1,878 research outputs found
B lifetime measurements with exclusively reconstructed B decays
Data collected with the BABAR detector at the PEP-II asymmetric B Factory at
SLAC are used to study the lifetime of the B0 and B+ mesons. The data sample
consists of 7.4 fb-1 collected near the Y(4S) resonance. B0 and B+ mesons are
fully reconstructed in several exclusive hadronic decay modes to charm and
charmonium final states. The B lifetime are determined from the flight length
difference between the two B mesons. The preliminary measurements of the
lifetimes are tau_{B0} = 1.506 +/- 0.052 (stat) +/- 0.029 (syst) ps tau_{B+} =
1.602 +/- 0.049 (stat) +/- 0.035 (syst) ps and of their ratio is
tau_{B+}/tau_{B0} = 1.065 +/- 0.044 (stat) +/- 0.021 (syst).Comment: 4 pages, 2 postscript figues, submitted to DPF200
Quark Mass Matrices in the A_4 Model
If the standard model of quark interactions is supplemented by a discrete A_4
symmetry (which may be relevant for the lepton sector), the spontaneous
breaking of the electroweak gauge symmetry allows arbitrary quark masses, but
all mixing angles are predicted to be zero. A pattern of the explicit breaking
of A_4 is proposed, which results in a realistic charged-current mixing matrix.Comment: 6 pages, no figur
Magnetic moments and electromagnetic radii of nucleon and in an extended GBE model
We derive the exchange currents of pseudoscalar, vector, and scalar mesons
from Feynman diagrams, and use them to calculate the magnetic form factors of
nucleon and . The magnetic moments and electromagnetic radii are
obtained by using those form factors and the parameters determined from the
masses of nucleon and . We find the magnetic moments and
electromagnetic radii of nucleon and can be produced very well
in the extended Goldstone-boson-exchange model (GBE) in which all of
pseudoscalar, vector and scalar meson nonet are included. The magnetic moments
of are closer to experiment values and results from lattice
calculation than the results obtained by the model without other mesons except
for pion and sigma.Comment: 15 pages,5 figure
Decays of b hadrons and a possible new four-quark interaction
A possibility is considered of explaining the low experimental value of the
ratio of the lifetimes tau(Lambda_b)/tau(B_d) by a new `centiweak' four-quark
interaction, i.e with a strength on the order of 10^{-2}G_F. It is noted that
the considered interaction can also improve agreement with the data on low
semileptonic branching ratio B_{sl}(B) in B meson decays with a simultaneous
slight decrease in the prediction for the average charm yield in those decays.
The proposed new interaction modifies within the present experimental limits
the predictions for differences of lifetimes among B mesons, and can thus be
probed by more precise data on these differences. A sample model is briefly
discussed, where the new interaction arises through a weak SU(2) singlet scalar
field with quantum numbers of a diquark.Comment: 10 page
On the Parity Degeneracy of Baryons
The gross features of the observed baryon excitation spectrum below 2 GeV are
well explained if the spectrum generating algebra of its intrinsic orbital
angular momentum states is o(4)*su(2)_I. The spins of the resonances are
obtained through the coupling of a Lorentz bi-spinor (1/2,0)+ (0,1/ 2) to a
multiplet of the type (j,j) in its O(4)/O(3) reduction. The parities of the
resonances follow from those of the O(3) members of the (j,j) multiplets. In
this way relativistic SL(2,C) representations are constructed. For example, the
first S11, P11, and D13 states with masses around 1500 MeV fit into the (1/2,
1/2)* [(1/2,0)+(0,1/2)] representation. The observed parities of the resonances
correspond to natural parities of the (1/2,1/2) states. The second P11, S11,
D13- together with the first P13, F15, D15, and (a predicted) F17 -resonances,
centered around 1700 MeV, are organized into the (3/2,3/2)*[(1/2,0)+(0,1/2)]
representation. I argue that the members of the (3/2,3/2) multiplet carry
unnatural parities and that in this region chiral symmetry is restored. In the
N(939)- N(1650) transition the chiral symmetry mode is changed, and therefore,
a chiral phase transition is predicted to take place.Comment: 9 pages, LaTex, 1 figure; published in Mod.Phys.Lett. A12 (1997)
2373; minor misprints corrected, no statement change
Mass effect in polarization investigation at BEPC/BES and the B-factory
We consider the annihilation process of an electron-positron pair into a pair
of heavier fermions when the initial electron and position beams are polarized.
By calculating the polarization of the final-state particles, we discuss in
detail the effect due to the produced particle masses in the -charm
energy region at BEPC/BES, and also compare the effect with that at the
B-factory. Such a study is useful for the design of possible polarization
investigation at the BEPC/BES facility and the B-factory.Comment: 7 latex pages, 4 figure
New U(1) Gauge Symmetry of Quarks and Leptons
Instead of anchoring the seesaw mechanism with the conventional heavy
right-handed neutrino singlet, a small Majorana neutrino mass may be obtained
just as well with the addition of a heavy triplet of leptons per family to the
minimal standard model of particle interactions. The resulting model is shown
to have the remarkable property of accommodating a new U(1) symmetry which is
anomaly-free and may thus be gauged. There are many possible phenomenological
consequences of this proposal which may be already relevant in explaining one
or two recent potential experimental discrepancies.Comment: minor word changes, to appear in MPL
S_4 Flavor Symmetry Embedded into SU(3) and Lepton Masses and Mixing
Based on an assumption that an S_4 flavor symmetry is embedded into SU(3), a
lepton mass matrix model is investigated. A Frogatt-Nielsen type model is
assumed, and the flavor structures of the masses and mixing are caused by VEVs
of SU(2)_L-singlet scalars \phi_u and \phi_d which are nonets (8+1) of the
SU(3) flavor symmetry, and which are broken into 2+3+3' and 1 of S_4. If we
require the invariance under the transformation (\phi^{(8)},\phi^{(1)}) \to
(-\phi^{(8)},+\phi^{(1)}) for the superpotential of the nonet field
\phi^{(8+1)}, the model leads to a beautiful relation for the charged lepton
masses. The observed tribimaximal neutrino mixing is understood by assuming two
SU(3) singlet right-handed neutrinos \nu_R^{(\pm)} and an SU(3) triplet scalar
\chi.Comment: 12 pages, no figure, to appear on JHE
Dalitz plot slope parameters for decays and two particle interference
We study the possible distortion of phase-space in the decays , which may result from final state interference among the decay products.
Such distortion may influence the values of slope parameters extracted from the
Dalitz plot distribution of these decays. We comment on the consequences on the
magnitude of violation of the rule in these decays.Comment: 17 pages, LaTex2e, 6 figures, v2 authors' affiliation modified, to
appear in Mod. Phys. Lett.
Regularizing the quark-level model
We show that the finite difference, , between quadratic and
logarithmic divergent integrals ,
as encountered in the linear model, is in fact regularization
independent.Comment: 9 pages, 2 figures, Latex, to appear in Mod. Phys. Lett.
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