We have estimated the limiting branching ratio of the R-parity violating (RPV) decay of the lighter top squark, $t_1\to l^{+}d$ $(l=e$ or $\mu$ and d is a down-type quark of any flavor), as a function of the top squark mass ${(m}_{t_1})$ for an observable signal in the di-lepton plus di-jet channel at the Tevatron Run-II experiment with $2{\mathrm{fb}}^{-1}$ luminosity. Our simulations indicate that the lepton number violating nature of the underlying decay dynamics can be confirmed via the reconstruction of $m_{t_1}.$ The above decay is interesting in the context of RPV models of neutrino mass where the RPV couplings $\left({\lambda }_{i3j}^{\prime }\right)$ driving the above decay are constrained to be small $(\lesssim {10}^{-3}–{10}^{-4})$ by the measured values of the neutrino oscillation parameters. If $t_1$ is the next lightest super particle—a theoretically well motivated scenario—then the RPV decay can compete with the R-parity conserving (RPC) modes which also have naturally suppressed widths. The model independent limiting branching ratio can delineate the parameter space in specific supersymmetric models, where the RPV decay is observable and predicts the minimum magnitude of the RPV coupling that will be sensitive to Run-II data. We have found it to be in the ballpark value required by models of neutrino mass, for a wide range of $m_{t_1}.$ A comprehensive future strategy for linking top squark decays with models of neutrino mass is sketched.

In the Abelian projection the Yang-Mills theory contains Abelian gauge fields (diagonal degrees of freedom) and the Abelian matter fields (off-diagonal degrees) described by a complicated action. The matter fields are essential for the breaking of the adjoint string. We obtain numerically the effective action of the Abelian gauge and the Abelian matter fields in quenched $\mathrm{SU}\left(2\right)\mathrm{}$ QCD and show that the Abelian matter fields provide an essential contribution to the total action even in the infrared region. We also observe the breaking of an Abelian analogue of the adjoint string using Abelian operators. We show that the adjoint string tension is dominated by the Abelian and the monopole contributions similarly to the case of the fundamental particles. We conclude that the adjoint string breaking can successfully be described in the Abelian projection formalism.

We study the perturbative Odderon in the quasidiffractive process ${\gamma }^{\left(*\right)}{\gamma }^{\left(*\right)}\to {\eta }_c{\eta }_c.$ At high energies this process is dominated by Odderon exchange and can be viewed as the theoretically cleanest test of the perturbative Odderon. We calculate the differential and total cross section, as well as the dependence on the energy and on the photon virtualities, taking into account the effects of resummation of logarithms of the energy. The results are compared with those obtained with a simple exchange of three noninteracting gluons. We present the expected cross section for this process at a future Linear Collider and discuss implications for other processes involving the perturbative Odderon.

A leading order (LO) analysis is presented that demonstrates that key top backgrounds to $\overrightarrow{H}{W}^{+}{W}^{-}\to {\mathcal{l}}^{\pm }{\mathcal{l}}^{\mp }{p}_T$ decays in weak boson fusion (WBF) and gluon fusion (GF) at the CERN Large Hadron Collider can be extrapolated from experimental data with an accuracy of order 5% to 10%. If LO scale variation is accepted as proxy for the theoretical error, parton level results indicate that the $t\overline{t}j$ background to the $\overrightarrow{H}\mathrm{WW}$ search in WBF can be determined with a theoretical error of about 5%, while the $t\overline{t}$ background to the $\overrightarrow{H}\mathrm{WW}$ search in GF can be determined with a theoretical error of better than 1%. Uncertainties in the parton distribution functions contribute an estimated 3% to 10% to the total error.

We apply the picture proposed in a previous Letter, which relates the hyperon polarization in unpolarized hadron-hadron collisions to the left-right asymmetry in singly polarized reactions, to the production of different hyperons in reactions using different projectiles and/or targets. We discuss the different ingredients of the proposed picture in detail and present the results for hyperon polarization in reactions such as pp, $K^{-}p,$ ${\pi }^{\pm }p,$ and ${\Sigma }^{-}p$ collisions. We compare the results with the available data and make predictions for future experiments.

Semileptonic decays of doubly heavy baryons are studied in the framework of the relativistic quark model. The doubly heavy baryons are treated in the quark-diquark approximation. The transition amplitudes of heavy diquarks bb and bc going, respectively, to bc and cc are explicitly expressed through the overlap integrals of the diquark wave functions in the whole accessible kinematic range. The relativistic baryon wave functions of the quark-diquark bound system are used for the calculation of the transition matrix elements, the Isgur-Wise function, and decay rates in the heavy quark limit.

