Improved jet substructure methods: Y-splitter and variants with grooming

Abstract

It has recently been demonstrated with Monte Carlo studies that combining the well-known Y-splitter and trimming techniques gives rise to important gains in the signal significance achievable for boosted electroweak boson tagging at high p t . Here we carry out analytical calculations that explain these findings from first principles of QCD both for grooming via trimming and via the modified mass-drop tagger (mMDT). We also suggest modifications to Y-splitter itself, which result in great simplifications to the analytical results both for pure Y-splitter as well as its combination with general grooming methods. The modifications also lead to further performance gains, while making the results largely independent of choice of groomer. We discuss the implications of these findings in the broader context of optimal methods for boosted object studies at hadron colliders.

Computing N -subjettiness for boosted jets

“…It has also seen many more recent developments, noticeably analytic studies of substructure observables (e.g. [10][11][12][13][14][15][16][17][18][19]), the use of substructure techniques to probe the quark-gluon plasma in high-energy heavy-ion collisions (e.g. [20][21][22][23][24]), the use of Machine Learning techniques (e.g.…”

Dichroic subjettiness ratios to distinguish colour flows in boosted boson tagging

“…If we take for example the case of the mMDT, this prefactor would be largely suppressed for the background -going from ∼ α s log(1/ρ) for full N -subjettiness to ∼ α s log(1/z cut ) for the dichroic method -while the signal would only be suppressed by a much smaller factor ∼ 1 − 2z cut . Additionally, measuring the tagged jet mass instead of the full jet mass significantly reduces ISR and non-perturbative effects which would otherwise affect the resolution of the signal mass peak (see also [28,29]). …”

“…To complete our Monte Carlo studies, in figure 13 we compare the performance of τ dichroic 21,groomed with various other tools: mMDT tagging alone, SoftDrop grooming alone (β = 2 as above), and also the Y m variant [29] of Y-splitter [43], combined either with SoftDrop (pre-)grooming or with trimming [44], as described in detail in ref. [29] (see also ref.…”

“…[29], the one that gave the best signal-to-background discrimination was Y m with trimming, shown as red solid squares in figure 13. Overall it performs less well than the mMDT plus τ dichroic 21,groomed combination with S fixed to 0.4, even though is has a broadly similar signal efficiency.…”

Predictions for energy correlators probing substructure of groomed heavy quark jets

“…Developments in jet substructure (see [36] for a recent review) have shown that the modified mass drop tagging algorithm (mMDT) or soft-drop grooming procedure robustly removes contamination from both underlying event and non-global color-correlations, see Refs. [21,22,37], and have been applied to study a wide variety of QCD phenomenology within jets [38][39][40][41][42][43][44][45][46].…”