9 research outputs found
Model-independent Z' searches at modern colliders
The model-independent constraints on the Abelian Z' couplings from the LEP data are applied to estimate the Z' production in experiments at hadron colliders. The Z' contribution to the Drell-Yan process at modern hadron colliders is analyzed. The results are compared with model-dependent predictions and present experimental data from the Tevatron and the LHC. The lower bounds on the Z' mass are derived and the Z' discovery limit in the LHC experiments is found.С помощью модельно-независимых ограничений на константы связи абелевого Z'-бозона получены оценки процессов рождения Z' в экспериментах на адронных коллайдерах. Изучен вклад Z'-бозона в процесс Дрелла-Яна. Проведено сравнение полученных результатов с модельно-зависимыми предсказаниями и экспериментальными данными ускорителей Tevatron и LHC. Получена нижняя граница значения массы Z'-бозона, а также предельные значения массы, при которых Z' будет обнаружен в эксперименте LHC.За допомогою модельно-незалежних обмежень констант зв’язку абелевого Z'-бозона отримано оцінки процесів народження Z'-бозона в експериментах на гадронних колайдерах. Досліджено внесок Z' в процес Дрелла-Яна. Виконано порівняння отриманих результатів з модельно-залежними результатами та експериментальними даними прискорювачів Tevatron та LHC. Отримана нижня границя маси Z'-бозона, а також граничні значення маси, при яких Z'-бозон буде знайдено в експериментах LHC
Sneutrino Identification in Lepton Pair Production at ILC with Polarized Beams
Numerous non-standard dynamics are described by contact-like effective
interactions that can manifest themselves in electron-positron collisions only
through deviations of the observables (cross sections, asymmetries) from the
Standard Model predictions. If such a deviation were observed, it would be
important to identify the actual source among the possible non-standard
interactions as many different new physics scenarios may lead to very similar
experimental signatures. We study the possibility of uniquely identifying the
indirect effects of s-channel sneutrino exchange, as predicted by
supersymmetric theories with R-parity violation, against other new physics
scenarios in high-energy e^+e^- annihilation into lepton pairs at the
International Linear Collider. These competitive models are interactions based
on gravity in large and in TeV-scale extra dimensions, anomalous gauge
couplings, Z' vector bosons and compositeness-inspired four-fermion contact
interactions. To evaluate the identification reach on sneutrino exchange, we
use as basic observable a double polarization asymmetry, that is particularly
suitable to directly test for such s-channel sneutrino exchange effects in the
data analysis. The availability of both beams being polarized plays a crucial
role in identifying the new physics scenario.Comment: 10 pages, 3 figure
Identification of extra neutral gauge bosons at the International Linear Collider
Heavy neutral gauge bosons, Z's, are predicted by many theoretical schemes of
physics beyond the Standard Model, and intensive searches for their signatures
will be performed at present and future high energy colliders. It is quite
possible that Z's are heavy enough to lie beyond the discovery reach expected
at the CERN Large Hadron Collider LHC, in which case only indirect signatures
of Z' exchanges may occur at future colliders, through deviations of the
measured cross sections from the Standard Model predictions. We here discuss in
this context the foreseeable sensitivity to Z's of fermion-pair production
cross sections at an e^+e^- linear collider, especially as regards the
potential of distinguishing different Z' models once such deviations are
observed. Specifically, we assess the discovery and identification reaches on
Z' gauge bosons pertinent to the E_6, LR, ALR and SSM classes of models, that
should be attained at the planned International Linear Collider (ILC). With the
high experimental accuracies expected at the ILC, the discovery and the
identification reaches on the Z' models under consideration could be increased
substantially. In particular, the identification among the different models
could be achieved for values of Z' masses in the discovery (but beyond the
identification) reach of the LHC. An important role in enhancing such reaches
is played by the electron (and possibly the positron) longitudinally polarized
beams. Also, although the purely leptonic processes are experimentally cleaner,
the measurements of c- and b-quark pair production cross sections are found to
carry important, and complementary, information on these searches.Comment: 21 page