176 research outputs found
CompHEP-PYTHIA interface: integrated package for the collision events generation based on exact matrix elements
CompHEP, as a partonic event generator, and PYTHIA, as a generator of final
states of detectable objects, are interfaced. Thus, integrated tool is proposed
for simulation of (almost) arbitrary collision processes at the level of
detectable particles. Exact (multiparticle) matrix elements, convolution with
structure functions, decays, partons hadronization and (optionally) parton
shower evolution are basic stages of calculations. The PEVLIB library of event
generators for LHC processes is described.Comment: Standard LaTeX, 4 pages. To appear in the proceedings of the Seventh
International Workshop on Advanced Computing and Analysis Technics in Physics
Research (ACAT2000, Fermilab, October 16-20, 2000
Control of Mooij correlations at the nanoscale in the disordered metallic Ta - nanoisland FeNi multilayers
Localisation phenomena in highly disordered metals close to the extreme
conditions determined by the Mott-Ioffe-Regel (MIR) limit when the electron
mean free path is approximately equal to the interatomic distance is a
challenging problem. Here, to shed light on these localisation phenomena, we
studied the dc transport and optical conductivity properties of nanoscaled
multilayered films composed of disordered metallic Ta and magnetic FeNi
nanoisland layers, where ferromagnetic FeNi nanoislands have giant magnetic
moments of 10^3-10^5 Bohr magnetons (\mu_B). In these multilayered structures,
FeNi nanoisland giant magnetic moments are interacting due to the indirect
exchange forces acting via the Ta electron subsystem. We discovered that the
localisation phenomena in the disordered Ta layer lead to a decrease in the
Drude contribution of free charge carriers and the appearance of the low-energy
electronic excitations in the 1-2 eV spectral range characteristic of
electronic correlations, which may accompany the formation of electronic
inhomogeneities. From the consistent results of the dc transport and optical
studies we found that with an increase in the FeNi layer thickness across the
percolation threshold evolution from the superferromagnetic to ferromagnetic
behaviour within the FeNi layer leads to the delocalisation of Ta electrons
from the associated localised electronic states. On the contrary, we discovered
that when the FeNi layer is discontinuous and represented by randomly
distributed superparamagnetic FeNi nanoislands, the Ta layer normalized dc
conductivity falls down below the MIR limit by about 60%. The discovered effect
leading to the dc conductivity fall below the MIR limit can be associated with
non-ergodicity and purely quantum (many-body) localisation phenomena, which
need to be challenged further.Comment: 29 pages, 8 figures. This is a post-peer-review, precopyedit version
of an article published in Scientific Reports. The final authenticated
version is available online at http://dx.doi.org/10.1038/s41598-020-78185-
Noncommutative geometry inspired black holes in higher dimensions at the LHC
When embedding models of noncommutative geometry inspired black holes into
the peridium of large extra dimensions, it is natural to relate the
noncommutativity scale to the higher-dimensional Planck scale. If the Planck
scale is of the order of a TeV, noncommutative geometry inspired black holes
could become accessible to experiments. In this paper, we present a detailed
phenomenological study of the production and decay of these black holes at the
Large Hadron Collider (LHC). Noncommutative inspired black holes are relatively
cold and can be well described by the microcanonical ensemble during their
entire decay. One of the main consequences of the model is the existence of a
black hole remnant. The mass of the black hole remnant increases with
decreasing mass scale associated with noncommutative and decreasing number of
dimensions. The experimental signatures could be quite different from previous
studies of black holes and remnants at the LHC since the mass of the remnant
could be well above the Planck scale. Although the black hole remnant can be
very heavy, and perhaps even charged, it could result in very little activity
in the central detectors of the LHC experiments, when compared to the usual
anticipated black hole signatures. If this type of noncommutative inspired
black hole can be produced and detected, it would result in an additional mass
threshold above the Planck scale at which new physics occurs.Comment: 21 pages, 7 figure
Study of a novel type of the optical modes in VCSELs
We study novel side-emitting modes in VCSEL microcavities. These modes correspond to π-shaped propagation along the mesa diameter, reflection from angled mesa walls and bottom Bragg reflector. We believe this study of π-modes is important for optimization of VCSEL design for improvement of efficiency
Supersymmetric Monojets at the Large Hadron Collider
Supersymmetric monojets may be produced at the Large Hadron Collider by the
process qg -> squark neutralino_1 -> q neutralino_1 neutralino_1, leading to a
jet recoiling against missing transverse momentum. We discuss the feasibility
and utility of the supersymmetric monojet signal. In particular, we examine the
possible precision with which one can ascertain the neutralino_1-squark-quark
coupling via the rate for monojet events. Such a coupling contains information
on the composition of the neutralino_1 and helps bound dark matter direct
detection cross-sections and the dark matter relic density of the neutralino_1.
It also provides a check of the supersymmetric relation between gauge couplings
and gaugino-quark-squark couplings.Comment: 46 pages, 10 figures. The appendix has been rewritten to correct an
error that appears in all previous versions of the appendix. This error has
no effect on the results in the main body of the pape
Interleaved Parton Showers and Tuning Prospects
General-purpose Monte Carlo event generators have become important tools in
particle physics, allowing the simulation of exclusive hadronic final states.
In this article we examine the Pythia 8 generator, in particular focusing on
its parton-shower algorithms. Some relevant new additions to the code are
introduced, that should allow for a better description of data. We also
implement and compare with 2 to 3 real-emission QCD matrix elements, to check
how well the shower algorithm fills the phase space away from the soft and
collinear regions. A tuning of the generator to Tevatron data is performed for
two PDF sets and the impact of first new LHC data is examined
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