22,848 research outputs found

    Chiral Symmetry and the Residual Mass in Lattice QCD with the Optimal Domain-Wall Fermion

    Full text link
    We derive the axial Ward identity for lattice QCD with domain-wall fermions, and from which we obtain a formula for the residual mass (45)-(46), that can be used to measure the chiral symmetry breaking due to the finite extension Ns in the fifth dimension. Furthermore, we obtain an upper bound for the residual mass in lattice QCD with the optimal domain-wall fermion.Comment: 27 pages, 3 figures, v3: new formula for the upper-bound of residual mas

    Exact Pseudofermion Action for Monte Carlo Simulation of Domain-Wall Fermion

    Get PDF
    We present an exact pseudofermion action for hybrid Monte Carlo simulation (HMC) of one-flavor domain-wall fermion (DWF), with the effective 4-dimensional Dirac operator equal to the optimal rational approximation of the overlap-Dirac operator with kernel H=cHw(1+dΞ³5Hw)βˆ’1 H = c H_w (1 + d \gamma_5 H_w)^{-1} , where c c and d d are constants. Using this exact pseudofermion action, we perform HMC of one-flavor QCD, and compare its characteristics with the widely used rational hybrid Monte Carlo algorithm (RHMC). Moreover, to demonstrate the practicality of the exact one-flavor algorithm (EOFA), we perform the first dynamical simulation of the (1+1)-flavors QCD with DWF.Comment: 13 pages, 4 figures, v2: Simulation of (1+1)-flavors QCD with DWF, and references added. To appear in Phys. Lett.

    Testing Electroweak Baryogenesis with Future Colliders

    Get PDF
    Electroweak Baryogenesis (EWBG) is a compelling scenario for explaining the matter-antimatter asymmetry in the universe. Its connection to the electroweak phase transition makes it inherently testable. However, completely excluding this scenario can seem difficult in practice, due to the sheer number of proposed models. We investigate the possibility of postulating a "no-lose" theorem for testing EWBG in future e+e- or hadron colliders. As a first step we focus on a factorized picture of EWBG which separates the sources of a stronger phase transition from those that provide new sources of CP violation. We then construct a "nightmare scenario" that generates a strong first-order phase transition as required by EWBG, but is very difficult to test experimentally. We show that a 100 TeV hadron collider is both necessary and possibly sufficient for testing the parameter space of the nightmare scenario that is consistent with EWBG.Comment: 26 pages + references, 10 figures. Fixed minor typos, updated TLEP and 100 TeV projections. Conclusions unchange

    Extended Conformal Symmetry in d≠4d\neq 4: Conformal Symmetry of Abelian Gauge Theory in the Physical Sector

    Full text link
    Abelian gauge theory in d≠4d\neq 4 spacetime dimensions is an example of a scale invariant theory which does not possess conformal symmetry -- the special conformal transformation(SCT) explicitly breaks the gauge invariance of the theory. In this work, we construct a non-local gauge-invariant extension of the SCT, which is compatible with the BRST formalism and defines a new symmetry of the physical Hilbert space of the Maxwell theory for any dimension d⩾3d\geqslant 3. We prove the invariance of the Maxwell theory in d⩾3d\geqslant 3 by explicitly showing that the gauge-invariant two-point correlation functions, the action, and the classical equation of motion are unchanged under such a transformation.Comment: 23 page

    Tevatron Asymmetry of Tops in a W',Z' Model

    Full text link
    Recent results from the CDF Collaboration indicate the the top-pair forward-backward asymmetry is largest in regions of high rapidity difference βˆ£Ξ”y∣|\Delta y| and invariant mass MttΛ‰.M_{t\bar t}. We show that experimental observations can be explained by our previously proposed Asymmetric Left-Right Model (ALRM). The gauge symmetry Uβ€²(1)Γ—SUβ€²(2)Γ—SU(2)U'(1)\times SU'(2)\times SU(2) is broken by a triplet Higgs in the primed sector. The Wβ€²W' boson has a (t,d)(t,d) right-handed coupling and the Zβ€²Z' boson has diagonal fermion couplings. We determine the model parameters to be MWβ€²=700M_{W'} = 700 GeV, MZβ€²=1M_{Z'}=1 TeV, and charged current coupling g2β€²=3g'_2=3. The Wβ€²W' and Zβ€²Z' total decay widths are of O(100\mathcal{O}(100 GeV). The signals from Zβ€²β†’ttΛ‰Z'\to t\bar t and Wβ€²β†’tbW'\to tb at the LHC will test the model.Comment: 14 pages, 7 figures; typos corrected, references added. Version to appear in PL
    • …
    corecore