CP violating phase s and s measurements at LHCb...s = 0:010 0:039 rad j j= 0 :957 0 017 Consistent...

CP violating phase φs and ∆Γs measurements at LHCb

Carlos Vazquez Sierra,

on behalf of LHCb collaboration

Universidade de Santiago de Compostela, Spain.

Beauty 2016, Marseille (France)

May 2, 2016

Carlos Vazquez Sierra Beauty 2016, Marseille (France) May 2, 2016 1 / 21

Introduction

φs is an interference phase which appears due to mixing-induced CP violation:We are mainly interested in the φs phase measured in b→ ccs processes, φccs

s :

B0s B0

sW W

b

s

s

b

t

t

Vtb Vts∗

V ∗ts Vtb

Mixing: φM = 2 arg(VtbV∗ts)

B0s

J/ψ

φ

W

b

s

s

c

c

s

V ∗cb

Vcs

Decay: φD = arg(VcbV∗cs)

φs = φM − 2φD → φccss = −2 arg

(−VcbV

∗cs

VtbV∗ts

)= −2βs

Do not confuse φccss with other φs phases measured in different processes, like φsss

s !φccss is experimentally accessed via the following time-dependent asymmetry (final state f ):

ACP(t) =ΓB0

s−ΓBs0

ΓB0s

+ΓBs0= Sf sin(∆mt)−Cf cos(∆mt)

cosh(∆Γt/2)+A∆Γ sinh(∆Γt/2)

λf =q

p

Af

Af

, φs = − arg(λf ), Cf =1− |λf |2

1 + |λf |2, Sf =

2I(λf )

1 + |λf |2, A∆Γ = −

2R(λf )

1 + |λf |2

I(λf ) 6= 0→ If there is no complex phase in CKM matrix → No CP violation!


Introduction

Why φccss ?

φccss is a “golden” phase (βs unitarity triangle: VusV

∗ub + VcsV

∗cb + VtsV

∗tb = 0):

Related to mixing in the heavy quark sector,Possible NP can modify φccs

s if new particles contribute to “box” diagrams:

B0s B0

sW,,NP W,,NP

b

s

s

b

t,,NP

t,,NP

Vtb Vts∗

V ∗ts Vtb

SM prediction is very precise:

φccss = −2βs = −0.0376 +0.0008

−0.0007 rad [CKMfitter, PRD 84 (2011) 033005†]

φccss is an excellent probe for possible NP!

φccss is measured by LHCb in B0

s→ J/ψK+K− and B0s→ J/ψπ+π− modes,

Also a contribution from B0s→ D+

s D−s decays is considered (see backup).† Including summer 2015 update.


The LHCb experiment

LHCb is an LHC experiment designed for heavy quark flavour physics,

The detector is a single-arm forward spectrometer, covering 2 < η < 5;

Tracking system consists of Vertex Locator (VELO, σIP ∼ 20µm for high pT tracks),followed by one tracking station upstream and three stations (δp/p ' 0.4%) downstreamof 4 T × m dipole magnet;

Particle identification is provided by two RICH detectors, calorimeters and muon system;

Calorimeter and muon stations provide 40 MHz input to hardware Level-0 trigger, while allother subdetectors are read out at 1 MHz.

Upgrade (see Gabriele’s talk):

Run I accumulated 3 fb−1,Run II: 2015-2018 (8 fb−1),LS2: 2018-2021,Run III: 2021-2023 (23 fb−1),HL-LHC era: +2025


A few words on LHCb flavor tagging

SS (same-side) tagger: [LHCb-CONF-2012-033], [LHCb, PRL 115 (2015) 031601]

Focus on the associated production with the signal B-meson,

In ∼ 50% of cases, a B0s (B0) meson is accompanied by a charged kaon (pion);

Calibration modes (SSK, interest in B0s decays): D+

s → φπ+.

8 New SSK algorithm developed: [LHCb-PAPER-2015-056, accepted by JINST]

Two neural networks: one to select kaons associated to a B0s meson, other to assign its flavor,

Calibrated using B0s→ D−s π

+ and B∗s2(5840)0→ B+K− modes (3.0 fb−1).

Tagging power of the new (old) SSK algorithm on B0s→ D−s π

+ decays ∼ 1.8 (1.2)%.

