The chromoelectric dipole moment of the top quark is calculated in a model with a vectorlike multiplet, which mixes with the third generation in an extension of the minimal supersymmetric standard model. Such mixings allow for new $CP$ violating phases. Including these new $CP$ phases, the chromoelectric dipole moment that generates an electric dipole of the top in this class of models is computed. The top chromoelectric dipole moment operator arises from loops involving the exchange of the $W$, the $Z$, as well as from the exchange involving the charginos, the neutralinos, the gluino, and the vectorlike multiplet and their superpartners. The analysis of the chromoelectric dipole moment operator of the top is more complicated than for the light quarks because the mass of the external fermion, in this case the top quark mass, cannot be ignored relative to the masses inside the loops. A numerical analysis is presented and it is shown that the contribution to the top electric dipole moment (EDM) could lie in the range $({10}^{-19}–{10}^{-18})\mathrm{ecm}$, consistent with the current limits on the EDM of the electron, the neutron and on atomic EDMs. A top EDM of size $({10}^{-19}–{10}^{-18})\mathrm{ecm}$ could be accessible in collider experiments such as at the LHC and at the International Linear Collider.

We perform a study on the predictions of electric-dipole moments of neutron, Mercury (Hg), Thallium (Tl), deuteron, and Radium (Ra) in the framework of next-to-minimal supersymmetric standard model with $CP$-violating parameters in the superpotential and soft-supersymmetry-breaking sector. We confine to the case in which only the physical tree-level $CP$ phase (${\varphi }_{\lambda }^{\prime }-{\varphi }_{\kappa }^{\prime }$), associated with the couplings of the singlet terms in the superpotential and with the vacuum-expectation-values, takes on a nonzero value. We found that the one-loop contributions from neutralinos are mostly small while the two-loop Higgs-mediated contributions of the Barr-Zee type diagrams dominate. We emphasize a scenario motivated by electroweak baryogenesis.

We demonstrate the ability to measure the $CP$ phase of a Higgs boson state by looking at the decays of heavy, Majorana neutrinos in the process $pp\to H\to NN$ at the LHC. This is shown for signals with both opposite-sign ($l^{\pm }{l}^{\mp }{W}^{\pm }{W}^{\mp }$) and same-sign ($l^{\pm }{l}^{\pm }{W}^{\mp }{W}^{\mp }$) leptonic final states. These signals are investigated in the general framework of a sequential fourth generation of fermions with an additional right-handed neutrino. Such a scenario would naturally give rise to heavy Majorana neutrinos as well as significant enhancements to Higgs production via gluon fusion due to the contributions of the new, heavy quark states running in the fermion loops. Combined with the low background inherent to a same-sign lepton signal, this could be a useful way to investigate the $CP$ nature of a Higgs boson state at the LHC.

We present the first evidence from lattice simulations that the magnetic monopoles in three-dimensional compact quantum electrodynamics (${\mathrm{cQED}}_3$) with $N_f=2$ and $N_f=4$ four-component fermion flavors are in a plasma phase. The evidence is based mainly on the divergence of the monopole susceptibility (polarizability) with the lattice size at weak gauge couplings. A weak four-Fermi term added to the ${\mathrm{cQED}}_3$ action enabled simulations with massless fermions. The exact chiral symmetry of the interaction terms forbids symmetry breaking lattice discretization counterterms to appear in the theory’s effective action. It is also shown that the scenario of a monopole plasma does not depend on the strength of the four-Fermi coupling. Other observables such as the densities of isolated dipoles and monopoles and the so-called specific heat show that a crossover from a dense monopole plasma to a dilute monopole gas occurs at strong couplings. The implications of our results on the stability of $U(1)$ spin liquids in two spatial dimensions are also discussed.

We reconsider chiral perturbation theory in a finite volume and develop a new computational scheme which smoothly interpolates the conventional $ϵ$ and $p$ regimes. The counting rule is kept essentially the same as in the $p$ expansion. The zero-momentum modes of Nambu-Goldstone bosons are, however, treated separately and partly integrated out to all orders as in the $ϵ$ expansion. In this new scheme, the theory remains infrared finite even in the chiral limit, while the chiral-logarithmic effects are kept present. We calculate the two-point function in the pseudoscalar channel and show that the correlator has a constant contribution in addition to the conventional cosh function of time $t$. This constant term rapidly disappears in the $p$ regime but it is indispensable for a smooth convergence of the formula to the $ϵ$ regime result. Our calculation is useful to precisely estimate the finite volume effects in lattice QCD simulations on the pion mass $M_{\pi }$ and kaon mass $M_K$, as well as their decay constants $F_{\pi }$ and $F_K$.

