138378034
PERFORMANCES OF THE AMS-02 ELECTROMAGNETIC CALORIMETER
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.
122329775
PERFORMANCES OF THE AMS-02 ELECTROMAGNETIC CALORIMETER
122504634
The AMS-02 lead-scintillating fibres Electromagnetic Calorimeter
Abstract The Electromagnetic Calorimeter (ECAL) of the AMS-02 experiment is a fine grained lead-scintillating fibres sampling calorimeter that allows for a precise three-dimensional imaging of the longitudinal and lateral shower development. It provides a high ( ≥ 10 6 ) electron/hadron discrimination with the other AMS-02 detectors [1] and good energy resolution. The calorimeter also provides a standalone photon trigger capability to AMS-02. The mechanical assembly was realized to ensure minimum weight, still supporting the intrinsically heavy calorimeter during launch. ECAL light collection system and electronics are designed to measure electromagnetic particles over a wide energy range, from GeV up to TeV. A full-scale flight-like model was tested using electrons and proton beams with energies ranging from 6 to 250 GeV.
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.
119105996
Boundary Behaviors for General Off-shell Amplitudes in Yang-Mills Theory
In this article, we analyze the boundary behaviors of pure Yang-Mills amplitudes under adjacent and non adjacent BCFW shifts in Feynman gauge. We introduce reduced vertexes for Yang-Mills fields, prove that these reduced vertexes are equivalent to the original vertexes as for the study of boundary behaviors, which greatly simplifies our analysis of boundary behaviors. Boundary behaviors for adjacent shifts are readily obtained using reduced vertexes. Then we prove a theorem on permutation sum and use it to prove the improved boundary behaviors for non-adjacent shifts. Based on the boundary behaviors, we find that it is possible to generalize BCFW recursion relation to calculate general tree level off shell amplitudes.
209930395
Extraction of the structure functions in tau -> 3 pi nu decay using Li model
The structure functions in the tau --> 3 pi nu decay are extracted using the model proposed by Li. The predictions of Li model are compared with KS ones and the data from OPAL experiment. It is found that predictions by the model for w(A)(Q(2)) are consistent with the data except for in the high energy region (Q(2) > 1.2 GeV2), and w(C), w(D), w(E) normalized to w(A) are in reasonable agreement with the experimental results. Correction factors to the Breit-Wigner distribution of a(1) and the Lagrangian of this decay are proposed to the model.
121905332
Measurement of the topological and hadronic decay branching fractions of the tau lepton with the L3 detector at LEP
Using the data collected with the L3 detector at LEP during 1992-1995 run at the Z(o) peak, corresponding to an integrated luminosity of 92.63 pb(-1), the topological and hadronic tau decay branching fractions are measured. Photon conversion, fake photon and backlash tracks are studied and rejected in the analysis. The decay channels are identified using a set of neural networks. The topological tau decay branching fractions are B(tau --> 1-prong) = 85.14 +/- 0.27 +/- 0.17%, B(tau --> 3-prong) = 14.63 +/- 0.13 +/- 0.10% and B(tau --> 5-prong) = 0.23 +/- 0.01 +/- 0.05%. The branching fractions of tau hadronic decays are determined: BR.(tau --> hv)=(12.51 +/- 0.12 +/- 0.13)%, BR(tau --> h pi (o)nu)=(25.38 +/- 0.18 +/- 0.14)% ,BR(tau --> h2 pi (o)nu)=(8.98 +/- 0.21 +/- 0.19)% ,BR(tau --> h greater than or equal to 3 pi (o)nu)=(1.77 +/- 0.14 +/- 0.15)% ,BR(tau --> 3hv)=(9.11 +/- 0.15 +/- 0.08)% ,BR(tau --> 3h pi (o)nu)=(4.77 +/- 0.19 +/- 0.10)% ,BR(tau --> 3h greater than or equal to 2 pi (o)nu)=(0.45 +/- 0.10 +/- 0.11)%, where the first error is statistical and the second systematic.
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.
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.
119188205
Initial Conditions with Flow from a McLerran Venugopalan model with Transverse Dynamics
Using a recursive solution of the Yang-Mills equation, we calculate analytic expressions for the gluon fields created in ultra-relativistic heavy ion collisions at small times τ. We have worked out explicit solutions for the fields and the energy momentum tensor up to 4th order in an expansion in τ. We generalize the McLerran-Venugopalan model to allow for a systematic treatment of averaged charge densities μ2 that vary as a function of transverse coordinates. This allows us to calculate radial, elliptic and directed flow of gluon fields. Our results can serve as initial conditions for hydrodynamic simulations of nuclear collisions that include initial flow.