dr. mukesh kumar (nithep/wits) title: "top quark physics in the vector color-octet model"

Top Quark Physics in the Vector Color-Octet Model

Mukesh Kumar

University of the Witwatersrand

September 2, 2014

A. Goyal, S. Dutta (Physicsl Review D 87, 094016 (2013))

Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 1 / 34

Outline

1 IntroductionTop QuarkAFB

AFB vs AC

2 Vector Color-Octet ModelModelObservables and Processes at TevatronConsistency at LHCConclusion


Top mass and issues/anomaly in SM

its heavy mass

strong coupling to EWSB mechanism (λt =√2mtv

≈ 1)

good for pQCD, no hadronization (mt > mW +mb, τhad ∼ 10−24s)spin information preserved due to rapid decay (τtop ∼ 10−25s)



its heavy mass


≈ 1)


|Vtb| measurement (t → Wb)



its heavy mass


≈ 1)



Hierarchy problem in the Higgs mass stabilization (affected due to large top mass)

m2H =

(

m0H

)2+

3Λ2UV

8π2v2

(

−4m2t + 2m2

W +m2Z +m2

H

)

→ New Physics Models → Vector-Like Quarks (?? in experiments . . . )



its heavy mass


≈ 1)



Hierarchy problem in the Higgs mass stabilization (affected due to large top mass)

m2H =

(

m0H

)2+

3Λ2UV

8π2v2

(

−4m2t + 2m2

W +m2Z +m2

H

)

→ New Physics Models → Vector-Like Quarks (?? in experiments . . . )

Forward-backward asymmetry in tt production at Tevatron→ Coloron Model→ Axigluon→ Z ′ etc . . .


Top Pair-Production & Mass at Tevatron

=1.96 TeVs cross section (pb) at t t→ pp

CDF dileptons * -18.8 fb 0.70 pb± 0.50 ± 7.47 0.86 pb±

CDF ANN l+jets -14.6 fb 0.40 pb± 0.38 ± 7.82 0.55 pb±

CDF SVX l+jets -14.6 fb 0.61 pb± 0.36 ± 7.32 0.71 pb±

CDF all-jets -12.9 fb 1.08 pb± 0.50 ± 7.21 1.19 pb±

CDF combined * -1up to 8.8 fb 0.40 pb± 0.31 ± 7.71 0.51 pb±

DØ dilepton -15.4 fb 0.85 pb± 7.36

DØ l+jets -15.6 fb 0.74 pb± 7.90

DØ combined -15.6 fb 0.56 pb± 0.20 ± 7.56 0.59 pb±

Tevatron combined *September 2012

= 172.5 GeVtfor m

-1up to 8.8 fb 0.36 pb± 0.20 ± 7.65 0.42 pb±

=1.96 TeVs cross section (pb) at t t→ pp6 7 8 9

Tevatron Run II Preliminary *=preliminary

)2 (GeV/ctM168 169 170 171 172 173 174 175 176 177 178 1790

7.3

CDF March'07 2.66± 12.40 2.20)±1.50 ±(

Tevatroncombination *

0.87± 173.20 0.71)±0.51 ±( syst)± stat ±(

MET+Jets * 1.79± 173.76 1.23)±1.30 ±(

Alljets 1.94± 172.70 1.28)±1.46 ±(

Dilepton 2.06± 171.02 1.14)±1.72 ±(

Lepton+jets 0.92± 173.18 0.75)±0.54 ±(

Mass of the Top Quark in Different Decay Channels

(* preliminary)March 2013

5

6

7

8

9

10

164 166 168 170 172 174 176 178 180 182

σto

t [p

b]

mtop [GeV]

PPbar → tt+X @ NNLO+NNLL

MSTW2008NNLO(68cl)

Theory (scales + pdf)Theory (scales)

CDF and D0, L=8.8fb-1

[arXiv:1303.6254]


