Dissipation of ripplon flow at the surface of superfluid <Superscript>4</Superscript>He

Within the framework of quantum hydrodynamics of a superfluid helium surface, the momentum relaxation rate caused by the annihilation of two ripplons with phonon creation, inelastic phonon scattering with ripplon annihilation, and in the case of helium films one-particle ripplon scattering from the surface-level inhomogeneities introduced by the substrate roughness (new relaxation mechanism) was obtained for a ripplon gas at T?0.25 K. The contribution from the inelastic phonon scattering is negligible at these temperatures. For a film at T≤0.15 K, one-particle scattering dominates, leading to a temperature dependence of the form K∝T^5/3 for the convective thermal conductance.At higher temperatures, phonon creation with annihilation of two ripplons is the dominant mechanism, giving K∝T^?3. These results are in quantitative agreement with the available experimental data.     

Rates for the reactions\bar pp \to \pi \phi andγ φ

We study ¯pp annihilation at rest intoπφ andγφ. Rescattering by ¯K^*K+K^*¯K and ρ⁺ρ^? for ¯pp→πφ states is sizable, of order (0.90 to 2.6) × 10^?4 in the branching ratio, but smaller than experiment. For ¯pp→γφ the rescattering contributions are negligible, but theγφ channel is well explained by aρφ intermediate state combined with vector meson dominance.     

A study of elastic photoproduction of low massK + K − pairs from hydrogen in the energy range 2.8–4.8 GeV

The results of an experiment to study elasticK ⁺ K ^? photoproduction are presented. Differential cross sections and spin density matrix elements for ?(1.019) production are stddied as a function of incident photon energy and over a wide range of momentum transfer,t (t _min >t>?1.5(GeV/c)²). Helicity conserving amplitudes are observed to dominate ? production throughout this range and the differential cross sections exhibit a forward diffractive peak which cannot be understood in terms of a simple exponential dependence. A new value of the photon ? coupling constant is determined and shown to be consistent withe ⁺ e ^? annihilation measurements. A detailed study of the energy dependence of the differential cross sections is made, including other experimental data, and the extracted effective Regge trajectory compared with other diffractive processes. A study of the dependence of theK ⁺ K ^? decay angular distribution on invariant mass reveals evidence for ans wave contribution interfering with thep wave ? which may be attributable to theS ^* meson.     

K^{-} nuclear quasi-bound states in a chirally motivated coupled-channel approach

K ^?? nuclear optical potentials are constructed from in-medium ${\bar K}N$ scattering amplitudes within a chirally motivated coupled-channel model. The strong energy and density dependence of the scattering amplitudes at and below threshold leads to K ^?? potential depths ?Re $V_{K^-}(\rho_0) \approx 80 -100$ ?MeV. Self consistent calculations of K ^?? nuclear quasi-bound states are discussed.     

Amplitude and natural-parity-exchange analysis of K±p → (Kπ)±p data at 10 GeV/c

High statistics data for the reactions K^±p → K_S⁰π^±p at 10 GeV/c are analysed. The K¹(1^?), K¹(2⁺), and K¹(3^?) resonance parameters and production cross sections are calculated. The Kπ production amplitudes are determined as a function of t and the produced Kπ mass. Isoscalar natural-parity-exchange (NPE) is dominant. The t dependence of the K^± NPE amplitudes have a cross-over at t = ?0.3 (GeV/c)² for both K¹(890) and K¹(1420) production, being more pronounced for the K¹(1420). Natural-parity-exchange interference effects are isolated. The NPE amplitudes are decomposed into pomeron-, f-, and ω-exchange contributions. S-wave Kπ production is found to be consistent with the Kπ partial-wave analyses of charge-exchange reactions.     

Interference effects inK − p→K − K + Λ at 4.2 GeV/c and the thresholdK\bar K S wave amplitude

We study the interference phenomena between the ? meson and the underlyingK ^? K ⁺ S wave in the reactionK ^? p→K ^? K ⁺ Λ at 4.2GeV/c. We perform an amplitude analysis of the double multipole moments and investigate the \(K\bar K \to K\bar K\) S wave amplitude.     

First observation of a particle-antiparticle asymmetry in the decay of neutral kaons into π0π0

CP violation has been observed as a time-dependent rate asymmetry between the decays ${?erline K}^0 ?ghtarrow ?^{0} ?^{0}$ and K⁰ → π⁰π{0}, where the neutral kaons are produced with definite and individually known strangeness in ${?r p}p ?ghtarrow{?erline K}^0 K^+?^- $ or p?p → K⁰ K^? π⁺. A special technique for the data analysis has been developed. The values obtained for ?₀₀ and ¦ η₀₀¦ are in agreement with those of previous measurements of CP violation.     

