1,288 research outputs found
Hidden local symmetry and color confinement
The hidden local symmetry is a successful model to describe the properties of
the vector mesons in QCD. We point out that if we identify this hidden gauge
theory as the magnetic picture of QCD, a linearized version of the model
simultaneously describes color confinement and chiral symmetry breaking. We
demonstrate that such a structure can be seen in the Seiberg dual picture of a
softly broken supersymmetric QCD. The model possesses exact chiral symmetry and
reduces to QCD when mass parameters are taken to be large. Working in the
regime of the small mass parameters, we show that there is a vacuum where
chiral symmetry is spontaneously broken and simultaneously the magnetic gauge
group is Higgsed. If the vacuum we find persists in the limit of large mass
parameters, one can identify the rho meson as the massive magnetic gauge boson,
that is an essential ingredient for color confinement.Comment: 20 pages, 3 figure
B-> D* zero-recoil formfactor and the heavy quark expansion in QCD: a systematic study
We present a QCD analysis of heavy quark mesons focussing on the B -> D*
formfactor at zero recoil, F_D*(1). An advanced treatment of the perturbative
corrections in the Wilsonian approach is presented. We estimate the
higher-order power corrections to the OPE sum rule and describe a refined
analysis of the nonresonant continuum contribution. In the framework of a
model-independent approach, we show that the inelastic contribution in the
phenomenological part of the OPE is related to the mQ-dependence of the
hyperfine splitting and conclude that the former is large, lowering the
prediction for F_D*(1) down to about 0.86. This likewise implies an enhanced
yield of radial and D-wave charm excitations in semileptonic B decays and
alleviates the problem with the inclusive yield of the wide excited states. We
also apply the approach to the expectation values of dimension 7 and 8 local
operators and to a few other issues in the heavy quark expansion.Comment: 70 pages, 13 figure
Bi-harmonic superspace for N=4 d=4 super Yang-Mills
We develop N=4 d=4 bi-harmonic superspace and use it to derive a novel form
for the low-energy effective action in N=4 super Yang-Mills theory. We solve
the N=4 supergauge constraints in this superspace in terms of analytic
superfields. Using these superfields, we construct a simple functional that
respects N=4 supersymmetry and scale invariance. In components, it reproduces
all on-shell terms in the four-derivative part of the N=4 SYM effective action;
in particular, the F^4/X^4 and Wess-Zumino terms. The latter comes out in a
novel SO(3) x SO(3)-invariant form.Comment: 1+19 pages; minor corrections, references adde
First histological observations on the incorporation of a novel nanocrystalline hydroxyapatite paste OSTIM(® )in human cancellous bone
BACKGROUND: A commercially available nanocrystalline hydroxyapatite paste Ostim(® )has been reported in few recent studies to surpass other synthetic bone substitutes with respect to the observed clinical results. However, the integration of this implantable material has been histologically evaluated only in animal experimental models up to now. This study aimed to evaluate the tissue incorporation of Ostim(® )in human cancellous bone after reconstructive bone surgery for trauma. METHODS: Biopsy specimens from 6 adult patients with a total of 7 tibial, calcaneal or distal radial fractures were obtained at the time of osteosynthesis removal. The median interval from initial operation to tissue sampling was 13 (range 3–15) months. Samples were stained with Masson-Goldner, von Kossa, and toluidine blue. Osteoid volume, trabecular width and bone volume, and cortical porosity were analyzed. Samples were immunolabeled with antibodies against CD68, CD56 and human prolyl 4-hydroxylase to detect macrophages, osteoblasts, and fibroblasts, respectively. TRAP stainings were used to identify osteoclasts. RESULTS: Histomorphometric data indicated good regeneration with normal bone turnover: mean osteoid volume was 1.93% of the trabecular bone mass, trabecular bone volume – 28.4%, trabecular width – 225.12 μm, and porosity index – 2.6%. Cortical and spongious bone tissue were well structured. Neither inflammatory reaction, nor osteofibrosis or osteonecrosis were observed. The implanted material was widely absorbed. CONCLUSION: The studied nanocrystalline hydroxyapatite paste showed good tissue incorporation. It is highly biocompatible and appears to be a suitable bone substitute for juxtaarticular comminuted fractures in combination with a stable screw-plate osteosynthesis