Forward-Backward Asymmetry

q

✖q

❣

t

✖t

q

✖q

❣

❣

t

✖t

q

✖q

❣

t

✖t

q

✖q

❣

t

✖t

tt

Tevat ron

- 2 -1 0 1 2

y

dΣ�d

y

AFB References

0.162± 0.047 CDF 8.7 fb−1 [CDF Note 10807]

0.196± 0.065 D0 5.4 fb−1 [arxiv:1107.4995]

0.06± 0.01 NLO QCD tt [PRD 78,73 (014008),77(014003)]

0.066 NLO (QCD+EW) tt POWHEG [CDF Note 10807]

AttFB = Nt (cos θ>0)−Nt (cos θ<0)

Nt (cos θ>0)+Nt (cos θ<0)

AFB = N(∆y>0)−N(∆y<0)N(∆y>0)+N(∆y<0)

, ∆y = yt − yt

Rapidity: y = 12ln(

E+pzE−pz

)


Forward-Backward Asymmetry vs Charge-Asymmetry

tt

Tevat ron

- 2 -1 0 1 2

y

dΣ�d

y

AFB = N(∆y>0)−N(∆y<0)N(∆y>0)+N(∆y<0)

,∆y = yt − yt

CDF: 16.2± 4.7%

SM: 6± 1%

Inconsistent

t

tLHC

- 3 - 2 -1 0 1 2 3

y

dΣ�d

y

AC = N(∆|y|>0)−N(∆|y|<0)N(∆|y|>0)+N(∆|y|<0)

,

∆|y | = |yt | − |yt |CMS: −1.3± 2.8(stat.)+2.9

−3.1(syst.)%

SM: 1.15± 0.06%

Consistent

Comparing predictions for AttFB and AC within a given model brings important

consequences for the model


Model

LqqV = gs

[

V0,A,µ8 uTAγµ(g

UL PL + gU

R PR)u +V0,A,µ8 dTAγµ(g

DL PL + gD

R PR)d

+(

V+,A,µ8 uTAγµ(CLPL + CRPR)d + h.c.

)]


Model

LqqV = gs

[

V0,A,µ8 uTAγµ(g

UL PL + gU


DL PL + gD

R PR)d

+(


)]

Model parameters:Couplings: Flavor Conserving (FC) λij = g

qig tj , Flavor Violating (FV) κij = gut

i gutj ,

(i,j)=(L,R) in units of gs strong couplingMasses of resonances: MV 0

8, M

V±8


Model

LqqV = gs

[

V0,A,µ8 uTAγµ(g

UL PL + gU


DL PL + gD

R PR)d

+(


)]



i gutj ,


8, M

V±8

Decay Width of Color-Octets:

ΓV8 =16αs [(g

2L + g 2

R){

M2V82

− m2q+m2

q′

4−

(

m2q−m2

q′

2MV8

)2}

+ 3mqmq′ gL gR ]λ12 (M2

V8,m2

q ,m2q′

)

M3V8

,

where λ(x , y , z) = x2 + y 2 + z2 − 2x · y − 2y · z − 2z · x


Model

LqqV = gs

[

V0,A,µ8 uTAγµ(g

UL PL + gU


DL PL + gD

R PR)d

+(


)]



i gutj ,


8, M

V±8

Decay Width of Color-Octets:

ΓV8 =16αs [(g

2L + g 2

R){

M2V82

− m2q+m2

q′

4−

(

m2q−m2

q′

2MV8

)2}

+ 3mqmq′ gL gR ]λ12 (M2

V8,m2

q ,m2q′

)

M3V8

,

where λ(x , y , z) = x2 + y 2 + z2 − 2x · y − 2y · z − 2z · xResonant effect through:

Top-Pair ProductionSingle-TopSame-sign TopDijet


Rate and Constraints on Vector Color-Octet resonants

√s @ LHC = 7 TeV, L = 5fb−1

MV

±,08

GeV N(ud → V+8 ) N(du → V−

8 ) N(uu → V 08 ) N(dd → V 0

8 )

