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Sökning: WFRF:(Alekseev M.)

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1.
  • Schael, S, et al. (författare)
  • Precision electroweak measurements on the Z resonance
  • 2006
  • Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
  • Forskningsöversikt (refereegranskat)abstract
    • We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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2.
  • Murari, A., et al. (författare)
  • A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
  • 2024
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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3.
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4.
  • Abreu, P., et al. (författare)
  • Measurement of the gluon fragmentation function and a comparison of the scaling violation in gluon and quark jets
  • 2000
  • Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 13:4, s. 573-589
  • Tidskriftsartikel (refereegranskat)abstract
    • The fragmentation functions of quarks and gluons are measured in various three-jet topologies in Z decays from the full data set collected with the DELPHI detector at the Z resonance between 1992 and 995. The results at different values of transverse momentum-like scales are compared. A parameterization of the quark and gluon fragmentation functions at a fixed reference scale is given. The quark and gluon fragmentation functions show the predicted pattern of scaling violations. The scaling violation for quark jets as a function of a transverse momentum-like scale is in a good agreement with that observed in lower energy e+e- annihilation experiments. For gluon jets it appears to be significantly stronger. The scale dependences of the gluon and quark fragmentation functions agree with the prediction of the DGLAP evolution equations from which the colour factor ratio CA/CF is measured to be: CA/CF = 2.26 ± 0.09stat. ± 0.06sys. ± 0.12clus.,scale..
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5.
  • Abreu, P., et al. (författare)
  • Study of dimuon production in photon-photon collisions and measurement of QED photon structure functions at LEP
  • 2001
  • Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 15-28
  • Tidskriftsartikel (refereegranskat)abstract
    • Muon pair production in the process e+e- → e+e- μ+μ- is studied using the data taken at LEP1 (√s ≃ mz) with the DELPHI detector during the years 1992-1995. The corresponding integrated luminosity is 138.5 pb-1. The QED predictions have been tested over the whole Q2 range accessible at LEP1 (from several GeV2/c4 to several hundred GeV2/c4) by comparing experimental distributions with distributions resulting from Monte Carlo simulations using various generators. Selected events are used to extract the leptonic photon structure function Fγ 2. Azimuthal correlations are used to obtain information on additional structure functions, Fγ A and Fγ B, which originate from interference terms of the scattering amplitudes. The measured ratios Fγ A/Fγ 2 and FγB/Fγ 2 are significantly different from zero and consistent with QED predictions.
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6.
  • Abreu, P., et al. (författare)
  • Search for sleptons in e+e- collisions at √s = 183 to 189 GeV
  • 2001
  • Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 29-42
  • Tidskriftsartikel (refereegranskat)abstract
    • Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb-1 have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay (ℓ̃ → ℓx̃), producing acoplanar lepton pairs plus missing energy, and the cascade decay (ℓ → ℓx̃0 2 → ℓγx̃0 1), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are mẽ ≤ 87 GeV/c2, mμ̃ ≤ 80 GeV/c2 and mτ̃ 75 GeV/c2, respectively, for values of μ=-200 GeV/c2 and tanβ=1.5.
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7.
  • Ablikim, M., et al. (författare)
  • Measurement of e(+)e(-) -> D(D)over-bar cross sections at the psi(3770) resonance
  • 2018
  • Ingår i: Chinese Physics C. - : IOP PUBLISHING LTD. - 1674-1137 .- 2058-6132. ; 42:8
  • Tidskriftsartikel (refereegranskat)abstract
    • We report new measurements of the cross sections for the production of D (D) over bar final states at the psi(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fb(-1) of e(+)e(-) annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D-0 and six D+ hadronic decay modes and use the ratio of the yield of fully reconstructed D (D) over bar events ("double tags") to the yield of all reconstructed D or (D) over bar mesons ("single tags") to determine the number of D-0(D) over bar (0) and D+D- events, benefiting from the cancellation of many systematic uncertainties. Combining these yields with an independent determination of the integrated luminosity of the data sample, we find the cross sections to be sigma(e(+)e(-) -> D-0(D) over bar (0)(-) )=(3.615 +/- 0.010 +/- 0.038) nb and sigma(e(+)e(-) -> D+D-)=(2.830 +/- 0.011 +/- 0.026) nb, where the uncertainties are statistical and systematic, respectively.
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8.
