B-physics results in ATLAS in Run2 Olya Igonkina (NIKHEF) for - PowerPoint PPT Presentation

B-physics results in ATLAS in Run2 Olya Igonkina (NIKHEF) for ATLAS collaboration Although ATLAS has very rich programme on measurements of b quark production I will focus on measurements of B hadrons decays Bs → μμ and Bs → J/ 𝜔 φ Olya Igonkina Moriond EW 2019 1

The Gain Huge cross-section of b-quarks - 2.5 million bb ̅ pairs per second in acceptance Huge luminosity ( 60 x LHCb ) High center-of-mass (Bs, Bc, etc are accessible) TO BE UPDATED Olya Igonkina Moriond EW 2019 2

The Challenge Huge cross-section of b-quarks - 2.5 million bb ̅ pairs per second in acceptance Huge luminosity ( 60 x LHCb ) High center-of-mass (Bs, Bc, etc are accessible) BUT.... what is not selected online is lost 150-200 bb ̅ pairs/s recorded Main “B-physics” trigger in ATLAS “low pT”, “very low mass” di-muon TO BE UPDATED Olya Igonkina Moriond EW 2019 3

B s → µµ with 2015-2016 run 2 data, 23 ifb Olya Igonkina Moriond EW 2019 4

B s → µµ Motivation SM examples of BSM ~3x10 -9 SUSY PDG: (2.7 ± 0.6) x 10 -9 D.M.Straub, arXiv:1205.6094v1 Olya Igonkina Moriond EW 2019 5

Methodology ATLAS, arXiv:1812.03017 2015-2016 13 TeV data (23 ifb) Select μμ pair, consistent with B/Bs candidate Separate Signal from Background using multivariate boosted decision trees (BDT) Compare observed N(signal) with B + → J/ ψ K + decays Signal and partial reco bkgr Peaking backgrounds Continuum background Olya Igonkina Moriond EW 2019 6

Methodology ATLAS, arXiv:1812.03017 2015-2016 13 TeV data (23 ifb) B + → J/ ψ K + Select μμ pair, consistent with B/Bs candidate Separate Signal from Background using multivariate boosted decision trees (BDT) Compare observed N(signal) with B + → J/ ψ K + decays ( s ) → µ + µ − ) = N d ( s ) ε J/ ψ K + f u B ( B 0 N J/ ψ K + × [ B ( B + → J/ ψ K + ) × B ( J/ ψ → µ + µ − )] × f d ( s ) ε µ + µ − Olya Igonkina Moriond EW 2019 7

Measurement ATLAS, arXiv:1812.03017 700 140 Events / 40 MeV Events / 40 MeV ATLAS ATLAS SM : 2015-2016 data 2015-2016 data 600 120 -1 -1 s = 13 TeV, 26.3 fb s = 13 TeV, 26.3 fb Total fit Total fit 0.1439 < BDT <= 0.2455 0.2455 < BDT <= 0.3312 Continuum background Continuum background 500 100 Br( B s → μμ ) =(3.65±0.23)x10 -9 - - b + X background b + X background → µ µ → µ µ Peaking background Peaking background 400 80 0 0 0 0 + - + - + - + - B + B B + B → µ µ → µ µ → µ µ → µ µ s s 300 60 Br( B 0 → μμ ) =(1.06±0.09)x10 -10 200 40 100 20 0 0 4800 5000 5200 5400 5600 5800 4800 5000 5200 5400 5600 5800 Dimuon invariant mass [MeV] Dimuon invariant mass [MeV] Best fit of Run 2 data : (a) (b) Br( B s → μμ ) =(3.2±0.9)x10 -9 70 Events / 40 MeV Events / 40 MeV 18 ATLAS ATLAS 2015-2016 data 2015-2016 data 16 60 -1 -1 s = 13 TeV, 26.3 fb s = 13 TeV, 26.3 fb Total fit Total fit Br( B 0 → μμ ) =(-1.3±2.1)x10 -10 0.3312 < BDT <= 0.4163 14 0.4163 < BDT <= 1 Continuum background Continuum background 50 + - + - b X background b X background → µ µ → µ µ 12 Peaking background Peaking background 40 0 0 10 0 0 + - + - + - + - B + B B + B → µ µ → µ µ → µ µ → µ µ s s 30 8 6 20 4 10 2 0 0 4800 5000 5200 5400 5600 5800 4800 5000 5200 5400 5600 5800 Dimuon invariant mass [MeV] Dimuon invariant mass [MeV] (c) (d) Expect Ns = 91, Nd = 10 Observe Ns = 80±22 , Nd = -12±20 Olya Igonkina Moriond EW 2019 8

