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Wyszukujesz frazę "Was, Z." wg kryterium: Autor


Tytuł:
Separating electroweak and strong interactions in Drell–Yan processes at LHC : leptons angular distributions and reference frames
Autorzy:
Richter-Wąs, Elżbieta
Wąs, Z.
Opis:
Among the physics goals of LHC experiments, precision tests of the Standard Model in the Strong and Electroweak sectors play an important role. Because of nature of the proton-proton processes, observables based on the measurement of the direction and energy of leptons provide the most precise signatures. In the present paper, we concentrate on the angular distribution of Drell–Yan process leptons, in the lepton-pair rest-frame. The vector nature of the intermediate state imposes that distributions are to a good precision described by spherical polynomials of at most second order. We show that with the proper choice of the coordinate frames, only one coefficient in this polynomial decomposition remains sizable, even in the presence of one or two high p_{T} jets. The necessary stochastic choice of the frames relies on probabilities independent from any coupling constants. This remains true when one or two partons accompany the lepton pairs. In this way electroweak effects can be better separated from strong interaction ones for the benefit of the interpretation of the measurements. Our study exploits properties of single gluon emission matrix elements which are clearly visible if a conveniently chosen form of their representation is used. We rely also on distributions obtained from matrix element based Monte Carlo generated samples of events with two leptons and up to two additional partons in test samples. Incoming colliding protons’ partons are distributed accordingly to PDFs and are strictly collinear to the corresponding beams.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
$\tau$-lepton pair spin in proton-proton LHC collisions for anomalous dipole moments
Autorzy:
Volkotrub, Yuriy
Was, Z.
Korchin, A. Yu.
Richter-Wąs, Elżbieta
Opis:
The spin correlations in the pair of $\tau$ leptons produced in high-energy proton-proton collisions are studied. The invariant mass of the $\tau$-lepton pair is chosen close to the Z-boson mass; in these conditions, Z-bos on exchange gives the dominant contribution to the Drell-Yan mechanism. The interaction of Z bosons with $\tau$ leptons, in addition to the Standard Model couplings, can include weak anomalous magnetic and electric dipole moments (or form factors) of the $\tau$ lepton. The dependence of elements of the pp spin-correlation matrix on the weak anomalous moments is determined for various regions of the rapidity of the $\tau$-lepton pair. Based on this calculation, we construct a semirealistic observable built on the momenta of pions in the $\tau^{\mp} \to \pi^{\mp} \nu_{\tau}$ and $\tau^{\pm} \to \rho^{\pm} \nu_{\tau} \to \pi^{\pm} \pi^{0} \nu_{\tau}$ decay channels, and we show that this observable can be sensitive to the weak anomalous dipole moments.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł

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