In this paper we study the identification of the boosted hadronically decaying top quarks using jet substructure in the center-of-mass frame of the jet. We demonstrate that the method can greatly reduce the QCD jet background while maintaining high identification efficiency of the boosted top quark even in a very high pileup condition. Applications to searches for heavy resonances that decay to a $t\overline{t}$ final state are also discussed.

In view of ongoing measurements of the Higgs-like boson at the LHC and direct searches for dark matter, we explore the possibility of accommodating the potential results in a simple new-physics model with discrete gauge symmetry as well as light neutrino masses. Specifically, we study collider and relic-density constraints on the new gauge coupling, predict the cross section of the dark matter scattering off nucleons, and compare it with current direct search data. We also discuss some of the implications if the dark matter is light. The new gauge sector of the model allows it to be compatible with the latest LHC information on the Higgs-like particle and simultaneously satisfy the requirements in its dark matter sector.

We study the sensitivity of anomalous $ZZ\gamma$ and $Z\gamma \gamma$ vertex couplings $h_3^{\gamma ,Z}$ and $h_4^{\gamma ,Z}$, which would be a powerful sign of new physics, via the subprocess $\gamma q\to Zq$ of the main reaction $pp\to p\gamma p\to ZqX$ at the LHC. We calculated limits on these couplings at 95% confidence level for various values of integrated luminosity. It is shown that the $pp\to p\gamma p\to ZqX$ reaction provides 1 order of magnitude improvement in the couplings $h_4^{\gamma ,Z}$ compared to the current experimental limits obtained in events dominated by $Z\gamma$ production from the LHC and Tevatron.

This Letter describes the search for an enhanced production rate of events with a charged lepton and a neutrino in high-energy $pp$ collisions at the LHC. The analysis uses data collected with the CMS detector, with an integrated luminosity of $5.0{\mathrm{fb}}^{-1}$ at $\sqrt{s}=7\mathrm{TeV}$, and a further $3.7{\mathrm{fb}}^{-1}$ at $\sqrt{s}=8\mathrm{TeV}$. No evidence is found for an excess. The results are interpreted in terms of limits on a heavy charged gauge boson ($W^{\prime }$) in the sequential standard model, a split universal extra dimension model, and contact interactions in the helicity-nonconserving model. For the last, values of the binding energy below 10.5 (8.8) TeV in the electron (muon) channel are excluded at a 95% confidence level. Interpreting the $\ell \nu$ final state in terms of a heavy $W^{\prime }$ with standard model couplings, masses below 2.90 TeV are excluded.

An amplitude analysis of the final state structure in the ${\overline{B}}_s^0\to J/\psi K^{+}{K}^{-}$ decay mode is performed using $1.0{\mathrm{fb}}^{-1}$ of data collected by the LHCb experiment in 7 TeV center-of-mass energy $pp$ collisions produced by the LHC. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. Resonant structures are observed in the $K^{+}{K}^{-}$ mass spectrum as well as a significant nonresonant $S$-wave contribution over the entire $K^{+}{K}^{-}$ mass range. The largest resonant component is the $\varphi (1020)$, accompanied by $f_0(980)$, $f_2^{\prime }(1525)$, and four additional resonances. The overall branching fraction is measured to be $\mathcal{B}({\overline{B}}_s^0\to J/\psi K^{+}{K}^{-})=(7.70\pm 0.08\pm 0.39\pm 0.60)\times {10}^{-4}$, where the first uncertainty is statistical, the second systematic, and the third due to the ratio of the number of ${\overline{B}}_s^0$ to $B^{-}$ mesons produced. The mass and width of the $f_2^{\prime }(1525)$ are measured to be $1522.2\pm {2.8}_{-2.0}^{+5.3}\mathrm{MeV}$ and $84\pm 6_{-5}^{+10}\mathrm{MeV}$, respectively. The final state fractions of the other resonant states are also reported.

In the framework of the Gotsman-Levin-Maor model for soft interaction with ${\alpha }_{\mathrm{IP}}^{\prime }(0)=0$, we propose a procedure based on Gribov’s partonic interpretation of the Pomeron, which enables one to calculate the diffractive mass distributions in hadron-hadron scattering. Using the analogy with deep-inelastic scattering, we associate the Pomeron-quark interaction with the Good-Walker sector of the hadron-hadron scattering, and the Pomeron-gluon sector with the $t$-channel Pomeron interactions. We present predicted mass distributions for the LHC energies.

An approach to developing a feasible neutrinoless double beta decay experiment capable of probing Majorana masses in the regime of the nondegenerate normal neutrino mass hierarchy is proposed. For such an experiment, this study suggests that ${}^{130}\mathrm{Te}$ is likely the best choice of candidate isotope and that metal-loaded liquid scintillator likely represents the best choice of detector technology. An evaluation of the required loading, scintillator properties and detector configuration is presented. While further development of Te-loaded liquid scintillator is required, recent progress in this area suggests that this task may not be insurmountable. This could open the door for a future experiment of unparalleled sensitivity that might be accommodated in a volume of the order of 10–20 kilotons. To the best of our knowledge, this is the first time that a potentially practical experimental approach to exploring Majorana neutrino masses in the nondegenerate normal hierarchy has been suggested.

