Measurement of the CKM angle charm mixing and … of the CKM angle g charm mixing and CP violation...

Measurement of the CKM angle g charm mixing and CP violation at LHCb

Outline: LHCb detector & data taking Measurements of CKM angle g Determination of D0-D0 mixing and CP violation parameters Summary

Pavel Krokovnyon behalf of the LHCb Collaboration

Budker INP & Novosibirsk University

28 May HQL 2018 Yamagata

LHCb Experiment

2

LHCb dataset Good tracking performance: momentum uncertainty 0.5-1.0%

Excellent vertexing: IP resolution (15+29/pT) mm Acceptance: 2 < η < 5

2.0 fb-1 @ 8 TeV

1.0 fb-1 @ 7 TeV

3Int. J. Mod. Phys. A30 (2015) 1530022

LHCb detector asymmetries

Measure raw asymmetries

4Int. J. Mod. Phys. A30 (2015) 1530022

N (x)−N ( x)N (x )+N (x )

CP asymmetry, detector asymmetry,production asymmetry

sum of

Sources of detector asymmetry:● Magnet sweeps opposite-charged particles

in different directions (detector not perfectly

symmetric)

● Different cross section of nuclear

interactions for particles and antiparticles

Solutions:● Regularly reverse polarity. Fiducial cuts to

remove most asymmetric regions

● Irreducible: measure in control

channels

Unitarity Triangleg is the least well constrained angle of the unitarity triangleNon-trivial triangle - CP-violationNot a triangle - Beyond SM Physics

5

How to measure gTwo amplitudes b→cW(us) [B-→D0K-] and b→uW(cs) [B-→D0K-] give same final state when both D and D decay to a common final state.No penguin contribution theoretically clean.⇒

6

● Amplitude ratios: ● Strong phases:

rB, r

D

dB, d

D

Experimental methods● GLW (Gronau, London, Wyler) [1991]: D→K+K-, p+p-

● ADS (Atwood, Dunietz, Soni) [1997,2001]: D→K+p-

● GGSZ (Giri, Grossman, Soer, Zupan) [2003]: D→K0Sp+p-

Dalitz plot DKS

0p+p- ds(m+

2, m-2) ~ |A|2dm

+2 dm

-2, m

±2 = m2(K

S0p±),

D0 amplitude: AD(m

+2, m

-2), D0 amplitude: A

D(m

-2, m

+2)

Amplitude of DKS

0p+p- from B+DK+ :

A

D(m

+2,m

-2) + r

BeidB + ig A

D(m

-2,m

+2)

7

ΑCP=Γ(B−→DCP K−

)−Γ(B+→DCP K+

)

Γ(B−→DCP K−

)+Γ(B+→DCP K+

)=

2 r Bsin (δ B+δ D)sin γ

1+rB2+2 r B cos(δ B+δ D)cos γ

ΑCP=Γ(B−→[K+

p - ]K− )−Γ(B+→[K - p+ ]K + )

