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SelectedSelected NewNew ResultsResults onon HeavyHeavy QuarksQuarks fromfrom XXXVI SLAC Summer Institute “Cosmic Accelerators” Tuesday, August 5, 2008 Alexandre (Sasha) Telnov Princeton University on behalf of the BABAR Collaboration SLAC, Mail Stop 35 2575 Sand Hill Road Menlo Park, CA 94025 [email protected] TheThe PEPPEP--IIII AcceleratorAccelerator ComplexComplex Reusing the SLAC linear accelerator (1966-present) and the PEP tunnel 467 ± 5 million BB pairs produced Nominal center-of-mass energy: 10.580 GeV — the ϒ(4S) bb resonance Beam energies: 9.0 GeV e−, 3.1 GeV e+ s e Number of bunches: up to 1722 il m .0 2 Peak luminosity: 12.1 x 1033 cm–1s–2 (original design: 3 x 1033 cm–1s–2) Best 24 hours: 911 pb–1 delivered (original design: 135 pb-1/day) − + 2200 m Peak beam currents: 2.05 A e , 3.03 A e circumference Luminous region (σX × σY): 125 µm × 4 µm SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 2 TheThe BBAABBARAR DetectorDetector Built by a collaboration of ~80 universities and labs from 11 countries SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 3 TheThe BBAABBARAR Detector:Detector: OutlineOutline Highlights to follow: SVT and DIRC Photon and KL detection, Electro-Magnetic Calorimeter Instrumented Flux Return electron identification 6580 crystals, Cesium Iodide doped with Thallium 12-18 layers of absorber (iron, brass) and muon detectors (RPC, LST) Detector of Internally Reflected Muon and KL identification Cherenkov Radiation Particle identification 1.5 T superconducting solenoid 144 polished Quartz bars, 4.9 m long 8 tons of water, ~11k photomultipliers Tracking and particle ID with dE/dx Proportional Drift Chamber ~29k gold-plated aluminum wires 40 layers of drift cells, ~1930 volt HV 80% helium, 20% isobutane Silicon Vertex Tracker 5 double-sided layers of Si strips Radiation-hard technology Jargon Vertexing, tracking, Track: Ionization trail left by a charged particle particle ID with dE/dx Tracking: What is the charged particle’s trajectory, momentum and charge (+/−)? Vertexing: Where did the track originate (and its parent decayed)? ParticleHigh ID: What is the charged particle’s type? SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 4 SiliconSilicon VertexVertex TrackerTracker (SVT)(SVT) Primary purpose: determine the particle’s decay point in (x, y, z) SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 5 AA DIRCDIRC ““QuartzQuartz”” BarBar HeCd laser light trapped inside by total internal reflection, 10 min exposure SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 6 Detector of Internally Reflected Cherenkov Light (DIRC) Cherenkov light cone projected onto PMTs, its opening angle measured β = v/c =1/(n cos θC) PMT + Base · ~11,000 DIRC: measures charged particle’s velocity PMT's Tracking (DCH+SVT): measures momentum Purified Water p = mβ/ (1 β2) − 17.25 mm Thickness Light (35.00 mm Width) Catcher p Bar Box Track DIRC “smiles” Trajectory Wedge PMT Surface Mirror Bar Window Standoff Box 91 mm 10mm 4.90 m 1.17 m 4 x 1.225 m Synthetic Fused Silica Quartz index of refraction n = 1.473 Bars glued end-to-end All hits within a ±300 ns trigger window Hits within 8 ns of expected arrival time SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 7 DIRC is BABAR’s dedicated Particle ID system DIRC+(DCH and SVT dE/dx): π/K/p; EMC: electrons; IFR: muons 0.84 electrons 0.82 muons pions 0.8 DIRC Cherenkov angle 0.78 kaons 0.76 protons 0.74 0.72 (for clarity, muons are not shown) 0.70123456 LAB momentum at DIRC, GeV/c SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 8 0 Example of a BB decay in BABAR: BB →→ φφKKS 4 tracks in the final state; also decay products of the other B (superconducting coil and IFR not shown) only the hits that correspond to reconstructed tracks and neutral candidates are shown (noise hits are removed) Electromagnetic Calorimeter (EMC) φ: a very small opening angle at decay point 2 Drift Chamber (DCH) mφ = 1019.5 MeV/c + – 2 DIRC φ → K K mK+ = 493.7 MeV/c 2 mφ− 2 mK+ = 32.1 MeV/c Neutrals SVT KS decays “weakly”: = 2.68 cm cτ Probably a slow pion from D* → Dπ Tracks of opposite charges curve in opposite directions in the magnetic field + – m = 497.6 MeV/c2 K → π π KS S 2 mπ+ = 139.6 MeV/c 2 mKS− 2 mπ+ = 218.5 MeV/c Run 29368, event hexID 249a4b/d610dd73 (June 27, 2002) From the dataset used in Phys.Rev.D69:011102 (2004) SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 