Publications (749)1643.48 Total impact

Article: Observation of η ′ → ω e + e
Physical Review D 09/2015; 92(5). DOI:10.1103/PhysRevD.92.051101 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a study of the process $e^+e^\to\pi^{\pm}(D\bar{D}^*)^{\mp}$ using data samples of 1092 pb$^{1}$ at $\sqrt{s}=4.23$ GeV and 826 pb$^{1}$ at $\sqrt{s}=4.26$ GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the $D$ meson pair and the bachelor $\pi^{\pm}$ in the final state, we confirm the existence of the charged structure $Z_c(3885)^{\mp}$ in the $(D\bar{D}^*)^{\mp}$ system in the two isospin processes $e^+e^\to\pi^+D^0D^{*}$ and $e^+e^\to\pi^+D^D^{*0}$. By performing a simultaneous fit, the statistical significance of $Zc(3885)^{\mp}$ signal is determined to be greater than 10$\sigma$, and its pole mass and width are measured to be $M_{\rm{pole}}$=(3881.7$\pm$1.6(stat.)$\pm$2.1(syst.)) MeV/$c^2$ and $\Gamma_{\rm{pole}}$=(26.6$\pm$2.0(stat.)$\pm$2.3(syst.)) MeV, respectively. The Born cross section times the $(D\bar{D}^*)^{\mp}$ branching fraction ($\sigma(e^+e^\to\pi^{\pm}Z_{c}(3885)^{\mp}) \times Br(Z_{c}(3885)^{\mp}\to(D\bar{D}^*)^{\mp})$) is measured to be $(141.4\pm7.9(\text{stat.})\pm12.8(\text{syst.})) \text{pb}$ at $\sqrt{s}=4.23$ GeV and $(108.4\pm6.9(\text{stat.})\pm9.1(\text{syst.})) \text{pb}$ at $\sqrt{s}=4.26$ GeV. The polar angular distribution of the $\pi^{\pm}$$Z_c(3885)^{\mp}$ system is consistent with the expectation of a quantum number assignment of $J^P=1^+$ for $Z_c(3885)^{\mp}$.  [Show abstract] [Hide abstract]
ABSTRACT: In an analysis of a 2.92~fb$^{1}$ data sample taken at 3.773~GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be $\mathcal B(D^0 \to K^e^+\nu_e)=(3.505\pm 0.014 \pm 0.033)\%$ and $\mathcal B(D^0 \to \pi^e^+\nu_e)=(0.295\pm 0.004\pm 0.003)\%$. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f_{+}^K(0)V_{cs}=0.7172\pm0.0025\pm 0.0035$ and $f_{+}^{\pi}(0)V_{cd}=0.1435\pm0.0018\pm 0.0009$. Combining these products with the values of $V_{cs(d)}$ from the SM constraint fit, we extract the hadronic form factors $f^K_+(0) = 0.7368\pm0.0026\pm 0.0036$ and $f^\pi_+(0) = 0.6372\pm0.0080\pm 0.0044$, and their ratio $f_+^{\pi}(0)/f_+^{K}(0)=0.8649\pm 0.0112\pm 0.0073$. These form factors and their ratio are used to test unquenched Lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of $f_+^{K(\pi)}(0) V_{cs(d)}$ and the lattice QCD value for $f^{K(\pi)}_+(0)$ are used to extract values of the CKM matrix elements of $V_{cs}=0.9601 \pm 0.0033 \pm 0.0047 \pm 0.0239$ and $V_{cd}=0.2155 \pm 0.0027 \pm 0.0014 \pm 0.0094$, where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for $f_+^\pi(0)/f_+^K(0)$, we determine the ratio $V_{cd}/V_{cs}=0.238\pm 0.004\pm 0.002\pm 0.011$, where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.  [Show abstract] [Hide abstract]
ABSTRACT: Using 2.92 fb$^{1}$ of electronpositron annihilation data collected at a centerofmass energy of $\sqrt{s}= 3.773$ GeV with the BESIII detector, we present an improved measurement of the branching fraction $\mathcal{B}(D^+ \to \omega e^+ \nu_{e}) = (1.63\pm0.11\pm0.08)\times 10^{3}$. The parameters defining the corresponding hadronic form factor ratios at zero momentum transfer are determined for the first time, we measure them to be $r_V = 1.24\pm0.09\pm0.06$ and $r_2 = 1.06\pm0.15 \pm 0.05$. The first and second uncertainties are statistical and systematic, respectively. We also search for the decay $D^+ \to \phi e^+ \nu_{e}$. An improved upper limit $\mathcal{B}(D^+ \to \phi e^+ \nu_{e}) < 1.3 \times 10^{5}$ is set at 90\% confidence level.  [Show abstract] [Hide abstract]
