We present the cross sections for production of up to four jets at the Large Hadron Collider, at next-to-leading order in the QCD coupling. We use the BlackHat library in conjunction with SHERPA and a recently developed algorithm for assembling primitive amplitudes into color-dressed amplitudes. We adopt the cuts used by ATLAS in their study of multijet events in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. We include estimates of nonperturbative corrections and compare to ATLAS data. We store intermediate results in a framework that allows the inexpensive computation of additional results for different choices of scale or parton distributions.

Using a sample of $106\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector at the BEPCII storage ring, we have made the first measurement of the $M1$ transition between the radially excited charmonium $S$-wave spin-triplet and the radially excited $S$-wave spin-singlet states: $\psi (3686)\to \gamma {\eta }_c(2S)$. Analyses of the processes $\psi (3686)\to \gamma {\eta }_c(2S)$ with ${\eta }_c(2S)\to K_S^0{K}^{\pm }{\pi }^{\mp }$ and $K^{+}{K}^{-}{\pi }^0$ give an ${\eta }_c(2S)$ signal with a statistical significance of greater than 10 standard deviations under a wide range of assumptions about the signal and background properties. The data are used to obtain measurements of the ${\eta }_c(2S)$ mass ($M\mathbf{(}{\eta }_c(2S)\mathbf{)}=3637.6\pm {2.9}_{\mathrm{stat}}\pm {1.6}_{\mathrm{syst}}\mathrm{MeV}/c^2$), width ($\Gamma \mathbf{(}{\eta }_c(2S)\mathbf{)}=16.9\pm {6.4}_{\mathrm{stat}}\pm {4.8}_{\mathrm{syst}}\mathrm{MeV}$), and the product branching-fraction ($\mathcal{B}\mathbf{(}\psi (3686)\to \gamma {\eta }_c(2S)\mathbf{)}\times \mathcal{B}\mathbf{(}{\eta }_c(2S)\to K\overline{K}\pi \mathbf{)}=(1.30\pm {0.20}_{\mathrm{stat}}\pm {0.30}_{\mathrm{syst}})\times {10}^{-5}$). Combining our result with a BABAR measurement of $\mathcal{B}\mathbf{(}{\eta }_c(2S)\to K\overline{K}\pi \mathbf{)}$, we find the branching fraction of the $M1$ transition to be $\mathcal{B}\mathbf{(}\psi (3686)\to \gamma {\eta }_c(2S)\mathbf{)}=(6.8\pm {1.1}_{\mathrm{stat}}\pm {4.5}_{\mathrm{syst}})\times {10}^{-4}$.

Limit-cycle oscillations induced by time delay are widely observed in various systems, but a systematic phase-reduction theory for them has yet to be developed. Here we present a practical theoretical framework to calculate the phase response function $Z(\theta )$, a fundamental quantity for the theory, of delay-induced limit cycles with infinite-dimensional phase space. We show that $Z(\theta )$ can be obtained as a zero eigenfunction of the adjoint equation associated with an appropriate bilinear form for the delay differential equations. We confirm the validity of the proposed framework for two biological oscillators and demonstrate that the derived phase equation predicts intriguing multimodal locking behavior.

It has been an experimental challenge to test the rupture of liquids with homogeneous nucleation of vapor bubbles. Many prior studies suffered from the ubiquitous presence of impurities in liquids or at container surfaces that spontaneously nucleate and grow under tension. Here, we propose a microfluidic approach to eliminate such impurities and obtain homogeneous bubble nucleation. We stretch the liquid dynamically via the interaction between a laser-induced shock and an air-liquid interface in a microchannel. Reproducible observations of the nucleation of vapor bubbles are obtained, supporting our claim of homogeneous nucleation. From comparisons of the distribution of vapor cavities with Euler flow simulations, the nucleation threshold for water at room temperature is predicted to be $-60\mathrm{MPa}$.

