Evidence of a broad structure at an invariant mass of 4.32 GeV/c2 in the reaction e+e- --> pi+pi-psi(2S) measured at BABAR

Precise Measurement of Born Cross Sections for e^{+}e^{-}→DD[over ¯] at sqrt[s]=3.80-4.95 GeV

Using data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 3.80 to 4.95 GeV, corresponding to an integrated luminosity of 20  fb^{-1}, a measurement of Born cross sections for the e^{+}e^{-}→D^{0}D[over ¯]^{0} and D^{+}D^{-} processes is presented with unprecedented precision. Many clear peaks in the line shape of e^{+}e^{-}→D^{0}D[over ¯]^{0} and D^{+}D^{-} around the mass range of G(3900), ψ(4040), ψ(4160), Y(4260), and ψ(4415), etc., are foreseen. These results offer crucial experimental insights into the nature of hadron production in the open-charm region.

First Observation of a Three-Resonance Structure in e^{+}e^{-}→Nonopen Charm Hadrons

We report the measurement of the inclusive cross sections for e^{+}e^{-}→nOCH (where nOCH denotes non-open charm hadrons) with improved precision at center-of-mass (c.m.) energies from 3.645 to 3.871 GeV. We observe three resonances: R(3760), R(3780), and R(3810) with significances of 8.1σ, 13.7σ, and 8.8σ, respectively. The R(3810) state is observed for the first time, while the R(3760) and R(3780) states are observed for the first time in the nOCH cross sections. Two sets of resonance parameters describe the energy-dependent line shape of the cross sections well. In set I [set II], the R(3810) state has mass (3805.7±1.1±2.7) [(3805.7±1.1±2.7)]  MeV/c^{2}, total width (11.6±2.9±1.9) [(11.5±2.8±1.9)]  MeV, and an electronic width multiplied by the nOCH decay branching fraction of (10.9±3.8±2.5) [(11.0±3.4±2.5)]  eV. In addition, we measure the branching fractions B[R(3760)→nOCH]=(25.2±16.1±30.4)%[(6.4±4.8±7.7)%] and B[R(3780)→nOCH]=(12.3±6.6±8.3)%[(10.4±4.8±7.0)%] for the first time. The R(3760) state can be interpreted as an open-charm (OC) molecular state, but containing a simple four-quark state component. The R(3810) state can be interpreted as a hadrocharmonium state.

Observation of Structures in the Processes e^{+}e^{-}→ωχ_{c1} and ωχ_{c2}

We present measurements of the Born cross sections for the processes e^{+}e^{-}→ωχ_{c1} and ωχ_{c2} at center-of-mass energies sqrt[s] from 4.308 to 4.951 GeV. The measurements are performed with data samples corresponding to an integrated luminosity of 11.0  fb^{-1} collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring. Assuming the e^{+}e^{-}→ωχ_{c2} signals come from a single resonance, the mass and width are determined to be M=(4413.6±9.0±0.8)  MeV/c^{2} and Γ=(110.5±15.0±2.9)  MeV, respectively, which is consistent with the parameters of the well-established resonance ψ(4415). In addition, we also use one single resonance to describe the e^{+}e^{-}→ωχ_{c1} line shape and determine the mass and width to be M=(4544.2±18.7±1.7)  MeV/c^{2} and Γ=(116.1±33.5±1.7)  MeV, respectively. The structure of this line shape, observed for the first time, requires further understanding.

Observation of Three Charmoniumlike States with J^{PC}=1^{--} in e^{+}e^{-}→D^{*0}D^{*-}π^{+}

The Born cross sections of the process e^{+}e^{-}→D^{*0}D^{*-}π^{+} at center-of-mass energies from 4.189 to 4.951 GeV are measured for the first time. The data samples used correspond to an integrated luminosity of 17.9  fb^{-1} and were collected by the BESIII detector operating at the BEPCII storage ring. Three enhancements around 4.20, 4.47, and 4.67 GeV are visible. The resonances have masses of 4209.6±4.7±5.9  MeV/c^{2}, 4469.1±26.2±3.6  MeV/c^{2}, and 4675.3±29.5±3.5  MeV/c^{2} and widths of 81.6±17.8±9.0  MeV, 246.3±36.7±9.4  MeV, and 218.3±72.9±9.3  MeV, respectively, where the first uncertainties are statistical and the second systematic. The first and third resonances are consistent with the ψ(4230) and ψ(4660) states, respectively, while the second one is compatible with the ψ(4500) observed in the e^{+}e^{-}→K^{+}K^{-}J/ψ process. These three charmoniumlike ψ states are observed in the e^{+}e^{-}→D^{*0}D^{*-}π^{+} process for the first time.

