A precise measurement of the cross section of the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}(\gamma )$ from threshold to an energy of 3 GeV is obtained with the initial-state radiation (ISR) method using $232{\mathrm{fb}}^{-1}$ of data collected with the BABAR detector at $e^{+}{e}^{-}$ center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}(\gamma ){\gamma }_{\mathrm{ISR}}$, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}(\gamma )$ is obtained with a systematic uncertainty of 0.5% in the dominant $\rho$ resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured $\pi \pi$ cross section from threshold to 1.8 GeV is $(514.1\pm 2.2(\mathrm{stat})\pm 3.1(\mathrm{syst}))\times {10}^{-10}$.

A massive body with the Schwarzschild interior metric (perfect fluid of constant density) develops a pressure singularity at the origin when the radius of the body $R$ approaches $9r_s/8$, where $r_s$ is the Schwarzschild radius. We show that a quantum scalar particle scattered in this gravitational field possesses a dense spectrum of narrow resonances. Their density and lifetimes tend to infinity in the limit $R\to 9r_s/8$, and we determine the cross section of the particle capture into these quasibound states. Therefore, a body that is not a black hole demonstrates black-hole-like absorption.

We compute the charged pion loop contribution to the light-by-light scattering amplitude for off-shell photons in chiral perturbation theory through next-to-leading order (NLO). We show that for small photon virtualities ($k^2\ll m_{\pi }^2$) the NLO contributions are relatively more important due to an accidental numerical suppression of the LO terms. This behavior is consistent with previous calculations of the hadronic light-by-light contribution to the muon anomalous magnetic moment, $a_{\mu }^{\mathrm{HLBL}}$, whose leading order value receives $\mathcal{O}(1)$ corrections from models incorporating some of the NLO physics. We also show that models employed thus far for the charged pion loop contribution to $a_{\mu }^{\mathrm{HLBL}}$ are not fully consistent with low-momentum behavior implied by quantum chromodynamics, having omitted potentially significant contributions from the pion polarizability.

Second-class weak currents can in the standard model be induced by chiral-symmetry breaking. In the specific case of the decay $\tau \to \omega \pi {\nu }_{\tau }$, dominated by the first-class vector current with the $\rho$ quantum numbers, such effects would manifest themselves by small axial vector (or, generally, nonvector) contributions to the decay rate. We present an attempt to estimate such effects, based on a vector and axial-vector dominance model of the relevant matrix elements supplemented by $\omega \mathrm{\text{−}}\rho$ mixing. We also give an indication on the amplitude directly mediated by $b_1(1235)\to \omega \pi$, in principle also allowed in the standard model by isotopic spin violation.

We propose a theoretical framework for analyzing two-body nonleptonic $D$ meson decays, based on the factorization of short-distance (long-distance) dynamics into Wilson coefficients (hadronic matrix elements of four-fermion operators). The parametrization of hadronic matrix elements in terms of several nonperturbative quantities is demonstrated for the $D\to PP$ decays, $P$ denoting a pseudoscalar meson. We consider the evolution of Wilson coefficients with energy release in individual decay modes, and the Glauber strong phase associated with the pion in nonfactorizable annihilation amplitudes, that is attributed to the unique role of the pion as a Nambu-Goldstone boson and a quark-antiquark bound state simultaneously. The above inputs improve the global fit to the branching ratios involving the ${\eta }^{\prime }$ meson and resolve the long-standing puzzle from the $D^0\to {\pi }^{+}{\pi }^{-}$ and $D^0\to K^{+}{K}^{-}$ branching ratios, respectively. Combining short-distance dynamics associated with penguin operators and the hadronic parameters determined from the global fit to branching ratios, we predict direct $CP$ asymmetries, to which the quark loops and the scalar penguin annihilation give dominant contributions. In particular, we predict $\Delta A_{CP}\equiv A_{CP}(K^{+}{K}^{-})-A_{CP}({\pi }^{+}{\pi }^{-})=-1.00\times {10}^{-3}$, lower than the LHCb and CDF data.