9 TimeTime--dependentdependent CPCP analysisanalysis atat BBABBAR Employs nearly all of analysis techniques available BB= 0 ()t − tag µ + ⇒=0 + π 0 BBrec ()t J/ψ µ Exclusive B 0 reconstruction Brec Υ()4S 0 0 − Effective B K S π flavor tagging − + e e efficiency 0 Q=31.2% Btag Tagging by kaon 250 µm ∆z − charge from separation K b→c→s most common Y(4S) − produces a ∆z Lepton tag is the coherent B pair: l most pure (94%) t →∆t ∆t ≈ ∆ z/ < βγ > c 6 non-overlapping B0 flavor tagging Neural Nets (or no tag) Analysis techniques commonly used to suppress backgrounds: ▪ Momentum and energy conservation ▪ Event shape ▪ Particle Identification ▪ Multidimensional Maximum Likelihood Fit SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 10 TheThe QuarkQuark MixingMixing MatrixMatrix The only Standard-Model source of CP violation in the quark sector The Cabibbo-Kobayashi-Maskawa matrix relates the electroweak (q′) and the mass (q) quark eigenstates: ⎛d′⎞ ⎛V V V ⎞ ⎛d ⎞ ⎛ 1− λ2 / 2 λ Aλ3 (ρ − iη)⎞ ud us ub ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ 2 2 4 6 ⎜ s′ ⎟ = ⎜Vcd Vcs Vcb ⎟ ⎜ s ⎟ VCKM = ⎜ − λ 1− λ / 2 Aλ ⎟ + O(λ ) + iO(λ ) ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ Aλ3 1− ρ − iη − Aλ2 1 ⎟ ⎝ b′⎠ ⎝Vtd Vts Vtb ⎠ ⎝ b ⎠ ⎝ () ⎠ † * * * V V =1 ⇒ Vud Vub + Vcd Vcb + Vtd Vtb = 0 the “unitarity triangle” Supersymmetry (SUSY): dozens In the Kobayashi-Maskawa model, a single B0 →π+π− of independent phases, most in * 0 + − ⎡ VtdVtb ⎤ phase is responsible for all CP violation in B →ρρ flavor-changing couplings; α ≡ arg − 0 0 ⎢ * ⎥ meson decays, making it uniquely testable B → (ρπ) effects should be seen in loops ⎣ VudVub ⎦ B0B0 mixing * b → ulν ⎡ VcdVcb ⎤ β ≡ arg − * α V ⎢ * ⎥ b t q = u,c,t u d V VtdVtb i V tb * ⎣ ⎦ d + u B-meson factories test W V * the Standard Model by ⎡ VudVub ⎤ gV ' overconstraining it γ ≡ arg − ij qj = d',s',b' * ⎢ * ⎥ γβVcdVcb ⎣ VcdVcb ⎦ 0 * 0 B → D π B → J/ψKS + 0 + 0 CKM matrix overview: e.g., The Review of Particle Physics, B → D K B →φKS CP b → clν and other C. Amsler et al. (Particle Data Group), Phys. Lett. B667, 1 (2008). 0 + − + − B →π π , K π (SU(3)flavor) penguin modes SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 11 FreshFresh fromfrom thethe ICHEPICHEP 20082008 ConferenceConference July 29 – August 5, 2008, PhiladelPhiladelphia,phia, http://ichep08.com SelectedSelected NewNew ResultsResults onon thethe UnitarityUnitarity TriangleTriangle AngleAngle ββ :: sin2β in the “golden” b→ccs modes B0 → (cc )K(*)0 sin2βeff in the b→ss s “penguin” modes 0 0 + – + – 0 B → η'K , φKS , f0(→K K )KS , K K KS , φKSπ sin2βeff in the b→ (uʉ,dd)s “penguin” modes 0 0 B → π KS, ωKS All quoted results are preliminary BABAR submitted more than 90 new results to ICHEP 2008 Please see ICHEP 2008 website and http://www-public.slac.stanford.edu/babar/ICHEP08_talks.htm for details SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 12 sin2sin2ββ inin thethe ““goldengolden”” bb→→ccccss modesmodes CP violation in b→ccs (sin2β≠0) first observed in 2001 BABAR with its final dataset, 465x106 BB pairs used: 0 BABAR 400 B tags preliminary sin2β = 0.691 ± 0.029 (stat) ± 0.014 (syst) B 0 tags BABAR-CONF-08/017 β ≡ φ HFAG sin(2 ) sin(2 1) ICHEP 2008 200 PRELIMINARY BaBar 0.691 ± 0.029 ± 0.014 Events / ( 0.4 ps ) Events / ( 0.4 ps ) ICHEP 2008 preliminary ψ 0 ± ± 0.4 Belle J/ K 0.642 0.031 0.017 PRL 98 (2007) 031802 0.2 ψ ± ± Belle (2S) KS HFAG 0.718 0.090 0.033 PRD 77, 091103(R) ICHEP 2008 0 Average 0.671 ± 0.024 -0.2 CP = –1 Raw AsymmetryRaw Asymmetry HFAG 0 -0.4 B → (J/ψ,ψ(2S),χc1,ηc)KS 0.5 0.6 0.7 0.8 300 → – HFAG estimated b ccs C ICHEP 2008 CP PRELIMINARY B 0 tags background 200 contribution BaBar 0.026 ± 0.020 ± 0.016 B 0 tags ICHEP 2008 preliminary ψ 0 ± ± 100 Belle J/ K -0.018 0.021 0.014 PRL 98 (2007) 031802 Events / ( 0.4 ps ) Events / ( 0.4 ps ) ψ ± ± Belle (2S) KS -0.039 0.069 0.049 PRD 77, 091103(R) 0.4 Average 0.005 ± 0.020 0.2 HFAG 0 -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 -0.2 CP = +1 No evidence for Direct CP violation in b→ccs Raw AsymmetryRaw Asymmetry 0 -0.4 B → J/ψ KL 0 0 raw asymmetry NB () − NB () as function of ∆t -5 0 5 0 0 ∆t (ps) NB()+ NB() SSI 2008: New Results on Heavy Quarks from BABAR Alexandre Telnov (Princeton), August 5, 2008 13 Decays dominated by gluonic penguins: 0 0 0 + − 0 B → η′K , φK , K K KS , π KS, ωKS , f0KS,etc.
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