akar simon fpcp2015 v1 - cern filesimon akar fpcp 2015, mixing-induced cp violation in bs decays 2 e...

Mixing-induced CP violation in Bs decays

FPCP 2015 Flavor Physics & CP Violation University of Nagoya, Japan

25-29 May 2015

Simon Akar on behalf of the LHCb collaboration,

including results from other collaborations

2FPCP 2015, Mixing-induced CP violation in Bs decaysSimon Akar

Outline

Direct decay

Mixing and decay

B0s

B0s

fCP

Measurement of 𝝓s

Constraining penguins in 𝝓s

Physics motivation

Measurement ingredients

1

2

3

4


Outline

Direct decay

Mixing and decay

B0s

B0s

fCP



Physics motivation


1

2

3

4

✦ CPV in interference between mixing and decay:

�s = arg

✓� VtsV ⇤

tb

VcsV ⇤cb

◆�s = �M � 2�D

= �2�s

Simon Akar 4FPCP 2015, Mixing-induced CP violation in Bs decays

Direct decay

Mixing and decay

B0s

�D

�M ��D

B0s

fCP

+

2

dominant “tree“contribution

Physics motivation


�s = arg

✓� VtsV ⇤

tb

VcsV ⇤cb

◆�s = �M � 2�D

= �2�s +��Peng.s


Direct decay

Mixing and decay

B0s

�D

�M ��D

B0s

fCP

+

2

+

higher order “penguin“

contributionsdominant

“tree“contribution

Physics motivation


�s = arg

✓� VtsV ⇤

tb

VcsV ⇤cb

◆�s = �M � 2�D

= �2�s +��Peng.s + �NP


Direct decay

Mixing and decay

B0s

�D

�M ��D

B0s

fCP

+

2

+ +


contributions

NP could be comparable to

penguins…dominant

“tree“contribution

Physics motivation


• 𝝓s determination via global fit to experimental results ignores contributions from penguin diagrams:

�s = arg

✓� VtsV ⇤

tb

VcsV ⇤cb

◆�s = �M � 2�D

= �2�s +��Peng.s + �NP


Direct decay

Mixing and decay

B0s

�D

�M ��D

B0s

fCP

+

2

+ +

�SM no Peng

s = �2�s = �0.0365+0.0013�0.0012

dominant “tree“contribution


contributions

NP could be comparable to

penguins…

Physics motivation

[CKMFitter]

http://arxiv.org/abs/1501.05013

✦ Toward a precise measurement of 𝝓s:


0.25

CDF

LHCb

ATLAS

Combined

SM

0.20

0.15

0.10

0.05

0-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

68% CL contours

( )

HFAG

Spring 2014

LHCb 1.0 fb–1

+ CDF 9.6 fb–1

+ ATLAS 4.9 fb1

+ D 8 fb– –1

D

Physics motivation

• 𝝓s measurement is an excellent probe for the presence of NP… • …but it is now mandatory to constrain penguin contributions!

State of the art at FPCP 2014


Outline

Direct decay

Mixing and decay

B0s

B0s

fCP



Physics motivation


1

2

3

4

✦ Time-dependent CP asymmetry:

‣ Mixing parameters:

‣ CP observables:

�� = �L � �H



ACP (t) =(B0

s(t) ! f)� (B0s (t) ! f)

(B0s(t) ! f) + (B0

s (t) ! f)=

Sf sin (�mt)� Cf cos (�mt)

cosh

��t2

�+A��sinh

��t2

�

�m = mH �mL

[New J.Phys. 15 (2013) 053021]

Sf = �⌘f2|�f | sin(�s)

1 + |�f |2, A�� = ⌘f

2|�f | cos(�s)

1 + |�f |2

�f = ⌘fq

p

A(B0s(t) ! f)

A(B0s (t) ! f)

= ⌘f |�f |ei�s

Sf =2=(�f )

1 + |�f |2, Cf =

1� |�f |2

1 + |�f |2, A�� = � 2<(�f )

1 + |�f |2


✦ Tagging, resolution and other nuisance effects:

‣ Decay time resolution:

‣ Tagging dilution:

- Initial B flavor efficiency: - Wrong tag rate: - Effective reduction in statistical power:

‣ Also need to account for detection/production asymmetries, acceptance effects on time and angular variables, …



Ameas

(t) = ACP (t) ⇥ Dres

⇥ Dtag

± Adet/prod

Dtag = (1� 2!)

