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.     

Quasi-elastic electroproduction of charged \rho -mesons on nucleons

The electroproduction of charged $ \rho$ -mesons on the nucleon at intermediate energy is discussed for quasi-elastic kinematics. It is shown that at these kinematics both the longitudinal $ \sigma_{{L}}^{}$ and transverse $ \sigma_{{T}}^{}$ cross-sections are dominated by the $ \rho$ -meson t -pole contribution, and thus the corresponding dσ _L(T)/dt data can give a valuable information on the $ \rho$ -meson component of the nucleon cloud. The differential cross-sections for the reaction p(e, e ^′ $ \rho^{+}_{}$ )n at Q ² = 2 , 3.5GeV^2 and at the invariant mass W = 3 and 4GeV are calculated on the basis of quasi-elastic knockout mechanism with form factors. Questions about the gauge invariance of the electroproduction amplitude are considered and it is noted an important difference between photo- and electroproduction amplitudes.     

CP-violating asymmetries in penguin-inducedB-meson decays beyond the leading logarithmic approximation

We investigate CP-violating phenomena both in semi-inclusive and exclusive penguin-inducedB-meson decays by using low energy effective Hamiltonians for |ΔB|=1, ΔC=ΔU=0 transitions including leading and next-to-leading order OCD corrections. In particular, we discuss the renormalization scheme dependences arising beyond the leading order and their explicit cancellation for the physical transition amplitudes. In order to estimate the hadronic matrix elements needed for the exclusive penguin modes, we apply both the Bauer, Stech, Wirbel model and the meson model of Brodsky and Lepage. Numerical results are presented for semi-inclusive \(b \to q'\bar qq(q',q \in \{ d,s\} )\) modes and the exclusive decaysB ^?→K ^? K ⁰, \(B^ - \to \pi ^ - \bar K^0 \) , and \(B_d^0 \to K^0 \bar K^0 \) .     

Leading/nonleading charm-production asymmetry in Σ− p interactions

The asymmetry between the spectra of leading and nonleading charmed mesons that was measured in Σ^? A interactions at p _L=340 GeV/c in the WA89 experiment is described within the Model of Quark-Gluon Strings (QGS model also known as QGSM) under the assumption that there is a fraction of charmed sea quark-antiquark pairs (intrinsic charm) in an interacting hyperon. It is shown that the asymmetries between D ^?-and D ⁺-meson spectra and between D _s ^? -and D _s ⁺ -meson spectra can be approximated by QGSM curves obtained with the same string-fragmentation parameter, a ₁=10, and the same intrinsic-charm fraction, $\delta _{c,\bar c} = 0.01$ , as those that were used in describing D _s ^? /D _s ⁺ -meson asymmetry of π^? A experiments in previous studies. The asymmetry between the spectra of Λ_c and $\bar \Lambda _c $ that was measured in Σ^? A collisions at p _L=600 GeV/c in the E781 experiment is also described within this scheme. The QGSM results are compared with the results of the calculations in the next-to-leading approximation of perturbative QCD that were performed by other authors.     

Study of Light Hypernuclei by the (e,e′K +) Reaction

We have been performing Λ hypernuclear spectroscopic experiments by the (e,e′K ⁺) reaction since 2000 at Thomas Jefferson National Accelerator Facility (JLab). The (e,e′K ⁺) experiment can achieve a few 100 keV (FWHM) energy resolution compared to a few MeV (FWHM) by the (K ^?, π ^?) and (π ⁺, K ⁺) experiments. Therefore, more precise Λ hypernuclear structures can be investigated by the (e,e′K ⁺) experiment. ${^{7}_{\Lambda}{\rm He}}$ , ${^{9}_{\Lambda}{\rm Li}}$ , ${^{10}_{\Lambda}{\rm Be}}$ , ${^{12}_{\Lambda}{\rm B}}$ , ${^{28}_{\Lambda}{\rm Al}}$ , and ${^{52}_{\Lambda}{\rm V}}$ were measured in the experiment at JLab Hall-C. In addition, ${^{9}_{\Lambda}{\rm Li}}$ , ${^{12}_{\Lambda}{\rm B}}$ , and ${^{16}_{\Lambda}{\rm N}}$ were measured in the experiment at JLab Hall-A.     

