8,300 research outputs found
Probing Contact Interactions at High Energy Lepton Colliders
Fermion compositeness and other new physics can be signalled by the presence
of a strong four-fermion contact interaction. Here we present a study of
and contact interactions using the
reactions: at future
linear colliders with TeV and colliders
with TeV. We find that very large compositeness scales can be
probed at these machines and that the use of polarized beams can unravel their
underlying helicity structure.Comment: 12 pg, to appear in the {\it Proceedings of the 1996 DPF/DPB Summer
Study on New Directions for High Energy Physics - Snowmass96}, Snowmass, CO,
25 June - 12 July, 199
Comment on 's and the H1 and ZEUS High Anomalies
We investigate the effects of extra neutral gauge bosons on the high
region of the cross section at GeV. We found
that the only models with electroweak strength coupling, typical of extended
gauge theories, that give a better fit to the H1 and ZEUS high data than
the standard model, are ruled out by existing data from the Tevatron. From
general scaling arguments, using the allowed contact interactions, the only
allowed models with 's would be those with strong couplings although even
in this case the statistical evidence is not compelling.Comment: Latex file uses revtex version 3, epsfig, 1 postscript figure is
attache
Properties of the Charmed P-wave Mesons
Two broad charmed mesons, the D_0^* and D_1', have recently been observed. We
examine the quark model predictions for the D_0^* and D_1' properties and
discuss experimental measurements that can shed light on them. We find that
these states are well described as the broad, j=1/2 non-strange charmed P-wave
mesons. Understanding the D_0^* and D_1' states can provide important insights
into the D_{sJ}^*(2317), D_{sJ}(2460) states whose unexpected properties have
led to renewed interest in hadron spectroscopy.Comment: 7 pages. Some additional discussion and reference
Options for the SELEX state D_{s\J}^+(2632)
We consider possible assignments for the D_{s\J}^+(2632), which was
recently reported in D and DK final states by the SELEX
Collaboration at Fermilab. The most plausible quark model assignment for this
state is the first radial excitation () of the
D, although the predicted mass and strong decay branching fractions
for this assignment are not in agreement with the SELEX data. The reported
dominance of D over DK appears especially problematic. An intriguing
similarity to the K is noted. --^3\D_1 configuration
mixing is also considered, and we find that this effect is unlikely to resolve
the branching fraction discrepancy. Other interpretations as a -hybrid
or a two-meson molecule are also considered, but appear unlikely. Thus, if this
state is confirmed, it will require reconsideration of the systematics of
charmed meson spectroscopy and strong decays.Comment: 6 revtex4 pages, 2 eps figure
Properties of the Strange Axial Mesons in the Relativized Quark Model
We studied properties of the strange axial mesons in the relativized quark
model. We calculated the decay constant in the quark model and showed how
it can be used to extract the mixing angle
() from the weak decay . The ratio is the most sensitive
measurement and also the most reliable since the largest of the theoretical
uncertainties factor out. However the current bounds extracted from the
TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain
at 68\% C.L. We also calculated the
strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube
breaking model and extracted a mixing angle of . Our analysis also indicates that the heavy quark limit does not give a
good description of the strange mesons.Comment: Revised version to be published in Phys. Rev. D. Minor changes. Latex
file uses revtex version 3 and epsfig, 4 postcript figures are attached. The
full postcript version with embedded figures is available at
ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9512.ps.
Spin-Orbit and Tensor Forces in Heavy-quark Light-quark Mesons: Implications of the New Ds state at 2.32 GeV
We consider the spectroscopy of heavy-quark light-quark mesons with a simple
model based on the non-relativistic reduction of vector and scalar exchange
between fermions. Four forces are induced: the spin-orbit forces on the light
and heavy quark spins, the tensor force, and a spin-spin force. If the vector
force is Coulombic, the spin-spin force is a contact interaction, and the
tensor force and spin-orbit force on the heavy quark to order are
directly proportional. As a result, just two independent parameters
characterize these perturbations. The measurement of the masses of three p-wave
states suffices to predict the mass of the fourth. This technique is applied to
the system, where the newly discovered state at 2.32 GeV provides the
third measured level, and to the system. The mixing of the two
p-wave states is reflected in their widths and provides additional constraints.
The resulting picture is at odds with previous expectations and raises new
puzzles.Comment: 6 pages, 1 figur
Unusual High-Energy Phenomenology of Lorentz-Invariant Noncommutative Field Theories
It has been suggested that one may construct a Lorentz-invariant
noncommutative field theory by extending the coordinate algebra to additional,
fictitious coordinates that transform nontrivially under the Lorentz group.
Integration over these coordinates in the action produces a four-dimensional
effective theory with Lorentz invariance intact. Previous applications of this
approach, in particular to a specific construction of noncommutative QED, have
been studied only in a low-momentum approximation. Here we discuss
Lorentz-invariant field theories in which the relevant physics can be studied
without requiring an expansion in the inverse scale of noncommutativity.
Qualitatively, we find that tree-level scattering cross sections are
dramatically suppressed as the center-of-mass energy exceeds the scale of
noncommutativity, that cross sections that are isotropic in the commutative
limit can develop a pronounced angular dependence, and that nonrelativistic
potentials (for example, the Coloumb potential) become nonsingular at the
origin. We consider a number of processes in noncommutative QED that may be
studied at a future linear collider. We also give an example of scattering via
a four-fermion operator in which the noncommutative modifications of the
interaction can unitarize the tree-level amplitude, without requiring any other
new physics in the ultraviolet.Comment: 24 pages LaTeX, 4 eps figures (v2: reference added, v3: minor
clarifications
High-Energy Calibration of a BGO detector of the GLAST Burst Monitor
The understanding of the instrumental response of the GLAST Burst Monitor BGO
detectors at energies above the energy range which is accessible by common
laboratory radiation sources (< 4.43 MeV), is important, especially for the
later cross-calibration with the LAT response in the overlap region between ~
20 MeV to 30 MeV. In November 2006 the high-energy calibration of the GBM-BGO
spare detector was performed at the small Van-de-Graaff accelerator at SLAC.
High-energy gamma-rays from excited 8Be* (14.6 MeV and 17.5 MeV) and 16O* (6.1
MeV) were generated through (p,gamma)-reactions by irradiating a LiF-target.
For the calibration at lower energies radioactive sources were used. The
results, including spectra, the energy/channel-relation and the dependence of
energy resolution are presented.Comment: 2 pages, 1 figure; to appear in the Proc. of the First Int. GLAST
Symp. (Stanford, Feb. 5-8, 2007), eds. S.Ritz, P.F.Michelson, and C.Meegan,
AIP Conf. Pro
The East Australian Current as a free inertial jet
Paths of the East Australian Current are calculated, employing the assumption that changes in the total cross-stream vorticity due to path curvature are balanced by changes in the planetary vorticity and vortex stretching. With reasonable assumptions for the velocity structure, the resulting paths follow the continental slope for the whole known length of the current and then gradually move into deeper water...
Are There Oscillations in the Baryon/Meson Ratio?
All available data indicate a surplus of baryon states over meson states for
energies greater than about 1.5 GeV. Since hadron-scale string theory suggests
that their numbers should become equal with increasing energy, it has recently
been proposed that there must exist exotic mesons with masses just above 1.7
GeV in order to fill the deficit. We demonstrate that a string-like picture is
actually consistent with the present numbers of baryon and meson states, and in
fact predicts regular oscillations in their ratio. This suggests a different
role for new hadronic states.Comment: 14 pages (RevTeX), McGill/92-0
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