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Register a new userMeasurement of e+e- --> D Dbar Cross Sections at the psi(3770) Resonance
قياس إطارات التقاط الضوئية ل e+e- --> D Dbar في تردد الحزمة psi(3770)
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إننا نقدم تقارير جديدة حول مقاطع الانتقال للحالات النهائية D Dbar في تردد الـ psi(3770). تضمنت مجموعة بياناتنا مسافة الضوء المكتسبة من 2.93/fb من بيانات الانفجار الكهربائي e+e- والتي تم جمعها وتحليلها باستخدام مكبر الكشف BESIII. نحن نعيد اعادة بناء ثلاث حالات D0 وستة حالات D+ بطرق هادئة ونستخدم نسبة الحاصل من عدد الحالات النهائية التي تم بنائها كاملا (العلامات المزدوجة) إلى عدد الحالات النهائية التي تم بنائها بشكل نصفي (العلامات المفردة) لتحديد عدد الحالات D0 D0bar و D+D-، مما يساعد على إلغاء العديد من الاعتبارات النظامية. من خلال دمج هذه الحاصلات مع تحديد مستقل لمسافة الضوء المكتسبة لمجموعة البيانات، نجد أن مقاطع الانتقال هي sigma(e+e- --> D0 D0bar)=(3.615 +- 0.010 +- 0.038) nb و sigma(e+e- --> D+D-)=(2.830 +- 0.011 +- 0.026) nb، حيث أن الاعتبارات هي الاحصائية والنظامية على التوالي.
We report new measurements of the cross sections for the production of D Dbar final states at the psi(3770) resonance. Our data sample consists of an integrated luminosity of 2.93/fb of e+e- annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D0 and six D+ hadronic decay modes and use the ratio of the yield of fully reconstructed D Dbar events (double tags) to the yield of all reconstructed D or Dbar mesons (single tags) to determine the number of D0 D0bar 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- --> D0 D0bar)=(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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Using 281 /pb of e^+ e^- collisions recorded at the psi(3770) resonance with the CLEO-c detector at CESR, we determine absolute hadronic branching fractions of charged and neutral D mesons using a double tag technique. Among measurements for three D^0 and six D^+ modes, we obtain reference branching fractions B(D^0 --> K^-pi^+) = (3.891 +- 0.035 +- 0.059 +- 0.035)% and B(D^+ --> K^-pi^+pi^+) = (9.14 +- 0.10 +- 0.16 +- 0.07)%, where the first uncertainty is statistical, the second is all systematic errors other than final state radiation (FSR), and the third is the systematic uncertainty due to FSR. We include FSR in these branching fractions by allowing for additional unobserved photons in the final state. Using an independent determination of the integrated luminosity, we also extract the cross sections sigma(e+e- --> D^0 D^0-bar) = (3.66+- 0.03 +- 0.06) nb and sigma(e+e- --> D^+ D^-) = (2.91+- 0.03 +- 0.05) nb at a center of mass energy, E_cm = 3774 +- 1 MeV.
We report first measurements of e+e- -> D(*)+D(*)- processes far above threshold. The cross-sections for e+e- -> DT*+DL*- and e+e- -> D+D*T- at sqrt{s}=10.58 GeV/c2 are measured to be 0.55 +- 0.03 +- 0.05 pb and 0.62 +- 0.03 +- 0.06 pb, respectively. We set upper limits on the cross-sections for e+e- -> DT*+DT*-, e+e- -> DL*+DL*-, e+e- -> D+D*L- and e+e- -> D+D- processes. The analysis is based on 88.9 fb-1 of data collected by the Belle experiment at the KEKB e+e- asymmetric collider.
The Born cross section of the process $e^{+}e^{-}rightarrowLambdabarLambda$ is measured at 33 center-of-mass energies between 3.51 and 4.60 GeV using data corresponding to the total integrated luminosity of 20.0 fb$^{-1}$ collected with the BESIII detector at the BEPCII collider. Describing the energy dependence of the cross section requires a justification from the $psi(3770)rightarrowLambdabarLambda$ decay, which is fitted with a significance of 4.9$sigma$ with the systematic uncertainty included. The lower bound on its branching fraction is $2.4times10^{-6}$ at the 90% confidence level (C.L.), at least five times larger than expected from predictions using a simple scaling approach. This result indicates the importance of effects from vector charmonium(-like) when interpreting data in terms of {it e.g.}, electromagnetic structure observables. There are no definite conclusions about the interplay with other vector charmonium(-like), and we set 90% C.L.upper limits for the products of the electronic widths and the branching fractions.
The cross sections of $e^+e^- rightarrow pi Z_c(3900) rightarrow pipi J/psi$ and $e^+e^- rightarrow pi Z_c(3900) rightarrow pi Dbar{D}^{*}$ have been measured by BESIII experiment. We try to perform a combined fit to the cross sections with one Breit-Wigner function, the fit results show the structures mass and width are $M=(4232pm5)$ MeV/$c^2$, $Gamma=(65pm21)$ MeV. The ratio $frac{mathcal{B}(Z_c(3900)rightarrow Dbar{D}^{*})}{mathcal{B}(Z_c(3900)rightarrowpi J/psi)}$ is determined to be $(16pm6)$. We also try to fit the cross sections with two Breit-Wigner functions, while we cant come to any definitive conclusions about the second structure. More measurements are desired to improve the understanding of $e^+e^- rightarrow pi Z_c(3900)$ line shape.
In two recent reactions by Belle producing $Dbar D$ and $Dbar D^*$ meson pairs, peaks above threshold have been measured in the differential cross sections, possibly indicating new resonances in these channels. We want to study such reactions from the point of view that the $D$ meson pairs are produced from already known or predicted resonances below threshold. Our study shows that the peak in the $Dbar D^*$ production is not likely to be caused by the X(3872) resonance, but the peak seen in $Dbar D$ invariant mass can be well described if the $Dbar D$ pair comes from the already predicted scalar X(3700) resonance.
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