2,653 research outputs found
Short-Wave Excitations in Non-Local Gross-Pitaevskii Model
It is shown, that a non-local form of the Gross-Pitaevskii equation allows to
describe not only the long-wave excitations, but also the short-wave ones in
the systems with Bose-condensate. At given parameter values, the excitation
spectrum mimics the Landau spectrum of quasi-particle excitations in superfluid
Helium with roton minimum. The excitation wavelength, at which the roton
minimum exists, is close to the inter-particle interaction range. It is shown,
that the existence domain of the spectrum with a roton minimum is reduced, if
one accounts for an inter-particle attraction.Comment: 5 pages, 5 figures, UJP style; presented at Bogolyubov Kyiv
Conference "Modern Problems of Theoretical and Mathematical Physics",
September 15-18, 200
Reversible and Irreversible Interactions of Poly(3-hexylthiophene) with Oxygen Studied by Spin-Sensitive Methods
Understanding of degradation mechanisms in polymer:fullerene
bulk-heterojunctions on the microscopic level aimed at improving their
intrinsic stability is crucial for the breakthrough of organic photovoltaics.
These materials are vulnerable to exposure to light and/or oxygen, hence they
involve electronic excitations. To unambiguously probe the excited states of
various multiplicities and their reactions with oxygen, we applied combined
magneto-optical methods based on multifrequency (9 and 275 GHz) electron
paramagnetic resonance (EPR), photoluminescence (PL), and PL-detected magnetic
resonance (PLDMR) to the conjugated polymer poly(3-hexylthiophene) (P3HT) and
polymer:fullerene bulk heterojunctions (P3HT:PCBM; PCBM =
[6,6]-phenyl-C61-butyric acid methyl ester). We identified two distinct
photochemical reaction routes, one being fully reversible and related to the
formation of polymer:oxygen charge transfer complexes, the other one,
irreversible, being related to the formation of singlet oxygen under
participation of bound triplet excitons on the polymer chain. With respect to
the blends, we discuss the protective effect of the methanofullerenes on the
conjugated polymer bypassing the triplet exciton generation
Measurement of decay rate and parameters at KEDR
Using the inclusive photon spectrum based on a data sample collected at the
peak with the KEDR detector at the VEPP-4M collider, we
measured the rate of the radiative decay as well
as mass and width. Taking into account an asymmetric photon
lineshape we obtained keV, MeV/, MeV.Comment: 6 pages, 3 figure
Evidence for B to K eta' gamma Decays at Belle
We present the results of a search for the radiative decay (B -> K eta'
gamma) and find evidence for (B^+ -> K^+ eta' gamma) decays at the 3.3 standard
deviation level with a partial branching fraction of (3.6 +/- 1.2 +/- 0.4) x
10e-6, where the first error is statistical and the second systematic. This
measurement is restricted to the region of combined (K eta') invariant mass
less than 3.4GeVc^2. A 90% confidence level upper limit of 6.4 x 10e-6 is
obtained for the decay (B^0 -> K^0 eta' gamma) in the same (K eta') invariant
mass region. These results are obtained from a 605 fb^-1 data sample containing
657 x 10e6 B anti-B pairs collected at the Upsilon(4S) resonance with the Belle
detector at the KEKB asymmetric-energy e^+e^- collider.Comment: 5 pages, 4 figures. Submitted to PRD-RC on 6/8/0
Measurement of the near-threshold cross section using initial-state radiation
We report measurements of the exclusive cross section for , where or , in the center-of-mass energy range from the threshold to with initial-state radiation. The
analysis is based on a data sample collected with the Belle detector with an
integrated luminosity of 673 .Comment: Presented at EPS07 and LP07 conferences, published in PRD(RC
Measurement of J/psi to eta_c gamma at KEDR
We present a study of the inclusive photon spectra from 5.9 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c
width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV,
G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
Measurement of B(J/psi->eta_c gamma) at KEDR
We present a study of the inclusive photon spectrum from 6.3 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of the radiative decay J/psi -> eta_c gamma,
eta_c width and mass. Taking into account an asymmetric photon line shape we
obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4
+- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.Comment: 6 pages, 1 figure. To be published in the proceedings of the 4th
International Workshop on Charm Physics (Charm2010), October 21-24, 2010,
IHEP, Beijin
Observation of b --> d gamma and Determination of |V_td/V_ts|
We report the observation of the flavor-changing neutral current process b
--> d gamma using a sample of 386*10^6 B meson pairs accumulated by the Belle
detector at the KEKB e+ e- collider. We measure branching fractions for the
exclusive modes B- --> rho- gamma, B0bar --> rho0 gammaand B0bar --> omega
gamma. Assuming that these three modes are related by isospin, we find Br(B -->
(rho,omega) gamma) = (1.32 +0.34-0.31(stat.) +0.10-0.09(syst.)) * 10^-6 with a
significance of 5.1 sigma. This result is used to determine the ratio of CKM
matrix elements |V_td/V_ts| to be 0.199 +0.026-0.025(exp.) +0.018-0.015(theo.).Comment: 5 pages, 2 figures, submitted to Physical Review Letter
Measurement of phi_3 with Dalitz plot analysis of B+ -> D(*)K(*)+ decay
We present a measurement of the unitarity triangle angle phi_3 using a Dalitz
plot analysis of the K0_S pi+ pi- decay of the neutral D meson from the B+- ->
D(*)K(*)+- process. The method employs the interference between D0 and D0bar to
extract the angle phi_3, strong phase Delta and the ratio r of suppressed and
allowed amplitudes. We apply this method to a 357 fb-1 data sample collected by
the Belle experiment. The analysis uses three modes: B+ -> DK+, B+ -> D*K+ with
D* -> Dpi0, and B+ -> DK*+ with K*+ -> K0_S pi+, as well as the corresponding
charge-conjugate modes. From a combined maximum likelihood fit to the three
modes, we obtain phi_3=53+15-18(stat)+-3(syst)+-9(model) degrees. The
corresponding two standard deviation interval is 8<phi_3<111 degrees.Comment: 18 pages, 6 figures, 7 tables. To be submitted to Phys. Rev.
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