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Beauty2005, 6/20/05, R.Itoh1 Measurements of 1 ( ) at Belle Ryosuke Itoh, KEK representing The Belle Collabration Beauty 2005 Assisi, Perugia, Italy 6/20/2005
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Beauty2005, 6/20/05, R.Itoh2 Outline 1. Introduction 2. Experimental Apparatus 3. Measurement of 1 in b c transitions 4. Measurement of 1 in b s transitions 5. Future plan of 1 measurements 6. Summary
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Beauty2005, 6/20/05, R.Itoh3 1. Introduction - The goal of B-factory experiment is the precise determination of the unitarity triangle 11 22 33 Unitarity Triangle V cd V cb * V ud V ub * V td V tb * sin2 1 non 0 value (CPV) is established in b c transitions. precision measurement as a reference Probing new physics effects in FCNC ( b s penguin) by comparing measured sin2 1 with the reference from b c. CP Violation ≡ non-zero angle Bd0Bd0 Bd0Bd0 f CP Bd0Bd0 Bd0Bd0 22 = Mixing induced CP Violation - sin2 1 0 SM
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Beauty2005, 6/20/05, R.Itoh4 b c transition _ d b _ c c s d _ w B0B0 J/ K0K0 b s transition d b _ _ s s s d _ gt B0B0 K0K0 , ’... w - Tree diagram dominates. - Negligible uncertainty from Penguins. sin2 1 (b s) : Sensitive probe of New Physics - Penguin diagram dominates. - In SM, sin2 1 is expected to be the same as that of b c. New coupling New Phase sin2 1 (b c) sin2 1 (b s) '.. +
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Beauty2005, 6/20/05, R.Itoh5 Measurement Technique - B 0 and B 0 mesons are produced from (4S) decay at B-factories. - To measure A CP, we need to know decay time difference ( t) of two B 0 mesons with the flavor of one tagged. Asymmetric collision e - (8.0GeV)e + (3.5GeV) B0B0 S B0B0 J/ l-l- KSKS lepton kaon charge flavor
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Beauty2005, 6/20/05, R.Itoh6 Reconstruction of B meson Energy difference: energy of B 0 candidate expected energy of B 0 Beam Constrained Mass: momentum of B 0 candidate - Performed using special kinematics on (4S)
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Beauty2005, 6/20/05, R.Itoh7 2. Experimental Setup Superconducti ng cavities (HER) e- e+ ARES copper cavities (LER) 8 GeV e- 3.5 GeV e+ Linac e+ target ARES copper cavities (HER) Belle detector KEKB B-Factory TRISTAN tunnel K L detector 14/15 layer RPC+Fe Electromagnetic Calorimeter CsI(Tl) 16X 0 Aerogel Cherenkov Counter n = 1.015~1.030 Si Vertex Detector 4 layer DSSD TOF counter 8.0 GeV e 3.5 GeV e + Central Drift Chamber Tracking + dE/dx 50-layers + He/C 2 H 4 KEKB Accelerator Belle Detector
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Beauty2005, 6/20/05, R.Itoh8 L peak = 1.58x10 34 cm -2 sec -1 (Design = 1x10 34 cm -2 sec -1 ) Ldt/24hrs = 1182.1/pb Ldt = 459/fb (by Jun. 15) “ continuous injection” ~30% increase
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Beauty2005, 6/20/05, R.Itoh9 3. Measurement of 1 in b c transitions poor flavor tag good flavor tag q CP =+1 q CP =-1 Data Sample : 140/fb; 4347 signals PRD 71, 072003 (2005) sin2 = 0.728 0.056 (stat) 0.023 (syst) | CP | = 1.007 0.041 (stat) 0.023 (syst) consistent with no-DCPV | CP |=1 A=0 J/ Ks only (253/fb) sin2 1 (J K s )=0.666±0.046
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Beauty2005, 6/20/05, R.Itoh10 Constraint on Unitarity Triangle (Belle+BaBar, as of CKM2005) * Ambiguity in 1 from sin2 1 value: sin2 1 = 0.726 1 = 23.3 o or 66.6 o * Measurement of cos2 1 can resolve the two-fold ambiguity
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Beauty2005, 6/20/05, R.Itoh11 Resolving 1 ambiguity : B 0 J/ K* decays * : +1 for B 0, -1 for B 0 * 1 : CP violating angle ( ) * A 0, A //, A T : decay amplitudes * m, B : mixing parameter, B lifetime Transversity Basis l+l+ J/ tr tr x z y K J -rest frame K*-rest frame l-l- * Time-dependent full angular analysis for decay products of B 0 J/ (l + l - )K*(K s 0 ) hep-ex/0504030 (PRL)
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Beauty2005, 6/20/05, R.Itoh12 Step 1: Measurement of decay amplitudes (253/fb) * No direct CPV observed - Evidence of final state interactions in phases * Time-integrated angular analysis for B 0 J/ K*(K + - ) Note: Phases are chosen to conserve s quark helicity arg(A 0 ) = 0 (def.)