We study how the interplay of dissipation and interactions affects the dynamics of a bosonic many-body quantum system. In the presence of both dissipation and strongly repulsive interactions, observables such as the coherence and the density fluctuations display three dynamical regimes: an initial exponential variation followed by a power-law regime, and finally a slow exponential convergence to their asymptotic values. These very long-time scales arise as dissipation forces the population of states disfavored by interactions. The long-time, strong coupling dynamics are understood by performing a mapping onto a classical diffusion process displaying non-Brownian behavior. While both dissipation and strong interactions tend to suppress coherence when acting separately, we find that strong interaction impedes the decoherence process generated by the dissipation.

Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center ($q=0$) wave vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene originating from a double-resonant Raman process with $q\ne 0$. The observed phonon renormalization effects are different from what is observed for the zone-center $q=0$ case. To explain our experimental findings, we explored the phonon self-energy for the phonons with nonzero wave vectors ($q\ne 0$) in single-layer graphene in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center $q=0$ processes. Within this framework, we resolve the identification of the phonon modes contributing to the $G^{\star }$ Raman feature at $2450{\mathrm{cm}}^{-1}$ to include the $\mathrm{iTO}+\mathrm{LA}$ combination modes with $q\ne 0$ and also the 2iTO overtone modes with $q=0$, showing both to be associated with wave vectors near the high symmetry point $\mathbf{K}$ in the Brillouin zone.

In high-resolution resonant inelastic x-ray scattering at the Ti $L$ edge of the charge-density-wave system $1T\mathrm{\text{−}}{\mathrm{TiSe}}_2$, we observe sharp low energy loss peaks from electron-hole pair excitations developing at low temperature. These excitations are strongly dispersing as a function of the transferred momentum of light. We show that the unoccupied bands close to the Fermi level can effectively be probed in this broadband material. Furthermore, we extract the order parameter of the charge-density-wave phase from temperature-dependent measurements.

One approach to super-resolution fluorescence microscopy, termed stochastic localization microscopy, relies on the nanometer scale spatial localization of individual fluorescent emitters that stochastically label specific features of the specimen. The precision of emitter localization is an important determinant of the resulting image resolution but is insufficient to specify how well the derived images capture the structure of the specimen. We address this deficiency by considering the inference of specimen structure based on the estimated emitter locations. By using estimation theory, we develop a measure of spatial resolution that jointly depends on the density of the emitter labels, the precision of emitter localization, and prior information regarding the spatial frequency content of the labeled object. The Nyquist criterion does not set the scaling of this measure with emitter number. Given prior information and a fixed emitter labeling density, our resolution measure asymptotes to a finite value as the precision of emitter localization improves. By considering the present experimental capabilities, this asymptotic behavior implies that further resolution improvements require increases in labeling density above typical current values. Our treatment also yields algorithms to enhance reliable image features. Overall, our formalism facilitates the rigorous statistical interpretation of the data produced by stochastic localization imaging techniques.

Using high-resolution microwave sky maps made by the Atacama Cosmology Telescope, we for the first time present strong evidence for motions of galaxy clusters and groups via microwave background temperature distortions due to the kinematic Sunyaev-Zel’dovich effect. Galaxy clusters are identified by their constituent luminous galaxies observed by the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. We measure the mean pairwise momentum of clusters, with a probability of the signal being due to random errors of 0.002, and the signal is consistent with the growth of cosmic structure in the standard model of cosmology.

Chameleon scalar fields are dark-energy candidates which suppress fifth forces in high density regions of the Universe by becoming massive. We consider chameleon models as effective field theories and estimate quantum corrections to their potentials. Requiring that quantum corrections be small, so as to allow reliable predictions of fifth forces, leads to an upper bound $m<0.0073(\rho /10\mathrm{g}{\mathrm{cm}}^{-3}{)}^{1/3}\mathrm{eV}$ for gravitational-strength coupling whereas fifth force experiments place a lower bound of $m>0.0042\mathrm{eV}$. An improvement of less than a factor of two in the range of fifth force experiments could test all classical chameleon field theories whose quantum corrections are well controlled and couple to matter with nearly gravitational strength regardless of the specific form of the chameleon potential.