Observation of Resonance Structures in e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) and Mass Measurement of ψ_{2}(3823)

Using a data sample corresponding to an integrated luminosity of 11.3  fb^{-1} collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we measure the product of the e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) cross section and the branching fraction B[ψ_{2}(3823)→γχ_{c1}]. For the first time, resonance structure is observed in the cross section line shape of e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) with significances exceeding 5σ. A fit to data with two coherent Breit-Wigner resonances modeling the sqrt[s]-dependent cross section yields M(R_{1})=4406.9±17.2±4.5  MeV/c^{2}, Γ(R_{1})=128.1±37.2±2.3  MeV, and M(R_{2})=4647.9±8.6±0.8  MeV/c^{2}, Γ(R_{2})=33.1±18.6±4.1  MeV. Though weakly disfavored by the data, a single resonance with M(R)=4417.5±26.2±3.5  MeV/c^{2}, Γ(R)=245±48±13  MeV is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the ψ_{2}(3823) state is measured as (3823.12±0.43±0.13)  MeV/c^{2}, which is the most precise measurement to date.

Electromagnetic Form Factor of Doubly-Strange Hyperon

The standard model of particle physics is a well-tested theoretical framework, but there are still some issues that deserve experimental and theoretical investigation. The Ξ resonances with strangeness S=−2, the so-called doubly-strange hyperon, can provide important information to further test the standard model by studying their electromagnetic form factors, such as probing the limitation of the quark models and spotting unrevealed aspects of the QCD description of the structure of hadron resonances. In this work, we review some recent studies of the electromagnetic form factors on doubly-strange hyperons in pair production from positron–electron annihilation experiment.

Charmonium and charmoniumlike states at the BESIII experiment

Charmonium is a bound state of a charmed quark and a charmed antiquark, and a charmoniumlike state is a resonant structure that contains a charmed quark and antiquark pair but has properties that are incompatible with a conventional charmonium state. While operating at center-of-mass energies from 2 to 5 GeV, the BESIII experiment can access a wide mass range of charmonium and charmoniumlike states, and has contributed significantly in this field. We review BESIII results involving conventional charmonium states, including the first observation of the M1 transition ψ(2S) → γη c (2S) and the discovery of the ψ2(3823) state; and report on studies of charmoniumlike states, including the discoveries of the Z c (3900) and Z c (4020) tetraquark candidates, the resolution of the fine structure of the Y(4260) state, the discovery of the new production process e + e - → γX(3872) and the uncovering of strong evidence for the commonality among the X(3872), Y(4260) and Z c (3900) states. The prospects for further research at BESIII and proposed future facilities are also presented.

Measurement of the Cross Section for e^{+}e^{-}→Ξ^{-}Ξ[over ¯]^{+} and Observation of an Excited Ξ Baryon

Using a total of 11.0  fb^{-1} of e^{+}e^{-} collision data with center-of-mass energies between 4.009 and 4.6 GeV and collected with the BESIII detector at BEPCII, we measure fifteen exclusive cross sections and effective form factors for the process e^{+}e^{-}→Ξ^{-}Ξ[over ¯]^{+} by means of a single baryon-tag method. After performing a fit to the dressed cross section of e^{+}e^{-}→Ξ^{-}Ξ[over ¯]^{+}, no significant ψ(4230) or ψ(4260) resonance is observed in the Ξ^{-}Ξ[over ¯]^{+} final states, and upper limits at the 90% confidence level on Γ_{ee}B for the processes ψ(4230)/ψ(4260)→Ξ^{-}Ξ[over ¯]^{+} are determined. In addition, an excited Ξ baryon at 1820  MeV/c^{2} is observed with a statistical significance of 6.2-6.5σ by including the systematic uncertainty, and the mass and width are measured to be M=(1825.5±4.7±4.7)  MeV/c^{2} and Γ=(17.0±15.0±7.9)  MeV, which confirms the existence of the J^{P}=3/2^{-} state Ξ(1820).

