Reactions with leading hadrons in meson-proton interactions at 250 GeV/c

Inelastic final states with one or two leading hadrons are studied in π⁺p and K⁺p interactions at 250 GeV/c. In reactions with two leading hadrons, the dependence of the average charge multiplicity of associated pions on their effective mass is essentially consistent with that observed in p?p and γγ-collisions, but differs from that obtained in e⁺e^? -annihilation. The multiplicity and (semi)inclusive characteristics of the π⁺-induced non-diffractive reactions are compared to predictions of current versions of the FRITIOF fragmentation model. We show that the hard-like sub-processes, essentially responsible for the production of leading hadrons with relatively large transverse momentum as well as for the relatively large multiplicity of associated pions, are not properly treated in the model.     

Search for charm production in neutron interactions near 250 GeV/c

We have searched for narrow two-body enhancements produced in the forward direction in n-Be interactions near 250 GeV/c. We find no significant signal in any channel and report upper limits for charm production times branching rate to be 200–1000 nb/nucleon for masses in the range 1.7 ? m ? 3.5 GeV/c².     

Observation and polarization measurements of B+/- -->phiK1 +/- and B +/- -->phiK2 *+/-

With the full BABAR data sample of 465 x 10(6) B(over)B pairs, we observe the decays B+/- -->phiK_(1)(1270) +/- and B +/- -->phiK*_(2)(1430)+/-. We measure the branching fractions (6.1+/-1.6+/-1.1) x 10(-6) and (8.4+/-1.8+/-1.0) x 10(-6) and the fractions of longitudinal polarization 0.46 (+0.12+0.06) _(-0.13-0.07) and 0.80(+0.09)_(-0.10)+/-0.03, respectively. We also report on the B+/- -->phiK*_(0)(1430)+/- decay branching fraction of (7.0+/-1.3+/-0.9) x 10(-6) and several parameters sensitive to CP violation and interference in the above three decays. Upper limits are placed on the B+/- decay rates to final states with phi and K_1(1400)+/-, K*(1410)+/-, K2(1770)+/-, or K_2(1820)+/-. Understanding the observed polarization pattern requires amplitude contributions from an uncertain source.     

Inclusive meson resonance production inK + p interactions at 250 GeV/c

A detailed analysis of the inclusive production of the vector mesonsφ,K ^*+,0(892) \(\bar K*^0 (892),\rho ^{ + ,0} ,\omega \) and the tensor mesonsK ₂ ^*0 )(1430) andf ₂(1270) inK ⁺ p interactions at 250 GeV/c is presented The data are compared with results at lower energies and with various quark-parton models. The production ofρ ⁰,K ^*0(892) and \(\bar K*^0 (892)\) increases at the same rate as a function ofs, is concentrated in the central region and is not reproduced by the models. Production of the tensor mesonsf ₂(1270) andK ₂ ^*0 (1340) is suppressed relative toρ ⁰ andK ^*0(892) by a factor of about 3.     

Two- and three-dimensional analysis of bose-einstein correlations inπ +/K+p interactions at 250 GeV/c

The NA22 data onπ ^? π ^? correlations are analyzed in terms of a number of two- and three-dimensional parametrizations (Gaussian space-time, Goldhaber, Bowler string-like, Bertsch hydrodynamical, Kopylov-Podgoretskii, etc.). Contrary to the results obtained for e⁺e^? andµp collisions, the Goldhaber parametrization, as well as string-like models, fail in describing the hadron-hadron data. Better fits are obtained in the framework of surface-emitting fireball-like models, both when including and excluding hydrodynamical expansion of nuclear matter. Our results indicate that pion radiation occurs at earlier stages of matter evolution than in nuclear collisions.     

Observation of wrong-sign tri-muon events in 250 GeV muon-nucleon interactions

Two trimuon events of the type μ⁺N→μ⁺μ⁺μ⁺X and one μ⁺N→μ⁺μ^?μ^?X have been observed in 250 GeV μ⁺ -iron interactions. The expected rate from the decay of hadrons (charm, π, K) is about one event. Other processes that may contribute are both beauty production and charm production with $\text{D}{}^0\text{?}\text{D}{}^0$ mixing. The data give upper limits of 12×10^?36 cm² for the cross section of beauty pair production by muons, and 20% for $\text{D}{}^0\text{?}\text{D}{}^0$ transitions due to mixing, both at 90% confidence level.