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.     

OnD→ππ andK\bar K decays

We have analysed the recent data onD→ππ and \(K\bar K\) decays from ARGUS, CLEO and E691. (i) We find that Bauer, Stech and Wirbel (BSW) model does fairly well in explaining all data if we assume that final state interactions simply rotate the amplitudes in the complex plane. However, to get a good fit one needs to raiseD→K transition amplitudes by (5–10)% over the BSW values and lowerD→π amplitudes by a similar amount. (ii) We show that all the data can also be understood in a coupled channel inelastic model. (iii) We also find that the Isgur, Scora, Grinstein and Wise (ISGW) model-form factors, if extrapolated to small momentum transfers (t) by a single pole formula, yield branching ratios too small in comparison to data. We propose an alternate scheme to interpolate between BSW form factors att=0 and ISGW form factors att=t _max.     

Study of the reactione + e −→K + K − in the energy range1350 \leqq \sqrt s \leqq 2400 MeV

Thee ⁺ e ^?→K ⁺ K ^? cross section has been measured from about 750 events in the energy interval \(1350 \leqq \sqrt s \leqq 2400 MeV\) with the DM2 detector at DCI. TheK ^± form factor |F _F ^±| cannot be explained by the ρ, ω, ? and ρ′(1600). An additional resonant amplitude at 1650 MeV has to be added as suggested by a previous experiment.     

Manifestation of a singlet heavy up-type quark in the branching ratios of rare decays K → πν \bar \nu , B → πν \bar \nu , and B → Kν \bar \nu

The implications of the model with a SU(2)-singlet up-type quark, heavy enough not to be produced at the LHC, namely, the contribution of the new quark to the branching ratios of the K → πν $ \bar \nu $ , B → πν $ \bar \nu $ , and B → Kν $ \bar \nu $ decays are investigated. It is shown that the deviation from the Standard Model can be up to 10% in the case of a 5-TeV quark. Precise measurements of these branching ratios in future experiments will allow for the observation of the contributions of the new quark or to impose stronger constraints on its mass.     

Observation of an isoscalar vector meson at ≃1650 MeV/c2 in thee^ + e^ - \to K\bar K\pi Equation>reaction

The \(e^ + e^ - \to K_s^0 K^ \pm \pi ^ \mp \) andK ⁺ K ^?π⁰ cross sections have been measured in the energy interval \(1350 \leqq \sqrt s \leqq 2400\) with the DM2 detector at DCI. The \(K_s^0 K^ \pm \pi ^ \mp \) cross section shows the contribution of an isoscalar vector meson at ≈1650 MeV/c² in agreement with a previous experiment. The low statisticsK ⁺ K ^?π⁰ measurement is consistent with the above result.     

Some comments on the branching ratios for \bar n p annihilation into ππ, K \bar K, and πη channels

We present some remarks on the $\bar n$ p partial branching ratios in flight at low momenta of antineutrons measured by the OBELIX Collaboration. A comparison is made to the known branching ratios from the p $\bar p$ -atomic states. The branching ratio for the reaction $\bar n$ p → π⁺π⁰ is found to be suppressed in comparison to what follows from the p $\bar p$ data. It is also shown that there is no so-called dynamical I=0 amplitude suppression for the process N $\bar N$ → K $\bar K$ .     

Scattering length expansion of the coupled channels\bar pp \to \bar \Lambda \Lambda and\bar \Lambda \Lambda \to \bar \Lambda \Lambda near theΛ production threshold

We fit the scattering lengths in the triplets-,p- andd- waves for the two channels \(\bar pp \to \bar \Lambda \Lambda\) and \(\bar \Lambda \Lambda \to \bar \Lambda \Lambda\) near theΛ production threshold to the differential cross section \(\frac{{d\sigma }}{{d\Omega }}(\bar pp \to \bar \Lambda \Lambda )\) and to the polarization P.     

On scalar resonances in ππ→ππ,K\bar K, ηη reactions

Carried out is the analysis of the new experimental data on theS-wave of the ππ→ \(K\bar K\) reaction in common with ππ→ππ one in the 1–1.6 Gev energy region. It is shown that new resonances are not required for the explanation of the data and for that the well-knownS ^* (980) and ε (1300–1400) resonances and their mixing only are enough. Once more confirmed is the possibility forS ^* (980) to be the \(qq\bar q\bar q\) from (9,0⁺) nonet of the \(qq\bar q\bar q\) mesons predicted by the MIT-bag model. Moreover, it is shown that the ε(1300–1400) resonance can be interpreted as a member of the second four-quark (9,0⁺)-nonet. We predict the bright manifestation of theS ^* and ε-resonances in the π⁺π^? →ηη reaction. The analysis of the data shows that the ε-meson cannot be a pureSU (3)-singlet and therefore it cannot pretend to the role of the gluonium. Discussed is critically the Törnqvist's analysis for scalar mesons.     

