arXiv subjects

Gang Li

Publications and source records attributed to Gang Li.

747 records · Page 42Linked to original sources

arXiv2007

Hadron Scattering in an Asymmetric Box

We propose to study hadron-hadron scattering using lattice QCD in an asymmetric box which allows one to access more non-degenerate low-momentum modes for a given volume. The conventional Lüscher's formula applicable in a symmetric box is modified accordingly. To illustrate the feasibility of this approach, pion-pion elastic scattering phase shifts in the I=2, J=0 channel are calculated within quenched approximation using improved gauge and Wilson fermion actions on anisotropic lattices in an asymmetric box. After the chiral and continuum extrapolation, we find that our quenched results for the scattering phase shifts in this channel are consistent with the experimental data when the three-momentum of the pion is below 300MeV. Agreement is also found when compared with previous theoretical results from lattice and other means. Moreover, with the usage of asymmetric volume, we are able to compute the scattering phases in the low-momentum range (pion three momentum less than about 350MeV in the center of mass frame) for over a dozen values of the pion three-momenta, much more than using the conventional symmetric box with comparable volume.

hep-lat↗

arXiv2006

Study of electromagnetic decay of $J/ψ$ and $ψ^\prime$ to vector and pseudoscalar

The electromagnetic decay contributions to $J/ψ(ψ^\prime)\to VP$, where $V$ and $P$ stand for vector and pseudoscalar meson, respectively, are investigated in a vector meson dominance (VMD) model. We show that $J/ψ(ψ^\prime)\to γ^*\to VP$ can be constrained well with the available experimental information. We find that this process has significant contributions in $ψ^\prime\to VP$ and may play a key role in understanding the deviations from the so-called "12% rule" for the branching ratio fractions between $ψ^\prime\to VP$ and $J/ψ\to VP$. We also address that the "12% rule" becomes very empirical in exclusive hadronic decay channels.

hep-ph↗

arXiv2005

Revisiting the OZI-forbidden Radiative Decays of Orthoquarkonia

It is interesting to investigate the OZI-forbidden radiative orthoquarkonium decays $J/ψ\to γπ^0, γη$ and $γη'$ in perturbative QCD. In this work without the approximations adopted in literature we carry out a full one-loop calculation which involves integrations of 4-point and 5-point loop functions. Our numerical results are in agreement with the present data. We also briefly discuss the decays of $J/ψ\to γ+ρ^0$, as well as $Υ\to π^0γ, ηγ, η'γ$.

hep-ph↗

arXiv2004

Higgs boson pair production in the little Higgs model at hadron colliders

The Higgs boson pair production process at hadron collider provides an opportunity for performing a study of the trilinear Higgs boson self-coupling. In this paper, we analyze the pair production of a neutral Higgs boson via both gluon-gluon and $b$-$\bar{b}$ fusions in the littlest Higgs (LH) model at the CERN LHC. We find that in some parameter space the relative corrections of the total cross section to the SM prediction may reach a value of 24% when $x ~ (=4 f v'/v^2)=0.95$ at the LHC. We conclude that if the parameter $x$ has a value above 0.8, the relative corrections contributed by the LH model reach values beyond 8% and can be observed at the LHC.

hep-ph↗

arXiv2000

Charge Conjugation Violation in Supernovae and The Neutron Shortage for R-Process Nucelosynthesis

Core collapse supernovae are dominated by energy transport from neutrinos. Therefore, some supernova properties could depend on symetries and features of the standard model weak interactions. The cross section for neutrino capture is larger than that for antineutrino capture by one term of order the neutrino energy over the nucleon mass. This reduces the ratio of neutrons to protons in the $ν$-driven wind above a protoneutron star by approximately 20 % and may significantly hinder r-process nucleosynthesis.

astro-ph↗

arXiv1999

Charge-conjugation violating neutrino interactions in supernovae

The well known charge conjugation violating interactions in the Standard Model increase neutrino- and decrease anti-neutrino- nucleon cross sections. This impacts neutrino transport in core collapse supernovae through "recoil" corrections of order the neutrino energy $k$ over the nucleon mass $M$. All $k/M$ corrections to neutrino transport deep inside a protoneutron star are calculated from angular integrals of the Boltzmann equation. We find these corrections significantly modify neutrino currents at high temperatures. This produces a large mu and tau number for the protoneutron star and can change the ratio of neutrons to protons. In addition, the relative size of neutrino mean free paths changes. At high temperatures, the electron anti-neutrino mean free path becomes {\it longer} than that for mu or tau neutrinos.

astro-ph↗

arXiv1999

Nucleosynthesis in Supernovae

astro-ph↗

arXiv1998

The Mu and Tau Number of Supernovae

The neutrino-nucleon cross section is slightly larger than that for $\barν-N$. Therefore, $\barν$ will escape more quickly from core collapse supernovae leaving the star $ν$ rich. A diffusion formalism is used to calculate the time evolution of the mu and tau lepton number densities. These quickly reach steady state equilibria. We estimate that a protoneutron star with a maximum temperature near 50 MeV will contain over 50 % more $ν_μ$ and $ν_τ$ than $\barν_μ$ and $\barν_τ$. Supernovae may be the only known systems with large mu and or tau lepton numbers.

hep-ph↗

arXiv1997

Cumulative Parity Violation in Supernovae

Supernovae provide a unique opportunity for large scale parity violation because they are dominated by neutrinos. We calculate the parity violating asymmetry A of neutrino emission in a strong magnetic field. We assume the neutrinos elastically scatter many times from slightly polarized neutrons. Because of multple interactions, A grows with the optical thickness of the proto-neutron star and may be much larger than previous estimates. As a result, the neutron star could recoil at a significant velocity.

astro-ph↗