Emerging Jets Pedro Schwaller DESY Hamburg LHC Searches for - PowerPoint PPT Presentation

Emerging Jets Pedro Schwaller DESY Hamburg LHC Searches for Long-Lived BSM Particles: 
 Theory Meets Experiment UMass Amherst Based on: 11/13/15 PS, Stolarski, Weiler, JHEP 1515 (2015)

2 What is an Emerging Jet? Tracking QCD Volume hadrons neutral, SM 
 singlet states (dark pions)

3 What is an Emerging Jet? Possible origin: Hidden sector with Tracking QCD Volume confining SU(N) hadrons gauge interactions “dark QCD” Bai, PS, PRD 2014 neutral, SM 
 PS, Stolarksi, Weiler, JHEP 2015 singlet states Also in “Hidden Valleys” (dark pions) Strassler, Zurek, 2006,2007 Han, Strassler, Zurek, 2007

4 Outline • Why Emerging Jets • Search Strategies for ATLAS/CMS • LHCb opportunities

5 Dark QCD • (Asymmetric) Dark Matter ‣ Stability (dark baryon), relic density Ω DM ≈ n B M DM ‣ Self interactions (small scale structure) ‣ Efficient annihilation p D ¯ p D → π D π D • Naturalness ‣ Twin Higgs (top partners w/ dark color) ‣ Relaxion (dark axion potential from dark QCD)

6 Dark QCD • SU(N) dark sector QCD dark QCD with neutral 
 X d “dark quarks” TeV • Confinement scale asymmetry Λ darkQCD sharing p D , . . . • DM is composite annihilation “dark proton” π D , . . . GeV p , n decay • “Dark pions” π , K , . . . unstable, long lived

7 Dark QCD • DM/Naturalness motivates Λ Dark ∼ few GeV Ω DM ∼ M DM ‣ e.g. Ω B M B • Dark pion lifetime possibly macroscopic ✓ M X ◆ 4 ✓ GeV ◆ 5 c τ ( π D → SM) ∼ M 4 X ∼ cm × m 5 TeV m π D π D Also: Important to close gap between prompt (multi-jet) and long lived (MET) searches for new physics

8 Should we have seen this already? Main differences: • ATLAS (arXiv:1409.0746) • Lower mass • Lower track multiplicities • CMS (arxiv:1411.6530) from individual vertices • Multiple displaced vertices • LHCb (arxiv:1412.3021) in same cone displaced dijet emerging jet (also: not trackless!)

9 Model • Mediators: L ⊃ κ Φ ¯ Q D d R ‣ Bifundamental scalar Φ L ⊃ g 0 ¯ Q D γ µ Q D Z 0 Z 0 ‣ or (Hidden Valleys!) µ + couplings to SM • Pair production of heavy bi-fundamental fields: 
 Φ q ¯ q Φ ∗ • Decay to quark - dark quark pairs: Two QCD jets, two Emerging Jets

10 Emerging Jets at the LHC • Characteristic: ‣ few/no tracks 
 in inner tracker • New “emerging” 
 jet signature • Universal for 
 large class of 
 composite DM 
 models!

11 Strategy Veto tracks here!

12 PS, Stolarski, Weiler, JHEP 2015 Benchmark Signal/Strategy • Pair production of 1 TeV bi-fundamental scalars • Trigger on 4 HCAL jets p T > 200 GeV • Require one or two “emerging jets:” 
 Jets with at most 0/1/2 tracks originating from a distance r < r cut Model A Model B • Two scenarios: 10 GeV 4 GeV Λ d 20 GeV 8 GeV m V 5 GeV 2 GeV m π d 150 mm 5 mm c τ π d

13 Dark Shower 80 Ê Ê e + e − → Q D ¯ Q D Ê 70 Pythia 8 Ê Ê Carloni, 60 dark ‡ Ê ‡ Sjostrand, n f = 7 Ê ‡ 2010 meson Ê ‡ 50 + modifications Ê ‡ multi- github.com/pedroschwaller/EmergingJets Ê ‡ ‡ n f = 2 Ê Ê 40 ‡ plicities ‡ Ê ‡ Ê ‡ ‡ ‡ ‡ ‡ Ê 30 Ê ‡ 20 0 1000 2000 3000 4000 s @ GeV D s ! 1 6 ✓ 1 4 + 5 n f ◆ h N (ˆ s ) i / exp s ) + log α s (ˆ s ) πα s (ˆ 54 π b 1 b 1

14 Cut Efficiencies Signal Background E ( 1 GeV, n, r ) ≥ 1, QCD E ( 1 GeV, n, r ) ≥ 1, Model A 0.100 1.0 � τ 0.8 0.010 fraction fraction 0.6 0 tracks 0.001 0.4 1 track 2 tracks 0.2 10 - 4 0.0 0.1 1 10 100 1000 0.1 1 10 100 1000 r [ mm ] r [ mm ] E ( 1 GeV, n, r ) ≥ 1, Model B • Factor 100-1000 improved S/B per jet , compared to ordinary 4-jet search

15 Composition of QCD backgrounds • QCD jets with p T,j > 200 GeV QCD Emerging Jets, n = 0 QCD Trackless Emerging Jets, n = 0 100 60 N tot = 688 80 N tot = 146 50 bottom charm 60 40 strange N jet N jet 30 40 20 20 10 0 0 0.1 1. 10. 100 1000 neutron strange g r @ mm D = 2 = 2 Track(s) appears at distance r Purely trackless jets 400 1000 3593 Flavour of long lived state identity of hardest particle 2187 bottom 300 800 m ange N 600 N 200 400 100 200 0 0 0.1 1. 10. 100 1000 neutron ange none g @ mm D