Direct measurements of (p, \gamma) cross-sections at astrophysical energies using radioactive beams and the Daresbury Recoil Separator

There are a number of astrophysical environments in which the path of nucleosynthesis proceeds through proton-rich nuclei. These nuclei have traditionally not been available as beams, and thus proton-capture reactions on these nuclei could only be studied indirectly. At the Holifield Radioactive Ion Beam Facility (HRIBF), some of the first direct measurements of (p, $ \gamma$ ) cross-sections on radioactive beams have been made. The Daresbury Recoil Separator (DRS) has been used to separate the recoils of interest from the unreacted primary beam and identify them in an isobutane-filled ionization counter. First data from ¹⁷F (p, $ \gamma$ ¹⁸Ne and ⁷Be (p, $ \gamma$ ⁸B measurements 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.     

Theoretical Investigation into Production of Double-Λ Hypernuclei from Stopped Ξ − on 6Li

We have investigated theoretically a feasible nuclear reaction to produce light double-Λ hypernuclei by choosing a suitable target. In the reaction from stopped Ξ ^? on ⁶Li target light doubly-strange nuclei, ${^5_{\Lambda\Lambda}{\rm H}}$ and ${^6_{\Lambda\Lambda}{\rm He}}$ , are produced: we have calculated the formation ratio of ${^5_{\Lambda\Lambda}{\rm H}}$ to ${^6_{\Lambda\Lambda}{\rm He}}$ for Ξ ^? absorptions from 2S, 2P and 3D orbitals of Ξ ^?–⁶Li atom by assuming a d?α cluster model for ⁶Li. From this cluster model the d?α relative wave functions has a node due to Pauli exclusion among nucleons belonging to d and α clusters. Two kinds of d?α wave functions, namely 1s relative wave function with a phenomenological one-range Gaussian (ORG) potential and that of an orthogonality-condition model (OCM) are used. It is found that the probability of ${^5_{\Lambda\Lambda}{\rm H}}$ formation is larger than that of ${^6_{\Lambda\Lambda}{\rm He}}$ for all absorption orbitals: in the case of the major 3D absorption their ratio is 1.08 for ORG and 1.96 for OCM. The dominant low momentum component of the d?α relative wave function favors the ${^5_{\Lambda\Lambda}{\rm H}}$ formation with a low Q value compared to the ${^6_{\Lambda\Lambda}{\rm He}}$ formation with a high Q value. We have also calculated momentum distributions of emitted particles, d and n, displaying continuum spectra for single-Λ hypernuclei, ${^4_{\Lambda}{\rm H}}$ and ${^5_{\Lambda}{\rm He}}$ , and line spectra for the ${^5_{\Lambda\Lambda}{\rm H}}$ and ${^6_{\Lambda\Lambda}{\rm He}}$ nuclei. Thus, our present theoretical analysis would be a significant contribution to experiments in the strangeness ?2 sector of hypernuclear physics.     

Formation of Light p-shell Ξ − Hypernucleus Via (K −, K +) Reaction

We have calculated ⁷Li(K ^?, K ⁺) reaction spectrum at ${p_{K^-} = 1.65}$ GeV/c and ${\theta_{K}^{+} = 0^\circ}$ within the framework of distorted wave impulse approximation (DWIA) using the ${[\Xi^-{-}^6{\rm He}(0^+)]-[\Xi^-{-}^6{\rm He}^*(2^+)]}$ coupled-channel Green’s function approach, and examined whether the peak corresponding to the Ξ ^? hypernuclear states can be visible in the reaction spectrum, by employing various Ξ ^??⁶He effective potentials.     

Search for the K L 0 → π0ν \tilde v decay at the INEP U-70 accelerator: The KLOD project

The rare decay K _L ⁰ → π⁰ν $ \tilde v $ branching ratio measurement is one of the clearest Standard Model test. Calculations based on the SM predict Br(K _L ⁰ → π⁰ν $ \tilde v $ ) ≈ 2.8 × 10^?11, but the most accurate experimental value Br(K _L ⁰ → π⁰ν $ \tilde v $ ) < 6.7 × 10^?8 (90% C.L.). We present design of a new experimental setup KLOD (U-70 accelerator, IHEP, Protvino) for K _L ⁰ → π⁰ν $ \tilde v $ branching ratio measurement. Sensitivity of the KLOD experiment will be enough for registration of 2.4 events K _L ⁰ → π⁰ν $ \tilde v $ for every 10 days of the data taking (according to SM predictions).     

