Safe jet vetoes

Abstract

Central jet vetoes are powerful tools for reducing QCD background in measurements and searches for electroweak and colorless, new physics processes in hadron collisions. In this letter, we report the key findings of a new philosophy to designing searches for such phenomena at hadron colliders, one designed and centered around a dynamical jet veto instead a static veto applied independently of other selection criteria. Specifically, we investigate the theoretical and phenomenological consequences of setting the jet veto scale to the transverse momentum (p T ) of the leading charged lepton ℓ in multi-lepton processes on an event-byevent basis. We consider the case of a TeV-scale heavy neutrino N decaying to the trilepton final state and find the following: (i) Perturbative uncertainties associated with the veto greatly reduce due to tying the veto scale to the hard process scale. (ii) The signal efficiency for passing the veto jumps to 95% and exhibits little-to-no dependence on the neutrino mass scale. (iii) Top quark and "fake" lepton rejection capabilities also improve compared to only vetoing heavy flavor-tagged jets above a fixed p T . This results in an increased sensitivity to active-sterile neutrino mixing by approximately an order of magnitude over the LHC's lifetime. For a Dirac neutrino with mass m N = 150 − 1000 GeV and the representative active-sterile mixing hypothesis |V e4 | = |V τ4 | with |V µ4 | = 0, we find that LHC experiments can probe |V e4 | 2 , |V τ4 | 2 6 × 10 −4 − 8 × 10 −3 , surpassing the global upper limit for m N < 450 GeV, with L = 3 ab −1 of data at √ s = 14 TeV. Due to the color structures of the heavy N production mechanisms considered, we argue that our results hold broadly for other color-singlet processes.

Model-independent search strategy for the lepton-flavor-violating heavy Higgs boson decay to $${\tau \mu }$$ at the LHC

“…This is not necessarily the case for the W +jets background, therefore requiring that E miss T < p µ T will help reducing it. Indeed, and more generally, what we will want to do is to look for events in which the leading particle is a muon, in a similar way to the dynamical jet veto proposed in [33].…”

Sleptons without hadrons

“…Among the several promising lines of such investigations are those that consider the impact of jet vetoes (i.e., the rejection of events featuring jets with a transverse momentum greater than some threshold p Veto T [15- * Electronic address: fuks@lpthe.jussieu.fr † Electronic address: knordstrom@lpthe.jussieu.fr ‡ Electronic address: richard.ruiz@uclouvain.be § Electronic address: sophie.williamson@kit.edu 19]) in measurements of and searches for heavy, colorless SM [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and beyond the SM [35][36][37][38][39][40][41][42] states. Interestingly, recent studies of multilepton searches for heavy, colorless exotic particles have demonstrated that dynamic jet vetoes can significantly improve discovery potential [41,42]. More specifically, a proposed analysis premised on setting p Veto T on an event-by-event basis to the hardness (p T ) of the event's leading lepton was found to improve sensitivity by roughly an order of magnitude.…”

Doubly charged Higgs boson production at hadron colliders

“…Taken together, we see that typical [102] experimental jet veto thresholds of p Veto T = 20 − 40 GeV, reduce triplet production cross sections severely and potentially discourage their use. However, we note that the criteria needed to employ a socalled dynamic (or event-based) jet veto [47][48][49], which can significantly improve jet veto efficiencies and background rejection rates, appear to be satisfied. Investigations into dynamic jet vetoes in triplet scalar searches is left to future work.…”

“…Following signifiant improvements in modeling soft jet activity in both color-singlet and QCD processes, the use of jet vetoes in direct searches for new phenomena is becoming increasingly standard at the LHC, as shown, for example, in Refs. [47][48][49][95][96][97]. With the TypeI-ISeesaw libraries it is possible to predict jet veto cross sections for triplet scalars up to NLO+NNLL(veto) using the MadGraph5 aMC@NLO-SCET formalism of Refs.…”

“…Consequently, studies and searches for Type II scalars using these tools are blind to significant, qualitative differences in jet activity between triplet scalar signal events and the leading background processes, and therefore cannot reliably exploit selection cuts that discriminate accordingly, e.g., jet vetoes. This is noteworthy as recent investigations show that event-based jet vetoes can substantially increase the discovery prospects of anomalous multileptonic events [47][48][49]. Beyond this limitation, no publicly available event generator describes loop-induced production and decay modes of triplet scalars.…”