PV

x

b

b

q

TV

Y

SV

X

YB0

same side

opposite side

SV

b ⟶ c b ⟶ X l–

c ⟶ s K– OS kaon (+NN)

l– OS muon OS electron

OS vertex charge OS charm

qu

X+SS pion (+BDT) SS proton SS kaon (+NN)

�


A few words on LHCb flavor tagging

PV

x

b

b

q

TV

Y

SV

X

YB0

same side

opposite side

SV

b ⟶ c b ⟶ X l–

c ⟶ s K– OS kaon (+NN)

l– OS muon OS electron

OS vertex charge OS charm

qu

X+SS pion (+BDT) SS proton SS kaon (+NN)

�

OS (opposite-side) tagger: [LHCb, EPJC 72 (2012) 2022]

Focus on the complementary b-quark: b→ cW (OS-electron/muon), and b→ c→ s (OS-kaon);

Calibration modes: B+→ J/ψK+, B+→ D0π+, B0→ J/ψK∗0, B0s→ D−s π

+, and B0→ D∗−s µ+X;

Typical tagging power of LHCb OS tagger algorithms ∼ 2.5%.

8 New OS-charm tagger developed: [LHCb, JINST 10 (2015) P10005]

Focus on b→ c transitions of the complementary b-quark (D±, Λ±c , D0),

Calibrated using B+→ J/ψK+ and B0→ J/ψK∗0 modes (3.0 fb−1).

Including the OS-charm tagger leads to an absolute net gain in tagging power of ∼ 0.11%.


CP violation in B0s→ J/ψK+K− decays (LHCb, PRL 114 (2015) 041801)

Full Run I of LHCb data (3.0 fb−1) analysed,

B0s→ J/ψ(→ µ−µ+)φ(→ K+K−) (P2VV decay):

Dominant K+K− P-wave (CP admixture): φ(1020),∼ 2.3% K+K− S-wave (CP-odd) contribution,Angular information needed to disentangle CP components!

Tagging power: ε(1− 2ω)2 = 3.73± 0.15%,

Decay time resolution ∼ 46 fs.

B0s

J/ψ

φ

W

b

s

s

c

c

s

θµ

µ+µ−K−K+θK

y

ϕhx

z

K+

µ−

µ+

B0s

K−

]2) [MeV/c-

K+ Kψm(J/5300 5350 5400

)2C

andi

date

s / (

2.5

MeV

/c

0

5000

10000

15000LHCb

Nsignal ∼ 96k

Combinatorial backg.

B0s signal

∼ 1.7k B0→ J/ψKπ

∼ 4.8k Λ0b→ J/ψpK

(statistically subtracted)


CP violation in B0s→ J/ψK+K− decays (LHCb, PRL 114 (2015) 041801)

Weighted maximum likelihood fit to decay time and helicity angles:

Decay time [ps]5 10

Can

dida

tes

/ (0.

2 ps

)

-110

1

10

210

310

410LHCb

Kθcos-1 -0.5 0 0.5 1

Can

dida

tes

/ 0.0

5

0

500

1000

1500

2000

2500

3000

3500

LHCb

µθcos-1 -0.5 0 0.5 1

Can

dida

tes

/ 0.0

5

0

500

1000

1500

2000

2500

3000

3500

LHCb

[rad]h

ϕ-2 0 2

rad

)π

Can

dida

tes

/ (0.

05

0

500

1000

1500

2000

2500

3000

3500

LHCb

φs = −0.058± 0.049± 0.006 rad

∆ms = 17.711 +0.055−0.057 ± 0.011 ps

−1

Γs = 0.6603± 0.0027± 0.0015 ps−1

∆Γs = 0.0805± 0.0091± 0.0032 ps−1

|λ| = 0.964 ± 0.019 ± 0.007

S-waveCP-evenCP-odd

B0s→ J/ψK+K− is a golden channel: measurement of φs , ∆ms , Γs , ∆Γs , |λ|;

Consistent with SM, no direct CP violation (|λ| = 1),

Systematics dominated by decay time efficiency, angular efficiency, and background subtraction,

No polarisation-dependent CP violation observed (see backup).

Most precise φccss measurement to date!


