1,743 research outputs found
Transverse momentum dependence in gluon distribution and fragmentation functions
We investigate the twist two gluon distribution functions for spin 1/2
hadrons, emphasizing intrinsic transverse momentum of the gluons. These
functions are relevant in leading order in the inverse hard scale in scattering
processes such as inclusive leptoproduction or Drell-Yan scattering, or more
general in hard processes in which at least two hadrons are involved. They show
up in azimuthal asymmetries. For future estimates of such observables, we
discuss specific bounds on these functions.Comment: 14 pages, revtex, 7 Postscript figure
Natural Theories of Ultra-Low Mass PNGB's: Axions and Quintessence
We consider the Wilson Line PNGB which arises in a U(1)^N gauge theory,
abstracted from a latticized, periodically compactified extra dimension U(1).
Planck scale breaking of the PNGB's global symmetry is suppressed, providing
natural candidates for the axion and quintessence. We construct an explicit
model in which the axion may be viewed as the 5th component of the U(1)_Y gauge
field in a 1+4 latticized periodically compactified extra dimension. We also
construct a quintessence PNGB model where the ultra-low mass arises from
Planck-scale suppressed physics itself.Comment: 20 pages, fixed typo and reference
Deuteron Electroweak Disintegration
We study the deuteron electrodisintegration with inclusion of the neutral
currents focusing on the helicity asymmetry of the exclusive cross section in
coplanar geometry. We stress that a measurement of this asymmetry in the quasi
elastic region is of interest for an experimental determination of the weak
form factors of the nucleon, allowing one to obtain the parity violating
electron neutron asymmetry. Numerically, we consider the reaction at low
momentum transfer and discuss the sensitivity of the helicity asymmetry to the
strangeness radius and magnetic moment. The problems coming from the finite
angular acceptance of the spectrometers are also considered.Comment: 30 pages, Latex, 7 eps figures, submitted to Phys.Rev.C e-mail:
[email protected] , [email protected]
Reply to Martinez-Garcia et al. and to Abreu and Punjabi
Abstract not availableBastien Lechat, Ph.D., Peter Catcheside, Ph.D. Amy Reynolds, Ph.D. Robert J. Adams, M.D. R. Doug McEvoy, M.D. Danny J. Eckert, Ph.D
Searching for Lee-Wick Gauge Bosons at the LHC
In an extension of the Standard Model(SM) based on the ideas of Lee and Wick,
Grinstein, O'Connell and Wise have found an interesting way to remove the usual
quadratically divergent contributions to the Higgs mass induced by radiative
corrections. Phenomenologically, the model predicts the existence of Terascale,
negative-norm copies of the usual SM fields with rather unique properties:
ghost-like propagators and negative decay widths, but with otherwise SM-like
couplings. The model is both unitary and causal on macroscopic scales. In this
paper we examine whether or not such states with these unusual properties can
be uniquely identified as such at the LHC. We find that in the extended strong
and electroweak gauge boson sector of the model, which is the simplest one to
analyze, such an identification can be rather difficult. Observation of heavy
gluon-like resonances in the dijet channel offers the best hope for this
identification.Comment: 17 pages, 4 figs; discussion adde
Parity violating target asymmetry in electron - proton scattering
We analyze the parity-violating (PV) components of the analyzing power in
elastic electron-proton scattering and discuss their sensitivity to the strange
quark contributions to the proton weak form factors. We point out that the
component of the analyzing power along the momentum transfer is independent of
the electric weak form factor and thus compares favorably with the PV beam
asymmetry for a determination of the strangeness magnetic moment. We also show
that the transverse component could be used for constraining the strangeness
radius. Finally, we argue that a measurement of both components could give
experimental information on the strangeness axial charge.Comment: 24 pages, Latex, 5 eps figures, submitted to Phys.Rev.
On the Role of Higher Twist in Polarized Deep Inelastic Scattering
The higher twist corrections to the spin dependent proton and
neutron structure functions are extracted in a model
independent way from experimental data on and found to be
non-negligible. It is shown that the NLO QCD polarized parton densities
determined from the data on g1, including higher twist effects, are in good
agreement with those found earlier from our analysis of the data on g1/F1 and
A1 where higher twist effects are negligible. On the contrary, the LO QCD
polarized parton densities obtained from the data on g1, including higher
twist, differ significantly from our previous results.Comment: 18 pages, latex, 6 figures, final version which will be published in
Phys. Rev. D, fig. 5 is changed, misprints in Table 2 are remove
Longitudinal quark polarization in transversely polarized nucleons.
Accounting for transverse momenta of the quarks, a longitudinal quark spin asymmetry exists in a transversely polarized nucleon target. The relevant leading quark distribution g_{1T}(x,k_T^2) can be measured in the semi-inclusive deep-inelastic scattering. The average k_T^2 weighted distribution function g^{(1)}_{1T} can be obtained directly from the inclusive measurement of g_2
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