Search for long-lived particles at CMS. TeVPA Brian Francis for the CMS Collaboration

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Roderick Cross
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1 Search for long-lived particles at CMS TeVPA 7 Brian Francis for the CMS Collaboration

Long-lived particles (LLP) at CMS Despite best efforts, no evidence yet of BSM physics at the LHC If it s not where we ve looked, hugely important to consider where we haven t!

2 Long-lived particles (LLP) at CMS Despite best efforts, no evidence yet of BSM physics at the LHC If it s not where we ve looked, hugely important to consider where we haven t! LLPs (cτ > ~5 microns) offer a wide variety of non-conventional signatures Many models predict LLPs: split/rpv SUSY, hidden valleys, magnetic monopoles Non-prompt signatures are easily missed by prompt searches CMS is already sensitive to a very wide range of particle lifetimes From well beyond the first and last active layers Search for long-lived particles at CMS TeVPA 7

3 neutral charged any charge vertex HSCP BSM quark anything conversion disappearing track di jet Search for long-lived particles at CMS TeVPA 7 Not pictured: Stopped HSCP

4 neutral charged any charge vertex HSCP BSM quark anything conversion disappearing track di jet Search for long-lived particles at CMS TeVPA 7 Not pictured: Stopped HSCP 4

5 Stopped Particle Search Considers HSCPs that become completely stopped within the detector May decay much later Two signatures searched for: Calorimeter (jets) Muon system (muons) 746 Both search in combined 5+6 dataset Search for decays out-of-time with colliding protons Backgrounds: Cosmic rays Beam halo Detector noise 5 Search for long-lived particles at CMS TeVPA 7

6 Stopped Particle Search: Calorimeter Signature Trigger on events out-of-time with proton collisions ( bunch crossings) Energetic jet (E > 7 GeV) Data collected over 7 hours of trigger livetime Data-driven background estimation m [GeV] CMS Preliminary L dt = fb s = TeV E g > GeV, E > 7 GeV t E jet > 7 GeV 95% CL Limits: ~ g observed ~ t observed ~ g expected (median) ~ g expected ±σ ~ g expected ±σ ~ t expected (median) ~ t expected ±σ ~ t expected ±σ No excess observed Places limits on gluino and stop lifetimes up to ~ days τ [s] 6 Search for long-lived particles at CMS TeVPA 7

Stopped Particle Search: Muon Signature 746 Requires two muons out-of-time with proton collisions ( bunch crossings), one each in upper/lower hemispheres Unique reconstruction with no beamspot

7 Stopped Particle Search: Muon Signature 746 Requires two muons out-of-time with proton collisions ( bunch crossings), one each in upper/lower hemispheres Unique reconstruction with no beamspot constraints Distinguish signal from cosmic muons by: Direction of each muon Time of flight difference between muons Data taken over 744 hours of trigger livetime No events observed Limits placed on gluino and stop lifetimes up to ~ days ) [pb] µ + µ - χ BF(χ ) qqχ BF(g ~ σ(pp g ~ g ~ ) LSP 7 Fraction of Entries / 5. ns 4 4 CMS Preliminary Data Cosmic Simulation ~ g qq χ, χ µ + µ - χ LSP 6: 6. fb ( TeV) (M = GeV, M =5 GeV, M =5 GeV) g ~ χ χ LSP mchamp µ ± µ ± ( Q = e, M = 6 GeV) 5 5 t DT [ns] CMS Preliminary : 9. fb ( TeV) σ theory (m = GeV) g ~ 95% CL Limits: Observed Expected ±σ Expected ±σ 4 6 τ [s] [pb] ε det ε stop BF σ µ ± ) [pb] ± BF(mchamp µ σ(pp mchamp mchamp) Fraction of Entries / 4. ns CMS Preliminary 6 CMS Preliminary 5 5 t RPC [ns] 5 Data Cosmic Simulation ~ g qq χ, χ µ + µ - χ : 9. fb ( TeV) σ theory (m = GeV) mchamp LSP (M = GeV, M =5 GeV, M =5 GeV) g ~ χ χ LSP mchamp µ ± µ ± ( Q = e, M = 6 GeV) 6: 6. fb ( TeV) 95% CL Limits: Observed Expected ±σ Expected ±σ τ [s] [pb] ε det ε stop BF σ 7 Search for long-lived particles at CMS TeVPA 7

