feasibility to study the bc meson and testing anomalous gauge couplings of
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Feasibility to Study the Bc Meson and Testing Anomalous Gauge Couplings of the Higgs Boson via Weak-Boson Scatterings at CMS. CMS Group Institute of High Energy Physics, Chinese Academy of Science. Guilin 2006.10.29. Feasibility to Study the Bc Meson at CMS. Outline Introduction - PowerPoint PPT PresentationTRANSCRIPT
Feasibility to Study the Bc Meson and
Testing Anomalous Gauge Couplings ofthe Higgs Boson via Weak-Boson Scatterings
at CMS
CMS Group
Institute of High Energy Physics, Chinese Academy of Science
Guilin 2006.10.29
Feasibility to Study the Bc Meson at CMS
Outline• Introduction
• Process & results – Production of Signal & Backgrounds
– Event selection, by studying Bc signal & backgrounds
– Results
• Summary
Introduction
Bc Meson
• The Bc meson is the lowest-mass bound state of a charm quark and a bottom anti-quark. It is the latest such meson predicted by the Standard Model.
• Because Bc meson carry flavor, it provides a new window for studying heavy-quark dynamics for the two different heavy quarks, which is very different from the window provided by quarkonium.
• Its mass is predicted to be
And its lifetime is predicted to be between 0.4 and 0.7 psV.V.Kiselev, PACS number:13.20.Gd,13.25.Gv, 11.55.HxV.V.Kiselev, PACS number:13.20.Gd,13.25.Gv, 11.55.Hx
TEVATRON: CDF (1998)
20 J/ψ lυ events, mass :6.40±0.39±0.13 GeV
life time :
03.046.0 18.016.0
ps
Recent results of Bc Meson
Experimental observation (CDF & D0 , Tevatron)
1998
2004
2005
CMS Experiment
CMS2008
Large Hadron Collider
CMS Experiment
Production of Bc at LHC
pp pp
LHC LHC (14TeV)(14TeV)
g-g fusion
Adavantages of study Bc at CMS1. Higher Collide Energy LHC: PP collider
2. Larger detector region than CDF The CMS detector has the similar structure as CDF ,but it has larger detector region than CDF. CMS: eta~(-2.5,2.5) CDF: eta~(-1.0,1.0) (RUN I) eta~(-1.5,1.5) (RUN II) (Muon system)
3. A better identification ability to muons The CMS detector has a better identification ability to muons ,this is mor
e useful for the channels which include muon/muons in the final state.
TeVs 14 TEVTRONLHCcc BB 20~
• The goal: to measure the mass and life time of Bc with a larger statistics.
• The first channel to look:
Bc → J/ψ π (J/ψ → µµ)
• First publication at about 1 fb-1
Goal & status
Process & results
The CMS Analysis chain
MC generatorHEPEVT
Ntuple
OSCAR
OSCAR
Ntuplesignal
Ntupleminbias
POOLSimHits/signal
POOLSimHits/minbias
POOLDigis DST ROOT
Tree“ data summary tape”
User
SimReader RecReader RecReader
1)digitization 2)reconstruction 3)analysis
ORCA
The CMS Fast Simulation
MC generatorHEPEVT
Ntuple
Ntuple
POOL
Simulation, Digis, and DST
ROOTTree
FAMOS
analysis
Generator of Bc signal• BCVEGPY IPT, Beijing, by Chang et al.• Russian package IHEP, Protvino, by Berezhnoy et al.• PYTHIA
BCVEGPY is used: faster agrees well with PYTHIA
Particle Decay channels σ (pb) Generated (*104)
Bc Bc→J/ψπ
(J/ψ→µµ )
1.781 5.2082
kine cut : Bc Pt≥10GeV |eta|≤2.0
Mu Pt≥4GeV |eta|≤2.2 Pion Pt≥2GeV |eta|≤2.4