XYZ states as hadronic molecules

In the past decade, a lot of new hadrons containing heavy quarks were discovered which do not fit into the scheme provided by the traditional quark models. Such states are known as the XYZ states and they are conventionally referred to as exotic ones. At present, there is no consensus on their nature, and different models and approaches have been suggested to explain their unusual properties. The talk is devoted to a brief overview of the molecule model for such exotic states.

Exclusive open-charm near-threshold cross sections in a coupled-channel approach

Data on 7 open-charm channels collected by the Belle Collaboration are analyzed simultaneously using a unitary approach based on a coupled channel model in a wide energy range $ \sqrt s $ = 3.7 − 4.7 GeV. The resulting fit provides a remarkably good overall description of the line shapes in all studied channels. Parameters of 5 vector charmonium resonances are extracted from the fit. It is demonstrated, that this approach could be used account for all exclusive channels and thus solve the long-term problem of the charmonium spectra near threshold.

Exotic hadrons from BESIII

We report the progress in the study of the exotic hadrons, also called XYZ states, at BESIII experiment with its unique data samples in e+ e− annihilation at center-of-mass energies of 3.8–4.6 GeV. The talk covers the observation of the Zc(3900) and Zc(4020) and new measurements related to them; updated measurement of the resonant parameters of the Y(4260) in e+ e−→ π+π− J/ψ and discovery of its new decay modes π+π−ψ(2S), ωχc0, π+π−hc, and D0D∗−π++c.c.; and observation of X(3872) in e+e− annihilation.

Vector states above open charm threshold at BESIII

Based on the the large XYZ data sample collected at BESIII detector, we study the vector states above charm threshold, including the traditional charmonium and charmonium-like states, Y in many decay modes. For example, e+e- → hc, π+π-J/Ψ,Ψ(3686); e+e- → η(ή)J/Ψ. Many charmonium and charmonium-like candidates are found, but some of them need to be confirmed further with much larger data.

Precise Measurement of the e^{+}e^{-}→π^{+}π^{-}J/ψ Cross Section at Center-of-Mass Energies from 3.77 to 4.60 GeV

The cross section for the process e^{+}e^{-}→π^{+}π^{-}J/ψ is measured precisely at center-of-mass energies from 3.77 to 4.60 GeV using 9  fb^{-1} of data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in a fit to the cross section. The first resonance has a mass of (4222.0±3.1±1.4)  MeV/c^{2} and a width of (44.1±4.3±2.0)  MeV, while the second one has a mass of (4320.0±10.4±7.0)  MeV/c^{2} and a width of (101.4_{-19.7}^{+25.3}±10.2)  MeV, where the first errors are statistical and second ones are systematic. The first resonance agrees with the Y(4260) resonance reported by previous experiments. The precision of its resonant parameters is improved significantly. The second resonance is observed in e^{+}e^{-}→π^{+}π^{-}J/ψ for the first time. The statistical significance of this resonance is estimated to be larger than 7.6σ. The mass and width of the second resonance agree with the Y(4360) resonance reported by the BABAR and Belle experiments within errors. Finally, the Y(4008) resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.

Evidence of Two Resonant Structures in e^{+}e^{-}→π^{+}π^{-}h_{c}

The cross sections of e^{+}e^{-}→π^{+}π^{-}h_{c} at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e^{+}e^{-}→π^{+}π^{-}J/ψ and e^{+}e^{-}→π^{+}π^{-}ψ(2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e^{+}e^{-}→π^{+}π^{-}h_{c} cross sections around 4.22 and 4.39  GeV/c^{2}, which we call Y(4220) and Y(4390), respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4_{-4.5}^{+5.5}±0.9)  MeV/c^{2} and a width of (66.0_{-8.3}^{+12.3}±0.4)  MeV for the Y(4220), and a mass of (4391.5_{-6.8}^{+6.3}±1.0)  MeV/c^{2} and a width of (139.5_{-20.6}^{+16.2}±0.6)  MeV for the Y(4390), where the first uncertainties are statistical and the second ones systematic. The statistical significance of Y(4220) and Y(4390) is 10σ over one structure assumption.

