Recent SUSY results in ATLAS · 2018. 11. 5. · candidate. Different aspects of SUSY searches,...
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PoS(CORFU2017)060 Recent SUSY results in ATLAS Judita Mamuži´ c * on behalf of the ATLAS Collaboration Instituto de Fisica Corpuscular (IFIC) / Consejo Superior de Investigaciones Cientificas (CSIC) - Universidad de Valencia (UV), Spain E-mail: [email protected] Supersymmetry (SUSY) is considered one of the best motivated extensions of the Standard Model. It postulates a fundamental symmetry between fermions and bosons, and introduces a set of new supersymmetric particles at the electroweak scale. It addresses the hierarchy and natu- ralness problem, gives a solution to the gauge couplings unification, and offers a cold dark matter candidate. Different aspects of SUSY searches, using strong, electroweak, third generation pro- duction, R-parity violation models, and long lived particles are being studied at the LHC. An overview of most recent results in SUSY searches using Run 2 ATLAS data, at 13 TeV with 36.1 fb -1 of integrated luminosity, was presented. Corfu Summer Institute 2017 ’School and Workshops on Elementary Particle Physics and Gravity’ 2-28 September 2017 Corfu, Greece * Speaker. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). https://pos.sissa.it/
Transcript of Recent SUSY results in ATLAS · 2018. 11. 5. · candidate. Different aspects of SUSY searches,...
PoS(CORFU2017)060
Recent SUSY results in ATLAS
Judita Mamužic∗ on behalf of the ATLAS CollaborationInstituto de Fisica Corpuscular (IFIC) / Consejo Superior de Investigaciones Cientificas (CSIC)- Universidad de Valencia (UV), SpainE-mail: [email protected]
Supersymmetry (SUSY) is considered one of the best motivated extensions of the StandardModel. It postulates a fundamental symmetry between fermions and bosons, and introduces aset of new supersymmetric particles at the electroweak scale. It addresses the hierarchy and natu-ralness problem, gives a solution to the gauge couplings unification, and offers a cold dark mattercandidate. Different aspects of SUSY searches, using strong, electroweak, third generation pro-duction, R-parity violation models, and long lived particles are being studied at the LHC. Anoverview of most recent results in SUSY searches using Run 2 ATLAS data, at 13 TeV with36.1 fb−1 of integrated luminosity, was presented.
Corfu Summer Institute 2017 ’School and Workshops on Elementary Particle Physics and Gravity’2-28 September 2017Corfu, Greece
∗Speaker.
c© Copyright owned by the author(s) under the terms of the Creative CommonsAttribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). https://pos.sissa.it/
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1. Introduction
Supersymmetry (SUSY) [1–6] is a well motivated extension of the Standard Model (SM).It postulates a fundamental symmetry between fermions and bosons, and introduces a new set ofSUSY particles at the electroweak scale, where for each fermion (boson) in the SM there is a boson(fermion) SUSY partner. SUSY can offer solutions to a number of phenomena not explained bythe SM. First, the radiative corrections to the Higgs boson mass become extremely large when afermion couples to the Higgs. However, the radiative corrections of boson couplings to the Higgsare of opposite sign, and can cancel out with the fermionic contributions. SUSY naturally imposesthis relation, and consequently allows large mass differences in the mass hierarchy of particles.Second, the Grand Unified Theories aim to provide one general description of electroweak andstrong interactions. When experimentally measured values of electromagnetic, weak and strongcoupling constants are extrapolated to high energies, these three never become equal. However,running of gauge couplings can be modified by introducing new physics between the electroweakand the Planck scale. When SUSY particles are included in the running of couplings, their evolutionto the high mass scale brings to unification of gauge couplings. Third, observations of visible stars(or galactic gas) rotation speeds around the galactic center and their radial distance from it (i.e.galaxy rotation curves), show that they do not fall as the visible matter distribution prediction.They can be explained by introducing a new type of weakly interacting and non-relativistic matter,i.e. cold dark matter, and accommodate for its current estimate from astronomical measurements.SUSY offers a weakly interacting and massive particle candidate as a solution to this problem.In proton-proton collisions, SUSY particles are expected to be produced in pairs, and a typicalsignature has long chains of consecutive decays.
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SUSY searches at the LHC [9] target a broad range of final states, where each analysis definesa set of selections with high sensitivity for considered models. They are grouped around productioncross sections, as shown in the Figure 1 (a). For R-parity conserving models these include modelsof q and g production, third generation production, and electroweak production. Also R-parityviolating, and models with long lived particles are considered. A typical SUSY analysis defines
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a set of selections on observables. The control regions (CR) are designed to be dominated bya certain SM background, and have no or very little expected signal events. They are used toestimate the number of events in the signal regions (SR) which are designed to maximize the signal-to-background ratio, while the performance of the estimate is validated in the so-called validationregions (VR), which are designed to be similar to the SRs. More details on a typical SUSY analysisin ATLAS [10] can be found in Ref. [11]. In this summary the highlights of SUSY searches arepresented, using 13 TeV p− p collision data, collected with the ATLAS experiment in 2015 and2016 with integrated luminosity of 36.1 fb−1, as shown in the Figure 1 (b).