About 30 1/fb Bc events were produced for efficiency study with both OSCAR/ORCA and FAMOS
Another independent 1/fb Bc were produced as data OSCAR_3_7_0 ORCA_8_7_3 FAMOS_1_3_2
Bc signal
Backgrounds
1. Other B hadrons’ decay include J/ψ
2. Prompt J/ψ
3. ccbar→μμx
4. bbbar →μμx
5. General QCD, W+jets, Z+jets
Backgrounds (1,2,3)generated by CMKIN & produced by FAMOS
Backgrounds (4,5)CMS official production with OSCAR/ORCA
Dataset σ(mb) Nevents
bb→mumu+ X 4.8*10-3 100,000
QCD 57.6 950,000
W+jets 1.56*10-4 880,000
Z+jets 3.82*10-5 710,000
J/Ψ candidates: 2 muons Pt ≥ 4.0 GeV , |η|<=2.2 2 muons share the same vertex 2 muons have different charge 2 muons’ invariant mass around the J/Ψ [3.0,3.2]GeV
Data Selection
Selection I
Bc → J/ψ π (J/ψ → µµ)
Pion candidate: Be not identified as a lepton Pt ≥ 2 GeV |η|<=2.4 Share the same vertex with 2 muons (J/Ψ vertex)
Selection II
Bc → J/ψ π (J/ψ → µµ)
Selection III
Signal selection cuts:• cos(thetasp)>0.8 thetasp: is the angle between the direction from the primary vertex to the second vertex and the direction of the reconstructed Bc momentum • PDLxy >60 μm (Proper decay length)• PDLxy /σ xy >2.5 P. V. S. V.
1fb-1
Selection IV
Bc mass window (6.25, 6.55) GeV
Summary of the Number of EventsBc 120±11
B+ 0.7±0.2
Bs 0.1
B0 0.9±0.3
Prompt J/ψ 0.1
QCD 0.7±0.1
Λb 0.1
ccbar 0.01
bbbar 0.01
Total Bkgs: 2.6±0.4
Normalize to 1fb-1
Bc number uncertainty
source:1. LO only
2. color singlet only (no color-octet available)
3. Values of inputs
mass of b quark, c quark ;
parton distribution function (pdf).
Kinematic fitting
Bc→J/ψπ, J/ψ→μμ
Totally 3 tracks:
2 muon tracks: J/ψ mass constraint
all the 3 tracks: share the same vertex
M(Bc):6402.0±22.0 MeVInput:6400MeV
cτ(Bc): 148.8±13.1 μm Input 150 μm
Systematic error
source: • Misalignment
1. muon momentum scale uncertainty
2. muon momentum resolution deterioration
3. vertex resolution deterioration• Efficiency uncertainty• Theoretical uncertainty• Cuts sensitivity
Summary of systematic error
Bc mass (MeV) Bc cτ (μm)
P scale 11 0.2
P smear 10 0.8
Vertex smear / 2.4
Cuts 0.1 0.2
Efficiency / 0.1
Theoretical / 1.5
Total 14.9 3.0
Summary
SummaryWith MC data, the feasibility for CMS to measure the mass and
the lifetime of Bc meson was studied.
The study focus on the decay channel Bc→J/ψπ.
120 events can be selected with the first 1 fb-1 data
Mass resolution is estimated to be
cτ resolution is
corresponding to the lifetime error to be
Uncertainty: effects of misalignment, theoretical uncertainty on the Bc Pt
distribution, and limited Monte Carlo statistics.
This study had been reported for 6 times at CERN.
This study had been written into 2 notes: CMS Notes & Analysis Notes
And Physics TDR.
The results can be available from the following website
http://cmsdoc.cern.ch/doc/notes/docs/NOTE2006_118
Continue…
Testing Anomalous Gauge Couplings ofthe Higgs Boson via Weak-Boson Scatterings
at CMS
Outline
1. Motivation
2. Extraction of anomalous coupling
constants via Neural Network
3. Study of signal and backgrounds
4. Summary & to do list
1. whether there exists a sub-TeV Higgs Boson.
