Search results for "hyperon"
showing 10 items of 118 documents
"Average P_H" of "Global polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons in Pb-Pb collisions at the LHC"
2021
The average $(\Lambda+\bar\Lambda) \times (2.76+5.02)$ global polarization in Pb-Pb collisions for centrality 15-50%.
Scattering Studies with Low-Energy Kaon-Proton Femtoscopy in Proton-Proton Collisions at the LHC
2020
The study of the strength and behaviour of the antikaon-nucleon ($\mathrm{\overline{K}N}$) interaction constitutes one of the key focuses of the strangeness sector in low-energy Quantum Chromodynamics (QCD). In this letter a unique high-precision measurement of the strong interaction between kaons and protons, close and above the kinematic threshold, is presented. The femtoscopic measurements of the correlation function at low pair-frame relative momentum of (K$^+$ p $\oplus$ K$^-$ $\overline{\mathrm{p}}$) and (K$^-$ p $\oplus$ K$^+$ $\overline{\mathrm{p}}$) pairs measured in pp collisions at $\sqrt{s}$ = 5, 7 and 13 TeV are reported. A structure observed around a relative momentum of 58 Me…
Measurement of spin-orbital angular momentum interactions in relativistic heavy-ion collisions
2020
The first evidence of spin alignment of vector mesons ($K^{*0}$ and $\phi$) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element $\rho_{00}$ is measured at midrapidity ($|y| <$ 0.5) in Pb-Pb collisions at a center-of-mass energy ($\sqrt{s_{\rm NN}}$) of 2.76 TeV with the ALICE detector. $\rho_{00}$ values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum ($p_{\rm T} <$ 2 GeV/$c$) for $K^{*0}$ and $\phi$ at a level of 3$\sigma$ and 2$\sigma$, respectively. No significant spin alignment is observed for the $K^0_S$ meson (spin = 0) in Pb-Pb collisions and for the vector mesons in $pp$ collisions. The meas…
Search for Baryonic Decays of \psi(3770) and \psi(4040)
2013
By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482 pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the BEPCII storage ring, we search for \psi(3770) and \psi(4040) decay to baryonic final states, including \Lambda\bar\Lambda\pi^+\pi^-, \Lambda \bar\Lambda\pi^0, \Lambda\bar\Lambda\eta, \Sigma^+ \bar\Sigma^-, \Sigma^0 \bar\Sigma^0, \Xi^-\bar\Xi^+ and \Xi^0\bar\Xi^0 decays. None are observed, and upper limits are set at the 90% confidence level.
Antineutrino induced Λ(1405) production off the proton
2015
We have studied the strangeness-changing antineutrino-induced reactions ${\overline{\ensuremath{\nu}}}_{l}p\ensuremath{\rightarrow}{l}^{+}\ensuremath{\phi}B$, with $\ensuremath{\phi}B={K}^{\ensuremath{-}}p$, ${\overline{K}}^{0}n$, ${\ensuremath{\pi}}^{0}\ensuremath{\Lambda}$, ${\ensuremath{\pi}}^{0}{\ensuremath{\Sigma}}^{0}$, $\ensuremath{\eta}\ensuremath{\Lambda}$, $\ensuremath{\eta}{\ensuremath{\Sigma}}^{0}$, ${\ensuremath{\pi}}^{+}{\ensuremath{\Sigma}}^{\ensuremath{-}}$, ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\Sigma}}^{+}$, ${K}^{+}{\ensuremath{\Xi}}^{\ensuremath{-}}$, and ${K}^{0}{\ensuremath{\Xi}}^{0}$, using a chiral unitary approach. These ten coupled channels are allowed t…
Charm production in the CERN hyperon beam
1994
First results on charm production by the Σ- hyperon beam experiment WA89 at CERN are presented. Estimates are given for thexF and nuclearA dependence of the inclusive cross-section of D-mesons. Preliminary results on charm baryon production are shown.
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{\…
Long-range chiral dynamics of Λ-hyperon in nuclear media
2008
We extend a chiral effective field theory approach to the Λ-nuclei interaction with the inclusion of the decuplet baryons. More precisely, we study the contributions due to the long-range two-pion exchange, with Σ and Σ* baryons in the internal baryonic lines considering Nh and Δh excitations. In particular, central and spin-orbit potentials are studied. For the former, regularization is needed and physical values of the cut-off give a large attraction, becoming necessary to include the repulsion of other terms not considered here. For the latter, in a model-independent framework, the inclusion of the decuplet supports the natural explanation of the smallness of the Λ-nuclear spin-orbit ter…
Pentaquark decay width in QCD sum rules
2005
In a diquark-diquark-antiquark picture of the pentaquark we study the decay $\Theta \rightarrow K^{+} n$ within the framework of QCD sum rules. After evaluation of the relevant three-point function, we extract the coupling $g_{\Theta nK}$ which is directly related to the pentaquark width. Restricting the decay diagrams to those with color exchange between the meson-like and baryon-like clusters reduces the coupling constant by a factor of four. Whereas a small decay width might be possible for a positive parity pentaquark, it seems difficult to explain the measured width for a pentaquark with negative parity.
The nature of Lambda (1405) hyperon resonance in chiral dynamics
2010
10th International Conference on Hypernuclear and Strange Particle Physics. Tokai, JAPAN, SEP 14-18, 2009