New variable separation approach: application to nonlinear diffusion equations

The concept of the derivative-dependent functional separable solution, as a generalization to the functional separable solution, is proposed. As an application, it is used to discuss the generalized nonlinear diffusion equations based on the generalized conditional symmetry approach. As a consequence, a complete list of canonical forms for such equations which admit the derivative-dependent functional separable solutions is obtained and some exact solutions to the resulting equations are described.Comment: 19 pages, 2 fig

Measurement of ψ(2S)\psi(2S) decays to baryon pairs

A sample of 3.95M $\psi(2S)$ decays registered in the BES detector are used to study final states containing pairs of octet and decuplet baryons. We report branching fractions for $\psi(2S)\to p\bar{p}$, $\Lambda\bar{\Lambda}$, $\Sigma^0\bar{\Sigma}{}^0$, $\Xi^-\bar{\Xi}{}^+$, $\Delta^{++}\bar{\Delta}{}^{--}$, $\Sigma^+(1385)\bar{\Sigma}{}^-(1385)$, $\Xi^0(1530)\bar{\Xi}{}^0(1530)$, and $\Omega^-\bar{\Omega}{}^+$. These results are compared to expectations based on the SU(3)-flavor symmetry, factorization, and perturbative QCD.Comment: 22 pages, 21 figures, 4 table

Measurement of the Total Cross Section for Hadronic Production by e+e- Annihilation at Energies between 2.6-5 Gev

Using the upgraded Beijing Spectrometer (BESII), we have measured the total cross section for $e^+e^-$ annihilation into hadronic final states at center-of-mass energies of 2.6, 3.2, 3.4, 3.55, 4.6 and 5.0 GeV. Values of $R$, $\sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$, are determined.Comment: Submitted to Phys. Rev. Let

Measurement of the Inclusive Charm Cross Section at 4.03 GeV and 4.14 GeV

The cross section for charmed meson production at $\sqrt{s} = 4.03$ and 4.14 GeV has been measured with the Beijing Spectrometer. The measurement was made using 22.3 $pb^{-1}$ of $e^+e^-$ data collected at 4.03 GeV and 1.5 $pb^{-1}$ of $e^+e^-$ data collected at 4.14 GeV. Inclusive observed cross sections for the production of charged and neutral D mesons and momentum spectra are presented. Observed cross sections were radiatively corrected to obtain tree level cross sections. Measurements of the total hadronic cross section are obtained from the charmed meson cross section and an extrapolation of results from below the charm threshold.Comment: 11 pages, 13 figures. The top level tex file is paper.tex. It builds the paper from other tex files in this .tar and the .eps file

Study of the P-wave charmonium state \chi_{cJ} in \psi(2S) decays

The processes $\psi(2S)\to \gamma \pi^+ \pi^-$, $\gamma K^+ K^-$ and $\gamma p \bar{p}$ have been studied using a sample of $3.7 \times 10^6$ produced $\psi(2S)$ decays. We determine the total width of the $\chi_{c0}$ to be $\Gamma^{tot}_{\chi_{c0}} = 14.3\pm 2.0\pm 3.0$ MeV. We present the first measurement of the branching fraction $B(\chi_{c0} \to p \bar{p}) = (16.3 \pm 4.4 \pm 5.4)\times 10^{-5}$, where the first error is statistical and the second one systematic. Branching fractions of $\chi_{c0,2} \to \pi^+ \pi^-$ and $K^+ K^-$ are also reported.Comment: 10 pages, revtex, 3 figures, 2 table

Measurement of proton electromagnetic form factors in e+e−→ppˉe^+e^- \to p\bar{p} in the energy region 2.00-3.08 GeV

The process of $e^+e^- \rightarrow p\bar{p}$ is studied at 22 center-of-mass energy points ($\sqrt{s}$) from 2.00 to 3.08 GeV, exploiting 688.5~pb$^{-1}$ of data collected with the BESIII detector operating at the BEPCII collider. The Born cross section~($\sigma_{p\bar{p}}$) of $e^+e^- \rightarrow p\bar{p}$ is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio ($|G_{E}/G_{M}|$) and the value of the effective ($|G_{\rm{eff}}|$), electric ($|G_E|$) and magnetic ($|G_M|$) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. $|G_{E}/G_{M}|$ and $|G_M|$ are determined with high accuracy, providing uncertainties comparable to data in the space-like region, and $|G_E|$ is measured for the first time. We reach unprecedented accuracy, and precision results in the time-like region provide information to improve our understanding of the proton inner structure and to test theoretical models which depend on non-perturbative Quantum Chromodynamics

Observation of ηc→ωω\eta_c\to\omega\omega in J/ψ→γωωJ/\psi\to\gamma\omega\omega

Using a sample of $(1310.6\pm7.0)\times10^6$ $J/\psi$ events recorded with the BESIII detector at the symmetric electron positron collider BEPCII, we report the observation of the decay of the $(1^1 S_0)$ charmonium state $\eta_c$ into a pair of $\omega$ mesons in the process $J/\psi\to\gamma\omega\omega$. The branching fraction is measured for the first time to be $\mathcal{B}(\eta_c\to\omega\omega)= (2.88\pm0.10\pm0.46\pm0.68)\times10^{-3}$, where the first uncertainty is statistical, the second systematic and the third is from the uncertainty of $\mathcal{B}(J/\psi\to\gamma\eta_c)$. The mass and width of the $\eta_c$ are determined as $M=(2985.9\pm0.7\pm2.1)\,$MeV/$c^2$ and $\Gamma=(33.8\pm1.6\pm4.1)\,$MeV.Comment: 13 pages, 6 figure

