Search for associated production of a Z boson with a single top quark and for tZ flavour-changing interactions in pp collisions at sqrt(s) = 8 TeV

Search for associated production of a Z boson with a single top quark and for tZ flavour-changing interactions in pp collisions at sqrt(s) = 8 TeV

CMS

Collaboration

2016

21 pages

Report number:

CMS-PAS-TOP-12-039

Experiments:

CERN-LHC-CMS

View in:

CERN Document Server

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Abstract:

A search for the production of a single top quark in association with a Z boson is presented, both to identify the expected standard model (SM) process and to search for flavour changing neutral current (FCNC) interactions. The data sample corresponds to an integrated luminosity of 19.7/fb recorded by the CMS experiment at the LHC in proton-proton collisions at sqrt(s) = 8 TeV. Final states with three leptons, electrons or muons, and at least one jet are investigated. A moderate excess of events compatible with SM tZq production is observed, and the corresponding cross section is measured to be

\sigma ({\rm tZq \rightarrow \ell} \nu {\rm b \ell^+ \ell^- q}) = 10^{+8}_{-7}

fb with a significance of 2.4

\sigma

. No presence of FCNC production of tZ(q) is observed and exclusion limits at 95% confidence level on the branching ratios of a top quark decaying to a Z boson and an up or a charm quark are found to be

BR({\rm t\rightarrow Zu}) < 0.017

% and

BR({\rm t \rightarrow Zu}) < 0.020

%, respectively.

Note:

Preliminary results

Data
p p: colliding beams
top: single production
neutral current: flavor changing
p p: scattering
interaction: flavor changing
Z0: associated production
top: branching ratio: upper limit
cross section: measured
CERN LHC Coll

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