Search results for "Lambda"
showing 10 items of 632 documents
Charmed baryon strong coupling constants in a light-front quark model
1998
Light-Front quark model spin wave functions are employed to calculate the three independent couplings g_{\Sigma_c \Lambda_c \pi}, f_{\Lambda_{c1} \Sigma_c \pi} and f_{\Lambda^{*}_{c1} \Sigma_c \pi} of S-wave to S-wave and P-wave to S-wave one-pion transitions. It is found that g_{\Sigma_c \Lambda_c \pi}=6.81 MeV^{-1}, f_{\Lambda_{c1} \Sigma_c \pi}=1.16 and f_{\Lambda^{*}_{c1} \Sigma_c \pi}=0.96 . 10^{-4} MeV^{-2}. We also predict decay rates for specific strong transitions of charmed baryons.
LHCb pentaquark as aD¯*Σc−D¯*Σc*molecular state
2015
We perform a theoretical analysis of the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{\ensuremath{-}}p$ reaction from where a recent LHCb experiment extracts a $\mathrm{\ensuremath{\Lambda}}(1405)$ contribution in the ${K}^{\ensuremath{-}}p$ spectrum close to threshold and two baryon states of hidden charm in the $J/\ensuremath{\psi}p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and ${J}^{P}$ of the experiment; concretely some states built up from the $J/\ensuremath{\psi}N$, ${\overline{D}}^{*}{\mathrm{\ensuremath{\Lambda}}}_{c}$, ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{c}$, …
Observation of theΩb−baryon and measurement of the properties of theΞb−andΩb−baryons
2009
The authors report the observation of the bottom, doubly-strange baryon {Omega}{sub b}{sup -} through the decay chain {Omega}{sub b}{sup -} {yields} J/{psi}{Omega}{sup -}, where J/{psi} {yields} {mu}{sup +} {mu}{sup -}, {Omega}{sup -} {yields} {Lambda}K{sup -}, and {Lambda} {yields} p {pi}{sup -}, using 4.2 fb{sup -1} of data from p{bar p} collisions at {radical}s = 1.96 TeV, and recorded with the Collider Detector at Fermilab. A signal is observed whose probability of arising from a background fluctuation is 4.0 x 10{sup -8}, or 5.5 Gaussian standard deviations. The {Omega}{sub b}{sup -} mass is measured to be 6054.4 {+-} 6.8(stat.) {+-} 0.9(syst.) MeV/c{sup 2}. The lifetime of the {Omega}…
Production ofΛ0,Λ¯0,Ξ±, andΩ±hyperons inpp¯collisions ats=1.96 TeV
2012
We report a set of measurements of inclusive invariant ${p}_{T}$ differential cross sections of ${\ensuremath{\Lambda}}^{0}$, ${\overline{\ensuremath{\Lambda}}}^{0}$, ${\ensuremath{\Xi}}^{\ifmmode\pm\else\textpm\fi{}}$, and ${\ensuremath{\Omega}}^{\ifmmode\pm\else\textpm\fi{}}$ hyperons reconstructed in the central region with pseudorapidity $|\ensuremath{\eta}|l1$ and ${p}_{T}$ up to $10\text{ }\text{ }\mathrm{GeV}/c$. Events are collected with a minimum-bias trigger in $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV using the CDF II detector at the Tevatron Collider. As ${p}_{T}$ increases, the slopes of the differential cross sections of the three particles are similar,…
$\Lambda_b^0$-baryon production in pp collisions in the general-mass variable-flavour-number scheme and comparison with CMS and LHCb data
2018
We calculate the next-to-leading-order cross section for the inclusive production of $\Lambda_b$ baryons in pp collisions in the general-mass variable-flavor-number scheme. We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in $e^+ e^-$ annihilation and compare our results for transverse-momentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC. We find satisfactory agreement in general, with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.
Neutrino conversions in a polarized medium
1997
Electron polarization induced by magnetic fields can modify the potentials relevant for describing neutrino conversions in media with magnetic fields. The magnitudes of polarization potentials are determined for different conditions. We show that variations of the electron polarization along the neutrino trajectory can induce resonant conversions in the active-sterile neutrino system, but cannot lead to level crossing in the active-active neutrino system. For neutrino flavour conversions the polarisation leads only to a shift of the standard MSW resonance. For polarizations $\lambda \lsim 0.04$ the direct modifications of the potential (density) due to the magnetic field pressure are smalle…
Global fit to b → cτν transitions
2019
Abstract We perform a general model-independent analysis of $$ b\to c\tau {\overline{\nu}}_{\tau } $$ b → cτ ν ¯ τ transitions, including measurements of ℛ D , ℛ D∗, their q 2 differential distributions, the recently measured longitudinal D* polarization $$ {F}_L^{D\ast } $$ F L D ∗ , and constraints from the $$ {B}_c\to \tau {\overline{\nu}}_{\tau } $$ B c → τ ν ¯ τ lifetime, each of which has significant impact on the fit. A global fit to a general set of Wilson coefficients of an effective low-energy Hamiltonian is presented, the solutions of which are interpreted in terms of hypothetical new-physics mediators. From the obtained results we predict selected $$ b\to c\tau {\overline{\nu}}_…
ΛNNandΣNNsystems at threshold
2007
We calculate the hypertriton binding energy and the $\ensuremath{\Lambda}d$ and $\ensuremath{\Sigma}d$ scattering lengths using baryon-baryon interactions obtained from a chiral constituent quark model. We study consistently the $\ensuremath{\Lambda}\mathit{NN}$ and $\ensuremath{\Sigma}\mathit{NN}$ systems by analyzing the effect of the $\ensuremath{\Sigma}\ensuremath{\leftrightarrow}\ensuremath{\Lambda}$ conversion. Our interactions correctly predict the hypertriton binding energy. The $(I,J)=(0,3/2)$ $\ensuremath{\Lambda}\mathit{NN}$ channel is also attractive and it might have a bound state. From the condition of nonexistence of a (0,3/2) $\ensuremath{\Lambda}\mathit{NN}$ bound state, an…
Critical view on the deeply boundK−ppsystem
2006
We briefly review the situation around the claimed deeply bound ${K}^{\ensuremath{-}}$ states in different recent experiments and concentrate particularly on the state ${K}^{\ensuremath{-}}\mathit{pp}$ advocated by the FINUDA collaboration in nuclear ${K}^{\ensuremath{-}}$ absorption. We perform a theoretical simulation of the process and show that the peak in the $\ensuremath{\Lambda}p$ spectrum that was interpreted as a deep ${K}^{\ensuremath{-}}\mathit{pp}$ bound state corresponds mostly to the process ${K}^{\ensuremath{-}}pp\ensuremath{\rightarrow}\ensuremath{\Lambda}p$ followed by final-state interactions of the produced particles with the daughter nucleus.
SU(3) Chiral approach to meson and baryon dynamics
1999
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\to\Lambda(1405)\gamma reaction and the N^\ast (1535)N^\ast(1535)\pi and \eta couplings.