200 2.2×108 1.2×108 2.1×108 1.3×108

500 8.1×106 3.5×106 7.0×106 4.2×106

900 6.9×105 2.3×105 5.3×105 3.0×105

Assuming a coupling constant and branching ratio of unity,the current mass lower bounds on the vector colored octetresonance states from CMS ≈ 1.6 TeV. [arxiv:1010.4309]

ATLAS exclusion limits are between 0.60 TeV - 2.10 TeV(considering the coupling of the order of strong coupling αs)[PRL 105,161801]


Framework

MadGraph/MadEvent version 4.5.2

Collider: Tevatron√s = 1.96 TeV

PDF Set: CTEQ6L1

αs = 0.13

Top quark mass mt = 172.5 GeV/c2

µF = µR = µ = mt


Framework

MadGraph/MadEvent version 4.5.2

Collider: Tevatron√s = 1.96 TeV

PDF Set: CTEQ6L1

αs = 0.13

Top quark mass mt = 172.5 GeV/c2

µF = µR = µ = mt

Collider: LHC√s = 7 TeV

mjj = 200 GeV, |∆η| ≤ 1.3, Both jet |η| ≤ 2.5


Top-Pair production at Tevatron (Flavor Conserving)

σtt References

7.50± 0.48 CDF 4.6 fb−1 [CDF Note 9913]

7.2± 0.37 SM NNLO [hep-ph/1205.3453]

6.8

7

7.2

7.4

7.6

7.8

8

8.2

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

σ i

n p

b

√λAA

200

GeV

350

GeV

500

GeV

700

GeV

900 G

eV

CDFSM NNLO

6.8

7

7.2

7.4

7.6

7.8

8

8.2

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

σ i

n p

b

√λRR20

0 G

eV

350 G

eV50

0 G

eV

700

GeV

900

GeV

CDFSM NNLO


Top-Pair production at Tevatron (Flavor Violating)

σtt References

7.50± 0.48 CDF 4.6 fb−1 [CDF Note 9913]

7.2± 0.37 SM NNLO [hep-ph/1205.3453]

6.8

7

7.2

7.4

7.6

7.8

8

8.2

0.2 0.4 0.6 0.8 1

σ i

n p

b

gutAA

200

GeV

350

GeV

500

GeV

700

GeV

900 GeV

CDF

SM NNLO

6.8

7

7.2

7.4

7.6

7.8

8

8.2

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

σ i

n p

b

gutRR

200

GeV

350

GeV

500

GeV

700

GeV

900 G

eV

CDF

SM NNLO


mtt & ∆y fit : Flavor-Conserving

Kinematic dependence of the asymmetry: [arXiv:1211.1003]

AFB(|∆y |) = N(∆y>0)−N(∆y<0)N(∆y>0)+N(∆y<0)

, ∆y = yt − yt

AFB(Mtt) =NF (Mtt )−NB (Mtt )

NF (Mtt )+NB (Mtt ), Mtt = invariant mass of top-antitop pair

χ2-Analysis: χ2 =∑

i

(Othi −Oexp

i)2

(δOi )2

Fitting points: (200 GeV, λAA = 0.30), (500 GeV, λRR = 0.11), (900 GeV,λNA = 0.35)

0

0.1

0.2

0.3

0.4

0.5

0.6

350 400 450 500 550 600 650 700 750 800

AFB

Mt-t GeV

NLOData

200(0.30)500(0.11)900(0.35)

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

AFB

∆ y

NLOData

200(0.30)500(0.11)900(0.35)


mtt & ∆y fit : Flavor-Violating

Kinematic dependence of the asymmetry:

AFB(|∆y |) = N(∆y>0)−N(∆y<0)N(∆y>0)+N(∆y<0)

, ∆y = yt − yt

AFB(Mtt) =NF (Mtt )−NB (Mtt )

NF (Mtt )+NB (Mtt ), Mtt = invariant mass of top-antitop pair

χ2-Analysis: χ2 =∑

i

(Othi −Oexp

i)2

(δOi )2

Fitting points: (200 GeV, gutR = −gut

L = 0.26), (500 GeV, gutR = −gut

L = 0.53), (900GeV, gut

R = 1.26 6= gutL = 0)

