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

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

Nov 19, 2023 308 likes •598 views

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 and Bs J/

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Olya Igonkina Moriond EW 2019

Olya Igonkina (NIKHEF) for ATLAS collaboration

B-physics results in ATLAS in Run2

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

1

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Olya Igonkina Moriond EW 2019

The Gain

Huge cross-section of b-quarks Huge luminosity ( 60 x LHCb ) High center-of-mass (Bs, Bc, etc are accessible)

2

TO BE UPDATED

  • 2.5 million bb̅ pairs per second in acceptance
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Olya Igonkina Moriond EW 2019

The Challenge

Huge cross-section of b-quarks Huge luminosity ( 60 x LHCb ) High center-of-mass (Bs, Bc, etc are accessible) BUT.... what is not selected online is lost 150-200 bb̅ pairs/s recorded

3

TO BE UPDATED Main “B-physics” trigger in ATLAS “low pT”, “very low mass” di-muon

  • 2.5 million bb̅ pairs per second in acceptance
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Olya Igonkina Moriond EW 2019

Bs→µµ

4

with 2015-2016 run 2 data, 23 ifb

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Olya Igonkina Moriond EW 2019

Bs→µµ Motivation

5 D.M.Straub, arXiv:1205.6094v1

SUSY

SM examples

  • f BSM

~3x10-9 PDG: (2.7 ± 0.6) x 10-9

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Olya Igonkina Moriond EW 2019

Methodology

6

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/ψK+ decays

Peaking backgrounds Signal and partial reco bkgr Continuum background

ATLAS, arXiv:1812.03017

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Olya Igonkina Moriond EW 2019

Methodology

7

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/ψK+ decays

ATLAS, arXiv:1812.03017

B(B0

(s) → µ+µ−) = Nd(s)

εµ+µ− εJ/ψK+ NJ/ψK+ × [B(B+ → J/ψK+) × B(J/ψ → µ+µ−)] × fu fd(s) B+→J/ψK+

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Olya Igonkina Moriond EW 2019

Measurement

SM : Br(Bs→μμ) =(3.65±0.23)x10-9 Br(B0→μμ) =(1.06±0.09)x10-10 Best fit of Run 2 data : Br(Bs→μμ) =(3.2±0.9)x10-9 Br(B0→μμ) =(-1.3±2.1)x10-10

8

4800 5000 5200 5400 5600 5800 Dimuon invariant mass [MeV] 100 200 300 400 500 600 700 Events / 40 MeV ATLAS

  • 1

= 13 TeV, 26.3 fb s 0.1439 < BDT <= 0.2455

2015-2016 data Total fit Continuum background X background

  • µ
+

µ → b Peaking background

  • µ
+

µ → + B

  • µ
+

µ →

s

B

(a)

4800 5000 5200 5400 5600 5800 Dimuon invariant mass [MeV] 20 40 60 80 100 120 140 Events / 40 MeV ATLAS

  • 1

= 13 TeV, 26.3 fb s 0.2455 < BDT <= 0.3312

2015-2016 data Total fit Continuum background X background

  • µ
+

µ → b Peaking background

  • µ
+

µ → + B

  • µ
+

µ →

s

B

(b)

4800 5000 5200 5400 5600 5800 Dimuon invariant mass [MeV] 10 20 30 40 50 60 70 Events / 40 MeV ATLAS

  • 1

= 13 TeV, 26.3 fb s 0.3312 < BDT <= 0.4163

2015-2016 data Total fit Continuum background X background

  • µ
+

µ → b Peaking background

  • µ
+

µ → + B

  • µ
+

µ →

s

B

(c)

4800 5000 5200 5400 5600 5800 Dimuon invariant mass [MeV] 2 4 6 8 10 12 14 16 18 Events / 40 MeV ATLAS

  • 1

= 13 TeV, 26.3 fb s 0.4163 < BDT <= 1

2015-2016 data Total fit Continuum background X background

  • µ
+

µ → b Peaking background

  • µ
+

µ → + B

  • µ
+

µ →

s

B

(d)

Expect Ns = 91, Nd = 10 Observe Ns = 80±22 , Nd = -12±20

ATLAS, arXiv:1812.03017

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Olya Igonkina Moriond EW 2019

