Area-preserving diffeomorphisms in gauge theory on a non-commutative plane. A lattice
study 424 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/38/071/38071435.pdf - Text Version by Bietenholz, W. (Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von
Neumann-Inst. fuer Computing NIC); Bigarini, A. (Univ. degli Studi di Perugia (Italy).
Dipt. di Fisica; INFN, Sezione di Perugia (Italy); Humboldt-Universitaet, Berlin (Germany).
Inst. fuer Physik); Torrielli, A. (Massachusetts Institute of Technology, Cambridge,
MA (United States). Center for Theoretical Physics, Lab. for Nuclear Sciences); Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany) Read MoreCollapse
[en]
We consider Yang-Mills theory with the U(1) gauge group on a non-commutative plane.
Perturbatively it was observed that the invariance of this theory under area-preserving
diffeomorphisms (APDs) breaks down to a rigid subgroup SL(2,R). Here we present explicit
results for the APD symmetry breaking at finite gauge coupling and finite non-commutativity.
They are based on lattice simulations and measurements of Wilson loops with the same
area but with a variety of different shapes. Our results confirm the expected loss
of invariance under APDs. Moreover, they strongly suggest that non-perturbatively
the SL(2,R) symmetry does not persist either. (orig.)$$$$
Comparison of Zgoubi and S-Code regarding the FFAG muon acceleration 10 MB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/38/105/38105276.pdf - Text Version by Fourrier, J. (Laboratoire de Physique Subatomique et de Cosmologie, Universite Joseph
Fourier / CNRS-IN2P3, 53 Avenue des Martyrs, F-38026 Grenoble (France)); Machida,
S. (Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot
OX11 0QX (United Kingdom)); Laboratoire de Physique Subatomique et de Cosmologie, Universite Joseph Fourier
/ CNRS-IN2P3, 53 Avenue des Martyrs, F-38026 Grenoble (France); Rutherford Appleton
Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX (United Kingdom) Read MoreCollapse
[en]
The high flux accelerator based neutrino source is foreseen as one of the next generation
facilities of particle physics. Called Neutrino Factory (NuFact), it will be based
on a muon storage ring where muons will decay, creating high flux neutrino beams.
Muons are supposed to be accelerated from 5 to 20 GeV before being injected into the
storage ring. In that purpose, Fixed Field Alternating Gradient accelerators (FFAG)
are one of the possibilities. Cell designs have been done and tracking studies are
on their way using codes such as MAD, S-Code or Zgoubi. In order to cross-check results
so obtained, we have performed comparisons between S-Code and Zgoubi at Rutherford
Appleton Laboratory. The present report will explain the different simulations done
and the results. The paper has the following contents: 1. Introduction; 2. Time of
Flight comparisons; 3. Particle acceleration with different emittances; 4. Bunch acceleration.
In conclusion it is shown that the difference of time of flight between the particle
1 and the others is comparable from Zgoubi to S- Code. Nevertheless, further investigation
is necessary to make sure that the same revolution time will be found with the same
initial conditions. Concerning the acceleration it was found that that the larger
the emittance the less efficient appears to be the acceleration. Particles on ellipses
10 to 40 π mm rad are accelerated beyond 9 GeV while particles on ellipse 50 π mm
rad are only accelerated up to 7.5 GeV and those on 60 π mm rad ellipse just reach
6 GeV. Thus, a beam whom emittance would be larger than 30 π mm rad would not be accelerated
enough to reach 10 GeV and to be injected into the second FFAG. In the same way as
for the first FFAG the larger the emittance the less efficient the acceleration. Particles
on ellipses 10 to 40 π mm rad are accelerated beyond 18 GeV while particles on ellipses
50 and 60 π mm rad are only accelerated up to 12 GeV. Thus, beams whom emittance is
lower than 30 π mm rad could be accelerated to an energy close to 20 GeV but not enough
yet. Further simulations should be done to find out if the acceleration to 20 GeV
is possible. As regarding the comparison between the codes it is easy to manage that
both codes give similar results for the longitudinal phase space. They have a good
agreement what makes the results reliable$$$$
We have studied some phenomenological aspects of the B meson physics by using lattice
QCD, which is a non perturbative method (based on the first principles of Quantum
Field Theory) of computing Green functions of the theory. Pionic couplings g_{1}
and g_{2}, parameterizing the effective chiral Lagrangian which describes
interactions between heavy-light mesons and soft pions, have been computed beyond
the quenched approximation (at N_{f} = 2). We have renormalized the operator
q-barγ_{μ}γ^{5}q non perturbatively by using chiral Ward identities.
