The presence of the light $CP$-odd scalar boson arising in the next-to-minimal supersymmetric model and the simplest little Higgs model dramatically changes the phenomenology of the Higgs sector. We suggest a practical strategy to discriminate the $CP$-odd scalar bosons between the two underlying models, produced in decays of the standard-model-like Higgs boson. We define the decay rate of “the non $b$-tagged jet pair,” with which we compute the ratio of decay rates into leptons and jets. The ratio shows quite different behavior in the next-to-minimal supersymmetric model and the simplest little Higgs model.

We extend the dipole formalism for massless and massive partons to random polarizations of the external partons. The dipole formalism was originally formulated for spin-summed matrix elements and later extended to individual helicity eigenstates. For efficiency reasons one wants to replace the spin sum by a smooth integration over additional variables. This requires the extension of the dipole formalism to random polarizations. In this paper we derive the modified subtraction terms. We only modify the real subtraction terms, the integrated subtraction terms do not require any modifications.

We first build a minimal model of vectorlike quarks where the dominant Higgs boson production process at LHC—the gluon fusion—can be significantly suppressed, being motivated by the recent stringent constraints from the search for direct Higgs production over a wide Higgs mass range. Within this model, compatible with the present experimental constraints on direct Higgs searches, we demonstrate that the Higgs ($h$) production via a heavy vectorlike top-partner ($t_2$) decay, $pp\to t_2{\overline{t}}_2$, $t_2\to th$, allows to discover a Higgs boson at the LHC and measure its mass, through the decay channels $h\to \gamma \gamma$ or $h\to ZZ$. We also comment on the recent hint in LHC data from a possible $\sim 125\mathrm{GeV}$ Higgs scalar, in the presence of heavy vectorlike top quarks.

General consequences of mass mixing between the ordinary $Z$ boson and a relatively light $Z_d$ boson, the “dark” $Z$, arising from a $U(1{)}_d$ gauge symmetry, associated with a hidden sector such as dark matter, are examined. New effects beyond kinetic mixing are emphasized. $Z\mathrm{\text{−}}{Z}_d$ mixing introduces a new source of low energy parity violation well explored by possible future atomic parity violation and planned polarized electron scattering experiments. Rare $K(B)$ meson decays into $\pi (K){\ell }^{+}{\ell }^{-}$ ($\ell =e$, $\mu$) and $\pi (K)\nu \overline{\nu }$ are found to already place tight constraints on the size of $Z\mathrm{\text{−}}{Z}_d$ mixing. Those sensitivities can be further improved with future dedicated searches at $K$ and $B$ factories as well as binned studies of existing data. $Z\mathrm{\text{−}}{Z}_d$ mixing can also lead to the Higgs decay $H\to Z{Z}_d$, followed by $Z\to {\ell }_1^{+}{\ell }_1^{-}$ and $Z_d\to {\ell }_2^{+}{\ell }_2^{-}$ or “missing energy,” providing a potential hidden sector discovery channel at the Large Hadron Collider. An illustrative realization of these effects in a 2 Higgs doublet model is presented.

The spectrum of baryons containing three $b$ quarks is calculated in nonperturbative QCD, using the lattice regularization. The energies of ten excited $bbb$ states with $J^P=\frac{1}{2}{}^{+}$, $\frac{3}{2}{}^{+}$, $\frac{5}{2}{}^{+}$, $\frac{7}{2}{}^{+}$, $\frac{1}{2}{}^{-}$, and $\frac{3}{2}{}^{-}$ are determined with high precision. A domain-wall action is used for the up, down, and strange quarks, and the bottom quarks are implemented with nonrelativistic QCD. The computations are done at lattice spacings of $a\approx 0.11\mathrm{fm}$ and $a\approx 0.08\mathrm{fm}$, and the results demonstrate the improvement of rotational symmetry as $a$ is reduced. A large lattice volume of $(2.7\mathrm{fm}{)}^3$ is used, and extrapolations of the $bbb$ spectrum to realistic values of the light sea-quark masses are performed. All spin-dependent energy splittings are resolved with total uncertainties of order 1 MeV, and the dependence of these splittings on the couplings in the nonrelativistic QCD action is analyzed.

On a cubic lattice the zero-momentum meson states have one of 20 possible ${\Lambda }^{PC}$ combinations where $\Lambda$ labels the irreducible representation of the octahedral group. Each continuum bottomonium state with specific $J^{PC}$ quantum numbers is contained within one or more of the lattice ${\Lambda }^{PC}$ states. In this work, bottomonium quark-antiquark operators are constructed for all 20 lattice ${\Lambda }^{PC}$ combinations which allows many continuum high angular momentum states to be accessible as ground states of their associated lattice channels. From a dynamical simulation, realistic results are obtained for $S$-, $P$-, $D$-, $F$- and $G$-wave bottomonium states.

