3,120 research outputs found
Search for a CP-odd Higgs boson decaying to Zh in pp collisions at root s=8 TeV with the ATLAS detector
No full textSee paper for full list of authors – 13 pages plus author list + cover pages (30 pages total), 5 figures, 2 tables, submitted to Phys. Lett. B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2013-06/International audienceA search for a heavy, CP-odd Higgs boson, , decaying into a boson and a 125 GeV Higgs boson, , with the ATLAS detector at the LHC is presented. The search uses proton--proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb. Decays of CP-even bosons to or pairs with the boson decaying to electron or muon pairs are considered, as well as decays with the boson decaying to neutrinos. No evidence for the production of an boson in these channels is found and the 95% confidence level upper limits derived for \sigma (gg\rightarrow A) \times \mbox{BR}(A \rightarrow Zh) \times \mbox{BR}(h \rightarrow f\bar{f}) are 0.098--0.013 pb for and 0.57--0.014 pb for in a range of 220--1000 GeV. The results are combined and interpreted in the context of two-Higgs doublet models
Role of the ATLAS Grid Information System (AGIS) in Distributed Data Analysis and Simulation
No full textAuthor Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery
No full textIn the version of this article initially published, the ATLAS Collaboration
author names, affiliations and acknowledgements were omitted and
have now been included in the HTML and PDF versions of the article
Measurement of the azimuthal anisotropy of charged particles in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions with ATLAS
No full textThe data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs offer new opportunities to study charged particle azimuthal anisotropy. The high-statistics Pb+Pb sample allows for a detailed study of the azimuthal anisotropy of produced particles. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of quark-gluon plasma and parton energy loss. New ATLAS measurements of differential and global Fourier harmonics of charged particles (v(n)) in 5.02 TeV Pb+Pb and 5.44 TeV Xe+Xe collisions in a wide range of transverse momenta, pseudorapidity (vertical bar eta vertical bar < 2.5) and collision centrality are presented. The higher order harmonics, sensitive to fluctuations in the initial state, are measured up to n = 7 using the two-particle correlation, cumulant and scalar product methods. The dynamic properties of QGP are studied using a recently-proposed modified Pearson's correlation coefficient, rho(v(n)(2), p(T)), between the event-wise mean transverse momentum and the magnitude of the flow vector in 5.02 TeV Pb+Pb and p+Pb collisions. Several important observations are made. The elliptic and triangular flow harmonics show an interesting universal p(T)-scaling. A linear correlation between the v(2) and v(3) coefficients at low and high p(T) ranges is observed and quantified. The correlation coefficient for v(2) is found to be negative in peripheral and positive in central Pb+Pb collisions. The value for v(3) is found to be much smaller than for v(2) and have similar centrality behavior as the v(2)
Measurements of azimuthal anisotropies of jet production in Pb+Pb collisions at √sNN = 5.02 TeV with the ATLAS detector
No full textThe azimuthal variation of jet yields in heavy-ion collisions provides information about the path-length dependence of the energy loss experienced by partons passing through the hot, dense nuclear matter known as the quark–gluon plasma. This paper presents the azimuthal anisotropy coefficients
v
2
,
v
3
, and
v
4
measured for jets in
Pb
+
Pb
collisions at
√
s
NN
=
5.02
TeV using the ATLAS detector at the LHC. The measurement uses data collected in 2015 and 2018, corresponding to an integrated luminosity of 2.2
nb
−
1
. The
v
n
values are measured as a function of the transverse momentum of the jets between 71 and 398 GeV and the event centrality. A nonzero value of
v
2
is observed in all but the most central collisions. The value of
v
2
is largest for jets with lower transverse momentum, with values up to 0.05 in mid-central collisions. A smaller, nonzero value of
v
3
of approximately 0.01 is measured with no significant dependence on jet
p
T
or centrality, suggesting that fluctuations in the initial state play a small but distinct role in jet energy loss. No significant deviation of
v
4
from zero is observed in the measured kinematic region
Author Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery
No full textSearch for Dark Matter Produced in Association with a Dark Higgs Boson Decaying into W^{±}W^{∓} or ZZ in Fully Hadronic Final States from sqrt[s]=13 TeV pp Collisions Recorded with the ATLAS Detector.
