The techni-dilaton (TD) is predicted in walking technicolor (WTC) arising as a pseudo—Nambu-Goldstone boson associated with the approximate scale symmetry spontaneously broken by techni-fermion condensation. The TD mass is therefore smaller than those of other techni-hadrons on the order of several TeVs, small enough to be within reach of the current LHC search. We present a new method to derive the TD couplings directly from the Ward-Takahashi identities, which enables us to explicitly calculate the quantities relevant to the TD LHC signatures. To set definite benchmarks, we take one-doublet and one-family models of WTC and discuss the TD signatures at the LHC, in comparison with those of the standard model (SM) Higgs. It is shown that the TD in the one-doublet model is invisible at the LHC, while the TD signals in the one-family model can be found as a large excess relative to the SM Higgs at around 125 GeV only in the diphoton channel.

Results are presented for hadron spectroscopy with gauge groups $SU(N)$ with $N=3$, 5, 7. Calculations use the quenched approximation. Lattice spacings are matched using the static potential. Meson spectra show independence on $N$ and vacuum-to-hadron matrix elements scale as $\sqrt{N}$. The baryon spectrum shows the excitation levels of a rigid rotor.

Five-dimensional dilaton models are considered as possible holographic duals of the pure gauge QCD vacuum. In the framework of these models, the QCD trace anomaly equation is considered. Each quantity appearing in that equation is computed by holographic means. Two exact solutions for different dilaton potentials corresponding to perturbative and nonperturbative $\beta$-functions are studied. It is shown that in the perturbative case, where the $\beta$-function is the QCD one at leading order, the resulting space is not asymptotically anti–de Sitter. In the nonperturbative case, the model considered presents confinement of static quarks and leads to a nonvanishing gluon condensate, although it does not correspond to an asymptotically free theory. Calculating the Nambu-Goto action, corresponding to a small circular Wilson loop, leads to an expression for the gluon condensate. The validity of the trace anomaly equation is considered for both models. It holds for the perturbative model and it does not hold for the nonperturbative one.

We study inclusive $b$-jet and $b\overline{b}$-dijet production at the CERN LHC invoking the hypothesis of gluon Reggeization in $t$-channel exchanges at high energy. The $b$-jet cross section includes contributions from open $b$-quark production and from $b$-quark production via gluon-to-bottom-pair fragmentation. The transverse-momentum distributions of inclusive $b$-jet production measured with the ATLAS detector at the CERN LHC in different rapidity ranges are calculated both within multi-Regge kinematics and quasi-multi-Regge kinematics. The $b\overline{b}$-dijet cross section is calculated within quasi-multi-Regge kinematics as a function of the dijet invariant mass $M_{jj}$, the azimuthal angle between the two jets $\Delta \varphi$, and the angular variable $\chi$. At the numerical calculation, we adopt the Kimber-Martin-Ryskin and Blümlein prescriptions to derive unintegrated gluon distribution function of the proton from its collinear counterpart for which we use the Martin-Roberts-Stirling-Thorne set. We find good agreement with measurements by the ATLAS and CMS Collaborations at the LHC at the hadronic c.m. energy of $\sqrt{S}=7\mathrm{TeV}$.

The isospin-2 $\pi \pi$ system provides a useful testing ground for determining elastic hadron scattering parameters from finite-volume spectra obtained using lattice QCD computations. A reliable determination of the excited state spectrum of two pions in a cubic box follows from variational analysis of correlator matrices constructed using a large basis of operators. A general operator construction is presented which respects the symmetries of a multihadron system in flight. This is applied to the case of $\pi \pi$ and allows for the determination of the scattering phase shifts at a large number of kinematic points, in both $S$-wave and $D$-wave, within the elastic region. The technique is demonstrated with a calculation at a pion mass of 396 MeV, where the elastic scattering is found to be well described by a scattering length parametrization.

The spontaneous breaking of linearly realized $\mathcal{N}=1$ supersymmetry implies the existence of a pseudo-Goldstone fermion, the goldstino, and of its complex scalar superpartner, the sgoldstino. The latter has generically sizable tree-level couplings to Standard Model (SM) gauge bosons while its couplings to SM fermions are suppressed. We consider a light sgoldstino, with a mass around 1 TeV, that mixes with a SM-like Higgs scalar at around 125 GeV. We show that such a mixing can enhance the Higgs to diphoton signal rate while evading all the relevant experimental bounds and without significantly affecting the other decay channels.