Dres = e��m2�2

t2

t / `m

p

!✏tag

�stat(�s) / 1p✏effN

✏e↵ = ✏tag(1� 2!)2 ⇠ O(%)


Outline

Direct decay

Mixing and decay

B0s

B0s

fCP

Physics motivation1

Measurement ingredients2

Measurement of 𝝓s: ‣ Bs → J/ψK+K− ‣ Bs → J/ψπ+π− ‣ Bs → D+SD−S ‣ Bs → J/ψK0S

3

Constraining penguins in 𝝓s: ‣ Bd → J/ψπ+π−

4

13Simon Akar

The LHCb experiment Detector overview

~12 MHz visible

interactions (2012)

Collisions@ 40 MHz

RICH detectorsK/π/p separation

Calorimetersenergy measurement particle identification

Muon system

Tracking systemmomentum resolution ∆p/p = 0.4% — 0.6%

Dipole magnet4 Tm normal conducting regular polarity switches

Vertex detectorreconstruct vertices decay time resolution: 46 fs IP reconstruction: 20 𝜇m

• Forward General-Purpose Detector at the LHC • ~30 % of heavy quark production cross-section with just 4% of solid angle

y

z

xz ~ 20 m y ~ 10 m x ~ 13 m

• Two-level trigger:- L0 hardware (12 → 1 MHz) - HLT software ( 1 → 0.005 MHz)

Very good 𝛆(𝝁) Good 𝛆(h)

FPCP 2015, Mixing-induced CP violation in Bs decays

Measurement of 𝝓s in Bs → J/𝜓 K+K− (3 fb-1)

✦ Analysis overview: • Measures 𝝓s, 𝜞s, ∆𝜞s and |𝜆|‣ Time-dependent tagged angular

analysis (using sWeights) - 3 P-wave + 1 S-wave components

- tagging power ~3.7%

‣ Fit simultaneously: - 6 bins of mKK

‣ Two fit models: - polarisation independent (baseline) - polarisation dependent

(necessary, if CPV does not affect all polarisation states equally)

14Simon Akar FPCP 2015, Mixing-induced CP violation in Bs decays

[Phys. Rev. Lett. 114 041801 (2015)]

]2) [MeV/c-K+m(K990 1002 1014 1026 1038 1050

)2Ca

ndid

ates

/ (1

.0 M

eV/c

210

310

410 LHCb

]2) [MeV/c-K+ Kψm(J/5300 5350 5400

)2Ca

ndid

ates

/ (2

.5 M

eV/c

0

5000

10000

15000LHCb~95k signal

events


✦ Results: (polarisation independent)

15Simon Akar



Kθcos-1 -0.5 0 0.5 1

Cand

idat

es /

0.05

0

500

1000

1500

2000

2500

3000

3500

LHCb

µθcos-1 -0.5 0 0.5 1

Cand

idat

es /

0.05

0

500

1000

1500

2000

2500

3000

3500

LHCb

[rad]h

ϕ-2 0 2

rad)

πCa

ndid

ates

/ (0

.05

0

500

1000

1500

2000

2500

3000

3500

LHCb

Decay time [ps]5 10

Cand

idat

es /

(0.2

ps)

-110

1

10

210

310

410LHCb

Total PDF CP-even CP-odd S-wave

• World most precise single measurement • Consistant with SM prediction

[Phys. Rev. Lett. 114 041801 (2015)]


