g a b Part 1: Matter-Antimatter Asymmetry New Results from the BaBar Experiment Part 1: Matter-Antimatter Asymmetry Part 2: CP Violation and the SM Part 3: Beyond the Standard Model K. Honscheid Dept. of Physics Ohio State University K. Honscheid, WSU Apr. 15, 2005

Matter, Energy and the Big Bang Einstein showed us that matter and energy are equivalent When matter and antimatter meet, they annihilate into energy Energy can also materialize as particle-antiparticle pair armed with this understand of antimatter we can revisit the issue of antimatter in the universe. Predict: nMatter/nPhoton~ 0 Exp: nb/ng~ (6.1 +/- 0.3) x 10-10 (WMAP) K. Honscheid, WSU Apr. 15, 2005

Transition to broken electroweak symmetry provides these conditions So how can this happen? In 1967, A. Sakharov showed that the generation of the net baryon number in the universe requires: Baryon number violation (Proton Decay) Thermal non-equilibrium C and CP violation (Asymmetry between particle and anti-particle) explain baryon number explain baryogenesis B violation to create net B number CP symmetry, which relates matter to antimatter, is necessary or the baryon violating processes would be cancelled out by anti-baryon violating processes Thermal non-equilibrium because in hot early universe, particle abundances are in equilibrium determined by temperature and mass, and since by CPT theorem particles and antiparticles have same mass then in thermal equilbirum have same abundance. Transition to broken electroweak symmetry provides these conditions K. Honscheid, WSU Apr. 15, 2005

Experimental Possibilities: Get equal amounts of matter and anti-matter Wait… See what’s left (in anything) K. Honscheid, WSU Apr. 15, 2005

PEP-II Asymmetric B Factory collide 9 GeV e- on 3.1 GeV e+ approved in fall 93 as presidential initiative, completed in 99, reached design lumi in 2000 While I will report mostly on BaBar results there is a competing experiment in Japan. The Belle detector and the KEK B factory are also working extremely well and there is a great scientific competition going on between the two collaborations. Stanford Linear Accelerator Center, Stanford, California K. Honscheid, WSU Apr. 15, 2005

The BaBar Experiment my goal is to present our results in a way that simplifies understanding – but simple should not be construed as easy. All these measurements are extremely difficult an require the talents of all these people. K. Honscheid, WSU Apr. 15, 2005

Preparing the Matter – Antimatter Sample B mesons contain a b quark and a light anti-quark. mB = 5.28 GeV (~5x mProton) BB Threshold The Upsilon(4S) - a copious, clean source of B meson pairs 1 of every 4 hadronic events is a BB pair No other particles produced in Y(4S) decay Equal amounts of matter and anti-matter motivation for asymmetric B factory Collect a few 108 B0 B0 pairs K. Honscheid, WSU Apr. 15, 2005

Analysis techniques Threshold kinematics: we know the initial energy of the system Event topology Signal Signal (spherical) explain that the initial state is known Delta E the beam energy is better known (2-3 MeV) than the reconstructed energy (20 MeV) -> mes Background Background (jet-structure) K. Honscheid, WSU Apr. 15, 2005

Searching for the Asymmetry 227 x 106 B0 Mesons Count B0K+ Decays 227 x 106 B0 Mesons Count B0K-+ Decays Is N(B0K+ ) equal to N(B0K-+ )? Introduce B->Kpi and explain importance of PID. Mention Cerenkov effect and particle’s velocity K. Honscheid, WSU Apr. 15, 2005

How to Tell a Pion from a Kaon Angle of Cherenkov light is related to particle velocity Transmitted by internal reflection Detected by~10,000 PMTs Particle Quartz bar Cherenkov light Active Detector Surface speed trap for particles K. Honscheid, WSU Apr. 15, 2005

background subtracted Searching for the Asymmetry 227 x 106 B0 Mesons Count B0K+ Decays 227 x 106 B0 Mesons Count B0K-+ Decays Is N(B0K+ ) equal to N(B0K-+ )? B0K+ BABAR B0K+ background subtracted BABAR K. Honscheid, WSU Apr. 15, 2005

Direct CP Violation in B Decays Using We obtain First confirmed observation of direct CP violation in B decays K. Honscheid, WSU Apr. 15, 2005

Part 2: CP Violation in the Standard Model CP Operator: coupling q’ q’ CP( ) = g g* q J q J Mirror To incorporate CP violation g ≠ g* (coupling has to be complex) Quantum-mechanically, the CP operator converts particles to anti-particles and also the coupling constants become the complex conjugates. no complex phases in strong and em interactions. what about the weak interaction? K. Honscheid, WSU Apr. 15, 2005

