An analysis of the decay $B^0\to J/\psi K^{*}(892{)}^0$ is presented using data, corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, collected in $pp$ collisions at a center-of-mass energy of 7 TeV with the LHCb detector. The polarization amplitudes and the corresponding phases are measured to be $|A_{\parallel }{|}^2=0.227\pm 0.004(\mathrm{stat})\pm 0.011(\mathrm{syst})$, $|A_{\perp }{|}^2=0.201\pm 0.004(\mathrm{stat})\pm 0.008(\mathrm{syst})$, ${\delta }_{\parallel }[\mathrm{rad}]=-2.94\pm 0.02(\mathrm{stat})\pm 0.03(\mathrm{syst})$, and ${\delta }_{\perp }[\mathrm{rad}]=2.94\pm 0.02(\mathrm{stat})\pm 0.02(\mathrm{syst})$. Comparing $B^0\to J/\psi K^{*}(892{)}^0$ and ${\overline{B}}^0\to J/\psi {\overline{K}}^{*}(892{)}^0$ decays, no evidence for direct $CP$ violation is found.

Measurements are presented of the production of primary $K_S^0$ and $\Lambda$ particles in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$ in the region transverse to the leading charged-particle jet in each event. The average multiplicity and average scalar transverse momentum sum of $K_S^0$ and $\Lambda$ particles measured at pseudorapidities $|\eta |<2$ rise with increasing charged-particle jet $p_{\mathrm{T}}$ in the range $1–10\mathrm{GeV}/c$ and saturate in the region $10–50\mathrm{GeV}/c$. The rise and saturation of the strange-particle yields and transverse momentum sums in the underlying event are similar to those observed for inclusive charged particles, which confirms the impact-parameter picture of multiple parton interactions. The results are compared to recent tunes of the pythia Monte Carlo event generator. The pythia simulations underestimate the data by 15%–30% for $K_S^0$ mesons and by about 50% for $\Lambda$ baryons, a deficit similar to that observed for the inclusive strange-particle production in non-single-diffractive proton-proton collisions. The constant strange- to charged-particle activity ratios with respect to the leading jet $p_{\mathrm{T}}$ and similar trends for mesons and baryons indicate that the multiparton-interaction dynamics is decoupled from parton hadronization, which occurs at a later stage.

Energy diffusion due to spontaneous localization (SL) for a relativistically fast moving particle is examined. Spontaneous localization is an alternative to standard quantum theory in which quantum state reduction is treated as a random physical process which is incorporated into the Schrödinger equation in an observer-independent way. These models make predictions in conflict with standard quantum theory one of which is nonconservation of energy. On the basis of proposed relativistic extensions of SL it is argued that for a single localized particle, nonrelativistic SL should remain valid in the rest frame of the particle. The implication is that relativistic calculations can be performed by transforming nonrelativistic results from the particle rest frame to the frame of an inertial observer. This is demonstrated by considering a relativistic stream of noninteracting particles of cosmological origin and showing how their energy distribution evolves as a result of SL as they traverse the Universe. A solution is presented and the potential for astrophysical observations is discussed.

The Layzer-Irvine equation describes energy conservation for a pressure less fluid interacting though quasi-Newtonian gravity in an expanding Universe. We here derive a Layzer-Irvine equation for scalar field theories where the scalar field is coupled to the matter fields, and show applications of this equation by applying it to $N$-body simulations of modified gravity theories. There it can be used as both a dynamical test of the accuracy of the solution and the numerical implementation when solving the equation of motion. We also present an equation that can be used as a new static test for an arbitrary matter distribution. This allows us to test the $N$-body scalar field solver using a matter distribution which resembles what we actually encounter in numerical simulations.

In a stationary electrovacuum, asymptotically flat black holes in scalar-tensor theories of gravity are described by the Kerr-Newman family of solutions, just as in general relativity. We show that there exist two mechanisms which can render Kerr black holes unstable when matter is present in the vicinity of the black hxole, as this induces an effective mass for the scalar. The first mechanism is a tachyonic instability that appears when the effective mass squared is negative, triggering the development of scalar hair—a black-hole version of “spontaneous scalarization.” The second instability is associated with superradiance and is present when the effective mass squared is positive and when the black-hole spin exceeds a certain threshold. The second mechanism is also responsible for a resonant effect in the superradiant scattering of scalar waves, with amplification factors as large as ${10}^5$ or more.