0

0.1

0.2

0.3

0.4

0.5

0.6

350 400 450 500 550 600 650 700 750 800

AFB

Mt-t GeV

NLOData

200(0.26)500(0.53)900(1.26)

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

AFB

∆ y

NLOData

200(0.26)500(0.53)900(1.26)


Spin-Correlation

1σ

d2σd cos θ+d cos θ−

= 14(1+C tt cos θ+ cos θ−),

C tt =σ↑↑+σ↓↓−σ↑↓−σ↓↑

σ↑↑+σ↓↓+σ↑↓+σ↓↑.

C tt = [σ(tR tL)+σ(tLtR )]−[σ(tR tR )+σ(tLtL)][σ(tR tL)+σ(tLtR )]+[σ(tR tR )+σ(tLtL)]

≡ NO−NS

NO+NS

C ttbeam C tt

helicity References

0.72± 0.69 0.48± 0.53 CDF 5.3 fb−1 [CDF Note 10211]

0.777 0.352 SM NLO [hep-ph/0403035]


Spin-Correlation

1σ

d2σd cos θ+d cos θ−

= 14(1+C tt cos θ+ cos θ−),

C tt =σ↑↑+σ↓↓−σ↑↓−σ↓↑

σ↑↑+σ↓↓+σ↑↓+σ↓↑.

C tt = [σ(tR tL)+σ(tLtR )]−[σ(tR tR )+σ(tLtL)][σ(tR tL)+σ(tLtR )]+[σ(tR tR )+σ(tLtL)]

≡ NO−NS

NO+NS

We found consistent region for modelparameters

C ttbeam C tt

helicity References

0.72± 0.69 0.48± 0.53 CDF 5.3 fb−1 [CDF Note 10211]

0.777 0.352 SM NLO [hep-ph/0403035]


Single-top Production at Tevatron



In FC s- and t- channel in 5 flavor scheme.




In FV combined s + t- channels-channel qq → tu, where q = d , s, c, bt-channel uq → tq,s + t-channel uu → tu and t + u-channel uu → tu

all via neutral color-octet V 08 exchange.




In FV combined s + t- channels-channel qq → tu, where q = d , s, c, bt-channel uq → tq,s + t-channel uu → tu and t + u-channel uu → tu

all via neutral color-octet V 08 exchange.

For a given FC coupling single top production can constrain the FV coupling moreseverely than the top-pair production.


Same-sign Top: Exclusion Plots at Tevatron

[CDF Note 10466] LL LR RR

σtt+t t× BR(W → lν)2 [fb] 54 51 44

0.2

0.5

0.8

1

1.2

1.5

1.8

2

0.2 0.5 0.8 1 1.2 1.5 1.8 2

|gRut

|

|gLut|

900 GeV700 GeV500 GeV350 GeV200 GeV


Top Pair-Production at LHC

[TeV]s

1 2 3 4 5 6 7 8

[p

b]

ttσ

1

10

210

ATLAS Preliminary

NLO QCD (pp)

Approx. NNLO (pp)

)pNLO QCD (p

) pApprox. NNLO (p

CDF

D0

32 pb±Single Lepton (8 TeV) 241

12 pb±Single Lepton (7 TeV) 179 pb

-14

+17Dilepton 173

81 pb±All-hadronic 167 pb-10

+11Combined 177

7 8

150

200

250


Top Pair-Production at LHC

[pb]tt

σ50 100 150 200 250 300 350

ATLAS Preliminary

= 7 TeVsData 2011,

Channel & Lumi.

