Search for anomalous top quark production at the early LHC

We present a detailed study of the anomalous top quark production with subsequent decay at the LHC induced by model-independent flavor-changing neutral-current couplings, incorporating the complete next-to-leading order QCD effects. Our results show that, taking into account the current limits from the Tevatron, the LHC with $\sqrt{s}=7$ TeV may discover the anomalous coupling at 5$\sigma$ level for a very low integrated luminosity of 61 pb$^{-1}$. The discovery potentials for the anomalous couplings at the LHC are examined in detail. We also discuss the possibility of using the charge ratio to distinguish the $tug$ and $tcg$ couplings.Comment: 4 pages, 3 figures, version appears in Phys. Rev. Let

t→cVt\to cV via SUSY FCNC couplings in the unconstrained MSSM

We recalculate the branching ratios for $t\to cV$ ($V=g,\gamma,Z$) induced by SUSY FCNC couplings within the general unconstrained MSSM framework using mass eigenstate approach. Our results show that the branching ratios for these decays are larger than ones reported in previous literatures in the MSSM with R-parity conservation, and they can reach $\sim 10^{-4}$, $\sim 10^{-6}$, and $\sim 10^{-6}$, respectively, for favorable parameter values allowed by current precise experiments. Thus, the branching ratios for $t\to cg$ and $t\to c\gamma$ may be measurable at the LHC.Comment: 15 pages, 3 figures, minor changs in the Table

Terahertz Atmospheric Windows for High Angular Resolution Terahertz Astronomy from Dome A

Atmospheric transmission from Dome A, Antarctica, presents new possibilities in the field of terahertz astronomy, where space telescopes have been the only observational tools until now. Using atmospheric transmission measurements from Dome A with a Fourier transform spectrometer, transmission spectra and long-term stabilities have been analyzed at 1.461 THz, 3.393 THz, 5.786 THz and 7.1 THz, which show that important atmospheric windows for terahertz astronomy open for a reasonable length of time in the winter season. With large aperture terahertz telescopes and interferometers at Dome A, high angular resolution terahertz observations are foreseen of atomic fine-structure lines from ionized gas and a water ice feature from protoplanetary disks.Comment: 6 pages, 3 figures, to appear in Advances in Polar Scienc

Soft Gluon Resummation Effects in Single Slepton Production at Hadron Colliders

We investigate QCD effects in the production of a single slepton at hadron colliders in the Minimal Supersymmetric Standard Model without R-parity. We calculate the total cross sections and the transverse momentum distributions at next-to-leading order in QCD. The NLO corrections enhance the total cross sections and decrease the dependence of the total cross sections on the factorization and renormalization scales. For the differential cross sections, we resum all order soft gluon effects to give reliable predictions for the transverse momentum distributions. We also compare two approaches to the non-perturbative parametrization and found that the results are slightly different at the Tevatron and are in good agreement at the LHC. Our results can be useful to the simulation of the events and to the future collider experiments.Comment: 26 pages, 12 figures, RevTeX4; Minor changes; Version to appear in PR

Threshold Resummation Effects in Direct Top Quark Production at Hadron Colliders

We investigate the threshold-enhanced QCD corrections to the cross sections for direct top quark productions induced by model-independent flavor changing neutral current couplings at hadron colliders. We use the soft-collinear effective theory to describe the incoming massless partons and use the heavy quark effective theory to treat the top quark. Then we construct the flavor changing operator based on the above effective theories, and resum the large logarithms near threshold arising from soft gluon emission. Our results show that the resummed QCD corrections further enhance the next-to-leading order cross sections significantly. Moreover, the resummation effects vastly reduce the dependence of the cross sections on the renormalization and factorization scales, especially in cases where the next-to-leading order results behave worse than the leading order results. Our results are more sensitive to the new physics effects. If signals of direct top quark production are found in future experiments, it is more appropriate to use our results as the theoretical inputs for extracting the anomalous couplings.Comment: 5 pages, 4 figures, use revtex4 and amsmath; version to appear in Phys. Rev.

Next-to-Leading Order QCD Corrections to the Direct Top Quark Production via Model-independent FCNC Couplings at Hadron Colliders

We calculated the next-to-leading order (NLO) QCD corrections to the cross sections for direct top quark productions induced by model--independent flavour changing neutral current couplings at hadron colliders. The NLO results increase the experimental sensitivity to the anomalous couplings. Our results show that the NLO QCD corrections enhance the leading order (LO) total cross sections at the Tevatron Run 2 about 60% for both of $\kappa_{tc}^g$ and $\kappa_{tu}^g$ couplings, and enhance the LO total cross sections at the LHC about 40% for $\kappa_{tc}^g$ couplings and 50% for $\kappa_{tu}^g$ couplings, respectively. Moreover, the NLO QCD corrections vastly reduce the dependence of the total cross sections on the renormalization or factorization scale, which leads to increased confidence in predictions based on these results.Comment: 15 pages, 4 figures; published versio

Quantum Stochastic Neural Network and Sentence Classification

Computers has been endowed with a part of human-like intelligence owing to the rapid development of the artificial intelligence technology represented by the neural networks. Facing the challenge to make machines more imaginative, we consider a quantum stochastic neural network (QSNN), and propose a learning algorithm to update the parameters governing the network evolution. The QSNN can be applied to a class of classification problems, we investigate its performance in sentence classification and find that the coherent part of the quantum evolution can accelerate training, and improve the accuracy of verses recognition which can be deemed as a quantum enhanced associative memory. In addition, the coherent QSNN is found more robust against both label noise and device noise so that it is a more adaptive option for practical implementation

Correlated Quantum Memory: Manipulating Atomic Entanglement via Electromagnetically Induced Transparency

We propose a feasible scheme of quantum state storage and manipulation via electromagnetically induced transparency (EIT) in flexibly $united$ multi-ensembles of three-level atoms. For different atomic array configurations, one can properly steer the signal and the control lights to generate different forms of atomic entanglement within the framework of linear optics. These results shed new light on designing the versatile quantum memory devices by using, e.g., an atomic grid.Comment: 5 pages, 1 figur