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 Introduction
Top Quark
AFB
AFB vs AC
2 Vector Color-Octet Model
Model
Observables and Processes at Tevatron
Consistency at LHC
Conclusion

Top mass and issues/anomaly in SM
its heavy mass
strong coupling to EWSB mechanism (t =
√2 mt
v
1)
good for pQCD, no hadronization (mt mW + mb, had 10−24s)
spin information preserved due to rapid decay (top 10−25s)

its heavy mass
√2 mt
v
1)
|Vtb| measurement (t → Wb)

its heavy mass
√2 mt
v
1)
Hierarchy problem in the Higgs mass stabilization (affected due to large top mass)
m2H
= m0H
2
+ 32
UV
4m2
82v2 −t + 2m2W
+ m2Z
+ m2H

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

its heavy mass
√2 mt
v
1)
Hierarchy problem in the Higgs mass stabilization (affected due to large top mass)
m2H
= m0H
2
+ 32
UV
4m2
82v2 −t + 2m2W
+ m2Z
+ m2H

→ New Physics Models → Vector-Like Quarks (?? in experiments . . . )
Forward-backward asymmetry in t¯t
production at Tevatron
→ Coloron Model
→ Axigluon
→ Z′ etc . . .

Top Pair-Production Mass at Tevatron
Tevatron Run II Preliminary *=preliminary
CDF dileptons * 7.47 ± 0.50 ± 0.70 pb 8.8 fb1
± 0.86 pb
CDF ANN l+jets 7.82 ± 0.38 ± 0.40 pb 4.6 fb1
± 0.55 pb
CDF SVX l+jets 7.32 ± 0.36 ± 0.61 pb 4.6 fb1
± 0.71 pb
CDF alljets
7.21 ± 0.50 ± 1.08 pb 2.9 fb1
± 1.19 pb
CDF combined * 7.71 ± 0.31 ± 0.40 pb up to 8.8 fb1
± 0.51 pb
DØ dilepton 7.36 ± 0.85 pb 5.4 fb1
DØ l+jets 7.90 ± 0.74 pb 5.6 fb1
DØ combined 7.56 ± 0.20 ± 0.56 pb 5.6 fb1
± 0.59 pb
Tevatron combined *
September 2012
= 172.5 GeV t for m
7.65 ± 0.20 ± 0.36 pb up to 8.8 fb1
± 0.42 pb
6 7 8 9
pp ® tt cross section (pb) at s=1.96 TeV
7.3
Mass of the Top Quark in Different Decay Channels
March 2013 (* preliminary)
Lepton+jets 173.18 ±0.92 (±0.54 ± 0.75)
Dilepton 171.02 ±2.06 (±1.72 ± 1.14)
Alljets 172.70 ±1.94 (±1.46 ± 1.28)
MET+Jets * 173.76 ±1.79 (±1.30 ± 1.23)
Tevatron
combination *
173.20 ±0.87 (±0.51 ± 0.71)
(± stat ± syst)
168 169 170 171 172 173 174 175 176 177 178 179
(GeV/c2) t M
0
CDF March'07 12.40 ±2.66 (±1.50 ± 2.20)
10
9
8
7
6
5
Theory (scales + pdf)
Theory (scales)
CDF and D0, L=8.8fb-1
PPbar ® tt+X @ NNLO+NNLL
MSTW2008NNLO(68cl)
164 166 168 170 172 174 176 178 180 182
stot [pb]
mtop [GeV]
[arXiv:1303.6254]

Forward-Backward Asymmetry
q
✖q
❣
t
✖t
q
✖q
❣
❣
t
✖t
q
✖q
❣
t
✖t
q
✖q
❣
t
✖t
t t
Tevat ron
- 2 -1 0 1 2
y
dΣdy
At¯t
FB = Nt (cos 0)−Nt (cos 0)
AFB = N(y0)−N(y0)
E−pz
2 ln E+pz
Rapidity: y = 1
AFB References
Nt (cos 0)+Nt (cos 0)
N(y0)+N(y0) , y = yt − y¯t
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 t¯t
[PRD 78,73 (014008),77(014003)]
0.066 NLO (QCD+EW) t¯t
POWHEG [CDF Note 10807]