Observation and study of the decay J/ψ→ϕηη′J/\psi\rightarrow\phi\eta\eta'

We report the observation and study of the decay $J/\psi\rightarrow\phi\eta\eta'$ using $1.3\times{10^9}$ $J/\psi$ events collected with the BESIII detector. Its branching fraction, including all possible intermediate states, is measured to be $(2.32\pm0.06\pm0.16)\times{10^{-4}}$. We also report evidence for a structure, denoted as $X$, in the $\phi\eta'$ mass spectrum in the $2.0-2.1$ GeV/$c^2$ region. Using two decay modes of the $\eta'$ meson ($\gamma\pi^+\pi^-$ and $\eta\pi^+\pi^-$), a simultaneous fit to the $\phi\eta'$ mass spectra is performed. Assuming the quantum numbers of the $X$ to be $J^P = 1^-$, its significance is found to be 4.4$\sigma$, with a mass and width of $(2002.1 \pm 27.5 \pm 21.4)$ MeV/$c^2$ and $(129 \pm 17 \pm 9)$ MeV, respectively, and a product branching fraction $\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.8 \pm 1.2 \pm 1.7)\times10^{-5}$. Alternatively, assuming $J^P = 1^+$, the significance is 3.8$\sigma$, with a mass and width of $(2062.8 \pm 13.1 \pm 7.2)$ MeV/$c^2$ and $(177 \pm 36 \pm 35)$ MeV, respectively, and a product branching fraction $\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.6 \pm 1.4 \pm 2.0)\times10^{-5}$. The angular distribution of $J/\psi\rightarrow\eta{}X$ is studied and the two $J^P$ assumptions of the $X$ cannot be clearly distinguished due to the limited statistics. In all measurements the first uncertainties are statistical and the second systematic.Comment: 10 pages, 6 figures and 4 table

First observations of hc→h_c \to hadrons

Based on $(4.48 \pm 0.03) \times 10^{8}$ $\psi(3686)$ events collected with the BESIII detector, five $h_c$ hadronic decays are searched for via process $\psi(3686) \to \pi^0 h_c$. Three of them, $h_c \to p \bar{p} \pi^+ \pi^-$, $\pi^+ \pi^- \pi^0$, and $2(\pi^+ \pi^-) \pi^0$ are observed for the first time, with statistical significances of 7.4$\sigma$, $4.9\sigma$, and 9.1$\sigma$, and branching fractions of $(2.89\pm0.32\pm0.55)\times10^{-3}$, $(1.60\pm0.40\pm0.32)\times10^{-3}$, and $(7.44\pm0.94\pm1.56)\times10^{-3}$, respectively, where the first uncertainties are statistical and the second systematic. No significant signal is observed for the other two decay modes, and the corresponding upper limits of the branching fractions are determined to be $B(h_c \to 3(\pi^+ \pi^-) \pi^0)<8.7\times10^{-3}$ and $B(h_c \to K^+ K^- \pi^+ \pi^-)<5.8\times10^{-4}$ at 90% confidence level.Comment: 17 pages, 16 figure

Measurements of Weak Decay Asymmetries of Λc+→pKS0\Lambda_c^+\to pK_S^0, Λπ+\Lambda\pi^+, Σ+π0\Sigma^+\pi^0, and Σ0π+\Sigma^0\pi^+

Using $e^+e^-\to\Lambda_c^+\bar\Lambda_c^-$ production from a 567 pb$^{-1}$ data sample collected by BESIII at 4.6 GeV, a full angular analysis is carried out simultaneously on the four decay modes of $\Lambda_c^+\to pK_S^0$, $\Lambda \pi^+$, $\Sigma^+\pi^0$, and $\Sigma^0\pi^+$. For the first time, the $\Lambda_c^+$ transverse polarization is studied in unpolarized $e^+e^-$ collisions, where a non-zero effect is observed with a statistical significance of 2.1$\sigma$. The decay asymmetry parameters of the $\Lambda_c^+$ weak hadronic decays into $pK_S^0$, $\Lambda\pi^+$, $\Sigma^+\pi^0$ and $\Sigma^0\pi^+$ are measured to be $0.18\pm0.43(\rm{stat})\pm0.14(\rm{syst})$, $-0.80\pm0.11(\rm{stat})\pm0.02(\rm{syst})$, $-0.57\pm0.10(\rm{stat})\pm0.07(\rm{syst})$, and $-0.73\pm0.17(\rm{stat})\pm0.07(\rm{syst})$, respectively. In comparison with previous results, the measurements for the $\Lambda\pi^+$ and $\Sigma^+\pi^0$ modes are consistent but with improved precision, while the parameters for the $pK_S^0$ and $\Sigma^0\pi^+$ modes are measured for the first time