اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدStudy of e$^+$e$^-$ $rightarrow text{p} overline{text{p}}pi^0$ in the Vicinity of the $psitext{(3770)}$
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The process $e^+e^-rightarrow poverline{p}pi^0$ has been studied by analyzing data collected at $sqrt{s}=3.773$ GeV, at $sqrt{s}=3.650$ GeV, and during a $psi(3770)$ line shape scan with the BESIII detector at the BEPCII collider. The Born cross section of $p overline{p} pi^0$ in the vicinity of the $psi(3770)$ is measured and the Born cross section of $psi(3770)rightarrow p overline{p} pi^0$ is extracted considering interference between resonant and continuum production amplitudes. Two solutions with the same probability and a significance of 1.5$sigma$ are found, and the Born cross section of $psi(3770)rightarrow p overline{p} pi^0$ is determined to be less than 0.22 pb at 90% confidence level and $33.8pm1.8pm2.1$ pb, respectively. Using the estimated cross section and a constant decay amplitude approximation, the cross section $sigma(poverline{p} rightarrow psi(3770) pi^0)$ is calculated for the kinematic situation of the planned $overline{text{P}}text{ANDA}$ experiment. The maximum cross section corresponding to the two solutions is expected to be less than $0.79$ nb at 90% confidence level and $122pm10$ nb at a center of mass energy of 5.26 GeV.
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Using 2917 $rm{pb}^{-1}$ of data accumulated at 3.773~$rm{GeV}$, 44.5~$rm{pb}^{-1}$ of data accumulated at 3.65~$rm{GeV}$ and data accumulated during a $psi(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-rightarrow pbar{p}$ is s
tudied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-rightarrowpsi(3770)rightarrow pbar{p}$, $sigma(e^+e^-rightarrowpsi(3770)rightarrow pbar{p})$, is found to have two solutions, determined to be ($0.059pm0.032pm0.012$) pb with the phase angle $phi = (255.8pm37.9pm4.8)^circ$ ($<$0.11 pb at the 90% confidence level), or $sigma(e^+e^-rightarrowpsi(3770)rightarrow pbar{p}) = (2.57pm0.12pm0.12$) pb with $phi = (266.9pm6.1pm0.9)^circ$ both of which agree with a destructive interference. Using the obtained cross section of $psi(3770)rightarrow pbar{p}$, the cross section of $pbar{p}rightarrow psi(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6pm42.9)$ nb.
Studies of $e^+e^- to D_s^+ overline{D}{}^{(*)0}K^-$ and the $P$-wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected with the BESIII detector at $sq
rt{s}= 4.600$ GeV. The processes of $e^+e^-to D_s^+ overline{D}{*}^{0} K^-$ and $D_s^+ overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$, respectively. The Born cross sections are measured to be $sigma^{B}(e^+e^-to D_s^+ overline{D}{*}^{0} K^-) = (10.1pm2.3pm0.8) pb$ and $sigma^{B}(e^+e^-to D_s^+ overline{D}{}^{0} K^-) = (19.4pm2.3pm1.6) pb$, and the products of Born cross section and the decay branching fraction are measured to be $sigma^{B}(e^+e^-to D_s^+D_{s1}(2536)^- + c.c.)cdotmathcal{B}(D_{s1}(2536)^- to overline{D}{*}^{0} K^-) = (7.5 pm 1.8 pm 0.7) pb$ and $sigma^{B}(e^+e^-to D_s^+ D^*_{s2}(2573)^- + c.c.)cdotmathcal{B}(D^*_{s2}(2573)^- to overline{D}{}^{0} K^-) = (19.7 pm 2.9 pm 2.0) pb$. For the $D_{s1}(2536)^-$ and $D^*_{s2}(2573)^-$ mesons, the masses and widths are measured to be $M(D_{s1}(2536)^-) = (2537.7 pm 0.5 pm 3.1)~MeV/c^2,$ $ Gamma(D_{s1}(2536)^-)) = (1.7pm 1.2 pm 0.6)~rm MeV,$ and $M(D^*_{s2}(2573)^-) = (2570.7pm 2.0 pm 1.7)~MeV/c^2,$ $Gamma(D^*_{s2}(2573)^-) = (17.2 pm 3.6 pm 1.1)~rm MeV.$ The spin-parity of the $D^*_{s2}(2573)^-$ meson is determined to be $J^P=2^{+}$. In addition, the process $e^+e^-to D_s^+ overline{D}{}^{(*)0} K^-$ are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the $90%$ confidence level on the cross sections are determined.
