11,644 research outputs found
Diffraction physics with ALICE at the LHC
The ALICE experiment is equipped with a wide range of detectors providing
excellent tracking and particle identification in the central region, as well
as forward detectors with extended pseudorapidity coverage, which are well
suited for studying diffractive processes. Cross section measurements of single
and double diffractive processes performed by ALICE in pp collisions at
~TeV will be reported. Currently, ALICE is studying
double-gap events in pp collisions at ~TeV, which give an insight
into the central diffraction processes: current status and future perspectives
will be discussed. The upgrade plans for diffraction studies, further extending
the pseudorapidity acceptance of the ALICE setup for the forthcoming Run 2 of
the LHC, will be outlined.Comment: 8 pages 5 figures, proceedings of talk given at XXXth International
Workshop on High Energy Physics "Particle and Astroparticle Physics,
Gravitation and Cosmology: Predictions, Observations and New Projects", June
23-27, 2014, in Protvino, Moscow region, Russi
Crucial Words and the Complexity of Some Extremal Problems for Sets of Prohibited Words
We introduced the notation of a set of prohibitions and give definitions of a
complete set and a crucial word with respect to a given set of prohibitions. We
consider 3 particular sets which appear in different areas of mathematics and
for each of them examine the length of a crucial word. One of these sets is
proved to be incomplete. The problem of determining lengths of words that are
free from a set of prohibitions is shown to be NP-complete, although the
related problem of whether or not a given set of prohibitions is complete is
known to be effectively solvable.Comment: 16 page
Characterization of Balanced Coherent Configurations
Let be a group acting on a finite set . Then acts on
by its entry-wise action and its orbits form the basis
relations of a coherent configuration (or shortly scheme). Our concern is to
consider what follows from the assumption that the number of orbits of on
is constant whenever and are
orbits of on . One can conclude from the assumption that the
actions of on 's have the same permutation character and are
not necessarily equivalent. From this viewpoint one may ask how many
inequivalent actions of a given group with the same permutation character there
exist. In this article we will approach to this question by a purely
combinatorial method in terms of schemes and investigate the following topics:
(i) balanced schemes and their central primitive idempotents, (ii)
characterization of reduced balanced schemes
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