26,801 research outputs found
Neutrino factory in stages: Low energy, high energy, off-axis
We discuss neutrino oscillation physics with a neutrino factory in stages,
including the possibility of upgrading the muon energy within the same program.
We point out that a detector designed for the low energy neutrino factory may
be used off-axis in a high energy neutrino factory beam. We include the
re-optimization of the experiment depending on the value of theta_13 found. As
upgrade options, we consider muon energy, additional baselines, a detector mass
upgrade, an off-axis detector, and the platinum (muon to electron neutrino)
channels. In addition, we test the impact of Daya Bay data on the optimization.
We find that for large theta_13 (theta_13 discovered by the next generation of
experiments), a low energy neutrino factory might be the most plausible minimal
version to test the unknown parameters. However, if a higher muon energy is
needed for new physics searches, a high energy version including an off-axis
detector may be an interesting alternative. For small theta_13 (theta_13 not
discovered by the next generation), a plausible program could start with a low
energy neutrino factory, followed by energy upgrade, and then baseline or
detector mass upgrade, depending on the outcome of the earlier phases.Comment: 23 pages, 10 (color) figures. Minor clarifications and changes. Final
version to appear in PR
Geometry of canonical self-similar tilings
We give several different geometric characterizations of the situation in
which the parallel set of a self-similar set can be described
by the inner -parallel set of the associated
canonical tiling , in the sense of \cite{SST}. For example,
if and only if the boundary of the
convex hull of is a subset of , or if the boundary of , the
unbounded portion of the complement of , is the boundary of a convex set. In
the characterized situation, the tiling allows one to obtain a tube formula for
, i.e., an expression for the volume of as a function of
. On the way, we clarify some geometric properties of canonical
tilings.
Motivated by the search for tube formulas, we give a generalization of the
tiling construction which applies to all self-affine sets having empty
interior and satisfying the open set condition. We also characterize the
relation between the parallel sets of and these tilings.Comment: 20 pages, 6 figure
Minimal Neutrino Beta Beam for Large theta_13
We discuss the minimum requirements for a neutrino beta beam if theta_13 is
discovered by an upcoming reactor experiment, such as Double Chooz or Daya Bay.
We require that both neutrino mass hierarchy and leptonic CP violation can be
measured to competitive precisions with a single-baseline experiment in the
entire remaining theta_13 range. We find that for very high isotope production
rates, such as they might be possible using a production ring, a (B,Li) beta
beam with a gamma as low as 60 could already be sufficient to perform all of
these measurements. If only the often used nominal source luminosities can be
achieved, for example, a (Ne,He) beta beam from Fermilab to a possibly existing
water Cherenkov detector at Homestake with gamma \sim 190-350 (depending on the
Double Chooz best-fit) could outperform practically any other beam technology
including wide-band beam and neutrino factory.Comment: 11 pages, 2 figures, 1 tabl
The crystal structure of Haloferax volcanii proliferating cell nuclear antigen reveals unique surface charge characteristics due to halophilic adaptation
Background:
The high intracellular salt concentration re
quired to maintain a halophilic lifestyle poses challenges to haloarchaeal proteins that must stay soluble, stable and functional in this extreme environment. Proliferating cell nuclear antigen (PCNA) is a fundamental protein involved in maintaining genome integrity, with roles in both DNA replication and repair. To investigate the halophilic adaptation of such a key protein we have crystallised and solved the structure of Haloferax volcanii PCNA
(HvPCNA) to a resolution of 2.0 Ã….
Results: The overall architecture of HvPCNA is very similar to other known PCNAs, which are highly structurally conserved. Three commonly observed adaptations in halophilic proteins are higher surface acidity, bound ions and increased numbers of intermolecular ion pairs (in oligomeric proteins). HvPCNA possesses the former two adaptations but not the latter, despite functioning
as a homotrimer. Strikingly, the positive surface charge considered key to PCNA's role as a sliding clamp is dramatically reduced in the halophilic protein. Instead, bound cations within the solvation shell of HvPCNA may permit sliding along negatively charged DNA by reducing electrostatic repulsion effects.