It is conventional to choose a typical momentum transfer of the process as the renormalization scale and take an arbitrary range to estimate the uncertainty in the QCD prediction. However, predictions using this procedure depend on the renormalization scheme, leave a nonconvergent renormalon perturbative series, and moreover, one obtains incorrect results when applied to QED processes. In contrast, if one fixes the renormalization scale using the principle of maximum conformality (PMC), all nonconformal $\{{\beta }_i\}$ terms in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC scale ${\mu }_R^{\mathrm{PMC}}$ and the resulting finite-order PMC prediction are both to high accuracy independent of the choice of initial renormalization scale ${\mu }_R^{\mathrm{init}}$, consistent with renormalization group invariance. As an application, we apply the PMC procedure to obtain next-to-next-to-leading-order (NNLO) predictions for the $t\overline{t}$-pair production at the Tevatron and LHC colliders. The PMC prediction for the total cross section ${\sigma }_{t\overline{t}}$ agrees well with the present Tevatron and LHC data. We also verify that the initial scale independence of the PMC prediction is satisfied to high accuracy at the NNLO level: the total cross section remains almost unchanged even when taking very disparate initial scales ${\mu }_R^{\mathrm{init}}$ equal to $m_t$, $20m_t$, and $\sqrt{s}$. Moreover, after PMC scale setting, we obtain $A_{\mathrm{FB}}^{t\overline{t}}\simeq 12.5\%$, $A_{\mathrm{FB}}^{p\overline{p}}\simeq 8.28\%$ and $A_{\mathrm{FB}}^{t\overline{t}}(M_{t\overline{t}}>450\mathrm{GeV})\simeq 35.0\%$. These predictions have a $1\sigma$ deviation from the present CDF and D0 measurements; the large discrepancy of the top quark forward-backward asymmetry between the standard model estimate and the data are, thus, greatly reduced.

We report an experimental and theoretical study of very low-energy photoelectrons in tunneling ionization process from noble gas atoms interacting with ultrashort intense infrared laser pulses. A universal peak structure with electron energy well below 1 eV in the photoelectron spectrum, corresponding to the double-hump structure in the longitudinal momentum distribution, is identified experimentally for all atomic species. Our quantum and semiclassical analysis reveal the role of long-range Coulomb potential in the production of this very low-energy peak structure.

We consider performing adiabatic rapid passage (ARP) using frequency-swept driving pulses to excite a collection of interacting two-level systems. Such a model arises in a wide range of many-body quantum systems, such as cavity QED or quantum dots, where a nonlinear component couples to light. We analyze the one-dimensional case using the Jordan-Wigner transformation, as well as the mean-field limit where the system is described by a Lipkin-Meshkov-Glick Hamiltonian. These limits provide complementary insights into the behavior of many-body systems under ARP, suggesting our results are generally applicable. We demonstrate that ARP can be used for state preparation in the presence of interactions, and identify the dependence of the required pulse shapes on the interaction strength. In general, interactions increase the pulse bandwidth required for successful state transfer, introducing new restrictions on the pulse forms required.

We experimentally investigate the effect of quantum resonance in the rotational excitation of the simplest quantum rotor—a diatomic molecule. Using the techniques of high-resolution femtosecond pulse shaping and rotational state-resolved detection, we measure directly the amount of energy absorbed by molecules interacting with a periodic train of laser pulses, and study their dependence on the train period. We show that the energy transfer is significantly enhanced at quantum resonance, and use this effect to demonstrate selective rotational excitation of two nitrogen isotopologs, ${}^{14}\mathrm{N}_2$ and ${}^{15}\mathrm{N}_2$. Moreover, by tuning the period of the pulse train in the vicinity of a fractional quantum resonance, we achieve selective rotational excitation of para- and ortho-isomers of ${}^{15}\mathrm{N}_2$.

Electron spin dynamics in Kapitza-Dirac scattering from a standing laser wave of high frequency and high intensity is studied. We develop a fully relativistic quantum theory of the electron motion based on the time-dependent Dirac equation. Distinct spin dynamics, with Rabi oscillations and complete spin-flip transitions, is demonstrated for Kapitza-Dirac scattering involving three photons in a parameter regime accessible to future high-power x-ray laser sources. The Rabi frequency and, thus, the diffraction pattern is shown to depend crucially on the spin degree of freedom.

