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Measurement of David Hutchcroft, University of Liverpool BEACH’06

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David Hutchcroft, BEACH’062 CKM angles CKM matrix is a unitary matrix that connects the mass eigenstates and weak eigenstates Elements appear in weak current interactions V ud V us V ub V cd V cs V cb V td V ts V tb 1 - c 2 c A c 3 ( - i ) = - c 1 - c 2 /2 A c 2 A c 3 ( 1 - - i ) - A c 2 1 V CKM = + O( c 4 ) [ c = sin c ] CP violation | V td | e -i | V ub | e -i A unitarity triangle : V * ub V ud + V * cb V cd + V * tb V td = 0 Wolfenstein parameterisation

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David Hutchcroft, BEACH’063 B Factories KEKII Both are asymmetric e + e − colliders and 4 detectors Use e + e − annihilation at (4s) resonance to make BB pairs Beam asymmetry means BB system has a relativisticly extended lifetime BaBar has collected 352 fb -1 and Belle has collected 610fb -1 1fb -1 ~ 1.1 million BB pairs

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David Hutchcroft, BEACH’064 CP violation Direct CP violation : Br(B 0 →f) ≠ Br(B 0 →f) Time integrated effect, event counting Indirect CP violation from mixing and decay interference Time dependant effect Relevant for CKM angle measurements Use coherence between B 0 and B 0 to decide what meson actually decayed Tag other side B decay Also measure t between decays t 0 tag B + e e 0 CP B t=0 K e + (4S) -

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David Hutchcroft, BEACH’065 Where B 0 is the physical state when it decays Indirect CP violationS ≠ 0 Direct CP violation C ≠ 0 Need to tag flavour of B using other B meson Must understand tag resolution and dilution [BaBar C = −A cp Belle]

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David Hutchcroft, BEACH’066 Tree decay B 0 B 0 mixing Penguin decay Decays depending on Tree decays of B 0 and B 0 to two charmless mesons depend on Trees onlyTrees + Penguins strong phase

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David Hutchcroft, BEACH’067 Separating trees and penguins Use an isospin relation between similar decays to measure the amount of each type of decay Used to set a limit on eff eff Gronau-London: PRL65, 3381 (1990) etc Need to measure all of the related decays of Penguin contribution depends on Br( ) Charged B decay is tree only

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David Hutchcroft, BEACH’068 Selecting B decays Backgrounds are predominantly non resonant annihilation so reconstruct B mesons Variables Other backgrounds are similar B decays Need to model all backgrounds in the fit Use unbinned maximum likelihood fit where E B * is the CM energy of the B meson The mass of the B system using the initial beam energy constraint, p * B is the CM frame B momentum BaBar m ES ≡ M bc Belle

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David Hutchcroft, BEACH’069 B0→B0→ 275×10 6 B pairs 666 43 signal events 227×10 6 B pairs 467 33 signal events Phys.Rev.Lett. 95 (2005) Phys.Rev.Lett. 95 (2005)

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David Hutchcroft, BEACH’0610 B0→B0→ S = −0.67±0.16±0.06 C = −0.56±0.12±0.06 S = −0.30±0.17±0.03 C = −0.09±0.15±0.04 So two comparable measurements of S = sin(2 eff ) Measurements of direct CP asymmetry less compatible

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David Hutchcroft, BEACH’0611 Using isospin in system using 253fb -1 using 227 x 10 6 BB PRL 94, (2005) PRL 94, (2005) Precision measurement of not possible with current stats.

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David Hutchcroft, BEACH’0612 B → ρρ Vector/Vector meson final state: both CP odd and even final states S, P, D wave components Need angular analysis to determine CP content of decay ρρ is almost 100% longitudinally polarised (CP even) Polarisation

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David Hutchcroft, BEACH’0613 B0→B0→ In system the amount of neutral decays is small Measure B 0 → events in 227 x 10 6 BB events Br < 1.1 x at 90% CL. Isospin triangle for is flattened compared to Phys.Rev.Lett. 94 (2005) eff

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David Hutchcroft, BEACH’0614 B±→±B±→± New result with 231 x 10 6 BB events Previous BaBar/Belle HFAG average hep−ex/ Better match to isospin model Smaller uncertainty on | eff − compared mode

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David Hutchcroft, BEACH’0615 B 0 → BaBar (227 x 10 6 BB)Belle (275 x 10 6 BB) PRL 95, (2005) PRL 96, (2006)

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David Hutchcroft, BEACH’0616 B 0 → analysis B 0 → → − is not a CP eigenstate 6 decays to disentangle: Tried by BaBar and Belle for just ± phase space Did not set limits on Can use a Dalitz plot analysis to get from decays Snyder & Quinn: Phys. Rev. D48, 2139 (1993) Convert to a square Dalitz plot Mostly resonant decays Move signal away from edges Simplifies analysis MC events

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David Hutchcroft, BEACH’0617 B 0 → Dalitz plot analysis Dalitz plot analysis yields CP asymmetries and strong phases of decays Using 213 x 10 6 BB events hep-ex/ m’ and ’ are variables in a square Daltiz plot 1184 ± 58 B → Signal events Blue bands are different types of backgrounds

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David Hutchcroft, BEACH’0618 Conclusion Combined constraints on gives single best measurement resolves 2-fold ambiguity from World Average: Global CKM Fit (w/o ): msms

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