203 research outputs found
Helicity Amplitudes for Charmonium Production in Hadron-Hadron and Photon-Hadron Collisions
We present the gluon-gluon and photon-gluon helicity amplitudes for color
singlet and octet charmonium production in polarized and unpolarized
hadron-hadron and photon-hadron collisions.Comment: 11 pages amstex no figure
Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation
We propose measurements of the deeply virtual Compton amplitude (DVCS),
gamma* to H H-bar gamma, in the timelike t = (p_{H} + p_{H-bar})^2 > 0
kinematic domain which is accessible at electron-positron colliders via the
radiative annihilation process e+ e- to H H-bar gamma. These processes allow
the measurement of timelike deeply virtual Compton scattering for a variety of
H H-bar hadron pairs such as pi+ pi-, K+ K-, and D D-bar as well as p p-bar. As
in the conventional spacelike DVCS, there are interfering coherent amplitudes
contributing to the timelike processes involving C= - form factors. The
interference between the amplitudes measures the phase of the C=+ timelike DVCS
amplitude relative to the phase of the timelike form factors and can be
isolated by considering the forward-backward e+ \leftrightarrow e- asymmetry.
The J=0 fixed pole contribution which arises from the local coupling of the two
photons to the quark current plays a special role. As an example we present a
simple model.Comment: 9 pages, 8 figures; v2 has improved kinematic discussio
A UV completion of scalar electrodynamics
In previous works, we constructed UV-finite and unitary scalar field theories
with an infinite spectrum of propagating modes for arbitrary polynomial
interactions. In this paper, we introduce infinitely many massive vector fields
into a U(1) gauge theory to construct a theory with UV-finiteness and
unitarity.Comment: 25 page
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
Associated production as a probe of the polarized gluon distribution
Associated production of and a has recently been proposed
as clean probe of the gluon distribution. The same mechanism can be used to
probe the polarized gluon content of the proton in polarized proton-proton
collisions. We study production at both polarized fixed
target and polarized collider energies.Comment: 16 pages (10 figures available from M.A.D.), MAD/PH/745, SNUTP 93-6,
YUMS 93-
From the exclusive photoproduction of heavy quarkonia at HERA to the EDDE at TeVatron and LHC
Exclusive photoproduction of heavy quarkonia at HERA is analyzed in the
framework of the Regge-eikonal approach together with the nonrelativistic bound
state formalism. Total and differential cross-sections for the process
are calculated. The model predicts
cross-sections of Exclusive Double Diffractive Events (EDDE) at TeVatron and
LHC.Comment: 14 pages, 6 figures, reference is adde
J/\psi production through resolved photon processes at e+ e- colliders
We consider J/psi photoproduction in e+ e- as well as linear photon
colliders. We find that the process is dominated by the resolved photon
channel. Both the once-resolved and twice-resolved cross-sections are sensitive
to (different combinations of) the colour octet matrix elements. Hence, this
may be a good testing ground for colour octet contributions in NRQCD. On the
other hand, the once-resolved J/psi production cross-section, particularly in a
linear photon collider, is sensitive to the gluon content of the photon. Hence
these cross-sections can be used to determine the parton distribution
functions, especially the gluon distribution, in a photon, if the colour octet
matrix elements are known.Comment: Added a figure on parametrisation dependence of photonic parton
densities and some reference
The heavy quark decomposition of the S-matrix and its relation to the pinch technique
We propose a decomposition of the S-matrix into individually gauge invariant
sub-amplitudes, which are kinematically akin to propagators, vertices, boxes,
etc. This decompsition is obtained by considering limits of the S-matrix when
some or all of the external particles have masses larger than any other
physical scale. We show at the one-loop level that the effective gluon
self-energy so defined is physically equivalent to the corresponding gauge
independent self-energy obtained in the framework of the pinch technique. The
generalization of this procedure to arbitrary gluonic -point functions is
briefly discussed.Comment: 11 uuencoded pages, NYU-TH-94/10/0
Professional boundaries: crossing a line or entering the shadows?
This article explores the professional boundaries guidance for social workers. It presents research findings from the formal literature, from agency codes of practice, from telephone interviews with regulatory and professional bodies and from an exercise using ‘snowballing techniques’ in which informants responded to brief scenarios illustrating boundary dilemmas. The findings suggest that formal research plays little part in the guidance that individuals use to help them determine professional boundaries. Similarly, only 10–15 per cent of informants made regular reference to regulatory and professional codes of practice, with an even smaller percentage quoting specific sections from these codes. A slightly larger group (15–20 per cent) made fairly regular reference to their agency's policy documents. However, a clear majority relied on their own sense of what is appropriate or inappropriate, and made their judgements with no reference to any formal guidance. Agency guidance tended to ignore the ambiguous areas of practice and seemed to act as an insurance policy, brought out and dusted off when something goes awry. The authors caution against ever-increasing bullet points of advice and prescription, and advance a notion of ethical engagement in which professionals exercise their ethical senses through regular discussion of professional boundary dilemmas
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