206
5 Direct Searches for New Physics
Events / bin
3
−
10
2
−
10
1
−
10
1
Data
& W+jets
f
t
t
p
t
t
Single t
Z+jets
400GeV
3
LQ
600GeV
3
LQ
800GeV
3
LQ
T
+jets, OS high S
h
τ μ
(13 TeV)
-1
35.9 fb
CMS
[GeV]
t
T
p
0
200
400
600
800
1000 1200
Prediction
Data
0.5
1
1.5
Events / bin
3
−
10
2
−
10
1
−
10
Data
& W+jets
f
t
t
p
t
t
Single t
Z+jets
400GeV
3
LQ
600GeV
3
LQ
800GeV
3
LQ
T
+jets, SS high S
h
τ μ
(13 TeV)
-1
35.9 fb
CMS
[GeV]
t
T
p
0
200
400
600
800
1000 1200
Prediction
Data
0.5
1
1.5
Fig. 5.30 Distributions in reconstructed top quark p T for events with a muon and a τ h candidate,
for opposite-sign (left) and same-sign (right) lepton charges. Taken from [1269]
1050 GeV is obtained for B(LQ → bτ ) = 1, for which this search has been optimised. A recent ATLAS search for top squarks in the t ¯
t+ p
miss
T
channel in all-hadronic
final states, using 139 fb
−1 of 13 TeV data [1165], can be reinterpreted as a LQ search
as well. The search is described above and relies on top tagging for the identification
of t decays. The obtained mass limit is 1240 GeV for B(LQ → tν) = 1.
The first search considering non-diagonal couplings in the quark and lepton generation matrix is a search for LQ → tμ, carried out by CMS with 35.9 fb
−1 of 13 TeV
data [1212]. The search considers μμ+jets and μμμ+jets final states, where the mass
of any two muons has to be greater than 111 GeV to suppress the Z +jets and Z V
backgrounds. This search considers only small-R jets, but large boosts of the t quarks
are taken into account by considering events where the hadronic t quark decay can be
reconstructed with only one or two small-R jets. For each event, the t → decay
is constructed from permutations of one or more of the seven p T -leading small-R
jets, one of the three p T -leading muons or the p T -leading electron, and p
miss
T . The
hadronic top quark candidates are constructed using all permutations of small-R
jets not assigned to the t → decay. The LQ candidates are assembled from top
quark candidates and the two p T -leading muons that have not been associated to
the leptonic top quark. A χ
2 variable that takes into account the mass of each top
quark candidate and the relative mass difference between the two LQ candidates is
used to select the best pair of LQ candidates for each event. The reconstructed LQ
mass is measured for events with three leptons, and the S T distribution is measured
for events with two leptons. While the former category has higher sensitivity for
LQ masses below 400 GeV, the latter category allows to probe high LQ masses.
The analysis excludes scalar LQ masses below 1420 GeV for B(LQ → tμ) = 1,
and a combination with searches for LQ → tτ [1269] and LQ → bν [1271] allows
5 Direct Searches for New Physics
Events / bin
3
−
10
2
−
10
1
−
10
1
Data
& W+jets
f
t
t
p
t
t
Single t
Z+jets
400GeV
3
LQ
600GeV
3
LQ
800GeV
3
LQ
T
+jets, OS high S
h
τ μ
(13 TeV)
-1
35.9 fb
CMS
[GeV]
t
T
p
0
200
400
600
800
1000 1200
Prediction
Data
0.5
1
1.5
Events / bin
3
−
10
2
−
10
1
−
10
Data
& W+jets
f
t
t
p
t
t
Single t
Z+jets
400GeV
3
LQ
600GeV
3
LQ
800GeV
3
LQ
T
+jets, SS high S
h
τ μ
(13 TeV)
-1
35.9 fb
CMS
[GeV]
t
T
p
0
200
400
600
800
1000 1200
Prediction
Data
0.5
1
1.5
Fig. 5.30 Distributions in reconstructed top quark p T for events with a muon and a τ h candidate,
for opposite-sign (left) and same-sign (right) lepton charges. Taken from [1269]
1050 GeV is obtained for B(LQ → bτ ) = 1, for which this search has been optimised. A recent ATLAS search for top squarks in the t ¯
t+ p
miss
T
channel in all-hadronic
final states, using 139 fb
−1 of 13 TeV data [1165], can be reinterpreted as a LQ search
as well. The search is described above and relies on top tagging for the identification
of t decays. The obtained mass limit is 1240 GeV for B(LQ → tν) = 1.
The first search considering non-diagonal couplings in the quark and lepton generation matrix is a search for LQ → tμ, carried out by CMS with 35.9 fb
−1 of 13 TeV
data [1212]. The search considers μμ+jets and μμμ+jets final states, where the mass
of any two muons has to be greater than 111 GeV to suppress the Z +jets and Z V
backgrounds. This search considers only small-R jets, but large boosts of the t quarks
are taken into account by considering events where the hadronic t quark decay can be
reconstructed with only one or two small-R jets. For each event, the t → decay
is constructed from permutations of one or more of the seven p T -leading small-R
jets, one of the three p T -leading muons or the p T -leading electron, and p
miss
T . The
hadronic top quark candidates are constructed using all permutations of small-R
jets not assigned to the t → decay. The LQ candidates are assembled from top
quark candidates and the two p T -leading muons that have not been associated to
the leptonic top quark. A χ
2 variable that takes into account the mass of each top
quark candidate and the relative mass difference between the two LQ candidates is
used to select the best pair of LQ candidates for each event. The reconstructed LQ
mass is measured for events with three leptons, and the S T distribution is measured
for events with two leptons. While the former category has higher sensitivity for
LQ masses below 400 GeV, the latter category allows to probe high LQ masses.
The analysis excludes scalar LQ masses below 1420 GeV for B(LQ → tμ) = 1,
and a combination with searches for LQ → tτ [1269] and LQ → bν [1271] allows