Hunting for elusive particles at LHC: Start of Run II Andrei Gritsan Johns Hopkins University July 25, 216 Johns Hopkins University QuarkNet Physics Workshop
Reaching Highest Energy mc 2 = E Andrei Gritsan, JHU LXXXV July 3, 214
Particles Resonances Bumps We often see particles as resonances most particles are not stable reconstruct from their decay products Andrei Gritsan, JHU
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
Particle Data Group: pdg.lbl.gov Andrei Gritsan, JHU
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
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
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
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
Periodic Table of Baryons: Proton, Neutron,... Three quarks make up a Baryon: Andrei Gritsan, JHU XXVI July 3, 214
Particle Data Group: Proton Andrei Gritsan, JHU
Like Periodic Table of Atoms Andrei Gritsan, JHU March 29, 27
From large What to makes small mass? to elementary What gives us mass? Molecules Atoms Nucleus Andrei Gritsan, JHU XXV July 3, 214
Particle Data Group: Quarks Andrei Gritsan, JHU
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
Particle Data Group: Bosons Andrei Gritsan, JHU
Hunting for New Particles
Producing New Particles Produce a resonance Detect its decay? x μν Τ μν?? ΧV μ V μ? Andrei Gritsan, JHU 18
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
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
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 18 16 14 12 8 6 4 2 5-5 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 1 12 13 14 15 16 m H = 125.4 GeV m γγ [GeV] Events / GeV Significance 4 3 2 1 1 2 4 2 2 ATLAS s = 8 TeV, 2.3 fb ~3σ (2.5σ LEE) Data Background model Significance (stat) Significance (stat + syst) WW+ZZ+WZ Selection 1.5 2 2.5 3 3.5 [TeV] m jj Events / 4 GeV Data - fitted background 4 3 2 1 1 ATLAS Preliminary Data Background-only fit s = 13 TeV, 3.2 fb 2 15 4 6 8 12 14 16 [GeV] 5 5 15 3.6σ (2σ LEE) 2 4 6 8 12 14 16 [GeV] Run Run Run-2 (215) m γγ m γγ Andrei Gritsan, JHU 21
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 3 8 6 4 2-2 CMS H γγ +.26 µ = 1.14.23 m H = 124.7 ±.34 GeV 19.7 fb (8 TeV) + 5.1 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 1 12 13 14 15 16 17 18 m γγ (GeV) 6 I II III 15 2 25 M G [GeV] 95% C.L. limit σ(pp S γγ) (fb) CMS Preliminary 8 6 4 2 2 5 3.4σ 3 3.3 fb (13 TeV) + 19.7 fb (8 TeV) 3 2-4 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
LHC Luminosity in 216 C6,ntegrated LumLnoVLty, SS, 216, p s = 13 TeV 7RtDl IntHJUDtHd LumLnRsLty (fb 1 ) 2 15 5 DDtD LncOuded fuom 216-4-22 22:48 to 216-7-24 17:6 87C C6 2nOLne LumLnosLty LHC DHlLvHUHd: 19.18 fb 1 C6 5HcRUdHd: 17.67 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) 2 15 5 ~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
Hunting for the Higgs Boson H(125)
The H(125) Resonance: 212-213 Andrei Gritsan, JHU 25
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
Mass of H(125) in Run 19.7 fb (8 TeV) + 5.1 fb (7 TeV) LHC combination: σ/σ SM 2. CMS H γγ + H ZZ Combined H γγ tagged H ZZ tagged 1.5 1. Events / 3 GeV 25 2 15 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 16 14 12 8 6 4 2 6.8σ s = 8 TeV, L = 19.7 fb kin D bkg >.5 1 12 13 14 15 m 4l (GeV) Events / GeV.5. 123 124 125 126 127 3 8 6 4 2 CMS H γγ m H 5.7σ +.26 µ = 1.14.23 m H = 124.7 ±.34 GeV (GeV) 19.7 fb (8 TeV) + 5.1 fb (7 TeV) Sum over all classes Data S+B fits (sum) B component ±1σ ±2σ 5 8 2 3 4 6 8 m 4l (GeV) Events / GeV 2 B component subtracted -2 1 12 13 14 15 16 17 18 m γγ (GeV) Andrei Gritsan, JHU 27
H ZZ 4l Andrei Gritsan, JHU LIII July 3, 25 July 214216
-- Re-discover Η(125) in Run-2 (215 data) Η ZZ μ=.82 +.57 -.43 m=123.4 +.8 GeV -.7 Events / 4 GeV 14 12 8 6 4 2 CMS Preliminary 2.8 fb (13 TeV) Data H(125) qq ZZ, Zγ* gg ZZ, Zγ* Z+X local p-value 1 1 2 3 4 5 CMS Preliminary Observed 4e Observed 4µ Observed 2e2µ Observed combined Expected 3σ 2.8 fb (13 TeV) 1σ 2σ 3σ 4σ 8 12 14 16 18 (GeV) m 4l 118 12 122 124 126 128 13 m H (GeV) Η γγ μ=.69 +.47 -.42 S/(S+B) Weighted Events / GeV 8 6 4 2 5 CMS H γγ Preliminary m H =125.9 GeV, µ=.7 2.7 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 = 125.9 GeV m H Observed 2.7fb (13 TeV) ~2σ 1 σ 2 σ Andrei Gritsan, JHU -5 1 12 13 14 15 16 17 18 m γγ (GeV) 29 116 118 12 122 124 126 128 13 132 134 m H (GeV)
Hunting for?x(~2)?x(75)
? X(~2) Hints for X(2) do not seem to be confirmed with new data σ 95% /σ theory 5 4 CMS Preliminary 2.2-2.6 fb (13 TeV) + 19.7 fb Asympt. CL S (8 TeV) Obs.(solid)/ Exp.(dashed) 3 2 1 hint (8 TeV) no hint (13 TeV) G bulk 8 TeV 13 TeV 8+13 TeV ~, k=.5 Andrei Gritsan, JHU 1 2 3 4 31 M Gbulk (TeV)
? 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 4 3 2 1 1 15 5 5 15 ATLAS Preliminary 3.6σ (2σ LEE) Data Background-only fit s = 13 TeV, 3.2 fb 2 4 6 8 12 14 16 [GeV] Run-2 (215) m γγ 95% C.L. limit σ(pp S γγ) (fb) CMS Preliminary 8 6 4 2 2 5 3.4σ 3 3.3 fb (13 TeV) + 19.7 fb (8 TeV) 3 2-4 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
Andrei Gritsan, JHU