γ-decay of the particle-hole states with the highest spins in208Pb

²⁰⁸Pb has been excited with inelastic heavy ion scattering of 350 MeV⁶⁴Ni and 420 MeV⁸²Se on a thick²⁰⁸Pb target. With - coincidence measurements 2 new decays of the 10⁺ isomer, namely a 34.5 keVE2-transition to 8 ₂ ⁺ and a 857.7 keVE3 transition to 7^– have been found and the wavefunctions of the participating levels deduced. An observed gamma cascade of 295.3, 348.0, 865.4 and 340.2 keV on top of the 10⁺ isomer is assigned to the particle-hole states with the highest spins 14^– 6744.1 keV13^– 6448.9 keV12⁺ 6100.9 keV11⁺ 5235.6 keV10⁺ 4895.4 keV.This work has been supported in part through the agreement on scientific cooperation between Poland and Germany.     

The\bar pp \to e^ + e^ - reaction at rest and the hierarchy of the annihilation ranges

A new procedure is devised to evaluate the proton form-factor at the ¯pp threshold from experimental data on ¯ppe ⁺ e ^– annihilation at rest. Comparison of the ¯ppe ⁺ e ^– and¯pp ^+– processes reveals that annihilation ranges for various channels are ranked in line with quark dynamics.This work has been funded in part by the German Federal Minister for Research and Technology (BMFT) under the contract number 06HD756     

SubthresholdK + production in proton-nucleus collisions

We analyzed theK ⁺ production at projectile energies below the free nucleon-nucleon threshold in proton-nucleus collisions and studied the contribution from different reaction channels to this process. It was shown that the secondary pion-nucleon (+N+K ⁺) channel significantly prevails over the direct (p+N+N+K ⁺) one. The momentum and angularK ⁺ spectra were calculated in the framework of different production channels in order to propose experimental measurements which allow to distinguish the mechanisms discussed. We also studiedK ⁺ d correlations and considered the deuteron reabsorption in the nuclear medium as well as the fast deuteron background. The features ofK ⁺ p correlations related to the different production channels were analyzed as well.     

Ways to measure the hairpin diagram in charmed meson decays

The possible presence of hairpin diagrams is analyzed in th model-independent quark-diagram scheme for two-body decays of charmed mesons. Current experimental data do not require the presence of hairpin diagrams inDVP (V: vector meson,P: pseudoscalar meson), in accordance with the OZI rule. However, there is a possible indication that they are important in the decay ofDPP. The measurement ofD _s ^{+ +} is crucial to test the mechanism of hairpin diagrams.     

The new element 111

In an experiment carried out to identify element 110, we have observed an-decay chain, that can be unambiguously assigned to²⁶⁹110. In a scries of preexperiments the excitation functions of the fusion reactions⁵⁰Ti +²⁰⁸Pb²⁵⁸104^* and⁵⁸Fe +²⁰⁸Pb²⁶⁶108^* were measured with high precision in order to get the optimum projectile energies for the production of these heavy elements. The cross-section maxima of the 1n evaporation channels were observed at excitation energies of 15.6 MeV and 13.4 MeV, respectively. These data result in an optimum excitation energy of 12.3 MeV of the compound nucleus for the production of²⁶⁹110 in the reaction⁶²Ni +²⁰⁸Pb²⁶⁹110 + 1n. In irradiations at the corresponding beam energy of 311 MeV we have observed a decay chain of 4 subsequent a decays. This can be assigned to the isotope with the mass number 269 of the element 110 on the basis of delayed - coincidences. The accurately measured decay data of the daughter isotopes of the elements 108 to 102, obtained in the previous experiments, were used. The isotope²⁶⁹110 decays with a hair-life of (270 _-120 ⁺¹³⁰⁰ ) s by emission of (11.132±0.020) MeV alpha particles. The production cross-section is (3.3 _-2.7 ^+6.2 ) pb.     

Study of coherent diffractive production reactions ofp+C→[Y 0 K +]+C type and observation of narrow structures in ∑ (1385)0 K + and ∑0 K + effective mass spectra

In the experiments at the SPHINX facility in 70 GeV proton beam of the IHEP accelerator the coherent diffractive production reactions on carbon nucleip+C [(1385)⁰ K ⁺+C andp+C[⁰ K ⁺]+C were investigated. The evidences for new baryon states were obtained in the study of hyperon-kaon effective mass spectra in these two reactions:X (2050) with massM=(2052±6) MeV and width =(35 _–35 ⁺²² ) MeV inM[(1385)⁰ K ⁺] andX(2000) withM=1999±6 MeV and =91±17 MeV inM[⁰ K ⁺]. The unusual features of these massive states (small enough decay widths, anomalously large branching ratios for decays with strange particles emission) make them very serious candidates for cryptoexotic pentaquark baryons with hidden strangeness.     

A theoretical prediction for exclusive decaysB→K(K*)η c

The decay rates for the exclusiveB decaysBK _c andBK* _c are calculated in the context of the heavy quark effective theory. We obtain(BK _c )/ (BK)=1.6±0.2 and(BK* _c )/ (K*)=0.39±0.04. These results lead to estimates BR(BK _c )=(0.11±0.02)% and BR(BK* _c )=(0.05±0.01)% if we use the central current experimental values forB(K, K ^*) branching ratios.     