We investigate theoretically and numerically a model of a supersolid in a dipole-blockaded Bose-Einstein condensate. The dependence of the superfluid fraction with an imposed thermal bath and a uniform boost velocity on the condensate is considered. Specifically, we observe a critical velocity for the nucleation of vortices in our system that is strongly linked to a steplike decrease in the superfluid fraction. We are able to use a scaling argument based on the energy required to activate a vortex, relating the critical temperature to the critical velocity, and find that this relationship is in good agreement with the numerical simulations carried out on the nonlocal Gross-Pitaevskii equation.

We have obtained some universal thermodynamic properties on glass transitions of molecular liquids. The heat capacity $C_p$ of glassy propene, which was vitrified by using a vapor-deposition technique, was measured with a newly developed adiabatic calorimeter. Propene has the lowest glass transition temperature ($T_g=56\mathrm{K}$), the largest $C_p$ jump at $T_g$ ($C_p^{\mathrm{lq}}/C_p^{\mathrm{gl}}\sim 2.5$), and the lowest residual entropy ($S_{\mathrm{res}}\sim R\ln 2$) compared with glass-forming molecules measured before. We have analyzed the present data with other hydrocarbon molecules vitrified by liquid quenching and obtained the following results: (1) The excess heat capacities are scaled well by using a Kauzmann temperature $T_{\mathrm{K}}$, (2) The size of the cooperative rearrangement region (CRR) frozen at $T_g$ increases with decreasing the temperature difference between $T_g$ and $T_{\mathrm{K}}$ (Kauzmann temperature), and (3) The simpler the molecule is, the larger the frozen CRR becomes. These are all supporting the validity of the Adam-Gibbs theory.

We have successfully determined the hitherto unknown sign of the $B_4^4$ Stevens crystal-field parameter of the tetragonal heavy-fermion compound ${\mathrm{CeCu}}_2{\mathrm{Si}}_2$ using vector $\widehat{\mathbf{q}}$-dependent nonresonant inelastic x-ray scattering experiments at the cerium $N_{4,5}$ edge. The observed difference between the two different directions, $\widehat{\mathbf{q}}\parallel [100]$ and $\widehat{\mathbf{q}}\parallel [110]$, is due to the anisotropy of the crystal-field ground state in the (001) plane and is observable only because of the utilization of higher than dipole transitions possible in nonresonant inelastic x-ray scattering. This approach allows us to go beyond the specific limitations of dc magnetic susceptibility, inelastic neutron scattering, and soft x-ray spectroscopy, and provides us with a reliable information about the orbital state of the $4f$ electrons relevant for the quantitative modeling of the quasiparticles and their interactions in heavy-fermion systems.

We have explored the spin liquid state in ${\mathrm{Tb}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ with vibrating-coil magnetometry down to $\sim 0.04\mathrm{K}$ under magnetic fields up to 5 T. We observe magnetic history dependence below $T^{*}\sim 0.2\mathrm{K}$ reminiscent of the classical spin ice systems ${\mathrm{Ho}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ and ${\mathrm{Dy}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$. The magnetic phase diagram inferred from the magnetization is essentially isotropic, without evidence of magnetization plateaus as anticipated for so-called quantum spin ice, predicted theoretically for [111] when quantum fluctuations renormalize the interactions. Instead, the magnetization for $T\ll T^{*}$ agrees semiquantitatively with the predictions of “all-in–all-out” (AIAO) antiferromagnetism. Taken together, this suggests that the spin liquid state in ${\mathrm{Tb}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ is akin to an incipient AIAO antiferromagnet.

We develop a mean-field theory for Escherichia coli chemotaxis based on the coupled spatiotemporal dynamics of the cell population and the mean receptor methylation level field. This multiscale model connects the cells’ population level motility behavior with the molecular level pathway dynamics. It reveals a simple scaling dependence of the chemotaxis velocity on the adaptation rate in exponential gradients. It explains the molecular origin of a maximum chemotaxis velocity. Simulations of our model in various spatiotemporal stimuli profiles show quantitative agreements with experiments. Moreover, it predicts a surprising reversal of chemotaxis group velocity in traveling wave environments. Our approach may be used to bridge molecular level pathway dynamics with cellular behavior in other biological systems.