We obtain g_{1} = 0.4/0.6 and g_{2} = -0.1/-0.3. We have estimated
from an un-quenched simulation (at N_{f} = 2) the strange quark mass: the
non perturbative renormalisation scheme RI-MOM has been applied. After the matching
in the MS scheme the result is m_{s}(2 GeV) = 101 ± 8(-0,+25) MeV. We have
proposed a method to calculate on the lattice the Heavy Quark Effective Theory form
factors of the semileptonic transitions B → D^{**} at zero recoil. The renormalisation
constant of the operator h-barγ_{i}γ^{5}D_{j}h has been computed
at one-loop order of the perturbation theory. We obtain τ_{1/2}(1) = 0.3/0.5
and τ_{3/2}(1) 0.5/0.7. Eventually the bag parameter B_{Bs}
associated the B_{s} - B_{s}-bar mixing amplitude in the Standard
Model has been estimated in the quenched approximation by using for the strange quark
an action which verifies the chiral symmetry at finite lattice spacing a. Thus systematic
errors are significantly reduced in the renormalisation procedure because the spurious
mixing of the four-fermion operator h-barγ_{μL}qh-barγ_{μL}q with
four-fermion operators of different chirality is absent. The result is B_{Bs}
= 0.92(3). (author)$$$$
We recall the algebraic statement that can be done for Petrov's classification. We
determine Petrov's class in some points of the axial symmetric stationary solution
given in 1953 by Papapetrou. We complete the determination of the Papapetrou non stationary
cylindric solution. (author)$$$$
Decoupled dirac equation in one-boson-Exchange potential model and Hartree-fock calculations 638 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/37/121/37121582.pdf - Text Version by Hanna, K.M.; Swelam, Sh.M. (Mathematics and Theoretical Physics Department, Atomic
Energy Authority, Cairo (Egypt)); Nafea, H.O. (Physics Department, Faculty of Science,
Zagazig University (Banha Branch), Banha (Egypt)) fromProceedings of the Fourth Conference on Nuclear and Particle Physics (NUPPAC-2003) Read MoreCollapse
[en]
On the basis of a semi-relativistic decoupled Dirac equation and self consistent Hartree-Fock
formulation, it is used the One-Boson-Exchange Potential (OBEP) model where each nucleon,
as a Dirac particle, is considered to be a source of a scalar (a) and vector (co)
fields, and is also acted upon by these fields, to get the ground state of some spherical
nuclei. An important mathematical advantage gained by the assumption that each nucleon
in the nucleus is moving under the influence of a common harmonic oscillator is that
(as shown by Talmi) the wave function of the two nucleons is separable in their relative
and center of mass (C.M) coordinates and the known Talmi-Moshinsky brackets. Three
different static nucleon-nucleon interaction forms are used to predict the ground
state energy for^{4}He nucleus$$$$
We report on software development to evaluate the expected performance of the PANDA
detector to measure the semileptonic form factor D_{s} → e + v + π,
η,η'. The related decay models in this chain are checked via a Dalitz
plot analysis; the present version of EvtGen in PandaRoot has been enhanced by a new
model describing the D_{s} → KKπ decay. With the help of theoretical
predictions of the cross section, the expected count rate is estimated.$$$$
In the presence of a quark chemical potential, a magnetic field induces an axial current
in the direction of the magnetic field. We compute this current in the Sakai-Sugimoto
model, a holographic model which, in a certain limit, is dual to large-N_{c}
QCD. We also compute the analogous vector current, for which an axial chemical potential
is formally introduced. This vector current can potentially be observed via charge
separation in heavy-ion collisions. After implementing the correct axial anomaly in
the Sakai-Sugimoto model we find an axial current in accordance with previous studies
and a vanishing vector current, in apparent contrast to previous weak-coupling calculations.
(author)$$$$
We develop a new implicit symplectic integrator and derive the first and second order
integration algorithms for it. We combine this integrator with a Yoshida composition
and with a Suzuki composition to get third order hybrid symplectic integrators. We
test the algorithms on an exactly solvable example from McMillan (1950 Phys. Rev.
79 498) of a particle in an electromagnetic wave and find very good results, including
long term stability and exact preservation of constants associated with symmetries.
We discuss the circumstances in which the new algorithms may be useful. (paper)$$$$
The present work deals with the search of third generation squarks in the framework
of the MSSM (minimal supersymmetric standard model) with R-parity conservation, for
small mass differences between these squarks and the lightest supersymmetric particle
(LSP). Data collected at centre-of-mass energies from 189 to 209 GeV by DELPHI detector,
corresponding to an integrated luminosity of 608 pb^{-1}, are analysed in
a search for three topologies. No evidence for deviations from the Standard Model
expectation is found. For a short lifetime stop a lower limit of 71 GeV/c^{2}
is set for the mass, independently of the mixing angle. Long-lived stop and s-bottom
of 97 GeV/c^{2} and 89 GeV/c^{2}, respectively, are also excluded.
For Δm > 5 GeV/c^{2} an intermediate lifetime stop with m < 52 GeV/c^{2}
is excluded for all mixing angles; for Δm > 2 GeV/c^{2}, the limit is set
to 54 GeV/c^{2} for a loft-handed stop only. (author)$$$$
Cosmology in general massive gravity theories http://dx.doi.org/10.1088/1475-7516/2014/05/036 by Comelli, D. (INFN — Sezione di Ferrara, I-35131 Ferrara (Italy)); Nesti, F.
(Gran Sasso Science Institute, viale Crispi 7, I-67100 L'Aquila (Italy)); Pilo,
L. (Dipartimento di Scienze Fisiche e Chimiche, Università di L'Aquila,
I-67010 L'Aquila (Italy)), E-mail: comelli@fe.infn.it, E-mail: fabrizio.nesti@aquila.infn.it,
E-mail: luigi.pilo@aquila.infn.it Read MoreCollapse
[en]
We study the cosmological FRW flat solutions generated in general massive gravity
theories. Such a model are obtained adding to the Einstein General Relativity action
a peculiar non derivative potentials, function of the metric components, that induce
the propagation of five gravitational degrees of freedom. This large class of theories
includes both the case with a residual Lorentz invariance as well as the case with
rotational invariance only. It turns out that the Lorentz-breaking case is selected
as the only possibility. Moreover it turns out that that perturbations around strict
Minkowski or dS space are strongly coupled. The upshot is that even though dark energy
can be simply accounted by massive gravity modifications, its equation of state w_{eff}
has to deviate from -1. Indeed, there is an explicit relation between the strong coupling
scale of perturbations and the deviation of w_{eff} from -1. Taking into account
current limits on w_{eff} and submillimiter tests of the Newton's law
as a limit on the possible strong coupling scale, we find that it is still possible
to have a weakly coupled theory in a quasi dS background. Future experimental improvements
on short distance tests of the Newton's law may be used to tighten the deviation
of w_{eff} form -1 in a weakly coupled massive gravity theory$$$$