arXiv subjects

M. Ablikim

Publications and source records attributed to M. Ablikim.

At least 865 records · Page 48Linked to original sources

arXiv2008

psi(2S) Radiative Decay Measurements

Using a sample of 14 million $\psip$ events collected with the BESII detector, branching fractions or upper limits on the branching fractions of $\psip$ decays into $γ\ppb$, $γ2(\pip\pim)$, $γ\kskp$, $γ\kap\kam\pip\pim$, $γ\kstarz\kam\pip+c.c.$, $γ\kstarz \kstarzb$, $γ\pip\pim\ppb$, $\gamma2(\kap\kam)$, $\gamma3(\pip\pim)$ and $\gamma2(\pip\pim)\kap\kam$ with hadron invariant mass less than 2.9$\gev/c^2$ are reported. We also report branching fractions of $\psip$ decays into $γ\ppb\piz$, $\ppb\piz\piz$, $2(\pip\pim)\piz$, $ω\pp$, $ωf_2(1270)$, $b_1^\pmπ^\mp$, $\piz\kskp$, $K^\pmρ^\mp\ks$, $\piz2(\pip\pim)\kap\kam$ and $γ\piz2(\pip\pim)\kap\kam$.

hep-ex↗

arXiv2008

Observation of Y(2175) in $J/ψ\to ηϕf_0(980)$

The decays of $J/ψ\to ηϕf_0(980) (η\to γγ, ϕ\to K^+K^-, f_0(980)\toπ^+π^-)$ are analyzed using a sample of $5.8 \times 10^{7}$ $J/ψ$ events collected with the BESII detector at the Beijing Electron-Positron Collider (BEPC). A structure at around $2.18 $GeV/$c^2$ with about $5σ$ significance is observed in the $ϕf_0(980)$ invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of $m=2.186\pm 0.010 (stat)\pm 0.006 (syst) $GeV/$c^2$ and $Γ=0.065\pm 0.023 (stat)\pm 0.017 (syst) $GeV/$c^2$, respectively, that are consistent with those of Y(2175), observed by the BABAR collaboration in the initial-state radiation (ISR) process $e^+e^-\toγ_{ISR}ϕf_0(980)$. The production branching ratio is determined to be $Br(J/ψ\toηY(2175))\cdot Br(Y(2175)\toϕf_0(980))\cdot Br(f_0(980)\toπ^+π^-)=(3.23\pm 0.75 (stat)\pm0.73 (syst))\times 10^{-4}$, assuming that the Y(2175) is a $1^{--}$ state.

hep-ex↗

arXiv2007

Search for the C-parity violating process J/psi->gamma gamma via psi(2S)->pi+pi- J/psi

Using 14.0\times 10^6 ψ(2S) events collected with the BES-II detector, the C-parity violating process J/psi->gamma gamma via psi(2S)->pi+pi- J/psi is studied. We determine a new upper limit for the J/psi->gamma gamma branching ratio of B(J/psi->gamma gamma)<2.2\times 10^{-5} at the 90% C.L., which is about 20 times lower than the previous measurement.

hep-ex↗

arXiv2007

Measurements of $J/ψ$ and $ψ(2S)$ decays into $Λ\barΛπ^0$ and $Λ\barΛη$

Using 58 million $J/ψ$ and 14 million $ψ(2S)$ events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays $J/ψ$ and $ψ(2S) \to Λ\barΛπ^0$ and $Λ\barΛη$ are measured. For the isospin violating decays, the upper limits are determined to be ${\cal B}(J/ψ\to Λ\barΛπ^0)<6.4\times 10^{-5}$ and ${\cal B}(ψ(2S) \to Λ\barΛπ^0)<4.9\times 10^{-5}$ at the 90% confidence level. The isospin conserving process $J/ψ\to Λ\barΛη$ is observed for the first time, and its branching fraction is measured to be ${\cal B}(J/ψ\to Λ\barΛη)=(2.62\pm 0.60\pm 0.44)\times 10^{-4}$, where the first error is statistical and the second one is systematic. No $Λ\barΛη$ signal is observed in $ψ(2S)$ decays, and ${\cal B}(ψ(2S) \to Λ\barΛη)<1.2\times 10^{-4}$ is set at the 90% confidence level. Branching fractions of $J/ψ$ decays into $Σ^+ π^- barΛ$ and $\barΣ^- π^+ Λ$ are also reported, and the sum of these branching fractions is determined to be ${\cal B}(J/ψ\to Σ^+π^- \barΛ + c.c.)=(1.52\pm 0.08\pm 0.16)\times 10^{-3}$.

