118607013
Permutation relations of generalized Yangian Invariants, unitarity cuts, and scattering amplitudes
A bstractWe find a permutation relation among the generalized Yangian Invariants — two Yangian Invariants with adjacent external lines exchanged are related by a simple kinematic factor — which is shown to be equivalent to U(1) decoupling and Bern-Carrasco-Johansson (BCJ) relation at the level of maximal helicity violating (MHV) amplitudes. We propose using unitarity cuts to study nonplanar amplitudes and to systematically reconstruct the integrands of nonplanar MHV amplitudes, up to a rational function which vanishes under all possible unitarity cuts. This is made possible with the newly found permutation relations by converting nonplanar on-shell diagrams into planar ones. As explicit examples the construction of one-loop double-trace MHV amplitudes of 4- and 5-point interactions are presented using on-shell diagrams. The kinematic factors and the resultant planar diagrams are carefully dealt with using the unitarity cut conditions. The first next-to-MHV amplitudes are addressed using generalized unitarity cuts. Their leading singularities can be identified as residues of the Grassmanian integrals. These examples also serve to demonstrate the power of the newly found relation of the generalized Yangian Invariants.
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.
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.
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.
122329775
PERFORMANCES OF THE AMS-02 ELECTROMAGNETIC CALORIMETER
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.
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.
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$^{-1}$.
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.
123818688
Search for a Higgs-like boson decaying to two photons in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV
We present a search for the Standard Model (SM) Higgs boson decaying to two photons using the 9.6 fb-1 of p$$\bar{p}$$ collisions at √s = 1.96 TeV collected by the D0 detector at the Tevatron from July 2002 to September 2011. The data corresponds to the complete data-set in the RunII period of the Tevatron. This thesis employs a multivariate technique, boosted decision trees, to optimize the discrimination of signal from background. No significant excess of data above theoretical prediction is observed, so limits on the ratio of the production cross section times the branching ratio to the SM value are set at 95% confidence level as a function of hypothetical Higgs boson mass. The expected and observed limits on this ratio are 8.7 and 12.8 respectively at 125 GeV. We also interpret the data in the fermiophobic Higgs model. The result has reached a sensitivity of 114 GeV, and we set a lower limit on the fermiophobic Higgs mass of MHf > 113 GeV.