| 1. |
- Ablikim, M., et al.
(författare)
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Measurement of the $D\to K^-\pi^+$ strong phase difference in $\psi(3770)\to D^0\overline{D}{}^0$
- 2014
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Ingår i: PHYSICS LETTERS B. - : Elsevier BV. - 0370-2693. ; 734
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Tidskriftsartikel (refereegranskat)abstract
- We study $D^0\overline{D}{}^0$ pairs produced in $e^+e^-$ collisions at $\sqrt{s}=3.773$ GeV using a data sample of 2.92 fb$^{-1}$ collected with the BESIII detector. We measure the asymmetry $\mathcal{A}^{CP}_{K\pi}$ of the branching fractions of $D \to K^-\pi^+$ in $CP$-odd and $CP$-even eigenstates to be $(12.7\pm1.3\pm0.7)\times10^{-2}$. $\mathcal{A}^{CP}_{K\pi}$ can be used to extract the strong phase difference $\delta_{K\pi}$ between the doubly Cabibbo-suppressed process $\overline{D}{}^{0}\to K^-\pi^+$ and the Cabibbo-favored process $D^0\to K^- \pi^+$. Using world-average values of external parameters, we obtain $\cos\delta_{K\pi} = 1.02\pm0.11\pm0.06\pm0.01$. Here, the first and second uncertainties are statistical and systematic, respectively, while the third uncertainty arises from the external parameters. This is the most precise measurement of $\delta_{K\pi}$ to date.
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| 2. |
- Ablikim, M., et al.
(författare)
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Observation of $e^+e^− → γX$(3872) at BESIII
- 2014
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Ingår i: PHYSICAL REVIEW LETTERS. - 1079-7114. ; 112:9
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Tidskriftsartikel (refereegranskat)abstract
- With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process $e^{+} e^{-} \to \gamma X(3872)$ is observed for the first time with a statistical significance of $6.3\sigma$. The measured mass of the $X(3872)$ is ($3871.9\pm 0.7_{\rm stat.}\pm 0.2_{\rm sys.}$) MeV/$c^2$, in agreement with previous measurements. Measurements of the product of the cross section $\sigma[e^{+} e^{-} \to \gamma X(3872)]$ and the branching fraction $\mathcal{B}[X(3872) \to \pi^{+} \pi^{-} J/\psi]$ at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process $Y(4260) \to \gamma X(3872)$.
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| 3. |
- Ablikim, M., et al.
(författare)
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Observation of electromagnetic Dalitz decays J/\psi \to P e^+e^-
- 2014
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Ingår i: PHYSICAL REVIEW D. - 2470-0010 .- 1550-7998 .- 1550-2368. ; 89:9
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Tidskriftsartikel (refereegranskat)abstract
- Based on a sample of (225.3\pm2.8)\times 10^{6} J/\psi events collected with the BESIII detector, the electromagnetic Dalitz decays of J/\psi \to P e^+e^-(P=\eta'/\eta/\pi^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/\psi \to \eta' e^+e^-, J/\psi \to \eta e^+e^- and J/\psi \to \pi^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/\psi\to \eta' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/\psi\to \eta e^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/\psi\to \pi^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic.
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| 4. |
- Ablikim, M., et al.
(författare)
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Precision measurements of $B(D^+ \rightarrow \mu^+ \nu_{\mu})$, the pseudoscalar decay constant $f_{D^+}$, and the quark mixing matrix element $|V_{\rm cd}|$
- 2014
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Ingår i: PHYSICAL REVIEW D. - 2470-0010 .- 1550-7998 .- 1550-2368. ; 89:5
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Tidskriftsartikel (refereegranskat)abstract
- We report a measurement of the branching fraction $B(D^+ \rightarrow \mu^+ \nu_{\mu}) = [3.71 \pm 0.19 (\rm stat) \pm 0.06 (\rm sys)]\times 10^{-4}$ based on 2.92 ${\rm fb^{-1}}$ of data accumulated at $\sqrt{s}=3.773$ GeV with the BESIII detector at the BEPCII collider. This measurement, in conjunction with the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\rm cd}|$ determined from a global Standard Model fit, implies a value for the weak decay constant $f_{D^+}=(203.2 \pm 5.3 \pm 1.8)$ MeV. Additionally, using this branching fraction measurement together with a Lattice QCD prediction for $f_{D^+}$, we find $|V_{\rm cd}|=0.2210\pm 0.0058 \pm 0.0047$. In either case, these are the most precise results for these quantities to date.
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| 5. |
- Atomassa, Ermias, et al.
