121114134
Measurement of the running of the electromagnetic coupling at large momentum-transfer at LEP
The evolution of the electromagnetic coupling, α, in the momentum-transfer range 1800 GeV2 < -Q2 < 21600 GeV2 is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies √s = 189-209 GeV. The running of α is parametrised as: α(Q2) = α0/1 - C Δα(Q2), where α ≡ α(Q2 = 0) is the fine-structure constant and C = 1 corresponds to the evolution expected in QED. A fit to the differential cross section of the e+e- → e+e- process for scattering angles in the range |cos θ| < 0.9 excludes the hypothesis of a constant value of α, C = 0, and validates the QED prediction with the result: C = 1.05±0.07±0.14, where the first uncertainty is statistical and the second systematic. © 2005 Elsevier B.V. All rights reserved.
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.
188198310
Preliminary design of BES-III trigger system
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-
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.
54185957
Colored resonant signals at the LHC: largest rate and simplest topology
We study the colored resonance production at the LHC in a most general approach. We classify the possible colored resonances based on group theory decomposition, and construct their effective interactions with light partons. The production cross section from annihilation of valence quarks or gluons may be on the order of 400–1000 pb at LHC energies for a mass of 1 TeV with nominal couplings, leading to the largest production rates for new physics at the TeV scale, and simplest event topology with dijet final states. We apply the new dijet data from the LHC experiments to put bounds on various possible colored resonant states. The current bounds range from 0.9 to 2.7 TeV. The formulation is readily applicable for future searches including other decay modes.
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.
119307246
Pseudoscalar meson and heavy vector meson scattering lengths
We have systematically studied the S-wave pseudoscalar meson and heavy vector meson scattering lengths to the third order with the chiral perturbation theory, which will be helpful to reveal their strong interaction. For comparison, we have presented the numerical results of the scattering lengths (1) in the framework of the heavy meson chiral perturbation theory and (2) in the framework of the infrared regularization. The chiral expansion converges well in some channels.
118168794
Observation of $Z_c(3900)$ both by BESIII and Belle
Using $525$ pb$^{-1}$ data collected with the BESIII detector at $e^+e^-$ central-of-mass energy 4.26 GeV, the BESIII Collaboration observed a charged charmoniumlike state $Z_c(3900)\to\pi^{\pm}J/\psi$ with mass $M[Z_c(3900)]=3899.0\pm 3.6 \pm 4.9$ MeV/c$^2$, and width $\Gamma[Z_c(3900)]=46\pm 10 \pm 20$ MeV. The significance of this state was estimated to be $>8\sigma$ in all kinds of systematic tests. Using $967$ fb$^{-1}$ data recorded by the Belle detector on or near $\Upsilon(nS)$, n=1, 2, $\cdots$, 5 resonances, the $e^+e^- \to \pi^+\pi^-J/\psi$ process has been studied through initial-state-radiation (ISR) method. Except for the $Y(4260)$ resonance, an intermediate state $Z(3900)^{\pm}$ has been observed in the $\pi^{\pm}J/\psi$ mass spectrum, with significance $>5.2\sigma$. The measured mass $M[Z(3900)^{\pm}]=3894.5\pm6.6\pm4.5$ MeV/c$^2$ and width $\Gamma[Z(3900)^{\pm}]=63\pm24\pm26$ MeV, shows good agreement with the BESIII measurement within errors, which means $Z_c(3900)$ and $Z(3900)^{\pm}$ is the same state.
118589904
Form factors for rare B decays: strategy, methodology, and numerical study
llare presentlyaround 10 percent [1]. So far, measurements are consistent with Standard Model expectations[2, 3]. Future experiments like LHCb are going to reduce the experimental uncertainties further.Thus, we are entering an era of precision ﬂavour physics, req uiring experimentalists and theoriststo focus on reducing statistical errors and employing multiple cross-checks to further quantifysystematic uncertainties.Lattice QCD can contribute to this by providing ﬁrst-principles nonperturbative calculationsof hadronic matrix elements relevant for rare B decays. In this report, we present our currentprogress in doing these computations. We use a non-relativistic effective action for the b quarkcalled moving NRQCD (mNRQCD) [4], which helps reduce discretisation errors in the ﬁnal statemeson at large recoil. This is achieved by giving the B meson a signiﬁcant velocity in the latticeframe, so that at a given q