Forward-Backward Asymmetry vs Charge-Asymmetry
t t
Tevat ron
- 2 -1 0 1 2
y
dΣdy
AFB = N(y0)−N(y0)
N(y0)+N(y0) ,
y = yt − y¯t
CDF: 16.2 ± 4.7%
SM: 6 ± 1%
Inconsistent
t
LHC t
- 3 - 2 -1 0 1 2 3
y
dΣdy
AC = N(|y|0)−N(|y|0)
N(|y|0)+N(|y|0) ,
|y| = |yt | − |y¯t
|
CMS: −1.3 ± 2.8(stat.)+2.9
−3.1(syst.)%
SM: 1.15 ± 0.06%
Consistent
Comparing predictions for At¯t
FB and AC within a given model brings important
consequences for the model

Model
Lq¯qV = gshV0,A,μ
8 ¯uTA
μ(gU
R PR)u +V0,A,μ
L PL + gU
8
¯dTA
μ(gD
L PL + gD
R PR)d
+V+,A,μ
8 ¯uTA
μ(CLPL + CRPR)d + h.c.i

Model
Lq¯qV = gshV0,A,μ
8 ¯uTA
μ(gU
R PR)u +V0,A,μ
L PL + gU
8
¯dTA
μ(gD
L PL + gD
R PR)d
+V+,A,μ
8 ¯uTA
Model parameters:
Couplings: Flavor Conserving (FC) ij = gq
i gt
j , Flavor Violating (FV) ij = gut
i gut
j ,
(i,j)=(L,R) in units of gs strong coupling
Masses of resonances: MV0
8
, M
±
8
V

Model
Lq¯qV = gshV0,A,μ
8 ¯uTA
μ(gU
R PR)u +V0,A,μ
L PL + gU
8
¯dTA
μ(gD
L PL + gD
R PR)d
+V+,A,μ
8 ¯uTA
Model parameters:
i gt
i gut
j ,
8
, M
±
8
V
Decay Width of Color-Octets:
6s [(g2
V8 = 1
R)nM2V
L + g2
8
2 −
m2
q+m2
4 − m2
q′
q−m2
2q′
o + 3mqmq′ gL gR]
2MV8
1
2 (M2V
8
q ,m2
,m2
q′ )
M3V
8
,
where (x, y, z) = x2 + y2 + z2 − 2x · y − 2y · z − 2z · x

Model
Lq¯qV = gshV0,A,μ
8 ¯uTA
μ(gU
R PR)u +V0,A,μ
L PL + gU
8
¯dTA
μ(gD
L PL + gD
R PR)d
+V+,A,μ
8 ¯uTA
Model parameters:
i gt
i gut
j ,
8
, M
±
8
V
Decay Width of Color-Octets:
6s [(g2
V8 = 1
R)nM2V
L + g2
8
2 −
m2
q+m2
4 − m2
q′
q−m2
2q′
o + 3mqmq′ gL gR]
2MV8
1
2 (M2V
8
q ,m2
,m2
q′ )
M3V
8
,
where (x, y, z) = x2 + y2 + z2 − 2x · y − 2y · z − 2z · x
Resonant effect through:
Top-Pair Production
Single-Top
Same-sign Top
Dijet

Rate and Constraints on Vector Color-Octet resonants
√s @ LHC = 7 TeV, L = 5fb−1
MV
±,0
8
GeV N(u¯d → V+
8 ) N(d ¯d → V0
8 ) N(d¯u → V− 8 ) N(u¯u → V0
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 octet
resonance 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 s )
[PRL 105,161801]