We construct $\mathcal{N}=2$, 4 supersymmetric Abelian projections of the $\mathcal{N}=6$ mass-deformed Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. There are well-defined dual background geometries for the $\mathcal{N}=2$ Abelian theory, while those geometries are unclear for the $\mathcal{N}=4$ Abelian theory. The $\mathcal{N}=2$ theory is built on the supersymmetric vacua of the mass-deformed ABJM theory, which are proven to have a one-to-one correspondence with the ${\mathbb{Z}}_k$ quotient of Lin-Lunin-Maldacena geometries. We select one special vacuum of the mass-deformed ABJM theory and show that the corresponding geometry is weakly curved at every point of the entire space transverse to the M2-branes in the large-$N$ limit.

We discuss the possibility that dark matter axions form a Bose-Einstein condensate (BEC) due to the gravitational self interactions. The formation of BEC occurs in the condensed regime, where the transition rate between different momentum states is large compared to the energy exchanged in the transition. The time evolution of the quantum state occupation number of axions in the condensed regime is derived based on the in-in formalism. We recover the expression for the thermalization rate due to self interaction of the axion field, which was obtained in the other literature. It is also found that the leading order contributions for interactions between axions and other species vanish, which implies that the axion BEC does not give any significant modifications on standard cosmological parameters.

Gravitational perturbations of neutron stars and black holes are well-known sources of gravitational radiation. If the compact object is immersed in or endowed with a magnetic field, the gravitational perturbations would couple to electromagnetic perturbations and potentially trigger synergistic electromagnetic signatures. We present a detailed analytic calculation of the dynamics of coupled gravitational and electromagnetic perturbations for both neutron stars and black holes. We discuss the prospects for detecting the electromagnetic waves in these scenarios and the potential that these waves have for providing information about their source.

In this short note, we perform the Hamiltonian analysis of bimetric gravity with one particular form of potential between two metrics. We find that this theory has eight secondary constraints. We identify four constraints that are the first-class constraints on condition when the interaction term obeys some specific condition. We show that for the form of the potential studied in this paper, this condition is obeyed, and hence we can interpret these first-class constraints as generators of the diagonal diffeomorphism.

In the investigation and resolution of the cosmological constant problem, the inclusion of the dynamics of quantum gravity can be a crucial step. In this work we suggest that the quantum constraints in a canonical theory of gravity can provide a way of addressing the issue: we consider the case of two-dimensional quantum dilaton gravity nonminimally coupled to a $U(1)$ gauge field, in the presence of an arbitrary number of massless scalar matter fields, intended also as an effective description of highly symmetrical higher-dimensional models. We are able to quantize the system nonperturbatively and obtain an expression for the cosmological constant $\Lambda$ in terms of the quantum physical states, in a generalization of the usual quantum field theory approach. We discuss the role of the classical and quantum gravitational contributions to $\Lambda$ and present a partial spectrum of values for it.

A class of higher dimensional rotating solutions in $R+f(R)$ theory coupled to a conformally invariant Maxwell field is presented. These solutions have asymptotically anti–de Sitter behavior but exist only for dimensions which are multiples of four. These solutions represent black branes with cylindrical or toroidal horizons and $k$ rotation parameters. We present the suitable counterterm which removes the divergences of the action in $R+f(R)$ gravity with constant curvature. We also compute the mass, the angular momenta, the entropy, the charge, and the electric potential of the black branes. Finally, we check that the conserved and thermodynamic quantities satisfy the first law of thermodynamics.

Using a full implementation of resummed perturbation theory (PT) from a multipoint propagator expansion, we put forward new theoretical predictions for the two-point statistics of matter fluctuations in redshift space. The predictions consistently include PT corrections up to the two-loop order and are based on an improved prescription of the redshift-space distortions that properly takes into account their non-Gaussian impact from a systematic low-$k$ expansion. In contrast to the previous studies that partly used standard PT calculations, the present treatment is able to provide a consistent prediction for both power spectra and correlation functions. These results are compared with $N$-body simulations with which a very good agreement is found up to the quadrupole moment. However, the theoretical predictions for the hexadecapole moment of the power spectra are found to significantly depart from the numerical results at low redshift. We examine this issue and find it to be likely related to an improper modeling of the redshift-space distortions damping effects on which this moment shows large dependence.