The Kobayashi-Maskawa Matrix The weak interaction can change the favor of quarks and lepton Quarks couple across generation boundaries Mass eigenstates are not the weak eigenstates The CKM Matrix rotates the quarks from one basis to the other Vcb Vub u d t c b s l l3 l2 l=cos(qc)=0.22 d’ Vud Vus Vub d s’ = Vcd Vcs Vcb s b’ Vtd Vtb b K. Honscheid, WSU Apr. 15, 2005

The Unitarity Triangle Visualizing CKM information from Bd decays The CKM matrix Vij is unitary with 4 independent fundamental parameters Unitarity constraint from 1st and 3rd columns: i V*i3Vi1=0 Testing the Standard Model Measure angles, sides in as many ways possible SM predicts all angles are large u Vud Vus Vub Vcd Vcs Vcb Vtd Vts Vtb c t CKM phases (in Wolfenstein convention) unitarity 4 parameters (3 real, 1 complex phase) many representations. Wolfenstein – matches hierarchy shown on previous slide In this representation the Vtd and Vub – the small elements in the corner carry a complex phase. UT will be our guide for the remainder of the talk. K. Honscheid, WSU Apr. 15, 2005

Understanding CP Violation in B  Kp Tree decay g A1 = a1 eif1 eid1 A1 = a1 e if1 B0 K-p+ + A2 = a2 eif2 eid2 Penguin decay A1 = a1 e-if1 eid1 A1 = a1 e -if1 B0 K+p- + A2 = a2 e-if2 eid2 include the strong phase (doesn’t change sign) more than one amplitude with different weak phase; (A = A1+A2) Now let’s revisit our B->Kpi decays and see if they fit into this model. A B meson decays by emitting a virtual W boson and converting into a u (or c) quark. This plus the remnant from the B make up the pi in the final state and the W hadronizes into the K. Here is Vub and with it the complex phase that changes sign in a CP operation. We call this a tree diagram. Define asymmetry since the amplitudes are squared the asymmetry is 0. Now this is a quark level description. The quarks hadronize via the strong interaction and there can be a strong phase. This does not change sign under CP. Still, no asymmetry. What we need is a second amplitude like this diagram (penguin – more about this later). You see we reach the same final state. Two amplitudes interfere and it is in this interference where we get a difference between the B0 and the B0bar decay. With a little bit of math in can be shown that weak phase difference strong phase difference great – bad (that’s also what made the interpretation of the Kaon results to difficult) need a way to eliminate or at least reduce strong uncertainties. Very difficult if we use two different decay diagrams. Fortunately, nature helps. because G(B) – G(B) G(B) + G(B) |A|2 – |A|2 |A|2 + |A|2 = 0 ~ 2 sin(f1 - f2) sin(d1 - d2) Asymmetry = = K. Honscheid, WSU Apr. 15, 2005

B0 B0 Mixing and CP Violation f = b A neutral B Meson CPV through interference between mixing and decay amplitudes Interference between ‘B  B  fCP’ and ‘B  fCP’ The SM allows B0 B0 oscillations N(B0)-N(B0) N(B0)+N(B0) the neutral B meson has a personality disorder. While it was created as B0 it doesn’t stay one. Like the other neutral mesons the SM allows B0 oscillations via this box diagram beautiful measurement of the oscillation as function of time. The mixing frequency has been measured to great accuracy and is about 0.5 ps-1 If we now select decays of a B0 to a CP eigenstate a state that can also be reached from a B0bar we can use the interference between the direct decay and the mixed decay to measure the CP phases Only one decay diagram – hadronic uncertainties cancel. the complex CKM phase is beta – with 2 Vtd couplings we will get 2beta in the asymmetry. If the B decay has no weak phase by itself we will measure sin(2beta) Mixing frequency Dmd  0.5 ps-1 B0 fraction ~ sin(Dmd Dt) K. Honscheid, WSU Apr. 15, 2005

Time-Dependent CP Asymmetries b c c CP Eigenstate: hCP = -1 W+ B0 s d d Amplitude of CP asymmetry Quark subprocess B0 mixing K0 mixing psi Ks time dependence – mixing part cpv amplitude but integrates to 0 need to measure time dependence – the lifetime of the B is only 1.5 ps – by the way. K. Honscheid, WSU Apr. 15, 2005

