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.
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.
1050696
Towards a relativistic KMS-condition
Abstract It is shown that, under quite general conditions, thermal correlation functions in relativistic quantum field theory have stronger analyticity properties in configuration space than those imposed by the KMS-condition. These analyticity properties may be understood as a remnant of the relativistic spectrum condition in the vacuum sector and lead to a Lorentz-covariant formulation of the KMS-condition involving all space-time variables.
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.
110772906
The use of waveform digitizers with drift chambers for D0
Abstract A prototype drift chamber cell with good space resolution, d E d x , and two particle separation has been constructed. A 100 MHz, 11 bit waveform digitizer readout scheme has been used for the tests.
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.
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.
121765828
Pion pion phase shift and form-factors in the decays k+- ---> pi+ pi- e+- nu(e)