LHCb performance for B s  J/   and B d  J/  K s decays Jeroen van Hunen

July 11, 2003Physics at LHC, Prague 2 B s  J/   and B d  J/  K s B d  J/  K s B s  J/    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 } single weak phase CP-symmetry

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 3 CP - Asymmetry CP-eigenstate, | f | = 1 :  = 0 (for B 0 d ) :

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 4   J/  = sin 2  s   J/  K s = sin 2  B s  J/   and B d  J/  K s

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 5 J/    +  - selection Two opposite charged muons with : P t > 0.5 GeV Vertex with a  2 < 9 Invariant mass within 50 MeV/c 2 of m J/   = 10 MeV  +  - mass (GeV)

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 6 Two opposite charged electrons one with P t > 0.8 GeV/c and one with P t > 1.8 GeV/c A vertex  2 < 6 vertex |Z| < 150 mm An invariant mass between 2.7 – 3.2 GeV/c 2 J/   e + e - selection  = 66 MeV e + e - mass (GeV)

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 7   K + K - selection Two opposite charged kaons with P t > 0.5 GeV, giving a vertex with a  2 12 GeV/c 2 Combine the J/  and  if the four tracks form a vertex with  2 < 20, then select the primary vertex with smallest IP (< 4mm) B s  J/   selection

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 8 B s  J/   selection Other constraints on the B s 0 : Proper time (consistency between the B s 0 momentum and the vector between the production and decay vertex) significance > 5 m B s within 50 MeV/c 2 of the nominal B s 0 mass  +  - K + K - Mass  +  - K + K - Mass  residual  =15MeV  = 38 fs bb-incl.

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 9 K s   +  - selection categoryfractionvertex Z res. LL  m LV  m TT  m Two oppositely charged pions, giving a vertex with a z position between meter, invariant mass within 60 (100 for TT) MeV/c 2 of m K s, and a combined P t >200 MeV/c.

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 10 B d  J/  (  +  - )K s selection J/  and K s make a vertex with  2 < 50 IP significance of K s 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) B d mass window 60 MeV/c 2 B d : combining J/  and K s

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 11 B d  J/  K s selection Results for the B d 0 mass : LL TT  =9 MeV J/  (  +  - ) K s (LL)  =12 MeV J/  (  +  - ) K s (TT) J/  (e + e - ) K s (LL)  =14 MeV LL

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 12 Annual yield and Background estimate for B s  J/   and B d  J/  K s Channel Annual yieldB/S B s  J/  (  +  - )  100k <0.3 (bb-incl) <0.7 (prompt J/  ) B s  J/  (  +  - ) K s 166k 0.6  0.1 (bb-incl) <0.4 (prompt J/  ) B s  J/  (e + e - ) K s 21k <0.84 (prompt J/  ) 3.4  0.5 (bb-incl)

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 13 Sensitivity studies for B s  J/   and B d  J/  K s

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 14 2  s  0.03 in SM : A(t)  two exponentials with lifetimes 1/  H and 1/  L Extracting  s from B s  J/   B s  J/    B s  J/   A  = odd & A 0,|| = even

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 15 Extracting  s from B s  J/   Extreme CP-Parameters:  s =15 0  s /  s = 0.5 untagged B s tagged  B s tagged  (ps)

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 16 Angular analysis to determine the sensitivity for: R(A  fraction),  s,  s and  s (for  ms and wrong tag fraction: fit D s  simultaneously) One year of LHCb data  s (Deg) R-R-  s (ps)  s /  s -  m s (ps -1 ) used sensitivity R = |A  | 2 /(|A 0 | 2 +|A || | 2 +|A  | 2 )  = 35% &  = 40% Sensitivity for  s from B s  J/  

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 17 Sensitivity for  from B s  J/  K s one year LHCb data |  used sensitivity  = 35%  = 35% Proper time

Jeroen van Hunen July 11, 2003Physics at LHC, Prague 18 Conclusions Sensitivity for  and  s One Year of LHCb Data ss Reconstruction of B s  J/   and B d  J/  K s decays : Good mass (9-15 MeV/c 2 ) & vertex (  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