CP violation in B0s→ J/ψπ+π− decays (LHCb, PLB 736 (2014) 186)


Tagging power: ε(1− 2ω)2 = 3.89± 0.23%,

Decay time resolution ∼ 40.5 fs,

B0s→ J/ψ(→ µ−µ+)π+π− with resonant structure:

Analysis of resonant structure: [LHCb, PRD 89 (2014) 092006],Dominant CP-odd π+π− > 97.7% @ 95% CL.

B0s

J/ψ

π+π−

W

b

s

s

c

c

s

) [GeV]-π+πm(

LHCb

0.5 1 1.5 2

Eve

nts/

(20

MeV

)

1

10

210

310

410 DataFitSignalBackground

(980)0f(1525)2f’(1270)2f(1500)0f(1790)0f

Five π+π− resonant states

) [MeV]-π+πψm(J/5300 5400 5500

Com

bina

tions

/ (5

MeV

)

0

1000

2000

3000

4000

5000

6000

7000 LHCbη′ , φ states + Λ0

b (2.3%)

B±→ J/ψh± (2.0%)

B0→ J/ψKπ

B0→ J/ψπ+π−


B0s signal

Nsignal ∼ 27k


CP violation in B0s→ J/ψπ+π− decays (LHCb, PLB 736 (2014) 186)

Unbinned maximum likelihood fit into a 20MeV/c2 window around the B0s peak.

Fit projections of m(π+π−) and of the helicity angles:

Com

bina

tions

/ (20

MeV

)

) [GeV]-π+πm(

-5

05

Com

bina

tions

/ 0.0

5

θcos

-5

0

5

hh

Com

bina

tions

/ 0.0

5

ψJ/θcos

-50

5

)πC

ombi

natio

ns/ (

0.1

χ-5

05

0

500

1000

1500

2000

2500

3000

3500

0.5 1 1.5 2

LHCb(a)

0

200

400

600

800

1000

1200

-1 -0.5 0 0.5 1

LHCb(b)

0

200

400

600

800

1000

1200

-1 -0.5 0 0.5 1

LHCb(c)

0

500

1000

1500

2000

2500

-2

LHCb(d)

20

B0s signal

Combinatorial background

φccss,ππ = 0.070± 0.068± 0.008 rad

|λππ| = 0.89 ± 0.05 ± 0.01

Combination with B0s→ J/ψK+K− results:

φccss = −0.010± 0.039 rad

|λ| = 0.957± 0.017

Consistent with SM, no direct CP violation (|λππ| = 1, assumed equal for all π+π− states),

Systematics dominated by the knowledge of the π+π− resonant model and the B0s − B

0s ratio,

Cross-check by measuring φccss,ππ considering 100% CP-odd π+π−: result consistent with simulation,

Combination with B0s→ J/ψK+K− results assuming same CP violation in decay for both modes.


Gluonic penguin pollution to φccss (see previous talk by Kristof)

But...Second-order contributions to φccs

s due to gluonic penguin diagrams (“penguin pollution”),

It is a pure SM effect, which could mimick possible NP:

φccss (measured) = −2βs + δP + δNP

Quest for possible NP is not an easy task, and penguin pollution make it even harder!

With the upgrade of current generation detectors, sensitivity continues to improve,

B0s

J/ψ

φ

W

b

s

s

c

c

s

B0s

J/ψ

φW

b

s s

s

c

c

u, c, t

Colour singletexchange

This effect must be estimated if we want to continue with the quest!


B0s→ J/ψK

∗0as a control channel (LHCb, JHEP 11 (2015) 082)

Decay-time integrated flavor-averaged analysis,


B0s→ J/ψ(→ µ+µ−)K

∗0(→ K+π−) (P2VV decay):

Dominant K+π− P-wave, non-neglectable S-wave.

Measure direct CP asymmetries and polarisation fractions,

Measure the branching fraction B(B0s→ J/ψK

∗0).

