119778744
Studies of hadronic event structure in E+ E- annihilation from 30-Gev to 209-Gev with the L3 detector
In this Report, QCD results obtained from a study of hadronic event structure in high energy e^+e^- interactions with the L3 detector are presented. The operation of the LEP collider at many different collision energies from 91 GeV to 209 GeV offers a unique opportunity to test QCD by measuring the energy dependence of different observables. The main results concern the measurement of the strong coupling constant, \alpha_s, from hadronic event shapes and the study of effects of soft gluon coherence through charged particle multiplicity and momentum distributions.
208868428
f1(1285) formation in two-photon collisions at LEP
Abstract The ηπ + π − final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb −1 . The f 1 (1285) meson is observed and the Q 2 dependence of its production is compared to different form factor models. The γγ -coupling parameter Γ γγ is found to be 3.5±0.6(stat.)±0.5(sys.) keV. The branching fraction Γ (f 1 (1285)→a 0 π )/ Γ (f 1 (1285)→ ηππ ) is also measured.
203030065
Search for anomalous couplings in the Higgs sector at LEP
Anomalous couplings of the Higgs boson are searched for through the processes e+e-→Hγ, e+e -→e+e-H and e+e -→HZ. The mass range 70 GeV<mH<190 GeV is explored using 602 pb-1 of integrated luminosity collected with the L3 detector at LEP at centre-of-mass energies s=189-209 GeV. The Higgs decay channels H→ff, H→γγ, H→Zγ and H→WW(*) are considered and no evidence is found for anomalous Higgs production or decay. Limits on the anomalous couplings d, d B, Δg1 Z, Δκγ and ξ2 are derived as well as limits on the H→γγ and H→Zγ decay rates. © 2004 Published by Elsevier B.V.
19719907
Trigger System of BESIII
The trigger system of Beijing Spectrometer III, part of the upgrade of Beijing Electron Positron Collider, has been designed and implemented, and is ready for installation. This paper describes briefly the system components, its characteristics, and some technical issues. The system consists mainly of four parts: MDC (drift chamber) tracking subsystem, EMC (electromagnetic calorimeter) subsystem, TOF (time of flight) subsystem and global trigger. Some highlights in designing of this system includes: trigger scheme optimization with software simulation; optical transmission between trigger and FEEs to realize isolation with FEEs to avoid ground loop current interference; designed with most latest FPGA (Xilinx Spartan 3, VirtexII Pro...) for simplicity, high reliability and easy maintenance and hence smaller system; FPGA in-system programming or firmware online downloadable via onboard, panel connector and/or VME bus for modification flexibility during commissioning. Different from the usual fix delay data transmission from FEE to trigger, the RocketIO has been used as SEDES.
126182293
Evidence of psi(3770) nonD anti-D decay to J / psi pi+ pi-
188198310
Preliminary design of BES-III trigger system
119452157
Quark condensate in one-flavor QCD
We compute the condensate in QCD with a single quark flavor using numerical simulations with the overlap formulation of lattice fermions. The condensate is extracted by fitting the distribution of low lying eigenvalues of the Dirac operator in sectors of fixed topological charge to the predictions of Random Matrix Theory. Our results are in excellent agreement with estimates from the orientifold large-N_c expansion.
119240667
Radiative return for heavy Higgs boson at a muon collider
Higgs boson properties could be studied with a high accuracy at a muon collider via the $s$-channel resonant production. We consider the situation where the center-of-mass energy of the muon collider is off the resonance above the Higgs mass. We discuss the discovery potential for a generic heavy Higgs boson and compare different production mechanisms, including the ``radiative return,'' $Z$-boson associated production and heavy Higgs pair production. These production mechanisms do not sensitively rely on a priori knowledge of the heavy Higgs boson mass. We include various types of two-Higgs-doublet models for the comparison. We conclude that the radiative return process could provide an important option for both the heavy Higgs discovery and direct measurement of invisible decays at a high energy muon collider.
119220539
Potential precision of a direct measurement of the Higgs boson total width at a muon collider
In the light of the discovery of a 126 GeV Standard-Model-like Higgs boson at the LHC, we evaluate the achievable accuracies for direct measurements of the width, mass, and the $s$-channel resonant production cross section of the Higgs boson at a proposed muon collider. We find that with a beam energy resolution of $R=0.01%$ (0.003%) and integrated luminosity of $0.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ ($1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$), a muon collider would enable us to determine the Standard-Model-like Higgs width to $\ifmmode\pm\else\textpm\fi{}0.35\text{ }\text{ }\mathrm{MeV}$ ($\ifmmode\pm\else\textpm\fi{}0.15\text{ }\text{ }\mathrm{MeV}$) by combining two complementary channels of the $W{W}^{*}$ and $b\overline{b}$ final states. A non-Standard-Model Higgs with a broader width is also studied. The unparalleled accuracy potentially attainable at a muon collider would test the Higgs interactions to a high precision.
125353618
Hamiltonian Reduction of WZNW Model Associated With Chiral Constraints
The constant constraints in the conventional Hamiltonian reductions of WZNW model are generalized to the case of arbitrary chiral constraints.It is shown that the reduced model is equivalent to a conformal integrable system at both classical and quantum levels.It is also found that the use of chiral constraints is equivalent to the Hamihonian reduction of the product phase space of WZNW model and free fields.
16381056
Lattice QCD calculation of form factors describing the rare decays $B \to K^* \ell^+ \ell^-$ and $B_s \to \phi \ell^+ \ell^-$
The rare decays $B^0 \to K^{*0} \mu^+ \mu^-$ and $B_s \to \phi \mu^+ \mu^-$ are now being observed with enough precision to test Standard Model predictions. A full understanding of these decays requires accurate determinations of the corresponding hadronic form factors. Here we present results of lattice QCD calculations of the $B \to K^*$ and $B_s \to \phi$ form factors; we also determine the form factors relevant for the tree-level decays $B_s \to K^* \ell \nu$. We use full-QCD configurations including 2+1 flavors of sea quarks using an improved staggered action, and we employ lattice non-relativistic QCD to describe the bottom quark.