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Test ofKobayashi-Maskawa Theoryat B-Factories Bhabha Centenary MeetingMumbai, India
First of all … • Let me celebrateProf. Homi J. Bhabhafor his great achievementsin the nuclear andhigh energy physics.
Then … • Let me extend mysincere congratulationsto Prof. Kobayashi andProf. Maskawa …
Introduction Brief history toward the B-factory experiment Test of the Kobayashi-Maskawa theory Other remarkable results from the B-factories Summary Contents
Antiparticle: A particle with a same mass as the normal particle but with an opposite charge and spin. • Amount of particles and antiparticles is considered equal right after the Big Bang. But the present universe consists only of particles. Mystery of Missing Antiparticles electron positron π+ π– Big Bang particle anti-particle particle Now
Discovery ofthe CPviolation(1964) • J.H.Christensonet al. discovered KLdecayed into 2 pions, which violates the CP conservation. • Kobayashi-Maskawa theory(1973) • They gave theoretical descriptionfor the CP-violatedphenomena. Violation of CP Symmetry Only particles remained while antiparticles didn’t. Particle’s rule ≠ Antiparticle’s rule
When # of quark generations is more than 2, the CP symmetry will be broken by an irreducible phase remained in the quark mixing matrix. Kobayashi-Maskawa Theory Quark mixing matrix for case of generation # = 2 Quark mixing matrix for case of generation # = 3 Irreducible complex phase violates CP symmetry.
B-factory experiment: a HEP experiment aiming mainly at the test of Kobayashi-Maskawa theory. B-Factory Experiment Quark mixing matrix for case of generation # = 3 Does the irreducible phase really exist? ↕ Does the CP really violatedbetween the b and anti-b quarks?
B0 and B0 changes itsflavor mutually througha box diagram. • Interference between “unmixed” and “mixed” decay amplitudes measures the irreducible phase in the quark mixing matrix. Mixing-Induced CP Violation _ b b B0 B0 d d _ _ t b d W W t d b Interference↓Irreduciblephase unmixed final state b B0 d _ B0 mixed final state b B0 b d d
B-Factories in the World Accelerator Detector Collaboration ~400 researchersfrom 14 countries/regions. Belle (Japan) Belle (Japan) Belle in Japan BaBarin US ~600 researchersfrom 10 countries/regions. BaBar (US) BaBar (US)
After the KM Theory A.I.Sanda andI.Bigi proposed an experimentto prove the KM theory (1981) KM theory (1973) TRISTAN experimentput large value forlower mass limitfor the top quark • ARGUSmeasured a large B0-B0mixingparameter (Δmd) (1987) _ It eventually turned outthat the verification of the KM theorywith a B-factory is well feasible.
F.Takasaki • Invented energy-asymmetric e+e– collider. • Built up “KEKB task force”(1989) together with H.Ozaki, et al. • Call for collaborators from all over the world to promote B-factory experiment more strongly. • M.Yamauchi • Gave several tens of lectures over Japan about attractive B physics cases (early 1990’s). Passionate People in KEK …
Collaboration meeting in Oct., 1993 • The 1st collaboration meeting(Osaka) • Collaboration meeting in Jan., 1994 • Vote for collaboration name (Nara) • Collaboration meeting in Feb., 1995 • Logo design of Belle(Tohoku) Establishment of “Belle” Agenda of the 1st “Unnamed-Collaboration” Meeting * Group Meeting #1: 7-Oct-1993 (Thu) at Osaka Univ. (Sigma Hall) 12:00 - 12:10 Goals of the meeting S. Suzuki (Nagoya) 12:10 - 14:10 Short reports Problems at Forward Angles J. Haba (Osaka) CsI Calorimeter M. Fukushima (KEK) Questions on PID M. Yamauchi (KEK) PDC/CDC A. Sugiyama (Nagoya) Requirements for B->pilnu S. Uno (KEK) Estimation of accuracy of phi-2 Y. Watanabe (TIT) Proto-typing of the KL Chamber A. Yamaguchi (Tohoku) 14:10 - 14:40 Detector Configuration for LOI K. Abe (KEK) 14:40 - 15:30 Prcoesses for writing LOI S. Noguchi (Nara) Time Table for Writing LOI S. Suzuki (Nagoya) Agenda of the 48th Belle General Meeting * Group Meeting #1: 7-Oct-1993 (Thu) at Osaka Univ. (Sigma Hall) 12:00 - 12:10 Goals of the meeting S. Suzuki (Nagoya) 12:10 - 14:10 Short reports Problems at Forward Angles J. Haba (Osaka) CsI Calorimeter M. Fukushima (KEK) Questions on PID M. Yamauchi (KEK) PDC/CDC A. Sugiyama (Nagoya) Requirements for B->pilnu S. Uno (KEK) Estimation of accuracy of phi-2 Y. Watanabe (TIT) Proto-typing of the KL Chamber A. Yamaguchi (Tohoku) 14:10 - 14:40 Detector Configuration for LOI K. Abe (KEK) 14:40 - 15:30 Prcoesses for writing LOI S. Noguchi (Nara) Time Table for Writing LOI S. Suzuki (Nagoya) electron collides on positron(flipped e) to produce B. Belle Peace Beat Bambi “Belle”means “beauty”in French. The b quark is often called “beauty quark.”
