Hunting for elusive particles at LHC: Start of Run II

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1 Hunting for elusive particles at LHC: Start of Run II Andrei Gritsan Johns Hopkins University July 25, 216 Johns Hopkins University QuarkNet Physics Workshop

2 Reaching Highest Energy mc 2 = E Andrei Gritsan, JHU LXXXV July 3, 214

3 Particles Resonances Bumps We often see particles as resonances most particles are not stable reconstruct from their decay products Andrei Gritsan, JHU

4 How do We See Particles We see semi-stable particles by tracks in matter: Table-top illustrations Complex multi-ton detectors Andrei Gritsan, JHU March 29, 27

5 Particle Data Group: pdg.lbl.gov Andrei Gritsan, JHU

6 How do We See Particles Most particles live too short to be seen directly see decay products: Time (decay) and energy (resonance) amplitudes: A(t) =A()e ie t/ h e Γ t/2 h A(t) 2 e Γ t/ h = e t/τ A(E) = A(t)e iet/ h dt = C (E E ) iγ /2 Γ = h τ Andrei Gritsan, JHU March 29, 27

7 Unstable Resonance Particles The Uncertainty Principle (part 1): Probability A(m) 2 Γ τ = h compare: E t h A(m) 2 = C (m m ) iγ /2 2 Breit-Wigner resonance Andrei Gritsan, JHU March 29, 27

8 Unstable particles decay Feynman diagram: Decay Dynamics Decay study elementary particles and interactions (this strong decay is mostly understood) Andrei Gritsan, JHU March 29, 27

9 Periodic Table of Mesons Quark-antiquark make up a Meson: ground state (L=S=) Vector meson S=1 h Andrei Gritsan, JHU March 29, 27

10 Periodic Table of Baryons: Proton, Neutron,... Three quarks make up a Baryon: Andrei Gritsan, JHU XXVI July 3, 214

11 Particle Data Group: Proton Andrei Gritsan, JHU

12 Like Periodic Table of Atoms Andrei Gritsan, JHU March 29, 27

13 From large What to makes small mass? to elementary What gives us mass? Molecules Atoms Nucleus Andrei Gritsan, JHU XXV July 3, 214

14 Particle Data Group: Quarks Andrei Gritsan, JHU

15 Anti-Matter: Mirror Object of Matter matter anti-matter leptons quarks Produced equal in Big Bang energy matter + antimatter anti-matter should behave differently than matter Andrei Gritsan, JHU LXXX July 3, 214

16 Particle Data Group: Bosons Andrei Gritsan, JHU

17 Hunting for New Particles

18 Producing New Particles Produce a resonance Detect its decay? x μν Τ μν?? ΧV μ V μ? Andrei Gritsan, JHU 18

19 LHC schedule: year plan LHC Epp=13 TeV, Phase thru 223/24 today Run-2 Run-3 thru 223/24 ~17 fb ~3-4 fb ~ fb ~3 fb today Phase-2 with Run-4 plan to start in 226, Snowmass: ~3 fb Legacy: Run (2-212) ~25 fb at 7 and 8 TeV Andrei Gritsan, JHU 19

20 Resonances in LHC Run-2 vs Run Produce a resonance? Y(~2TeV) H(125)?X (75) low mass intermediate mass high mass ~3 fb in Run-2 at 13 TeV (215) ~3-4 fb in Run-2 at 13 TeV (216) compared to ~2 fb in Run at 8 TeV (212) Andrei Gritsan, JHU 2

21 Hints of Bumps from ATLAS H(125) is one particle surely discovered Several hints in either Run I or Run II excited interest - especially when ATLAS and CMS saw something similar H(125) γγ? X(2) ZZ, WW, ZW? X(75) γγ weights / GeV weights - fitted bkg L dt = 4.5 fb, L dt = 2.3 fb, S/B weighted sum s = 7 TeV s = 8 TeV Signal strength categories 5.2σ ATLAS Data Signal+background Background Signal m H = GeV m γγ [GeV] Events / GeV Significance ATLAS s = 8 TeV, 2.3 fb ~3σ (2.5σ LEE) Data Background model Significance (stat) Significance (stat + syst) WW+ZZ+WZ Selection [TeV] m jj Events / 4 GeV Data - fitted background ATLAS Preliminary Data Background-only fit s = 13 TeV, 3.2 fb [GeV] σ (2σ LEE) [GeV] Run Run Run-2 (215) m γγ m γγ Andrei Gritsan, JHU 21