✦ Analysis overview: • Performed on 2011 data • Measures 𝝓s, 𝜞s and ∆𝜞s

‣ Time-dependent tagged angular analysis (classic fit) - including background contribution - S-wave compatible with 0 - tagging power ~1.5% - |𝝀| fixed to unity

✦ Results:


Measurement of 𝝓s in Bs → J/𝜓 K+K− (4.9 fb-1)[Phys. Rev. D. 90, 052007 (2014)]

• Consistant with SM & world average • Expect an update with 2012 data soon…


✦ Analysis overview: • Performed on 2012 data • Measures 𝝓s and ∆𝜞s

‣ Time-dependent tagged angular analysis (classic fit) - including background contribution - S-wave compatible with 0 - tagging power ~1.0% - |𝝀| fixed to unity (let free for syst.)

✦ Preliminary results:

[rad]s

φ-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

]-1 [p

ssΓ∆

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

CMS

CMS Preliminary-1=8 TeV L=20 fbs

68% C.L.90% C.L.95% C.L.Standard Model


Measurement of 𝝓s in Bs → J/𝜓 K+K− (20 fb-1)[CMS-PAS-BPH-13-012]

• Consistant with SM & world average

http://cds.cern.ch/record/1744869

Bs → J/𝜓𝜼’

B− → J/𝜓K−

Bs signalB0 signal

B0 → J/𝜓Kπ

Combinatorial

✦ Analysis overview: • Measures 𝝓s, and |𝜆| ‣ Time-dependent flavor-tagged

amplitude analysis - ~27k signal events - classic fit (signal + background) - study ππ invariant-mass up to

mππ ~2.3 GeV - tagging power ~3.9% - amplitude fit performed only

on events within ± 20 MeV from the Bs mass peak

- includes 5 resonant + 1 non-resonant amplitudes

Measurement of 𝝓s in Bs → J/𝜓 π+π− (3 fb-1)


[Phys. Lett. B 736 (2014) 186]


✦ Results:

�s = 0.070± 0.068± 0.008 rad

Measurement of 𝝓s in Bs → J/𝜓 π+π− (3 fb-1)


[Phys. Lett. B 736 (2014) 186]

|�| = 0.89± 0.05± 0.01

for 𝜆 fixed to one (no direct CPV)

Comb

inatio

ns/ (2

0 MeV

)

0500

100015002000250030003500

) [GeV]-π+πm(0.5 1 1.5 2 -5

05

LHCb(a)

Comb

inatio

ns/ 0

.05

0200400600800

10001200

-π+πθcos -1 -0.5 0 0.5 1-5

05

LHCb(b)

Comb

inatio

ns/ 0

.05

0200400600800

10001200

ψJ/θcos -1 -0.5 0 0.5 1-5

05

LHCb(c)

)πCo

mbina

tions

/ (0.1

0200400600800

10001200140016001800200022002400

χ-2 -5

05

LHCb(d)

0 2.

• World second most precise single measurement • Consistant with SM prediction & world average

�s = 0.075± 0.067± 0.008 rad


✦ Analysis overview: • Measures 𝝓s and |𝜆| ‣ Time-dependent flavor-tagged

analysis (classic fit) - purely CP-even mode

(no angular fit needed) - Ds reconstructed as KKπ, Kππ or πππ - Using B0 → D−D+

S as control channel - tagging power ~5.3%

✦ Results:

Measurement of 𝝓s in Bs → D+SD−S (3 fb-1)

✦


[Phys. Rev. Lett. 113 (2014) 211801]

]2c) [MeV/s− Ds

+M(D5300 5350 5400 5450

)2 cCa

ndid

ates

/ (5

MeV

/

0

200

400

600

800s− Ds

+ D→s0

B−π+K− K+

s D→s0

B

s−* Ds

+ D→s0

B−s D+ D→

0B

−s D+

cΛ →0bΛ

Combinatorial

LHCb(a)

Decay time [ps]5 10

Cand

idat

es /

(0.1

ps)

