Search results for "lambda"
showing 10 items of 632 documents
Chiral coupled channel dynamics of theΛ(1520)and theK−p→π0π0Λreaction
2005
We study the $\ensuremath{\Lambda}(1520){D}_{03}$ in a chiral coupled channel approach. This resonance appears to be dynamically generated from the interaction of the decuplet of baryons and the octet of mesons in s wave, and its treatment is improved here with the phenomenological inclusion of the $\overline{K}N$ and $\ensuremath{\pi}\ensuremath{\Sigma}$ channels in d wave. Since the most important building block in $\ensuremath{\Lambda}(1520)$ is the $\ensuremath{\pi}{\ensuremath{\Sigma}}^{*}(1385){P}_{13}$ channel, we study the ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\pi}{\ensuremath{\Sigma}}^{*}(1385)({\ensuremath{\pi}}^{0}\ensuremath{\Lambda})$ reaction in the region …
Unitary coupled channel analysis of theΛ(1520)resonance
2006
We study the � (1520) resonance in a coupled-channel approach involving the π� (1385) ,K� (1530), ¯ KN, and π� channels. Implementing unitarity in coupled channels, we make an analysis of the relative importance of the different mechanisms that contribute to the dynamical structure of this resonance. From experimental information on some partial wave amplitudes and constraints imposed by unitarity, we get a comprehensive description of the amplitudes and hence the couplings to the different channels. We test these amplitudes in different reactions like K − p → �π π, γp → K + K − p, γp → K + π 0 π 0 � ,a ndπ − p → K 0 K − p and find a fair
Rare baryon decaysΛb→Λℓ+ℓ−(ℓ=e,μ,τ) andΛb→Λγ: Differential and total rates, lepton- and hadron-side forward-backward asymmetries
2013
Using the covariant constituent quark model previously developed by us, we calculate the differential rate and the forward-backward asymmetries on the lepton and hadron side for the rare baryon decays ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$, $\ensuremath{\tau}$) and ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma}$. We use helicity methods to write down a threefold joint angular decay distribution for the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\…
Measurements of baryon pair decays of chi(cJ) mesons
2013
Using 106 $\times 10^{6}$ $\psi^{\prime}$ decays collected with the BESIII detector at the BEPCII, three decays of $\chi_{cJ}$ ($J=0,1,2$) with baryon pairs ($\llb$, $\ssb$, $\SSB$) in the final state have been studied. The branching fractions are measured to be $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Lambda\bar\Lambda) =(33.3 \pm 2.0 \pm 2.6)\times 10^{-5}$, $(12.2 \pm 1.1 \pm 1.1)\times 10^{-5}$, $(20.8 \pm 1.6 \pm 2.3)\times 10^{-5}$; $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{0}\bar\Sigma^{0})$ = $(47.8 \pm 3.4 \pm 3.9)\times 10^{-5}$, $(3.8 \pm 1.0 \pm 0.5)\times 10^{-5}$, $(4.0 \pm 1.1 \pm 0.5) \times 10^{-5}$; and $\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{+}\bar\Sigma^{-})$ = $(45.4 \pm…
Λ(1520)andΣ(1385)in the nuclear medium
2006
Recent studies of the {lambda}(1520) resonance within chiral unitary theory with coupled channels find the resonance as a dynamically generated state from the interaction of the decuplet of baryons and the octet of mesons, essentially a quasibound state of {pi}{sigma}{sup *}(1385) in this case, although the coupling of the {lambda}(1520) to the KN and {pi}{sigma} makes this picture only approximate. The {pi}{sigma}{sup *}(1385) decay channel of the {lambda}(1520) is forbidden in free space for the nominal mass of the {sigma}{sup *}(1385), but the coupling of the {pi} to ph components in the nuclear medium opens new decay channels of the {lambda}(1520) in the nucleus and produces a much larg…
Weak decay ofΛc+for the study ofΛ(1405)andΛ(1670)
2015
We study the ${\mathrm{\ensuremath{\Lambda}}}_{c}$ decay process to ${\ensuremath{\pi}}^{+}$ and the meson-baryon final state for the analysis of $\mathrm{\ensuremath{\Lambda}}$ resonances. Considering the Cabibbo-Kobayashi-Maskawa matrix, color suppression, diquark correlation, and the kinematical condition, we show that the final meson-baryon state should be in a pure $I=0$ combination, when the meson-baryon invariant mass is small. Because the $I=1$ contamination usually makes it difficult to analyze $\mathrm{\ensuremath{\Lambda}}$ resonances directly from experiments, the ${\mathrm{\ensuremath{\Lambda}}}_{c}$ decay is an ideal process to study $\mathrm{\ensuremath{\Lambda}}$ resonances.…
Measurement of the production fraction times branching fractionf(b→Λb)·B(Λb→J/ψΛ)
2011
The \Lambda_b(udb) baryon is observed in the decay \Lambda_b --> J/\psi \Lambda using 6.1 fb^{-1} of p\bar{p} collisions collected with the D0 detector at \sqrt{s}=1.96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B^0 --> J/\psi K^0_s is measured to be 0.345 \pm 0.034 (stat.) \pm 0.033 (syst.) \pm 0.003 (PDG). Using the world average value of f(b --> B^0)B(B^0 --> J/\psi K^0_s) = (1.74 \pm 0.08) \times 10^{-5}, we obtain f(b --> \Lambda_b)B(\Lambda_{b} --> J/\psi \Lambda) = (6.01 \pm 0.60 (stat.) \pm 0.58 (syst.) \pm 0.28 (PDG)) \times 10^{-5}. This measurement represents an improvement in precision by about a factor of thre…
Infinite momentum frame calculation of semileptonic heavyΛb→Λctransitions including HQET improvements
1997
We calculate the transition form factors that occur in heavy {Lambda}-type baryon semileptonic decays such as, e.g., in {Lambda}{sub b}{r_arrow}{Lambda}{sub c}{sup +}+l{sup {minus}}+{bar {nu}}{sub l}. We use Bauer-Stech-Wirbel-type infinite momentum frame wave functions for the heavy {Lambda}-type baryons which we assume to consist of a heavy quark and a light spin-isospin zero diquark system. The form factors at q{sup 2}=0 are calculated from the overlap integrals of the initial and final {Lambda}-type baryon states. To leading order in the heavy mass scale the structure of the form factors agrees with the HQET predictions including the normalization at zero recoil. The leading order {omeg…
Hidden-charm pentaquark state inΛb0→J/ψpπ−decay
2016
We study here the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\ensuremath{\pi}}^{\ensuremath{-}}$ reaction in analogy to the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/\ensuremath{\psi}p$ mass distribution around 4450 MeV, which is associated in the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ experiment to an exotic pentaquark baryonic state, although in ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\en…
Λb and Λc baryon decays at finite values of heavy quark masses
2000
Semileptonic decays of Lambda_b and Lambda_c baryons are studied within the Relativistic Three-Quark Model using finite heavy quark mass values. Employing the same parameters as have been used previously for the description of exclusive decays of heavy baryons in the heavy quark limit we calculate the six form factors of the process and the corresponding decay rates. Our calculation shows that the ``finite mass'' corrections are important in heavy-to-light transitions and are not negligible in heavy-to-heavy transitions.