Search results for " Anni"
showing 10 items of 847 documents
Searches for sleptons and squarks in e(+)e(-) collisions at 189 GeV
1999
The data collected at a centre-of-mass energy of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 173.6 pb$^{-1}$, are analysed in a search for the scalar partners of quarks and leptons predicted in supersymmetric models. No evidence for any such particles was found in the decay channels $\sle \to \ell \chi$, $\stop \rightarrow \mathrm{c}\neu$, $\stop \rightarrow \mathrm{b}\ell\snu$, $\sbot \rightarrow \mathrm{b}\neu$, and $\mathrm{\tilde{q}} \rightarrow \mathrm{q}\neu$. Improved mass lower limits have been obtained in the framework of the Minimal Supersymmetric Standard Model.
Search for charged Higgs bosons in e^{+}e^{-}$ collisions at √s=172 GeV
1998
This paper presents results on charged Higgs boson production, based on LEP data collected at √s = 172 GeV, that complement the previous DELPHI results obtained at centre of mass energies up to 161 GeV. The charged Higgs bosons are assumed to be pair produced and to decay either into a quark pair or into τVτ. The three different possible final states are included in the analysis. Data from ring imaging Cherenkov and microvertex detectors are used to identify the quarks as a cs pair. The number of candidates found is compatible with the background expected from standard processes. Combining the results of the present analysis with those of the previous analysis at lower energies, a new lower…
Test of the flavour independence of αs
1995
Abstract Using about 950000 hadronic events collected during 1991 and 1992 with the ALEPH detector, the ratios r b = α s b α s udsc and r uds = α s uds α s cb have been measured in order to test the flavour independence of the strong coupling constant α s . The analysis is based on event-shape variables using the full hadronic sample, two b -quark samples enriched by lepton tagging and lifetime tagging, and a light-quark sample enriched by lifetime antitagging. The combined results are r b = 1.002±0.023 and r uds = 0.971 ± 0.023.
Measurement of Azimuthal Asymmetries in Inclusive Charged Dipion Production ine+e−Annihilations ats=3.65 GeV
2016
We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process e(+) e(-) -> pi pi X based on a data set of 62 pb(-1) at the center-of-mass energy of 3.65 GeV collected with the SESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-d…
Resummed jet rates for heavy quark production in e+e– annihilation
2004
Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates in electron-positron annihilation. Predictions are given for production of bottom quarks at LEP and top quarks at the Linear Collider.
Improved Measurement ofB+→ρ+ρ0and Determination of the Quark-Mixing Phase Angleα
2009
We present improved measurements of the branching fraction ${\cal B}$, the longitudinal polarization fraction $f_L$, and the direct {\ensuremath{CP}\xspace} asymmetry {\ensuremath{{\cal A}_{CP}}\xspace} in the $B$ meson decay channel $B^+\to\rho^+\rho^0$. The data sample was collected with the {{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}} detector at SLAC. The results are ${\cal B} (\Bp\ra\rprz)=(23.7\pm1.4\pm1.4)\times10^{-6}$, $f_L=0.950\pm0.015\pm0.006$, and $\Acp=-0.054\pm0.055\pm0.010$, where the uncertainties are statistical and systematic, respectively. Based on these results, we perform an isospin analysis and determine the CKM weak phase ang…
Improved measurements of electroweak parameters from Z decays into fermion pairs
1992
The properties of the Z resonance are measured on the basis of 190000 Z decays into fermion pairs collected with the ALEPH detector at LEP. Assuming lepton universality, M(Z) = (91.182 +/- 0.009exp +/- 0.020L;P) GeV, GAMMA(Z) = (2484 +/- 17) MeV, sigma(had)0 = (41.44 +/- 0.36) nb, and GAMMA(had)/GAMMA(ll) = 21.00 +/- 0.20. The corresponding number of light neutrino species is 2.97 +/- 0.07. The forward-backward asymmetry in leptonic decays is used to determine the ratio of vector to axial-vector coupling constants of leptons: g(V)2(M(Z)2)/g(A)2(M(Z)2) = 0.0072 +/- 0.0027. Combining these results with ALEPH results on quark charge and bbBAR asymmetries, and tau-polarization, sin2 theta(W)(M(…
Inclusive production of neutral vector mesons in hadronic Z decays
1996
Data on the inclusive production of the neutral vector mesons rho(0)(770), omega(782), K*(0)(892), and phi (1020) in hadronic Z decays recorded with the ALEPH detector at LEP are presented and compared to Monte Carlo model predictions. Bose-Einstein effects are found to be important in extracting a reliable value for the p(0) production rate. An average p(0) multiplicity of 1.45 +/- 0.21 per event is obtained. The omega is detected via its three pion decay mode omega --> pi(+)pi(-)pi(0) and has a total rate of 1.07 +/- 0.14 per event. The multiplicity of the K*(0) is 0.83 +/- 0.09, whilst that of the phi is 0.122 +/- 0.009, both measured using their charged decay modes. The measurements pro…
First Evidence for cos2β>0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity
2018
We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] p…
Evidence forB0→ρ0ρ0Decays and Implications for the Cabibbo-Kobayashi-Maskawa Angleα
2007
We search for the decays B(0) --> rho(0)rho(0), B(0) --> rho(0)f(0)(980), and B(0) --> f(0)(980)f(0)(980) in a sample of about 384 x 10(6) Upsilon(4S) --> BB[over] decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at Stanford Linear Accelerator Center. We find evidence for B(0) --> rho(0)rho(0) with 3.5 sigma significance and measure the branching fraction B = (1.07 +/- 0.33 +/- 0.19) x 10(-6) and longitudinal polarization fraction f(L) = 0.87 +/- 0.13 +/- 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix unitarity angle alpha due to penguin contributio…