Conclusion: The extent to which individual proteins
adapt to halophilic conditions varies, presumably due to their diverse characteristics and roles within the cell. The number of ion pairs observed in the HvPCNA monomer-monomer interface wasunexpectedly low. This may reflect
the fact that the trimer is intrinsically stable over a wide range of salt concentrations and therefore
additional modifications for trimer maintenance in high salt conditions are not required. Halophilic
proteins frequently bind anions and cations and in
HvPCNA cation binding may compensate for the
remarkable reduction in positive charge in the pore region, to facilitate functional interactions with DNA. In this way,
HvPCNA may harness its environment as opposed to simply surviving in extreme halophilic conditions
Lattice-type self-similar sets with pluriphase generators fail to be Minkowski measurable
A long-standing conjecture of Lapidus claims that under certain conditions,
self-similar fractal sets fail to be Minkowski measurable if and only if they
are of lattice type. The theorem was established for fractal subsets of
by Falconer, Lapidus and v.~Frankenhuijsen, and the forward
direction was shown for fractal subsets of , , by
Gatzouras. Since then, much effort has been made to prove the converse. In this
paper, we prove a partial converse by means of renewal theory. Our proof allows
us to recover several previous results in this regard, but is much shorter and
extends to a more general setting; several technical conditions appearing in
previous versions of this result have now been removed.Comment: 20 pages, 6 figure
Heavy Hyperon--Antihyperon Production
Based on the experience from the production of anti-Lambda Lambda and
anti-Sigma Sigma pairs at LEAR (experiment PS185) it is suggested to continue
the investigations towards the heavier antihyperon--hyperon pairs anti-Xi Xi
and anti-Omega Omega in view of: (1) the production dynamics of the heavier
antihyperon--hyperon out of the anti-p p annihilation (2) a comparison of the
(3s 3anti-s quark system) anti-Omega Omega to the (3 (anti-s s)) 3 phi meson
production, where both systems have similar masses (3.345 and 3.057,
respectively) and identical valence quark content. A systematic study of the
antihyperon--hyperon production with increasing strangeness content is
interesting for the following reasons: The anti-Omega Omega production is the
creation of two spin 3/2 objects out of the two spin 1/2 anti-p p particles.
Results of the PS185 experiments prove a clear dominance of the spin triplet
anti-s s dissociation. In the Omega anti-Omega the three s-quarks (three anti-s
quarks) are aligned to spin 3/2 each. If the three anti-s s pairs are now all
in spin triplet configurations when created out of the gluonic interaction they
should have spin parity quantum number as 3^- as long as Omega anti-Omega is
created with relative L=0 angular momentum. The comparison of the Omega
anti-Omega baryon pair to the phi phi phi three meson production (where the
three anti-s s quark pairs might not but can be produced without relative
correlation) would provide a unique determination of the intermediate matter
state. Measurements of excitation functions and polarization transfers should
be used to examine these gluon rich anti-p p --> anti-Omega Omega and anti-p p
--> phi phi phi reaction channels. Such experiments should be performed at the
PANDA detector at the FAIR facility of the GSI.Comment: 4 pages, 2 figures, Presented at LEAP05: International Conference on
Low Energy Antiproton Physics, Bonn - Juelich, Germany, May 16-22, 200
Pointwise tube formulas for fractal sprays and self-similar tilings with arbitrary generators
In a previous paper by the first two authors, a tube formula for fractal
sprays was obtained which also applies to a certain class of self-similar
fractals. The proof of this formula uses distributional techniques and requires
fairly strong conditions on the geometry of the tiling (specifically, the inner
tube formula for each generator of the fractal spray is required to be
polynomial). Now we extend and strengthen the tube formula by removing the
conditions on the geometry of the generators, and also by giving a proof which
holds pointwise, rather than distributionally.
Hence, our results for fractal sprays extend to higher dimensions the
pointwise tube formula for (1-dimensional) fractal strings obtained earlier by
Lapidus and van Frankenhuijsen.
Our pointwise tube formulas are expressed as a sum of the residues of the
"tubular zeta function" of the fractal spray in . This sum ranges
over the complex dimensions of the spray, that is, over the poles of the
geometric zeta function of the underlying fractal string and the integers
. The resulting "fractal tube formulas" are applied to the important
special case of self-similar tilings, but are also illustrated in other
geometrically natural situations. Our tube formulas may also be seen as fractal
analogues of the classical Steiner formula.Comment: 43 pages, 13 figures. To appear: Advances in Mathematic
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