A. Bay LPHE EPF Lausanne1 Summary B factories and LHCb

A. Bay LPHE EPF Lausanne 1

Summary

B factories and LHCb

CP & T violation only in K0 system ???

Since 1964, CP and or T violation was searched for in othersystems than K0, other particles decays, EDM...

No other signal until 2001...

production of(4s) (10.58GeV/c2) = 0.425(4s) B0 B0

BaBar (SLAC) and Belle (KEK)

in 2001: observation of CP violation in the B mesonsystem, using "asymmetric collider" B factories.KEKB machine:

8 GeVelectrons

3.5GeV positron

KEKB24% Y(4s)76% continuum

year 2003: crossing the(psychological) luminositybarrier of 1034 cm-2s-1

1.5807 1034

on 18-May-2005

Luminosity trend in the last

30 years

BaBar and Belle

Study of the time dependent asymmetry in decay rates ofB0 and anti-B0

m = mass difference of "mass eigenstates" ~ 0.49 1012 h/s

ACP(t) =N(B 0 → J /Ψ KS) − N(B0 → J /Ψ KS)

+(t) = S sin Δm t( )

CP violated S ≠ 0

CP measurements at B factories

Difficult: B0 mean life 1.54 10 s. Lorentz boost very small.B factories are asymmetric: the c.m. is moving.The two B decay at different position ~ on the z axis.We measure de difference z of the 2 vertices. r is small.

Δz cβγΔt ~ 200 m at Belle

zz1 z2

CP measurements at B factories

zz1 z2

B0 and anti-B0 oscillate coherently (QM entangled state).When the first decays, the other is known to be of the oppositeflavour use the other side to infer the flavour, B0 or anti-B0,of the fCP parent

e+ → B0

e− → B 0 ⎧ ⎨ ⎩

region of B0 & B0

coherentevolution

Belle experiment

Central Drift Chamber He/C2H5(Pt/Pt)2=(0.0019 Pt)2+(0.0030)2

CsI(Tl) 16X0

E/E ~ 1.8% @1GeV

Aerogel Cherenkov n=1.015~1.030

Si Vertex detector3 layers mid 2003now 4 layers Impact parameter resolution 55m for p=1GeV/c

TOF counter

SC solenoid 1.5T

8GeV e

3.5GeV e

Started in 1999~300 physicists from ~60 institutes in14 countries.

/ KL detection 14/15 layers of RPC+Fe : efficiency > 90%<2% fake at p > 1GeV/c

Particle ID : dE/dx in CDC dE/dx =6.9% TOF TOF = 95ps Aerogel Cerenkov ACC Efficiency = ~90%, Fake rate = ~6% 3.5GeV/c

Silicon Vertex Detector SVD Impact parameter resolution 55m for p=1GeV/c at normal incidenceCentral Drift Chamber CDC (Pt/Pt)2 = (0.0019 Pt)2 + (0.0030)2 K/ separation : dE/dx in CDC dE/dx =6.9% TOF TOF = 95ps Aerogel Cerenkov ACC Efficiency = ~90%, Fake rate = ~6% 3.5GeV/c, e : CsI crystals ECL E/E ~ 1.8% @ E=1GeV e : efficiency > 90% ~0.3% fake for p > 1GeV/cKL and : KLM (RPC) : efficiency > 90% <2% fake at p > 1GeV/c

Ldt ≈∫ 400 fb

4 108 B pairs

spatial resolution for Blepton + Xz (lepton) ~ 100 m

Belle micro-vertex detector

Belle event

Particle ID in Belle

Particle ID uses information fromACC, TOF, dE/dx( CDC)

Prob to be a K{ } =L(K)

L(π) + L(K)

Barrel ACC

Endcap ACC

p (GeV/c)

Experimental program: measure sides and anglesof the CKM matrix

* CP violated in the SM => the area of triangle 0* Any inconsistency could be a signal of the existence of phenomena not included in the SM

~Vub ~Vtd

Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

⎜ ⎜ ⎜

⎟ ⎟ ⎟

Use B mesonsphenomenology

t quark

oscillations

CP asymmetries

b quark

decays

Analysis and results

•Continuum rejection•Kinematics at the Y(4s)

•The Unitary triangle: determination of Vub

" Vcb" Vtd" " "

•No time for other topics

~Vub ~Vtd

Continuum rejection24% Y(4s)76% continuumfrom event topology which

is ~spherical for BB, jet like for continuumand angular distributions

Build Likelihood L for B and qq hypothesisusing event shape variables and cos B

0 0.2 0.4 0.6 0.8 1

LB + L qq

How to find a B meson?Kinematics variables at the Y(4S)