Γ(B−→[K +p - ]K−

)+Γ(B+→[K - p+]K+

)=

2 r Br D sin(δB+δD)sin γ

r B2+r D

2+2 r Br D cos (δB+δD)cos γ

ADS: B±→D(*)K± and B±→D(*)π±

8Physics Letters B 777 (2018) 16-30

GLW: B±→D(*)K± and B±→D(*)π±

9

Physics Letters B 777 (2018) 16-30

Dataset:1.0 fb-1 @ √s=7 TeV2.0 fb-1 @ √s=8 TeV2.0 fb-1 @ √s=13TeV

RCP

= 0.989 ± 0.013 ± 0.010

ACP

=+0.124 ±0.012 ±0.002

A = ACP

+Adet

+Aprod

Results: B±→D(*)K± and B±→D(*)π±

10

Physics Letters B 777 (2018) 16-30


B±→DK*±

11JHEP 11 (2017) 156


ADS: B±→DK*±

12

JHEP 11 (2017) 156

GLW: B±→DK*±

13

JHEP 11 (2017) 156

Results: B±→DK*±

14

JHEP 11 (2017) 156

RCP+

= 1.18 ± 0.08 ± 0.02

ACP+

= +0.08 ± 0.06 ± 0.01

RkpADS

= 0.0011 ± 0.004 ± 0.001

AkpADS

= -0.81 ± 0.17 ± 0.04

RkpppADS

= 0.0011 ± 0.005 ± 0.003

AkpppADS

= -0.45 ± 0.21 ± 0.14

GGSZ method

15LHCb paper 2018-017


x± ≡ r

B cos(d

B ± g) and y

± = r

B sin(d

B ± g)

GGSZ results

16

LHCb paper 2018-017PRELIMINARY

PRELIMINARY

PRELIMINARY

Measurement of CP violation in B0→D∓p±

17arXiv:1805.03448

Dataset:1.0 fb-1 @ √s=7 TeV2.0 fb-1 @ √s=8 TeV


18

arXiv:1805.03448


19

arXiv:1805.03448

g combination

20LHCb CONF 2018-002

g combination


Bs0→D

s∓K± time-dep

B0→DK*0

B0→DK+p-

B0→D∓p± time-dep

B+→DK+

B+→D*K+

B+→DK*+

B+→DK+p+p-

D0-D0 mixing and CP violation in D0→K+π−

22

Right-sign (RS) D0→K-π+ is dominated by CF decay

Wrong-sign (WS) D0→K+π-

has two sources:

Mixing amplitude is time-dependent

Ratio R(t) = ΓWS

(t)/ΓRS

(t) depends on x and y:

R( t)=RD+√RD y '(

tτ )+

x' 2+ y ' 2

4(

tτ )

2

( x 'y ')=(

cosd sin d−sin d cos d)(

xy )

R±(t)=RD

±+√RD

± y '±(

tτ )+

x '±2+ y '±2

4(

tτ )

2 ICPV: x’+ ≠ x’−

and/or y’+ ≠ y’−

DCPV: RD

+ ≠ RD

-

D0-D0 mixing and CP violation by D0→K+π−

23Phys Rev D97, 031101 (2018)

177 106

RS events 0.72 106

WS events



24Phys Rev D97, 031101 (2018)


25Phys Rev D97, 031101 (2018)

RD = 3.454 ± 0.028 ± 0.014

y` = 5.28 ± 0.45 ± 0.27x`2 = 0.039 ± 0.023 ± 0.014

RD = 3.454 ± 0.028 ± 0.014

y`+ = 5.01 ± 0.48 ± 0.29(x`+)2 = 0.061 ± 0.026 ± 0.016y`- = 5.54 ± 0.48 ± 0.29(x`-)2 = 0.016 ± 0.026 ± 0.016

RD

+ = 3.454 ± 0.040 ± 0.020y`+ = 5.01 ± 0.64 ± 0.38(x`+)2 = 0.061 ± 0.032 ± 0.019R

D- = 3.454 ± 0.040 ± 0.020

y`- = 5.54 ± 0.64 ± 0.38(x`-)2 = 0.016 ± 0.033 ± 0.020

AD= (−0.1 ± 9.1)×10−3

26

Conclusion LHCb continue efforts to measure CKM angle g.

Combined result is still limited by statistics.

Further progress expected after LHCb upgrade. Most precisest

GGSZ method requires preciest measurement of strong phase

difference δD on D0→K

S0p+p- Dalitz plot BES III can do it. ⇒

D0-D0 mixing parameters have been measured in D0→K+π−. CP

violation is found consistent with zero.