20 Dec 2012Theory (approx. NNLO)

= 172.5 GeVtfor m

stat. uncertaintytotal uncertainty

(lumi)±(syst) ±(stat) ± tt

σ

Single lepton -10.70 fb 7 pb± 9 ± 4 ±179

Dilepton -10.70 fb pb- 7+ 8 - 11

+ 14 6 ±173

All hadronic-11.02 fb

6 pb± 78 ± 18 ±167

Combination 7 pb± - 7+ 8 3 ±177

νµ X→Single lepton, b -14.66 fb

3 pb± 17 ± 2 ±165

+ jetshadτ -11.67 fb 46 pb± 18 ±194

+ leptonhadτ -12.05 fb 7 pb± 20 ± 13 ±186

All hadronic-14.7 fb

6 pb± - 57+ 60 12 ±168


Top Mass at LHC

[GeV]topm155 160 165 170 175 180 185 190 195

1

9

syst.⊕JSF 0.71± stat. 0.51±173.20 Tevatron Average May 2013

syst.⊕JSF 0.91± stat. 0.38±173.36 CMS Average September 2012

-1 = 4.7 fbint

CONF-2013-046, L

ATLAS 2011, l+jets* 1.35± 0.67 ± 0.27 ± 0.23 ±172.31

-1 = 4.7 fbint

CONF-2012-082, L

ATLAS 2011, dilepton* 3.00± 1.60 ±175.20

-1 = 2.05 fbint

CONF-2012-030, L

ATLAS 2011, all jets* 3.80± 2.10 ±174.90

-1 = 1.04 fbint

Eur. Phys. J. C72 (2012) 2046, L

ATLAS 2011, l+jets 2.27± 0.43 ± 0.61 ±174.53

-1 = 35 pbint

CONF-2011-033, L

ATLAS 2010, l+jets* 4.90± 4.00 ±169.30

(*Preliminary)-1 - 4.7 fb-1 = 35 pbint

summary - May 2013, LtopATLAS m

syst. ± bJSF ± JSF ± stat. ±

stat. uncertainty bJSF uncertainty⊕ JSF ⊕stat.

total uncertainty

ATLAS Preliminary


Top-Pair Production

164

166

168

170

172

174

176

178

180

182

7.2 7.4 7.6 7.8 8 8.2

σ t- tL

HC

(pb

)

σt-tTevatron (pb)

200 GeV,λAA =0.30

500 GeV,λRR =0.11

900 GeV,λNA =0.35

NNLO

165

166

167

168

169

170

171

7.2 7.4 7.6 7.8 8 8.2

σ t- tL

HC

(pb

)

σt-tTevatron (pb)

200 GeV,gutR=-gut

L=0.26

500 GeV,gutR=-gut

L=0.53

900 GeV,gutR=1.26,gut

L=0

NNLO

σtt(pb) References

173.3± 10.1 [ATLAS-CONF-2012-134]

165.2 SM NNLO [hep-ph/1205.3453]


Forward-Backward Asymmetry vs Charge-Asymmetry

-0.02

-0.01

0

0.01

0.02

0.03

0.05 0.1 0.15 0.2 0.25 0.3

AC

AFB

200 GeV,λAA =0.30

500 GeV,λRR =0.11

900 GeV,λNA =0.35

Theory-0.01

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

0.05 0.1 0.15 0.2 0.25

AC

AFB

200 GeV,gutR=-gut

L=0.26

500 GeV,gutR=-gut

L=0.53


L=0

Theory

AC References

−0.013± 0.028(stat.)+0.029−0.031(syst.) [CMS/1112.5100]


Spin-Correlation at Tevatron & LHC

Spin-Correlation

0.16

0.17

0.18

0.19

0.2

0.21

0.22

0.23

0.24

0.25

0.26

0.46 0.48 0.5 0.52 0.54 0.56 0.58 0.6 0.62

Ct- tL

HC

Ct-tTevatron

200 GeV,λAA =0.30

500 GeV,λRR =0.11

900 GeV,λNA =0.35

0.16

0.17

0.18

0.19

0.2

0.21

0.22

0.23

0.24

0.25

0.26

-0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

Ct- tL

HC

Ct-tTevatron

200 GeV,gutR=-gut

L=0.26

500 GeV,gutR=-gut

L=0.53


L=0

C tthelicity References

0.24± 0.02(stat.)± 0.08(syst.) [CMS/TOP-12-004-PAS]