We present a systematic study of the different mechanisms leading to $WW$ pair production at the Large Hadron Collider (LHC), both in the same-sign and opposite-sign channels, and we emphasize that the former offers much better potential for investigating non-resonant $W_L{W}_L$ scattering. We propose a new kinematic variable to isolate the $W_L{W}_L$ scattering component in same-sign $WW$ production at the LHC. Focusing on purely leptonic $W$ decay channels, we show that it considerably improves the LHC capabilities to shed light on the electroweak symmetry breaking mechanism after collecting $100{\mathrm{fb}}^{-1}$ of data at $\sqrt{s}=14\mathrm{TeV}$. The new variable is less effective in the opposite-sign $WW$ channel due to different background composition.

We present the possible signatures appearing in general realizations of the minimal supersymmetric standard model based on 14 unrelated mass parameters at the supersymmetry scale. The parameters of the general minimal supersymmetric standard model are reduced by assuming a degeneracy of the sfermions of the first two generations with the same quantum numbers. We also assume no mass splitting between neutral and charged Higgsinos. We do allow for separate soft breaking terms for the third-generation sfermons. We consider all possible resulting $14!\approx 9\times {10}^{10}$ relevant mass orderings and check for the dominant decay cascades and the corresponding collider signatures. In determining the dominant decay modes we assume that mixing between sparticles is subdominant. As preferred signatures, we consider charged leptons, missing transverse momentum, jets, and $W$, $Z$ or Higgs bosons. We include also the cases of bi- and trilinear $R$-parity violation and show that specific signatures can be used to distinguish the different scenarios.

The current results of LHC experiments exclude a large area of the light new particle region, namely, natural parameter space, in supersymmetric extension models. One of the possibilities for achieving the correct electroweak symmetry breaking naturally is the low-scale messenger scenario. Actually, the next-to-minimal supersymmetric standard model with TeV scale mirage mediation realizes the natural electroweak symmetry breaking with various mass spectra. In this paper, we show the possible mass spectrum in the scenario, e.g., the degenerate and/or hierarchical mass spectrum, and discuss these features.

The $t\mathrm{\text{−}}b\mathrm{\text{−}}\tau$ unification with positive Higgs mass parameter $\mu$ in the minimal supersymmetric standard model prefers “just so” Higgs splitting and a light gluino $\lesssim 500\mathrm{GeV}$ which appears to be ruled out by the recent LHC searches. We reanalyze constraints on soft supersymmetry breaking parameters in this scenario, allowing independent splittings among squarks and Higgs doublets at the grand unification scale, and show that it is possible to obtain $t\mathrm{\text{−}}b\mathrm{\text{−}}\tau$ unification and satisfy experimental constraints on gluino mass without raising supersymmetry breaking scale to very high value $\sim 20\mathrm{TeV}$. We discuss the origin of independent squark and Higgs splittings in realistic $SO(10)$ models. Just so Higgs splitting can be induced without significantly affecting the $t\mathrm{\text{−}}b\mathrm{\text{−}}\tau$ unification in $SO(10)$ models containing Higgs fields transforming as $10+\overline{126}+126+210$. This splitting arises in the presence of nonuniversal boundary conditions from mixing between 10 and other Higgs fields. Similarly, if additional matter fields are introduced then their mixing with the matter multiplet 16 is shown to generate the squark splitting required to raise the gluino mass within the $t\mathrm{\text{−}}b\mathrm{\text{−}}\tau$ unified models with positive $\mu$.