hep-ex↗

arXiv2007

Measurement of $\psip$ Radiative Decays

Using 14 million psi(2S) events accumulated at the BESII detector, we report first measurements of branching fractions or upper limits for psi(2S) decays into gamma ppbar, gamma 2(pi^+pi^-), gamma K_s K^-pi^++c.c., gamma K^+ K^- pi^+pi^-, gamma K^{*0} K^- pi^+ +c.c., gamma K^{*0}\bar K^{*0}, gamma pi^+pi^- p pbar, gamma 2(K^+K^-), gamma 3(pi^+pi^-), and gamma 2(pi^+pi^-)K^+K^- with the invariant mass of hadrons below 2.9GeV/c^2. We also report branching fractions of psi(2S) decays into 2(pi^+pi^-) pi^0, omega pi^+pi^-, omega f_2(1270), b_1^\pm pi^\mp, and pi^0 2(pi^+pi^-) K^+K^-.

hep-ex↗

arXiv2007

Determination of the $ψ(3770)$, $ψ(4040)$, $ψ(4160)$ and $ψ(4415)$ resonance parameters

$R$ measurement data taken with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV is fitted to determine resonance parameters (mass, total width, electron width) of the high mass charmonium states, $ψ(3770)$, $ψ(4040)$, $ψ(4160)$ and $ψ(4415)$. Various effects, including the relative phases between the resonances, interferences, the energy-dependence of the full widths, and the initial state radiative correction, are examined. The results are compared to previous studies.

hep-ex↗

arXiv2007

Measurements of psi(2S) decays to octet baryon-antibaryon pairs

With a sample of 14 million psi(2S) events collected by the BESII detector at the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4, (3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4, respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter alpha is determined to be 0.82+-0.17+-0.04.

hep-ex↗

arXiv2006

Direct Measurements of the Branching Fractions for the Semileptonic Decays $D^0 \to K^-μ^+ν_μ$ and $D^0 \to π^-μ^+ν_μ$

Based on the data sample of 33 pb$^{-1}$ collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, the absolute branching fractions for the semileptonic decays $D^0\to K^-μ^+ν_μ$ and $D^0\toπ^-μ^+ν_μ$ have been measured. In the system recoiling against $7584\pm198\pm341$ singly tagged $\bar D^0$ mesons, $87.2\pm13.6$ events for $D^0\to K^-μ^+ν_μ$ and $9.3\pm7.4$ events for $D^0\toπ^-μ^+ν_μ$ are observed. These yield the absolute branching fractions to be $BF(D^0\to K^-μ^+ν_μ)= (3.55\pm0.56\pm0.59)%$ and $BF(D^0\toπ^-μ^+ν_μ)= (0.38\pm0.30\pm0.10)%$. The measured branching fraction for $D^0\to K^-μ^+ν_μ$ was previously used to determine the ratio $Γ(D^0\to K^-μ^+ν_μ)/ Γ(D^+\to \bar K^0μ^+ν_μ)$ combining the previously measured branching fraction for $D^+\to \bar K^0μ^+ν_μ$ by the BES Collaboration.

hep-ex↗

arXiv2006

Measurements of branching fractions for inclusive K0~/K0 and K*(892)+- decays of neutral and charged D mesons

Using the data sample of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied inclusive K0~/K0 and K*(892)+- decays of D0 and D+ mesons. The branching fractions for the inclusive K0~/K0 and K*(892)- decays are measured to be BF(D0 to K0~/K0 X)=(47.6+-4.8+-3.0)%, BF(D+ to K0~/K0 X)=(60.5+-5.5+-3.3)%, BF(D0 to K*- X)=(15.3+- 8.3+- 1.9)% and BF(D+ to K*- X)=(5.7+- 5.2+- 0.7)%. The upper limits of the branching fractions for the inclusive K*(892)+ decays are set to be BF(D0 to K*+ X)<3.6% and BF(D+ to K*+ X) <20.3% at 90% confidence level.

