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.     

Lambda Hypernuclei in a Chiral Hadronic Model

Nuclear matter calculations in a chiral hadronic model have been performed. It has been found that the scalar and the vector potentials and binding energies per nucleon in the chiral hadronic model are very close to those of the microscopic relativistic Brueckner-Hartree-Fock calculations. The good results for finite nuclei can be obtained in the mean field approximation only if scalar mass rns and coupling constant g8 have been improved with the fixed values of c^28 = g^28(M/rn8)^2 as those given by the original parameter sets of the chiral hadronic model. Then the chiral hadronic model is extended to lambda hypernuclei. Our results predicted by the chiral hadronic model are compared with those by the nonlinear Walecka model. It has been shown that the hadronic model can also be used to describe lambda hypernuclei successfully.     

Strong decay of $$\Lambda _c(2940)$$ as a 2 P state in the $$\Lambda _c$$Λc family

Considering the mass, parity and \(D^0 p\) decay mode, we tentatively assign the \(\Lambda _c(2940)\) as the \(P-\)wave states with one radial excitation. Then, via studying the strong decay behavior of the \(\Lambda _c(2940)\) within the \(^3P_0\) model, we obtain that the total decay widths of the \(\Lambda _{c1}(\frac{1}{2}^-,2P)\) and \(\Lambda _{c1}(\frac{3}{2}^-,2P)\) states are 16.27 and 25.39 MeV, respectively. Compared with the experimental total width \(27.7^{+8.2}_{-6.0}\pm 0.9^{+5.2}_{-10.4}~\mathrm {MeV}\) measured by LHCb Collaboration, both assignments are allowed, and the \(J^P=\frac{3}{2}^-\) assignment is more favorable. Other \(\lambda \)-mode \(\Sigma _c(2P)\) states are also investigated, which are most likely to be narrow states and have good potential to be observed in future experiments.     

$$\Lambda _b \rightarrow \pi ^- (D_s^-) \Lambda _c(2595),~\pi ^- (D_s^-) \Lambda _c(2625)$$ decays and $$DN,~D^*N$$DN,D∗N molecular components

From the perspective that \(\Lambda _c(2595)\) and \(\Lambda _c(2625)\) are dynamically generated resonances from the \(DN,~D^*N\) interaction and coupled channels, we have evaluated the rates for \(\Lambda _b \rightarrow \pi ^- \Lambda _c(2595)\) and \(\Lambda _b \rightarrow \pi ^- \Lambda _c(2625)\) up to a global unknown factor that allows us to calculate the ratio of rates and compare with experiment, where good agreement is found. Similarly, we can also make predictions for the ratio of rates of the, yet unknown, decays of \(\Lambda _b \rightarrow D_s^- \Lambda _c(2595)\) and \(\Lambda _b \rightarrow D_s^- \Lambda _c(2625)\) and make estimates for their individual branching fractions.     

\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.     

在200GeV极化质子质子对撞中产生的反Lambda粒子的极化

We study the polarization of produced (-Λ)in (√s)=200GeV polarized proton-proton collision at RHIC/PHENIX, and also the polarization as a function of its rapidity which may be sensitivity to the quark helicity distributions of the proton and to the polarized fragmentation functions of the quark into the baryon. For polarized data collected in 2003 a very clean (-Λ) peakin (-p)π invariant mass spectrum in the mid-rapidity(|η| ＜ 0.35) is obtained. In this letter, we report the calculation process of P(-Λ) as extracted from the data.     

在200GeV极化质子质子对撞中产生的反Lambda粒子的极化

We study the polarization of produced Λ in s=200GeV polarized proton-proton collision at RHIC/PHENIX, and also the polarization as a function of its rapidity which may be sensitivity to the quark helicity distributions of the proton and to the polarized fragmentation functions of the quark into the baryon. For polarized data collected in 2003 a very clean Λ peak in pπ⁺ invariant mass spectrum in the mid-rapidity(|η|<0.35) is obtained. In this letter, we report the calculation process of P_Λ as extracted from the data.     