High-spin levels in138Ce and140Nd Observed in the (α, 4n γ) reactions

Levels of¹³⁸Ce and¹⁴⁰Nd have been studied using the¹³⁸Ba(α,4nγ)¹³⁸Ce and¹⁴⁰Ce(α, 4nγ)¹⁴⁰Nd reactions. Singleγ-ray spectra,γ-γ coincidence spectra, angular and time distributions with respect to the beam bursts have been measured. A number of higher excited states with excitation energies up to about 5 MeV and with spin value up to 12 are populated in both nuclei. The lower states with spins and parities 7^?, 5^?, 6^? and 10⁺ can be explained by two-quasiparticle neutron configurations of the types (h _11/2 ^?1 ,d _3/2 ^?1 ) 7^? , (h _11/2 ^?1 ,S _1/2 ^?1 ) 5^?, 6^? and (h _11/2 ^?2 ) 10⁺. Several high-spin states observed in¹³⁸Ce and¹⁴⁰Nd can be explained qualitatively as four-quasiparticle states with two-proton-two-neutron configurations. The 3^? state at an energy of 2,137.4 keV is observed in¹³⁸Ce. The evidence for the existence of the low-lying 3^? states in¹⁴⁰Nd at 2,124.0 keV is discussed. Beside the known 9.6 ms (7^?) isomeric state in¹³⁸Ce another state at 3,538.5keV (10⁺) with a half life of about 200 ns has been observed. The observed levels in the¹³⁸Ce and¹⁴⁰Nd nuclei are compared with theoretical predictions using delta force interaction.     

{\Xi} Hypernucler States Predicted by the New Interaction Model ESC08c

The features of the new interaction model ESC08c in ${\Lambda N}$ , ${\Sigma N}$ and ${\Xi N}$ channels are demonstrated single hyperon potentials ${U_Y(Y=\Lambda, \Sigma, \Xi)}$ in nuclear matter on the basis of the G-matrix theory. (K ^?, K ⁺) productions of ${\Xi}$ hypernuclei are studied with ${\Xi}$ -nucleus folding potentials.     

Quark-diagram estimates ofCP violation in two-body baryonicB_d^0 - \bar B_d^0 decays

CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of \(B_d^0 - \bar B_d^0 \) system. We discuss two feasible experimental circumstances: the symmetrice ⁺ e ^? collisions (i) on theZ ⁰ resonance to produce incoherent \(B_d^0 \bar B_d^0 \) states, and (ii) just above the ?(4S) resonance to produceC=even \(B_d^0 \bar B_d^0 \) states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb \(\bar b\) pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB _d ⁰ , \(\bar B_d^0 \to p\bar p\) , \(\Delta ^ + \bar \Delta ^ - \) , \(p\bar \Delta ^ - \) , \(\Delta ^ + \bar p\) , \(n\bar n\) , \(\Delta ^0 \bar \Delta ^0 \) , \(n\bar \Delta ^0 \) , \(\Delta ^0 \bar n\) , \(\Sigma _c^ + \bar \Sigma _c^ - \) , \(\Lambda _c^ + \bar \Lambda _c^ - \) , \(\Sigma _c^ + \bar \Lambda _c^ - \) , \(\Lambda _c^ + \bar \Sigma _c^ - \) , \(\Sigma _c^0 \bar \Sigma _c^0 \) , \(\Xi _c^0 \bar \Xi _c^0 \) , which should be interesting for experimental observation.     

Production of Ξ−-Hypernuclei via the (K −, K +) Reaction in a Quark-Meson Coupling Model

We study the production of Ξ^?-hypernuclei, ${^{12}{_{\Xi^-}}}$ Be and ${^{28}{_{\Xi^-}}}$ Mg, via the (K ^?, K ⁺) reaction within a covariant effective Lagrangian model, employing the bound Ξ^? and proton spinors calculated by the latest quark-meson coupling model. The present treatment yields the 0° differential cross sections for the formation of simple s-state Ξ^? particle-hole states peak at a beam momentum around 1.0 GeV/c with a value in excess of 1 μb.     