Further results are expected. Please see LHCb upgrade talk by

Preema Pais on Friday.

g=(74.0−5.8+5.0 )o

27

Backup

Search for CP asymmetry in B-→D- D0

28

LHCb paper 2018-007

Submitted to JHEP

Dataset:2.0 fb-1 @ √s=7 TeV1.0 fb-1 @ √s=8 TeV

Interference in B→ DK

● No penguin contribution ⇒theoretically clean

● The only CP-violating parameter that can be measured solely in tree-level processes

● g precision is limited by small branching ratios

Best theoretically clean way of measuring g is based on interference between b→cus and b→ucs tree level amplitudes. E.g., B±→DK± followed by D→f and B→DK± followed by D→f, where f is a common final state

29

Atwood-Dunietz-Soni method

30PRL 78, 3357 (1997);

PRD 63, 036005 (2001)D. Atwood, I. Dunietz and A. Soni,

Doubly Cabibbo suppressed (DCS) D decays can be used tomeasure g. E.g. [K-p+]K- can be reached in two ways:● Cabibbo favored (CF) B-→D0K- followed by DCS D0→K+p-

● DCS B-→D0K- followed by CF D0→K+p-

Gronau-London-Wyler method

31

СР eigenstate of D-meson is used (DCP).

CP-even : DCP K+K–, π+ π –

RCP=Br (B→DCP K ) /Br (B→DCP π )

Br (B→D0 K ) /Br (B→D0 π )=1+r B

2 +2 rB cos δ cos γ

Double ratio:

ΑCP=Br (B−

→DCP K−)−Br (B+

→DCP K+)

Br (B−→DCP K−

)+Br (B+→DCP K+

)=

2 rB sin δ sin γ

1+r B2 +2 r Bcos δ cos γ

СР-asymmetry:

2 equations, 3 unknowns ),,( gdBr

[Phys. Lett. B 253 (1991) 483][Phys. Lett. B 265 (1991) 172]

g

g

Dalitz method

32[A. Bondar, unpublished (2002)][A. Giri, Yu. Grossman, A. Sofer, J. Zupan, PRD 68, 054018 (2003)]

Information from Dalitz plot analysis of DKS

0p+p- from B±->DK±

Dalitz plot density: ds(m+

2, m-2) ~ |A|2dm

+2dm

-2, where m

±2 = m2(K

S0p±)

Flavour D amplitude: AD(m

+2, m

-2)

CP -conservation in DKS

0p+p- decays: AD(m

+2, m

-2) = A

D(m

-2, m

+2)

Amplitude of DKS

0p+p- from B+DK+ :

AB (m

+2, m

-2) = A

D (m

+2, m

-2) + r

BeidB + ig A

D(m

-2, m

+2) =

Required to know phase diference between AD(m+2, m-

2) and AD(m-

2, m+2). Taken from e+e-DD (CLEOc)

GGSZ method

33[A. Giri, Yu. Grossman, A. Sofer, J. Zupan, PRD 68, 054018 (2003)]

)](2[ 2iiiiiBiBi ysxcKKKrKhN

Number of events in B-plotNumber of events in D0-plot: Ki

C (m+2 , m−

2)=cos( δD(m+

2 , m−2)−δ D(m−

2 ,m+2))

S (m+2 , m−

2)=sin (δD(m+

2 ,m−2)−δD(m−

2 , m+2))

PCP±(m+2 ,m−

2)=|f D± f̄ D|

2=PD+ P̄D±2√PD P̄D C

PCorr(m+2 , m−

2 , m+' 2 , m−

' 2)=|f D f̄ D'− f̄ D f D

'|2=

=PD P̄D'+ P̄D PD

'−2√PD P̄D PD

' P̄D'(C C'

+S S')

DCPKSπ+π–:

ψ(3770)(KSπ+π–)D (KSπ+π–)D :

where)cos( 3d Brx

y±=r Bsin (δ±ϕ3 )Free parameters

g combination


GGSZ systematic uncertainties

36

LHCb paper 2018-017


37Phys Rev D97, 031101 (2018)

Interference in B→ DK

Neglible theoretical uncertainty (Zupan and Brod 2013)Theory uncertainty on ~10-7 - [arXiv:1308.5663]

38

Measurement of the CKM angle charm mixing and … of the CKM angle g charm mixing and CP violation...

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Transcript of Measurement of the CKM angle charm mixing and … of the CKM angle g charm mixing and CP violation...