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

Towards an Understanding of the New Charm and Charm-Strange Mesons

The observation of the D_{sJ}^*(2317), D_{sJ}(2460), and SELEX D^*_{sJ}(2632) states with properties differing considerably from what was expected has led to a renewed interest in hadron spectroscopy. In addition to these states, non-strange partners of the D_{sJ} states have also been observed. Understanding the D_0^* and D_1' states can provide important insights into the D_{sJ} states. In this contribution I examine quark model predictions for the D_0^* and D_1' states and discuss experimental measurements that can shed light on them. I find that these states are well described as the broad, j=1/2 non-strange charmed P-wave mesons. In the latter part of this writeup I discuss the c bar{s} possibilities for the SELEX D^*_{sJ}(2632) and measurements that can shed light on it.Comment: Talk presented at the 1st Meeting of the APS Topical Group on Hadronic Physics (Fermilab, Oct 24-26, 2004). 4 pages uses jpcon

First Observation of a New Narrow D_sJ Meson at 2632MeV/c^2

We report the first observation of a charm-strange meson D_sJ(2632) at a mass of 2632.5+/-1.7 MeV/c^2 in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D_s eta and D^0 K^+. In the D_s eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c^2. There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c^2 in the decay mode D^0 K^+. The relative branching ratio Gamma(D^0 K^+)/\Gamma(D_s eta) is 0.14+/-0.06. The full version of this paper has been accepted for publication in PRL (hep-ex/0406045). Here I have reproduced only the mass difference signal plots for the D_s eta and D^0 K^+ decay modes.Comment: 2 pages, 2 figures, to be published in the proceedings of "XXIV Physics in Collision", Boston, June 200

The ALICE CPV Detector

The Charged-Particle Veto (CPV) detector of ALICE at the LHC is presented. Physics motivation for the detector, its construction and operation in physics runs are shortly discussed. Readout electronics and data taking conditions are described. Special attention is focused on CPV automation via the detector control system. Different states of the detector and protection algorithms implemented into the control system are described

Reduction Techniques for Graph Isomorphism in the Context of Width Parameters

We study the parameterized complexity of the graph isomorphism problem when parameterized by width parameters related to tree decompositions. We apply the following technique to obtain fixed-parameter tractability for such parameters. We first compute an isomorphism invariant set of potential bags for a decomposition and then apply a restricted version of the Weisfeiler-Lehman algorithm to solve isomorphism. With this we show fixed-parameter tractability for several parameters and provide a unified explanation for various isomorphism results concerned with parameters related to tree decompositions. As a possibly first step towards intractability results for parameterized graph isomorphism we develop an fpt Turing-reduction from strong tree width to the a priori unrelated parameter maximum degree.Comment: 23 pages, 4 figure