We present results on the axial and the electromagnetic form factors of the nucleon, as well as on the first moments of the nucleon generalized parton distributions using maximally twisted mass fermions. We analyze two $N_f=2+1+1$ ensembles having pion masses of 213 MeV and 373 MeV each at a different value of the lattice spacing. The lattice scale is determined using the nucleon mass computed on a total of 17 $N_f=2+1+1$ ensembles generated at three values of the lattice spacing, $a$. The renormalization constants are evaluated nonperturbatively with a perturbative subtraction of $\mathcal{O}(a^2)$ terms. The moments of the generalized parton distributions are given in the $\overline{\mathrm{MS}}$ scheme at a scale of $\mu =2\mathrm{GeV}$. We compare with recent results obtained using different discretization schemes. The implications on the spin content of the nucleon are also discussed.

We present next-to-leading order QCD predictions for the total cross section and for a comprehensive set of transverse-momentum distributions in $W+5$-jet production at the Large Hadron Collider. We neglect the small contributions from subleading-color virtual terms, top quarks, and some terms containing four quark pairs. We also present ratios of total cross sections, and use them to obtain an extrapolation formula to an even larger number of jets. We include the decay of the $W$ boson into leptons. This is the first such computation with six final-state vector bosons or jets. We use BlackHat together with sherpa to carry out the computation.

We study the cross section for the photoproduction reaction $\gamma N\to hX$ in fixed-target scattering at COMPASS, where the hadron $h$ is produced at large transverse momentum. We investigate the role played by higher-order QCD corrections to the cross section. In particular we address large logarithmic “threshold” corrections to the rapidity-dependent partonic cross sections, which we resum to all orders at next-to-leading accuracy. In our comparison to the experimental data we find that the threshold contributions are large and improve the agreement between data and theoretical predictions significantly.

In this paper we examine thoroughly the single (anti-)top quark production associated with a lightest neutralino at the possible CERN Large Hadron Electron Collider. We calculate the full next-to-leading order (NLO) QCD corrections to the process, including all the nonresonant diagrams, and do not assume the production and decay factorization for the possible resonant top squarks in the $R$-parity violating minimal supersymmetric standard model with 19 unrelated parameters. We investigate numerically the effects of the relevant supersymmetry parameters on the cross section, and present the transverse momentum distributions of the final (anti-)top quark at both the leading order (LO) and the QCD NLO. We find that the NLO QCD corrections enhance the LO cross sections in most chosen parameter space, and the NLO QCD impacts on the transverse momentum distributions of the final (anti-)top quark might be resolvable in some cases. We conclude that even with recently known experimental constraints on the supersymmetry parameters, the production rate could still achieve notable value in the admissible parameter space.

The high parton density present at high energies and large nuclei is expected to modify the lepton-hadron cross section and the associated observables. In this paper we analyze the impact of the high density effects in the average inelasticity and the neutrino-nucleus cross section at ultrahigh energies. We compare the predictions associated to the linear Dokshitzer-Gribov-Lipatov-Altarelli-Parisi dynamics with those from the color glass condensate formalism, which includes nonlinear effects. Our results demonstrated that the nonlinear effects reduce the average inelasticity and that the predictions of the distinct approaches for the neutrino-nucleus cross section at ultrahigh energies are similar.

We study the melting temperature of heavy mesons in the hot medium of light quarks. By solving the covariant Schrödinger equations at finite temperature for mesons $D$, $\varphi$, and $J/\psi$, we obtained the temperature dependence of their masses, binding energies, and averaged sizes and found the flavor dependence of the melting temperature: $T_D\simeq T_{\varphi }<T_{J/\psi }$. The sequential melting temperature can explain the difference in meson elliptic flow observed in heavy ion collisions.