Prof. John Ellis @ SymmetryMagazine.org

]2c [MeV/+π−K ψJ/m5200 5300 5400 5500 5600

)2 cC

andi

date

s / (

11.1

MeV

/

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Data

Total PDF

signal0

B

signals0B

Combinatorial bkg−πp ψJ/ → b

0Λ

LHCb

(backgrounds statistically subtracted)

Nsignal ∼ 1.8k


B0s→ J/ψK

∗0as a control channel (LHCb, JHEP 11 (2015) 082)

Weighted maximum likelihood fit in bins of m(K+π−) and one of the angles,

Fit projections of the helicity angles:

)K

θcos(1− 0.5− 0 0.5 1

Can

dida

tes

/ 0.1

40−

20−

0

20

40

60

80

100

120

LHCb

)µθcos(1− 0.5− 0 0.5 1

Can

dida

tes

/ 0.1

0

20

40

60

80

100

120

LHCb

(rad)h

ϕ2− 0 2

]-1

Can

dida

tes

/ 0.3

1 [r

ad

0

20

40

60

80

100

120

LHCb S-P wave interference

S-wave

P-wave odd + P-P wave interference

P-wave even

Total

f0 = 0.497± 0.025± 0.025

f‖ = 0.179± 0.027± 0.013

ACP0 = −0.048± 0.057± 0.020

ACP‖ = 0.171± 0.152± 0.028

ACP⊥ = −0.049± 0.096± 0.025

B(B0s→ J/ψK

∗0) = (4.14± 0.18± 0.26± 0.24 (fd/fs))× 10−5

Angular acceptance corrected by iterative procedure from simulation: [T. du Pree, CERN-THESIS-2010-124];

Production and detection asymmetry taken into account: [LHCb, PRL 114 (2015) 041601 & JHEP 07 (2014) 041];

Systematics dominated by angular acceptance corrections.


Combining B0→ J/ψρ0 and B0s→ J/ψK

∗0results

Results dominated by B0→ J/ψρ0 (SU(3) flavor symmetry broken by 20%− 30%):

−180 −150 −120 −90 −60 −30 0 30 60 90 120 150 180

θ0 [deg]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

a0

LHCb

C0(B0 → J/ψρ0)

S0(B0 → J/ψρ0)

ACP0 (B0

s → J/ψK∗0

)

H0(B0 → J/ψρ0)

H0(B0s → J/ψK

∗0)

a0 = 0.01+0.10−0.01

θ0 = −(83+97−263)

◦

39 % C.L.68 % C.L.90 % C.L.

−180 −150 −120 −90 −60 −30 0 30 60 90 120 150 180

θ‖ [deg]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

a‖

LHCb

C‖(B0 → J/ψρ0)

S‖(B0 → J/ψρ0)

ACP‖ (B0

s → J/ψK∗0

)

H‖(B0 → J/ψρ0)

H‖(B0s → J/ψK

∗0)

a‖ = 0.07+0.11−0.05

θ‖ = −(85+72−63)

◦

39 % C.L.68 % C.L.90 % C.L.

−180 −150 −120 −90 −60 −30 0 30 60 90 120 150 180

θ⊥ [deg]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

a⊥

LHCb

C⊥(B0 → J/ψρ0)

S⊥(B0 → J/ψρ0)

ACP⊥ (B0

s → J/ψK∗0

)

H⊥(B0 → J/ψρ0)

H⊥(B0s → J/ψK

∗0)

a⊥ = 0.04+0.12−0.04

θ⊥ = (38+142−218)

◦

39 % C.L.68 % C.L.90 % C.L.

[LHCb, PLB 742 (2015) 38-49] [LHCb, JHEP 11 (2015) 082]

δ0P = 0.000 +0.009

−0.011+0.004−0.009 rad

δ‖P = 0.001 +0.010

−0.014 ± 0.008 rad

δ⊥P = 0.003 +0.010−0.014 ± 0.008 rad

Penguin pollution in φccss is small and under control!


Observation of Bs0→ ψ(2S)K+π− decays (LHCb, PLB 747 (2015) 484)

Decay-time integrated flavor-averaged analysis,


This mode is a potential candidate for:Search for exotic states (tetraquark),Estimate penguin pollution in φs measured in ψ(2S) modes.

Measure the P-wave (K∗0) fraction and the K∗0 longitudinal fraction,

Measure the neutral B-meson mass difference,

Measure B(Bs0→ ψ(2S)K∗0) and B(Bs

0→ ψ(2S)K+π−).

