1,185 research outputs found
How many sigmas is the solar neutrino effect?
The minimal standard electroweak model can be tested by allowing all the
solar neutrino fluxes, with undistorted energy spectra, to be free parameters
in fitting the measured solar neutrino event rates, subject only to the
condition that the total observed luminosity of the sun is produced by nuclear
fusion. The rates of the five experiments prior to SNO (chlorine, Kamiokande,
SAGE, GALLEX, Super-Kamiokande) cannot be fit by an arbitrary choice of
undistorted neutrino fluxes at the level of 2.5 sigma (formally 99% C.L.).
Considering just SNO and Super-Kamiokande, the discrepancy is at the 3.3 sigma
level(10^{-3} C.L.). If all six experiments are fit simultaneously, the formal
discrepancy increases to 4 sigma (7*10^{-5} C.L.). If the relative scaling in
temperature of the nuclear reactions that produce 7Be and 8B neutrinos is taken
into account, the formal discrepancy is at the 7.4 sigma level.Comment: 1 figure; related information at http://www.sns.ias.edu/~jn
Recursion Rules for Scattering Amplitudes in Non-Abelian Gauge Theories
We present a functional derivation of recursion rules for scattering
amplitudes in a non-Abelian gauge theory in a form valid to arbitrary loop
order. The tree-level and one-loop recursion rules are explicitly displayed.Comment: 18 pages, RevTeX, 2 postscript figures, a reference added, minor
typographical errors correcte
Quantum integrability of the Alday-Arutyunov-Frolov model
We investigate the quantum integrability of the Alday-Arutyunov-Frolov (AAF)
model by calculating the three-particle scattering amplitude at the first
non-trivial order and showing that the S-matrix is factorizable at this order.
We consider a more general fermionic model and find a necessary constraint to
ensure its integrability at quantum level. We then show that the quantum
integrability of the AAF model follows from this constraint. In the process, we
also correct some missed points in earlier works.Comment: 40 pages; Replaced with published version. Appendix and comments
adde
On-Shell Recursion Relations for Generic Theories
We show that on-shell recursion relations hold for tree amplitudes in generic
two derivative theories of multiple particle species and diverse spins. For
example, in a gauge theory coupled to scalars and fermions, any amplitude with
at least one gluon obeys a recursion relation. In (super)gravity coupled to
scalars and fermions, the same holds for any amplitude with at least one
graviton. This result pertains to a broad class of theories, including QCD, N=4
SYM, and N=8 supergravity.Comment: 19 pages, 3 figure
Large Extra Dimension Effects on the Spin Configuration of the Top Quark Pair at e^+ e^- Colliders
Large extra dimension effects on the spin configuration of the top quark pair
at the process are studied. It is shown that the TeV
scale quantum gravity effects cause significant deviations from the Standard
Model predictions for the spin configuration in the off-diagonal basis: they
lead to substantial cross sections of the like-spin states of the top quark
pair, which vanish in the SM; they weaken the pure dominance of the processes,
the Up-Down (Down-Up) spin states for the left-handed (right-handed) beam. In
addition it is shown that the angular cut is very effective
to determine the sign of the quantum gravity corrections.Comment: A discussion on the angular distribution is added with a tabl
Probability of a Solution to the Solar Neutrino Problem Within the Minimal Standard Model
Tests, independent of any solar model, can be made of whether solar neutrino
experiments are consistent with the minimal Standard Model (stable, massless
neutrinos). If the experimental uncertainties are correctly estimated and the
sun is generating energy by light-element fusion in quasi-static equilibrium,
the probability of a standard-physics solution is less than 2%. Even when the
luminosity constraint is abandoned, the probability is not more than 4%. The
sensitivity of the conclusions to input parameters is explored.Comment: PRL, Revtex, 1 figure, 5 page
Simplifying Algebra in Feynman Graphs, Part III: Massive Vectors
A T-dualized selfdual inspired formulation of massive vector fields coupled
to arbitrary matter is generated; subsequently its perturbative series modeling
a spontaneously broken gauge theory is analyzed. The new Feynman rules and
external line factors are chirally minimized in the sense that only one type of
spin index occurs in the rules. Several processes are examined in detail and
the cross-sections formulated in this approach. A double line formulation of
the Lorentz algebra for Feynman diagrams is produced in this formalism, similar
to color ordering, which follows from a spin ordering of the Feynman rules. The
new double line formalism leads to further minimization of gauge invariant
scattering in perturbation theory. The dualized electroweak model is also
generated.Comment: 39 pages, LaTeX, 8 figure
The Mikheyev-Smirnov-Wolfenstein Effect as a Probe of the Solar Interior
We relate the MSW effect to the efective absorption of the electronic
collective motion energy by retaining the imaginary part of the index of
refraction associated with the charged-current scattering and show that the
small angle MSW solution to the solar neutrino anomaly can be used as a probe
of the physical conditions of the solar interior if it is correct. We find that
the constraint on the absorption imposed by the small angle MSW solution and
the theoretical estimate of the absorption by the Boltzmann kinetic theory are
consistent, which shows that a consistent theoretical picture can be developed
when plasma absorption processes are taken into account.Comment: 4 pages, no figure, REVTeX, to appear in Phys. Rev.
Complete Equivalence Between Gluon Tree Amplitudes in Twistor String Theory and in Gauge Theory
The gluon tree amplitudes of open twistor string theory, defined as contour
integrals over the ACCK link variables, are shown to satisfy the BCFW
relations, thus confirming that they coincide with the corresponding amplitudes
in gauge field theory. In this approach, the integration contours are specified
as encircling the zeros of certain constraint functions that force the
appropriate relation between the link variables and the twistor string
world-sheet variables. To do this, methods for calculating the tree amplitudes
using link variables are developed further including diagrammatic methods for
organizing and performing the calculations.Comment: 38 page
Towards Field Theory Amplitudes From the Cohomology of Pure Spinor Superspace
A simple BRST-closed expression for the color-ordered super-Yang-Mills
5-point amplitude at tree-level is proposed in pure spinor superspace and shown
to be BRST-equivalent to the field theory limit of the open superstring 5-pt
amplitude. It is manifestly cyclic invariant and each one of its five terms can
be associated to the five Feynman diagrams which use only cubic vertices. Its
form also suggests an empirical method to find superspace expressions in the
cohomology of the pure spinor BRST operator for higher-point amplitudes based
on their kinematic pole structure. Using this method, Ansaetze for the 6- and
7-point 10D super-Yang-Mills amplitudes which map to their 14 and 42
color-ordered diagrams are conjectured and their 6- and 7-gluon expansions are
explicitly computed.Comment: 14 pages, harvmac, v4: trivial edits in the text to comply with JHEP
refere
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