Search results for "baryon"
showing 10 items of 759 documents
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.…
Study ofJ/ψ→pp¯andJ/ψ→nn¯
2012
The decays J/psi -> p (p) over bar and J/psi -> n (n) over bar have been investigated with a sample of 225.2 x 10(6) J/psi events collected with the BESIII detector at the BEPCII e(+)e(-) collider. The branching fractions are determined to be B(J/psi -> p (p) over bar) = (2.112 +/- 0.004 +/- 0.031 x 10(-3) and B(J/psi -> n (n) over bar) =(2.07 +/- 0.01 +/- 0.17) x 10(-3). Distributions of the angle theta between the proton or antineutron and the beam direction are well described by the form 1 + alpha cos(2)theta, and we find alpha = 0.595 +/- 0.012 +/- 0.015 for J/psi -> p (p) over bar and alpha = 0.50 +/- 0.04 +/- 0.21 for J/psi -> n (n) over bar. Our branching- fraction results suggest a …
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…
ɛ-type contribution to baryon asymmetry from colored Higgs triplets
1991
In scenarios where the cosmological baryon asymmetry is generated in the decay of heavy colored Higgs triplets at the one-loop level (at least two triplets are needed), it is shown that in addition to the conventional triangle loop ({epsilon}{prime}-type effect), a new kind of diagram must be considered. This new type of diagram has its origin in the mixing of the two Higgs fields ({epsilon}-type effect). The mixing of the two Higgs fields violates {ital CP} provided they have at least two common decay channels. For small mixing angles, the new contribution can be bigger than the conventional one.
Pion photo- and electro-production and the chiral MAID interface
2016
We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order q 4 . The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/). We explain how our program works and how it can be used for further analysis.
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…
Measurement ofj/?-decays into channels containing charged and neutral antinucleons
1981
Using the nonmagnetic BONANZA detector for the detection of antineutrons and antiprotons, we measured branching ratios of theJ/ψ into baryonic final states. Our measurements give the new results:\(BR\left( {{J \mathord{\left/ {\vphantom {J {\psi \to \overline {\Sigma ^ - } }}} \right. \kern-\nulldelimiterspace} {\psi \to \overline {\Sigma ^ - } }}\Sigma ^ - } \right) = \left( {0.24 \pm 0.26} \right)\% ;BR\left( {{J \mathord{\left/ {\vphantom {J {\psi \to }}} \right. \kern-\nulldelimiterspace} {\psi \to }}\bar nn\pi ^ + \pi ^ - } \right) = \left( {0.38 \pm 0.36} \right)\% \) and an independent test for the data of the magnetic detectors.