CP violation in B decays Philip Clark University of Bristol The BaBar Collaboration
Outline Brief introduction to CP violation in the B meson system. The PEP-II storage ring and BaBar detector. Performance of the experiment. Physics results B lifetimes B mixing CP asymmetry Conclusions and future prospects 47247031472,943800,84 0,8:70203941!;4,93,822097083/0.,894!00389,908!8#0; 099
Why is CP violation interesting? :3/,2039,822097 00/0/9405,32,9907,392,9907,82209789,793 174239,822097..43/9438 00/894-0-0990790890/ 48920,8:7020398841,7,704317422084388902 %0894190$9,3/,7/4/0,34;07.43897,390$570/.943893/0503/039 20,8:7020398 70.970,90/94902,880307,9320.,382 974:902,97 :3/,2039,25.,94381475,79.058.8
Three types of CP violation in B decays!;4,943323..:7803909430:97,2,8800389,908,70/1107039 174290!00389,908!;4,9433/0.,..:783 ± /0.,80390,259:/0147,/0.,,3/98!.43:,90,;0/11070392,39:/08!;4,943390390710703.0-09003/0.,89,3/94:923..:783/0.,8913,89,908.4224394-49,3/
More on the types of CP violation 438/07/0.,89413,!00389,9081!,..088-094-49,3/ /0.,8 5072039,20,8:7,-06:,3993/0503/039415,80.43;039438 q p A A CP λ η fcp f f CP q p A A f f CP CP CP symmetry is conserved if and only if:- q p =1 A A f f CP CP =1 Im λ = 0 If violated you get CP violation in :- 1. Mixing 2. Decay 3. Interference between decays with and without mixing
CKM matrix unitarity: b u l ν Unitarity Triangle B ππ B πρ V ud V ub * α (=ρ,=η) V td V tb * B 0 B 0 mixing B ργ V B Κπ B D 0 cpk ud V * ub γ CP violation V cd V cb * b * * + VcdVcb + VtdVtb c l ν = 0 β B J/ψΚ 0, B ψ(2s)κ S
The unitarity triangle (cont.) %08/08,70/0907230/-20,8:70203984190 2,39:/08410020398!,82209708941! 20,8:708,3084197,30 38420.,8089904734904709.,,2-:908 4,419058.85747,28944;07.43897,397,30.79.,9089897:.9:7041$
CP violation in the interference between decays with and without mixing B 0 B 0 B 0 (t) f CP B 0 (t) f CP B 0 B 0 A CP = A(B 0 (t) -> f CP ) 2 - A(B 0 (t) -> f CP ) 2 A(B 0 (t) -> f CP ) 2 + A(B 0 (t) -> f CP ) 2 A CP (t) = - Im(λ) sin( mt) Alternatively:- A CP (t) = - η CP sin(2φ) sin( mt) where φ = α, β, or γ 4790/0., 588 Im(λ) = sin(2β)
Existing Constraints on the Unitarity Triangle η 1 0.8 0.6 Errors are dominated by theoretical uncertainties! m d m s / m d 0.4 ε K 0.2 V ub /V cb 0-1 -0.5 0 0.5 1 Constraints come from - CP violation in K 0 mesons - V ub and V cb measurement - B d and B s mixing ρ 4.07,.07$,5,.0 0-07/07 055
The asymmetric B-factory concept 0 Г 0 >=Υ(48 >=.0,384:7.041 8 0:97,88902Υ$ > 0;4;08.407039 03430 /0.,8904907,845548901,;4:7 472, 8/434997,;01,7034:3Υ$708917,2094 20,8:70 9 =µ2 3,822097.1,.947080705745480/94 89:/!;4,9433208438 4489908,4390-0,2/70.943849097,;0,20,8:7,-0 /89,3.0-0147090/0.,,43/090723,94341 9 #06:708,94730 Г 0.4/07 9,822097.-0,2030708 :73.43;078434190!!,3/%789,3 822097. 0 Г 0.4/078 94,822097.1,.94708,8.425090/
The anatomy of a CP event J /Ψ= >=µ + µ e + e - >Υ(4 >Υ(4S) tagging B decays Β= >J /Ψ=Κ s t ~ z / β=γ=c Κ s >=π + π coherent evolution
Experimental Approach!74/:.02,3 5,78 #0.43897:.94303,!00389,908:.,8 > Ψ= 8 %,904907 94/0907230981,;47,9909204198/0., 090723090920-090039094 /0.,8:8390-4489,4390-0,2/70.943 9 βγ. 425,70 9 /897-:9438147 1 Г,3/ 1 9,0/0;0398 B tagged,3,82209780;/03.0147 ( f + )!;4,943 B tagged ( f - ) η CP sin 2φ sin ( m t)
The B meson factory PEP-II 0'(0 0 Г 2(0 0 Г.2 8 ( 39 5- /,( 083 #0,.0/ 08