We present a detailed analysis of a recently introduced version of causal dynamical triangulations that does not rely on a distinguished time slicing. Focusing on the case of $2+1$ spacetime dimensions, we analyze its geometric and causal properties, present details of the numerical setup, and explain how to extract “volume profiles.” Extensive Monte Carlo measurements of the system show the emergence of a de Sitter universe on large scales from the underlying quantum ensemble, similar to what was observed previously in standard causal dynamical triangulation quantum gravity. This provides evidence that the distinguished time slicing of the latter is not an essential part of its kinematical setup.

In previous work it was shown that, in accord with the Brandenberger-Vafa mechanism, three is the maximum number of spatial dimensions that can grow large cosmologically from an initial thermal fluctuation. Here we complement that work by considering the possibility of successive fluctuations. Suppose an initial fluctuation causes at least one dimension to grow, and suppose successive fluctuations occur on time scales of order ${\alpha }^{\prime 1/2}$. If the string coupling is sufficiently large, we show that such fluctuations are likely to push a three-dimensional subspace to a large volume where winding modes annihilate. In this setting, three is the preferred number of large dimensions. Although encouraging, a more careful study of the dynamics and statistics of fluctuations is needed to assess the likelihood of our assumptions.

We propose a model for the spontaneous $CP$ violation based on $SU(2{)}_L\times U(1{)}_Y\times A_4\times CP\times Z_2$ symmetry for quarks and leptons in a seesaw framework. We investigate a link between the $CP$ phase in the Cabibbo-Kobayashi-Maskawa (CKM) matrix and $CP$ phase in the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix by using the present data of quark sector. In our model $CP$ is spontaneously broken at high energies, after breaking of flavor symmetry, by a complex vacuum expectation value of $A_4$ triplet and gauge singlet scalar field. And, certain effective dimension-5 operators are considered in the Lagrangian as an equal footing, in which the quarks lead to the CKM matrix of the quark mixing. However, the lepton Lagrangian still keep renormalizability, which gives rise to a nondegenerate Dirac neutrino Yukawa matrix, a unique $CP$-phase, and the nonzero value of ${\theta }_{13}\simeq 9°$ as well as two large mixing angles ${\theta }_{12}$, ${\theta }_{23}$. We show that the generated $CP$ phase “$\xi$” from the spontaneous $CP$ violation could become a natural source of leptogenesis as well as $CP$ violations in the CKM and PMNS. Interestingly enough, we show that, for around $\xi \simeq 110°(140°)$, we obtain the measured CKM $CP$ phase ${\delta }_{CP}^q\simeq 70°$ for normal (inverted) hierarchy. For the measured value of ${\theta }_{13}$ we favor the PMNS $CP$ phase around 30°, 200°, and $|{\theta }_{23}-45°|\to 0$ for normal mass hierarchy and around 60°, 110°, 230°, $|{\theta }_{23}-45°|\to 5°$ for inverted one. As a numerical study in the lepton sector, we show low-energy phenomenologies and leptogenesis for the normal and inverted case, respectively, and a interplay between them.

We study a supersymmetric phenomenon that can give spectacular signals at the LHC: oscillations of neutralinos. Such oscillations can be naturally realized in $R$-symmetric models, where additional fields are introduced as Dirac mass partners of gauginos and Higgsinos. Majorana masses for gauginos, necessarily generated from anomaly mediation, can create tiny mass splittings between degenerate mass eigenstates, causing states produced at the LHC to oscillate between neutralinos and their Dirac partner fields. Scenarios where such states decay with displaced vertices can lead to striking signatures at the LHC, where the oscillation can be visible directly in the distribution of displaced vertex lengths. We elaborate on the theory and LHC phenomenology of this feature within a specific scenario of a Higgsino decaying with a displaced vertex into a gravitino and a $Z$ boson.

We study the charge parity ($CP$) violation of the universal seesaw model, especially its quark sector. The model is based on $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{Y^{\prime }}$. In order to count the number of parameters in the quark sector, we use the degree of freedom of the weak basis transformation. For the $N(3)$-generation model, the number of $CP$ violating phases in the quark sector is identified as $3N^2-3N+1$ (19). We also construct 19 $CP$ violating weak basis invariants of Yukawa coupling matrices and $SU(2)$ singlet quark mass matrices in the three-generation universal seesaw model. The quark interaction terms induced by neutral currents are given as an exact formula. Both the charged current and the neutral current are expressed in terms of the mass basis by finding the transformations from the weak basis to the mass basis. Finally, we calculate the mixing matrix element approximately, assuming that the $SU(2{)}_R$ breaking scale $v_R$ is much larger than the electroweak breaking scale $v_L$.

