Search for anomalous production of highly boosted Z bosons decaying to dimuons in proton-proton collisions at sqrt(s) = 7 TeV

TL;DR

This study searches for highly boosted Z bosons decaying to dimuons in proton-proton collisions at 7 TeV, finding no deviations from the standard model and setting new mass exclusion limits on excited quarks.

Contribution

First search for anomalous high-pt Z bosons decaying to dimuons at 7 TeV, providing constraints on excited quark models and contact interactions.

Findings

Observed transverse-momentum distribution matches standard model.

Excluded excited quark masses below 1.94 TeV for certain models.

Excluded excited quark masses below 2.22 TeV for contact interaction models.

Abstract

Results are reported from a search for the anomalous production of highly boosted Z bosons with large transverse momentum and decaying to dimuons. Such Z bosons may be produced in the decays of new heavy particles. The search uses pp collision data at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 5.0 inverse femtobarns recorded with the CMS detector. The shape of the observed transverse-momentum distribution of Z bosons is consistent with standard model expectations. Constraints are obtained on models predicting the production of excited quarks decaying via electroweak processes. Assuming a compositeness scale that is equal to the excited quark mass as well as transition coupling strengths between Z bosons and excited quarks that are equal to standard model couplings to quarks, masses of excited quarks below 1.94 TeV are excluded at the 95% confidence level. For excited quark production via a novel contact interactions, masses below 2.22 TeV are excluded, even if the excited quarks do not couple to gluons.