382 research outputs found
The Three-Nucleon System at Next-To-Next-To-Leading Order
We calculate higher order corrections for the three-nucleon system up to
next-to-next-to-leading within an effective field theory with contact
interactions alone. We employ a subtraction formalism previously developed and
for which it has been shown that no new three-body force counterterm is needed
for complete renormalization up to this order. We give results for the
neutron-deuteron phaseshifts and the triton binding energy. Our results are in
very good agreement with experimental results and calculations using realistic
nucleon-nucleon potentials.Comment: 4 pages, 2 eps figures, revised version to appear in PR
Dispersion -box correction to the weak charge of the proton
We consider elastic scattering of electrons off a proton target. The parity
violating (PV) asymmetry arises at leading order in due to
interference of and exchange. The radiative corrections to this
leading mechanism were calculated in the literature and included in
experimental analyses, except for box and cross-box contributions.
We present here a dispersion calculation of these corrections in forward
kinematics. We demonstrate that at the GeV energies of current PV experiments,
such corrections are not suppressed by the small vector weak charge of the
electron, as occurs in the atomic PV. Our results suggest that the current
theoretical uncertainty in the analysis of the QWEAK experiment might be
substantially underestimated, and more accurate account of the dispersion
corrections are needed in order to interprete the PV data.Comment: 4 pages, 3 figures, revtex
Reconstructing a Z' Lagrangian using the LHC and low-energy data
We study the potential of the LHC and future low-energy experiments to
precisely measure the underlying model parameters of a new Z' boson. We
emphasize the complimentary information obtained from both on- and off-peak LHC
dilepton data, from the future Q-weak measurement of the weak charge of the
proton, and from a proposed measurement of parity violation in low-energy
Moller scattering. We demonstrate the importance of off-peak LHC data and
Q-weak for removing sign degeneracies between Z' couplings that occur if only
on-peak LHC data is studied. A future precision measurement of low-energy
Moller scattering can resolve a scaling degeneracy between quark and lepton
couplings that remains after analyzing LHC dilepton data, permitting an
extraction of the individual Z' couplings rather than combinations of them. We
study how precisely Z' properties can be extracted for LHC integrated
luminosities ranging from a few inverse femtobarns to super-LHC values of an
inverse attobarn. For the several example cases studied with M_Z'=1.5 TeV, we
find that coupling combinations can be determined with relative uncertainties
reaching 30% with 30 fb^-1 of integrated luminosity, while 50% is possible with
10 fb^-1. With SLHC luminosities of 1 ab^-1, we find that products of quark and
lepton couplings can be probed to 10%.Comment: 36 pages, 17 figure
Constraints on a Parity-Conserving/Time-Reversal-Non-Conserving Interaction
Time-Reversal-Invariance non-conservation has now been unequivocally
demonstrated in a direct measurement at CPLEAR. What about tests of
time-reversal-invariance in systems other than the kaon system? Tests of
time-reversal-invariance belong to two classes: searches for parity violating
(P-odd)/time-reversal-invariance-odd (T-odd) interactions, and for P-even/T-odd
interactions (assuming CPT conservation this implies C-conjugation
non-conservation). Limits on a P-odd/T-odd interaction follow from measurements
of the electric dipole moment of the neutron (with a present upper limit of 6 x
10^-26 e.cm [95% C.L.]). It provides a limit on a P-odd/T-odd pion-nucleon
coupling constant which is less than 10^-4 times the weak interaction strength.
Experimental limits on a P-even/T-odd interaction are much less stringent.
Following the standard approach of describing the nucleon-nucleon interaction
in terms of meson exchanges, it can be shown that only charged rho-meson
exchange and A_1 meson exchange can lead to a P-even/T-odd interaction. The
better constraints stem from measurements of the electric dipole moment of the
neutron and from measurements of charge-symmetry breaking in neutron-proton
elastic scattering. The latter experiments were executed at TRIUMF (497 and 347
MeV) and at IUCF (183 MeV). Weak decay experiments may provide limits which
will possibly be comparable. All other experiments, like gamma decay
experiments, detailed balance experiments, polarization - analyzing power
difference determinations, and five-fold correlation experiments with polarized
incident nucleons and aligned nuclear targets, have been shown to be at least
an order of magnitude less sensitive.Comment: 15 pages LaTeX, including 5 PostScript figures. Uses ijmpe1.sty. To
appear in International Journal of Modern Physics E (IJMPE). Slight change in
short abstrac
Towards a knowledge-rich learning environment in preparatory secondary education
In this case study a novel educational programme for students in preparatory vocational education was studied. The research questions were: (1) Which teaching/learning processes occur in a simulated workplace using the concept of a knowledge-rich workplace? (2) What is the role of models and modelling in the teaching/learning processes? The curriculum project consisted of design and construction tasks. The students were collaboratively involved in the process of designing a tricycle for a real customer. This real-life activity creates opportunities for students to develop and use models, which can be used in more than in one context. The case study explored how the teachers deal with the students' explicit and implicit need for knowledge and skills. The main findings are that teachers more often provide this knowledge, rather than guide the students in reconstructing it, and towards the end of the project, knowledge tended to remain situated
Model Calculations for the Two-Fragment Electro-Disintegration of He
Differential cross sections for the electro-disintegration process are calculated, using a model in which
the final state interaction is included by means of a nucleon-nucleus (3+1)
potential constructed via Marchenko inversion. The required bound-state wave
functions are calculated within the integrodifferential equation approach
(IDEA). In our model the important condition that the initial bound state and
the final scattering state are orthogonal is fulfilled. The sensitivity of the
cross section to the input interaction in certain kinematical regions
is investigated. The approach adopted could be useful in reactions involving
few cluster systems where effective interactions are not well known and exact
methods are presently unavailable. Although, our Plane-Wave Impulse
Approximation results exhibit, similarly to other calculations, a dip in the
five-fold differential cross-section around a missing momentum of , it is argued that this is an artifact of the omission of re-scattering
four-nucleon processes.Comment: 16 pages, 6 figures, accepted for publication by Phys.Rev.
Updated Report Acceleration of Polarized Protons to 120-150 GeV/c at Fermilab
The SPIN@FERMI collaboration has updated its 1991-95 Reports on the
acceleration of polarized protons in Fermilab's Main Injector, which was
commissioned by Fermilab. This Updated Report summarizes some updated Physics
Goals for a 120-150 GeV/c polarized proton beam. It also contains an updated
discussion of the Modifications and Hardware needed for a polarized beam in the
Main Injector, along with an updated Schedule and Budget.Comment: 30 pages, 12 figure
Parity Violation in Proton-Proton Scattering at 221 MeV
The parity-violating longitudinal analyzing power, Az, has been measured in
pp elastic scattering at an incident proton energy of 221 MeV. The result
obtained is Az =(0.84 +/- 0.29 (stat.) +/- 0.17 (syst.)) x 10^{-7}. This
experiment is unique in that it selects a single parity violating transition
amplitude, 3P2-1D2, and consequently directly constrains the weak meson-nucleon
coupling constant h^pp_rho When this result is taken together with the existing
pp parity violation data, the weak meson-nucleon coupling constants h^pp_rho
and h^pp_omega can, for the first time, both be determined.Comment: 8 pages RevTeX4, 3 PostScript figures. Conclusion revised. New
information about weak coupling constants adde
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