]2c) [MeV/−π+(2S) Kψm(5200 5300 5400 5500

)2 cC

andi

date

s/ (

6 M

eV/

10

210

310

410 LHCb

Pul

l

-6-4-20246

B0 (∼ 24k) and B0s (∼ 0.3k)

Exclusive b→ ψ(2S)X

Combinatorial

]4c/2) [GeV−π+(K2m1 2

]4 c/2)

[GeV

− π(2

S)ψ(2

m

14

15

16

17

18

19

2021

22

2324

LHCb

∼ 15 MeV/c2 mass window around the B0s


Observation of Bs0→ ψ(2S)K+π− decays (LHCb, PLB 747 (2015) 484)

Unbinned maximum likelihood fit to m(ψ(2S)K+π−) and the helicity angles:

µθcos-1 -0.5 0 0.5 1

Can

dida

tes

/ ( 0

.20

)

0

10

20

30

40

50LHCb

-1 -0.5 0 0.5 1

Pull

-3-2-10123

[rad]φ-2 0 2

Can

dida

tes

/ ( 0

.63

rad

)

0

10

20

30

40

50

60LHCb

-2 0 2

Pull

-2-1012

Kθcos-1 -0.5 0 0.5 1

Can

dida

tes

/ ( 0

.13

)

0

10

20

30

40

50

60

70 LHCb

-1 -0.5 0 0.5 1

Pull

-3-2-10123

]2c) [GeV/−π+m(K1 1.5

)2 cC

andi

date

s / (

0.0

4 G

eV/

0

20

40

60

80

100

120

140

160

LHCb

1 1.5

Pull

-6-4-202

f0 = 0.524± 0.056± 0.029

f (K∗0) = 0.645± 0.049± 0.049

No significant structureseen in m(ψ(2S)K+π−)

K∗0 longitudinal fractionand B-meson massdifference compatiblewith previous results.

Systematics dominatedby the fit (amplitude)model.

CombinatorialS-waveP-wave (K∗0)

B(Bs0→ ψ(2S)K+

π−)/B(B0→ ψ(2S)K+

π−) = (5.38± 0.36± 0.22± 0.31 (fs/fd ))%

B(Bs0→ ψ(2S)K∗0)/B(B0→ ψ(2S)K∗0) = (5.58± 0.57± 0.40± 0.32 (fs/fd ))%

M(Bs0)−M(B0) = 87.45± 0.44± 0.09 MeV/c2


Summary and prospects

8 NEW HFAG spring ’16 combination (summer ’15 + latest ATLAS results):

0.4 0.2 0.0 0.2 0.4

0.06

0.08

0.10

0.12

0.14

ATLAS 19.2 fb 1

CMS19.7 fb 1

CDF 9.6 fb 1

DØ 8 fb 1

SM

68% CL contours( )

b

HFAGSpring 2016

LHCb3 f 1

Combined

φccss = −0.033± 0.033 rad

∆Γs = 0.083± 0.006 ps−1

Compatible with SM estimations:[arXiv:1511.09466] [CKMfitter, PRD 84 (2011) 033005]

φccss = −0.0376 +0.0008

−0.0007 rad

∆Γs = 0.088± 0.020 ps−1

Prospects:Add new modes to increase φccs

s statistics:B0

s→ ψ(2S)φ,B0

s→ J/ψ(→ e+e−)φ,B0

s→ J/ψK+K− and B0s→ J/ψπ+π− update.

Gluonic penguin pollution to φccss measured at LHCb:

Observation of the mode Bs0→ ψ(2S)K+π− which can contribute to these estimations,

Penguin pollution to φccss measured through B0→ J/ψρ0 and B0

s→ J/ψK∗0

modes:

Pollution found to be small and not greater than 21 mrad!


Summary and prospects

Future estimations (only σstat) for LHCb: [LHCb-PUB-2014-040]

Decay mode Run I (3 fb−1) Run II (8 fb−1) HL-LHC era (+Run IV) Theory[σstat(φs) (rad)] (2010-2012) (2015-2018) (+2028, +46 fb−1) limitB0

s→ J/ψK+K− 0.049 0.025 0.009 ∼ 0.003B0

s→ J/ψπ+π− 0.068 0.035 0.012 ∼ 0.01

Year2015 2020 2025 2030 2035

) sφ(st

atσ

0.01

0.02

0.03

0.04

0.05

0.06

0.07

KKψ J/→ s0LHCb B

ππψ J/→ s0LHCb B

KKψ J/→ s0) for B

sφ(statσSM


A final word about φs measurements...