  • Ablikim, M., et al. (författare)
  • Measurement of the integrated Luminosities of cross-section scan data samples around the psi(3770) mass region
  • 2018
  • Ingår i: Chinese Physics C. - : SCIENCE PRESS. - 1674-1137 .- 2058-6132. ; 42:6
  • Tidskriftsartikel (refereegranskat)abstract
    • To investigate the nature of the psi(3770) resonance and to measure the cross section for e(+)e(-) -> D (D) over bar, a cross-section scan data sample, distributed among 41 center-of-mass energy points from 3.73 to 3.89 GeV, was taken with the BESIII detector operated at the BEPCII collider in the year 2010. By analyzing the large angle Bhabha scattering events, we measure the integrated luminosity of the data sample at each center-of-mass energy point. The total integrated luminosity of the data sample is 76.16 +/- 0.04 +/- 0.61 pb(-1), where the first uncertainty is statistical and the second systematic.
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9.
  • Ablikim, M., et al. (författare)
  • Evidence for e+e−→γηc(1S) at center-of-mass energies between 4.01 and 4.60 GeV
  • 2017
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 96:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We present first evidence for the process e(+)e(-) -> gamma eta(c)(1S) at six center-of-mass energies between 4.01 and 4.60 GeV using data collected by the BESIII experiment operating at BEPCII. We measure the Born cross section at each energy using a combination of twelve eta(c)(1S) decay channels. We also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the Y(4260), we measure a peak Born cross section sigma(peak)(e(+)e(-) -> gamma eta(c)(1S)) = 2.11 +/- 0.49 (stat.) +/- 0.36 (syst.) pb with a statistical significance of 4.2 sigma.
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10.
  • Ablikim, M., et al. (författare)
  • First measurement of e(+)e(-) -> pK(S)(0)(n)over-barK(-) + c.c. above open charm threshold
  • 2018
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 98:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The process e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb(-1). The Born cross section of e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the pK(-), nK(S)(0), pK(S)(0), nK(+), p (n) over bar, or (KSK-)-K-0 invariant mass distributions except for Lambda(1520). The Born cross sections of e(+)e(-) -> Lambda(1520)(n) over barK(S)(0) + c.c. and e(+)e(-) -> Lambda(1520)(p) over barK(+) + c.c. are measured, and the 90% confidence level upper limits on the Born cross sections of e(+)e(-) -> Lambda(1520)(Lambda) over bar (1520) are determined at the seven center-of-mass energies. There is an evident difference in line shape and magnitude of the measured cross sections between e(+)e(-) -> Lambda(1520)(-> pK(-))(n) over barK(S)(0) and e(+)e(-) -> pK-(Lambda) over bar (1520)(-> (n) over barK(S)(0)).
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11.
  • Ablikim, M., et al. (författare)
  • Measurement of the Absolute Branching Fraction of the Inclusive Decay Lambda(+)(c) -> Lambda plus X
  • 2018
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on an e(+)e(-) collision data sample corresponding to an integrated luminosity of 567 pb(-1) taken at the center-of-mass energy of root s = 4.6 GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay Lambda(+)(c) -> Lambda + X to be B(Lambda(+)(c) -> Lambda + X) = (38.2(-2.2)(+2.8) +/- 0.9)% using the double-tag method, where X refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain A(CP) [B(Lambda(+)(c) -> Lambda + X) - B((Lambda) over bar (-)(c) -> (Lambda) over bar + X)]/[B(Lambda(+)(c) -> Lambda + X) + B((Lambda) over bar (-)(c) -> (Lambda) over bar + X)] = (2.1(-6.6)(+7.0) +/- 1.6)%, a statistically limited result with no evidence of CP violation.
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12.
  • Ablikim, M., et al. (författare)
  • Observation of psi(3686) -> eta ' e(+)e(-)
  • 2018
  • Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 783, s. 452-458
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a data sample of 448.1 x 10(6) psi(3686) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay psi(3686) -> eta'e(+)e(-), with significances of 7.0 sigma and 6.3 sigma when reconstructing the eta' meson via its decay modes eta' -> gamma pi(+)pi(-) and eta' -> pi(+)pi(-) eta (eta -> gamma gamma), respectively. The weighted average branching fraction is determined to be B(psi(3686) -> eta'e(+)e(-)) = (1.90 +/- 0.25 +/- 0.11) x 10(-6), where the first uncertainty is statistical and the second systematic.
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13.
