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Trees, penguins and boxes at LHCb
Prospects for CP violation measurements at LHCb

?
To: LHCb

Tristan du Pree (Nikhef) On behalf of the LHCb collaboration
14th Lomonosov conference 1 19-25 Aug 2009, Moscow


B-physics
Ç Study CKM-matrix

Rare B-decays at LHCb: See (previous) talk by N. Serra

Ç BR's and CPV
BR(B+ )

V CKM

V V |V | e ud us ub Vcd Vcs Vcb |V | e-i -|V | eis V td ts tb

-i



CPV at BaBar B0J/K
s

asymmetry

~sin 2
2

24 Aug 2009 14th Lomonosov Conf., Moscow

Tristan du Pree Nikhef

t (ps)


Example
Im

A

1

A

2

CP violation
Atot

A2
A1

e

i

2 amplitudes Ç Relative weak phase w
- Flips sign under CP

w

Ç Relative strong phase
- Does not flip sign under CP Re

e

i

CP
Im

Ç |Atot|2 = |A1+A2|2 Ç Need both nonzero and w for CP asymmetry:

| Atot |2 - | Atot |2 =
i

e

A1

A2

e

- i

-4| A1 || A2 |sin sin
w

w

Atot

Re

3


Current status CKM
Vud Vus |Vub | e-i Vcs Vcb Vcd |Vtd | e-i -|Vts | eis Vtb


VCKM



Status: Ç SM CKM mechanism explanation of CP violation
- - - - eff (penguins) |Vub|(B+) vs "K puzzle" s (related to s)

Ç Some interesting deviations

- No significant inconsistencies

Ç Unitarity: VCKM VCKM = 1 Ç 4 free parameters Ç Of which one complex phase Perform different measurements to overconstrain CKM matrix
24 Aug 2009 14th Lomonosov Conf., Moscow

Ç Big uncertainty in

Subject today

Stronger constraints needed!

- To overconstrain CKM matrix and discover New Physics

Tristan du Pree Nikhef

4


LHCb
Ç Forward arm spectrometer Ç ~20mx10mx10m Ç L = (2-5) x 1032 cm-2 s-1 Ç bb ~ 500 b (10% Bs) Ç `1 year' = 2.0 fb-1 Produce O(1011) Bs per year Expect to reconstruct: O(100k) BsJ/ per year

CP Ç Ç Ç Ç

violation research: with trees with loops s s with penguins
5


CP violation at LHCb
with time dependent osc Ç Bs DsK Ç B D* Ç Ç Ç with direct CPV B DK (glw) B DK (ads) More bodies s Ç Bs J/

Brown = box Green = tree Black = penguin

s with penguins Ç Bs

with loops Ç B hh
24 Aug 2009 14th Lomonosov Conf., Moscow

Advantages of LHCb Ç Number of Bs's Ç Proper time and mass resolution Ç Particle ID
Tristan du Pree Nikhef

6


The Bs mixing phase

s equivalent of in Bd system
0 s
ACP = N N
B f B f

s
-N +N
s B f B f

If s=0:

B

(in general s0)

= sin(-2

CKM

+ sNP ) sin mt s

+

e

i

CKM s

"s"

B

0 s

?
To: LHCb

B

0 s
7


Time dependent CPV
Ç Final state f is a ccss CP-eigenstate
__

DsK: LHCb: t ~ 40fs Time res. important

e

i

s

B

0 s

t

W

-

B f
0

B

0 s

f f
B
0 s
t

Vts

s
Amplitude: sin(s)

CP

W

+

B f
0

B
e

0 s
s

Vts*

s
8

- i


CP-even vs CP-odd
Ç Initial Bs: J=0 Ç Different final spin states Different angular momenta L in final states Different CP: factor (-1)L CP-even and CP-odd opposite proper time behaviour

L=1
B
s

J/

L=0,2
Blue: total Green: CP-even Red: CP-odd

If s=0:

(simplified expression, in general s0)

ACP ~ |Aeven|2sinssinmst -|Aodd|2sinssinmst
9


Angular analysis
Ç 4 particles: 3 decay angles Ç Angles of daughter particles in rest frame parents Ç Angular distribution: information about spin polarizations CP states different angular distributions Perform angular analysis to separate CP-even & CP-odd
Blue: total Green: CP-even Red: CP-odd

If s=0:

(simplified expression, in general s0)

ACP ~ |Aeven|2

sinssinmst

(1 + cos2)/2 (1 - cos2)
10

-|Aodd|2

sinssinmst


LHCb sensitivity: (s)
Ç Simultaneous likelihood analysis in mass, time, angles and tagging flavour Ç Using mass sideband to model background
Green = signal Red = background Blue = sum

Expectation from toy MC Ç 2.0 fb-1: (s) ~ 1.8Ê

24 Aug 2009 14th Lomonosov Conf., Moscow

Tristan du Pree Nikhef

11


Sensitivity: (s)
0.2 fb-1 (8 TeV): Ç
LHCb(s

)<

TeVatron

(s)

2.0 fb-1 (14 TeV): Ç If TeVatron = true: LHCb 5 discovery!

