23 research outputs found
Towards a precise determination of the topological susceptibility in the SU(3) Yang-Mills theory
An ongoing effort to compute the topological susceptibility for the SU(3)
Yang-Mills theory in the continuum limit with a precison of about 2% is
reported. The susceptibility is computed by using the definition of the charge
suggested by Neuberger fermions for two values of the negative mass parameter
s. Finite volume and discretization effects are estimated to meet this level of
precision. The large statistics required has been obtained by using PCs of the
INFN-GRID. Simulations with larger lattice volumes are necessary in order to
better understanding the continuum limit at small lattice spacing values.Comment: 8 pages, 2 figures, The XXVII International Symposium on Lattice
Field Theory - LAT2009,July 26-31 2009,Peking University, Beijing, Chin
Large statistics study of the topological charge distribution in the SU(3) gauge theory
We present preliminary results for a high statistics study of the topological
charge distribution in the SU(3) Yang-Mills theory obtained by using the
definition of the charge suggested by Neuberger fermions. We find statistical
evidence for deviations from a gaussian distribution. The large statistics
required has been obtained by using PCs of the INFN-GRID.Comment: Talk given at the 24th International Symposium on Lattice Field
Theory (Lattice 2006), Tucson, Arizona, 23-28 Jul 200
On The Possible Detection Of Massive Stable Exotic Particles At The LHC
The possible detection of massive quasi-stable exotic particles at the high
luminosity hadronic colliders is discussed. In the coming ten years the LHC,
now under preparation, has the best opportunity to observe them at the TeV
scale. The present design of the ATLAS detector,that has been almost
irreversibly decided, may turn out to be flexible enough to allow the detection
of this interesting class of exotic particles. The trigger acceptance, the
track reconstruction and the particle identification are studied. The necessity
of a good measurement of the ionization loss in the muon sector of the
detectors is recommended.Comment: 12 Latex pages, 4 figures JPE
Searching a doubly charged Higgs boson at Hera
The production of a single exotic Higgs particle is studied at Hera. Within
the present limits on the Yukawa couplings this doubly charged particle,
suggested by the left-right symmetric models, can be observed at Hera up to
values of its mass of about 150 GeV.Comment: 9 pages, Prep. Univ. of Rome "La Sapienza" n. 980 15/11/1993 3
figures not included Latex file ([email protected]
Theta dependence of the vacuum energy in the SU(3) gauge theory from the lattice
We report on a precise computation of the topological charge distribution in
the SU(3) Yang--Mills theory. It is carried out on the lattice with high
statistics Monte Carlo simulations by employing the definition of the
topological charge suggested by Neuberger's fermions. We observe significant
deviations from a Gaussian distribution. Our results disfavour the theta
behaviour of the vacuum energy predicted by instanton models, while they are
compatible with the expectation from the large Nc expansion.Comment: Plain latex, 4 pages, 2 figure
Gribov Copies and Smeared Correlation Functions in Lattice QCD
We study the influence of Gribov copies in the Coulomb gauge on the smeared
hadronic correlation functions that are involved in the determination of the B
meson decay constant. We find that the residual gauge freedom associated to
Gribov copies induces observable noise effects, though at the level of
numerical accuracy of our simulation these effects are not relevant to the
final determination of f_B. Our results indicate that such effects may become
important on bigger lattices.Comment: 12pgs., preprint n. 892, June 24, 1992, Dipartimento di Fisica Univ.
of Rome "La Sapienza
Gribov Noise on the Lattice Axial Current Renormalisation Constant
We study the influence of Gribov copies, in the Landau gauge, on the lattice
renormalisation constant of the axial current, obtained from a Ward identity on
quark state correlation functions, with the Clover action, in quenched SU(3)
gauge theory. A comparison between the gauge invariant determination of the
renorma= lization constant and the gauge dependent one is discussed. We find
that the residual gauge freedom associated to Gribov copies induces observable
effects, which, at the level of numerical accuracy of our simulation, are
included in the statistical uncertainty inherent in a Monte Carlo simulation.
Doubling the statistics suggests that the fluctuation due to the lattice Gribov
ambiguity scales down at least as fast as a pure statistical error.Comment: 17pp (including figures), LaTe
Testing the Quasi-temporal Gauge on the Lattice
We investigate the viability of the quasi-temporal gauge on the lattice. This
is a complete gauge fixing condition that can be implemented on the lattice at
a very low computational cost. As a test case, using the Clover action, we have
evaluated the (gauge invariant) renormalisation constant of the non-singlet
axial current, using Ward identities extracted from quark states. Our result is
in reasonable but not complete agreement with previous values obtained from
Ward identities both on hadronic states and on quark states in the Landau
gauge. We observe large fluctuations due to lattice Gribov copies. The
influence of finite volume effects is expected to be non-negligible in the case
we are considering.Comment: 10 pages, uuencoded Postscript file including 2 figure
Remarks on the forces generated by two-neutrino exchange
A brief up-to-date review of the long range forces generated by two neutrino
exchange is presented. The potential due to exchange of a massive
neutrino-antineutrino pair between particles carrying weak charge might be
larger than expected if the neutrinos have not only masses but also magnetic
moments close to the present experimental bounds. It still remains too small to
be observable.Comment: 10 pages, 3 figures. One figure added. Accepted for publication in
EPJ