Ulrich Uwer

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• Ulrich Uwer
• University of Heidelberg
• On behalf of the LHCb collaboration

Beauty 2003, Carnegie Mellon University,
Pittsburgh, PA, USA
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Physics Goals
At 2x1032 cm-2s-1 ?1012 bb pairs produced / yr
2? B0 ?J/?(??)K
2? ? B0 ?D_ ?
? B0 ?D0 K0
? and ? B0 ? ? ?? Bs ? K K?
? ? ?? Bs? DS K
?? Bs? J/?(??)?
?????? B0? ? ?? , ??

• CPV measurements in many decay channels

• pure hadronic and multi-body final states.
• new decay channels in particular Bs decays

• precise determination of CKM elements
  measurement of b?uW (tree) phase
• overconstraining the Unitarity Triangles
  disentangle the tree phases from phases of
  oscillations (loops) and penguins

• Study rare and loop-suppressed decays

Search and filter-out effects of New Physics
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Example New Physics in B mixing
B(s)B(s) mixing phase
Fd 2? FdNP Fs 2? FsNP
Observation of new phase

• CPV in B0 ? J/? Ks sin(2?FdNP)
• B0 ? D? sin(2?FdNP?)
• Bs? J/?? sin(2? FsNP)
• Bs? DsK sin(2? FsNP?)
• Rate of B0? D0 K0, D0K0, D0CP K0
  ?

Redundant measurements necessary to disentangle
CKM phases from New Physics
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Discovery Potential
In 1 year e.g. ?(B?? D?K?) ? 70
sin?d(B0?J/?Ks) ? 0.022

• 2007 ?BABARBELLE ?

?
reference channel
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Monte Carlo Simulation

• Full Geant 3.2 simulation
• PYTHIA 6.2 tuned on SPS(UA5) and Tevatron (CDF)
  data
• Multiple pp interactions and spill-over effects
  included
• Size of beam spot (?z5cm)
• Complete description of material from TDRs
• Individual detector responses tuned on test beam
  results
• Trigger simulation and full reconstruction
• Full simulation of L0 and L1 triggers
  cuts tuned for max. efficiency at limited output
  rate (1 MHz L0, 40 KHz L1)
• Full reconstruction including pattern recognition
• Simulated samples
• Signal samples
• Background samples 10 M incl. bb events ? 4
  min 30 M min. bias events ? 2 sec

T1 T2 T3
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Detector Performance
Bs?Ds??(K)
?core5.1 MeV
Ds mass (GeV)
Proper time resolution (fs)
Ds vtx z resolution (mm)
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Bs?Ds? / Bs?DsK Separation

• Bs ? Ds??? is a physics background for Bs ? Ds??
  K??
• BR(Bs ? Ds???) / BR(Bs ? Ds??K??) 12
• ?(Bs ? Ds??? ) / ?(Bs ? Ds??K??) 1 after PID
  and mass cuts

Bs?DsK
Bs?Ds?
Bs?DsK
Bs?Ds?
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Event Yield (untagged)
1 year (107s) at L 2x1032 cm-2 s-1
Channel Trig (L0L1) e tot Yield B/S
B0 ? pp- 34 0.69 26 k lt 0.7
B0 ? K p- 33 0.94 135 k 0.16
Bs? K-? 37 0.55 5.3 k lt 1.3
Bs ? K K- 31 0.99 37 k 0.3
Bs ?Ds-p 31 0.34 80 k 0.3
Bs ?Ds-K- 30 0.27 5.4 k lt 1.0
B0 ?J/y(m-m) KS 61 1.39 216 k 0.8
B0 ?J/y(e-e ) KS 27 0.16 26 k 1.0
Bs ?J/y (m-m )f 64 1.67 100 k lt 0.3
Bs ?J/y (e-e )f 28 0.32 20 k 0.7
B0 ??? 36 0.03 4.4 k lt 7
B0 ?K0 g 38 0.16 35 k lt 0.7
Bs ??? 34 0.22 9.3 k lt 2.4
norm. to 4? ?
?tot edet erec/det esel/rec eTri g
0.12?0.92?0.18?0.34
( for B0 ? pp- )
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Flavour Tagging
Tagging tracks large impact par.
Kaon tag
Tag ?Tag () w () ?eff ()
Muon 11 35 1.0
Electron 5 36 0.4
Kaon 17 31 2.4
Vertex Charge 24 40 1.0
Frag. kaon (Bs) 18 33 2.1
Combined B0 (decay dependent Combined Bs trigger select.) Combined B0 (decay dependent Combined Bs trigger select.) Combined B0 (decay dependent Combined Bs trigger select.) 4
Combined B0 (decay dependent Combined Bs trigger select.) Combined B0 (decay dependent Combined Bs trigger select.) Combined B0 (decay dependent Combined Bs trigger select.) 6