Mutualistic root endophytism is not associated with the reduction of saprotrophic traits and requires a noncompromised plant innate immunity

During a compatible interaction, the sebacinoid root-associated fungi Piriformospora indica and Sebacina vermifera induce modification of root morphology and enhance shoot growth in Arabidopsis thaliana. The genomic traits common in these two fungi were investigated and compared with those of other root-associated fungi and saprotrophs. The transcriptional responses of the two sebacinoid fungi and of Arabidopsis roots to colonization at three different symbiotic stages were analyzed by custom-designed microarrays. We identified key genomic features characteristic of sebacinoid fungi, such as expansions for gene families involved in hydrolytic activities, carbohydrate-binding and protein-protein interaction. Additionally, we show that colonization of Arabidopsis correlates with the induction of salicylic acid catabolism and accumulation of jasmonate and glucosinolates (GSLs). Genes involved in root developmental processes were specifically induced by S. vermifera at later stages during interaction. Using different Arabidopsis indole-GSLs mutants and measurement of secondary metabolites, we demonstrate the importance of the indolic glucosinolate pathway in the growth restriction of P. indica and S. vermifera and we identify indole-phytoalexins and specifically indole-carboxylic acids derivatives as potential key players in the maintenance of a mutualistic interaction with root endophytes.

Observation of e+e- → γX(3872) at BESIII

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process e+e-→ γX(3872) is observed for the first time with a statistical significance of 6.3σ. The measured mass of the X(3872) is (3871.9 ± 0.7s tat ± 0.2 syst)  MeV/c(2), in agreement with previous measurements. Measurements of the product of the cross section σ[e+e- → γX(3872)] and the branching fraction B[X(3872)→π+π-J/ψ] at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process Y(4260) → γX(3872).

How the Z(c)(3900) reveals the spectra of charmonium hybrids and tetraquarks

The recently discovered Z(c)(3900) meson is a flavor-exotic tetraquark whose constituents consist of a charm quark and antiquark and a light quark and antiquark. We identify such heavy tetraquark mesons as analogs of quarkonium hybrids, with the gluon field replaced by an isospin-1 excitation of the gluon and light-quark fields. Given the identification of Y(4260) as a ground-state charmonium hybrid, lattice QCD calculations of the charmonium spectrum by the Hadron Spectrum Collaboration can be used to estimate the masses of the four lowest spin-symmetry multiplets of charmonium hybrids. We make the assumption that the isospin-1 Born-Oppenheimer potentials, whose energy levels are tetraquarks, have the same shapes as the flavor-singlet Born-Oppenheimer potentials, whose energy levels are hybrids. Given the identification of Z(c)(3900) as a charmonium tetraquark, lattice QCD calculations of the charmonium hybrid spectrum can then be used to estimate the masses of the four lowest spin-symmetry multiplets of charmonium tetraquarks.

Very broad X(4260) and the resonance parameters of the ψ(3D) vector charmonium state

We argue that the X(4260) enhancement contains a wealth of information on 1-- cc spectroscopy. We discuss the shape of the X(4260) observed in the Okubo-Zweig-Iizuka-forbidden process e+e-→π+π-J/ψ, in particular, at and near vector charmonium resonances as well as open-charm threshold enhancements. The resulting very broad X(4260) structure does not seem to classify itself as a 1-- cc resonance, but its detailed shape allows us to identify new vector charmonium states with higher statistics than in open-charm decay. Here, we estimate the resonance parameters of the ψ(3D). Our approach also provides an explanation for the odd dip in the π+π-J/ψ data precisely at the ψ(4415) resonance.

Charmed baryonium

We reanalyze the published data on the Y(4630)-->Lambda(c) Lambda(c) and the Y(4660)-->psi(2S)pi pi with a consistent ansatz and we find that the two observations are likely to be due to the same state Y(B), produced via initial state radiation (ISR), with M(Y(B))=4660.7+/-8.7 MeV and Gamma(Y(B))=61+/-23 MeV. Under this hypothesis and reanalyzing the e+e- -->J/psi pi pi gamma(ISR) spectrum we find B(Y(B))-->Lambda(c) Lambda(c))/B(Y(B))-->psi(2S)pi pi)=117+/-44, B(Y(B))-->J/psi pi pi)/B(Y(B))-->psi(2S)pi pi)<0.46@90% C.L., B(Y(4350)-->J/psi pi pi)/B(Y(4350)-->psi(2S)pi pi)<3.4x10(-3)@90% C.L., and B(Y(B))-->psi(2S)sigma)/B(Y(B))-->psi(2S)f0)=2.0+/-0.3. These conclusions strongly support the hypothesis of Y(B) being the first observation of a charmed baryonium constituted by four quarks. Analyzing the mass spectrum we show that Y(4350) and Y(B) are, respectively, consistent with the ground state and first radial excitation of the l=1 state.

