A
bstract
Constraints on selected mediator-based dark matter models and a scalar dark energy model using up to 37 fb
−1
s
= 13 TeV
pp
collision data collected by the ATLAS detector at the LHC during ...2015-2016 are summarised in this paper. The results of experimental searches in a variety of final states are interpreted in terms of a set of spin-1 and spin-0 single-mediator dark matter simplified models and a second set of models involving an extended Higgs sector plus an additional vector or pseudo-scalar mediator. The searches considered in this paper constrain spin-1 leptophobic and leptophilic mediators, spin-0 colour-neutral and colour-charged mediators and vector or pseudo-scalar mediators embedded in extended Higgs sector models. In this case, also
s
= 8 TeV
pp
collision data are used for the interpretation of the results. The results are also interpreted for the first time in terms of light scalar particles that could contribute to the accelerating expansion of the universe (dark energy).
Single- and double-differential cross-section measurements are presented for the production of top-quark pairs, in the lepton + jets channel at particle and parton level. Two topologies, resolved and ...boosted, are considered and the results are presented as a function of several kinematic variables characterising the top and
t
t
¯
system and jet multiplicities. The study was performed using data from
pp
collisions at centre-of-mass energy of 13 TeV collected in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider (LHC), corresponding to an integrated luminosity of
36
fb
-
1
. Due to the large
t
t
¯
cross-section at the LHC, such measurements allow a detailed study of the properties of top-quark production and decay, enabling precision tests of several Monte Carlo generators and fixed-order Standard Model predictions. Overall, there is good agreement between the theoretical predictions and the data.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A technique is presented to measure the efficiency with which
c
-jets are mistagged as
b
-jets (mistagging efficiency) using
t
t
¯
events, where one of the
W
bosons decays into an electron or muon ...and a neutrino and the other decays into a quark–antiquark pair. The measurement utilises the relatively large and known
W
→
c
s
branching ratio, which allows a measurement to be made in an inclusive
c
-jet sample. The data sample used was collected by the ATLAS detector at
s
=
13
TeV
and corresponds to an integrated luminosity of 139 fb
-
1
. Events are reconstructed using a kinematic likelihood technique which selects the mapping between jets and
t
t
¯
decay products that yields the highest likelihood value. The distribution of the
b
-tagging discriminant for jets from the hadronic
W
decays in data is compared with that in simulation to extract the mistagging efficiency as a function of jet transverse momentum. The total uncertainties are in the range 3–17%. The measurements generally agree with those in simulation but there are some differences in the region corresponding to the most stringent
b
-jet tagging requirement.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
A search for heavy neutral Higgs bosons and
Z
′ bosons is performed using a data sample corresponding to an integrated luminosity of 36.1 fb
−1
from proton-proton collisions at
s
=
13
TeV ...recorded by the ATLAS detector at the LHC during 2015 and 2016. The heavy resonance is assumed to decay to
τ
+
τ
−
with at least one tau lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2-2.25 TeV for Higgs bosons and 0.2-4.0 TeV for
Z
′ bosons. The data are in good agreement with the background predicted by the Standard Model. The results are interpreted in benchmark scenarios. In the context of the hMSSM scenario, the data exclude tan
β >
1
.
0 for
m
A
= 0
.
25 TeV and tan
β >
42 for
m
A
= 1
.
5 TeV at the 95% confidence level. For the Sequential Standard Model,
Z
SSM
′
with
m
Z′
< 2.42 TeV is excluded at 95% confidence level, while
Z
NU
′
with
m
Z
′
< 2.25 TeV is excluded for the non-universal
G
(221) model that exhibits enhanced couplings to third-generation fermions.
A
bstract
Inclusive jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of
s
=
8
TeV recorded by the ATLAS experiment at the Large Hadron Collider at ...CERN. The total integrated luminosity of the analysed data set amounts to 20
.
2 fb
−1
. Double-differential cross-sections are measured for jets defined by the anti-
k
t
jet clustering algorithm with radius parameters of
R
= 0
.
4 and
R
= 0
.
