1,736,358 research outputs found
The dS/dS Correspondence
We present a holographic duality for the de Sitter static patch which
consolidates basic features of its geometry and the behavior of gravity and
brane probes, valid on timescales short compared to the decay or Poincare
recurrence times. Namely de Sitter spacetime in dimensions with
curvature radius is holographically dual to two conformal field theories on
, cut off at an energy scale 1/R where they couple to each other
and to dimensional gravity. As part of our analysis, we study brane
probes in de Sitter and thermal Anti de Sitter spaces, and interpret the terms
in the corresponding DBI action via strongly coupled thermal field theory. This
provides a dual field theoretic interpretation of the fact that probes take
forever to reach a horizon in general relativity.Comment: 29 pages, harvmac big; 3 figures; v2: references added, minor typo
fixe
Ds+ -- Ds- Asymmetry in Photoproduction
Considering of the possible difference in strange and antistrange quark
distributions inside nucleon, we investigate the Ds+ -- Ds- asymmetry in
photoproduction in the framework of heavy-quark recombination mechanism. We
adopt two distribution models of strange sea, those are the light-cone
meson-baryon fluctuation model and the effective chiral quark model. Our
results show that the asymmetry induced by the strange quark distributions is
distinct, which is measurable in experiments. And, there are evident
differences between the predictions of our calculation and previous estimation.
Therefore, the experimental measurements on the Ds+ -- Ds- asymmetry may impose
a unique restriction on the strange-antistrange distribution asymmetry models.Comment: 11 page, 5 figure
Suppressed Decays of D_s^+ Mesons to Two Pseudoscalar Mesons
Using data collected near the Ds*+ Ds- peak production energy Ecm = 4170 MeV
by the CLEO-c detector, we study the decays of Ds+ mesons to two pseudoscalar
mesons. We report on searches for the singly-Cabibbo-suppressed Ds+ decay modes
K+ eta, K+ eta', pi+ K0S, K+ pi0, and the isospin-forbidden decay mode Ds+ to
pi+ pi0. We normalize with respect to the Cabibbo-favored Ds+ modes pi+ eta,
pi+ eta', and K+ K0S, and obtain ratios of branching fractions: Ds+ to K+ eta /
Ds+ to pi+ eta = (8.9 +- 1.5 +- 0.4)%, Ds+ to K+ eta' / Ds+ to pi+ eta' = (4.2
+- 1.3 +- 0.3)%, Ds+ to pi+ K0S / Ds+ to K+ K0S = (8.2 +- 0.9 +- 0.2)%, Ds+ to
K+ pi0 / Ds+ to K+ K0S = (5.0 +- 1.2 +- 0.6)%, and Ds+ to pi+ pi0 / Ds+ to K+
K0S < 4.1% at 90% CL, where the uncertainties are statistical and systematic,
respectively.Comment: 9 pages postscript,also available through
http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PR
Study of Cabibbo Suppressed Decays of the Ds Charmed-Strange Meson involving a KS
We study the decay of Ds meson into final states involving a Ks and report
the discovery of Cabibbo suppressed decay modes Ds -> Kspi-pi+pi+ (179 +/- 36
events) and Ds -> Kspi+ (113 +/-26 events). The branching ratios for the new
modes are Gamma(Ds -> Kspi-pi+pi+)/Gamma(Ds -> KsK-pi+pi+) = 0.18 +/- 0.04 +/-
0.05 and Gamma(Ds -> Kspi+)/Gamma(Ds -> KsK+) = 0.104 +/- 0.024 +/- 0.013.Comment: 11 pages, 6 figure
Observation of the DsJ(2317) and DsJ(2457) in B decays
We report the first observation of the B --> Dbar DsJ(2317) and B --> Dbar
DsJ(2457) decays based on 123.8 10^6 BBar events collected with the Belle
detector at KEKB. We observe the DsJ(2317) decay to Ds pi0 and DsJ(2457) decay
to the Ds* pi0 and Ds gamma final states. We also set 90% CL upper limits for
the decays DsJ(2317) --> Ds* gamma, DsJ(2457) --> Ds* gamma, DsJ(2457) --> Ds
pi0 and DsJ(2457) --> Ds pi+ pi-.Comment: 6 pages, 3 figures. A few minor corrections. Replaced by version