We study the fragmentation of (light) quarks and gluons to hadrons inside a jet of cone size $R$. This allows for a more exclusive analysis of fragmentation than is currently the case. The shape of semi-inclusive cross sections in the hadron energy fraction $z$ is described by fragmenting jet functions, which we calculate in terms of $R$ and the jet energy $E$. We introduce a new joint resummation to sum the double logarithms of $R$ and $1-z$ in the fragmenting jet functions, which has a similar application to initial-state radiation at hadron colliders. Our results at next-to-leading logarithmic order indicate that the resummation of the threshold logarithms of $1-z$ is already important for $z\gtrsim 0.5$ and improves the convergence of perturbation theory. Our framework may be used to analyze LHC and RHIC data and to test and tune Monte Carlo event generators.

We have examined nonstandard $\gamma \nu \overline{\nu }$ and $\gamma \gamma \nu \overline{\nu }$ couplings via $\nu \overline{\nu }$ production in $e\gamma$ and $\gamma \gamma$ collisions at the Compact Linear Collider (CLIC). We obtain 95% confidence level bounds on $\gamma \nu \overline{\nu }$ and $\gamma \gamma \nu \overline{\nu }$ couplings by considering the backscattered photon distribution function for incoming photons and initial state radiation and beamstrahlung effect for initial state electrons in the $e\gamma$ and $\gamma \gamma$ collider modes of the linear collider. We indicate that the reaction $\gamma \gamma \to \nu \overline{\nu }$ provides more than 15 orders of magnitude improvement in neutrino-two photon couplings compared to LEP limits.

The ratio of branching fractions of the radiative $B$ decays $B^0\to K^{*0}\gamma$ and $B^{0}s\to \varphi \gamma$ has been measured using $0.37{\mathrm{fb}}^{-1}$ of $pp$ collisions at a center of mass energy of $\sqrt{s}=7\mathrm{TeV}$, collected by the LHCb experiment. The value obtained is $\frac{\mathcal{B}(B^0\to K^{*0}\gamma )}{\mathcal{B}(B^{0}s\to \varphi \gamma )}=1.12\pm {0.08}_{-0.04-0.08}^{+0.06+0.09}$, where the first uncertainty is statistical, the second systematic, and the third is associated with the ratio of fragmentation fractions $f_s/f_d$. Using the world average for $\mathcal{B}(B^0\to K^{*0}\gamma )=(4.33\pm 0.15)\times {10}^{-5}$, the branching fraction $\mathcal{B}(B^{0}s\to \varphi \gamma )$ is measured to be $(3.9\pm 0.5)\times {10}^{-5}$, which is the most precise measurement to date.

A generic search is presented for a heavy particle decaying to $WZ\to \ell \nu {\ell }^{\prime }{\ell }^{\prime }$ ($\ell$, ${\ell }^{\prime }=e$, $\mu$) final states. The data were recorded by the ATLAS detector in $\sqrt{s}=7\mathrm{TeV}$ $pp$ collisions at the Large Hadron Collider and correspond to an integrated luminosity of $1.02{\mathrm{fb}}^{-1}$. The transverse mass distribution of the selected $WZ$ candidates is found to be consistent with the standard model expectation. Upper limits on the production cross section times branching ratio are derived using two benchmark models predicting a heavy particle decaying to a $WZ$ pair.

A value for the mass of the $\eta$ meson has been determined at the COSY-ANKE facility through the measurement of a set of deuteron laboratory beam momenta and associated ${}^3\mathrm{He}$ center-of-mass momenta in the $dp\to {}^3\mathrm{He}X$ reaction. The $\eta$ was then identified by the missing-mass peak and the production threshold determined. The individual beam momenta were fixed with a relative precision of $3\times {10}^{-5}$ for values around $3\mathrm{GeV}/c$ by using a polarized deuteron beam and inducing an artificial depolarizing spin resonance, which occurs at a well-defined frequency. The final-state momenta in the two-body $dp\to {}^3\mathrm{He}\eta$ reaction were investigated in detail by studying the size of the ${}^3\mathrm{He}$ momentum ellipse with the forward detection system of the ANKE spectrometer. Final alignment of the spectrometer for this high precision experiment was achieved through a comprehensive study of the ${}^3\mathrm{He}$ final-state momenta as a function of the center-of-mass angles, taking advantage of the full geometrical acceptance. The value obtained for the mass, $m_{\eta }=(547.873\pm {0.005}_{\mathrm{stat}}\pm {0.027}_{\mathrm{syst}})\mathrm{MeV}/c^2$, is consistent and competitive with other recent measurements, in which the meson was detected through its decay products.