Results ATLAS, arXiv:1812.03017 SM : Br( B s → μμ ) =(3.65±0.23)x10 -9 Br( B 0 → μμ ) =(1.06±0.09)x10 -10 Best fit of Run 2 data : Br( B s → μμ ) =(3.2±0.9)x10 -9 Br( B 0 → μμ ) =(-1.3±2.1)x10 -10 Run 1 + Run 2 result @ 95% CL Br( B s → μμ ) =(2.8±0.8)x10 -9 Br( B 0 → μμ ) < 2.1x10 -10 B 0 limit is most stringent at the moment Olya Igonkina Moriond EW 2019 9

B s → J/ ψ (µµ) φ (K + K - ) with 2015-2017 run 2 data, 80 ifb Olya Igonkina Moriond EW 2019 10

B s unitary triangle V us V ∗ ub + V cs V ∗ cb + V ts V ∗ tb = 0 V ts V ∗ tb ~1 V us V ∗ α s V cs V ∗ ub cb V cs V ∗ cb ~O( λ 2 ) γ s β s 1 φ s = -2 β s = - 0.0363 ± 0.016 rad Charles et al, PRD84,033005 Olya Igonkina Moriond EW 2019 11

CPV in B s → J/ ψφ→ µµK + K - ATLAS-CONF -2019-009 ↕ ︎ φ s # B s Γ s ↔ ︎ ↘ ︎ Δ m decay time, ps Olya Igonkina Moriond EW 2019 12

CPV in B s → J/ ψφ→ µµK + K - ATLAS-CONF -2019-009 The final state : CP-odd (L=1) and 2 CP-even (L=0,2) states + non-resonant S-wave B s → J/ ψ K + K - θ T - angle between p(µ + ) and normal to x-y plane in J/ ψ rest frame φ T - angle between x-axis and p xy (µ + ) in J/ ψ rest frame ψ T - angle between p(K + ) and -p(J/ ψ ) in φ rest frame Olya Igonkina Moriond EW 2019 13

B s tagging ATLAS-CONF -2019-009 Calibration channel Muon? B + → J/ ψ K + Electrons? Secondary vertex? Tag charge Q P trk q i · p k T i i Q = P trk p k i T i harge distribution. E ffi ciency [ % ] E ff ective Dilution [ % ] Tagging Power [ % ] Tag method 4 . 50 ± 0 . 01 43 . 8 ± 0 . 2 0 . 862 ± 0 . 009 Tight muon 1 . 57 ± 0 . 01 41 . 8 ± 0 . 2 0 . 274 ± 0 . 004 Electron Low- p T muon 3 . 12 ± 0 . 01 29 . 9 ± 0 . 2 0 . 278 ± 0 . 006 Jet 5 . 54 ± 0 . 01 20 . 4 ± 0 . 1 0 . 231 ± 0 . 005 Total 14 . 74 ± 0 . 02 33 . 4 ± 0 . 1 1 . 65 ± 0 . 01 Olya Igonkina Moriond EW 2019 14