Testing the nature of the Λ(1520) in the J/ψ → \bar \Lambda K-p and J/ψ → \bar \Lambda π+π-Λ reactions

We study the reactions J/ψ → $ \bar \Lambda $ K ^- p and J/ψ → $ \bar \Lambda $ π⁺π^-Λ with a unitary chiral approach. We predict the ratio of the invariant-mass distributions of these two reactions at the Λ(1520) peak position, which is free of the unknown production mechanism and reflects only the properties of the Λ(1520) . An experimental measurement of this ratio will provide the couplings of the Λ(1520) to its decay channels, allowing to test the predictions of the chiral unitary approach on this resonance, which appears as dynamically generated in that approach.     

Spin transfer to Λ and \bar \Lambda hyperons in deep inelastic scattering at HERMES

Preliminary results on the spin transfer to the Λ and $\bar \Lambda$ hyperons measured by the HERMES Collaboration are presented. Longitudinal spin transfer directed along the virtual-photon momentum in the Λ rest frame is found to be D _LL ^Λ = 0.19 ± 0.04_stat ± 0.02_syst, the transverse component being compatible with zero. For $\bar \Lambda$ both longitudinal and transverse components are compatible with zero within statistical errors of ±0.1.     

Λ and\bar \Lambda polarization inK ± P interactions at 32 GeV/c

Data on Λ and \(\bar \Lambda \) polarization inK ^± p interactions at 32 GeV/c are presented. A comparison is made between the results of these two experiments as well as with the data at lower energies. The contribution of the different production mechanisms to the Λ( \(\bar \Lambda \) ) polarization are discussed.     

Spin correlations in the ΛΛ and Λ$$ \bar \Lambda $$ systems generated in relativistic heavy-ion collisions

Spin correlations for the ΛΛ and Λ$ \bar \Lambda $ \bar \Lambda pairs, generated in relativistic heavy-ion collisions, and related angular correlations at the joint registration of hadronic decays of two hyperons, in which space parity is not conserved, are analyzed. The correlation tensor components can be derived from the double angular distribution of products of two decays by the method of “moments”. The properties of the “trace” of the correlation tensor (a sum of three diagonal components), determining the relative fractions of the triplet states and singlet state of respective pairs, are discussed. Spin correlations for two identical particles (ΛΛ) and two nonidentical particles (Λ$ \bar \Lambda $ \bar \Lambda ) are considered from the viewpoint of the conventional model of one-particle sources. In the framework of this model, correlations vanish at sufficiently large relative momenta. However, under these conditions, in the case of two nonidentical particles (Λ$ \bar \Lambda $ \bar \Lambda ) a noticeable role is played by two-particle annihilation (two-quark, two-gluon) sources, which lead to the difference of the correlation tensor from zero. In particular, such a situation may arise when the system passes through the “mixed phase.”     

Λ\bar \Lambda longitudinal polarization: A signature for the formation of a quark-gluon plasma in heavy ion collisions

The high relative abundance ofs \(\bar s\) quarks in the quark-gluon plasma will result in peculiar hadronization ratios whereby the Ξ/Λ ratio should be much higher than in usual processes. As a result the Λ( \(\bar \Lambda\) ) should exhibit a sizeable longitudinal polarization due to their importantΞ( \(\bar \Xi\) ) filiation. Discussing such spin effect, the report starts with the determination of theW spin, a recent and successful application of the helicity formalism.     

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.     

Longitudinal spin transfer to Λ and \bar \Lambda in polarized proton-proton collisions at √s = 200 GeV at STAR

The longitudinal spin transfer D _LL of Λ and $\bar \Lambda$ hyperons is expected to be sensitive to the helicity distribution function of strange (anti-)quarks, and to the polarized fragmentation functions. We report new results on D _LL , extracted from √s = 200 GeV polarized pp collisions recorded at the STAR detector during the 2009 RHIC run. These new results cover mid-rapidity |η| < 1.2, with extended p _T up to 6 GeV/c.     

