Search for new physics in events with same-sign dileptons and b jets in pp collisions at $ \sqrt{s}=8 $ TeV

Abstract

A search for new physics is performed using events with isolated same-sign leptons and at least two bottom-quark jets in the final state. Results are based on a sample of proton-proton collisions collected at a center-of-mass energy of 8 TeV with the CMS detector and corresponding to an integrated luminosity of 10.5 fb −1 . No excess above the standard model background is observed. Upper limits are set on the number of events from non-standard-model sources and are used to constrain a number of new physics models. Information on acceptance and efficiencies is also provided so that the results can be used to confront an even broader class of new physics models.

Multi-tops at the LHC

“…But even at the kinematic limit and 8 TeV, it is largely sufficient for a large majority of events to pass the most selective QCD-background-reducing cuts used in CMS lepton analyses (see [12]). Since we focus on events where two tops decay leptonically, there is also a large amount of E T coming from the undetected neutrinos, which again is typically sufficient to be distinguished from QCD events.…”

“…These leptons will be accompanied by a large number of b-jets and jets. The CMS search for same-sign dileptons production associated with b-jets (2SSL+b) presented in [12] is sensitive to such final states, so we reproduced their analysis on simulated events from our model to set limits on our parameter space. We specialised to the signal region 7 of the search (SR7), whose selection criteria are detailed in table 2, due to its low background expectation value.…”

“…However they both have drawbacks that make [12] seem most relevant: the first only focuses on opposite sign dileptons and hence will have a larger background and put weaker limits while in the latter, only signal regions SR3b and SR3L would be sensitive due to the chargino invariant mass cut of the others. However, SR3b does not use E T in its selection which allows for more QCD background and SR3L does not use b-tagging information.…”

XQCAT: eXtra Quark Combined Analysis Tool

“…We also have accounted for the updated α T analysis [65] and same-sign [66] search at 8 TeV, based on 11.7 fb −1 and 10.5 fb −1 of luminosity, respectively. It has also been checked that the selected searches are uncorrelated and therefore it is possible to statistically combine them without the need of a correlation matrix, thereby yielding 95% eCL bounds at 7 TeV (combination of 4 searches), 8 TeV (combination of 2 searches) and 7+8 TeV (combination of 6 searches).…”

Same sign di-lepton candles of the composite gluons

“…A jet is identified as a b-jet if it is close (∆R < 0.2) to a b-quark. For the b-tagging efficiency ( b ) we use the prescription from reference [63] which gives b = 0.71 for 90 GeV < p T < 170 GeV and at higher (lower) p T it decreases linearly with a slope of -0.0004 (-0.0047) GeV −1 . Moreover, the probability of mis-tagging a c-jet (light jet) as a b-jet is taken to be 20% (0.73%) [64].…”