The recent results from the ATLAS and CMS Collaborations show that the allowed range for a standard model Higgs boson is now restricted to a very thin region, if one excludes a very heavy Higgs. Although those limits are presented exclusively in the framework of the standard model, the searches themselves remain sensitive to other Higgs models. We recast the limits within a generic supersymmetric framework that goes beyond the usual minimal extension. Such a generic model can be parametrized through a supersymmetric effective Lagrangian with higher-order operators appearing in the Kähler potential and the superpotential, an approach whose first motivation is to alleviate the fine-tuning problem in supersymmetry with the most dramatic consequence being a substantial increase in the mass of the lightest Higgs boson as compared to the minimal supersymmetic model. We investigate in this paper the constraints set by the LHC on such models. We also investigate how the present picture will change when gathering more luminosity. Issues of how to combine and exploit data from the LHC dedicated to searches for the standard model Higgs to such supersymmetry inspired scenarios are discussed. We also discuss the impact of invisible decays of the Higgs in such scenarios.

A classification is given of models in which there are several Higgs $SU(2{)}_L$ doublets that form an irreducible multiplet of a non-Abelian symmetry $G_{\Phi }$, under which the quarks and leptons do not transform (thus giving minimal flavor changing for the fermions). It is found that different groups $G_{\Phi }$ and irreducible representations $R_{\Phi }$ of the Higgs fields under $G_{\Phi }$ lead to very distinctive spectra of the extra Higgs doublets, including different numbers of “inert Higgs” that could play the role of dark matter, different mass relations, and different patterns of $SU(2{)}_L$-breaking splittings within the Higgs doublets.

With a minimally modified dispersion relation for neutrinos, we reconsider the constraints on superluminal neutrino velocities from bremsstrahlung effects in the laboratory frame. Employing both the direct calculation approach and the virtual $Z$-boson approach, we obtain the generic decay width and energy loss rate of a superluminal neutrino with general energy. The Cohen-Glashow’s analytical results for neutrinos with a relatively low energy are confirmed in both approaches. We employ the survival probability instead of the terminal energy to assess whether a neutrino with a given energy is observable or not in the OPERA experiment. Moreover, using our general results we perform systematical analyses on the constraints arising from the Super-Kamiokande and IceCube experiments.

New color octet vectors below the TeV scale could explain the anomalous $t\overline{t}$ forward-backward asymmetry observed at the Tevatron experiments, while being consistent with the current LHC data. These models generally lead to four-top final states at the LHC at observable levels. We compute the four-top production cross section at the LHC in a model with a massive color octet vector as a function its mass, its width, and its coupling to the top quark. Octet masses in the vicinity of the $t\overline{t}$ threshold are generally excluded by present limits on the production of same-sign dileptons and trileptons. Masses above 650 GeV are allowed, quite independently of the couplings, but they can be probed with the luminosity of $5{\mathrm{fb}}^{-1}$ already collected at the LHC, up to around 800 GeV. The four-top production cross section is increased by a factor $\sim 2$ with $\sqrt{s}=8\mathrm{TeV}$ and by up to almost 2 orders of magnitude with $\sqrt{s}=14\mathrm{TeV}$, thus greatly increasing the reach for massive gluons after the LHC energy upgrade.

We present the calculations of the complete next-to-leading order QCD corrections to the total cross section, invariant mass distribution, and the forward-backward asymmetry ($A_{\mathrm{FB}}$) of top quark pair production mediated by the $W^{\prime }$ boson. Our results show that in the best fit point in the parameter space allowed by data at the Tevatron, the next-to-leading order corrections change the new physics contributions to the total cross section slightly, but increase the $A_{\mathrm{FB}}$ in the large invariant mass region by about 9%. Moreover, we evaluate the total cross section and charge asymmetry ($A_C$) of top pair production at the LHC, and find that both total cross section and $A_C$ can be used to distinguish new physics from the standard model with the integrated luminosity increasing.

In this work, we construct a phenomenological effective model for the heavy-light-quark systems, which consist of $(u,d,c,b)$ quarks, i.e., extended nonlocal chiral-quark model (ExNLChQM) to compute the heavy-meson weak-decay constants $f_D$ and $f_B$. ExNLChQM is based on the heavy-quark effective field theory as well as the dilute-instanton-vacuum configuration. In ExNLChQM, a certain portion of the heavy-meson mass is considered to be generated from the nontrivial QCD-vacuum contribution, similar to the light quarks in usual instanton approaches. Hence, the effective heavy- and light-quark masses become momentum-dependent and play the role of a smooth UV regulator. Employing a generic external-field method applied to the effective action from ExNLChQM, we obtain $f_D=(169.28\sim 234.57)\mathrm{MeV}$ and $f_B=(165.41\sim 229.21)\mathrm{MeV}$ from the numerical results, depending on different model parameters. These values are in relatively good agreement with experimental data and various theoretical estimations. We also discuss the heavy-quark effects on the QCD vacuum, and the decay constants $f_{D^{*}}$ and $f_{B^{*}}$ in terms of the heavy-quark spin symmetry.

