A
bstract
We study the validity of effective field theory (EFT) interpretations of monojet searches for dark matter at the LHC for vector and axial-vector interactions. We show that the EFT approach ...is valid when the mediator has mass
m
med
greater than 2.5 TeV. We find that the current limits on the contact interaction scale Λ in the EFT apply to theories that are perturbative for dark matter mass
m
DM
<
800 GeV. However, for all values of
m
DM
in these theories, the mediator width is larger than the mass, so that a particle-like interpretation of the mediator is doubtful. Furthermore, consistency with the thermal relic density occurs only for 170 ≲
m
DM
≲ 510 GeV. For lighter mediator masses, the EFT limit either under-estimates the true limit (because the process is resonantly enhanced) or over-estimates it (because the missing energy distribution is too soft). We give some ‘rules of thumb’ that can be used to estimate the limit on Λ (to an accuracy of ~ 50 %) for any
m
DM
and
m
med
from knowledge of the EFT limit. We also compare the relative sensitivities of monojet and dark matter direct detection searches finding that both dominate in different regions of the
m
DM
-
m
med
plane. Comparing only the EFT limit with direct searches is misleading and can lead to incorrect conclusions about the relative sensitivity of the two search approaches.
We use MasterCode to perform a frequentist analysis of the constraints on a phenomenological MSSM model with 11 parameters, the pMSSM11, including constraints from
∼
36
/fb of LHC data at 13 TeV and ...PICO, XENON1T and PandaX-II searches for dark matter scattering, as well as previous accelerator and astrophysical measurements, presenting fits both with and without the
(
g
-
2
)
μ
constraint. The pMSSM11 is specified by the following parameters: 3 gaugino masses
M
1
,
2
,
3
, a common mass for the first-and second-generation squarks
m
q
~
and a distinct third-generation squark mass
m
q
~
3
, a common mass for the first-and second-generation sleptons
m
ℓ
~
and a distinct third-generation slepton mass
m
τ
~
, a common trilinear mixing parameter
A
, the Higgs mixing parameter
μ
, the pseudoscalar Higgs mass
M
A
and
tan
β
. In the fit including
(
g
-
2
)
μ
, a Bino-like
χ
~
1
0
is preferred, whereas a Higgsino-like
χ
~
1
0
is mildly favoured when the
(
g
-
2
)
μ
constraint is dropped. We identify the mechanisms that operate in different regions of the pMSSM11 parameter space to bring the relic density of the lightest neutralino,
χ
~
1
0
, into the range indicated by cosmological data. In the fit including
(
g
-
2
)
μ
, coannihilations with
χ
~
2
0
and the Wino-like
χ
~
1
±
or with nearly-degenerate first- and second-generation sleptons are active, whereas coannihilations with the
χ
~
2
0
and the Higgsino-like
χ
~
1
±
or with first- and second-generation squarks may be important when the
(
g
-
2
)
μ
constraint is dropped. In the two cases, we present
χ
2
functions in two-dimensional mass planes as well as their one-dimensional profile projections and best-fit spectra. Prospects remain for discovering strongly-interacting sparticles at the LHC, in both the scenarios with and without the
(
g
-
2
)
μ
constraint, as well as for discovering electroweakly-interacting sparticles at a future linear
e
+
e
-
collider such as the ILC or CLIC.
We discuss the potential impacts on the CMSSM of future LHC runs and possible
e
+
e
-
and higher-energy proton–proton colliders, considering searches for supersymmetry via
/
E
T
events, precision ...electroweak physics, Higgs measurements and dark matter searches. We validate and present estimates of the physics reach for exclusion or discovery of supersymmetry via
/
E
T
searches at the LHC, which should cover the low-mass regions of the CMSSM parameter space favoured in a recent global analysis. As we illustrate with a low-mass benchmark point, a discovery would make possible accurate LHC measurements of sparticle masses using the MT2 variable, which could be combined with cross-section and other measurements to constrain the gluino, squark and stop masses and hence the soft supersymmetry-breaking parameters
m
0
,
m
1
/
2
and
A
0
of the CMSSM. Slepton measurements at CLIC would enable
m
0
and
m
1
/
2
to be determined with high precision. If supersymmetry is indeed discovered in the low-mass region, precision electroweak and Higgs measurements with a future circular
e
+
e
-
collider (FCC-ee, also known as TLEP) combined with LHC measurements would provide tests of the CMSSM at the loop level. If supersymmetry is not discovered at the LHC, it is likely to lie somewhere along a focus-point, stop-coannihilation strip or direct-channel
A
/
H
resonance funnel. We discuss the prospects for discovering supersymmetry along these strips at a future circular proton–proton collider such as FCC-hh. Illustrative benchmark points on these strips indicate that also in this case FCC-ee could provide tests of the CMSSM at the loop level.