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Beauty2005, 6/20/05, R.Itoh13 Step2: Simultaneous determination of sin2 1 and cos2 1 - Fix decay amplitudes to measured values. - Fit inputs : t, flavor, wrong tag fraction, E, M bc (standard CP fit) + three transversity angles - Free parameters : sin2 1, cos2 1 Results: sin2 1 = 0.24 ± 0.31 ± 0.05 cos2 1 = +0.56 ± 0.79 ± 0.11 +0.87 ± 0.74 ± 0.12 (sin2 1 is fixed at 0.726) * Cannot exclude the other choice with a high confidence level. - Statistical error is still large (only ~2 from the other choice). - Ambiguity in the choice of phases in decay amplitudes. study to resolve the ambiguity is now going on. Consistent with a choice of 1 = 23.3 o (Sample : 363 events)
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Beauty2005, 6/20/05, R.Itoh14 4. Measurement of 1 in b s transition 4. Measurement of 1 in b s transition(253/fb) a) B 0 K 0 Nsig = 139 14 purity = 0.63 s: K + K Ks Events/(50MeV/c) Nsig=36 15 purity = 0.17 L : K + K K L w/ ECL or KLM Good tags Poor tags S = 0.73 fit 0 “sin2 1 ”= 0.06 0.33 0.09 A = 0.08 0.22 0.09 “sin2 1 ”= 0.06 0.33 0.09 A = 0.08 0.22 0.09
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Beauty2005, 6/20/05, R.Itoh15 b) B 0 KsKsKs Poor tags Good tags -S = 0.73 fit 16 3918 21 2 ( ( 8816750117total 7212832 96 3 ( N sig total w/o VTX w/ VTX “sin2 1 ”= 1.26 0.68 0.18 A = 0.54 0.34 0.08
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Beauty2005, 6/20/05, R.Itoh16 c) B 0 Ks Raw Asymmetry Good tags “sin2 1 ” = 0.75 0.64 A = 0.26 0.48 0.15 0.13 0.16 Nsig = 31 7 (7.3 ) purity = 0.56
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Beauty2005, 6/20/05, R.Itoh17 d) B 0 K s 0 Ks track IP profile B vertex Vertexing by Ks only Ks 0 Nsig=168 18 purity 0.55 “sin2 1 ” = +0.30 0.59 0.11 A = 0.12 0.20 0.07 “sin2 1 ” = +0.30 0.59 0.11 A = 0.12 0.20 0.07 Validated by J/ Ks (use Ks only) Good tags S = 0.73 fit Raw Asymmetry (+low purity: Nsig=83(0.17))
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Beauty2005, 6/20/05, R.Itoh18 e) Other modes Nsig = 399 28 purity = 0.56 Nsig = 512 27 purity = 0.61 K+K-KSK+K-KS ’K S Nsig = 94 14 purity = 0.53 f 0 (980)K S S = 0.73 fit “sin2 1 ” = +0.49 0.25 A = - 0.08 0.14 A = - 0.08 0.14 “sin2 1 ” = +0.65 0.18 A = - 0.19 0.12 A = - 0.19 0.12 good tags “sin2 1 ” = -0.47 0.42 A = -0.39 0.28 A = -0.39 0.28 good tags
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Beauty2005, 6/20/05, R.Itoh19 Summary of sin2 1 eff (b s) measured by Belle - sin2 1 (b c) sin2 1 (b s) ~ 2.4 difference - Averaged with BaBar's measurements ~3.8 difference sin2 1 eff (b s) = 0.39 ± 0.11 (ave.) New Physics????? - Need more statistics (O(100) times) to confirm the difference * Measuremet by K 0 only (theoretically clean) - Possibility of small discrepancies within the SM framework * Rescattering * Contamination of b u tree in some modes will be updated at LP05 with 350/fb (with 253/fb)