24 Aug 2009 14th Lomonosov Conf., Moscow

Tristan du Pree Nikhef

12


Bs
Ç Compare: phase(tree) & phase(penguin)

K
s

= 2

mix

+ 2

decay s

2 ( SM ) =
mix s

+ 2

decay s

0( SM )

Ç Bs angular analysis ð la BsJ/
(sin(Ks))=0.23 ()=4.6Ê
13


(1) BsDsK: time-dependent oscillation

with trees

e

i

s

B
e
i
s

0 s

e

i

B B
e

0 s 0 s
s

f
s

CP
e

i

- i

B

0 s

e

- i

f

Amplitude: sÁ(+s)
With 2.0fb-1:

(+s)=9Ê-12Ê 14


(2) Decay time independent CPV in BDK
Theoretically clean measurement of Vub

with trees

Ç ~VcbVus* Ç D0
- Relative strong phase - Relative weak phase

Ç ~VubVcs* Ç D0

Ç Sum of amplitudes leads to CPV

For interference: need a common final D0&D0 state
24 Aug 2009 14th Lomonosov Conf., Moscow Tristan du Pree Nikhef

15


(2) Decay time independent CPV
Ç GLW: Choose CP-even final state
- D0K+K-, D0 +- DCP is CP-even D0-D0 mixture

with trees

PID by RICH important

Without RICH

Ç Rates + Ç Rates (CP-conjugated) - The combination gives two solutions of Combination of

With RICH
16

all methods after 2.0 fb-1: () = 4-5Ê


with loops
Bhh
Interfere bu tree diagram with penguins: Vub*

Particle ID crucial Ç Mass resolution Ç RICH
(like previous page)

17


LHCb with 2 fb-1
with time dependent osc Ç Bs DsK Ç B D* (-s) = 9Ê-12Ê Ç Ç Ç with direct CPV B DK (glw) B DK (ads) More bodies s Ç Bs J/

Brown = box Green = tree Black = penguin

(s) = 1.8Ê

s with penguins Ç Bs (



) = 4 .6 Ê

() = 4-5À Advantages of LHCb Ç Number of Bs's Ç Proper time and mass resolution Ç Particle ID
18

with loops Ç B hh

() = 7À (s) = 2.8À-3.4À

24 Aug 2009 14th Lomonosov Conf., Moscow

Tristan du Pree Nikhef


Conclusions
Ç CKM model successful in describing CP violation
- ...but and s poorly constrained - ...and inconsistencies at the horizon?

Ç Many different methods to study diagrams
- Standard model diagrams (trees) - Possible new physics contributions (boxes, penguins)

Ç LHCb will drastically improve the sensitivity to the CKM angles and s
24 Aug 2009 14th Lomonosov Conf., Moscow Tristan du Pree Nikhef

19


Something new in the box of BsJ/?


BACK-UP


Unitarity Triangle
Ç Constraints following from unitarity of CKM matrix
- Three complex numbers add up to zero
VCKM VCKM = 1

VCK

M

Vud Vus Vub = Vcd Vcs Vcb V td Vts Vtb

Ç Performing different measurements, overconstrain 4 free parameters in CKM matrix
- To test consistency of CKM model - Inconsistency (e.g. triangle doesn't close) new physics

22


UT after 5 years of LHCb
in case of no new physics

23


Current status UT

experimental constraints on unitary CKM matrix
Ç CKM mechanism explanation of CPV
- No significant inconsistencies

Ç Some interesting deviations
- - - - eff (penguins) B vs "K puzzle" s

Subject today

Ç Biggest uncertainty in Stronger constraints needed!
- To constrain CKM & discover NP

24


Present status
__ __ 2(,) (s,s) -

s

UTs

p-value(SM): 3.4% (~2.1)

Left: Indirect (UTs)
s

Right: Direct (BsJ/ TeVatron) [15À-34À]U[56À-75À] @68%CL

1.03ÀÁ0.05À

2.0 fb-1 LHCB: (s) ~ 0.9À
25


LHC Ç 27 k m Ç Proton-proton Ç s = 14 TeV? Ç Re-start this fall

Ç Ç Ç Ç Ç

LHCb

L = (2-5)x1032cm-2s-1 bb~500b (10% Bs) `1 year' = 2.0fb-1 Produce O(1011) Bs per y. Expect to reconstruct: O(100k) BsJ/ per y.
26


Present status

s

p-value(SM): 3.4% (~2.1)

Indirect (CKM fit) s -2.1ÀÁ0.1À

Direct (BsJ/ TeVatron) [-30À,-68À]U[-112À,-150À] @68%CL

2.0 fb-1 LHCB: (s) ~ 1.8À
27