Evidence continues to grow in the MiniBooNE (MB) antineutrino mode supporting a low-energy excess compatible with the MB neutrino mode and possibly also confirming the results of the LSND experiment. At least one sterile neutrino is required to explain the anomalies consistent with the observations of other experiments. At the same time, there is a strong tension between the positive signals of LSND and MB and the null results of ${\nu }_e$ and ${\nu }_{\mu }$ disappearance experiments. We explore a scenario, first proposed in [A. E. Nelson, Phys. Rev. D 84, 053001 (2011).], where the presence of an additional heavy sterile neutrino (with mass well above an eV) can alleviate tension between LSND, MB and the null results of disappearance experiments. We compare and contrast this $3+1+1$ scenario with the more standard $3+1$ scenario and carry out global fits to all oscillation data including new 2011 MB $\overline{\nu }$ data. We find that the tension can be somewhat alleviated and that a phenomenologically viable window for the heavy neutrino, consistent with rare decays and big bang nucleosynthesis constraints, can be found if the fifth neutrino has a mass of order $0.3–10\mathrm{GeV}$. We also find, however, that the 2011 MB $\overline{\nu }$ data exacerbates the tension with null experiments in both the $3+1$ and $3+1+1$ models when the lowest energy bins are included, resulting in little improvement in the global fit. We also discuss the implications of an additional neutrino for the reactor and gallium anomalies, and show that an oscillation explanation of the anomalies is disfavored by cosmological considerations, direct searches, and precision electroweak tests.

We employ the Nyström method with the extended Simpson’s rule to solve numerically the Schrödinger equation in momentum space with the screened Cornell potential. Two peculiar phenomena, furcation and deviation of the first point, occur in the obtained eigenfunctions. By applying the Landé subtraction method to remove or relieve the singularities in the integrands, the furcation phenomenon disappears, the deviation of the first point is weakened, and the obtained eigenvalues have high accuracy.

We consider light top squarks (stops) in the minimal supersymmetric Standard Model at the Large Hadron Collider. Here, we assume that the lightest neutralino is the lightest supersymmetric particle (LSP) and the lighter stop is the next-to-LSP. Stop pair production is difficult to probe at the Large Hadron Collider for small stop-LSP mass splitting. It has been shown previously that even in this case stop detection is possible if one considers stop pair production in association with one hard jet. We reconsider this supersymmetric monojet signature and go beyond previous works by including the full Standard Model background and optimizing the cuts, working at the hadron level and including detector effects. As a result, a larger portion of the stop-LSP mass plane becomes accessible to monojet searches.

Recent LHC data suggest an excess in the Higgs decay channels into $\gamma \gamma$ and $ZZ$ at $\sim 125\mathrm{GeV}$. The current excess in the diphoton channel is twice that expected from a standard model (SM) Higgs boson; while this may well change with more statistics, it is interesting to consider the implications should the result persist. Here, we assess whether the next-to-minimal supersymmetric standard model with a neutralino dark matter candidate could explain this excess when astrophysical constraints (e.g., no overproduction of gamma rays and radio emission in the galaxy, no anomalous excess in the dark matter direct detection experiments, and no dark matter overabundance) are imposed on the neutralino. This enables us to disregard unphysical regions of the parameter space even though the Higgs signal is compatible with the observed excess. The result of our analysis is that there are configurations of the parameter space that can explain the signal strength reported by the ATLAS and CMS Collaborations for a Higgs mass within the required range. Should the observed signal strength finally be compatible with SM expectations, it would be difficult to distinguish between the discovery of SM Higgs boson and a SM-like Higgs boson from the next-to-minimal supersymmetric standard model, unless one performs dedicated searches of very light Higgs bosons and possibly investigates peculiar signatures of supersymmetric particles. We also propose a new $\mathrm{\text{jets}}+\mathrm{\text{missing}}$ $E_T$ signal for the case where the lightest supersymmetric particle is a singlino-like neutralino.

We study the high-luminosity fixed-target neutrino experiments at MiniBooNE, MINOS and T2K and analyze their sensitivity to light stable states, focusing on MeV–GeV scale dark matter. Thermal relic dark matter scenarios in the sub-GeV mass range require the presence of light mediators, whose coupling to the Standard Model facilitates annihilation in the early universe and allows for the correct thermal relic abundance. The mediators in turn provide a production channel for dark matter at colliders or fixed targets, and as a consequence the neutrino beams generated at fixed targets may contain an additional beam of light dark matter. The signatures of this beam include elastic scattering off electrons or nucleons in the (near-)detector, which closely mimics the neutral current scattering of neutrinos. We determine the event rate at modern fixed target facilities and the ensuing sensitivity to sub-GeV dark matter.