Fall ’12: σtotal(φs)/φs was more than 600%...

Spring ’16: σtotal(φs)/φs = 100%


Thanks for your attention!

In loving memory of the 66 kV cable-chewing fouine


Backups


The CKM (Cabibbo·Kobayashi·Maskawa) matrix

The CKM (Cabibbo·Kobayashi·Maskawa) matrix, VCKM:

Contains information related to the coupling strength of weak interactions,

VCKM is a 3× 3 (SM) complex matrix which describes quark mixing,

Unitarity (V †V = I) is required (probability conservation in QM),

No relative quark phases + unitarity = three angles + one complex phase,

Wolfenstein parametrisation (A, ρ, η ∼ 1; λ ∼ O(10−1), iη = complex phase):

VCKM =

Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

=

1− λ2/2 λ Aλ3(ρ− iη)−λ 1− λ2/2 Aλ2

Aλ3(1− ρ− iη) −Aλ2 1

+O(λ4)

Pattern of coupling strengths in VCKM:

|VCKM| ∼

1 O(10−1) O(10−3)O(10−1) 1 O(10−2)O(10−3) O(10−2) 1


The CKM (Cabibbo·Kobayashi·Maskawa) matrix

Unitarity implies:three unity relations for diagonals,six orthogonal relations for off-diagonals.

Unitarity triangles (six orthogonality relations → six unitarity triangles)

For this talk: βs unitarity triangle (VusV∗ub + VcsV

∗cb + VtsV

∗tb = 0).


CP violation in B0s→ D+

s D−s decays (LHCb, PRL 113 (2014) 211801)


B0s→ D+

s D−s is CP-even: no angular analysis required!

Candidates reconstructed into four final states:

Combinations of D±s into Kππ, KKπ, πππ.

Tagging power: ε(1− 2ω)2 = 5.33± 0.18%,

Decay time resolution ∼ 54 fs.

]2c) [MeV/s− Ds

+M(D5300 5350 5400 5450

)2 cC

andi

date

s / (

5 M

eV/

0

200

400

600

800s−

Ds+ D→s

0B

−π+K−

K+s D→s

0B

s−*

Ds+ D→s

0B

−s D+ D→

0B

−s D+

cΛ →0bΛ

Combinatorial

LHCb

(a)

Nsignal ∼ 3.3k

]2c) [MeV/s+ D

−M(D

5250 5300 5350 5400 5450

)2 cC

andi

date

s / (

5 M

eV/

0

2000

4000

s+ D

− D→0B

s+ D

− D→s

0B

+π−K+K

− D→

0B

s+ D

* D→0B

Combinatorial

LHCb

(b)

Ncontrol ∼ 21k

Control for decay time calibration


CP violation in B0s→ D+

s D−s decays (LHCb, PRL 113 (2014) 211801)

Unbinned maximum likelihood fit to background-subtracted distribution of decay time:

Decay time [ps]5 10

Can

dida

tes

/ (0.

1 ps

)

1

10

210LHCb

φccss = 0.02± 0.17± 0.02 rad

|λ| = 0.91 +0.18−0.15 ± 0.02

Consistent with SM, no direct CP violation (|λ| = 1),

Decay time uncertainty calibrated from simulation,

Systematics dominated by the decay time resolution.


More HFAG spring ’16 plots


Polarisation-dependence in φccss ?

Results from B0s→ J/ψK+K− analysis are obtained under the assumption that φccs

s

and |λ| are independent of the final-state polarisation.

The condition can be relaxed to allow the measurement of these quantitiesseparately for each polarisation: [W. Wang et al, PRD 89 (2014) 094010], [LHCb, PRL 114

(2015) 041801].

There is no evidence for a polarisation-dependent CP violation in these decays.