  • Ablikim, M., et al. (författare)
  • Search for invisible decays of omega and phi with J/psi data at BESIII
  • 2018
  • Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 98:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a data sample of (1310.6 +/- 7.0) x 10(6) J/psi events collected with the BESIII detector operating at the BEPCII collider, we perform the first experimental search for invisible decays of a light vector meson (V = omega, phi) via J/psi -> V-eta decays. The decay of eta -> pi(+)pi(-)pi(0) is utilized to tag the V meson decaying into the invisible final state. No evidence for a significant invisible signal is observed, and the upper limits on the ratio of branching fractions at the 90% confidence level are determined to be B(omega -> invisible)/B(omega -> pi(+)pi(-)pi(0)) < 8.1 x 10(-5) and B(phi -> invisible)/B(phi -> K+K-) < 3.4 x 10(-4). By using the world average values of B(omega -> pi(+)pi(-)pi(0) and B(phi -> K+K-,) the upper limits on the decay branching fractions at the 90% confidence level are set as B(omega -> invisible) < 7.3 x 10(-5) and B(phi -> invisible) < 1.7 x 10(-4), respectively.
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14.
  • Ablikim, M., et al. (författare)
  • Search for the rare decay of ψ(3686)→Λ+c¯pe+e−+c.c. at BESIII
  • 2018
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 97:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on a data sample of (448.1 +/- 2.9) x 10(6)Psi(3686) decays collected with the BESIII experiment, a search for the flavor changing neutral current transition Psi(3686) -> Lambda(+)(c) pe(+) e(-) + c.c. is performed for the first time. No signal candidates are observed and the upper limit on the branching fraction of Psi(3686) -> Lambda(+)(c) pe(+) e(-) is determined to be 1.7 x 10(-6) at the 90% confidence level. The result is consistent with expectations from the standard model, and no evidence for new physics is found.
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15.
  • Ablikim, M., et al. (författare)
  • Branching fraction measurement of J/ψ→KSKL and search for J/ψ→KSKS
  • 2017
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 96:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a sample of 1.31 x 10(9) J/Psi events collected with the BESIII detector at the BEPCII collider, we study the decays of J/Psi -> KSKL and KSKS. The branching fraction of J/Psi -> KSKL is determined to be B(J/Psi -> KSKL) = (1.93 +/- 0.01 (stat) +/- 0.05 (syst)) x 10(-4), which significantly improves on previous measurements. No clear signal is observed for the J/Psi -> KSKS process, and the upper limit at the 95% confidence level for its branching fraction is determined to be B(J/Psi -> KSKS) < 1.4 x 10(-8), which improves on the previous searches by 2 orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.
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16.
  • Ablikim, M., et al. (författare)
  • Improved measurements of X-cJ -> Sigma(+) (Sigma)over-bar(-) and Sigma(0)(Sigma)over-bar(0) decays
  • 2018
  • Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 97:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a data sample of (448.1 +/- 2.9) x 10(6) psi (3686) events collected with the BESIII detector at the BEPCII collider, we present measurements of branching fractions for the decays X-cJ -> Sigma(+) (Sigma) over bar (-) and Sigma(0) (Sigma) over bar (0) The decays X-c1.2 -> Sigma(+) (Sigma) over bar (-) and Sigma (Sigma) over bar (0) are observed for the first time, and the branching fractions for X-c0 -> Sigma(+) (Sigma) over bar (-) and Sigma(0) (Sigma) over bar (0) decays are measured with improved precision. The branching fraction ratios between the charged and neutral modes are consistent with the prediction of isospin symmetry.
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17.
  • Ablikim, M., et al. (författare)
  • Measurements of absolute branching fractions for Lambda(+)(c) -> Xi K-0(+) and Xi(1530)K-0(+)
  • 2018
  • Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 783, s. 200-206
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first measurements of absolute branching fractions for the W-exchange-only processes Lambda(+)(c) -> Xi K-0(+) and Lambda(+)(c)-> Xi(1530)K-0(+) with the double-tag technique, by analyzing an e(+)e(-) collision data sample, that corresponds to an integrated luminosity of 567 pb(-1) collected at a center-of-mass energy of 4.6 GeV by the BESIII detector. The branching fractions are measured to be B(Lambda(+)(c)-> Xi K-0(+)) = (5.90 +/- 0.86 +/- 0.39) x 10(-3) and B(Lambda(+)(c)-> Xi(1530)K-0(+)) = (5.02 +/- 0.99 +/- 0.31) x 10(-3), where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.
