Search results for " ANN"
showing 10 items of 1343 documents
Measurement of inclusive production of light meson resonances in hadronic decays of the Z0
1993
A study of inclusive production of the meson resonances ρ0, K*0 (892), f{hook}0 (975) and f{hook}2 (1270) in hadronic decays of the Z0 is presented. The measured mean meson multiplicity per hadronic event is 0.83 ± 0.14 for the ρ0 0.64 ± 0.24 for the K*0 (892), 0.10 ± 0.04 for the f{hook}0 (975) in the momentum range p > 0.05pbeam (xp > 0.05) and 0.11 ± 0.05 for the f{hook}2 (1270) for xp > 0.1. These values and the corresponding differential cross sections ( 1 σhadr) dσ dxp for the vector mesons are in good agreement with the predictions of the JETSET 7.3 PS and HERWIG 5.4 models. The f{hook}2 (1270) production is overestimated by HERWIG but its xp-shape is correctly reproduced. T…
Observation of theχc2(2P)meson in the reactionγγ→DD¯atBABAR
2010
A search for the Z(3930) resonance in gamma gamma production of the DDbar system has been performed using a data sample corresponding to an integrated luminosity of 384 fb^-1 recorded by the BABAR experiment at the PEP-II asymmetric-energy electron-positron collider. The DDbar invariant mass distribution shows clear evidence of the Z(3930) state with a significance of 5.8 sigma. We determine mass and width values of (3926.7 +- 2.7 +- 1.1) MeV/c^2 and (21.3 +- 6.8 +- 3.6) MeV, respectively. A decay angular analysis provides evidence that the Z(3930) is a tensor state with positive parity and C-parity (J^PC = 2^++); therefore we identify the Z(3930) state as the chi_c2(2P) meson. The value of…
Measurement of the branching fraction, polarization, andCPasymmetries inB0→ρ0ρ0decay, and implications for the CKM angleα
2008
We study B^0→ρ^0ρ^0 decays in a sample of 465×10^6 Υ(4S)→BB events collected with the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider located at the Stanford Linear Accelerator Center (SLAC). We measure the branching fraction B=(0.92±0.32±0.14)×10^(-6) and longitudinal polarization fraction f_L=0.75_(-0.14)^(+0.11)±0.05, where the first uncertainty is statistical and the second is systematic. The evidence for the B^0→ρ^0ρ^0 signal has a significance of 3.1 standard deviations, including systematic uncertainties. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S_L^(00)=(0.3±0.7±0.2) and C_L^(00)=(0.…
Measurement of the Effective b quark Fragmentation Function At the Z resonance
1995
Using a sample of about 1.46 million hadronic Z decays collected between 1991 and 1993 with the ALEPH detector at LEP, the energy distribution of the B-0 and B-+/- mesons produced at the Z resonance is measured by reconstructing semileptonic decays B --> l nu(l)D(X) or B --> l nu(l)D*(+)(X). The charmed mesons are reconstructed through the decay modes D-0 --> K(-)pi(+), D-0, --> K(-)pi(+)pi(-)pi(+),D+ --> K(-)pi(+)pi(+), and D*(+) --> D-0 pi(+). The neutrino energy is estimated from the missing energy in the lepton hemisphere. Accounting for B* and B** production, the shape of the scaled energy distribution x(E)((b)) for mesons containing a b quark is compared to the predictions of differen…
Measurement of triple gauge WWγ couplings at LEP2 using photonic events
1998
A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV,corresponding to a total integrated luminosity of about 80 pb**-1.The measured distributions are in agreement with Standard Model predictions, leading to constraints on W W gamma gauge coupling parameters Delta(kappa_gamma) and lambda_gamma. The results from the fit to the cross sectionsand to the energy and angular distributions of the photons are: Delta(kappa_gamma) = 0.05 +1.15/-1.10 (stat) +/- 0.25 (syst) lambda_gamma = 0.05 +1.55/-1.45 (stat) +/- 0.30 (syst) A study of events with photons and missing energy has been pe…
Single- and multi-photon production in e+e− collisions at a centre-of-mass energy of 183 GeV
1998
The production of final states involving one or more energetic photons from e(+)e(-) collisions is studied in a sample of 58.5 pb(-1) of data recorded at a centre-of-mass energy of 183 GeV by the ALEPH detector at LEP. The e(+)e(-) --> v (v) over bar gamma(gamma) and e(+)e(-) --> gamma gamma(gamma) cross sections are measured. The data are in good agreement with predictions based on the Standard Model and are used to set upper limits on the cross sections for anomalous photon production in the context of two supersymmetric models and for various extensions to QED. In particular, in the context of a super-light gravitino model a cross section upper limit of 0.38 pb is placed on the process e…
New ISR Cross Section Results on e + e − → π + π − π 0 π 0 and e + e − → π + π − η from BaBar
2017
Abstract Two new hadronic cross sections measured by the BaBar experiment are presented: e + e − → π + π − π 0 π 0 and e + e − → π + π − η . For both channels, the contribution to the anomalous magnetic moment of the muon is calculated.
Tau anomalous magnetic moment form factor at Super B/Flavor factories
2008
The proposed high-luminosity B/Flavor factories offer new opportunities for the improved determination of the fundamental physical parameters of standard heavy leptons. Compared to the electron or the muon case, the magnetic properties of the $\tau$ lepton are largely unexplored. We show that the electromagnetic properties of the $\tau$, and in particular its magnetic form factor, may be measured competitively in these facilities, using unpolarized or polarized electron beams. Various observables of the $\tau$'s produced on top of the $\Upsilon$ resonances, such as cross-section and normal polarization for unpolarized electrons or longitudinal and transverse asymmetries for polarized beams,…
Search for lepton-number violatingB+→X−ℓ+ℓ′+decays
2014
We report on a search for eleven lepton-number violating processes B^+→X^−l^+l'^+ with X^−=K^−, π^−, ρ^−, K^(*−), or D^− and l^+/l'^+=e^+ or μ^+, using a sample of 471±3 million BB events collected with the BABAR detector at the PEP-II e^+e^− collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range (1.5–26)×10_(−7).
e+e−→π+π−π+π−,K+K−π+π−, andK+K−K+K−cross sections at center-of-mass energies 0.5–4.5 GeV measured with initial-state radiation
2005
We study the process $e^+e^-\to\pi^+\pi^-\pi^+\pi^-\gamma$, with a hard photon radiated from the initial state. About 60,000 fully reconstructed events have been selected from 89 $fb^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that these data can be compared with the corresponding direct $e^+e^-$ measurements. From the $4\pi$-mass spectrum, the cross section for the process $e^+e^-\to\pi^+\pi^-\pi^+\pi^-$ is measured for center-of-mass energies from 0.6 to 4.5 $GeV/c^2$. The uncertainty in the cross section measurement is typically 5%. We also measure the cross sections for the final states $K^+ K^- \pi^+\pi^-$ an…