We show that grand unified theories based on $SO(10)$ generate naturally the next-to-leading baryon number violating operators of dimension seven. These operators, which violate $(B-L)$, lead to unconventional decays of the nucleon such as $n\to e^{-}{K}^{+}$, $e^{-}{\pi }^{+}$ and $p\to \nu {\pi }^{+}$. In two-step breaking schemes of nonsupersymmetric $SO(10)$, nucleon lifetime for decays into these modes is found to be within reach of experiments. We also identify supersymmetric scenarios where these decays may be accessible, consistent with gauge coupling unification. Further, we show that the $(B-L)$ asymmetry generated in the decays of GUT scale scalar bosons and/or gauge bosons can explain consistently the observed baryon asymmetry of the universe. The induced $(B-L)$ asymmetry is sphaleron-proof, and survives down to the weak scale without being erased by the electroweak interactions. This mechanism works efficiently in a large class of nonsupersymmetric and supersymmetric $SO(10)$ models, with either a ${126}_H$ or a ${16}_H$ Higgs field employed for rank reduction. In minimal models the induced baryon asymmetry is tightly connected to the masses of quarks, leptons and neutrinos and is found to be compatible with observations.

We present the results of $1+1+1$ flavor $\mathrm{QCD}+\mathrm{QED}$ simulation at the physical point, in which the dynamical quark effects in QED and the up-down quark mass difference are incorporated by the reweighting technique. The physical quark masses together with the lattice spacing are determined with $m_{{\pi }^{+}}$, $m_{K^{+}}$, $m_{K^0}$ and $m_{{\Omega }^{-}}$ as physical inputs. Calculations are carried out using a set of $2+1$ flavor QCD configurations near the physical point generated by the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action at $\beta =1.9$ on a ${32}^3\times 64$ lattice. We evaluate the values of the up, down and strange quark masses individually with nonperturbative QCD renormalization.

In view of the recent neutrino oscillation data pointing to a nonvanishing value for the smallest mixing angle (${\theta }_z$), we derive and find explicit realizations of the $(Z_2{)}^3$ flavor symmetry which characterizes, for the neutrino mass matrix, uniquely a variant of the tripartite form, originally conceived to lead to the tribimaximal mixing with ${\theta }_z=0$, so as to allow now for a nontribimaximal pattern with nonzero ${\theta }_z$. We impose this flavor symmetry in a setting including the charged leptons and we see that it can make room, through higher-order terms involving new standard model singlet scalars, for the mass hierarchy of charged leptons. Moreover, within a type-I seesaw mechanism augmented with the flavor symmetry, certain patterns occurring in both the Dirac and the Majorana neutrino mass matrices can accommodate all types of mass hierarchies in the effective neutrino mass matrix, but no lepton/baryon asymmetry can be generated. Finally, we discuss how type-II seesaw mechanism, when supplemented with the flavor symmetry, could be used to interpret the observed baryon asymmetry through leptogenesis.

We explore the combined physics potential of T2K and $\mathrm{NO}\nu \mathrm{A}$ in light of the moderately large measured value of ${\theta }_{13}$. For ${sin}^{2}2{\theta }_{13}=0.1$, which is close to the best fit value, a 90% C.L. evidence for the hierarchy can be obtained only for the combinations (Normal hierarchy, $-170°\le {\delta }_{CP}\le 0°$) and (Inverted hierarchy, $0°\le {\delta }_{CP}\le 170°$), with the currently planned runs of $\mathrm{NO}\nu \mathrm{A}$ and T2K. However, the hierarchy can essentially be determined for any value of ${\delta }_{CP}$, if the statistics of $\mathrm{NO}\nu \mathrm{A}$ are increased by 50% and those of T2K are doubled. Such an increase will also give an allowed region of ${\delta }_{CP}$ around its true value, except for the $CP$ conserving cases ${\delta }_{CP}=0$ or $\pm 180°$. We demonstrate that any measurement of ${\delta }_{CP}$ is not possible without first determining the hierarchy. We find that comparable data from a shorter baseline ($L\sim 130\mathrm{km}$) experiment will not lead to any significant improvement.