Several intermediate states of the reaction channels $e^{+}e^{-} rightarrow pi^{+} pi^{-} D^{0} bar{D}^{0}$ and $e^{+}e^{-} rightarrow pi^{+} pi^{-} D^{+}D^{-}$ are studied using the data samples collected with the BESIII detector at center-of-mass e
nergies above 4.08 GeV. For the first time in this final state, a $psi(3770)$ signal is seen in the $Dbar{D}$ invariant mass spectrum, with a statistical significance of $5.2sigma$ at $sqrt{s} = 4.42$ GeV. There is also evidence for this resonance at $sqrt{s}$ = 4.26 and 4.36 GeV with statistical significance of 3.2$sigma$ and 3.3$sigma$, respectively. In addition, the Born cross section of $e^{+}e^{-}to pi^{+}pi^{-}psi(3770)$ is measured. The proposed heavy-quark-spin-symmetry partner of the $X(3872)$, the state $X_{2}(4013)$, is also searched for in the $Dbar{D}$ invariant mass spectra. No obvious signal is found. The upper limit of the Born cross section of the process $e^{+}e^{-}to rho^{0}X_{2}(4013)$ combined with the branching fraction is measured. Also, the processes $e^{+}e^{-}to D_{1}(2420)bar{D} + c.c.$ are investigated. The neutral mode with $D_{1}(2420)^{0}to D^{0}pi^{+}pi^{-}$ is reported with statistical significance of 7.4$sigma$ at $sqrt{s} = 4.42$ GeV for the first time, and evidence with statistical significance of 3.2$sigma$ and 3.3$sigma$ at $sqrt{s}$ = 4.36 and 4.60 GeV is seen, respectively. No evident signal for the process $e^{+}e^{-}to D_{1}(2420)^{0}bar{D}^{0} + c.c., D_{1}(2420)^{0}to D^{*+}pi^{-}$ is reported. Evidence for $e^{+}e^{-}to D_{1}(2420)^{+}D^{-} +~c.c., D_{1}(2420)^{+}to D^{+}pi^{+}pi^{-}$ is reported with statistical significance of 3.1$sigma$ and 3.0$sigma$ at $sqrt{s}$ = 4.36 and 4.42 GeV, respectively.
The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6
GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function $e(x)$, which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function $G_1^perp$. A clear sign change is observed around the $rho$ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.
The results of searches for $B^{0}_{(s)} rightarrow J/{psi} p overline{p}$ and $B^{+} to J/{psi} p overline{p} {pi}^{+}$ decays are reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb$^{-1}$ of $pp$ c
ollisions, collected with the LHCb detector. An excess with 2.8$,sigma$ significance is seen for the decay $B^{0}_{s} to J/{psi} p overline{p}$ and an upper limit on the branching fraction is set at the 90 % confidence level: ${cal B}(B^{0}_{s} to J/{psi} p overline{p}) < 4.8 times 10^{-6}$, which is the first such limit. No significant signals are seen for $B^{0} to J/{psi} p overline{p}$ and $B^{+} to J/{psi} p overline{p} {pi}^{+}$ decays, for which the corresponding limits are set: ${cal{B}}(B^{0} to J/{psi} p overline{p}) < 5.2 times 10^{-7}$, which significantly improves the existing limit; and ${cal{B}}(B^{+} to J/{psi} p overline{p} {pi}^{+}) < 5.0 times 10^{-7}$, which is the first limit on this branching fraction.
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