20,899 research outputs found
Neutral scalar Higgs bosons in the USSM at the LHC
We study the possibility of discovering neutral scalar Higgs bosons in the
-extended supersymmetric standard model (USSM) at the CERN Large Hadron
Collider (LHC), by examining their productions via the exotic quark loop in the
gluon fusion process at leading order. It is possible in some parameter region
that the neutral scalar Higgs bosons may have stronger couplings with the
exotic quarks than with top quark. In this case, the exotic quarks may
contribute more significantly than top quark in productions of the neutral
scalar Higgs bosons in the gluon fusion process. We find that there is indeed
some parameter region in the USSM that supports our speculations.Comment: 18 pages; changed content; JPhys
Contiguous 3d and 4f magnetism: towards strongly correlated 3d electrons in YbFe2Al10
We present magnetization, specific heat, and 27Al NMR investigations on
YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic
susceptibility at low temperatures is strongly enhanced at weak magnetic
fields, accompanied by a ln(T0/T) divergence of the low-T specific heat
coefficient in zero field, which indicates a ground state of correlated
electrons. From our hard X-ray photo emission spectroscopy (HAXPES) study, the
Yb valence at 50 K is evaluated to be 2.38. The system displays valence
fluctuating behavior in the low to intermediate temperature range, whereas
above 400 K, Yb3+ carries a full and stable moment, and Fe carries a moment of
about 3.1 mB. The enhanced value of the Sommerfeld Wilson ratio and the dynamic
scaling of spin-lattice relaxation rate divided by T [27(1/T1T)] with static
susceptibility suggests admixed ferromagnetic correlations. 27(1/T1T)
simultaneously tracks the valence fluctuations from the 4f -Yb ions in the high
temperature range and field dependent antiferromagnetic correlations among
partially Kondo screened Fe 3d moments at low temperature, the latter evolve
out of an Yb 4f admixed conduction band.Comment: To appear in Phys. Rev. Let
Avalanche-Induced Current Enhancement in Semiconducting Carbon Nanotubes
Semiconducting carbon nanotubes under high electric field stress (~10 V/um)
display a striking, exponential current increase due to avalanche generation of
free electrons and holes. Unlike in other materials, the avalanche process in
such 1D quantum wires involves access to the third sub-band, is insensitive to
temperature, but strongly dependent on diameter ~exp(-1/d^2). Comparison with a
theoretical model yields a novel approach to obtain the inelastic optical
phonon emission length, L_OP,ems ~ 15d nm. The combined results underscore the
importance of multi-band transport in 1D molecular wires
Non-factorizable contribution in nonleptonic weak interactions of K mesons
Two pion decays of K mesons, K_L-K_S mass difference, two photon and the
Dalitz decays of K_L are studied systematically by assuming that their
amplitude is given by a sum of factorizable and non-factorizable ones. The
former is estimated by using a naive factorization while the latter is assumed
to be dominated by dynamical contributions of various hadron states.Comment: 23 pages,1 figur
Color-octet mechanism and J/psi polarization at LEP
Polarized heavy quarkonium productions in decays are considered. We
find that polarizations of the produced quarkonia are independent of that of
the parent Z^0 provided that one considers the energy distribution or the total
production rate. Produced J/psi's via the color-octet and the color- singlet
mechanisms are expected to be 19% and 29% longitudinally polarized,
respectively. The energy dependence of eta_{1,8}(x)=\frac{dGamma_{1,8}^L}{dx}
/\frac{dGamma_{1,8}}{d x} is very sensitive to the production mechanism, and
therefore the measurement of \eta(x)_exp will be an independent probe of the
color-octet mechanism.Comment: 15 pages, minor changes, version to be published in Phys. Rev.
Meanders and the Temperley-Lieb algebra
The statistics of meanders is studied in connection with the Temperley-Lieb
algebra. Each (multi-component) meander corresponds to a pair of reduced
elements of the algebra. The assignment of a weight per connected component
of meander translates into a bilinear form on the algebra, with a Gram matrix
encoding the fine structure of meander numbers. Here, we calculate the
associated Gram determinant as a function of , and make use of the
orthogonalization process to derive alternative expressions for meander numbers
as sums over correlated random walks.Comment: 85p, uuencoded, uses harvmac (l mode) and epsf, 88 figure
Search for X(3872) in gamma gamma Fusion and ISR at CLEO
We report on a search for the X(3872) state using 15.1 fb^{-1} of e+ e-
annihilation data taken with the CLEO III detector in the sqrt{s} = 9.46-11.30
GeV region. Separate searches for the production of X(3872) in untagged gamma
gamma fusion and e+ e- annihilation following initial state radiation are made
by taking advantage of the unique correlation of J/psi -> l+ l- in X(3872)
decay into J/psi pi+ pi-. No signals are observed in either case, and 90%
confidence upper limits are established as (2J+1)Gamma_{gammagamma}(X(3872))B(X
-> J/psi pi+ pi-) J/psi pi+ pi-) < 8.3
eV.Comment: 4 pages, 2 figures, to appear in the proceedings of the 1st Meeting
of the APS Topical Group on Hadronic Physics, Fermilab, Oct. 24-26, 200
Two-point motional Stark effect diagnostic for Madison Symmetric Torus
A high-precision spectral motional Stark effect (MSE) diagnostic provides internal magnetic field measurements for Madison Symmetric Torus (MST) plasmas. Currently, MST uses two spatial views-on the magnetic axis and on the midminor (off-axis) radius, the latter added recently. A new analysis scheme has been developed to infer both the pitch angle and the magnitude of the magnetic field from MSE spectra. Systematic errors are reduced by using atomic data from atomic data and analysis structure in the fit. Reconstructed current density and safety factor profiles are more strongly and globally constrained with the addition of the off-axis radius measurement than with the on-axis one only
Hadronic production calculated in the NRQCD factorization formalism
The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes
how to write quarkonium production rates as a sum of products of short-distance
coefficients times non-perturbative long-distance NRQCD matrix elements. We
present, in the true spirit of the factorization formalism, a detailed
calculation of the inclusive cross section for hadronic production. We
find that in addition to the well known {\it color-singlet} production
mechanisms, there are equally important mechanisms in which the pair
that forms the is initially produced in a {\it color-octet} state, in
either a , , or angular-momentum
configuration. In our presentation, we emphasize the ``matching'' procedure,
which %is the method that allows us to determine the short-distance
coefficients appearing in the factorization formula. We also point out how one
may systematically include relativistic corrections in these calculations.Comment: 25 pages, 3 postscript figures, use Revtex and epsfig.sty We fixed
some typos, added some text regarding a reference, and changed some
equations. The file will be available at http://phenom.physics.wisc.edu
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