In this work we compare the Gunion-Bertsch approximation of the leading order perturbative QCD radiation matrix element to the exact result. To this end, we revisit the derivation of the Gunion-Bertsch approximation as well as perform extensive numerical comparisons of the Gunion-Bertsch and the exact result. We find that when employing the matrix elements to obtain rates or cross sections from phase space integration, the amplitude by Gunion and Bertsch deviates from the correct result in characteristic regions of the phase space. We propose an improved version of the Gunion-Bertsch matrix element which agrees very well with the exact result in all phase space regions.

We study electroweak Sudakov effects in single $W$, $Z$ and $\gamma$ production at large transverse momentum using soft collinear effective theory. We present a factorized form of the cross section near the partonic threshold with both QCD and electroweak effects included and compute the electroweak corrections arising at different scales. We analyze their size relative to the QCD corrections as well as the impact of strong-electroweak mixing terms. Numerical results for the vector-boson cross sections at the Large Hadron Collider are presented.

Determination of the neutrino mass hierarchy in a reactor neutrino experiment at the medium baseline is discussed. Observation of the interference effects between the $\Delta m_{31}^2$ and $\Delta m_{32}^2$ oscillations enables a relative measurement independent of the knowledge of the absolute mass-squared difference. With a 20 kton liquid scintillator detector of the $3\%/\sqrt{E(\mathrm{MeV})}$ energy resolution, the Daya Bay II experiment at a baseline of $\sim 50\mathrm{km}$ from reactors of total thermal power 36 GW can determine the mass hierarchy at a confidence level of $\Delta {\chi }_{\mathrm{MH}}^2\sim (10÷12)$ ($3÷3.5\sigma$) in six years after taking into account the real spatial distribution of reactor cores. We show that the unknown residual energy nonlinearity of the liquid scintillator detector has limited impact on the sensitivity due to the self-calibration of small oscillation peaks. Furthermore, an extra increase of $\Delta {\chi }_{\mathrm{MH}}^2\simeq 4(9)$ can be obtained, by including the precise measurement of the effective mass-squared difference $\Delta m_{\mu \mu }^2$ of expected relative error 1.5% (1%) from ongoing long-baseline muon neutrino disappearance experiments. The sensitivities from the interference and from absolute measurements can be cross-checked. When combining these two, the mass hierarchy can be determined at a confidence level of $\Delta {\chi }_{\mathrm{MH}}^2\sim (15÷20)$ ($4\sigma$) in six years.

We derive an alternative representation of the leading-order contribution to the polarization operator in strong-field quantum electrodynamics with a plane-wave electromagnetic background field, which is manifestly symmetric with respect to the external photon momenta. Our derivation is based on a direct evaluation of the corresponding Feynman diagram, using the Volkov representation of the dressed fermion propagator. Furthermore, the validity of the Ward-Takahashi identity is shown for general loop diagrams in an external plane-wave background field.

We use the holographic hardwall model to calculate the masses of light glueball states with odd spin and $P=C=-1$ associated with odderons. Considering Dirichlet and Neumann boundary conditions we obtain expressions for the odderon Regge trajectories consistent with those calculated using other approaches.

We compute the expectation value of the $1/2$ BPS circular Wilson loop in $\mathcal{N}=6$ superconformal Chern-Simons (ABJM) theory at two loops in perturbation theory. The result shows perfect agreement with the prediction from localization and the proposed framing factor.

We review the $OSp(1|4)$-invariant formulation of $N=1$, $D=4$ supergravity and present its noncommutative extension, based on a $\star$ product originating from an Abelian twist with deformation parameter $\theta$. After the use of a geometric generalization of the Seiberg-Witten map, we obtain an extended (higher-derivative) supergravity theory, invariant under usual $OSp(1|4)$ gauge transformations. Gauge fixing breaks the $OSp(1|4)$ symmetry to its Lorentz subgroup and yields a Lorentz-invariant extended theory for which the classical limit $\theta \to 0$ is the usual $N=1$, $D=4$ anti–de Sitter supergravity.