No full textSeveral extensions of the Standard Model predict the production of dark matter particles at the LHC. An uncharted signature of dark matter particles produced in association with VV=W^{±}W^{∓} or ZZ pairs from a decay of a dark Higgs boson s is searched for using 139 fb^{-1} of pp collisions recorded by the ATLAS detector at a center-of-mass energy of 13 TeV. The s→V(qq[over ¯])V(qq[over ¯]) decays are reconstructed with a novel technique aimed at resolving the dense topology from boosted VV pairs using jets in the calorimeter and tracking information. Dark Higgs scenarios with m_{s}>160 GeV are excluded
Search for a new heavy scalar particle decaying into a Higgs boson and a new scalar singlet in final states with one or two light leptons and a pair of τ-leptons with the ATLAS detector
No full textA search for a new heavy scalar particle X decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle S is presented. The search uses a proton-proton (pp) collision data sample with an integrated luminosity of 140 fb−1 recorded at a centre-of-mass energy of √s = 13 TeV with the ATLAS detector at the Large Hadron Collider. The most sensitive mass parameter space is explored in X mass ranging from 500 to 1500 GeV, with the corresponding S mass in the range 200–500 GeV. The search selects events with two hadronically decaying τ-lepton candidates from H → τ+τ− decays and one or two light leptons (ℓ = e, μ) from S → VV (V = W, Z) decays while the remaining V boson decays hadronically or to neutrinos. A multivariate discriminant based on event kinematics is used to separate the signal from the background. No excess is observed beyond the expected SM background and 95% confidence level upper limits between 72 fb and 542 fb are derived on the cross-section σ(pp → X → SH) assuming the same SM-Higgs boson-like decay branching ratios for the S → VV decay. Upper limits on the visible cross-sections σ(pp → X → SH → WWττ) and σ(pp → X → SH → ZZττ) are also set in the ranges 3–26 fb and 6–33 fb, respectively
Longitudinal flow decorrelations in Xe+Xe collisions at √sNN=5.44 TeV with the ATLAS detector
No full textThe first measurement of longitudinal decorrelations of harmonic flow amplitudes
v
n
for
n
=
2
–
4
in
Xe
+
Xe
collisions at
√
s
N
N
=
5.44
TeV
is obtained using
3
μ
b
−
1
of data with the ATLAS detector at the LHC. The decorrelation signal for
v
3
and
v
4
is found to be nearly independent of collision centrality and transverse momentum (
p
T
) requirements on final-state particles, but for
v
2
a strong centrality and
p
T
dependence is seen. When compared with the results from
Pb
+
Pb
collisions at
√
s
N
N
=
5.02
TeV
, the longitudinal decorrelation signal in midcentral
Xe
+
Xe
collisions is found to be larger for
v
2
, but smaller for
v
3
. Current hydrodynamic models reproduce the ratios of the
v
n
measured in
Xe
+
Xe
collisions to those in
Pb
+
Pb
collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between
Xe
+
Xe
and
Pb
+
Pb
. The results on the system-size dependence provide new insights and an important lever arm to separate effects of the longitudinal structure of the initial state from other early and late time effects in heavy-ion collisions
Search for type-III seesaw heavy leptons in pp collisions at root s=8 TeV with the ATLAS detector
No full textA search for the pair production of heavy leptons (N-0, L-+/-) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N-0 -> W(+/-)l(+/-) (l = e, mu, tau) and L-+/- -> W(+/-)v (v = v(e), v(mu), v(tau)) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair production is observed. Heavy leptons with masses below 325-540 GeV are excluded at the 95% confidence level, depending on the theoretical scenario considered.ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1103/PhysRevD.92.032001</p
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