22 Hints of Bumps from CMS H(125) is one particle surely discovered Several hints in either Run I or Run II excited interest - especially when ATLAS and CMS saw something similar H(125) γγ? X(2) ZZ, WW, ZW? X(75) γγ Events / GeV Events / GeV CMS H γγ +.26 µ = m H = ±.34 GeV 19.7 fb (8 TeV) fb (7 TeV) Sum over all classes Data S+B fits (sum) B component ±1σ ±2σ σ 95% (pp G bulk ) [pb] -2 1 Frequentist CL observed S -3 CMS L = 19.7 fb at s = 8 TeV Frequentist CL expected ± 1σ S Frequentist CL expected ± 2σ S σ (pp G =.5 TH bulk ), k/m Pl 5.7σ ~2σ 2 B component subtracted m γγ (GeV) 6 I II III M G [GeV] 95% C.L. limit σ(pp S γγ) (fb) CMS Preliminary σ fb (13 TeV) fb (8 TeV) m Γ = 1.4 Expected limit ± 1 σ ± 2 σ Observed limit (1.6σ LEE) Run Run Run-2 (215) m S J= 3 3 (GeV) Andrei Gritsan, JHU 22

23 LHC Luminosity in 216 C6,ntegrated LumLnoVLty, SS, 216, p s = 13 TeV 7RtDl IntHJUDtHd LumLnRsLty (fb 1 ) DDtD LncOuded fuom :48 to :6 87C C6 2nOLne LumLnosLty LHC DHlLvHUHd: fb 1 C6 5HcRUdHd: fb 1 25 ASU 2 Dy 9 Dy 16 Dy 23 Dy 3 Dy 6 Jun 13 Jun 2 Jun 27 Jun 4 Jul 11 Jul 18 Jul DDtH (87C) ~3 fb in Run-2 at 13 TeV (215) ~3-4 fb in Run-2 at 13 TeV (216) compared to ~2 fb in Run at 8 TeV (212) Andrei Gritsan, JHU

24 Hunting for the Higgs Boson H(125)

25 The H(125) Resonance: Andrei Gritsan, JHU 25

26 The Higgs Boson: H(125) Why discuss H(125) window to Beyond SM (extended sector, dark matter, etc) techniques applicable to any new particle the only LHC discovery so far Follow PDG check-list mass lifetime width quantum numbers coupling strength Andrei Gritsan, JHU 26

27 Mass of H(125) in Run 19.7 fb (8 TeV) fb (7 TeV) LHC combination: σ/σ SM 2. CMS H γγ + H ZZ Combined H γγ tagged H ZZ tagged Events / 3 GeV CMS Mass = position of two bumps H ZZ, γγ 35 Data 3 m H =126 GeV Zγ*,ZZ Z+X s = 7 TeV, L = 5.1 fb ; Events / 3 GeV σ s = 8 TeV, L = 19.7 fb kin D bkg > m 4l (GeV) Events / GeV CMS H γγ m H 5.7σ +.26 µ = m H = ±.34 GeV (GeV) 19.7 fb (8 TeV) fb (7 TeV) Sum over all classes Data S+B fits (sum) B component ±1σ ±2σ m 4l (GeV) Events / GeV 2 B component subtracted m γγ (GeV) Andrei Gritsan, JHU 27

28 H ZZ 4l Andrei Gritsan, JHU LIII July 3, 25 July

29 -- Re-discover Η(125) in Run-2 (215 data) Η ZZ μ= m= GeV -.7 Events / 4 GeV CMS Preliminary 2.8 fb (13 TeV) Data H(125) qq ZZ, Zγ* gg ZZ, Zγ* Z+X local p-value CMS Preliminary Observed 4e Observed 4µ Observed 2e2µ Observed combined Expected 3σ 2.8 fb (13 TeV) 1σ 2σ 3σ 4σ (GeV) m 4l m H (GeV) Η γγ μ= S/(S+B) Weighted Events / GeV CMS H γγ Preliminary m H =125.9 GeV, µ= fb (13 All categories summed S/(S+B) weighted sum Data S+B fit sum B component ±1 σ ±2 σ TeV) B component subtracted Local p-value -2 CMS Preliminary H γγ Expected Expected = GeV m H Observed 2.7fb (13 TeV) ~2σ 1 σ 2 σ Andrei Gritsan, JHU m γγ (GeV) m H (GeV)

30 Hunting for?x(~2)?x(75)

31 ? X(~2) Hints for X(2) do not seem to be confirmed with new data σ 95% /σ theory 5 4 CMS Preliminary fb (13 TeV) fb Asympt. CL S (8 TeV) Obs.(solid)/ Exp.(dashed) hint (8 TeV) no hint (13 TeV) G bulk 8 TeV 13 TeV 8+13 TeV ~, k=.5 Andrei Gritsan, JHU M Gbulk (TeV)

32 ? X(75) Waiting for ICHEP conference in Chicago next week new data from 216 will tell? X(75) γγ on ATLAS? X(75) γγ on CMS Events / 4 GeV Data - fitted background ATLAS Preliminary 3.6σ (2σ LEE) Data Background-only fit s = 13 TeV, 3.2 fb [GeV] Run-2 (215) m γγ 95% C.L. limit σ(pp S γγ) (fb) CMS Preliminary σ fb (13 TeV) fb (8 TeV) m Γ = 1.4 Expected limit ± 1 σ ± 2 σ Observed limit (1.6σ LEE) Run-2 (215) m S J= 3 3 (GeV) Andrei Gritsan, JHU

33 Andrei Gritsan, JHU