each pT (Υ) bin calculate: σ(χb→Υγ) σ(Υ) = Nχb→Υγ NΥ × Υ χb→Υγ = Nχb→Υγ NΥ × 1 reco γ Calculate for each Υ(nS), n = 1, 2, 3 and χb(mP), m = 1, 2, 3 Get N from ﬁts: NΥ from m(µ+µ−) and Nχb→Υγ from [m(µ+µ−γ) − m(µ+µ−)] (for better resolution) Compute eﬃciency from Monte-Carlo simulation Luminosity = 1015 ± 35pb−1, data collected in year 2011. Sasha Mazurov (University of Ferrara) Update on χb studies 19 December 2012 3 / 11
on top of RooFit toolkit and unbinned maximum likelihood ﬁts were performed. For NΥ: invariant mass Signal: sum of 3 Crystal Ball functions Background: exponential function. For Nχb→Υ(1S)γ : mass diﬀerence Signal: 3 Gauss functions Background: √ x × e−τx × (c1 + a1x + a2x2) + e−τx × (c2 + a3x + a4x2) (not enough resolution to separate χb(0,1,2) ) Sasha Mazurov (University of Ferrara) Update on χb studies 19 December 2012 4 / 11
Background subtraction We can reduce the background by tightening cut on pT (γ) Can make a precise measurement of mχb(3P) Sasha Mazurov (University of Ferrara) Update on χb studies 19 December 2012 9 / 11
Studying the production of χb particles in LHCb, through the reconstruction of χb → Υγ decays, with the Υ decaying to µ+µ−. 2 Determined χb → Υ(1S)γ yields as a function of pT (Υ(1S)). 3 Measured mass of the χb(3P) state, which has been recently observed at LHC and TeVatron. 4 Finalize analysis (eﬃciencies, other decays,...). Sasha Mazurov (University of Ferrara) Update on χb studies 19 December 2012 11 / 11