B s → J/ ψφ fit 6 × 10 ATLAS-CONF 0.3 /10 rad Data ATLAS Preliminary -1 s = 13 TeV, 80.5 fb Total Fit -2019-009 π Background Entries / Signal 0.2 80 ifb @ 13 TeV 0.1 Unbinned Likelihood fit σ 3 (data-fit)/ 2 using mass, proper decay 1 0 − 1 2 − time, its uncertainty, − 3 − 4 − 3 − 2 − 1 0 1 2 3 φ [rad] T tagging probability and 6 × 10 Entries / 0.1 Data ATLAS Preliminary transversity angles -1 Total Fit s = 13 TeV, 80.5 fb Background Signal 0.2 Extract φ s , Γ s , ΔΓ s , A 0 , A ‖ , A S , δ ⊥ , δ ‖ , δ ⊥ - δ s 0.1 σ (data-fit)/ 3 2 3 1 10 × 0 Entries / 0.2 ps Entries / 3 MeV 7 10 − 1 50 ATLAS Preliminary ATLAS Preliminary Data Data − 2 -1 -1 s = 13 TeV, 80.5 fb Total Fit s = 13 TeV, 80.5 fb 3 − Total Fit 4 − Signal 6 1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1 − − − − − 10 Background 0 *0 B J/ K cos( θ ) → ψ T d 40 - Signal Λ → J/ ψ p K B 5 6 10 Prompt J/ 10 ψ × Entries / 0.1 Data ATLAS Preliminary -1 Total Fit 30 s = 13 TeV, 80.5 fb 4 10 Background Signal 0.2 3 10 20 2 10 10 0.1 10 σ σ 3 3 (data-fit)/ (data-fit)/ 2 2 σ (data-fit)/ 3 1 1 2 1 0 0 0 1 1 − − 1 − 2 2 − 2 − − 3 − 3 3 − − 4 − − 4 4 1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1 − − − − − − 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6 0 2 4 6 8 10 12 14 cos( ) ψ T Olya Igonkina B Mass [GeV] Moriond EW 2019 Proper Decay Time [ps] 15 s

B s → J/ ψφ results ATLAS-CONF -2019-009 Run 2 result Olya Igonkina Moriond EW 2019 16

B s → J/ ψφ results ATLAS-CONF -2019-009 ATLAS Run 1 and Run 2 combination Uncertainties on φ s , ΔΓ s , Γ s and helicity function parameters are very similar to that of LHCb! 60 ifb of 2018 data are still to be added Olya Igonkina Moriond EW 2019 17

courtesy of Lison Bernet Olya Igonkina Moriond EW 2019 18

ARE courtesy of Lison Bernet Olya Igonkina Moriond EW 2019 19

Summary ATLAS produces huge amount of B hadrons Only selected final states (notably with 2 energetic muons) can be recorded Beautiful new measurements of rare decays and heavy states B s → μμ with 36 ifb of run 2 data (140 ifb available) agrees with SM and other measurements no sign of B 0 → μμ in ATLAS data B s → J/ ψφ with 80 ifb of run 2 data (140 ifb available) Single measurement precision is comparable to LHCb reaching the sensitivity to test SM prediction More results are on the way. Stay tuned with news from ATLAS-B-factory Olya Igonkina Moriond EW 2019 20

Backup Olya Igonkina Moriond EW 2019 21

B hadrons production at LHC proton - (anti)proton cross sections 9 9 10 10 8 8 σ tot σ 10 σ σ 10 7 7 10 10 Tevatron LHC 6 6 10 10 LHCb -1 5 5 10 10 -2 s σ σ σ σ b 33 cm 4 4 10 10 3 3 10 10 events / sec for L = 10 ATLAS jet > √ σ jet (E T σ √ s/20) σ σ √ √ 2 2 10 10 ( nb ) ) ) ) σ σ σ W σ 1 1 10 10 σ ( ( ( σ σ σ σ Z σ σ σ 0 0 10 10 jet > 100 GeV) σ σ σ σ jet (E T -1 -1 10 10 -2 -2 10 10 σ σ σ WW σ -3 -3 10 10 σ t σ σ σ σ ZZ σ σ σ -4 -4 10 σ ggH σ σ σ 10 { σ σ WH σ σ M H =125 GeV -5 -5 10 10 σ VBF σ σ σ -6 -6 LHCb 10 10 η 1 WJS2012 -7 -7 10 10 η 2 0.1 1 10 √ √ s (TeV) √ √ W.J. Stirling 2.5 millions of b quark pairs produced per second in ATLAS acceptance Olya Igonkina Moriond EW 2019 22