1,117 research outputs found
Searching for the signal of dark matter and photon associated production at the LHC beyond leading order
We study the signal of dark matter and photon associated production induced
by the vector and axial-vector operators at the LHC, including the QCD
next-to-leading order (NLO) effects. We find that the QCD NLO corrections
reduce the dependence of the total cross sections on the factorization and
renormalization scales, and the factors increase with the increasing of the
dark matter mass, which can be as large as about 1.3 for both the vector and
axial-vector operators. Using our QCD NLO results, we improve the constraints
on the new physics scale from the results of the recent CMS experiment.
Moreover, we show the Monte Carlo simulation results for detecting the
\gamma+\Slash{E}_{T} signal at the QCD NLO level, and present the integrated
luminosity needed for a discovery at the 14 TeV LHC . If the signal
is not observed, the lower limit on the new physics scale can be set.Comment: 19 pages, 18 figures, 2 tables, version published in Phys.Rev.
Renormalization-group improved predictions for Higgs boson production at large
We study the next-to-next-to-leading logarithmic order resummation for the
large Higgs boson production at the LHC in the framework of
soft-collinear effective theory. We find that the resummation effects reduce
the scale uncertainty significantly and decrease the QCD NLO results by about
in the large region. The finite top quark mass effects and the
effects of the NNLO singular terms are also discussed.Comment: 31 pages, 17 figures, version published in Phys.Rev.
Phenomenology of an Extended Higgs Portal Inflation Model after Planck 2013
We consider an extended inflation model in the frame of Higgs portal model,
assuming a nonminimal coupling of the scalar field to the gravity. Using the
new data from Planck and other relevant astrophysical data, we obtain
the relation between the nonminimal coupling and the self-coupling
needed to drive the inflation, and find that this inflationary model
is favored by the astrophysical data. Furthermore, we discuss the constraints
on the model parameters from the experiments of particle physics, especially
the recent Higgs data at the LHC.Comment: 21 pages, 8 figures; Version published in EPJ
Hubble Tension: The Evidence of New Physics
The CDM model provides a good fit to most astronomical observations
but harbors large areas of phenomenology and ignorance. With the improvements
in the precision and number of observations, discrepancies between key
cosmological parameters of this model have emerged. Among them, the most
notable tension is the 4 to 6 deviation between the Hubble
constant () estimations measured by the local distance ladder and the
cosmic microwave background (CMB) measurement. In this review, we revisit the
tension based on the latest research and sort out evidence from
solutions to this tension that might imply new physics beyond the CDM
model. The evidence leans more towards modifying the late-time universe.Comment: 39 pages, 6 figures, 3 tables, accepted for publication in Universe
(invited review for Special Issue: Advances in Astrophysics and Cosmology -
in Memory of Prof. Tan Lu
Constraints on flavor-changing neutral-current couplings from the signal of associated production with QCD next-to-leading order accuracy at the LHC
We study a generic Higgs boson and a top quark associated production via
model-independent flavor-changing neutral-current couplings at the LHC,
including complete QCD next-to-leading order (NLO) corrections to the
production and decay of the top quark and the Higgs boson. We find that QCD NLO
corrections can increase the total production cross sections by about 48.9% and
57.9% for the and coupling induced processes at the LHC,
respectively. After kinematic cuts are imposed on the decay products of the top
quark and the Higgs boson, the QCD NLO corrections are reduced to 11% for the
coupling induced process and almost vanish for the coupling induced
process. Moreover, QCD NLO corrections reduce the dependence of the total cross
sections on the renormalization and factorization scales. We also discuss
signals of the associated production with the decay mode t \rightarrow
bl^{+}E \slash_{T}, H \rightarrow b\bar{b} and production with the
decay mode \bar{t} \rightarrow H\bar{q}, t\rightarrow bl^{+}E \slash_{T}. Our
results show that, in some parameter regions, the LHC may observe the above
signals at the level. Otherwise, the upper limits on the FCNC
couplings can be set.Comment: 28 pages, 14 figures, 5 tables; version published in PR
Single nonmagnetic impurity resonance in FeSe-based 122-type superconductors as a probe for pairing symmetry
We study the effect of a single non-magnetic impurity in
AFeSe (A=K, Rb, or Cs) superconductors by considering
various pairing states based on a three-orbital model consistent with the
photoemission experiments. The local density of states on and near the impurity
site has been calculated by solving the Bogoliubov-de Gennes equations
self-consistently. The impurity-induced in-gap bound states are found only for
attractive impurity scattering potential, as in the cases of doping of Co or
Ni, which is characterized by the strong particle-hole asymmetry, in the
nodeless wave pairing state. This property may be used to probe
the pairing symmetry of FeSe-based 122-type superconductors.Comment: 7 pages, 7 figure
First-principles prediction of coexistence of magnetism and ferroelectricity in rhombohedral Bi2FeTiO6
First principles calculations based on the density functional theory within
the local spin density approximation plus U(LSDA+U)scheme, show rhombohedral
BiFeTiO is a potential multiferroic in which the magnetism and
ferroelectricity coexist . A ferromagnetic configuration with magnetic moment
of 4 per formula unit have been reported with respect to the minimum
total energy. Spontaneous polarization of 27.3 C/cm, caused mainly by
the ferroelectric distortions of Ti, was evaluated using the berry phase
approach in the modern theory of polarization. The Bi-6s stereochemical
activity of long-pair and the `d-ness' criterion in off-centring of Ti were
coexisting in the predicted new system. In view of the oxidation state of
Bi,Fe,Ti, and O from the orbital-resolved density
of states of the Bi-6p, Fe-3d,Ti-3d, and O-2p states,the valence state of
BiFeTiO in the rhombohedral phase was found to be
BiFeTiO.Comment: 22 pages, 9 figures. submitted to Physics Letters
Thermal properties of MECDP copolyesters
MECDP copolyesters based on poly(ethylene terephthalate) were prepared with sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate and poly(ethylene glycol) units as modifiers. Thermal properties of these copolyesters were characterized by differential scanning calorimetry and thermal gravity analyzer. Experimental results indicated that glass transition temperature, melting temperature and thermal degradation temperature reduced with increasing the poly(ethylene glycol) content. The incorporation of poly(ethylene glycol) increased the flexibility and irregularity of molecular chains which led to lower crystallinity, and bought more ether bonds into molecular chains. Besides, the thermal degradation under oxygen condition happened easily compared to that under nitrogen condition
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