234 research outputs found
Search for Higgs boson decays to a photon and a Z boson with the ATLAS detector
No full textA search for the Standard Model Higgs Boson in the decay channel , , where is presented. The analysis is based on 4.5fb and 20.3fb of proton-proton collisions at 7 TeV and 8 TeV, respectively, recorded with the ATLAS detector at the LHC in 2011 and 2012. No significant excess above the Standard Model prediction is observed. The results are interpreted by setting limits on Higgs production within this channel
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
Strong constraints on jet quenching in centrality-dependent +Pb collisions at 5.02 TeV from ATLAS
No full textJet quenching is the process of color-charged partons losing energy via interactions with quark-gluon plasma droplets created in heavy-ion collisions. The collective expansion of such droplets is well described by viscous hydrodynamics. Similar evidence of collectivity is consistently observed in smaller collision systems, including and +Pb collisions. In contrast, while jet quenching is observed in Pb+Pb collisions, no evidence has been found in these small systems to date, raising fundamental questions about the nature of the system created in these collisions. The ATLAS experiment at the Large Hadron Collider has measured the yield of charged hadrons correlated with reconstructed jets in 0.36 nb of +Pb and 3.6 pb of collisions at 5.02 TeV. The yields of charged hadrons with GeV near and opposite in azimuth to jets with or 60 GeV, and the ratios of these yields between +Pb and collisions, , are reported. The collision centrality of +Pb events is categorized by the energy deposited by forward neutrons from the struck nucleus. The values are consistent with unity within a few percent for hadrons with GeV at all centralities. These data provide new, strong constraints which preclude almost any parton energy loss in central +Pb collisions
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
Measurement of jet p(T) correlations in Pb+Pb and pp collisions at root s(NN)=2.76 TeV with the ATLAS detector
No full textMeasurements of dijet Pt correlations in Pb+Pb and pp collisions at a nucleon-nucleon centre-of-mass energy of root s(NN) = 2.76 TeV are presented. The measurements are performed with the ATLAS detector at the Large Hadron Collider using Pb+Pb and pp data samples corresponding to integrated luminosities of 0.14 nb(-1)and 4.0 pb(-1) respectively. Jets are reconstructed using the anti-k(t) algorithm with radius parameter values R = 0.3 and R = 0.4. A background subtraction procedure is applied to correct the jets for the large underlying event present in Pb+Pb collisions. The leading and sub-leading jet transverse momenta are denoted p(T1) and p(T2). An unfolding procedure is applied to the two-dimensional (p(T1) , p(T2)) distributions to account for experimental effects in the measurement of both jets. Distributions of (1/N)dN/dx(J), where X-J = p(T2)/p(T1) , are presented as a function of p(T1) and collision centrality. The distributions are found to be similar in peripheral Pb+Pb collisions and pp collisions, but highly modified in central Pb+Pb collisions. Similar features are present in both the R = 0.3 and R = 0.4 results, indicating that the effects of the underlying event are properly accounted for in the measurement. The results are qualitatively consistent with expectations from partonic energy loss models. (c) 2017 The Author. Published by Elsevier B.V
Search for heavy neutral leptons in decays of W bosons using a dilepton displaced vertex in √s = 13 TeV pp collisions with the ATLAS detector
No full textA search for a long-lived, heavy neutral lepton (
N
) in
139
fb
−
1
of
√
s
=
13
TeV
p
p
collision data collected by the ATLAS detector at the Large Hadron Collider is reported. The
N
is produced via
W
→
N
μ
or
W
→
N
e
and decays into two charged leptons and a neutrino, forming a displaced vertex. The
N
mass is used to discriminate between signal and background. No signal is observed, and limits are set on the squared mixing parameters of the
N
with the left-handed neutrino states for the
N
mass range
3
GeV
<
m
N
<
15
GeV
. For the first time, limits are given for both single-flavor and multiflavor mixing scenarios motivated by neutrino flavor oscillation results for both the normal and inverted neutrino-mass hierarchies
Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in root s(NN)=5.02 TeV p+Pb collisions measured by the ATLAS experiment
No full textMeasurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p + Pbcollision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of root sNN= 5.02 TeV. Charged particles are reconstructed over pseudorapidity |eta| < 2.3and transverse momentum between 0.1GeVand 22GeVin a dataset corresponding to an integrated luminosity of 1 mu b(-1). The results are presented in the form of chargedparticle nuclear modification factors, where the p + Pbcharged-particle multiplicities are compared between central and peripheral p + Pbcollisions as well as to charged-particle cross sections measured in ppcollisions. The p + Pbcollision centrality is characterized by the total transverse energy measured in -4.9<eta<-3.1, which is in the direction of the outgoing lead beam. Three different estimations of the number of nucleons participating in the p + Pbcollision are carried out using the Glauber model and two Glauber-Gribov colour-fluctuation extensions to the Glauber model. The values of the nuclear modification factors are found to vary significantly as a function of rapidity and transverse momentum. Abroad peak is observed for all centralities and rapidities in the nuclear modification factors for chargedparticle transverse momentum values around 3GeV. The magnitude of the peak increases for more central collisions as well as rapidity ranges closer to the direction of the outgoing lead nucleus. (C) 2016 The Author(s). Published by Elsevier B.V
DataSheet3_Proteoglycans play a role in the viscoelastic behaviour of the canine cranial cruciate ligament.xlsx