• Lepton
• Kaon other B
• Vertex charge
• Fragmentation kaon near Bs

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Physics Sensitivity
Reference measurements sin(2?) from
B0?J/?Ks ?ms from Bs?Ds? CPV
measurements sin(2?) and ??s from Bs?J/??
Bs?DsK ? from B0??? and Bs?KK
B0?D0K0 Radiative decays b?s? penguins
CP reach evaluation
all numbers for 1 yr

• Generate many fast MC samples
• Signal efficiencies (including tagging) as well
  as background levels and shapes taken from full
  simulation studies
• extract physics parameter from each sample
• for CP asymmetries, fit together a second fast MC
  sample of flavour-specific decays to extract the
  mistag from the data

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sin?d in B?J/?Ks
Annual B0?J/?(??)Ks yield 216k Background
B/S 0.8 Tagging probability 45 Mistag
probability w 37 MC simulation of many
experiments ?(sin(?d)) 0.022
(measurement of mistag rate w through
simulated B0?J/?(??)K evts)
sinFd sin(2?)
Adir ? 0 ? New Physics beyond SM
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?ms with Bs?Ds(KK?)?-
Annual event yield 80k Background B/S
0.32 Tagging probability 55 Mistag
probability w 33 Proper time res.
33 fs (core)
Statistical precision / yr
?ms (ps-1) 15 20 25 30
?(?ms) 0.009 0.011 0.013 0.016
5? observation of Bs oscillation 68 ps-1 / yr
error ?A of oscillation amplitude
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Fs and ?Gs with Bs?J/?F
The gold plated decay of Bs SU(3) analogue of
Bd ?J/?Ks ACP in SM ?
Fs -2? -2?2? -0.04
Problem PS ? VV 3 contributing
amplitudes 2 CP even, 1 CP odd ? fit
angular distribution of decay states
(transversity angle ?tr) as function of proper
time.
event yield (??) / yr 100k background B/S
lt0.3 tagging efficiency
50 Mis-tag rate 33 proper
time resolution 38 fs
?(?) 2 O
If ?G/G is 0.1, can do a 5? discovery in one year
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? from Bs?Ds?K?
Time dependent Bs?Bs asymmetries

• Interference between 2 tree diagrams due to Bs
  mixing
• Measure ? ? ?s from time-dependent rates
  Bs?Ds? K? and Bs?Ds?K? (
  CP-conjugates)
• Use ?s from Bs?J/??

5 yrs of data, ?ms20 ps-1
event yield (??) / yr 5.4k background B/S
lt1.0 tagging efficiency
54 Mistag rate w 33 (extract
from Bs?Ds?)
After 1 year, if ??s/?s 0.1, 55 lt ? lt
105O ?20 lt ?T1/T2 lt 20O
?ms 20 25 30
?(?Fs) 14 0 16 0 18 0
No theoretical uncertainty insensitive to new
physics in B mixing
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? from B?????? and Bs?K?K?
In both decays large b ?d(s) penguin
contributions to b ?u
Measurement of time-dependent CP asymmetry for
both decays ? Adir and Amix w/ strong phase
contribution of unknown magnitude
Adir (B0? ??-) f1(d, ?, ?) Amix(B0?
??-) f2(d, ?, ?, ?d) Adir (Bs?KK? )
f3(d, ?, ?) Amix(Bs?KK? ) f4(d, ?, ?,
?s) U-spin symmetryd d and ? ?