Framework
MadGraph/MadEvent version 4.5.2
Collider: Tevatron √s = 1.96 TeV
PDF Set: CTEQ6L1
s = 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
s = 0.13
Top quark mass mt = 172.5 GeV/c2
μF = μR = μ = mt
Collider: LHC √s = 7 TeV
mjj = 200 GeV, || ≤ 1.3, Both jet || ≤ 2.5

Top-Pair production at Tevatron (Flavor Conserving)
t¯t
References
7.50 ± 0.48 CDF 4.6 fb−1 [CDF Note 9913]
7.2 ± 0.37 SM NNLO [hep-ph/1205.3453]
8.2
8
7.8
7.6
7.4
7.2
7
6.8
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
s in pb
ÖlAA
200 GeV
350 GeV
500 GeV
700 GeV
900 GeV
CDF
SM NNLO
8.2
8
7.8
7.6
7.4
7.2
7
6.8
350 GeV
500 GeV
700 GeV
CDF
SM NNLO
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
s in pb
ÖlRR
200 GeV
900 GeV

Top-Pair production at Tevatron (Flavor Violating)
t¯t
References
7.50 ± 0.48 CDF 4.6 fb−1 [CDF Note 9913]
7.2 ± 0.37 SM NNLO [hep-ph/1205.3453]
8.2
8
7.8
7.6
7.4
7.2
7
6.8
0.2 0.4 0.6 0.8 1
s in pb
gut
AA
200 GeV
350 GeV
500 GeV
700 GeV
900 GeV
CDF
SM NNLO
8.2
8
7.8
7.6
7.4
7.2
7
6.8
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
s in pb
gut
RR
200 GeV
350 GeV
500 GeV
700 GeV
900 GeV
CDF
SM NNLO

mt¯t
y fit : Flavor-Conserving
Kinematic dependence of the asymmetry: [arXiv:1211.1003]
AFB(|y|) = N(y0)−N(y0)
, t
¯t
¯t
¯y = yt yN(y0)+N(y0) − AFB(Mt) = NF (Mt)−NB (Mtt )
¯NF (Mt¯t
)+NB (Mt¯t
) , Mt¯t
= invariant mass of top-antitop pair
2-Analysis: 2 = Pi
i −Oexp
(Oth
i )2
(Oi )2
Fitting points: (200 GeV, AA = 0.30), (500 GeV, RR = 0.11), (900 GeV,
NA = 0.35)
0.6
0.5
0.4
0.3
0.2
0.1
0
350 400 450 500 550 600 650 700 750 800
AFB
Mt-t
GeV
NLO
Data
200(0.30)
500(0.11)
900(0.35)
0.5
0.4
0.3
0.2
0.1
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
AFB
D y
NLO
Data
200(0.30)
500(0.11)
900(0.35)

mt¯t
y fit : Flavor-Violating
Kinematic dependence of the asymmetry:
AFB(|y|) = N(y0)−N(y0)
, t
¯t
¯t
¯y = yt yN(y0)+N(y0) − AFB(Mt) = NF (Mt)−NB (Mtt )
¯NF (Mt¯t
)+NB (Mt¯t
) , Mt¯t
= invariant mass of top-antitop pair
2-Analysis: 2 = Pi
i −Oexp
(Oth
i )2
(Oi )2
Fitting points: (200 GeV, gut
L = 0.26), (500 GeV, gut
R = −gut
R = −gut
L = 0.53), (900
R = 1.266= gut
GeV, gut
L = 0)
0.6
0.5
0.4
0.3
0.2
0.1
0
350 400 450 500 550 600 650 700 750 800
AFB
Mt-t
GeV
NLO
Data
200(0.26)
500(0.53)
900(1.26)
0.5
0.4
0.3
0.2
0.1
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
AFB
D y
NLO
Data
200(0.26)
500(0.53)
900(1.26)