BABAR Collaboration: 9 Countries, 72 Institutes China [1/6] Inst. of High Energy Physics, Beijing Germany [3/21] Ruhr U Bochum TU Dresden U Rostock France [5/50] LAPP, Annecy LAL Orsay LPNHE des Universités Paris 6/7 Ecole Polytechnique CEA, DAPNIA, CE-Saclay United Kingdom [10/80] U of Birmingham U of Bristol Brunel University U of Edinburgh U of Liverpool Imperial College Queen Mary & Westfield College Royal Holloway, University of London U of Manchester Rutherford Appleton Laboratory 554 physicists Italy [12/89] INFN Bari INFN Ferrara INFN Frascati INFN Genova INFN Milano INFN Napoli INFN Padova INFN Pavia INFN Pisa INFN Roma INFN Torino INFN Trieste Canada [4/16] U of British Columbia McGill U U de Montréal U of Victoria Norway [1/3] U of Bergen Russia [1/13] Budker Inst., Novosibirsk USA [35/276] Caltech, Pasadena UC, Irvine UC, Los Angeles UC, San Diego UC, Santa Barbara UC, Santa Cruz U of Cincinnati U of Colorado Colorado State Elon College Florida A&M U of Iowa Iowa State U LBNL LLNL U of Louisville U of Maryland U of Massachusets MIT U of Mississippi Mount Holyoke College Northern Kentucky U U of Notre Dame ORNL/Y-12 U of Oregon U of Pennsylvania Prairie View A&M Princeton SLAC U of South Carolina Stanford U U of Tennessee U of Texas at Dallas Vanderbilt U of Wisconsin Yale U
Instrumented Flux Return DIRC stand-off box 10752 PMTs in water Electro Magnetic Calorimeter Quartz bars Drift Chamber e + (3.1 GeV) - e (9.0 GeV) Silicon Vertex Detector
Silicon Vertex Tracker (SVT) 22 Five layer double-sided Si Very low mass Stand-alone tracking device for P T < 120 MeV/c Radiation hard z-resolution of 70µm on CP vertex
Drift Chamber %7,.37084:943
Detector of Internally Reflected Cherenkov Light (DIRC): Θ c resolution: cosθ c =1/nβ
Cherenkov angles for π=and K from D * D 0 π +,==D 0 K - π + π K
Electromagnetic calorimeter σ E E 1% = 4 E 1.2% #,/,943039.2 40707,/:8.2!0,028843 32 0389.2 %20.4389,39 38 90/ 5494380'
Instrumented Flux Return (IFR) µ 011.03.,3/π 1,07,90,77080.94341# Large solid angle coverage for muon id (P>1 GeV/c) and to detect neutral hadrons (K 0 L )
Summary:- unique features of BaBar 822097.-0,28 70,90,20,3260 µm ;0790805,7,943 4;0732,35,79.0/0;.0# 4709,382,5805,7,943:5943.4 GeV/c9 389239419-,.74:3/8 7,/0/802039,94341,/743./090.947# 574;/08-09907 70.43897:.943 ",-9949,0/,9,.4393:4:8,9 7,90,3/-908 0;039809,;07,0 /0,/920938-09003-:3..748838!! 38%0;,9743 38 38
BaBar daily recorded luminosity Design value
PEP-II/BaBar integrated luminosity
Exclusive B reconstruction 302,9.;,7,-08 E = E * 1 2 σ ( E) 25MeV /423,90/-/090.947 7084:943 s E (GeV) B 0 D * π + (Kπ) m σ 2 * 2 ES = s P B 1 2 ( m ES ) 3MeV /423,90/--0,2 03078570,/ m ES (GeV/c 2 )
Exclusive B Decays to Charmonium Branching ratios B 0 J/ψK s (π + = π ) 0., 7,3.3 7,.943 PRELIMINARY ψ 1742 8 π Г π 1742 8 π π 1742 ψ Г ψ Г Г ψ Г ψπ B + J/ψK + χ. χ. Г χ.... Г Ψ$ Г Ψ$ Г
Exclusive B decays to Charmonium
B lifetime measurement B 1 partially reconstructed σ z ~ 140 µm B 2 fully reconstructed σ z ~ 60-100 µm e e + 9 GeV 3.1GeV z γ B γβcτ B 260 µm Method / 05 βγ.τ Β :70.43897:.9,,703:2-07418 0,8:70.43;079 94 9 99490 9/897-:9431479010920 '9,94:3/0789,3/90/090.947;07907084:943
Reconstructed hadronic B sample 1- B 0 /B 0 B + /B - ±.,3//,908 ±.,3//,908 47/8,70898,250411:70.43897:.90/8