Evidence for a narrow near-threshold structure in the J/psivarphi mass spectrum in B;{+} --> J/psivarphiK;{+} decays

Evidence is reported for a narrow structure near the J/psivarphi threshold in exclusive B;{+} --> J/psivarphiK;{+} decays produced in p[over]p collisions at sqrt[s] = 1.96 TeV. A signal of 14 +/- 5 events, with statistical significance in excess of 3.8 standard deviations, is observed in a data sample corresponding to an integrated luminosity of 2.7 fb;{-1}, collected by the CDF II detector. The mass and natural width of the structure are measured to be 4143.0 +/- 2.9(stat) +/- 1.2(syst) MeV/c;{2} and 11.7_{-5.0};{+8.3}(stat) +/- 3.7(syst) MeV/c;{2}.

Possibility of deeply bound hadronic molecules from single pion exchange

Pion exchange in an S wave between hadrons that are themselves in a relative S wave can shift energies by hundreds of MeV. In the case of charmed mesons D, D;{*}, D0, D1, a spectroscopy of quasimolecular states may arise consistent with enigmatic charmonium states observed above 4 GeV in e;{+}e;{-} annihilation. A possible explanation of Y(4260) --> psipipi and Y(4360) --> psi;{'}pipi is found. Searches in DD[over]3pi channels as well as B decays are recommended to test this hypothesis.

Measurement of the e;{+}e;{-}-->bb[over ] Cross Section between sqrt[s]=10.54 and 11.20 GeV

We report e;{+}e;{-}-->bb[over ] cross section measurements by the BABAR experiment performed during an energy scan in the range of 10.54 to 11.20 GeV at the SLAC PEP-II e;{+}e;{-} collider. A total relative error of about 5% is reached in more than 300 center-of-mass energy steps, separated by about 5 MeV. These measurements can be used to derive precise information on the parameters of the Upsilon(10860) and Upsilon(11020) resonances. In particular we show that their widths may be smaller than previously measured.

Observation of a near-threshold enhancement in the e+e- -->Lambda+_(c)Lambda-_(c) cross section using initial-state radiation

We report a measurement of the exclusive e+ e- -->Lambda+_(c)Lambda-_(c) cross section as a function of center-of-mass energy near the Lambda+_(c)Lambda-_(c) threshold. A clear peak with a significance of 8.2sigma is observed in the Lambda+_(c)Lambda-_(c) invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=[4634 (+8)_(-7)(stat)(+5)_(-8)(syst)] MeV/c(2) and Gamma_(tot)=[92 (+40)_(-24)(stat)(+10)_(-21)(syst)] MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Upsilon(4S) resonance and nearby continuum with an integrated luminosity of 695 fb(-1) at the KEKB asymmetric-energy e+ e- collider.

Observation of a resonancelike structure in the pi +- psi' mass distribution in exclusive B-->Kpi +- psi' decays

A distinct peak is observed in the pi +/- psi' invariant mass distribution near 4.43 GeV in B-->K pi +/- psi' decays. A fit using a Breit-Wigner resonance shape yields a peak mass and width of M=4433+/-4(stat)+/-2(syst) MeV and Gamma=45-13+18(stat)-13+30(syst) MeV. The product branching fraction is determined to be B(B 0-->K -/+Z+/-(4430)) x B(Z+/-(4430)-->pi+/-psi')=(4.1+/-1.0(stat)+/-1.4(syst)) x 10(-5), where Z+/-(4430) is used to denote the observed structure. The statistical significance of the observed peak is 6.5 sigma. These results are obtained from a 605 fb(-1) data sample that contains 657 x 10(6) BB pairs collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider.

Observation of two resonant structures in e+ e- -->pi+ pi- psi(2S) via initial-state radiation at Belle

The cross section for e+ e- --> pi+ pi- psi(2S) between threshold and sqrt[s]=5.5 GeV is measured using 673 fb(-1) of data on and off the Upsilon(4S) resonance collected with the Belle detector at KEKB. Two resonant structures are observed in the pi+ pi- psi(2S) invariant-mass distribution, one at 4361 +/- 9 +/- 9 MeV/c2 with a width of 74 +/- 15 +/- 10 MeV/c2, and another at 4664 +/- 11 +/- 5 MeV/c2 with a width of 48 +/- 15 +/- 3 MeV/c2, if the mass spectrum is parametrized with the coherent sum of two Breit-Wigner functions. These values do not match those of any of the known charmonium states.