Decay constants of pseudoscalar and vector mesons with improved holographic wavefunction

We calculate the decay constants of light and heavy-light pseudoscalar and vector mesons with improved soft-wall holographic wavefuntions, which take into account the effects of both quark masses and dynamical spins. We find that the predicted decay constants, especially for the ratio fV/fP, based on light-front holographic QCD, can be significantly improved, once the dynamical spin effects are taken into account by introducing the helicity-dependent wavefunctions. We also perform detailed χ2 analyses for the holographic parameters （i.e. the mass-scale parameter κ and the quark masses）, by confronting our predictions with the data for the charged-meson decay constants and the meson spectra. The fitted values for these parameters are generally in agreement with those obtained by fitting to the Regge trajectories. At the same time, most of our results for the decay constants and their ratios agree with the data as well as the predictions based on lattice QCD and QCD sum rule approaches, with only a few exceptions observed.

Large angle radiation effect on jet measurement in pp collisions at s^(1/2)=7 TeV at the LHC

Jet measurement is an ideal probe to explore the properties of the hot dense matter created in ultra- relativistic heavy-ion collisions. Recent results at the LHC show that large angle radiation is non-negligible, but the mechanisms and phenomenology of large angle radiation are still unclear and hotly debated. Considering the coexistence and competition of different physics mechanisms qualitatively, it is assumed that the radiation angle is enhanced randomly over a wide range based on the collinear approximation. Its effects on di-jet momentum imbalance, jet fragmentation function and jet shape are studied in pp collisions at 7 TeV. The results show that di-jet asymmetry is insensitive to large angle radiation, while jet shape and jet fragmentation functions are more sensitive and could explain experimental data well. We conclude that de-collimated radiation cannot be ignored for soft jets, and there is a contribution from large angle radiation （Ф 〉 0.7） of about 8%, which is significant for jet intrinsic structure measurement at PT,jeT 〈80 GeV/c.

HTL resummation in the light cone gauge

The light cone gauge with light cone variables is often used in p QCD calculations in relativistic heavyion collision physics. The Hard Thermal Loops（HTL） resummation is an indispensable technique for hot QCD calculation. It was developed in covariant gauges with conventional Minkowski varaiables; we shall extend this method to the light cone gauge. In the real time formalism, using the Mandelstam-Leibbrant prescription of（n·K）-1,we calculate the transverse and longitudinal components of the gluon HTL self energy, and prove that there are no infrared divergences. With this HTL self energy, we derive the HTL resummed gluon propagator in the light cone gauge. We also calculate the quark HTL self energy and the resummed quark propagator in the light cone gauge and find it is gauge independent. As application examples, we analytically calculate the damping rates of hard quarks and gluons with the HTL resummed gluon propagator in the light cone gauge and showed that they are gauge independent. The final physical results are identical to those computed in covariant gauge, as they should be.

Poisson baseline of net-charge fluctuations in relativistic heavy ion collisions

Taking doubly charged particles, positive-negative charge pair production and the effects of volume fluctuations into account, the Poisson baseline of the fluctuations of net-charge is studied. Within the Poisson baseline, the cumulants of net-charge are derived. Comparing to the Skellam baseline of net-charge, we infer that doubly charged particles broaden the distributions of net-charge, while positive-negative charge pairs narrow the distributions. Using the ratios of doubly charged particles and positive-negative charge pairs from neutral resonance decays to the total positive charges from THERMINATOR 2, the first four orders of moments and the corresponding moment products are calculated in the Poisson baseline for Au ＋ Au collisions at √sNN=200 GeV at RHIC/STAR. We find that the standard deviation is mainly influenced by the resonance decay, while the third and fourth order moments and corresponding moment products are mainly modified and fit the data of RHIC/STAR much better after including the effects of volume fluctuations.

Comparing potential-driven DBI-inspired non-minimal kinetic coupling(Dinkic) inflation with observational data

In our previous work [1], a new kind of inflation model was proposed, which has the interesting property that its perturbation equation of motion gets a correction of k4, due to the non-linearity of the kinetic term.Nonetheless, the scale-invariance of the power spectrum remains valid, both in large-k and small-k limits. In this paper, we investigate in detail the spectral index, the index running and the tensor/scalar ratio in this model, especially in the potential-driven case, and compare the results with the current PLANCK/BICEP observational data.We also discuss the tensor spectrum in this case, which is expected to be tested by future observations of primordial gravitational waves.