1993 Letter of Intent • 1995 Technical Design Report • Dec., 1998Completion of detector construction • Jan., 1999Cosmic ray data taking with Belledetector • Feb., 1999First e+e– collision • May, 1999Enroll Belledetector to collision point • Jun. 4, 1999First physics event Start of Belle
Irreducible Phase Measurement Quark mixing matrix for case of generation # = 3 Unitarity condition among elements iη Forms “Unitarity Triangle” Irreducible phase exists↔ φ1 ≠0 ρ O
The interior angle φ1 comes to a distribution of “the time duration Δt between pair-created two B meson decays” as sin2φ1. Phenomenology of CP Violation [ps]
Measurement Scheme of sin2φ1 BCP e– e+ fCP(J/ψK0) Υ(4S) Btag Flavor tag Δz • Reconstruct B meson in BfCP(e.g.:J/ψK0) decay. • Determine the Δt ≈ Δz/velocity,where Δzis a displacement of the two B decays. • Tag flavor of Bmeson (B0 or B0). • Determine sin2φ1from a combination of above information using the maximum-likelihood fit method.
The First Measurements in 2001 Belle @29.1 fb–1 φ1» 0↕Large CP ViolationSuccess of the KM test ! BaBar _ @23M BB pairs
The Latest sin2φ1 BelleandBaBarare continuing data collection,and updating the sin2φ1periodically. _ Belle: 535M BB pairs; K.-F. Chen et al., Phys. Rev. Lett. 98, 031802 (2007). BaBar: 465M BB pairs; B.Aubertet. al., arXiv:0808.1903 [hep-ex] (2008). _
Snapshots in Hard Workers’ Room Comfortable bed Snapshots in Room #215 in KEK – Record of hard workers – Comfortableworking environment Nutritious food Plenty fluid intake
Convergence of Unitarity Triangle All measurements from B-factories and others converges to a single apex at >95% confidence level. iη Belle and BaBaralso measures φ2, φ3, Vcb, Vub, and Vtd as well as φ1. We can conclude a success of the KM theory, as well as a success of the B-factory experiments. ρ O
New Hints from B-Factories Several phenomenological hintsbeyond the SM from B-factories New particles like X(3872) First observation of pure leptonicB decay _ Unexpectedly large D0-D0 mixing Difference in CP violation btw B0 andB+ and many other hints Verification of the KM theory. Establishment of the SM.
Difference in CPV btwB0/B+ B0K–π+ B0K+π– OppositeCP violationbtw B0and B+ B–K–π0 B+K+π0 Nature 452, 332 (2008) Is this a hint for new physics ? Need more data to conclude.
_ B–τ–ντ b τ– Br prediction by the SM W– ,H– B– ντ u If a charged Higgs particle exists,the measured Br will be deviated from the prediction. Detection of B–τ–ντ is quite difficult because the decay finalstate includes 2 or more neutrinos. The first detection in2006. Signal bump Limit is given onthemH - tanβplane. Background
_ Unexpectedly large D0-D0was foundfrom the lifetime difference betweenD0 K+K–and D0 K+π–. Unexpectedly Large D0-D0 Mixing _ (2008 W.A.) ΔΓ/2Γ Δm/2Γ
_ CP Violation through D0-D0 Mixing CP Violation through D0-D0 Mixing _ _ _ t c d The CP violation in the neutralD meson system can be probedthrough D0-D0mixing as well as the one through B0-B0 mixing. Discovery of the CP violation can be a hint of new physics. W W t d c _ _ (2008 W.A.) Need more data to conclude.
New Particles ΥbΥ(1S) π+π– ΥbΥ(2S) π+π– A new bb resonancebeside the Υ(5S)? X(3872) B+X(3872) K+ X(3872) J/ψπ+π– A new particle, whichcan never be ccresonances. Υb _ _ Z(4430)+ B0Z(4430) K– Z(4430)+ψ(2S)π+ A new particle withcharge, which cannever be cc resonanceBound state of 4quark resonance? Many other new particles arebeing discovered: Y(4260), X(3940), Y(3940),Y(4325), X(4160), Y(4008)… _
Hunt for New Physics Present B-factory Upgraded B-factory NewPhysics NewPhysics • Many attractive and feasible physics cases are awaiting us. • We have been making several efforts toward Belle-II: detector design, feasibility study, and so on. • Several hints for new physics beyond the SM have been found.
Belle andBaBar had succeeded in the test of Kobayashi-Maskawa theory. • These experiments have been discovering several hints of new physics beyond the Standard Model. • To figure out the genuine particle physics more precisely, we have starteddesign of upgraded B-factory experiment. Summary