Top-invariant mass and pT Distributions @ 7 TeV LHC

Top-Quark invariant mass

10-2

10-1

100

101

400 600 800 1000 1200 1400

dσ

/dm

t- t (

pb/2

0 G

eV)

mt-t (GeV)

SM200 GeV,λAA =0.30500 GeV,λRR =0.11900 Gev,λNA =0.35

Top-Quark pT

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600 700dσ

/dp

T (p

b/1

0 G

eV)

pT (GeV)

SM200 GeV,λAA =0.30500 GeV,λRR =0.11900 GeV,λNA =0.35


Color-Octet and Dijet @ 7 TeV LHC

Dijet invariant mass

10-3

10-2

10-1

100

101

102

103

104

200 400 600 800 1000 1200 1400 1600 1800

dσ

/dm

jj (p

b/5

0 G

eV)

mjj (GeV)

SM200 GeV,λAA =0.30500 GeV,λRR =0.11900 GeV,λNA =0.35

Dijet pT

10-2

10-1

100

101

102

103

0 50 100 150 200 250 300 350 400 450 500dσ

/dp

Tj

(p

b/1

0 G

eV)

pTj (GeV)

SM200 GeV,λAA =0.30500 GeV,λRR =0.11900 Gev,λNA =0.35


Conclusion

Appreciable Contribution to AttFB and C tt without transgressing 1-σ experimental

production cross-section at Tevatron

χ2 analysis: favorable focus points ⇒ Possible solution for AFB anomaly

Large parameter-region is allowed by 1- and 2-σ experimental observation for both s

and t- channel single top production

FCNC parameters are more sensitive for single top w .r .t pair-production

Consistent with the non-observability of large Same-sign top events

pT and invaraint-mass distribution of top and dijet production with experimentaldata give some favorable parameters

Parameter space are consistent with tt cross-section, measured charge asymmetryand spin-correlation at LHC

The benchmark points are consistent with all the observables w.r.t low energystringent bounds from B and D physics


Update: pp → YY → jjjj

[arXiv: 1303.2699]

3-jets with ET > 20 GeV and∑

jetsET > 130 GeV

Within radius of ∆R = 0.4

After trigger selection, at least 4 jetswith ET > 15 GeV and |η| < 2.4

❪✷✥�✁✂✄☎❨❘✁✆✝✞✟✞☎✁ ✠✟✆✆ ✠✺✡ ✶✡✡ ✶✺✡ ☛✡✡ ☛✺✡ ✸✡✡ ✸✺✡ ✹✡✡ ✹✺✡ ✺✡✡

☞☞☞☞✌✍✎✏✑

➤

✒✒

➤✎✭✎s

✶

✶✡

✓✶✡

❊✔✕✖✗✘✖✙ ✚✛✜✛✘ ✢✘ ✣✤✦ ✧★❖✩✪✖✫✬✖✙ ✚✛✜✛✘

✮✯➧❊✔✕✖✗✘✖✙ ✚✛✜✛✘✮✓➧❊✔✕✖✗✘✖✙ ✚✛✜✛✘

✧❈✚❈✫❈✰ ★❖✪✘❈✕ ✱✲✢✫✳ ✴★❖

✵✻✼ ✽✾✿❀❀❂❁❃❄❅ ❚❡❱❆♣♣➢❇▲ ❞t ❂ ❅❃❅ ❢❜

❉❉❉❉❋●●❋♣♣


THANK YOU ALL !!


BACKUP SLIDES


Issues!!

Anomaly cancellation in Axi-gluon case and |gqA | < |g t

A|Solution: Non-universal models

introducing exotic quarks (vector-like quarks) [arxiv: 1101.5203, Bai et.al.; arxiv:9903387, 0911.2955, Frampton et.al.]extending the gauge sector so that new color-octet spin-1 fields does not change thestructure of the couplings (only the value of coupling constant changes) [arxiv:0908.3116, 1103.0956, Zerwekh]