N\bar N annihilation at rest into πππ andK\bar K\pi in the3 P 0 model and selection rules on the πρ,K\bar K* and\bar KK* production

\(N\bar N\) annihilation into three pseudoscalar mesons especially πππ and \(K\bar K\pi \) are studied in the quark pair creation model or the³ P ₀ model in which two \(q\bar q\) pairs are annihilated and two \(q\bar q\) pairs are created with quantum numbers of the vacuum or³ P ₀. The correlations of two pions to form ?,f ₂ and the resonance AX(1565) which is recently found by the ASTERIX group are taken into account. A proper treatment of the symmetry among the three pions in the final state shows that the \({}^{31}S_0 p\bar p\) annihilation into ?π is suppressed in agreement with the experiment. We calculate the cosθ distribution or the distribution of the Dalitz plot as the function of the angle between the direction of emission of one decay pion in the resonance centre of mass and the line of flight of the resonance. The interferences of π⁺ρ⁺, π^?ρ⁺ and π⁰ρ⁰ in the isospin 0 channels and π^±ρ^? and π⁰ f ₂ in the isospin 1 channel reproduce the peaks. The cos θ distribution for the P-wave \(p\bar p\) annihilation into πAX depends strongly on the size of the pion since the amplitude interfers with the π^±ρ^? amplitude which is sensitive to the size of the pion. The same model qualitatively explains the \(p\bar p\) annihilation into \(K\bar K\pi \) in whichK or \(\bar K\) and π are correlated to formK* \(\bar K\) or \(\bar K\) *K final states. We can qualitatively reproduce different patterns of the cos θ distribution for theK ^*+ andK ^*0.     

Thermodynamic properties of Rb2ZnCl4 associated with three phase transitions

Transitions were observed by heat capacity measurements at 74.6 K, 195.2 K, and 303 K. They are a soft mode transition (ΔH_t = 30 J mol^?1, ΔS_t = 0.42 J K^?1 mol^?1), a first-order commensurate-incommensurate transition (ΔH_t = 6.2 J mol^?1ΔS_t = 0.032 J K^?1 mol^?1), and a second-order incommensurate-normal transition, respectively.     

Study of theK + K − π+ π− system centrally produced in the reactions π+ p→π+(K + K − π+ π−)p andpp→p(K + K − π+ π−)p at 85 GeV/c

The reactions π⁺ p→π⁺(K ⁺ K ^? π⁺ π^? p andpp→p(K ⁺ K ^? π⁺ π^?)p where the (K ⁺ K ^? π⁺ π^?) system is centrally produced have been studied at 85 GeV/c. 48% of the final state proceeds through single or double vector meson resonant production i.e.,K ^*0(890) (37%), ? (4%),ρ ⁰ (7%). Evidence is found for associatedK ^*0 (890) \(\bar K\) ^*o (890) production (6.4±1.1%) with a cross section ten times higher than that found for associated ? ? production in the same experiment.     

Backward production of a spin-parity 1+ Kϱ resonance at 1.28 GeV

A (K_ππ)⁺ mass enhancement is observed in the reactions K^?p → Ξ ?K^o+π⁺π^o? when events with a small (K^? → Ξ^?) four momentum transfer squared are selected. The signal is also visible in the reaction K^?p → Ξ^?π⁺+ neutrals. The enhancement, centered at 1.28 GeV, is seen to decay preferentially into K? with spin-parity J^P = 1⁺. The cross section for K^?p→ Ξ^?C⁺(1.28) with C⁺ → K? at 4.15 GeV/c incident K^? momentum is (6.2 ± 0.6) μb.     

Exclusiveb→s rare decays of beauty

The exclusive beauty decaysB→Kl ⁺ l ^? andB→K ^* l ⁺ l ^? are studied using a hadronic model based on QCD sum rules embedded in a general vector meson dominance framework. Both the short and the long distance contributions tot he above decays are considered. As a byproduct, the rates forB→KΨ, B→K ^* Ψ,B→KΨ′ andB→K ^* Ψ′ are obtained.     

Effect of hydrostatic pressure on the magnetocrystalline anisotropy constant K1 of iron and nickel

Previous values of the pressure dependence of the magnetocrystalline anisotropy constant K₁ of iron and nickel were revised. These values of K₁^?1 ($\text{dK}{}_1\text{dp}$) depend on the magnetic field for iron, and do not for nickel. The value in iron extrapolated to infinitely strong magnetic field is ?7.8×10^?6 bar^?1 at room temperature and ?7.3×10^?6 bar^?1 at 77K, and in nickel at 15 KOe is ?7.5×10^?6 bar^?1 at room temperature and ?2.8×10^?6 bar^?1 at 77K.     

A partial wave analysis of the Q enhancement in the reaction K−p→K−π−π+p at 3.95 GeV/c

We present results on the partial wave analysis of the Kππ system in the mass interval 1.1 to 1.6 GeV/c², in the reaction K^?p→K^?π^?π⁺p at 3.95 GeV/c. Our results are compared to those at higher energies, and we note certain differences. In particular, we find very much less of the ?K decay mode of the 1⁺S 0⁺ wave. In addition, the relative phase between the 1⁺S 0⁺ (K¹π) and the 2⁺D 1⁺ (K¹π) wave has been measured.     