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18.
  • Ablikim, M., et al. (författare)
  • Observation of a(0)(0)(980)-f(0)(980) Mixing
  • 2018
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first observation of a(0)(0)(980)-f(0)(980) mixing in the decays of J/psi -> phi f(0)(980) -> phi a(0)(0)(980) -> phi eta pi(0) and chi(c1) -> a(0)(0)(980)pi(0) -> f(0)(980)pi(0)->pi(+)pi(-)pi(0), using data samples of 1.31 x 10(9) J/psi events and 4.48 x 10(8) psi (3686) events accumulated with the BESIII detector. The signals of f(0)(980) -> a(0)(0)(980) and a(0)(0)(980) -> f(0)(980) mixing are observed at levels of statistical significance of 7.4 sigma and 5.5 sigma, respectively. The corresponding branching fractions and mixing intensities are measured and the constraint regions on the coupling constants, g(a0K+K-) and g(f0K+K-), are estimated. The results improve the understanding of the nature of a(0)(0)(980) and f(0)(980).
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19.
  • Ablikim, M., et al. (författare)
  • Observation of the Semileptonic Decay D-0 -> a(0)(980)(-)e(+)nu(e) and Evidence for D+ -> a(0)(980)(0)e(+)nu(e)
  • 2018
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Using an e(+)e(-) collision data sample of 2.93 fb(-1) collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D-0 -> a(0)(980)(-)e(+)nu(e) and evidence for D+ -> a(0)(980)(0)e(+)nu(e) with significances of 6.4 sigma and 2.9 sigma, respectively. The absolute branching fractions are determined to be B(D-0 -> a(0)(980)(-)e(+)nu(e)) x B(a(0)(980)(-) -> eta pi(-)) = [1.33(-0.29)(+0.33)(stat) +/- 0.09(syst)] x 10(-4) and B(D+ -> a(0)(980)(0)e(+)nu(e)) x B(a(0)(980)(0) -> eta pi(0)) = [1.66(-0.66)(+0.81)(stat) +/- 0.11(syst) x 10(-4). This is the first time the a(0)(980) meson has been measured in a D-0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling a(0)(980) states.
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20.
  • Ablikim, M., et al. (författare)
  • Search for the rare decays D -> h(h((')))e(+) e(-)
  • 2018
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We search for rare decays of D mesons to hadrons accompanied by an electron-positron pair (h(h((')))e(+)e(- )),using an e(+)e(-) collision sample corresponding to an integrated luminosity of 2.93 fb(-1) collected with the BESIII detector at root s = 3.773 GeV. No significant signals are observed, and the corresponding upper limits on the branching fractions at the 90% confidence level are determined. The sensitivities of the results are at the level of 10(-5)-10(-6), providing a large improvement over previous searches.
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21.
  • Ablikim, M., et al. (författare)
  • Measurement of branching fractions for psi(3686) -> gamma eta ', gamma eta, and gamma pi(0)
  • 2017
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 96:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a data sample of 448 x 10(6) psi(3686) events collected with the BESIII detector operating at the BEPCII storage ring, the decays psi(3686) -> gamma eta and psi(3686) -> gamma pi(0) are observed with a statistical significance of 7.3 sigma and 6.7 sigma, respectively. The branching fractions are measured to be B(psi(3686) -> gamma eta) = (0.85 +/- 0.18 +/- 0.05) x 10(-6) and B(psi(3686) ->gamma pi(0)) = (0.95 +/- 0.16 +/- 0.05) x 10(-6). In addition, we measure the branching fraction of psi(3686) -> gamma eta' to be B(psi(3686) -> gamma eta') = (125.1 +/- 2.2 +/- 6.2)x10(-6), which represents an improvement of precision over previous results.
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22.
  • Ablikim, M., et al. (författare)
  • Precision Measurement of the e(+)e(-) -> Lambda(+)(c)(Lambda)over-bar(c)(-) Cross Section Near Threshold
  • 2018
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 120:13
  • Tidskriftsartikel (refereegranskat)abstract
    • The cross section of the e(+)e(-) -> Lambda(+)(c)(Lambda) over bar (-)(c) process is measured with unprecedented precision using data collected with the BESIII detector at root s = 4574.5, 4580.0, 4590.0 and 4599.5 MeV. The nonzero cross section near the Lambda(+)(c)(Lambda) over bar (-)(c) production threshold is cleared. At center-of-mass energies root s = 4574.5 and 4599.5 MeV, the higher statistics data enable us to measure the Lambda(c) polar angle distributions. From these, the.c electric over magnetic form-factor ratios (vertical bar G(E)/G(M)vertical bar) are measured for the first time. They are found to be 1.14 +/- 0.14 +/- 0.07 and 1.23 +/- 0.05 +/- 0.03, respectively, where the first uncertainties are statistical and the second are systematic.
