Towards an effective description for the J/ψ decays

2006

Recently, the BES collaboration has published an extensive partial wave analysis of experimental data on J/ψ → φπ + π − , J/ψ → ωπ + π − , J/ψ → φK + K − and J/ψ → ωK + K −. These new results are analyzed here, with full account of detection efficiencies, in the framework of a chiral unitary description with coupled-channel final state interactions between ππ and KK pairs. The emission of a dimeson pair is described in terms of the strange and nonstrange scalar form factors of the pion and the kaon, which include the final state interaction and are constrained by unitarity and by matching to the next-to-leading-order chiral expressions. This procedure allows for a calculation of the S-wave component of the dimeson spectrum including the f0(980) resonance, and for an estimation of the low-energy constants of Chiral Perturbation Theory, in particular the large Nc suppressed constants L r 4 and L r 6. The decays in question are also sensitive to physics associated with OZI violation in the 0 ++ channel. It is found that the S-wave contributions to φπ + π − , φK + K − and ωπ + π − given by the BES partial-wave analysis may be very well fitted up to a dimeson center-of-mass energy of ∼ 1.2 GeV, for a large and positive value of L r 4 and a value of L r 6 compatible with zero. An accurate determination of the amount of OZI violation in the J/ψ → φπ + π − decay is achieved, and the S-wave contribution to ωK + K − near threshold is predicted.

Physical Review D, 2005

Physical Review D, 2008

Using data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct photon momentum spectrum in the decay J/ψ(1S) → γgg, via the "tagged" process: e + e − → ψ(2S); ψ(2S)→ J/ψ π + π − ; J/ψ → γ+X. Including contributions from two-body radiative decay processes, we find the ratio of the inclusive direct photon branching fraction to that of the dominant three-gluon branching fraction (R γ = B(ggγ)/B(ggg)) to be R γ = 0.137 ± 0.001 ± 0.016 ± 0.004, where the errors shown are statistical, systematic, and the model-dependent uncertainty related to the extrapolation to zero photon energy. The shape of the scaled photon energy spectrum in J/ψ → ggγ is observed to be very similar to that of Υ → ggγ. The R γ value obtained is roughly consistent with that expected by a simple quark-charge scaling (R γ ∼ (q c /q b ) 2 ) of the value determined at the Υ(1S), but somewhat higher than the value expected from the running of the strong coupling constant.

Physical Review D

Using the data samples of 1.31 × 10 9 J/ψ events and 4.48 × 10 8 ψ(3686) events collected with the BESIII detector, partial wave analyses on the decays J/ψ and ψ(3686) → π + π -η ′ are performed with a relativistic covariant tensor amplitude approach. The dominant contribution is found to be J/ψ and ψ(3686) decays to ρη ′ . In the J/ψ decay, the branching fraction B(J/ψ → ρη ′ ) is determined to be (7.90 ± 0.19(stat) ± 0.49(sys)) × 10 -5 . Two solutions are found in the ψ(3686) decay, and the corresponding branching fraction B(ψ(3686) → ρη ′ ) is (1.02 ± 0.11(stat) ± 0.24(sys)) × 10 -5 for the case of destructive interference, and (5.69 ± 1.28(stat) ± 2.36(sys)) × 10 -6 for constructive interference. As a consequence, the ratios of branching fractions between ψ(3686) and J/ψ decays to ρη ′ are calculated to be (12.9 ± 1.4(stat) ± 3.1(sys))% and (7.2 ± 1.6(stat) ± 3.0(sys))%, respectively. We also determine the inclusive branching fractions of J/ψ and ψ(3686) decays to π + π -η ′ to be (1.36 ± 0.02(stat) ± 0.08(sys)) × 10 -4 and (1.51 ± 0.14(stat) ± 0.23(sys)) × 10 -5 , respectively.

The European Physical Journal C, 2010

J/ψ → V P decays and the quark and gluon content of the η and η ′ Abstract. The η-η ′ pseudoscalar mixing angle and the gluonium content of the η ′ meson are deduced from an updated phenomenological analysis of J/ψ decays into a vector and a pseudoscalar meson. In absence of gluonium, the value of the mixing angle in the quark-flavour basis is found to be φP = (40.7 ± 2.3) • . In presence of gluonium, the values for the mixing angle and the gluonic content of the η ′ wave function are φP = (44.6 ± 4.4) • and Z 2 η ′ = 0.29 +0.18 −0.26 , respectively. The newly reported values of B(J/ψ → ρπ) by the BABAR and BES Collaborations are crucial to get a consistent description of data.