The masses of two-gluon glueballs are studied with a semirelativistic potential model whose interaction is a scalar linear confinement supplemented by a one-gluon exchange mechanism. The gluon is massless but the leading corrections of the dominant part of the Hamiltonian are expressed in terms of a state-dependent constituent gluon mass. The Hamiltonian depends only on three parameters: the strong coupling constant, the string tension, and a gluon size, which removes all singularities in the leading corrections of the potential. Accurate numerical calculations are performed with a Lagrange mesh method. The masses predicted are in rather good agreement with lattice results and with some experimental glueball candidates.

Assuming a tricritical point of two-flavor QCD in the space of temperature, baryon number chemical potential, and quark mass, we study the change of the associated soft mode along the critical line within the Ginzburg-Landau approach and the Nambu–Jona-Lasinio model. The ordering density along the chiral critical line is the scalar density whereas a linear combination of the scalar, baryon number, and energy densities becomes the proper ordering density along the critical line with finite quark masses. It is shown that the critical eigenmode shifts from the sigma-like fluctuation of the scalar density to a hydrodynamic mode at the tricritical point, where we have two ordering densities, the scalar density and a linear combination of the baryon number and energy densities. We argue that the appearance of the critical eigenmode with hydrodynamic character is a logical consequence of divergent susceptibilities of the conserved densities.

We study the effects of a nonzero strangeness chemical potential ${\mu }_S$ on the color-flavor locked phase of dense quark matter. It is found that, depending on the value of ${\mu }_S,$ both the antikaon and kaon condensations may occur in color-flavor locked quark matter. The consequences of these condensations for the phase diagram of dense quark matter are investigated.

The photoproduction of bottom quarks in events with two jets and a muon has been measured with the ZEUS detector at HERA using an integrated luminosity of 110 ${\mathrm{pb}}^{\mathrm{-}1}$. The fraction of jets containing b quarks was extracted from the transverse momentum distribution of the muon relative to the closest jet. Differential cross sections for bottom production as a function of the transverse momentum and pseudorapidity of the muon, of the associated jet and of $x_{\gamma }^{\mathrm{jets}},$ the fraction of the photon’s momentum participating in the hard process, are compared with MC models and QCD predictions made at next-to-leading order. The latter give a good description of the data.

We derive the contribution of massless fermions to the 1-loop effective action for static $A_4$ and $A_i$ fields at high temperatures, for the $\mathrm{SU}\left(2\right)\mathrm{}$ gauge group assuming that gluon fields are slowly varying but allowing for an arbitrary amplitude of $A_4.$

A weakly coupled new neutral gauge boson forms a narrow resonance that is hard to discover directly in $e^{+}{e}^{-}$ collisions. However, if the gauge boson mass is below the center-of-mass energy, it can be produced through processes where the effective energy is reduced due to initial-state radiation and beamstrahlung. It is shown that at a high-luminosity linear collider, such a gauge boson can be searched for with very high sensitivity, leading to a substantial improvement compared to existing limits from the Tevatron and also extending beyond the expected reach of the LHC in most models. If a new vector boson is discovered either at the Tevatron Run II, the LHC, or the linear collider, its properties can be determined at the linear collider with high precision, thus helping to reveal the origin of the new boson.

We examine the neutralino relic density in the presence of a light top squark, such as the one required for the realization of the electroweak baryogenesis mechanism, within the minimal supersymmetric standard model. We show that there are three clearly distinguishable regions of parameter space, where the relic density is consistent with WMAP and other cosmological data. These regions are characterized by annihilation cross sections mediated by either light Higgs bosons, Z bosons, or by the co-annihilation with the lightest top squark. Tevatron collider experiments can test the presence of the light top squark in most of the parameter space. In the co-annihilation region, however, the mass difference between the light top squark and the lightest neutralino varies between 15 and 30 GeV, presenting an interesting challenge for top squark searches at hadron colliders. We present the prospects for direct detection of dark matter, which provides a complementary way of testing this scenario. We also derive the required structure of the high energy soft supersymmetry breaking mass parameters where the neutralino is a dark matter candidate and the top squark spectrum is consistent with electroweak baryogenesis and the present bounds on the lightest Higgs boson mass.

