A study of the Kπ system Mikhail Kozyulin, (CERN, BINP) 1

Introduction In the latest Bs  J/ψK* paper the Kpi spectum was shown, but analysed only qualitatively S-wave mass lineshape is still not well understood We would like to have better control of the waves that can enter K* region 2 Some isobar test Some K-matrix test

Introduction In addition, a higher Kpi peak is clearly visible, but neither BR(branching rations) nor polarization fractions were reported Mass fit favoured K*2(1430) rather than K*0(1430). But difficult to prove or extract exact yield without angular analysis that separates spin My summer student project: Perform an angular study of the Kpi spectrum in Bd  J/psiKpi in order to see the actual mass shape of the different waves This will allow us to: Search for an Spin-2 signal  K*2 See the mass lineshape of the S-wave …. 3

Strategy Angular analysis in bins of Kpi mass. – MC test – data 4

MC Implemented RooFit model (in helicity basis) with S and P waves and tested in generator level. Good agreement with true values for the amplitudes (including As compatible with 0). 5

Angular acceptance

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Data 1. Fit in angular and B mass spectrum. Model=Bs+Bd+bkg, each Bs and Bd =Swave+Pwave. Acceptance with per event weights. 2. Cut in Bmass – M(Bd)+-20MeV 8 M(K*) MeV

Fit with S-,P-wave Blue: fit function Red: Bd Pink: background Black: Bs 9

Blue: fit function Red: Bd Pink: background Black: Bs 10 Fit with S-,P-wave

Construct the fit model using Urania’s tools Use Urania.Helicity to get symbolic pdf given the spin list for intermediate X  Kπ states : 0, 1, 2 Use Urania.RooInterfaces to create a RooFit C++ class out of the symbolic pdf op2 = D.RooClassGenerator(func, [x,y,z]+TransAmpModuli.values()+TransAmpPhases.values(),"RooB") op2.makePdf(integrable = kTRUE) op2.doIntegral(1,(x,-1,1)) ….. op2.doIntegral(7,(x,-1,1),(y,-1,1),(z,-Pi,Pi)) op2.overwrite()  We can use this procedure for higher and higher waves if necessary 11 Adding now the D wave …..

S - wave P - wave f L = 0 f L = 1 f L = 0.5 D - wave f L,2 = 0 f L,2 = 1 f L,2 = 0.5 Altogether 12

Fit with S-,P-,D-waves 13

P - wave f L = 0 f L = 1 f L =

15 P - wave f L = 0 f L = 1 f L = 0.5 S - wave

16 P - wave f L = 0 f L = 1 f L = 0.5 S - wave

D - wave f L,2 = 0 f L,2 = 1 f L,2 = 0.5 S - wave 17

D - wave f L,2 = 0 f L,2 = 1 f L,2 =

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Conclusion We have performed an angular analysis of Bd->J/ψKπ in bins of Kπ mass. Decided to neglect background. Angular acceptance maybe not very accurate (MC10, interpolated parameters,…) but hope is good enough to identify the dominant wave in each bin. Clear evidence of spin 2, favouring K*2(1430) instead of K*0(1430). S-wave seems to be the main amplitude in ( MeV), but small variation in phases causes big changes in wave shapes, probably interferences play a dominant role in that region. 24