Modern Physics Letters A

We discuss the U(1)_X extensions of the standard model with focus on the Stueckelberg mechanism for mass growth for the extra U(1)_X gauge boson. The assumption of an axionic connector field which carries dual U(1) quantum numbers, i.e. quantum numbers for the hypercharge U(1)_Y and for the hidden sector gauge group U(1)_X, allows a nontrivial mixing between the mass growth for the neutral gauge vector bosons in the SU(2)_L × U(1)_Y sector and the mass growth for the vector boson by the Stueckelberg mechanism in the U(1)_X sector. This results in an extra Z′ which can be very narrow, but still detectable at the Large Hadron Collider (LHC). The U(1)_X extension of the minimal supersymmetric standard model is also considered and the role of the Fayet–Illiopoulos term in such an extension discussed. The U(1)_X extensions of the SM and of the MSSM lead to new candidates for dark matter.

A regular wormhole solution in gravity coupled with a phantom scalar and electromagnetic fields is found. The solution exists for a special choice of the parameter f of the potential term. The mass m of a wormhole filled with a phantom and electrostatic fields is calculated. It is shown that close to some point f₀, a small value of the mass m is the remainder of two large masses of the phantom and electrostatic fields. The connection with the renormalization procedure in quantum filed theory is considered. The connection between Wheeler's idea "mass without mass" and renormalization procedure in quantum field theory is discussed.

Most of current Monte Carlo studies on the Higgs searching are based on LO, or NLO calculation. However, in recent years, the next-to-next-to-leading order (NNLO) corrections have been computed for some physics process, and found that the cross section increases the kinematics changes. As the results, the analysis results could be impacted by these high order QCD corrections. We use standard Monte Carlo generator for LO, as well as MC@NLO for NLO and ResBos for NNLO at 7 TeV of LHC to evaluate this impact for physics channel of the Higgs, mass at 165 GeV, to WW, then W decay to lepton and neutrino as the final states. We found the signal rate could be effected by ratio of 1:2.6:3.4 for LO, NLO and NNLO using the same standard H→WW→lνlν searching analysis process.⁶

The kinematical model j(z) = j₀ and dynamical model w_de(z) = w₀, are constrained from the latest observational data: Union2 data including 557 type Ia supernovae (SNIa), 15 observational Hubble data (OHD), baryon acoustic oscillation (BAO) data from Sloan Digital Sky Survey (SDSS) and Two-degree Field Galaxy Redshift Survey (2dFGRS) and CMB data from seven-year WMAP. We get the current values of deceleration parameter q₀, jerk parameter j₀, dimensionless matter density Ω_m, equation of state for dark energy w₀ and transition redshift z_T. Furthermore, it is shown that for both kinematical and dynamical models, the constraint results support for the cosmic concordance model, ΛCDM.

We show that the transverse momentum (p_T) spectrum of Z boson production measured at Fermilab Tevatron can be well reproduced by leading-order event generators if Z + 1 jet processes are included with a proper solution for the double-count problem and if the parton shower (PS) branch kinematics are defined appropriately. The choice of the PS evolution variable does not definitely determine the low-p_T behavior. Our new event generator employing the limited leading-log (LLL) subtraction and a built-in leading-log PS reproduces the spectrum very well, not only in large p_T regions but also at low p_T down to p_T = 0.

We find exact solution of the Einstein equations in the context of the braneworld scenario. We assumed a generalized Chaplygin gas equation of state for bulk. This study displays a constant energy density and pressure for bulk in late time. It is shown that our assumptions impose a specific equation of state on brane. In this work, we obtain a decelerate universe in early time and late time. In the end, it is shown that under some assumption we can obtain equation of state of cosmological constant for bulk.

In this paper, we investigate the validity of the generalized second law of thermodynamics (GSLT) in the DGP braneworld. The boundary of the universe is assumed to be enclosed by the dynamical apparent horizon or the event horizon. The universe is chosen to be homogeneous and isotropic and the validity of the first law has been assumed here. The matter in the universe is taken in the form of non-interacting two-fluid system: one component is the holographic dark energy and the other component is in the form of dust.