Dr. Mukesh Kumar (NITheP/Wits) TITLE: "Top quark physics in the Vector Color-Octet Model"
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Transcript of 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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 2 / 34
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)
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 3 / 34
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)
|Vtb| measurement (t → Wb)
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 3 / 34
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)
|Vtb| measurement (t → Wb)
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 . . . )
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 3 / 34
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)
|Vtb| measurement (t → Wb)
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 . . .
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 3 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 4 / 34
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
d�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
)
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 5 / 34
Forward-Backward Asymmetry vs Charge-Asymmetry
tt
Tevat ron
- 2 -1 0 1 2
y
d�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
d�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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 6 / 34
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.
)]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 7 / 34
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 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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 7 / 34
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 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
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 7 / 34
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 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
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 7 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 8 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 9 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 9 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 10 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 11 / 34
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)
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 12 / 34
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)
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 13 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 14 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 14 / 34
Single-top Production at Tevatron
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 15 / 34
Single-top Production at Tevatron
In FC s- and t- channel in 5 flavor scheme.
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 16 / 34
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.
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 16 / 34
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.
For a given FC coupling single top production can constrain the FV coupling moreseverely than the top-pair production.
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 16 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 17 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 18 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 19 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 20 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 21 / 34
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
900 GeV,gutR=1.26,gut
L=0
Theory
AC References
−0.013± 0.028(stat.)+0.029−0.031(syst.) [CMS/1112.5100]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 22 / 34
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
900 GeV,gutR=1.26,gut
L=0
C tthelicity References
0.24± 0.02(stat.)± 0.08(syst.) [CMS/TOP-12-004-PAS]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 23 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 24 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 25 / 34
Same-sign Top: Exclusion Plots at LHC
CMS
0.2
0.5
0.8
1
1.2
1.5
1.7
0.2 0.5 0.8 1 1.2 1.5 1.7
|gRut |
|gLut|
900 GeV700 GeV500 GeV350 GeV200 GeV
ATLAS
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1|g
Rut |
|gLut|
900 GeV700 GeV500 GeV350 GeV200 GeV
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 26 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 27 / 34
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 ❂ ❅❃❅ ❢❜
❉❉❉❉❋●●❋♣♣
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 28 / 34
THANK YOU ALL !!
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 29 / 34
BACKUP SLIDES
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 30 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 31 / 34
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
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 32 / 34
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]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 32 / 34
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]
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...
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 32 / 34
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)
]}
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 33 / 34
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
]
Mukesh Kumar (University of the Witwatersrand) Top Quark Physics in the Vector Color-Octet Model September 2, 2014 34 / 34