ABSTRACT: We extract the $e^+e^\rightarrow \pi^+\pi^$ cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb$^{1}$ taken at a centerofmass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor $F_\pi^2$ as well as the contribution of the measured cross section to the leading order hadronic vacuum polarization contribution to $(g2)_\mu$. We find this value to be $a_\mu^{\pi\pi,\rm LO}(600900\;\rm MeV) = (372.5 \pm 2.6_{\rm stat} \pm 3.4_{\rm sys})\cdot 10^{10}$.  [Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^\rightarrow \pi\pi X$. These asymmetries can be attributed to the Collins fragmentation function, which describes the behavior of a hadron produced from a transversely polarized quark. This work is performed using a data set of 62 $\rm{pb}^{1}$ at the centerofmass energy $\sqrt{s}=3.65$ GeV collected with the BESIII detector at the BEPCII storage rings, where the corresponding fourmomentum transfer of the virtual photon, $Q^2$, is close to the energy scale of the existing semiinclusive DIS experimental data. We observe a nonzero asymmetry, which increases with increasing pion momentum and also indicates a larger spindependent Collins effect than at higher energy scale. The dependence of the asymmetry on the transverse momentum of hadrons to the reference axis is also investigated. The measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon, and are valuable to explore the energy evolution of the spindependent fragmentation function.  [Show abstract] [Hide abstract]
ABSTRACT: Based on a sample of \etapr mesons produced in the radiative decay $J/\psi\to\gamma\eta^{\prime}$ in $1.31\times 10^9$ $J/\psi$ events collected with the BESIII detector, the decay $\eta^{\prime}\to\omega e^{+} e^{}$ is observed for the first time, with a statistical significance of $8\sigma$. The branching fraction is measured to be $\mathcal{B}(\eta^{\prime}\to\omega e^{+} e^{})=(1.97\pm0.34(\text{stat})\pm0.17(\text{syst}))\times10^{4}$, which is in agreement with theoretical predictions. The branching fraction of $\eta^{\prime}\to\omega\gamma$ is also measured to be $(2.55\pm0.03(\text{stat})\pm0.16(\text{syst}))\times10^{2}$, which is the most precise measurement to date, and the relative branching fraction $\frac{\mathcal{B}(\eta^{\prime}\to \omega e^{+}e^{})}{\mathcal{B}(\eta^{\prime}\to \omega \gamma)}$ is determined to be $(7.71\pm1.34(\text{stat})\pm0.54(\text{syst}))\times10^{3}$.  [Show abstract] [Hide abstract]
ABSTRACT: The possibility to compute nucleon electromagnetic form factors in the timelike region by analytic continuation of their spacelike expressions has been explored in the framework of the Skyrme model. We have developed a procedure to solve analytically Fourier transforms of the nucleon electromagnetic current and hence to obtain form factors defined in all kinematical regions and fulfilling the firstprinciples requirements. The results are discussed and compared to data, both in spacelike and timelike region.  [Show abstract] [Hide abstract]
ABSTRACT: We report the observation of the X(3823) state in the process e^{+}e^{}→π^{+}π^{}X(3823)→π^{+}π^{}γχ_{c1} with a statistical significance of 6.2σ, in data samples at centerofmass energies sqrt[s]=4.230, 4.260, 4.360, 4.420, and 4.600 GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the X(3823) state is (3821.7±1.3±0.7) MeV/c^{2}, where the first error is statistical and the second systematic, and the width is less than 16 MeV at the 90% confidence level. The products of the Born cross sections for e^{+}e^{}→π^{+}π^{}X(3823) and the branching ratio B[X(3823)→γχ_{c1,c2}] are also measured. These measurements are in good agreement with the assignment of the X(3823) state as the ψ(1 ^{3}D_{2}) charmonium state.Physical Review Letters 07/2015; 115(1):011803. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report a study of the process $e^{+} e^{} \to (D^{*} \bar{D}^{*})^{0} \pi^0$ using $e^+e^$ collision data samples with integrated luminosity of $1092 \rm{pb}^{1}$ at $\sqrt{s}=4.23 \rm{GeV}$ and $826 \rm{pb}^{1}$ at $\sqrt{s}=4.26 \rm{GeV}$ collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the $(D^{*} \bar{D}^{*})^{0}$ mass threshold in the $\pi^0$ recoil mass spectrum, which we denote as $Z_{c}(4025)^{0}$. Assuming a BreitWigner line shape, its pole mass and pole width are determined to be $(4025.5^{+2.0}_{4.7}\pm3.1) \rm{MeV}/c^2$ and $(23.0\pm 6.0\pm 1.0) \rm{MeV}$, respectively. The statistical significance of the observation is $7.4\sigma$. The Born cross sections of $e^{+}e^{}\to Z_{c}(4025)^{0} \pi^0\to (D^{*} \bar{D}^{*})^{0}\pi^0$ are measured to be $(61.6\pm8.2\pm9.0) \rm{pb}$ at $\sqrt{s}=4.23 \rm{GeV}$ and $(43.4\pm8.0\pm5.4) \rm{pb}$ at $\sqrt{s}=4.26 \rm{GeV}$. The first uncertainties are statistical and the second are systematic.  [Show abstract] [Hide abstract]