(författare)
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Feasibility studies for nucleon structure measurements with PANDA
- 2014
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X. ; 81
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Tidskriftsartikel (refereegranskat)abstract
- The study of nucleon structure is one of the main physics goals of PANDA to be built at the FAIR accelerator complex. The excellent particle identification performance of the PANDA detector will enable measurements of exclusive channels p̄ p -> e^+e^- and p̄ p -> pi^0 J/psi -> pi^0e^+e^- to extract the electromagnetic form factors of protons and pi-nucleon Transition Distribution Amplitudes (pi-N TDAs). After a brief description of the PANDA apparatus and a method to handle momentum resolution degradation due to Bremsstrahlung, the physics of pi-N TDAs is discussed. An estimate for the expected signal to background ratio for p̄ p -> pi^0 J/psi -> pi^0e^+e^- that takes into account the main background source is given.
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| 6. |
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| 7. |
- Destefanis, Marco, et al.
(författare)
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Spin studies via Drell-Yan processes at PANDA
- 2014
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- The nucleon structure is still not completely understood. A transverse momentum dependent description of the nucleon structure is a crucial milestone for several forthcoming studies in a wide range of experimental scenarios. By means of antiproton beams, possibly polarized in a later stage of the project, with a beam momentum up to 15 GeV/c, which will be available at the future FAIR facility, the nonperturbative region of QCD is planned to be investigated. One of the main goals of the forthcoming experiments at FAIR is the study of Drell-Yan lepton pairs by means of proton-antiproton annihilations, taking also advantage of the expected high luminosity. The Drell-Yan production is a unique tool to access the spin dependent properties of the nucleon, and in particular its transverse degrees of freedom. Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs), i.e. the Boer-Mulders function, the Sivers function, and the Transversity, could be deeply investigated by means of experimental angular asymmetries. In later stages of FAIR, single- and double-spin asymmetries could be investigated as well. The Drell-Yan physics program which could be accessed at FAIR with the PANDA experiment will be discussed in details, in the light of existing results in the field.
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| 8. |
- Fioravanti, Elisa, et al.
(författare)
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Experimental overview of the PANDA experiment
- 2014
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 503
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Tidskriftsartikel (refereegranskat)abstract
- The physics program of the (anti-Proton ANhiliation ar DArmstadt) experiment will address various questions related to the strong interactions by employing a multi-purpose detector system at the High Energy Storage Ring (HESR) for anti-protons of the upcoming Facility for Anti-proton and Ion Research (FAIR). The excellent antiproton beam resolution of Δp/p ~ 10−5 and the high luminosity =2×1032cm−2 s−1 will allow the precise measurement of the charmonium and open charm spectroscopy, the search for exotic hadrons like multiquarks, glueballs and hybrids, the study of in-medium modifications of hadrons and the nucleon structure.
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| 9. |
- Iazzi, Felice, et al.
(författare)
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Doubly strange system physics with antiprotons at PANDA
- 2014
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X. ; 71
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Tidskriftsartikel (refereegranskat)abstract
- The study of the doubly strange hyper-systems represents a step forward in understanding the unexplored world of the strange matter in the frame of a better knowledge of the hyperon-nucleon and hyperon-nucleus interaction. The production of double hyper-systems, up to now, have been based on the use of kaon beams through a double strangeness exchange reaction. A new technique has been designed by the PANDA Collaboration, which will use the antiprotons at 3 GeV/c of the HESR facility at FAIR to create doubly strange hyperons and drive them into nuclear targets. This technique requires the use of 2 targets, located inside and outside the beam pipe. In spite of the constraints arising from the presence of a solid target inside an antiproton ring, the technique looks promising in terms of rate of hyperons and hyper-nuclei produced. After a review of the physics items that will be investigated in the hyper-nuclear section of PANDA experiment, the characteristics of the antiprotons facility, the results of the feasibility study of the 2-target technique, the design of the hyper-nuclear set-up in PANDA and the expected rates of the double hyper-nuclei will be presented.
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| 10. |
- Ma, Binsong, et al.
(författare)
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A new method for electron momentum reconstruction in the PANDA experiment
- 2014
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 503
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Tidskriftsartikel (refereegranskat)abstract
- The Kalman Filter in existing PANDARoot framework of experiment is not optimally suited for electrons, for which the highly non-Gaussian Bremsstrahlung process yields a tail in the momentum resolution distribution. A new method was therefore developed to improve the electron momentum reconstruction with an event by event procedure. The improvements of the electron momentum resolution will be shown. The interest of the method for the electromagnetic channels studies will also be presented.
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