Physical Review Letters, 2000

Physical Review Letters, 1982

Evidence for a new resonance 0 * nn in the process J/$ -t yrln is presented.

The European Physical Journal C, 2007

The decay J/ψ → ωpp is studied using a 5.8 × 10 7 J/ψ event sample accumulated with the BES II detector at the Beijing Electron-Positron Collider. The decay branching fraction is measured to be B(J/ψ → ωpp) = (9.8 ± 0.3 ± 1.4) × 10 −4. No significant enhancement near the pp mass threshold is observed, and an upper limit of B(J/ψ → ωX(1860))B(X(1860) → pp) < 1.5 × 10 −5 is determined at the 95% confidence level, where X(1860) designates the near-threshold enhancement seen in the pp mass spectrum in J/ψ → γpp decays.

Journal of High Energy Physics

The decays $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → J/ψπ+π−K+K− are studied using a data set corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → $$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 and $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → χc1(3872)K+K−, where the K+K−pair does not originate from a ϕ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χc1(3872)ϕ, $$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 , ψ(2S)ϕ and χc1(3872)K+K− states are reported. A structure, denoted as X(4740), is observed in the J/ψϕ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be$$ {\displaystyle \begin{array}{c}{m}_{\mathrm{X}(4...

Physical Review D, 2013

With a sample of 225.3 million J/ψ events taken with the BESIII detector, the decay J/ψ → γ3(π + π −) is analyzed. A structure at 1.84 GeV/c 2 is observed in the 3(π + π −) invariant mass spectrum with a statistical significance of 7.6σ. The mass and width are measured to be M = 1842.2 ± 4.2 +7.1 −2.6 MeV/c 2 and Γ = 83 ± 14 ± 11 MeV. The product branching fraction is determined to be B(J/ψ → γX(1840)) × B(X(1840) → 3(π + π −)) = (2.44 ± 0.36 +0.60 −0.74) × 10 −5. No η ′ signals are observed in the 3(π + π −) invariant mass spectrum, and the upper limit of the branching fraction for the decay η ′ → 3(π + π −) is set to be 3.1 × 10 −5 at a 90% confidence level. Within the framework of Quantum Chromodynamics (QCD), the existence of gluon self-coupling suggests that in addition to conventional meson and baryon states, there may exist bound states such as glueballs, hybrid states and multiquark states. Experimental searches for glueballs and hybrid states have been carried out for many years, and so far no conclusive evidence has been found. The establishment of new forms of hadronic matter beyond simple quark-antiquark system remains one of the main interests in experimental particle physics. Decays of the J/ψ particle have always been regarded as an ideal environment in which to study light hadron spectroscopy and search for new hadrons. At BESII, important advances in light hadron spectroscopy were made using studies of J/ψ radiative decays [1-3]. Of interest is the observation of the X(1835) state in J/ψ → γπ + π − η ′ 112 decay, which was confirmed recently by BESIII [4] and 113 CLEO-c [5]. Since the discovery of the X(1835), many 114 possible interpretations have been proposed, such as a 115 pp bound state [6-9], a glueball [10, 11], or a radial 116 excitation of the η ′ meson [12, 13]. In the search for 117 the X(1835) in other J/ψ hadronic decays, BESIII re-118 ported the first observation of the X(1870) in J/ψ → 119 ωπ + π − η [14]. More recently, BESIII performed spin-120 parity analyses of threshold structures, the X(pp), ob-are the efficiencies for J/ψ → π 0 3(π + π −) MC events 220 to pass J/ψ → γ3(π + π −) and J/ψ → π 0 3(π + π −) se-221 lection criteria, respectively. The selection criteria for 222 J/ψ → π 0 3(π + π −) are similar to those applied to J/ψ → 223 γ3(π + π −) except for the requirement of an additional 224 photon. The background analysis shows that the struc-225 ture at 1.84 GeV/c 2 in the 3(π + π −) mass spectrum does 226 not come from background events. 