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.
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.
121082248
Prospects of B/c mesons at the Compact Muon Solenoid
The results of two Monte Carlo generators for production of Bc mesons in pp collisions are compared at the large hadron collider energy (s)1/2 = 14 TeV. In the study, the produced Bc mesons were forced to decay into the final states Bslν, Bsπ, J/ψlν, and J/ψπ. We have estimated that about 104 decays of Bc are expected to be recorded during the first year of the CMS running with a lepton trigger. Many Bc studies can be carried out by using these events with a statistical error at the level of 10−2.
119474898
The topological branching fractions of $\tau$ decay at LEP
The paper has heen withdrawn.
124197197
Structure functions in tau ---> 3 pi neutrino decay
120081744
Study on The Property of tau Hadronic Decays
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.
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.
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.
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.
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.