Experimental evidence for the box anomaly inη/η′ decays and the electric charge of quarks

Motivated by nearly unanimous claim that the observed mass spectrum ^+- is not that expected from pure ⁰ dominance, we reanalyze all the published data on / ^+- decays. We find non-resonant contributions. In order to evaluate precisely the magnitude of these terms, we also refit the e⁺e^{- +-} data to get reliably the ⁰ parameters and decay amplitude. We show that identifying the non-resonant contribution with the box anomaly predicted by QCD and chiral theories, one achieves a consistent picture. Several checks are performed which show the consistency of our fitted parameters. From four measurements, we determinef ₁,f ₈ and _PS on purely experimental grounds, and we find them in the expected range. Presently available data allow for two solutions, one is consistent with QCD, the other favours integral charge quark models. We show that presently available data do not allow to choose among these two solutions. We discuss the interrelation of uncertainties in e⁺e^{- +-} physics with our two solutions.     

Experimental study of π− π+ system at low invariant-masses

We report on results of an experiment to study the reaction ^– p ^{– +} in the incident pion momentum region between 295 and 450 MeV/c. A departure from phase space was observed in invariant-mass spectra and angular distributions which cannot be explained with and resonance production. It indicates aI=0,J ^P = 0^{+ – +} final-state interaction.Deceased     

Studies of the reactionπ − p→η ′ π 0 n at 38 and 100 GeV/c

The production of ⁰ system in ^– _p charge-exchange interactions at ^– momenta 38 GeV/c and 100 GeV/c has been studied. The 2 and ^{0 0} decay modes of leading to 4 and 8 final states respectively have been detected. No statistically significant peak is observed in the ⁰ mass spectrum in the range of 1.2 GeV÷2.1 GeV. An upper limit of 6·10^–3 has been established for thea ₂ ⁰ (1320) ⁰ branching ratio.     

On the possibilities to study the exotic state 1−+ in photoproduction of the πη, πη′ systems

We show that photoproduction experiments provide propitious conditions to study the exotic state 1^–+ in the and channels. For unpolarized photons contributions from natural and unnatural parity exchanges do not interfere with each other, a fact which permits to estimate the correctness of phase shift analyses. In photoproduction of the ⁺ system in the mass range ofa ₂(1320) a more stringent limit on the product (1^–+)Br(1^–+) can be obtained than in experiments on Primakoff production on nuclei. Particularly favourable is the study of the state 1^–+ in the coherent photoproduction of the ⁰ and ⁰ systems on nuclei, with significantly enlarged statistics and a simplified phase shift analysis.     

AssociateJ/ψ+γ production: a clean probe of gluon densities

Production of strange and charm particles by hadron-proton collisions is analyzed in terms of a fire-ball (FB) model assuming the multiplicity of secondaries of a given massm, to be proportional to the FB mass: n(m)M ^*, the FB kinematics being determined by the Feynman-Yang scaling, as in the case of production. It is found that (m)1/m ² and that, using this property together with the scaling, no-free-parameter fits to currently available data of strange and charm particles frompp and p collisions are satisfactory, as well as for the photoproduction of charm mesonD and charm hyperon _c .     

K s →π+π−γ: a laboratory for meson dynamics

We discuss the decayK _{s +–} in the framework of chiral perturbation theory. The direct emission in this decay can be an useful test of meson dynamics.     

K→ππγ decays: A search for novel couplings in kaon decays

We analyzeK decays in the framework of Chiral Perturbation Theory. We study the different Dalitz plot distributions, trying to find regions whereo(p ⁶) contributions could be more easily detected. To fulfill this program we compute all theo(p ⁴) loop and counterterm contributions, finding a substantial agreement with the existing calculations and adding some small missing terms inK _S ^+–.Work supported in part by the Human Capital and Mobility Program, EEC Contract N. CHRX-CT920026     

A measurement of the π0, η and η′ electromagnetic form factors

We present measurement of the ^0*, ^* and ^* form factors. The ⁰-form factor is for the first time observed in the space-like region. The transition form factor of the -meson is determined from its decay modes ^+–0, ^+– and the neutral decay mode . The decay of the is observed in the decay channels , ^+– with and in the four charged prong final state stemming from ^+– with the decaying into ^+–(⁰/). All form factors agree well with a simple -pole predicted by the vector meson dominance model and also with the QCD inspired Brodsky-Lepage model.     

The influence of shape changes on the alpha decay in the191Bi m,g →187Tl→183Au chain

The¹⁹¹Bi^{m,g 187}T1 ¹⁸³Au a-decay chain has been studied using mass — separated sources. The a — branching ratios have been measured. Out of the reduced a — decay widths, it is clear that the s_1/2 — S_1/2 and h_9/2 h_9/2 transitions are not hindered although they involve strong shape changes.     

K^0 - \bar K^0 mixing and the chiral-bag model

TheB-parameter is determined by the chiralbag model calculation of the amplitude. This is correlated with theK⁺⁰ decay amplitude. The theoretical magnitude ofB-parameter depends on the final state interaction effects inK2 decays. Without the final state interaction correction one findsB(µ _B ² )0.37, with the correction includedB(µ _B ² )0.9. Similar connection between theoretical prediction of theK⁺⁰ decay amplitude and calculated value ofB parameter seems to exist in other approaches too.     