227 To extract the number of signal events associated with 228 the peaking structure, an unbinned maximum likelihood 229 fit is applied to the six pion mass spectrum. The fit in-230 cludes three components: a signal shape, shapes for the 231 J/ψ → π 0 3(π + π −) background and other backgrounds, 232 which have the same final states, but not contribute to 233 the structure around 1.84 GeV/c 2. The signal shape is 234 described with a Breit-Wigner function modified by the 235 effects of the phase space factor and the detection effi-236 ciency, which is determined by a phase-space MC simu-237 lation of J/ψ → γ3(π + π −). The Breit-Wigner function 238 is convolved with a Gaussian function to account for the 239 detector resolution (5.1 MeV/c 2 , determined from MC 240 simulation). For the background shape, the contribution 241 from the J/ψ → π 0 3(π + π −) background, which is fixed 242 in the fit and shown by the dash-dotted line in Fig. 2, is 243 represented by the re-weighted 3(π + π −) invariant mass 244 spectrum, while other contributions are represented by a 245 third-order polynomial. The total background is shown 246 as the dashed line in Fig. 2. 247 The fit yields 632±93 events in the peak at 1842.2±4.2 248 MeV/c 2 and a width of Γ=83±14 MeV. The statistical 249 significance of the signal is determined from the change 250 in log likelihood and the change of number of degrees 251 of freedom (d.o.f) in the fit with and without the struc-252 ture X(1840). Different possibilities have been studied by 253 varying the fit range and the background shapes and by 254 removing the phase space factor. Among all possibilities 255 the smallest statistical significance was 7.6σ correspond-256 ing to −2∆lnL=67 and ∆d.o.f=3. With the detection ef-257 ficiency, (11.5±0.1)%, obtained from the phase space MC 258 simulation, the product branching fraction is measured 259 to be B(J/ψ → γX(1840)) × B(X(1840) → 3(π + π −)) = 260 (2.44 ± 0.36) × 10 −5 , where the error is statistical only. 261 No η ′ events are observed in the 3(π + π −) mass spec-262 trum. The upper limit at the 90% confidence level is 263 2.44 events with the confidence intervals suggested in 264 Ref. [25]. The detection efficiency in the mass region 265 [0.928, 0.988] GeV/c 2 is determined to be (7.8 ± 0.1)% 266 from the MC simulation. Since only the statistical error 267 is considered when we obtain the 90% upper limit of 268 the number of events, the upper limit of the number of 269 events is shifted up by one sigma of the total system-270 atic uncertainty shown below in Table I. With the num-271 ber of J/ψ events and the measured B(J/ψ → γη ′) = 272 (5.16 ± 0.15)× 10 −3 [17], the upper limit of the branching 273 fraction is obtained to be B(η ′ → 3(π + π −)) < 3.1×10 −5. 274 Sources of systematic errors and their corresponding 275 contributions to the measurement of the branching frac-276 tions are summarized in Table I. The uncertainties in 277 tracking and photon detection have been studied [26] 278 and the difference between data and MC is about 2% 279 per charged track and 1% per photon, which is taken as 280 the systematic error. Uncertainty associated with the 4C 281 kinematic fit comes from the inconsistency between data 282 and MC simulation of the fit; this difference is reduced by 283 correcting the track helix parameters of MC simulation, 284 as described in detail in Ref. [27]. In this analysis, we 285 take the efficiency with correction as the nominal value, 286 and take the difference between the efficiencies with and 287 without correction as the systematic uncertainty from 288 the kinematic fit. The background uncertainty is deter-289 mined by changing the background functions and the fit 290 range. The uncertainties from the mass spectrum fit in-291 clude contributions from the variation of the phase space 292 factor and the possible impact of other resonances (eg. 293 f 2 (2010)). The systematic error for the P 2 tγ selection cri-294 terion is estimated with the sample of J/ψ → π 0 3(π + π −) 295 by comparing the efficiency of this requirement between 296 MC and data. For the detection efficiency uncertainty 297 due to the unknown spin-parity of the structure, we use 298 the difference between phase space and a pseudoscalar 299 meson hypothesis. The uncertainties from MC statistics, 300 the branching fraction of J/ψ → γη ′ [17] and the flux 301 of J/ψ events [18] are also considered. We assume all of 302 these sources are independent, and take the total system-303 atic error to be their sum in quadrature.