Assuming the Majorana nature of neutrinos, we recently performed a scan of leptonic mixing patterns derived from finite discrete groups of order less than 1536. Here we show that the 3 groups identified there as giving predictions close to experiment also contain another class of Abelian subgroups that predict an interesting leading-order quark mixing pattern where only the Cabibbo angle is generated at leading order. We further broaden our study by assuming that neutrinos are Dirac particles and find 4 groups of order up to 200 that can predict acceptable quark and leptonic mixing angles. Since large flavor groups allow for a multitude of leading-order mixing patterns, we define a measure that is suitable to compare the predictivity of a given flavor group, taking this fact into account. We give the result of this measure for a wide range of discrete flavor groups and identify the group $(Z_{18}\times Z_6)⋊{\mathcal{S}}_3$ as being most predictive in the sense of this measure. We further discuss alternative measures and their implications.

We construct a simple example for self-induced flavor conversion in dense neutrino gases, showing new solutions that violate the symmetries of initial conditions. Our system consists of two opposite momentum modes 1 and 2, each initially occupied with equal densities of ${\nu }_e$ and ${\overline{\nu }}_e$. Restricting solutions to symmetry under $1\leftrightarrow 2$ allows for the usual bimodal instability (“flavor pendulum”) in the inverted neutrino mass hierarchy and stability (no self-induced flavor conversion) in the normal hierarchy (NH). Lifting this symmetry restriction allows for a second pendulumlike solution that occurs in NH, where the modes 1 and 2 swing in opposite directions in flavor space. Any small deviation from 1–2 symmetry in the initial condition triggers the new instability in NH. This effect corresponds to the recently identified multi-azimuth angle instability of supernova neutrino fluxes. Both cases show explicitly that solutions of the equations of collective flavor oscillations need not inherit the symmetries of initial conditions, although this has been universally assumed.

A regularization procedure developed by D. V. Fursaev and S. N. Solodukhin, [Phys. Rev. D 52, 2133 (1995)] for the integral curvature invariants on manifolds with conical singularities is generalized to the case of squashed cones. In general, the squashed conical singularities do not have rotational $O(2)$ symmetry in a subspace orthogonal to a singular surface $\Sigma$ so that the surface is allowed to have extrinsic curvatures. A new feature of the squashed conical singularities is that the surface terms in the integral invariants, in the limit of a small angle deficit, now depend also on the extrinsic curvatures of $\Sigma$. A case of invariants which are quadratic polynomials of the Riemann curvature is elaborated in different dimensions and applied to several problems related to entanglement entropy. The results are in complete agreement with computations of the logarithmic terms in entanglement entropy of 4D conformal theories [S. N. Solodukhin, Phys. Lett. B 665, 305 (2008)]. Among other applications of the suggested method are logarithmic terms in entanglement entropy of nonconformal theories and a holographic formula for entanglement entropy in theories with gravity duals.

Cluster abundances are oddly insensitive to canonical early dark energy. Early dark energy with sound speed equal to the speed of light cannot be distinguished from a quintessence model with the equivalent expansion history for $z<2$ but negligible early dark energy density, despite the different early growth rate. However, cold early dark energy, with a sound speed much smaller than the speed of light, can give a detectable signature. Combining cluster abundances with cosmic microwave background (CMB) power spectra can determine the early dark energy fraction to 0.3% and distinguish a true sound speed of 0.1 from 1 at 99% confidence. We project constraints on early dark energy from the Euclid cluster survey, as well as the Dark Energy Survey, using both current and projected Planck CMB data, and assess the impact of cluster mass systematics. We also quantify the importance of dark energy perturbations, and the role of sound speed during a crossing of $w=-1$.

We investigate nonsingular bounce realizations in the framework of ghost-free generalized Galileon cosmology, which furthermore can be free of the anisotropy problem. Considering an ekpyroticlike potential we can obtain a total equation of state larger than 1 in the contracting phase, which is necessary for the evolution to be stable against small anisotropic fluctuations. Since such a large equation of state forbids the Galileon field to generate the desired form of perturbations, we additionally introduce the curvaton field which can in general produce the observed nearly scale-invariant spectrum. In particular, we provide approximate analytical and exact semianalytical expressions under which the bouncing scenario is consistent with observations. Finally, the combined Galileon-curvaton system is free of the big rip after the bounce.

We prove an exact relation between the tensor and the scalar primordial power spectra generated during inflation. Such a mapping considerably simplifies the derivation of any power spectra as they can be obtained from the study of the tensor modes only, which are much easier to solve. As an illustration, starting from the second order slow-roll tensor power spectrum, we derive in a few lines the next-to-next-to-leading order power spectrum of the comoving curvature perturbation in generalized single field inflation with a varying speed of sound.