Time-dependent analysis requires B0 flavor tagging We need to know the flavour of the B at a reference t=0. Dz = Dt gbc At t=0 we know this meson is B0 B 0 rec B 0 (4S) bg =0.56 l - (e-, m -) B 0 tag The two mesons oscillate coherently : at any given time, if one is a B0 the other is necessarily a B0 In this example, the tag-side meson decays first. It decays semi-leptonically and the charge of the lepton gives the flavour of the tag-side meson : l - = B 0 l + = B 0. Kaon tags also used. Dt picoseconds later, the B 0 (or perhaps its now a B 0) decays. There is an additional slight complication as our B0B0bar pair is in a coherent state Tagging explain lepton tag. We also use a kaon tag from a subsequent D decay. Combined the tagging efficiency is roughly 30% K. Honscheid, WSU Apr. 15, 2005

Step by Step Approach to CP Violation B tagged 1. Start with a few x 108 B0 B0 pairs (more is better) 2. Reconstruct one B0 in a CP eigenstate decay mode 3. Tag the other B to make the matter/antimatter distinction 4. Determine the time between the two B0 decays, Dt 5. Plot Dt distribution separately for B and B tagged events 6. Extract ACP and sin2b Dt (ps) sin 2b sinDmDt okay, let’s do it detector resolution amplitude modified by misttags. ACP(Dt) Dt (ps) K. Honscheid, WSU Apr. 15, 2005

Results: sin 2b and the observation of CP 227 million BB pairs J/yKs and other b  cc s final states CP = -1 B  J/ Ks0, Ks0  p+p-, p0p0 B  (2S) Ks0 B  c1 Ks0 B  J/ K*0, K*0  Ks0 B  c Ks0 7730 events (1-2w) sin(2b) w = mis-tag fraction With this device and the rest of the BaBar detector we then collected almost 230 million BB events and analyzed the data looking for psiKs final states plus, of course, a tag for the other B in the event. We ended up with 7730 events and shown here is the decay time difference for B0 tags and B0bar tags clear difference. no asymmetry in the background. The second plot shows the raw asymmetry and the fit result is CP = +1 B  J/ KL0 BaBar result: sin2b = 0.722  0.040  0.023 K. Honscheid, WSU Apr. 15, 2005

b g a The Unitarity Triangle (0,0) (0,1) (r,h) Vub Vud Vcd Vcb * Vtd Vtb g a b Successfully reached the main goal of the B factory program now let’s go for more [23.3 ± 1.5]o K. Honscheid, WSU Apr. 15, 2005

yKs is not the only CP Eigenstate Access to a from the interference of a b→u decay (g) with B0B0 mixing (b) B0B0 mixing Tree decay g a = p - b - g harder because of the lower BR sin2a ACP(t)=sin(2a)sin(DmdDt). K. Honscheid, WSU Apr. 15, 2005

Time-dependent ACP of B0→p+p- Blue : Fit projection Red : qq background + B0→Kp cross-feed found about 500 events BR result in fact obtained from 97MBB K. Honscheid, WSU Apr. 15, 2005

Houston, we have a problem q pp Kp B0  p+p- B0  K+p- B0p+p- 157  19 (4.7  0.6  0.2) x 10-6 B0K+p- 589  30 (17.90.9 0.7) x 10-6 Penguin/Tree ~ 30% K. Honscheid, WSU Apr. 15, 2005

The route to sin(2a): Penguin Pollution Access to a from the interference of a b→u decay (g) with B0B0 mixing (b) B0B0 mixing Tree decay Penguin decay  g Inc. penguin contribution now the formalism gets slightly more complicated the “C” term direct CP violation due to the interference of the T and P decays but our sin(2a) term gets also modified and the question is how can we obtain a from aeff? How can we obtain α from αeff ? Time-dep. asymmetry : NB : T = "tree" amplitude P = "penguin" amplitude K. Honscheid, WSU Apr. 15, 2005

How to estimate |a-aeff| : Isospin analysis Use SU(2) to relate decay rates of different hh final states (h  {p,r}) Need to measure several related B.F.s 2|-eff| not enough data but maybe we can limit a-aeff if A00 is very small… look for this decay Difficult to reconstruct. Limiting factor in analysis Gronau, London : PRL65, 3381 (1990) K. Honscheid, WSU Apr. 15, 2005

Now we need B0→p0p0 |a-aeff |< 35° 61±17 events in signal peak (227MBB) Signal significance = 5.0s Detection efficiency 25% 3 B.F.s B0p+p- B+  p+p0 B0  p0p0 2 asymmetries Cp+p- Cp0p0 Using isospin relations and Large penguin pollution ( P/T ) Isospin analysis not currently viable in the B→pp system |a-aeff |< 35° B±→r±p0 we indeed found 60 decays with manageable background not good enough Time-integrated result gives : K. Honscheid, WSU Apr. 15, 2005

