897 research outputs found
Colorless States in Perturbative QCD: Charmonium and Rapidity Gaps
We point out that an unorthodox way to describe the production of rapidity
gaps in deep inelastic scattering, recently proposed by Buchm\"uller and
Hebecker, suggests a description of the production of heavy quark bound states
which is in agreement with data. The approach questions the conventional
treatment of the color quantum number in perturbative QCD.Comment: 14 pages, plain Latex, 9 postscript figures included. Uses epsf.sty.
Postscript file of paper with figures also available at
http://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-919.ps.Z or at
ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-919.ps.
Nonresonant Contributions in B->rho pi Decay
We consider nonresonant contributions in the Dalitz plot analysis of B->rho
pi->pi^+ pi^- pi^0 decay and their potential impact on the extraction of the
CKM parameter alpha. In particular, we examine the role of the heavy mesons B^*
and B_0, via the process B->pi (B^*, B_0)->pi^+ pi^- pi^0, and their
interference with resonant contributions in the rho-mass region. We discuss the
inherent uncertainties and suggest that the effects may be substantially
smaller than previously indicated.Comment: 15 pages, 3 figures; minor changes, version to appear in Phys. Rev.
Dynamical ionization ignition of clusters in intense and short laser pulses
The electron dynamics of rare gas clusters in laser fields is investigated
quantum mechanically by means of time-dependent density functional theory. The
mechanism of early inner and outer ionization is revealed. The formation of an
electron wave packet inside the cluster shortly after the first removal of a
small amount of electron density is observed. By collisions with the cluster
boundary the wave packet oscillation is driven into resonance with the laser
field, hence leading to higher absorption of laser energy. Inner ionization is
increased because the electric field of the bouncing electron wave packet adds
up constructively to the laser field. The fastest electrons in the wave packet
escape from the cluster as a whole so that outer ionization is increased as
well.Comment: 8 pages, revtex4, PDF-file with high resolution figures is available
from http://mitarbeiter.mbi-berlin.de/bauer/publist.html, publication no. 24.
Accepted for publication in Phys. Rev.
Quasi-coherent fluctuations limiting the pedestal growth on Alcator C-Mod: experiment and modelling
Performance predictions for future fusion devices rely on an accurate model of the pedestal structure. The candidate for predictive pedestal structure is EPED, and it is imperative to test the underlying hypotheses to further gain confidence for ITER projections. Here, we present experimental work testing one of the EPED hypotheses, namely the existence of a soft limit set by microinstabilities such as the kinetic ballooning mode. This work extends recent work on Alactor C-Mod (Diallo et al 2014 Phys. Rev. Lett. 112 115001), to include detailed measurements of the edge fluctuations and comparisons of edge simulation codes and experimental observations
Observing Direct CP Violation in Untagged B-Meson Decays
Direct CP violation can exist in untagged B-meson decays to self-conjugate,
three-particle final states; it would be realized as a population asymmetry in
the untagged decay rate across the mirror line of the Dalitz plot of the
three-body decay. We explore the numerical size of this direct CP-violating
effect in a variety of B-meson decays to three pseudoscalar mesons; we show
that the resulting asymmetry is comparable to the partial rate asymmetry in the
analogous tagged decays, making the search for direct CP violation in the
untagged decay rate, for which greater statistics accrue, advantageous.Comment: 31 pages, REVTeX4, 1 eps figure, references added, typos corrected,
version to appear in PR
Quantitative Tests of Color Evaporation: Charmonium Production
The color evaporation model simply states that charmonium production is
described by the same dynamics as production, {\em i.e.}, by the
formation of a colored pair. Its color happens to be bleached by
soft final-state interactions. We show that the model gives a complete picture
of charmonium production including low-energy production by proton, photon and
antiproton beams, and high-energy production at the Tevatron and HERA. Our
analysis includes the first next-to-leading-order calculation in the color
evaporation model.Comment: 12 pages (with embedded figures), Latex2.09, uses epsf.sty and
epsfig.sty. Z-compressed postscript version also available at
http://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-942.ps.Z or at
ftp://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-942.ps.
Grain Surface Models and Data for Astrochemistry
AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of âŒ25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
Measurement of three-jet differential cross sections d sigma-3jet / d M-3jet in p anti-p collisions at sqrt(s)=1.96 TeV
We present the first measurement of the inclusive three-jet differential
cross section as a function of the invariant mass of the three jets with the
largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96
TeV. The measurement is made in different rapidity regions and for different
jet transverse momentum requirements and is based on a data set corresponding
to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at
the Fermilab Tevatron Collider. The results are used to test the three-jet
matrix elements in perturbative QCD calculations at next-to-leading order in
the strong coupling constant. The data allow discrimination between
parametrizations of the parton distribution functions of the proton.Comment: 10 pages, 4 figures, 2 tables, submitted to Phys. Lett. B, corrected
chi2 values for NNPD
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