We construct a “Chern-Simons-like” action for $\mathcal{N}=1$ topologically massive supergravity from the Chern-Simons actions of $\mathcal{N}=1$ supergravity and conformal supergravity. We convert this action into Hamiltonian form and use this to demonstrate that the theory propagates a single massive $(2,\frac{3}{2})$ supermultiplet.

Models of inflation involving non-Abelian gauge field backgrounds can produce gravitational waves at an observable level with a preferred handedness. This asymmetry comes about because the non-Abelian background generates parity violation in the action for perturbations. In the specific model we study, chromonatural inflation, these gravitational waves can be produced at observable levels even when no field makes a super-Planckian field excursion, thus evading a common formulation of the Lyth bound. Unfortunately, when considered in concert with the scalar fluctuations, this chiral enhancement of the gravitational waves makes the model observationally inviable.

We consider models of xenophobic dark matter, in which isospin-violating dark matter–nucleon interactions significantly degrade the response of xenon direct detection experiments. For models of near-maximal xenophobia, with neutron-to-proton coupling ratio $f_n/f_p\approx -0.64$, and dark matter mass near 8 GeV, the regions of interest for CoGeNT and CDMS-Si and the region of interest identified by Collar and Fields in CDMS-Ge data can be brought into agreement. This model may be tested in future direct, indirect, and collider searches. Interestingly, because the natural isotope abundance of xenon implies that xenophobia has its limits, we find that this xenophobic model may be probed in the near future by xenon experiments. Near-future data from the LHC and Fermi-LAT may also provide interesting alternative probes of xenophobic dark matter.

We study coupling constants of the standard model-like Higgs boson with the gauge bosons $hZZ$ and $hWW$ and fermions $hf\overline{f}$ in the general Higgs sector which contains higher isospin representations with arbitrary hypercharge. In the Higgs sectors with exotic Higgs representations, the $hZZ$ and $hWW$ coupling constants can be larger than those in the standard model. We calculate deviations in the Higgs boson couplings from standard model values in the model with a real or complex triplet field, the Georgi-Machacek model and the model with a septet scalar field. We also study deviations in the event rates of $h\to Z{Z}^{*}$, $h\to W{W}^{*}$, $h\to \gamma \gamma$, $h\to b\overline{b}$ and $h\to \tau \tau$ channels.

I study group theory (Kleiss-Kuijf) relations between purely multiquark primitive amplitudes at tree level and prove that they reduce the number of independent primitives to $(n-2)!/(n/2)!$, where $n$ is the number of quarks plus antiquarks, in the case where quark lines have different flavors. I give an explicit example of an independent basis of primitives for any $n$ which is of the form $\mathcal{A}(1,2,\sigma )$, where $\sigma$ is a permutation based on a Dyck word.

A comprehensive study of the impact of new physics on different observables for $B_s\to \varphi {\ell }^{+}{\ell }^{-}$ is carried out. We examine the new physics models, such as $Z^{\prime }$ and universal extra dimension models, where the effects of new physics come through the modification of Wilson coefficients. We analyze these effects through the theoretical prediction of the branching ratio, the forward-backward asymmetry, lepton polarization asymmetries, and the helicity fractions of the final-state meson. These observables will definitely be measured in present and future colliders with great precision. We also point out that hadronic uncertainties in various physical observables are small, which make them an ideal probe to establish new physics. Therefore, the measurements of these observables for the same decay would permit the detection of physics beyond the Standard Model and will also help us to distinguish between different new physics scenarios.

The $X(3872)$ has non-charmonium-like properties, such as decay processes that seem to violate isospin, and a mass that lies unexpectedly close to the $D^0$ ${\overline{D}}^{0*}$ threshold. An effective field theory that includes both charmoniumlike (short-distance) and moleculelike (meson bound state) properties is used to analyze the $X(3872)$ as it is produced in the decay of $\psi (4160)$. This is a route that BESIII may be able to measure. We find that the correlation between the angular distribution of the outcoming photon [or $X(3872)$] and the polarization of the $\psi (4160)$ source may be used to provide information on whether short-distance or long-distance effects dominate.