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Beauty2005, 6/20/05, R.Itoh20 5. Future plan of 1 measurements - Statistics! Statistics! Statistics! for more precise measurements - Current luminosity (1.5x10 34 /cm 2 /sec) is not enough to obtain required statistics in a reasonable time. => need ~ 5 x 10 35 /cm 2 /sec Interaction Region Crab crossing =30mrad. y*=3mm New QCS Linac upgrade More RF power Damping ring New Beam pipe Increase beam currents 1.6 A (LER) / 1.2 A (HER) → 9.6 A (LER) / 4.1 A (HER) Smaller y * 6 mm→3 mm Increase y 0.05→0.28(W-S) L=3.5x10 35 cm -2 s -1 8GeV (e+, 4.1A) 3.5GeV (e-, 9.6A) SuperKEKB
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Beauty2005, 6/20/05, R.Itoh21 KEKB Upgrade Scenario ~10 10 "clean” BB/year !! & similar number of + - L peak = 1.5 10 34 cm -2 s -1 L tot = 450fb -1 (June, 05) 1.5x10 34 450 fb -1 5x10 34 ~1 ab -1 5x10 35 ~10 ab -1 L peak (cm -2 s - 1 ) L int Crab cavities Major upgrade of KEKB & Belle detector (>1yr shutdown) world records !
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Beauty2005, 6/20/05, R.Itoh22 Physics Reach at SuperKEKB SuperKEKB5ab -1 50ab -1 LHCb 2fb -1 Physics at Super B Factory (hep-ex/0406071) CKM w/ FCNC CPV (b s) and rich physics SuperB LHCb complementary
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Beauty2005, 6/20/05, R.Itoh23 6. Summary The CP parameter sin2 1 was measured by Belle for b c and b s transitions. The sin2 1 value measured for b c transition is sin2 1 (b c) = 0.728 0.056 (stat) 0.023 (syst). Trying to resolve two-fold ambiguity in 1 from sin2 1 using B 0 J/ K* decays. The result is consistent with the choice of 1 =22.3 o, however, the other choice cannot be excluded with present statistics. The average sin2 1 value for b s transition is sin2 1 (b s) = 0.39 0.11 (averaged by HFAG). More statistics is necessary to study the discrepancy. SuperKEKB
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Beauty2005, 6/20/05, R.Itoh24 Backup Slides
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Beauty2005, 6/20/05, R.Itoh25 The Belle Collaboration 13 countries, 57 institutes, ~400 members IHEP, Vienna ITEP Kanagawa U. KEK Korea U. Krakow Inst. of Nucl. Phys. Kyoto U. Kyungpook Nat’l U. EPF Lausanne Jozef Stefan Inst. / U. of Ljubljana / U. of Maribor U. of Melbourne Aomori U. BINP Chiba U. Chonnam Nat’l U. U. of Cincinnati Ewha Womans U. Frankfurt U. Gyeongsang Nat’l U. U. of Hawaii Hiroshima Tech. IHEP, Beijing IHEP, Moscow Nagoya U. Nara Women’s U. National Central U. Nat’l Kaoshiung Normal U. National Taiwan U. National United U. Nihon Dental College Niigata U. Osaka U. Osaka City U. Panjab U. Peking U. U. of Pittsburgh Princeton U. Riken Saga U. USTC Seoul National U. Shinshu U. Sungkyunkwan U. U. of Sydney Tata Institute Toho U. Tohoku U. Tohuku Gakuin U. U. of Tokyo Tokyo Inst. of Tech. Tokyo Metropolitan U. Tokyo U. of Agri. and Tech. Toyama Nat’l College U. of Tsukuba Utkal U. VPI Yonsei U.
