4,534 research outputs found
FIESTA 2: parallelizeable multiloop numerical calculations
The program FIESTA has been completely rewritten. Now it can be used not only
as a tool to evaluate Feynman integrals numerically, but also to expand Feynman
integrals automatically in limits of momenta and masses with the use of sector
decompositions and Mellin-Barnes representations. Other important improvements
to the code are complete parallelization (even to multiple computers),
high-precision arithmetics (allowing to calculate integrals which were undoable
before), new integrators and Speer sectors as a strategy, the possibility to
evaluate more general parametric integrals.Comment: 31 pages, 5 figure
Four Loop Massless Propagators: a Numerical Evaluation of All Master Integrals
We present numerical results which are needed to evaluate all non-trivial
master integrals for four-loop massless propagators, confirming the recent
analytic results of[1]and evaluating an extra order in \ep expansion for each
master integral
Period- and mirror-maps for the quartic K3
We study in detail mirror symmetry for the quartic K3 surface in P3 and the
mirror family obtained by the orbifold construction. As explained by Aspinwall
and Morrison, mirror symmetry for K3 surfaces can be entirely described in
terms of Hodge structures. (1) We give an explicit computation of the Hodge
structures and period maps for these families of K3 surfaces. (2) We identify a
mirror map, i.e. an isomorphism between the complex and symplectic deformation
parameters, and explicit isomorphisms between the Hodge structures at these
points. (3) We show compatibility of our mirror map with the one defined by
Morrison near the point of maximal unipotent monodromy. Our results rely on
earlier work by Narumiyah-Shiga, Dolgachev and Nagura-Sugiyama.Comment: 29 pages, 3 figure
Suppression of grasshopper sound production by nitric oxide-releasing neurons of the central complex
The central complex of acridid grasshoppers integrates sensory information pertinent to reproduction-related acoustic communication. Activation of nitric oxide (NO)/cyclic GMP-signaling by injection of NO donors into the central complex of restrained Chorthippus biguttulus females suppresses muscarine-stimulated sound production. In contrast, sound production is released by aminoguanidine (AG)-mediated inhibition of nitric oxide synthase (NOS) in the central body, suggesting a basal release of NO that suppresses singing in this situation. Using anti-citrulline immunocytochemistry to detect recent NO production, subtypes of columnar neurons with somata located in the pars intercerebralis and tangential neurons with somata in the ventro-median protocerebrum were distinctly labeled. Their arborizations in the central body upper division overlap with expression patterns for NOS and with the site of injection where NO donors suppress sound production. Systemic application of AG increases the responsiveness of unrestrained females to male calling songs. Identical treatment with the NOS inhibitor that increased male song-stimulated sound production in females induced a marked reduction of citrulline accumulation in central complex columnar and tangential neurons. We conclude that behavioral situations that are unfavorable for sound production (like being restrained) activate NOS-expressing central body neurons to release NO and elevate the behavioral threshold for sound production in female grasshoppers
The P Experiment: A Positron Source Demonstrator for Future Lepton Colliders
The PSI Positron Production (P or P-cubed) experiment is a demonstrator
for a e+ source and capture system with potential to improve the
state-of-the-art e+ yield by an order of magnitude. The experiment is driven by
the FCC-ee injector study and will be hosted in the SwissFEL facility at the
Paul Scherrer Institute in Switzerland. This paper is an overview of the P
design at an advanced stage, with a particular emphasis on a novel e+ capture
system and its associated beam dynamics. Additionally, a concept for the
experiment diagnostics is presented, as well as the key points of the ongoing
installation works
Search for a Technicolor omega_T Particle in Events with a Photon and a b-quark Jet at CDF
If the Technicolor omega_T particle exists, a likely decay mode is omega_T ->
gamma pi_T, followed by pi_T -> bb-bar, yielding the signature gamma bb-bar. We
have searched 85 pb^-1 of data collected by the CDF experiment at the Fermilab
Tevatron for events with a photon and two jets, where one of the jets must
contain a secondary vertex implying the presence of a b quark. We find no
excess of events above standard model expectations. We express the result of an
exclusion region in the M_omega_T - M_pi_T mass plane.Comment: 14 pages, 2 figures. Available from the CDF server (PS with figs):
http://www-cdf.fnal.gov/physics/pub98/cdf4674_omega_t_prl_4.ps
FERMILAB-PUB-98/321-
Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab
We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using
a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with
the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass
distribution is obtained that is consistent with W decay and inconsistent with
the background prediction by 3.3 standard deviations. From this peak we measure
the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the
presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet
channel.Comment: 20 pages, 4 figures, submitted to PR
Measurement of the B0 anti-B0 oscillation frequency using l- D*+ pairs and lepton flavor tags
The oscillation frequency Delta-md of B0 anti-B0 mixing is measured using the
partially reconstructed semileptonic decay anti-B0 -> l- nubar D*+ X. The data
sample was collected with the CDF detector at the Fermilab Tevatron collider
during 1992 - 1995 by triggering on the existence of two lepton candidates in
an event, and corresponds to about 110 pb-1 of pbar p collisions at sqrt(s) =
1.8 TeV. We estimate the proper decay time of the anti-B0 meson from the
measured decay length and reconstructed momentum of the l- D*+ system. The
charge of the lepton in the final state identifies the flavor of the anti-B0
meson at its decay. The second lepton in the event is used to infer the flavor
of the anti-B0 meson at production. We measure the oscillation frequency to be
Delta-md = 0.516 +/- 0.099 +0.029 -0.035 ps-1, where the first uncertainty is
statistical and the second is systematic.Comment: 30 pages, 7 figures. Submitted to Physical Review
Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV
We report on a search for anomalous production of events with at least two
charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1
sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a
signal region containing low background from Standard Model processes. To avoid
bias, we fix the final cuts before examining the event yield in the signal
region using control regions to test the Monte Carlo predictions. We observe no
events in the signal region, consistent with an expectation of
0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new
physics processes in both a signature-based context as well as within a
representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to
figures and updated and expanded reference
- …