5.2 5.24 5.28 GeV/c2

GeV/c2

Mbc = (E beam* )2 −

E = EB* − E beam

Gather candidates Band calculate (pB,EB).Boost to c.m. (pB

*,EB*)

"beam constrained mass"

Ebeam* ≡

Example:B D0

Determination of Vcb

World Average: |Vcb| (inclusive) (42.0 0.6 0.8) 10-3

|Vcb| (exclusive) (40.2 +2.1 ) 10-3

Vcb = (40.2 ±1.9)10−3

48π 3MD*

3 MB 0 − MD*( )

2g(y)Vcb

2F(y)2

g(y) known function of y

B 0 → D*+e−ν e

F(y) hadronic form factor

plus ~5% error on F(1)

Determination of Vub

0 1 2 3 GeV/cLepton momentum

(in c.m.)

Exemple: use lepton momentum distributionfrom inclusive semileptonic decays

B → Xul ν

Less than 10% of thespectrum background free

hep-ex/0305037, with reconstruction

|Vub| (10-3) = 3.96 0.17(stat) 0.44(syst) 0.29(theo) 0.34(bc) 0.26(bu)

Average(inclusive) Vub=(4.12±0.13±0.60)10-3

Determination of Vtd

0 3 6 9 ps

Probability1

Starting from a pure sampleof B0, for instance,a B0 component builds upin a time scale of a few ps:

P(B0)∝ e−t /τ 1+ cos Δmd t( )[ ]

P(B 0)∝ e−t /τ 1− cos Δmd t( )[ ]

measure oscillation frequency

Vtd ∝ Δmd

region of B0 & B0

coherentevolution

md with di-lepton events

* KEK-B boost <Δz> cβγ ~ 200 m

zz1 z2

* Tag B flavour from semileptonic B0 X l B0 X l

* B0 and B0 oscillate coherently (QM entangled state).When the first decays, the other is known to be of the oppositeflavour.

t ~ z/c

md from di-lepton events .2

-12 -8 -4 0 GeV2

NMissing mass

Background: B+ X l B X l

Selection strategy of the "soft pion tag"B0 D* l Br3%

D0 Br70%

Event selection:- 1st lepton P*> 1.8 GeV- 1 pion of opposite sign P* < 1 GeV- 2nd lepton P*> 1.3 GeV- cut on M

(Frederic Ronga, PhD thesis, 2003)

md from di-lepton events .3

Get z distributionsfor "Same Sign"and "Opposite Sign"leptons couplesand fit for md...

J/ l+ l toinfer resolution

-2 -1 0 1 2 z (mm)

0 1 2 z (mm)

Asymmetry(t) =OS −SS

OS + SS(t)

F. Ronga

average

md and Vtd HEP-PH/0206171

Vtd ∝ Δmd fB BB

Bagparameter

B decayconstant

|Vtd | ~ (8±2)10-3

~20% error !

UT sides

The UnitaryTriangle

inferred from its sides

and fromK0 data

Vub/Vcb

From K0

md & ms

Excluded area has <0.05 CL

from B0 J/ Ks

VtdVtb

Interference between the 2 amplitudes gives a "time-dependent CPV"

AsymCP (t) =N(B 0 → J /Ψ KS ) − N(B0 → J /Ψ KS )

N(B 0 → J /Ψ KS ) + N(B0 → J /Ψ KS )(t)∝ SCP sin Δmd t( )

CKM phase 0 !

CKM phase = 0

Golden ChannelGolden Channel

Any "direct" CP violation ?

No "direct CPV" expected in SM in B J/ Ks, but who knows ?...

CKM phase = 0

AsymCP (t) =N (B

0→ J / Ψ KS ) − N (B

0→ J / Ψ KS )

+(t)∝ ACP cos Δmd t( ) + SCP sin Δmd t( )

Time dependent asymmetry measurement

zz1 z2

e+ → B0

e− → B 0 ⎧ ⎨ ⎩

region of B0 & B0

coherentevolution

ACP (t) =N (B

0→ J / Ψ KS ) − N (B

0→ J / Ψ KS )

N (B 0

→ J / Ψ KS ) + N (B0

→ J / Ψ KS

Need to "tag" the flavour: B0 or B0.B0 and B0 oscillate coherently (QM entangled state) use the other side to infer the flavour

t ~ z/c

b ccs reconstruction

140 fb1, 152M BB pairs

B 0 J/KL

b ccs (J/KL excluded)

5417 events are used in the fit.pB GeV/c

A large CP asymmetry has been observed!