We calculate, for the first time, cross sections for single and central-diffractive as well as exclusive diffractive production of dilepton pairs in proton-proton collisions. Several differential distributions are shown. The inclusive diffractive processes are calculated using diffractive parton distributions extracted from the analysis of diffractive structure function and dijet production at HERA. We find that the inclusive single-diffractive Drell-Yan process is by about 2 orders of magnitude smaller than the ordinary Drell-Yan process. The central-diffractive processes are smaller by 1 order of magnitude compared to single-diffractive ones. We consider also exclusive production of dilepton pairs. The exclusive photon-pomeron (pomeron-photon) process constitutes a background to the QED photon-photon process proposed to be used for controlling luminosity at LHC. Both processes are compared then in several differential distributions. We find a region of the phase space where the photon-pomeron or pomeron-photon contributions can be larger than the photon-photon one.

The Roper resonance is considered as a mixed state of a three-quark core configuration and a hadron-molecular component $N+\sigma$. Based on this ansatz we study electroproduction of the Roper resonance. The strong and electromagnetic couplings induced by the quark core are calculated in the ${}^{3}P_0$ model. The contribution of the vector-meson cloud to the electromagnetic transition is given in the framework of the vector-meson dominance model. Results are compared with the recent JLab electroproduction data.

We define and compute from data the strong couplings of the $X(3872)$ with both of the possible quantum numbers assignments $J^{\mathrm{PC}}=1^{++}$, $2^{-+}$. We use these to compute cross sections for $J/\psi$ resonance scattering into $D{\overline{D}}^{*}$. As an application of the results obtained we revise the calculation of the $J/\psi$ absorption in a hot hadron gas to confront with recent RHIC observations in Au-Au collisions.

The strange quark polarization puzzle, i.e. the contradiction between the negative polarized strange quark density obtained from analyses of inclusive deep inelastic scattering data and the positive values obtained from combined analyses of inclusive and semi-inclusive deep inelastic scattering data using de Florian, Sassot, Stratmann fragmentation functions, is discussed. To this end the results of a new combined next-to-leading order QCD analysis of the polarized inclusive and semi-inclusive deep inelastic scattering data, using the Hirai, Kumano, Nagai, Sudoh (HKNS) fragmentation functions, are presented. It is demonstrated that the polarized strange quark density is very sensitive to the kaon fragmentation functions, and if the set of HKNS fragmentation functions is used, the polarized strange quark density obtained from the combined analysis turns out to be negative and well consistent with values obtained from the pure deep inelastic scattering analyses.

The nonperturbative renormalization of four-quark operators plays a significant role in lattice studies of flavor physics. For this purpose, we define regularization-independent symmetric momentum-subtraction (RI/SMOM) schemes for $\Delta S=1$ flavor-changing four-quark operators and provide one-loop matching factors to the $\overline{\mathrm{MS}}$ scheme in naive dimensional regularization. The mixing of two-quark operators is discussed in terms of two different classes of schemes. We provide a compact expression for the finite one-loop amplitudes, which allows for a straightforward definition of further RI/SMOM schemes.

We use partially conserved axial vector current in the small $Q^2$ region in order to calculate the Adler sum rule and the production of hadrons in the low-energy region where resonances dominate. We find very good agreement with the sum rule and with the computed cross sections. We find a value $C_5^A(0)$ close to the Goldberger-Treiman prediction. The formalism is general and can be applied to other reactions shedding light into the dynamical transition from resonances to deep inelastic scattering.

We consider a model where sterile neutrinos can propagate in a large compactified extra dimension giving rise to Kaluza-Klein (KK) modes and the standard model left-handed neutrinos are confined to a 4-dimensional spacetime brane. The KK modes mix with the standard neutrinos modifying their oscillation pattern. We examine former and current experiments such as CHOOZ, KamLAND, and MINOS to estimate the impact of the possible presence of such KK modes on the determination of the neutrino oscillation parameters and simultaneously obtain limits on the size of the largest extra dimension. We found that the presence of the KK modes does not essentially improve the quality of the fit compared to the case of the standard oscillation. By combining the results from CHOOZ, KamLAND, and MINOS, in the limit of a vanishing lightest neutrino mass, we obtain the stronger bound on the size of the extra dimension as $\sim 1.0(0.6)\mu \mathrm{m}$ at 99% C.L. for normal (inverted) mass hierarchy. If the lightest neutrino mass turns out to be larger, 0.2 eV, for example, we obtain the bound $\sim 0.1\mu \mathrm{m}$. We also discuss the expected sensitivities on the size of the extra dimension for future experiments such as Double CHOOZ, T2K, and NOνA.