1

10

210LHCb

sPlot

~3350 signal events

• Consistant with SM & world average



✦ Analysis overview: • First time-dependent CPV measurements

in this channel

• Flavor-tagged time-dependent analysis: ‣ simultaneous fit to a mixed sample of

many Bd and few Bs events (100/1)

‣ use of multivariate selection trained on Bd proxy

‣ split sample in two categories: - Downstream KS (no velo hits) - Long KS (velo hits → better resolution)

‣ tagging power: - Bs ~ 3.8% / Bd ~ 2.6%

‣ also fits for sin2𝞫 (as cross-check) - see previous talk

)2 cEv

ents

/ ( 2

MeV

/

1

10

210

3100SKLong

LHCb

)2c (MeV/0SKψJ/m

5200 5300 5400 5500

Pull

-5

0

5

)2 cEv

ents

/ ( 2

MeV

/

1

10

210

310

4100SKDownstream

LHCb

)2c (MeV/0SKψJ/m

5200 5300 5400 5500Pu

ll-5

0

5

Bs

Bd

Bs

Bd

combi. bkg.

combi. bkg.

Article submitted to JHEP [arXiv:1503.07055]

Measurement of TDCP asymmetries in Bs → J/𝜓 K0S (3 fb-1)


Cand

idates

/ ( 0.

15 ps

)

1

10

210

310 0SKDownstream

LHCb

(ps)t5 10 15

Pull

-5

0

5

Cand

idates

/ ( 0.

15 ps

)

1

10

210

310 0SKLong

LHCb

(ps)t5 10 15

Pull

-5

0

5

combi. bkg.Bs

Bd

✦ Preliminary results: combi. bkg.Bs

Bd



Recent prediction: [arXiv:1412.6834]

• Successful proof of concept waiting for more statistics

• Can be used to estimate the penguin effects in sin2𝞫 as well as in 𝝓s





Outline

Direct decay

Mixing and decay

B0s

B0s

fCP

Physics motivation1

Measurement ingredients2

Measurement of 𝝓s: ‣ Bs → J/ψK+K− ‣ Bs → J/ψπ+π− ‣ Bs → D+SD−S ‣ Bs → J/ψK0S

3

Constraining penguins in 𝝓s: ‣ Bd → J/ψπ+π−

4

✦ Analysis overview: • Measures 2𝞫eff and 𝞪CP

• Similar to Bs → J/𝜓 π+π− ‣ Time-dependent flavor-tagged

angular analysis (classic fit) - ~ 18k signal events

✦ Results:


[Phys. Lett. B742 (2015) 38]

Measurement of 𝞫 in Bd → J/𝜓 π+π− (3 fb-1)

) [GeV]-π+πm(0.5 1 1.5 2

Comb

inatio

ns/ (1

8.6 M

eV)

0200400600800

100012001400

DataFitSignalBackground(770)ρ(500)0f(1270)2f(782)ω(1450)ρ(1700)ρ

LHCb

) [MeV]-S+S\m(J/5300 5400 5500

Com

bina

tions

/ (5

MeV

)

0

1000

2000

3000

4000

5000

6000

7000LHCb

Bs → J/𝜓𝜼’

B− → J/𝜓K−

Bs signalB0 signal

B0 → J/𝜓Kπ

Combinatorial

↵CP =1� |�f |1 + |�f |

CJ/ ⇢0 = �0.063± 0.056(stat)+0.019�0.014(syst)

SJ/ ⇢0 = �0.66+0.13�0.12(stat)

+0.09�0.03(syst)

↵CP (B0 ! J/ ⇢0) = �(32± 28(stat)+7

�9(syst))⇥ 10�3

2�e↵(B0 ! J/ ⇢0) = (41.7± 9.6(stat)+2.8�6.3(syst))

�

Used in penguin contribution estimation (next slide)

Most precise CP asymmetry measurement in this mode

Limits on penguin effects in 𝝓s



Limits on penguin effects in 𝝓s Measurement of 𝞫 in Bd → J/𝜓 π+π− (3 fb-1)

