Medium modifications of kaons in pion matter

Kaon in-medium masses and mean-field potentials are calculated in isotopically symmetric pion matter to one loop of chiral perturbation theory. The results are extended to BNL RHIC temperatures using experimental data on piK scattering phase shifts. The kaon in-medium broadening results in an acceleration of the phi-->K(-)K decay. The increased apparent dilepton branching of the phi mesons, observed recently by the NA50, NA49, and PHENIX Collaborations at RHIC, is interpreted in terms of rescattering of secondary kaons inside the pion matter.     

Coherent transmission of neutral kaons in matter and forward scattering amplitudes

A method is proposed which enables simultaneous measurement of total cross sections of K and $\text{K}$ with proton or nucleus and the difference of real parts of forward scattering amplitudes.     

Tau decays into kaons

Predictions for semi-leptonic decay rates of theτ lepton into two meson final statesK ^?π⁰ v _τ, $\overline {K^0 } \pi - v_\tau $ ,K ⁰ K ^? v _τ, and three meson final statesK ^?π^? K ⁺ v _τ, $K^0 \pi ^ - \overline {K^0 } v_\tau $ ,K _sπ^? K _s v _τ,K _sπ^? K _L v _τ,K _Lπ^? K _L v _τ,K ^?π⁰ K ⁰ v _τ, π⁰π⁰ K ^? v _τ,K ^?π^?π⁺ v _τ, π^? K ⁰π⁰ v _τ are derived. The hadronic matrix elements are expressed in terms of form factors, which can be predicted by chiral Lagrangians supplemented by informations about all possible low-lying resonances in the different channels. Isospin symmetry relations among the different final states are carefully taken into account. The calculated branching ratios are compared with measured decay rates where data are available.     

Tau decays with neutral kaons

The branching ratio of the lepton to a neutral kaon meson is measured from a sample of approximately 200,000 decays recorded by the OPAL detector at centre-of-mass energies near the resonance. The measurement is based on two samples which identify one-prong decays with and mesons. The combined branching rat ios are measured to be where the first error is statistica l and the second systematic. Received: 29 October 1999 / Published online: 24 February 2000     

Interferometry of pions and kaons in high energy collisions

A hydrodynamic model which reproduces the observed rapidity and transverse momentum spectra of mesons and baryons is applied to the study of Bose-Einstein correlations. The pion correlations are found to be strongly affected by resonance decays, except for pairs of large transverse momenta.For S+S at 200 A GeV, in the central rapidity region the effective longitudinal source radii for pions and kaons differ by a factor of 2, the transverse radii by a factor of 1.3. The lifetime of the source can be extracted from kaon interferometry.     

CPT symmetry and neutral kaons

We discuss the accuracy of CPT invariance tests in the neutral kaon decays. The possible CPT non-invariance is parametrized by amplitudes of two types: (i) CP violating, but T conserving, and (ii) T violating, but CP conserving. It is shown that the experimental data are consistent with CPT symmetry essentially within two standard deviations.The source of this not quite satisfactory agreement is the experimental value of the phase φ₀₀ of the ratio $\text{A(}\text{K}{}_{\mathrm{L}}{}^0\text{→π}{}^0\text{π}{}^0\text{)}\text{A(}\text{K}{}_{\mathrm{S}}{}^0\text{→π}{}^0\text{π}{}^0\text{)}$, which differs by two standard deviations from the phase φ_+? of the ratio $\text{A(}\text{K}{}_{\mathrm{L}}{}^0\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}\text{A(}\text{K}{}_{\mathrm{S}}{}^0\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ decay amplitude. We argue that to get better agreement with CPT invariance, the value of the phase φ₀₀ has to be equal to the value of the phase φ_+? within the errors of the latter. New, more accurate measurements of the phase φ₀₀ would be very interesting to rest CPT invariance, especially taking into account that neutral kaons allow the test with much better accuracy than any other particle.     

Collision rate of pions and kaons at finite temperature

The energy dependence of the pion and kaon collision rates at finite-temperature are calculated in the approximation that resonances dominate the scattering, as for example, ππ→?→ππ andKπ→K ^*→Kπ. A general formula is derived for the contribution of resonances with arbitrary spin and isospin. Numerical results are given. For very narrow resonances the calculation is performed analytically.     

