56412229
The introduction to BES computing environment
Beijing Electron Spectrometer (BES) is the experiment on Beijing Electron-Positron Collider (BEPC) started in 1980s. The computing facilities were built on VAX and HP-UX and upgraded to PC/Linux between 1995 and 1998. From 2004, BEPC started to be upgraded. The luminosity will increases by 100 times. The new detector BESIII is being built and will be operational in 2007. The paper describes the computing environment for the current BESII experiment and future BESIII experiment.
118695723
Spinor formalism for massive fields with half-integral spin
In this article, we extend the spinor technique for calculating helicity amplitudes to general massive fields of half-integer spins. We find that the little group generators can be represented as first-order differential operators in the spinor formalism. We use the spinor forms of the generators to get the explicit form of the massive fields of any spin and any helicity. We also deal with the three-particle S-matrix by these spinor form generators, and find that we are able to extend the explicit form of the three-particle vertex obtained by Benincasa and Cachazo to the massive case. We present the explicit expressions for the amplitudes with external particles of the lowest helicities up to −3/2. Group theory, in the form of raising operators of the little group, then dictates other amplitudes with higher helicity in the same spin multiplets. The formalism allows one, in principle, to determine the electromagnetic form-factors of charged particles of arbitrary helicities, without additional assumptions about the underlying lagrangian. We find that restrictions which follow from gauge and Lorentz invariance are nearly as restrictive as in the massless case.
63535218
Performance analysis of Cluster File System on Linux
With the development of Linux and improvement of PC’s performance, PC cluster used as high performance computing system is becoming much popular. The performance of I/O subsystem and cluster file system is critical to a high performance computing system. In this work the basic characteristics of cluster file systems and their performance are reviewed. The performance of four distributed cluster file systems, AFS, NFS, PVFS and CASTOR, were measured. The measurements were carried out on CERN Linux 7.3.3 using standard I/O performance benchmarks. Measurements show that for single-server single-client configuration, NFS, CASTOR and PVFS have better performance and write rate slightly increases while the record size becomes larger. CASTOR has the best throughput when the number of write processes increases. PVFS and CASTOR are tested on multi-server and multi-client system. The two file systems nicely distribute data I/O to all servers. CASTOR RFIO protocol shows the best utilization of network bandwidth and optimised to large data size files. CASTOR also has better scalability as a cluster file system. Based on the test some methods are proposed to improve the performance of cluster file system.
118331286
Complexified Ward Identity in pure Yang-Mills theory at tree-level
Up until now, the BCFW technique has been a widely used method in getting the amplitudes in various theories. Usually, the vanishing of the boundary term is necessary for the efficiency of the method. However, there are also many kinds of amplitudes which will have boundary terms. Hence it will be nice if it is possible to get the boundary terms in an efficient manner. As is well-known, in gauge theory the Ward identity imposes constraints on the form of the amplitude. In [1], we studied the Ward identity with a pair of shifted lines and the implied recursion relations. In this article, we discuss the complexified Ward identity in more detail. In particular we give a proof of the complexified Ward identity directly from the Feynman rules in Feynman-Lorentz gauge. Furthermore, we give more examples in calculating the one-line off-shell currents using this technique.
62209352
Volunteer Clouds and Citizen Cyberscience for LHC Physics
Computing for the LHC, and for HEP more generally, is traditionally viewed as requiring specialized infrastructure and software environments, and therefore not compatible with the recent trend in volunteer computing, where volunteers supply free processing time on ordinary PCs and laptops via standard Internet connections. In this paper, we demonstrate that with the use of virtual machine technology, at least some standard LHC computing tasks can be tackled with volunteer computing resources. Specifically, by presenting volunteer computing resources to HEP scientists as a volunteer cloud, essentially identical to a Grid or dedicated cluster from a job submission perspective, LHC simulations can be processed effectively. This article outlines both the technical steps required for such a solution and the implications for LHC computing as well as for LHC public outreach and for participation by scientists from developing regions in LHC research.
119663113
Ward Identity implied recursion relation at loop level
119092405
Photoproduction of heavy quarkonium at the ILC
We study the photoproduction of the heavy quarkonium at the future International Linear Collider (ILC) within the nonrelativistic QCD theory. We focus on the production channel via the subprocess $\gamma\gamma \to |[Q\bar{Q'}]_{\bf 1}(n)>+Q'+\bar{Q}$, where $Q$ and $Q'$ stand for heavy $c$- or $b$-quark, respectively. $|[Q\bar{Q'}]_{\bf 1}(n)>$ stands for color-singlet $S$-wave quarkonium, i.e., $\eta_{c}(|[c\bar{c}]_{\bf 1}(^1S_0)>)$, $J/\psi(|[c\bar{c}]_{\bf 1}(^3S_1)>)$, $B_{c}(|[c\bar{b}]_{\bf 1}(^1S_0)>)$, $B^*_{c}(|[c\bar{b}]_{\bf 1}(^3S_1)>)$, $\eta_{b}(|[b\bar{b}]_{\bf 1}(^1S_0)>)$, and $\Upsilon(|[b\bar{b}]_{\bf 1}(^3S_1)>)$, respectively. To improve the calculation efficiency, we adopt the improved helicity amplitude approach to deal with the difficulty of calculating the expressions for the yields when the quark masses cannot be neglected. Total and differential photoproduction cross sections, together with their uncertainties, have been presented. It is noted that sizable amount of $|c\bar{c}>$-charmonium and $|c\bar{b}>$-quarkonium events can be generated at the ILC. More specifically, we predict $(2.8^{+1.0}_{-0.7})\times 10^{6}$ $\eta_c$, $(5.4^{+1.9}_{-1.3})\times 10^{6}$ $J/\psi$, $(8.3^{+2.2}_{-1.8})\times 10^{4}$ $B_c$, $(4.3^{+1.1}_{-0.9})\times 10^{5}$ $B_c^*$, $(9.0^{+1.7}_{-1.4})\times 10^{3}$ $\eta_b$, and $(1.6\pm0.3)\times 10^{4}$ $\Upsilon$ events to be generated in one operation year at the ILC under the condition of $\sqrt{S}=500$ GeV and ${\cal L}\simeq 10^{36}$cm$^{-2}$s$^{-1}$.
