4,404 research outputs found

    Measurement of the e+eK+Kπ+πe^+e^- \to K^+K^-\pi^+\pi^- cross section with the CMD-3 detector at the VEPP-2000 collider

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    The process e+eK+Kπ+πe^+e^- \to K^+K^-\pi^+\pi^- has been studied in the center-of-mass energy range from 1500 to 2000\,MeV using a data sample of 23 pb1^{-1} collected with the CMD-3 detector at the VEPP-2000 e+ee^+e^- collider. Using about 24000 selected events, the e+eK+Kπ+πe^+e^- \to K^+K^-\pi^+\pi^- cross section has been measured with a systematic uncertainty decreasing from 11.7\% at 1500-1600\,MeV to 6.1\% above 1800\,MeV. A preliminary study of K+Kπ+πK^+K^-\pi^+\pi^- production dynamics has been performed

    Study of the process e+eppˉe^+e^-\to p\bar{p} in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector

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    Using a data sample of 6.8 pb1^{-1} collected with the CMD-3 detector at the VEPP-2000 e+ee^+e^- collider we select about 2700 events of the e+eppˉe^+e^- \to p\bar{p} process and measure its cross section at 12 energy ponts with about 6\% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio GE/GM=1.49±0.23±0.30|G_{E}/G_{M}| = 1.49 \pm 0.23 \pm 0.30

    Measurement of the e+eπ+πe^+e^-\to\pi^+\pi^- cross section from threshold to 1.2 GeV with the CMD-3 detector

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    The cross section of the process e+eπ+πe^+e^-\to\pi^+\pi^- has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on a full dataset collected below 1 GeV during three data taking seasons, corresponding to an integrated luminosity of about 62 pb1^{-1}. In the dominant ρ\rho-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around ϕ\phi-resonance the π+π\pi^+\pi^- production cross section was measured for the first time with high energy resolution. The forward-backward charge asymmetry in the π+π\pi^+\pi^- production has also been measured. It shows the strong deviation from the theoretical prediction based on conventional sQED framework and is in good agreement with GVDM and dispersive-based predictions. The impact of presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed.Comment: 52 pages, 36 figures; cosmetic changes of the text, fix fig.2 , fix comment on used selection cuts in the attached radiative correction tabl

    Measurement of the pion formfactor with CMD-3 detector and its implication to the hadronic contribution to muon (g-2)

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    The cross section of the process e+eπ+πe^+e^-\to\pi^+\pi^- has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on an integrated luminosity of about 88 pb1^{-1} out of which 62 pb1^{-1} constitutes a full dataset collected by CMD-3 at center-of-mass energies below 1 GeV. In the dominant region near ρ\rho-resonance a systematic uncertainty of 0.7% has been reached. The impact of presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed.Comment: 6 pages, 3 figure

    Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1 of pp collisions at s=13TeV with the ATLAS experiment

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    A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5)
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