No full textProteoglycans (PGs) are minor extracellular matrix proteins, and their contributions to the mechanobiology of complex ligaments such as the cranial cruciate ligament (CCL) have not been determined to date. The CCLs are highly susceptible to injuries, and their extracellular matrix comprises higher PGs content than the other major knee ligaments. Hence these characteristics make CCLs an ideal specimen to use as a model in this study. This study addressed the hypothesis that PGs play a vital role in CCL mechanobiology by determining the biomechanical behaviour at low strain rates before and after altering PGs content. For the first time, this study qualitatively investigated the contribution of PGs to key viscoelastic characteristics, including strain rate dependency, hysteresis, creep and stress relaxation, in canine CCLs. Femur-CCL-tibia specimens (n = 6 pairs) were harvested from canine knee joints and categorised into a control group, where PGs were not depleted, and a treated group, where PGs were depleted. Specimens were preconditioned and cyclically loaded to 9.9 N at 0.1, 1 and 10%/min strain rates, followed by creep and stress relaxation tests. Low tensile loads were applied to focus on the toe-region of the stress-strain curves where the non-collagenous extracellular matrix components take significant effect. Biochemical assays were performed on the CCLs to determine PGs and water content. The PG content was ∼19% less in the treated group than in the control group. The qualitative study showed that the stress-strain curves in the treated group were strain rate dependent, similar to the control group. The CCLs in the treated group showed stiffer characteristics than the control group. Hysteresis, creep characteristics (creep strain, creep rate and creep compliance), and stress relaxation values were reduced in the treated group compared to the control group. This study suggests that altering PGs content changes the microstructural organisation of the CCLs, including water molecule contents which can lead to changes in CCL viscoelasticity. The change in mechanical properties of the CCLs may predispose to injury and lead to knee joint osteoarthritis. Future studies should focus on quantitatively identifying the effect of PG on the mechanics of intact knee ligaments across broader demography.</p
DataSheet2_Proteoglycans play a role in the viscoelastic behaviour of the canine cranial cruciate ligament.zip
No full textProteoglycans (PGs) are minor extracellular matrix proteins, and their contributions to the mechanobiology of complex ligaments such as the cranial cruciate ligament (CCL) have not been determined to date. The CCLs are highly susceptible to injuries, and their extracellular matrix comprises higher PGs content than the other major knee ligaments. Hence these characteristics make CCLs an ideal specimen to use as a model in this study. This study addressed the hypothesis that PGs play a vital role in CCL mechanobiology by determining the biomechanical behaviour at low strain rates before and after altering PGs content. For the first time, this study qualitatively investigated the contribution of PGs to key viscoelastic characteristics, including strain rate dependency, hysteresis, creep and stress relaxation, in canine CCLs. Femur-CCL-tibia specimens (n = 6 pairs) were harvested from canine knee joints and categorised into a control group, where PGs were not depleted, and a treated group, where PGs were depleted. Specimens were preconditioned and cyclically loaded to 9.9 N at 0.1, 1 and 10%/min strain rates, followed by creep and stress relaxation tests. Low tensile loads were applied to focus on the toe-region of the stress-strain curves where the non-collagenous extracellular matrix components take significant effect. Biochemical assays were performed on the CCLs to determine PGs and water content. The PG content was ∼19% less in the treated group than in the control group. The qualitative study showed that the stress-strain curves in the treated group were strain rate dependent, similar to the control group. The CCLs in the treated group showed stiffer characteristics than the control group. Hysteresis, creep characteristics (creep strain, creep rate and creep compliance), and stress relaxation values were reduced in the treated group compared to the control group. This study suggests that altering PGs content changes the microstructural organisation of the CCLs, including water molecule contents which can lead to changes in CCL viscoelasticity. The change in mechanical properties of the CCLs may predispose to injury and lead to knee joint osteoarthritis. Future studies should focus on quantitatively identifying the effect of PG on the mechanics of intact knee ligaments across broader demography.</p
DataSheet1_Proteoglycans play a role in the viscoelastic behaviour of the canine cranial cruciate ligament.docx
No full textProteoglycans (PGs) are minor extracellular matrix proteins, and their contributions to the mechanobiology of complex ligaments such as the cranial cruciate ligament (CCL) have not been determined to date. The CCLs are highly susceptible to injuries, and their extracellular matrix comprises higher PGs content than the other major knee ligaments. Hence these characteristics make CCLs an ideal specimen to use as a model in this study. This study addressed the hypothesis that PGs play a vital role in CCL mechanobiology by determining the biomechanical behaviour at low strain rates before and after altering PGs content. For the first time, this study qualitatively investigated the contribution of PGs to key viscoelastic characteristics, including strain rate dependency, hysteresis, creep and stress relaxation, in canine CCLs. Femur-CCL-tibia specimens (n = 6 pairs) were harvested from canine knee joints and categorised into a control group, where PGs were not depleted, and a treated group, where PGs were depleted. Specimens were preconditioned and cyclically loaded to 9.9 N at 0.1, 1 and 10%/min strain rates, followed by creep and stress relaxation tests. Low tensile loads were applied to focus on the toe-region of the stress-strain curves where the non-collagenous extracellular matrix components take significant effect. Biochemical assays were performed on the CCLs to determine PGs and water content. The PG content was ∼19% less in the treated group than in the control group. The qualitative study showed that the stress-strain curves in the treated group were strain rate dependent, similar to the control group. The CCLs in the treated group showed stiffer characteristics than the control group. Hysteresis, creep characteristics (creep strain, creep rate and creep compliance), and stress relaxation values were reduced in the treated group compared to the control group. This study suggests that altering PGs content changes the microstructural organisation of the CCLs, including water molecule contents which can lead to changes in CCL viscoelasticity. The change in mechanical properties of the CCLs may predispose to injury and lead to knee joint osteoarthritis. Future studies should focus on quantitatively identifying the effect of PG on the mechanics of intact knee ligaments across broader demography.</p
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