• Method proposed by R. Fleischer
• use B?????? and Bs?K?K? together
• exploit U-spin flavour symmetry for P/T ratio
  described by d and ?

4 measurements (CP asymmetries) and 3 unknown
(?, d and ?) ? can solve for ?
Fs (Bs?J/??) Fd (B0?J/?Ks)
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? from B?????? and Bs?K?K?
Adir?? , Amix?? , AdirKK , AmixKK and w
(mistag), A?K ,,, A?K,,, ?G, ?m, G, m and ?
resolutions (17 par.) from fit to B??????
(26k / yr) Bs?K?K? (37k / yr)
B??K?? (135k / yr) Bs?K?? (5.3k / yr)
? p.d.f. F(d, ?, ?)
fake solution
68 and 95 CL regions(for ?input 65 deg)
B?????? (95CL)
If ?ms 20 ps?1, ??s/?s0.1, d 0.3, ? 160
deg, 55 lt ? lt 105 deg
Bs?K?K? (95CL)

?(?) 4?6 deg
U-spin symmetry assumed sensitive to new
physics in penguins
d vs ?
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? from B?? D?K? and B?? D?K?
Variant of the Gronau-Wyler method proposed by
I.Dunietz A ( B?? DCPK? ) A3 1/?2 (
A(B?? D0K?) A(B?? D0 K? ) ) 1/?2 (
A1 A2 ei (??) )
together with CC decays ?
two triangle relations for amplitudes
Measure 6 decay rates
55 lt ? lt 105 deg ?20 lt ? lt 20 deg
yield/yr B/S
B?? D0 (K??) K?(K??) 0.5k 1.8
B?? D0 (K??) K?(K??) 3.4k 0.3
B?? DCP (KK) K? (K??) 0.6k 1.4
?(?) 7?8 deg
cc
sensitive to new phase in DCP
?65o, ?0
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B0?K0? and Bs???

• In SM
• loop-suppressed b?s? transitions
• BR( B0? K0 ?) (4.3?0.4) 10-5
• expected direct CP violation lt1 for B0?K0 ?
• expected CP violation in mixing 0 for Bs? ??

?64MeV
?65MeV
1 yr B/S
B0 ?K0 (K?-) ? 35k lt0.7
Bs ?? (KK-) ? 9.3k lt2.4
?(ACP) 0.01 (1year)
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B0?K0 ??-

• SM
• BR(B0?K0 ??-) (1.2 ? 0.4) x 10-6
• Measurement determines Vts
• Variables sensitive to New Physics
• ??- invariant mass distribution
• ??- forward-backward asymmetry ?FBA ? (?, B
  direction in ??- CMS)

Annual yield (SM) 4.4k Efficiency 0.7 Backgr
ound (B/S) lt2 ?(BR) 3 ?(ACP) 3
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Conclusion

• LHCb can study many different B-meson decay
  modes with high precision
• excellent particle identification capability
• excellent mass and decay-time resolution
• LHCb can fully exploit the large B-meson yields
  at LHC from the start-up
• flexible, robust and efficient trigger
• design luminosity of 2x1032 is lower than typical
  LHC luminosity
• LHCb detector will be ready for data taking in
  2007 at LHC start-up
• detector production is on schedule
• installation of detectors will start end of next
  year
• LHCb will offer soon an excellent opportunity to
• determine precisely the CKM parameters through
  phase meas.
• spot New Physics by overconstraining the
  Unitarity Triangles