ABSTRACT: The decay $Z_c(3900)^\pm\to\omega\pi^\pm$ is searched for using data samples collected with the BESIII detector operating at the BEPCII storage ring at centerofmass energies $\sqrt{s}=4.23$ and $4.26$~GeV. No significant signal for the $Z_c(3900)^\pm$ is found, and upper limits at the 90\% confidence level on the Born cross section for the process $e^+e^\to Z_c(3900)^\pm\pi^\mp\to\omega\pi^+\pi^$ are determined to be $0.26$ and $0.18$ pb at $\sqrt{s}=4.23$ and 4.26 GeV, respectively.  [Show abstract] [Hide abstract]
ABSTRACT: We study $D_{s}^{+}$ decays to final states involving the $\eta'$ with a 482\,pb$^{1}$ data sample collected at $\sqrt{s}$ = 4.009\,GeV with the \mbox{BESIII} detector at the BEPCII collider. We measure the branching fractions $\mathcal{B}(D^+_{s}\rightarrow \eta'X)$ = (8.8$\pm$1.8$\pm$0.5)\% and $\mathcal{B}(D_{s}^{+}\rightarrow \eta'\rho^{+})$ = ($5.8\pm1.4\pm0.4$)\% where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the nonresonant branching ratio $\mathcal{B}(D_{s}^{+}\rightarrow \eta'\pi^+\pi^0)<5.1\%$ at the 90\% confidence level. Our results are consistent with CLEO's recent measurements and help to resolve the disagreement between the theoretical prediction and CLEO's previous measurement of $\mathcal{B}(D_{s}^{+}\rightarrow \eta'\rho^{+})$.  [Show abstract] [Hide abstract]
ABSTRACT: Based on a sample of $1.31 \times 10^9$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider, Dalitz plot analyses of selected 79,625 $\eta\rightarrow\pi^{+}\pi^{}\pi^0$ events, 33,908 $\eta\rightarrow\pi^0\pi^0\pi^0$ events and 1,888 $\eta^{\prime}\rightarrow\pi^0\pi^0\pi^0$ events are performed. The measured matrix elements of $\eta\rightarrow\pi^+\pi^\pi^0$ are in reasonable agreement with previous measurements. The Dalitz plot slope parameters of $\eta\rightarrow\pi^0\pi^0\pi^0$ and $\eta^{\prime}\rightarrow\pi^0\pi^0\pi^0$ are determined to be $0.055 \pm 0.014 \pm 0.004$ and $0.640 \pm 0.046 \pm 0.047$, respectively, where the first uncertainties are statistical and the second systematic. Both values are consistent with previous measurements, while the precision of the latter one is improved by a factor of three. Final state interactions are found to have an important role in those decays.  [Show abstract] [Hide abstract]
ABSTRACT: We report an observation of the process $J/\psi\rightarrow\gamma X(1835)\rightarrow\gamma K^0_S K^0_S\eta$ at low $K^0_S K^0_S$ mass with a statistical significance larger than 12.9$\sigma$ using a data sample of $1.31 \times 10^{9}$ $J/\psi$ events collected with the BESIII detector. In this region of phase space the $K^0_S K^0_S$ system is dominantly produced through the $f_0(980)$. By performing a partial wave analysis, we determine the spinparity of the $X(1835)$ to be $J^{PC}=0^{+}$. The mass and width of the observed $X(1835)$ are $1844\pm9(\text{stat})^{+16}_{25}(\text{syst})$~\MeV~and $192^{+20}_{17}(\text{stat})^{+62}_{43}(\text{syst})$~MeV, respectively, which are consistent with the results obtained by BESIII in the channel $J/\psi\rightarrow\gamma\pi^+\pi^\eta^{\prime}$.  [Show abstract] [Hide abstract]
ABSTRACT: An amplitude analysis of the $\pi^{0}\pi^{0}$ system produced in radiative $J/\psi$ decays is presented. In particular, a piecewise function that describes the dynamics of the $\pi^{0}\pi^{0}$ system is determined as a function of $M_{\pi^{0}\pi^{0}}$ from an analysis of the $(1.311\pm0.011)\times10^{9}$ $J/\psi$ decays collected by the BESIII detector. The goal of this analysis is to provide a description of the scalar and tensor components of the $\pi^0\pi^0$ system while making minimal assumptions about the properties or number of poles in the amplitude. Such a modelindependent description allows one to integrate these results with other related results from complementary reactions in the development of phenomenological models, which can then be used to directly fit experimental data to obtain parameters of interest. The branching fraction of $J/\psi \to \gamma \pi^{0}\pi^{0}$ is determined to be $(1.15\pm0.05)\times10^{3}$, where the uncertainty is systematic only and the statistical uncertainty is negligible.  [Show abstract] [Hide abstract]