We consider the linear perturbations for the single scalar field inflation model interacting with an additional triad of scalar fields. The background solutions of the three additional scalar fields depend on spatial coordinates with a constant gradient $\alpha$ and the ensuing evolution preserves the homogeneity of the cosmological principle. After we discuss the properties of background evolution including an exact solution for the exponential-type potential, we investigate the linear perturbations of the scalar and tensor modes in the background of the slow-roll inflation. In our model with small $\alpha$, the comoving wave number has a lower bound $\sim \alpha M_{\mathrm{P}}$ to have well-defined initial quantum states. We find that cosmological quantities, for instance, the power spectrums and spectral indices of the comoving curvature and isocurvature perturbations, and the running of the spectral indices have small corrections depending on the lower bound. Similar behaviors happen for the tensor perturbation with the same lower bound.

Following a recent suggestion by Weinberg, we use the large-$N$ expansion in QCD to discuss the decay amplitudes of tetraquarks into ordinary mesons as well as their mixing properties. We find that the flavor structure of the tetraquark is a crucial ingredient to determine both this mixing as well as the decays. Although in some cases tetraquarks should be expected to be as narrow as ordinary mesons, they may get to be even narrower, depending on this flavor structure.

Compactified Yang-Mills theories with one universal extra dimension were found [Phys. Rev. D 82, 116012 (2010)] to exhibit two types of gauge invariance: the standard gauge transformations (SGTs) and the nonstandard gauge transformations (NSGTs). In the present work we show that these transformations are not exclusive to compactified scenarios. Introducing a notion of hidden symmetry, based on the fundamental concept of canonical transformation, we analyze three different gauge systems, each of which is mapped to a certain effective theory that is invariant under the so-called SGTs and NSGTs. The systems under discussion are (i) four-dimensional pure $SU(3)$ Yang-Mills theory, (ii) four-dimensional $SU(3)$ Yang-Mills with spontaneous symmetry breaking, and (iii) pure Yang-Mills theory with one universal compact extra dimension. The canonical transformation that induces the notion of hidden symmetry maps objects with well-defined transformation laws under a gauge group $G$ to well-defined objects under a nontrivial subgroup $H\subset G$. In the case where spontaneous symmetry breaking is present, the set of SGTs corresponds to the group into which the original gauge group is broken, whereas the NSGTs are associated with the broken generators and can be used to define the unitary gauge. For system (iii), the SGTs coincide with the gauge group $SU(N,{\mathcal{M}}^4)$, whereas the NSGTs do not form a group; in this system the “fundamental” theory and the effective one are shown to be classically equivalent.

We reanalyze the LHC bounds on light third-generation squarks in natural supersymmetry, where the sparticles have masses inversely proportional to their leading-log contributions to the electroweak symmetry breaking scale. Higgsinos are the lightest supersymmetric particles; top and bottom squarks are the next-to-lightest sparticles that decay into both neutral and charged Higgsinos with well-defined branching ratios determined by Yukawa couplings and kinematics. The Higgsinos are nearly degenerate in mass, once the bino and wino masses are taken to their natural (heavy) values. We consider three scenarios for the stop and sbottom masses: (I) ${\tilde{t}}_R$ is light; (II) ${\tilde{t}}_L$ and ${\tilde{b}}_L$ are light; and (III) ${\tilde{t}}_R$, ${\tilde{t}}_L$, and ${\tilde{b}}_L$ are light. Dedicated stop searches are currently sensitive to scenarios II and III but not scenario I. Sbottom-motivated searches ($2b+\mathrm{MET}$) impact both squark flavors due to $\tilde{t}\to b{\tilde{\chi }}_1^{+}$ as well as $\tilde{b}\to b{\tilde{\chi }}_{1,2}^0$, constraining scenarios I and III with somewhat weaker constraints on scenario II. The totality of these searches yields relatively strong constraints on natural supersymmetry. Two regions that remain are (1) the “compressed wedge,” where $(m_{\tilde{q}}-|\mu |)/m_{\tilde{q}}\ll 1$ and (2) the “kinematic limit” region, where $m_{\tilde{q}}\gtrsim 600–750\mathrm{GeV}$, at the kinematic limit of the LHC searches. We calculate the correlated predictions for Higgs physics, demonstrating that these regions lead to distinct predictions for the lightest Higgs couplings that are separable with $\simeq 10\%$ measurements. We show that these conclusions remain largely unchanged once the minimal supersymmetric standard model is extended to the nonminimal supersymmetric standard model in order to naturally obtain a large enough mass for the lightest Higgs boson consistent with LHC data.