156 research outputs found
Resumming the color-octet contribution to e+ e- -> J/psi + X
Recent observations of the spectrum of J/psi produced in e+ e- collisions at
the Upsilon(4S) resonance are in conflict with fixed-order calculations using
the Non-Relativistic QCD (NRQCD) effective field theory. One problem is that
leading order color-octet mechanisms predict an enhancement of the cross
section for J/psi with maximal energy that is not observed in the data.
However, in this region of phase space large perturbative corrections (Sudakov
logarithms) as well as enhanced nonperturbative effects are important. In this
paper we use the newly developed Soft-Collinear Effective Theory (SCET) to
systematically include these effects. We find that these corrections
significantly broaden the color-octet contribution to the J/psi spectrum. Our
calculation employs a one-stage renormalization group evolution rather than the
two-stage evolution used in previous SCET calculations. We give a simple
argument for why the two methods yield identical results to lowest order in the
SCET power counting.Comment: 27 pages, 7 figure
Power counting and effective field theory for charmonium
We hypothesize that the correct power counting for charmonia is in the
parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as
is HQET). This power counting leads to predictions which differ from those
resulting from the usual velocity power counting rules of NRQCD. In particular,
we show that while Lambda_QCD/m_c power counting preserves the empirically
verified predictions of spin symmetry in decays, it also leads to new
predictions which include: A hierarchy between spin singlet and triplet octet
matrix elements in the J/psi system. A quenching of the net polarization in
production at large transverse momentum. No end point enhancement in radiative
decays. We discuss explicit tests which can differentiate between the
traditional and new theories of NRQCD.Comment: 18 pages, 1 figure Replaced plot of the psi polarization parameter
alpha as a function of transverse momentum. Alpha is now closer to zero for
large transverse moment
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
Charmonium production at neutrino factories
At existing and planned neutrino factories (high energy and high intensity
neutrino beam facilities) precision studies of QCD in neutrino-nucleon
interactions are a realistic opportunity. We investigate charmonium production
in fixed target neutrino experiments. We find that production in
neutrino-nucleon collision is dominated by the color octet NRQCD matrix
element in a neutral current process, which is not accessible in photo or
leptoproduction. Neutrino experiments at a future Muon Collider will acquire
sufficient event rate to accurately measure color octet matrix element
contributions. The currently running high energy neutrino experiments, NOMAD
and NuTeV could also observe several such events.Comment: 13 pages Latex, with five embedded eps figures. Cosmetic fixups in
the figures, otherwise unchange
Inclusive wave charmonium productions in decays
The inclusive wave charmonium production rates in decays are
considered using the Bodwin-Braaten-Lepage (BBL) approach, including the
relativistic corrections and the color-octet mechanism suggested as a possible
solution to the puzzle at the Tevatron. We first consider
relativistic and radiative corrections to and
Light Hadrons (LH), in order to determine two
nonperturbative parameters, , , in the
factorization formulae for these decays. Using these two matrix elements and
including the color-octet state contribution, we get a
moderate increase in the decay rates for decays into . Our results, for GeV, get closer to the recent CLEO data.