ABSTRACT: Using a sample of 1.31 billion $J/\psi$ events collected with the BESIII detector at the BEPCII collider, the decays $J/\psi \to \phi \pi^{+}\pi^{}\pi^{0}$ and $J/\psi \to \phi \pi^{0}\pi^{0}\pi^{0}$ are investigated. The isospin violating decay $J/\psi \to \phi \pi^{0} f_{0}(980)$ with $f_{0}(980) \to \pi\pi$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $\pi^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/\psi \to \phi\eta'$, the branching fractions of $\eta' \to \pi^{+}\pi^{}\pi^{0}$ and $\eta' \to \pi^{0}\pi^{0}\pi^{0}$, as well as their ratio, are also measured.  [Show abstract] [Hide abstract]
ABSTRACT: Using $2.92$ fb$^{1}$ of electronpositron annihilation data collected at $\sqrt{s} = 3.773$~GeV with the BESIII detector, we report the results of a search for the flavorchanging neutral current process $D^0\to\gamma\gamma$ using a doubletag technique. We find no signal and set an upper limit at $90\%$ confidence level for the branching fraction of $B(D^0\to\gamma\gamma) < 3.8\times10^{6}$. We also investigate $D^0$meson decay into two neutral pions, obtaining a branching fraction of $B(D^0\to\pi^0\pi^0) = (8.24\pm0.21(\text{stat.})\pm0.30(\text{syst.}))\times10^{4}$, the most precise measurement to date and consistent with the current world averagePhysical Review D 05/2015; 91(11). DOI:10.1103/PhysRevD.91.112015 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Using the data sets taken at centerofmass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e+e > gamma_ISR X(3872) > gamma_ISR pi+piJ/psi via the Initial State Radiation technique. The production of a resonance with quantum numbers J^PC = 1^++ such as the X(3872) via single photon e+e annihilation is forbidden, but is allowed by a nexttoleading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction Gamma_ee^X(3872)Br(X(3872) > pi+piJ\psi) < 0.13 eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the psi(3686) to be Gamma_ee^psi(3686) = 2231 + 18 + 99 eV.  [Show abstract] [Hide abstract]
ABSTRACT: Using data samples collected at center of mass energies of $\sqrt{s}$ = 4.009, 4.226, 4.257, 4.358, 4.416 and 4.599 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the isospin violating decay $Y(4260)\rightarrow J/\psi \eta \pi^{0}$. No signal is observed, and upper limits on the cross section $\sigma(e^{+}e^{}\rightarrow J/\psi \eta \pi^{0})$ at the 90\% confidence level are determined to be 3.6, 1.7, 2.4, 1.4, 0.9 and 1.9 pb, respectively.  [Show abstract] [Hide abstract]
ABSTRACT: We present a search for a neutral, longlived particle L that is produced in e[superscript +]e[superscript ] collisions and decays at a significant distance from the e[superscript +]e[superscript ] interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an e[superscript +]e[superscript ] data sample with a luminosity of 489.1 fb[superscript 1] collected by the BABAR detector at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and just below the ϒ(4S). Fitting the twotrack mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible twobody L decay modes as a function of the L mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction B(B → X[subscript s]L), where X[subscript s] is a strange hadronic system.
Publication Stats
2k  Citations  
1,643.48  Total Impact Points  
Top Journals
Institutions

2004–2012

Università degli Studi di Perugia
 Department of Physics
Perugia, Umbria, Italy


2006–2010

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy


2008–2009

Centro FERMI
Roma, Latium, Italy 
University of Surrey
Guilford, England, United Kingdom


2005–2007

RuhrUniversität Bochum
 Institut für Experimentalphysik I
Bochum, North RhineWestphalia, Germany 
University of Milan
Milano, Lombardy, Italy