Next-to-leading order fragmentation functions for pions and kaons

We present new sets of fragmentation functions for charged pions and kaons, both at leading and next-to-leading order. They are fitted to TPC data taken at energy =29 GeV and describe excellently a wealth of othere ⁺ e ^– data on charged-hadron production, ranging from =5.2 GeV way up to LEP 1 energy. They also agree with data on the production of neutral pions and kaons, if one makes the natural assumption that the respective fragmentation functions are related to the charged counterparts bySU(2) symmetry. We also list simple parameterizations of thex andQ ² dependence of our results, which may be implemented conveniently in applications.Supported by Bundesministerium für Forschung und Technologie, Bonn, Germany, under Contract 05 6 HH 93P (5), and by EEC ProgramHuman Capital and Mobility through NetworkPhysics at High Energy Colliders under Contract CHRX-CT93-0357 (DG12 COMA)     

One-prong \tau decays with kaons

Cross-sections for hadronic, and lepton pair final states in collisions at =183 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. Forward-backward asymmetries for the leptonic final states have also been measured. Cross-sections and asymmetries are also presented for data recorded in 1997 at =130 and 136 GeV. The results are used to measure the energy dependence of the electromagnetic coupling constant , and to place limits on new physics as described by four-fermion contact interactions or by the exchange of a new heavy particle such as a leptoquark, or of a squark or sneutrino in supersymmetric theories with R-parity violation. Received: 3 July 1998 / Published online: 15 October 1998     

Quantum marking and quantum erasure for neutral kaons

The neutral kaon system is shown to be suitable to discuss extensions and tests of Bohr's complementarity principle through the quantum marking and quantum erasure techniques suggested by Scully and Drühl [Phys. Rev. A 25, 2208 (1982)]]. Strangeness oscillations play the role of the traditional interference pattern linked to wavelike behavior, whereas the different propagation in free space of the K(S) and K(L) components mimics the two possible interferometric paths taken by particlelike objects.     

The interaction of kaons with nucleons and nuclei

This paper reviews the essential requirements for observing stimulated emission of recoilles gamma radiation, categorizes and discusses the difficulties attending various proposals for creating an ultrashort-wave radiation source based on the Mössbauer effect.     

High energy quantum teleportation using neutral kaons

We describe a scheme of stochastic implementations of quantum teleportation and entanglement swapping in terms of neutral kaons. In this scheme, the kaon whose state is to be teleported collides with one of the two entangled kaons in an Einstein–Podolsky–Rosen state. Subsequent detection of the outgoing particles of the collision completes the two-qubit projection on Alice side. There appear novel features, which connects quantum information science with fundamental laws of particle physics.     

A spectator-quark-model for the photoproduction of kaons

A simple model for the photoproduction of kaons off protons with a lambda hyperon in the final state is presented. In a quark model, the interaction is modelled by the pair-creation of the (anti-) strange quarks in the final state which recombine with the three quarks of the proton to form the lambda and kaon. The calculated scattering cross sections for photon energies up toE _ν = 1.9 GeV are compared to experiment. The pair-creation process is found to have a significant contribution to the total cross section.     

Low energy parameters for scattering of pions and kaons

We calculate scattering lengths and some effective range parameters for processes ππ → ππ, ππ →K¯k, K¯k → K¯k, the last at both 2π andK¯k thresholds. The calculations are made (i) using experimental data (when possible), (ii) using the Veneziano model.     

Observation of B decays to two kaons

Using 449x10(6) BB[over ] pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider, we observe clear signals for B(+)-->K[over ](0)K(+) and B(0)-->K[over ](0)K(0) decays with 5.3sigma and 6.0sigma significance, respectively. We measure the branching fractions B(B(+)-->K[over ](0)K(+))=(1.22(-0.28-0.16)(+0.32+0.13))x10(-6) and B(B(0)-->K[over ](0)K(0))=(0.87(-0.20)(+0.25)+/-0.09)x10(-6), and partial-rate asymmetries A(CP)(B(+)-->K[over ](0)K(+))=0.13(-0.24)(+0.23)+/-0.02 and A(CP)(B(0)-->K[over ](0)K(0))=-0.58(-0.66)(+0.73)+/-0.04. From a simultaneous fit, we also obtain B(B(+)-->K(0)pi(+))=(22.8(-0.7)(+0.8)+/-1.3)x10(-6) and A(CP)(B(+)-->K(0)pi(+))=0.03+/-0.03+/-0.01. The first and second error in the branching fractions and the partial-rate asymmetries are statistical and systematic, respectively. No signal is observed for B(0)-->K(+)K(-) decays, and for this branching fraction, we set an upper limit of 4.1x10(-7) at the 90% confidence level.