We describe a likelihood analysis using MasterCode of variants of the MSSM in which the soft supersymmetry-breaking parameters are assumed to have universal values at some scale
M
in
below the ...supersymmetric grand unification scale
M
GUT
, as can occur in mirage mediation and other models. In addition to
M
in
, such ‘sub-GUT’ models have the 4 parameters of the CMSSM, namely a common gaugino mass
m
1
/
2
, a common soft supersymmetry-breaking scalar mass
m
0
, a common trilinear mixing parameter
A
and the ratio of MSSM Higgs vevs
tan
β
, assuming that the Higgs mixing parameter
μ
>
0
. We take into account constraints on strongly- and electroweakly-interacting sparticles from
∼
36
/fb of LHC data at 13 TeV and the LUX and 2017 PICO, XENON1T and PandaX-II searches for dark matter scattering, in addition to the previous LHC and dark matter constraints as well as full sets of flavour and electroweak constraints. We find a preference for
M
in
∼
10
5
to
10
9
GeV
, with
M
in
∼
M
GUT
disfavoured by
Δ
χ
2
∼
3
due to the
BR
(
B
s
,
d
→
μ
+
μ
-
)
constraint. The lower limits on strongly-interacting sparticles are largely determined by LHC searches, and similar to those in the CMSSM. We find a preference for the LSP to be a Bino or Higgsino with
m
χ
~
1
0
∼
1
TeV
, with annihilation via heavy Higgs bosons
H
/
A
and stop coannihilation, or chargino coannihilation, bringing the cold dark matter density into the cosmological range. We find that spin-independent dark matter scattering is likely to be within reach of the planned LUX-Zeplin and XENONnT experiments. We probe the impact of the
(
g
-
2
)
μ
constraint, finding similar results whether or not it is included.
We discuss the allowed parameter spaces of supersymmetric scenarios in light of improved Higgs mass predictions provided by FeynHiggs 2.10.0. The Higgs mass predictions combine Feynman-diagrammatic ...results with a resummation of leading and subleading logarithmic corrections from the stop/top sector, which yield a significant improvement in the region of large stop masses. Scans in the pMSSM parameter space show that, for given values of the soft supersymmetry-breaking parameters, the new logarithmic contributions beyond the two-loop order implemented in FeynHiggs tend to give larger values of the light CP-even Higgs mass,
M
h
, in the region of large stop masses than previous predictions that were based on a fixed-order Feynman-diagrammatic result, though the differences are generally consistent with the previous estimates of theoretical uncertainties. We re-analyse the parameter spaces of the CMSSM, NUHM1 and NUHM2, taking into account also the constraints from CMS and LHCb measurements of
BR
(
B
s
→
μ
+
μ
-
)
and ATLAS searches for
/
E
T
events using 20/fb of LHC data at 8 TeV. Within the CMSSM, the Higgs mass constraint disfavours
tan
β
≲
10
, though not in the NUHM1 or NUHM2.
We report the results of a global analysis of dark matter simplified models (DMSMs) with leptophobic mediator particles of spin one, considering the cases of both vector and axial-vector interactions ...with dark matter (DM) particles and quarks. We require the DMSMs to provide all the cosmological DM density indicated by Planck and other observations, and we impose the upper limits on spin-independent and -dependent scattering from direct DM search experiments. We also impose all relevant LHC constraints from searches for monojet events and measurements of the dijet mass spectrum. We model the likelihood functions for all the constraints and combine them within the MasterCode framework, and probe the full DMSM parameter spaces by scanning over the mediator and DM masses and couplings, not fixing any of the model parameters. We find, in general, two allowed regions of the parameter spaces: one in which the mediator couplings to Standard Model (SM) and DM particles may be comparable to those in the SM and the cosmological DM density is reached via resonant annihilation, and one in which the mediator couplings to quarks are
≲
10
-
3
and DM annihilation is non-resonant. We find that the DM and mediator masses may well lie within the ranges accessible to LHC experiments. We also present predictions for spin-independent and -dependent DM scattering, and present specific results for ranges of the DM couplings that may be favoured in ultraviolet completions of the DMSMs.
