119302009
The Gauss-Bonnet-Chern mass of conformally flat manifolds
In this paper we show positive mass theorems and Penrose type inequalities for the Gauss-Bonnet-Chern mass, which was introduced recently in \cite{GWW}, for asymptotically flat CF manifolds and its rigidity.
119275897
A new mass for asymptotically flat manifolds
Abstract In this paper we introduce a mass for asymptotically flat manifolds by using the Gauss–Bonnet curvature. We first prove that the mass is well-defined and is a geometric invariant, if the Gauss–Bonnet curvature is integrable and the decay order τ satisfies τ > n − 4 3 . Motivated by an elegant idea of Lam [35] , we then show a positive mass theorem for this new mass for asymptotically flat graphs over R n . Moreover we obtain various Penrose type inequalities in this case. In these Penrose type inequalities we establish relationship between the new mass and various geometric integrals.
118617483
A positive mass theorem in the Einstein-Gauss-Bonnet theory
As an interesting application of the Einstein-Gauss-Bonnet theory and our work on the Gauss-Bonnet-Chern mass (Ge, Wang, Wu), we obtain a positive mass theorem for asymptotically flat graphs in $\R^{n+1}$ under a condition that $R+\alpha L_2$ is non-negative, where $R$ is the scalar curvature, $\alpha\in\R$ a constant and $L_2$ the second Gauss-Bonnet curvature. A Penrose type inequality is also obtained in the case $\alpha>0$.
119300428
Why X(3915) is so narrow as a $\chi_{c0}(2P)$ state
New resonance X(3915) was identified as the charmonium $\chi_{c0}(2P)$ by BABAR Collaboration, but there seems still open question of this assignment: why its full width is so narrow? To answer this question, we calculate the Okubo-Zweig-Iizuka (OZI) allowed strong decays $X(3915)\to D \bar D$, where X(3915) is assigned as a $\chi_{c0}(2P)$ state, and estimate its full width in the cooperating framework of $^3/!P_0^{}$ model and the Bethe-Salpeter (BS) method using the Mandelstam Formalism, during which non-perturbative QCD effects of the hadronic matrix elements are well considered by overlapping integral over the relativistic Salpeter wave functions of the initial and finial states. We find the node structure of $\chi_{c0}(2P)$ wave function resulting in the narrow width of X(3915) and show the dependence of the decay width on the variation of the initial mass of X(3915). We point out that the rate of $\frac{\Gamma(X(3915)\to D^+ D^-)}{\Gamma(X(3915)\to D^0 \bar D^0)}$ is crucial to confirm whether X(3915) is the $\chi_{c0}(2P)$ state or not.
15593532
Decay constants of heavy vector mesons in relativistic Bethe-Salpeter method
Abstract In a previous Letter, we computed the decay constants of heavy pseudoscalar mesons in the framework of relativistic (instantaneous) Bethe–Salpeter method (full 0 − Salpeter equation), in this Letter, we solve the full 1 − Salpeter equation and compute the leptonic decay constants of heavy–heavy and heavy–light vector mesons. The theoretical estimate of mass spectra of these heavy–heavy and heavy–light vector mesons are also presented. Our results for the decay constants and mass spectra include the complete relativistic contributions. We find F D s ∗ ≈ 375 ± 24 , F D ∗ ≈ 340 ± 23 ( D ∗ 0 , D ∗ ± ) , F B s ∗ ≈ 272 ± 20 , F B ∗ ≈ 238 ± 18 ( B ∗ 0 , B ∗ ± ) , F B c ∗ ≈ 418 ± 24 , F J / Ψ ≈ 459 ± 28 , F Ψ ( 2 S ) ≈ 364 ± 24 , F ϒ ≈ 498 ± 20 and F ϒ ( 2 S ) ≈ 366 ± 27 MeV .
122831377
PERFORMANCE OF THE DIAGNOSTICS FOR NSLS-II LINAC COMMISSIONING
The National Synchrotron Light Source II (NSLS-II) is a state of the art 3-GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac, a 3-GeV booster synchrotron and associated transfer lines. The transfer lines not only provide a means to deliver the beam from one machine to another, they also provide a suite of diagnostics and utilities to measure the properties of the beam to be delivered. In this paper we discuss the suite of diagnostics that will be used to commission the NSLS-II linac and measure the beam properties. The linac to booster transfer line can measure the linac emittance with a three screens measurement or a quadrupole scan. Energy and energy spread are measured in a dispersive section. Total charge and charge uniformity are measured with wall current monitors in the linac and transformers in the transfer line. We show that the performance of the diagnostics in the transfer line will be sufficient to ensure the linac meets its specifications and provides a means of trouble shooting and studying the linac in future operation.
119180431
Empirical constraints on parton energy loss in nucleus–nucleus collisions at RHIC
Abstract We present empirical features of parton energy loss in nucleus–nucleus collisions at RHIC through studies of the spectra and nuclear modification factors ( R A A ) for charged hadrons, neutral pions ( π 0 ) and non-photonic electrons. The flat distribution of R A A at high transverse momentum ( p T ) for a given collision centrality is consistent with a scenario where parton energy loss Δ p T is proportional to p T . The centrality dependence of the parton energy loss indicates the absence of path length dependence in the magnitude of energy loss. The lack of strong path length dependence suggests a dynamical picture where the dense partonic medium undergoes rapid expansion and the density of the medium falls rapidly in the first a few Fermi interval, which may be much shorter than the full path length. Implications of the empirical constraints on the parton energy loss will also be discussed.
55938998
BEAM DIAGNOSTICS USING BPM SIGNALS FROM INJECTED AND STORED BEAMS IN A STORAGE RING
Many modern light sources are operating in top-off injection mode or are being upgraded to top-off injection mode. The storage ring always has the stored beam and injected beam for top-off injection mode. So the BPM data is the mixture of both beam positions and the injected beam position cannot be measured directly. We propose to use dedicated wide band BPM electronics in the NSLS II storage ring to retrieve the injected beam trajectory with the singular value decomposition (SVD) method. The beam position monitor (BPM) has the capability to measure bunch-by-bunch beam position. Similar electronics can be used to measure the bunch-by-bunch beam current which is necessary to get the injection beam position. The measurement precision of current needs to be evaluated since button BPM sum signal has position dependence. The injected beam trajectory can be measured and monitored all the time without dumping the stored beam. We can adjust and optimize the injected beam trajectory to maximize the injection efficiency. We can also measure the storage ring acceptance by mapping the injected beam trajectory.