CP Violation Studies in B Decays

Transcription

1 Violation Stuies in B Decays Vivek Sharma University of California San Diego vsharma@ucs.eu Ringberg Phenomenology Workshop on Heavy Flavors : Rottach-Egern, Germany 23

2 Special Thanks! Gautier Hamel e Monchenault Gabriella Sciolla Shahram Rahatlou H. Sagawa I have rawn heavily from their recent talk(s) at FP 2, APS 3, Morion 3, CKM 3

3 The Roa Map For Unerstaning Violation in B Decays Reminer : Promising ways to look for New Physics in B Decays measure/constrain the other 2 angles Im (,) Ru γ ( ρ,η) α UT Rt β R c ( 1, ) measure sin2β in several ecays sensitive to ifferent short-istance physics Re On the roa to γ A ream for now (See Fleischer s talk) improve UT sie measurements (Discusse this yesteray)

4 Asymmetry Measurements at Asymmetric B Factory : in Picture βγ Υ(4S) =.55 z µ Distinguish B an B «Flavor Tag Tag» - e Υ ( 4s) + e B tag Κ B B Coherent BB pair z t < βγ > c B rec z - µ K s - π + µ B J/ψ K ss B π+ π -- B ΦK...etc. + π

5 Asymmetry in B Decays : Notation 2iβ ~ e t= B B mixing ecay A f A f t f (η f ) A N ( B ( t) f) N ( B ( t) ( t) = N ( B ( t) f ) + N ( B ( t) = C f cos( mt) + S f sin( mt) f f ) ) C f = 1 1+ λ λ f f 2 2 S f = 2Imλ 1+ λ f f 2 q = A f λf ηf p A f Scenario 1 :Only one amplitue contributes: A (t) = - (Im λ) sin( mt) Im λ=sin2β, sin2α, etc Scenario 2 :More than one amplitue contributes both sin an cos terms present - S f : epens on Imλ sensitive to UT angles - C f : epens on λ, irect

6 Data Samples For Sin2β Stuies: Babar Samples of B ecays to flavor-specific final states Note: charge conjugate ecays are implie, unless specifie Nov June 22 ata 82 fb 1 on-peak 88 million BB pairs energy-substitute mass energy ifference before tagging an vertexing cuts Samples of B ecays to -eigenstates with charmonium (not shown) = 1 = +1 mixe angular analysis (not shown)

7 Textbook Example of Violation in the B System 22 leptontagge events Select events with a B caniate reconstructe into a -eigenstate containing a Charmonium meson an a K-short e.g. Require the presence of a fast lepton (e or µ) in the rest of the event Split the event sample accoring to the charge of the lepton (call B-tag the sample with positively-charge leptons, an Bbar-tag the other sample) Plot the proper time ifference t between the two ecays (euce from the istance between the two vertices along the boost axis) Violation in the B system is not a small effect! Interpret the observe timeepenent asymmetry in terms of Violation amplitue sin2β although ~9 million Y(4S) ecays neee!

8 Fits to the Proper time ifference Spectrum (all flavourtags) Unbinne maximum likelihoo fit to t istribution =-1 =+1 sin(2β) =.741 ±.67 stat ±.34 syst

9 Belle: Violation in b ccs Transition sin2φ 1 =.719 ±.74(stat) ±.35(syst) B f B 78 fb 1 N N B B + N N B B vs. t

10 Measurement of sin2β Babar This measurement is statistics limite at least 1 inverse attobarn neee to reach the level of systematic errors main systematic errors: knowlege of mis-tagging probabilities an time resolution function systematics inclue possible subtle effects ue to QM interference in the ecays of the two B mesons Note: 1 inverse attobarn 1 times present statistics Some (excellent) assumptions are usually mae in such analyses irect violation in J/ψ K S -like ecays is negligible J/ψ K S an J/ψ K L measure the same angle β the two neutral B mass eigenstates have same lifetime inirect violation in BB mixing can be neglecte T is an exact symmetry Phys. Rev. Lett. 89 (22) 2182 Experimental Focus now: start testing these assumptions (I will be very brief about this nothing unusual foun)

11 Search for Direct V in B J/ψ K - In SM: expect very little irect violation B b W Dominant iagram: color-suppresse tree c c s J/ ψ K B b g t,c,u W c c s Gluonic penguin iagam J/ψ K Experimentally No funamental way to istinguish between irect V an inirect V in mixing from the measurement of λ Stuy V for isopsin-relate charge moe To be upate with more statistics 2.7 fb 1 ~13 caniates Phys. Rev. D-RC 65 (21)