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23.
  • Ablikim, M., et al. (författare)
  • Study of eta(1475) and X(1835) in radiative J/psi decays to gamma phi
  • 2018
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The decay J/psi -> gamma gamma phi is studied using a sample of 1.31 x 10(9) J/psi events collected with the BESIII detector. Two structures around 1475 MeV/c(2) and 1835 MeV/c(2) are observed in the gamma phi invariant mass spectrum for the first time. With a fit on the gamma phi invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/c(2) is found to favor an assignment as the eta(1475) and the mass and width for the structure around 1835 MeV/c(2) are consistent with the X(1835). The statistical significances of the two structures are 13.5 sigma and 6.3 sigma, respectively. The results indicate that both eta(1475) and X(1835) contain a sizeable s (s) over bar component.
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24.
  • Meyer, E., et al. (författare)
  • The state of the art in beyond 5G distributed massive multiple-input multiple-output communication system solutions
  • 2022
  • Ingår i: Open Research Europe. - : F1000 Research Ltd. - 2732-5121. ; 2
  • Forskningsöversikt (refereegranskat)abstract
    • Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.
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25.
  • Abreu, P, et al. (författare)
  • A measurement of alpha(s) from the scaling violation in e(+)e(-) annihilation
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 398:1-2, s. 194-206
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The hadronic fragmentation functions of the various quark flavours and of gluons are measured in a study of the inclusive hadron production from Z(0) decays with the DELPHI detector and are compared with the fragmentation functions measured elsewhere at e
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26.
  • Abreu, P, et al. (författare)
  • A precise measurement of the B-d(0) meson lifetime using a new technique
  • 1997
  • Ingår i: ZEITSCHRIFT FUR PHYSIK C-PARTICLES AND FIELDS. - : SPRINGER VERLAG. - 0170-9739. ; 74:1, s. 19-32
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • From data recorded by DELPHI between 1991 and 1994, which corresponds to 3.2 million hadronic Z(0) decays, a measurement of the <(B-d(0))over bar> meson lifetime, based on the inclusive reconstruction of 3520 +/- 150 semileptonic decays of the type <(B-d(
  •  
27.
  •  
28.
  • Abreu, P, et al. (författare)
  • An upper limit for Br(Z(0)->ggg) from symmetric 3-jet Z(0) hadronic decays
  • 1996
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 389:2, s. 405-415
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • An upper limit for BR(Z(0) --> 3g) is obtained from a correlation method, which distinguishes statistically between quark and gluon jets by using the difference in their charged particle multiplicity distributions. From the sample of threefold symmetric t
  •  
29.
  •  
30.
  • Abreu, P, et al. (författare)
  • Identified particles in quark and gluon jets
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 401:1-2, s. 118-130
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • A sample of about 1.4 million hadronic Z decays, selected among the data recorded by the DELPHI detector at LEP during 1994, was used to measure for the first time the momentum spectra of K+, K-0, p, Lambda and their antiparticles in gluon and quark jets.
  •  
31.
  • Abreu, P, et al. (författare)
  • Kaon interference in the hadronic decays of the Z(0)
  • 1996
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 379:1-4, s. 330-340
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The first measurement of like-sign charged kaon correlations in hadronic decays of the Z(0) is presented, based on data collected by the DELPHI detector. The charged kaons are identified by means of ring imaging Cherenkov detectors. A significant enhancem
  •  
32.
  • Abreu, P, et al. (författare)
  • m(b) at M-Z
  • 1998
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 418:3-4, s. 430-442
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The value of the Lr quark, mass at the M-Z scale defined in the <(MS)over bar> renormalization scheme, m(b)(M-Z), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI detector to be m(b)(M-Z) = 2.67 +/- 0.25 (stat.)
  •  
33.