✦ Limits on penguin effects:

• Assuming perfect SU(3) flavor symmetry:

A(B0s ! J/ �) = A0

h1� ✏a0ei✓

0ei�

iA(B0 ! J/ ⇢0) = A

h1� aei✓ei�

i|�f | =

��1� aei✓e�i�

1� aei✓ei�

��

�2� =�2�e↵ � 2�

�= �arg

✓1� aei✓e�i�

1� aei✓ei�

◆↵CP =

1� |�f |1 + |�f |

a = a0 ✓ = ✓0

✏ ⌘ �2c/(1� �2

c) = 0.0534

��s = � arg

(�0

fe2i� � 1) + ✏(�0

f � 1)

(�0fe

2i� � 1) + ✏(�0f � 1)e2i�

!where �0

f ⌘ |�f |e�i�2��s = � arg

(�0

fe2i� � 1) + ✏(�0

f � 1)

(�0fe

2i� � 1) + ✏(�0f � 1)e2i�

!where �0

f ⌘ |�f |e�i�2�

��s 2 [�1.05�, 1.18�] at 95% C.L.

[deg]θ0 100 200 300

a

LHCb

00.05

0.10.150.2

0.250.3

0.350.4

,

,

95% C.L.68% C.L.

�2� =⇣2�J/ ⇢ � 2�J/ K0

S

⌘= (�0.9± 9.7(stat)+2.8

�6.3(syst))�

�2� =⇣2�J/ ⇢ � 2�J/ K0

S

⌘= (�0.9± 9.7(stat)+2.8

�6.3(syst))�

First experimental constraint on penguin contribution on 𝝓s

[Phys. Lett. B742 (2015) 38]

��s ⇠ �✏�2�




0.25

CDF

LHCb

ATLAS

Combined

SM

0.20

0.15

0.10

0.05

0-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

68% CL contours

( )

HFAG

Spring 2014

LHCb 1.0 fb–1

+ CDF 9.6 fb–1

+ ATLAS 4.9 fb1

+ D 8 fb– –1

D

In summaryState of the art at FPCP 2014



In summary

1.5 1.0 0.5 0.0 0.5 1.0 1.5

0.00

0.05

0.10

0.15

0.20

ATLAS 4.9 fb1

CMS 20 fb1

CDF 9.6 fb1

DØ 8 fb1

LHCb 3 fb1

SM

68% CL contours

( )

Combined

State of the art at FPCP 2015

0.25

CDF

LHCb

ATLAS

Combined

SM

0.20

0.15

0.10

0.05

0-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

68% CL contours

( )

HFAG

Spring 2014

LHCb 1.0 fb–1

+ CDF 9.6 fb–1

+ ATLAS 4.9 fb1

+ D 8 fb– –1

D



In summaryState of the art at FPCP 2015

0.4 0.2 0.0 0.2 0.4

0.06

0.08

0.10

0.12

0.14

LHCb

3 fb1

ATLAS 4.9 fb1

CMS

20 fb1

CDF 9.6 fb1

DØ 8 fb1

Combined

SM

68% CL contours

( )

�ccss = �0.015± 0.035�s = �M � 2�D

= �2�s +��Peng.s + �NP

�ccss = �0.015± 0.035

�SM no Peng

s = �2�s = �0.0365+0.0013�0.0012

[HFAG]

[CKMFitter]

��Peng.s = 0.001± 0.010

�NP =??