We consider Yukawa theory in which the fermion mass is induced by a Higgs-like scalar. In our model the fermion mass exhibits a temporal dependence, which naturally occurs in the early Universe setting. Assuming that the complex fermion mass changes as a tanh-kink, we construct an exact, helicity-conserving, $CP$-violating solution for the positive- and negative-frequency fermionic mode functions, which is valid in both the weak and strong $CP$ violation cases. Using this solution we then study the fermionic currents in both the initial vacuum and finite-density/-temperature setting. Our result shows that—due to a potentially large state squeezing—fermionic currents can exhibit a large oscillatory magnification. Having in mind applications to electroweak baryogenesis, we then compare our exact results with those obtained in a gradient approximation. Even though the gradient approximation does not capture the oscillatory effects of squeezing, it describes quite well the averaged current, obtained by performing a mode sum. Our main conclusion is that while the agreement with the semiclassical force is quite good in the thick-wall regime, the difference is sufficiently significant to motivate a more detailed quantitative study of baryogenesis sources in the thin-wall regime in more realistic settings.

We investigate a (super-)renormalizable and ghost-free theory of gravity, showing that under a natural (exponential) ansatz of the form factor and a suitable truncation it can give rise to the Starobinsky inflationary theory in cosmological frameworks, and thus offering a theoretical justification of its origin. We study the corresponding inflationary evolution and we examine the generation of curvature perturbations, adapting the $f(R)$-like equations in a symmetry-reduced Friedmann-Lemaître-Robertson-Walker metric. Furthermore, we analyze how the ultraviolet regime of a simply renormalizable and unitary theory of gravity is also compatible with the Starobinsky action, and hence we show that such a theory could account for an inflationary phase of the Universe in the ultraviolet regime.

We consider the performance of the ATLAS and CMS searches for events with missing transverse energy, which were originally motivated by supersymmetry, in constraining extensions of the standard model based on extra dimensions, in which the mass differences between recurrences at the same level are generically smaller than the mass hierarchies in typical supersymmetric models. We consider first a toy model with pair-production of a single vector-like quark $U_1$ decaying into a spin-zero stable particle $A_1$ and jet, exploring the sensitivity of the CMS ${\alpha }_T$ and ATLAS $m_{\mathrm{eff}}$ analysis to $M_{U_1}$ and the $U_1\mathrm{\text{−}}{A}_1$ mass difference. For this purpose we use versions of the Delphes generic detector simulation with CMS and ATLAS cards, which have been shown to reproduce the published results of CMS and ATLAS searches for supersymmetry. We then explore the sensitivity of these searches to a specific model with two universal extra dimensions, whose signal is dominated by the pair production of quark recurrences, including searches with leptons. We find that the LHC searches have greater sensitivity to this more realistic model, due partly to the contributions of signatures with leptons, and partly to events with large missing transverse energy generated by the decays of higher-level Kaluza-Klein recurrences. We find that the CMS ${\alpha }_T$ analysis with $\sim 5/\mathrm{fb}$ of data at 7 TeV excludes a recurrence scale of 600 GeV at a confidence level above 99%, increasing to 99.9% when combined with the CMS single-lepton search, whereas a recurrence scale of 700 GeV is disfavored at the 72% confidence level.

We present the first lattice QCD determination of the ${\Lambda }_b\to \Lambda$ transition form factors that govern the rare baryonic decays ${\Lambda }_b\to \Lambda {\ell }^{+}{\ell }^{-}$ at leading order in heavy-quark effective theory. Our calculations are performed with $2+1$ flavors of domain-wall fermions, at two lattice spacings and with pion masses down to 227 MeV. Three-point functions with a wide range of source-sink separations are used to extract the ground-state contributions. The form factors are extrapolated to the physical values of the light-quark masses and to the continuum limit. We use our results to calculate the differential branching fractions for ${\Lambda }_b\to \Lambda {\ell }^{+}{\ell }^{-}$ with $\ell =e$, $\mu$, $\tau$ within the standard model. We find agreement with a recent CDF measurement of the ${\Lambda }_b\to \Lambda {\mu }^{+}{\mu }^{-}$ differential branching fraction.

Searches for dark matter at colliders typically involve signatures with energetic initial-state radiation without visible recoil particles. Searches for monojet or monophoton signatures have yielded powerful constraints on dark matter interactions with Standard Model particles. We extend this to the mono-$Z$ signature and reinterpret an ATLAS analysis of events with a $Z$ boson and missing transverse momentum to derive constraints on dark matter interaction mass scale and nucleon cross sections in the context of effective field theories describing dark matter which interacts via heavy mediator particles with quarks or weak bosons.

In view of recent measurements of the mixing angle ${\theta }_{13}$, we investigate the possibility to determine the difference of two $CP$ Majorana phases of the neutrino mixing matrix from the study of neutrinoless double-beta decay. We show that if cosmological measurements will reach the sensitivity of 0.1 eV for the sum of neutrino masses, i.e., the mass value of the lightest neutrino will be strongly constrained, the long-baseline neutrino oscillation experiments will determine inverted hierarchy of neutrino masses and if neutrinoless double-beta decay will be observed, this determination might be possible. The required experimental accuracies and the uncertainties in the calculated nuclear matrix elements of the process are discussed in this context.