  • Abreu, P, et al. (författare)
  • Measurement and interpretation of the W-pair cross-section in e(+)e(-) interactions at 161 GeV
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 397:1-2, s. 158-170
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • In 1996 LEP ran at a centre-of-mass energy of 161 GeV, just above the threshold of W-pair production. DELPHI accumulated data corresponding to an integrated luminosity of 9.93 pb(-1), and observed 29 events that are considered as candidates for W-pair pro
  •  
34.
  • Abreu, P, et al. (författare)
  • Measurement of B-d(0)-(B-d(0))over-bar oscillations
  • 1997
  • Ingår i: ZEITSCHRIFT FUR PHYSIK C-PARTICLES AND FIELDS. - : SPRINGER VERLAG. - 0170-9739. ; 76:4, s. 579-598
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • B-d(0) meson oscillations are measured in hadronic Z(0) decays using the charge of a lepton or the mean charge of an event hemisphere to sign the presence of a b or a (b) over bar quark when it is produced, and using the charge of a lepton emitted at larg
  •  
35.
  • Abreu, P, et al. (författare)
  • Measurement of correlations between pions from different W's in e(+)e(-)->W+W- events
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 401:1-2, s. 181-191
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Correlations between pions from different W's in e(+)e(-) --> W+W- events are studied using data collected by the DELPHI detector at LEP running at a centre-of-mass energy of 172 GeV in 1996. At the present level of statistics, no enhancement of the corre
  •  
36.
  • Abreu, P, et al. (författare)
  • Measurement of the multiplicity of gluons splitting to bottom quark pairs in hadronic Z(0) decays
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 405:1-2, s. 202-214
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • An inclusive measurement of the average multiplicity of b (b) over bar pairs from gluons, g(b (b) over bar), in hadronic Z(0) events collected by the DELPHI experiment at LEP, is presented. A counting technique, based on jet b-tagging in 4-jet events, has
  •  
37.
  • Abreu, P, et al. (författare)
  • Measurement of the quark and gluon fragmentation functions in Z(0) hadronic decays
  • 1999
  • Ingår i: EUROPEAN PHYSICAL JOURNAL C. - : SPRINGER VERLAG. - 1434-6044. ; 6:1, s. 19-33
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The transverse, longitudinal and asymmetric components of the fragmentation function are measured from the inclusive charged particles produced in e(+)e(-) collisions at LEP. As in deep inelastic scattering, these data are important for tests of QCD. The
  •  
38.
  • Abreu, P, et al. (författare)
  • Measurement of the spin density matrix for the rho(0), K*(0)(892) and phi produced in Z(0) decays
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 406:3, s. 271-286
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The spin density matrix elements for the rho(0), K-*0(892) and phi produced in hadronic Z(0) decays are measured in the DELPHI detector. There is no evidence for spin alignment of the K-*0(892) and phi, in the region x(p) less than or equal to 0.3 (x(p) =
  •  
39.
  • Abreu, P, et al. (författare)
  • Measurement of the transverse spin correlation in Z->tau(+)tau(-) decays
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 404:1-2, s. 194-206
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The measurement of the correlation between the transverse spin components of tau(+)tau(-) pairs collected during 1992 to 1994 with the DELPHI detector at LEP1 is presented. A value C-TT = 0.87 +/- 0.20 (stat.)(-0.12)(+0.10) (syst.) was obtained for the co
  •  
40.
  • Abreu, P, et al. (författare)
  • Measurement of the triple gluon vertex from double quark tagged 4-jet events
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 414:3-4, s. 401-418
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The 4-jet events collected by the DELPHI experiment at LEP1 in 1992, 1993 and 1994 are analysed to determine the contribution of the triple-gluon vertex. Two of the four jets are tagged as jets from b- or c-quarks using lifetime and lepton transverse mome
  •  
41.
  • Abreu, P, et al. (författare)
  • Measurement of the W-pair cross-section and of the W mass in e(+)e(-) interactions at 172 GeV
  • 1998
  • Ingår i: EUROPEAN PHYSICAL JOURNAL C. - : SPRINGER VERLAG. - 1434-6044. ; 2:4, s. 581-595
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • From a data sample of 9.98 pb(-1) integrated luminosity, collected by DELPHI at a centre-of-mass energy of 172 GeV, 118 events were selected as W-pair candidates. From these, the branching fraction Br(W --> q (q) over bar) was measured to be 0.660(-0.037)
  •  
42.
