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تسجيل مستخدم جديدProduction of tau lepton pairs with high pT jets at the LHC and the TauSpinner reweighting algorithm
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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.
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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 $tau$-
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 $tau$-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 $tau$-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 $tau$ polarization are presented.
The tau-lepton plays an important role in the physics program at LHC. Its spin can be used for separation of signal from background or in measuring properties of New Particles decaying to tau leptons. The TauSpinner package represents a tool to mod
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