Two-proton multiplets in theN=82 nucleus 62 144 Sm82 from in-beamγ-measurements

In a high sensitivity (,2n) in-beam study of ₆₂ ¹⁴⁴ Sm₈₂, with the Kölner Würfel OSIRIS -detector array including a Compton polarimeter, we have identified the complete two-proton multiplets d ₅ ^2/–2 , d ₅ ^2/–1 g ₇ ^2/–1 , g ₇ ^2/–2 , h_11/2d ₅ ^2/–1 and the 9^– to 4^– members of the h_11·/2g ₇ ^2/–1 multiplet.Work partially supported by CICYT (Spain).     

Inclusive measurement of [`(p)]\bar p annihilation at rest in gaseous hydrogen to final states containingρ andf2

Antiproton annihilation at rest in gaseous hydrogen (16 bar pressure) to the final states (770)X andf ₂(1270)X, whereX stands for one or more neutral mesons, has been studied at LEAR using the CPLEAR detector. Relative branching ratios are given forX = ⁰,2 ⁰, 3 ⁰ in the case, and forX = ⁰, in thef ₂ case. The annihilation channel has not been measured before. The fraction of P-wave annihilation is deduced from the ratiof ₂ ⁰/ ⁰ to be 0.38±0.07, in good agreement with the result previously obtained by CPLEAR from the ratioK ⁺ K ^-/ ^{+ -}.     

Contributions toΛ c + →πΣ,πΛ andp\bar K^0 from excited states

We consider contributions to _c ⁺ , and from excited states. The calculations are performed within the MIT-bag model and a heavy quark bag model. Because the mass of _c ⁺ is rather big compared to the strange baryons, excited baryon states with mass close to that of _c ⁺ in some cases give significant pole contributions to the decay amplitudes of _c ⁺ .     

High-spin states of odd-odd156Ho

High spin states in the nucleus¹⁵⁶Ho have been studied via the fusion-evaporation reaction¹⁴⁰Ce(¹⁹F,3n)¹⁵⁶Ho at the beam energy of 82 MeV.- coincidences, E, I and excitation functions have been measured. With two rotationally-aligned bands identified as [h_11/2] [i_13/2], we found two new bands with a signature splitting, whose structure is believed to arise from either [h_9/2] or [f_7/2] coupled to [h_11/2]. Our placement of rays belonging to these new bands suggests that the previously known level scheme should be corrected. We also found many new low-energy rays in the low excitation energy. As compared to¹⁵⁴Ho, the present nucleus with two more neutrons becomes more collective, and shows well-observed rotationally-aligned bands with a clear signature splitting.Communicated by B. Herskind     

Study of theπ + π − γ system centrally produced in the reactionpp→p f (π + π − γ)p s at 300 GeV/c

The reactionppp _f ( ^{+ –} )p _s , where the ^{+ –} system is centrally produced, has been studied at 300 GeV/c. The ^{+ –} mass spectrum shows evidence for a ⁰ decay mode of the (958) andf ₁ (1285). The branching ratio (f ₁(1285) ^{+ +})/(f ₁(1285) ⁰ ) is found to be 5.0±0.7. No evidence is found for a ⁰(770) decay mode of theE/f ₁ (1420) for which an upper limit BR (E/f ₁(1420) ⁰ )<0.08 at=" 95%=" cl=" is=">     

The decays of theρ′1 andω′1 mesons

New measurements of the reactione ⁺ e ^– confirm previous evidence for the decay₁ and provide a strong constraint on the mass of the₁. The results from a detailed analysis of these data are compared with those from a corresponding analysis of new data on the reactione ⁺ e ^–. It is shown that in accord with expectation. This identification of a strong₁ decay supports a previous claim that the₁ and theC(1480), observed in the channel, cannot be different manifestations of the same particle.     

Observation of the decaya 2 − (1320)→π − η′

The reaction ^– C ^– C has been studied at 36 GeV/c. A clear signal for the decaya ₂ ^– (1320) ^– · is observed in the ^– mass spectrum. The measured ratio of branchings is BR (a ₂ ^{– –} )/BR(a ₂ ^{– –} );(3.4±0.8±0.5)·10^–2.     

Production off2(1270) andf0(975) mesons by photons and hadrons of energy 65–175 GeV

Measurements are reported of inclusive production of -mesons in the beam fragmentation region in p, p andKp collisions. Results include a small but significant departure from VMD, and a pronounced rise in the/ ⁰ ratio with increasingp _T .     

Evidence for higher twist mechanisms in highp ⊥π− p events with prompt ρ0 production at 38 GeV/c

The ^– p interactions with at least one charged secondary produced at polar angle 90° in c.m.s. and having the transverse momentum above 1 GeV/c were investigated. The data were obtained using streamer chamber magnetic spectrometer RISK at 38 GeV/c beam from Serpukhov accelerator. The analyzis of associated production in reconstructed events suggests, that if the transverse momentum of a pair of oppositely charged secondaries compensates the trigger particlep practically completely, this pair is the product of the ⁰ decay in marked fraction of such events. We observed a large spin-alignment for the ⁰-mesons selected as described above: the probability of zero spin projection onto the normal to the ⁰ production plane is equal to ₀₀ ^T =0.86±0.23. The enhancement of the number of events, in which the ⁰ picks up practically full momentum transfer carrying by the exchange, and also the enlarged tensor polarization for the ⁰-mesons in these events could be qualitatively explained as manifestation of direct ⁰-production via the QCD higher twist processes in the highp ^– p collisions. At the same time, the observed effects are markedly larger than the values predicted with QCD model in which the higher twist corrections were included.