Spin-Correlation
1

d2
d cos +d cos −
4 (1+Ct¯t
= 1
cos + cos −),
Ct¯t
= ↑↑+↓↓−↑↓−↓↑
↑↑+↓↓+↑↓+↓↑
.
Ct¯t
= [(¯t
R tL)+(¯t
LtR )]−[(¯t
R tR )+(¯t
LtL)]
[(¯t
R tL)+(¯t
LtR )]+[(¯t
R tR )+(¯tLtL)]
≡ NO−NS
NO+NS
Ct¯t
beam Ct¯t
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
1

d2
d cos +d cos −
4 (1+Ct¯t
= 1
cos + cos −),
Ct¯t
= ↑↑+↓↓−↑↓−↓↑
↑↑+↓↓+↑↓+↓↑
.
Ct¯t
= [(¯t
R tL)+(¯t
LtR )]−[(¯t
R tR )+(¯t
LtL)]
[(¯t
R tL)+(¯t
LtR )]+[(¯t
R tR )+(¯tLtL)]
≡ NO−NS
NO+NS
We found consistent region for model
parameters
Ct¯t
beam Ct¯t
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- channel
s-channel q¯q ! t¯u, where q = d, s, c, b
t-channel u¯q ! t¯q,
s + t-channel u¯u ! t¯u and t + u-channel uu ! tu
all via neutral color-octet V0
8 exchange.

In FV combined s + t- channel
s-channel q¯q ! t¯u, where q = d, s, c, b
t-channel u¯q ! t¯q,
s + t-channel u¯u ! t¯u and t + u-channel uu ! tu
all via neutral color-octet V0
8 exchange.
For a given FC coupling single top production can constrain the FV coupling more
severely than the top-pair production.

Same-sign Top: Exclusion Plots at Tevatron
[CDF Note 10466] LL LR RR
¯t × BR(W → l)2 [fb] 54 51 44
tt+¯t
2
1.8
1.5
1.2
1
0.8
0.5
0.2
0.2 0.5 0.8 1 1.2 1.5 1.8 2
ut|
|gR
ut|
|gL
900 GeV
700 GeV
500 GeV
350 GeV
200 GeV

Top Pair-Production at LHC
NLO QCD (pp)
Approx. NNLO (pp)
NLO QCD (pp)
Approx. NNLO (pp)
CDF
D0
Single Lepton (8 TeV) 241 ± 32 pb
Single Lepton (7 TeV) 179 ± 12 pb
Dilepton 173
+17 pb
14
Allhadronic
167 ± 81 pb
Combined 177 +11
pb 10
250
200
1 2 3 4 5 6 7 8
s [TeV]
[pb] tt s
102
10
1
ATLAS Preliminary
7 8
150

Top Pair-Production at LHC
ATLAS Preliminary
+ 8 177 ± 3
168 ± 12 + 60
50 100 150 200 250 300 350
tt [pb] s
Data 2011, s = 7 TeV
Channel Lumi.
20 Dec 2012
Theory (approx. NNLO)
= 172.5 GeV t for m
stat. uncertainty
total uncertainty
±(stat) ±(syst) ±(lumi) tt s
Single lepton 0.70 fb1
179 ± 4 ± 9 ± 7 pb
Dilepton 1
0.70 fb pb 7
+ 8 11
173 ± 6 + 14
All hadronic
1.02 fb1
167 ± 18 ± 78 ± 6 pb
Combination ± 7 pb 7
Single lepton, b ® Xμn
1
4.66 fb
165 ± 2 ± 17 ± 3 pb
+ jets had t 1.67 fb1
194 ± 18 ± 46 pb
+ lepton had t 2.05 fb1
186 ± 13 ± 20 ± 7 pb
All hadronic
4.7 fb1
± 6 pb 57