• Entered era of precise CPV measurement in the Bs system • First step in controlling penguin contributions • Precision will further increase with LHC RunII & Upgrades

adding statistics and new measurements!

http://www.slac.stanford.edu/xorg/hfag/osc/fall_2014/#DMS


29Simon Akar

Spare slides


★Mixing-induced CP violation in penguin dominated transitions: ‣ Bs → 𝝓𝝓

★Complementary material on measurements ‣ Bd(s) → π+π−(K+K−)

�ssss

�ccss

[Phys. Rev. D90, 052011 (2014)]

[Phys. Lett. B 741 (2015) 1]Analysis not presented here. Making use of CKM angle 𝜸 as input in the determination of −2𝞫s



✦ Analysis overview: • 𝝓s in b → sss transitions: ‣ Dominated by gluonic penguin loops ‣ Good sensitivity to NP ‣ SM prediction 𝝓s(b → sss) ~ 0

• Time-dependent flavor-tagged angular analysis (using sWeights): ‣ ~ 4000 signal events

✦ Results:


Measurement of CP violation in Bs → 𝝓𝝓 (3 fb-1)[Phys. Rev. D90, 052011 (2014)]

Bd → 𝝓K*

𝜦b → 𝝓pK

Combinatorial

Bs → 𝝓𝝓−

−

2012


31Simon Akar

Measurement of 𝝓s Motivations for the Upgrades

• Will be on the verge of reaching theoretical uncertainties!

Statistical uncertainties[CERN-LHCC-2012-007] LHCb Upgrade TDR

�ccss

�ssss

[ATL-PHYS-PUB-2013-010]



Measurement of 𝝓s in Bs → J/𝜓 K+K− (3 fb-1)[Phys. Rev. Lett. 114 041801 (2015)]




✦ Results: (polarisation independent)

Kθcos-1 -0.5 0 0.5 1

Cand

idat

es /

0.05

0

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1000

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µθcos-1 -0.5 0 0.5 1

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es /

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[rad]h

ϕ-2 0 2

rad)

πCa

ndid

ates

/ (0

.05

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LHCb

Decay time [ps]5 10

Cand

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es /

(0.2

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410LHCb


[Phys. Rev. Lett. 114 041801 (2015)]


✦ Systematics: (polarisation independent)


Measurement of 𝝓s in Bs → J/𝜓 K+K− (3 fb-1)[Phys. Rev. Lett. 114 041801 (2015)]




✦ Results: (polarisation dependent)

Kθcos-1 -0.5 0 0.5 1

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idat

es /

0.05

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3500

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es /

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[rad]h

ϕ-2 0 2

rad)

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ndid

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/ (0

.05

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410LHCb


[Phys. Rev. Lett. 114 041801 (2015)]




✦ Systematics: (polarisation dependent)

[Phys. Rev. Lett. 114 041801 (2015)]




✦ Results:

[Phy

s. R

ev. D

. 90,

052

007

(201

4)]

[CM

S-P

AS

-BP

H-1

3-01

2]





✦ Systematics:

[Phy

s. R

ev. D

. 90,

052

007

(201

4)]

[CM

S-P

AS

-BP

H-1

3-01

2]





✦ Tagging:

[Phy

s. R

ev. D

. 90,

052

007

(201

4)]

[CM

S-P

AS

-BP

H-1

3-01

2]



✦ Systematics:


Measurement of 𝝓s in Bs → D+SD−S (3 fb-1)[Phys. Rev. Lett. 113 (2014) 211801]


✦ Systematics:





✦ Systematics:


[Phys. Lett. B742 (2015) 38]

Measurement of 𝞫 in Bd → J/𝜓 π+π− (3 fb-1)Limits on penguin effects in 𝝓s


✦ ππ spectrum resonant composition:


[Phys. Lett. B742 (2015) 38]

Measurement of 𝞫 in Bd → J/𝜓 π+π− (3 fb-1)

) [GeV]-π+πm(0.5 1 1.5 2

Comb

inatio

ns/ (1

8.6 M

eV)

0200400600800

100012001400

DataFitSignalBackground(770)ρ(500)0f(1270)2f(782)ω(1450)ρ(1700)ρ

LHCb

Limits on penguin effects in 𝝓s


akar simon fpcp2015 v1 - cern filesimon akar fpcp 2015, mixing-induced cp violation in bs decays 2 e...

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