2. Squark and gluino production
The production of q and g (strong production) has the highest cross section at the LHC, andtherefore represents a very important search. High sensitivity to a large number of SUSY modelscan be achieved targeting a final state with jets, possible leptons, and missing transverse momen-tum. There are two main approaches in the searches for strong production used in ATLAS. One isthe conventional, where a typical discriminating variable is the effective mass (Meff), defined as ascalar sum of transverse momentum of all jets, possible leptons, and missing transverse momen-tum. It is a good measure of all activity in the event, and is expected to have larger values forthe SUSY events, compared to the SM background. The second approach is done using RecursiveJigsaw Reconstruction (RJR) variables [12]. These are kinematic variables defined on the event-by-event basis, designed to use approximations of the rest frames of the invisible (SUSY) particlesin each event. They have shown to have very good sensitivity for searches with compressed SUSYmass spectrum.
The analysis with a veto on a lepton, multiple jets and missing transverse momentum [13]targets the production of q and g. Due to a large production cross section and a very generalselection, it has the sensitivity to a highest number of SUSY models. The main target of theanalysis are the decays of q and g into quarks and χ0
1 , the lightest symmetrical particle (LSP), andtheir one-step decays with intermediate W± or a Z0 boson. A number of signal regions using theconventional and RJR analyses was designed to maximize the sensitivity to models with differentq , g and χ0
1 masses. No significant excess was seen in any of the signal regions, as shown inthe Figure 2. Interpretation was done in a number of SUSY models. In Figure 3 exclusion ofq and g pair production models, with direct and one-step decays, can be seen. For each model, asignificant improvement in sensitivity of around 500 GeV for q and g mass exclusion, compared tothe previous analysis, using lower luminosity at 13 TeV p− p collisions, is achieved. The q massis excluded up to around 1600 GeV, and g is excluded up to around 2 TeV.
The analysis with multiple jets and missing transverse momentum targets the strong productionof models with long decay chains [14]. A typical targeted model is a g pair production with a two-step decay, where g decays into quarks with intermediate χ
±1 , which decays into χ0
2 with a W± ,and χ0
2 decays into and Z0 and a χ01 LSP. A number of signal regions was defined, using selections
with large jet multiplicity, and b-jet multiplicity. No significant excess was observed in any of thesignal regions, and exclusion limits were set on the considered models. A large improvement inthe analysis sensitivity was achieved, of around 400 GeV for all g masses, and in the region of
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compressed mass spectrum in the diagonal of the g vs χ01 plane, compared to the previous 13 TeV
search. Gluino masses up to around 1800 GeV were excluded, as shown in the Figure 4.A distinctive signature of SUSY is with at least two same-sign leptons, and this analysis is
targeted with a search with two same-sign or three leptons [15]. Signal regions were optimizedfor a number of R-parity conserving and R-parity violating models, which differ in the selection ona number of leptons, same-sign requirement and b-jet multiplicity. No significant excess was ob-served in any of the signal regions, and exclusion limits were set on a number of SUSY models. Inthe exclusion of the g pair production with a two-step decay, a large improvement in sensitivity for
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the g masses of about 500 GeV was achieved, and in the region with compressed mass spectrum.Gluino masses up to around 1600 GeV were excluded, as shown in the Figure 5.
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Figure 5: Analysis with two same-sign or three leptons [15]. No significant excess in any of thesignal regions seen (a), and exclusion limits for the g pair production with a two-step decay (b).
In addition to searches with light (u and d) quarks, an analysis of SUSY models with decaysof a g with third generation quarks (b and t) [16] needs to be considered. The signal regions wereoptimized for models with direct and one-step decays of g with b and t quarks. No significantexcess was observed in any of the signal regions, and exclusion limits were set. Gluino masses upto about 1.8 - 2 TeV were excluded, as shown in the Figure 6.
In the Figure 7 a comparison of strong production searches is shown. Highest exclusion inthe g masses of around 2 TeV is reached by the analysis with no leptons, 2-6 jets and missingtransverse momentum, and it is comparable to the reach of the gluino mediated third generationsearches, which in addition have a higher coverage toward the higher χ0
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Figure 6: Gluino mediated third generation search [16]. No significant excess in any of the signalregions, exclusion limits for direct gluino decays with b and t quarks (b).
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Figure 7: Strong production analyses summary [17]. Exclusion curves shown for different g de-cays.
3. Third generation production
A strong motivation for third generation searches is given by the Higgs mass measurement[18, 19], which seems to be unnaturally light, and the existing q and g exclusion limits whichreach up to the TeV scale. The dominant contribution to the Higgs mass comes from the divergentterm of the top-quark. If SUSY exists, and t has masses ≤ 1 TeV, loop diagrams of the top-quarkcan cancel out to a large extent, which gives a natural solution to the mass hierarchy problem.In addition, large splitting between t1 and t2 can be achieved due to large t Yukawa couplings,so effects of the renormalization group equations are high for the third generation squarks, whichbrings to low t1 masses compared to first generation q masses. In this light, a dedicated search forlight t is well motivated.
In order to obtain good sensitivity for a variety of typical signatures of t decays, in optimiza-tion a simplified model approach was used, where χ0
1 LSP was assumed to be bino-like [20], seemore details in the Figure 8. For mass differences of ∆m = mt1 −m
χ01
higher than the stop massmt1 , a t pair production with the direct decays of t with a t quark was used in optimization. Simi-larly, one-step decays with b quarks and intermediate χ
±1 decaying into a W± and χ0
1 LSP, wereconsidered for the ∆m > mW± +mb. Further dedicated selections were optimized for even lower∆m, where the W± decays off-shell, and for t decaying into a c quark and χ0
1 LSP. No significantexcess was seen in any of the signal regions, and exclusion limits were set. A large improvement insensitivity, of about 250 GeV in the t mass for the low χ0
1 , and strongly improved coverage for thelower ∆m models, was achieved compared to 13 TeV searches with lower integrated luminosity.
