562 research outputs found
Dynamical Computation on Coefficients of Electroweak Chiral Lagrangian from One-doublet and Topcolor-assisted Technicolor Models
Based on previous studies deriving the chiral Lagrangian for pseudo scalar
mesons from the first principle of QCD, we derive the electroweak chiral
Lagrangian and build up a formulation for computing its coefficients from
one-doublet technicolor model and a schematic topcolor-assisted technicolor
model. We find that the coefficients of the electroweak chiral Lagrangian for
the topcolor-assisted technicolor model are divided into three parts: direct
TC2 interaction part, TC1 and TC2 induced effective Z' particle contribution
part, and ordinary quarks contribution part. The first two parts are computed
in this paper and we show that the direct TC2 interaction part is the same as
that in the one-doublet technicolor model, while effective Z' contributions are
at least proportional to the p^2 order parameter \beta_1 in the electroweak
chiral Lagrangian and typical features of topcolor-assisted technicolor model
are that it only allows positive T and U parameters and the T parameter varies
in the range 0\sim 1/(25\alpha), the upper bound of T parameter will decrease
as long as Z' mass become large. The S parameter can be either positive or
negative depending on whether the Z' mass is large or small. The Z' mass is
also bounded above and the upper bound depend on value of T parameter. We
obtain the values for all the coefficients of the electroweak chiral Lagrangian
up to order of p^4.Comment: 52 pages, 15 figure
Next-to-leading order QCD predictions for associated production at the CERN Large Hadron Collider
We calculate the complete next-to-leading-order (NLO) QCD corrections
(including SUSY QCD corrections) to the inclusive total cross sections of the
associated production processes in the minimal
supersymmetric standard model (MSSM) at the CERN Large Hadron Collider (LHC).
Our results show that the enhancement of the total cross sections from the NLO
QCD corrections can reach for 200 GeV GeV and
. The scale dependence of the total cross section is improved by
the NLO corrections, which is less than 5%. We also show the Monte Carlo
simulation results for the signature including the
complete NLO QCD effects, and find an observable signature above the standard
model (SM) background for a normal luminosity of 100 fb at the LHC.Comment: Published version in Phys.Rev.
Black hole scalarizations induced by parity violations
It is well-known that parity symmetry is broken in the weak interaction but
conserved for Einstein's general relativity and Maxwell's electromagnetic
theory. Nevertheless, parity symmetry could also be violated in the
gravitational/electromagnetic sectors if a fundamental scalar field couples to
the parity-violating gravitational/electromagnetic curvature terms. Such
parity-violating terms, which flip signs under reversed spatial directions, can
inevitably lead to a negative effective mass squared for the scalar field
perturbations near nonspherically symmetric black holes and thus are expected
to trigger tachyonic instability. As illustrative examples, we show that the
scalar field coupled to gravitational/electromagnetic Chern-Simons terms near a
Kerr-Newmann spacetime can develop tachyonic instabilities, leading to
equilibrium scalar field configurations in certain parameter regions of black
holes. This instability, which is an indication of the black hole scalarization
process, can occur in a broad class of nonspherically symmetric black holes and
parity-violating theories.Comment: 9 pages, 3 figures, 1 tabl
Model independent analysis of top quark forward-backward asymmetry at the Tevatron up to \mathcal{O}(\as^2/\Lambda^2)
We present the complete calculations of the forward-backward asymmetry
() and the total cross section of top quark pair production induced
by dimension-six four quark operators at the Tevatron up to
\mathcal{O}(\as^2/\Lambda^2). Our results show that next-to-leading order
(NLO) QCD corrections can change and the total cross section by
about 10%. Moreover, NLO QCD corrections reduce the dependence of
and total cross section on the renormalization and factorization scales
significantly. We also evaluate the total cross section and the charge
asymmetry () induced by these operators at the Large Hadron Collider
(LHC) up to \mathcal{O}(\as^2/\Lambda^2), for the parameter space allowed by
the Tevatron data. We find that the value of induced by these
operators is much larger than SM prediction, and LHC has potential to discover
these NP effects when the measurement precision increases.Comment: 25 pages, 10 figures; final version in PR
Production properties of deuterons, helions and tritons via an analytical nucleon coalescence method in Pb-Pb collisions at TeV
We improve a nucleon coalescence model to include the coordinate-momentum
correlation in nucleon joint distributions, and apply it to Pb-Pb collisions at
TeV to study production properties of deuterons (),
helions (He) and tritons (). We give formulas of the coalescence factors
and , and naturally explain their behaviors as functions of the
collision centrality and the transverse momentum per nucleon . We
reproduce the transverse momentum spectra, averaged transverse momenta and
yield rapidity densities of , He and , and find the system effective
radius obtained in the coalescence production of light nuclei behaves similarly
to Hanbury Brown-Twiss interferometry radius. We particularly give expressions
of yield ratios , He, , He, , He,
He and argue their nontrivial behaviors can be used to distinguish
production mechanisms of light nuclei.Comment: 12 pages, 8 figures, 1 tabl
General bubble expansion at strong coupling
The strongly-coupled system like the quark-hadron transition (if it is of
first order) is becoming an active play-yard for the physics of cosmological
first-order phase transitions. However, the traditional field theoretic
approach to strongly-coupled first-order phase transitions is of great
challenge, driving recent efforts from holographic dual theories with explicit
numerical simulations. These holographic numerical simulations have revealed an
intriguing linear correlation between the phase pressure difference (pressure
difference away from the wall) to the non-relativistic terminal velocity of an
expanding planar wall, which has been reproduced analytically alongside both
cylindrical and spherical walls from perfect-fluid hydrodynamics in our
previous study but only for a bag equation of state. We have also found in our
previous study a universal quadratic correlation between the wall pressure
difference (pressure difference near the bubble wall) to the non-relativistic
terminal wall velocity regardless of wall geometries. In this paper, we will
generalize these analytic relations between the phase/wall pressure difference
and terminal wall velocity into a more realistic equation of state beyond the
simple bag model, providing the most general predictions so far for future
tests from holographic numerical simulations of strongly-coupled first-order
phase transitionsComment: 22 pages, 10 figure
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