The implication of the fourth-generation quarks in the $B\to K^{*}{\ell }^{+}{\ell }^{-}$ ($\ell =\mu ,\tau$) decays when $K^{*}$ meson is longitudinally or transversely polarized is presented herein. In this context, the dependence of the branching ratio with polarized $K^{*}$ and the helicity fractions ($f_{L,T}$) of $K^{*}$ meson were studied. It was observed that the polarized branching ratios as well as helicity fractions are sensitive to the new physics (NP) parameters, especially when the final-state leptons are tauons. Hence, the measurements of these observables at LHC can serve as a good tool to investigate the indirect searches of new physics beyond the standard model.

In the framework of the nonrelativistic quantum chromodynamics factorization formalism, we study the processes of $\psi (nS)$ and ${\rm Y}(nS)$ decay into a lepton pair or a charm pair associated with two jets up to the next-to-leading order in velocity expansion. We present the analytic expressions for the differential decay rate to the invariant mass of the lepton pair or charm pair. We find that the ratio of the next-to-leading order short-distance coefficient to the leading order one is in the range from $-5.5$ to $-12.4$. The relativistic corrections are so large that they modify the leading order prediction significantly. Utilizing the analytic expressions, we also investigate the relativistic corrections in different kinematic regions and their dependence on the masses of the initial-state quarkonium and the final-state fermion. In addition, we study the momentum distribution of $D^{*+}$ in the process ${\rm Y}(1S)\to c\overline{c}gg\to D^{*+}X$.

We present the azimuthal correlations in the decay products of the top quark pair created in the process $gg\to t\overline{t}\to b\overline{b}{W}^{+}{W}^{-}$ calculated in leading-order QCD. We then discuss deviations in this distribution that could arise from new physics contributions, focusing, in particular, on the case of a new heavy scalar coupling to the top quark and produced via the gluon fusion mechanism. Within this scenario, we consider two cases: one in which the top quark is the only particle with a significant coupling to the scalar and another in which there are additional heavy fermions that modify the effective coupling of the scalar to gluons. We discuss the effects on the overall cross section and azimuthal correlations of the top quark decay products, with particular emphasis on the effect of interference between the QCD and new physics contributions and on the existence of $CP$-nonconserving couplings.

We investigate $\mathcal{N}=1$ supersymmetric gauge theories where monopole condensation triggers supersymmetry breaking in a metastable vacuum. The low-energy effective theory is an O’Raifeartaigh-like model of the kind investigated recently by Shih where the $R$ symmetry can be spontaneously broken. We examine several implementations with varying degrees of phenomenological interest.

Dynamics and collapse of collisionless self-gravitating systems is described by the coupled collisionless Boltzmann and Poisson equations derived from $f(R)$ gravity in the weak field approximation. Specifically, we describe a system at equilibrium by a time-independent distribution function $f_0(x,v)$ and two potentials ${\Phi }_0(x)$ and ${\Psi }_0(x)$ solutions of the modified Poisson and collisionless Boltzmann equations. Considering a small perturbation from the equilibrium and linearizing the field equations, it can be obtained a dispersion relation. A dispersion equation is achieved for neutral dust-particle systems where a generalized Jeans wave number is obtained. This analysis gives rise to unstable modes not present in the standard Jeans analysis (derived assuming Newtonian gravity as weak filed limit of $f(R)=R$). In this perspective, we discuss several self-gravitating astrophysical systems whose dynamics could be fully addressed in the framework of $f(R)$ gravity.

We consider the effect of the electron cloud about a vorton in the CFL-$K^0$ high-density phase by numerically solving the ultrarelativistic Thomas-Fermi equation about a toroidal charge. Including electrons removes the electric monopole contribution to the energy, and noticeably decreases the equilibrium radius of these stable vortex loops.

In standard cosmologies, dark energy (DE) interacts only gravitationally with dark matter (DM). There could be a nongravitational interaction in the dark sector, leading to changes in the effective DE equation of state, in the redshift dependence of the DM density and in structure formation. We use cosmic microwave background, baryon acoustic oscillation and supernova data to constrain a model where the energy transfer in the dark sector is proportional to the DE density. There are two subclasses, defined by the vanishing of momentum transfer either in the DM or the DE frame. We conduct a Markov-Chain Monte Carlo analysis to obtain best-fit parameters. The background evolution allows large interaction strengths, and the constraints from cosmic microwave background anisotropies are weak. The growth of DM density perturbations is much more sensitive to the interaction, and can deviate strongly from the standard case. However, the deviations are degenerate with galaxy bias and thus more difficult to constrain. Interestingly, the integrated Sachs-Wolfe signature is suppressed since the nonstandard background evolution can compensate for high growth rates. We also discuss the partial degeneracy between interacting DE and modified gravity, and how this can be broken.

