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
17302766
Algebraic Quantum Field Theory: A Status Report
Algebraic quantum field theory is an approach to relativistic quantum physics, notably the theory of elementary particles, which complements other modern developments in this field. It is particularly powerful for structural analysis but has also proven to be useful in the rigorous treatment of models. In this contribution a non-technical survey is given with emphasis on interesting recent developments and future perspectives. Topics covered are the relation between the algebraic approach and conventional quantum field theory, its significance for the resolution of conceptual problems (such as the revision of the particle concept) and its role in the characterization and possibly also construction of quantum field theories with the help of modular theory. The algebraic approach has also shed new light on the treatment of quantum field theories on curved spacetime and made contact with recent developments in string theory (algebraic holography).
16365366
Nuclearity and Thermal States in Conformal Field Theory
We introduce a new type of spectral density condition, that we call L2- nuclearity. One formulation concerns lowest weight unitary representations of $$SL(2,\mathbb R)$$ and turns out to be equivalent to the existence of characters. A second formulation concerns inclusions of local observable von Neumann algebras in Quantum Field Theory. We show the two formulations to agree in chiral Conformal QFT and, starting from the trace class condition $${\rm Tr}(e^{-\beta L_{0}}) < \infty$$ for the conformal Hamiltonian L0, we infer and naturally estimate the Buchholz-Wichmann nuclearity condition and the (distal) split property. As a corollary, if L0 is log-elliptic, the Buchholz-Junglas set up is realized and so there exists a β-KMS state for the translation dynamics on the net of C*-algebras for every inverse temperature β > 0. We include further discussions on higher dimensional spacetimes. In particular, we verify that L2-nuclearity is satisfied for the scalar, massless Klein-Gordon field.
11137586
Quantum statistics and locality
It is shown that two observers have mutually commuting observables if they are able to prepare in each subsector of their common state space some state exhibiting no mutual correlations. This result establishes a heretofore missing link between statistical and locality (commensurability) properties of observables in relativistic quantum physics. The analysis is based on a discussion of coincidence experiments and leads to a quantitative measure of deviation from locality. Hence, it may be applied in intrinsically nonlocal theories such as string theory and field theory on noncommutative spacetime.
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.
16799561
Quantum Delocalization of the Electric Charge
The classical Maxwell–Dirac and Maxwell–Klein–Gordon theories admit solutions of the field equations where the corresponding electric current vanishes in the causal complement of some bounded region of Minkowski space. This poses the interesting question of whether states with a similarly well localized charge density also exist in quantum electrodynamics. For a large family of charged states, the dominant quantum corrections at spacelike infinity to the expectation values of local observables are computed. It turns out that certain moments of the charge density decrease no faster than the Coulomb field in spacelike directions. In contrast to the classical theory, it is therefore impossible to define the electric charge support of these states in a meaningful way.
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.
120539815
Experimental tests of discrete symmetries in the decays k+- ---> pi+ pi- e+- nu(e)
118465845
Recent results on charm from Fermilab experiment E-687
About 10{sup 4} charm decays have been reconstructed from first-run data of Fermilab experiment E687 using the Fermilab Wide-Band Photon Spectrometer with the world's highest energy photon beam. The success of techniques for isolating and reconstructing charm event samples based on two complementary vertexing strategies is illustrated. Preliminary results are presented. These include lifetime value of (0.50 {plus minus} 0.06 {plus minus} 0.03)ps for the D{sub s}{sup +}, and (0.20 {plus minus} 0.03 {plus minus} 0.03)ps for the {Lambda}{sub c}{sup +}. Preliminary values for the D{sup +} and D{sup 0} lifetimes are consistent with currently accepted world averages. Signals for the Cabibbo-suppressed decays D{sup 0} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup +}{pi}{sup {minus}}, D{sup +} {yields} K{sup +}K{sup {minus}}{pi}{sup +}, and D{sup +} {yields} {phi}{pi}{sup +} are shown; for B(D{sup 0} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup +}{pi}{sup {minus}})/B(D{sup 0} {yields} K{sup {minus}}{pi}{sup +}{pi}{sup +}{pi}{sup {minus}}) our preliminary value is 0.10 {plus minus} 0.02 {plus minus} 0.02. Preliminary values for ratios B(D{sup 0} {yields} {ovr K}{sup 0}K{sup +}K{sup {minus}})/B(D{sup 0} {yields} {ovr K}{sup 0}{pi}{sup +}{pi}{sup {minus}}) and B(D{sup 0} {yields} {ovr K}{sup 0}{phi})/B(D{sup 0} {yields} {ovr K}{sup 0}{pi}{sup +}{pi}{sup {minus}}) are 0.20 {plus minus} 0.06 and 0.16 {plus minus} 0.06. Preliminary results are givenmore » for cross sections of D*{sup {plus minus}} and D{sup {plus minus}} photoproduction on a Be target for the p{sup 2}{sub {tau}} dependence of D{sup {minus plus}} photoproduction and for the ratios D{double prime}/D*{sup +} and D*{sup {minus}}/D{sup {minus plus}}. The energy dependence of the total open charm photoproduction cross section is compared with model predictions for photon energies up to 350 GeV. 18 refs., 5 figs.« less
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.
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.