2. Discriminate the EWSB sector of the new physics model from that of the SM.
Motivation
---------
p
p u
u
d
d
W
W
W
W
+
+
+
+H
l+
v
l
v
+
Zhang Bin and Kuang Yuping et. al. (Tsinghua Univ.)
proposed a sensitive way of testing AHVVC via VV (V =
W+ , Z0 ) scatterings, especially the WW scatterings at LHC and provided the matrix element level generator .
It is
among them, fw and fww are the most sensitive ones.
Hence, only fw and fww are considered.
To suppress backgrounds, the cuts suggested by theorists
Distribution of the number of events with fw
Normalized to 300 fb-1
mH=115 GeV
For the small number of events, large fluctuation occurred.
For the number of events fluctuated according Poisson distribution, the neural network can make the resolution of parameter fw better after taking the distribution of two leptons’ invariant mass as one of the inputs.
1.5
2.5
1.5 / 33 0.26
2.5 / 60 0.32
fw
fw
Extract anomalous coupling constant
fw via Neural Network
Neural Networkinputs:
(1) number of events
(2) distribution of the invariant mass of 2 leptons.
outputs: anomalous coupling constants fwtraining: fw =0 ,1,2,3,4
evaluate: fw =1.5 ,2.5
Distribution of two leptons’ invariant mass
Normalized to 300 fb-1
2200 ~
4000960 ~
2200480 ~
9600 ~
480
two leptons’ invariant mass (GeV)
4 3 2 1bin
Evaluated f w = 1.5
26.018.0 5.1 wfsigma
Evaluated f w = 2.5
32.017.0 5.2 wfsigma
Study of signal and backgrounds
Reconstruction results of the Signal
channels Sigma Events/300 fb-1
Obtained via Grid job or reconstructed by myself
WZ 3l 4.4E-10 (mb) 132000 40000
ZZ 4l 1.6E-11 (mb) 4800 40000
Z0 t t 4l + X 1.7 (fb) 510 1000
W+ t t 3l + X 3.0 (fb) 900 1000
t t 4l + X 1.25E-9 (mb) 375000 121000
Zbb_4l+(njets) 2E-11 (mb) 6000 129000
Zbb_cc_4l+(njets) 8E-12 (mb) 2400 3000
ZWjets_leptonic 2.6E-9 (mb) 780000 50000
ZZjets_leptonic 1.5E-10 (mb) 45000 100000
Backgrounds
_
_
_
Comparison of the Signal & Backgroundsafter the basic Cuts
—2 lepton’s invariant mass and tagging jet’s pt
(Taking WZ→3 l as example)
No background of the channels listed in the table can exits, after adding all cuts suggested by theorists to the backgrounds with the limited statistics. so we suggest to relax the cuts in order to get more signal events, which is what we will to do.
channels Sigma background events
Obtained via Grid job
WZ 3l 4.4E-10 (mb) 0 40000
ZZ 4l 1.6E-11 (mb) 0 40000
Z t t 4l+X 1.7 (fb) 0 1000
Wt t 3l+X 3 (fb) 0 1000
t t 4l + X 1.25E-9 (mb) 0 121000
Zbb_4l+(njets) 2E-11 (mb) 0 129000
Zbb_cc 4l+(njets) 8E-12 (mb) 0 3000
ZWjets_leptonic 2.6E-9 (mb) 0 50000
ZZjets_leptonic 1.5E-10 (mb) 0 100000
Summary• Extracting anomalous coupling constant fw via Neural N
etwork, we can get more sensitivity results using the number of events & invariant mass of 2 leptons than that using the number of events only on the theory.
• After studying the signal and backgrounds, using the cuts we can cut off all the backgrounds considered with limited number of events available.
To do list
• Further study of signal and backgrounds, then find out the best proper cuts.
• Try other ways to fix the anomalous coupling constants.
The End Thanks !