A unified formalism for γγ→meson and ψ-γX with possible tests for hybrid and gluonic hadrons

The couplings of conventional and hybrid mesons to (real and virtual) and their production amplitudes in M are described in a unified manner. Existing results for heavy quarks are recovered, extensions to light quarks and to virtual couplings are made and phenomenological applications discussed. In particular we discuss relativistic corrections to 0⁺, 1⁺, 2⁺ for both real and virtual photons and offer a resolution to a long standing puzzle in perturbative QCD concerning the helicity structure of 2⁺⁺. We suggest that the production off ₂ (1720) involves gluons in an essential way or that this meson hasJ2.     

Search forN ϕ (1960) baryon

In the experiments at the SPHINX facility in the 70 GeV proton beam of the IHEP accelerator the diffractive production reactionsp+N[(1385)⁰ K ⁺] +N andp+N[(1385)⁰ K ⁺]+N+ (neutral particles) were studied. In the effective mass spectra of the [(1385)⁰ K ⁺] system in these processes there were no signals from the anomalously narrow baryon stateN (1960) which had been observed earlier in the measurement at the BIS-2 setup.SPHINX Collaboration (IHEP-ITEP)     

Observing b → s μ+μ− decays at hadron colliders

We examine the prospects for observing weak flavour-changing neutral current (FCNC) decays ofB mesons at hadron colliders, including effects of anomalousWWZ vertices. Since it is very difficult to measure the inclusive rate B X_s ^+– one should consider exclusive modes such as BK^{* + –} and B K^{+ –}. Even though this requires one to compute hadronic matrix elements, we show that experimentally observable quantities (ratios of decay rates) are not strongly parametrisation dependent. Some possibilities for reducing the theoretical uncertainties from other experimental data are discussed.     

An analysis of dibaryon resonance spectra by GSAP,AUTSPAN and SAMPO-80 codes

Narrow dibaryon resonances observed in elastic and inelastic hadron scattering channels atM _NN ^* =1875–2300 MeV/c² are characterized by the relative resolution (FWHM/M _pp ^* ) 10^–3 comparable to that provided by Ge(Li) detectors in the case of gamma-ray spectroscopy. The gamma-ray spectrum analysis codes GSAP, AUTSPAN and SAMPO-80 have been used to analyse the effective mass distributions of dibaryons from the reactions dp (pn) p, dp (pp) n, np pp^–, and pppp studied at the Dubna synchrophasotron. The produced results suggest these codes to be reliable software tools in the new spectroscopic region of interest.On leave fromNuclear Physics Institute, Czechosl. Acad. Sci., 250 68 e near Prague, Czechoslovakia.     

Experimental study of hard photon radiation processes at HERA

We present an experimental study of theepe+p andepe+X processes using data recorded by the H1 detector in 1993 at the electron-proton collider HERA. These processes are employed to measure the luminosity with an accuracy of 4.5 %. A subsample of theepe+X events in which the hard photon is detected at angles 0.45 mrad with respect to the incident electron direction is used to verify experimentally the size of radiative corrections to theepeX inclusive cross section and to investigate the structure of the proton in theQ ² domain down to 2 GeV², lower than previously attained at HERA.Supported by the Bundesministerium für Forschung und Technologie, FRG under contract numbers 6AC17P, 6AC47P, 6DO57I, 6HH17P, 6HH27I, 6HD17I, 6HD27I, 6KI17P, 6MP17I, and 6WT87P     

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.     

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.     

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.     

Proton-proton and deuteron-deuteron correlations in interactions of relativistic helium nuclei with protons

The reactions⁴Hep pp+X,³Hep pp+X and⁴Hep ddp have been investigated and the correlation function has been measured for protons and deuterons with small relative momenta. Strong positive correlation has been observed for protons related mainly to the final state interactions in¹S₀ state. The root mean square radius of the proton source calculated from the correlation function has been found to be equal to (1.7±0.3) fm and (2.1±0.3) fm for⁴He and³He respectively. It agrees with the known radii of these nuclei.We would like to thank Dr R. Lednicky for discussion, helpful suggestions and for making available the computer program that calculates the theoreticalpp correlation function. The authors also thank Dr D.H. Boal for providing the results of the two-deuteron correlation function calculations.     

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=">     

A study of the decays of tau leptons produced on theZ resonance at LEP

From the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb^–1 taken during the 1990 run of LEP at centre of mass energies between 88.2 GeV an 94.2 GeV, the tau decays and their charge conjugates have been studied. The following branching ratios have been measured; , , Br(^{– –} (K^–)v)=11.9±0.7±0.7%, BR (^{– –} v)= 22.4±0.8±1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, _s (m) = 0.26 _–0.12 ^+0.09 . Extrapolating the _s value fromm tom _Z yields _s (m_Z) = 0.109 _–0.028 ^+0.012 .The average polarizationP of taus produced in Z ^{s s} decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes isP =–0.24±0.07. This value ofP gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of /a = 0.12 ± 0.04, and hence a value of the effective electroweak mixing parameter sin² _W(m _Z ² ).     

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.     

CP violation in charmlessB 0 decays: A coupled channel approach

We consider the CP-violating asymmetry betweenB ⁰f and f in the case thatf is a CP-eigenstate containing no charmed quarks. The asymmetry is assumed to arise as a result of mixing with other channelsf having the same quantum numbers but containing ac pair. Inelastic unitarity is implemented by means of the K-Matrix formalism, in which the constraints of CPT are manifestly satisfied. The formalism is applied to a hypothetical two-channel problemB ⁰M ,M , and then to a realistic four-channel situationB ^{0 + –}, ^{0 0},D ⁺ D ^–,D ^{0 0}. Asymmetries and branching ratios are estimated for the decaysB ^{0 + –}, ^{0 0}.