118371112
Observational constraints on Tachyon and DBI inflation
We present a systematic method for evaluation of perturbation observables in non-canonical single-field inflation models within the slow-roll approximation, which allied with field redefinitions enables predictions to be established for a wide range of models. We use this to investigate various non-canonical inflation models, including Tachyon inflation and DBI inflation. The Lambert function will be used extensively in our method for the evaluation of observables. In the Tachyon case, in the slow-roll approximation the model can be approximated by a canonical field with a redefined potential, which yields predictions in better agreement with observations than the canonical equivalents. For DBI inflation models we consider contributions from both the scalar potential and the warp geometry. In the case of a quartic potential, we find a formula for the observables under both non-relativistic (sound speed cs2 ~ 1) and relativistic behaviour (cs2 1) of the scalar DBI inflaton. For a quadratic potential we find two branches in the non-relativistic cs2 ~ 1 case, determined by the competition of model parameters, while for the relativistic case cs2 → 0, we find consistency with results already in the literature. We present a comparison to the latest Planck satellite observations. Most of the non-canonical models we investigate, including the Tachyon, are better fits to data than canonical models with the same potential, but we find that DBI models in the slow-roll regime have difficulty in matching the data.
119280900
Observational constraints on K-inflation models
We extend the ModeCode software of Mortonson, Peiris and Easther [1] to enable numerical computation of perturbations in K-inflation models, where the scalar field no longer has a canonical kinetic term. Focussing on models where the kinetic and potential terms can be separated into a sum, we compute slow-roll predictions for various models and use these to verify the numerical code. A Markov chain Monte Carlo analysis is then used to impose constraints from WMAP7 data on the addition of a term quadratic in the kinetic energy to the Lagrangian of simple chaotic inflation models. For a quadratic potential, the data do not discriminate against addition of such a term, while for a quartic (λ4) potential inclusion of such a term is actually favoured. Overall, constraints on such a term from present data are found to be extremely weak.
119087982
Inhomogeneous reheating scenario with DBI fields
We discuss a new mechanism which can be responsible for the origin of the primordial perturbation in inflationary models, the inhomogeneous DBI reheating scenario. Light DBI fields fluctuate during inflation, and finally create the density perturbations through modulation of the inflation decay rate. In this note, we investigate the curvature perturbation and its non-Gaussianity from this new mechanism. Presenting generalized expressions for them, we show that the curvature perturbation not only depends on the particular process of decay but is also dependent on the sound speed cs from the DBI action. More interestingly we find that the non-Gaussianity parameter fNL is independent of cs. As an application we exemplify some decay processes which give a viable and detectable non-Gaussianity. Finally we find a possible connection between our model and the DBI-Curvaton mechanism.
118740978
Constraints on Randall-Sundrum model from the events of dijet production with QCD next-to-leading order accuracy at the LHC
We study the dijet production in Randall-Sundrum model at the LHC with QCD next-to-leading(NLO) order accuracy. Our results show that the QCD NLO corrections can increase the total cross sections by more than $80\%$ and reduce the scale dependence. We also explore in detail several important kinematic distributions at the NLO level. Moreover, we discuss the upper limits of the KK graviton excluded mass range and the allowed parameter space for the coupling constant and KK graviton mass, using the experiment data.
123786527
Decay constants fp of unequal-mass pseudoscalar mesons in a Bethe-Salpeter framework using a generalized structure of hadron-quark vertex function
120721773
PRELIMINARY COMMISSIONING OF SUPERCONDUCTING MAGNETS AND CRYOGENIC SYSTEM OF BEPC II
A helium cryogenic system with cooling capacity of 1 kW at 4.5 K was set up at Institute of High Energy Physics, Chinese Academy of Sciences, Beijing. This helium refrigerating system is dedicated for the cooling of two superconducting radio frequency (SRF) cavities, two interaction region superconducting collision quadrupole (SCQ) magnets, a detector superconducting solenoid magnet (SSM), which are the key items of the upgrade project of Beijing Electron-Positron Collider (BEPC II). Commissioning with the detector and SCQ magnets was carried out, which will be introduced in this paper. The cryogenic system shows very robust as SSM quench. This paper presents the overall status and some test results of superconducting and cryogenic system.
119009381
Generalized structure of hadron-quark vertex function in Bethe-Salpeter framework : applications to leptonic decays of V-mesons
We employ the framework of the Bethe–Salpeter equation under a covariant instantaneous ansatz to study the leptonic decays of vector mesons. The structure of the hadron–quark vertex function Γ is generalized to include various Dirac covariants (other than iγ ⋅ e) from their complete set. They are incorporated in accordance with a naive power counting rule order-by-order in powers of the inverse of the meson mass. The decay constants for ρ, ω and mesons are calculated with the incorporation of leading-order covariants.
118850750
Exotic hadron production in quark combination model
The philosophy on production of exotic hadrons (multi-quark states) in the framework of quark combination model is investigated, taking f0(980) as an example. The production rate and pT spectra of f0(980) considered as (ss̄) or (sq̄s̄q) respectively, are calculated and compared in Au+Au collisions at √ sNN = 200GeV . The unitarity of various combination models, when open for exotic hadron production, is addressed.