Resolution function 9 resolution function!8.8 090.9477084:943 :7#$7084:943147 20,8:73 9 8,-4:9 58 %88831.,39.425,70/94 90109208 58 43;4:90/9 0:80,7084:94313147 t.85,7,209070/,88:2 41/1107039,:88,38 20,8:70/.470 9,8 4:9078
B Lifetime Measurements B 0 /B 0 B + /B - PRELIMINARY t (ps) τ B 0 = 1.546 ± 0.032 (stat) ± 0.022 (syst) ps [PDG= 1.548 ± 0.032] t (ps) τ B + = 1.673 ± 0.032 (stat) ± 0.022 (syst) ps [PDG= 1.653 ± 0.028] τ B +/ τ B 0 = 1.082 ± 0.026 (stat) ± 0.011 (syst) [PDG= 1.062 ± 0.029]
Flavour tagging:- B 0 or B 0 %,90 1,;4:7:8390.,7041059438,43847845438 leptons: b l, b l + p*>1.0 GeV/c (e ± ), p*>1.1 GeV/c (µ ± ) k a o ns: b K, b K + NT1 & NT2: b(-1/3) c(+2/3) s(-1/3) W- ν W+ e,µ (-1) Neural network mainly to recover unidentified leptons, slow pions from D*,9047 11.03. ε 89, ω ":,9 " 05943 ± ± ±,43 ± ± ± % ± ± ± % ± ± ± %49, ± ±
An Event of the CP Sample A candidate in the Golden Mode B 0 CP with: J J 0 / ψ KS, K + / ψ µ µ 0 S π + π A negative kaon is found in the decay products of the other B meson, which is therefore tagged as a B z is measured precisely, thanks to the Silicon Vertex Detector 0
Mixing and Sin2β analysis procedure Reconstruct one B fully in CP eigenstate or flavour eigenstate Other B partially reconstructed and flavour tagged Measure =z Fit for =t = =z/cγβγ B Mixing:- PDF( t)= exp( t /τ B ) ( 1 ± (1-2ω) cos( m t) ) R( t) CP violation:- PDF( t)= exp( t /τ B ) ( 1 ± (1-2ω) sin2β sin( m t) ) R( t) (1-2ω) is the dilution due to mistag R( t) is the vertex resolution function
Detector Effects on CP and Mixing Samples CP events B tagged B tagged Perfect detector Mixing events unmixed mixed + Mistag effect + Vertex resolution effect
Mixing result from B flav events Events/ 0.4 ps 400 300 200 100 4000 300 200 100 0 Unmixed Events Mixed Events BABAR -10-5 0 5 10 t (ps) Asymmetry 1 0.8 0.6 0.4 0.2 0-0.2-0.4-0.6-0.8 BABAR -1 0 2 4 6 8 10 12 t (ps) M d = 0.519 ± 0.020 ± 0.016 ps -1 (preliminary)
2 Events / 2.5 MeV/c 100 80 60 BABAR ( B 0 ) = J/ψ K S K S π + π 2 Events / 2.5 MeV/c 20 18 16 14 12 10 BABAR ( B 0 ) = J/ψ K S K S π 0 π 0 40 8 6 20 4 2 0 5200 5210 5220 5230 5240 5250 5260 5270 5280 5290 5300 2 Beam-Energy Substituted Mass (MeV/c ) 0 5200 5210 5220 5230 5240 5250 5260 5270 5280 5290 5300 2 Beam-Energy Substituted Mass (MeV/c ) BaBar golden modes 2 Events / 2.5 MeV/c 22 20 18 16 14 12 10 8 6 4 2 BABAR ( B 0 ) = ψ(2s) K S K S π + π 0 5200 5210 5220 5230 5240 5250 5260 5270 5280 5290 5300 2 Beam-Energy Substituted Mass (MeV/c )
t distributions of tagged CP events
A CP ( t) 1 0.5 Golden Modes a) 0 sin2β= 0.25 ± 0.22 (stat) Asymmetry -0.5-1 1 0.5 J/Ψ=K L b) sin2β= 0.87 ± 0.51 (stat) 0-0.5-1 -5 0 5 Combined: sin2β===0.34 ± 0.20 ± 0.05 t (ps)
Our sin2β measurement and the unitarity triangle 4.07,.07$,5,.0 0-07/07 055 Allowed blue region obtained with the new sin2β meas.
Comparison of Sin2β measurements $2,077478,3/ 097020,70/,9,809 3σ!
PEP-II/BaBar luminosity projections 500 18 Integrated Lumi [fb-1] 400 300 200 100 16 14 12 10 8 6 4 2 Peak Lumi [10**33] Yearly Lumi Cumulative Lumi Peak Lumi 0 1999 2000 2001 2002 2003 2004 mid 2005 0 Yearly Lumi 2 23 40 70 95 110 70 Cumulative Lumi 2 25 65 135 230 340 410 Peak Lumi 1 2 5 7.5 10 12 17 Year
Conclusions and future prospects!!,3/,,7,704507,93,9/083;,:0,33058.8708:98/:094.4204:98443 $42041902,3708:98841,7 83β=== ± ± / ± ± 58 5702 7:380:3/07, 090,78!,394,..:2:,904;071-!70.84383β,=' :- '.- 20,8:7020398 $3α /090723,943,3/.43897,39843$3γ $0,7.147/70.9!;4,943