448 research outputs found
A new algorithm for anisotropic solutions
We establish a new algorithm that generates a new solution to the Einstein
field equations, with an anisotropic matter distribution, from a seed isotropic
solution. The new solution is expressed in terms of integrals of an isotropic
gravitational potential; and the integration can be completed exactly for
particular isotropic seed metrics. A good feature of our approach is that the
anisotropic solutions necessarily have an isotropic limit. We find two examples
of anisotropic solutions which generalise the isothermal sphere and the
Schwarzschild interior sphere. Both examples are expressed in closed form
involving elementary functions only.Comment: 16 pages, to appear in Pramana - J. Phy
Compact anisotropic spheres with prescribed energy density
New exact interior solutions to the Einstein field equations for anisotropic
spheres are found. We utilise a procedure that necessitates a choice for the
energy density and the radial pressure. This class contains the constant
density model of Maharaj and Maartens (Gen. Rel. Grav., Vol 21, 899-905, 1989)
and the variable density model of Gokhroo and Mehra (Gen. Rel. Grav., Vol 26,
75-84, 1994) as special cases. These anisotropic spheres match smoothly to the
Schwarzschild exterior and gravitational potentials are well behaved in the
interior. A graphical analysis of the matter variables is performed which
points to a physically reasonable matter distribution.Comment: 22 pages, 3 figures, to appear in Gen. Rel. Gra
Search for the h_c meson in B^+- ->h_c K^+-
We report a search for the meson via the decay chain , \etac \gamma with and
. No significant signals are observed. We obtain upper limits on the
branching fractions for in bins of the
invariant mass. The results are based on an analysis of 253
fb of data collected by the Belle detector at the KEKB
collider.Comment: 12 pages, 6 figures, submitted to Phys. Rev.
Nonlocal Equation of State in Anisotropic Static Fluid Spheres in General Relativity
We show that it is possible to obtain credible static anisotropic spherically
symmetric matter configurations starting from known density profiles and
satisfying a nonlocal equation of state. These particular types of equation of
state describe, at a given point, the components of the corresponding
energy-momentum tensor not only as a function at that point, but as a
functional throughout the enclosed configuration. To establish the physical
plausibility of the proposed family of solutions satisfying nonlocal equation
of state, we study the constraints imposed by the junction and energy
conditions on these bounded matter distributions.
We also show that it is possible to obtain physically plausible static
anisotropic spherically symmetric matter configurations, having nonlocal
equations of state\textit{,}concerning the particular cases where the radial
pressure vanishes and, other where the tangential pressures vanishes. The later
very particular type of relativistic sphere with vanishing tangential stresses
is inspired by some of the models proposed to describe extremely magnetized
neutron stars (magnetars) during the transverse quantum collapse.Comment: 21 pages, 1 figure, minor changes in the text, references added, two
new solutions studie
Study of the Baryon-Antibaryon Low-Mass Enhancements in Charmless Three-body Baryonic B Decays
The angular distributions of the baryon-antibaryon low-mass enhancements seen
in the charmless three-body baryonic B decays B+ -> p pbar K+, B0 -> p pbar Ks,
and B0 -> p Lambdabar pi- are reported. A quark fragmentation interpretation is
supported, while the gluonic resonance picture is disfavored. Searches for the
Theta+ and Theta++ pentaquarks in the relevant decay modes and possible
glueball states G with 2.2 GeV/c2 < M-ppbar < 2.4 GeV/c2 in the ppbar systems
give null results. We set upper limits on the products of branching fractions,
B(B0 -> Theta+ p)\times B(Theta+ -> p Ks) Theta++
pbar) \times B(Theta++ -> p K+) G K+) \times