B → rr: Sometimes you have to be lucky P → VV decay three possible ang mom states: S wave (L=0, CP even) P wave (L=1, CP odd) D wave (L=2, CP even) r helicity angle We are lucky: ~100% longitudinally polarized! Transverse component taken as zero in analysis PRL 93 (2004) 231801 K. Honscheid, WSU Apr. 15, 2005

Time dependent analysis of B→r+r- Maximum likelihood fit in 8-D variable space very clean tags 32133 events in fit sample fine but what about rho0rho0? K. Honscheid, WSU Apr. 15, 2005

Searching for B→r0r0 B (B→r+r-) = 33 x 10-6 Similar analysis used to search for r0r0 Dominant systematic stems from the potential interference from B→a1±p± (~22%) c.f. B→p+p- B.F.= 4.7 x 10-6 and B→p0p0 B.F.= 1.2 x 10-6 B (B→r+r-) = 33 x 10-6 K. Honscheid, WSU Apr. 15, 2005

Isospin analysis using B→rr The small rate of means |a-aeff | is small[er] P/T is small in the B→rr system (…Relative to B→pp system) No isospin violation (~1%) No EW Penguins (~2%) |a-aeff |< 11° K. Honscheid, WSU Apr. 15, 2005

a g b The Unitarity Triangle (0,0) (0,1) (r,h) Vub Vud Vcd Vcb * Vtd Vtb g b [103 ± 11]o a being able to measure 2 angles is already a surprise but let’s go for 3 [23.3 ± 1.5]o K. Honscheid, WSU Apr. 15, 2005

The 3rd Angle: g Basic Idea Color suppressed no help due to mixing unless we have Bs mesons D0-kk or pp, Kspi0 acp depends strongly on ratio which is not well known. K. Honscheid, WSU Apr. 15, 2005

First Look at the Data Only a loose bound on rB with current statistics: (rB)2 = 0.19±0.23 BABAR-CONF-04/039 just a first look Several other methods are being investigated More data would help a lot… K. Honscheid, WSU Apr. 15, 2005

Combined Experimental Constraint on g BABAR & Belle combined more data and this might actually work K. Honscheid, WSU Apr. 15, 2005

g a b The Unitarity Triangle [103 ± 11]o (0,0) Vub Vud Vcd Vcb * Vtd Vtb a b so here we are. 5 years into the B factory program and we not only have established CPV in the B system but we have also measured the three angles of the UT (okay 2 ½) I leave it as an exercise for you to add up the three angles and compare the result to 180. [51+20-34]o [23.3 ± 1.5]o K. Honscheid, WSU Apr. 15, 2005

Putting it all together The complex phase in the CKM matrix correctly describes CPV in the B meson system. Based on SM CPV the baryon to photon ratio in the universe should be nb/ng~ 10-20 Experimentally we find nb/ng~ (6.1±0.3) x 10-10 (WMAP) h this is a confusing plot because it combines 30 years worth of information. Consistent But not enough r K. Honscheid, WSU Apr. 15, 2005

Part 3: Consistency Checks Part 3: Beyond the Standard Model Part 3: Consistency Checks FCNC transitions bsg and bdg are sensitive probes of new physics Precise Standard Model predictions. Experimental challenges for bdg (Brg Bwg) Continuum background Background from bsg (BK*g) (50-100x bigger) Ali et al hep-ph/0405075 this could give Vtd – one of the UT sides. Maybe this is too long or too short? K. Honscheid, WSU Apr. 15, 2005

Combined B0r0g,B0wg,B-r-g results No signals observed No signals but the limits on Vtd become meaningful @90% CL K. Honscheid, WSU Apr. 15, 2005

CKM constraints from Br(w)g BABAR BF ratio upper limit < 0.029 → |Vtd/Vts| < 0.19 (90% CL) Ali et al. hep-ph/0405075 (z2,DR) = (0.85,0.10) no theory error (z2,DR) = (0.75,0.00) with theory error Penguins are starting to provide meaningful CKM constraint rg 95% CL BABAR allowed region (inside the blue arc) K. Honscheid, WSU Apr. 15, 2005

New CP Violating Phases in Penguin Decays? + mixing lCP = -e-2b t s d W - Vtb Vts* + mixing lCP = -e-2b we could also look for new phases due to new heavy particles in penguin loops + mixing lCP = -e-2b K. Honscheid, WSU Apr. 15, 2005