12 B b W Coul (sin2β)j/ψk s an (sin2β)j/ψk L Differ? In the absence of c c s J/ ψ How goo is the relation? K t,c,u inirect V in K mixing: negligible only possible effect: wrong-flavor ecays s s mixing no possible interference between an K purity 96% new preliminary result B b? c c J/ψ s K, K no such thing in SM! From time-epenent rates, measure: no sizable eviation from (SM expectation) Grossman, Kagan & Ligeti Phys. Lett. B538 (22) 327

13 Sin2β in other moes: Β φk beam energysubstitute mass ~175 events KK mass ~5 events B Pure penguin ecay, therefore potentially a place to look for New Physics Branching fractions an A b u, W g internal penguin B b u, g t,c,u W flavor-singlet penguin s s s u, s s s u, φ φ K K φ helicity new results with 89 million BB pairs woul be enhance in case of large FS rescattering

14 Time-Depenent Asymmetry: B φk S In SM, expect Sample Results Assuming no irect V Correlation: 7% C= Gooness-of-fit: 23% Fit on control sample (charge ecays) (expect zero) new results (supercee ICHEP22) 84 million BB pairs

15 Time-Depenent Asymmetry B η K S mostly? compatible with isospin-symmetry Results prelim. results with 89 million BB pairs to be submitte to PRL If non-sss contribution negligible, expect

16 Time-Depenent Asymmetry B J/ψπ B b W c c tree: color- an Cabibbo-suppresse J/ ψ π B b g t,c,u W c c J/ψ π penguin: competing weak phase? If penguin contribution negligible Sample Results prelim. result with 89 million BB pairs submitte to PRL

17 Sample B D + D B b W c c Cabibbo-suppresse tree ( ) D D ( )+ B b W u,c,t g b penguin c c D ( ) ( )+ D Results (Note: non- moes) time-integrate asymmetry If penguins are negligible new result with 89 million BB pairs submitte to PRL

18 B D + D Sample (before flavor-tagging) Vector-Vector ecay (L=,1,2) possible mix of = +1 an = 1 Transversity analysis mostly -even efine -even parameter If penguin contribution negligible Results

19 Putting it all together Theorist! Warning : Prospects for Ambulance chasing ahea!

20 .741 Summary of sin2β Results from BaBar C sin2β reference sin2β pure penguin mostly penguin? color- & CKM-suppr tree competing penguin CKM-suppresse tree small penguin pollution All alternate BABAR measurements agree with the reference sin2β within two stanar eviations, or better but consistently on the low sie

21 Average of Measurements of sin2β From Belle & BaBar Golen moe 7% measurement

22 B b B ππ/kπ & Quest for α W u u π, ρ π +, ρ + B Simultaneous ππ/kπ analysis penguins cannot be neglecte b W u,c,t g c c π, ρ π +, ρ + final results with 89 million BB pairs DIRC Phys. Rev. Lett. 89 (22) Note: signal-enriche plots after optimize cut on likelihoo ratio, with projection of fitte likelihoo superimpose Events per 2 MeV/c (a) Events per 1 MeV (b) Events per 2 MeV/c (c) Events per 1 MeV () continuum GeV/c 2 m ES GeV E continuum GeV/c 2 m ES GeV E

23 Asymmetry in Β π + π T = Tree P = Penguin u b W V ub u u b V tb W g * V t u Significant contribution from both iagrams: P/T ~ 1/3 from Br(B Kπ)/Br(B ππ) A N ( B ( t) f) N ( B ( t) f) t) = = C cos( mt) S sin( mt) ππ + ππ N( B ( t) f ) + N( B ( t) f ) ( S ππ sin2α eff relate to angle α through isospin analysis C ππ irect violation Grossman Quinn : α α < C.L. eff

24 Babar: Time-Depenent Asymmetry: B π + π A N( B ( t) f) N( B ( t) f) t) = = C cos( mt) S sin( mt) ππ + ππ N( B ( t) f ) + N( B ( t) f ) ( N ππ =157 ± 2 2 (a) B tags Events / 1 ps 2 (b) B tags A ππ / 2 ps (c) S C ππ ππ =.2 ±.34 ±. 5 =.3 ±.25 ± t (ps) BABAR No asymmetry seen in B π + π

