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LHCb performance for B s J/ and B d J/ K s decays Jeroen van Hunen. B s J/ and B d J/ K s. }. B d J/ K s B s J/ . CP eigenstate and a mixture of CP-odd and CP-even states. . }. no CPV in decay. If fcp 0. CP-symmetry. single weak phase. - PowerPoint PPT Presentation
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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
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