In addition to using simplified models with a bino χ01 LSP, more realistic mass spectrum
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>0
�m
>m t1
�m
>m
W
+m
b
�m
>0
�m
>m t1
�m
>m
W
+m
b
�m > 0
�m > mt1
�m > mW + mb
�m = mt1� m�0
1
0 100 200 3000 100 200 300 0 100 200 3000 100 200 300
0100
200
300
010
020
030
0
t 1!
c�01
�m
>m
t
mt1< m�0
1
m�10
[GeV] mt1[GeV]
mt 1
[GeV
]m
�0 1
[GeV
]
(a) Analysis strategy
(b) t t direct and one step decay [GeV]
1t~m
200 300 400 500 600 700 800 900 1000
[GeV
]10 χ∼
m
0
100
200
300
400
500
600
700
800
1
0χ∼ W b →1t~
/ 1
0χ∼ t →1t~
1
0χ∼ b f f' →1t~
/ 1
0χ∼ W b →1t~
/ 1
0χ∼ t →1t~
1
0χ∼ b f f' →1t~
/ 1
0χ∼ W b →1t~
/ 1
0χ∼ t →1t~
1
0χ∼ b f f' →1t~
/ 1
0χ∼ c →1t~
-1=8 TeV, 20 fbs
t
) < m
10
χ∼,1t~
m(
∆W
+ m
b
) < m
10
χ∼,1t~
m(
∆) <
01
0χ∼,
1t~ m
(∆
1
0χ∼ t →1t~
/ 1
0χ∼ W b →1t~
/ 1
0χ∼ c →1t~
/ 1
0χ∼ b f f' →1t~
production, 1t~1t
~ Status: Dec 2017
ATLAS Preliminary
1
0χ∼W b
1
0χ∼c
1
0χ∼b f f'
Observed limits Expected limits All limits at 95% CL
-1=13 TeV, 36.1 fbs
0L [1709.04183]
1L [1711.11520]
2L [1708.03247]
Monojet [1711.03301]
Run 1 [1506.08616]
(c) t analysis summary [17].
Figure 8: t pair production analysis strategy using simplified models [20] (a) and exclusion limits[17] (b).
and other LSP mixtures need to be considered for t pair production. For this, dedicated modelspecifications in Phenomenological Minimal SUSY Model (pMSSM) [22,23] were used, as shownin the Figure 9. Models motivated by gauge unification at the GUT scale predict a wino χ0
1 LSP,and have χ
±1 and χ0
2 masses in between third generation squarks, and χ01 LSP. Models motivated
by obtaining natural SUSY, have a Higgsino LSP, and favor light χ±1 , χ0
2 and χ01 LSP, with a
large mass difference compared to t1. Models that predict a dark matter candidate produced in theright amount favor a bino-Higgsino mixture, where third generation squarks have a higher masscompared to all neutralinos and charginos, with χ0
1 even slightly lighter. Dedicated analyses wereoptimized to target these scenarios. No significant excess was seen in any of the searches, and
9
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
t 1,b
1,�
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,(b1)
a)
pure
bin
oLSP
b)
win
oN
LSP
c)
hig
gsi
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d)
bin
o/hig
gsi
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mix
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pure
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b)
win
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gsi
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b)
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gsi
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d)
bin
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gsi
no
mix
sparticlemasses(a
)Mas
ssp
ectr
uman
dL
SPm
ixin
g.
[GeV
]1t~
m55
060
065
070
075
080
085
090
095
0
[GeV] 0
1 χ∼ m
100
200
300
400
500
600
± 1χ∼
+ m
b m
< t~ m
)1
M × =
22
M (0 1χ∼
m × 2≈ 0 2χ∼
m≈ ± 1χ∼ m
pro
duct
ion,
1b~ 1b~ , 1t~ 1t~W
ino
NLS
P m
odel
:
1t~→
0 1,2
χ∼, t
± 1χ∼
b
1b~→
0 1,2
χ∼, b
± 1χ∼
t 0 1χ∼
W
→ ± 1χ∼
<0:
µ0 1χ∼
, h
0 1χ∼ Z
→ 0 2χ∼
>0:
µ0 1χ∼
(do
min
ant)
, Z
0 1χ∼ h
→ 0 2χ∼
= 600 GeV1
b~m
= 700 GeV1
b~m
= 800 GeV1
b~m
= 900 GeV1
b~m
Obs
erve
d lim
it)
exp
σ1±E
xpec
ted
limit
(<
0µ
>0
µ
AT
LA
S
-1 =
13
TeV
, 36.
1 fb
s Lim
it at
95%
CL
(b)W
ino
LSP
[GeV
]1t~
m40
050
060
070
080
090
010
00
[GeV] 0
1 χ∼ m
100
200
300
400
500
600
700
01
χ∼ +
mt
m < t~
m
+10
GeV
0 1χ∼ =
m0 2χ∼
m+
5 G
eV,
0 1χ∼ =
m± 1χ∼
m p
rodu
ctio
n,1t~ 1t~
Hig
gsin
o LS
P m
odel
:
1t~→
0 1,2
χ∼, t
± 1χ∼
b
0 1χ∼ W
→ ± 1χ∼
0 1χ∼, Z
0 1χ∼
h
→ 0 2χ∼
≈) 0 1χ∼
, t± 1χ∼, b0 2χ∼
B(t
: (45
, 10,
45)
%β
, sm
all t
anLt~
: (33
, 33,
33)
%β
, lar
ge ta
nLt~
: (25
, 50,
25)
%Rt~
Obs
erve
d lim
it
)ex
pσ1±
Exp
ecte
d lim
it (
Lt~ ≈ 1t~)β
(larg
e ta
nLt~ ≈ 1t~
Rt~ ≈ 1t~
AT
LA
S
-1 =
13
TeV
, 36.