Gluonic penguin pollution to φccss (see previous talk by Kristof)

How?Non-perturbative hadronic effects are difficult to calculate in perturbative QCD:[U. Nierste et al, PRL 115 (2015) 061802], [W. Wang et al, PRD 89 (2014) 094010];

Also, penguin-to-tree ratio is suppressed by ∼ 95% (|λ2|) in B0s→ J/ψφ decays...

Not a good start...The solution is an effective approach:

[R. Fleischer et al, PRD 79 (2009) 014005], [K. De Bruyn et al, JHEP 03 (2015) 145];

1 Construct two penguin parameters related to B0s→ J/ψφ penguin-to-tree ratio,

2 Measure certain observables in two control channels: B0s→ J/ψK

∗0and B0→ J/ψρ0,

3 Relate those with the penguin parameters by assuming SU(3) flavor symmetry,4 Obtain an estimation for δP for each polarisation state f from a combined fit.

Penguin-to-tree ratio is not suppressed in these control channels!


An effective approach (see previous talk by Kristof)

Using B0→ J/ψρ0 as a control channel:

Measure 2βJ/ψρ0and compute the difference with 2βJ/ψK0

S .

For the fit: Sf and Cf are used, along with a decay-specific hadronic observable Hf .

bW-

c}cd

}

B0J/ψ

(a)

}dd

π +

}

B0-

d

π

J/ψ(b)

b

t,c,u cc}

uu}

}d π +

-

d

πuu}

Tree-level diagram Penguin diagram

Using B0s→ J/ψK

∗0as a control channel:

Measure CP asymmetries and polarisation fractions, along with the branching fractionnormalised to B0

s→ J/ψφ.

For the fit: ACPf and ff are used, along with a decay-specific Hf constructed from thebranching fraction.

B0s

J/ψ

K∗0

W

b

s

s

c

c

d

(c)Tree-level diagram

B0s

J/ψ

K∗0W

b

s s

d

c

c

u, c, t

Colour singletexchange

(d) Penguin diagram


B0→ J/ψρ0 as a control channel (LHCb, PLB 742 (2015) 38-49)


Same analysis procedure as with B0s→ J/ψπ+π−,

B0→ J/ψ(→ µ−µ+)π+π− with resonant structure:

Six resonant states: [LHCb, PRD 90 (2014) 012003],B0→ J/ψρ0(770) has the largest fraction: ∼ 65%!

Tagging power: ε(1− 2ω)2 = 3.26± 0.17%,

Decay time resolution ∼ 40 fs. ) [GeV]-π+πm(0.5 1 1.5 2

Com

bina

tions

/ (18

.6 M

eV)

0

200

400

600

800

1000

1200

1400DataFitSignalBackground(770)ρ(500)0f(1270)2f(782)ω(1450)ρ(1700)ρ

LHCb

B0s to η′ , φ states + Λ0

b

B±→ J/ψh±

B0→ J/ψKπ

B0s→ J/ψπ+π−


B0 signal

Nsignal ∼ 18k

Unbinned maximum likelihood fit into a20 MeV/c2 window around the B0 peak:

αCP =1− |λ|1 + |λ|

= (−32± 28 +9−7)× 103

βJ/ψρ0 = (41.7± 9.6 +2.8

−6.3)o

∆2β = (0.9± 9.7 +2.8−6.3)o

Systematics dominated by the knowledge of the resonant model,Large uncertainty dependent on the SU(3) symmetry breaking estimation.


Implications of φccss in New Physics (NP)

[S. Stone (2013), arXiv:1212.6374]

Other sources with NP prospects: [J. Charles et al, PRD 89 (2014) 033016].


Penguin phenomenology (B0s→ J/ψφ) [R. Fleischer et al, PRD 79 (2009) 014005]

Decay amplitude taking into account both penguins and tree-level:

Af = Nf [1 + εaf eiθf e iγ ] (1)

A penguin to tree-level ratio can be extracted from (1):

af eiθf ≡ Rb

[A

(u)fP − A

(t)fP

A(c)fT + A

(c)fP − A

(t)fP

](2)

f ∈ {0,⊥, ‖}: given polarization of final state.

A(c)fT , A

(j)fP : tree amplitude and penguin amplitude respectively, where j ∈ {u, c, t}.

