LHCb performance for

Bs J/ and Bd  J/ Ks 

decays

Jeroen van Hunen

July 11, 2003 Physics at LHC, Prague 2Jeroen van Hunen

1qp

1f

f

AA

fcp

cpffcp

fcp

fcpfcp A

Apq

AA

pq

Bs J/ and Bd  J/ Ks 

Bd  J/ Ks 

Bs J/

1fcp

CP violated

(interference mixing and decay)

} CP eigenstate and a mixture of CP-odd and CP-even states

If fcp 0

no CPV in decay

no CPV in mixing} fcpfcp single weak phase

CP-symmetry

July 11, 2003 Physics at LHC, Prague 3Jeroen van Hunen

CP - Asymmetry 

CP-eigenstate, |f| = 1 :

)2/sinh()2/cosh()sin(

ttmt

Afcp

fcpfcp

)2/sinh(2)2/cosh()1(

)sin(2)cos()1()()()()(

2

2

tt

mtmttRtRtRtR

Aff

ff

ff

fff

= 0 (for B0d) :

)sin( mtA fcpfcp

July 11, 2003 Physics at LHC, Prague 4Jeroen van Hunen

cscb

cscb

tstb

tstbJJ VV

VVVVVV

*

*

*

*

*

*

*

*

*

*

cscd

cscd

cscb

cscb

tdtb

tdtbKJKJ VV

VVVVVV

VVVV

ss

J/ = sin 2s

J/Ks = sin 2

dBpq

Kpq

sBpq

Bs J/ and Bd  J/ Ks 

July 11, 2003 Physics at LHC, Prague 5Jeroen van Hunen

J/ +- selection

• Two opposite charged muons with :

• Pt > 0.5 GeV

•Vertex with a 2 < 9

• Invariant mass within 50 MeV/c2 of mJ/

= 10 MeV

+- mass (GeV)

July 11, 2003 Physics at LHC, Prague 6Jeroen van Hunen

• Two opposite charged electrons one with Pt > 0.8 GeV/c and one with Pt > 1.8 GeV/c

• A vertex 2 < 6

• vertex |Z| < 150 mm

• An invariant mass between 2.7 – 3.2 GeV/c2

J/ e+e-selection

= 66 MeV

e+e- mass (GeV)

July 11, 2003 Physics at LHC, Prague 7Jeroen van Hunen

K+K- selection

• Two opposite charged kaons with Pt > 0.5 GeV, giving a vertex with a 2 < 9, an invariant mass within 20 MeV/c2 of m, and P > 12 GeV/c2

• Combine the J/ and if the four tracks form a vertex with 2 < 20, then select the primary vertex with smallest IP (< 4mm)

Bs J/ selection

July 11, 2003 Physics at LHC, Prague 8Jeroen van Hunen

Bs J/ selection

Other constraints on the Bs0 :

• Proper time (consistency between the Bs0 momentum and the vector

between the production and decay vertex) significance > 5

• mBs within 50 MeV/c2 of the nominal Bs

0 mass

+-K+K- Mass +-K+K- Mass residual =15MeV = 38 fsbb-incl.

July 11, 2003 Physics at LHC, Prague 9Jeroen van Hunen

Ks +- selection

category fraction vertex Z res.LL 0.29 107 mLV 0.09 182 mTT 0.62 199 m

• Two oppositely charged pions, giving a vertex with a z position between 0 - 3 meter, invariant mass within 60 (100 for TT) MeV/c2 of mKs

, and a combined Pt >200 MeV/c.

July 11, 2003 Physics at LHC, Prague 10Jeroen van Hunen

Bd J/ (+-)Ks selection

• J/ and Ks make a vertex with 2 < 50

• IP significance of Ks with respect to J/ vtx < 3.5 (< 8 for TT)

• IP significance of Ks pions with respect to the primary vtx > 4 (2 for TT)

• significance of the distance between primary and J/ vtx > 1.2(LL), 3.1(LV), 2.4(TT)

• Bd mass window 60 MeV/c2

Bd : combining J/ and Ks

July 11, 2003 Physics at LHC, Prague 11Jeroen van Hunen

Bd J/ Ks selection

Results for the Bd0 mass :

LL TT=9 MeV

J/ (+-) Ks (LL)

=12 MeV

J/ (+-) Ks (TT) J/ (e+e-) Ks (LL)

=14 MeVLL

July 11, 2003 Physics at LHC, Prague 12Jeroen van Hunen

Annual yield and Background estimatefor Bs J/ and Bd J/ Ks

Channel Annual yield B/SBs J/ (+-) 100k <0.3 (bb-incl)

<0.7 (prompt J/ )Bs J/ (+-) Ks 166k 0.60.1 (bb-incl)

<0.4 (prompt J/ ) Bs J/ (e+e-) Ks 21k <0.84 (prompt J/ )

3.4 0.5 (bb-incl)

July 11, 2003 Physics at LHC, Prague 13Jeroen van Hunen

Sensitivity studies for Bs J/ and Bd J/ Ks

July 11, 2003 Physics at LHC, Prague 14Jeroen van Hunen

2s 0.03 in SM :

A(t) two exponentials with

lifetimes 1/H and 1/L

Extracting s from Bs J/

)(sin43)()(cos1

83)()(

)cos()( 2222

||2

0

tAtAtAd

td

Bs J/

Bs J/

sstt tmeeAtA L 2)sin()0()(

2

||,0

2

||,0

sstt tmeeAtA H 2)sin()0()( 22

sstt tmeeAtA L 2)sin()0()(

2

||,0

2

||,0

sstt tmeeAtA H 2)sin()0()( 22

A = odd & A0,|| = even

July 11, 2003 Physics at LHC, Prague 15Jeroen van Hunen

Extracting s from Bs J/

Extreme

CP-Parameters:

s=150

s/s = 0.5

untagged

Bs tagged

Bs tagged

0 1 2 3 4 (ps)

July 11, 2003 Physics at LHC, Prague 16Jeroen van Hunen

Angular analysis to determine the sensitivity for:

R(A fraction), s , s and s

(for ms and wrong tag fraction: fit Ds simultaneously)

One year of LHCb data

s

(Deg)R-

s

(ps)s/ s

-ms

(ps-1)used 0.860 0.2 1.5 0.1 20

sensitivity 3.50 0.0085 0.011 0.026 0.038

R = |A|2/(|A0|2 +|A|||2 +|A|2 )

= 35% & = 40%

Sensitivity for s from Bs J/

July 11, 2003 Physics at LHC, Prague 17Jeroen van Hunen

Sensitivity for from Bs J/ Ks

2

2

1

)sin()2sin(2)cos()1(

f

ff

mtmtA

one year LHCb data||

used 1 26.10

sensitivity 0.024 0.60

= 35% = 35%

Proper time

July 11, 2003 Physics at LHC, Prague 18Jeroen van Hunen

Conclusions

Sensitivity for and s

One Year of LHCb Data s

0.60 3.50

Reconstruction of Bs J/ and Bd  J/ Ks  decays :

• Good mass (9-15 MeV/c2) & vertex (107-199 m) resolution

Excellent proper time resolution (38 fs) allows to follow the oscillations of the decay rates accurately.

• High annual yields with low background rates

Precise determination of CKM angles and s