Decay Angular Analysis Research Articles

Observation of theχc2(2P)meson in the reactionγγ→DD¯atBABAR

A search for the Z(3930) resonance in gamma gamma production of the DDbar system has been performed using a data sample corresponding to an integrated luminosity of 384 fb^-1 recorded by the BABAR experiment at the PEP-II asymmetric-energy electron-positron collider. The DDbar invariant mass distribution shows clear evidence of the Z(3930) state with a significance of 5.8 sigma. We determine mass and width values of (3926.7 +- 2.7 +- 1.1) MeV/c^2 and (21.3 +- 6.8 +- 3.6) MeV, respectively. A decay angular analysis provides evidence that the Z(3930) is a tensor state with positive parity and C-parity (J^PC = 2^++); therefore we identify the Z(3930) state as the chi_c2(2P) meson. The value of the partial width Gamma_(gamma gamma)xB(Z(3930)-> DDbar) is found to be (0.24 +- 0.05 +- 0.04) keV.

New charm results from ARGUS

Recent results on hadronic D 0 decays and P-wave charmed mesons are discussed. The data have been collected with the ARGUS detector 1 at the e + e − storage ring DORIS II at centre-of-mass energies around 10 GeV. This presentation includes the observation of several new hadronic D 0 decays, the first measurement of an isospin mass splitting in the P-wave D meson sector, a decay angular analysis attempting to decompose the D ∗(2420) 0, and the observation of a candidate for an L = 1 D s meson.

Radiative decay of J/ psi into eta (1430) and nearby states.

Radiative decays of $\frac{J}{\ensuremath{\psi}}$ into ${K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$, ${K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$, $\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, and $\ensuremath{\rho}\ensuremath{\gamma}$ have been studied in the $\ensuremath{\eta}(1430)$ mass range from the $8.6\ifmmode\times\else\texttimes\fi{}{10}^{6}\frac{J}{\ensuremath{\psi}}'\mathrm{s}$ produced in the DM2 experiment at the Orsay ${e}^{+}{e}^{\ensuremath{-}}$ storage ring (DCI). The $\ensuremath{\eta}(1430)$ is observed in both ${K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and ${K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ channels. A three-body decay-angular analysis of the whole signal supports a ${J}^{P}={0}^{\ensuremath{-}}$ assignment. A substantial $K{K}^{*}(892)$ dynamics is present whereas the significance of the ${a}_{0}(980)\ensuremath{\pi}$ contribution cannot be evaluated. The $\ensuremath{\eta}(1430)$ is not observed in the $\ensuremath{\eta}\ensuremath{\pi}\ensuremath{\pi}$ channel which shows a peak in the $\frac{{f}_{1}(1285)}{\ensuremath{\eta}(1275)}$ mass range and a new state at 1398 MeV/${\mathit{c}}^{2}$, \ensuremath{\simeq}50 MeV/${\mathit{c}}^{2}$ wide. An ${a}_{0}(980)\ensuremath{\pi}$ intermediate-state contribution is present at least in the latter state. Finally, the low-statistics $\ensuremath{\rho}\ensuremath{\gamma}$ final state gives no evidence of $\ensuremath{\eta}(1430)$ production.

An experimental review of P-wave charmed mesons

A review of the experimental information currently available concerning P-wave charmed mesons is presented. Recent results include the first observation of a candidate for an L=1 D s meson, the first measurement of an isospin mass splitting in the P-wave D meson sector, and a decay angular analysis attempting to determine the spin-parity of the D ∗(2420).

Resonance decomposition of the D ∗(2420) 0 through a decay angular analysis

Using data collected with the ARGUS detector, we have performed a decay angular analysis of the enhancement, previously known as the D ∗ (2420), seen in the final state D ∗(2010) +π −. We thereby exhibit that the observed broad structure is actually due to two relatively narrow resonances, one of which is identified as the D ∗(2459) 0, while the massof the other is measured to be (2414±2±5) MeV/ c 2. The results of the analysis are in good agreement with the interpretation of the two states as L=1 D mesons of spin-parities 2 + and 1 + respectively.

Coherent production of low-mass pπ +π −states in the interaction of 18.6 GeV/cprotons with 4He nuclei

A specially developed scintillator and spark chamber spectrometer has been used to measure recoiling 4He target nuclei, and a magnetic spark chamber spectrometer to measure forward-going pπ +π −particles, selecting coherent events by four-momentum balance. Two enhancements in the pπ +π −mass spectrum are found at 1.49 and 1.71 GeV/ c 2. The branching ratio of the quasi-two-body stateΔ ++π −is42 ± 8%in the 1.71 GeV/ c 2 mass region. The tslope, as a function of pπ +π −mass, is consistent with what can be predicted using the impulse approximation. The decay angular analysis indicates the presence of several interfering states in the 1.5 GeV/c 2mass region and of one state of spin3/2, possibly5/2, in the 1.7 GeV/c 2mass region. There is some preference shown for t-channelhelicity conservation. The data are very similar to results obtained with photon targets, which provides independent support for the hypothesis that vacuum exchange is dominant in the production of low-mass pπ +π −states in pp interactions around 20 GeV/c.