ε = λ2

(1−λ2)≈ λ2

(λ2 ≡ |Vus |2 ≈ 0.05)

B0s → J/ψφ (b → ccs) decay:

penguins are “suppressed to thetree-level” by a factor ε ≈ λ2![10.1103/PhysRevD.79.014005]


Penguin phenomenology (B0s→ J/ψK

∗0) [R. Fleischer et al, PRD 79 (2009) 014005]

B0s → J/ψφ (b → ccs) decay:

→ Penguins suppressed to the tree level by λ2 ∼ 0.222.

B0s → J/ψK

∗0(b → ccd) decay:

→ Penguins not suppressed to the tree level.

Phenomenology:

Penguin parameters:

B0s→ J/ψφ: θf , af .

B0s→ J/ψK

∗0: θ′f , a′f .

SU(3) flavour: θf =θ′f , af =a′f .

Shift on φs due to penguinpollution in B0

s→ J/ψφ:

tan ∆φfs =

2εaf cos θf sin γ+ε2af2 sin 2γ

1+2εaf cos θf cos γ+ε2af2 cos 2γ

tan ∆φfs is measured using

B0s→ J/ψK

∗0: penguin to tree

not suppressed!

Measurements:

We measure two observablesfor each final state polarizationf , Hf and ACP

f (next slide).

Hf and ACPf form a non trivial

system with two equations andtwo unknowns: θf , af .


Penguin phenomenology (B0s→ J/ψK

∗0) [R. Fleischer et al, PRD 79 (2009) 014005]

The observable Hf (as a function of the polarization fractions and the BR):

Hf =1− λ2

λ2

∣∣∣∣∣Af

A′f

∣∣∣∣∣2ff (B0

s→ J/ψK∗0

)B(B0s→ J/ψK

∗0)

ff (B0s→ J/ψφ)B(B0

s→ J/ψφ)=

1− 2af cos θf cos γ + af2 sin 2γ

1 + 2εaf cos θf cos γ + ε2af 2

Direct CP violation observable ACPf :

ACPf =

NBs0

f − NB0

sf

NBs0

f + NB0

sf

=2af sin θf sin γ

1− 2af cos θf cos γ + af 2

Solving this system for the three final polarization states (f = 0,⊥, ‖)allows us to obtain penguin parameters af and θf , and from them, obtain δfP.

At the end, we need to measureHf and ACP

f using the B0s→ J/ψK

∗0decay!


Penguin phenomenology (B0→ J/ψρ0) [R. Fleischer et al, PRD 79 (2009) 014005]

Penguin parameters already present in the measurement of 2βB0→J/ψρ0

!

CB0→J/ψρ0

f =2af sin θf sin γ

1− 2af cos θf cos γ + af 2

SB0→J/ψρ0

f = −ηf[ sin(φd)− 2af cos θf sin(φd + γ) + af

2 sin(φd + 2γ)

1− af cos θf cos γ + af 2

]where (inputed to the fit as Gaussian constraints):

γ = (73.2+ 6.3−7.0)o is the CKM angle: [CKMfitter, PRD 91 (2015) no. 7 073007],

φd = 0.767± 0.029 rad is 2βB0→J/ψK0S : [K. De Bruyn, CERN-THESIS-2015-126].


SU(3) symmetry breaking [LHCb, JHEP 11 (2015) 082]

Combined fit using B0→ J/ψρ0 and B0s→ J/ψK

∗0results:

[LHCb, JHEP 11 (2015) 082], [LHCb, PLB 742 (2015) 38-49]


Maximum Likelihood Fit [Y. Xie, arXiv:0905.0724]

B0s→ J/ψK+K− fit, [LHCb, PRL 114 (2015) 041801]:

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

)2C

andi

date

s / (

1.0

MeV

/c

210

310

410 LHCb

Fit to background-subtracted data (sFit) in bins of K+K− mass to account for S-wave.


B0s→ J/ψK+K− systematics [LHCb, PRL 114 (2015) 041801]


CP violating phase s and s measurements at LHCb...s = 0:010 0:039 rad j j= 0 :957 0 017 Consistent...

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Transcript of CP violating phase s and s measurements at LHCb...s = 0:010 0:039 rad j j= 0 :957 0 017 Consistent...