accepted to publication in Phys. Rev. Let
Evidence for B- -> Ds+ K- l- nubar and search for B- -> Ds*+ K- l- nubar
We report measurements of the decays B- -> Ds(*)+ K- l- nubar in a data
sample containing 657x10^6 BBbar pairs collected with the Belle detector at the
KEKB asymmetric-energy e+e- collider. We observe a signal with a significance
of 6 sigma for the combined Ds and Ds* modes and find the first evidence of the
B- -> Ds+ K- l- nubar decay with a significance of 3.4 sigma. We measure the
following branching fractions: BF(B- -> Ds+ K- l nubar) = (0.30 +/- 0.09(stat)
+0.11 -0.08(syst)) x 10^-3 and BF(B- -> Ds*+ K- l- nubar) = (0.59 +/-
0.12(stat) +/- 0.15(syst)) x 10^-3 and set an upper limit BF(B- -> Ds*+ K- l-
nubar) < 0.56 x 10^-3 at the 90% confidence level. We also present the first
measurement of the Ds+K- invariant mass distribution in these decays, which is
dominated by a prominent peak around 2.6 GeV/c^2.Comment: Submitted to Phys. Rev.
Search for the W-exchange decays B0 --> Ds(*)- Ds(*)+
We report a search for the decays , , in a sample of 232
million decays to \BBb ~pairs collected with the \babar detector
at the PEP-II asymmetric-energy storage ring. We find no significant
signal and set upper bounds for the branching fractions: and at 90% confidence level.Comment: 8 pages, 2 figures, submitted to PRD-R
Measurement of Charm Production Cross Sections in e+e- Annihilation at Energies between 3.97 and 4.26 GeV
Using the CLEO-c detector at the Cornell Electron Storage Ring, we have
measured inclusive and exclusive cross sections for the production of D+, D0
and Ds+ mesons in e+e- annihilations at thirteen center-of-mass energies
between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final
states consisting of two charm mesons (DD, D*D, D*D*, Ds+Ds-, Ds*+Ds-, and
Ds*+Ds*-) and for processes in which the charm-meson pair is accompanied by a
pion. No enhancement in any final state is observed at the energy of the
Y(4260).Comment: 19 pages, postscript also available through
http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PR
Improved Measurement of the Pseudoscalar Decay Constant
We present a new determination of the Ds decay constant, f_{Ds} using 5
million continuum charm events obtained with the CLEO II detector. Our value is
derived from our new measured ratio of widths for Ds -> mu nu/Ds -> phi pi of
0.173+/- 0.021 +/- 0.031. Taking the branching ratio for Ds -> phi pi as (3.6
+/- 0.9)% from the PDG, we extract f_{Ds} = (280 +/- 17 +/- 25 +/- 34){MeV}. We
compare this result with various model calculations.Comment: 23 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Evidence for Special Relativity with de Sitter Space-Time Symmetry
I show the formulation of de Sitter Special Relativity (dS-SR) based on
Dirac-Lu-Zou-Guo's discussions. dS-SR quantum mechanics is formulated, and the
dS-SR Dirac equation for hydrogen is suggested. The equation in the earth-QSO
framework reference is solved by means of the adiabatic approach. It's found
that the fine-structure "constant" in dS-SR varies with time. By means
of the relation of the CDM model, 's time-dependency
becomes redshift -dependent. The dS-SR's predictions of
agree with data of spectra of 143 quasar absorption
systems, the dS-space-time symmetry is SO(3,2) (i.e., anti-dS group) and
the universal parameter (de Sitter ratio) in dS-SR is estimated to be
. The effects of dS-SR become visible at the
cosmic space-time scale (i.e., the distance ). At that scale
dS-SR is more reliable than Einstein SR. The -variation with time is an
evidence of SR with de Sitter symmetry.Comment: 5 pages, 3 figure
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