Backup slides
Cross section comparison
• Bc vs other B
σ(other B) =1000 σ( Bc) • LHC vs TEVATRON 20 times larger
H.C. Chang X.G. Wu
Pt cut (GeV) 0 5 50 100
TEVATRON/LHC 6.3% 5.2% 1.0% 0.3%
1. Bc→J/Ψlν(J/Ψ→l+l-)
Bc→J/ψµν(J/ψ→µµ)Bc→J/ψeν(J/ψ→µµ)Bc→J/ψµν(J/ψ→ee)Bc→J/ψeν(J/ψ→ee)
2. Bc→J/Ψπ(J/Ψ→l+ l-)
Bc→J/ψπ(J/ψ→µµ)Bc→J/ψπ(J/ψ→ee)
Bc decay and interface with OSCAR:
Force Bc to decay with the final states we needand interface with OSCAR (Implemented within SIMUB ) SIMUB is one of CMS Supported generator packages ,which is dedicated for simulation of B-meson production and decays. http://cmsdoc.cern.ch/~shulga/SIMUB/SIMUB.html
G.M. Chen S.H. Zhang IHEP BeijingA.A. Belkov S. Shulga JINR Dubna (Russia)
Number decay channels Branch Ratio Nev σ(pb)after
Kine cut
5110 B0 → JPsi + K0 0.08% 170000 16.040
5111 B0 → JPsi + K0* 0.14% 290000 28.288
5112 B0 → chi_c1 + K0 0.19% 120000 11.192
5113 B0 → chi_c1+ K0 * 0.25% 150000 14.808
Background of Bc→J/ψπ (J/ψ→µµ) from B0
channels Branch Ratio
JPsi → mu+ mu- 5.88%
chi_c1 → JPsi + γ 31.6%
K0* → Random
K- Pi+
K0 Pi0
K0 γ
66.5%33.3%
0.2%
Kinematic cuts at generator llevel
Mu: pt ≥ 4.0GeV |eta| ≤ 2.4
K : pt ≥ 2.0GeV |eta| ≤ 2.7
More than 10 fb-1 bkg from B0 were produced
Number decay channels Branch Ratio
Nev σ(pb) after kine cut
5210 B+ → JPsi + K+ 0.08% 170000 16.056
5211 B+ → JPsi + K+* 0.14% 290000 28.611
5212 B+ → chi_c1 + K+ 0.19% 120000 11.150
5213 B+ → chi_c1+ K+* 0.25% 150000 14.921
Background of Bc→J/ψπ (J/ψ→µµ) from B+
channels Branch Ratio
JPsi → mu+ mu- 5.88%
chi_c1 → JPsi + γ 31.6%
K+* → Random
K0 Pi+
K+ Pi0
K+ γ
66.6%33.3%
0.1%
Kine cut:
Mu: pt ≥ 4.0GeV |eta| ≤ 2.4
K : pt ≥ 2.0GeV |eta| ≤ 2.7
More than 10 fb-1 bkg from B+ were produced
Number decay channels Branch Ratio
Nev σ(pb) after kine cut
5310 Bs → JPsi + phi 0.14% 30000 2.215
5311 Bs → JPsi + eta 0.04% 40000 3.198
5312 Bs → JPsi + eta’ 0.04% 30000 2.968
5313 Bs → chi_c1+ eta 0.1% 30000 2.064
5314 Bs → chi_c1+ eta’ 0.09% 20000 1.738
5315 Bs → chi_c1+ phi 0.25% 30000 2.583
Background of Bc→J/ψπ (J/ψ→µµ) from Bs
channels Branch Ratio
JPsi → mu+ mu- 5.88%
phi → K+ K- 48.9%
chi_c1 → JPsi + γ 31.6%
eta → Random 1
eta’ → Random 1
Kine cut
Mu: pt ≥ 4.0GeV |eta| ≤ 2.4
K : pt ≥ 2.0GeV |eta| ≤ 2.7
More than 10 fb-1 bkg from Bs were produced
Background of Bc→J/ψπ (J/ψ→µµ) from Λ0b
Number decay channels Branch Ratio Nsel σ(pb) after kine cut
51220 Lambda_b0 →
JPsi + Lambda0
0.22% 130000 12.797