We investigate an index theorem for a Bogoliubov-de Gennes Hamiltonian describing a topological superconductor with Yang-Mills-Higgs couplings in arbitrary dimensions. We find that the index of the Bogoliubov-de Gennes Hamiltonian is determined solely by the asymptotic behavior of the Higgs fields and is independent of the gauge fields. It can be nonvanishing if the dimensionality of the order parameter space is equal to the spatial dimensions. In the presence of point defects, localized zero energy states appear at the defects. The consistency of the index with the existence of zero energy bound states is examined explicitly in a vortex background in two dimensions and in a monopole background in three dimensions.

Sources of long wavelength radiation are naturally described by an effective field theory (EFT) which takes the form of a multipole expansion. Its action is given by a derivative expansion where higher order terms are suppressed by powers of the ratio of the size of the source over the wavelength. In order to determine the Wilson coefficients of the EFT, i.e. the multipole moments, one needs the mapping between a linear source term action and the multipole expansion form of the action of the EFT. In this paper we perform the multipole expansion to all orders by Taylor expanding the field in the source term and then decomposing the action into symmetric trace-free tensors which form irreducible representations of the rotation group. We work at the level of the action, and we obtain the action to all orders in the multipole expansion and the exact expressions for the multipole moments for a scalar field, electromagnetism, and linearized gravity. Our results for the latter two cases are manifestly gauge invariant. We also give expressions for the energy flux and the (gauge dependent) radiation field to all orders in the multipole expansion. The results for linearized gravity are a component of the EFT framework NRGR and will greatly simplify future calculations of gravitational wave observables in the radiation sector of NRGR.

Recently, inspired by Eddington’s theory, an alternative gravity called Eddington-inspired Born-Infeld gravity was proposed by Bañados and Ferreira. It is equivalent to Einstein’s general relativity in vacuum, but deviates from it when matter is included. Interestingly, it seems that the cosmological singularities are prevented in this theory. Based on the new theory, we investigate a thick brane model with a scalar field presenting in the five-dimensional background. A domain wall solution is obtained, and further, we find that at low energy the four-dimensional Einstein gravity is recovered on the brane. Moreover, the stability of gravitational perturbations is ensured in this model.

We achieve a group theoretical quantization of the flat Friedmann-Robertson-Walker model coupled to a massless scalar field adopting the improved dynamics of loop quantum cosmology. Deparemetrizing the system using the scalar field as internal time, we first identify a complete set of phase space observables whose Poisson algebra is isomorphic to the $\mathfrak{s}\mathfrak{u}(1,1)$ Lie algebra. It is generated by the volume observable and the Hamiltonian. These observables describe faithfully the regularized phase space underlying the loop quantization: they account for the polymerization of the variable conjugate to the volume and for the existence of a kinematical nonvanishing minimum volume. Since the Hamiltonian is an element in the $\mathfrak{s}\mathfrak{u}(1,1)$ Lie algebra, the dynamics is now implemented as SU(1, 1) transformations. At the quantum level, the system is quantized as a timelike irreducible representation of the group SU(1, 1). These representations are labeled by a half-integer spin, which gives the minimal volume. They provide superselection sectors without quantization anomalies and no factor ordering ambiguity arises when representing the Hamiltonian. We then explicitly construct SU(1, 1) coherent states to study the quantum evolution. They not only provide semiclassical states but truly dynamical coherent states. Their use further clarifies the nature of the bounce that resolves the big bang singularity.

We derive a linearized kinetic equation for fermionic excitations with an ultrasoft momentum, $g^{2}T$, from the Kadanoff-Baym equation in a Yukawa model and quantum electrodynamics (QED) at extremely high $T$, where $g$ is the coupling constant. We show that this equation is equivalent to the self-consistent equation in the resummed perturbation theory used in the analysis of the fermion spectrum with the ultrasoft momentum at the leading order. Furthermore, we derive the equation that determines the $n$-point function with external lines for a pair of fermions and ($n-2$) bosons with ultrasoft momenta in QED.