The light-quark correlator in the axial-vector channel is used, in conjunction with finite energy QCD sum rules at finite temperature, in order to (a) establish a relation between chiral-symmetry restoration and deconfinement, and (b) determine the temperature behavior of the $a_1(1260)$ width and coupling. Results indicate that deconfinement takes place at a slightly lower temperature than chiral-symmetry restoration, although this difference is not significant given the accuracy of the method. The behavior of the $a_1(1260)$ parameters is consistent with quark-gluon deconfinement, as the width grows and the coupling decreases with increasing temperature.

We consider the implications of low-energy precision tests of parity violation on $t$-channel mediator models explaining the top $A_{FB}$ excess measured by the CDF and D0 Collaborations. Flavor-violating $u\mathrm{\text{−}}t$ or $d\mathrm{\text{−}}t$ couplings of new scalar or vector mediators generate at one-loop an anomalous contribution to the nuclear weak charge. As a result, atomic parity violation constraints disfavor at $\gtrsim 3\sigma$ $t$-channel models that give rise to a greater than 20% $A_{FB}$ at the parton level for $M_{t\overline{t}}>450\mathrm{GeV}$ while not producing too large a $t\overline{t}$ cross section. Even stronger constraints are expected through future measurements of the proton weak charge by the Qweak experiment.

We propose a new mechanism for generating a single transverse spin asymmetry (STSA) in polarized proton-proton and proton-nucleus collisions in the high-energy scattering approximation. In this framework the STSA originates from the $q\to qG$ splitting in the projectile (proton) light-cone wave function followed by a perturbative ($C$-odd) odderon interaction, together with a $C$-even interaction, between the projectile and the target. We show that some aspects of the obtained expression for the STSA of the produced quarks are in qualitative agreement with experiment: STSA decreases with decreasing projectile $x_F$ and is a nonmonotonic function of the transverse momentum $k_T$. In our framework the STSA peaks at $k_T$ near the saturation scale $Q_s$. Our mechanism predicts that the quark STSA in proton-nucleus collisions should be much smaller than in proton-proton collisions. We also observe that in our formalism the STSA for prompt photons is zero.

We investigate the electrical conductivity ($\sigma$) of quark matter via the Kubo formula at finite temperature and zero quark density ($T\ne 0$, $\mu =0$) in the presence of an external strong magnetic field. For this purpose, we employ the dilute instanton-liquid model, taking into account its temperature modification with the trivial-holonomy caloron distribution. By doing that, the momentum and temperature dependences for the effective quark mass and model renormalization scale are carefully evaluated. From the numerical results, it turns out that $\sigma \approx (0.02–0.15){\mathrm{fm}}^{-1}$ for $T=(0–400)\mathrm{MeV}$ with the relaxation time $\tau =(0.3–0.9)\mathrm{fm}$. In addition, we also parametrize the electrical conductivity as $\sigma /T\approx (0.46,0.77,1.08,1.39)C_{\mathrm{EM}}$ for $\tau =(0.3,0.5,0.7,0.9)\mathrm{fm}$, respectively. These results are compatible with other theoretical estimations, including those from the lattice QCD simulations. It also turns out that the external magnetic field plays only a minor role for $\sigma$ even for the very strong one $B_0\sim m_{\pi }^2\times 10$ and becomes relatively effective for $T\lesssim 200\mathrm{MeV}$. Moreover, we compute the soft photon emission rate from the quark-gluon plasma, using the electrical conductivity calculated.

We analyze spacetime momentum currents on a classical string world sheet, study their generic connection via AdS/CFT correspondence to the instantaneous energy loss of the dual field theory degrees of freedom and suggest a general formula for computing energy loss in a time-dependent string configuration. Applying this formula to the case of falling strings, generally dual to light quarks, reveals that the energy loss does not display a well-pronounced Bragg peak at late times, as previously believed. Finally, we comment on the possible implications of this result to the jet quenching phenomena in heavy ion collisions.

We investigate the problem of the dynamical collapse of a self-gravitating complex charged scalar field in Einstein-Maxwell-dilaton theory with a phantom coupling for the adequate fields in the system under consideration. We also consider two simplifications, i.e., the separate collapses of phantom Maxwell and phantom scalar fields under the influence of Einstein gravity. One starts with the regular spacetime and leads the evolution through the formation of the horizons and the final singularity. We discuss the structures of spacetimes emerging in the process of the dynamical collapse and comment on the role of the considered fields in its course.

We provide a detailed discussion of the multifield trajectories and inflationary dynamics of the recently proposed model of chromo-natural inflation, which allows for slow roll inflation on a steep potential with the aid of classical non-Abelian gauge fields. We show that slow roll inflation can be achieved across a wide range of the parameter space. We demonstrate that chromo-natural inflation includes trajectories that match those found in gauge-flation and describe how the theories are related.