Top Mass at LHC
summary May
2013, L top ATLAS m
ATLAS 2010, l+jets* 169.30 ± 4.00 ± 4.90
CONF2011033,
L
= 35 pb1
int ATLAS 2011, l+jets 174.53 ± 0.61 ± 0.43 ± 2.27
= 1.04 fb1
int
Eur. Phys. J. C72 (2012) 2046, L
ATLAS 2011, all jets* 174.90 ± 2.10 ± 3.80
CONF2012030,
L
= 2.05 fb1
int ATLAS 2011, dilepton* 175.20 ± 1.60 ± 3.00
CONF2012082,
L
= 4.7 fb1
int ATLAS 2011, l+jets* 172.31 ± 0.23 ± 0.27 ± 0.67 ± 1.35
CONF2013046,
L
= 4.7 fb1
int CMS Average September 2012
JSFÅsyst. ± 0.91 stat. 173.36 ± 0.38
Tevatron Average May 2013
155 160 165 170 175 180 185 190 195
[GeV] top m
9
1
JSFÅsyst. ± 0.71 stat. 173.20 ± 0.51
= 35 pb1
4.7
fb1
(*Preliminary)
int
± stat. ± JSF ± bJSF ± syst.
stat. uncertainty
stat. Å JSF Å bJSF uncertainty
total uncertainty
ATLAS Preliminary

Top-Pair Production
182
180
178
176
174
172
170
168
166
164
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 GeV,l N A =0.35
NNLO
7.2 7.4 7.6 7.8 8 8.2
LHC (pb)
st-t
Tevatron (pb)
st-t
171
170
169
168
167
166
165
200 GeV,gut
R=-gut
L=0.26
500 GeV,gut
R=-gut
L=0.53
900 GeV,gut
R=1.26,gut
L=0
7.2 7.4 7.6 7.8 8 8.2
LHC (pb)
st-t
Tevatron (pb)
st-t
NNLO
t¯t
(pb) References
173.3 ± 10.1 [ATLAS-CONF-2012-134]
165.2 SM NNLO [hep-ph/1205.3453]

Forward-Backward Asymmetry vs Charge-Asymmetry
0.03
0.02
0.01
0
-0.01
-0.02
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 GeV,l N A =0.35
0.05 0.1 0.15 0.2 0.25 0.3
AC
AFB
Theory
0.03
0.025
0.02
0.015
0.01
0.005
0
-0.005
-0.01
200 GeV,gut
0.05 0.1 0.15 0.2 0.25
AC
AFB
R=-gut
L=0.26
500 GeV,gut
R=-gut
L=0.53
900 GeV,gut
R=1.26,gut
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
0.26
0.25
0.24
0.23
0.22
0.21
0.2
0.19
0.18
0.17
0.16
0.46 0.48 0.5 0.52 0.54 0.56 0.58 0.6 0.62
LHC
Ct-t
Tevatron
Ct-t
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 GeV,l N A =0.35
0.26
0.25
0.24
0.23
0.22
0.21
0.2
0.19
0.18
0.17
0.16
-0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6
LHC
Ct-t
Tevatron
Ct-t
200 GeV,gut
R=-gut
L=0.26
500 GeV,gut
R=-gut
L=0.53
900 GeV,gut
R=1.26,gut
L=0
Ct¯t
helicity 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
101
100
10-1
10-2
400 600 800 1000 1200 1400
(pb/20 GeV)
ds/dmt-t
mt-t
(GeV)
SM
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 Gev,l N A =0.35
Top-Quark pT
101
100
10-1
10-2
10-3
0 100 200 300 400 500 600 700
ds/dpT (pb/10 GeV)
pT (GeV)
SM
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 GeV,l N A =0.35