The recent results on Higgs boson searches from LHC experiments provide significant guidance in exploring the minimal supersymmetric (SUSY) standard model (MSSM) Higgs sector. If we accept the existence of a SM-like Higgs boson in the mass window of 123 GeV–127 GeV as indicated by the observed $\gamma \gamma$ events, there are two distinct mass regions (in $m_A$) left in the MSSM Higgs sector: (a) the lighter $CP$-even Higgs boson being SM-like and the non-SM-like Higgs bosons all heavy and nearly degenerate above 300 GeV (an extended decoupling region); (b) the heavier $CP$-even Higgs boson being SM-like and the neutral non-SM-like Higgs bosons all nearly degenerate around 100 GeV (a small non-decoupling region). On the other hand, due to the strong correlation between the Higgs decays to $W^{+}{W}^{-}$ and to $\gamma \gamma$ predicted in the MSSM, the apparent absence of a $W^{+}{W}^{-}$ final state signal is in direct conflict with the $\gamma \gamma$ peak. If we consider the $W^{+}{W}^{-}$ channel on its own, the absence of the $W^{+}{W}^{-}$ signal would imply that the SM-like Higgs boson has reduced coupling to $W^{\pm }$, and that the other non-SM-like Higgs bosons should not be too heavy and do not decouple. If both the $\gamma \gamma$ excess and the absence of a $W^{+}{W}^{-}$ signal continue, new physics beyond the MSSM will be required. A similar correlation exists between the $W^{+}{W}^{-}$ and ${\tau }^{+}{\tau }^{-}$ channels: a reduced $W^{+}{W}^{-}$ channel would force the ${\tau }^{+}{\tau }^{-}$ channel to be larger. Future searches for the SM-like Higgs boson at the LHC will provide critical tests for the MSSM prediction. We also study the signals predicted for the non-SM-like Higgs bosons and emphasize the potential importance of the electroweak processes $pp\to H^{+}{H}^{-}$, $H^{\pm }{A}^0$, which are independent of the SUSY parameters except for their masses. In addition, there may be sizable contributions from $pp\to H^{\pm }{h}^0$, $A^0{h}^0$ and $W^{\pm }{H}^0$, $Z{H}^0$ in the low-mass non-decoupling region, which may serve to discriminate the model parameters. We allow variations of the relevant SUSY parameters in a broad range and demonstrate the correlations and constraints on these parameters and associated SUSY particles.

Interference effects are widely neglected in searches for new physics. This is the case in recent publications on searches for $W^{\prime }$ bosons using leptonic final states. We examine the effects of interference on distributions frequently used to determine mass limits for possible $W^{\prime }$ bosons and show that there are important qualitative effects on the behavior of the new physics signal. There are two main consequences. First, exclusion limits where interferences effects have not been considered are likely to have been overestimated. Second, presenting experimental results as a function of a transverse mass cut rather than in terms of the contribution of new physics to the total cross section would be more informative.

The renormalization scale uncertainty can be eliminated by the principle of maximum conformality (PMC) in a systematic, scheme-independent way. Applying the PMC for the $t\overline{t}$-pair hadroproduction at the next-to-next-to-leading-order level, we have found that the total cross sections ${\sigma }_{t\overline{t}}$ at both the Tevatron and LHC remain almost unchanged when taking very disparate initial scales ${\mu }_R^{\mathrm{init}}$ equal to $m_t$, $10m_t$, $20m_t$ and $\sqrt{s}$, which is consistent with renormalization group invariance. As an important new application, we apply PMC scale setting to study the top quark forward-backward asymmetry. We observe that the more convergent perturbative series after PMC scale-setting leads to a more accurate top quark forward-backward asymmetry. The resulting PMC prediction on the asymmetry is also free from the initial renormalization scale dependence. Because the next-to-leading-order PMC scale has a dip behavior for the $(q\overline{q})$ channel at small subprocess collision energies, the importance of this channel to the asymmetry is increased. We observe that the asymmetries $A_{\mathrm{FB}}^{t\overline{t}}$ and $A_{\mathrm{FB}}^{p\overline{p}}$ at the Tevatron will be increased by 42% in comparison to the previous estimates obtained by using conventional scale setting; i.e., we obtain $A_{\mathrm{FB}}^{t\overline{t},\mathrm{PMC}}\simeq 12.5\%$ and $A_{\mathrm{FB}}^{p\overline{p},\mathrm{PMC}}\simeq 8.28\%$. Moreover, we obtain $A_{\mathrm{FB}}^{t\overline{t},\mathrm{PMC}}(M_{t\overline{t}}>450\mathrm{GeV})\simeq 35.0\%$. These predictions have a $1\sigma$ deviation from the present CDF and D0 measurements; the large discrepancies of the top quark forward-backward asymmetry between the standard model estimate and the CDF and D0 data are thus greatly reduced.

In a series of papers, we have established the existence of two gauge-invariant decompositions of the nucleon spin, which are physically nonequivalent. The orbital angular momenta of quarks and gluons appearing in these two decompositions are gauge-invariant dynamical orbital angular momenta and “generalized” canonical orbital angular momenta with gauge-invariance, respectively. The key quantity, which characterizes the difference between these two types of orbital angular momenta is what-we-call the potential angular momentum. We argue that the physical meaning of the potential angular momentum in the nucleon can be made more transparent, by investigating a related but much simpler example from electrodynamics. We also make clear several remaining issues in the spin and momentum decomposition problem of the nucleon. We clarify the relationship between the evolution equations of orbital angular momenta corresponding to the two different decompositions above. We also try to answer the question whether the two different decompositions of the nucleon momentum really lead to different evolution equations, thereby predicting conflicting asymptotic values for the quark and gluon momentum fractions in the nucleon.