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When it comes to top, no pairing is beyond belief !

On Thursday, 16th of June, at the LHCP international conference in Lund, Sweden, the CMS experiment presented the very first cross section measurement of the top pair (tt) production at 5.02 TeV center-of-mass (c.o.m) energy. The measurement tracks the evolution of the tt cross section as a function of c.o.m energy, crucial for the extraction of the top-quark pole mass, while it can be used to constrain the gluon distribution function at the un-explored large longitudinal parton momentum fraction regime. Future measurements of the tt cross section in nuclear collisions at the same nucleon-nucleon c.o.m energy would profit from the availability of such a reference measurement in pp collisions, without the need to extrapolate from measurements at different c.o.m energies.
By Georgios Konstantinos Krintiras on June 16, 2016
Additional information:

In November 2015 the LHC delivered proton-proton collisions at 5.02 TeV, with CMS having being fully efficient and having managed to collect 26pb-1 of low pileup proton-proton collision data. The fraction of tt events initiated by gluon-gluon collisions grows monotonically with center-of-mass energy, rendering this new data set partially complementary to the higher energy samples. This study exploited candidate events with an electron-muon pair of opposite charge, accompanied by the presence of at least two jets (from the hadronization of the b quarks). The cross section is extracted with an event-counting experiment approach, and found in agreement with the SM expectation (CMS-PAS-TOP-16-015). The final uncertainty of the measurement was found to be almost 30%, the latter greatly dominated by the statistical precision.

The CP3 members Georgios Krintiras and Andrea Giammanco were involved in this measurement.

Reference url: https://cds.cern.ch/record/2161499/

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