Showing papers by "Yang Li published in 2008"

The LHCb detector at the LHC

Abstract: The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

{sup 13}N+p elastic resonance scattering via a thick-target method

Abstract: The {sup 13}N+p elastic resonance scattering has been studied in inverse kinematics via a thick-target method. A {sup 13}N secondary beam of 47.8{+-}1.5 MeV produced by the {sup 2}H({sup 12}C,{sup 13}N)n reaction was used to bombard a 9.33 mg/cm{sup 2} (CH{sub 2}){sub n} target. The recoil protons were detected by a {delta}E-E silicon counter telescope at {theta}{sub lab}=15 deg. The performance of the setup was checked by {sup 12}C+p elastic resonance scattering with the same (CH{sub 2}){sub n} target. The excitation function for the {sup 13}N(p,p) elastic scattering was obtained in the energy interval of E{sub c.m.}{approx}0.5-3.2 MeV and was analyzed by using a multilevel R-matrix code MULTI7. Several low-lying excited states in {sup 14}O were surveyed. Our results confirm a very recent 2{sup -} assignment to the 6.8 MeV level and agree with the observation of a new 0{sup -} level at 5.7 MeV with a width of 400(45) keV.

Probing the low- x structure of nuclear matter with diffractive hadron production in pA collisions

Abstract: We argue that hadron production in coherent diffraction of protons on a heavy nucleus provides a very sensitive probe of the low-x QCD dynamics. This process probes the BFKL dynamics in protons and the nonlinear gluon evolution in nuclei. We calculate the diffractive hadron production cross sections in the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) kinematic regions. To study the nuclear effects we introduce the diffractive nuclear modification factor. We show that, unlike the nuclear modification factor for inclusive hadron production that has very interesting dynamics at RHIC but is expected to be almost completely saturated at the LHC, the nuclear modification factor for diffractive production exhibits a nontrivial behavior at both RHIC and LHC.

Gluon multiplicity in coherent diffraction of onium on a heavy nucleus

Abstract: We derive the cross section for the diffractive gluon production in high energy onium-nucleus collisions that includes the low-x evolution effects in the rapidity interval between the onium and the produced gluon and in the rapidity interval between the gluon and the target nucleus. We analyze our result in two limiting cases: when the onium size is much smaller than the saturation scale and when its size is much larger than the saturation scale. In the later case the gluon multiplicity is very small in the quasiclassical case and increases when the low-x evolution effects in onium become significant. We discuss the implications of our result for the Relativistic Heavy Ion Collider, Large Hadron Collider, and Electron Ion Collider phenomenology.

Adaptive Directional Relay and Direction Comparison Protection Based on Instantaneous Power for UHV Transmission Lines

Abstract: The paper presents a directional relay and a direction comparison protection scheme based on instantaneous power for UHV transmission line, in which instantaneous passive power was defined using Hilbert transform. Using instantaneous active power and instantaneous passive power measured at the relaying point, the relay can determine the fault direction in very short time since the fault occurs, even in 2 ms. The operation time performance depends on the characteristics of fault generated travelling waves. If the fault occurs as the voltage is crossing zero, direction determination will be based on post-fault power-frequency voltage and current, and the operation time will be less than 20 ms. And the paper proposes direction comparison protection scheme integrated with the directional relay. Simulation studies show that the directional relay and the protection are with high speed operation, excellent reliability, sensitivity, and adaptability, and it is an ideal protection of UHV transmission lines.

Baryon enhancement in high-density QCD and relativistic heavy ion collisions

Abstract: We argue that the collinear factorization of the fragmentation functions in high energy nuclear collisions breaks down at transverse momenta $p_T \lesssim Q_s/g$ due to high parton densities in the colliding hadrons and/or nuclei. We find that gluon recombination dominates in that $p_T$ region. We calculate the inclusive cross-section for $\pi$ meson and nucleon production using the low energy theorems for the scale anomaly in QCD, and compare our quantitative baryon-to-meson ratio to the RHIC data.

Baryon enhancement in high-density QCD and relativistic heavy ion collisions

Abstract: We argue that the collinear factorization of the fragmentation functions in high-energy nuclear collisions breaks down at transverse momenta PT ≤ Q s /g due to high parton densities in the colliding hadrons and/or nuclei. We find that gluon recombination dominates in that PT region. We calculate the inclusive cross section for π meson and nucleon production using the low-energy theorems for the scale anomaly in QCD, and compare our quantitative baryon-to-meson ratio to the RHIC data.