hep-ex↗

arXiv2006

Production of $σ$ in $ψ(2S)\to π^{+}π^{-}J/ψ$

Using 14M $ψ(2S)$ events accumulated by BESII at the BEPC, a Covariant Helicity Amplitude Analysis is performed for $ψ(2S)\toπ^+π^-J/ψ, J/ψ\to μ^+μ^-$. The $π^+π^-$ mass spectrum, distinctly different from phase space, suggests $σ$ production in this process. Two different theoretical schemes are used in the global fit to the data. The results are consistent with the existence of the $σ$. The $σ$ pole position is determined to be $(552^{+84}_{-106})-i(232^{+81}_{-72})$ MeV/$c^2$.

hep-ex↗

arXiv2006

Direct measurement of the absolute branching fraction for $D^+ \to {\bar K}^0μ^+ν_μ$ and determination of $ Γ(D^0 \to K^-μ^+ν_μ)/Γ(D^+ \to {\bar K}^0μ^+ν_μ)$

The absolute branching fraction for the decay $D^+ \to {\bar K}^0μ^+ν_μ$ is determined using $5321 \pm 149 \pm160$ singly tagged $D^-$ sample from the data collected around 3.773 GeV with the BESII detector at the BEPC collider. In the system recoiling against the singly tagged $D^-$ mesons, $28.7 \pm 6.4$ events for $D^+ \to {\bar K}^0μ^+ν_μ$ are observed. These yield the absolute branching fraction to be $BF(D^+ \to {\bar K}^0μ^+ν_μ) = (10.3\pm2.3\pm0.8)%$. The ratio of the two partial widths for the decays $D^0 \to K^-μ^+ν_μ$ and $D^+ \to {\bar K}^0μ^+ν_μ$ is determined to be $Γ(D^0 \to K^-μ^+ν_μ)/Γ(D^+ \to {\bar K}^0μ^+ν_μ) = 0.87 \pm 0.24 \pm 0.15$.

hep-ex↗

arXiv2006

Partial wave analyses of J/psi to gamma pi^+ pi^- and gamma pi^0 pi^0

Results are presented on J/psi radiative decays to pi^+pi^- and pi^0pi^0 based on a sample of 58M J/psi events taken with the BESII detector. Partial wave analyses are carried out using the relativistic covariant tensor amplitude method in the 1.0 to 2.3 GeV/c^2 pipi mass range. There are conspicuous peaks due to the f_2(1270) and two 0^++ states in the 1.45 and 1.75 GeV/c^2 mass regions. The first 0^++ state has a mass of 1466\pm 6\pm 20 MeV/c^2, a width of 108^{+14}_{-11}\pm 25 MeV/c^2, and a branching fraction B(J/psi \to γf_0(1500) \toγπ^+π^-) = (0.67\pm0.02\pm0.30) \times 10^{-4}. Spin 0 is strongly preferred over spin 2. The second 0^++ state peaks at 1765^{+4}_{-3}\pm 13 MeV/c^2 with a width of 145\pm8\pm69 MeV/c^2. If this 0^++ is interpreted as coming from f_0(1710), the ratio of its branching fractions to pipi and K\bar K is 0.41^{+0.11}_{-0.17}.

hep-ex↗

arXiv2006

First observation of $ψ(2S) \to p \bar{n} π^- +c.c.$

Using 14 million $ψ(2S)$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider, the branching fractions of $ψ(2S)$ decays to $p \bar{n} π^-$ and $\bar{p} n π^+$ and the branching fractions of the main background channels $ψ(2S) \to p \bar{n} π^-π^0$, $ψ(2S) \to γχ_{c0} \to γp \bar{n} π^-$, $ψ(2S) \to γχ_{c2} \to γp \bar{n} π^-$, and $ψ(2S) \to γχ_{cJ} \to γp \bar{n} π^- π^0$ are determined. The contributions of the $N^{\ast}$ resonances in $ψ(2S) \to p \bar{n} π^- +c.c.$ are also discussed.