119276990
Heavy quarkonium production through the semi-exclusive $e^+e^-$ annihilation channels round the $Z^0$ peak
Within the framework of the non-relativistic QCD, we present a detailed discussion on the heavy quarkonium production at the leading order in $\alpha_s$ at a $e^+ e^-$ collider with the collision energy around the $Z^0$ peak. Quarkonia are produced through the semi-exclusive channels $e^{+}e^{-} \rightarrow |H_{Q\bar{Q}}\rangle +X$ with $X=Q\bar{Q}$ or $gg$, where $Q$ indicates a heavy quark (respectively $b$ or $c$). It is noted that in addition to the color-singlet 1S-level quarkonium states, the 2S and 1P color-singlet states and the color-octet $|(Q\bar{Q})[1^3S_1^{({\bf 8})}]g\rangle$ state also provide sizable contributions. The heavy quarkonium transverse momentum and rapidity distributions for the $e^+ e^-$ collision energy $E_{cm}=m_Z$ are presented. For both charmonium and bottomonium production via the $Z^0$ propagator, there is approximate "spin degeneracy" between the spin-triplet and spin-singlet quarkonium states. Uncertainties for the total cross sections are estimated by taking $m_c=1.50\pm0.15$ GeV and $m_b=4.90\pm0.15$ GeV. Around $E_{cm}=m_{Z}$, due to the $Z^0$-boson resonance effect, total cross sections for the channels via the $Z^0$-propagator become much larger than the channels via the virtual photon propagator. We conclude that, in addition to the $B$ factories as BaBar and Belle and the hadronic colliders as Tevatron and LHC, such a super $Z$-factory will present an excellent platform for studying the heavy quarkonium properties.
118388381
Heavy quarkonium production through the top quark decays via flavor changing neutral currents
The production of the heavy charmonium and $(c\bar{b})$-quarkonium, through the top quark semi-exclusive decays via the flavor changing neutral currents (FCNC), has been systematically studied within the non-relativistic QCD. In different to the conventional squared amplitude approach, to simplify the results as much as possible, we adopt the `improved trace technology' to do our calculation, which deals with the hard scattering directly at the amplitude level. If assuming the higher excited heavy-quarkonium states, such as the color-singlet and spin-triplet $S$-wave state $|[^3S_1]_{\bf 1}\rangle$, the color-singlet $P$-wave states $|[^1P_1]_{\bf 1}\rangle$ and $|[^3P_J]_{\bf 1}\rangle$ (with $J=0,1,2$), and the two color-octet components $|[^1S_0]_{\bf 8}g\rangle$ and $|[^3S_1]_{\bf 8}g\rangle$, decay to the ground color-singlet and spin-singlet $S$-wave state $|[^1S_0]_{\bf 1}\rangle$ with 100% efficiency via the electromagnetic or hadronic radiations, we obtain the total decay width: $\Gamma_{t\to |(c\bar{c})[^1S_0]_{\bf 1}\rangle} = 171.1^{+147.7}_{-68.8}$ KeV and $\Gamma_{t\to |(c\bar{b})[^1S_0]_{\bf 1}\rangle} =7.32^{+2.49}_{-1.75}$ KeV, where the uncertainties are caused by varying $m_t=172.0\pm4.0$ GeV, $m_b=4.90\pm0.40$ GeV and $m_c=1.50\pm0.25$ GeV. At the LHC with the center-of-mass energy $\sqrt{S}=14$ TeV and a high luminosity ${\cal L}\propto 10^{34}{\rm cm}^{-2}{\rm s}^{-1}$, sizable heavy-quarkonium events can be produced through the top quark decays via FCNC.
120081744
Study on The Property of tau Hadronic Decays
123396645
Calibration and performance of the AMS-02 time of flight detector in space
AMS-02 is a high energy particle detector deployed in May 19, 2011 on board of the International Space Station (ISS) where it is expected to be in operation for the ISS lifetime of at least a decade. The main goal of AMS-02 is the detection of cosmic rays and gammas from the GeV to the TeV energy region to search for anti-matter, dark matter and understanding the origin of the cosmic rays. The AMS-02 time of flight (TOF) detector provides the trigger to experiment and allows precise measurements of the cosmic rays velocity and charge magnitude from hydrogen to iron and above. With the data set acquired during the first two and a half years of operation in space, a precise time-dependent calibration for time, velocity and charge measured by the TOF had been developed. The TOF calibration methods are described and the AMS-02 TOF performance in space is presented. (C) 2014 Elsevier B.V. All rights reserved.