25 Belle: B π + π Reconstruction JPS 3 Mass Energy ifference from expecte value ( GeV if signal) B ππ+kπ B ππ B Kπ 76 B π + π caniates in signal region Number of expecte signal is

26 Belle: Asymmetry in B π + π 78 fb 1 B B + π π + π π S A = 1.23 ± = C =+.77 ±.27 ±.8 78 φ 95% C.L. When fixe S = an A =, the probability to observe such large violation is less than.1%. K. Abe et al. [Belle Collaboration], submitte to Phys. Rev. D, arxiv:hep-ex/

27 Belle Asymmetry Fits for C & S : B π + π aaaaa

28 Belle : Confience Region

29 Constraints on φ 2 : Βelle

30 Constraints on φ 2 : Βelle (Sagawa, KEK3)

31 BaBar: B ρ ± π an B ρ ± Κ Relate to the angle α Compare to B ππ: Higer BF: B(B ρπ) ~ 4 x B(B ππ) Smaller penguins expecte b but challenging analysis Not a eigenstate 4 configurations: B ρ ± π, B ρ ± π 3π final state killer combinatorial backgrouns Analysis strategy Pseuo two-boy analysis avoi interference regions of Dalitz plot Continuum backgroun suppresse by NN Simultaneous fit for ρ + π an ρ + Κ W α u u ρ,π π +,ρ +

32 B ρ ± π an B ρ ± Κ Combine Maximum Likelihoo fit measures: BF(B ρπ)= (22.6±1.8±2.2) 1-6 BF(B ρκ)= (7.3±1.3±1.3) 1-6 Inication for small penguins ρπ ρk an 6 other parameters relate to : A, A, C ρπ, S ρπ, C ρπ, S ρπ N(ρπ) = 428 ± 34 N(ρΚ) = 12 ± 2 BaBar Preliminary

33 Time-(in)epenent Asymmetry : B ρ ± π (Κ ) Time integrate irect : K A ρ =.28 ±.17 ±.8 =.18 ±.8 ±. 3 ρπ A Time epenent : C ρπ =.36 ±.18 ± BaBar Preliminary.4 -- B backg. -- all backg. S ρπ =.19 ±.24 ±.3 BaBar Preliminary First Asymmetry step towars between a measurement rates: + of C ρπ α in = B ρπ -.19ecays. ±.4 Full Dalitz S = analysis.15 ± with.25 more ±.3 ata ρπ

34 Prospects for γ & sin2β+γ Μeasurements Difficult now because either asymmetry is very small or large ata sample or theoretical prejuice is require Β ± D K ± Theoretically clean (Gronau & Wyler, Dunietz 1991 saga) Interference between b u (cs) an b c (us) Small accessible Branching Fractions ~ 1-7 B D (*) + π, ρ, a 1 Theoretically clean measurement of 2β+γ Interference between b u (c) an b c (u) Tiny, tiny asymmetries (in progress) B D (*) K (*) : observation of large rate by Belle B ππ, Kπ Interference between penguin an tree iagrams Take ratios of Br s to eliminate epenence on strong phases Moel epenent - relies on assumptions of factorization, SU(3) Leave it to theorists to issect this

35 Progress in B ± D K± γ Isospin analysis 2 A(B + D + K + ) 2A( B + D K ) - A(B + D K + 2 A(B K ) ) + 2 ( - A B DK ) 2γ A(B - D K - ) where D D ± = D are eigenstates : ± D 2 A(B + Measurements: D K + ) = - A(B D K - ) BaBar Preliminary R R A BF ( B BF ( B D D = K π ) ) = (8.31 ±.35 ±.2 )% + + BF ( B D K ) + BF ( B D K ) + BF ( B D π ) + BF ( B D π ) = + BF ( B BF ( B D K ) ) BF ( B ( B + = + + D K + BF D K D + K ) ) = = (8.8.6 ± 1.6 ± ±.17.5)% ±.6

36 Summary of V Stuies Violation in B Decays establishe Sin2β in golen moe is a ~7% measurement Disagreement (>2σ) between Belle & Babar on V in B->pi pi Some tantalizing results (B ΦΚ)! All V searches are statistics limite Hope to get 5 fb -1 each by 26