hep-ex↗

arXiv2006

Measurements of $\psip$ decays into $γK\bar{K}π$ and $γη\pipi$

Radiative decays of the $\psip$ into $γK\bar{K}π$ and $γη\pipi$ final states are studied using 14 million $\psip$ events collected with the BESII detector. Branching fractions or upper limits on the branching fractions of $\psip$ and $\xcj$ decays are reported. No significant signal for $\etafl/\etafh$ is observed in the $K\bar{K}π$ or $η\pipi$ mass spectra, and upper limits on the branching fractions of $\psip\rarγ\etaf$, $\etaf\rar K\bar{K}π$ and $η\pipi$ are determined.

hep-ex↗

arXiv2006

Observation of a broad 1^-- resonant structure around 1.5 GeV/$c^2$ in the K^+K^- mass spectrum in J/psi --> K^+K^-pi^0

A broad peak is observed at low K^+K^- invariant mass in J/psi --> K^+K^-pi^0 decays found in a sample of 5.8\times 10^7 J/psi events collected with the BESII detector. A partial wave analysis shows that the J^PC of this structure is 1^--. Its pole position is determined to be (1576^{+49}_{-55}(stat)^{+98}_{-91}(syst)) MeV/c^2 - i(409^{+11}_{-12}$(stat)^{+32}_{-67}(syst)) MeV/c^2. These parameters are not compatible with any known meson resonances.

hep-ex↗

arXiv2006

Measurements of the absolute branching fractions for D->Kbar pi e+ nu_e, D-> Kbar e+nu_e and determination of Gamma(D+ -> K0bar e+ nu_e)/Gamma(D+ -> K0bar e+nu_e)

Using the data of about 33 pb$^{-1}$ collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic decays $D^+ \to K^-π^+ e^+ν_e$, $D^0 \to \bar K^0π^-e^+ν_e$, $D^+ \to \bar K^{*0}e^+ν_e$ and $D^0 \to K^{*-}e^+ν_e$. The absolute branching fractions for the decays are measured to be ${BF}(D^+ \to K^-π^+e^+ν_e)=(3.50\pm0.75\pm0.27)%$, ${BF}(D^0 \to \bar K^0π^-e^+ν_e)=(2.61\pm1.04\pm0.28)%$, ${BF}(D^+ \to \bar K^{*0}e^+ν_e)=(5.06\pm1.21\pm0.40)%$ and ${BF}(D^0 \to K^{*-}e^+ν_e)=(2.87\pm 1.48\pm 0.39)%$. The ratio of the vector to pseudoscalar semileptonic decay rates $Γ(D^+\to\bar K^{*0}e^+ν_e)/Γ(D^+\to\bar K^0e^+ν_e)$ is determined to be $0.57\pm0.17\pm0.02$.

hep-ex↗

arXiv2006

Search for D to phi l nu and measurement of the branching fraction for D to phi pi

Using a data sample of integrated luminosity of about 33 pb$^{-1}$ collected around 3.773 GeV with the BESII detector at the BEPC collider, the semileptonic decays $D^+ \to ϕe ^+ν_e$, $D^+ \to ϕμ^+ν_μ$ and the hadronic decay $D^+ \to ϕπ^+$ are studied. The upper limits of the branching fractions are set to be $BF(D^+ \to ϕe ^+ν_e) <$ 2.01% and $BF(D^+ \to ϕμ^+ ν_μ) <$ 2.04% at the 90% confidence level. The ratio of the branching fractions for $D^+ \to ϕπ^+$ relative to $D^+ \to K^-π^+π^+$ is measured to be $0.057 \pm 0.011 \pm 0.003$. In addition, the branching fraction for $D^+ \to ϕπ^+$ is obtained to be $(5.2 \pm 1.0 \pm 0.4) \times 10^{-3}$.

hep-ex↗

arXiv2006

Measurements of $Jψ$ decays into $ωπ^0$, $ωη$, and $ωη'$

Based on $5.8 \times 10^7 Jψ$ events collected with BESII at the Beijing Electron-Positron Collider (BEPC), the decay branching fractions of $Jψ\toωπ^0$, $ωη$, and $ωη'$ are measured using different $η$ and $η'$ decay modes. The results are higher than previous measurements. The $ωπ^0$ electromagnetic form factor is also obtained.

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