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