Line strengths,spin-splittings,and forbidden transitions in the (101) band of 14N16O2

Measurements of line strengths in the (101) and (111)-(010) bands of ¹⁴N¹⁶O₂ have been made at a resolution of 0.02 cm^?1 in the region 2863 to 2934 cm^?1. The strength data in the (101) band were analyzed to determine a vibrational band strength and coefficients of the F factor. Each subband for K_?1 ≤ 9 was analyzed separately and all the F-factor coefficients in terms of the rotational quantum number, N, were found to be too small to be of significance. However, F was found to be dependent on K_?1 and the experimentally determined subband strengths were least-squares fitted to the expression S_v⁰·F, where S_v⁰ = 68.3 cm^?2 atm^?1 at 296 K and F = 1 + (2.899 × 10^?3)K_?1 + (4.08 × 10^?3)K_?1² ? (2.34 × 10^?4)K_?1³. The integrated strengths for the (101) and (111)-(010) bands were found to be 70.9 ± 2.3 and 2.7 ± 0.3 cm^?2 atm^?1 at 296 K, respectively. Also included in this study are measurements of line center positions in the two bands and spin-splittings in the (101) band. Recent frequency measurements of lines with K_?1 ≤ 8 in the (101) band have been made at a resolution of 0.0033 cm^?1 by V. Dana and J. P. Maillard (J. Mol. Spectrosc.71, 1–4) (1978)) for the region above 2889 cm^?1 and our values are in excellent agreement with theirs. Separations of the split lines measured in this work (K_?1 ≤ 10) agree well with calculated values using expressions which include the η_aaaaK_?1⁴ term with η′_aaaa = ?1.70 ± 0.15 × 10^?4 cm^?1 as derived for the (101) state. Three forbidden (ΔN ≠ ΔJ, ΔK_?1 = 0) transitions in the (101) band were observed with their identifications based on the agreement between measured and calculated line positions and strengths.     

A search for K−p → Λγ and K−p → Σ0γ at rest

A search has been made for photons from the reactions K^?p → Λγ and K^?p → Σ⁰γ produced by K^? stopping in a liquid hydrogen target. No signal from these reactions was found; upper limits on the branching ratios are K^?p → Λγ/K^?p → anything ? 4 × 10^?4, K^?p → Σ⁰γ/K^?p → anything ? 4 × 10^?3. The first of these is in conflict with a theoretical prediction using recent values for coupling constants and scattering amplitudes. This may reflect the influence of the Λ(1405) on the radiative capture.     

Models for D → Kπℓν decay

We present the predictions of various models for D → Kπ?ν decay for the K-π system in the region of the K¹ resonance. In this system both vector and axial vector currents can be studied. One of these models also applies to the D → K?ν decay mode. Also, tests are given for general Kπ?ν of the pure vector hypothesis for the (c, s) current.     

f 0(980) and a 0(980) resonances near the thresholds of the γγ → K + K − and γγ → K 0 K̇ 0 reactions

High-statistical data on the γγ → K ⁺ K ^? and γγ → K ⁰ K? ⁰ reactions constitute the last missing link in investigations of light scalar mesons f ₀(980) and a ₀(980) in photon-photon collisions. It is expected that the manifestation of the four-quark structure of the f ₀(980) and a ₀(980) resonances in these reactions will be very peculiar. The possibilities of the observation of scalar contributions in the γγ → K ⁺ K ^? and γγ → K ⁰ K? ⁰ reactions near their thresholds at modern colliders have been estimated.     

A spin-parity analysis of the K+K+K− system produced in the reaction K+p → K+K+K−p

We present the first spin-parity analysis of the K⁺K⁺K^?) system produced in the reaction K⁺p → K⁺K⁺K^?p, and show that the general features of this system resemble those of the (ππ⁺π^?) and Kπ⁺π^?) systems produced in the reactions π(K)p → π(K)π⁺π^?p. There is a low mass enhancement, (47 ± 11)% of which corresponds to 1⁺ states decaying to Kø. At higher (K⁺K⁺K^?) masses 2^? → Kf′ becomes increasingly significant and at all masses there is a 0^? contribution of roughly 30%.     

On the possible existence of a vector meson ϱ' (1250)

By combining new results obtained at C.M. energies of 1.2 and 1.3 GeV with previous data obtained at lower energies from the e⁺e^? annihilation process e⁺e^? → π⁺π^?π^oπ^o, we get an indication in favour of the existence of a new vector meson of the ? type, ?' (1250), the first daughter of the ? in the predictions of the Veneziano model. Further results on the annihilation process e⁺e^? → π (1600) → π⁺π^?π⁺π^? are also presented.