Partial wave analysis of $\bar pp \to \bar \Lambda \Lambda$

A partial wave analysis of PS185 data for is presented. A ³ S ₁ cusp is identified in the inverse process at threshold, using detailed balance to deduce cross sections from . Partial wave amplitudes for ³ P ₀, ³ F ₃, ³ D ₃ and ³ G ₃ exhibit a behaviour very similar to resonances observed in Crystal Barrel data. With this identification, the data then provide evidence for a new I = 0, J ^PC = 1^- resonance with mass MeV, MeV, coupling to both ³ S ₁ and ³ D ₁.Received: 4 June 2004, Published online: 9 July 2004     

Properties ofe^ + e^ - \to h\bar h in the\Upsilon (b\bar b)-continuum

The unflavored hadrons frome ⁺ e ^? annihilation in the \(\Upsilon (b\bar b)\) -continuum are analyzed in terms of the covariant Boltzmann distribution with an equilibrium temperature 151 MeV according to the Stefan's law. It is found that the effective fugacities of quark contents are approximately equal to the reciprocals of those from othere ⁺ e ^? annihilations outside the γ-continuum, whereas the fireballs are practically stationary, reflecting the decay at rest of \(B\bar B\) mesons produced by thee ⁺ e ^? annihilation.     

A study of the high-energy reaction\bar PP \to \bar PP

The high-energy behavior of the reaction atP _L =8 GeV/c andP _L =16 GeV/c is studied in the context of O(3,1) symmetry. In view of the many exchanged particles, approximate equivalence relations ins-channel amplitudes are used which cut down the unknown parameters to a manageable set of adjustable constants. Our analysis has essentially explained the characteristic features of this reaction, which are (i) the ending of the forward peak at |t| 0.6 (GeV/c)²; (ii) developing of a shoulder at larger |t|'s; and (iii) decreasing of the differential cross section at the shoulder for 16 GeV/c at a slower rate than 8 GeV/c.On leave of absence from Department of Physics, University of Azarabadgan, Tabriz, Iran.     

Antibaryon\left( {\bar p,\bar \Lambda } \right) production in relativistic nuclear collisions

The relativistic meson field theory is used to study the effects of the in-medium interaction on the predicted antibaryon abundancy in hot hadronic matter. It is demonstrated that subtreshold production of antiprotons in high energy heavy ion collisions at E_lab =1–2 GeV/nucleon is enhanced by 2–3 orders of magnitude as compared to a standard fireball model estimate. Furthermore, we show that after the inclusion of interactions the anti-hyperon yields, e.g. \(\bar \Lambda \) /π ^? are enhanced by about a factor ten. Predicted yields are in excess of the data measured by the NA35 and WA85 collaborations at CERN. The annihilation of antibaryons in surrounding matter at the final stage of the reaction may essentially reduce their abundancy.     

Manifestation of the bound state \bar NN (1870) in the annihilation process \bar pd \to p_s 5\pi

It is shown that the existence of an N?N bound state with a mass of approximately 1870 MeV and width 10 MeV follows from analysis of the experimental data on the momentum distribution of recoil protons in the annihilation process p?d→p _s5π.     

\bar v_e + d \to \bar v_e + n + pat reactor energies

The deuteron disintegration process \(\bar v_e + d \to \bar v_e + n + p\) is calculated at reactor energies using the antineutrino spectra given by various authors. Numerical results are presented and compared with the experimental and other theoretical results.     

Charmed meson rescattering in the reaction $$ \bar pd \uparrow \bar DDN $$

We examine the possibility to extract information about the DN and interactions from the reaction. We utilize the notion that the open-charm mesons are first produced in the annihilation of the antiproton on one nucleon in the deuteron and subsequently rescatter on the other (the spectator) nucleon. The latter process is then exploited for investigating the DN and interactions. We study different methods for isolating the contributions from the D ⁰ p and D ⁻ p rescattering terms.     

Charged hadron multiplicities in high energy\bar v_\mu n and\bar v_\mu pinteractions

Charged hadron multiplicity distributions in \(\bar v_\mu n\) and \(\bar v_\mu p\) interactions in the energy range \(5< E_{\bar v}< 150GeV\) GeV are presented. They are obtained from about \(6000\bar v_\mu \) charged current events produced in BEBC filled with deuterium. Multiplicity moments are studied as a function of the invariant mass of the hadronic systemW. Results on multiplicity distributions in the forward and backward directions in the hadronic c.m.s. are presented and discussed within the framework of the quark parton model. Values for the average charge of the forward jet are also determined and compared with other experimental data.     

Discrimination ofp\bar p \to t\bar t events by a neural network classifier

Neural network and conventional statistical techniques are compared in the problem of discriminating \(p\bar p \to t\bar t\) events, with top quarks decaying into anything, from the associated hadronic background at the energy of the Fermilab collider. The NN we develop for this sake is an improved version of Kohonen's learning vector quantization scheme. Performance of the NN as a \(t\bar t\) event classifier is found to be less satisfactory than that achievable by statistical methods. We conclude that the probable reasons for the are: i) the NN approach presents advantages only when dealing with event distributions in the feature space which substantially differ from Gaussians; ii) NN's require much larger training sets of events than statistical discrimination in order to give comparable results.     

Proton spectrum from\bar pd \to 5\pi p at rest and the elementary\bar pnannihilation

We calculate the shape of the proton spectator distribution in \(\bar pd \to 5\pi p\) at low proton momenta. The sensitivity to atomicS- andP-state orbits and to the size of elementarys- andp-wave annihilation is discussed. Implications for the elementary annihilation amplitude \(\bar pn \to 5\pi \) subthreshold are presented.     

Resonance structures in the \Lambda \bar \Lambda system

The results of studying the $\Lambda \bar \Lambda $ system produced in the reaction π^? p→ $\Lambda \bar \Lambda $ n at a π^?-meson energy of 40 GeV are reported. Experimental data (～2300 events) were obtained on the ITEP 6-meter spectrometer with a beam of the IHEP U-70 accelerator. The invariant-mass spectra for the events dominated by the singlet or triplet $\Lambda \bar \Lambda $ states were found to differ considerably from each other. The data give evidence for the existence of resonance $\Lambda \bar \Lambda $ states of the system in the mass regions near 2.3, 2.5, and 2.8 GeV.     

Incomplete GIM cancellation inK_L \to \bar \mu \mu decay

Weak contributions to the decay \(K_L \to \bar \mu \mu \) are evaluated over the whole energy spectrum and it is found that terms which survive the GIM cancellation because of the size of the top quark mass are comparable in size to the ones previously kept. Corresponding bounds on the K-M mixing matrix elements are given.     

The process\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma as an alternative to\pi ^0 \to v\bar v

The process \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) is investigated as an alternative to \(\pi ^0 \to v\bar v\) . It is shown that the experimental bound on the branching fraction for missing energy (in the form of \(\lambda _\gamma \bar \lambda _\gamma \) and/or \(v\bar v\) ) may be understood in terms of \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) for the kinematically allowed photino mass, if the squark mass is >8 GeV.     

$$\Lambda _c \to p\bar K^0 \pi \pi $$ and $$\Lambda _c \to p\bar K^0 $$ decay rates

Zeitschrift für Physik C Particles and Fields - Available phase space suppresses the decay $\Lambda _c^ + \to p\overline {K^0 } \pi ^ + \pi ^ - $ in comparison with the decay $\Lambda _c^ +...