16 S/B Model A Model B QCD 4-jet Tree level 14.6 14.6 410,000 fb ≥ 4 jets, | η | < 2 . 5 p T (jet) > 200 GeV 4.9 8.4 48,000 fb H T > 1000 GeV E (1 GeV , 0 , 3 mm) ≥ 1 4.1 4.1 45 fb E (1 GeV , 0 , 3 mm) ≥ 2 1.8 0.8 ∼ 0 . 08 fb E (1 GeV , 0 , 100 mm) ≥ 1 1.7 . 0 . 01 8.5 fb E (1 GeV , 0 , 100 mm) ≥ 2 0.2 . 0 . 01 . 0 . 02 fb • Can still add paired di-jet cuts • Will also catch some displaced vertex & SIMP signals, possibly photon jets

17 Reach ATLAS/CMS Model A, 14 TeV, 100 fb - 1 Model B, 14 TeV, 100 fb - 1 1000 1000 300 300 100 mm 100 mm 2 s 2 s 100 100 c t 0 @ mm D c t 0 @ mm D 5 s 5 s 30 30 5 s 5 s 10 10 3.0 mm 2 s 3.0 mm 2 s 3.0 3.0 1.0 1.0 400 600 800 1000 1200 1400 1600 400 600 800 1000 1200 1400 1600 M X @ GeV D M X @ GeV D • Optimistic scenario (no non-collisional BGs) • More realistic studies under way at CMS (ATLAS soon?)

18 Other New Physics M. Kagan’s W RPV ⊃ 1 • RPV SUSY 00 talk (monday) 2 λ ijk U i D j D k • One of the last “natural” MSSM scenarios QCD jet q ˜ q χ 1 Emerging jet q ¯ q χ 1 Emerging jet ¯ ˜ q long lived ¯ q QCD jet

19 RPV SUSY sensitivity RPV model, M c = 100 GeV, 14 TeV, 100 fb - 1 • Competitive with 3000 displaced vertex 1000 searches 2 s 300 100 c t 0 @ mm D • Less model 30 100 mm dependent 10 5 s 5 s 3.0 • “Natural SUSY” 2 s 3.0 mm 1.0 scenario with top jets 0.3 to be done 600 800 1000 1200 1400 1600 é @ GeV D M q

Beyond ATLAS/CMS

21 LHCb opportunities • Z’ mediator is difficult to trigger at ATLAS/CMS 
 Same if dominant production is off-shell 
 q q D q q D Z 0 q q D q q D • Reconstruct individual dark pions, differentiate 
 using lifetime, mass, decay products • Emerging jets without (hard) trigger requirements?

22 Off-shell production u γ µ u )( ¯ Q D γ µ Q D ), or O u = 1 / Λ 2 (¯ 10 - 5 L = 5 TeV pb ê GeV 10 - 6 10 - 7 L = 10 TeV 10 - 8 0 1000 2000 3000 4000 M inv @ GeV D ◆ 4 ✓ TeV σ ( pp → ¯ • Total rate: × N d × N F Q D Q D ) ≈ 8 . 2 pb × Λ √

23 Forward region 12 0.10 Model A 10 Model B 0.08 % of events 8 0.06 6 Model A 0.04 4 Model B 0.02 2 0 0.00 0 5 10 15 20 25 30 0 20 40 60 80 100 N p D with 2 < h < 5 » p Π D » @ GeV D • Fraction of all signal • Momentum (not pT) events with N dark distribution of dark pions in pions in 2 < η < 5 2 < η < 5

24 Decay characteristics 0.5 Model B 0.4 0.3 0.2 Model A 0.1 0.0 2 4 6 8 10 12 14  charged tracks per p D • Number of charged tracks from dark pion decays • Also depend on flavour structure - some more work! • Beyond LHC: SHiP, PADME, FCC?

25 Summary • “Dark QCD” motivated in many BSM scenarios, in particular: DM and Naturalness • Emerging jets are smoking gun, good prospects for ATLAS/CMS ‣ Test TeV scale mediators without MET or Leptons ‣ Also sensitive to other displaced scenarios • LHCb, SHiP could be complementary - in “progress”

Supplemental Material

27 pT weighted strategy 1 • Displaced fraction of jet X p i F ( r ) = T p calo − jet T L xy >r ( = ) Model A QCD 0.20 1 Highest 2nd 0.100 0.15 Highest: r = 3mm 0.010 0.10 2nd: r = 3mm 0.001 2nd: r = 100mm 0.05 Highest: r = 100mm 10 - 4 0.00 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 F ( r = 100 mm ) F

Shapes & Substructure?

29 Jet Shape(s) 1 X p i • Girth 
 T ∆ R i p jet T i Model A Model B 0.10 0.10 Model A Model B 0.08 0.08 QCD QCD 0.06 0.06 0.04 0.04 0.02 0.02 0.00 0.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.00 0.05 0.10 0.15 0.20 0.25 0.30 • Model discrimination (?) • Subtleties: Might loose hardest dark meson, etc…

30 What if c τ ≪ mm ? • No displaced tracks. Can we still discriminate QCD and dark QCD jets? • Sub-jets from 
 1000 individual dark 
 pion decays 800 R Decay, fi @ mm D 100 600 400 Probably discussed 8 years ago 10 in context of Hidden Valleys 200 0 Much better tools 
 - 6 - 4 - 2 0 2 4 6 1 now available!!! 0 10 20 30 40 50 60 P T , Meson @ GeV D