We update the phenomenological constraints of the nonstandard neutrino interactions (NSNI) with electrons including in the analysis, for the first time, data from LAMPF, Krasnoyarsk, and the latest Texono observations. We assume that NSNI modify the cross section of elastic scattering of (anti)neutrinos off electrons, using reactor and accelerator data, and the cross section of the electron-positron annihilation, using the four LEP experiments, in particular, new data from DELPHI. We find more restrictive allowed regions for the NSNI parameters: $-0.11<{\epsilon }_{ee}^{eR}<0.05$ and $-0.02<{\epsilon }_{ee}^{eL}<0.09$ (90% C.L.). We also recalculate the parameters of tauonic flavor obtaining $-0.35<{\epsilon }_{\tau \tau }^{eR}<0.50$ and $-0.51<{\epsilon }_{\tau \tau }^{eL}<0.34$ (90% C.L.). Although more severe than the limits already present in the literature, our results indicate that NSNI are allowed by the present data as a subleading effect, and the standard electroweak model continues consistent with the experimental panorama at 90% C.L. Further improvement on this picture will deserve a lot of engagement of upcoming experiments.

We present branching fraction and $CP$ asymmetry measurements as well as angular studies of $B\to \varphi \varphi K$ decays using $464\times {10}^6$ $B\overline{B}$ events collected by the BABAR experiment. The branching fractions are measured in the $\varphi \varphi$ invariant mass range below the ${\eta }_c$ resonance ($m_{\varphi \varphi }<2.85\mathrm{GeV}$). We find $\mathcal{B}(B^{+}\to \varphi \varphi K^{+})=(5.6\pm 0.5\pm 0.3)\times {10}^{-6}$ and $\mathcal{B}(B^0\to \varphi \varphi K^0)=(4.5\pm 0.8\pm 0.3)\times {10}^{-6}$, where the first uncertainty is statistical and the second systematic. The measured direct $CP$ asymmetries for the $B^{\pm }$ decays are $A_{CP}=-0.10\pm 0.08\pm 0.02$ below the ${\eta }_c$ threshold ($m_{\varphi \varphi }<2.85\mathrm{GeV}$) and $A_{CP}=0.09\pm 0.10\pm 0.02$ in the ${\eta }_c$ resonance region ($m_{\varphi \varphi }$ in [2.94, 3.02] GeV). Angular distributions are consistent with $J^P=0^{-}$ in the ${\eta }_c$ resonance region and favor $J^P=0^{+}$ below the ${\eta }_c$ resonance.

Recently, Gliozzi has shown that, under certain conditions, it is possible to derive the Dirac-Born-Infeld action for an Abelian gauge field of a D-brane. Also, the action turns out to be invariant with respect to a nonlinear realization of the full Poincaré group. A crucial role is played by the transformation properties of the gauge field under the nonlinear realization. The aim of this paper is to point out that these transformation properties are derived directly from the gauge fixing of the diffeomorphisms of the brane and the necessary compensating reparametrization when one performs a Lorentz transformation.

We study supercurrent conservation for the four-dimensional Wess-Zumino model formulated on the lattice. The formulation is one that has been discussed several times, and uses Ginsparg-Wilson fermions of the overlap (Neuberger) variety, together with an auxiliary fermion (plus superpartners), such that a lattice version of $U(1{)}_R$ symmetry is exactly preserved in the limit of vanishing bare mass. We show that the almost naive supercurrent is conserved at one loop. By contrast we find that this is not true for Wilson fermions and a canonical scalar action. We provide nonperturbative evidence for the nonconservation of the supercurrent in Monte Carlo simulations.

The vacuum neutrino mixing is known to exhibit an approximate $\mu -\tau$ symmetry, which was shown to be preserved for neutrino propagating in matter. This symmetry reduces the neutrino transition probabilities to very simple forms when expressed in a rephasing invariant parametrization introduced earlier. Applications to long baseline experiments are discussed.

We analyze the structure of the high multiplicity events observed by the CMS Collaboration at the LHC. We argue that the bulk of the observed correlations is due to the production of a pair of jets with $p_t>15\mathrm{GeV}/\mathrm{c}$. We also suggest that high multiplicity events are due to a combination of three effects: high underlying multiplicity for collisions at small impact parameters, upward fluctuations of the gluon density in the colliding protons, and production of hadrons in the fragmentation of dijets. The data analysis is suggested, which may clarify the underlying dynamics of the high multiplicity events and probe fluctuations of the gluon field as a function of $x$.

A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$. The data sample corresponds to an integrated luminosity of $42{\mathrm{pb}}^{-1}$. No significant deviation from the standard model is observed in the dimuon mass spectrum, allowing the following 95% C.L. limits to be set on the energy scale of contact interactions: $\Lambda >4.9\mathrm{TeV}$ (4.5 TeV) for constructive (destructive) interference in the left-left isoscalar compositeness model. These limits are the most stringent to date for $\mu \mu qq$ contact interactions.

We apply a generic framework of linear sigma models for revealing a mechanism of the mysterious phenomenon, the chiral magnetic effect, in quark-gluon plasma. An electric current arises along a background magnetic field, which is given rise to by Q-balls (nontopological solitons) of the linear sigma model with axial anomaly. We find additional alternating current due to quark mass terms. The mesonic Q-balls, baby boson stars, may be created in heavy-ion collisions.