BBººππ++ππ--: status of : status of analysisanalysis
Vitaliano CiulliRiccardo Ranieri
Nicolò Magini
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 2
Generated BGenerated Bººππ++ππ--
ACPsin(2α)
b -_ _
b
At least 1 μ
•ptμ>4 GeV/c
•lημl<2.6
At least 1 BBººππ++ππ--
•ptB>8 GeV/c
•lηπl<2.4
Hard interaction pt>10 GeV/c^
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 3
MC SignalMC Signal9196 events simulated (4384 digitized)
PYTHIA 6.152 CMSIM 122 ORCA 5.1.2 (oohit) [ORCA 5.1.2 (digi)]
Cross section σ=4622 fb
32.7% Gluon Splitting
20.6% Flavour Excitation
46.7% Pair Production
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 4
Decay reconstructionDecay reconstruction
ForwardKalmanFilter + ConnectionMachinept>0.8 GeV/c
lηl<2.4Well identified muonCombinatorial on other
opposite-charge tracks
lMBrec(GeV/c2)-5.2794l<1
? 50 MeV/c2 Resolution ?
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 5
BackgroundBackground
Br(BºK+π-) = (1.72±0.27)x10-5 4xBr(Bºπ+π-)
5.24 GeV/c2 mass peak 50 MeV/c2 resolution½ bkg
over signal S/B=1/2
Other Two-body decaysS/B=1/1
Estimation of Two-body BackgroundS/B1/3
CMS-TN 1994/328 CP Violation Study of the BBdd
ººππ++ππ-- decay for the Technical Proposal
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 6
More on BackgroundMore on BackgroundOfficial muon MC production http://cmssun4.pd.infn.it/~ugs/cms/hlt/prod2001_new.html
PYTHIA 6.152 CMSIM 121 ORCA 5.1.1 (oohit) ORCA 5.1.2 (digi)
dataset mu_MB1mu_pt4 (at least a true muon pt>4 GeV/c no pt cut)
Events: 106562 Lumi: 0.4071 nb-1
σ=262 μb
High lumi (=10 nb-1s-1) Rate =
10 nb-1s-1x262 μb= 2.62 MHz
^
Rate = 400 KHz
CMS-IN 2000/053 CMS-NOTE 2001/011
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 7
List of cutsList of cuts
Kinematic cuts: ptB>10 GeV/c
ptπ>5 GeV/c
I=ΣΔR<1(pt/ptB)<0.1
Vertex cuts: SIP=tIP/σIP>3
cos(Δα)>0.995χ2
vtx<10
Mass cut: lMBrec(GeV/c2)-5.29l<1x0.05
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 8
Some plotsSome plots
SIP=tIP/σIP>3ptB>10 GeV/c
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 9
Some numbers on Some numbers on signal…signal…
Cuts Nsim Eff. N(60 fb-1)
MC signal 4384 1 277320
Reco BBºº 3729 .851±.005 235900±1400
Kinematic 513 .117±.005 32500±1400
Vertex 322 .073±.003 20200±800
Mass 167 .038±.003 10500±800
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 10
……and backgroundand background
Cuts Nsim Eff. N(60 fb-1)
MC background
11993
1 16x1012
Fake BBºº 3767 .314±.005 (5.02±0.08)x1010
only
Kinematic12 (3.2±0.9)x10-3
only Vertex 1 (2.7-1.7+4.6)x10-
4
only Mass 178 .473±.035
K+V+M 0 (1.2-0.8+2.0)x10-
8
1.9-1.3+3.2 x105
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 11
L1+L2 TriggerL1+L2 TriggerL1+L2 Trigger cuts pt
μ>10 GeV/c Events used: 11993 After trigger: 306
Efficiency ε=2.55%
High lumi Rate= 70 KHz
CMS-NOTE 2001/011
Results on L2 trigger reconstruction in single and di-muon topologies
Rate=30 KHz
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 12
Single muon TriggerSingle muon Triggeronly L1+L2 Trigger cuts pt
μ>10 GeV/c
Signal Efficiency (9.1±0.4)%Background Efficiency (2.55±0.14)%
Total selection EfficiencySignal (3.4±0.9)x10-3
Background (3.2-2.1+5.6)x10-10
3 Years Low Luminosity (3x20 fb-1=60 fb-1)
Nsig=940±250 Nbkg=4800-3300+9000
N2body=2800±800
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 13
Sensitivity to sin(2α)Sensitivity to sin(2α)
Time integrated analysis sensitivity:
CMS-TN 1994/328 CP Violation Study of the BBddººππ++ππ--
decay for the Technical Proposal
1 Year Low Luminosity 10 fb-1
NNNS
BS
D
+1=))α2(sin(δ D~0.416
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 14
Concl…Concl…
4 aspects to be investigated further:1. Two-body decay backgroundestimated 2800±800 @ 60 fb-1
(events BBººKπ needed)2. Bug-fix on BBºº lifetime
this MC: =13.85 ps instead of 1.56 ps(decay length normalized to expected
one)new MC signal =1.56 ps
(some changes on Vertex cuts efficiencies…)
TISB-Pisa,12 Ottobre 2001
BBººππ++ππ--: status of analysis Riccardo Ranieri 15
……usionusion
3. New strategies to reject combinatorial background in udsc events(more statistics needed)
4. New ideas to enlarge Trigger Rate of signal events
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