1 fb
s Lim
it at
95%
CL
(c)H
iggs
ino
LSP
[GeV
]1t~
m50
060
070
080
090
0
[GeV] 0
1 χ∼ m
200
300
400
500
600
) =
20-
50 G
eV0 1χ∼ , 0 2χ∼
m(
∆ p
rodu
ctio
n,1b~ 1b~
+
1t~ 1t~B
ino/
Hig
gsin
o m
ix m
odel
:
1t~→
0 1,2,
3χ∼
, t
± 1χ∼b
1b~→
0 1,2,
3χ∼
, b
± 1χ∼t
0 1,2
χ∼ W
* → ± 1χ∼
0 1,2
χ∼, Z
*/h*
± 1χ∼
W*
→ 0 3χ∼0 1χ∼
Z*/
h*
→ 0 2χ∼O
bser
ved
limit
)ex
pσ1±
Exp
ecte
d lim
it (
Lt~ ≈ 1t~Rt~ ≈ 1t~
AT
LA
S
-1 =
13
TeV
, 36.
1 fb
s Lim
it at
95%
CL
(d)B
ino-
Hig
gsin
oL
SP
Figu
re9:
Stop
pair
prod
uctio
nan
alys
isst
rate
gyus
ing
pMSS
Min
spir
edm
odel
s[2
0].T
ypic
alm
asss
pect
rum
and
LSP
mix
ing
(a),
and
inte
rpre
tatio
n(b
).
10
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
[GeV]1b
~m200 400 600 800 1000 1200
[GeV
]0 1χ∼
m
0
100
200
300
400
500
600
700
800
900
10000
1χ∼ b → 1b
~Bottom squark pair production,
-1=13 TeV, 36.1 fbs
ATLAS
=8 TeVs, -1 + 2 b-jets, 20.1 fbT
missATLAS E
=13 TeVs, -1 + 2 b-jets, 3.2 fbT
missATLAS E
Best b0L SR
)theorySUSYσ1 ±Observed limit (
)expσ1 ±Expected limit (
forb
idden
01χ∼
b
→ 1b~
(a) bb direct decay
[GeV]1b
~m300 400 500 600 700 800 900 1000
[GeV
]0 1χ∼
m
100
200
300
400
500
600
700
800 at 50% BR
+
1χ∼ / t
0
1χ∼ b → 1b
~Bottom squark pair production,
-1=13 TeV, 36.1 fbs
ATLAS
=8 TeVs, -1 + 2b, 20.1 fbTmissATLAS 1L + E
Best b0L limits (exp)
Best b0L limits (obs)
Best b1L limits (exp)
Best b1L limits (obs)
Best combined SR
)theorySUSYσ1 ±Observed limit (
)expσ1 ±Expected limit (
forb
idden
+1χ∼
t →
1b~
(b) bb one-step decay
Figure 10: Search for b pair production [21].
exclusion limits were set on these models [20]. These are the first exclusions of pMSSM inspiredmodels in ATLAS, dedicated for t pair production, with these given motivations.
In addition to t pair production, a complementary search is done using the b quark production[21]. Typical final states in the analysis include a b pair production, with a direct decay into a bquark and χ0
1 LSP, or b one-step decay modes via χ±1 with a W± in the decay chain. For the
direct production, an improvement in the sensitivity of about 100 GeV in the b mass is achieved,while for the combined direct and one-step decays in the b pair production an impressive 400 GeVimprovement is achieved for the b mass exclusion, and significant improvement in sensitivity isachieved for the compressed mass spectrum towards the diagonal in the b vs χ0
1 plane, comparedto the previous searches. The exclusion limits of b reach about 900-1000 GeV for direct andcombined decays, as shown in Figure 10.
4. Electroweak production
If the masses of squarks and gluinos are significantly large, the production of χ0, χ±1 and ˜ can
be dominant. As the limits of the strong production are reaching about 2 TeV, the studies of theelectroweak production become well motivated. Typical searches consider final states with two orthree leptons, with and without jets, in the χ
±1 pair, ˜ pair, and χ0
2 χ±1 production [24]. Significant
improvement in the sensitivity to considered models was obtained, compared to previous searches,by using the analyses with multiple bin fits. The analyses with χ0
2 χ±1 production, with W± and
11
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
Z0 in the decay chains were using the binned invariant mass of two leptons. Models with ˜ in thedecay chain were using the binned information of the mT 2 variable, which is a good measure of themissing transverse momentum in-balance in the event. No significant excess was observed in anyof the signal regions, and exclusion limits were set, as shown in the Figure 11.
A comparison of recent searches using the electroweak production [17] is shown in Figure12. A number of final states for the ˜ and χ0
2 χ±1 production is targeted. The highest exclusion
limits were set for the χ02 χ±1 production, with decays via ˜ or ν up to 1.16 TeV for χ0
2 /χ±1 masses.