The exact two-particle energy eigenstates in a generic asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relations with the elastic scattering phases of the two particles in the continuum are obtained for both $D_4$ and $D_2$ symmetries. These results can be viewed as a generalization of the corresponding formulas in a cubic box obtained by Lüscher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these formulas are also discussed.

We explore the analytic structure of the gluon and quark propagators of Landau gauge QCD from numerical solutions of the coupled system of renormalized Dyson-Schwinger equations and from fits to lattice data. We find sizable negative norm contributions in the transverse gluon propagator indicating the absence of the transverse gluon from the physical spectrum. A simple analytic structure for the gluon propagator is proposed. For the quark propagator we find evidence for a masslike singularity on the real timelike momentum axis, with a mass of 350 to 500 MeV. Within the Green’s function approach that is employed, we identify a crucial term in the quark-gluon vertex that leads to a positive definite Schwinger function for the quark propagator.

We apply the background field method to calculate the moments of the pion two-particle twist-3 distribution amplitude ${\phi }_p\left(\xi \right)$ in QCD sum rules. In this paper, we do not use the equation of motion for the quarks inside the pion since they are not on shell and introduce a new parameter $m_0^p$ to be determined. We get the parameter $m_0^p\approx 1.30\mathrm{GeV}$ in this approach. If assuming the expansion of ${\phi }_p\left(\xi \right)$ in the series in Gegenbauer polynomials $C_n^{1/2}\left(\xi \right),$ one can obtain its approximate expression which can be determined by its first few moments.

We describe the use of doubly unintegrated parton distributions in hadron-hadron collisions, using the ${(z,k}_t)$-factorization prescription where the transverse momentum of the incoming parton is generated in the last evolution step. We apply this formalism to calculate the transverse momentum ${(P}_T)$ distributions of produced W and Z bosons and compare the predictions to Tevatron run 1 data. We find that the observed $P_T$ distributions can be generated almost entirely by the leading order $q_1{q}_2\to W,Z$ subprocesses, using known and universal doubly unintegrated quark distributions. We also calculate the $P_T$ distribution of the standard model Higgs boson at the LHC, where the dominant production mechanism is by gluon-gluon fusion.

A light collective ${\theta }^{+}$ baryon state (with strangeness +1) was predicted via rigid-rotor collective quantization of SU(3) chiral soliton models. This paper explores the validity of this treatment. A number of rather general analyses suggest that predictions of exotic baryon properties based on this approximation do not follow from large $N_c$ QCD. These include an analysis of the baryon’s width, a comparison of the predictions with general large $N_c$ consistency conditions of the Gervais-Sakita-Dashen-Manohar type; an application of the technique to QCD in the limit where the quarks are heavy; a comparison of this method with the vibration approach of Callan and Klebanov; and the ${1/N}_c$ scaling of the excitation energy. It is suggested that the origin of the problem lies in an implicit assumption in the that the collective motion is orthogonal to vibrational motion. While true for non-exotic motion, the Wess-Zumino term induces mixing at leading order between collective and vibrational motion with exotic quantum numbers. This suggests that successful phenomenological predictions of ${\theta }^{+}$ properties based on rigid-rotor quantization were accidental.

We discuss the energy scale profile of the bimaximal mixing which is given at the grand unified theory (GUT) energy scale in the minimal supersymmetry model, associated with an assumption that $Y_{\nu }^{†}{Y}_{\nu }$ is diagonal, where $Y_{\nu }$ is the neutrino-Yukawa coupling matrix. In this model, the Dirac mass matrix which appears in the seesaw neutrino mass matrix is determined by three neutrino masses, two relative Majorana phases and three heavy Majorana masses. All CP phases are related by two Majorana phases. We show that the requirement that the solar mixing angle moves from the maximal mixing at GUT to the observed one as the energy scale decreases by the renormalization effect. We discuss the leptogenesis and the lepton flavor violation process by assuming the universal soft breaking terms.

An analysis of spontaneously broken chiral symmetry in light-cone field theory is presented. The nonlocality inherent to light-cone field theory requires revision of the standard procedure in the derivation of Ward-Takahashi identities. We derive the general structure of chiral Ward-Takahashi identities and construct them explicitly for various model field theories. Gell-Mann–Oakes–Renner relations and relations between fermion propagators and the structure functions of Nambu-Goldstone bosons are discussed and the necessary modifications of the Ward-Takahashi identities due to the axial anomaly are indicated.