Results

9 ATLAS, arXiv:1812.03017

SM : Br(Bs→μμ) =(3.65±0.23)x10-9 Br(B0→μμ) =(1.06±0.09)x10-10 Best fit of Run 2 data : Br(Bs→μμ) =(3.2±0.9)x10-9 Br(B0→μμ) =(-1.3±2.1)x10-10 Run 1 + Run 2 result @ 95% CL Br(Bs→μμ) =(2.8±0.8)x10-9 Br(B0→μμ) < 2.1x10-10

B0 limit is most stringent at the moment

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Olya Igonkina Moriond EW 2019

Bs→ J/ψ(µµ) φ(K+K-)

10

with 2015-2017 run 2 data, 80 ifb

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VusV ∗

ub

VcsV ∗

cb

VtsV ∗

tb

VcsV ∗

cb

VusV ∗

ub + VcsV ∗ cb + VtsV ∗ tb = 0

Olya Igonkina Moriond EW 2019

Bs unitary triangle

11

βs αs γs

φs = -2 βs = - 0.0363 ± 0.016 rad

1 ~1 ~O(λ2)

Charles et al, PRD84,033005

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Olya Igonkina Moriond EW 2019

CPV in Bs→J/ψφ→µµK+K-

12

ATLAS-CONF

  • 2019-009

Δm

φs

↕︎

↔︎ ↘︎ Γs

decay time, ps # Bs

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Olya Igonkina Moriond EW 2019

CPV in Bs→J/ψφ→µµK+K-

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The final state : CP-odd (L=1) and 2 CP-even (L=0,2) states + non-resonant S-wave Bs→J/ψK+K-

ATLAS-CONF

  • 2019-009

θT - angle between p(µ+) and normal to x-y plane in J/ψ rest frame φT - angle between x-axis and pxy(µ+) in J/ψ rest frame ψT - angle between p(K+) and -p(J/ψ) in φ rest frame

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Q = Ptrk

i

qi · pk

T i

Ptrk

i

pk

T i

Olya Igonkina Moriond EW 2019

Bs tagging

14

Muon? Electrons? Secondary vertex? Tag charge Q

Calibration channel B+→J/ψK+

harge distribution.

Tag method Efficiency [%] Effective Dilution [%] Tagging Power [%] Tight muon 4.50 ± 0.01 43.8 ± 0.2 0.862 ± 0.009 Electron 1.57 ± 0.01 41.8 ± 0.2 0.274 ± 0.004 Low-pT 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

ATLAS-CONF

  • 2019-009
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Olya Igonkina Moriond EW 2019

Bs→J/ψφ fit

80 ifb @ 13 TeV Unbinned Likelihood fit using mass, proper decay time, its uncertainty, tagging probability and transversity angles Extract φs, Γs, ΔΓs, A0, A‖, AS , δ⊥, δ‖, δ⊥-δs

15

0.1 0.2 0.3

6

10 × /10 rad π Entries /

Data Total Fit Background Signal

ATLAS Preliminary

  • 1

= 13 TeV, 80.5 fb s

3 − 2 − 1 − 1 2 3

[rad]

T

φ 4 − 3 − 2 − 1 − 1 2 3 σ (data-fit)/ 0.1 0.2

6

10 × Entries / 0.1

Data Total Fit Background Signal

ATLAS Preliminary

  • 1

= 13 TeV, 80.5 fb s

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

)

T

θ cos( 4 − 3 − 2 − 1 − 1 2 3 σ (data-fit)/ 0.1 0.2

6

10 × Entries / 0.1 ATLAS Preliminary

  • 1

= 13 TeV, 80.5 fb s Data Total Fit Background Signal

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

)

T

ψ cos( 4 − 3 − 2 − 1 − 1 2 3 σ (data-fit)/

10 20 30 40 50

3

10 × Entries / 3 MeV ATLAS Preliminary

  • 1

= 13 TeV, 80.5 fb s

Data Total Fit Signal

*0

K ψ J/ →

d

B

  • p K

ψ J/ →

B

Λ

5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6

Mass [GeV]

s

B 4 − 3 − 2 − 1 − 1 2 3 σ (data-fit)/ 10

2

10

3

10

4

10

5

10

6

10

7

10 Entries / 0.2 ps Data Total Fit Background Signal ψ Prompt J/ ATLAS Preliminary

  • 1

= 13 TeV, 80.5 fb s

2 4 6 8 10 12 14

Proper Decay Time [ps] 4 − 3 − 2 − 1 − 1 2 3 σ (data-fit)/

ATLAS-CONF

  • 2019-009
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Olya Igonkina Moriond EW 2019

