354449
The Resolvent Algebra: A New Approach to Canonical Quantum Systems
The standard C*–algebraic version of the algebra of canonical commutation relations, the Weyl algebra, frequently causes difficulties in applications since it neither admits the formulation of physically interesting dynamical laws nor does it incorporate pertinent physical observables such as (bounded functions of) the Hamiltonian. Here a novel C*–algebra of the canonical commutation relations is presented which does not suffer from such problems. It is based on the resolvents of the canonical operators and their algebraic relations. The resulting C*–algebra, the resolvent algebra, is shown to have many desirable analytic properties and the regularity structure of its representations is surprisingly simple. Moreover, the resolvent algebra is a convenient framework for applications to interacting and to constrained quantum systems, as we demonstrate by several examples.
118373042
New Light on Infrared Problems: Sectors, Statistics, Spectrum and All That
Within the general setting of algebraic quantum field theory, a new approach to the analysis of the physical state space of a theory is presented; it covers theories with long range forces, such as quantum electrodynamics. Making use of the notion of charge class, which generalizes the concept of superselection sector, infrared problems are avoided. In fact, on this basis one can determine and classify in a systematic manner the proper charge content of a theory, the statistics of the corresponding states and their spectral properties. A key ingredient in this approach is the fact that in real experiments the arrow of time gives rise to a Lorentz invariant infrared cutoff of a purely geometric nature.
120571075
Local properties of equilibrium states and the particle spectrum in quantum field theory
AbstractIt is shown that in a quantum field theory describing free, scalar particles with masses mi, i∈ℕ there exist locally normal equilibrium states with finite energy density for all temperature β>0 if and only if 
$$\Sigma _{i = 1}^\infty {\text{ e}}^{ - \beta m_i } < \infty $$
. This result lends support to the conjecture that the nuclearity criterion proposed by Buchholz and Wichmann is sensitive to the thermodynamical properties of field-theoretic models.
119148237
New Light on Infrared Problems: Sectors, Statistics, Symmetries and Spectrum
A new approach to the analysis of the physical state space of a theory is presented within the general setting of local quantum physics. It also covers theories with long range forces, such as quantum electrodynamics. Making use of the notion of charge class, an extension of the concept of superselection sector, infrared problems are avoided by restricting the states to observables localized in a light cone. The charge structure of a theory can be explored in a systematic manner. The present analysis focuses on simple charges, thus including the electric charge. It is shown that any such charge has a conjugate charge. There is a meaningful concept of statistics: the corresponding charge classes are either of Bose or of Fermi type. The family of simple charge classes is in one-to-one correspondence with the irreducible unitary representations of a compact Abelian group. Moreover, there is a meaningful definition of covariant charge classes. Any such class determines a continuous unitary representation of the Poincaré group or its covering group satisfying the relativistic spectrum condition. The resulting particle aspects are also briefly discussed.
54540534
How small is the phase space in quantum field theory
The existing compactness and nuclearity conditions characterizing phase space properties of a quantum field theory are compared and found to be particularly sensitive either in the infrared or the ultraviolet domain. A sharpened condition combining both features is proposed and shown to be satisfied in free field theory in four space-time dimensions Nous comparons les conditions connues de compacite et de nuclearite qui caracterisent les proprietes d'espace de phase d'une theorie quantique des champs. Nous montrons qu'elles sont particulierement adaptees soit au domaine ultraviolet ou infrarouge. Nous proposons une nouvelle condition qui combine ces deux aspects et qui est verifiee pour le champ libre en dimension quatre
17472486
On the Manifestations of Particles
The mathematical description of stable particle-like systems appearing in relativistic quantum field theory at large, respectively small scales or non-zero temperatures is discussed.
121765828
Pion pion phase shift and form-factors in the decays k+- ---> pi+ pi- e+- nu(e)
120539815
Experimental tests of discrete symmetries in the decays k+- ---> pi+ pi- e+- nu(e)
123787086
$D^0$ hot topics
The authors present recent D0 results based on approximately 1 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV recorded at the Fermilab Tevatron. Preliminary results on a search for the flavor changing neutral current process D{sup +} {yields} {pi}{sup +}{mu}{sup +}{mu}{sup -}, a measurement of the Cp violation parameter in B mixing, {epsilon}{sub B}, and a two sided limit on the B{sub s} oscillation frequency {Delta}m{sub s} are presented. The limits on {epsilon}{sub B} and {Beta}(D{sup +} {yields} {pi}{sup +}{mu}{sup +}{mu}{sup -}) are the world's best limits. The two sided bound on {Delta}m{sub s} is the first direct indication by a single experiment that {Delta}m{sub s} is bounded from above.
119779374
Neural network based neutral particles reconstruction with the E687 hadron calorimeter
Abstract We present a neutral particle reconstruction algorithm based on a neural network approach applied to the E687 hadron calorimeter. A measurement of the invariant mass of the Σ ± → nπ ± is presented to verify the reliability of the reconstruction. The reconstructed invariant mass of the charmed meson D + → K L 0 π + π + π − is also presented to show the possible application of this technique to charmed particles decaying into a neutral hadron. An example of this would be Λ c + → n K − π + π + .
120794627
Performance of a large liquid argon shower detector used at Fermilab
Abstract Details of the construction and operation of a lead, liquid argon electromagnetic calorimeter used in Fermilab experiment E515 are presented. The system had an active projected area of 1.2×2.4 m 2 . Its performance in low intensity electron beams and in exposure to intense, high multiplicity 200 GeV/ c π − Be interactions are described.