8 neutral charged any charge vertex HSCP BSM quark anything conversion disappearing track di jet Search for long-lived particles at CMS TeVPA 7 Not pictured: Stopped HSCP 8

Disappearing Tracks Search Charged LLPs decaying in the inner tracker to neutral or un-reconstructed particles Striking signature of a disappearing track: Missing outer hits in the inner tracker Very

9 Disappearing Tracks Search Charged LLPs decaying in the inner tracker to neutral or un-reconstructed particles Striking signature of a disappearing track: Missing outer hits in the inner tracker Very small associated calorimeter energy No hits in the muon system Trigger on MET from radiated jet arxiv:4.66 (Run I) Entries / unit. Stat. uncert. W lν 4 GeV χ ± (cτ = cm) Diboson Z ll 4 GeV χ ± (cτ = cm) Z νν 4 GeV χ ± (cτ = cm) tt Single t.8 QCD.6.4. CMS Simulation (8 TeV) outer N miss Entries / 5 GeV.8.6 Simulation (8 TeV) CMS Stat. uncert. W lν 4 GeV χ ± (cτ = cm) Diboson Z ll 4 GeV χ ± (cτ = cm) Z νν 4 GeV χ ± (cτ = cm) tt Single t QCD [GeV] E calo Simulation 9 Search for long-lived particles at CMS TeVPA 7

10 Disappearing Tracks Search arxiv:4.66 (Run I) Very small instrumental backgrounds: Un-reconstructed charged s Fake tracks tracker hit combinations not produced by a single particle No excess observed in 8 TeV (Run I) data Cross section limits placed on AMSB chargino production The Run II analysis is well under way! Specialized trigger requiring MET and isolated track Completely data-driven background estimation Pixel tracker upgrade: additional layer since 7! [ns] τ χ ± Expected limit ± σ Expected limit ± σ Expected limit Observed limit 9.5 fb m ± χ [GeV] Entries / unit CMS (8 TeV) CMS tanβ = 5, µ > 9.5 fb (8 TeV) Data Stat. uncert. Fake bkgd τ bkgd µ bkgd e bkgd outer N miss Search for long-lived particles at CMS TeVPA 7

11 neutral charged any charge vertex HSCP BSM quark anything conversion disappearing track di jet Search for long-lived particles at CMS TeVPA 7 Not pictured: Stopped HSCP

12 Displaced eµ Search 546 Targets RPV pair production Requires an e-µ pair with opposite charge Discriminates from SM backgrounds with impact parameter (d) BG-4 BG-4 Search for long-lived particles at CMS TeVPA 7

Displaced eµ Search 546 No excess observed in orthogonal search regions µm < d < cm Currently updating with 6 data Expanding search to include ee, µµ decays Will also benefit from 7 pixel tracker

13 Displaced eµ Search 546 No excess observed in orthogonal search regions µm < d < cm Currently updating with 6 data Expanding search to include ee, µµ decays Will also benefit from 7 pixel tracker upgrade e d [μm] 5 CR I CR III CR II SR I SR II CR IV μ d [μm] SR III 5 [cm] top squark cτ CMS Preliminary ± std. deviation.6 fb ( TeV) ± std. deviation Expected Observed top squark mass [GeV] Search for long-lived particles at CMS TeVPA 7

14 Summary and Final state ee/µµ pairs TeV Outlook More important than ever to search where we haven t before Many signatures require nonconventional analysis techniques Many upcoming results from CMS with the current 8.5/fb TeV dataset 7 is well under way! Upgraded pixel detector with new 4th barrel layer and rd endcap disk on each side µµ pairs in muon system eµ pairs µµ pairs (dark s) 5 s using ECAL timing 6 s using conversions 7 vertices 5 8 jets short, highly ionizing disappearing tracks disappearing tracks kinked tracks fractionally charged particles HSCPs 488 (5) 58 (6) Search for long-lived particles at CMS TeVPA 7 4 stopped particles 5 delayed muons 6 many more! (jets) 746 (muons) 4