Color-Octet and Dijet @ 7 TeV LHC
Dijet invariant mass
104
103
102
101
100
10-1
10-2
10-3
200 400 600 800 1000 1200 1400 1600 1800
ds/dmjj (pb/50 GeV)
mjj (GeV)
SM
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 GeV,l N A =0.35
Dijet pT
103
102
101
100
10-1
10-2
0 50 100 150 200 250 300 350 400 450 500
(pb/10 GeV)
ds/dpTj
(GeV)
pTj
SM
200 GeV,l A A =0.30
500 GeV,l R R =0.11
900 Gev,l N A =0.35

Same-sign Top: Exclusion Plots at LHC
CMS
1.7
1.5
1.2
1
0.8
0.5
0.2
0.2 0.5 0.8 1 1.2 1.5 1.7
ut|
|gR
ut|
|gL
900 GeV
700 GeV
500 GeV
350 GeV
200 GeV
ATLAS
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
ut|
|gR
ut|
|gL
900 GeV
700 GeV
500 GeV
350 GeV
200 GeV

Conclusion
Appreciable Contribution to At¯t
FB and Ct¯t
without transgressing 1- experimental
production cross-section at Tevatron
2 analysis: favorable focus points ⇒ Possible solution for AFB anomaly
Large parameter-region is allowed by 1- and 2- 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 experimental
data give some favorable parameters
Parameter space are consistent with t¯t
cross-section, measured charge asymmetry
and spin-correlation at LHC
The benchmark points are consistent with all the observables w.r.t low energy
stringent bounds from B and D physics

Update: p¯p ! YY ! jjjj
[arXiv: 1303.2699]
3-jets with ET 20 GeV and
Pjets ET 130 GeV
Within radius of R = 0.4
After trigger selection, at least 4 jets
with ET 15 GeV and || 2.4
✶✡✓
✶✡
▲ ❞t ❂ ❅❃❅ ❢❜ ➢❇ ♣♣ ❆❂❁❃❄❅ ❚❡❱ ✵✻✼ ✽✾✿❀❀
✺✡ ✶✡✡ ✶✺✡ ☛✡✡ ☛✺✡ ✸✡✡ ✸✺✡ ✹✡✡ ✹✺✡ ✺✡✡
❘✁✆✝✞✟✞☎✁ ✠✟✆✆ ✠❨ ✥✁✂✄☎✷❪
☞☞☞☞✌ ✍ ✎ ✏ ✑
➤
✒ ✒
➤✎✭ ✎
s
✶
❊✔✕✖✗✘✖✙ ✚✛✜✛✘ ✢✘ ✣✤✦ ✧★
❖✩✪✖✫✬✖✙ ✚✛✜✛✘
❊✔✕✖✗✘✖✙ ✚✛✜✛✘ ➧ ✯✮
❊✔✕✖✗✘✖✙ ✚✛✜✛✘ ➧ ✓ ✮
✧❈✚❈✫❈✰ ★❖
✪✘❈✕ ✱✲✢✫✳ ✴★❖
♣♣ ❋ ●● ❋ ❉❉❉❉

THANK YOU ALL !!

BACKUP SLIDES

Issues!!
Anomaly cancellation in Axi-gluon case and |gq
A| |gt
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 the
structure 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 of
coupling is forbidden if we assume that strong interactions (QCD) is parity
conserving while in case of coloron, gauge invariance protect this kind of interaction
terms with dimension 4 or less [Zerwekh, Rosenfeld arXiv: 0103159] (however
possible to construct such non-renormalizable dimension-6 interaction [Chivukula et
al arXiv: 0109029])
Coloron production via gluon-fusion (one-loop) is typically 4 orders of magnitude
smaller 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 small
results 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) CD
L,312
R,312
+ CD
L,31CD
− 27CD
R,311/2
D − ¯D
: MG′ (600TeV) CU
L,212
R,212
+ CU
L,21CU
R,211/2
− 60CU
etc...

Top-Pair Production: FC, FV Channel
d ˆFC
d cos
=

Dr. Mukesh Kumar (NITheP/Wits) TITLE: "Top quark physics in the Vector Color-Octet Model"

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