Bs→J/ψφ results

16

Run 2 result

ATLAS-CONF

  • 2019-009
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Olya Igonkina Moriond EW 2019

Bs→J/ψφ results

17

ATLAS Run 1 and Run 2 combination Uncertainties on φs, ΔΓs, Γs and helicity function parameters are very similar to that of LHCb! 60 ifb of 2018 data are still to be added

ATLAS-CONF

  • 2019-009
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Olya Igonkina Moriond EW 2019 18

courtesy of Lison Bernet

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Olya Igonkina Moriond EW 2019 19

ARE

courtesy of Lison Bernet

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Olya Igonkina Moriond EW 2019

Summary

20

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 Bs→μμ with 36 ifb of run 2 data (140 ifb available) agrees with SM and other measurements no sign of B0→μμ in ATLAS data Bs→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

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Olya Igonkina Moriond EW 2019

Backup

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Olya Igonkina Moriond EW 2019

B hadrons production at LHC

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σ σ σ σZZ σ σ σ σWW σ σ σ σWH σ σ σ σVBF MH=125 GeV

WJS2012

σ σ σ σjet(ET

jet > 100 GeV)

σ σ σ σjet(ET

jet > √

√ √ √s/20) σ σ σ σggH

LHC Tevatron

events / sec for L = 10

33 cm

  • 2s
  • 1

σ σ σ σb σ σ σ σtot

proton - (anti)proton cross sections

σ σ σ σW σ σ σ σZ σ σ σ σt

σ σ σ σ ( ( ( (nb) ) ) ) √ √ √ √s (TeV)

{

W.J. Stirling

LHCb ATLAS

η1 η2

2.5 millions of b quark pairs produced per second in ATLAS acceptance

LHCb

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Olya Igonkina Moriond EW 2019

Bs→µµ

23 Altmannshofer et al, JHEP 1705 (2017) 076

Introduction New physics in scalar operators Future Bs μμ measurements

Complementarity with Higgs searches

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 10 20 30 40 50 60 70 80

m A HTeVL tanΒ present status

fÆtt BRHBsÆmmL

Altmannshofer et al. 1702.05498

Bs μ μ is complementary to Higgs physics (H A τ τ ) Two disjoint solutions corresponding to different overall signs

  • f the amplitude.

How to disentangle?

David Straub (Universe Cluster) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Introduction New physics in scalar operators Future Bs μμ measurements

Constraint on LQ parameter space

Scenario with CS CP 0, λL chosen to explain b sμμ anomalies

500 1000 1500 2000 2500 mLQ [GeV] −0.010 −0.008 −0.006 −0.004 −0.002 0.000 0.002 0.004 Re(λbµ

R )

Leptoquark U1; present situation

David Straub (Universe Cluster) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

MSSM LQ Bs→µµ Bs→µµ

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Olya Igonkina Moriond EW 2019

input to Bs→µµ BDT

24

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Olya Igonkina Moriond EW 2019

Bs→µµ

25

ciencies Rε = ε(B+ → J/ψ K+)/ε(B0

(s) → µ+µ−) enters

Both channels are measured in the fiducial acceptance

Systematics on efficiency ratio Systematics on Br(Bs, B0→µµ)

is 0.1176 ± 0.0009 (stat.) ± 0.0047 (syst.), with

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Olya Igonkina Moriond EW 2019

Bs→J/ψφ

26

Table 2: Fraction of events f+1 and f−1 with cone charges of +1 and −1, respectively, for signal and background events and for the different tag methods. The remaining fraction, 1 − f+1 − f−1, is the fraction of events from the continuous part of the distributions, and not explicitly shown in the table. Only statistical uncertainties are quoted.

Tag method Signal Background f+1 [%] f−1 [%] f+1 [%] f−1 [%] Tight muon 6.9 ± 0.3 7.5 ± 0.3 4.7 ± 0.1 4.9 ± 0.1 Electron 20 ± 1 19 ± 1 16.8 ± 0.2 17.3 ± 0.2 Low-pt muon 10.9 ± 0.5 11.7 ± 0.5 7.0 ± 0.1 7.6 ± 0.1 Jet 4.51 ± 0.15 4.58 ± 0.16 3.76 ± 0.03 3.86 ± 0.03

Table 3: Relative fractions of signal and background events tagged using the different tag methods. The efficiencies include both the continuous and discrete contributions. Only statistical uncertainties are quoted.

