ar X iv : h ep - p h / 95 06 24 7 v 1 6 J un 1 99 5 Reason of Large Scale Difference of the Results in the nn̄ Oscillation Problem

ar X iv : h ep - p h / 95 06 25 0 v 1 6 J un 1 99 5 CERN - TH / 95 - 121 Jet Physics in Deeply Inelastic Scattering at HERA ∗

We give an overview of jet physics in deeply inelastic scattering at HERA. The problem of jet definitions, the scale dependence of jet cross sections and some applications are discussed.

ar X iv : h ep - p h / 95 06 25 9 v 1 7 J un 1 99 5 CERN – TH / 95 – 83 hep - ph / 9506259 May 1995 MULTIPLE HARD

ar X iv : h ep - p h / 95 06 24 5 v 1 6 J un 1 99 5 The triple pomeron interaction in the perturbative QCD

The triple pomeron interaction is studied in the perturbative approach of BFKL-Bartels. At finite momentum transfers √ −t the contribution factorizes in the standard manner with a triple-pomeron vertex proportional to 1/ √ −t. At t = 0 the contribution is finite, although it grows faster with energy than for finite t and does not factorize.

ar X iv : h ep - p h / 96 12 41 4 v 1 1 9 D ec 1 99 6 Cause of Disparity between the Results for the nn̄ Transition Problem

We show that there is a double counting in the standard model of n¯ n mixing in the medium, resulting in full cancellation of leading terms. The direct calculation of n¯ n transition, annihilation is performed. For lower limit on the free-space n¯ n oscillation time we get τ min ∼ 10 31 y.

ar X iv : h ep - p h / 95 06 25 4 v 1 7 J un 1 99 5 Effects of the U A ( 1 ) Anomaly on η → 2 γ Decay

We study the η → 2γ decay using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't Hooft instanton induced interaction. The η meson mass and the η → 2γ decay width are reproduced simultaneously with a rather strong instanton induced interaction. The calculated η decay constant is f η = 2.23f π and it suggests that the η meson is no longer the Goldstone boson.