Eve
nts
/ 2
0 G
eV
1−10
1
10
210
310
410
ATLAS1 = 13 TeV, 36.1 fbs
SR2SFloose
Data
Total SM
Z + jets
VV
Top
Reducible
Other
) = (400,1) GeV 1
0χ∼,l~m(
) = (500,1) GeV 1
0χ∼,l~m(
[GeV]ll
m100 150 200 250 300 350 400 450 500
Data
/ S
M
0
1
2
(a) mll
Eve
nts
/ 1
5 G
eV
1−10
1
10
210
310
410
ATLAS1 = 13 TeV, 36.1 fbs
SR2SFloose
Data
Total SM
Z + jets
VV
Top
Reducible
Other
) = (400,1) GeV 1
0χ∼,l~m(
) = (500,1) GeV 1
0χ∼,l~m(
[GeV]T2
m100 150 200 250 300 350 400
Data
/ S
M
0
1
2
(b) mT 2
) [GeV]±
1χ∼)/m(
0
2χ∼m(
100 200 300 400 500 600 700
) [G
eV
]0 1
χ∼m
(
0
50
100
150
200
250
300
350
400
450
500
1=13 TeV, 36.1 fbs
ATLAS
0
1χ∼ Z
0
1χ∼ W →
0
2χ∼
±
1χ∼
All limits at 95% CL
)Theory
SUSYσ1 ±Observed limit (
)expσ1 ±Expected limit (
ATLAS 8 TeV arXiv:1403.5294
(c) χ02 χ0
1 with W±Z0
) [GeV]±
1χ∼)/m(
0
2χ∼m(
200 400 600 800 1000 1200
) [G
eV
]0 1
χ∼m
(
0
200
400
600
800
1000
1200
1=13 TeV, 36.1 fbs
ATLAS
0
1χ∼) ν ν l l (
0
1χ∼ ν l →) ν ν
∼l (Ll~ ν
∼), l ν ν∼l(
Ll~ ν
Ll~ →
0
2χ∼
±
1χ∼
All limits at 95% CL
)Theory
SUSYσ1 ±Observed limit (
)expσ1 ±Expected limit (
ATLAS 8 TeV arXiv:1402.7029
(d) χ02 χ0
1 with ˜
Figure 11: Search for electroweak production using two or three leptons [24], using multibin fitfor in mll (left) and mT 2 (right) and interpretation (bottom).
12
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
) [GeV]3
0χ∼, 2
0χ∼, 1
±χ∼m( 200 400 600 800 1000 1200
) [G
eV]
0 1χ∼m
(
0
200
400
600
800
1000
1200
Expected limits Observed limits
2l, arXiv:1803.02762, arXiv:1403.5294 ν∼/ Ll~
via 2l, arXiv:1509.07152 ν∼/ Ll
~via
, arXiv:1708.07875, arXiv:1407.0350τ 2τν∼/ Lτ∼via 2l, arXiv:1403.5294 via WW
−1χ∼ +1χ∼
2l+3l, arXiv:1803.02762, arXiv:1509.07152 ν∼/ Ll~
via 2l compressed, arXiv:1712.08119 via WZ 2l+3l, arXiv:1803.02762, arXiv:1403.5294 via WZ
+3l, arXiv:1501.07110±l±+lγγ lbb+l via Wh
02χ∼±
1χ∼
, arXiv:1708.07875τ 2τν∼/ Lτ∼via 02χ∼/
±
1χ∼ ±1χ∼
3l+4l, arXiv:1509.07152 Rl~
via 0
3χ∼ 02χ∼
All limits at 95% CL
PreliminaryATLAS -1=8,13 TeV, 20.3-36.1 fbs March 2018
) ]3
0χ∼, 2
0χ∼, 1
±χ∼ ) + m( 1
0χ∼ ) = 0.5 [ m( ν∼/ L
τ∼/ Ll~
m(
)1
0χ∼
) = m
(
20χ∼
m(
)1
0χ∼
) = 2 m(
2
0χ∼m(
Figure 12: Electroweak production analyses summary [17]. Exclusion curves shown for differentproductions and decays.
5. Long lived particles
The searches for SUSY models where sparticles are long lived, require dedicated analyses.The search for the the long lived χ
±1 is targeted using the so-called disappearing-track analysis
[17]. The production with long lived χ±1 , χ0
1 and initial-state-radiation jet, where χ±1 decays
into a pion and χ01 LSP, and similarly, a g pair production, where g can decay into two quarks
and χ01 LSP or into two quarks and long lived χ
±1 , which decays into a pion and χ0
1 LSP, wereconsidered. The long lived χ
±1 leaves hits in the inner parts of the detector (Pixel), and decays into
a pion and χ01 LSP, and has no counterparts of the track in the further parts of the tracking detector
(SCT), as shown in the Figure 13 (a). The improved sensitivity of the analysis makes use of theimplemented additional layer in the Pixel detector, and improves the sensitivity towards shorter lifetimes of the long lived χ
±1 . No significant excess was observed in any of the signal regions, and a
comparison to previous searches [17] is shown in the Figure 13 (b).
6. R-parity violation
In addition to R-parity conserving models, the searches for R-parity violating models (RPV)need to be considered. Due to R-parity violating terms in the SUSY hyperpotential, in these mod-els lepton and baryon number violation are allowed. This brings to a variety of final states notconsidered in standard searches, and dedicated analyses were set in place. A broad range of newRPV searches were considered compared to analyses with lower luminosity, but no significant ex-cess was observed in any of the dedicated signal regions [26]. Exclusion limits were set, and forgluino pair production, with g decaying into a t and t , where t decays into a b and s quark, g isexcluded up to masses of about 1600 GeV. Similarly, for a g pair production, with a decay into a
13
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
ATLAS Simulation
π+
χ01
~χ+
1~
(a) “Disappearing track“ analysis strategy.