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Beauty2005, 6/20/05, R.Itoh26 Procedure of CP fitting Flavor Tagging Vertex Reconstrunction Tag flavor : q Wrong tag fraction : Decay time difference: t Resolution parameters: , Event Reconstruction Bkg fraction :f BG CP eigenvalue: f Transversity angles (J/ K*) Maximum Likelihood Fit Mixing : m Lifetime : B Free parameters
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Beauty2005, 6/20/05, R.Itoh27 Tagging and t resolution parameters perfect tagging & time resolution observed mistagging & finite time resolution Wrong tagging fraction Resolution function R and w are determined from data using flavor specific decays B D (*)- +, +, a 1 + and J/ K *0 …
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Beauty2005, 6/20/05, R.Itoh28 Continuum Background Suppression BB - Continuum Bkg (~3×BB) Y (4S) _ Event Shape (Jet-like) (Spherical) candidate B 0 Z θBθB e-e- e+e+ B meson continuum cosθ B 10 Br(b s) = 10 -5 ~10 -6 for each modes
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Beauty2005, 6/20/05, R.Itoh29 Vertex reconstruction w/ K S trajectory Sufficient resolution obtained if SVT has hits of K S tracks Ks B vertex K+K+ K-K- electro n (8GeV ) positro n (3.5Ge V) (4S) resonan ce B1B1 B2B2 ++ -- K+K+ -- Ks trajectory IP profile B vertex Reconstruct B K S X(Y)vertex using K s trajectory and boost trajectory or IP profile Good tags +0.68 0.10 +0.65 0.05 S +0.02 0.04 +0.01 0.04 A w/ K S w/ J/ Validated with J/ Ks: w/ K S vtx w/o J/ vtx
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Beauty2005, 6/20/05, R.Itoh30 Theoretical uncertainties of “ sin2 1 ” ● amount of possible discrepancies Δsin2β have been evaluated for some modes: – model independent upper limits based on SU(3) flavor symmetry and measured b d,sqq B.R. ● [Grossman et al,Phys Rev D58; Grossman et al., Phys Rev D68; Gronau, Rosner, Phys.Lett. B564; Gronau et al., Phys.Lett.B579; Gronau, at al. Phys.Lett.B596; Chiang at al., Phys.Rev.D70] – estimates of deviations based on QCD-motivated specific models; some have difficulties to reconcile with measured B.R. (errors summed in quadrature) ● 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 2xΔsin2β also shown: naive upper limit based on final state quark content, CKM (λ 2 ) and loop/tree (= 0.2-0.3) suppression factors [Kirkby,Nir, Phys. Lett. B592 (PDG review);Hoecker, hep-ex/0410069] Taken from talk slides by M.Morandin(INFN/Padoba) shown at Moriond EW (2005).
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Beauty2005, 6/20/05, R.Itoh31 K S /K L Results S = 0.00 0.33 A = 0.06 0.22 S = 2.0 A = 0.6 1.2 K L only K S only
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Beauty2005, 6/20/05, R.Itoh32 -even fraction in |K 0 K 0 > can be determined by |K S K S > system CP = 1 CP = odd CP = even Using isospin symmetry, CP component in B→K + K − K 0 S decay CP component in B→K + K − K 0 S decay
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Beauty2005, 6/20/05, R.Itoh33 Systematic errors on S +0.13 0.16 0.01 0.02 0.01 0.10 +0.01 0.10 0.07 0.04 0.01 Ks 0.10 <0.01 0.03 0.01 0.02 0.03 0.05 0.02 0.06 K* 0.08 <0.01 0.04 0.01 0.05 0.03 0.01 0.02 f 0 Ks 0.04 <0.01 0.02 0.01 0.03 <0.01 0.01 K + K - Ks 0.09 <0.01 0.01 <0.01 +0.08 0.06 0.01 0.04 0.01 K 0 <0.01 tag side interference 0.010.03fit bias 0.020.07signal fraction <0.010.02physics parameters <0.010.04background t shape 0.030.05resolution 0.04 0.01 ’ Ks 0.11TOTAL 0.01flavor tag 0.02VTX Ks 0 KKK S : effective sin2 1 0.17 for CP-even fraction
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