We construct a radiative inverse seesaw model with local $B-L$ symmetry, and investigate the flavor structure of the lepton sector and the fermionic dark matter. Neutrino masses are radiatively generated through a kind of inverse seesaw framework. The Pontecorvo-Maki-Nakagawa-Sakata matrix is derived from each mixing matrix of the neutrino and charged lepton sector with a large Dirac $CP$ phase. We show that the annihilation processes via the interactions with Higgses, which are independent on the lepton flavor violation, have to be dominant in order to satisfy the observed relic abundance by WMAP. The new interactions with Higgses allow us to be consistent with the direct detection result reported by XENON100, and it is possible to verify the model by the exposure of XENON100 (2012).

One may ask whether the conformal field theory (CFT) restricted to a subset $b$ of the anti-de Sitter (AdS) boundary has a well-defined dual restricted to a subset $H(b)$ of the bulk geometry. The Poincaré patch is an example, but more general choices of $b$ can be considered. We propose a geometric construction of $H$. We argue that $H$ should contain the set $C$ of causal curves with both endpoints on $b$. Yet $H$ should not reach so far from the boundary that the CFT has insufficient degrees of freedom to describe it. This can be guaranteed by constructing a superset $L$ of $H$ from light-sheets off boundary slices and invoking the covariant entropy bound in the bulk. The simplest covariant choice is $L=L^{+}\cap L^{-}$, where $L^{+}$ ($L^{-}$) is the union of all future-directed (past-directed) light-sheets. We prove that $C=L$, so the holographic domain is completely determined by our assumptions: $H=C=L$. In situations where local bulk operators can be constructed on $b$, $H$ is closely related to the set of bulk points where this construction remains unambiguous under modifications of the CFT Hamiltonian outside of $b$. Our construction leads to a covariant geometric renormalization-group flow. We comment on the description of black hole interiors and cosmological regions via AdS/CFT.

We propose a simple framework to split neutrinos with a slight departure from tribimaximal—where two of the neutrinos are Majorana type which provide thermal leptogenesis. We propose a model based on $S_3$ flavor symmetry. The Dirac neutrino with a tiny Yukawa coupling explains primordial inflation and the cosmic microwave background radiation, where the inflaton is the gauge invariant flat direction. The observed baryon asymmetry, and the scale of inflation are intimately tied to the observed reactor angle $\sin {\theta }_{13}$, which can be further constrained by the LHC and the $0\nu \beta \beta$ experiments. The model also provides the lightest right-handed sneutrino as a part of the inflaton to be the dark matter candidate.

In a new simple application of the non-Abelian discrete symmetry $A_4$ to charged-lepton and neutrino mass matrices, we show that for the current experimental central value of ${sin}^{2}2{\theta }_{13}\simeq 0.1$, leptonic $CP$ violation is necessarily large, i.e., $|\tan {\delta }_{CP}|>1.3$. This result is of broad interest because $CP$ violation in the leptonic sector is closely connected to the origin of the observed matter-antimatter asymmetry of the Universe through leptogenesis.

We calculate the Coulomb ghost propagator $G(|\mathbf{p}|)$ and the static Coulomb potential $V_C(|\mathbf{r}|)$ for $SU(2)$ Yang-Mills theory on the lattice. In view of possible scaling violations related to deviations from the Hamiltonian limit we use anisotropic lattices to improve the temporal resolution. We find that the ghost propagator is infrared enhanced with an exponent ${\kappa }_{\mathrm{gh}}\gtrsim 0.5$ while the Coulomb potential exhibits a string tension larger than the Wilson string tension, ${\sigma }_C\simeq 2\sigma$. This agrees with the Coulomb “scaling” scenario derived from the Gribov-Zwanziger confinement mechanism.

We explicitly confirm the expectation that generic Lovelock gravity in $D$ dimensions has a unitary massless spin-2 excitation around any one of its constant curvature vacua just like the cosmological Einstein gravity. The propagator of the theory reduces to that of Einstein’s gravity, but scattering amplitudes must be computed with an effective Newton’s constant which we provide. Tree-level unitarity imposes a single constraint on the parameters of the theory yielding a wide range of unitary region. As an example, we explicitly work out the details of the cubic Lovelock theory.