Search for pair-produced massive coloured scalars in four-jet final states with the ATLAS detector in proton–proton collisions at $\sqrt{s} = 7\ \mbox{TeV}$

Abstract

A search for pair-produced massive coloured scalar particles decaying to a four-jet final state is performed by the ATLAS experiment at the LHC in proton-proton collisions at √ s = 7 TeV. The analysed data sample corresponds to an integrated luminosity of 4.6 fb −1 . No deviation from the Standard Model is observed in the invariant mass spectrum of the two-jet pairs. A limit on the scalar gluon pair production cross section of 70 pb (10 pb) is obtained at the 95 % confidence level for a scalar gluon mass of 150 GeV (350 GeV). Interpreting these results as mass limits on scalar gluons, masses ranging from 150 GeV to 287 GeV are excluded at the 95 % confidence level.

Towards an understanding of jet substructure

“…Another part of the reason is that at higher orders the wrong-branch contribution involves a Sudakov-type suppression, coming from the probability that the harder prong of the jet was less massive than the softer one, even though it has an energy that is at least a factor of 1/y cut larger than the softer prong. The small contribution from the wrong-branch configurations is illustrated 11 In the phase-space region where θ ∼ θ23 ∼ R, the approximation of strongly ordered angles is inappropriate. The determination of the exact onset of the wrong-branch issue would require a full treatment of that region.…”

“…[4][5][6][7] for studies on QCD jets and refs. [8][9][10][11][12][13][14] for searches). The taggers' and groomers' action is twofold: they aim to suppress or reshape backgrounds, while retaining signal jets and enhancing their characteristic jet-mass peak at the W/Z/Higgs/top/etc.…”

LHC constraints on color octet scalars

“…We begin with both scalars decaying to dijets, for which we suppress the decay into top-pairs with η U = 0 and the decay into W j with λ 2 = −5. In the upper panels of Figure 5 we compare the model to published results from ATLAS at 7 TeV which cover the low mass region, 150 − 350 GeV [40] using their acceptance cuts p T j > 80 GeV and |η j | < 1.4. For the mass region up to 1 TeV we compare in the middle panels with the CMS preliminary results at 7 TeV [41], in this case with the acceptance cuts given by p T j > 110 GeV, |η j | < 2.5 and ∆R jj > 0.7.…”

Probing light stops with stoponium

“…Such a RPV stop is challenging to probe with direct searches at LHC. Despite its large production cross section, the signature of four jets (paired dijet resonances) is difficult to disentangle from the QCD background, and stops as light as ∼ 100 GeV are still allowed [19,20,76] although some range of the stop masses 200-350 GeV has recently been excluded [77].…”

“…In fact, this may be [75,81,82]. Stops with prompt RPV decays in the red-shaded region are also constrained from RPV searches [76]. Stoponium can therefore be relevant for a broad range of RPV couplings, λ 10 −2 , and the current exclusion from stoponium resonances is shown as blue-hatched.…”