Likelihood analysis of the minimal AMSB model Bagnaschi, E.; Borsato, M.; Sakurai, K. ...
European physical journal. C, Particles and fields,
04/2017, Letnik:
77, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We perform a likelihood analysis of the minimal anomaly-mediated supersymmetry-breaking (mAMSB) model using constraints from cosmology and accelerator experiments. We find that either a wino-like or ...a Higgsino-like neutralino LSP,
χ
~
1
0
, may provide the cold dark matter (DM), both with similar likelihoods. The upper limit on the DM density from Planck and other experiments enforces
m
χ
~
1
0
≲
3
TeV
after the inclusion of Sommerfeld enhancement in its annihilations. If most of the cold DM density is provided by the
χ
~
1
0
, the measured value of the Higgs mass favours a limited range of
tan
β
∼
5
(and also for
tan
β
∼
45
if
μ
>
0
) but the scalar mass
m
0
is poorly constrained. In the wino-LSP case,
m
3
/
2
is constrained to about
900
TeV
and
m
χ
~
1
0
to
2.9
±
0.1
TeV
, whereas in the Higgsino-LSP case
m
3
/
2
has just a lower limit
≳
650
TeV
(
≳
480
TeV
) and
m
χ
~
1
0
is constrained to
1.12
(
1.13
)
±
0.02
TeV
in the
μ
>
0
(
μ
<
0
) scenario. In neither case can the anomalous magnetic moment of the muon,
(
g
-
2
)
μ
, be improved significantly relative to its Standard Model (SM) value, nor do flavour measurements constrain the model significantly, and there are poor prospects for discovering supersymmetric particles at the LHC, though there are some prospects for direct DM detection. On the other hand, if the
χ
~
1
0
contributes only a fraction of the cold DM density, future LHC
-based searches for gluinos, squarks and heavier chargino and neutralino states as well as disappearing track searches in the wino-like LSP region will be relevant, and interference effects enable
BR
(
B
s
,
d
→
μ
+
μ
-
)
to agree with the data better than in the SM in the case of wino-like DM with
μ
>
0
.
Supersymmetric dark matter after LHC run 1 Bagnaschi, E. A.; Buchmueller, O.; Cavanaugh, R. ...
European physical journal. C, Particles and fields,
10/2015, Letnik:
75, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Different mechanisms operate in various regions of the MSSM parameter space to bring the relic density of the lightest neutralino,
χ
~
1
0
, assumed here to be the lightest SUSY particle (LSP) and ...thus the dark matter (DM) particle, into the range allowed by astrophysics and cosmology. These mechanisms include coannihilation with some nearly degenerate next-to-lightest supersymmetric particle such as the lighter stau
τ
~
1
, stop
t
~
1
or chargino
χ
~
1
±
, resonant annihilation via direct-channel heavy Higgs bosons
H
/
A
, the light Higgs boson
h
or the
Z
boson, and enhanced annihilation via a larger Higgsino component of the LSP in the focus-point region. These mechanisms typically select lower-dimensional subspaces in MSSM scenarios such as the CMSSM, NUHM1, NUHM2, and pMSSM10. We analyze how future LHC and direct DM searches can complement each other in the exploration of the different DM mechanisms within these scenarios. We find that the
τ
~
1
coannihilation regions of the CMSSM, NUHM1, NUHM2 can largely be explored at the LHC via searches for
/
E
T
events and long-lived charged particles, whereas their
H
/
A
funnel, focus-point and
χ
~
1
±
coannihilation regions can largely be explored by the LZ and Darwin DM direct detection experiments. We find that the dominant DM mechanism in our pMSSM10 analysis is
χ
~
1
±
coannihilation: parts of its parameter space can be explored by the LHC, and a larger portion by future direct DM searches.
The CMSSM and NUHM1 after LHC Run 1 Buchmueller, O.; Cavanaugh, R.; Roeck, A. De ...
