Bottom Fermion Fusion initial states

Andrea Delgado, Denis Rathjens, Mykhailo Dalchenko, Peisi Huang

May 18, 2017

1 / 12 Table of contents

1 Motivation of BFF initial states

2 BFF kinematic properties BFF vs QCD

2 / 12 The usefulness of special initial states

g q Specific initial states are utilized 2 in various ways to search for new physics: 1 Direct dark matter production q1 DM +1 jet → Monojet searches 2 New physics + Vector Boson q0 Fusion quark jets → VBF 1 searches These kinds of analyses utilize q1 known physics for the initial state to suppress Standard W /Z 0 Model backgrounds W /Z Z As a bonus, different initial q states make these analyses 2 complementary by design So let’s add a state to the list q0 2 3 / 12 Bottom Fermion Fusion

b Utilizes the only reliably identifiable jet state (bottom g quarks) Is a handle on physics coupling b to 3rd generation quarks Z 0 b → +0 jet states suppressed in direct production by bottom g PDFs → +1 jet radiative diagrams 1 suppressed by e. g. M2 Z0 b

4 / 12 Suppression of +0 jet initial states

b

Z 0

b

Bottom states directly from the parton distribution functions are very rare Having a bottom + anti-bottom initial state carrying appreciable momenta is exceedingly unlikely

5 / 12 Suppression of +1 jet initial states

Z 0 b g b

b Z 0 g b

Taking a gluon from one proton Having a gluon split to bb solves most of the necessary solves the radiative suppression, momentum supply for heavy but adds a g → bb branching resonance production ratio factor in addition to the But radiating e. g. a Z’ is bottom pdf suppressed by a factor of 1 in M2 Z0 addition to the bottom pdf

6 / 12 Table of contents

1 Motivation of BFF initial states

2 BFF kinematic properties BFF vs QCD

7 / 12 Kinematics of BFF compared to likely backgrounds

If the BFF-produced heavy resonance decays hadronically, a final state with 4 bottom jets is likely b → The dominant background in this scenario is QCD (gg → bbbb, as well as misidentified jets) g → Subdominant backgrounds include DY in Z+2 bottom jets and di-boson b production Z 0 b If the BFF-produced heavy resonance decays leptonically, we’d expect two g bottoms and two leptons in the final states → The dominant background in this b scenario is ttbar → Subdominant backgrounds include DY +2 jets and di-boson production

8 / 12 ∆Φ34=BFF vs ∆Φ12=Z’

Z’ 500 GeV QCD

Zp vs BFF hypotheses angular separations Zp vs BFF hypotheses angular separations 34 -2 34 Φ 3 10 Φ 3 10-2 ∆ ∆

2.5 2.5

2 -3 2 10 10-3

1.5 1.5

1 -4 1 10 10-4

0.5 0.5

0 0 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 ∆φ ∆φ 12 12 If a heavy resonance is produced, the BFF jets are most likely to be the least energetic jets in the event

So taking the 3rd and 4th leading jet (generator jet level, pT (4) > 30 GeV) denotes the BFF system The first two leading jets are hypothesized to originate from a Z’ here

9 / 12 Scalar transverse momenta gap between Z’ and BFF

Z’ 500 GeV QCD

Σ p (Z') - Σ p (BFF) Σ p (Z') - Σ p (BFF) T T T T 0.08

−1 0.07 10

0.06 fraction of events fraction of events 10−2 0.05

− 0.04 10 3

0.03

10−4 0.02

0.01 − 10 5 0 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 ∆Σ p (Z'-BFF) [GeV] ∆Σ p (Z'-BFF) [GeV] T T Depending on the resonance mass, a large gap between the BFF jet transverse momenta and the Z’ jet transverse momenta will occur For QCD, a large gap is the least likely case Thereby, in heavy resonance cases the background is more easily suppressed

10 / 12 Sign products of BFF vs Z’ hypotheses

Z’ 500 GeV QCD

sign(η ×η ) BFF vs Z' sign(η ×η ) BFF vs Z' 1 2 1 2 0.3 BFF

0.27 BFF η η 4 4 0.265 0.29

0.28 0.26 sign product sign product 2 2 0.27 0.255 0.26 0.25 0 0 0.25 0.245 0.24 0.24 -2 -2 0.23 0.235 0.22 -4 0.23 -4 0.21 0.225 -4 -2 0 2 4 -4 -2 0 2 4 sign product η sign product η Z' Z' The BFF production is, unlike for VBF, very central There are slight differences in the forward-backward configurations of the jet systems with respect to QCD

11 / 12 Conclusions

Additional jets in initial states have their place in complementary ways to access new physics (Monojet or VBF) Bottom Fermion Fusion initial states might be yet another way to access new physics coupling to third generation quarks Preliminary look into discriminating variables are somewhat promising with respect to QCD and ttbar

12 / 12