χ±1p
p
χ01
χ01
π±
j
g
gχ±
1
p
p
χ01
χ01
π±
(b) Long lived χ±1
[ns]τ
1−10 1 10
[GeV
]1± χ∼
Low
er li
mit
on m
100
200
300
400
500
600
700
800
900
1000Expected limits
Observed limits arXiv:1712.02118Disappearing track (pixel-only)
arXiv:1506.05332Pixel dE/dx arXiv:1411.6795Stable charged
arXiv:1310.3675Disappearing track
95% CL limits.
not includedtheorySUSYσ
=13 TeVs, -136 fb
=8 TeVs, -118.4-20.3 fb
PreliminaryATLAS
Status: December 2017]0
W~
[~1
0χ∼ ±π → ]±
W~
[~1
±χ∼
=1)γβ=0, η(r for Inner Detector Calo MS
Sta
ble
[m]τc
2−10 1−10 1 10
(c) Long lived χ±1 summary [17].
Figure 13: Long lived χ±1 analysis strategy (a) [17] and excluion summary (b) [25].
pair of t quarks and intermediate χ±1 or χ0
1 , where both of these sparticles decay into three quarks,g masses are excluded up to about 2 TeV, as shown in the Figure 14.
7. Conclusion
A broad range of improvements were implemented for the SUSY analyses using the 36.1 fb−1ofATLAS data. No significant excess in any of the signal regions was observed, and exclusion limitswere set. In the q and g production, optimization for different regions of model parameter spacebrings to large improvements in the sensitivity of g and q masses, compared to searches with lowerluminosity. In the searches for the third generation production, impressive improvements were ob-tained in the sensitivity of the analyses for standard and compressed mass regions. In addition, anew type of models were considered using the pMSSM parameter space selection, targeting wellmotivated LSP mixture scenarios. In the electroweak production, higher sensitivity was obtained
14
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
g
g
t
t
p
p
t
λ′′323
s
b
t
λ′′323
s
b
) [GeV]g~m(
1000 1500
) [G
eV]
t~m
(
500
1000
1500
2000
-1 = 13 TeV, 36.1 fbs )theorySUSYσ 1 ±Obs. limit (
)expσ 1 ±Exp. limit (
sbt → t~t → g~
m(t)
≤) g~m(
-1 = 8 TeV, 20 fbs bs→ t
~ATLAS
All limits at 95% CL
ATLAS
(a) RPV gg direct decay
g
g
χ01
χ01
p
p
t t
λ′′112
u
ds
t t
λ′′112
sdu
) [GeV]g~m(
1500 2000
) [G
eV]
10 χ∼m
(
0
500
1000
1500
2000
2500
-1 = 13 TeV, 36.1 fbs )theorySUSYσ 1 ±Obs. limit (
)expσ 1 ±Exp. limit (
udst t→ 1
0χ∼ t t→ g~
)1
0χ∼
2 m(t) + m(
≤) g~m(
All limits at 95% CL
ATLAS
(b) RPV gg one-step decay
Figure 14: R-parity violating models interpretation [26], g pair production with t decaying intotwo quarks (left), and g pair production with χ0
1 and χ±1 decaying to three quarks (right).
using improved searches and higher luminosity. For the long lived particles, limits on the long livedχ±1 were set, which benefited from the newly added Pixel detector layer. In addition to R-parity
conserving models, limits were set on a broad range of R-parity violating models. In the Figure 15a summary of recent SUSY searches in ATLAS is shown [17]. Future searches in ATLAS areplanned to use more than two times higher luminosity, and a large number of improvements are setin place. On the one side in extending the sensitivity for uncovered and difficult parameterspace ofexisting searches, and on the other side in improving the searches by using a large number of newwell motivated physics scenarios.
Acknowledgements
The author acknowledges support by the Spanish MINEICO under the project FPA2015-65652-C4-1-R and by the Severo Ochoa Excellence Centre Project SEV-2014-0398.
15
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
Mod
ele,µ,τ,γ
Jets
Em
iss
T
∫ Ldt
[fb−
1 ]M
ass
limit
Ref
eren
ce
InclusiveSearches 3rdgen.gmed.
3rdgen.squarksdirectproduction
EWdirect
Long-livedparticles RPV
Oth
er
qq,q→
qχ0 1
02-
6je
tsYe
s36
.1m
(χ0 1)<
200
GeV
,m(1
stge
n.q)
=m(2
ndge
n.q)
1712
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321.
57Te
Vq
qq,q→
qχ0 1
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pres
sed)
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o-je
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0 1)<
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eV17
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3301
710
GeV
q
gg,g→
qqχ
0 10
2-6
jets
Yes
36.1
m(χ
0 1)<
200
GeV
1712
.023
322.
02Te
Vg
gg,g→
qqχ± 1→
qqW± χ
0 10
2-6
jets
Yes
36.1
m(χ
0 1)<
200
GeV
,m(χ± )=
0.5(
m(χ
0 1)+
m(g
))17
12.0
2332
2.01
TeV
g
gg,g→
qq(ℓℓ)χ
0 1ee,µµ
2je
tsYe
s14
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300
GeV
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5791
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g
gg,g→
qq(ℓℓ/νν
)χ0 1
3e,µ
4je
ts-
36.1
m(χ
0 1)=
0G
eV17
06.0
3731
1.87
TeV
g
gg,g→
qqW
Zχ
0 10
7-11
jets
Yes
36.1
m(χ
0 1)<
400
GeV
1708
.027
941.
8Te
Vg
GM
SB
(ℓN
LSP
)1-
2τ
+0-
1ℓ
0-2
jets
Yes
3.2
1607
.059
792.