Search for Θ+(1540) in exclusive proton-induced reaction p + C(N) \to \Theta ^ + \bar \kappa ^0 + C(N) at the energy of 70 GeV

A search for narrow Θ⁺(1540), a candidate for a pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction $p + C(N) \to \Theta ^ + \bar \kappa ^0 + C(N)$ on carbon nuclei or quasifree nucleons at $E_{beam} = 70GeV(\sqrt s = 11.5GeV)$ studying nK ⁺, pK _S ⁰ , and pK _L ⁰ decay channels of Θ⁺(1540) in four different final states of the $\Theta ^ + \bar K^0 $ system. In order to assess the quality of the identification of the final states with neutron or K _L ⁰ , we reconstructed Λ(1520) → nK _S ⁰ and ? → K _L ⁰ K _S ⁰ decays in the calibration reactions p + C(N) → Λ (1520)K ⁺+C(N) and p+C(N) → p?+C(N). We found no evidence for a narrow pentaquark peak in any of the studied final states and decay channels. Assuming that the production characteristics of the $\Theta ^ + \bar K^0 $ system are not drastically different from those of the Λ(1520)K ⁺ and p? systems, we established upper limits on the cross-section ratios $\sigma (\Theta ^ + \bar K^0 )/\sigma (\Lambda (1520)K^ + ) < 0.02$ and $\sigma (\Theta ^ + \bar K^0 )/\sigma (p\phi ) < 0.15$ at 90% C.L. and a preliminary upper limit for the forward-hemisphere cross section $\sigma (\Theta ^ + \bar K^0 )$ nb/nucleon.     

Simplicial Ricci Flow

We construct a discrete form of Hamilton’s Ricci flow (RF) equations for a d-dimensional piecewise flat simplicial geometry, ${{\mathcal S}}$ . These new algebraic equations are derived using the discrete formulation of Einstein’s theory of general relativity known as Regge calculus. A Regge–Ricci flow (RRF) equation can be associated to each edge, ?, of a simplicial lattice. In defining this equation, we find it convenient to utilize both the simplicial lattice ${{\mathcal S}}$ and its circumcentric dual lattice, ${{\mathcal S}^*}$ . In particular, the RRF equation associated to ? is naturally defined on a d-dimensional hybrid block connecting ? with its (d?1)-dimensional circumcentric dual cell, ? ^*. We show that this equation is expressed as the proportionality between (1) the simplicial Ricci tensor, Rc _? , associated with the edge ${\ell\in{\mathcal S}}$ , and (2) a certain volume weighted average of the fractional rate of change of the edges, ${\lambda\in \ell^*}$ , of the circumcentric dual lattice, ${{\mathcal S}^*}$ , that are in the dual of ?. The inherent orthogonality between elements of ${\mathcal S}$ and their duals in ${{\mathcal S}^*}$ provide a simple geometric representation of Hamilton’s RF equations. In this paper we utilize the well established theories of Regge calculus, or equivalently discrete exterior calculus, to construct these equations. We solve these equations for a few illustrative examples.     

Recent results on antiproton annihilation in 4He

With experimental data of ${\bar p}$ annihilation at rest on nuclei of ⁴He, collected by the Obelix spectrometer (LEAR, CERN), we have studied a number of reactions with 4 and 5 charged particles in the final state, distinguishing the annihilations on more than one nucleon, and with strangeness production. The main results of our observations are: (a) a higher (up to 20 times) strangeness production in ⁴He than in H; (b) the evidence of a possible signature of a $\overline{K}pp$ ( $\overline{K} ppn$ ) bound state; (c) a measurement of a double strangeness production (2K ⁺) and a hint for some production yields of double-strange bound systems like 2K ^?2n; (d) a signal compatible with the baryonic $\Theta^+(1530)$ resonance, interpreted as a pentaquark system.     

\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Energy dependence of e + e − → 6π and e + e − → N\bar N cross sections near N\bar N the threshold

Using recent BABAR, CMD-3 and SND data, the sum of e ⁺ e ^? → 3(π⁺π^?), 2(π⁺π^?π⁰), \(p\bar p\) , \(n\bar n\) cross sections is obtained. Unlike e ⁺ e ^? 3(π⁺π^?) and e ⁺ e ^? → 2(π⁺π^?π⁰) processes, no structures in total cross section are found near the \(N\bar N\) threshold within the limits of measurement errors.