In the standard model in universal extra dimensions (UED) the mass of the Higgs field is driven to the cutoff of the higher-dimensional theory. This re-introduces a small hierarchy since the compactification scale 1/R should not be smaller than the weak scale. In this paper we study possible solutions to this problem by considering five-dimensional theories where the Higgs field potential vanis...

where i denotes the color of a quark and f its flavor. DμΨ i = ∂μΨ i + igAμ(t )jΨ j where t are matrices representing the gauge group generators in the quark representation; in QCD the quarks belong to the fundamental 3 representation of the SU(3)C so t a is 1 2 ×Gell-Mann matrix λ. The Quantum ChromoDynamics is more complicated, even at the Lagrangian level: including the gauge-fixing and the ...

Are heavy quarks produced thermally or only by hard parton collisions? What is the probability that a produced heavy quark or antiquark is observed in a given resonance?

A new approach to determine the LHC luminosity is investigated. Instead of employing the proton–proton luminosity measurement, we suggest to measure directly the parton– parton luminosity. It is shown that the electron and muon pseudorapidity distributions, originating from the decay of W, W and Z bosons produced at 14 TeV pp collisions (LHC), constrain the x distributions of sea and valence qu...

The subject of the nucleon’s spin composition has been intensely studied and has produced important and surprising insights, beginning with the revelation that the majority of its spin is carried by quark and gluonic orbital angular momenta and gluon spin rather than by quark helicity. In addition, considerable effort has gone into understanding, predicting and measuring the transversity distri...

Corrections to the exact heavy–quark symmetry results are expected to follow the 1/mQ mass effect of the heavy–quark. We show, by an explicit calculation, that there is something other than the mass effect that suppresses the breaking of the spin symmetry.

The Minimal Supersymmetric Standard Model (MSSM) provides an abundant opportunity for discovering New Physics in CP -violating and/or flavor-changing b quark processes. In fact, the most general version of the MSSM provides an over-abundance, with 12 masses, 30 mixing angles and 27 phases in the (s)quark sector, beyond those of the Standard Model. Of these, the LHC has only limited ability to g...

The generation of the baryon asymmetry of the universe is considered in the standard model of the electroweak theory with simple extensions of the Higgs sector. The propagation of quarks of masses up to about 5 GeV are considered, taking into account their markedly different dispersion relations due to propagation through the hot elec-troweak plasma. It is shown that the contribution of these l...

We show how the operator product expansion evaluated in the approximation of ignoring gluons leads to the covariant formulation of the quark parton model. We discuss the connection with other formulations and show how the free quark model prediction, g2 = 0, changes smoothly into the Wandzura-Wilczek (WW) relation for quark masses small relative to the nucleon mass. Previous contradictory parto...

We compute the three-loop relation between the pole and the minimally subtracted quark mass allowing for virtual effects from a second massive quark. We also consider the analogue effects for the on-shell wave function renormalization constant. PACS numbers: 12.38.Bx 12.38.-t 14.65.Dw 14.65.Fy