6 and are presented as a function of the jet transverse momentum, in the range between 70 GeV and 2.5 TeV and in six bins of the absolute jet rapidity, between 0 and 3
.
0. The measured cross-sections are compared to predictions of quantum chromodynamics, calculated at next-to-leading order in perturbation theory, and corrected for non-perturbative and electroweak effects. The level of agreement with predictions, using a selection of different parton distribution functions for the proton, is quantified. Tensions between the data and the theory predictions are observed.
A
bstract
A search for Higgs boson pair production via vector-boson fusion (VBF) in the
b
b
¯
b
b
¯
final state is carried out with the ATLAS experiment using 126 fb
−
1
of proton- proton collision ...data delivered at
s
= 13 TeV by the Large Hadron Collider. This search is sensitive to VBF production of additional heavy bosons that may decay into Higgs boson pairs, and in a non-resonant topology it can constrain the quartic coupling between the Higgs bosons and vector bosons. No significant excess relative to the Standard Model expectation is observed, and limits on the production cross-section are set at the 95% confidence level for a heavy scalar resonance in the context of an extended Higgs sector, and for non-resonant Higgs boson pair production. Interpretation in terms of the coupling between a Higgs boson pair and two vector bosons is also provided: coupling values normalised to the Standard Model expectation of
κ
2
V
< −
0
.
76 and
κ
2
V
>
2
.
90 are excluded at the 95% confidence level in data.
A
bstract
Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the
H
→
ZZ
*
→ 4
ℓ
decay channel. The proton-proton collision data ...were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb
−1
. The inclusive fiducial cross section in the
H
→
ZZ
*
→ 4ℓ decay channel is measured to be 3.62 ± 0.50(stat)
− 0.20
+ 0.25
(sys) fb, in agreement with the Standard Model prediction of 2
.
91 ± 0
.
13 fb. The cross section is also extrapolated to the total phase space including all Standard Model Higgs boson decays. Several differential fiducial cross sections are measured for observables sensitive to the Higgs boson production and decay, including kinematic distributions of jets produced in association with the Higgs boson. Good agreement is found between data and Standard Model predictions. The results are used to put constraints on anomalous Higgs boson interactions with Standard Model particles, using the pseudo-observable extension to the kappa-framework.
A
bstract
A search is conducted for new resonances decaying into a
W W
or
W Z
boson pair, where one
W
boson decays leptonically and the other
W
or
Z
boson decays hadronically. It is based on ...proton-proton collision data with an integrated luminosity of 36.1 fb
−1
collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of
s
=
13
TeV in 2015 and 2016. The search is sensitive to diboson resonance production via vector-boson fusion as well as quark-antiquark annihilation and gluon-gluon fusion mechanisms. No significant excess of events is observed with respect to the Standard Model backgrounds. Several benchmark models are used to interpret the results. Limits on the production cross section are set for a new narrow scalar resonance, a new heavy vector-boson and a spin-2 Kaluza-Klein graviton.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The measurement of the jet energy resolution is presented using data recorded with the ATLAS detector in proton-proton ...collisions at ... The sample corresponds to an integrated luminosity of 35 pb^sup -1^. Jets are reconstructed from energy deposits measured by the calorimeters and calibrated using different jet calibration schemes. The jet energy resolution is measured with two different in situ methods which are found to be in agreement within uncertainties. The total uncertainties on these measurements range from 20 % to 10 % for jets within |y|<2.8 and with transverse momenta increasing from 30 GeV to 500 GeV. Overall, the Monte Carlo simulation of the jet energy resolution agrees with the data within 10 %.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for pair-produced charged Higgs bosons in the framework of Two Higgs Doublet Models (2HDMs). The data of the four experiments ...have been statistically combined. The results are interpreted within the 2HDM for Type I and Type II benchmark scenarios. No statistically significant excess has been observed when compared to the Standard Model background prediction, and the combined LEP data exclude large regions of the model parameter space. Charged Higgs bosons with mass below 80
(Type II scenario) or 72.5
(Type I scenario, for pseudo-scalar masses above 12
) are excluded at the 95 % confidence level.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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