  • Abreu, P, et al. (författare)
  • Observation of charge-ordering in particle production in hadronic Z(0) decay
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 407:2, s. 174-184
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Analysis of the rapidity structure of charge correlations in hadronic events from Z(0) decays gives evidence for chain-like charge-ordering of particle production along the thrust axis, as predicted by 'QCD-motivated' string-like fragmentation models. (C)
  •  
43.
  • Abreu, P, et al. (författare)
  • Rapidity correlations in Lambda baryon and proton production in hadronic Z(0) decays
  • 1998
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 416:1-2, s. 247-256
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • In an analysis of multihadronic events recorded at LEP by DELPHI in the years 1992 through 1994, rapidity correlations of Lambda-Lambda, proton-proton, and Lambda-proton pairs are compared with each other and with the predictions of the string fragmentati
  •  
44.
  • Abreu, P, et al. (författare)
  • Search for charginos, neutralinos and gravitinos at LEP
  • 1998
  • Ingår i: EUROPEAN PHYSICAL JOURNAL C. - : SPRINGER VERLAG. - 1434-6044. ; 1:1-2, s. 1-20
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • An update of the searches for charginos and neutralinos in DELPHI is presented, based mainly on recent data collected at centre-of-mass energies of 161 GeV and 172 GeV. No signal is found. For a sneutrino with mass above 300 GeV/c(2) and a mass difference
  •  
45.
  • Abreu, P, et al. (författare)
  • Search for excited leptons in e(+)e(-) collisions at root s=161 GeV
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 393:1-2, s. 245-260
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • A search with the DELPHI detector at LEP for excited leptons (e*, mu*, tau* and nu*) decaying through gamma, W or Z transitions is reported. The data used correspond to an integrated luminosity of 10 pb(-1) e(+)e(-) centre-of-mass energy at an e of 161 Ge
  •  
46.
  • Abreu, P, et al. (författare)
  • Search for neutral and charged Higgs bosons in e(+)e(-) collisions at root s=161 GeV and 172 GeV
  • 1998
  • Ingår i: EUROPEAN PHYSICAL JOURNAL C. - : SPRINGER VERLAG. - 1434-6044. ; 2:1, s. 1-37
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • A search for neutral and charged Higgs bosons has been performed in the data collected by the DELPHI detector at centre-of-mass energies of 161 GeV and 172 GeV. The analysis assumes either the pair-production of charged Higgs bosons, H+/-, or the producti
  •  
47.
  • Abreu, P, et al. (författare)
  • Search for neutral heavy leptons produced in Z decays
  • 1997
  • Ingår i: ZEITSCHRIFT FUR PHYSIK C-PARTICLES AND FIELDS. - : SPRINGER VERLAG. - 0170-9739. ; 74:1, s. 57-71
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Weak isosinglet Neutral Heavy Leptons (nu(m)) have been searched for using data collected by the DELPHI detector corresponding to 3.3 x 10(6) hadronic Z(0) decays at LEP1. Four separate searches have been performed, for short-lived nu(m) production giving
  •  
48.
  • Abreu, P, et al. (författare)
  • Search for stable heavy charged particles in e(+)e(-) collisions at root s=130-136, 161 and 172 GeV
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 396:1-4, s. 315-326
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • A search for stable or long-lived heavy charged particles in e(+)e(-) interactions at energies of 130-136, 161 and 172 CeV has been performed using the data taken by the DELPHI experiment at LEP. The search is based on particle identification provided by
  •  
49.
  • Abreu, P, et al. (författare)
  • Search for the B-c meson
  • 1997
  • Ingår i: PHYSICS LETTERS B. - : ELSEVIER SCIENCE BV. - 0370-2693. ; 398:1-2, s. 207-222
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • In a sample of 3.02 million hadronic Z(0) decays collected by the DELPHI detector, 270 J/psi --> e(+)e(-) candidates have been selected. A search for fully reconstructed B-c(+/-) mesons has yielded one B-c(+/-) --> J/psi pi(+/-) candidate, no B-c(+/-) -->
  •  
50.
  • Abreu, P, et al. (författare)
  • Tuning and test of fragmentation models based on identified particles and precision event shape data
  • 1996
  • Ingår i: ZEITSCHRIFT FUR PHYSIK C-PARTICLES AND FIELDS. - : SPRINGER VERLAG. - 0170-9739. ; 73:1, s. 11-59
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Event shape and charged particle inclusive distributions are measured using 750000 decays of the Z to hadrons from the DELPHI detector at LEP, These precise data allow a decisive confrontation with models of the hadronization process, Improved tunings of
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