N  for 2012 Zhiyong Wang May, 12,2015 Charmonium group meeting 1

Outline Motivation How? Data set Event selection Some plots Background Systematic uncertainty 2

Motivation N ψ’ is important in all ψ′ analyses, including studies both of the direct decays of the ψ′, as well as its daughters, χ cJ, h c, and η c. Its precision will have a direct impact on the measurements of itself and its daugthers. 3

How ？ We use the inclusive hadronic channel. Large branching ratio: B(  hadron)~98% High precision:  B/B=0.13%. f=Lum. ψ’ /Lum. off-resonance × s off-resonance / Unlike σ(e + e −  e + e − ， μ + μ − ) ， σ(e + e −  +  − ) doesn’t vary with 1/s

Data Set  data run , 803 runs, ~510 pb -1. Off-resonance data: 3.55 GeV( tau scan) run , 184runs, 23.5 pb -1 Inclusive MC: 363.7M Boss Version: 664p03 5

Event selection Track level Charged Polar angle |cos  |<0.93 Vertex: |Vz|<10.0 cm,|Vr|<1.0 cm Neutral E>25 MeV for barrel E>50 MeV for End-cap Event level Ngood>2, no limit N good =2, P 0.4 N good =1, at least  0, E visible /E cm >0.4 E visible = sum of all track energy, taking all charged track as pion 6

How to tag the signal events,V z One event, one entry Signal region Sideband region 7

Some distributions N good =2 N good =1 Bhabha MC) Inclusive MC 8 e + e −  e + e − +X ( X=lepton pair, hadrons)

Some comparisons (after removing sideband and QED contributions) 9

2009 data 2012 data Charged multiplicity 10

E visible N good >2 N good =2 N good =1all N good >2 N good =2 N good =1 all

cos  N good >2N good =2 N good =1 all N good >2 N good =2 N good =1 all

Neutral multiplicity N good >2 N good =2 N good =1 N good >2 N good =2 N good =1 all

Preliminary result 2012 data, N obs = M Inclusive MC, N obs = M, N gen = M 2009, 3.65 GeV, N obs = 2.226M 2012, tau scan, GeV, N obs = 1.325M Lum. Normalized factor,f= (Bhabha), 20.56(e+e − ϒϒ ) 14

Systematic error (1) Polar angle difference between |cos  |<0.93 and |cos  |<0.8 Background contamination With and without E vis /E cm cut. 0.09% Have nothing to do with N good >2 Choice of sideband region Sideband region: 6-10cm  7-11cm. Signal region Sideband region 15

N obs determination The difference between counting and fitting. Vertex selection 1cm-2cm Momentum and opening angle 0.04% (part of data). Only for Ngood=2 events. Scale factor negligible. The difference between different continuum data (09 GeV, 12 tau Systematic error (2) 16 N = signal region – sideband region N = Fit with double Gaussian

0-prong (N good =0) events (~2.5% according to topo. ) 0-prong contains the known decay modes, Pure neutral process (e.g. γπ 0 π 0,γηη )<1%. The difference between data and inclusive MC is 10%. 10×1%~0.1% Systematic error (3) 17 Normalized continuum background withτ-can data

Tracking Supposing that there is a difference of  (  =1%,or 2%) between data and MC per track. The probability for a N-prong event to change a 0-prong events can be expressed: P =  N negligible Systematic error (3) 18 Assuming 1% Assuming 2%

charged multiplicity N chrg N evt (×10 5 ) eff. Matrix > > N_data (unfolded) = N 0 +N 2 +N 4 +N 8 +N >10 =341.1M The difference between direct calculation and unfolded is Systematic error (3) 19

Event Start Time (EST) In 09 data, we cite Guan Yinhui’s work. Studying by control sample J/  3 ,     pp, and     J/ ,J/  l  l . ~0.1% between data and MC. Trigger efficiency Cite Nik&Zhuk’s results. Negligible. B(  hadron) From PDG, 0.13%. Systematic error (4) 20

Systematic uncertainty (%) Background contamination0.09 N obs determination0.30 Choice of sideband region0.26 Vertex selection0.21 Momentum and opening angle0.04 Scaling factor (f)negligible 0-prong events0.1 TrackingNegligible Charged multiplicity0.19%  0 mass 0.05 Trigger efficiencyNegligible B(  hadron) 0.13 Total data:0.81% (CPC, 37(6), (2013) 21

Backup 22

Ngood=1 Ngood=2 Ngood>2 Ngood=1 Ngood=2 Ngood>2 23

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