Search for New Physics in e mu X Data at D0 Using Sleuth: A Quasi-Model-Independent Search Strategy for New Physics
We present a quasi-model-independent search for the physics responsible for
electroweak symmetry breaking. We define final states to be studied, and
construct a rule that identifies a set of relevant variables for any particular
final state. A new algorithm ("Sleuth") searches for regions of excess in those
variables and quantifies the significance of any detected excess. After
demonstrating the sensitivity of the method, we apply it to the semi-inclusive
channel e mu X collected in 108 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV
at the D0 experiment during 1992-1996 at the Fermilab Tevatron. We find no
evidence of new high p_T physics in this sample.Comment: 23 pages, 12 figures. Submitted to Physical Review
Ratio of the Isolated Photon Cross Sections at \sqrt{s} = 630 and 1800 GeV
The inclusive cross section for production of isolated photons has been
measured in \pbarp collisions at GeV with the \D0 detector at
the Fermilab Tevatron Collider. The photons span a transverse energy ()
range from 7-49 GeV and have pseudorapidity . This measurement is
combined with to previous \D0 result at GeV to form a ratio
of the cross sections. Comparison of next-to-leading order QCD with the
measured cross section at 630 GeV and ratio of cross sections show satisfactory
agreement in most of the range.Comment: 7 pages. Published in Phys. Rev. Lett. 87, 251805, (2001
Limits on WWZ and WW\gamma couplings from p\bar{p}\to e\nu jj X events at \sqrt{s} = 1.8 TeV
We present limits on anomalous WWZ and WW-gamma couplings from a search for
WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p
-> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron
Collider during the 1992-1995 run. The data sample corresponds to an integrated
luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling
parameters, the 95% CL limits on the CP-conserving couplings are
-0.33<lambda<0.36 (Delta-kappa=0) and -0.43<Delta-kappa<0.59 (lambda=0), for a
form factor scale Lambda = 2.0 TeV. Limits based on other assumptions are also
presented.Comment: 11 pages, 2 figures, 2 table
Search For Heavy Pointlike Dirac Monopoles
We have searched for central production of a pair of photons with high
transverse energies in collisions at TeV using of data collected with the D\O detector at the Fermilab Tevatron in
1994--1996. If they exist, virtual heavy pointlike Dirac monopoles could
rescatter pairs of nearly real photons into this final state via a box diagram.
We observe no excess of events above background, and set lower 95% C.L. limits
of on the mass of a spin 0, 1/2, or 1 Dirac
monopole.Comment: 12 pages, 4 figure
The Dijet Mass Spectrum and a Search for Quark Compositeness in bar{p}p Collisions at sqrt{s} = 1.8 TeV
Using the DZero detector at the 1.8 TeV pbarp Fermilab Tevatron collider, we
have measured the inclusive dijet mass spectrum in the central pseudorapidity
region |eta_jet| < 1.0 for dijet masses greater than 200 Gev/c^2. We have also
measured the ratio of spectra sigma(|eta_jet| < 0.5)/sigma(0.5 < |eta_jet| <
1.0). The order alpha_s^3 QCD predictions are in good agreement with the data
and we rule out models of quark compositeness with a contact interaction scale
< 2.4 TeV at the 95% confidence level.Comment: 11 pages, 4 figures, 2 tables, submitted to Phys. Rev. Let
Search for High Mass Photon Pairs in p-pbar --> gamma-gamma-jet-jet Events at sqrt(s)=1.8 TeV
A search has been carried out for events in the channel p-barp --> gamma
gamma jet jet. Such a signature can characterize the production of a
non-standard Higgs boson together with a W or Z boson. We refer to this
non-standard Higgs, having standard model couplings to vector bosons but no
coupling to fermions, as a "bosonic Higgs." With the requirement of two high
transverse energy photons and two jets, the diphoton mass (m(gamma gamma))
distribution is consistent with expected background. A 90(95)% C.L. upper limit
on the cross section as a function of mass is calculated, ranging from
0.60(0.80) pb for m(gamma gamma) = 65 GeV/c^2 to 0.26(0.34) pb for m(gamma
gamma) = 150 GeV/c^2, corresponding to a 95% C.L. lower limit on the mass of a
bosonic Higgs of 78.5 GeV/c^2.Comment: 9 pages, 3 figures. Replacement has new H->gamma gamma branching
ratios and corresponding new mass limit
- …