Two gluons and one massive spin-1 color octet: In axigluon model this kind ofcoupling is forbidden if we assume that strong interactions (QCD) is parityconserving while in case of coloron, gauge invariance protect this kind of interactionterms with dimension 4 or less [Zerwekh, Rosenfeld arXiv: 0103159] (howeverpossible to construct such non-renormalizable dimension-6 interaction [Chivukula etal arXiv: 0109029])

Coloron production via gluon-fusion (one-loop) is typically 4 orders of magnitudesmaller than quark annihilation contribution at LHC [Chivukula et al arXiv:1303.1120]


Constraints from Flavor Physics on vector color octets

nonuniversal FCNC couplings between the up quarks of the first and third gen.

keeping u-t coupling large and simultaneously making c-t and u-c couplings smallresults no strong bounds

CC sector can be controlled by align the mixing matrix with CKM






Ref. [arXiv: 1101.5203]






Ref. [arXiv: 1101.5203]

Bd (Bs): MG ′ & (100TeV)

[

(

CDL,31

)2+

(

CDR,31

)2− 27CD

L,31CDR,31

]1/2

D − D: MG ′ & (600TeV)

[

(

CUL,21

)2+

(

CUR,21

)2− 60CU

L,21CUR,21

]1/2

etc...


Top-Pair Production: FC, FV Channel

d σFC

d cos θ=

πβα2s

9s

{(

2− β2 sin2 θ)

+1

2

s(s −m2V 08)

(s −m2V 08)2 +m2

V 08Γ2V 08

×[

(gqL + g

qR)(g

tL + g

tR)(

2− β2 sin2 θ)

+ (gqL − g

qR)(g

tL − g

tR)(

2β cos θ)]

+1

4

s2

(s −m2V 08)2 +m2

V 08Γ2V 08

×[

(gqL

2+ g

qR

2)(g t

L2+ g

tR2)(

1 +2g t

LgtR

g tL2 + g t

R2(1− β2) + (β cos θ)2

)

+ (gqL

2 − gqR

2)(g t

L2 − g

tR2)(

2β cos θ)]}

,whereβ =√

1− 4m2t /s

the top quark velocity in c.m. frame of reference of qq.

d σFV

d cos θ=πβα2

s

9s

{(

2− β2 sin2 θ)

− 1

6

s

(t −m2V 08)(1 + β cos θ)2(gut

L2+ g

utR

2)

+1

4

s2

(t −m2V 08)2

[

(gutL

4+ g

utR

4)(

1 + β cos θ)2

+ 8gutL

2gutR

2(1 + β2)

]}


Constraints on FV couplings: Same-Sign Top quark

L4F = 12CLL

Λ2 (uLγµtL)(uLγµtL) +

12CRR

Λ2 (uRγµtR)(uRγµtR)− 1

2CLR

Λ2 (uLγµtL)(uRγµtR)−

12

C ′LR

Λ2 (uLaγµtLb )(uRb

γµtRa) + h.c.

σtt+t t = 2[

14.48Λ4 (|CLL|2 + |CRR |2)+ 1.811

Λ4 (|CLR |2 + |C ′LR |2)− 0.52

Λ4 Re(CLRC′∗LR)

]

fb ·TeV4.

[arxiv:1108.3562]

Set limit on vector or axial-vector Z ′ boson for CLL = CRR = ∓ 12CLR ≡ C

[CDF Note 10466] LL LR RR

σtt+t t× BR(W → lν)2 [fb] 54 51 44

|C |/Λ2 [TeV−2] 4.1 11.3 3.7

d σ

d cos θ=

πβα2s

(t −m2V 08)2

s

18

[

2(gutL

4+ g

utR

4) + g

utL

2gutR

2(1 + β cos θ)2

]

+2πβα2

s

(t −m2V 08)(u −m2

V 08)

s

9

[

(gutL

4+ g

utR

4)− 2gut

L2gutR

2m2t

s

]

+πβα2

s

(u −m2V 08)2

s

18

[

2(gutL

4+ g

utR

4) + g

utL

2gutR

2(1− β cos θ)2

]


dr. mukesh kumar (nithep/wits) title: "top quark physics in the vector color-octet model"

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