As a byproduct, we prefer a larger decay rate for LH
compared to the present data.Comment: 12 page
Fragmentation Functions for Lepton Pairs
We calculate the fragmentation function for a light quark to decay into a
lepton pair to leading order in the QCD coupling constant. In the formal
definition of the fragmentation function, a QED phase must be included in the
eikonal factor to guarantee QED gauge invariance. We find that the longitudinal
polarization fraction is a decreasing function of the factorization scale, in
accord with the intuitive expectation that the virtual photon should behave
more and more like a real photon as the transverse momomentum of the
fragmenting quark increases.Comment: 13 pages, 4 figures, normalization corrected, text abbreviate
The complete chloroplast genome of pearl millet (Pennisetum glaucum (L.) R. Br.) and comparative analysis within the family poaceae
The complete chloroplast (cp) genome sequence of Pearl millet (Pennisetum glaucum [L.] R. Br.), an important grain and forage crop in the family Poaceae, is reported in this study. The complete cp genome sequence of P. glaucum is 138,172 bp in length with 38.6% overall GC content and exhibits a typical quadripartite structure comprising one pair of inverted repeat (IR) regions (22,275 bp) separated by a small single-copy (SSC) region (12,409 bp) and a large single-copy (LSC) region (81,213). The P. glaucum cp genome encodes 110 unique genes, 76 of which are protein-coding genes, 4 ribosomal RNA (rRNA) genes, 30 transfer RNA (tRNA) genes and 18 duplicated genes in the IR region. Nine genes contain one or two introns. Whole genome alignments of cp genome were performed for genome-wide comparison. Locally collinear blocks (LCBs) identified among the cp genomes showed that they were well conserved with respect to gene organization and order. This newly determined cp genome sequence of P. glaucum will provide valuable information for the future breeding programs of valuable cereal crops in the family Poaceae
Noncommutative brane-world, (Anti) de Sitter vacua and extra dimensions
We investigate a curved brane-world, inspired by a noncommutative D3-brane,
in a type IIB string theory. We obtain, an axially symmetric and a spherically
symmetric, (anti) de Sitter black holes in 4D. The event horizons of these
black holes possess a constant curvature and may be seen to be governed by
different topologies. The extremal geometries are explored, using the
noncommutative scaling in the theory, to reassure the attractor behavior at the
black hole event horizon. The emerging two dimensional, semi-classical, black
hole is analyzed to provide evidence for the extra dimensions in a curved
brane-world. It is argued that the gauge nonlinearity in the theory may be
redefined by a potential in a moduli space. As a result, D=11 and D=12
dimensional geometries may be obtained at the stable extrema of the potential.Comment: 17 pages, 1 figur
Thermodynamic and gravitational instability on hyperbolic spaces
We study the properties of anti--de Sitter black holes with a Gauss-Bonnet
term for various horizon topologies (k=0, \pm 1) and for various dimensions,
with emphasis on the less well understood k=-1 solution. We find that the zero
temperature (and zero energy density) extremal states are the local minima of
the energy for AdS black holes with hyperbolic event horizons. The hyperbolic
AdS black hole may be stable thermodynamically if the background is defined by
an extremal solution and the extremal entropy is non-negative. We also
investigate the gravitational stability of AdS spacetimes of dimensions D>4
against linear perturbations and find that the extremal states are still the
local minima of the energy. For a spherically symmetric AdS black hole
solution, the gravitational potential is positive and bounded, with or without
the Gauss-Bonnet type corrections, while, when k=-1, a small Gauss-Bonnet
coupling, namely, \alpha << {l}^2 (where l is the curvature radius of AdS
space), is found useful to keep the potential bounded from below, as required
for stability of the extremal background.Comment: Shortened to match published (PRD) version, 18 pages, several eps
figure
Understanding museum vacationers’ eco-friendly decision-making process: Strengthening the VBN framework
In the present research, the process of vacationers’ pro-environmental decision formation for environmentally responsible museums was examined. This research employed and broadened the value-belief-norm theory, using satisfaction with green product use, green trust, and frequency of past behavior for green product use as predictors. A structural equation modeling was utilized for modeling comparisons and hypothesis testing. A measurement model tested using the data gathered at museums was found to satisfactorily fit to the data. Newly integrated constructs significantly improved the prediction power of the theory. In addition, results of the structural equation modeling generally supported the proposed relationships. Moreover, a salient role of moral norm was identified. As expected, new environmental paradigm, awareness of consequences, ascribed responsibility, and moral norm played an important mediating role. A parsimonious model with greater prediction power than the original value-belief-norm theory was produced through modeling comparisons and the process of testing relationships among research variables. Our results offer a sufficient understanding of vacationers’ pro-environmental intention for eco-friendly museums
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