3,168 research outputs found
Quantum Hall Effect in Thin Films of Three-Dimensional Topological Insulators
We show that a thin film of a three-dimensional topological insulator (3DTI)
with an exchange field is a realization of the famous Haldane model for quantum
Hall effect (QHE) without Landau levels. The exchange field plays the role of
staggered fluxes on the honeycomb lattice, and the hybridization gap of the
surface states is equivalent to alternating on-site energies on the AB
sublattices. A peculiar phase diagram for the QHE is predicted in 3DTI thin
films under an applied magnetic field, which is quite different from that
either in traditional QHE systems or in graphene.Comment: 4 pages, 4 figure
A topological look at the quantum spin Hall state
We propose a topological understanding of the quantum spin Hall state without
considering any symmetries, and it follows from the gauge invariance that
either the energy gap or the spin spectrum gap needs to close on the system
edges, the former scenario generally resulting in counterpropagating gapless
edge states. Based upon the Kane-Mele model with a uniform exchange field and a
sublattice staggered confining potential near the sample boundaries, we
demonstrate the existence of such gapless edge states and their robust
properties in the presence of impurities. These gapless edge states are
protected by the band topology alone, rather than any symmetries.Comment: 5 pages, 4 figure
Top-Quark Decay at Next-to-Next-to-Leading Order in QCD
We present the complete calculation of the top-quark decay width at
next-to-next-to-leading order in QCD, including next-to-leading electroweak
corrections as well as finite bottom quark mass and boson width effects. In
particular, we also show the first results of the fully differential decay
rates for top-quark semileptonic decay at
next-to-next-to-leading order in QCD. Our method is based on the understanding
of the invariant mass distribution of the final-state jet in the singular limit
from effective field theory. Our result can be used to study arbitrary
infrared-safe observables of top-quark decay with the highest perturbative
accuracy.Comment: 5 pages, 6 figures; version accepted for publication in Physical
Review Letter
Resummation prediction on top quark transverse momentum distribution at large pT
We study the factorization and resummation of t-channel top quark transverse
momentum distribution at large pT in the SM at both the Tevatron and the LHC
with soft-collinear effective theory. The cross section in the threshold region
can be factorized into a convolution of hard, jet and soft functions. In
particular, we first calculate the NLO soft functions for this process, and
give a RG improved cross section by evolving the different functions to a
common scale. Our results show that the resummation effects increase the NLO
results by about 9%-13% and 4%-9% when the top quark pT is larger than 50 and
70 GeV at the Tevatron and the 8 TeV LHC, respectively. Also, we discuss the
scale independence of the cross section analytically, and show how to choose
the proper scales at which the perturbative expansion can converge fast.Comment: 32 pages, 10 figures, version published in Phys.Rev.
Thermodynamics of hadrons using the Gaussian functional method in the linear sigma model
We investigate thermodynamics of hadrons using the Gaussian functional method
(GFM) at finite temperature. Since the interaction among mesons is very large,
we take into account fluctuations of mesons around their mean field values
using the GFM. We obtain the ground state energy by solving the Schr\"{o}dinger
equation. The meson masses are obtained using the energy minimization
condition. The resulting mass of the Nambu-Goldstone boson is not zero even in
the spontaneous chiral symmetry broken phase due to the non-perturbative
effect. We consider then the bound state of mesons using the Bethe-Salpeter
equation and show that the Nambu-Goldstone theorem is recovered. We investigate
further the behavior of the meson masses and the mean filed value as functions
of temperature for the cases of chiral limit and explicit chiral symmetry
breaking.Comment: 5 pages, 8 figures, contribution to proceedings of XV International
Conference on Hadron Spectroscopy-Hadron 201
Next-to-leading order QCD corrections to associated production via the flavor-changing neutral-current couplings at hadron colliders
We present the complete next-to-leading order (NLO) QCD corrections to
associated production induced by the model-independent and
flavor-changing neutral-current couplings at hadron colliders, respectively.
Our results show that, for the coupling the NLO QCD corrections can
enhance the total cross sections by about 60% and 42%, and for the
coupling by about 51% and 43% at the Tevatron and LHC, respectively. The NLO
corrections, for the couplings, can enhance the total cross sections by
about 27%, and by about 42% for the coupling at the LHC. We also consider
the mixing effects between the and couplings for this process,
which can either be large or small depending on the values of the anomalous
couplings. Besides, the NLO corrections reduce the dependence of the total
cross sections on the renormalization or factorization scale significantly,
which lead to increased confidence on the theoretical predictions. And we also
evaluate the NLO corrections to several important kinematic distributions.Comment: Published version in Phys. Rev.
Threshold Resummation Effects in Neutral Higgs Boson Production by Bottom Quark Fusion at the CERN Large Hadron Collider
We investigate the QCD effects in the production of neutral Higgs bosons via
bottom quark fusion in both the standard model and the minimal supersymmetric
standard model at the CERN Large Hadron Collider. We include the
next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) and
the threshold resummation effects. We use the soft-collinear effective theory
to resum the large logarithms near threshold from soft gluon emission. Our
results show that the resummation effects can enhance the total cross sections
by about 5% compared with the NLO results.Comment: 29pages, 14 figures, version to appear in Physical Review
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