5,296 research outputs found
Production of tau tau jj final states at the LHC and the TauSpinner algorithm: the spin-2 case
The TauSpinner algorithm is a tool that allows to modify the physics model of
the Monte Carlo generated samples due to the changed assumptions of event
production dynamics, but without the need of re-generating events. With the
help of weights -lepton production or decay processes can be modified
accordingly to a new physics model. In a recent paper a new version TauSpinner
ver.2.0.0 has been presented which includes a provision for introducing
non-standard states and couplings and study their effects in the
vector-boson-fusion processes by exploiting the spin correlations of
-lepton pair decay products in processes where final states include also
two hard jets. In the present paper we document how this can be achieved taking
as an example the non-standard spin-2 state that couples to Standard Model
particles and tree-level matrix elements with complete helicity information
included for the parton-parton scattering amplitudes into a -lepton pair
and two outgoing partons. This implementation is prepared as the external (user
provided) routine for the TauSpinner algorithm. It exploits amplitudes
generated by MadGraph5 and adopted to the TauSpinner algorithm format.
Consistency tests of the implemented matrix elements, reweighting algorithm and
numerical results for observables sensitive to polarization are
presented.Comment: 17 pages, 6 figures; version published in EPJ
Production of \uptau τ lepton pairs with high p T jets at the LHC and the TauSpinner reweighting algorithm
The TauSpinner algorithm allows to modify the physics of the Monte Carlo
generated samples due to the changed assumptions of event production dynamics,
without re-generating events. To each event it attributes weights: the spin
effects of tau-lepton production or decay, or the production mechanism are
modified. There is no need to repeat the detector response simulation. We
document the extension to 2 to 4 processes in which the matrix elements for the
parton-parton scattering amplitudes into a tau-lepton pair and two outgoing
partons are used. Tree-level matrix elements for the Standard Model processes,
including the Higgs boson production are used. Automatically generated codes by
MadGraph5 have been adapted. Tests of the matrix elements, reweighting
algorithm and numerical results are presented. For averaged tau lepton
polarisation, we perform comparison of 2 to 2 and 2 to 4 matrix elements used
to calculate the spin weight in pp to tau tau j j events. We show, that for
events with tau-lepton pair close to the Z-boson peak, the tau-lepton
polarisation calculated using 2 to 4 matrix elements is very close to the one
calculated using 2 to 2 Born process only. For the m_(tautau) masses above the
Z-boson peak, the effect from including 2 to 4 matrix elements is also
marginal, however when restricting into subprocesses qq,q bar q to tau tau j j
only, it can lead to a 10% difference on the predicted tau-lepton polarisation.
Choice of electroweak scheme can have significant impact. The modification of
the electroweak or strong interaction can be performed with the re-weighting
technique. TauSpinner v.2.0.0, allows to introduce non-standard couplings for
the Higgs boson and study their effects in the vector-boson-fusion. The
discussion is relegated to forthcoming publications.Comment: 33 pages 7 figure
Order and disorder in the Local Evolutionary Minority Game
We study a modification of the Evolutionary Minority Game (EMG) in which
agents are placed in the nodes of a regular or a random graph. A neighborhood
for each agent can thus be defined and a modification of the usual relaxation
dynamics can be made in which each agent updates her decision scheme depending
upon the options made in her immediate neighborhood. We name this model the
Local Evolutionary Minority Game (LEMG). We report numerical results for the
topologies of a ring, a torus and a random graph changing the size of the
neighborhood. We focus our discussion in a one dimensional system and perform a
detailed comparison of the results obtained from the random relaxation dynamics
of the LEMG and from a linear chain of interacting spin-like variables at a
finite temperature. We provide a physical interpretation of the surprising
result that in the LEMG a better coordination (a lower frustration) is achieved
if agents base their actions on local information. We show how the LEMG can be
regarded as a model that gradually interpolates between a fully ordered,
antiferromagnetic system and a fully disordered system that can be assimilated
to a spin glass.Comment: 12 pages, 8 figures, RevTex; omission of a relevant reference
correcte
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