15 Backups 5 Search for long-lived particles at CMS TeVPA 7

16 7 Proton Collisions 6 Search for long-lived particles at CMS TeVPA 7

17 7 Proton Collisions Mµµ:.4 TeV 7 Search for long-lived particles at CMS TeVPA 7

18 neutral charged any charge vertex HSCP BSM quark anything conversion disappearing track di jet Search for long-lived particles at CMS TeVPA 7 Not pictured: Stopped HSCP 8

19 Heavy Stable Charged Particle (HSCP) search Very unique signature: Large ionization energy loss in detectors (de/dx or Ih) Long time-of-flight to muon detectors (β ) 58 9 Search for long-lived particles at CMS TeVPA 7

20 neutral charged any charge vertex HSCP BSM quark anything conversion disappearing track di jet Search for long-lived particles at CMS TeVPA 7 Not pictured: Stopped HSCP

Displaced Jets Search 56654 _ ~ _ t! d s (RPV) jet substructure (projection) LHC8 projection ATLAS µ spect prompt paired dijets ATLAS HCAL charged stable charge-stripped CMS dijet arxiv:5.

21 Displaced Jets Search _ ~ _ t! d s (RPV) jet substructure (projection) LHC8 projection ATLAS µ spect prompt paired dijets ATLAS HCAL charged stable charge-stripped CMS dijet arxiv:5.59 Long-lived neutral particles decaying to a jet (or jets) within the detector Highly sensitive Run I analysis searched for dijets sharing a vertex Run II analysis developed a jet-based tagging strategy Now sensitive to single jets Able to place limits on RPV stop models Search for long-lived particles at CMS TeVPA 7

$Displaced Jets Search 56654 Jet tagging variables: Vertex α: fraction of jet s track PT associated to vertex (cut on highest α vertex) Track IPsig: transverse impact parameter wrt PV, divided by its$

22 Displaced Jets Search Jet tagging variables: Vertex α: fraction of jet s track PT associated to vertex (cut on highest α vertex) Track IPsig: transverse impact parameter wrt PV, divided by its error Cut on median IP D sig for the jet Track Θ: angle between track PT and the direction from the PV and the track s innermost hit Cut on median ΘD for jet Image credit: J. Hardenbrook Jets /. CMS Preliminary.6 fb ( TeV) mm mm mm mm QCD Data Jets /....8 CMS Preliminary.6 fb ( TeV) mm mm mm mm QCD Data Jets /.8 CMS Preliminary.6 fb ( TeV).4 mm mm. mm mm. QCD Data Jet α max log (IP D sig ) log (Θ D ) Search for long-lived particles at CMS TeVPA 7

23 Displaced Jets Search [mm] cτ X CMS Preliminary Jet-Jet: pp X, X.6 fb ( TeV) qq 4 upper limit at 95% CL [fb] BR σ [mm] cτ ~ t CMS Preliminary.6 fb ( TeV) ~ ~ ~ B-Lepton: pp t t*, t bl Observed ± σ theory Expected ± σ experiment 4 upper limit at 95% CL [fb] BR σ Very small backgrounds No excess observed Limits set on several models as a function of particle lifetime and mass m X [GeV] m~ [GeV] t upper limit 95% CL [fb] σ x BR 4 CMS Preliminary Jet-Jet.6 fb ( TeV) cτ [mm] Exp. Limit ± σ exp Obs. Limit m X =5 GeV m X = GeV m X = GeV m X = GeV upper limit 95% CL [fb] σ x BR 4 CMS Preliminary B-Lepton.6 fb ( TeV) cτ [mm] Exp. Limit ± σ exp Obs. Limit m~ = GeV t m~ = GeV t ~ ~ t t* σ NLO+NLL m~ = GeV t m~ =6 GeV t m~ =8 GeV t m~ = GeV t Search for long-lived particles at CMS TeVPA 7

Searches for long-lived particles at CMS

Searches for long-lived particles at CMS After a few year s of LHC running, CMS has published several searches for long-lived, exotic particles. What motivates these searches? What strengths & weaknesses