اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدFurther evidence for the $Sigma^{*}$ resonance with $J^P=1/2^-$ around 1380 MeV
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The unquenched quark models predict the new particle $Sigma^*$ with spin parity $J^P=1/2^-$ and its mass is around the well established $Sigma^*(1385)$ with $J^P=3/2^+$. Here by using the effective Lagrangian approach we study kp reaction at the range of $Lambda^{*}(1520)$ peak, comparing the resulting total cross section, and $pi^+pi^-$, $Lambdapi^+$, $Lambdapi^-$ invariant squared mass distributions for various incident $K^-$ momenta, as well as the production angular distribution of the $Lambda$ with the data from the Lawrence Berkeley Laboratory 25-inch hydrogen bubble chamber, we find that, apart from the existing resonance $Sigma^{*}(1385)$ with $J^P=3/2^+$, there is a strong evidence for the existence of the new resonance $Sigma^{*}$ with $J^P=1/2^-$ around 1380 MeV. Higher statistic data on relevant reactions are needed to clarify the situation.
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Distinctive patterns are predicted by quenched quark models and unquenched quark models for the lowest SU(3) baryon nonet with spin parity $J^P=1/2^-$. While the quenched quark models predict the lowest $1/2^-$ $Sigma^*$ resonance to be above 1600 Me
V, the unquenched quark models predict it to be around $Sigma^*(1385)$ energy. Here we re-examine some old data of the $kp to la$ reaction and find that besides the well established $Sigma^{*}(1385)$ with $J^P=3/2^+$, there is indeed some evidence for the possible existence of a new $Sigma^{*}$ resonance with $J^P=1/2^-$ around the same mass but with broader decay width. Higher statistic data on relevant reactions are needed to clarify the situation.
We study the photoproduction of the $Lambda(1405)$ and $Sigma(1400)$ hyperon resonances, the latter of which is not a well established state. We evaluate the $s$-, $t$- and $u$-channel diagrams in the Born approximation by employing the effective Lag
rangians. A new ingredient is the inclusion of a nucleon resonance $N^*(1895)$ that is dynamically generated with predictions for its coupling to the $KLambda(1405)$ and $KSigma(1400)$ channels. To extend the applicability of the model to energies beyond the threshold region, we consider a Regge model for the $t$-channel $K$- and $K^*$-exchanges. Our results are in good agreement with the CLAS data available on $Lambda(1405)$, while for $Sigma(1400)$ we predict observables for its production. We also provide polarization observables for both hyperon productions, which can be useful in future experimental investigations. The present study provides new information on the nucleon resonance $N^*(1895)$ which can be an alternative source for generating the hyperon resonances $Lambda(1405)$ and $Sigma(1400)$.
The hadronic reaction pp --> Sigma+ K0 p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K0 p subsystem at 1530 +- 5 MeV/c2 wi
th a significance of 4 - 6 standard deviations, depending on background assumptions. The upper limit of 18 +- 4 MeV/c2 (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4 +- 0.1(stat) +- 0.1(syst) microbarn. Since a resonance in this subsystem must have strangeness S = + 1 we claim it to be the Theta+ state for which very recently evidence was found in various experiments.
We report the first evidence for the decay Sigma+ -> p mu+ mu- from data taken by the HyperCP experiment(E871) at Fermilab. Based on three observed events, the branching ratio is B(Sigma+ -> p,mu+,mu-) = [8.6 +6.6,-5.4(stat) +/-5.5(syst)] x 10**-8. T
he narrow range of dimuon masses may indicate that the decay proceeds via a neutral intermediate state, Sigma+ -> p P0, P0 -> mu+ mu-, with a P0 mass of 214.3 +/- 0.5 MeV/c**2 and branching ratio B(Sigma+ -> p P0; P0 -> mu+ mu-) = [3.1 +2.4,-1.(stat) +/-1.5(syst)] x 10**-8.
We measured the branching fractions of the decays $chi_{cJ}toSigma^{-}bar{Sigma}^{+}$ for the first time using the final states $nbar{n}pi^{+}pi^{-}$. The data sample exploited here is $448.1times10^{6}$ $psi(3686)$ events collected with BESIII. We f
ind $mathcal{B}(chi_{cJ}rightarrowSigma^{-}bar{Sigma}^{+}) = (51.3pm2.4pm4.1)times10^{-5},, (5.7pm1.4pm0.6)times10^{-5},, rm{and}~ (4.4pm1.7pm0.5)times10^{-5}$, for $J=0,1,2$, respectively, where the first uncertainties are statistical and the second systematic.
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