European physical journal. C, Particles and fields,
06/2014, Letnik:
74, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We analyze the impact of data from the full Run 1 of the LHC at 7 and 8 TeV on the CMSSM with
μ
>
0
and
<
0
and the NUHM1 with
μ
>
0
, incorporating the constraints imposed by other experiments such ...as precision electroweak measurements, flavour measurements, the cosmological density of cold dark matter and the direct search for the scattering of dark matter particles in the LUX experiment. We use the following results from the LHC experiments: ATLAS searches for events with
E
/
T
accompanied by jets with the full 7 and 8 TeV data, the ATLAS and CMS measurements of the mass of the Higgs boson, the CMS searches for heavy neutral Higgs bosons and a combination of the LHCb and CMS measurements of
BR
(
B
s
→
μ
+
μ
-
)
and
BR
(
B
d
→
μ
+
μ
-
)
. Our results are based on samplings of the parameter spaces of the CMSSM for both
μ
>
0
and
μ
<
0
and of the NUHM1 for
μ
>
0
with 6.8
×
10
6
, 6.2
×
10
6
and 1.6
×
10
7
points, respectively, obtained using the MultiNest tool. The impact of the Higgs-mass constraint is assessed using FeynHiggs 2.10.0, which provides an improved prediction for the masses of the MSSM Higgs bosons in the region of heavy squark masses. It yields in general larger values of
M
h
than previous versions of FeynHiggs, reducing the pressure on the CMSSM and NUHM1. We find that the global
χ
2
functions for the supersymmetric models vary slowly over most of the parameter spaces allowed by the Higgs-mass and the
E
/
T
searches, with best-fit values that are comparable to the
χ
2
/
dof
for the best Standard Model fit. We provide 95 % CL lower limits on the masses of various sparticles and assess the prospects for observing them during Run 2 of the LHC.
The pMSSM10 after LHC run 1 de Vries, K. J.; Bagnaschi, E. A.; Buchmueller, O. ...
European physical journal. C, Particles and fields,
09/2015, Letnik:
75, Številka:
9
Journal Article
Recenzirano
Odprti dostop
We present a frequentist analysis of the parameter space of the pMSSM10, in which the following ten soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale
M
SUSY
...≡
m
t
~
1
m
t
~
2
: the gaugino masses
M
1
,
2
,
3
, the first-and second-generation squark masses
m
q
~
1
=
m
q
~
2
, the third-generation squark mass
m
q
~
3
, a common slepton mass
m
ℓ
~
and a common trilinear mixing parameter
A
, as well as the Higgs mixing parameter
μ
, the pseudoscalar Higgs mass
M
A
and
tan
β
, the ratio of the two Higgs vacuum expectation values. We use the MultiNest sampling algorithm with
∼
1.2
×
10
9
points to sample the pMSSM10 parameter space. A dedicated study shows that the sensitivities to strongly interacting sparticle masses of ATLAS and CMS searches for jets, leptons
+
signals depend only weakly on many of the other pMSSM10 parameters. With the aid of the Atom and Scorpion codes, we also implement the LHC searches for electroweakly interacting sparticles and light stops, so as to confront the pMSSM10 parameter space with all relevant SUSY searches. In addition, our analysis includes Higgs mass and rate measurements using the HiggsSignals code, SUSY Higgs exclusion bounds, the measurements of
BR
(
B
s
→
μ
+
μ
-
)
by LHCb and CMS, other
B
-physics observables, electroweak precision observables, the cold dark matter density and the XENON100 and LUX searches for spin-independent dark matter scattering, assuming that the cold dark matter is mainly provided by the lightest neutralino
χ
~
1
0
. We show that the pMSSM10 is able to provide a supersymmetric interpretation of
(
g
-
2
)
μ
, unlike the CMSSM, NUHM1 and NUHM2. As a result, we find (omitting Higgs rates) that the minimum
χ
2
=
20.5
with 18 degrees of freedom (d.o.f.) in the pMSSM10, corresponding to a
χ
2
probability of 30.8 %, to be compared with
χ
2
/
d
.
o
.
f
.
=
32.8
/
24
(
31.1
/
23
)
(
30.3
/
22
)
in the CMSSM (NUHM1) (NUHM2). We display the one-dimensional likelihood functions for sparticle masses, and we show that they may be significantly lighter in the pMSSM10 than in the other models, e.g., the gluino may be as light as
∼
1250
GeV
at the 68 % CL, and squarks, stops, electroweak gauginos and sleptons may be much lighter than in the CMSSM, NUHM1 and NUHM2. We discuss the discovery potential of future LHC runs,
e
+
e
-
colliders and direct detection experiments.
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