult to search for at the LHC due to the low visible energy release from their decays. However, the wino pair production reaction ${\tilde{W}}_2^{\pm }{\tilde{Z}}_4\to (W^{\pm }{\tilde{Z}}_{1,2})+(W^{\pm }{\tilde{W}}_1^{\mp })$ also occurs at substantial rates and leads to final states including equally opposite-sign and same-sign diboson production. We propose a novel search channel for LHC14 based on the same-sign diboson plus missing $E_T$ final state which contains only modest jet activity. Assuming gaugino mass unification, and an integrated luminosity $\gtrsim 100{\mathrm{fb}}^{-1}$, this search channel provides a reach for supersymmetry well beyond that from usual gluino pair production.

Probing the origin of neutrino mass by disentangling the seesaw mechanism is one of the central issues of particle physics. We address it in the minimal left-right symmetric model and show how the knowledge of light and heavy neutrino masses and mixings suffices to determine their Dirac Yukawa couplings. This in turn allows one to make predictions for a number of high and low energy phenomena, such as decays of heavy neutrinos, neutrinoless double beta decay, electric dipole moments of charged leptons, and neutrino transition moments. We also discuss a way of reconstructing the neutrino Dirac Yukawa couplings at colliders such as the LHC.

The properties of the orbitally excited ($L=1$) $B_s^0$ states are studied by using $1.0{\mathrm{fb}}^{-1}$ of $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ collected with the LHCb detector. The first observation of the $B_{s2}^{*}(5840{)}^0$ meson decaying to $B^{*+}{K}^{-}$ is reported, and the corresponding branching fraction measured relative to the $B^{+}{K}^{-}$ decay mode. The $B_{s1}(5830{)}^0\to B^{*+}{K}^{-}$ decay is observed as well. The width of the $B_{s2}^{*}(5840{)}^0$ state is measured for the first time, and the masses of the two states are determined with the highest precision to date. The observation of the $B_{s2}^{*}(5840{)}^0\to B^{*+}{K}^{-}$ decay favors the spin-parity assignment $J^P=2^{+}$ for the $B_{s2}^{*}(5840{)}^0$ meson. In addition, the most precise measurement of the mass difference $m(B^{*+})-m(B^{+})=45.01\pm 0.30(\mathrm{stat})\pm 0.23(\mathrm{syst})\mathrm{MeV}/c^2$ is obtained.

There has been much speculation as to the origin of the $\Delta I=1/2$ rule ($\mathrm{Re}{A}_0/\mathrm{Re}{A}_2\simeq 22.5$). We find that the two dominant contributions to the $\Delta I=3/2$, $K\to \pi \pi$ correlation functions have opposite signs, leading to a significant cancelation. This partial cancelation occurs in our computation of $\mathrm{Re}{A}_2$ with physical quark masses and kinematics (where we reproduce the experimental value of $A_2$) and also for heavier pions at threshold. For $\mathrm{Re}{A}_0$, although we do not have results at physical kinematics, we do have results for pions at zero momentum with $m_{\pi }\simeq 420\mathrm{MeV}$ $[\mathrm{Re}{A}_0/\mathrm{Re}{A}_2=9.1(2.1)]$ and $m_{\pi }\simeq 330\mathrm{MeV}$ $[\mathrm{Re}{A}_0/\mathrm{Re}{A}_2=12.0(1.7)]$. The contributions which partially cancel in $\mathrm{Re}{A}_2$ are also the largest ones in $\mathrm{Re}{A}_0$, but now they have the same sign and so enhance this amplitude. The emerging explanation of the $\Delta I=1/2$ rule is a combination of the perturbative running to scales of $O(2\mathrm{GeV}$), a relative suppression of $\mathrm{Re}{A}_2$ through the cancelation of the two dominant contributions, and the corresponding enhancement of $\mathrm{Re}{A}_0$. QCD and electroweak penguin operators make only very small contributions at such scales.

We present an extraction of the lowest three moments of the proton longitudinal structure function $F_L$ from world data between $Q^2=0.75$ and $45(\mathrm{GeV}/c{)}^2$. The availability of new $F_L$ data at low Bjorken $x$ from HERA and at large $x$ from Jefferson Lab allows the first determination of these moments over a large $Q^2$ range, relatively free from uncertainties associated with extrapolations into unmeasured regions. The moments are found to be underestimated by leading twist structure function parametrizations, especially for the higher moments, suggesting either the presence of significant higher twist effects in $F_L$ and/or a larger gluon distribution at high $x$.

The tunneling dynamics in relativistic strong-field ionization is investigated with the aim to develop an intuitive picture for the relativistic tunneling regime. We demonstrate that the tunneling picture applies also in the relativistic regime by introducing position dependent energy levels. The quantum dynamics in the classically forbidden region features two time scales, the typical time that characterizes the probability density’s decay of the ionizing electron under the barrier (Keldysh time) and the time interval which the electron spends inside the barrier (Eisenbud-Wigner-Smith tunneling time). In the relativistic regime, an electron momentum shift as well as a spatial shift along the laser propagation direction arise during the under-the-barrier motion which are caused by the laser magnetic field induced Lorentz force. The momentum shift is proportional to the Keldysh time, while the wave-packet’s spatial drift is proportional to the Eisenbud-Wigner-Smith time. The signature of the momentum shift is shown to be present in the ionization spectrum at the detector and, therefore, observable experimentally. In contrast, the signature of the Eisenbud-Wigner-Smith time delay disappears at far distances for pure quasistatic tunneling dynamics.