51221 Lambda_b0 → chi_c1+ Lambda0
0.44% 70000 6.642
channels Branch Ratio
JPsi → mu+ mu- 5.88%
chi_c1 → JPsi + γ 31.6%
Lambda0 → Random
Kine cut
Mu: pt ≥ 4.0GeV |eta| ≤ 2.4
More than 10 fb-1 bkg from Λb were produced
Number decay channels Branch Ratio N(sel) σ(pb) after kine cut
4430 g (γ) + g (γ) →
JPsi
Chi_c0
Chi_c1
Chi_c2
5.88%
0.7% * 5.88%
31.6% * 5.88%
13.5% * 5.88%
10000
10000
40000
180000
0.440
0.794
3.902
17.553
4431 g (q) + g (q) →
c cbar + g (q)
5.88% 260000 217.57
Background of Bc→J/ψπ (J/ψ→µµ) from prompt J/ψ
Kine cut:
Mu: pt ≥ 4.0GeV |eta| ≤ 2.4
channels Branch Ratio
JPsi → mu+ mu- 5.88%
chi_c0 → JPsi + γ 0.7%
chi_c1 → JPsi + γ 31.6%
chi_c2 → JPsi + γ 13.5%
More than 10 fb-1 bkg from 4430 were produced. Only 1 fb-1 events fromChannel 4431
)(/ _01 Jc
)(/ _0 Jc
_/ J
)(/ _02 Jc
)()( gg(1)
PYTHIA
_/ Jgccqgqg _
)()((2)
PYTHIA
Backgound estimation
None of the QCD, W+jets, Z+jets,ccbar and bbbar passed the selection.As the number of events produced is lessthan one 1/fb, the number of backgroundevents from these samples will be estimatedstep by step
QCD background estimation
selection efficiency
1. two muons
pT>4GeV, |η|<2.2 ε(2μ)
2. J/ψreconctruction
same vertex,
mass(μμ) : (3.0,3.2) ε(rec)
3. Final cuts
Lxy/σ>2.5, PDL>60μm
cos(thesp)>0.8
mass(J/ψ,π): (6.25, 6.55) ε(prompt)
The total efficiency is ε(2μ)*ε(rec)* ε(prompt)
Dataset σ(mb) No. of events getted using Grid
No. of
Single Mu
(>= 1 Mu)
No. of
Double Mu
(>= 2Mu)
jm03b_qcd_0_15 55.22 23999 10 0
jm03b_qcd_15_20 1.50006 44999 122 1
jm03b_qcd_20_30 0.641733 89999 461 4
jm03b_qcd_30_50 0.155929 92997 933 12
jm03b_qcd_50_80 0.02093883 198993 4382 126
jm03b_qcd_80_120 0.002949713 90000 3408 147
jm03b_qcd_120_170 0.000499656 70000 3872 248
jm03b_qcd_170_230 0.000100995 40000 3130 247
jm03b_qcd_230_300 2.3855*10-5 50000 4963 453
jm03b_qcd_300_380 6.39108*10-6 243983 31873 3769
jm03b_qcd_380_470 1.88967*10-6 5000 744 111
Kine cut: Mu: pt ≥ 4.0GeV |eta| ≤ 2.2
ε(2μ) can be estimated from QCD samples
ε(rec) estimation
• Using ccbar→μμx sample
total: 210,000
The number of events pass 2 muon selection: 147778, reconstructed J/ψ: 192
ε(rec)= (1.3±0.1) × 10-3
ε(prompt) estimation
• Using prompt J/ψ sample• The number of events pass the above selection is 434,5
66• Enlarge the mass window from (6.25,6.55) to (5.0,8.0), 27 events obtained assuming random distribution of the 27 eventsε(prompt)=(6.55-6.25)/(8-5)*27/434566= (6.2±1.2) ×10-6
Prompt J/ψ