\bar K K and\bar p p off-shell annihilations fromK − +p → Λ + pions at 4.2 GeV/c

We have investigated the properties of off-shell \(\bar K\) K and \(\bar p\) p annihilations into pions by using the interactionsK ^? p → Λ + pions at 4.2 GeV/c. The properties considered are multiplicities, hadronic temperatures and angular distributions. These properties appear more akin to those of \(\bar p\) p annihilations in flight than to that of \(\bar p\) p annihilation at rest despite the fact that the annihilation energy is small.     

Extracting angular correlations from the rare decay \bar Bd \to \bar K*^0 μ + μ − at LHCb

$ \bar Bd \to \bar K*^0 $ μ ⁺ μ ^? is a rare flavor-changing neutral-current decay. It proceeds via a b → s quark transition and is sensitive to many classes of new physics model. In this article the theoretical framework relevant to making a measurement at LHCb, the precision flavor experiment at the Large Hadron Collider, will be introduced. Progress made towards using a full angular analysis to extract A _FB, the forward-backward asymmetry of the μ pair, will be covered and its implications for the precision of the A _FB zero-crossing-point measurement discussed.     

The $$\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\nu_\tau$$ Decay in the Nambu–Jona-Lasinio Model

The width of the \(\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\nu_\tau\) decay is calculated within the Nambu–Jona-Lasinio model taking into account four channels of the formation of the \(\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\) pair—the contact interaction and three channels with intermediate axial-vector, vector, and pseudoscalar mesons. Leading contributions arise from the contact interaction and axial-vector channel with an intermediate ground-state K₁(1270) meson. Our theoretical estimate adequately reproduces the measured \(\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\nu_\tau\) decay width.     

What we can learn from γγ→ππ,K \bar K in the resonance region

The two photon couplings of hadronic states are believed to be key pointers to their parton constitutents. With the aim of studying these, we present a method of analysing data on γγ→ππ (andK \(\bar K\) ), which embodies the constraints of unitarity and analyticity while respecting the QED low energy theorem required by gauge invariance. We apply this analysis to presently available data on ππ production and find that within the existing uncertainties few definitive conclusions can yet be drawn in the resonance region. For instance, even the claim that thef-resonance has a largely helicity two coupling is shown not to be established. We illustrate the importance of the angular dependence of the data to reach almost all conclusions not only on the helicity structure off-production but also on the couplings of the scalar states to this vital channel. In the near threshold region, however, we confirm the overwhelming dominance of the QED Born amplitude modified by final state interactions in contradiction with several recent datasets on the π⁺π^? channel. We show how the new Crystal Ball experiment on π⁺0⁰ production not only confirms this conclusion on the near threshold cross-section but angular analysis of their data with its better statistics using the method we present should shed light on the nature of the scalar mesons in the 1 GeV region.     

Measurement of beam-recoil observables Ox , Oz and target asymmetry T for the reaction \gammap → K+ \Lambda

The double polarization (beam-recoil) observables $\ensuremath O_x$ and $\ensuremath O_z$ have been measured for the reaction $ \gamma$ p → K ⁺ $ \Lambda$ from threshold production to $\ensuremath E_{\gamma} \sim 1500$ MeV. The data were obtained with the linearly polarized beam of the GRAAL facility. Values for the target asymmetry T could also be extracted despite the use of an unpolarized target. Analyses of our results by two isobar models tend to confirm the necessity to include new or poorly known resonances in the 1900MeV mass region.     

\bar{K} Condensation in Neutron Star Matter with Δ Quartet

In the framework of relativistic mean field theory, the condensations of K^- and \bar{K}⁰ in neutron star matter including baryon octet and Δ quartet are studied. We find that in this case K^- and \bar{K}⁰ condensations canoccur at relative shallow optical potential depth of \bar{K} from -80 MeV to -160 MeV. Both K^- and \bar{K}⁰ condensations favor the appearances of Δ resonances. With \bar{K} condensations all the Δ quartet can appear well inside the maximum mass stars. The appearances of Δ resonances change the composition and distribution of particles at high densities. The populations ofΔ resonances can enhance K^- condensation. It is found that in the core of massive neutron stars, neutron star matter includes rich particle species, such as antikaons, baryon octet, and Δ quartet. In the presence of Δ resonances and \bar{K} condensation, the EOS becomes softer and results in smaller maximum mass stars. Furthermore the impact of antikaon condensations,hyperons, and Δ resonances on direct Urca process with nucleons is also discussed briefly.     

Vibrational states of the Pt(111)–$$ \left( {\sqrt {3} \times \sqrt {3} } \right) $$ R30°–K surface structure

Vibrational spectrum of the ordered Pt(111)–( ?3 ×?3 ) \left( {\sqrt {3} \times \sqrt {3} } \right) R30°–K surface superstructure formed on the platinum surface with adsorption of 1/3 ML potassium is calculated with the use of the interatomic interaction potentials obtained in the strong bond approximation. Relaxation of the surface, dispersion of the surface phonons, local density of vibrational states, and polarization of phonon modes of adatoms and atoms of the substrate are discussed in the work. The theoretical results obtained agree well with the available experimental data.