659 research outputs found
Helicity conservation and factorization-suppressed charmless B decays
Toward the goal of extracting the weak angle alpha, the decay B^0/B^0-bar to
a_0^{+/-}pi^{-/+} was recently measured. The decay B^0 to a_0^+pi^- is not only
forbidden in the factorization limit of the tree interaction, but also strongly
suppressed for the penguin interaction if short-distance QCD dominates. This
makes extraction of alpha very difficult from a^{+/-}\pi^{-/+}. We examine the
simlar factorization-suppressed decays, in particular, B^0\to b_1^+pi^-. The
prospect of obtaining alpha is even less promising with b_1^{+/-}pi^{-/+}. To
probe how well the short-distance dominance works, we emphasize importance of
testing helicity conservation in the charmless B decays with spins.Comment: The version to appear in Phys. Rev. D after minor alteration
Insights into the magnetic dead layer in La0.7Sr0.3MnO3 thin films from temperature, magnetic field and thickness dependence of their magnetization
Experimental investigations of the magnetic dead layer in 7.6 nm thick film of La0.7Sr0.3MnO3 (LSMO) are reported. The dc magnetization (M) measurements for a sample cooled to T = 5 K in applied field H = 0 reveal the presence of negative remanent magnetization (NRM) in the M vs. H (magnetic field) measurements as well as in the M vs. T measurements in H = 50 Oe and 100 Oe. The M vs. T data in ZFC (zero-field-cooled) and FC (field-cooled) protocols are used to determine the blocking temperature TB in different H. Isothermal hysteresis loops at differ- ent T are used to determine the temperature dependence of saturation magnetization (MS), remanence (MR) and coercivity HC. The MS vs. T data are fit to the Bloch law,MS (T)=M0 (1–BT 3/2),showingagoodfitforT \u3c100Kandyieldingthe nearest-neighbor exchange constant J/kB 18 K. The variations of TB vs. H andHC vs. T are well described by the model often used for randomly oriented mag- netic nanoparticles with magnetic domain diameter ≈ 9 nm present in the dead-layer of thickness d =1.4 nm. Finally, the data available from literature on the thickness (D) variation of Curie temperature (TC) and MS of LSMO films grown under 200, 150, and 0.38 mTorr pressures of O2 are analyzed in terms of the finite-size scaling, with MS vs. D data fit to MS (D) = MS(b)(1-d/D) yielding the dead layer thickness d = 1.1 nm, 1.4 nm and 2.4 nm respectively
In vitro micropropagation and ex vitro acclimation of Bupleurum kaoi - An endangered medicinal plant native to Taiwan
This study reports an improved protocol for in vitro-shoot multiplication and ex vitro acclimation of Bupleurum kaoi, an endangered medicinal herb. Nodal segments were cultured in half-strength Murashige and Skoog (MS) basal medium supplemented with different concentrations of benzyladenine (BA) and kinetin. The presence of 0.25 mg l(-1) BA induced the highest number of shoots per explant after 8 wk of culture. Although BA was more effective than kinetin on shoot multiplication, it induced hyperhydric shoots at all concentrations tested. The use of dispense paper (DP) instead of aluminum foil (AF) for container closure was found to reduce hyperhydricity and improve ex vitro acclimation. The best survival rate (61%) was obtained when plantlets were grown in MS basal medium containing 0.5 mg l(-1) indole-3-butyric acid and 0.1-0.2 mg l(-1) alpha-naphthaleneacetic acid using DP as container closure. Leaves of the plant treated with AF6 (two layers of AF as container closure and 6 wk of incubation) lacked epicuticular wax and possessed larger stomata, higher stomata density, and fewer functional stomata compared to those of plants treated with AF2+DP4 (two layers of AF for 2 wk, then replaced AF by three layers of DP for 4 wk) and ex vitro-acclimated plantlets
Helicity conservation in inclusive nonleptonic decay B to VX: Test of long-distance final state interaction
The polarization measurement in the inclusive B decay provides us with a
simple test of how much the long-distance final-state interaction takes place
as the energy of the observed meson varies in the final state. We give the
expectation of the perturbative QCD for the energy dependence of the helicity
fractions in a semiquantitative form. Experiment will tell us for which decay
processes the perturbative calculation should be applicable.Comment: 15 pages in Revtex with 3 figures embedde
Final-state interaction and s-quark helicity conservation in B -> J/psi K*
The Section of charm quark spin conservation is deleted since it involves
more dynamical assumptions than previously stated. A few comments are added in
view of new experimental results.Comment: To replace the earlier version of hep-ph/0106354. Minor additions and
one deletion with no change in the main argument nor the conclusio
Bulk-sensitive photoemission spectroscopy of A_2FeMoO_6 double perovskites (A=Sr, Ba)
Electronic structures of Sr_2FeMoO_6 (SFMO) and Ba_2FeMoO_6 (BFMO) double
perovskites have been investigated using the Fe 2p->3d resonant photoemission
spectroscopy (PES) and the Cooper minimum in the Mo 4d photoionization cross
section. The states close to the Fermi level are found to have strongly mixed
Mo-Fe t_{2g} character, suggesting that the Fe valence is far from pure 3+. The
Fe 2p_{3/2} XAS spectra indicate the mixed-valent Fe^{3+}-Fe^{2+}
configurations, and the larger Fe^{2+} component for BFMO than for SFMO,
suggesting a kind of double exchange interaction. The valence-band PES spectra
reveal good agreement with the LSDA+U calculation.Comment: 4 pages, 3 figure
Internal W-emmission and W-exchange Contributions to {\bf B}\to {{\bf D}^{(*)} Decays
We evaluate external -emission, internal -emission and -exchange
contributions to nonleptonic decays based on the perturbative
QCD formalism including Sudakov effects, whose ratio is found to be
at the amplitude level. We observe that the internal
-emission contribution is additive to the external -emission
contribution, and that the -exchange contribution is negligible and mainly
imaginary, its real part being at least one order of magnitude smaller than the
imaginary part. Our predictions are consistent with the CLEO data and with
those obtained by the Bauer-Stech-Wirbel method.Comment: 13 pages, Latex, 1 Postscript fil
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Observation of Orbitally Excited B_s Mesons
We report the first observation of two narrow resonances consistent with
states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed
as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+,
\bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1})
= 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let
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