Dataset σ(mb) ε(2 mu) Total ε N1fb-1
jm03b_qcd_0_15 55.22 (1.736256
±0.17363)e-7
(1.40157
±0.19937)e-15
0.077
±0.011
jm03b_qcd_15_20 1.50006 (7.35045
±0.06025)e-6
(5.93353
±0.29930)e-14
0.089
±0.004
jm03b_qcd_20_30 0.641733 (4.444494
±2.222247)e-5
(3.58775
±1.04850)e-13
0.230
±0.067
jm03b_qcd_30_50 0.155929 (1.290364
±0.372496)e-4
(1.04161
±0.13080)e-12
0.162
±0.020
jm03b_qcd_50_80 0.02093883 (6.331881
±0.56409)e-4
(5.11131
±0.25650)e-12
0.107
±0.005
jm03b_qcd_80_120 0.002949713 (1.633333
±0.134715)e-3
(1.31848
±0.06467)e-11
0.039
±0.002
ε(JPsi →Bkg) = (6.2±1.2 ) ×10-6
ε(2mu→JPsi) = (1.3±0.1) × 10-3
QCD background contribution
Dataset σ(mb) ε(2 mu) Total ε N1fb-1
jm03b_Wjets_0_20 1.110015*10-4 (5.13333
±0.5850)e-4
(4.14380
±0.22887)e-12
(4.5997
±0.2541)e-4
jm03b_Wjets_20_50 2.729528*10-5 (1.4350
±0.08471)e-3
(1.15838
±0.05297)e-11
(3.1618
±0.1446)e-4
jm03b_Wjets_50_85 1.006911*10-5 (2.880
±0.120)e-3
(2.32483
±0.10225)e-11
(2.34090
±0.1030)e-4
jm03b_Wjets_85_150 6.30697*10-6 (4.4650
±0.149416)e-3
(3.60430
±0.15630)e-11
(2.2732
±0.0986)e-4
jm03b_Wjets_150_250 1.20248*10-6 (7.740
±0.27821)e-3
(6.24799
±0.27202)e-11
(7.5131
±0.3271)e-5
jm03b_Wjets_250_400 2.632455*10-7 (1.123333
±0.061192)e-2
(9.0679
±0.40713)e-11
(2.3871
±0.1072)e-5
ε(JPsi →Bkg) = (6.213095±1.19571 ) ×10-6
ε(2mu→JPsi) = (1.299246±0.093765) × 10-3
W+Jets has none
Muon momentum scale uncertainty
Δ(1/pT)=0.0005/GeV (Albert De Roeck)
Bc mass changes by 11 MeV
cτ changes by 0.2 μm
Muon momentum resolution
I. Belotelov et al
CMS note
2006/017
Muon momentumwere smearedaccording to This result
Mass: 11 MeVCtau: 0.8μm
Vertex resolution
P. Vanlaer et al, CMS note 2006/029Primary Vertex : x, y: smear 5.7μm, z:3.7μmSecond Vertex: x, y: smear 12.4 μ m , z: 11.4μmcτ: 2.4 μ m
Cuts sensitivity
• Momentum cuts changed by one σ
• Other cuts changed by 10%
mass: 0.1 MeV
cτ : 0.2 μm
Efficiency uncertainty
To estimate theefficiency uncertaintysqrt(N) events subtracted , efficiencyrecalculated
cτ: 0.1 μm
Theoretical uncertainty
Bc events were reweighted according the their Bc pT, sothat the Bc pT distribution agrees with Gouz’s distributioncτ: 2.4μm
Muon momentum resolution
CMS 1/fb:Mass: 22.0(fit) ±14.9(syst) MeV lifetime: 0.044(fit) ±0.010(syst) ps
Outlook (Real data 2008)
• J/ψ+ 1track will be selected as a control sample
• B+ → J/ψ+K+ will be used to estimate the Bc efficiency
• J/ψ peak side band will be used for the Bc background estimation