The adiabatic inhomogeneities of the scalar curvature lead to a compressible flow affecting the dynamics of the hydromagnetic nonlinearities. The influence of the plasma on the evolution of a putative magnetic field is explored with the aim of obtaining an effective description valid for sufficiently large scales. The bulk velocity of the plasma, computed in the framework of the $\Lambda \mathrm{CDM}$ scenario, feeds back into the evolution of the magnetic power spectra leading to a (nonlocal) master equation valid in Fourier space and similar to the ones discussed in the context of wave turbulence. Conversely, in physical space, the magnetic power spectra obey a Schrödinger-like equation whose effective potential depends on the large-scale curvature perturbations. Explicit solutions are presented both in physical space and in Fourier space. It is argued that curvature inhomogeneities, compatible with the WMAP 7 yr data, shift the magnetic diffusivity scale to lower wave numbers.

The possibility to violate baryon or lepton number without introducing any new flavor structures, beyond those needed to account for the known fermion masses and mixings, is analyzed. With four generations, but only three colors, this minimality requirement is shown to lead to baryon number conservation, up to negligible dimension-18 operators. In a supersymmetric context, this same minimality principle allows only superpotential terms with an even number of flavored superfields, hence effectively enforcing R parity both within the minimal supersymmetric standard model and in a grand unified theory context.

We present a renormalizable flavor model with $Z_4$ as flavor symmetry in both the quark and lepton sectors. The model is constructed with a minimal approach and no right-handed neutrinos are introduced. In this approach a minimum number of two SU(2) Higgs doublets and one scalar singlet are required in order to obtain the Nearest Neighbor Interaction form for charged fermions and to generate neutrino masses radiatively. For the quark sector we follow the charge assignations made by Branco et al. in reference [G. C. Branco, D. Emmanuel-Costa, and C. Simoes, Phys. Lett. B 690, 62 (2010).]. All fermion masses and mixing angles in the model are in agreement with current experimental data and only the inverted hierarchy for the neutrino mass spectrum is allowed. Since neutrinos are Majorana the contribution to neutrinoless double beta decay is also analyzed.

We address the problem of a search at the LHC for a neutralino whose mass is around 10 GeV, i.e. in the range of interest for present data of direct search for dark matter particles in the galactic halo. This light neutralino is here implemented in an effective Minimal Supersymmetric extension of the Standard Model at the electroweak scale without requirement of a gaugino mass unification at a grand unification scale. In this model, light neutralinos that have the right cosmological properties and are able to explain current results of direct dark matter detection naturally arise. Within this model we identify a specific benchmark which maximizes chances of detection at the LHC, and we determine its prospects of reconstructing the main features of the light neutralino framework at different stages of the LHC runs. Our main result is that the LHC will hardly properly reconstruct the mass of such a light neutralino, due to the intrinsic difficulty in reconstructing the mass of light stable particles in relativistic events. However, the associated measurement of the mass of the heavier neutralinos allows us to point toward the right pattern of gaugino nonuniversality. Other relevant parameters of this model, like slepton and squark masses, can be reconstructed to a good level of precision.

Nonstandard decays of the Higgs boson produced at the Large Hadron Collider can lead to signatures which can easily be missed due to nonadapted trigger or search strategies. Keeping electroweak symmetry breaking standard model-like, we classify the phenomenology of an evasive Higgs boson into three categories and discuss how they can be described in an effective field theory. We comment on how one can improve the search strategies to also detect such an evasive Higgs.

This paper is a first report on the determination of ${\Lambda }_{\overline{\mathrm{MS}}}$ from lattice simulations with $2+1+1$ twisted-mass dynamical flavors via the computation of the ghost-gluon coupling renormalized in the MOM Taylor scheme. We show this approach allows a very good control of the lattice artefacts and confirm the picture from previous works with quenched and ${\mathrm{N}}_f=2$ twisted-mass field configurations, which prove the necessity to include nonperturbative power corrections in the description of the running. We provide an estimate of ${\Lambda }_{\overline{\mathrm{MS}}}$ in very good agreement with experimental results. To our knowledge, it is the first calculation with a dynamical charm quark which makes the running up to ${\alpha }_s(M_Z)$ much safer.

We derive the expression for the nonperturbative coupling of a hadron to two external currents from its underlying structure in QCD. Microscopically, the action of each current is resolved to a coupling with dressed quarks. The Lorentz structure of the currents is arbitrary and thereby allows to describe the hadron’s interaction with photons as well as mesons in the same framework. We analyze the ingredients of the resulting four-point functions and explore their potential to describe a variety of processes relevant in experiments. Possible applications include Compton scattering, the study of two-photon effects in hadron form factors, pion photo- and electroproduction on a nucleon, nucleon-pion or pion-pion scattering.