Tag method Signal Background efficiency [%] efficiency [%] Tight muon 4.00 ± 0.06 3.16 ± 0.01 Electron 1.87 ± 0.04 1.48 ± 0.01 Low-pT muon 2.91 ± 0.05 2.64 ± 0.01 Jet 14.4 ± 0.1 11.96 ± 0.02 Untagged 76.7 ± 0.3 80.77 ± 0.05

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Olya Igonkina Moriond EW 2019

Bs→J/ψφ

27

Table 5: Summary of systematic uncertainties assigned to the physical parameters of interest.

φs ∆Γs Γs |Ak(0)|2 |A0(0)|2 |AS(0)|2 δ? δk δ? δS [rad] [ps1] [ps1] [rad] [rad] [rad] Tagging 1.7 ⇥102 0.4⇥103 0.3 ⇥103 0.2 ⇥103 0.2 ⇥103 2.3 ⇥103 1.9 ⇥102 2.2 ⇥102 2.2 ⇥103 Acceptance 0.7 ⇥103 <104 <104 0.8 ⇥103 0.7 ⇥103 2.4 ⇥103 3.3 ⇥102 1.4 ⇥102 2.6 ⇥103 ID alignment 0.7 ⇥103 0.1 ⇥103 0.5 ⇥103 <104 <104 <104 1.0 ⇥102 7.2 ⇥103 <104 S–wave phase 0.2 ⇥103 < 104 <104 0.3 ⇥103 <104 0.3 ⇥103 1.1 ⇥102 2.1 ⇥102 8.3 ⇥103 Background angles model: Choice of fit function 1.8 ⇥103 0.8 ⇥103 <104 1.4 ⇥103 0.7 ⇥103 0.2 ⇥103 8.5 ⇥102 1.9 ⇥101 1.8 ⇥103 Choice of pT bins 1.3 ⇥103 0.5 ⇥103 <104 0.4 ⇥103 0.5 ⇥103 1.2 ⇥103 1.5 ⇥103 7.2 ⇥103 1.0 ⇥103 Choice of mass interval 0.4 ⇥103 0.1 ⇥103 0.1 ⇥103 0.3 ⇥103 0.3 ⇥103 1.3 ⇥103 4.4 ⇥103 7.4 ⇥103 2.3 ⇥103 Dedicated backgrounds: B0

d

2.3 ⇥103 1.1 ⇥103 <104 0.2 ⇥103 3.1 ⇥103 1.4 ⇥103 1.0 ⇥102 2.3 ⇥102 2.1 ⇥103 Λb 1.6 ⇥103 0.4 ⇥103 0.2 ⇥103 0.5 ⇥103 1.2 ⇥103 1.8 ⇥103 1.4 ⇥102 2.9 ⇥102 0.8 ⇥103 Fit model: Time res. sig frac 1.4 ⇥103 1.1 ⇥103 <104 0.5 ⇥103 0.6 ⇥103 0.6 ⇥103 1.2 ⇥102 3.0 ⇥102 0.4 ⇥103 Time res. pT bins 3.3 ⇥103 1.4 ⇥103 0.1 ⇥102 < 104 < 104 0.5 ⇥103 6.2 ⇥103 5.2 ⇥103 1.1 ⇥103 Total 1.8 ⇥102 0.2 ⇥102 0.1 ⇥102 0.2 ⇥102 0.4 ⇥102 0.4 ⇥102 9.7 ⇥102 2.0 ⇥101 0.1 ⇥101

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Olya Igonkina Moriond EW 2019

Bs→J/ψφ

28

Table 7: Fit correlations between the physical parameters of interest.

∆Γ Γs |A||(0)|2 |A0(0)|2 |AS(0)|2 δk δ? δ? δS φs 0.111 0.038 0.000 0.008 0.015 0.019 0.001 0.011 ∆Γ 1 0.563 0.092 0.097 0.042 0.036 0.011 0.009 Γs 1 0.139 0.040 0.103 0.105 0.041 0.016 |A||(0)|2 1 0.349 0.216 0.571 0.223 0.035 |A0(0)|2 1 0.299 0.129 0.056 0.051 |AS(0)|2 1 0.408 0.175 0.164 δk 1 0.392 0.041 δ? 1 0.052