Search results for "RULE"
showing 10 items of 1403 documents
Precision Measurement of the Mass and Lifetime of the Ξ[0 over b] Baryon
2014
Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb$^{-1}$ collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 $\Xi_b^0\to\Xi_c^+\pi^-$, $\Xi_c^+\to pK^-\pi^+$ signal decays are reconstructed. From this sample, the first measurement of the $\Xi_b^0$ baryon lifetime is made, relative to that of the $\Lambda_b^0$ baryon. The mass differences $M(\Xi_b^0)-M(\Lambda_b^0)$ and $M(\Xi_c^+)-M(\Lambda_c^+)$ are also measured with precision more than four times better than the current world averages. The resulting values are $\frac{\tau_{\Xi_b^0}}{\tau_{\Lambda_b^0}} = 1.006\pm0.018\pm0.010$, $M(\Xi_b^0) - M(\Lambda_b^0) = 172.44\pm0.39\pm…
Odd parity bottom-flavored baryon resonances
2013
The LHCb Collaboration has recently observed two narrow baryon resonances with beauty. Their masses and decay modes look consistent with the quark model orbitally excited states Lambda(b)(5912) and Lambda(b)*(5920), with quantum numbers J(P) = 1/2(-) and 3/2(-), respectively. We predict the existence of these states within a unitarized meson-baryon coupled-channel dynamical model, which implements heavy-quark spin symmetry. Masses, quantum numbers and couplings of these resonances to the different meson-baryon channels are obtained. We find that the resonances Lambda(0)(b)(5912) and Lambda(0)(b)(5920) are heavy-quark spin symmetry partners, which naturally explains their approximate mass de…
Compton scattering off pions and electromagnetic polarizabilities
2019
The electric ($\alpha_\pi$) and magnetic ($\beta_\pi$) Compton polarizabilities of both the charged and the neutral pion are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD). Pion polarizabilities affect the shape of the $\gamma\pi\to\gamma\pi$ Compton scattering angular distribution at back scattering angles and $\gamma\gamma\to\pi\pi$ absolute cross sections. Theory derivations are given of the $\gamma\pi\to\gamma\pi$ Compton scattering differential cross section, dispersion relations, and sum rules in terms of the polarizabilities. We review experimental charged and neutral polarizability studies and theoretical predictions. The $\pi^0$ polarizabilities we…
Strangeness-changing scalar form factors
2001
30 páginas, 2 tablas, 10 figuras.-- arXiv:hep-ph/0110193v1
First observation of strong OZI rule violation in πN interactions
1996
The data of the CERN WA56 experiment that triggered the fast proton produced in the $\pi^{+}p$ and $\pi^{-}p$ interactions at beam momenta 20 GeV/c and 12 GeV/c, respectively, are used to analyse the final states $ p_{f} \phi (\omega)\pi^{\pm}$. A large excess (up to two orders of magnitude) of the $\phi/\omega$ cross sections ratio over the OZI prediction is observed.
Hidden and open $$\bar ss$$ production in $$\bar pp$$ annihilation at restannihilation at rest
1994
New branching ratios for\(\bar pp\) annihilation at rest into final states with a\(K\bar K\) pair or φ-meson are being measured with the Crystal Barrel detector at LEAR. The yield of φγ, relative to ωγ, appears to violate the OZI rule as strongly as φπ relative to ωπ.
Dispersion Approach to Pion Photoproduction and GDH Sum Rule
1999
Pion photoproduction has been analyzed in the framework of dispersion relations at constant t. The results for S-wave pion production at threshold and P-wave production in the Δ (1232) resonance region are presented and compared to the data and theoretical expectations. The predictions for the GDH sum rule are shown to be very sensitive to the threshold S-wave amplitude.
Multipole strength distributions and form factors forE1,E2/E0, andE3 fromU238(e,e’f) coincidence experiments
1987
A model-independent multipole analysis of $^{238}\mathrm{U}$(e,e'f) coincidence data, taken at four momentum transfers (0.2\ensuremath{\le}${q}_{\mathrm{eff}\mathrm{\ensuremath{\le}}0.7}$ ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$; \ensuremath{\omega}=4--22 MeV) yields both E1, E2/E0, and E3 form factors and strength distributions. The E2/E0 strength distribution in the fission channel shows two distinct bumps centered at \ensuremath{\omega}\ensuremath{\simeq}10 and 14 MeV, exhausting up to 12 MeV (19\ifmmode\pm\else\textpm\fi{}2)% of the isoscalar E2 sum rule. The extracted form factors can be described within a hydrodynamical model by use of parameters ${c}_{\mathrm{tr}/{c}_{0}=1.2}$ and …
Quasielastic proton knockout from 16O.
1994
The spectral function of the $^{16}\mathrm{O}$(e,e'p${)}^{15}$N reaction has been measured in quasielastic parallel kinematics. Momentum distributions are extracted for transitions to several discrete states, with emphasis on the low-lying positive parity states of $^{15}\mathrm{N}$. Spectroscopic factors and bound state wave functions are deduced from a DWIA analysis employing five different optical potentials. Coupled channels effects are investigated for the first four states of $^{15}\mathrm{N}$ and are found to be minimal. The spectroscopic results of the 1/${2}^{\mathrm{\ensuremath{-}}}$ ground state and the first 3/${2}^{\mathrm{\ensuremath{-}}}$ excited state indicate a 28%\ifmmode\…
Seawater carbonate chemistry and shell mineralogy, microstructure, and mechanical strength of four Mediterranean gastropod species near a CO2 seep
2017
Marine CO2 seeps allow the study of the long-term effects of elevated pCO2 (ocean acidification) on marine invertebrate biomineralization. We investigated the effects of ocean acidification on shell composition and structure in four ecologically important species of Mediterranean gastropods (two limpets, a top-shell snail, and a whelk). Individuals were sampled from three sites near a volcanic CO2 seep off Vulcano Island, Italy. The three sites represented ambient (8.15 pH), moderate (8.03 pH) and low (7.73 pH) seawater mean pH. Shell mineralogy, microstructure, and mechanical strength were examined in all four species. We found that the calcite/aragonite ratio could vary and increased sign…