B(G -> p pbar) < 4.1 \times 10^{-7} at the 90% confidence level. The analysis
is based on a 140 fb^{-1} data sample recorded on the Upsilon(4S) resonance
with the Belle detector at the KEKB asymmetric-energy e+e- collider.Comment: 14 pages, 13 figure files, update of hep-ex/0409010 for journal
submisssio
Evidence of the Purely Leptonic Decay B- --> tau- nu_tau-bar
We present the first evidence of the decay B- --> tau- nu_tau-bar using 414
fb^-1 of data collected at the Upsilon(4S) resonance with the Belle detector at
the KEKB asymmetric-energy e+e- collider. Events are tagged by fully
reconstructing one of the B mesons in hadronic modes. We detect the signal with
a significance of 3.5 standard deviations including systematics, and measure
the branching fraction to be Br(B- --> tau- nu_tau-bar) = (1.79
+0.56-0.49(stat) +0.46-0.51(syst))*10^-4. This implies that f_B = 0.229
+0.036-0.031(stat) +0.034-0.037(syst) GeV and is the first direct measurement
of this quantity.Comment: 6 pages, 3 figures, to appear in Physical Review Letter
Observation of B+->Lambda_c+Lambda_c-K+ and B0->Lambda_c+Lambda_c^-K0 decays
We report first measurements of the doubly charmed baryonic B decays
B->Lambda_c+Lambda_c-K. The B+->Lambda_c+Lambda_c-K+ decay is observed with a
branching fraction of (6.5+1.0-0.9+-1.1+-3.4)x10^{-4} and a statistical
significance of 15.4sigma. The B0->Lambda_c+Lambda_c-K0 decay is observed with
a branching fraction of (7.9+2.9-2.3+-1.2+-4.2)x10^{-4} and a statistical
significance of 6.6sigma. The branching fraction errors are statistical,
systematic, and the error resulting from the uncertainty of Lambda_c+->pK-pi+
decay branching fraction. The analysis is based on 357fb-1 of data accumulated
at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e+e-
collider.Comment: 10 pages, 3 figure
Study of CP Violating Effects in Time Dependent Decays
We report measurements of time dependent decay rates for decays and extraction of CP violation parameters
containing . Using fully reconstructed events from a data sample collected at the resonance, we obtain
the CP violation parameters for and decays, , where is
the ratio of the magnitudes of the doubly-Cabibbo-suppressed and
Cabibbo-favoured amplitudes, and is the strong phase
difference between them. Under the assumption of being
close to either 0 or , we obtain and .Comment: 9 pages, 3 figures, Submitted to Physical Review Letter
Measurement of the wrong-sign decays D0 -> K+ pi- pi0 and D0 -> K+ pi- pi+ pi-, and search for CP violation
Using 281 fb^-1 of data from the Belle experiment recorded at or near the
Upsilon(4S) resonance, we have measured the rates of the ``wrong-sign'' decays
D0 -> K+ pi- pi0 and D0 -> K+ pi- pi+ pi- relative to those of the
Cabibbo-favored decays D0 -> K- pi+ pi0 and D0 -> K- pi+ pi+ pi-. These
wrong-sign decays proceed via a doubly Cabibbo-suppressed amplitude or via
D0-D0bar mixing; the latter has not yet been observed. We obtain
R_WS(Kpipi0)=[0.229 +/-0.017(stat.) +0.013-0.009(sys.)]% and R_WS(K3pi)=[0.320
+/-0.019(stat.) +0.018-0.013(sys.)]%. The CP asymmetries are measured to be
-0.006 +/- 0.053 and -0.018 +/- 0.044 for the K+ pi- pi0 and K+ pi- pi+ pi-
final states, respectively.Comment: 10 pages, 3 figures, submitted to PRL, Lepton-Photon 2005 Conference
in Uppsala, Sweden and HEP2005 Europhysics Conference in Lisboa, Portuga
Observation of B0->pi0pi0
We report the first observation of the decay B0->pi0pi0, using a 253/fb data
sample collected at the Upsilon(4S) resonance with the Belle detector at the
KEKB e+e- collider. The measured branching fraction is BF(B0->pi0pi0) = {2.32
+0.4-0.5(stat) +0.2-0.3(syst)} x 10^-6, with a significance of 5.8 standard
deviations including systematic uncertainties. We also make the first
measurement of the direct CP violating asymmetry in this mode.Comment: 6 pages, 2 figures, submitted to ICHEP04, Beijing and Physical Review
Letters. v2: a possible pile-up background is checked and a systematic error
for it is include
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