Update on BfKo Belle 114 ± 12 events 98 ± 18 events preliminary hep-ex/0502019 preliminary 114 ± 12 events SM Belle [BELLE-CONF-0435] 98 ± 18 events we could also look for new phases due to new heavy particles in penguin loops K. Honscheid, WSU Apr. 15, 2005

Reaching for more statistics – B 0   K 0 revisited Analysis does not require that ss decays through f resonance, it works with non-resonant K+K- as well 85% of KK is non-resonant – can select clean and high statistics sample But not ‘golden’ due to possible additional SM contribution with ss popping But need to understand CP eigenvalue of K+K-KS: - f has well defined CP eigenvalue of +1, - CP of non-resonant KK depends angular momentum L of KK pair Perform partial wave analysis Estimate fraction of S wave (CP even) and P wave (CP odd) and calculate average CP eigenvalue from fitted composition K+K- Nsig = 452 ± 28 (excl.  res.) OK Not OK K. Honscheid, WSU Apr. 15, 2005

CP analysis of B  K+K- KS Result of angular analysis Result consistent with cross check using iso-spin analysis (Belle) Result of time dependent CP fit hfSK+K-KS/(2fCP-even-1)] = +0.55 ±0.22 ± 0.04 ±0.11 (stat) (syst) (fCP-even) K. Honscheid, WSU Apr. 15, 2005

More penguin exercises – B0  KS KS KS hep-ex/0502013 More penguin exercises – B0  KS KS KS Use beam line as constraint and accept only KS with sufficient number of SVX hits. Decay B0  KS KS KS is ‘golden’ penguin – little SM pollution expected Although 3-body decay, only L=even partial waves allowed: CP(KSKSKS) = CP(KS) = even Result consistent with SM Gershon, Hazumi hep-ph/0402097 s d K0 hfK0 K. Honscheid, WSU Apr. 15, 2005

IP-Constrained Vertexing Same technique as Ksp0 hep-ex/0503011 beam p0 B0 p + p - inflated beam 4mm 200mm KS Constrain decay products to beam-spot in x-y: Vertex precision depends on number of hits in SVT For 4 hits, Dt resolution as good as with charged-tracks (60% events) Crosscheck with J/yKS: K. Honscheid, WSU Apr. 15, 2005

Combined “sin2b” Results Dsin2β ~ -2.9 s Dsin2β ~ -2.9 s + sin2βPenguin = 0.43 ±0.07 Dsin2β ~ -3.7 s …but comparison ignores subleading diagrams ! K. Honscheid, WSU Apr. 15, 2005

Corrections: b→s Decay Amplitude ~ VubVus* penguin Decays involving Vub enter with decay phase g Doubly-CKM suppressed w.r.t dominant diagram Contributes to all b sss modes color-allowed tree color-suppressed tree Contribute to h’Ks, f0Ks, wKs, but not fKs [in KKKs (requires ss popup from soft g)] Contribute to non-resonant KKKs (requires ss popup from soft g) K. Honscheid, WSU Apr. 15, 2005

Adding Theoretical Uncertainties size of possible discrepancies Δsin2β have been evaluated for some modes: estimates of deviations based on QCD-motivated specific models; some have difficulties to reconcile with measured B.R. Beneke at al, NPB675 Ciuchini at al, hep-ph/0407073 Cheng et al, hep-ph/0502235 Buras et al, NPB697 Charles et al, hep-ph/0406184 model independent upper limits based on SU(3) flavor symmetry and measured b d,sqq B.R. [Grossman et al, PRD58; Grossman et al, PRD68; Gronau, Rosner, PLB564; Gronau et al, PLB579; Gronau et al, PLB596; Chiang et al, PRD70] 2xΔsin2β ‘naive’ upper limit based on final state quark content, CKM (λ2) and loop/tree (= 0.2-0.3) suppression factors [Kirkby,Nir, PLB592; Hoecker, hep-ex/0410069] K. Honscheid, WSU Apr. 15, 2005

Conclusion Almost 40 years after the discovery of CP violation in the kaon system we are finally in a position to improve our understanding of CP violation in the Standard Model Belle and BaBar give consistent results for sin2b. Both work extremely well The SM prediction of a single phase in the CKM matrix as cause of CP violation appears to be correct. We now know how to distinguish between matter and anti-matter aliens. New Physics will be needed to explain the baryon asymmetry in the universe Will we find hints in CP phases and/or rare decays? Stay tuned as more data is coming in. K. Honscheid, WSU Apr. 15, 2005