World average (October 2005): SCP = 0.726 ± 0.037

ACP~ 0, compatible with no direct CPV

SM: SCP = sin(2) => or 66.3°)

J/KL is OK

AsymCP (t) =N (B

0→ J / Ψ KS ) − N (B

0→ J / Ψ KS )

+(t)∝ ACP cos Δmd t( ) + SCP sin Δmd t( )

SM & KM model is verified !

= 23.7°± 2.1° = 66.3°± 2.1°

UT with sin2

The UnitaryTriangle

fit including sides,

K0 data,and

b sss, a B0 Ks puzzle ?

b to s transition is second order

(gluonic penguin).Prediction from SM: ~

same value of sin(2) as in ccs because no additional

phase from the loop.

??????

squark

unless new physics entersthe loop. For instance:

B0 Ks .2

6811 signals106 candidates in the fitpurity = 0.640.10efficiency = 27.3%

B 0 KS

5.2 5.4 5.28 GeV/c2

SφKs = −0.96 ± 0.50−0.11+0.09

AφKs = −0.15 ± 0.29 ± 0.07

SφKs = +0.45 ± 0.43± 0.07

Beam-Energy Constrained Masssin2(ccs)

from BD0K D0 Ks +-

See A.Giri, Yu.Grossman, A.Soffer, J.Zupan hep-ph/0303187

A1 ~ VcbVus* ~ Aλ3

A2 ~ VubVcs* ~ Aλ3 ρ + iη( ) ~ exp iγ{ }

D0 and D0 decay to same final state mixed state is produced:

˜ D 0 = D 0 + ae iθ D0

˜ D 0 = D 0 + ae i(δ +γ ) D0

Dalitz's analysis with variables and

m2(Ks,π +)

m2(Ks,π −)

a, , unknown

from BD0K D0 Ks +- .2

0.5 1 1.5 2 2.5 3

m2(Ks,π +)

m2(Ks,π −)D0 Ks +- as a sum of 2 body decays

Fit Dalitz plot witha, , as free parameters

a = 0.33±0.10±0.03±0.03 = 162° +20

-25 ±12°±24° = 95° +25

-20 ±13°±10°

90%CL: 61°< < 142° preliminary

Belle:very, verypreliminary

from B0

Asym t( ) = Aππ cos Δmd t( ) + Sππ sin Δmd t( )

A = 0S = sin(2+2)= sin(2)

without penguin contributions:

Isospin analysis needed for the extraction of .Need to measure also B0 B+

This is not the case: large"penguin pollution" expected(but intrinsically interesting..!)

Consider B0 first:

Phys Rev

from ~231 : A = +0.58 0.15 0.07 S = 1.00 ± 0.21 ± 0.07

charmless 3-body B decay

continuum

syst. primarily frombackground fraction

BABAR:

A = 0.30 ± 0.25 ± 0.04

S = .02 ± 0.34 ± 0.05

hep-ex/0401029

BaBardirectCVP

First signal from B0

Mbc [GeV/c2]

using 152 M BB: Br(B0 ) = (1.7 ± 0.6 ± 0.2)10-6

continuum

BABAR: Br(B0 ) = (2.1 ± 0.6 ± 0.3)10-6

Phys. Rev. Lett. 91 (2003) 261801

(hep-ph/0306058 gives 74° < < 132°... )

Global fit of data from all sources

Test of SM in quark sector:check the triangle !

Does SM give a coherent picture of CP violation ?

Unitary triangle can be build using its sides

or the angles.

Other information comes form CPV with Kaons and B.

All the information must be consistent (else new physics ? or measurement error ? or bad supporting theory ?)

Test of SM in quark sector

Summer 2004

sin(2) = 0.726 ± 0.037 from J/K0

sin(2) = 0.734 ± 0.043 from sides

(68% and 95% CL contours)

from sides

Summer 2005

sin(2) = 0.687 ± 0.032 from J/K0

sin(2) = 0.793 ± 0.033 from sides 2.3

2005 test not sogood...

Compare unitarity triangle from CP-violating processes K CPV in K sector and sin(2) CPV in B sector

with unitarity triangle measured from the sides only i.e.from

CP-conserving processes

(|Vub| and md, ms)

Test of SM in quark sector .2

Measure unitarity triangle only from the angles in B decays: sin(2) from B0 (cc)K0 interference of bc amplitude with B0_B0 mixing (or +) from B , , interference of bu amplitude with B0 _B0 mixing from B D(*)K interference of bc and bu amplitudes

Test passed.

Compare again with trianglefrom (CP conserving) side measurements

sin(2) from bs penguin

Naive average of all bs modesdeviated from B(cc)K0 modesby 3.8 in 2003, now only 2.6

sin(2)eff=0.43±0.07to be comparedwith all charmoniumresult 0.726±0.036

A. Bay LPHE EPF Lausanne1 Summary B factories and LHCb

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