Search results for "VERTEX"
showing 10 items of 225 documents
Gluon mass generation in the massless bound-state formalism
2013
We present a detailed, all-order study of gluon mass generation within the massless bound-state formalism, which constitutes the general framework for the systematic implementation of the Schwinger mechanism in non-Abelian gauge theories. The main ingredient of this formalism is the dynamical formation of bound states with vanishing mass, which give rise to effective vertices containing massless poles; these latter vertices, in turn, trigger the Schwinger mechanism, and allow for the gauge-invariant generation of an effective gluon mass. This particular approach has the conceptual advantage of relating the gluon mass directly to quantities that are intrinsic to the bound-state formation its…
Heavy neutrino searches at the lhc with displaced vertices
2013
Sterile neutrinos with masses in the range (1-100) GeV, have been searched for in a variety of experiments. Here, we discuss the prospects to search for sterile neutrinos at the LHC using displaced vertices. Two different cases are discussed: (i) the standard model extended with sterile neutrinos and (ii) right-handed neutrinos in a left-right symmetric extension of the standard model. A dedicated displaced vertex search will allow to probe parts of the parameter space not accessible to other searches, but will require large luminosity in both cases.
Status of the DØ Detector
2003
During the data-taking period from 1992 to 1996 (Run I), the Tevatron experiments CDF and DO collected about 125pb¯1 of proton-antiproton collision data at center of mass energies of 1.8 TeV. Since then, the Fermilab accelerator complex has been upgraded to provide collisions at 1.96 TeV and an initial design luminosity of 8.6 × 1031cm¯2s¯1. The new data-taking period (Run II) has started in March 2001 and is expected to deliver more than 10fb¯1 by the year 2007. This dataset is the basis for a rich physics program, including precision mass measurements of the W-boson and top-quark as well as the possibility to discover a light Higgs boson[1].
A study of λ+c decays into pK−π+, pK−π+π0and pK−π+π0π0
1993
Abstract In the CERN NA32 experiment a high-resolution silicon vertex detector and a purely topological approach were used to collect a clean sample of λ + c decays into pK − π + with or without additional neutral particles. We study the subresonant structure of the λ c + peak obtaining BR (λ c + → p K ∗0 (892)) = 0.35 −0.07 +0.06 ±0.03 with respect to the total λ c + → pK − π + decay. We also determine branching ratios for some channels with neutral decay products, namely BR( λ c + → pK − π + π 0 ) = 0.73±0.12±0.05 and BR( λ c + → pK − π + π 0 π 0 = 0.16±0.07±0.03, again with respect to the total λ c + → pK − π + decay.
Measurement of the mass and width of the charmed meson D∗+ (2010)
1992
Abstract Using a high-resolution silicon vertex detector we have observed a very clean signal of 127 D∗+. After a careful study of the experimental resolution of our apparatus we have measured m( D ∗++ )−m( D 0 ) = 145.39±0.06±0.03 MeV . We have also obtained a 90% CL upper limit to γ(D∗+) of 131 keV.
Pion induced pion production on deuterium: A Quasifree process
1992
Abstract A detailed experimental analysis of the π+d → π+π−pp in-plane coincidence data first presented by Rui et al. is compared to an expanded version of the Oset and Vicente-Vacas model for pion-induced pion production on a free nucleon. This extended model averages over Fermi motion to describe the assumed quasifree nature of the process occurring on the deuteron and includes nine additional diagrams to account for the N ∗ → N (ππ) p-wave reaction channels. Experimental effects such as pion energy loss in the target and in the detectors, pion decay and muon detection are investigated and incorporated into the comparison of experimental data and theory. Inclusion of Fermi motion was foun…
Commutators of second-class axial currents with normal weak currents and consequences for particle decays
1981
Second-class weak axial currents are studied in the framework of normal weak and electromagnetic currents. Equal time commutators between normal and abnormal axial currents and the isoscalar electromagnetic current are postulated and their consequences are worked out. A number of predictions for masses, coupling constants and decay properties are derived and are compared to available data.
Experimental study of the triple-gluon vertex
1991
Abstract In four-jet events from e+e− →Z0 →multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle θ NR ∗ and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor Nc to the fermionic Casimir operator C F : N c C F = 2.55 ± 0.55 ( stat. ) ± 0.4 ( fragm. + models…
MEASUREMENT OF THE GAMMA(B-B-OVER-BAR)/GAMMA(HAD) BRANCHING RATIO OF THE Z BY DOUBLE HEMISPHERE TAGGING
1995
Two measurements of {Mathematical expression} are presented. Both measurements use 250000 Z decays taken with the DELPHI detector in 1991 and rely mainly on the precision of the microvertex detector. One tagging method is as simple as possible so that background rates can be reliably predicted by simulation. The other one uses a more involved tagging technique and reduces the dependence on simulation as much as possible. Combining both results, {Mathematical expression} is found to be 0.2209±0.0041(stat.)±0.0042(syst.)±0.0018 {Mathematical expression}. © 1995 Springer-Verlag.
Hadronic τ Decays as New Physics Probes in the LHC Era
2019
We analyze the sensitivity of hadronic tau decays to non-standard interactions within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the $\tau \to \pi\pi\nu_\tau$ channel representing an unexpected powerful New Physics probe. We find that the ratios of non-standard couplings to the Fermi constant are bound at the sub-percent level. These bounds are complementary to the ones from electroweak precision observable…