Stable exponential cosmological solutions with two factor spaces in the Einstein–Gauss–Bonnet model with a $$\Lambda $$-term

We study D-dimensional Einstein–Gauss–Bonnet gravitational model including the Gauss–Bonnet term and the cosmological term \(\Lambda \). We find a class of solutions with exponential time dependence of two scale factors, governed by two Hubble-like parameters \(H >0\) and h, corresponding to factor spaces of dimensions \(m >2\) and \(l > 2\), respectively. These solutions contain a fine-tuned \(\Lambda = \Lambda (x, m, l, \alpha )\), which depends upon the ratio \(h/H = x\), dimensions of factor spaces m and l, and the ratio \(\alpha = \alpha _2/\alpha _1\) of two constants (\(\alpha _2\) and \(\alpha _1\)) of the model. The master equation \(\Lambda (x, m, l,\alpha ) = \Lambda \) is equivalent to a polynomial equation of either fourth or third order and may be solved in radicals. The explicit solution for \(m = l\) is presented in “Appendix”. Imposing certain restrictions on x, we prove the stability of the solutions in a class of cosmological solutions with diagonal metrics. We also consider a subclass of solutions with small enough variation of the effective gravitational constant G and show the stability of all solutions from this subclass.     

Study of theA-dependence of inclusivep,\bar p,Λ and\bar \Lambda production in π±-Nucleus interactions at 30 GeV/c

We present the first results on the production of fast (p>10 GeV/c)p, \(\bar p\) , Λ and \(\bar \Lambda \) from π^± hydrogen and nucleus interactions at 30 GeV/c using the CERN Ω′ spectrometer. We have used five nuclear targets (C, Al, Cu, Sn, Pb) to study theA-dependence of the inclusive particle distributions in the region 0.3<x _F <0.6. The high statistical level of our experiment allows us to demonstrate the differentA-behaviour of baryon and antibaryon inclusive reactions. We relate this difference to the final state interaction inside a nucleus using the formation-zone model.     

Leading-particle effects in the spectra of Λc and \bar \Lambda _c produced in Σ− p, pp, and π − p interactions

The spectra of leading and nonleading charmed baryons (Λ_c and $\bar \Lambda _c$ ) and the asymmetries between these spectra measured in Σ^? A, π ^? A, and pA collisions at p _L =600 GeV/c in the E781 experiment are simultaneously described within the framework of the Quark-Gluon String Model (QGSM). It is shown that the charmed baryon spectra can be fitted by QGSM curves calculated with the parameter of diquark fragmentation, $a_f^{\Lambda _c } = 0.006$ . It was found in this experiment that the asymmetry between the spectra of Λ_c and $\bar \Lambda _c$ in π ^? A collisions is of nonzero value. It might be described in our model only assuming that the string junction is transferred from target proton into the kinematical region of pion projectile fragmentation.     

A partial wave analysis of thef′ region in the reactionK^ - p \to K\bar K\Lambda ^0 at 8.25 GeV/c

A partial wave analysis of theK \(\bar K\) system produced by 8.25 GeV/cK ^? mesons in the reaction \(K^ - p \to K\bar K\Lambda ^{ 0} \) has been performed, taking into account the information provided by the Λ⁰ decay. Thef′ region is dominated byD ₀ ^(?) andD ₁ ⁽⁺⁾ waves. We see no evidence for the production of new 0⁺⁺ states in the mass region 1.05 to 1.75 GeV.     

Determinations of $$|V_{cb}|$$ and $$|V_{ub}|$$|Vub| from baryonic $$\Lambda _b$$Λb decays

We present the first attempt to extract \(|V_{cb}|\) from the \(\Lambda _b\rightarrow \Lambda _c^+\ell \bar{\nu }_\ell \) decay without relying on \(|V_{ub}|\) inputs from the B meson decays. Meanwhile, the hadronic \(\Lambda _b\rightarrow \Lambda _c M_{(c)}\) decays with \(M=(\pi ^-,K^-)\) and \(M_c=(D^-,D^-_s)\) measured with high precisions are involved in the extraction. Explicitly, we find that \(|V_{cb}|=(44.6\pm 3.2)\times 10^{-3}\), agreeing with the value of \((42.11\pm 0.74)\times 10^{-3}\) from the inclusive \(B\rightarrow X_c\ell \bar{\nu }_\ell \) decays. Furthermore, based on the most recent ratio of \(|V_{ub}|/|V_{cb}|\) from the exclusive modes, we obtain \(|V_{ub}|=(4.3\pm 0.4)\times 10^{-3}\), which is close to the value of \((4.49\pm 0.24)\times 10^{-3}\) from the inclusive \(B\rightarrow X_u\ell \bar{\nu }_\ell \) decays. We conclude that our determinations of \(|V_{cb}|\) and \(|V_{ub}|\) favor the corresponding inclusive extractions in the B decays.