0Te
Vg
GG
M(b
ino
NLS
P)
2γ
-Ye
s36
.1cτ
(NLS
P)<
0.1
mm
ATLA
S-C
ON
F-20
17-0
802.
15Te
Vg
GG
M(h
iggs
ino-
bino
NLS
P)
γ2
jets
Yes
36.1
m(χ
0 1)=
1700
GeV
,cτ(
NLS
P)<
0.1
mm
,µ>
0AT
LAS
-CO
NF-
2017
-080
2.05
TeV
g
Gra
vitin
oLS
P0
mon
o-je
tYe
s20
.3m
(G)>
1.8×1
0−4
eV,m
(g)=
m(q
)=1.
5Te
V15
02.0
1518
F1/
2sc
ale
865
GeV
gg,g→
bbχ
0 10
3b
Yes
36.1
m(χ
0 1)<
600
GeV
1711
.019
011.
92Te
Vg
gg,g→
ttχ
0 10-
1e,µ
3b
Yes
36.1
m(χ
0 1)<
200
GeV
1711
.019
011.
97Te
Vg
b 1b 1
,b1→
bχ0 1
02
bYe
s36
.1m
(χ0 1)<
420
GeV
1708
.092
6695
0G
eVb 1
b 1b 1
,b1→
tχ± 1
2e,µ
(SS
)1
bYe
s36
.1m
(χ0 1)<
200
GeV
,m(χ± 1
)=m
(χ0 1)
+100
GeV
1706
.037
3127
5-70
0G
eVb 1
t 1t 1
,t1→
bχ± 1
0-2
e,µ
1-2
bYe
s4.
7/13
.3m
(χ± 1
)=2m
(χ0 1)
,m(χ
0 1)=
55G
eV12
09.2
102,
ATLA
S-C
ON
F-20
16-0
77t 1
117-
170
GeV
200-
720
GeV
t 1t 1
t 1,t
1→W
bχ0 1
ortχ
0 10-
2e,µ
0-2
jets
/1-2
bYe
s20
.3/3
6.1
m(χ
0 1)=1
GeV
1506
.086
16,1
709.
0418
3,17
11.1
1520
t 190
-198
GeV
0.19
5-1.
0Te
Vt 1
t 1t 1
,t1→
cχ0 1
0m
ono-
jet
Yes
36.1
m(t 1
)-m
(χ0 1)=
5G
eV17
11.0
3301
90-4
30G
eVt 1
t 1t 1
(nat
ural
GM
SB
)2
e,µ
(Z)
1b
Yes
20.3
m(χ
0 1)>
150
GeV
1403
.522
2t 1
150-
600
GeV
t 2t 2
,t2→
t 1+
Z3
e,µ
(Z)
1b
Yes
36.1
m(χ
0 1)=
0G
eV17
06.0
3986
290-
790
GeV
t 2t 2
t 2,t
2→t 1+
h1-
2e,µ
4b
Yes
36.1
m(χ
0 1)=
0G
eV17
06.0
3986
320-
880
GeV
t 2
ℓ L,Rℓ L,R
,ℓ→ℓχ
0 12
e,µ
0Ye
s36
.1m
(χ0 1)=
0AT
LAS
-CO
NF-
2017
-039
90-5
00G
eVℓ
χ+ 1χ− 1
,χ+ 1→ℓν
(ℓν)
2e,µ
0Ye
s36
.1m
(χ0 1)=
0,m
(ℓ,ν
)=0.
5(m
(χ± 1
)+m
(χ0 1))
ATLA
S-C
ON
F-20
17-0
3975
0G
eVχ± 1
χ± 1χ∓ 1/χ
0 2,χ+ 1→τν
(τν)
,χ0 2→ττ
(νν)
2τ
-Ye
s36
.1m
(χ0 1)=
0,m
(τ,ν
)=0.
5(m
(χ± 1
)+m
(χ0 1))
1708
.078
7576
0G
eVχ± 1
χ± 1χ
0 2→ℓ Lνℓ
Lℓ(νν
),ℓνℓ Lℓ(νν
)3
e,µ
0Ye
s36
.1m
(χ± 1
)=m
(χ0 2),
m(χ
0 1)=
0,m
(ℓ,ν
)=0.
5(m
(χ± 1
)+m
(χ0 1))
ATLA
S-C
ON
F-20
17-0
391.
13Te
Vχ± 1,χ
0 2χ± 1χ
0 2→Wχ
0 1Zχ
0 12-
3e,µ
0-2
jets
Yes
36.1
m(χ± 1
)=m
(χ0 2),
m(χ
0 1)=
0,ℓ
deco
uple
dAT
LAS
-CO
NF-
2017
-039
580
GeV
χ± 1,χ
0 2χ± 1χ
0 2→Wχ
0 1hχ
0 1,h→
bb/W
W/ττ/γγ
e,µ,γ
0-2
bYe
s20
.3m
(χ± 1
)=m
(χ0 2),
m(χ
0 1)=
0,ℓ
deco
uple
d15
01.0
7110
χ± 1,χ
0 227
0G
eVχ
0 2χ0 3,χ
0 2,3→ℓ Rℓ
4e,µ
0Ye
s20
.3m
(χ0 2)
=m(χ
0 3),
m(χ
0 1)=
0,m
(ℓ,ν
)=0.
