X(1835): A Possible Baryonium?

We point out that (1) the large $p\bar p$ coupling and suppressed mesonic coupling of X(1835) and (2) the suppression of the three-body strange final states strongly indicate that X(1835) may be a $p\bar p$ baryonium. We also point out that the branching ratio of $X(1835)\to\eta \pi\pi$ should be bigger than that of $X(1835)\to\eta^\prime \pi\pi$. If BES further confirms the non-observation of X(1835) in the $\eta\pi\pi$ channel, that will be very puzzling. Finally, X(1835) may be used a tetraquark generator if X(1835) is really established as a baryonium state.Comment: Comments and suggestions welcom

The Role of Tensor Force in Heavy-Ion Fusion Dynamics

The tensor force is implemented into the time-dependent Hartree-Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The role of tensor force on fusion dynamics is systematically investigated for $^{40}\mathrm{Ca}+\mathrm{^{40}Ca}$, $^{40}\mathrm{Ca}+\mathrm{^{48}Ca}$, $^{48}\mathrm{Ca}+\mathrm{^{48}Ca}$, $^{48}\mathrm{Ca}+\mathrm{^{56}Ni}$, and $^{56}\mathrm{Ni}+\mathrm{^{56}Ni}$ reactions which vary by the total number of spin-unsaturated magic numbers in target and projectile. A notable effect on fusion barriers and cross sections is observed by the inclusion of tensor force. The origin of this effect is analyzed. The influence of isoscalar and isovector tensor terms is investigated with the T$IJ$ forces. These effects of tensor force in fusion dynamics are essentially attributed to the shift of low-lying vibration states of colliding partners and nucleon transfer in the asymmetric reactions. Our calculations of above-barrier fusion cross sections also show that tensor force does not significantly affect the dynamical dissipation at near-barrier energies

Renormalization group improved predictions for ttˉW±t\bar{t}W^\pm production at hadron colliders

We study the factorization and resummation of the $t\bar{t}W^\pm$ production at hadron colliders. The cross section in the threshold limit can be factorized into a convolution of hard and soft functions and parton distribution functions with the soft-collinear effective theory. We calculate the next-to-leading order soft function for the associated production of the heavy quark pair and colorless particle, and we perform the resummation calculation with the next-to-next-to-leading logarithms accuracy. Our results show that the resummation effects reduce the dependence of the cross section on the scales significantly and increase the total cross section by $7-13\%$ compared with NLO QCD results.Comment: 23 pages, 7 figures and 2 tables; final version in PR

Light axigluon and single top production at the LHC

The light axigluon model can explain the Tevatron $t\overline{t}$ forward-backward asymmetry and at the same time satisfy the constraints from the electroweak precision measurement and the $ATLAS$ and $CMS$ data, which induces the flavor changing ($FC$) couplings of axigluon with the $SM$ and new quarks. We investigate the effects of these $FC$ couplings on the s- and t-channel single top productions at the $LHC$ and the $FC$ decays $Z\rightarrow \overline{b}s+b\overline{s}$, $t\rightarrow c\gamma$ and $cg$. Our numerical results show that the light axigluon can give significantly contributions to single top production and the rare top decays $t\rightarrow c\gamma$ and $cg$.Comment: 22 pages, 8 figures; references added, contributions of new quarks to rare decay processes adde

Intrinsically Motivated Learning of Visual Motion Perception and Smooth Pursuit

We extend the framework of efficient coding, which has been used to model the development of sensory processing in isolation, to model the development of the perception/action cycle. Our extension combines sparse coding and reinforcement learning so that sensory processing and behavior co-develop to optimize a shared intrinsic motivational signal: the fidelity of the neural encoding of the sensory input under resource constraints. Applying this framework to a model system consisting of an active eye behaving in a time varying environment, we find that this generic principle leads to the simultaneous development of both smooth pursuit behavior and model neurons whose properties are similar to those of primary visual cortical neurons selective for different directions of visual motion. We suggest that this general principle may form the basis for a unified and integrated explanation of many perception/action loops.Comment: 6 pages, 5 figure

Four-part differential leukocyte count using μflow cytometer

This paper reports the four-part differential leukocyte count (DLC) of human blood using a MEMS microflow (μflow) cytometer. It is achieved with a two-color laser-induced fluorescence (LIF) detection scheme. Four types of leukocytes including neutrophils, eosinophils, lymphocytes and monocytes are identified in blood samples, which are stained by fluorescein isothiocyanate (FITC) and propidium iodide (PI). The DLC results show good correlation with the count from a commercial hematology analyzer. The whole system is also implemented into a portable instrument for space application