5(m
(χ0 2)+
m(χ
0 1))
1405
.508
6χ
0 2,3
635
GeV
GG
M(w
ino
NLS
P)w
eak
prod
.,χ
0 1→γG
1e,µ
+γ
-Ye
s20
.3cτ<
1m
m15
07.0
5493
W11
5-37
0G
eVG
GM
(bin
oN
LSP
)wea
kpr
od.,χ
0 1→γG
2γ
-Ye
s36
.1cτ<
1m
mAT
LAS
-CO
NF-
2017
-080
1.06
TeV
W
Dire
ctχ+ 1χ− 1
prod
.,lo
ng-li
vedχ± 1
Dis
app.
trk
1je
tYe
s36
.1m
(χ± 1
)-m
(χ0 1)∼
160
MeV
,τ(χ± 1
)=0.
2ns
1712
.021
1846
0G
eVχ± 1
Dire
ctχ+ 1χ− 1
prod
.,lo
ng-li
vedχ± 1
dE/d
xtr
k-
Yes
18.4
m(χ± 1
)-m
(χ0 1)∼
160
MeV
,τ(χ± 1
)<15
ns15
06.0
5332
χ± 1
495
GeV
Sta
ble,
stop
ped
gR
-had
ron
01-
5je
tsYe
s27
.9m
(χ0 1)
=100
GeV
,10µ
s<τ(
g)<
1000
s13
10.6
584
g85
0G
eVS
tabl
eg
R-h
adro
ntr
k-
-3.
216
06.0
5129
1.58
TeV
gM
etas
tabl
eg
R-h
adro
ndE
/dx
trk
--
3.2
m(χ
0 1)=1
00G
eV,τ>
10ns
1604
.045
201.
57Te
Vg
Met
asta
ble
gR
-had
ron,
g→qqχ
0 1di
spl.
vtx
-Ye
s32
.8τ(
g)=
0.17
ns,m
(χ0 1)=
100
GeV
1710
.049
012.
37Te
Vg
GM
SB
,sta
bleτ,χ
0 1→τ(
e,µ
)+τ(
e,µ
)1-
2µ
--
19.1
10<
tanβ<
5014
11.6
795
χ0 1
537
GeV
GM
SB
,χ0 1→γG
,lon
g-liv
edχ
0 12γ
-Ye
s20
.31<τ(χ
0 1)<
3ns
,SP
S8
mod
el14
09.5
542
χ0 1
440
GeV
gg,χ
0 1→eeν/
eµν/µµν
disp
l.ee/eµ/µµ
--
20.3
7<
cτ(χ
0 1)<
740
mm
,m(g
)=1.
3Te
V15
04.0
5162
χ0 1
1.0
TeV
LFV
pp→ν τ+
X,ντ→
eµ/eτ/µτ
eµ,eτ,µτ
--
3.2
λ′ 31
1=0.
11,λ
132/
133/
233=
0.07
1607
.080
791.
9Te
Vν τ
Bili
near
RP
VC
MS
SM
2e,µ
(SS
)0-
3b
Yes
20.3
m(q
)=m
(g),
cτLS
P<
1m
m14
04.2
500
q,g
1.45
TeV
χ+ 1χ− 1
,χ+ 1→
Wχ
0 1,χ
0 1→eeν,
eµν,µµν
4e,µ
-Ye
s13
.3m
(χ0 1)>
400G
eV,λ
12k,
0(k=
1,2)
ATLA
S-C
ON
F-20
16-0
751.
14Te
Vχ± 1
χ+ 1χ− 1
,χ+ 1→
Wχ
0 1,χ
0 1→ττν e,eτντ
3e,µ
+τ
-Ye
s20
.3m
(χ0 1)>
0.2×
m(χ± 1
),λ
133,
014
05.5
086
χ± 1
450
GeV
gg,g→
qqχ
0 1,χ
0 1→
qqq
04-
5la
rge-
Rje
ts-
36.1
m(χ
0 1)=1
075
GeV
SU
SY-
2016
-22
1.87
5Te
Vg
gg,g→
ttχ
0 1,χ
0 1→
qqq
1e,µ
8-10
jets
/0-4
b-
36.1
m(χ
0 1)=
1Te
V,λ
112,
017
04.0
8493
2.1
TeV
ggg
,g→
t 1t,
t 1→
bs1
e,µ
8-10
jets
/0-4
b-
36.1
m(t 1
)=1
TeV,λ
323,
017
04.0
8493
1.65
TeV
g
t 1t 1
,t1→
bs0
2je
ts+
2b
-36
.717
10.0
7171
100-
470
GeV
t 148
0-61
0G
eVt 1
t 1t 1
,t1→
bℓ2
e,µ
2b
-36
.1B
R(t 1→
be/µ
)>20
%17
10.0
5544
0.4-
1.45
TeV
t 1
Sca
larc
harm
,c→
cχ0 1
02
cYe
s20
.3m
(χ0 1)<
200
GeV
1501
.013
25c
510
GeV
Mas
ssc
ale
[TeV
]10−1
1
√ s=7,
8Te
V√ s
=13
TeV
ATL
AS
SU
SY
Sea
rche
s*-9
5%C
LLo
wer
Lim
itsD
ecem
ber2
017
ATLA
SP
relim
inar
y√ s
=7,
8,13
TeV
*Onl
ya
sele
ctio
nof
the
avai
labl
em
ass
limits
onne
wst
ates
orph
enom
ena
issh
own.
Man
yof
the
limits
are
base
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edm
odel
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orth
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ptio
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ade.
Figu
re15
:AT
LA
SSU
SYse
arch
essu
mm
ary
[17]
.
16
PoS(CORFU2017)060
Recent SUSY results in ATLAS Judita Mamužic
References
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18
